@article{xue_yu_huang_2021, title={A Family of Ultrahigh Efficiency Fractional dc-dc Topologies for High Power Energy Storage Device}, volume={9}, ISSN={["2168-6785"]}, DOI={10.1109/JESTPE.2020.2966177}, abstractNote={The application of a nonisolated bidirectional fractional dc–dc topology is proposed for high power energy storage device in this article. The proposed topology has the benefits of ultrahigh efficiency, simple structure, and low cost because it processes only a fractional of the total power. With the existence of an extra-low voltage (LV) power source, the converter voltage stress is only the difference between the dc bus and high voltage (HV) power source, therefore, low-cost LV transistors can be used in HV high power applications. Since a majority of the power is transferred directly between the energy storage device and dc bus, ultrahigh system efficiency can be achieved. Converter operating principle and design considerations such as battery capacity calculation methodologies and over voltage protection (OVP) are presented. A GaN transistor-based prototype is fabricated. Experimental results of a 1.2-kW battery energy storage prototype are presented to validate the analysis. The system efficiency is higher than 99% when a wide input–output voltage range is achieved. The fractional converter is convincing in achieving high efficiency and high conversion power with reduced cost for energy storage devices.}, number={2}, journal={IEEE JOURNAL OF EMERGING AND SELECTED TOPICS IN POWER ELECTRONICS}, author={Xue, Fei and Yu, Ruiyang and Huang, Alex}, year={2021}, month={Apr}, pages={1420–1427} }
 @article{wang_huang_blaabjerg_ruan_mertens_ji_2020, title={Guest Editorial: WBG semiconductor power electronics for industrial and automotive applications}, volume={13}, ISSN={["1755-4543"]}, DOI={10.1049/iet-pel.2020.0051}, number={3}, journal={IET POWER ELECTRONICS}, author={Wang, Jun and Huang, Alex Q. and Blaabjerg, Frede and Ruan, Xinbo and Mertens, Axel and Ji, Bing}, year={2020}, month={Feb}, pages={391–393} }
 @article{zhu_wang_huang_booth_zhang_2019, title={7.2-kV Single-Stage Solid-State Transformer Based on the Current-Fed Series Resonant Converter and 15-kV SiC MOSFETs}, volume={34}, ISSN={["1941-0107"]}, DOI={10.1109/TPEL.2018.2829174}, abstractNote={This paper proposes a novel two-level single-stage direct ac–ac converter for realizing a 7.2-kV medium-voltage (MV) solid-state transformer (SST) based on 15-kV SiC mosfets. A new current-fed series resonant converter (CFSRC) topology is proposed to address major challenges in MV ac–ac converters such as achieving zero-voltage switching (ZVS) for the MV mosfets across wide voltage and load ranges and minimizing system capacitance. The topology is analyzed with both time-domain analysis and first harmonic approximation to provide useful equations for circuit design. Constant deadtime strategy is adopted, allowing partial ZVS to occur at low-voltage (LV) levels. ZVS behavior over wide voltage range is investigated, and calculation of the associated loss from partial ZVS is presented. System parameters are optimized based on the tradeoff between conduction loss and switching loss. The 15-kV mosfet has been tested continuously at a park voltage of 10 kV and 37 kHz, indicating stable device operation and an extremely high voltage × frequency figure of merit. Moreover, inherent cycle-by-cycle current limiting in the proposed CFSRC under output short-circuit circumstance is realized by paralleling diodes to the LV resonant capacitors. Without employing any additional current sensors, the input and circulating currents are limited to a safe range automatically when the short-circuit occurs. This paper presents detailed short-circuit protection operating principles and peak resonant current equation to aid the design of the resonant tank. A full-scale and compact SST that converts 7.2 kV ac to 240 V ac is developed to verify the theoretical analysis. This is the highest reported voltage rating for two-level-based power converters without device series connection. ZVS is verified and achieved over wide voltage and load ranges with a peak efficiency of 97.8%. A short-circuit experiment is conducted at 3-kV peak voltage to verify the analysis. Experimental results closely match the theoretical analysis.}, number={2}, journal={IEEE TRANSACTIONS ON POWER ELECTRONICS}, author={Zhu, Qianlai and Wang, Li and Huang, Alex Q. and Booth, Kristen and Zhang, Liqi}, year={2019}, month={Feb}, pages={1099–1112} }
 @article{huang_huang_yu_liu_yu_2019, title={High-Efficiency and High-Density Single-Phase Dual-Mode Cascaded Buck-Boost Multilevel Transformerless PV Inverter With GaN AC Switches}, volume={34}, ISSN={["1941-0107"]}, DOI={10.1109/TPEL.2018.2878586}, abstractNote={This paper introduces a high-efficiency and high-density single-phase dual-mode cascaded buck–boost multilevel transformerless photovoltaic (PV) inverter for residential application. This inverter topology combines a regulated cascaded H-bridge multilevel inverter stage with an unregulated GaN-based ac boost converter. The cascaded H-bridge inverter and the ac boost share a common inductor. Compared with the traditional cascaded H-bridge PV inverter, this topology significantly enlarges the input voltage range due to the additional ac boost. And, a flexible number of PV panels can be used. To control the multiple dc-link PV voltages and to reduce the switching loss of the ac boost, this paper further introduces a dual-mode operation. The two modes are buck mode and buck–boost mode. To maximize the utilizations of the dc-link voltages, this paper presents a minimized ac boost duty-cycle generation strategy with feedforward. Then, a dual-mode modulation based on the boost feedforward duty-cycle generation is introduced. This paper also uses an indirect current control for this inverter, since the ac boost is an unregulated stage. The ac boost stage is implemented with two interleaved phases and the ac switches based on the 650-V E-mode GaN FETs. Finally, an 8-port 2-kW prototype based on this topology is developed and demonstrated. Compared with the state-of-the-art microinverter-based 2-kW PV inverter system, the developed inverter prototype achieves 40% reduction of the total power loss, 25% improvement of the power density, 37.5% reduction of the power connectors, 50% reduction of the device count, and 87.5% reduction of the main magnetic count. Operating with natural convection cooling, this PV inverter achieves 98.0% efficiency at 60% of load and 97.8% efficiency at full load. The power density of the packaged PV inverter is 5.8 W/in3.}, number={8}, journal={IEEE TRANSACTIONS ON POWER ELECTRONICS}, author={Huang, Qingyun and Huang, Alex Q. and Yu, Ruiyang and Liu, Pengkun and Yu, Wensong}, year={2019}, month={Aug}, pages={7474–7488} }
 @book{power electronics in renewable energy systems and smart grid: technology and applications_2019, ISBN={["978-1-11-951562-3"]}, DOI={10.1002/9781119515661}, journal={POWER ELECTRONICS IN RENEWABLE ENERGY SYSTEMS AND SMART GRID: TECHNOLOGY AND APPLICATIONS}, year={2019}, pages={1–694} }
 @article{jiang_sung_baliga_wang_lee_huang_2018, title={Electrical Characteristics of 10-kV 4H-SiC MPS Rectifiers with High Schottky Barrier Height}, volume={47}, ISSN={["1543-186X"]}, DOI={10.1007/s11664-017-5812-2}, number={2}, journal={JOURNAL OF ELECTRONIC MATERIALS}, author={Jiang, Yifan and Sung, Woongje and Baliga, Jayant and Wang, Sizhen and Lee, Bongmook and Huang, Alex}, year={2018}, month={Feb}, pages={927–931} }
 @inproceedings{liu_yu_chen_huang_huang_2018, title={Real-time adaptive timing control of synchronous rectifiers in high frequency GaN LLC converter}, DOI={10.1109/apec.2018.8341324}, abstractNote={This paper presents an adaptive synchronous rectification (SR) control method for high frequency GaN LLC converter. This novel SR control scheme adaptively controls SR on time as well as accurate turn-on and turn-off tuning. Zero crossing detection (ZCD) of the transformer secondary-side current is achieved by Rogowski coil and its auxiliary circuits. ZCD signals are sent to digital signal processor (DSP) for further signal processing and PWM modulation. The SR method is applicable for a wide range of load current and wide range of switching frequency. To verify the proposed SR control method, a 2.1 kW GaN LLC converter prototype is demonstrated with 400V input voltage and 48V output voltage.}, booktitle={Thirty-third annual ieee applied power electronics conference and exposition (apec 2018)}, author={Liu, Z. R. and Yu, R. Y. and Chen, T. X. and Huang, Q. Y. and Huang, A. Q.}, year={2018}, pages={2214–2220} }
 @article{ma_xu_huang_wang_zou_2018, title={Single-phase hybrid-H6 transformerless PV grid-tied inverter}, volume={11}, ISSN={["1755-4543"]}, DOI={10.1049/iet-pel.2018.5009}, abstractNote={Transformerless inverter for grid-tied photovoltaic (PV) system has been widely used due to lower cost, higher efficiency and lighter weight. Various transformerless inverter topologies have been proposed to meet the safety requirement of low leakage current and obtain the reactive power capability. To get better performance, a novel transformerless hybrid-H6 inverter with an improved modulation technique is proposed in this study. By adopting the improved modulation technique, two symmetry paths are realised to share the current during the freewheeling mode. Thus, without paralleling any additional capacitors to the switch, the inverter can reduce the influence of junction capacitance on common mode voltage naturally which results in mitigating the leakage current issue. Thanks to the dead time reduction through the improved modulation, the qualities of output waveforms are improved. Moreover, reactive power control is achieved without any modification of the inverter structure. Finally, a 1 kW prototype is simulated and tested to verify the theoretical analysis of this study. Not only the reactive power capability is obtained for the proposed inverter, but also the small common mode voltage fluctuation is achieved at the same time. In addition, the total harmonic distortion of the current is decreased by more than 1.7%.}, number={15}, journal={IET POWER ELECTRONICS}, author={Ma, Lan and Xu, Hongbing and Huang, Alex Q. and Wang, Xiaodong and Zou, Jianxiao}, year={2018}, month={Dec}, pages={2440–2449} }
 @article{wang_huang_guo_yu_yu_huang_2018, title={Soft-Switched Modulation Techniques for an Isolated Bidirectional DC-AC}, volume={33}, ISSN={["1941-0107"]}, DOI={10.1109/tpel.2017.2661965}, abstractNote={Two carrier-based unipolar-sinusoidal pulse width modulation (SPWM)-oriented modulation techniques for an isolated bidirectional dc–ac converter are proposed, compared, and validated in this paper. The dc–ac converter is composed of a full-bridge (FB) inverter cascaded with a cycloconverter through a high-frequency transformer. Both modulation techniques proposed in this paper can realize zero-voltage switching (ZVS) for the FB inverter and zero-current switching or ZVS for the cycloconverter in all load range, and are able to suppress the voltage spikes introduced by the transformer leakage inductance as well. In order to increase the converter efficiency and power density, we propose to utilize SiC MOSFETs for the converter. The first modulation technique enables the utilization of Si-SiC hybrid switches with no synchronous rectification (SR), for the purpose of lowering the converter cost. The second modulation technique requires all switches to be SiC MOSFETs, but with SR, which increases the converter efficiency. A 400-V dc to 240-V ac 1.2-kW prototype has been developed to validate the effectiveness and performance of the proposed carrier-based unipolar-SPWM-oriented modulation techniques.}, number={1}, journal={IEEE TRANSACTIONS ON POWER ELECTRONICS}, author={Wang, Mengqi and Huang, Qingyun and Guo, Suxuan and Yu, Xiaohang and Yu, Wensong and Huang, Alex Q.}, year={2018}, month={Jan}, pages={137–150} }
 @article{xue_yu_huang_2017, title={A 98.3% Efficient GaN Isolated Bidirectional DC-DC Converter for DC Microgrid Energy Storage System Applications}, volume={64}, ISSN={["1557-9948"]}, DOI={10.1109/tie.2017.2686307}, abstractNote={This paper presents a novel 400 to 12 V isolated bidirectional dc–dc converter based on a phase-shift-controlled-modified dual-active-bridge power stage. The proposed converter consists of a half-bridge and center tap with active clamp circuit, which has promising performance for low-voltage high-current applications. 650 V gallium-nitride high electron mobility transistors are used on the high voltage side to avoid issues encountered using Si superjunction MOSFETs in phase-shift-controlled-bidirectional power conversions. The operation principle and power transfer characteristic are obtained based on a time-domain analysis of the inductor current. Design methodology and criteria and converter's efficiency analysis are discussed. Both the analysis and experiments verify that the proposed converter is capable of achieving low power loss and high power density in soft-switching and hard-switching modes. Experimental results are presented for a 1-kW, 400 V-to-12 V dc–dc prototype converter operating at 100 kHz switching frequency. A power density of 30 W/in3  and a peak efficiency of 98.3% in a wide input/output voltage range are achieved.}, number={11}, journal={IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS}, author={Xue, Fei and Yu, Ruiyang and Huang, Alex Q.}, year={2017}, month={Nov}, pages={9094–9103} }
 @article{song_peng_huang_2017, title={A Medium-Voltage Hybrid DC Circuit Breaker, Part I: Solid-State Main Breaker Based on 15 kV SiC Emitter Turn-OFF Thyristor}, volume={5}, ISSN={["2168-6777"]}, DOI={10.1109/jestpe.2016.2609845}, abstractNote={This paper discusses the design of a 10 kV and 200 A hybrid dc circuit breaker suitable for the protection of the dc power systems in electric ships. The proposed hybrid dc circuit breaker employs a Thompson coil based ultrafast mechanical switch (MS) with the assistance of two additional solid-state power devices. A low-voltage (80 V) metal–oxide–semiconductor field-effect transistors (MOSFETs)-based commutating switch (CS) is series connected with the MS to realize the zero current turn-OFF of the MS. In this way, the arcing issue with the MS is avoided. A 15 kV SiC emitter turn-OFF thyristor-based main breaker (MB) is parallel connected with the MS and CS branch to interrupt the fault current. A stack of MOVs parallel with the MB are used to clamp the voltage across the hybrid dc circuit breaker during interruption. This paper focuses on the electronic parts of the hybrid dc circuit breaker, and a companion paper will elucidate the principle and operation of the fast acting MS and the overall operation of the hybrid dc circuit breaker. The selection and design of both the high-voltage and low-voltage electronic components in the hybrid dc circuit breaker are presented in this paper. The turn-OFF capability of the MB with and without snubber circuit is experimentally tested, validating its suitability for the hybrid dc circuit breaker application. The CSs’ conduction performances are tested up to 200 A, and its current commutating during fault current interruption is also analyzed. Finally, the hybrid dc circuit breaker demonstrated a fast current interruption within 2 ms at 7 kV and 100 A.}, number={1}, journal={IEEE JOURNAL OF EMERGING AND SELECTED TOPICS IN POWER ELECTRONICS}, author={Song, Xiaoqing and Peng, Chang and Huang, Alex Q.}, year={2017}, month={Mar}, pages={278–288} }
 @article{peng_song_huang_husain_2017, title={A Medium-Voltage Hybrid DC Circuit Breaker-Part II: Ultrafast Mechanical Switch}, volume={5}, ISSN={["2168-6777"]}, DOI={10.1109/jestpe.2016.2609391}, abstractNote={This paper presents the test results of an ultrafast (less than 2 ms) medium-voltage hybrid dc circuit breaker prototype that consists of three switching devices: a 15-kV silicon carbide (SiC) emitter turn-off thyristor as the main breaker (MB), a fast acting mechanical switch, and a commutating switch (CS) to quickly divert the primary current to the MB for arcless interruption. The hybrid dc circuit breaker prototype can interrupt a circuit in less than 2 ms in dc power systems up to 10 kV, such as in electric ships. The ultrafast operations and extremely low loss can effectively limit the fault current level and switching transients in all medium-voltage systems, and can provide intelligent and fast protection function for smart power distribution and critical loads in a modernized grid. The design considerations of the three switching devices of the hybrid dc circuit breaker are presented. This paper focuses on the ultrafast mechanical switch and the testing of the hybrid dc circuit breaker, while a companion paper addresses the high-voltage solid-state main switch and the low-voltage solid-state CS.}, number={1}, journal={IEEE JOURNAL OF EMERGING AND SELECTED TOPICS IN POWER ELECTRONICS}, author={Peng, Chang and Song, Xiaoqing and Huang, Alex Q. and Husain, Iqbal}, year={2017}, month={Mar}, pages={289–296} }
 @article{wang_zhu_yu_huang_2017, title={A Medium-Voltage Medium-Frequency Isolated DC-DC Converter Based on 15-kV SiC MOSFETs}, volume={5}, ISSN={["2168-6777"]}, DOI={10.1109/jestpe.2016.2639381}, abstractNote={In this paper, a novel isolated dc–dc converter topology for medium-voltage (MV) applications is proposed by combining the advantages of resonant converters and dual active bridge (DAB) converters. In normal load scenario, this converter operates in an open loop resonant mode with a fixed switching frequency equals to the resonant frequency of the series resonant tank. Thus, zero voltage turn on at primary side and zero current turn off at secondary side are secured from zero to full load. When overload happens, the resonant capacitors will be clamped to the output voltage by the additional paralleled diodes. The proposed converter automatically switches to resonant and DAB mixed operation mode; therefore, the resonant current is naturedly limited. With zero to full load range soft switching and fast overload protection, the proposed topology is especially suitable for MV medium frequency applications utilizing high-voltage SiC MOSFETs. The converter operation modes are analyzed using time-domain waveforms and graphical state trajectory to derive the quantitative relationship between duty cycle, output voltage, and the overload current. Based on these relationships, a predictive duty cycle control is proposed to further limit the overload current of the resonant tank by sensing the output voltage. Combing the proposed topology and the predictive control, cycle-by-cycle overload and short-circuit protections are achieved. To fully utilize the capability of the 15-kV SiC MOSFET, magnetizing inductance, dead time, MV transformer, and resonant components are optimized with the operating range of 6–12 kV and 20–100 kHz. An experimental prototype running at 6 kV and 40 kHz is successfully tested with peak efficiency exceeding 98%. Test waveforms at no load and 10-kW full load validate the zero to full load range soft switching capability. Short circuit protection test demonstrates a 25- $\mu \text{s}$  overload protection speed.}, number={1}, journal={IEEE JOURNAL OF EMERGING AND SELECTED TOPICS IN POWER ELECTRONICS}, author={Wang, Li and Zhu, Qianlai and Yu, Wensong and Huang, Alex Q.}, year={2017}, month={Mar}, pages={100–109} }
 @article{li_jiang_huang_guo_deng_zhang_she_2017, title={A SiC Power MOSFET Loss Model Suitable for High-Frequency Applications}, volume={64}, ISSN={["1557-9948"]}, DOI={10.1109/tie.2017.2703910}, abstractNote={The reduced chip size and unipolar current conduction mechanism make silicon carbide (SiC) metal–oxide–semiconductor field-effect transistors (MOSFETs) suitable for high-frequency power electronics applications. Modeling the switching process of the SiC power MOSFET with parasitic components is important for achieving higher efficiency and power density system design. Therefore, this paper proposes a new concise yet accurate switching loss model for SiC power MOSFETs. Addressing the limitations in experimental measurements, numerical simulations are conducted to validate the proposed model taking the output capacitance Coss discharge and charge into consideration. The role of the parasitic components in the second-order model is discussed in depth for switching losses. Furthermore, this paper also provides guidelines in designing the gate driver for ultrafast SiC power MOSFETs.}, number={10}, journal={IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS}, author={Li, Xuan and Jiang, Junning and Huang, Alex Q. and Guo, Suxuan and Deng, Xiaochuan and Zhang, Bo and She, Xu}, year={2017}, month={Oct}, pages={8268–8276} }
 @inproceedings{hambridge_lu_huang_yu_2017, title={A frequency based real-time electricity rate for residential prosumers}, DOI={10.1109/pesgm.2017.8273834}, abstractNote={The emergence of distributed generation has made a case for a deregulated, competitive, transactive energy market, operating at the level of the traditional residential consumer. These new energy players, prosumers, will interact as the larger energy generators do under the supervision of Independent System Operators (ISOs), but with their own Distributed System Operators (DSOs). This work proposes a prosumer energy management scheme, broken into a day-ahead schedule and a realtime adjustment, mirroring the ISO market structure. Within this framework, a dynamic rate can be designed and tested for the prosumer. A time-of-use (TOU) rate was combined with a frequency based, real-time dynamic rate to produce a hybrid rate that the prosumer can optimize for during its day-ahead and real-time dispatch. This hybrid rate can be calculated every one minute and applied autonomously from the grid frequency, providing secondary frequency regulation and an incentive for better solar management and use of energy storage. Such a real-time rate is the first designed for price-reactive control. In simulation, the real-time hybrid rate is compared to conventional TOU and flat rates and the final daily energy costs are calculated for a variety of residential load types with a realistic distributed solar generation curve gathered from Pecan Street Inc. Dataport. Under the one minute hybrid rate, the results indicate a near zero energy bill can be achieved for a prosumer with day-time load and smart use of energy storage.}, booktitle={2017 ieee power & energy society general meeting}, author={Hambridge, S. and Lu, N. and Huang, A. Q. and Yu, R. Y.}, year={2017} }
 @inproceedings{huang_yu_huang_yu_2017, title={Adaptive zero-voltage-switching control and hybrid current control for high efficiency GaN-based MHz totem-pole PFC rectifier}, DOI={10.1109/apec.2017.7930937}, abstractNote={This paper presents an adaptive Zero-Voltage-Switching control (ZVS) method and a hybrid current control strategy for the GaN-based MHz Totem-pole PFC rectifier. This novel ZVS control achieves the minimum ZVS time margin and maximum switching frequency clamping by adaptively controlling the synchronous rectifier (SR) turn off current. This adaptive SR turn off current control is a unified control strategy based on a proposed unified analytical converter model. The analytical model and the control strategy are applicable for full-range of input voltage and full-range of load for ZVS Totem-pole PFC. In addition, a dual-loop current control strategy is also proposed in this paper. This dual-loop current controller uses the outer average current control loop to directly regulates the inductor average current. The inner current control loop combines the peak current controller and the time based SR turn off current controller. The proposed SR turn off current control for ZVS is adaptively controlled by this time based controller. To verify the proposed ZVS control method and the hybrid current controller, a 1.5kW GaN-based MHz Totem-pole PFC prototype is demonstrated with full-range ZVS, 99% peak efficiency and high quality AC current.}, booktitle={2017 thirty second annual ieee applied power electronics conference and exposition (apec)}, author={Huang, Q. Y. and Yu, R. Y. and Huang, A. Q. and Yu, Wensong}, year={2017}, pages={1763–1770} }
 @article{wang_guo_huang_yu_huang_2017, title={An Isolated Bidirectional Single-Stage DC-AC Converter Using Wide-Band-Gap Devices With a Novel Carrier-Based Unipolar Modulation Technique Under Synchronous Rectification}, volume={32}, ISSN={["1941-0107"]}, DOI={10.1109/tpel.2016.2564360}, abstractNote={A novel carrier-based unipolar-sinusoidal pulse width modulation (SPWM)-oriented modulation technique with synchronous rectification for isolated bidirectional single-stage high-frequency-ac link dc-ac converters using SiC MOSFET is presented in this paper. The dc-ac converter is composed of a full-bridge (FB) inverter cascaded with a cycloconverter through a high-frequency transformer. A carrier-based unipolar-SPWM-oriented modulation technique with synchronous rectification is proposed to realize zero-voltage-switching (ZVS) for the FB inverter and zero-current or zero-voltage-switching (ZVS/ZCS) for the cycloconverter in all load ranges, and to suppress the voltage spikes introduced by the transformer leakage inductance as well. In order to increase the switching frequency, efficiency, and power density, this paper proposes to utilize SiC MOSFETs for the converter. Synchronous rectification is implemented to further increase the converter efficiency. With the novel modulation technique, there are two switches in the cycloconverter that are continuously on at each interval, which eliminates on-fourth of the switching loss. A simulation model and a 400 VDC-240 VAC, 1.2=kW prototype have been developed to validate the effectiveness and performance of the proposed unipolar soft-switching modulation technique and SiC converter.}, number={3}, journal={IEEE TRANSACTIONS ON POWER ELECTRONICS}, author={Wang, Mengqi and Guo, Suxuan and Huang, Qingyun and Yu, Wensong and Huang, Alex Q.}, year={2017}, month={Mar}, pages={1832–1843} }
 @inproceedings{tang_huang_2017, title={Assessment of medium voltage SiC MOSFET advantages in medium voltage drive application}, DOI={10.1109/ecce.2017.8095867}, abstractNote={This paper proposes a hypothetic silicon carbide (SiC) metal oxide semiconductor field effect transistor (MOSFET) power module for the medium voltage (MV) variable frequency drive (VFD). A peer-to-peer comparison between commercial silicon (Si) insulated-gate bipolar transistor (IGBT) and the proposed SiC MOSFET module results in some promising results to support the introduction of SiC power modules for the MV VFD market.}, booktitle={2017 ieee energy conversion congress and exposition (ecce)}, author={Tang, H. N. and Huang, A. Q.}, year={2017}, pages={801–807} }
 @inproceedings{luo_su_huang_2017, title={Bit-energy: An innovative bitcoin-style distributed transactional model for a competitive electricity market}, DOI={10.1109/pesgm.2017.8274639}, abstractNote={This paper proposes an innovative Bitcoin-style distributed transactional model, “Bit-Energy,” to enable transparent, auditable, and peer-to-peer energy transactions between active market participants directly without a central intermediary (e.g., distribution system operator) using radically different Internet-of-Things (IoT) technologies. The proposed distributed platform is fully compatible with the existing distribution grid infrastructure. Case studies demonstrate the accuracy, robustness, effectiveness, and scalability of the proposed Bit-Energy platform under various operating conditions. The distributed platform contained in this paper can apply to many other smart grid applications.}, booktitle={2017 ieee power & energy society general meeting}, author={Luo, J. W. and Su, W. C. and Huang, A. Q.}, year={2017} }
 @inproceedings{sen_song_zhang_huang_2017, title={Continuous switching operation of 15 kV FREEDM super-cascode}, DOI={10.1109/ecce.2017.8096751}, abstractNote={High voltage and wide bandgap (WBG) semiconductor devices like the 15 kV SiC MOSFET have attracted a lot of attention because of their potential applications in high voltage and high power converters. However, they are not commercially available at present and their high cost might be a hindrance to their widespread adoption in future. To address the commercial unavailability and the high cost issues of the 15 kV SiC MOSFET, the 15 kV FREEDM Super-Cascode, which is based on 1.2 kV SiC MOSFET and JFETs series connection, is designed and developed. In this paper, the high switching frequency operation of the newly developed 15 kV, 40 A FREEDM Super-Cascode is tested and reported for the first time. A 7.2 kV ac rms input, 400 V dc output, 40 kW converter is designed using the 15 kV FREEDM Super-Cascode, whose switching frequency varies from 15 to 64 kHz.}, booktitle={2017 ieee energy conversion congress and exposition (ecce)}, author={Sen, S. and Song, X. Q. and Zhang, L. Q. and Huang, A. Q.}, year={2017}, pages={4366–4372} }
 @inproceedings{lei_huang_2017, title={Data center power distribution system reliability analysis tool based on Monte Carlo next event simulation method}, DOI={10.1109/ecce.2017.8096406}, abstractNote={High reliability is extremely important for uninterruptable power supplies (UPS) such as those used in the modern data centers. It is necessary to comprehensively and precisely evaluate reliability of different UPS system's architectures before constructing the data center. In this paper, a novel reliability analysis and simulation tool for data center power distribution system is proposed. The basic algorithm of this software tool is based on Monte Carlo next event simulation method but novel enhancements are made to make it suitable for large system reliability analysis. Specially, a novel dependent event generator allows the correct modeling of important events such as the battery discharge event and breaker trip event. Moreover, a multi-thread algorithm is developed to significantly increase the calculation speed with high precision. Several typical data center architectures are analyzed with the proposed software tool and their reliability performance are compared.}, booktitle={2017 ieee energy conversion congress and exposition (ecce)}, author={Lei, Y. and Huang, A. Q.}, year={2017}, pages={2031–2035} }
 @inproceedings{zhu_wang_chen_zhang_huang_2017, title={Design and implementation of a 7.2kV single stage AC-AC solid state transformer based on current source series resonant converter and 15 kV SiC MOSFET}, DOI={10.1109/ecce.2017.8095938}, abstractNote={This paper introduces a 97% efficiency medium voltage (MV) Solid State Transformer (SST) based on two-level single stage (TLSS) topology and 15 kV SiC MOSFETs. Series resonant converter (SRC) is implemented as the main stage and is identified as a current source (CS) SRC for the first time. Equivalent resonant frequency of the proposed CS-SRC is analyzed in both time domain and frequency domain. Resonant frequency calculation equation is derived and can be used to accurately design the resonant tank. Zero voltage switching (ZVS) for 15 kV SiC MOSFET in CS-SRC topology under extremely wide input voltage from 0V to 10 kV is analyzed and designed at a medium frequency (MF) of 40 kHz. Partial discharge for the 15 kV SiC MOSFET's parasitic capacitor are explained and the associated turn on loss equations are derived. Magnetizing inductance Lm and deadtime tdead are further optimized based on the trade-off between the turn on loss and conduction loss of the semiconductor devices. A fully functional and compact SST based on the proposed concept is developed and tested with an input of voltage of 7.2 kVac and from 1 kW to 12 kW. The efficiency is higher than 97% under most load conditions.}, booktitle={2017 ieee energy conversion congress and exposition (ecce)}, author={Zhu, Q. L. and Wang, L. and Chen, D. and Zhang, L. Q. and Huang, A. Q.}, year={2017}, pages={1288–1295} }
 @inproceedings{naeimi_huang_2017, title={Design and optimization of high conversion ratio quasi square wave buck converters}, DOI={10.1109/wipda.2017.8170538}, abstractNote={With fast growth of data centers and automotive electronics, DC-DC converters are the crucial modules, which deliver power to these systems. High conversion ratio (HCR) step down DC-DC converters are gaining growing attention for usage in these high tech emerging applications. The main design challenge of these converters is maximizing conversion ratio, efficiency, and power density simultaneously. In this paper, we have advanced and expanded design procedure for Quasi Square Wave (QSW) buck converter, which is promising candidate to overcome aforementioned challenges. The procedure is essential for precise calculation of design parameters and components selection to avoid iterations after implementation. We also introduce development of an optimization approach based on detailed power loss analysis. We utilized this approach here to design optimum LS and HS FETs; and obtain power loss break down. The 1 MHz designed buck converter steps down voltage from 48 V to 1.8 V at 30 A of output current.}, booktitle={2017 IEEE 5th Workshop on Wide Bandgap Power Devices and Applications (WIPDA)}, author={Naeimi, Y. and Huang, A.}, year={2017}, pages={148–152} }
 @inproceedings{guo_liu_zhang_huang_2017, title={Design and optimization of the high frequency transformer for a 800V/1.2MHz SiC LLC resonant converter}, DOI={10.1109/ecce.2017.8096892}, abstractNote={The LLC resonant converter is very suitable for high frequency and high power density applications due to its excellent characteristics such as load independent ZVS turn-on, low turn-off current. The high frequency high voltage transformer is a key component in the LLC that provides galvanic isolation and power conversion. In order to improve the power density, the frequency can be pushed to several hundred kHz or megahertz range especially if advanced power devices such as the SiC MOSFET is used. However, optimal design of the transformer is a grand challenge which must consider magnetic core material, core and winding loss, and transformer thermal performance. In this paper, a megahertz high voltage transformer is designed for a high voltage SiC LLC resonant converter. The loss model and thermal model of the transformer are analyzed in details. The high frequency magnetic core materials are reviewed and compared. A comprehensive transformer optimization design method is proposed to maximize the utilization of the transformer, achieving the maximum power density with minimum transformer loss. A 1.2 MHz 4.5 kW transformer prototype is built and tested in the 800V SiC LLC resonant converter.}, booktitle={2017 ieee energy conversion congress and exposition (ecce)}, author={Guo, S. X. and Liu, P. K. and Zhang, L. Q. and Huang, A. Q.}, year={2017}, pages={5317–5323} }
 @inproceedings{xue_yu_huang_2017, title={Fractional converter for high efficiency high power battery energy storage system}, DOI={10.1109/ecce.2017.8096866}, abstractNote={A family of bidirectional fractional DC-DC converter for high voltage, high power battery energy storage system is proposed in this paper. The proposed converter has the benefits of low cost, high efficiency since it only processes part of the total converted power. One extra low voltage battery pack is needed; however, it can be from a different voltage rail or seamlessly integrated with the high voltage battery pack. System efficiency and battery capacity calculation methodologies are given in details. A proof-of-concept fractional converter based on GaN transistor was fabricated. Experimental results of a 1.2kW prototype are presented to validate the analysis. With the proposed converter, a peak equivalent efficiency of 99.63% in a wide input/output voltage range are achieved. It is shown that the fractional converter can greatly reduce the cost of energy storage system while achieve high efficiency and high power-density in potential applications.}, booktitle={2017 ieee energy conversion congress and exposition (ecce)}, author={Xue, F. and Yu, R. Y. and Huang, A.}, year={2017}, pages={5144–5150} }
 @inproceedings{wang_zhu_yu_huang_2017, title={Full ZVS soft- start of a SiC medium voltage series resonant DC-DC converter using variable frequency variable duty Cycle control}, DOI={10.1109/ifeec.2017.7992331}, abstractNote={A novel variable frequency variable duty cycle (VFVD) control scheme using off-line digital control by only sensing the output voltage is proposed. Designed for a 6 kV 40 kHz series resonant DC-DC converter in solid state transformer application, it realizes cycle-by-cycle resonant current limiting and zero voltage switching (ZVS) at any load condition. According to the state plane analysis, with a certain output voltage, the resonant current can be well controlled by modifying the on-time, and ZVS of the medium voltage (MV) SiC devices can be ensured by adjusting the switching frequency. By sensing the output voltage, a digital controller with off-line lookup table can be easily implemented. Full ZVS together with fast current limiting greatly improves the reliability of the MV medium frequency converter.}, booktitle={2017 IEEE 3rd International Future Energy Electronics conference and ECCE Asia (IFEEC 2017-ECCE Asia)}, author={Wang, L. and Zhu, Q. L. and Yu, Wensong and Huang, A. Q.}, year={2017}, pages={1855–1860} }
 @article{chen_xu_huang_2017, title={Integration of DC Microgrids as Virtual Synchronous Machines Into the AC Grid}, volume={64}, ISSN={["1557-9948"]}, DOI={10.1109/tie.2017.2674621}, abstractNote={A smart and autonomous integration concept for dc microgrids into the legacy ac grid is proposed based on the virtual synchronous machine (VSM) concept. It utilizes a dc–ac converter as a universal VSM-based interface (VSMBI) between the ac grid and various distributed energy resources (DER) connected on the dc side. The control strategy of it includes: 1) a frequency regulation improved from previous VSM works, which is suitable for the microgrid integration; 2) an improved dual droop control between the ac frequency and the dc side energy storages; 3) a power system stabilizer to enhance the system stability. Under this concept, the VSMBI integrates the DERs, loads and energy storages in the dc microgrid into a VSM. The VSMBI and the dc microgrid together will respond to short-term and long-term requirements of the grid frequency regulation, and achieve autonomous power management for the ac grid and the dc microgrid. It is therefore an important step forward in supporting high DER penetration. The concept, its design and small-signal analysis are presented in this paper. Its effectiveness and functions are verified by simulation and experimental results.}, number={9}, journal={IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS}, author={Chen, Dong and Xu, Yizhe and Huang, Alex Q.}, year={2017}, month={Sep}, pages={7455–7466} }
 @inproceedings{wang_huang_zhu_2017, title={Multi-objective optimization of medium voltage SiC DC-DC converter based on modular input-series-output-parallel (ISOP) architecture}, DOI={10.1109/ifeec.2017.7992111}, abstractNote={This paper aims to comprehensively investigate the efficiency, power density and overall cost of input series output parallel (ISOP) medium voltage (MV) all silicon carbide (SiC) DC-DC converter in solid state transformers (SST). The medium voltage capability can be achieved by using either high voltage devices or multiple low voltage cells in series. Voltage rating of semiconductor devices, magnetic components, capacitors vary with the number of cells in series. In order to investigate the optimized number of cells, precise components' models with different voltage ratings are required, especially for the already complicated semiconductor devices. SiC MOSFET's on-resistance, output capacitance and cost models with arbitrary blocking voltages are derived based on physical device scaling law. Using these mathematical MOSFET models together with transformer and capacitor models, multi-objective optimization of an ISOP DC-DC converter system is conducted. Optimization results shows that a higher power density can be achieved by greater number of cells but single stage converter can reach higher efficiency and lower cost.}, booktitle={2017 IEEE 3rd International Future Energy Electronics conference and ECCE Asia (IFEEC 2017-ECCE Asia)}, author={Wang, L. and Huang, A. Q. and Zhu, Q. L.}, year={2017}, pages={627–632} }
 @article{huang_2017, title={Power Semiconductor Devices for Smart Grid and Renewable Energy Systems}, volume={105}, ISSN={["1558-2256"]}, DOI={10.1109/jproc.2017.2687701}, abstractNote={Modern civilization is related to the increased use of electric energy for industry production, human mobility, and comfortable living. Highly efficient and reliable power electronic systems, which convert and process electric energy from one form to the other, are critical for smart grid and renewable energy systems. The power semiconductor device, as the cornerstone technology in a power electronics system, plays a pivotal role in determining the system efficiency, size, and cost. Starting from the invention and commercialization of silicon bipolar junction transistor 60 years ago, a whole array of silicon power semiconductor devices have been developed and commercialized. These devices enable power electronics systems to reach ultrahigh efficiency and high-power capacity needed for various smart grid and renewable energy system applications such as photovoltaic (PV), wind, energy storage, electric vehicle (EV), flexible ac transmission system (FACTS), and high voltage dc (HVDC) transmission. In the last two decades, newer generations of power semiconductor devices based on wide bandgap (WBG) materials, such as SiC and GaN, were developed and commercialized further pushing the boundary of power semiconductor devices to higher voltages, higher frequencies, and higher temperatures. This paper reviews some of the major power semiconductor devices technologies and their potential impacts and roadmaps.}, number={11}, journal={PROCEEDINGS OF THE IEEE}, author={Huang, Alex Q.}, year={2017}, month={Nov}, pages={2019–2047} }
 @article{cai_bodle_mathieu_amos_hamouda_bernacki_mccarty_loboa_2017, title={Primary cilia are sensors of electrical field stimulation to induce osteogenesis of human adipose-derived stem cells}, volume={31}, ISSN={["1530-6860"]}, DOI={10.1096/fj.201600560r}, abstractNote={In this study, we report for the first time that the primary ciliumacts as a crucial sensor for electrical field stimulation (EFS)–enhanced osteogenic response in osteoprogenitor cells. In addition, primary cilia seem to functionally modulate effects of EFS‐induced cellular calciumoscillations. Primary cilia are organelles that have recently been implicated to play a crucial sensor role for many mechanical and chemical stimuli on stem cells. Here, we investigate the role of primary cilia in EFS‐enhanced osteogenic response of human adipose‐derived stem cells (hASCs) by knocking down 2 primary cilia structural proteins, polycystin‐1 and intra flagellar protein‐88. Our results indicate that structurally integrated primary cilia are required for detection of electrical field signals in hASCs. Further more, by measuring changes of cytoplasmic calcium concentration in hASCs during EFS, our findings also suggest that primary ciliamay potentially function as a crucial calcium‐signaling nexus in hASCs during EFS.—Cai, S., Bodle, J. C., Mathieu, P. S., Amos, A., Hamouda, M., Bernacki, S., McCarty, G., Loboa, E. G. Primary cilia are sensors of electrical field stimulation to induce osteogenesis of human adipose‐derived stem cells. FASEB J. 31, 346–355 (2017) www.fasebj.org}, number={1}, journal={FASEB JOURNAL}, author={Cai, Shaobo and Bodle, Josephine C. and Mathieu, Pattie S. and Amos, Alison and Hamouda, Mehdi and Bernacki, Susan and McCarty, Greg and Loboa, Elizabeth G.}, year={2017}, month={Jan}, pages={346–355} }
 @misc{she_huang_lucia_ozpineci_2017, title={Review of Silicon Carbide Power Devices and Their Applications}, volume={64}, ISSN={["1557-9948"]}, DOI={10.1109/tie.2017.2652401}, abstractNote={Silicon carbide (SiC) power devices have been investigated extensively in the past two decades, and there are many devices commercially available now. Owing to the intrinsic material advantages of SiC over silicon (Si), SiC power devices can operate at higher voltage, higher switching frequency, and higher temperature. This paper reviews the technology progress of SiC power devices and their emerging applications. The design challenges and future trends are summarized at the end of the paper.}, number={10}, journal={IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS}, author={She, Xu and Huang, Alex Q. and Lucia, Oscar and Ozpineci, Burak}, year={2017}, month={Oct}, pages={8193–8205} }
 @article{gao_she_husain_huang_2017, title={Solid-State-Transformer-Interfaced Permanent Magnet Wind Turbine Distributed Generation System With Power Management Functions}, volume={53}, ISSN={["1939-9367"]}, DOI={10.1109/tia.2017.2679679}, abstractNote={The higher penetration of wind energy poses increasing demand for grid support and power management functions of a wind energy conversion system (WECS). This paper investigates a medium-voltage solid-state transformer (SST)-interfaced permanent magnet synchronous generator system with integrated active power management and reactive power compensation functions. Specifically, a WECS consisting of wind turbines, SSTs, and dc loads is presented. In addition, a distributed power management algorithm is proposed for a dc network with local wind turbine controls incorporated to achieve a self-contained power-balanced condition without the need for energy storage or communication devices. Scenarios considered include the grid-connected mode, the islanding mode, and the mode transitions. Simulation results are provided to verify the effectiveness of the proposed strategy. Additionally, the concept is experimentally verified using a scaled-down laboratory prototype.}, number={4}, journal={IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS}, author={Gao, Rui and She, Xu and Husain, Iqbal and Huang, Alex Q.}, year={2017}, pages={3849–3861} }
 @article{song_huang_lee_peng_2017, title={Theoretical and Experimental Study of 22 kV SiC Emitter Turn-OFF (ETO) Thyristor}, volume={32}, ISSN={["1941-0107"]}, DOI={10.1109/tpel.2016.2616841}, abstractNote={Controllable three terminal high voltage (<inline-formula><tex-math notation="LaTeX">$>$</tex-math> </inline-formula>10 kV) power switches based on silicon carbide (SiC) material are gaining significant attentions since silicon (Si) power switches such as insulated gate bipolar transistors (IGBTs) are typically designed for much lower blocking voltages. After more than 30 years of commercial development, there is a fundamental limitation in designing Si IGBTs with more than 6.5 kV voltage rating. On the other hand, the voltage barrier for SiC power devices could easily exceed 10 kV. In this paper, a world record 22 kV SiC p-type emitter turn-<sc>OFF</sc> (ETO) (p-ETO) thyristor is reported and analyzed as a promising candidate for high-voltage applications, such as solid-state circuit breaker, HVdc, flexible alternating current transmission system (FACTS), and motor drives. The device is based on a 2 cm<sup>2 </sup> 22 kV p-type SiC gate turn-<sc>off</sc> thyristor (p-GTO) structure. Its static performances are analyzed exhibiting a high voltage (22 kV) blocking characteristic, ultralow leakage current, and a low forward voltage drop ( <inline-formula><tex-math notation="LaTeX">$\sim$</tex-math></inline-formula>7 V at 100 A) for a broad range of temperatures. The dynamic performances including turn-<sc>on</sc> and turn-<sc>off</sc> are studied. Key switching characteristics such as turn-<sc>off</sc> storage time, turn-<sc>off</sc> loss, <italic>dv/dt</italic>, and <italic> di/dt</italic> are presented and analyzed. In addition, the large reverse biased safe operation area (RBSOA) of the 22 kV SiC ETO is theoretically analyzed and verified by simulations and experimental tests.}, number={8}, journal={IEEE TRANSACTIONS ON POWER ELECTRONICS}, author={Song, Xiaoqing and Huang, Alex Q. and Lee, Meng-Chia and Peng, Chang}, year={2017}, month={Aug}, pages={6381–6393} }
 @article{lucia_she_huang_2017, title={Wide Bandgap Devices and Power Conversion Systems-Part I}, volume={64}, ISSN={["1557-9948"]}, DOI={10.1109/tie.2017.2738718}, number={10}, journal={IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS}, author={Lucia, Oscar and She, Xu and Huang, Alex Q.}, year={2017}, month={Oct}, pages={8190–8192} }
 @article{lucia_she_huang_2017, title={Wide Bandgap Devices and Power Conversion Systems-Part II}, volume={64}, ISSN={["1557-9948"]}, DOI={10.1109/tie.2017.2744398}, abstractNote={This Part II of this “Special Section on Wide Bandgap Devices and Power Conversion Systems” covers broad research areas related to wide bandgap devices and their applications and complements those research results published in Part I. The guest editors hope that this Special Section helps establish the state-of-the-art of WBG devices and power conversion systems and helps envision future devices, systems, and applications to bring industrial electronics to a new and exciting era of innovation.}, number={11}, journal={IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS}, author={Lucia, Oscar and She, Xue and Huang, Alex Q.}, year={2017}, month={Nov}, pages={8959–8961} }
 @inproceedings{song_huang_liu_zhang_2016, title={1200v/200a freedm-pair: loss and cost reduction analysis}, DOI={10.1109/wipda.2016.7799928}, abstractNote={FREEDM-Pair is an innovative power semiconductor switch which reduces the loss and cost through the hybrid integration of a Si IGBT and a SiC MOSFET. During the turn-off of the FREEDM-Pair, the Si IGBT is turned off first under ZVS condition and after a carefully selected delay time, the Si MOSFET is turn-off. In this way, the IGBT's turn-off loss is significantly reduced due to the ZVS turn-off condition. During the delay time, the current will be carried by the MOSFET only. During the turn-on, the SiC MOSFET and the IGBT can be turned on at the same time. Due to faster turn-on speed of the MOSFET, the IGBT is also turned on under the ZVS condition. Another advantage of the FREEDM-Pair is the better conduction characteristics compared to the Si IGBT by combining both the unipolar and bipolar devices' advantages in current conduction. Therefore the FREEDM-Pair provides an ideal option to realize the tradeoff between the cost and performance, and can be applied to main stream applications which currently use IGBT. Previously, the 6.5-kV FREEDM-Pairs results have been published and analyzed. In this paper, loss and cost reduction of a 1200V/200A FREEDM-Pair is presented and analyzed for the first time.}, booktitle={2016 IEEE 4th Workshop on Wide Bandgap Power Devices and Applications (wipda)}, author={Song, X. Q. and Huang, A. Q. and Liu, P. K. and Zhang, L. Q.}, year={2016}, pages={152–157} }
 @inproceedings{song_huang_zhang_liu_ni_2016, title={15kV/40A FREEDM super-cascode: A cost effective SiC high voltage and high frequency power switch}, DOI={10.1109/ecce.2016.7854643}, abstractNote={High voltage wide bandgap (WBG) semiconductor devices like the 15kV SiC MOSFET have attracted great attentions because of its potential applications in high voltage and high frequency power converters. However, these devices are not commercially available at the moment and their high cost due to expensive material growth and fabrication may limit their widespread adoption in the future. In this paper, a 15kV/40A three terminal power switch, the FREEDM Super-Cascode, is reported for the first time which is based on series connection of 1.2kV SiC power devices. The design and operation principle of the FREEDM Super-Cascode are introduced and the performance including the static blocking capability, conduction characteristics over a wide range of temperatures, and dynamic switching performances are analyzed. In addition, the thermal resistance of the FREEDM Super-Cascode is measured and the power dissipation capability is projected. The FREEDM Super-Cascode costs only one third of the estimated high voltage SiC MOSFETs, and will facilitate early applications of SiC in very high voltage and high frequency power converters.}, booktitle={2016 ieee energy conversion congress and exposition (ecce)}, author={Song, X. Q. and Huang, A. Q. and Zhang, L. Q. and Liu, P. K. and Ni, X. J.}, year={2016} }
 @article{peng_husain_huang_lequesne_briggs_2016, title={A Fast Mechanical Switch for Medium-Voltage Hybrid DC and AC Circuit Breakers}, volume={52}, ISSN={["1939-9367"]}, DOI={10.1109/tia.2016.2539122}, abstractNote={The paper presents the design and experimental results of a Thomson coil based fast mechanical switch for hybrid AC and DC circuit breakers rated at 30 kV voltage and 630 A current. The compact design with optimized circuit parameters and geometric dimensions of components targets 2 mm travel within 1 ms when driven by a 2 mF capacitor bank pre-charged to 500 V. The use and design of a disc spring as the damping and holding mechanism is presented. Structural design of a complete switch assembly rather than just the actuator is given. Experimental results show that the switch can travel 1.3 mm in the first 1 ms, and 3.1 mm in the first 2 ms when driven by a 360 V 2 mF capacitor bank. Such fast mechanical switches facilitate hybrid circuit breaker interruptions within 2 or 3 milliseconds for ultra fast and highly efficient protections in 5-35 kV medium voltage DC as well as AC systems.}, number={4}, journal={IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS}, author={Peng, Chang and Husain, Iqbal and Huang, Alex Q. and Lequesne, Bruno and Briggs, Roger}, year={2016}, pages={2911–2918} }
 @article{rezaei_lee_huang_2016, title={A High-Efficiency Flyback Micro-inverter With a New Adaptive Snubber for Photovoltaic Applications}, volume={31}, ISSN={["1941-0107"]}, DOI={10.1109/tpel.2015.2407405}, abstractNote={Based on the hybrid operation of interleaved flyback micro-inverter in Discontinuous and Boundary Conduction Modes (DCM and BCM), a novel adaptive snubber is proposed in this paper. The proposed snubber limits the drain-to-source voltage overshoot of the flyback's main switch during the turn-off process, enabling the use of lower voltage MOSFETs. It also recovers the stored energy in the leakage inductance of the flyback transformer and provides soft switching for the main flyback switch by limiting the rising slope of the MOSFET voltage during the turn off process resulting in higher efficiency. Exploiting the natural resonant of the flyback converter in BCM the adopted controller provides ZVS and ZCS for the main switch during the BCM operation. The operation of the flyback micro-inverter with associated controllers is analytically studied, and considerations for an optimum design aiming to higher efficiency are presented. Performance of the flyback micro-inverter with the proposed adaptive snubber and the corresponding controllers are experimentally verified based on a 250W interleaved flyback micro-inverter hardware setup.}, number={1}, journal={IEEE TRANSACTIONS ON POWER ELECTRONICS}, author={Rezaei, Mohammad Ali and Lee, Kui-Jun and Huang, Alex Q.}, year={2016}, month={Jan}, pages={318–327} }
 @inproceedings{tian_huang_teng_lu_bai_brown_mcammond_2016, title={A novel energy balanced variable frequency control for input-series-output-parallel modular EV fast charging stations}, DOI={10.1109/ecce.2016.7854730}, abstractNote={At present time, the most common electrical vehicle (EV) chargers employ a two-stage design, i.e., a front-end AC/DC stage + an isolated DC/DC converter. In this paper, an isolated dual-active-bridge (DAB) based single-stage AC/DC converter was proposed, which has the power-factor-correction (PFC) and zero-voltage-switching (ZVS) functions over the full-load range. By reducing one power stage and eliminating the large DC link capacitor, a high efficiency and high power density are achieved. Such topology can be used as a modular building block to scale up to 50kW by serial connecting the input terminals and paralleling output terminals. A novel energy-balanced variable switching frequency control for such input-series-output-parallel (ISPO) modular designed is proposed. A single-phase d-q transformation is implemented to achieve zero steady-state error. Simulation analysis and experimental validation are presented.}, booktitle={2016 ieee energy conversion congress and exposition (ecce)}, author={Tian, Q. and Huang, A. Q. and Teng, H. and Lu, J. C. and Bai, K. and Brown, A. and McAmmond, M.}, year={2016} }
 @inproceedings{tian_huang_bai_lu_teng_mcammond_brown_2016, title={A novel light load performance enhanced variable-switching-frequency and hybrid single-dual-phase-shift control for single-stage dual-active-bridge based AC/DC converter}, DOI={10.1109/iecon.2016.7793438}, abstractNote={Full-bridge power-factor-correction (PFC) front-end + dual-active-bridge (DAB) AC/DC topology is widely used in industry, e.g., electrical vehicle on-board charger. Such two-stage topology limits the system efficiency, and the bulky DC link bus capacitor makes the system power density relatively low. Compared to the two-stage design, the single-stage design, unfolding bridge + DAB, eliminates the bulky DC link bus capacitor and operates the front-end with only 60Hz switching frequency, thereby has the potential to increase the system power density and efficiency. A novel variable-switching-frequency and hybrid single-dual-phase-shift (VSF-SDPS) control strategy is proposed and analyzed for the DAB based single-stage topology. The proposed VSF-SDPF control consists of two phase shifts to guarantee Zero-Voltage-Switching (ZVS) over the full range of the AC line voltage, and frequency modulation to achieve boost PFC. The conventional front-end PFC is simplified to an unfolding bridge by changing DAB control strategy to achieve PFC and ZVS at the same time. Besides, a special ZVS boundary is utilized to solve the grid current distortion problem when the switching frequency saturated, which is especially severe at light load condition. Simulation results and experimental validation are presented under 50Vrms AC line voltage and 200V DC battery voltage test condition.}, booktitle={Proceedings of the iecon 2016 - 42nd annual conference of the ieee industrial electronics society}, author={Tian, Q. and Huang, A. Q. and Bai, H. and Lu, J. C. and Teng, H. and Mcammond, M. and Brown, A.}, year={2016}, pages={1227–1232} }
 @inproceedings{wang_zhu_yu_huang_2016, title={A study of dynamic high voltage output charge measurement for 15 kV SiC MOSFET}, DOI={10.1109/ecce.2016.7854789}, abstractNote={Newly developed 15 kV silicon carbide (SiC) power MOSFETs with fast switching capability enable the reduction of size, weight and complexity of medium voltage power converters. In medium voltage and high frequency applications, zero voltage switching (ZVS) is necessary since significant amount of energy is stored in MOSFETs' parasitic output capacitors. Recovering these energy is important for high conversion efficiency while ZVS also reduces the dV/dt significantly in these devices. To guarantee complete ZVS, it is crucial to accurately characterize the output charge of devices. In this paper, existing high voltage capacitance and output charge measurement techniques are reviewed. A dynamic half-bridge test method for 15kV SiC MOSFETs' output charge measurement is thoroughly analyzed and experimentally verified up to 6 kV. Output capacitance model is then derived using the measured results. The test circuit not only reflects the realistic ZVS scenario, but also achieves high accuracy (<1% error) without resorting to special equipment or complex configuration which are usually necessary in high voltage test. System level design consideration, error analysis and accuracy certification for this high voltage tester is also given in the paper.}, booktitle={2016 ieee energy conversion congress and exposition (ecce)}, author={Wang, L. and Zhu, Q. L. and Yu, Wensong and Huang, A. Q.}, year={2016} }
 @inproceedings{peng_mackey_husain_huang_lequesne_briggs_2016, title={Active damping of ultra-fast mechanical switches for hybrid AC and DC circuit breakers}, DOI={10.1109/ecce.2016.7854816}, abstractNote={An active damping method for Thomson coil actuated ultra-fast mechanical switches is proposed, including its control. Ultra fast mechanical switches are crucial for both DC and AC circuit breakers that require fast-acting, current-limiting capabilities. However, fast motion means high velocity at the end of travel, resulting in over-travel, bounce, fatigue, and other undesirable effects. The active damping proposed in this paper not only avoids such issues, but actually enables faster travel by removing limitations that would otherwise be necessary. This active damping mechanism is applicable in particular to medium and high voltage circuit breakers, but can be extended to actuators in general. A 15kV/630A/1ms mechanical switch, designed to enable the fast protection of medium voltage DC circuits, is used as a testbed for the concept. It is based on the principle of repulsion forces (Thomson coil actuator). By energizing a second coil, higher opening speeds can be damped with limited over-travel range of the movable contact. The overall structure is simple, and the size of the overall switch is minimized. To validate the concept and to study the timing control for best active damping performance, both finite element modeling and experimental studies have been carried out.}, booktitle={2016 ieee energy conversion congress and exposition (ecce)}, author={Peng, C. and Mackey, L. and Husain, I. and Huang, A. and Lequesne, B. and Briggs, R.}, year={2016} }
 @inproceedings{gao_husain_huang_2016, title={An autonomous power management strategy based on DC bus signaling for solid-state transformer interfaced PMSG wind energy conversion system}, DOI={10.1109/apec.2016.7468353}, abstractNote={The solid-state transformer (SST) enabled DC/AC Microgrid provides an effective solution for distributed renewable energy resources (DRER) integration with conventional utility grid. This paper investigates a DC network system consisting of wind turbines, SST, and DC loads. Without any energy storage devices, an autonomous power management strategy based on improved DC bus signaling (DBS) is proposed to achieve system stable operation and power balance under various scenarios, specifically system grid-connected mode, islanding mode, and the mode transition. The extreme conditions were emphasized and analyzed as a testament to verify the feasibility of proposed control. DC bus voltage level and its gradient information have been employed as the only indication for distinguishing different modes and control implementation. System power management competence has been simulated and verified with MATLAB/Simulink.}, booktitle={Apec 2016 31st annual ieee applied power electronics conference and exposition}, author={Gao, R. and Husain, I. and Huang, A. Q.}, year={2016}, pages={3383–3388} }
 @inproceedings{guo_liu_yu_zhang_huang_2016, title={Analysis and loss comparison of megahertz high voltage isolated dc/dc converters utilizing integrated sic mosfet module}, DOI={10.1109/wipda.2016.7799955}, abstractNote={Silicon Carbide (SiC) MOSFETs are being increasingly utilized in medium and high power electronics converters (>1 kW) because of the significantly lower switching and conduction losses when compared with conventional power switches such as the Si IGBT. SiC MOSFET based converters operating at high frequency can achieve high efficiency and high power density at the same time. Minimum switching loss can be achieved in the SiC MOSFET with carefully designed gate driving condition and DC link layout, such as the integrated SiC MOSFET module discussed in this paper. Multi-megahertz switching frequency could be realized by the proposed SiC MOSFET module with proper soft switching topology. This paper analyzes three isolated DC/DC converters, namely the asymmetrical half bridge converter, phase shift full bridge converter, and LLC resonant converter. The loss model of the SiC MOSFET is developed and utilized in the analysis. Comparisons are carried out from the device loss and soft switching requirement point of view. The LLC resonant converter is deemed more suitable for multi-megahertz application. A 4.5 kW 1.2 MHz LLC resonant converter prototype is developed and it demonstrates a peak efficiency of 97% at 4 kW.}, booktitle={2016 IEEE 4th Workshop on Wide Bandgap Power Devices and Applications (wipda)}, author={Guo, S. X. and Liu, P. K. and Yu, R. Y. and Zhang, L. Q. and Huang, A. Q.}, year={2016}, pages={291–296} }
 @article{sung_baliga_huang_2016, title={Area-Efficient Bevel-Edge Termination Techniques for SiC High-Voltage Devices}, volume={63}, ISSN={["1557-9646"]}, DOI={10.1109/ted.2016.2532602}, abstractNote={This paper reviews the bevel-edge termination techniques for silicon carbide (SiC) power devices, such as bevel junction termination extension (JTE), resistive-bevel termination, bevel-assisted JTE, and positive-bevel termination. The proposed bevel-edge termination techniques significantly reduce the chip size for SiC power devices. PiN diodes and test structures were fabricated to quantify the relative performance of the proposed structures. Quantitative comparison in chip size reduction, process schemes, and future research directions is discussed in detail.}, number={4}, journal={IEEE TRANSACTIONS ON ELECTRON DEVICES}, author={Sung, Woongje and Baliga, B. Jayant and Huang, Alex Q.}, year={2016}, month={Apr}, pages={1630–1636} }
 @inproceedings{peng_huang_2016, title={Converting HVAC to HVDC grids: A novel switched conductor HVDC Scheme}, DOI={10.1109/tdc.2016.7520008}, abstractNote={This paper proposes a novel HVDC concept using a switched conductor scheme by converting AC circuits into DC to increase transmission capacity by 73.6%. The switched conductor HVDC scheme (SC-HVDC) modifies a thyristor based bipolar HVDC scheme and utilizes two additional active valves to achieve better utilization of the conducting circuit. Detailed analysis and calculation have proved this scheme very efficient in utilization of semiconductor devices and transformer equipment. PSCAD study has verified the feasibility of the SC-HVDC scheme. Comparison of SC-HVDC with HVAC transmission, bi-polar HVDC and tri-polar HVDC transmission technologies concludes that the switched conductor HVDC scheme has high power transfer capability, high equipment utilization, and simple control.}, booktitle={2016 IEEE/PES Transmission and Distribution Conference and Exposition (T&D)}, author={Peng, C. and Huang, A. Q.}, year={2016} }
 @inproceedings{guo_zhang_lei_li_yu_huang_2016, title={Design and application of a 1200V ultra-fast integrated silicon carbide MOSFET module}, DOI={10.1109/apec.2016.7468151}, abstractNote={With the commercial introduction of wide bandgap power devices such as Silicon Carbide (SiC) and Gallium Nitride (GaN) in the last few years, the high power and high frequency power electronics applications have gained more attention. The fast switching speed and high temperature features of SiC MOSFET break the limit of the traditional silicon MOSFET. However, the EMI problem under high dI/dt and dV/dt is an unneglectable problem. The overshoot and oscillation on drain-source voltage and gating signal could cause breakdown of the switches. This paper proposes a 1200V integrated SiC MOSFET module. With the ultra-fast gate driver integrated with the SiC MOSFET, the parasitic inductance and capacitance could be reduced dramatically, which accordingly suppress the EMI problem caused by the parasitic parameters. Thus zero gate resistance could be adopted in the module to further increase the switching speed. The switching performance of the integrated SiC module is shown better than the discrete package device. The switching loss of the SiC MOSFET module is measured by the inverter level measurement and composition method. Zero switching loss could be achieved when the drain current is lower than a critical value. The module has been tested at 1.5MHz and 3.38MHz switching frequency to prove its high speed capability. For isolated topology applications, the impact of high frequency on the power density and efficiency is discussed in this paper.}, booktitle={Apec 2016 31st annual ieee applied power electronics conference and exposition}, author={Guo, S. X. and Zhang, L. Q. and Lei, Y. and Li, X. and Yu, Wensong and Huang, A. Q.}, year={2016}, pages={2063–2070} }
 @inproceedings{xue_yu_huang_2016, title={Design considerations of an isolated GaN bidirectional DC-DC converter}, DOI={10.1109/ecce.2016.7855016}, abstractNote={This paper investigates three design considerations of a novel bidirectional dc-dc converter for distributed energy storage device. They are the layout for minimum loop inductance and heat dissipation, gate drive power supply for high side Gallium-Nitride (GaN) device and high resolution digital PWM control methodology. The special package of the available GaN devices requires a PCB layout method that takes into account the thermal design as well as the switching loop inductance. Besides, the high dv/dt will introduce a circulating current in the high-side gate drivers and power supplies. This current should be minimized. Furthermore, conventional digital PWM modules is not precise enough for high frequency (usually >50kHz) converter modulation and will cause limited cycle oscillation. A high resolution digital phase-shift modulation scheme is utilized to improve the resolution of the phase-shift control for the 150 kHz converter. In the end, an optimized engineering design method is proposed. The experimental results are analyzed on a 1kW bidirectional dc-dc converter to verify the concepts.}, booktitle={2016 ieee energy conversion congress and exposition (ecce)}, author={Xue, F. and Yu, R. Y. and Huang, A. Q.}, year={2016} }
 @inproceedings{peng_huang_husain_lequesne_briggs_2016, title={Drive circuits for ultra-fast and reliable actuation of Thomson coil actuators used in hybrid AC and DC circuit breakers}, DOI={10.1109/apec.2016.7468279}, abstractNote={Thomson coil actuators (also known as repulsion coil actuators) are well suited for vacuum circuit breakers when fast operation is desired such as for hybrid AC and DC circuit breaker applications. This paper presents investigations on how the actuator drive circuit configurations as well as their discharging pulse patterns affect the magnetic force and therefore the acceleration, as well as the mechanical robustness of these actuators. Comprehensive multi-physics finite-element simulations of the Thomson coil actuated fast mechanical switch are carried out to study the operation transients and how to maximize the actuation speed. Different drive circuits are compared: three single switch circuits are evaluated; the pulse pattern of a typical pulse forming network circuit is studied, concerning both actuation speed and maximum stress; a two stage drive circuit is also investigated. A 630 A, 15 kV / 1 ms prototype employing a vacuum interrupter with 6 mm maximum open gap was developed and tested. The total moving mass accelerated by the actuator is about 1.2 kg. The measured results match well with simulated results in the FEA study.}, booktitle={Apec 2016 31st annual ieee applied power electronics conference and exposition}, author={Peng, C. and Huang, A. and Husain, I. and Lequesne, B. and Briggs, R.}, year={2016}, pages={2927–2934} }
 @inproceedings{tan_song_pcng_liu_huang_2016, title={Hierarchical protection architecture for 380v dc data center application}, DOI={10.1109/ecce.2016.7855145}, abstractNote={The DC distribution system is becoming an appealing spot due to its higher energy efficiency in recent years. Nowadays, it has been already applied in data centers, commercial buildings, electrical vehicles charger station and DC micro grid systems, etc. However, there are a lot of challenges in DC application which is not critical in traditional AC system, such as arcing, capacitive charging and discharging, etc. All of them make the protection strategy and architecture an important issue for DC application. In this paper, one 3-level hierarchy circuit protection architecture is proposed with developed solid state circuit protection hardware. It is designed with considering the power rating for DC data center load conditions. Analysis and experimental results based on 380V DC voltage have been conducted and discussed.}, booktitle={2016 ieee energy conversion congress and exposition (ecce)}, author={Tan, K. and Song, X. Q. and Pcng, C. and Liu, P. and Huang, A. Q.}, year={2016} }
 @inproceedings{liu_zhang_huang_guo_lei_2016, title={High bandwidth current sensing of sic mosfet with a si current mirror}, DOI={10.1109/wipda.2016.7799937}, abstractNote={SiC Intelligent Power Module (IPM) with high bandwidth integrated current sensors is a future trend to improve the device protection capability and chip utilization. In this work, an integrated current sensing scheme for Silicon Carbide (SiC) MOSFET power module using a Si MOSFET current mirror is proposed, analyzed and tested. The use of Si MOSFET not only lowers the overall cost, but compensates the temperature variation as well. The influence of device mismatching on sensing accuracy are discussed. Optimal selection and trade-off of sensing resistor value are calculated. Discrete device circuit and conceptual DBC-based module are tested to verify the scheme's feasibility and performance. The results show good steady state accuracy and high bandwidth performance.}, booktitle={2016 IEEE 4th Workshop on Wide Bandgap Power Devices and Applications (wipda)}, author={Liu, P. K. and Zhang, L. Q. and Huang, A. Q. and Guo, S. X. and Lei, Y.}, year={2016}, pages={200–203} }
 @inproceedings{wang_huang_yu_huang_2016, title={High-frequency AC distributed power delivery system}, DOI={10.1109/apec.2016.7468394}, abstractNote={A novel high-frequency-AC (HFAC) distributed power delivery system is presented in this paper. The target applications of the proposed system are the aerial and ground transportation, and renewable energy systems. Unlike traditional line-frequency-AC (LFAC) or DC distributed power delivery system, the bus frequency of the proposed system can be set at tens or hundreds of kilo-Hertz, so as the power transmission frequency. As a result, 50 or 60 Hz transformers will be eliminated from the system. DC arcing flash will not exist as well with the utilization of HFAC bus. In this paper, single-stage isolated bi-directional power electronics interfaces are developed which enables distributed AC and DC sources or loads to access the main HFAC bus. Soft-switching is also realized for all the semiconductor devices in the power electronics interface. Distributed control architecture is developed so that each source or load can operate independently. Simulation results are provided to validate the distributed control architecture. A scaled-down hardware demonstration, with the bus specification of 54 kHz and 400 VAC, is presented to validate the proposed architecture of the HFAC distributed power delivery system.}, booktitle={Apec 2016 31st annual ieee applied power electronics conference and exposition}, author={Wang, M. Q. and Huang, Q. Y. and Yu, Wensong and Huang, A. Q.}, year={2016}, pages={3648–3654} }
 @inproceedings{song_huang_peng_zhang_2016, title={Improved 6.5kV FREEMD-pair based on SiC JFET and Si IGBT}, DOI={10.1109/apec.2016.7467883}, abstractNote={The newly proposed FREEDM-Pair is an ideal and economical solution to address high cost issue in high power SiC power devices. The FREEDM-Pair, in which a Si IGBT and a SiC JFET are connected in parallel, combines the advantages of SiC JFET's low switching losses and Si IGBT's superior forward conduction characteristics. One issue of the JFET based FREEDM-Pair is the incompatible gate drive voltage for the SiC JFET and Si IGBT which complicates the gate driver design and increases the total cost. Also, the high voltage SiC JBS reverse diode in FREEDM-Pair is indispensable for the reverse current conduction, leading to higher cost and larger package size. To address these issues, an improved FREEDM-Pair is proposed in this paper, in which the SiC JBS diode is eliminated and the normally-off SiC JFET is operated in cascode configuration to unify the gate driver voltage level and speed up the switching of the JFET. The design and operation of improved FREEDM-Pair is elaborated and experimental results verified its advantages. Also, the affordable cost demonstrates that this promising concept is an ideal step to introduce high voltage SiC power devices.}, booktitle={Apec 2016 31st annual ieee applied power electronics conference and exposition}, author={Song, X. Q. and Huang, A. Q. and Peng, C. and Zhang, L. Q.}, year={2016}, pages={269–275} }
 @inproceedings{zhu_wang_zhang_yu_huang_2016, title={Improved medium voltage AC-DC rectifier based on 10kV SiC MOSFET for solid state transformer (SST) application}, DOI={10.1109/apec.2016.7468196}, abstractNote={An improved bidirectional medium voltage AC-DC converter based on 10kV silicon carbide (SiC) MOSFETs for SST (Solid State Transformer) application is presented in this paper. Avalanche breakdown of the reverse blocking silicon diode and bridge arm shoot-through problems in traditional high voltage bridge-type AC-DC converters are solved. Shoot-through currents are limited to low di/dt events that are readily controlled, allowing zero dead-time operation. The reverse recovery dissipation of the SiC MOSFET is eliminated because no freewheeling current will flow through the body diode. This increases the efficiency as well as the reliability of the SiC MOSFET. Detailed power stage operating principles and energy transfer mechanism are described. A unique customized 10kV SiC MOSFET/JBS diode power module is developed and tested, which further reduces parasitic parameters and simplifies converter wire connection. This topology is therefore a very good choice for median voltage applications.}, booktitle={Apec 2016 31st annual ieee applied power electronics conference and exposition}, author={Zhu, Q. L. and Wang, L. and Zhang, L. Q. and Yu, Wensong and Huang, A. Q.}, year={2016}, pages={2365–2369} }
 @inproceedings{huang_yu_huang_2016, title={Independent DC link voltage control of cascaded multilevel PV inverter}, DOI={10.1109/apec.2016.7468249}, abstractNote={For the independent DC link voltage control of the single phase cascaded multilevel PV inverter, this paper proposes an improved control strategy that consists only one total voltage loop and n feed-forward-based weighting factors. Actually, the multiple modulation signals have predictable ratios with each other because the series connection of the outputs of the H-bridges. Utilizing this feature, this proposed control strategy directly generates the weighting factors by the DC link input powers and voltage references which are independent with the output of the voltage feedback loop. The voltage feedback loop controls the sum of the DC link voltages while the feed-forward signals force the ratio between DC link voltages to be equal to the ratio between the references at steady state. Compared with the previous control strategies that contain at least n voltage controllers, the proposed control structure is much simplified. Besides, the small signal modeling and controller design of the inner current and outer voltage loop are also included in this paper. In addition, the adaptive gain is proposed to keep the loop gain unchanged even at the situation of weak irradiation. This control strategy is verified by the simulated and experimental results with accurate DC link control and more than 99.5% MPPT efficiency for each H-bridge even at severe irradiation mismatch conditions.}, booktitle={Apec 2016 31st annual ieee applied power electronics conference and exposition}, author={Huang, Q. Y. and Yu, Wensong and Huang, A. Q.}, year={2016}, pages={2727–2734} }
 @inproceedings{xue_yu_huang_2016, title={Loss analysis of a high efficiency GaN and Si device mixed isolated bidirectional DC-DC converter}, DOI={10.1109/apec.2016.7468399}, abstractNote={High conversion efficiency is always desired in energy storage device (ESD). In this work a high efficiency GaN and Si device mixed isolated bidirectional dc-dc converter is proposed in the distributed ESD application. To optimize the efficiency of the bidirectional half-bridge push-pull active clamp converter over a wide input/output voltage and load range, it is necessary to accurately predict the dissipated power for each power component so as to identify and properly design the heavily loaded components. This paper describes a universal method to predict the power losses of the converter. Loss models are provided to calculate total component losses using the current and voltage information derived from the steady state inductor current calculator. Details of loss breakdown are given. With the presented converter prototype, a top efficiency of 98.3% and an output power of 1 kW in a wide input/output voltage range is achieved. The loss analysis provides valuable information for designing an efficiency optimized converters in the application.}, booktitle={Apec 2016 31st annual ieee applied power electronics conference and exposition}, author={Xue, F. and Yu, R. Y. and Huang, A. Q.}, year={2016}, pages={3677–3683} }
 @inproceedings{huang_wang_tian_zhu_chen_yu_2016, title={Medium voltage solid state transformers based on 15 kV SiC MOSFET and JBS diode}, DOI={10.1109/iecon.2016.7793121}, abstractNote={This paper discusses the advancements in the development of the medium voltage solid state transformer (SST) based on 15 kV SiC MOSFET and JBS diode. Designed for 7.2 kV single phase distribution grid applications, the medium voltage SST converts high voltage AC to low voltage 240/120V ac. The use of ultra-high voltage SiC devices allows the simplification of the power conversion circuit topology. This paper presents the characteristics of the high voltage SiC MOSFET devices as well as the topology innovations to achieve ultra-efficient SST design. Specifically, three different designs are discussed which utilize three-stage, two-stage and single stage power conversion topologies to achieve the AC to AC conversion.}, booktitle={Proceedings of the iecon 2016 - 42nd annual conference of the ieee industrial electronics society}, author={Huang, A. Q. and Wang, L. and Tian, Q. and Zhu, Q. L. and Chen, D. and Yu, Wensong}, year={2016}, pages={6996–7003} }
 @article{huang_2016, title={Medium-Voltage Solid-State Transformer Technology for a Smarter and Resilient Grid}, volume={10}, ISSN={["1941-0115"]}, DOI={10.1109/mie.2016.2589061}, abstractNote={The most important impact of power electronics on our society in the last 50 years has been the elimination of the 60-Hz ac power delivery system for consumer electronic products. Central to this achievement is the use of silicon (Si) power devices and pulsewidth modulation (PWM) techniques in delivering regulated ac and dc powers to low-voltage (LV) loads such as light-emitting diodes and computers. These solid-state power electronic converters have provided our society numerous benefits, including high-quality power and substantial energy savings. They also form the core technology for integrating renewable energies such as wind and solar into our power grid. Figure 1 shows a typical power delivery architecture commonly found in computer supplies and data centers. The incoming universal ac grid power is converted by a power factor correction circuit to 400 V dc before it is stepped down to a lower voltage dc intermediate bus, such as 12 V, and then it powers the digital loads at voltages as low as 1 V by a point-of-load converter. Si power metal-oxide-semiconductor field-effective transistor (MOSFET) transistors from 20 V to 700 V are almost exclusively used in this application with switching frequencies from tens of kilohertz to one megahertz. Emerging devices based on gallium nitride (GaN) heterojunction field effect transistors reduce the switching and conduction losses when compared with Si power MOSFETs and are, therefore, poised to compete in these applications, driven by the need for higher energy efficiency and higher power density.}, number={3}, journal={IEEE INDUSTRIAL ELECTRONICS MAGAZINE}, author={Huang, Alex Q.}, year={2016}, month={Sep}, pages={29–42} }
 @inproceedings{tan_liu_ni_peng_song_huang_2016, title={Performance evaluation of multiple Si and SiC solid state devices for circuit breaker application in 380VDC delivery system}, DOI={10.1109/apec.2016.7467990}, abstractNote={The DC power delivery system is becoming an appealing research topic and real world solution due to its higher energy efficiency compare with AC delivery system. It has already been applied in data centers, commercial buildings, electrical vehicle charge stations and micro grid systems, etc. Among many new issues that need to be addressed for the DC power delivery system, ultra-fast and accurate protection is one of them. The 1200V SiC devices has been developed by many manufacturers in recent years which makes them good candidates in DC circuit breaker application. In this paper, the 380V DC circuit breaker employing solid state devices for DC power delivery system has been proposed and introduced. The criteria of device characteristics particularly for DC solid state circuit breaker application is discussed and defined. Characteristics of 4 different Si and SiC solid state devices in similar power rating have been compared based on defined criteria. The pros and cons of different devices candidates is introduced with test results for DC circuit breaker application.}, booktitle={Apec 2016 31st annual ieee applied power electronics conference and exposition}, author={Tan, K. and Liu, P. K. and Ni, X. J. and Peng, C. and Song, X. Q. and Huang, A. Q.}, year={2016}, pages={983–989} }
 @inproceedings{wang_xue_huang_liu_2016, title={Physics understanding of high temperature behavior of gallium nitride power transistor}, DOI={10.1109/wipda.2016.7799961}, abstractNote={This paper presents static and dynamic characterization of 100V and 650V Gallium Nitride power transistor from root temperature to 150°C, and a physical explanation of the device on-resistance behavior at elevated temperature was provided. This device physics-based understanding would benefit those application engineers who selects GaN HEMT power transistor to design a robust and energy efficient power electronic system, considering the device degradation in high temperature ambient.}, booktitle={2016 IEEE 4th Workshop on Wide Bandgap Power Devices and Applications (wipda)}, author={Wang, S. Z. and Xue, F. and Huang, A. Q. and Liu, S. Y.}, year={2016}, pages={324–327} }
 @inproceedings{zhu_wang_zhang_yu_huang_ni_2016, title={Practical consideration and implementation of a medium voltage SiC AC-DC rectifier}, DOI={10.1109/ecce.2016.7855240}, abstractNote={The implementation of a novel bidirectional medium voltage AC-DC converter based on 10kV SiC MOSFET is presented in this paper. The improved topology allows the removal of the reverse blocking silicon diode in medium voltage SiC MOSFET module. Shoot-through problems and avalanche of the integrated silicon diode in traditional medium voltage bridge-type AC-DC converters are solved, allowing zero dead-time operation with no current flowing through the body diode. The number of parasitic capacitors at each swing point are reduced by half, greatly reducing the dominant turn on losses caused by these capacitors. A unique customized four-in-one 10kV SiC MOSFET/JBS diode power module with high voltage isolation capability is developed and tested, which reduces parasitic parameters and simplifies converter complexity. Section based winding method is further used to reduce the inductor parasitic capacitance by 40%, helping to reduce the dominant turn-on losses by 13%. Anti-windup and feed forward control are implemented to achieve better performance. Soft start combining with a high voltage relay and fuse are used to limit the inrush current and overshoot voltage during the start-up process. Delta-sigma based fiber optical high voltage sensor is designed and implemented to achieve higher than 10kV voltage sensing capability.}, booktitle={2016 ieee energy conversion congress and exposition (ecce)}, author={Zhu, Q. L. and Wang, L. and Zhang, L. Q. and Yu, Wensong and Huang, A. Q. and Ni, X. J.}, year={2016} }
 @inproceedings{hambridge_huang_lu_2016, title={Proposing a frequency based real-time energy market and economic dispatch strategy}, DOI={10.1109/pesgm.2016.7741320}, abstractNote={Smart grid technology and the Energy Internet are reliant on a new, competitive, deregulated energy market, that supports energy transactions among energy players: utilities, consumers, and prosumers, alike. Such an energy market is being developed to ensure grid reliability, health, and economic operation with the emergence of microgrids, distributed renewable generation, Distributed Energy Storage Devices (DESDs), controllable loads, and Energy Cells. The solid-state transformer (SST) presents a new opportunity to regulate power flow from Energy Cells to the grid in real-time. As the proposed Energy Router of the smart grid, the SST will facilitate energy transactions as an intelligent node, providing communication, frequency and power management. In this work, a frequency based real-time energy market is proposed. Here, it is demonstrated that the grid frequency is a real-time price signal (measured by the SST) which can be used to autonomously calculate the real-time energy price for all energy players, reducing the need to establish complicated networks to determine the market clearing price. In addition to providing a real-time price, frequency based pricing increases grid reliability as energy players respond to frequency deviations and provide frequency regulation as an ancillary service. A simulation was designed to respond to the steady-state frequency deviation in five minute intervals. A pricing curve and DESD response curve were designed to identify key parameters and solve for optimal solutions that benefit energy producers and consumers.}, booktitle={2016 ieee power and energy society general meeting (pesgm)}, author={Hambridge, S. and Huang, A. Q. and Lu, N.}, year={2016} }
 @article{liu_gu_wei_qian_sun_huang_2016, title={Repetitive Unclamped-Inductive-Switching-Induced Electrical Parameters Degradations and Simulation Optimizations for 4H-SiC MOSFETs}, volume={63}, ISSN={["1557-9646"]}, DOI={10.1109/ted.2016.2604253}, abstractNote={In this paper, the electrical parameter degradations of high-voltage 4H-SiC MOSFETs under repetitive unclamped-inductive-switching (UIS) stresses were investigated experimentally. The holes injection and trapping into the gate oxide above the JFET region is identified to be the main degradation mechanism, resulting in the increase of OFF-state drain-source leakage current (IDSS) and the decrease of ON-state resistance (Rdson). However, during the repetitive UIS stresses, there is not obvious degradation observed for the threshold voltage (Vth) of the device. Moreover, three improved SiC MOSFETs structures, one with step gate oxide above the JFET region, one with step p-body region, and another one with floated shallow p-well in the middle of JFET region, were proposed to reduce the degradations under the repetitive UIS stresses.}, number={11}, journal={IEEE TRANSACTIONS ON ELECTRON DEVICES}, author={Liu, Siyang and Gu, Chunde and Wei, Jiaxing and Qian, Qinsong and Sun, Weifeng and Huang, Alex Q.}, year={2016}, month={Nov}, pages={4331–4338} }
 @inproceedings{tan_peng_liu_song_huang_2016, title={Zero standby power high efficiency hot plugging outlet for 380VDC power delivery system}, DOI={10.1109/apec.2016.7467863}, abstractNote={The DC power delivery system is becoming an appealing research topic and real world solution due to its higher energy efficiency compared with AC delivery system. It has already been applied in data centers, commercial buildings, electrical vehicle charge stations and micro grid systems, etc. However, the electrical arc and related potential for fire and human injury is a main safety concern for the DC system. Besides, the inrush current caused by the load capacitance when hot plugged in to the DC system is also a major issue that must be considered when designing DC system. In this paper, a smart hot plugging outlet is proposed and developed by embedding solid state device into the DC outlet. Besides, over temperature and dual threshold over current protections have been also integrated to realize current limiting and trip function for each outlet. Analysis and experimental results based on 380V DC, which is a common voltage level adopted in data centers and DC micro grids, are discussed and presented.}, booktitle={Apec 2016 31st annual ieee applied power electronics conference and exposition}, author={Tan, K. and Peng, C. and Liu, P. K. and Song, X. Q. and Huang, A. Q.}, year={2016}, pages={132–137} }
 @inproceedings{song_huang_lee_peng_cheng_o'brien_ogunniyi_scozzie_palmour_2015, title={22 kV SiC emitter turn-off (ETO) thyristor and Its dynamic performance including SOA}, DOI={10.1109/ispsd.2015.7123443}, abstractNote={Ultra-high voltage (>10 kV) power devices based on SiC are gaining significant attentions since Si power devices are typically at lower voltage levels. In this paper, a world record 22kV Silicon Carbide (SiC) p-type ETO thyristor is developed and reported as a promising candidate for ultra-high voltage applications. The device is based on a 2cm2 22kV p type gate turn off thyristor (p-GTO) structure. Its static as well as dynamic performances are analyzed, including the anode to cathode blocking characteristics, forward conduction characteristics at different temperatures, turn-on and turn-off dynamic performances. The turn-off energy at 6kV, 7kV and 8kV respectively is also presented. In addition, theoretical boundary of the reverse biased safe operation area (RBSOA) of the 22kV SiC ETO is obtained by simulations and the experimental test also demonstrated a wide RBSOA.}, booktitle={Proceedings of the international symposium on power semiconductor}, author={Song, X. Q. and Huang, A. Q. and Lee, M. C. and Peng, C. and Cheng, L. and O'Brien, H. and Ogunniyi, A. and Scozzie, C. and Palmour, J.}, year={2015}, pages={277–280} }
 @inproceedings{guo_zhang_lei_li_xue_yu_huang_2015, title={3.38 Mhz operation of 1.2kV SiC MOSFET with integrated ultra-fast gate drive}, DOI={10.1109/wipda.2015.7369298}, abstractNote={With the commercialization of wide bandgap power devices such as SiC MOSFETs and JBS diodes, power electronics converters used in the harsh environments such as hybrid electric vehicles and aerospace attract more and more attentions. The low loss, high temperature and fast switching capabilities are utilized in the converters to improve the power density and efficiency. However, the EMI problem caused by the fast switching is a major constrain for improving switching frequency. For this reason, an integrated SiC module with 1.2kV MOSFET and ultra-fast gate drive circuits is proposed and developed. Two 1.2kV SiC MOSFETs bare dies and two high current gate driver chips are integrated in a compact integrated module package to reduce the parasitic inductance. 0Ω gate resistor therefore can be used in this module to improve the device at maximum speed. Noise free operation of the tested module is verified even under extremely high dV/dt and dI/dt conditions. The ultra-low turn-off loss of the module is being demonstrated. Finally, the integrated module is demonstrated in two megahertz converters: an 800W 1.5MHz synchronous boost converter and a 3.38MHz half bridge inverter. The era for high voltage-megahertz switching has arrived.}, booktitle={WiPDA 2015 3rd IEEE Workshop on Wide Bandgap Power Devices and Applications}, author={Guo, S. X. and Zhang, L. Q. and Lei, Y. and Li, X. and Xue, F. and Yu, Wensong and Huang, A. Q.}, year={2015}, pages={390–395} }
 @inproceedings{lee_wang_huang_2015, title={4H-SiC 15kV n-IGBT physics-based sub-circuit model implemented in Simulink/Matlab}, DOI={10.1109/apec.2015.7104478}, abstractNote={A physics-based 15kV 4H-SiC n-IGBT sub-circuit model implemented in Simulink/Matlab is demonstrated in this work. Two-phase voltage ramp during the switching before and after punch through is well predicted. Simulated with a simple 4H-SiC Schottky diode model, the switching results is experimentally verified. The current bump during turn-off and current overshoot during turn-on are well-predicted and can be explained by the instantaneous output capacitances of the IGBT and Schottky diode. The computing speed for the full turn-on and off with stray inductance is approximately 2 minutes.}, booktitle={2015 thirtieth annual ieee applied power electronics conference and exposition (apec 2015)}, author={Lee, M. C. and Wang, G. Y. and Huang, A. Q.}, year={2015}, pages={1051–1057} }
 @inproceedings{huang_song_zhang_2015, title={6.5 kV Si/SiC hybrid power module: An ideal next step?}, DOI={10.1109/iwipp.2015.7295979}, abstractNote={Silicon carbide (SiC) power switches such as JFET or MOSFET have demonstrated their superior advantages over silicon (Si) power devices such as IGBT, especially in terms of significantly reduced switching losses. A major issue facing large scale adoption of SiC power devices is still the much higher cost. This paper proposes that Si/SiC hybrid power module (HPM) should be a natural next step moving forward for high voltage applications to address the cost issue. In the proposed Si/SiC HPM, a SiC JFET is connected in parallel with Si IGBT to combine the advantages of both IGBT and JFET. A 6.5 kV HPM is developed based on Si IGBT and SiC JFET as an example to demonstrate its superior cost/performance. The switching loss can be reduced by more than 70% at a cost of about 70% higher compared to Si IGBT. This work is especially essential for high voltage applications such as medium voltage motor drive, FACTS and HVDC systems.}, booktitle={2015 IEEE International Workshop on Integrated Power Packaging (IWIPP)}, author={Huang, A. Q. and Song, X. Q. and Zhang, L. Q.}, year={2015}, pages={64–67} }
 @inproceedings{song_huang_2015, title={6.5kV FREEDM-Pair: Ideal high power switch capitalizing on Si and SiC}, DOI={10.1109/epe.2015.7309243}, abstractNote={6.5kV Si IGBTs have been used widely in median voltage drives, HVDC, FACTs and traction systems. However, the large switching losses of the Si IGBT limit its switching frequency to only 100Hz to 1kHz. On the other hand, wide bandgap (WBG)power devices such as Silicon Carbide (SiC) MOSFET or JFET have demonstrated their superior advantages over Si IGBT, especially in terms of significantly reduced switching losses. A major issue facing large scale adoption of SiC power devices is still the much higher cost. This paper proposes that the FREEDM-Pair, a Si/SiC hybrid switch, should be an ideal and cost effective switch for high power applications. In the proposed FREEDM-Pair, a SiC MOSFET is connected in parallel with Si IGBT to combine the advantages of IGBT and MOSFET. A 6.5kV FREEDM-Pair is developed as an example to demonstrate its superior cost/performance. Experimental results demonstrated 70% switching loss reduction and the FREEDM-Pair cost is estimated to be only 50% higher than 6.5kV Si IGBT.}, booktitle={2015 17th european conference on power electronics and applications (epe'15 ecce-europe)}, author={Song, X. Q. and Huang, A. Q.}, year={2015} }
 @inproceedings{song_huang_lee_wang_2015, title={A dynamic measurement method for parasitic capacitances of high voltage SiC MOSFETs}, DOI={10.1109/ecce.2015.7309788}, abstractNote={The voltage dependent parasitic capacitances in high voltage semiconductor power devices such as MOSFET, JFET and IGBT play a vital role in the understanding and modeling of the device switching performance. In this paper, a simple but effective parasitic capacitance measurement method is proposed. The output capacitance Coss and the reverse transfer capacitance Crss can be measured simultaneously and directly in the proposed parasitic capacitance tester (PCT). The input capacitance Ciss is measured based on gate driver waveforms during the turn on transient. To verify the effectiveness of the proposed method, a 10kV SiC MOSFET parasitic capacitances are measured as an example. The measured parasitic capacitance results are compared with those from a conventional LCR meter and theoretical calculation. Furthermore, a Matlab/Simulink compact circuit model for the 10kV SiC MOSFET is developed based on the measured parasitic capacitances, whose results also validate the effectiveness of the proposed method.}, booktitle={2015 ieee energy conversion congress and exposition (ecce)}, author={Song, X. Q. and Huang, A. Q. and Lee, M. J. and Wang, G. Y.}, year={2015}, pages={935–941} }
 @inproceedings{rezaei_lee_huang_2015, title={A high efficiency flyback micro-inverter with a new adaptive snubber for photovoltaic applications}, DOI={10.1109/ecce.2015.7310126}, abstractNote={Based on the hybrid operation of interleaved flyback micro-inverter in discontinuous and boundary conduction modes (DCM and BCM), a novel adaptive snubber is proposed in this paper. The proposed snubber limits the drain-to-source voltage overshoot of the flyback's main switch during the turn-off process, enabling the use of lower voltage MOSFETs. It also recovers the stored energy in the leakage inductance of the flyback transformer and provides soft switching for the main flyback switch by limiting the rising slope of the MOSFET voltage during the turn-off process resulting in higher efficiency. Exploiting the natural resonant of the flyback converter in BCM, the adopted controller provides ZVS and ZCS for the main switch during the BCM operation. The operation of the flyback micro-inverter with associated controllers is analytically studied, and considerations for an optimum design aiming to higher efficiency are presented. Performance of the flyback micro-inverter with the proposed adaptive snubber and the corresponding controllers is experimentally verified based on a 250W interleaved flyback micro-inverter hardware setup.}, booktitle={2015 ieee energy conversion congress and exposition (ecce)}, author={Rezaei, M. A. and Lee, K. J. and Huang, A. Q.}, year={2015}, pages={3308–3313} }
 @inproceedings{wang_zhu_yu_huang_2015, title={A medium voltage bidirectional DC-DC converter combining resonant and dual active bridge converters}, DOI={10.1109/apec.2015.7104486}, abstractNote={In this paper, an isolated bidirectional dc-dc converter for medium voltage application is proposed. It combines the resonant converter and dual active bridge converter (DAB). Under normal load condition, this isolated converter operates at resonant point to achieve zero voltage (ZVS) turn on at primary side and zero current (ZCS) turn off at secondary side. When over current happens, the voltage across the resonant capacitor will be clamped by paralleled diode and the converter will automatically switch to resonant and DAB mixed operation mode, therefore cycle-by-cycle over current protection is achieved with constant switching frequency. Different operation modes are analyzed for the proposed circuits using time domain waveform and state trajectory. Detailed theoretical analysis and design procedure for transformer, resonant tank and semiconductor devices are discussed. Performance of the proposed circuit is verified by a 3 kV to 200 V, 2.5 kW experimental prototype with high voltage SiC devices.}, booktitle={2015 thirtieth annual ieee applied power electronics conference and exposition (apec 2015)}, author={Wang, L. and Zhu, Q. L. and Yu, Wensong and Huang, A. Q.}, year={2015}, pages={1104–1111} }
 @inproceedings{ji_lee_wang_misra_huang_2015, title={A new AlGaN/GaN power HFET employing partial deep trench drain structure for high voltage application}, DOI={10.1109/wipda.2015.7369277}, abstractNote={A new AlGaN/GaN heterojuction field effect transistor (HFET) employing the partial deep trench drain structure for high voltage application has been proposed and verified successfully to achieve low leakage current and small Rdson. In order to reduce leakage current and on-resistance of HFET devices, we propose a partial deep trench on drain edge adjacent to access region for the first time, which contributes to reducing the surface electric field under the off-state. In addition, trenched area under drain Ohmic metal enhances Ohmic contact on the surface of AlGaN layer which reduces contact resistivity of drain Ohmic contact. The proposed deep trench drain successfully reduces Ohmic contact resistance under the on-state and leakage current under the off-state at the same time.}, booktitle={WiPDA 2015 3rd IEEE Workshop on Wide Bandgap Power Devices and Applications}, author={Ji, I. H. and Lee, B. and Wang, S. Z. and Misra, Veena and Huang, A. Q.}, year={2015}, pages={147–149} }
 @inproceedings{chen_yu_ni_huang_2015, title={A new modulation technique to reduce leakage current without compromising modulation index in PV systems}, DOI={10.1109/ecce.2015.7309724}, abstractNote={The transformerless grid-connected PV system suffers from leakage current and neutral voltage imbalance if three-level inverters are utilized. This paper first investigates the common-mode voltage (CM voltage) reduction/elimination methods in three-phase PV inverters, especially three-level inverters. Several mainstream common-mode voltage reduction/elimination methods, including AZSPWM, 2MV1Z, 3MV, 3MV120, are compared in terms of CM voltage reduction/elimination performance, switching losses, modulation index, linear region and neutral point voltage balancing ability. Then a new topology and modulation scheme are proposed, which reduce the frequency of the CM voltage to the order of line frequency and could reach a 100% modulation index. This method is discussed in detail and is verified by simulation.}, booktitle={2015 ieee energy conversion congress and exposition (ecce)}, author={Chen, Z. P. and Yu, Wensong and Ni, X. J. and Huang, A.}, year={2015}, pages={460–465} }
 @inproceedings{xue_yu_yu_huang_du_2015, title={A novel bi-directional DC-DC converter for distributed energy storage device}, DOI={10.1109/apec.2015.7104489}, abstractNote={This paper presents a high efficiency, low-cost bidirectional isolated dc-dc converter for distributed energy storage device (DESD). Derived from dual active bridge (DAB), the proposed converter consists of a half-bridge circuit at high voltage side and a push-pull circuit with active clamp at low voltage side. The proposed topology is attractive in low voltage and high current applications and it also reduces the number of switching transistors such that the cost and complexity are considerably reduced. With single phase-shift control strategy, all the switches operate in zero-voltage switching (ZVS) condition without increasing circuit complexity. Besides, planar transformer is implemented where the low voltage windings consist of PCB trace and external copper foils. A 380V to 12V DC, 500W DESD hardware prototype has been designed, fabricated, and tested. Experimental results verify the validity of the proposed bi-directional converter, which has 97.3% peak efficiency and maintains greater than 92% efficiency over a load range between 100W and 600W.}, booktitle={2015 thirtieth annual ieee applied power electronics conference and exposition (apec 2015)}, author={Xue, F. and Yu, R. Y. and Yu, Wensong and Huang, A. Q. and Du, Y.}, year={2015}, pages={1126–1130} }
 @inproceedings{peng_husain_huang_lequesne_briggs_2015, title={A past mechanical switch for medium voltage hybrid DC and AC circuit breakers}, booktitle={2015 ieee energy conversion congress and exposition (ecce)}, author={Peng, C. and Husain, I. and Huang, A. and Lequesne, B. and Briggs, R.}, year={2015}, pages={5211–5218} }
 @inproceedings{wang_huang_yu_huang_2015, title={An Isolated Bi-directional high-frequency-AC link DC-AC converter using hybrid SiC switches with carrier-based unipolar modulation technique}, DOI={10.1109/ifeec.2015.7361625}, abstractNote={A novel isolated bi-directional soft-switched high-frequency-AC (HFAC) link DC-AC converter using SiC MOSFET and IGBT hybrid switches is presented in this paper. The DC-AC converter is composed of a full-bridge (FB) inverter cascaded with a cycloconverter through a high-frequency transformer. In order to increase the converter efficiency, and to push the transformer frequency to 50-100 kHz, SiC MOSFETs are preferable devices compared to the traditional IGBTs or SCRs. A unipolar-SPWM-oriented modulation technique is proposed to realize zero-voltage-switching (ZVS) for FB and zero-current-switching (ZCS) for cycloconverter, and to suppress the voltage spikes introduced by the transformer leakage inductance as well. With the novel modulation technique, half of the AC switches in the cycloconverter work under transformer frequency and the rest work at line frequency (60 Hz). Therefore a SiC-IGBT hybrid switch structure is proposed for the cycloconverter. Simulation model and a 400 VDC to 240 VAC, 3 kW prototype have been developed to validate the effectiveness and performance of the proposed unipolar soft-switching modulation technique and the hybrid switch structure.}, booktitle={2015 IEEE 2nd International Future Energy Electronics Conference (IFEEC)}, author={Wang, M. Q. and Huang, Q. Y. and Yu, Wensong and Huang, A. Q.}, year={2015} }
 @inproceedings{li_huang_2015, title={An integrated high efficiency ultra-low power single chip DC/AC inverter for driving liquid crystal electro-optic lenses}, DOI={10.1109/apec.2015.7104811}, abstractNote={An integrated high efficiency, ultra-low power liquid crystal driver for electro-optic diffractive lenses is presented in this paper. The proposed LC driver provides an adjustable 3V to 15V RMS square wave output voltage to drive a liquid crystal in the electro-optic lens, which can be modeled as a 5nF capacitive load. This application is powered by a 3V lithium button cell or energy harvest devices. A reconfigurable hysteretic 2×/3×/4×/5× switched capacitor charge pump is developed for DC-DC conversion to maintain high power efficiency over the entire output power range. An improved H-bridge driving scheme is used to reduce the DC/AC inversion power loss. In addition, an auto-sink scheme is developed to speed up output transaction from high to low in different output modes. Implemented in a 0.25μm 5V VGS, 12-45V VDS BCD technology, the proposed LC driver achieves peak power efficiency of 98%. The transaction time of LC driver output from high to low is 48us, which is 219 times faster than that when auto-sink scheme is disabled.}, booktitle={2015 thirtieth annual ieee applied power electronics conference and exposition (apec 2015)}, author={Li, X. M. and Huang, A.}, year={2015}, pages={3208–3211} }
 @inproceedings{wang_huang_yu_huang_2015, title={An isolated bi-directional soft-switched DC-AC converter using wide-band-gap devices with novel carrier-based unipolar modulation technique under synchronous rectification}, DOI={10.1109/apec.2015.7104672}, abstractNote={A novel carrier-based unipolar-SPWM-oriented modulation technique with synchronous rectification for isolated bi-directional soft-switched high-frequency-AC (HFAC) link DC-AC converter using SiC MOSFET is presented in this paper. The DC-AC converter is composed of a full-bridge (FB) inverter cascaded with a cycloconverter through a high-frequency transformer. In order to increase the efficiency and power density, we proposed to utilize SiC MOSFETs for the converter. A carrier-based unipolar-SPWM-oriented modulation technique is proposed to realize zero-voltage-switching (ZVS) for FB and zero-current or zero-voltage-switching (ZVS/ZCS) for cycloconverter in all load range, and to suppress the voltage spikes introduced by the transformer leakage inductance as well. Synchronous rectification is implemented to further increase the converter efficiency. With the novel modulation technique, 1/4 of the AC switches in the cycloconverter are always on which eliminates 1/4 of the switching loss. Simulation model and a 400 VDC to 240 VAC, 1.2 kW prototype have been developed to validate the effectiveness and performance of the proposed unipolar soft-switching modulation technique and SiC converter.}, booktitle={2015 thirtieth annual ieee applied power electronics conference and exposition (apec 2015)}, author={Wang, M. Q. and Huang, Q. Y. and Yu, Wensong and Huang, A. Q.}, year={2015}, pages={2317–2324} }
 @inproceedings{zong_zhu_yu_huang_2015, title={Auxiliary power supply for solid state transformer with ultra high voltage capacitive driving}, DOI={10.1109/apec.2015.7104472}, abstractNote={This paper proposes an auxiliary power supply (APS) for solid state transformers (SST), which is able to handle extremely high input voltage. Input series output parallel (ISOP) structure is used and only one controller IC is adopted to regulate the output voltage, which simplifies the structure and reduces the cost effectively. Capacitive driving is used to drive multiple switches in different modules of the APS. The proposed capacitive driving method is able to transfer gate signal and driving energy simultaneously even for thousands of volts, which largely reduces the cost and size of the APS. Finally the proposed auxiliary power supply is verified and demonstrated through a 12W prototype.}, booktitle={2015 thirtieth annual ieee applied power electronics conference and exposition (apec 2015)}, author={Zong, S. and Zhu, Q. L. and Yu, Wensong and Huang, A. Q.}, year={2015}, pages={1008–1013} }
 @article{sung_huang_baliga_2015, title={Bevel Junction Termination Extension-A New Edge Termination Technique for 4H-SiC High-Voltage Devices}, volume={36}, ISSN={["1558-0563"]}, DOI={10.1109/led.2015.2427654}, abstractNote={A new edge termination method, referred to as a bevel junction termination extension (Bevel-JTE), is presented for high-voltage silicon carbide devices. The 4H-SiC PiN rectifiers, with a breakdown voltage of 1600 V (~95% of the theoretical value), were fabricated using Bevel-JTEs. The Bevel-JTE technique significantly reduces the chip size by decreasing space occupied by edge termination while providing broad process latitude for parameter variations, such as implantation dose and activation anneal condition.}, number={6}, journal={IEEE ELECTRON DEVICE LETTERS}, author={Sung, Woongje and Huang, Alex Q. and Baliga, B. Jayant}, year={2015}, month={Jun}, pages={594–596} }
 @inproceedings{song_huang_ni_zhang_2015, title={Comparative evaluation of 6kV Si and SiC power devices for medium voltage power flectronics applications}, DOI={10.1109/wipda.2015.7369289}, abstractNote={In order to better assist researchers to select the appropriate power device for medium voltage power electronics applications, this paper presents a comparative evaluation on three typical 6kV level Si and SiC power devices, including 6.5kV/25A Si IGBT from ABB, 6.5kV/15A normally off SiC JFET from USCi and a FREEDM System Center developed 6kV/26A SiC series-connected JFET. The 6.5kV Si IGBT and 6.5kV SiC JFET are packaged in the same module to minimize the effect of different parasitic inductance on the comparison. The 6kV SiC series-connected JFET is developed based on one 1.2kV SiC MOSFET from Cree and four 1.2kV SiC JFETs from Infineon, in this paper, named FREEDM Super-Cascode. A short introduction on the three selected devices are first given, then their forward conduction and switching performances are compared. Also, some additional features are discussed and compared, including the device size, cost, gate driver circuit complexity.}, booktitle={WiPDA 2015 3rd IEEE Workshop on Wide Bandgap Power Devices and Applications}, author={Song, X. Q. and Huang, A. Q. and Ni, X. J. and Zhang, L. Q.}, year={2015}, pages={160–165} }
 @inproceedings{peng_huang_song_2015, title={Current commutation in a medium voltage hybrid DC circuit breaker using 15 kV vacuum switch and SiC devices}, DOI={10.1109/apec.2015.7104661}, abstractNote={Analysis and experimental study of current commutation in an ultra-fast, current limiting, hybrid DC circuit breaker for medium voltage applications is reported in this paper. The hybrid DCCB consists a fast acting 15 kV mechanical switch, a low voltage commutating switch, a single 15 kV Silicon Carbide Emitter Turn Off Thyristor (ETO) device, and a stack of MOVs. The proof-of-concept prototype is able to conduct 45 A normal current and interrupt a maximum of more than 100 A fault current at medium voltage level in less than 4 milliseconds, which is one order of magnitude faster compared to conventional mechanical circuit breakers that typically take 40-100 ms. This paper has presented the operation principle of a hybrid DC circuit breaker and analyzed the current commutation process. Based on the analysis, guidelines are given in the paper to select and design the commutating switch.}, booktitle={2015 thirtieth annual ieee applied power electronics conference and exposition (apec 2015)}, author={Peng, C. and Huang, A. Q. and Song, X. Q.}, year={2015}, pages={2244–2250} }
 @inproceedings{zhabelova_yavarian_vyatkin_huang_2015, title={Data center energy efficiency and power quality: An alternative approach with solid state transformer}, DOI={10.1109/iecon.2015.7392279}, abstractNote={Data center evolved to become large power consumers. Its supporting infrastructure, such as cooling and power distribution, consumes resources e.g. electric power and money. In fact, most money is spent on power conditioning and cooling systems. Therefore, the efficiency of data center and power quality are important topics and can be addressed by careful design. There is a need for research into application of innovative design and state-of-the-art technology for optimizing power supply in data centers. The paper investigates potential of a state-of-the-art technology such as solid state transformer (SST). The simulation proves that SST has potential to improve operational efficiency. SST shows better control of voltage, current and reactive power of the facility, eliminating need for additional devices such as power conditioners and reducing power loss. These results lead to the next stage of the project that involves developing an optimal data center design with SST and investigating data center potential in demand response applications.}, booktitle={Iecon 2015 - 41st annual conference of the ieee industrial electronics society}, author={Zhabelova, G. and Yavarian, A. and Vyatkin, V. and Huang, A. Q.}, year={2015}, pages={1294–1300} }
 @inproceedings{huang_peng_song_2015, title={Design and development of a 7.2 kV/200A hybrid circuit breaker based on 15 kV SiC emitter turn-off (ETO) thyristor}, DOI={10.1109/ests.2015.7157909}, abstractNote={This paper deals with the design of a 7.2 kV, 200 A hybrid AC circuit breaker employing a 15 kV Silicon Carbide (SiC) Emitter Turn-off (ETO) thyristor device as the main semiconductor switch and presents the test results to verify the functions of both the high voltage and low voltage electronic components of the medium voltage hybrid circuit breaker. The hybrid circuit breaker consists a fast acting mechanical switch, a low voltage commutating switch in series with that mechanical switch, a single 15 kV SiC ETO Thyristor device, and a stack of MOVs. This paper focuses on the electronic parts and a companion paper would elucidate the principle and operation of the fast acting mechanical switch. To fulfill bidirectional interruption capability of the high voltage semiconductor device, the SiC ETO is equipped with a low cost silicon diode bridge; a snubber capacitor is equipped in parallel with this diode bridge to alleviate voltage stress of the ETO during turn-off transients. A compact low voltage commutating switch based on silicon MOSFETs has been built and tested up to the full current rating.}, booktitle={2015 IEEE Electric Ship Technologies Symposium (ESTS)}, author={Huang, A. and Peng, C. and Song, X. Q.}, year={2015}, pages={306–311} }
 @inproceedings{falahi_huang_2015, title={Design consideration of an MMC-HVDC system based on 4500V/4000A emitter turn-off (ETO) thyristor}, DOI={10.1109/ecce.2015.7310149}, abstractNote={Excessive power loss is a major concern in high voltage and high power applications and is considered one of the main drawbacks of VSC-HVDC system when compared with traditional HVDC system based on thyristor technology. This is primarily caused by high switching loss associated with switching devices used in the VSC-HVDC. This issue can be largely addressed by using the emerging MMC-HVDC topology, which requires much lower switching frequency than traditional VSC-HVDC. Emitter turn-off thyristor (ETO) is one of the best high power switching devices packed with many advanced features. ETO thyristor based MMC-HVDC system is therefore an extremely attractive choice for ultra-high voltage and high power HVDCs. This paper discusses the operation principle of ETO based MMC-HVDC as well as its design and loss comparison with other solutions.}, booktitle={2015 ieee energy conversion congress and exposition (ecce)}, author={Falahi, G. and Huang, A. Q.}, year={2015}, pages={3462–3467} }
 @inproceedings{ni_gao_song_huang_yu_2015, title={Development of 6kV SiC hybrid power switch based on 1200V SiC JFET and MOSFET}, DOI={10.1109/ecce.2015.7310240}, abstractNote={Series-connected power switch provides a viable solution to implement high voltage and high frequency converters. By using the commercially available 1200V Silicon Carbide (SiC) Junction Field Effect Transistor (JFET) and Metal Oxide semiconductor Filed-effect Transistor (MOSFET), a 6 kV SiC hybrid power switch concept and its application are demonstrated. To solve the parameter deviation issue in the series device structure, an optimized voltage control method is introduced, which can guarantee the equal voltage sharing under both static and dynamic state. Without Zener diode arrays, this strategy can significantly reduce the turn-off switching loss. Moreover, this hybrid MOSFET-JFETs concept is also presented to suppress the silicon MOSFET parasitic capacitance effect. In addition, the positive gate drive voltage greatly accelerates turn-on speed and decreases the switching loss. Compared with the conventional super-JFETs, the proposed scheme is suitable for series-connected device, and can achieve better performance. The effectiveness of this method is validated by simulations and experiments, and promising results are obtained.}, booktitle={2015 ieee energy conversion congress and exposition (ecce)}, author={Ni, X. J. and Gao, R. and Song, X. Q. and Huang, A. Q. and Yu, Wensong}, year={2015}, pages={4113–4118} }
 @inproceedings{xue_yu_yu_huang_2015, title={Distributed energy storage device based on a novel bidirectional DC-DC converter with 650V GaN transistors}, DOI={10.1109/pedg.2015.7223038}, abstractNote={This paper presents a distributed energy storage device (DESD) based on a novel isolated bidirectional DC-DC converter with 650V GaN transistors. The device integrates a low-voltage (13.2V) Li-ion battery pack, an embedded bidirectional DC-DC converter and wireless communication system. The three parts are packaged together, thus it can be directly connected to high-voltage (380V) DC grid, enabling a modular approach for battery energy storage systems. Two 650V enhancement mode GaN transistors are used at the high voltage side. Compared with Si device, three improvements can be achieved in the application: expanding the operation range to light load, reducing switching loss and EMI, increasing the total efficiency of charging and discharging operation. The power stage design as well as a loss analysis of GaN is based on a steady state analysis and PSpice simulation. A 400V to 12V DC, 1kW converter for 1kWh DESD prototype is designed, fabricated, and tested. Experimental results verify the validity of the proposed DESD and the performance improved by using GaN transistors.}, booktitle={Ieee international symposium on power electronics for distributed}, author={Xue, F. and Yu, R. Y. and Yu, Wensong and Huang, A. Q.}, year={2015}, pages={369–374} }
 @inproceedings{peng_husain_huang_2015, title={Evaluation of design variables in Thompson coil based operating mechanisms for ultra-fast opening in hybrid AC and DC circuit breakers}, DOI={10.1109/apec.2015.7104673}, abstractNote={The paper presents the operation transient analysis and multi-physics complexities in the design of a Thompson coil based ultra-fast mechanical switch for hybrid AC and DC circuit breakers. The electromagnetic, mechanical and thermal behavior of the switch has been analyzed through simulation using a multi-physics finite element software. The design variables have been classified into lumped circuit and geometric parameters; the sensitivity analysis by means of systematic and comprehensive simulations on these parameters helped establish the design guidelines. The switch has been designed with optimization for both the circuit parameters and geometrical dimensions of components targeting 2 mm travel for separation within 1 ms.}, booktitle={2015 thirtieth annual ieee applied power electronics conference and exposition (apec 2015)}, author={Peng, C. and Husain, I. and Huang, A. Q.}, year={2015}, pages={2325–2332} }
 @inproceedings{mclamara_huang_2015, title={GaN HEMT based 250W CCM photovoltaic micro-inverter}, DOI={10.1109/apec.2015.7104359}, abstractNote={The high speed, conductivity, and voltage blocking capability of the GaN HEMT facilitates higher efficiency, and smaller size of switched mode power supply designs. Characteristics such as these are important in the solar energy field, in which every extra Watt of harvestable power is extremely valuable. In this paper, the design and experimental results of a 250W 240VAC photo-voltaic micro-inverter utilizing commercially available enhancement-mode GaN HEMTs are presented. The design philosophy is centered on leveraging the advantages of GaN while applying analytics to maximizing efficiency and minimizing device stress. To that end, the nuances of employing GaN devices with respect to parasitic resonance, layout dependent performance, and thermal considerations are also presented for the purpose of executing a robust design.}, booktitle={2015 thirtieth annual ieee applied power electronics conference and exposition (apec 2015)}, author={McLamara, J. W. and Huang, A. Q.}, year={2015}, pages={246–253} }
 @inproceedings{xue_yu_yu_huang_2015, title={GaN transistor based Bi-directional DC-DC converter for stationary energy storage device for 400V DC microgrid}, DOI={10.1109/icdcm.2015.7152029}, abstractNote={This paper presents a novel GaN transistor based bidirectional isolated DC-DC converter for stationary energy storage device (SESD) for 400V DC microgrid. The improvements achieved in the application includes: first, benefitting from the internal ultra-fast free-wheeling diode, the converter's operation range can be expended to light load conditions (switches operate in hard switching). The light load efficiency can be greatly increased. Second, because of its low switching loss and on state resistance, the heavy load efficiency is increased. Third, the snubber inductor which is indispensable in Si device based converter can now be omitted in the GaN version. The power stage design as well as a loss analysis of GaN is based on a steady state analysis and PSpice simulation. Experimental results are presented for a 500 W bidirectional dc-dc converter prototype.}, booktitle={2015 IEEE First International Conference on DC microgrids (ICDCM)}, author={Xue, F. and Yu, R. Y. and Yu, Wensong and Huang, A. Q.}, year={2015} }
 @inproceedings{song_huang_lee_peng_2015, title={High voltage Si/SiC hybrid switch: An ideal next step for SiC}, DOI={10.1109/ispsd.2015.7123446}, abstractNote={Silicon carbide (SiC) power switches such as MOSFET or JFET have demonstrated their superior advantages over silicon (Si) power devices such as IGBT, especially in terms of significantly reduced switching losses. A major issue facing large scale adoption of SiC power devices is still the much higher cost. This paper proposes that Si/SiC hybrid switch should be a natural next step moving forward for high voltage applications to address the cost issue. In the proposed Si/SiC hybrid switch, a SiC MOSFET is connected in parallel with Si IGBT to combine the advantages of IGBT and MOSFET. This concept can also works well with SiC JFET. A 6.5 kV Si IGBT and SiC MOSFET hybrid switch is developed as an example to demonstrate its superior cost/performance. The switching loss can be reduced by more than 70% at a cost of only 50% higher compared to Si IGBT. This work is especially essential for high voltage applications such as medium voltage motor drive, FACTS and HVDC systems.}, booktitle={Proceedings of the international symposium on power semiconductor}, author={Song, X. Q. and Huang, A. Q. and Lee, M. C. and Peng, C.}, year={2015}, pages={289–292} }
 @inproceedings{najm_huang_2015, title={Integrated DC/DC parallel PnP PV architecture method for powering residential buildings}, DOI={10.1109/icdcm.2015.7152071}, abstractNote={This paper proposes a novel integrated plug and play (PnP) DC/DC parallel PV architecture for powering residential buildings. The scheme is based on low cost PV converters (first stage) integrated into one mechanical enclosure along with a second stage grid tied centralized inverter or converter in the case of DC powered applications. The technique limits the requirements of the first stage converters to operation in the maximum power point tracking (MPPT) while supporting power curtailment. All communications to the grid or to other applications are proposed to be provided by the said centralized inverter or converter. Furthermore, a novel approach to improve the racking installation time is also proposed in this paper. The outcome of the said configuration as well as the proposed racking improvement method is a lower cost and simpler to implement PnP system. System configuration and the proposed improved racking installation diagrams as well as experimental results are illustrated in this paper.}, booktitle={2015 IEEE First International Conference on DC microgrids (ICDCM)}, author={Najm, E. M. and Huang, A. Q.}, year={2015}, pages={371–376} }
 @inproceedings{xue_yu_guo_yu_huang_2015, title={Loss analysis of GaN Devices in an isolated bidirectional DC-DC converter}, DOI={10.1109/wipda.2015.7369261}, abstractNote={GaN devices have emerged as a possible replacement for silicon devices in various power conversion applications and as an enabler of new applications not previously possible. This paper presents a 600V Gallium-Nitride (GaN) device based isolated bidirectional DC-DC converter applied in battery energy storage systems. Apart from the features of low turn-off loss, low output capacitance and low drain-source on-state resistance, the most salient one in our bidirectional DC-DC converter application is the ultra-fast freewheeling "body diode" that GaN devices have when compared with Si devices. To distinguish the above mentioned performances of GaN from those of the comparable Si devices, a figure of merit for power devices operating in synchronous rectifying mode is proposed. The converter's operating principle is analyzed in steady state. Switching losses of high voltage and low voltage side switches are simulated based on detailed PSpice models. The converter's safe operation area is extended by using GaN device is explained by calculating the loss in hard switching mode. A thermal simulation is conducted to predict its temperature. Experimental results are presented for a 1 kW, 380-to-12 V prototype DC-DC converter, which demonstrate the validity of the analysis and simulation.}, booktitle={WiPDA 2015 3rd IEEE Workshop on Wide Bandgap Power Devices and Applications}, author={Xue, F. and Yu, R. Y. and Guo, S. X. and Yu, Wensong and Huang, A. Q.}, year={2015}, pages={201–205} }
 @inproceedings{hu_gao_alex_2015, title={Power management strategy of hybrid electric vehicles based on particle swarm optimization}, DOI={10.1109/itec.2015.7165795}, abstractNote={The Power management strategy of HEV using global optimization techniques can achieve optimum control solution. However, the “a priori” nature of the trip information and heavy computational cost prohibit it from being utilized in real world application. In this paper, a power management strategy using particle swarm optimization (PSO) is proposed. The aim is to achieve real time implementation and sub-optimal control solution without requiring the “a priori” knowledge of the driving cycle. Using pricewise linearization, at each time step, normalized comprehensive energy loss for each power split scenario is obtained and normalized over the traveling distance. The power split strategy that minimizes the normalized comprehensive energy loss is considered optimal. However, searching for the optimal power split is mathematically challenging and time consuming. To address the real time implementation, PSO algorithm is employed as the global minima searching tool. Simulation study on a series-parallel configuration passenger vehicle has been performed. In addition, Dynamic Programming (DP) technique has also been implemented in the simulation for the comparison purpose. The simulation results demonstrated that the proposed control strategy is able to achieve comparable fuel economy with global optimization while feasible for real time implementation.}, booktitle={2015 IEEE Transportation Electrification Conference and Expo (ITEC)}, author={Hu, C. J. and Gao, Y. M. and Alex, Q. H.}, year={2015} }
 @inproceedings{huang_wang_yu_huang_2015, title={Power-weighting-based multiple input and multiple output control strategy for single-phase PV cascaded H-bridge multilevel grid-connected inverter}, DOI={10.1109/apec.2015.7104646}, abstractNote={This paper presents a power-weighting-based multiple input and multiple output control strategy and performance improvements schemes for single-phase PV cascaded H-bridge multilevel grid-connected inverter. The truly individual MPPT block for each H-bridge converter realizes independent MPPT, and the sum of each voltage reference provides the system voltage reference for the voltage loop. And the sum of each PV voltage is the system voltage feedback. The output of the voltage controller delivers the peak value of the sinusoidal current reference. The output of this central current controller is assigned directly according to the PV power weighting factors to create the coordinated control signals for PWM generation of each H-bridge respectively. This approach makes the control structure for this cascaded multilevel inverter have only one central dual loop controller, and the PWM generation will be decoupled from the voltage controllers. This feature is similar with the single H-bridge inverter's dual loop control. Furthermore, to improve the dynamic response of the voltage loops, a sample and hold block at double line frequency is included in each voltage loop. Therefore, the voltage loop bandwidth will increase to 25~30Hz and the MPPT speed will be much faster as well. Besides, the power-based duty-ratio feed-forward technique is proposed to improve the current loop performance. Finally, simulated and experimental results are provided to verify the performance of the proposed control approaches.}, booktitle={2015 thirtieth annual ieee applied power electronics conference and exposition (apec 2015)}, author={Huang, Q. Y. and Wang, M. Q. and Yu, Wensong and Huang, A. Q.}, year={2015}, pages={2148–2153} }
 @inproceedings{liang_huang_liu_chang_2015, title={SiC reversely switched dynistor (RSD) for pulse power application}, DOI={10.1109/ispsd.2015.7123447}, abstractNote={This paper reports the world's first SiC reversely switched dynistor (RSD) work. The device structure of 1200V SiC RSD is designed. The two-dimensional numerical model of SiC RSD is established with full consideration of the SiC material parameters and the important physical effects in power device. The blocking characteristics and turn-on characteristics are simulated. The operation principle based on the turn-on controlled by the reverse plasma injection is explained. The influence factors on the switching performance, especially on the residual voltage, including the device parameters and the external conditions, are discussed. The experiment reports the high di/dt pulse output acquired recently based on Si RSD integrated module. The di/dt of 8.85kA/μs is acquired at 1500V discharge voltage, with the peak current of 3.7kA.}, booktitle={Proceedings of the international symposium on power semiconductor}, author={Liang, L. and Huang, A. Q. and Liu, C. and Chang, W. G.}, year={2015}, pages={293–296} }
 @inproceedings{hambridge_huang_yu_2015, title={Solid state transformer (SST) as an energy router: Economic dispatch based energy routing strategy}, DOI={10.1109/ecce.2015.7309991}, abstractNote={The Solid State Transformer (SST) is a revolutionary technology being developed by the authors. It has a tremendous number of features, which include power management, fault management and energy management. Its autonomous and distributed power management capability enables large-scale integration of distributed energy resources (DER) into the power grid. Specifically, it supports AC or DC connected Energy Cells: a combination of DERs, energy storage devices and loads. The SST can achieve real-time power flow regulation via the Energy Cell, therefore forming the foundation of its capability to become a real-time Energy Router. This paper introduces an economic based energy routing strategy that utilizes energy storage to reduce consumption of grid power. Predictive photovoltaic and load forecasting are used to optimize charging and discharging of energy storage. This rule-based algorithm is implemented and demonstrated in a SST enabled 380 V DC Energy Cell.}, booktitle={2015 ieee energy conversion congress and exposition (ecce)}, author={Hambridge, S. and Huang, A. Q. and Yu, R. Y.}, year={2015}, pages={2355–2360} }
 @inproceedings{gao_husain_wang_huang_2015, title={Solid-state transformer interfaced PMSG wind energy conversion system}, DOI={10.1109/apec.2015.7104517}, abstractNote={The solid-state transformer (SST) has been regarded as an emerging technology where emphasis is mainly on the design of the device. To explore its system integration opportunities, this paper proposes and demonstrates a SST interfaced permanent magnet synchronous generator (PMSG) wind energy conversion system. The system integration issues along with wind turbine level control methods have been presented and simulated for power management. Moreover, the lab hardware prototype has been set up, which consists of an induction motor based wind turbine emulator (WTE), PMSG, pulse-width modulation (PWM) rectifier, SST, and resistive load bank. Experiments have been carried out to validate the proposed system and control strategy.}, booktitle={2015 thirtieth annual ieee applied power electronics conference and exposition (apec 2015)}, author={Gao, R. and Husain, I. and Wang, F. and Huang, A. Q.}, year={2015}, pages={1310–1317} }
 @inproceedings{wang_huang_wang_song_ni_ryu_grider_schupbach_palmour_2015, title={Static and dynamic performance characterization and comparison of 15 kV SiC MOSFET and 15 kV SiC n-IGBTs}, DOI={10.1109/ispsd.2015.7123431}, abstractNote={This paper presents the static and dynamic performance of 15 kV SiC IGBTs with 2 um and 5 um field-stop buffer layer thicknesses respectively and compares them with 15 kV SiC MOSFET in term of loss and switching capability. Their switching energy for different gate resistors and temperature have been reported and compared. A 5 kHz 10.5 kW 8 kV boost converter has been built and tested using these three devices respectively. The MOSFET based boost converter has the highest efficiency 99.39% which is the highest reported efficiency for a high voltage SiC device based converter. PLECS loss models can be developed for these devices based on the characterization data to simplify the simulation of a variety circuits or applications which potentially utilize these devices.}, booktitle={Proceedings of the international symposium on power semiconductor}, author={Wang, G. Y. and Huang, A. Q. and Wang, F. and Song, X. Q. and Ni, X. J. and Ryu, S. H. and Grider, D. and Schupbach, M. and Palmour, J.}, year={2015}, pages={229–232} }
 @inproceedings{xue_zhao_yu_yu_huang_2015, title={Stationary energy storage system based on modular high voltage battery modules}, DOI={10.1109/icdcm.2015.7152028}, abstractNote={This paper focuses on the design and control of a stationary energy storage system based on multiple modular high voltage battery modules. The system achieves bi-directional power flow directly from 400V dc grid to the 12V battery modules via a bi-directional dc-dc converter with high conversion ratio as an interface. One merit of such a system is its extensibility and scalability for higher power rating for future use by dispatching more battery modules together. A 2kWh energy storage system prototype which is made up by one grid-connected solid state transformer (SST) emulator and two bi-directional dc-dc converters are designed, fabricated and tested. Based on the modified droop control, a double-loop digital control system for the SST emulator and a single-loop digital control system for the dc-dc converter are implemented respectively. At last, experimental results are presented to verify the proposed distributed control strategy.}, booktitle={2015 IEEE First International Conference on DC microgrids (ICDCM)}, author={Xue, F. and Zhao, Y. L. and Yu, R. Y. and Yu, Wensong and Huang, A. Q.}, year={2015} }
 @inproceedings{sung_huang_baliga_ji_ke_hopkins_2015, title={The first demonstration of symmetric blocking SiC gate turn-off (GTO) thyristor}, ISBN={9781479962594 9781479962617}, url={http://dx.doi.org/10.1109/ISPSD.2015.7123438}, DOI={10.1109/ispsd.2015.7123438}, abstractNote={This paper reports the development of symmetric blocking SiC p-GTO thyristors. The proposed thyristor structure features a positive bevel edge termination implemented by orthogonal dicing technique. In this paper, a detailed design of the device structure, forward current-voltage characteristics, and symmetric blocking capabilities are discussed.}, note={\urlhttps://ieeexplore.ieee.org/document/7123438/}, booktitle={2015 IEEE 27th International Symposium on Power Semiconductor Devices & IC's (ISPSD)}, publisher={IEEE}, author={Sung, Woongje and Huang, Alex Q. and Baliga, B. J. and Ji, Inhwan and Ke, Haotao and Hopkins, Douglas C.}, year={2015}, month={May}, pages={257–260} }
 @inproceedings{liang_huang_sung_lee_song_peng_cheng_palmour_scozzie_2015, title={Turn-on capability of 22 kV SiC Fmitter Turn-off (ETO) Thyristor}, DOI={10.1109/wipda.2015.7369275}, abstractNote={The turn-on characteristics for the SiC p-ETO are researched in this paper. By establishing the two-dimensional numerical model of the SiC p-ETO, the influence of the device parameters and external circuit conditions on the turn-on speed is discussed. The experiments agree with the simulated results well. The npn turn-on mode of ETO is captured in a high di/dt experiment, which proves the existence of the FBSOA for this time hence the possibility of its application in converters without di/dt snubber. According to the intrinsic temperature limitation of the SiC material, the simulation shows that the peak power density of the SiC p-ETO during turn-on could reach several tens of MW/cm2.}, booktitle={WiPDA 2015 3rd IEEE Workshop on Wide Bandgap Power Devices and Applications}, author={Liang, L. and Huang, A. Q. and Sung, W. J. and Lee, M. C. and Song, X. Q. and Peng, C. and Cheng, L. and Palmour, J. and Scozzie, C.}, year={2015}, pages={192–195} }
 @inproceedings{wang_wang_huang_yu_ni_2014, title={A 3.6kV high performance solid state transformer based on 13kV SiC MOSFET}, DOI={10.1109/pedg.2014.6878693}, abstractNote={This paper presents the development of a distribution network solid state transformer (SST) based on high voltage (13kV) SiC MOSFET and JBS diode. This distribution SST is composed with a medium voltage ac/dc rectifier, medium voltage medium frequency dc/dc converter and a low voltage inverter. It's able to be interfaced to 3.6kV distribution grid and output both a 400V dc and 240/120V ac. This paper presents the characterization of the high voltage SiC MOSFET devices, and the design of rectifier and dc/dc converter. The test results of its grid-connected operation including pre-charge, start up, regeneration, etc. are included to show the functionalities of the designed SST prototype.}, booktitle={Ieee international symposium on power electronics for distributed}, author={Wang, F. and Wang, G. Y. and Huang, A. and Yu, Wensong and Ni, X. J.}, year={2014} }
 @article{su_huang_2014, title={A game theoretic framework for a next-generation retail electricity market with high penetration of distributed residential electricity suppliers}, volume={119}, ISSN={["1872-9118"]}, DOI={10.1016/j.apenergy.2014.01.003}, abstractNote={This paper proposes an innovative game theoretic framework for a next-generation retail electricity market (“Energy Internet”) with high penetration of distributed residential electricity suppliers (“Energy Cells”). The envisioned Energy Internet is developed for plug-and-play of a large number of distributed renewable energy generation and energy storage. The residential customers, referred as Energy Cells, are not only the electricity consumers but can also be the electricity suppliers by locally operating and managing their own distributed generators, distributed energy storage devices, and dispatchable loads. This paper formulates a set of mathematical models of the retail electricity market participants with a number of local and global constraints. A numerical case study is performed to validate the proposed next-generation retail electricity market framework using game-theoretic methodologies. The numerical simulation results demonstrate the effectiveness of the proposed market clearing scheme with high penetration of distributed residential electricity suppliers.}, journal={APPLIED ENERGY}, author={Su, Wencong and Huang, Alex Q.}, year={2014}, month={Apr}, pages={341–350} }
 @inproceedings{du_huang_xue_yu_2014, title={A modular integrated Li-ion battery pack with a multi-core based transformer isolated bidirectional DC-DC converter}, DOI={10.1109/epe.2014.6910785}, abstractNote={The paper presented a new energy storage device based on low-voltage (12.8V) Li-ion battery pack with an embedded DC-DC converter. The batteries and converter are packaged together. The integrated battery pack can be directly connected to high-voltage (400V) DC grid, enabling a modular approach for battery energy storage systems.}, booktitle={2014 16th european conference on power electronics and applications (epe'14-ecce europe)}, author={Du, Y. and Huang, A. Q. and Xue, F. and Yu, R. Y.}, year={2014} }
 @inproceedings{wang_huang_2014, title={A novel single stage AC/DC converter for fast charging applications with unity power factor}, DOI={10.1109/apec.2014.6803559}, abstractNote={This paper introduces a single phase AC/DC converter with unity power factor input at grid side. The proposed topology consists of a diode bridge followed by an asymmetrical DAB circuit working in boost mode. The DAB is utilized to regulate both DC output voltage and averaged input current. With single-side PWM modulation, the DAB can possess advantages such as lower RMS currents and larger soft switching range. Zero cycling current can also be achieved to reduce power losses. Simulation and some experimental test have been carried out to verify the effectiveness of proposed converter.}, booktitle={2014 twenty-ninth annual ieee applied power electronics conference and exposition (apec)}, author={Wang, F. and Huang, A.}, year={2014}, pages={1860–1865} }
 @inproceedings{peng_huang_2014, title={A protection scheme against DC Faults VSC based DC Systems with bus capacitors}, DOI={10.1109/apec.2014.6803800}, abstractNote={This paper describes a novel protection method to limit the fault currents caused by short circuit in a voltage source converter (VSC) based DC systems with capacitors connected to the DC bus. Analyzing the development of DC fault current in such DC systems shows that capacitor discharge dominates the very rapid fault current rising at the instance of faults. If this high slope fault current surge is not limited, stored energy in the capacitor will cause hazard to personals as well as connected equipment. If the discharging current from the DC bus capacitor is not limited, it will require much higher break capability of the DC breakers. Therefore a novel protection method is proposed to limit the DC fault currents by detecting and interrupting the DC capacitor discharge using a solid state circuit breaker (capacitor SSCB) which is connected in series with the DC bus capacitor. Implementing this new method will effectively reduce peak value of the fault current, alleviate current stress of diodes in VSC bridges, in a way that only local current information is required. It needs no external control signals, and power loss of this capacitor SSCB is relatively low. Both simulations and tests have proved this method to be effective.}, booktitle={2014 twenty-ninth annual ieee applied power electronics conference and exposition (apec)}, author={Peng, C. and Huang, A. Q.}, year={2014}, pages={3423–3428} }
 @article{lee_huang_2014, title={An injection efficiency model to characterize the injection capability and turn-off speed for > 10 kV 4H-SiC IGBTs}, volume={93}, ISSN={["1879-2405"]}, DOI={10.1016/j.sse.2013.12.008}, abstractNote={This work analytically formulates the relationship among the followings for characterization purpose: (i) γE (injection efficiency), (ii) excess charge stored during on-state and (iii) charge extraction rate and voltage ramp before punch-through during the turn-off. Injection efficiency is expressed in terms of JR (reference current density), Jb (buffer layer reference current), and JT (terminal current). Both JR and Jb are lumped parameters and can be extracted without any knowledge of parameters in the emitter and buffer layer. While γE is simply the ratio of minority to total current, injection capacity is defined mathematically in this work as an index of the tendency of the excess carriers being injected from emitter and then stored in the drift region. 4H-SiC p- and n-IGBT will be discussed side-by-side throughout the discussion. The adaptability of this injection efficiency model will be examined under different emitter conditions and buffer layer lifetimes. This work is also applicable to silicon devices.}, journal={SOLID-STATE ELECTRONICS}, author={Lee, Meng-Chia and Huang, Alex Q.}, year={2014}, month={Mar}, pages={27–39} }
 @inproceedings{guo_huang_2014, title={Control and analysis of the high efficiency split phase PWM inverter}, DOI={10.1109/apec.2014.6803641}, abstractNote={The traditional power switch phase leg is widely used in the power electronic devices. However, the short through of the phase leg is always a problem for reliability, efficiency, higher switching frequency. Besides, both of power device turn-on/turn-off time and the reverse recovery time of poor performance body diodes will limit the switching frequency and power conversion efficiency. This paper proposes a new split phase PWM inverter which could split the MOSFET based phase legs by coupled inductor to prevent the short through and disable poor performance body diode. The extended Schottky diodes could be adopted to eliminate reverse recovery loss. By using the traditional bipolar or unipolar PWM control schemes, the circulating current which is caused by the feature of inductors will exist in the circuit and will increase power loss. An advanced unipolar PWM control strategy is proposed in this paper to minimize circulation current and to improve power conversion efficiency. Simulation is done to verify the better performance of split phase PWM inverter and the proposed advanced unipolar PWM control strategy.}, booktitle={2014 twenty-ninth annual ieee applied power electronics conference and exposition (apec)}, author={Guo, S. X. and Huang, A. Q.}, year={2014}, pages={2415–2420} }
 @article{she_huang_ni_2014, title={Current Sensorless Power Balance Strategy for DC/DC Converters in a Cascaded Multilevel Converter Based Solid State Transformer}, volume={29}, ISSN={["1941-0107"]}, DOI={10.1109/tpel.2013.2256149}, abstractNote={This letter proposes a current sensorless controller for balancing the power in the dc/dc stage of a cascaded multilevel converter based solid state transformer. It is revealed that the equalization of the active power component of duty cycles in the cascaded multilevel rectifier stage can be a good indicator of power balance in the dc/dc stage. Additionally, the power balance of the dc/dc stage can guarantee the voltage balance in the rectifier stage if the differences among the power devices are negligible. Based on this principle, a novel power balance controller without sensing any current in the dc/dc stage is proposed. In the end, experimental results in a seven-level three-stage solid state transformer are provided for verifying the proposed method.}, number={1}, journal={IEEE TRANSACTIONS ON POWER ELECTRONICS}, author={She, Xu and Huang, Alex Q. and Ni, Xijun}, year={2014}, month={Jan}, pages={17–22} }
 @article{she_yu_wang_huang_2014, title={Design and Demonstration of a 3.6-kV-120-V/10-kVA Solid-State Transformer for Smart Grid Application}, volume={29}, ISSN={["1941-0107"]}, DOI={10.1109/tpel.2013.2293471}, abstractNote={Solid-state transformer (SST) has been regarded as one of the most important emerging technologies for traction system and smart grid application. This paper presents the system design and performance demonstration of a high-voltage SST lab prototype that works as the active grid interface in smart grid architecture. Specifically, the designs of the key components of the system, including both power stage and controller platform, are presented. In addition, the advanced control system is developed to achieve high-performance operation. Furthermore, integration issues of SST with dc microgrid are presented. Lastly, tests under different scenarios are conducted to verify the following advanced features of the presented SST technology: 1) VAR compensation; 2) voltage regulation; 3) source voltage sag operation; and 4) microgrid integration.}, number={8}, journal={IEEE TRANSACTIONS ON POWER ELECTRONICS}, author={She, Xu and Yu, Xunwei and Wang, Fei and Huang, Alex Q.}, year={2014}, month={Aug}, pages={3982–3996} }
 @inproceedings{tan_huang_martin_2014, title={Development of solid state arc-free socket for DC distribution system}, DOI={10.1109/apec.2014.6803624}, abstractNote={DC distribution systems have become more appealing in recent years due to its higher energy efficiency. They have already been applied in data centers, commercial buildings, electrical vehicles charger stations and DC micro grid systems, etc. However, electrical arcing is a common phenomenon in DC applications. Arcing and the related potential for fire and electric shock is the main safety problem in DC applications. In this paper, a totally arc-free socket is proposed and developed by embedding a solid state device. It is designed to handle various load conditions. In addition, over temperature and over current protection features have been embedded for realizing trip functions for each single outlet. Simulation and experimental results based on 380V DC, which is a common medium voltage applied in data centers and DC micro grids, has been discussed.}, booktitle={2014 twenty-ninth annual ieee applied power electronics conference and exposition (apec)}, author={Tan, K. and Huang, A. Q. and Martin, A.}, year={2014}, pages={2300–2305} }
 @inproceedings{ji_lee_wang_misra_huang_choi_2014, title={High voltage AlGaN/GaN HFET employing low taper angle field-plate for stable forward blocking capability}, DOI={10.1109/ispsd.2014.6856028}, abstractNote={A new high voltage AlGaN/GaN heterojuction field effect transistor (HFET) employing low taper angle field-plate (LTA-FP) has been proposed and verified experimentally to achieve stable forward blocking capability with low leakage current. Proposed device with a LTA-FP of 10 degrees, fabricated by adopting a new taper etching process, exhibits stable forward blocking capability with low leakage current (2 orders of magnitude smaller) under repetitive high voltage stress, whereas the conventional device with steep FP of 70 degree shows that unstable behavior under the same stress. These experimental results indicate that the proposed LTA-FP suppresses the electric field concentration at the gate edge successfully and is an effective approach to secure the stable blocking characteristics of GaN based high voltage devices.}, booktitle={Proceedings of the international symposium on power semiconductor}, author={Ji, I. H. and Lee, B. M. and Wang, S. Z. and Misra, Veena and Huang, A. Q. and Choi, Y. H.}, year={2014}, pages={269–272} }
 @article{su_wang_zhang_huang_2014, title={Model predictive control-based power dispatch for distribution system considering plug-in electric vehicle uncertainty}, volume={106}, ISSN={["1873-2046"]}, DOI={10.1016/j.epsr.2013.08.001}, abstractNote={As an important component of Smart Grid, advanced plug-in electric vehicles (PEVs) are drawing much more attention because of their high energy efficiency, low carbon and noise pollution, and low operational cost. Unlike other controllable loads, PEVs can be connected with the distribution system anytime and anywhere according to the customers’ preference. The uncertain parameters (e.g., charging time, initial battery state-of-charge, start/end time) associated with PEV charging make it difficult to predict the charging load. Therefore, the inherent uncertainty and variability of the PEV charging load have complicated the operations of distribution systems. To address these challenges, this paper proposes a model predictive control (MPC)-based power dispatch approach. The proposed objective functions minimize the operational cost while accommodating the PEV charging uncertainty. Case studies are performed on a modified IEEE 37-bus test feeder. The numerical simulation results demonstrate the effectiveness and accuracy of the proposed MPC-based power dispatch scheme.}, journal={ELECTRIC POWER SYSTEMS RESEARCH}, author={Su, Wencong and Wang, Jianhui and Zhang, Kuilin and Huang, Alex Q.}, year={2014}, month={Jan}, pages={29–35} }
 @article{du_wang_wang_huang_2014, title={Modeling of the High-Frequency Rectifier With 10-kV SiC JBS Diodes in High-Voltage Series Resonant Type DC-DC Converters}, volume={29}, ISSN={["1941-0107"]}, DOI={10.1109/tpel.2013.2288642}, abstractNote={The superior material properties of the wide bandgap silicon carbide (SiC) semiconductors enable excellent device characteristics such as low on-resistance, high breakdown voltage, fast switching speed, high temperature operation, etc. 10-kV SiC junction barrier Schottky (JBS) diode prototype made by Cree was characterized in this paper first. The high-voltage (HV) and high-frequency rectifier consisting of SiC JBS diodes in dc-dc converters can potentially benefit from the device characteristics. However, capacitive current in both forward and reverse recovery process is observed due to the junction capacitance when the SiC JBS diode is turned on and off, which increases the reactive power and reduces the rectifier output power and voltage. To better utilize the devices, the rectifier operation is analyzed in consideration of the impact of the JBS diode parasitic capacitance. Two equivalent circuit models, the series and the parallel input impedance model, are proposed. The distributed junction capacitance of JBS diodes is lumped into the equivalent input capacitance such that the input impedance and output voltage, two critical parameters in HV dc-dc converter design, can be predicted from the models. Experiment setup of SiC JBS diode rectifier was built and the test results verified the modeling work.}, number={8}, journal={IEEE TRANSACTIONS ON POWER ELECTRONICS}, author={Du, Yu and Wang, Jun and Wang, Gangyao and Huang, Alex Q.}, year={2014}, month={Aug}, pages={4288–4300} }
 @article{yu_she_zhou_huang_2014, title={Power Management for DC Microgrid Enabled by Solid-State Transformer}, volume={5}, ISSN={["1949-3061"]}, DOI={10.1109/tsg.2013.2277977}, abstractNote={A novel distributed power management scheme is proposed in this paper for a DC microgrid system, which is enabled by Solid-State transformer (SST). The proposed system includes distributed renewable energy resource (DRER) and distributed energy storage device (DESD). The proposed distributed control algorithm, which only relies on the local information and guarantees full utilization of each module in the system based on their characteristics, is applied to both SST and DC microgrid. To this end, a simulation platform is developed in MATLAB/Simulink, in which Photovoltaic (PV), fuel cell and battery are selected as the typical DRERs and DESD, respectively. Lastly, several typical case studies are carried out and the simulation results verify the proposed distributed power management.}, number={2}, journal={IEEE TRANSACTIONS ON SMART GRID}, author={Yu, Xunwei and She, Xu and Zhou, Xiaohu and Huang, Alex. Q.}, year={2014}, month={Mar}, pages={954–965} }
 @article{rezaei_wang_huang_cheng_palmour_scozzie_2014, title={Static and Dynamic Performance Evaluation of > 13 kV SiC-ETO and Its Application as A Solid-State Circuit Breaker}, volume={778-780}, ISBN={["*****************"]}, ISSN={["0255-5476"]}, DOI={10.4028/www.scientific.net/msf.778-780.1025}, abstractNote={This study addresses the transient and steady-state performance of a >13 kV SiC ETO as a Solid-State Circuit Breaker (SSCB). The developed SiC-ETO is based on a 1 cm2, 15 kV SiC p-GTO with an extremely low differential resistance. Static performance of the device, including the on-state voltage drop at different temperatures and different currents has been carried out in this paper. Furthermore, transient performance of the device, including the turn off energy of the device has been studied. Also, the superior performance of the p-type SiC-ETO has been exploited to design and implement a solid-state circuit breaker. The studies verify the superiority of the SiC p-ETO compared to other solid state devices for this application.}, journal={SILICON CARBIDE AND RELATED MATERIALS 2013, PTS 1 AND 2}, author={Rezaei, Mohammad Ali and Wang, Gangyao and Huang, Alex Q. and Cheng, Lin and Palmour, John W. and Scozzie, Charles}, year={2014}, pages={1025-+} }
 @inproceedings{rezaei_wang_huang_cheng_scozzie_2014, title={Static and dynamic characterization of a > 13kV SiC p-ETO device}, DOI={10.1109/ispsd.2014.6856049}, abstractNote={This study addresses the transient and steady-state performance of a >13 kV SiC p-ETO. The developed SiC p-ETO is based on a 1 cm2, 15 kV SiC p-GTO with an extremely low differential resistance. Static performance of the device, including the on-state voltage drop at different temperatures and different currents is carried out in this paper. Furthermore, transient performance of the device, including the turn off energy and also the Safe Operating Area (SOA) of the device has been studied. Also, the superior performance of the p-type SiC-ETO has been exploited to design and implement a solid-state circuit breaker. The studies verify the superiority of the SiC pETO compared to other solid state devices for this application.}, booktitle={Proceedings of the international symposium on power semiconductor}, author={Rezaei, M. A. and Wang, G. Y. and Huang, A. Q. and Cheng, L. and Scozzie, C.}, year={2014}, pages={354–357} }
 @article{chen_huang_yu_2013, title={A High Step-Up Three-Port DC-DC Converter for Stand-Alone PV/Battery Power Systems}, volume={28}, ISSN={["1941-0107"]}, DOI={10.1109/tpel.2013.2242491}, abstractNote={A three-port dc–dc converter integrating photovoltaic (PV) and battery power for high step-up applications is proposed in this paper. The topology includes five power switches, two coupled inductors, and two active-clamp circuits. The coupled inductors are used to achieve high step-up voltage gain and to reduce the voltage stress of input side switches. Two sets of active-clamp circuits are used to recycle the energy stored in the leakage inductors and to improve the system efficiency. The operation mode does not need to be changed when a transition between charging and discharging occurs. Moreover, tracking maximum power point of the PV source and regulating the output voltage can be operated simultaneously during charging/discharging transitions. As long as the sun irradiation level is not too low, the maximum power point tracking (MPPT) algorithm will be disabled only when the battery charging voltage is too high. Therefore, the control scheme of the proposed converter provides maximum utilization of PV power most of the time. As a result, the proposed converter has merits of high boosting level, reduced number of devices, and simple control strategy. Experimental results of a 200-W laboratory prototype are presented to verify the performance of the proposed three-port converter.}, number={11}, journal={IEEE TRANSACTIONS ON POWER ELECTRONICS}, author={Chen, Yen-Mo and Huang, Alex Q. and Yu, Xunwei}, year={2013}, month={Nov}, pages={5049–5062} }
 @inproceedings{she_huang_ni_2013, title={A cost effective power sharing strategy for a cascaded multilevel converter based Solid state transformer}, DOI={10.1109/ecce.2013.6646725}, abstractNote={This paper proposes a power sharing strategy for DC/DC stage of a cascaded multilevel converter based solid state transformer. It is revealed that the equalization of the active power component of duty cycles in the cascaded multilevel rectifier stage can be a good indicator of power balance in the DC/DC stage. Additionally, the power balance of the DC/DC stage can guarantee the voltage balance in the rectifier stage if the differences among the power devices are negligible. Based on this principle, a novel power balance controller without sensing any current in the DC/DC stage is proposed. Both simulation and experimental results in a seven-level three-stage solid state transformer are provided for verifying the proposed method.}, booktitle={2013 ieee energy conversion congress and exposition (ecce)}, author={She, X. and Huang, A. Q. and Ni, X. J.}, year={2013}, pages={372–379} }
 @inproceedings{yu_huang_burgos_li_du_2013, title={A fully autonomous power management strategy for DC microgrid bus voltages}, DOI={10.1109/apec.2013.6520706}, abstractNote={A typical DC microgrid is investigated in this paper. Two unidirectional DC/DC converters for photovoltaic (PV), and two bidirectional DC/DC converters for batteries are included in the proposed DC microgrid system embodying multiple renewable energy sources and energy storage devices. In order to manage the system operation, a fully autonomous power management strategy, namely adaptive DC bus voltage signal, is proposed. In the proposed control algorithm, the DC microgrid system can operate in islanding mode, DC source-connection mode, featuring seamless transitions between these two modes. Experimental results verify that the proposed power management strategy can be applied to a DC microgrid stably and achieve good performance.}, booktitle={2013 twenty-eighth annual ieee applied power electronics conference and exposition (apec 2013)}, author={Yu, X. W. and Huang, A. and Burgos, R. and Li, J. and Du, Y.}, year={2013}, pages={2876–2881} }
 @inproceedings{lee_huang_huang_brunt_2013, title={An analytical investigation of the effect of varied buffer layer designs on the turn-off speed for 4H-SiC IGBTs}, DOI={10.1109/wipda.2013.6695559}, abstractNote={We propose a criterion to quantify the relationship between buffer layer parameters at a given total charge and turn-off speed for 4H-SiC IGBTs. Three phases of voltage ramp are analytically discussed during the inductive load turn-off by solving each corresponding continuity equation. Extra emphasis will be placed on Phase II - a transition phase in between the initial voltage ramp and punch-through.}, booktitle={2013 1st IEEE Workshop on Wide Bandgap Power Devices and Applications (WiPDA)}, author={Lee, M. C. and Huang, X. and Huang, A. and Brunt, E.}, year={2013}, pages={44–47} }
 @article{chen_huang_li_wang_gu_2013, title={Analysis and Comparison of Medium Voltage High Power DC/DC Converters for Offshore Wind Energy Systems}, volume={28}, ISSN={["1941-0107"]}, DOI={10.1109/tpel.2012.2215054}, abstractNote={Offshore wind farm with an internal medium-voltage dc (MVDC)-grid collection connected HVDC transmission may be an option to harvest offshore wind energy. High-power MV dc/dc converters with high-step-up conversion ratios are the key components for the internal MVDC grid. In this paper, a high-efficiency step-up resonant switched-capacitor converter for offshore wind energy system is studied, which is characterized by the soft-switching condition for all switches and diodes. This significantly reduces switching losses and higher switching frequency is feasible to reduce the overall system volume and weight. The comparisons with other two kinds of topologies are also presented; moreover, the possible specification requirements of high power MV dc/dc converters are analyzed and set. The operation principle of the proposed converter has been successfully verified by simulation and experiment results.}, number={4}, journal={IEEE TRANSACTIONS ON POWER ELECTRONICS}, author={Chen, Wu and Huang, Alex Q. and Li, Chushan and Wang, Gangyao and Gu, Wei}, year={2013}, month={Apr}, pages={2014–2023} }
 @inproceedings{hu_huang_gao_2013, title={Comprehensive lost minimization strategy for parallel plug-in hybrid electric vehicles}, DOI={10.1109/itec.2013.6573501}, abstractNote={Plug-in hybrid electric vehicles (PHEVs) have two energy inputs, the petroleum fuel and electric energy from the utility grid. Due to the different operation costs, the energy management has significant effects on the fuel economy. In this paper, an energy management strategy, stemmed from the AER-focused and blended strategy, is developed. It features the “smart” utilization of the stored electric energy and meanwhile provides intensive electric range. A traffic pattern identification algorithm is proposed. Using the historic and current traffic data, the algorithm can identify the highway and urban traffic pattern, which provides the guidance of the “smart” utilization. In addition, an innovative real time control algorithm for charge sustenance is proposed. It computs the comprehensive energy loss of the hybrid drive train. The operation points with the minimum comprehensive energy loss is found to be the optimized engine and motor operation points. Simulation results show that significant improvement of fuel efficiency can be achieved.}, booktitle={2013 IEEE Transportation Electrification Conference and Expo (ITEC)}, author={Hu, C. J. and Huang, A. Q. and Gao, Y. M.}, year={2013} }
 @inproceedings{yu_she_huang_2013, title={Hierarchical power management for DC microgrid in islanding mode and solid state transformer enabled mode}, DOI={10.1109/iecon.2013.6699381}, abstractNote={A hierarchical power management scheme is proposed in this paper for a typical DC Microgrid. Different from other Microgrids, the DC Microgrid can interface to the distribution system by Solid-State transformer (SST). The hierarchical power management strategy includes three control levels: 1) primary control for DC Microgrid to implement distributed operation 2) secondary control for the DC Microgrid bus voltage recovery to achieve seamless mode switch 3) tertiary control to manage the battery charge and discharge. The DC Microgrid can operate in islanding mode, including the individual control for distributed renewable energy source (DRER) and distributed energy storage device (DESD). In addition, the DC microgrid can operate in SST-enabled mode to interface to the distribution system. The DC Micorgrid can seamlessly switch between islanding mode and SST-enable mode. The consideration of state of charge (SOC) for battery is also involved into the tertiary control. To this end, a lab test-bed is constructed to verify the system performance. Lastly, several typical case studies are carried out and the experimental results verify the proposed power management strategy.}, booktitle={39th annual conference of the ieee industrial electronics society (iecon 2013)}, author={Yu, X. W. and She, X. and Huang, A.}, year={2013}, pages={1656–1661} }
 @article{lee_choi_kirkpatrick_huang_misra_2013, title={Improved high-temperature device transport properties and off-state characteristics of AlGaN/GaN power devices with atomic layer deposition (ALD) HfAlO high-k dielectric}, volume={28}, ISSN={["1361-6641"]}, DOI={10.1088/0268-1242/28/7/074016}, abstractNote={The effect of the atomic layer deposition (ALD) HfAlO high-k dielectric on device transport properties and breakdown characteristics of an AlGaN/GaN metal–oxide–semiconductor hetero-junction field-effect transistor (MOS-HFET) was evaluated based on temperature-dependent measurements. It was found that the MOS-HFET device with a HfAlO gate dielectric shows high-channel mobility greater than the Schottky HFET device for the measured temperature range (25–150 °C). In the case of off-state breakdown characteristics, the MOS-HFET device greatly suppressed gate leakage currents for measured temperatures (25–200 °C) resulting in improvements in off-state breakdown characteristics. In contrast, large gate/drain leakage currents were observed for the Schottky HFET device at high temperature (>100 °C) resulting in about 200 V of breakdown voltage reduction. It was also found that the ALD HfAlO layer reduced surface leakage current by passivating the GaN surface effectively. Therefore, the MOS-HFET structure with the HfAlO gate dielectric is very attractive for GaN-based high-power and high-temperature device applications.}, number={7}, journal={SEMICONDUCTOR SCIENCE AND TECHNOLOGY}, author={Lee, B. and Choi, Y. H. and Kirkpatrick, C. and Huang, A. Q. and Misra, V.}, year={2013}, month={Jul} }
 @inproceedings{wang_wang_magai_lei_huang_das_2013, title={Performance comparison of 1200V 100A SiC MOSFET and 1200V 100A silicon IGBT}, DOI={10.1109/ecce.2013.6647124}, abstractNote={This paper presents the characteristics of the first commercial 1200V 100A SiC MOSFET module and compares it with state-of-the-art silicon IGBT with the same rating. The results show that the 1200V SiC MOSFET has faster switching speed and much lower loss compared with silicon IGBT. Moreover, the silicon IGBT switching loss will increase significantly for higher operation temperature, while the SiC MOSFET switching loss is almost the same for different temperature. A loss model has been implemented in PLECs in order to simulation the losses. An 11kW singlephase inverter prototype with 600V dc bus and 380Vac output voltage has been built for evaluating and comparing the SiC MOSFET and Si IGBT performance. The test results match with the simulation very well and show that with 40 kHz switching frequency the inverter efficiency can be increased to 98.5% from 96.5% if replacing the Si IGBT with the SiC MOSFET module.}, booktitle={2013 ieee energy conversion congress and exposition (ecce)}, author={Wang, G. Y. and Wang, F. and Magai, G. and Lei, Y. and Huang, A. and Das, M.}, year={2013}, pages={3230–3234} }
 @inproceedings{yu_she_ni_wang_huang_2013, title={Power management strategy for DC microgrid interfaced to distribution system based on solid state transformer}, DOI={10.1109/ecce.2013.6647394}, abstractNote={A typical DC microgrid, which can be enabled by Solid State Transformer (SST), is investigated in this paper. One unidirectional DC/DC converter for photovoltaic (PV), one bidirectional DC/DC converters for battery, and a SST based on distribution system level, are included in the proposed DC microgrid system. In order to manage the system operation, a distributed power management strategy is proposed. In the proposed control algorithm, not only the DC microgrid system can interface to the distribution system, but each module in the system can be distributed based on its own characteristics. Experimental results verify that the proposed power management strategy can be applied to a DC microgrid stably and achieve good performance.}, booktitle={2013 ieee energy conversion congress and exposition (ecce)}, author={Yu, X. W. and She, X. and Ni, X. J. and Wang, G. Y. and Huang, A.}, year={2013}, pages={5131–5136} }
 @inproceedings{su_huang_2013, title={Proposing a electricity market framework for the energy internet}, DOI={10.1109/pesmg.2013.6672224}, abstractNote={Smart Grid is drawing increasing attentions and reshaping the traditional view of power systems in the last decade. The Future Renewable Electric Energy Delivery and Management (FREEDM) Systems provide a promising solution to accommodate the high penetration of intermittent renewable energy resources and the emerging Smart Grid technologies. As a future automated and flexible electric power distribution system, the envisioned FREEDM systems enable the customers to fully participate in a deregulated electricity market. The customers are not only the price-takers but also the electricity suppliers by locally operating and managing their own Distributed Generators (DGs), Distributed Energy Storage Devices (DESDs), and dispatchable loads. This paper proposes a novel framework for a deregulated electricity market to enable the “Energy Internet” in a residential distribution system. It can achieve the flexible energy/power dispatch by allowing the customers to maximize their own benefits and compete with each other. Some game-theoretic methodologies (e.g., Nikaido-Isoda function and relaxation algorithm) are applied to determine the equilibrium solutions in a deregulated electricity market. A numerical case study is performed to validate the proposed approach. Accordingly, the numerical simulation results demonstrate the effectiveness and accuracy of the proposed framework for clearing the deregulated electricity market price enabling the “Energy Internet”.}, booktitle={2013 ieee power and energy society general meeting (pes)}, author={Su, W. C. and Huang, A. Q.}, year={2013} }
 @inproceedings{huang_wang_li_huang_baliga_2013, title={Short-circuit capability of 1200V SiC MOSFET and JFET for fault protection}, DOI={10.1109/apec.2013.6520207}, abstractNote={The short-circuit capability of power switches is crucial for the fault protection. In this paper, 1200V SiC MOSFET and normally-off SiC JFET have been characterized and their short-circuit capabilities have been studied and analyzed at 400V DC bus voltage. Due to different physics in the channels, SiC MOSFET and SiC JFET show different types of temperature coefficient. During the short-circuit operation, the saturation current, Isat, of SiC MOSFET increases for several microseconds before the gentle decreasing while that of SiC JFET decreases drastically from the very beginning. The SiC MOSFETs failed after short-circuit operations of 80μs and 50μs at 10V and 15V gate bias respectively while the SiC JFET could survive a short-circuit time more than 1.4msec.}, booktitle={2013 twenty-eighth annual ieee applied power electronics conference and exposition (apec 2013)}, author={Huang, X. and Wang, G. Y. and Li, Y. S. and Huang, A. Q. and Baliga, B. J.}, year={2013}, pages={197–200} }
 @inproceedings{huang_baliga_huang_suvorov_capell_cheng_agarwal_2013, title={SiC Symmetric Blocking Terminations Using Orthogonal Positive Bevel Termination and Junction Termination Extension}, DOI={10.1109/ispsd.2013.6694475}, abstractNote={Symmetric blocking power semiconductor switches require two edge terminations, one for the reverse blocking junction and the other one for the forward blocking junction. In this work, we demonstrated 1100V SiC symmetric blocking edge terminations using orthogonal positive bevel (OPB) termination and a one-zone Junction Termination Extension (JTE). The OPB was formed by orthogonally sawing 45° V-shape trenches into the SiC wafer with a diamond-coated dicing blade. The surface damage was then repaired with dry-etch in SF6/O2 plasma, which reduced the leakage current by around two orders of magnitude. As limited by field reach-through, both the OPB and the JTE terminations show breakdown voltage of 1100V. The P+P-N+ diodes fabricated on the same wafer with the OPB termination showed 1610V avalanche breakdown which was around 83% of ideal value.}, booktitle={Proceedings of the international symposium on power semiconductor}, author={Huang, X. and Baliga, B. J. and Huang, A. Q. and Suvorov, A. and Capell, C. and Cheng, L. and Agarwal, A.}, year={2013}, pages={179–182} }
 @inproceedings{she_huang_2013, title={Solid state transformer in the future smart electrical system}, DOI={10.1109/pesmg.2013.6672768}, abstractNote={The concept of the solid state transformer has been investigated extensively in the past decade with the emphasis mainly focused on the circuit topology investigation. With the technology being more and more mature and acceptable, the application issue of solid state transformer in the future smart electrical system needs to be investigated. This paper characterizes and summarizes the main features of the solid state transformer, and correspondingly presents possible application areas of solid state transformer in the future smart electrical system. The future distribution system architecture is proposed and a new wind energy system is presented based on the multifunctional utilization of SST. Simulation results are given to demonstrate the proposal.}, booktitle={2013 ieee power and energy society general meeting (pes)}, author={She, X. and Huang, A.}, year={2013} }
 @article{zhao_wang_bhattacharya_huang_2013, title={Voltage and Power Balance Control for a Cascaded H-Bridge Converter-Based Solid-State Transformer}, volume={28}, ISSN={["1941-0107"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84878813627&partnerID=MN8TOARS}, DOI={10.1109/tpel.2012.2216549}, abstractNote={The solid-state transformer (SST) is an interface device between ac distribution grids and dc distribution systems. The SST consists of a cascaded multilevel ac/dc rectifier stage, a dual active bridge (DAB) converter stage with high-frequency transformers to provide a regulated 400-V dc distribution, and an optional dc/ac stage that can be connected to the 400-V dc bus to provide residential 120/240 V $_{\rm ac}$. However, due to dc-link voltage and power unbalance in the cascaded modules, the unbalanced dc-link voltages and power increase the stress of the semiconductor devices and cause overvoltage or overcurrent issues. This paper proposes a new voltage and power balance control for the cascaded H-Bridge converter-based SST. Based on the single-phase dq model, a novel voltage and the power control strategy is proposed to balance the rectifier capacitor voltages and the real power through parallel DAB modules. Furthermore, the intrinsic power constraints of the cascaded H-Bridge voltage balance control are derived and analyzed. With the proposed control methods, the dc-link voltage and the real power through each module can be balanced. The SST switching model simulation and the prototype experiments are presented to verify the performance of the proposed voltage and power balance controller.}, number={4}, journal={IEEE TRANSACTIONS ON POWER ELECTRONICS}, author={Zhao, Tiefu and Wang, Gangyao and Bhattacharya, Subharshish and Huang, Alex Q.}, year={2013}, month={Apr}, pages={1523–1532} }
 @article{she_huang_wang_burgos_2013, title={Wind Energy System With Integrated Functions of Active Power Transfer, Reactive Power Compensation, and Voltage Conversion}, volume={60}, ISSN={["1557-9948"]}, DOI={10.1109/tie.2012.2216245}, abstractNote={As the power of wind energy system increases, the control of their active and reactive power becomes increasingly more important from a system standpoint given that these are typical frequency and voltage control parameters. In this paper, a family of wind energy systems with integrated functions of active power transfer, reactive power compensation, and voltage conversion is proposed. The proposed wind energy systems using solid-state transformer (SST) can effectively suppress the voltage fluctuation caused by the transient nature of wind energy without additional reactive power compensator and, as such, may enable the large penetration of wind farm (WF) into the power grid. To this end, a simulation study for WF driven by squirrel-cage induction generators is presented to verify the effectiveness of the proposed system. In addition, a modular-type high-voltage and high-power three-phase SST topology is presented for the proposed system, and its basic building block, which is a single-phase SST, is analyzed. The functions of SST in the presented wind energy system are verified in a single-phase laboratory prototype with scaled-down experiments. Lastly, cost issue of the proposed technology is analyzed with comparison to the traditional one.}, number={10}, journal={IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS}, author={She, Xu and Huang, Alex Q. and Wang, Fei and Burgos, Rolando}, year={2013}, month={Oct}, pages={4512–4524} }
 @article{sung_van brunt_baliga_huang_2012, title={A Comparative Study of Gate Structures for 9.4-kV4H-SiC Normally On Vertical JFETs}, volume={59}, ISSN={["0018-9383"]}, DOI={10.1109/ted.2012.2203337}, abstractNote={This paper reports the development of 9.4-kV 4H-SiC normally on lateral-channel vertical JFETs. The developed JFETs utilize a buried layer to create a lateral conduction channel, shielding the source from the effects of drain bias. The lowest measured <formula formulatype="inline"><tex Notation="TeX">$R_{\rm on, sp}$</tex></formula> was 127 <formula formulatype="inline"><tex Notation="TeX">$\hbox{m}\Omega\cdot\hbox{cm}^{2}$</tex></formula>. Measurements indicate that the channel resistivity can be further reduced by channel optimization. The fabricated JFETs exhibit pentode-like <formula formulatype="inline"><tex Notation="TeX">$I_{D}$</tex></formula>–<formula formulatype="inline"><tex Notation="TeX">$V_{\rm DS}$ </tex></formula> characteristics with a high forward direct-current blocking gain of over 500. This paper provides a comparative study of gate structures in order to achieve the lowest on -state switching losses and to provide stable forward blocking characteristics for a normally on JFET.}, number={9}, journal={IEEE TRANSACTIONS ON ELECTRON DEVICES}, author={Sung, Woongje and Van Brunt, Edward and Baliga, B. Jayant and Huang, Alex Q.}, year={2012}, month={Sep}, pages={2417–2423} }
 @article{chen_huang_2012, title={A Low-Loss Gate Drive for Emitter Turn-Off Thyristor (ETO)}, volume={27}, ISSN={["1941-0107"]}, DOI={10.1109/tpel.2012.2203146}, abstractNote={This letter introduces a new and energy-efficient gate drive circuit for emitter turn-off thyristor (ETO). The proposed circuit is a buck converter with two controllers that obtains power from gate current when the ETO gate voltage is negative, thus reducing power dissipation of the ETO gate drive and significantly mitigating a limitation of current ETO self-power designs. Various on-state gate current circuits are discussed and simulated. Experimental results verify the proposed circuit's operation and low-power consumption performance. The proposed circuit can be used in integrated gate-commutated thyristor and gate-commutated thyristor as well.}, number={12}, journal={IEEE TRANSACTIONS ON POWER ELECTRONICS}, author={Chen, Qian and Huang, Alex Q.}, year={2012}, month={Dec}, pages={4827–4831} }
 @inproceedings{chen_yu_huang_2012, title={A New nonisolated three-port DC-DC converter with high step-up/down ratio}, DOI={10.1109/ecce.2012.6342633}, abstractNote={A new nonisolated three-port dc-dc converter integrating PV and battery power is proposed in this paper. The topology includes two coupled inductors and two active-clamp circuits. The coupled inductors are used to achieve high step up/down gain and to reduce the voltage stress on both primary and auxiliary switches. Two sets of active-clamp circuits in the proposed converter are used to recycle the energy stored in the leakage inductors. Therefore, the system efficiency can be improved. Charging/discharging transition of the battery is autonomous while tracking the maximum power of PV source and regulating the output voltage simultaneously. When the charging voltage is too high, the control loop of PV port will be switched from maximum power point tracking (MPPT) to battery voltage regulation. Experimental results of a 200W laboratory prototype are presented to verify the performance of the proposed three-port converter.}, booktitle={2012 IEEE Energy Conversion Congress and Exposition (ECCE)}, author={Chen, Y. M. and Yu, X. W. and Huang, A. Q.}, year={2012}, pages={1520–1526} }
 @article{sung_baliga_huang_2012, title={A Novel 4H-SiC Fault Isolation Device with Improved Trade-off between On-state Voltage Drop and Short Circuit SOA}, volume={717-720}, ISBN={["978-3-03785-419-8"]}, ISSN={["0255-5476"]}, DOI={10.4028/www.scientific.net/msf.717-720.1045}, abstractNote={This paper aims to introduce a solid-state fault isolation device (FID) for the short circuit protection application in the power distribution systems. The key performance of a FID is to have a low on-state loss and a strong short circuit safe operating area (SCSOA). As a FID, a novel 15kV 4H-SiC field controlled diode (FCD) with a p+buried layer is proposed to provide an improved trade-off between the on-state forward voltage drop and the saturation current. Dynamic response to the fault and the application example of the proposed FCD are described in this paper.}, journal={SILICON CARBIDE AND RELATED MATERIALS 2011, PTS 1 AND 2}, author={Sung, Woongje and Baliga, B. J. and Huang, Alex Q.}, year={2012}, pages={1045–1048} }
 @inproceedings{lin_huang_fan_2012, title={A high fidelity wide bandwidth (HFWB) buck converter with switching ripple cancellation for wireless communication application}, DOI={10.1109/apec.2012.6165980}, abstractNote={This paper presents a ripple based fixed on time control scheme for a novel high efficiency linear transmitter. To support FCC power emission mask, this control scheme needs to have a wide bandwidth and to achieve high fidelity. Moreover, in order to improve linearity at far band due to extreme stringent emission mask regulation of the FCC, an auxiliary cancellation branch is adopted. The theoretical derivation in frequency domain is given to prove the system stability and high control bandwidth. Detailed large and small signals analyses of the modulator design are also presented in this paper. The simulation results are provided to verify the proposed design.}, booktitle={2012 twenty-seventh annual ieee applied power electronics conference and exposition (apec)}, author={Lin, P. C. and Huang, A. Q. and Fan, J. W.}, year={2012}, pages={1258–1265} }
 @inproceedings{du_huang_wang_lukic_2012, title={A novel high step-up ratio bi-directional DC-DC converter}, DOI={10.1109/apec.2012.6165870}, abstractNote={High step-up ratio bi-directional DC-DC converter is attractive in energy storage systems for renewable energy generation and in electric vehicle applications. A novel high step-up ratio bi-directional DC-DC converter and its alternative topology which can achieve soft switching in full load range and wide voltage range are proposed. The operation principle of the converter is analyzed in this paper. The modulation strategy and the optimum operation region are presented. A 400kHz 14.4V to 360V prototype was built to verify the analysis and the operation of the proposed converter. Zero voltage switching of all the switches was verified by experimental waveforms. The tested converter efficiency at 450W is 94.1%.}, booktitle={2012 twenty-seventh annual ieee applied power electronics conference and exposition (apec)}, author={Du, Y. and Huang, A. Q. and Wang, M. Q. and Lukic, S. M.}, year={2012}, pages={524–531} }
 @inproceedings{she_huang_ni_burgos_2012, title={AC Circulating Currents Suppression in Modular Multilevel Converter}, DOI={10.1109/iecon.2012.6388809}, abstractNote={Modular multilevel converter is a next generation multilevel converters for medium to high voltage conversion applications, such as medium voltage motor drive and high voltage direct current transmission. One potential issue of this type of converter is the AC circulating current, which increases the current stress and brings additional conduction loss to the system. This paper proposes modified control architecture for modular multilevel converters, aiming at suppressing the AC components in the circulating current. Specifically, a proportional-resonant type minor loop is incorporated to regulate the most AC components of the circulating current to zero in addition to the DC regulation loop. The proposed minor loop can also be applied to single phase MMC, which is not available in previous methods. Simulation results for a three-phase MMC operating as an inverter are provided to demonstrate the feasibility of the proposed method.}, booktitle={38th annual conference on ieee industrial electronics society (iecon 2012)}, author={She, X. and Huang, A. and Ni, X. J. and Burgos, R.}, year={2012}, pages={191–196} }
 @inproceedings{lee_huang_huang_2012, title={An accurate prediction of two-dimensional carrier density profile in IGBT and its significances on steady-state and transient analysis}, DOI={10.1109/ecce.2012.6342637}, abstractNote={This work presents a piecewise two-dimensional steady-state analytical model for insulated gate bipolar transistor (IGBT). The proposed model can accurately describes the dependence of carrier density profile on the ratio of accumulation gate width (Lg) to the half cell width (Lcell) without ignoring the recombination in the drift region. The drift region of IGBT is divided into four regions in this model. By determining the boundary that separates one- and two-dimensional regions, the carrier density profiles in the four regions can be derived with proper boundary conditions. The model is originally developed for, but not limited to, 4H-SiC p-IGBT. The results of proposed model are in good agreement with the simulation results at varied current densities and with different values of Lg/Lcell. The I-V curves in the linear region generated by the proposed model match well with the simulated results. The error of the amount of stored charge generated by one-dimensional model will also be examined.}, booktitle={2012 IEEE Energy Conversion Congress and Exposition (ECCE)}, author={Lee, M. C. and Huang, X. and Huang, A. Q.}, year={2012}, pages={1496–1502} }
 @article{li_huang_liang_bhattacharya_2012, title={Analysis and Design of Active NPC (ANPC) Inverters for Fault-Tolerant Operation of High-Power Electrical Drives}, volume={27}, ISSN={["1941-0107"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84855387046&partnerID=MN8TOARS}, DOI={10.1109/tpel.2011.2143430}, abstractNote={Compared with neutral-point-clamped (NPC) inverters, active NPC (ANPC) inverters enable a substantially increased output power and an improved performance at zero speed for high-power electrical drives. This paper analyzes the operation of three-level (3L) ANPC inverters under device failure conditions, and proposes the fault-tolerant strategies to enable continuous operating of the inverters and drive systems under single and multiple device open- and short-failure conditions. Therefore, the reliability and robustness of the electrical drives are greatly improved. Moreover, the proposed solution adds no additional components to standard 3L-ANPC inverters; thus, the cost for robust operation of drives is lower. Simulation and experiment results are provided for verification. Furthermore, a comprehensive comparison for the reliability function of 3L-ANPC and 3L-NPC inverters is presented. The results show that 3L-ANPC inverters have higher reliability than 3L-NPC inverters when a derating is allowed for the drive system under fault-tolerant operation. If a derated operation is not allowed, the two inverters have similar reliability for device open failure, while 3L-NPC inverters have higher reliability than 3L-ANPC inverters for device short failure.}, number={2}, journal={IEEE TRANSACTIONS ON POWER ELECTRONICS}, author={Li, Jun and Huang, Alex Q. and Liang, Zhigang and Bhattacharya, Subhashish}, year={2012}, month={Feb} }
 @inproceedings{kadavelugu_wang_bhattacharya_huang_2012, title={Auxiliary power supply for Solid State Transformers}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84870892973&partnerID=MN8TOARS}, DOI={10.1109/ecce.2012.6342647}, abstractNote={In contrast to traditional 60 Hz transformer, solid state transformer (SST) offers power flow control, integration of renewables and maintaining grid stability in high renewable penetration scenario. Like a typical power converter, SST requires low voltage (24 V dc) power for its control and sensing circuits. In running condition, this power is derived from its low voltage dc bus at 400 V. But it is challenging to derive it during start-up, because the only source available during start-up is the distribution grid at 7.2 kV, 60 Hz. Due to high input voltage (7.2 kV, 60 Hz), deriving a control supply of about 150 W, even for just start-up duration of about 200 ms, presents a novel power electronics problem. In this paper, two solutions have been proposed to address this issue, by taking a 20 kVA, 6.5 kV Si IGBT and 15 kV SiC MOSFET based SSTs as the reference converters. The first solution is generic and is based on storing the required start-up energy in a dc capacitance. This is based on developing a cost-effective high voltage switch using low voltage IGBTs with self-driven functionality. The second solution, applicable only to SST topologies with high voltage ac capacitive filter, is to tap the energy from the capacitor itself. The fundamental constraints considered for both the solutions are practical feasibility at high voltage (7.2 kV ac or over 10 kV dc), power loss, size, weight and cost-effectiveness. Experimental validation of extracting continuous power for the IGBT gate driver ICs from the snubber is presented with 200 V input. And, the results of the auxiliary power derivation from the filter capacitor are shown with 5.7 kV ac input.}, booktitle={2012 IEEE Energy Conversion Congress and Exposition, ECCE 2012}, author={Kadavelugu, A. and Wang, G. and Bhattacharya, Subhashish and Huang, A.}, year={2012}, pages={1426–1432} }
 @inproceedings{she_huang_2012, title={Circulating Current Control of Double-Star Chopper-Cell Modular Multilevel Converter for HVDC System}, DOI={10.1109/iecon.2012.6388594}, abstractNote={Modular multilevel converter is regarded as a promising technology in high voltage application, such as off-shore wind farm system. This paper proposes control technique for modular multilevel converters, aiming at suppressing the AC components in the circulating current. Specifically, an additional proportional-resonant control loop is designed to regulate the AC component of the circulating current to zero. The proposed method can effectively suppress the AC circulating current even in the unbalanced/fault condition. Simulation results for a 10MVA, 25KV DC system are provided to demonstrate the feasibility of the proposed method.}, booktitle={38th annual conference on ieee industrial electronics society (iecon 2012)}, author={She, X. and Huang, A.}, year={2012}, pages={1234–1239} }
 @article{she_huang_zhao_wang_2012, title={Coupling Effect Reduction of a Voltage-Balancing Controller in Single-Phase Cascaded Multilevel Converters}, volume={27}, ISSN={["1941-0107"]}, DOI={10.1109/tpel.2012.2186615}, abstractNote={This paper presents a new voltage-balancing controller for cascaded multilevel converters, especially for single-phase cascaded multilevel converters. It proposes a control algorithm that devotes itself not only to balancing the floating dc capacitors but also to eliminating the coupling effect between the voltage-balancing controller and the original system controller (controller without additional voltage-balancing controllers). Specifically, the average model in the d-q coordinate frame is derived and the control law is established. Then, the coupling effect between the voltage-balancing controller and the original system controller is identified and a new expression for duty cycle modification is proposed thus to eliminate the effect. Furthermore, this paper gives the design considerations of the pro- posed method, including the derivation of key transfer functions and effective voltage-balancing area, for the completeness of the discussion. Moreover, the reference generation techniques of the voltage-balancing controller are also discussed. This paper investigates the voltage imbalance in the soft-start process caused by an unsuitable reference, and presents a simple modified reference generation solution. Finally, both simulation and experimental results verify the performance of the proposed control system.}, number={8}, journal={IEEE TRANSACTIONS ON POWER ELECTRONICS}, author={She, Xu and Huang, Alex Q. and Zhao, Tiefu and Wang, Gangyao}, year={2012}, month={Aug}, pages={3530–3543} }
 @inproceedings{wang_lu_wang_huang_2012, title={Development of distributed grid intelligence platform for solid state transformer}, DOI={10.1109/smartgridcomm.2012.6486031}, abstractNote={This paper introduces the development of a platform intended as a distributed controller for grid intelligence (DGI) system at FREEDM Systems Center. This platform serves as both a hard real-time local converter controller and a communication node for distributed deployment of energy management schemes. One of the converter devices it controls is the solid state transformer (SST), one of the key elements to interface renewable energy sources into distribution system in FREEDM Center. Both the hardware design and software structure for SST control are presented in this paper. For the communication part, the Distributed Network Protocol (DNP) 3.0 is adopted to congregate multiple SSTs to balance local generation and demands in a coordinated manner. Experiment results are presented to show that this distributed platform has good performance.}, booktitle={2012 IEEE Third International Conference on Smart Grid Communications (SmartGridComm)}, author={Wang, F. and Lu, X. and Wang, Wenye and Huang, A.}, year={2012}, pages={481–485} }
 @inproceedings{van brunt_huang_butschen_de doncker_2012, title={Dual-GCT design criteria and voltage scaling}, DOI={10.1109/ecce.2012.6342394}, abstractNote={Global optimization has been performed to derive optimal Dual-GCT structures for 3.3 kV, 5 kV, and 6.5 kV class devices by using numerical simulation results. A treatment of all relevant physical concepts for both standard- and Dual-GCTs are taken into account in the optimization process, providing an insight into the effect of design parameters such as minority carrier lifetime, buffer region design, and device geometry. The results indicate that within the scope of a Dual Active Bridge power converter application, the Dual-GCT can provide more than 54 % improvement in the current density when compared to equivalent conventional devices for each of the device ratings examined, which verifies the scalability of the Dual-GCT concept.}, booktitle={2012 IEEE Energy Conversion Congress and Exposition (ECCE)}, author={Van Brunt, E. and Huang, A. Q. and Butschen, T. and De Doncker, R. W.}, year={2012}, pages={2596–2603} }
 @inproceedings{wang_huang_wang_she_burgos_2012, title={Feed-forward control of solid state transformer}, DOI={10.1109/apec.2012.6165964}, abstractNote={The solid state transformer (SST) can be viewed as an energy router for electricity in an analogous way to what network routers are for information. The SST impact on the system can be hence paramount, especially in terms of stability since it is essentially an active closed-loop regulated power converter. Within the SST itself however, with its different ac-dc, dc-dc and dc-ac stages, stability is also crucial, as it is well understood that for cascaded converter systems the interaction between stages is the cause of instability from a small-signal perspective. This paper represents an initial quest into the SST stability study, exploring two feed-forward control schemes for the ac-dc and dc-dc converter stages. Simulation and experimental results with a 7.2 kV ac 400 V dc, 20 kW laboratory prototype are presented for validation purposes.}, booktitle={2012 twenty-seventh annual ieee applied power electronics conference and exposition (apec)}, author={Wang, F. and Huang, A. and Wang, G. Y. and She, X. and Burgos, R.}, year={2012}, pages={1153–1158} }
 @inproceedings{liang_huang_guo_2012, title={High efficiency switched capacitor buck-boost converter for PV application}, DOI={10.1109/apec.2012.6166090}, abstractNote={A switched capacitor buck-boost DC/DC converter is proposed for the parallel connected distributed photovoltaic (PV) power generation application: an uncontrolled switched capacitor resonant converter is in parallel connection with a buck-boost converter where their outputs are summed to support the load. The switched capacitor converter is operated with a fixed conversion gain whereas the buck-boost converter is controlled to do the MPPT regulation and only a small portion of energy flows through it. In order to obtain ZVS for switched capacitor circuit in the full load range, an auxiliary inductor is added. The converter's performance has been evaluated on a 240W experimental prototype. The test results show that 92.5% efficiency is achieved to generate 200V high output voltage from a 60 cells crystalline PV module with Vmpp=30V.}, booktitle={2012 twenty-seventh annual ieee applied power electronics conference and exposition (apec)}, author={Liang, Z. G. and Huang, A. Q. and Guo, R.}, year={2012}, pages={1951–1958} }
 @article{du_lukic_jacobson_huang_2012, title={Modulation Technique to Reverse Power Flow for the Isolated Series Resonant DC-DC Converter With Clamped Capacitor Voltage}, volume={59}, ISSN={["1557-9948"]}, DOI={10.1109/tie.2011.2175669}, abstractNote={The series resonant dc-dc converter with clamped capacitor voltage exhibits excellent characteristics in forward operating mode, including simple control, high reliability, soft switching, high power density, and inherently limited load fault current. However, the conventional single angle phase-shift modulation that works well in the forward mode cannot reverse the power flow. In this paper, we propose a modulation strategy for reverse-mode operation by utilizing three phase-shift angles afforded by the two active full bridges of the circuit. We identify the optimal modulation trajectories in 3-D modulation space and implement a lookup-table-based modulator for power flow control. A high-fidelity simulation model of a 35-kW 750-V input, 300-600-V output, and 50-kHz insulated-gate bipolar-transistor-based converter was used for verification. The proposed modulation scheme and efficiency calculations were validated on a scaled-down (15-kW) prototype. The power loss distribution was analyzed for further converter efficiency optimization.}, number={12}, journal={IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS}, author={Du, Yu and Lukic, Srdjan M. and Jacobson, Boris S. and Huang, Alex Q.}, year={2012}, month={Dec}, pages={4617–4628} }
 @article{lee_kirkpatrick_choi_yang_huang_misra_2012, title={Normally-off AlGaN/GaN MOSHFET using ALD SiO2 tunnel dielectric and ALD HfO2 charge storage layer for power device application}, volume={9}, ISSN={["1862-6351"]}, DOI={10.1002/pssc.201100422}, abstractNote={Abstract}, number={3-4}, journal={PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 9, NO 3-4}, author={Lee, Bongmook and Kirkpatrick, Casey and Choi, Young-hwan and Yang, Xiangyu and Huang, Alex Q. and Misra, Veena}, year={2012}, pages={868–870} }
 @article{huang_van brunt_baliga_huang_2012, title={Orthogonal Positive-Bevel Termination for Chip-Size SiC Reverse Blocking Devices}, volume={33}, ISSN={["1558-0563"]}, DOI={10.1109/led.2012.2215003}, abstractNote={Symmetric blocking power semiconductor switches require positive-bevel edge terminations for the reverse blocking p-n junction. This technique has been extensively applied to silicon wafer-size devices with high current ratings. In this letter, we propose and experimentally demonstrate, for the first time, that an orthogonal positive-bevel termination can be used for the reverse blocking junction of chip-size SiC devices. The edge termination was formed by sawing the SiC wafer with a V-shaped dicing blade. For proof of concept, our experiment was done on a SiC wafer with a 15.8-μm 6.1 × 1015 cm-3 p-type epitaxial layer grown on an N+ substrate. The positive-bevel termination resulted in a breakdown voltage of over 1000 V as limited by reach-through breakdown even without removal of damage from the sawing. The leakage current was found to be reduced by two orders of magnitude after reactive ion etching of the SiC bevel surface to remove the sawing damage.}, number={11}, journal={IEEE ELECTRON DEVICE LETTERS}, author={Huang, Xing and Van Brunt, Edward and Baliga, B. Jayant and Huang, Alex Q.}, year={2012}, month={Nov}, pages={1592–1594} }
 @inproceedings{yu_wang_huang_2012, title={Power management strategy for plug and play DC microgrid}, DOI={10.1109/isgteurope.2012.6465882}, abstractNote={DC microgrid is getting more and more attention as an effective and efficient solution to integrate different kinds of renewable energy storage and energy resources with DC loads. A typical DC microgrid envisioned for future DC powered residential homes is investigated in this paper, including distributed power management strategy design, plug and play function implementation, communication ports to monitor the system performance. In this power management strategy, each module in the system is in the distributed control and can be plugged and unplugged into the system without affecting the system performance. Furthermore, the communication ports guarantee all modules information can be sent to the control center to monitor the whole system information.}, booktitle={2012 3rd ieee pes innovative smart grid technologies europe (isgt europe)}, author={Yu, X. W. and Wang, F. and Huang, A. Q.}, year={2012} }
 @inproceedings{huang_wang_lee_huang_2012, title={Reliability of 4H-SiC SBD/JBS diodes under repetitive surge current stress}, DOI={10.1109/ecce.2012.6342436}, abstractNote={The reliability of power diode under surge current stress is crucial to the applications like motor drives. In this paper, the single and repetitive surge reliability of the 4H-SiC Schottky Barrier Diodes (SBDs) and Junction Barrier Schottky (JBS) diodes have been tested and the corresponding failure mechanisms studied. The single surge test results of two SBDs and three JBS didoes suggest a 450W/mm2 constant power line of the safe operation area for single surge current with a half sinusoidal pulse width of 8.3ms. The stress tests show no degradation of SBDs up to 10,000 cycles of surge current below 34.9A/mm2. The JBS diodes show VF degradation after surge stress at different current levels, which might be dependent on the hole injection levels. The aluminum metallization and bipolar degradation are the main limits for the reliability of SiC diodes under surge conditions.}, booktitle={2012 IEEE Energy Conversion Congress and Exposition (ECCE)}, author={Huang, X. and Wang, G. Y. and Lee, M. C. and Huang, A. Q.}, year={2012}, pages={2245–2248} }
 @inproceedings{she_burgos_wang_wang_huang_2012, title={Review of solid state transformer in the distribution system: From components to field application}, DOI={10.1109/ecce.2012.6342269}, abstractNote={The emergence of high power converters makes the modern power grid more active than it was before. One of the research directions in this area is the solid state transformer, which aims at replacing the traditional 50/60 Hz power transformer by means of high frequency isolated AC/AC solid state conversion techniques. This paper presents a systematical technology review essential for the development of solid state transformer in the distribution system, especially focusing on the following four areas: high voltage and high frequency power devices, high power and high frequency transformers, AC/AC converter topologies, and applications of solid state transformer in the distribution system. For each category, the state-of-art technologies are reviewed and possible research directions are presented. It is concluded that the solid state transformer is an emerging technology for the modernization of the future smart grid.}, booktitle={2012 IEEE Energy Conversion Congress and Exposition (ECCE)}, author={She, X. and Burgos, R. and Wang, G. Y. and Wang, F. and Huang, A. Q.}, year={2012}, pages={4077–4084} }
 @inproceedings{huang_wang_jiang_huang_2012, title={Ruggedness analysis of 600V 4H-SiC JBS diodes under repetitive avalanche conditions}, DOI={10.1109/apec.2012.6166048}, abstractNote={The repetitive avalanche reliability of power rectifiers is crucial to the safe operation of the hard switching power converters under extreme conditions as well as transient voltage suppression (TVS) applications. In this paper, the ruggedness of two state-of-art 4H-SiC Junction Barrier Schottky (JBS) diodes under repetitive avalanche stresses has been studied. Two different post-stress behaviors have been observed: VF degradation and BV drifting for the two different JBS diodes. The VF degradation could happen to the device that avalanches in the active area. However, for the device that avalanches in the edge termination, the repetitive avalanche stress greatly increases the breakdown voltage for about 100V. These results bring new concerns for SiC devices that are expected to be operated in avalanche conditions.}, booktitle={2012 twenty-seventh annual ieee applied power electronics conference and exposition (apec)}, author={Huang, X. and Wang, G. Y. and Jiang, L. and Huang, A. Q.}, year={2012}, pages={1688–1691} }
 @inproceedings{chen_tan_huang_2012, title={Self-power emitter turn-off thyristor (SPETO) based circuit breaker for power distribution system}, DOI={10.1109/ecce.2012.6342564}, abstractNote={Compared to mechanical solution, solid-state circuit breaker (SSCB) offers enormous advantages in terms of switching speed and maintenance. With fast switching performance, high current turn-off capability, self-power and built-in sensor functions, SPETO is a very promising high power switching device for the application of SSCB in power distribution system. The experimental results show that the SPETO based SSCB can turn off current quickly and works well with self-power function, and therefore is suitable for SSCB in power distribution system.}, booktitle={2012 IEEE Energy Conversion Congress and Exposition (ECCE)}, author={Chen, Q. and Tan, K. and Huang, A. Q.}, year={2012}, pages={2017–2021} }
 @inproceedings{she_wang_burgos_huang_2012, title={Solid state transformer interfaced wind energy system with integrated active power transfer, reactive power compensation and voltage conversion functions}, DOI={10.1109/ecce.2012.6342508}, abstractNote={As the power of wind energy system increases, the control of their active and reactive power becomes increasingly more important from a system standpoint given that these are typical frequency and voltage control parameters. In this paper a family of wind energy systems with integrated active power transfer, reactive power compensation and voltage-conversion functionality is proposed. The proposed wind energy systems using solid state transformer (SST) can effectively suppress the voltage fluctuation caused by the transient nature of wind energy without additional reactive power compensator and as such may enable the large penetration of wind farm (WF) into the distribution system. To this end, a simulation study for WF driven by squirrel-cage induction generators is presented to verify the effectiveness of the proposed system. In addition, a modular type high voltage and high power three-phase SST topology is presented for the proposed system, and its basic building block, which is a single-phase SST, is analyzed. The function of SST in the presented wind energy system is verified in a single-phase laboratory prototype with scaled down experiments.}, booktitle={2012 IEEE Energy Conversion Congress and Exposition (ECCE)}, author={She, X. and Wang, F. and Burgos, R. and Huang, A. Q.}, year={2012}, pages={3140–3147} }
 @article{kirkpatrick_lee_choi_huang_misra_2012, title={Threshold voltage stability comparison in AlGaN/GaN FLASH MOS-HFETs utilizing charge trap or floating gate charge storage}, volume={9}, ISSN={["1862-6351"]}, DOI={10.1002/pssc.201100421}, abstractNote={Abstract}, number={3-4}, journal={PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 9, NO 3-4}, author={Kirkpatrick, Casey and Lee, Bongmook and Choi, YoungHwan and Huang, Alex and Misra, Veena}, year={2012}, pages={864–867} }
 @inproceedings{rezaei_huang_2012, title={Ultra fast protection of radial and looped electric power grid using a novel solid-state protection device}, DOI={10.1109/ecce.2012.6342765}, abstractNote={Exploiting the fast operation of solid-state Fault Isolation Devices (FIDs), this paper presents a novel over-current protection scheme for radial and looped electric power distribution systems. The main feature of the proposed protection scheme is that it ensures the maximum restoration of the system in less than a quarter of the electric cycle. Due to the inherent characteristics of the solid-state devices, the FID is also able to limit the fault current to the maximum allowable fault current level of the system, thus reducing the thermal and mechanical stress on transformers and other power system equipments. Using the inherent characteristics of the solid state devices, a novel fault detection criteria is also proposed that eliminates the necessity of the current sensor or transformer (CT) for detecting the over-current fault. These advantages are all achieved without requiring communication between FIDs. Performance of the FID with the proposed protection scheme is demonstrated based on an all-analog logic-level grid-voltage scale experimental setup. The experiments demonstrate the capability of the proposed protection scheme to fulfill the demands of highly inter-connected electric power distribution systems.}, booktitle={2012 IEEE Energy Conversion Congress and Exposition (ECCE)}, author={Rezaei, M. A. and Huang, A.}, year={2012}, pages={610–614} }
 @inproceedings{wang_huang_li_2012, title={ZVS range extension of 10A 15kV SiC MOSFET based 20kW dual active half bridge (DHB) DC-DC converter}, DOI={10.1109/ecce.2012.6342631}, abstractNote={SiC MOSFET is favorable for high voltage applications due to its fast switching speed, low loss and high voltage rating compared with silicon power devices. This paper presents the switching performance of 10A 15kV SiC MOSFET and analyzes its switching loss when considering the impact of parasitic capacitance. A 20 kHz 20 kW Dual Active Half Bridge (DHB) dc-dc converter based on this new device is designed with full ZVS range. Simulation and experiment results are given to validate the analysis.}, booktitle={2012 IEEE Energy Conversion Congress and Exposition (ECCE)}, author={Wang, G. Y. and Huang, A. and Li, C. S.}, year={2012}, pages={1533–1539} }
 @article{liang_guo_li_huang_2011, title={A High-Efficiency PV Module-Integrated DC/DC Converter for PV Energy Harvest in FREEDM Systems}, volume={26}, ISSN={["1941-0107"]}, DOI={10.1109/tpel.2011.2107581}, abstractNote={The future renewable electric energy delivery and management (FREEDM) system provides a dc interface for alternative energy sources. As a result, photovoltaic (PV) energy can be easily delivered through a dc/dc converter to the FREEDM system's dc bus. The module-integrated converter (MIC) topology is a good candidate for a PV converter designed to work with the FREEDM system. This paper compares the parallel connected dc MIC structure with its counterpart, the series connected MIC architecture. From the presented analysis, the parallel connected architecture was shown to have more advantages. In this paper, a high-efficiency dual mode resonant converter topology is proposed for parallel connected dc MICs. This new resonant converter topology can change resonant modes adaptively depending on the panel operation conditions. The converter achieves zero-voltage switching for primary-side switches and zero-current switching for secondary-side diodes for both resonant modes. The circulation energy is minimized particularly for 5-50% of the rated power level. Thus, the converter can maintain a high efficiency for a wide input range at different output power levels. This study explains the operation principle of the proposed converter and presents a dc gain analysis based on the fundamental harmonic analysis method. A 240-W prototype with an embedded maximum power point tracking controller was built to evaluate the performance of the proposed converter. The prototype's maximum efficiency reaches 96.5% and an efficiency increase of more than 10% under light load conditions is shown when compared with a conventional LLC resonant converter.}, number={3}, journal={IEEE TRANSACTIONS ON POWER ELECTRONICS}, author={Liang, Zhigang and Guo, Rong and Li, Jun and Huang, Alex Q.}, year={2011}, month={Mar}, pages={897–909} }
 @article{sung_van brunt_baliga_huang_2011, title={A New Edge Termination Technique for High-Voltage Devices in 4H-SiC-Multiple-Floating-Zone Junction Termination Extension}, volume={32}, ISSN={["0741-3106"]}, DOI={10.1109/led.2011.2144561}, abstractNote={A new edge termination method, referred to as multiple-floating-zone junction termination extension (MFZ-JTE), is presented for high-voltage devices in 4H-SiC. 4H-SiC PiN rectifiers with a breakdown voltage of 10 kV (about 88% of the theoretical value) were fabricated using MFZ-JTEs. The MFZ-JTE technique only requires a single pattern-and-implant step while providing significant process latitude for parameter variations such as implantation dose and activation anneal condition.}, number={7}, journal={IEEE ELECTRON DEVICE LETTERS}, author={Sung, Woongje and Van Brunt, Edward and Baliga, B. J. and Huang, Alex Q.}, year={2011}, month={Jul}, pages={880–882} }
 @article{li_bhattacharya_huang_2011, title={A New Nine-Level Active NPC (ANPC) Converter for Grid Connection of Large Wind Turbines for Distributed Generation}, volume={26}, ISSN={["1941-0107"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-79957505632&partnerID=MN8TOARS}, DOI={10.1109/tpel.2010.2093154}, abstractNote={Wind power is one of the most promising emerging renewable energy technologies for distributed generation (DG). In this paper, a new nine-level active neutral-point-clamped (9L ANPC) converter is proposed for the grid connection of large wind turbines (WTs) to improve the waveform quality of the converter output voltage and current. Therefore, the bulky passive grid filters can be reduced or even removed. The topology, operating principles, control schemes, and main features, as well as semiconductor device selection of the proposed converter are presented in detail. The floating capacitor voltage control based on redundant switching states and capacitor prioritization is detailed. A comparison between the new topology and other existing 9L topologies is presented to illustrate the characteristics and performance of the new converter. The proposed 9L ANPC converter is studied in the case of the grid connection of a 6-MW WT without using passive grid filters in DG systems. Simulation and experiment results are presented to validate the proposed converter topology and control schemes. The proper operation and the compliance to the harmonic limit standards of the filterless grid-connected WT system are verified by simulation results.}, number={3}, journal={IEEE TRANSACTIONS ON POWER ELECTRONICS}, author={Li, Jun and Bhattacharya, Subhashish and Huang, Alex Q.}, year={2011}, month={Mar}, pages={961–972} }
 @inproceedings{chen_huang_lukic_svensson_li_wang_2011, title={A comparison of medium voltage high power DC/DC converters with high step-up conversion ratio for offshore wind energy systems}, DOI={10.1109/ecce.2011.6063822}, abstractNote={As one of the most important renewable energy sources, wind is widely utilized now. As well as onshore trend, offshore wind farms have also been continuing its growth rapidly due to much better wind conditions. One of the interesting options for offshore wind farms is a wind farm with an internal medium voltage DC (MVDC)-grid collection connected to a high voltage direct current (HVDC) transmission. Medium voltage high power DC/DC converters with high step-up conversion ration are the key components in the MVDC-grid collection offshore wind farms. In this paper, a review of medium voltage high power DC/DC converter topologies with high step-up conversion ratio is presented. The advantages and disadvantages of these converters are discussed. Finally, this paper lists some major challenges for the high power MVDC converters.}, booktitle={2011 IEEE Energy Conversion Congress and Exposition (ECCE)}, author={Chen, W. and Huang, A. and Lukic, S. and Svensson, J. and Li, J. and Wang, Z. Y.}, year={2011}, pages={584–589} }
 @inproceedings{liang_guo_huang_2011, title={A high efficiency DC MIC for PV energy harvest in FREEDM systems}, DOI={10.1109/apec.2011.5744612}, abstractNote={The future renewable electric energy delivery and management (FREEDM) system provides a DC interface for alternative energy sources. As a result, photovoltaic (PV) energy can be easily delivered through a DC/DC converter to the FREEDM system's DC bus, without the requirement of an additional DC/AC inverter. For this PV converter, the module integrated converter (MIC) is a good candidate. In this paper, two types of DC MIC structures, parallel connected MICs and series connected MICs, have been compared; the parallel connected MICs have been shown to have more advantages. Then a high efficiency dual mode resonant converter topology is proposed for parallel connected DC MICs. The new resonant converter can change resonant modes adaptively depending on the panel voltage and generated power level. The operation principle of the proposed converter is explained and a DC gain analysis is performed based on the fundamental harmonic analysis (FHA) method. For performance evaluation, a 240W prototype has been built. Compared to LLC converter, the light load to medium load efficiency has been improved greatly and the maximum efficiency reaches 96.5% in the experiment.}, booktitle={Annual ieee conference on applied power electronics conference and}, author={Liang, Z. G. and Guo, R. and Huang, A. Q.}, year={2011}, pages={301–308} }
 @inproceedings{guo_liang_huang_2011, title={A high efficiency transformerless step-up DC-DC converter with high voltage gain for LED backlighting applications}, DOI={10.1109/apec.2011.5744767}, abstractNote={Single Boost converter has several limitations in driving a long LED string although it can have perfect current match between each LED. Extreme duty cycle and low efficiency are the two major drawbacks. In this paper, a high efficiency step-up DC-DC converter with high voltage gain for LED backlighting applications is proposed. Without using a transformer, a multi-modes charge-pump is cascaded with a Boost converter to achieve high gain. The charge-pump is unregulated and can switch between 1x, 2x, and 3x mode according to the output requirement. The LED current is regulated by controlling the duty cycle of the Boost converter. The charge pump is located at the low current side therefore can have very high efficiency. The Boost converter is located at the low voltage side and can operate at a relatively low duty cycle, thus the efficiency is improved. The proposed solution can achieve high voltage gain as well as high overall efficiency. The control will also be benefited by the two stage solution. Theoretical efficiency derivations are given in this paper. A prototype is built and the experiment shows a maximum 10.5% efficiency improvement when driving 11 LEDs from 2.7V input voltage.}, booktitle={Annual ieee conference on applied power electronics conference and}, author={Guo, R. and Liang, Z. G. and Huang, A. Q.}, year={2011}, pages={1350–1356} }
 @inproceedings{she_huang_wang_zhao_wang_yao_2011, title={A new voltage-balancing controller in cascaded multilevel converters}, DOI={10.1109/ecce.2011.6063766}, abstractNote={Voltage-balancing controller in cascaded multilevel converters has been discussed extensively in previous literatures where several effective methods have been proposed. The coupling effect between a voltage-balancing controller and the original system controller is however not addressed comprehensively. This paper proposes a new voltage-balancing controller for single-phase cascaded multilevel converters in a d-q coordinate. The theoretical finding shows that the proposed method can effectively eliminate the coupling between two controllers in both steady and dynamic state. Simulation and experimental results validate the proposed method.}, booktitle={2011 IEEE Energy Conversion Congress and Exposition (ECCE)}, author={She, X. and Huang, A. Q. and Wang, G. Y. and Zhao, T. F. and Wang, F. and Yao, W. X.}, year={2011}, pages={177–184} }
 @inproceedings{chen_huang_2011, title={Analysis of impact of self-power function on emitter turn-off thyristor}, DOI={10.1109/ecce.2011.6064013}, abstractNote={Self-power emitter turn-off thyristor (SPETO) is a high power switching device which could provide power for its gate drive during operation. Self-power function reduces the system cost and makes the mechanical structure compact, whereas it may bring extra harmonic when SPETO is to be utilized in high power utilities. In this paper, the impact of self-power function on extra harmonic is analyzed; the ideas to attenuate the impact are presented and verified by the analysis, simulation and experimental results.}, booktitle={2011 IEEE Energy Conversion Congress and Exposition (ECCE)}, author={Chen, Q. and Huang, A. Q.}, year={2011}, pages={1868–1872} }
 @inproceedings{wang_huang_2011, title={Capacitor energy variation based designer-side switching losses analysis for integrated synchronous buck converters in CMOS technology}, DOI={10.1109/apec.2011.5744736}, abstractNote={This paper introduces a designer-side switching loss analysis characterized by evaluating parasitic capacitor's energy variation and related losses for integrated synchronous Buck converters in CMOS technology (ISBC). After categorizing losses related to power FET parasitic capacitors' charging/discharging currents as charging/discharging losses (C_loss), it is noticed that the ratio of charging/discharging losses over capacitor's energy variation (ROCL) presents two extreme values; one of which is almost 100% and the other one is ignorable. Also, the same capacitor might encounter different ROCL when switching event is different. Five typical kinds of charging/discharging circuits are further classified in terms of ROCL. In order to evaluate parasitic capacitor's energy variation in a complete switching event, a hypothesis equation is adopted to cope with the variation of capacitance because of the operation mode shift of the power FET. At the same time, a process is introduced about how to verify the hypothesis and extract the unit width variables involved in the energy variation evaluation. The proposed switching losses analysis can provide losses breakdown in terms of semiconductor process technology data. At the same time, the analysis overcomes limitations in previous methods and supports the switching losses analysis for those advanced ISBC utilizing power stage width segmentation technology for the sake of wide load range efficiency. Transistor level simulation in Cadence environment verifies the analysis.}, booktitle={Annual ieee conference on applied power electronics conference and}, author={Wang, X. P. and Huang, A. Q.}, year={2011}, pages={1130–1137} }
 @inproceedings{wang_she_wang_kadavelugu_zhao_huang_yao_2011, title={Comparisons of different control strategies for 20kVA solid state transformer}, DOI={10.1109/ecce.2011.6064196}, abstractNote={This paper presents and compares different control strategies for 20kVA silicon IGBT based solid state transformer (SST). The SST has a cascaded seven level rectifier stage, three output parallel Dual Active Bridge (DAB) DC/DC stage and an inverter stage. The voltage of the three high voltage capacitors must be balanced for the safe operation of the IGBTs, however, the mismatch of power devices parameters and variance of high frequency transformer leakage inductance of the DAB stage will cause voltage unbalance for these capacitors as well as the power unbalance of the three output parallel DAB stages. This paper analyzed these effects and discussed the limitations and merits for several different control strategies. The newly proposed control strategy for the SST has been determined as the most suitable strategy in terms of performance and simplicity. Simulation and experiment results are presented to validate the analysis.}, booktitle={2011 IEEE Energy Conversion Congress and Exposition (ECCE)}, author={Wang, G. Y. and She, X. and Wang, F. and Kadavelugu, A. and Zhao, T. F. and Huang, A. and Yao, W. X.}, year={2011}, pages={3173–3178} }
 @inproceedings{wang_huang_2011, title={Considerations on the optimal power stage segmentation algorithm for MHz integrated synchronous Buck DC-DC converters}, DOI={10.1109/ispsd.2011.5890821}, abstractNote={For those MHz integrated synchronous Buck DC-DC converters (ISBC), a power stage segmentation technique might be applied for the sake of improving light load efficiency. The paper discusses the difference about efficiency in the case that losses contributions from Cds and Cgd in inactive power FET subcells are considered or not and indicates the existence of efficiency optimization's saturation effect in respect to the number of active power FET cells. After that, the paper presents the variation characteristics of power FET rdson using On-Semi SCN05 technology's eight manufacturing runs and temperature shift as two example cases. The variation of rdson implies that practical efficiency might deviate from an expected one, provided that the number of active power FET subcells is selected to be linearly proportional to the load current as that implemented in nowadays power FET width segmentation algorithms. Finally, the paper suggests a novel segmentation algorithm with automatic rdson compensation ability.}, booktitle={Proceedings of the international symposium on power semiconductor}, author={Wang, X. P. and Huang, A. Q.}, year={2011}, pages={184–187} }
 @inproceedings{wang_baek_elliott_kadavelugu_wang_she_dutta_liu_zhao_yao_et al._2011, title={Design and hardware implementation of Gen-1 silicon based solid state transformer}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-79955785263&partnerID=MN8TOARS}, DOI={10.1109/apec.2011.5744766}, abstractNote={This paper presents the design and hardware implementation and testing of 20kVA Gen-1 silicon based solid state transformer (SST), the high input voltage and high voltage isolation requirement are two major concerns for the SST design. So a 6.5kV 25A dual IGBT module has been customized packaged specially for this high voltage low current application, and an optically coupled high voltage sensor and IGBT gate driver has been designed in order to fulfill the high voltage isolation requirement. This paper also discusses the auxiliary power supply structure and thermal management for the SST power stage.}, booktitle={Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC}, author={Wang, G. and Baek, S. and Elliott, J. and Kadavelugu, A. and Wang, F. and She, X. and Dutta, S. and Liu, Y. and Zhao, T. and Yao, W. and et al.}, year={2011}, pages={1344–1349} }
 @article{zhang_huang_2011, title={Model-based fault detection of hybrid fuel cell and photovoltaic direct current power sources}, volume={196}, ISSN={["1873-2755"]}, DOI={10.1016/j.jpowsour.2011.01.089}, abstractNote={Abstract Hybrid DC power sources which consist of fuel cells, photovoltaic and lithium-ion batteries provide clean, high efficiency power supply. This hybrid DC power sources can be used in many applications. In this work, a model-based fault detection methodology for this hybrid DC power sources is presented. Firstly, the dynamic models of fuel cells, photovoltaic and lithium-ion batteries are built. The state space model of hybrid DC power sources is obtained by linearizing these dynamic models in operation points. Based on this state space model the fault detection methodology is proposed. Simulation results show that model-based fault detection methodology can find the fault on line, improve the generation time and avoid permanent damage to the equipment.}, number={11}, journal={JOURNAL OF POWER SOURCES}, author={Zhang, Liyan and Huang, Alex Q.}, year={2011}, month={Jun}, pages={5197–5204} }
 @inproceedings{she_lukic_huang_bhattacharya_baran_2011, title={Performance evaluation of solid state transformer based microgrid in FREEDM systems}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-79955771308&partnerID=MN8TOARS}, DOI={10.1109/apec.2011.5744594}, abstractNote={A new concept of solid state transformer based microgrid system is presented in this paper. By utilizing 400V DC bus generated from Gen-I solid state transformer proposed by FREEDM systems center, integration issues of DC microgrid and solid state transformer are analyzed. Zonal DC microgrid concept is applied to this novel system with the consideration of burden minimization to the existing AC grid. The future grid architecture is described by using this solid state transformer based integrated microgrid system.}, booktitle={Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC}, author={She, X. and Lukic, Srdjan and Huang, A.Q. and Bhattacharya, Subhashish and Baran, M.}, year={2011}, pages={182–188} }
 @article{shi_gou_yuan_zhao_huang_2011, title={Research on Voltage and Power Balance Control for Cascaded Modular Solid-State Transformer}, volume={26}, ISSN={["1941-0107"]}, DOI={10.1109/tpel.2011.2106803}, abstractNote={The solid-state transformer (SST) is one of the key elements in power electronic-based microgrid systems. The single-phase SST consists of a modular multilevel ac-dc rectifier, a modular dual active bridge (DAB) dc-dc converter with high-frequency transformers, and a dc-ac inverter stage. However, due to dc bus voltage and power unbalancing in each module, the modular SST often presents instability problems making its design difficult and causing unpredictable behavior. Moreover, the unbalanced dc-link voltages increase the stress of the semiconductor devices, and also cause high harmonic distortions of grid current, therefore, necessitating the use of a bigger ac filter. This paper presents a novel single-phase d-q vector-based common-duty-ratio control method for the multilevel rectifier, and a voltage feedforward and feedback based controller for the modular DAB converter. With the proposed control methods, the dc-link voltage and power in each module can be balanced. In addition, the low-distortion grid current, unity power factor, and bidirectional power flow can be achieved. Simulation and experimental results are presented to validate the proposed control methods.}, number={4}, journal={IEEE TRANSACTIONS ON POWER ELECTRONICS}, author={Shi, Jianjiang and Gou, Wei and Yuan, Hao and Zhao, Tiefu and Huang, Alex Q.}, year={2011}, month={Apr}, pages={1154–1166} }
 @inproceedings{du_lukic_jacobson_huang_2011, title={Review of high power isolated Bi-directional DC-DC converters for PHEV/EV DC charging infrastructure}, DOI={10.1109/ecce.2011.6063818}, abstractNote={PHEV/EV DC charging infrastructure attracts more and more attention recently. High power isolated bi-directional DC-DC converters provide galvanic isolation, V2G capability and reduce the cost and footprint of the system. Maintaining high power efficiency in wide vehicle battery pack voltage range is required. Three full bridge based high power bi-directional DC-DC converters are conceptually designed for this application and their advantages and disadvantages are addressed. Experimental test bench is built and efficiency evaluation for bi-directional operation is reported.}, booktitle={2011 IEEE Energy Conversion Congress and Exposition (ECCE)}, author={Du, Y. and Lukic, S. and Jacobson, B. and Huang, A.}, year={2011}, pages={553–560} }
 @article{huang_crow_heydt_zheng_dale_2011, title={The Future Renewable Electric Energy Delivery and Management (FREEDM) System: The Energy Internet}, volume={99}, ISSN={["1558-2256"]}, DOI={10.1109/jproc.2010.2081330}, abstractNote={This paper presents an architecture for a future electric power distribution system that is suitable for plug-and-play of distributed renewable energy and distributed energy storage devices. Motivated by the success of the (information) Internet, the architecture described in this paper was proposed by the NSF FREEDM Systems Center, Raleigh, NC, as a roadmap for a future automated and flexible electric power distribution system. In the envisioned “Energy Internet,” a system that enables flexible energy sharing is proposed for consumers in a residential distribution system. The key technologies required to achieve such a vision are presented in this paper as a result of the research partnership of the FREEDM Systems Center.}, number={1}, journal={PROCEEDINGS OF THE IEEE}, author={Huang, Alex Q. and Crow, Mariesa L. and Heydt, Gerald Thomas and Zheng, Jim P. and Dale, Steiner J.}, year={2011}, month={Jan}, pages={133–148} }
 @article{guo_yang_huang_endredy_2010, title={A High Efficiency Regulated Charge Pump over Wide Input and Load Range}, ISSN={["1048-2334"]}, DOI={10.1109/apec.2010.5433355}, abstractNote={A multi-modes regulated charge pump with improved efficiency over wide input and load range is proposed in this paper. The output voltage is regulated to 5V when input is 4.5–2.7V. By alternating the switch network, it can realize 2x, 1.5x, and 1.33x conversion modes, which improves the efficiency over wide input range. During each mode, the output voltage is regulated by a controlled current source. The regulated charge pump is designed for a very wide load range (10mA to 500mA). A hybrid control scheme is proposed and analyzed to achieve a high efficiency over desired load range. Both of the simulation and test results are provided to verify the control scheme. The results show that the total loss at light load can be reduced by 56% to 83%.}, journal={2010 TWENTY-FIFTH ANNUAL IEEE APPLIED POWER ELECTRONICS CONFERENCE AND EXPOSITION (APEC)}, author={Guo, Rong and Yang, Liyu and Huang, Alex and Endredy, John}, year={2010}, pages={1172–1176} }
 @article{zhou_liang_huang_2010, title={A High-Dynamic Range Current Source Gate Driver for Switching-Loss Reduction of High-Side Switch in Buck Converter}, volume={25}, ISSN={["1941-0107"]}, DOI={10.1109/tpel.2009.2039649}, abstractNote={In this letter, a high-dynamic range current source gate driver (HD-CSD) circuit is proposed to reduce the switching loss of the high-side switch in buck converter with wide variation of the gate resistance. Hard switching loss is the major loss in high-side switch and limits the high switching-frequency application of dc-dc converter. Comparing with conventional voltage source gate driver (VSD) and the reported four switches CSD (4S-CSD), the proposed HD-CSD behaves more like the ideal current source driver which can realize the fast switching of power switches to reduce the switching loss. In addition, with proposed HD-CSD, impact of gate resistance that limits the switching speed of the power switch can be greatly reduced. Experimental results are presented to show the power efficiency improvement of buck converter with HD-CSD high-side driver comparing with VSD and 4S-CSD high-side drivers at switching frequency of 1 MHz.}, number={6}, journal={IEEE TRANSACTIONS ON POWER ELECTRONICS}, author={Zhou, Xin and Liang, Zhigang and Huang, Alex}, year={2010}, month={Jun}, pages={1439–1443} }
 @article{zhou_liang_huang_2010, title={A New Resonant Gate Driver for Switching Loss Reduction of High Side Switch in Buck Converter}, ISSN={["1048-2334"]}, DOI={10.1109/apec.2010.5433425}, abstractNote={In this paper, a new resonant gate driver circuits is proposed to reduce the switching loss of high side switch in buck converter. Hard switching causes major parts of the power loss in high side switch and limits high switching frequency application of DC-DC converter. The proposed resonant gate driver behaves more like the ideal current source driver which can fast turn-on/turn-off power switch to reduce switching loss. In addition, with proposed resonant gate driver, impact of parasitic gate resistance on switching speed of power switch can be greatly reduced. Test results show that, for buck converter with 12V input voltage, 1.3V output voltage, 10A load current and 5.5Ω gate resistance, comparing to conventional driver, with the proposed resonant gate driver for high side switch, total efficiency of buck converter can be improved by more than 3.5%.}, journal={2010 TWENTY-FIFTH ANNUAL IEEE APPLIED POWER ELECTRONICS CONFERENCE AND EXPOSITION (APEC)}, author={Zhou, Xin and Liang, Zhigang and Huang, Alex}, year={2010}, pages={1477–1481} }
 @article{park_fan_wang_huang_2010, title={A Sample-Data Model for Double Edge Current Programmed Mode Control (DECPM) in High-Frequency and Wide-Range DC-DC Converters}, volume={25}, ISSN={["1941-0107"]}, DOI={10.1109/tpel.2009.2036618}, abstractNote={This paper focuses on a sample-data model for double edge current programmed mode control (DECPM) and its application to high-frequency and wide-range dc-dc converters. Steady-state conditions and subharmonic oscillation issues for DECPM are addressed. By combining the conventional peak and valley current programmed mode control, a sample-data model for DECPM is proposed. A small signal model for DECPM is developed by deriving the modulation gains (Fm) and the sampling gains (He) for DECPM from the proposed sample-data model. The sampling frequency dependence on the duty ratio and a large current loop gain at high frequency for DECPM are emphasized. The analytical results are verified by the simulation. Finally, DECPM is proposed as a method to control the high-frequency and wide-range dc-dc converters. A 10-MHz four-switch buck boost converter is implemented with DECPM to verify the viability of its application to high-frequency and wide-range converters.}, number={4}, journal={IEEE TRANSACTIONS ON POWER ELECTRONICS}, author={Park, Jinseok and Fan, Jiwei and Wang, Xiaopeng and Huang, Alex}, year={2010}, month={Apr}, pages={1023–1033} }
 @inproceedings{sung_huang_baliga_2010, title={A novel 4H-SiC IGBT structure with improved trade-off between short circuit capability and on-state voltage drop}, booktitle={Proceedings of the international symposium on power semiconductor}, author={Sung, W. and Huang, A. Q. and Baliga, B. J.}, year={2010}, pages={217–220} }
 @inproceedings{bawa_huang_ghovanloo_2010, title={An efficient 13.56 MHz active back-telemetry rectifier in standard CMOS technology}, DOI={10.1109/iscas.2010.5537296}, abstractNote={In this paper, we present the design of a high-frequency (HF) rectifier implemented in a 0.5-μm 3M/2P 5V standard CMOS process for wireless power transmission across short-range inductive links. The rectifier has been optimized for 13.56 MHz ISM band, and achieves power conversion efficiency (PCE) of ~83% and voltage conversion ratio > 92% in post-layout simulations. We have successfully incorporated a dual-mode back-telemetry capability in this rectifier with little area or efficiency overhead, which tolerates wide load-fluctuations at the secondary side. With these improvements, this active back-telemetry rectifier (ABTR) is geared towards increasing the overall system efficiency, data transfer rate, and reading range in applications such as implantable microelectronic devices (IMD) and radio frequency identification (RFID).}, booktitle={2010 ieee international symposium on circuits and systems}, author={Bawa, G. and Huang, A. Q. and Ghovanloo, M.}, year={2010}, pages={1201–1204} }
 @article{hu_yuan_xu_huang_2010, title={An optimal design of magnetostrictive material (MsM) based energy harvester}, volume={7647}, ISSN={["1996-756X"]}, DOI={10.1117/12.847623}, abstractNote={In this study, an optimal vibration-based energy harvesting system using magnetostrictive material (MsM) has been designed to power the Wireless Intelligent Sensor Platform (WISP), developed at North Carolina State University. A linear MsM energy harvesting device has been modeled and optimized to maximize the power output. The effects of number of MsM layers and glue layers, and load matching on the output power of the MsM energy harvester have been analyzed. From the measurement, the open circuit voltage can reach 1.5 V when the MsM cantilever beam operates at the 2nd natural frequency 324 Hz. The AC output power is 0.97 mW, giving power density 279 μW/cm3. Since the MsM device has low open circuit output voltage characteristics, a full-wave quadrupler has been designed to boost the rectified output voltage. To deliver the maximum output power to the load, a complex conjugate impedance matching between the load and the MsM device has been implemented using a discontinuous conduction mode (DCM) buck-boost converter. The maximum output power after the voltage quadrupler is now 705 μW and power density reduces to 202.4 μW/cm3, which is comparable to the piezoelectric energy harvesters given in the literature. The output power delivered to a lithium rechargeable battery is around 630 μW, independent of the load resistance.}, journal={SENSORS AND SMART STRUCTURES TECHNOLOGIES FOR CIVIL, MECHANICAL, AND AEROSPACE SYSTEMS 2010}, author={Hu, Jingzhen and Yuan, Fuh-Gwo and Xu, Fujun and Huang, Alex Q.}, year={2010} }
 @article{wang_zhou_park_guo_huang_2010, title={Analysis of Process-Dependent Maximal Switching Frequency, Choke Effect, and Its Relaxed Solution in High-Resolution DPWM}, volume={25}, ISSN={["1941-0107"]}, DOI={10.1109/tpel.2009.2025272}, abstractNote={This letter uses the fanout-of-4 (FO4) metric to analyze the semiconductor process (SP) dependent maximal switching frequency (MSF) of a digital pulsewidth modulator (DPWM). After discussing the choke effect in a self-oscillating hybrid (SOH) DPWM and its impact on MSF, this letter further shows that separating the voltage-controlled oscillator (VCO) and the delay mux line is an effective way to relax the choke effect so that the MSF in the SOH could be almost doubled, together with 10%-20% power saving. Taking a low-cost AMI06 SP and 9-bit-resolution specification as an example, this letter predicts that 8 MHz switching frequency could be achieved with the proposed SOH. The SOH chip was custom-designed and fabricated in a 0.703 mm2 die via the metal oxide semiconductor implementation service (MOSIS) educational program. The chip test demonstrated that the MSF is 7.4 MHz with 1.07 mA power consumption, and the adjustable switching frequency range is from 1.8 to 7.4 MHz.}, number={1}, journal={IEEE TRANSACTIONS ON POWER ELECTRONICS}, author={Wang, Xiaopeng and Zhou, Xin and Park, Jinseok and Guo, Rong and Huang, Alex Q.}, year={2010}, month={Jan}, pages={152–157} }
 @article{li_huang_bhattacharya_jing_2010, title={Application of Active NPC Converter on Generator Side for MW Direct-driven Wind Turbine}, ISSN={["1048-2334"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77952213746&partnerID=MN8TOARS}, DOI={10.1109/apec.2010.5433381}, abstractNote={3L-NPC topology is usually used in MW wind turbine (WT) systems with full-scale converter configuration. However, due to its drawback of unequal device loss distribution, the converter rated power, and thus the WT unit capacity is limited. Moreover, in cased of device failure in generator converter, in order to protect the WT system, the converter has to shut down to disconnect the WT. This paper presents the application of active NPC (ANPC) converter on generator side. Loss-balancing schemes are discussed, and thermal performance of NPC and ANPC generator converters are compared. Also, the control scheme of generator converter under single device failure condition is proposed to maintain the WT in service and continue to provide real power, which brings benefits in the reliable and economic aspects to the WT system. Simulation results are provided to validate the proposed control methods.}, journal={2010 TWENTY-FIFTH ANNUAL IEEE APPLIED POWER ELECTRONICS CONFERENCE AND EXPOSITION (APEC)}, author={Li, Jun and Huang, Alex Q. and Bhattacharya, Subhashish and Jing, Wei}, year={2010}, pages={1010–1017} }
 @article{bhattacharya_zhao_wang_dutta_baek_du_parkhideh_zhou_huang_2010, title={Design and Development of Generation-I Silicon based Solid State Transformer}, ISSN={["1048-2334"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77952195486&partnerID=MN8TOARS}, DOI={10.1109/apec.2010.5433455}, abstractNote={The Solid State Transformer (SST) is one of the key elements proposed in the National Science Foundation (NSF) Generation-III Engineering Research Center (ERC) “Future Renewable Electric Energy Delivery and Management” (FREEDM) Systems Center. The SST is used to enable active management of distributed renewable energy resources, energy storage devices and loads. In this paper, the Generation-I SST single-phase 20kVA, based on 6.5kV Si-IGBT is proposed for interface with 12kV distribution system voltage. The SST system design parameters, overall system efficiency, high frequency transformer design, dual active bridge converter, auxiliary power supply and gate drives are investigated. Design considerations and experimental results of the prototype SST are reported.}, journal={2010 TWENTY-FIFTH ANNUAL IEEE APPLIED POWER ELECTRONICS CONFERENCE AND EXPOSITION (APEC)}, author={Bhattacharya, Subhashish and Zhao, Tiefu and Wang, Gangyao and Dutta, Sumit and Baek, Seunghun and Du, Yu and Parkhideh, Babak and Zhou, Xiaohu and Huang, Alex Q.}, year={2010}, pages={1666–1673} }
 @article{liang_alesi_zhou_huang_2010, title={Digital Controller Development for Grid-Tied Photovoltaic Inverter with Model Based Technique}, ISSN={["1048-2334"]}, DOI={10.1109/apec.2010.5433570}, abstractNote={The main objective for a grid-tied photovoltaic (PV) inverter is to feed the harvested energy from PV panels to the grid with high efficiency and high power quality. A digital controller is the “heart” of the PV system: it calculates the maximum power point (MPP) and regulates the output current to meet the utility inter-connection standards. This paper introduced a new approach “model based design” to develop current controller for PV inverter. This design methodology filled the gap between computer simulation and hardware implementation of the digital controller and made an easy way for the implementation of complex and high level algorithm in a digital signal processor (DSP) [1]. The inverter's small signal model in D-Q rotating frame is derived and a double loop current controller is designed. The performance of the developed controller has been verified by both of the simulation in MATLAB and experimental results from a 2kW single phase PV inverter prototype.}, journal={2010 TWENTY-FIFTH ANNUAL IEEE APPLIED POWER ELECTRONICS CONFERENCE AND EXPOSITION (APEC)}, author={Liang, Zhigang and Alesi, Larry and Zhou, Xiaohu and Huang, Alex Q.}, year={2010}, pages={849–853} }
 @article{song_huang_2010, title={Fault-Tolerant Design and Control Strategy for Cascaded H-Bridge Multilevel Converter-Based STATCOM}, volume={57}, ISSN={["1557-9948"]}, DOI={10.1109/tie.2009.2036019}, abstractNote={Cascaded H-bridge multilevel converter (CHMC) is a promising topology for flexible ac transmission systems such as static synchronous compensator (STATCOM) applications. Attention was drawn to the issue of converter reliability due to the large number of power devices used in CHMC applications. This paper proposed an effective fault-tolerant strategy by using H-bridge building block (HBBB) redundancy in CHMC-based STATCOM. The operating principle and the control strategy of the fault tolerance are proposed and discussed. The controller design consideration for the fault-tolerant STATCOM is presented. The proposed fault-tolerant control strategy is implemented on a seven-level CHMC-based STATCOM simulation platform and a five-level CHMC-based STATCOM hardware prototype. Simulation and experimental results are illustrated to verify the feasibility of the proposed fault-tolerant design with the HBBB redundancy.}, number={8}, journal={IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS}, author={Song, Wenchao and Huang, Alex Q.}, year={2010}, month={Aug}, pages={2700–2708} }
 @inproceedings{du_baek_bhattacharya_huang_2010, title={High-voltage high-frequency transformer design for a 7.2kV to 120V/240V 20kVA solid state transformer}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-78751558902&partnerID=MN8TOARS}, DOI={10.1109/iecon.2010.5674828}, abstractNote={Solid state transformer (SST) exhibits good features such as high power density, small volume and weight, controlled power factor, voltage sag ride through, etc. compared with traditional line frequency transformer. The 7.2kV AC to 120V/240V AC 20kVA solid state transformer is a key component of the future renewable electric energy delivery and management (FREEDM) systems as the interface between the 7.2kV distribution grid and the low voltage residential micro-grid. Three cascaded 6.7kVA high-voltage high-frequency transformers operating at 3kHz are employed to convert voltage from 3800V high voltage DC link of each cascaded stage to 400V low voltage DC link. The transformer is required to withstand at least 15kV high frequency voltage insulation continuously. Transformer magnetic core materials were reviewed and compared. Winding layout alternatives for leakage, magnetizing inductance and insulation were compared. An insulation strategy based on split core and separate winding structure with inserted insulation layer between the C cores was proposed. One 6.7kVA high voltage high frequency transformer prototype was built and the test results were reported.}, booktitle={IECON Proceedings (Industrial Electronics Conference)}, author={Du, Y. and Baek, S. and Bhattacharya, Subhashish and Huang, A.Q.}, year={2010}, pages={493–498} }
 @inproceedings{chen_huang_2010, title={Improvement of gate drive for self-power emitter turn-off thyristor (speto)}, DOI={10.1109/iecon.2010.5675201}, abstractNote={Self-power emitter turn-off thyristor (SPETO) is a high power switching device which could provide power for its gate drive during operation. Self-power function reduces the system cost and makes the mechanical structure compact, whereas it may bring extra harmonic when SPETO is being utilized in power utilities. In this paper, the impact of self-power function on extra harmonic is analyzed. The ideas to improve SPETO gate drive hence reduce extra harmonic are presented and verified by simulation.}, booktitle={Iecon 2010: 36th annual conference of the ieee industrial electronics society}, author={Chen, Q. A. and Huang, A. Q.}, year={2010} }
 @inproceedings{lim_huang_2010, title={Low-dropout (LDO) regulator output impedance analysis and transient performance enhancement circuit}, DOI={10.1109/apec.2010.5433489}, abstractNote={This paper presents a low-dropout regulator with a transient performance enhancement circuit. The transient performance enhancement circuit improves the transient response time by sinking a remaining current in a power delivery path. Due to the limited control bandwidth, traditional LDO could not respond rapidly to the load transients. As a result, a large output voltage spike can be occurred and the output voltage settling time is long during the load transients. In this paper, the stability conditions and the output impedance of LDO are discussed, and the output voltage spike and current distributions in the power delivery path are analyzed. The theoretical analysis will be confirmed by the cadence simulation results.}, booktitle={Annual ieee conference on applied power electronics conference and}, author={Lim, S. and Huang, A. Q.}, year={2010}, pages={1875–1878} }
 @inproceedings{zhou_liu_bhattacharya_huang_2010, title={New inductor current feedback control with active harmonics injection for inverter stage of solid state transformer}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-78751540900&partnerID=MN8TOARS}, DOI={10.1109/iecon.2010.5675216}, abstractNote={Solid state transformer (SST) is considered the key unit for power processing and conversion in the future distributed renewable energy network. The role of SST is to enable the active management of distributed energy resources, energy storage devices and different type of loads in a distribution grid. Inverter stage of SST supplies sinusoidal voltage to the users. In this paper an improved inductor current control based on active harmonics injection is proposed to overcome the drawback of inferior performance of conventional inductor current feedback control for the nonlinear loads. The inductor current overshoot during the load transient is investigated by using both capacitor current feedback control and inductor current feedback control. The inductor current feedback control has the capability to limit current overshoot even with a smaller inductor, which shows the potential to further reduce the size and weight of the passive components.}, booktitle={IECON Proceedings (Industrial Electronics Conference)}, author={Zhou, X. and Liu, Y. and Bhattacharya, Subhashish and Huang, A.}, year={2010}, pages={593–598} }
 @article{teleke_baran_bhattacharya_huang_2010, title={Optimal Control of Battery Energy Storage for Wind Farm Dispatching}, volume={25}, ISSN={["1558-0059"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77956056892&partnerID=MN8TOARS}, DOI={10.1109/tec.2010.2041550}, abstractNote={Integrating a battery energy storage system (BESS) with a large wind farm can make a wind farm more dispatchable. This paper focuses on development of a control strategy for optimal use of the BESS for this purpose. The paper considers an open-loop optimal control scheme to incorporate the operating constraints of the BESS, such as state of charge limits, charge/discharge current limits, and lifetime. The goal of the control is to have the BESS to provide as much smoothing as possible, so that the wind farm can be dispatched on an hourly basis based on the forecasted wind conditions. The effectiveness of this control strategy has been tested by using an actual wind farm data. Furthermore, a real-time implementation strategy using model predictive control is also proposed. Finally, it is shown that the control strategy is very important in improving the BESS performance for this application.}, number={3}, journal={IEEE TRANSACTIONS ON ENERGY CONVERSION}, author={Teleke, Sercan and Baran, Mesut E. and Bhattacharya, Subhashish and Huang, Alex Q.}, year={2010}, month={Sep}, pages={787–794} }
 @article{hu_xu_huang_yuan_2010, title={Optimal design of a vibration-based energy harvester using magnetostrictive material (MsM)}, volume={20}, ISSN={0964-1726 1361-665X}, url={http://dx.doi.org/10.1088/0964-1726/20/1/015021}, DOI={10.1088/0964-1726/20/1/015021}, abstractNote={In this study, an optimal vibration-based energy harvesting system using magnetostrictive material (MsM) was designed and tested to enable the powering of a wireless sensor. In particular, the conversion efficiency, converting from magnetic to electric energy, is approximately modeled from the magnetic field induced by the beam vibration. A number of factors that affect the output power such as the number of MsM layers, coil design and load matching are analyzed and explored in the design optimization. From the measurements, the open-circuit voltage can reach 1.5 V when the MsM cantilever beam operates at the second natural frequency 324 Hz. The AC output power is 970 µW, giving a power density of 279 µW cm − 3. The attempt to use electrical reactive components (either inductors or capacitors) to resonate the system at any frequency has also been analyzed and tested experimentally. The results showed that this approach is not feasible to optimize the power. Since the MsM device has low output voltage characteristics, a full-wave quadrupler has been designed to boost the rectified output voltage. To deliver the maximum output power to the load, a complex conjugate impedance matching between the load and the MsM device is implemented using a discontinuous conduction mode (DCM) buck-boost converter. The DC output power after the voltage quadrupler reaches 705 µW and the corresponding power density is 202 µW cm − 3. The output power delivered to a lithium rechargeable battery is around 630 µW, independent of the load resistance.}, number={1}, journal={Smart Materials and Structures}, publisher={IOP Publishing}, author={Hu, J and Xu, F and Huang, A Q and Yuan, F G}, year={2010}, month={Dec}, pages={015021} }
 @article{du_zhou_bai_lukic_huang_2010, title={Review of Non-isolated Bi-directional DC-DC Converters for Plug-in Hybrid Electric Vehicle Charge Station Application at Municipal Parking Decks}, ISSN={["1048-2334"]}, DOI={10.1109/apec.2010.5433359}, abstractNote={There is a growing interest on plug-in hybrid electric vehicles (PHEV's) due to energy security and green house gas emission issues, as well as the low electricity fuel cost. As battery capacity and all-electric range of PHEV's are improved, and potentially some PHEV's or EV's need fast charging, there is increased demand to build high power off-board charging infrastructures. A charge station architecture for municipal parking decks has been proposed, which has a DC microgrid to interface with multiple DC-DC chargers, distributed renewable power generations and energy storage, and provides functionalities of normal and rapid charging, grid support such as reactive and real power injection (including V2G), current harmonic filtering and load balance. Several non-isolated bidirectional DC-DC converters suited for charge station applications have been reviewed and compared, as the major focus of this paper. Half bridge converter is a good candidate but it is difficult to maintain high efficiency in wide battery pack voltage range. A variable frequency pulse width modulation (VFPWM) scheme is proposed to mitigate this issue. Finally three-level bi-directional DC-DC converter is suggested to be employed in this application. A 10kW prototype verifies that 95.1–97.9% full load efficiency can be achieved in charging mode with 180–360V battery pack voltage. In addition, the inductor size is only one third of the half bridge counterpart, which is a great advantage for high power converters.}, journal={2010 TWENTY-FIFTH ANNUAL IEEE APPLIED POWER ELECTRONICS CONFERENCE AND EXPOSITION (APEC)}, author={Du, Yu and Zhou, Xiaohu and Bai, Sanzhong and Lukic, Srdjan and Huang, Alex}, year={2010}, pages={1145–1151} }
 @article{lim_fan_huang_2010, title={Transient-voltage-clamp circuit design based on constant load line impedance for voltage regulator module}, volume={57}, DOI={10.1109/tie.2010.2042419}, abstractNote={A transient-voltage-clamp (TVC) circuit acts as a replacement of bulk capacitors, which is required for voltage regulator (VR) module (VRM) to clamp output voltage spikes. With the TVC circuit, VRM size is greatly reduced with similar transient performance. This paper presents a new TVC circuit. This TVC circuit is designed based on the constant load line impedance which is recently given by Intel's VRM11.0. The TVC circuit works in parallel with VR decoupling capacitors to achieve faster voltage regulation. The impedances of the VR, output capacitors, and the proposed TVC circuit are analyzed. The TVC circuit design procedure is described, and the transient performance and power consumption are discussed. The theoretical analysis is verified by simulation results. Moreover, the proposed TVC circuit is fabricated with a 0.6-μm CMOS process, and experimental results verify the simulation results and theoretical analysis.}, number={12}, journal={IEEE Transactions on Industrial Electronics}, author={Lim, S. and Fan, J. W. and Huang, A. Q.}, year={2010}, pages={4085–4094} }
 @article{zhao_wang_zeng_dutta_bhattacharya_huang_2010, title={Voltage and Power Balance Control for a Cascaded Multilevel Solid State Transformer}, ISSN={["1048-2334"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77952178838&partnerID=MN8TOARS}, DOI={10.1109/apec.2010.5433584}, abstractNote={In this paper, a 20kVA Solid State Transformer (SST) based on 6.5kV IGBT is proposed for interface with 7.2kV distribution system voltage. The proposed SST consists of a cascaded multilevel AC/DC rectifier stage, a Dual Active Bridge (DAB) converter stage with high frequency transformers and a DC/AC inverter stage. Based on the single phase d-q vector control, a novel control strategy is proposed to balance the rectifier capacitor voltages and the real power through the DAB parallel modules. Furthermore, the power constraints of the voltage balance control are analyzed. The SST switching model simulation demonstrates the effectiveness of the proposed voltage and power balance controller. A 3kW SST scale-down prototype is implemented. The experiment results verify the single phase d-q vector controller for the SST cascaded multilevel rectifier.}, journal={2010 TWENTY-FIFTH ANNUAL IEEE APPLIED POWER ELECTRONICS CONFERENCE AND EXPOSITION (APEC)}, author={Zhao, Tiefu and Wang, Gangyao and Zeng, Jie and Dutta, Sumit and Bhattacharya, Subhashish and Huang, Alex Q.}, year={2010}, pages={761–767} }
 @article{wang_zhou_li_zhao_huang_callanan_husna_agarwal_2009, title={10-kV SiC MOSFET-Based Boost Converter}, volume={45}, ISSN={["1939-9367"]}, DOI={10.1109/tia.2009.2031915}, abstractNote={10-kV silicon carbide (SiC) MOSFETs are currently being developed by a number of organizations in the U.S. with prospective applications in high-voltage and high-frequency power-electronic systems. The aim of this paper is to demonstrate the high-frequency and high-temperature capability of 10-kV SiC MOSFETs in the application of a dc/dc boost converter. In this study, 10-kV SiC MOSFET and junction barrier Schottky (JBS) diode were characterized and modeled in SPICE. Following this, a dc/dc boost converter based on a 10-kV 10-A MOSFET and a 10-kV 5-A JBS diode was designed and tested under continuous operation for frequencies up to 25 kHz. The boost converter had an output voltage of 4 kV, an output power of 4 kW, and operated with a junction temperature of 174degC for the SiC MOSFET. The fast-switching speed, low losses, and high-temperature operation capability of 10-kV SiC MOSFETs demonstrated in the dc/dc boost converter make them attractive for high-frequency and high-voltage power-conversion applications.}, number={6}, journal={IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS}, author={Wang, Jun and Zhou, Xiaohu and Li, Jun and Zhao, Tiefu and Huang, Alex Q. and Callanan, Robert and Husna, Fatima and Agarwal, Anant}, year={2009}, pages={2056–2063} }
 @inproceedings{li_huang_jing_2009, title={7MVA ETO Light NPC converter for multi-MW direct-driven wind turbine application}, DOI={10.1109/pemwa.2009.5208382}, abstractNote={Direct-driven wind turbine with a PM generator and a full-scale converter is considered to be a preferred solution for wind power generation, especially for offshore application. As the power ratings of wind turbines increase to MW level, medium voltage converter becomes more competitive. The emitter turn-off (ETO) thyristor is a novel semiconductor device that is suitable for high power applications. This paper proposes a 7MVA ETO Light neutral-point-clamped (NPC) converter as the utility interface for direct-driven large wind turbine application. The converter hardware configuration, the component selection and design are presented. The thermal characteristics and performance of the proposed converter are analyzed in detail.}, booktitle={2009 IEEE power Electronics and Machines in Wind Applications}, author={Li, J. and Huang, A. Q. and Jing, W.}, year={2009}, pages={36–42} }
 @inproceedings{fan_zhou_yang_huang_2009, title={A low power high noise immunity boost DC-DC converter using the differential difference amplifiers}, DOI={10.1145/1594233.1594249}, abstractNote={A new boost converter using the differential difference amplifiers (DDAs) in the control loop is proposed. Compared with the traditional current mode boost converters, the circuitry of this controller is much simpler and consumes less power by eliminating the loop compensation, current sensing, and slope compensation circuits. A large duty ripple voltage generated by an Rr-Cr network is compared with the DDAs' outputs to get the duty cycles and changes the boost converter from a second order to a first order system. The large noise margin of the duty ripple voltage also gives this control excellent noise immunity performance.}, booktitle={ISLPED 09}, author={Fan, J. W. and Zhou, X. and Yang, L. Y. and Huang, A.}, year={2009}, pages={63–68} }
 @inproceedings{zhao_zeng_bhattacharya_baran_huang_2009, title={An average model of solid state transformer for dynamic system simulation}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-71849090346&partnerID=MN8TOARS}, DOI={10.1109/pes.2009.5275542}, abstractNote={The Solid State Transformer (SST) is one of the key elements proposed in the National Science Foundation (NSF) Generation-III Engineering Research Center (ERC) “Future Renewable Electric Energy Delivery and Management” (FREEDM) Systems Center established in 2008. The SST is used to enable active management of distributed renewable energy resources, energy storage devices and loads. In this paper, a 20kVA solid state transformer based on 6.5kV IGBT is proposed for interface with 12kV distribution system voltage. The average model and control scheme of SST including AC/DC rectifier, Dual Active Bridge (DAB) converter and DC/AC inverter are developed to enable dynamic system level simulation. The developed average model is verified by comparing with the detailed switching model simulation. The dynamic system level SST simulation verifies the proposed controller and the corresponding average model illustrates the functionalities and advantages of the SST in FREEDM system.}, booktitle={2009 IEEE Power and Energy Society General Meeting, PES '09}, author={Zhao, T. and Zeng, J. and Bhattacharya, Subhashish and Baran, M.E. and Huang, A.Q.}, year={2009}, pages={1516–1523} }
 @inproceedings{li_liu_bhattacharya_huang_2009, title={An optimum PWM strategy for 5-level active NPC (ANPC) converter based on real-time solution for THD minimization}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-72449155137&partnerID=MN8TOARS}, DOI={10.1109/ecce.2009.5316229}, abstractNote={The recently introduced active NPC (ANPC) converter is becoming an attractive topology of multilevel converter family. This paper presents the analysis of the 5-level ANPC converter with an optimum PWM strategy to achieve the minimized total harmonic distortion (THD) for high power or high frequency applications. Instead of relying on the conventional look-up table based on off-line calculated solutions, the switching angles of the optimum PWM are calculated through a real-time algorithm, which is time-efficient and therefore easy to implement in real-time by digital processors. The control scheme of balancing the floating capacitors voltages is also proposed. Simulation results verify the performance of the proposed strategies.}, booktitle={2009 IEEE Energy Conversion Congress and Exposition, ECCE 2009}, author={Li, J. and Liu, Y. and Bhattacharya, Subhashish and Huang, A.Q.}, year={2009}, pages={1976–1982} }
 @inproceedings{wang_du_bhattacharya_huang_2009, title={Characterization, modeling of 10-kV SiC JBS diodes and their application prospect in X-ray generators}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-72449197461&partnerID=MN8TOARS}, DOI={10.1109/ecce.2009.5315963}, abstractNote={The 10-kV Silicon Carbide (SiC) Junction Barrier Schottky (JBS) diodes are currently being developed by a number of organizations in the United States with the aim to enable their applications in high voltage power conversions. The aim of this paper is to characterize and model the 10-kV SiC JBS diode so that their prospect and benefits in power electronic systems can be provided. Using the SPICE model of the 10-kV 5A SiC JBS diode, the advantages of 10-kV SiC JBS diodes in the application of X-ray generators were shown by PSPICE simulations for the first time. The simulation results predict that the 10-kV SiC JBS diodes based high voltage rectifiers in X-ray generators can greatly reduce the number of series diodes required and power loss than compared to the 1-kV silicon ultra fast recovery diodes based rectifiers.}, booktitle={2009 IEEE Energy Conversion Congress and Exposition, ECCE 2009}, author={Wang, J. and Du, Y. and Bhattacharya, Subhashish and Huang, A.Q.}, year={2009}, pages={1488–1493} }
 @article{chen_huang_2009, title={Control Power Self-Generation and Sensor Integration in Emitter Turn-Off Thyristor}, volume={45}, ISSN={["1939-9367"]}, DOI={10.1109/tia.2009.2023552}, abstractNote={This paper highlights the improved design and demonstration of the control power self-generation in the emerging new power semiconductor switch ETO. It also discusses the method utilized to achieve complete sensor integrations in the ETO. Conventional high power devices require dedicated external power supplies with isolation capability to operate. The isolation transformer lowers the system reliability and increases the cost of the power converter. At the same time, conventional converters rely on expensive external sensors to gather the voltage, current and temperature information. The emerging ETO is a fully optical controlled power switch: the internal control power is self- generated; voltage, current and temperature sensors are also integrated in the device}, number={5}, journal={IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS}, author={Chen, Bin and Huang, Alex Q.}, year={2009}, pages={1715–1728} }
 @article{teleke_baran_huang_bhattacharya_anderson_2009, title={Control Strategies for Battery Energy Storage for Wind Farm Dispatching}, volume={24}, ISSN={["1558-0059"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-70049103778&partnerID=MN8TOARS}, DOI={10.1109/TEC.2009.2016000}, abstractNote={Integrating a battery energy storage system (BESS) with a large wind farm can smooth out the intermittent power from the wind farm. This paper focuses on development of a control strategy for optimal use of the BESS for this purpose. The paper considers a conventional feedback-based control scheme with revisions to incorporate the operating constraints of the BESS, such as state of charge limits, charge/discharge rate, and lifetime. The goal of the control is to have the BESS provide as much smoothing as possible so that the wind farm can be dispatched on an hourly basis based on the forecasted wind conditions. The effectiveness of this control strategy has been tested by using an actual wind farm data. Finally, it is shown that the control strategy is very important in determining the proper BESS size needed for this application.}, number={3}, journal={IEEE TRANSACTIONS ON ENERGY CONVERSION}, author={Teleke, Sercan and Baran, Mesut E. and Huang, Alex Q. and Bhattacharya, Subhashish and Anderson, Loren}, year={2009}, month={Sep}, pages={725–732} }
 @inproceedings{yang_fan_huang_2009, title={Controller design issues and solutions for buck converters with phase shedding and AVP functions}, DOI={10.1109/ecce.2009.5316266}, abstractNote={For buck converters with high output current, multi-phase interleaving is popular. To improve light load efficiency, some phases can be shut down at light load. This is called phase shedding. Adaptive Voltage Positioning (AVP) is normally another requirement for high output current buck. Previous papers provided AVP design guidelines for buck converters without phase shedding. With phase shedding, are these design guidelines still valid? How to design the controller so that the output transient response doesn't get worse? This paper points out the controller design issues for buck converters with phase shedding and AVP. It is shown that the output will have worse transient response if the controller is designed in the same way as without phase shedding. New design guidelines are developed in this paper to solve the problem, which are verified by simulation and experimental results.}, booktitle={2009 IEEE Energy Conversion Congress and Exposition, Vols 1-6}, author={Yang, L. Y. and Fan, J. W. and Huang, A. Q.}, year={2009}, pages={2335–2341} }
 @inproceedings{liu_p._g._c._huang_langston_steurer_litzenberger_anderson_adapa_et al._2009, title={Controller hardware-in-the-loop validation for a0 10 MVA ETO-based STATCOM for wind farm application}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-72449158355&partnerID=MN8TOARS}, DOI={10.1109/ecce.2009.5316033}, abstractNote={This paper reports experimental validation of a Static Synchronous Compensation (STATCOM) by controller hardware-in-the-loop (CHIL) testing with a real-time digital simulator (RTDS). The controller is designed and developed for a 10 MVA STATCOM for voltage regulation at the PCC of a 50 MW wind farm connected to a 69kV utility grid. Emitter Turn-off (ETO) thyristors are switching devices in the multilevel inverter. The STATCOM controller was developed for a cascade multilevel inverter and has been validated on a laboratory test-bench. The CHIL testing of the controller is done with detailed scaled model of the 50 MW wind farm and 69kV utility system. The experimental results from the RTDS for both steady state and dynamic changes in the STATCOM output validate the STATCOM controller design and performance.}, booktitle={2009 IEEE Energy Conversion Congress and Exposition, ECCE 2009}, author={Liu, Y. and P., Liang Z. and G., Song Z. and C., Bhattacharya W. and Huang, S. and Langston, A. and Steurer, J. and Litzenberger, M. and Anderson, W. and Adapa, L. and et al.}, year={2009}, pages={1398–1403} }
 @article{wang_huang_2009, title={Design and Characterization of High-Voltage Silicon Carbide Emitter Turn-off Thyristor}, volume={24}, ISSN={["1941-0107"]}, DOI={10.1109/TPEL.2009.2013861}, abstractNote={A novel MOS-controlled silicon carbide (SiC) thyristor device, the SiC emitter turn-off thyristor (ETO), as a promising technology for future high-voltage and high-frequency switching applications has been developed. The world's first 4.5-kV SiC p-type ETO prototype based on a 0.36 cm2 SiC p-type gate turn-off (GTO) shows a forward voltage drop of 4.6 V at a current density of 25 A/cm2 and a turn-off energy loss of 9.88 mJ. The low loss shows that the SiC ETO could operate at a 4-kHz frequency with a conventional thermal management system. This frequency capability is about four times higher than the 4.5-kV-class silicon power devices. The numerical simulations and theoretical analysis have been carried out to show the potentially improved performance of the high-voltage SiC ETOs. The results show that the high-voltage (10-kV) SiC n-type ETO has much better tradeoff performance than that of the p-type ETO due to a smaller current gain of the lower bipolar transistor in the SiC n-type GTO. Further improvement of the 10-kV SiC n-type ETO can be made with the optimum design of the drift layer carrier lifetime and buffer layer doping concentration of the 10-kV SiC GTO. The theoretical analysis and numerical simulation shows the SiC ETO also has the excellent reverse bias safe operating area. The experimental and theoretical studies show that the SiC ETO is a promising candidate for high-voltage (> 5 kV) power conversion applications.}, number={5-6}, journal={IEEE TRANSACTIONS ON POWER ELECTRONICS}, author={Wang, Jun and Huang, Alex Q.}, year={2009}, pages={1189–1197} }
 @article{fan_li_lim_huang_2009, title={Design and characterization of differentially enhanced duty ripple control (DE-DRC) for step-down converter}, volume={24}, DOI={10.1109/TPEL.2009.2028889}, abstractNote={A new control method, differentially enhanced duty ripple control (DE-DRC), is proposed for step-down converters. The control method uses a differentially enhanced loop to amplify the output error with positive and negative differential difference amplifiers (DDAs), and a duty ripple loop to include the input voltage and the duty cycle information into the control scheme. The duty ripple loop generates a very large control ripple voltage, and the control ripple is compared with a negative control voltage to trigger an on-pulse generator to get the duty cycle. Because of the large duty ripple voltage with a big noise margin and the low pass filter effect of DDAs, the proposed DE-DRC can achieve good noise immunity. The easily configured positive and negative DDA gains can separately adjust the high and low frequency portion of the loop transfer function, and push the control bandwidth to high frequency to achieve fast transient response. Because of a unique first-order character of the inner duty ripple loop, this control can also completely eliminate the double pole peaking from the output impedance and achieve ideal closed loop output impedance in the control bandwidth, which is preferred for adaptive voltage position designs.}, number={12}, journal={IEEE Transactions on Power Electronics}, author={Fan, J. W. and Li, X. N. and Lim, S. and Huang, A. Q.}, year={2009}, pages={2714–2725} }
 @inproceedings{zhou_lukic_bhattacharya_huang_2009, title={Design and control of grid-connected converter in bi-directional battery charger for plug-in hybrid electric vehicle application}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-72149131445&partnerID=MN8TOARS}, DOI={10.1109/vppc.2009.5289691}, abstractNote={A new bi-directional power converter for Plug-in Hybrid Electric Vehicles (PHEV) is proposed based on a typical household circuitry configuration. This converter can achieve three major functions: battery charger mode, vehicle to grid mode (V2G) and vehicle to home mode (V2H), which are the main topics of integration of PHEVs with the grid. The detailed converter design is presented. An improved AC/DC controller is proposed in order to achieve low input current harmonics for the charger mode. The Proportional resonant+harmonics selective compensation method is utilized for the V2G mode, and capacitor current feedback and proportional resonant control methods are adopted for the V2H mode. Compared with conventional PI controllers, the proposed controllers greatly enhance the grid-connected converter's performance in the aspects of low harmonics output and robustness against background noise.}, booktitle={5th IEEE Vehicle Power and Propulsion Conference, VPPC '09}, author={Zhou, X. and Lukic, Srdjan and Bhattacharya, Subhashish and Huang, A.}, year={2009}, pages={1716–1721} }
 @article{sung_wang_huang_baliga_2009, title={Design and investigation of frequency capability of 15kV 4H-SiC IGBT}, ISBN={["978-1-4244-3525-8"]}, ISSN={["1943-653X"]}, DOI={10.1109/ispsd.2009.5158054}, abstractNote={15kV 4H-SiC n-channel asymmetric and symmetric IGBTs were designed to minimize the on state and switching power loss. A Current Enhancement Layer was adopted to reduce the forward voltage drop for each IGBTs. For the asymmetric IGBT, it was found that the frequency capability of the device was affected most by adjusting the buffer region parameters such as doping concentration, thickness, and lifetime. For the symmetric IGBT, the p+ substrate doping concentration and drift region lifetime were investigated to obtain maximum switching frequency capability. A comparison of frequency capabilities between power MOSFETs, asymmetric, and symmetric IGBTs has been made. IGBTs provide lower power loss than power MOSFETs up to approximately 7 kHz.}, journal={2009 21ST INTERNATIONAL SYMPOSIUM ON POWER SEMICONDUCTOR DEVICES & ICS}, author={Sung, Woongje and Wang, Jun and Huang, Alex Q. and Baliga, B. Jayant}, year={2009}, pages={271–274} }
 @inproceedings{lim_huang_2009, title={Design of a transient voltage clamp (TVC) for 4 switch buck boost (4SBB) converter}, DOI={10.1109/ecce.2009.5316503}, abstractNote={This paper presents a new design methodology of the transient voltage clamp (TVC), which operates by controlling inductor current slew rate in 4 Switch Buck Boost Converter (4SBB). When 4SBB operates in boost mode, the TVC circuit changes inductor current slew rate during load current step-down to achieve a faster voltage regulation. Due to the slow inductor current slew rate, traditional 4SBB could not respond rapidly to the load current transient. As a result, a large output voltage spike can be occurred during load transient. The specific function of the TVC is to control unused switches when 4SBB operates in boost mode. The main challenge in applying the TVC is how to control unused switches during load current transient. In this paper, how to control the inductor current slew rate and transient response are discussed. The theoretical analysis will be confirmed by the cadence simulation results.}, booktitle={2009 IEEE Energy Conversion Congress and Exposition, Vols 1-6}, author={Lim, S. and Huang, A. Q.}, year={2009}, pages={180–182} }
 @inproceedings{li_huang_bhattacharya_lukic_2009, title={ETO Light multilevel converters for large electric vehicle and hybrid electric vehicle drives}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-72149086393&partnerID=MN8TOARS}, DOI={10.1109/vppc.2009.5289513}, abstractNote={multilevel converters are very popular for high power AC drives to meet the power demands for large electric/hybrid electric vehicles. Emitter Turn-off (ETO) thyristor is one of the present state-of-the-art high power semiconductor devices. The newest version of ETO (Gen-4 ETO) is more intelligent and reliable. Packed with advanced features as well as superior performance, ETO device and ETO-based power converters are very attractive for large electric drives. This paper presents the ETO Light neutral-point-clamped (NPC) converter design and thermal analysis. The modular digital controller architecture for this converter is proposed in order to improve the system reliability and increase its expansion flexibility. As a solution to further increase the converter output power, the ETO Light active NPC (ANPC) converter is presented, and moreover its fault tolerant capability is discussed.}, booktitle={5th IEEE Vehicle Power and Propulsion Conference, VPPC '09}, author={Li, J. and Huang, A. and Bhattacharya, Subhashish and Lukic, Srdjan}, year={2009}, pages={1455–1460} }
 @inproceedings{huang_liu_chen_li_song_2009, title={Emitter turn-off (ETO) thyristor, ETO light converter and their grid applications}, DOI={10.1109/pes.2009.5275226}, abstractNote={In today's electric power system, solid state power electronics technology plays more and more important roles and the demand for mega-watt level power ratings is increasing. The development of mega-watt power converters strongly depends on the state-of-the-art of power semiconductor technology, cooling technology and digital controller. The authors have been involved in the development of the Emitter Turn-Off (ETO) thyristor, an emerging power semiconductor switch for high power applications. Packed with advanced features as well as superior performance, ETO based power electronics systems are very attractive for various grid applications. In this paper, the authors will present the ETO device, ETO Light converter that are under development at the NSF FREEDM Systems Center. Moreover, the authors will explain how these developments will facilitate grid applications: static synchronous compensator (STATCOM) without/with energy storage, direct connection of wind turbine, High Voltage Direct Current (HVDC) application, power flow control and solid-state circuit breaker and current limiter.}, booktitle={2009 ieee power & energy society general meeting, vols 1-8}, author={Huang, A. and Liu, Y. and Chen, Q. and Li, J. and Song, W. C.}, year={2009}, pages={1861–1868} }
 @article{huang_baliga_2009, title={FREEDM System: Role of Power Electronics and Power Semiconductors in Developing an Energy Internet}, ISBN={["978-1-4244-3525-8"]}, ISSN={["1943-653X"]}, DOI={10.1109/ispsd.2009.5157988}, abstractNote={The Future Renewable Electric Energy Delivery and Management (FREEDM) Systems Center is a National Science Foundation (NSF) Generation-III Engineering Research Center (ERC) established in 2008 with the mission to develop the fundamental and enabling technologies necessary for a new and paradigm shifting power grid infrastructure, the FREEDM System. This paper will highlight the role of power electronics and power semiconductors in developing an energy internet. The revolutionary impact of high voltage SiC and GaN power devices in utility and FREEDM System is discussed.}, journal={2009 21ST INTERNATIONAL SYMPOSIUM ON POWER SEMICONDUCTOR DEVICES & ICS}, author={Huang, Alex Q. and Baliga, Jay}, year={2009}, pages={9–12} }
 @article{jung_huang_2009, title={Improved Breakdown-Voltage Complementary MOSFET in a 0.18 mu m Standard CMOS process for Switch Mode Power Supply (SMPS) applications}, ISBN={["978-1-4244-3525-8"]}, ISSN={["1943-653X"]}, DOI={10.1109/ispsd.2009.5158046}, abstractNote={In this paper, a novel improved breakdown-voltage (BV) complementary MOSFET for SMPS applications is introduced in a standard 0.18µm VLSI (Very Large Scale Integration) process without any extra processes. Proposed NMOS and PMOS breakdown voltages have been improved up to 22.6V (∼3.5-times increase) and 13.2V (∼2-times increase) each. And the merged-charge effect (charge-coupling) through STI (Shallow Trench Isolation) which contributes to the higher breakdown voltage in a standard CMOS process is explained. A novel higher breakdown voltage CMOS shows the lowest FOMs among the same voltage rate devices good enough for high-frequency and low power applications. Finally, novel improved BV devices are integrated as power switches with VLSI low-voltage CMOS for SMPS applications. And ISE-TCAD and Cadence-SPICE simulations show that the designed monolithic buck-converter including parasite components achieves 88% high-efficiency.}, journal={2009 21ST INTERNATIONAL SYMPOSIUM ON POWER SEMICONDUCTOR DEVICES & ICS}, author={Jung, Jeesung and Huang, Alex Q.}, year={2009}, pages={239–242} }
 @inproceedings{song_zhou_liang_bhattacharya_huang_2009, title={Modeling and control design of distributed power flow controller based-on per-phase control}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-72449137681&partnerID=MN8TOARS}, DOI={10.1109/ecce.2009.5316307}, abstractNote={The distributed power flow controller (DPFC) based-on Emitter Turn-Off (ETO) light converter is one newly proposed solid state power electronics technology based Flexible AC Transmission System (FACTS) devices which is effective to control the active power flow through the transmission lines. This modular DPFC has low cost, high reliability and makes it possible to have the transformerless connection to the existing power grid. In this paper, the development and analysis of modeling techniques and feedback schemes based on per phase control of DPFC are proposed. The simulation results and experimental results show the consistency of the propose model and the feasibility of the feedback control design for the DPFC per-phase operation.}, booktitle={2009 IEEE Energy Conversion Congress and Exposition, ECCE 2009}, author={Song, W. and Zhou, X. and Liang, Z. and Bhattacharya, Subhashish and Huang, A.Q.}, year={2009}, pages={3262–3267} }
 @inproceedings{zhou_fan_huang_2009, title={Monolithic DC offset self-calibration method for adaptive on-time control buck converter}, DOI={10.1109/ecce.2009.5316520}, abstractNote={In this paper, a monolithic self-calibration method is proposed to reduce DC offset of output voltage in buck converter with adaptive on-time control. The calibration system senses the average output voltage of converter and dynamically reduces offset by digital tuning the comparing reference. DC offset at output voltage caused by parasitic ESR, ESL of filter capacitor and loop delay can be effectively calibrated. The proposed calibration method doesn't impact fast transient response of the converter. Moreover, the calibration system can also be generally used to reduce output voltage DC offset of converter with bang-bang control.}, booktitle={2009 IEEE Energy Conversion Congress and Exposition, Vols 1-6}, author={Zhou, X. and Fan, J. W. and Huang, A.}, year={2009}, pages={176–179} }
 @inproceedings{zhou_wang_lukic_bhattacharya_huang_2009, title={Multi-function bi-directional battery charger for plug-in hybrid electric vehicle application}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-72449142726&partnerID=MN8TOARS}, DOI={10.1109/ecce.2009.5316226}, abstractNote={A new multi-function bi-directional battery charger for plug-in hybrid electric vehicles (PHEV) is proposed based on the power circuitry configuration of an American house. This bi-directional charger can achieve three functions including battery charging, vehicle to grid (V2G) and vehicle to home (V2H), all of which are the major research areas of PHEV's integration with the power grid. The integration infrastructure and practical design issues are analyzed. The multiple control loop designs are presented for the three operation modes. Simulation and experimental results verify the functions and performance of the proposed charger. With the capability of achieving multiple functions, the bi-directional charger will contribute and enhance grid related research of PHEVs.}, booktitle={2009 IEEE Energy Conversion Congress and Exposition, ECCE 2009}, author={Zhou, X. and Wang, G. and Lukic, Srdjan and Bhattacharya, Subhashish and Huang, A.}, year={2009}, pages={3930–3936} }
 @article{wang_huang_baliga_2009, title={RBSOA Study of High Voltage SiC Bipolar Devices}, ISBN={["978-1-4244-3525-8"]}, ISSN={["1063-6854"]}, DOI={10.1109/ispsd.2009.5158052}, abstractNote={Rapid improvement of 4H-SiC material quality and maturation of SiC device processing have enabled the development of high voltage SiC bipolar devices for high voltage switching applications. As one of the major concern of bipolar devices, the onset of dynamic avalanche breakdown and reverse biased safe operating area (RBSOA) of SiC pnp and npn transistors have been systematically analyzed in this paper. The theoretical analysis predicts the onset power density of dynamic avalanche breakdown of SiC bipolar devices is more than twenty times larger than that of Si bipolar devices, and SiC bipolar devices have a near square RBSOA. The predicted rugged turn-off behavior of SiC bipolar devices is verified by numerical simulations of 10-kV SiC emitter turn-off thyristors (ETOs). The excellent ruggedness of SiC bipolar devices make them attractive for high voltage (≥10-kV) switching applications.}, journal={2009 21ST INTERNATIONAL SYMPOSIUM ON POWER SEMICONDUCTOR DEVICES & ICS}, author={Wang, Jun and Huang, Alex Q. and Baliga, B. Jayant}, year={2009}, pages={263–266} }
 @article{liu_hong_huang_2009, title={Real-Time Algorithm for Minimizing THD in Multilevel Inverters With Unequal or Varying Voltage Steps Under Staircase Modulation}, volume={56}, ISSN={["1557-9948"]}, url={http://dx.doi.org/10.1109/tie.2009.2015360}, DOI={10.1109/TIE.2009.2015360}, abstractNote={Different modulation methods have been proposed to control the multilevel inverters. This paper focuses on the staircase modulation that is very popular for multilevel inverters with low switching frequencies. Nonreal-time algorithms for the staircase modulation cannot be applied practically in multilevel inverters with varying voltage steps, since the sizes of lookup tables would be huge. We propose a real-time algorithm for multilevel inverters with unequal or varying voltage steps under the staircase modulation. The algorithm results in the minimal total harmonic distortion (THD) of the output voltage of the inverter, which is proved by rigorous mathematical derivations in this paper. A new expression of THD is presented to simplify the derivation significantly. Computational complexity of the algorithm is analyzed to estimate the time cost of the calculation. We implemented the algorithm on a digital signal processor and provide experimental results that verify the performance of the proposed algorithm.}, number={6}, journal={IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Liu, Yu and Hong, Hoon and Huang, Alex Q.}, year={2009}, month={Jun}, pages={2249–2258} }
 @article{liu_hong_huang_2009, title={Real-Time Calculation of Switching Angles Minimizing THD for Multilevel Inverters With Step Modulation}, volume={56}, ISSN={["0278-0046"]}, url={http://dx.doi.org/10.1109/tie.2008.918461}, DOI={10.1109/TIE.2008.918461}, abstractNote={Multilevel inverters have been widely applied in industries. A family of optimal pulsewidth modulation (PWM) methods for multilevel inverters, such as step modulation, can generate output voltage with less harmonic distortion than popular modulation strategies, such as the carrier-based sinusoidal PWM or the space vector PWM. However, some drawbacks limit the application of optimal PWM. One of such crucial drawback is that the optimal switching angles could not be calculated in real-time and one has to rely on lookup tables with precalculated angles. We propose a novel real-time algorithm for calculating switching angles that minimizes total harmonic distortion (THD) for step modulation. We give a mathematical proof that the output voltage has the minimum THD. We implemented the algorithm on a digital signal processor and provide experimental results that verify the performance of the proposed algorithm.}, number={2}, journal={IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Liu, Yu and Hong, Hoon and Huang, Alex Q.}, year={2009}, month={Feb}, pages={285–293} }
 @inproceedings{huang_2009, title={Renewable energy system research and education at the nsf freedm systems center}, DOI={10.1109/pes.2009.5275511}, abstractNote={The Future Renewable Electric Energy Delivery and Management (FREEDM) Systems Center is a new National Science Foundation (NSF) Generation-III Engineering Research Center (ERC) established in 2008 with the mission to develop the fundamental and enabling technologies necessary for a new and paradigm shifting power grid infrastructure, the FREEDM System. The center involves more than fifty professors and one hundred fifty graduate and undergraduate students from five US universities and two international universities, as well as more than sixty companies and national laboratories in 28 states and 9 countries. This paper will highlight center version, mission and research and education.}, booktitle={2009 ieee power & energy society general meeting, vols 1-8}, author={Huang, A. Q.}, year={2009}, pages={5170–5175} }
 @article{liu_huang_song_bhattacharya_tan_2009, title={Small-Signal Model-Based Control Strategy for Balancing Individual DC Capacitor Voltages in Cascade Multilevel Inverter-Based STATCOM}, volume={56}, ISSN={["1557-9948"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-67649366309&partnerID=MN8TOARS}, DOI={10.1109/TIE.2009.2017101}, abstractNote={This paper presents a new feedback control strategy for balancing individual DC capacitor voltages in a three-phase cascade multilevel inverter-based static synchronous compensator. The design of the control strategy is based on the detailed small-signal model. The key part of the proposed controller is a compensator to cancel the variation parts in the model. The controller can balance individual DC capacitor voltages when H-bridges run with different switching patterns and have parameter variations. It has two advantages: 1) the controller can work well in all operation modes (the capacitive mode, the inductive mode, and the standby mode) and 2) the impact of the individual DC voltage controller on the voltage quality is small. Simulation results and experimental results verify the performance of the controller.}, number={6}, journal={IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS}, author={Liu, Yu and Huang, Alex Q. and Song, Wenchao and Bhattacharya, Subhashish and Tan, Guojun}, year={2009}, month={Jun}, pages={2259–2269} }
 @article{xu_liu_huang_2009, title={Two-Phase Interleaved Critical Mode PFC Boost Converter With Closed Loop Interleaving Strategy}, volume={24}, ISSN={["1941-0107"]}, DOI={10.1109/TPEL.2009.2019824}, abstractNote={This paper presents a two-phase interleaved critical mode (CRM) power factor correction (PFC) boost converter with a novel closed loop interleaving technique. This new interleaving technique makes each phase work at ideally CRM. Natural current sharing and precise 180° phase shift are achieved. The scheme can be easily integrated into a PFC control chip. Full-order averaged model of CRM boost is derived to analyze the stability of the converter. The loop response and stability of the closed-phase regulation loop have been analyzed. A 400 W two-phase interleaved CRM PFC boost converter prototype is built. This proposed scheme is verified by simulation and experimental results.}, number={12}, journal={IEEE TRANSACTIONS ON POWER ELECTRONICS}, author={Xu, Xiaojun and Liu, Wei and Huang, Alex Q.}, year={2009}, month={Dec}, pages={3003–3013} }
 @article{wang_zhao_li_huang_callanan_husna_agarwal_2008, title={Characterization, modeling, and application of 10-kV SiC MOSFET}, volume={55}, ISSN={["1557-9646"]}, DOI={10.1109/TED.2008.926650}, abstractNote={Ten-kilovolt SiC MOSFETs are currently under development by a number of organizations in the United States, with the aim of enabling their applications in high-voltage high-frequency power conversions. The aim of this paper is to obtain the key device characteristics of SiC MOSFETs so that their realistic application prospect can be provided. In particular, the emphasis is on obtaining their losses in various operation conditions from the extensive characterization study and a proposed behavioral SPICE model. Using the validated MOSFET SPICE model, a 20-kHz 370-W dc/dc boost converter based on a 10-kV 4H-SiC DMOSFET and diodes is designed and experimentally demonstrated. In the steady state of the boost converter, the total power loss in the 15.45-mm2 SiC MOSFET is 23.6 W for the input power of 428 W. The characterization study of the experimental SiC MOSFET and the experiment of the SiC MOSFET-based boost converter indicate that the turn-on losses of SiC MOSFETs are the dominant factors in determining their maximum operation frequency in hard-switched circuits with conventional thermal management. Replacing a 10-kV SiC PiN diode with a 10-kV SiC JBS diode as a boost diode and using a small external gate resistor, the turn-on loss of the SiC MOSFET can be reduced, and the 10-kV 5-A SiC MOSFET-based boost converter is predicted to be capable of a 20-kHz operation with a 5-kV dc output voltage and a 1.25-kW output power by the PSpice simulation with the MOSFET model. The low losses and fast switching speed of 10-kV SiC MOSFETs shown in the characterization study and the preliminary demonstration of the boost converter make them attractive in high-frequency high-voltage power-conversion applications.}, number={8}, journal={IEEE TRANSACTIONS ON ELECTRON DEVICES}, author={Wang, Jun and Zhao, Tiefu and Li, Jun and Huang, Alex Q. and Callanan, Robert and Husna, Fatima and Agarwal, Anant}, year={2008}, month={Aug}, pages={1798–1806} }
 @article{gao_huang_krishnaswami_richmond_agarwal_2008, title={Comparison of static and switching characteristics of 1200 V 4H-SiCBJT and 1200 V Si-IGBT}, volume={44}, ISSN={["1939-9367"]}, DOI={10.1109/TIA.2008.921408}, abstractNote={In this paper, static and switching characteristics of a 1200 V 4H-silicon carbide (SiC) bipolar junction transistor (BJT) at a bus voltage of 600 V are reported for the first time. Comparison was made between the SiC BJT and a 1200 V Si insulated gate bipolar transistor (IGBT). The experimental data show that the SiC BJT has much smaller conduction and switching losses than the Si IGBT. The SiC BJT also shows an extremely large reverse bias safe operation area, and no second breakdown was observed. This removes one of the most unattractive aspects of the BJT. The results prove that, unlike Si BJTs, BJTs in 4H-SiC are good competitors for Si IGBTs.}, number={3}, journal={IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS}, author={Gao, Yan and Huang, Alex Q. and Krishnaswami, Sumi and Richmond, Jim and Agarwal, Anant K.}, year={2008}, pages={887–893} }
 @article{liu_bhattacharya_song_huang_2008, title={Control Strategy for Cascade Multilevel Inverter based STATCOM with Optimal Combination Modulation}, ISBN={["978-1-4244-1667-7"]}, ISSN={["0275-9306"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-52349084808&partnerID=MN8TOARS}, DOI={10.1109/pesc.2008.4592734}, abstractNote={Static synchronous compensation (STATCOM) is a flexible AC transmission system (FACTS) device connected in shunt to the network for generating or absorbing reactive power. The STATCOM is used to regulate voltage, control power factor and stabilize power flow. The transformerless STATCOM is attractive due to low cost and power losses. Cascaded multilevel inverters are viable topologies for the transformerless STATCOM since each power semiconductor device only sustains low voltage. To meet IEEE 519 standard and keep low switching frequency, an optimal combination modulation strategy is used, which leads to some challenges in designing the controller, such as extra switching and the balancing of individual dc capacitor voltages. In this paper, the design of the controller is specified. Simulation results and experimental results are shown to verify the performance of the proposed control strategy.}, journal={2008 IEEE POWER ELECTRONICS SPECIALISTS CONFERENCE, VOLS 1-10}, author={Liu, Yu and Bhattacharya, Subhashish and Song, Wenchao and Huang, Alex Q.}, year={2008}, pages={4812–4818} }
 @article{zhang_wang_jonas_callanan_sumakeris_ryu_das_agarwal_palmour_huang_2008, title={Design and characterization of high-voltage 4H-SiC p-IGBTs}, volume={55}, ISSN={["1557-9646"]}, DOI={10.1109/TED.2008.926627}, abstractNote={High-voltage p-channel 4H-SiC insulated gate bipolar transistors (IGBTs) have been fabricated and characterized. The devices have a forward voltage drop of 7.2 V at 100 A/cm2 and a -16 V gate bias at 25degC, corresponding to a specific on-resistance of 72 mOmega ldr cm2 and a differential on-resistance of 26 mmOmega ldr cm2. Hole mobility of 12 cm2/V ldr s in the inversion channel with a threshold voltage of -6 V was achieved by optimizing the n+ well doping profile and gate oxidation process. A novel current enhancement layer was adopted to reduce the JFET resistance and enhance conductivity modulation by improving hole current spreading and suppressing the electron current conduction through the top n-p-n transistor. Inductive switching results have shown that the p-IGBT exhibited a turn-off time of ~1 mus and a turn-off energy loss of 12 m J at 4-kV dc-link voltage and 6-A load current at 25degC. The turn-off trajectory from the measured inductive load switching waveforms and numerical simulations shows that the p-IGBT had a near-square reverse bias safe operating area. Numerical simulations have been conducted to achieve an improved tradeoff between forward voltage drop and switching off energy by investigating the effects of drift layer lifetime and p-buffer layer parameters. The advantages of SiC p-IGBTs, such as the potential of very low ON-state resistance, slightly positive temperature coefficient, high switching speed, small switching losses, and large safe operating area, make them suitable and attractive for high-power high-frequency applications.}, number={8}, journal={IEEE TRANSACTIONS ON ELECTRON DEVICES}, author={Zhang, Qingchun and Wang, Jun and Jonas, Charlotte and Callanan, Robert and Sumakeris, Joseph J. and Ryu, Sei-Hyung and Das, Mrinal and Agarwal, Anant and Palmour, John and Huang, Alex Q.}, year={2008}, month={Aug}, pages={1912–1919} }
 @article{han_huang_baran_bhattacharya_litzenberger_anderson_johnson_edris_2008, title={STATCOM impact study on the integration of a large wind farm into a weak loop power system}, volume={23}, ISSN={["1558-0059"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-40849120152&partnerID=MN8TOARS}, DOI={10.1109/TEC.2006.888031}, abstractNote={Recently, renewable wind energy is enjoying a rapid growth globally to become an important green electricity source to replace polluting and exhausting fossil fuel. However, with wind being an uncontrollable resource and the nature of distributed wind induction generators, integrating a large-scale wind-farm into a power system poses challenges, particularly in a weak power system. In the paper, the impact of STATCOM to facilitate the integration of a large wind farm into a weak power system is studied. First, an actual weak power system with two nearby large wind farms is introduced. Based on the field SCADA data analysis, the power quality issues are highlighted and a centralized STATCOM is proposed to solve them, particularly the short-term (seconds to minutes) voltage fluctuations. Second, a model of the system, wind farm and STATCOM for steady-state and dynamic impact study is presented, and the model is validated by comparing with the actual field data. Using simulated PV and QV curves, voltage control and stability issues are analyzed, and the size and location of STATCOM are assessed. Finally, a STATCOM control strategy for voltage fluctuation suppression is presented and dynamic simulations verify the performance of proposed STATCOM and its control strategy}, number={1}, journal={IEEE TRANSACTIONS ON ENERGY CONVERSION}, author={Han, Chong and Huang, Alex Q. and Baran, Mesut E. and Bhattacharya, Subliashish and Litzenberger, Wayne and Anderson, Loren and Johnson, Anders L. and Edris, Abdel-Aty}, year={2008}, month={Mar}, pages={226–233} }
 @article{gao_huang_agarwal_zhang_2008, title={Theoretical and experimental analyses of safe operating area (SOA) of 1200-V 4H-SiC BJT}, volume={55}, ISSN={["1557-9646"]}, DOI={10.1109/TED.2008.926682}, abstractNote={The safe operating area (SOA) of 1200-V SiC bipolar junction transistor (BJT) is investigated by experiments and simulations. The SiC BJT is free of the second breakdown even under the turn-off power density of 3.7 MW/cm2. The theoretical boundary of reverse-biased SOA caused by the false turn-on is obtained by simulations. The short-circuit capability of the 1200-V SiC BJT is also investigated theoretically and experimentally. Self-heating is considered by the nonisothermal simulation, and 1800-K maximum local temperature is the simulated critical temperature of device failure. The surface condition is very critical for short-circuit capability. From simulations, when the interface trap density increases, the critical temperature decreases. This is believed to be the reason why the experimental results show much shorter short-circuit withstand time than the simulation showed.}, number={8}, journal={IEEE TRANSACTIONS ON ELECTRON DEVICES}, author={Gao, Yan and Huang, Alex Q. and Agarwal, Anant K. and Zhang, Qingchun}, year={2008}, month={Aug}, pages={1887–1893} }
 @misc{wu_huang_zhu_zhang_2007, title={Apparatus and method for continuous conduction mode boost voltage power factor correction with an average current control mode}, volume={7,256,569}, number={2007 Aug. 14}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Wu, C. C. and Huang, Q. and Zhu, N. and Zhang, X.}, year={2007} }
 @inproceedings{zhao_wang_huang_agarwal_2007, title={Comparisons of SiC MOSFET and Si IGBT based motor drive systems}, ISBN={9781424412600}, DOI={10.1109/07ias.2007.51}, abstractNote={With the rapid development of silicon carbide (SiC) material quality, SiC power devices are gaining tremendous attentions in power electronics. In this paper, a SiC device based motor drive system is performed to provide a quantitative estimate of the system improvement. Two 60 kW motor drive systems based on SiC MOSFET/Schottky diode and Si IGBTs are designed. The power losses of the two inverters with sinusoidal pulse width modulation (SPWM) control are calculated analytically. By comparing the efficiencies, sizes and temperatures of the two designed systems, SiC device shows the superior advantages of smaller loss, better efficiency and smaller size in the same motor drive application.}, booktitle={Conference record of the 2007 IEEE Industry Applications Conference forty-second IAS annual meeting}, publisher={New York:  IEEE}, author={Zhao, T. F. and Wang, J. and Huang, A. Q. and Agarwal, A.}, year={2007}, pages={331–335} }
 @article{wang_huang_wang_2007, title={Development of a scalable power semiconductor switch (SPSS)}, volume={22}, ISSN={["1941-0107"]}, DOI={10.1109/TPEL.2006.889892}, abstractNote={This paper presents the design and development of a 4800-V, 300-A, 10-kHz scalable power semiconductor switch (SPSS) based on series connecting low voltage insulated gate bipolar transistors (IGBTs). The static and dynamic voltage balance among IGBTs is achieved using a hybrid approach of active clamp circuit and an active gate control that is also effective during tail current phase. The developed SPSS derives its control power directly from the main power bus. Control, packaging, and thermal characteristics are an integral part of the SPSS design. From a user's standpoint, the SPSS is a three-terminal optically controlled high-power switch. Experimental evaluation of the prototype SPSS shows it fully achieved the design objectives. In principle, the approach can be extended to building switches with higher voltages, currents, and switching frequencies, or even with other types of devices than IGBTs}, number={2}, journal={IEEE TRANSACTIONS ON POWER ELECTRONICS}, author={Wang, Hongfang and Huang, Alex Q. and Wang, Fei}, year={2007}, month={Mar}, pages={364–373} }
 @misc{huang_edris_ingram_sirisukprasert_2007, title={Method and circuit for cascaded pulse width modulation}, volume={7,230,837}, number={2007 Jun. 12}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Huang, Q. and Edris, A.-A. and Ingram, M. R. and Sirisukprasert, S.}, year={2007} }
 @misc{li_huang_dewhirst_2007, title={Method for selective expression of therapeutic genes by hyperthermia}, volume={7,183,262}, number={2007 Feb. 27}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Li, C. Y. and Huang, Q. and Dewhirst, M. W.}, year={2007} }
 @article{zhang_huang_2007, title={Monolithic/Modularized voltage regulator channel}, volume={22}, ISSN={["1941-0107"]}, DOI={10.1109/TPEL.2007.900466}, abstractNote={To achieve higher power density and design flexibility with unlimited phase number, the concept of monolithic/modularized voltage regulator channel (MVRC) is introduced to be a generic power integrated circuit (IC) solution for both central processing unit (CPU) and point-of-load (POL) power management. Novel control architecture and analog circuits are invented to implement the MVRC concept. Tolerance analysis and hardware testing verified that the MVRC approach is suitable for today's and even future's microprocessor power management.}, number={4}, journal={IEEE TRANSACTIONS ON POWER ELECTRONICS}, author={Zhang, Xin and Huang, Alex}, year={2007}, month={Jul}, pages={1162–1176} }
 @article{duan_huang_2006, title={Current-mode variable-frequency control architecture for high-current low-voltage DC-DC converters}, volume={21}, ISSN={["0885-8993"]}, DOI={10.1109/TPEL.2006.878031}, abstractNote={For controlling high-current low-voltage dc–dc converters, the control methods with variable switching frequency have the potential to achieve fast transient response and high efficiency. However, some issues in practical design limit the usefulness of the conventional variable-frequency control methods, such as the voltage-mode hysteretic control. This letter presents a novel implementation of current-mode variable-frequency control. The system architecture features a dual-loop feedback and a unique structure with symmetric signal paths for voltage and current signals. The symmetric structure provides practical advantages for integrated controller design to achieve accurate control on the droop resistance (or the load-line resistance). The system dynamics are analyzed with the small-signal model. Design guidelines are derived for simple compensation circuits to achieve constant output impedance. With variable switching frequency, the system achieves good dynamic response without requiring high switching frequency at steady-state. The system performance was verified by a two-channel interleaved controller chip implemented with CMOS technology.}, number={4}, journal={IEEE TRANSACTIONS ON POWER ELECTRONICS}, author={Duan, Xiaonung and Huang, Alex Q.}, year={2006}, month={Jul}, pages={1133–1137} }
 @article{zhang_huang_chen_atcitty_ingram_2006, title={Development and experimental demonstration of a self-powered ETO (SPETO)}, volume={42}, ISSN={["1939-9367"]}, DOI={10.1109/TIA.2006.882657}, abstractNote={This paper presents the design and experimental demonstration of a superior high-power-device self-powered emitter turn-off thyristor (SPETO). Different from conventional high-power devices which require external power input for their gate drivers, the SPETO achieves optically controlled turn on and turn off, and all of the internal power required is self-obtained. A low-loss gate-drive circuit is implemented which allows the simple power-up operation. During a normal switching operation, the SPETO obtains a power for the gate drive during its turn-on operation. A novel switching strategy is also introduced to minimize the gate-drive power requirement. The SPETO greatly reduces costs and increases the reliability of power converters since no external power supply for device gate drive is required. Therefore, the SPETO is suitable for high-power high-frequency voltage-source-converter applications}, number={6}, journal={IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS}, author={Zhang, Bin and Huang, Alex Q. and Chen, Bin and Atcitty, Stanley and Ingram, Michael}, year={2006}, pages={1387–1394} }
 @misc{wu_huang_duan_2006, title={High-speed PWM control apparatus for power converters with adaptive voltage position and its driving signal generating method}, volume={7,109,692}, number={2006 Sep. 19}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Wu, C. C. and Huang, Q. and Duan, X. M.}, year={2006} }
 @misc{huang_2005, title={Emitter turn-off thyristors (ETO)}, volume={6,933,541}, number={2005 Aug. 23}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Huang, A. Q.}, year={2005} }
 @article{deng_duan_sun_ma_huang_chen_2005, title={Monolithically integrated boost converter based on 0.5-mu m CMOS process}, volume={20}, ISSN={["1941-0107"]}, DOI={10.1109/TPEL.2005.846551}, abstractNote={Today and in the future, a huge market arises for mobile power . Efficient performance, functionality, small profile and low cost are the most desired features for mobile power management integrated circuits. Compared with the discrete-switching dc-dc converter, monolithic integration offers many benefits and new design challenges. In this paper, a monolithically integrated high-efficiency boost dc-dc converter for nickel metal hydride or alkaline battery-powered applications is designed based on the low-voltage CMOS process. Several novel concepts are proposed for compensator design, low-voltage startup, light-load efficiency and power device optimization.}, number={3}, journal={IEEE TRANSACTIONS ON POWER ELECTRONICS}, author={Deng, HF and Duan, XM and Sun, N and Ma, Y and Huang, AQ and Chen, D}, year={2005}, month={May}, pages={628–638} }
 @misc{huang_zhou_xu_2005, title={Solid-state DC circuit breaker}, volume={6,952,335}, number={2005 Oct. 4}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Huang, Q. and Zhou, X. and Xu, Z.}, year={2005} }
 @misc{bai_sun_huang_2004, title={Method and circuits for reducing dead time and reverse recovery loss in buck regulators}, volume={6,737,842}, number={2004 May 18}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Bai, Y. and Sun, N. and Huang, A. Q.}, year={2004} }
 @misc{huang_2003, title={Semiconductor structures with trench contacts}, volume={6,630,711}, number={2003 Oct. 7}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Huang, Q.}, year={2003} }
 @misc{li_a. q._motto_2002, title={Diode-assisted gate turn-off thyristor}, volume={6,426,666}, number={2002 Jul. 30}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Li, Y. Huang and A. Q. and Motto, K.}, year={2002} }
 @misc{huang_2002, title={Semiconductor structures with trench contacts}, volume={6,437,399}, number={2002 Aug. 20}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Huang, Q.}, year={2002} }
 @misc{huang_2000, title={Semiconductor structures with trench contacts}, volume={6,037,628}, number={2000 Mar. 14}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Huang, Q.}, year={2000} }
 @misc{huang_2000, title={Trench contact process}, volume={6,110,799}, number={2000 Aug. 29}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Huang, Q.}, year={2000} }
 @misc{huang_1999, title={Trench emitter controlled thyristor}, volume={5,998,811}, number={1999 Dec. 7}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Huang, Q.}, year={1999} }
 @misc{ekkaneth-madathil_huang_amaratunga_kumagai_1998, title={Semiconductor device}, volume={5,744,830}, number={1998 Apr. 28}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Ekkaneth-Madathil, S. and Huang, Q. and Amaratunga, G. A. J. and Kumagai, N.}, year={1998} }
 @misc{huang_1997, title={Conductivity-modulation semiconductor}, volume={5,665,988}, number={1997 Sep. 9}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Huang, Q.}, year={1997} }
 @misc{huang_1997, title={Semiconductor device and control method}, volume={5,621,229}, number={1997 Apr. 15}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Huang, Q.}, year={1997} }