@article{wang_yu_mann_meyer_tarmoom_chenetz_zhang_speer_2023, title={Isolated 3-Level DCDC Converter With Complete ZVS Using Magnetizing Inductors}, volume={38}, ISSN={["1941-0107"]}, DOI={10.1109/TPEL.2022.3212202}, abstractNote={An isolated dc–dc converter with dedicated 3-level modulation is proposed to achieve a 4:1 output voltage range, and complete zero-voltage-switching (ZVS) of all active switches using the magnetizing inductors. The single input 3-level modulation scheme coordinates the phase-shift, duty cycle, and switching frequency to ensure 1) the magnetizing currents are independent of load voltage and current; 2) the output voltage is proportional to the modulation input. As a result, the dual half- and full-bridge modes of the switching network are unified and modeled as a voltage-controlled voltage source, with the same control parameters for both modes of operation. In addition, the magnetizing-to-series inductance ratios of the leading and lagging transformers are increased to 100 and 25 times, respectively. Therefore, the circulating current is low, and the series inductors can be integrated into the transformers. The proposed topology is intended for high-power applications with a wide output voltage range but less input voltage variation. A <inline-formula><tex-math notation="LaTeX">$\text{30}\,\text{kW}$</tex-math></inline-formula> prototype with a power density of <inline-formula><tex-math notation="LaTeX">$\text{7.2}\,\text{kW}/\text{L}$</tex-math></inline-formula> and an output voltage of <inline-formula><tex-math notation="LaTeX">$\text{165}\,\text{V}$</tex-math></inline-formula>-<inline-formula><tex-math notation="LaTeX">$\text{680}\,\text{V}$</tex-math></inline-formula> was built and tested to verify the characteristics and feasibility of the proposed H8 topology plus modulation scheme.}, number={2}, journal={IEEE TRANSACTIONS ON POWER ELECTRONICS}, author={Wang, Dakai and Yu, Wensong and Mann, Greg and Meyer, Dennis and Tarmoom, Ehab and Chenetz, Steven and Zhang, Xuning and Speer, Kevin}, year={2023}, month={Feb}, pages={1910–1923} }
 @article{awal_montes_teng_wang_bipu_yu_lukic_husain_2023, title={Medium Voltage Solid State Transformer for Extreme Fast Charging Applications}, ISSN={["1048-2334"]}, DOI={10.1109/APEC43580.2023.10131285}, abstractNote={A modular and scalable solid state transformer (SST) with direct medium voltage (MV) AC connectivity is proposed to enable DC extreme fast charging (XFC) of electric vehicles. Single-phase-modules (SPMs), each consisting of an active-front-end (AFE) stage and an isolated DC-DC stage, are connected in input-series-output-parallel (ISOP) configuration. The modular hardware is co-designed with decentralized control of the DC-DC stages where voltage and power balancing are achieved by each SPM using only its local sensor feedback; a centralized controller (CC) regulates the low voltage (LV) DC bus through the AFE stages without any sensor feedback form the SPMs. The controller architecture contrasts sharply with the prior art for MV AC to LV DC SSTs where high-speed bidirectional communication among SPMs and a CC are required for module-level voltage and power balancing, which severely limits the scalability and practical realization of higher voltage and higher power units. Detailed small-signal analysis and controller design guidelines are developed. Furthermore, a soft start-up strategy is presented. The proposed converter and control structure are validated through simulation and experimental results.}, journal={2023 IEEE APPLIED POWER ELECTRONICS CONFERENCE AND EXPOSITION, APEC}, author={Awal, M. A. and Montes, Oscar Andres and Teng, Fei and Wang, Dakai and Bipu, Md Rashed Hasan and Yu, Wensong and Lukic, Srdjan and Husain, Iqbal}, year={2023}, pages={1528–1535} }
 @article{yang_liu_yu_husain_2023, title={Sequence Prediction for SiC MOSFET Active Gate Driving With a Recurrent Neural Network}, volume={4}, ISSN={["2644-1241"]}, DOI={10.1109/OJIA.2023.3291637}, abstractNote={This article develops a recurrent neural network (RNN) with an encoder–decoder structure to predict the driving sequence of SiC MOSFET active gate drivers (AGDs). With a set of switching targets as the input, the predictor generates an optimal active gate driving sequence to improve the switching transient. The development is based on a hybrid platform across MATLAB, PyTorch, and LTspice. A high-fidelity switching model is implemented in MATLAB to obtain reliable training data. The sequence predictor is trained with PyTorch. The predicted sequence is verified on an example Buck circuit in LTspice. In contrast to the state-of-the-art approach, the proposed method avoids exhaustive search in a large solution space; the sequence length is dynamically predicted per the driving strength at each step. The AGD sequences generated by the predictor effectively and precisely improve the switching transients, making the proposed sequence predictor an integral and valuable component for active gate driving.}, journal={IEEE OPEN JOURNAL OF INDUSTRY APPLICATIONS}, author={Yang, Li and Liu, Yuxuan and Yu, Wensong and Husain, Iqbal}, year={2023}, pages={227–237} }
 @article{chen_yu_wang_2022, title={Bidirectional H8 AC-DC Topology Combining Advantages of Both Diode-Clamped and Flying-Capacitor Three-Level Converters}, volume={10}, ISSN={["2168-6785"]}, DOI={10.1109/JESTPE.2021.3088390}, abstractNote={A three-level bidirectional ac–dc converter with H8 topology is proposed to combine the advantages of both neutral-point clamped and flying-capacitor (FC) three-level converters for medium-voltage (MV) ac–dc solid-state transformer (SST) applications. The innovative H8 converter features self-balanced capacitor voltage, common-mode voltage elimination, and small capacitance of the FCs. The proposed carrier-based modulation enables the H8 converter to operate under both active and reactive power conditions. A 10-kVA ac–dc converter prototype with 1.7-kV SiC MOSFETs and 3.3-kV SiC diodes verifies the feasibility and advantages of the proposed topology and the modulation method. The capacitance of the FCs in the H8 converter is reduced by 45 times compared to that of the FC converters. The H8 converter efficiency is tested up to 99% at 2-kV dc voltage. The proposed H8 converter is suitable for the next-generation PV inverter, grid-forming inverter, MV fast charger, and SST applications.}, number={4}, journal={IEEE JOURNAL OF EMERGING AND SELECTED TOPICS IN POWER ELECTRONICS}, author={Chen, Siyuan and Yu, Wensong and Wang, Dakai}, year={2022}, month={Aug}, pages={3643–3651} }
 @article{kercher_yu_husain_2022, title={Feedforward Deadtime Compensation Using Current Zero Crossing Detection}, ISSN={["2329-3721"]}, DOI={10.1109/ECCE50734.2022.9947454}, abstractNote={A feedforward deadtime compensation algorithm for inverters is proposed, utilizing current zero crossing detection (ZCD) to generate a current direction signal for the feedforward input. Conventional deadtime compensation relies on information from a standard current sensor, which may not capture current ripple behavior accurately due to latency, frequency response, and noise limitations. The ZCD and hardware logic circuits operate at extremely high speed, and the feedforward compensation algorithm has minimal computational requirements. Simulation results show a significant improvement in load current total harmonic distortion (THD). The proposed circuit was constructed, and hardware testing with a SiC inverter showed similar performance to simulation.}, journal={2022 IEEE ENERGY CONVERSION CONGRESS AND EXPOSITION (ECCE)}, author={Kercher, Michael and Yu, Wensong and Husain, Iqbal}, year={2022} }
 @article{wen_yu_geiger_husain_2022, title={Selective Gate Driver in SiC Inverter to Improve Fuel Economy of Electric Vehicles}, ISSN={["2329-3721"]}, DOI={10.1109/ECCE50734.2022.9947706}, abstractNote={This paper proposes a selective gate driver (SGD) strategy that can adjust gate resistance based on estimations of relatively slow operating variables for each switching cycle (tens of $\mu\mathrm{s}$) to improve the fuel economy of electric vehicles and maintain the system reliability. With a conventional gate driver (CGD), switching energy loss, drain-source voltage changing rate, and drain-source voltage overshoot are fixed and constrained. The proposed SGD with multi-level gate resistance selection, which uses a single digital channel to match various inverter operating conditions, such as various dc-link voltage and varying output load currents, is developed. The proposed SGD can reduce switching energy loss while maintaining the drain-source voltage overshoot within the requirement with no need for ultra-fast dynamic control. An inverter simulation model with SGD incorporated in an electric vehicle system model for energy analysis is presented. The comparison of CGD and the proposed SGD shows that up to 1.24% improvement in energy saving for an HWFET driving cycle with the Tesla Model 3 electric vehicle is achieved. Furthermore, the SGD overcomes the implementation challenges due to the inherent feedback delay in the existing adaptive gate driver (AGD) method, which requires adjusting the gate drive strength in the nanoseconds range.}, journal={2022 IEEE ENERGY CONVERSION CONGRESS AND EXPOSITION (ECCE)}, author={Wen, Luowei and Yu, Wensong and Geiger, John and Husain, Iqbal}, year={2022} }
 @article{wang_yu_2022, title={Soft-Switching dv/dt Filter with Ultra High Power Density and 50% Power Loss Savings for 150 kW SiC Motor Drives}, ISSN={["2329-3721"]}, DOI={10.1109/ECCE50734.2022.9947467}, abstractNote={This paper presents a SiC-based soft-switching dv/dt filter using a parallel inductor to achieve ultra-high efficiency and limit the output dv/dt below 6V/ns for high-power motor drive applications. All main SiC devices are switched with the fastest speed and minimized switching loss due to the zero-voltage-switching under any input/output voltage and load conditions. The filter inductor RMS current is reduced by 86% using an inductor in parallel instead of in series with the load. The proposed matrix solenoid air-core filter inductor with near field leakage flux cancellation increases the energy density by two times compared to the toroidal shape. Compared to the motor drives with passive dv/dt filters, the total power loss of the motor drive with the soft-switching dv/dt filter is reduced by 50%, and the dv/dt filter volume reduction is by 90%. Simulation and experimental results and comparisons demonstrate the feasibility and advantages of the soft-switching dv/dt filter.}, journal={2022 IEEE ENERGY CONVERSION CONGRESS AND EXPOSITION (ECCE)}, author={Wang, Dakai and Yu, Wensong}, year={2022} }
 @article{rahman_kercher_yu_husain_2021, title={Comparative Evaluation of Current Sensors for High-Power SiC Converter Applications}, ISSN={["1048-2334"]}, DOI={10.1109/APEC42165.2021.9487428}, abstractNote={An evaluation procedure for comparative analysis of various current sensor technologies is proposed in which performance parameters such as latency and resolution are measured under realistic conditions for a high-power SiC converter. Testing techniques are developed to allow fair comparison between dissimilar sensor types. Experimental data is given for an open-loop Hall Effect sensor and two types of shunt-based sensors utilizing Delta-Sigma modulators.}, journal={2021 THIRTY-SIXTH ANNUAL IEEE APPLIED POWER ELECTRONICS CONFERENCE AND EXPOSITION (APEC 2021)}, author={Rahman, Dhrubo and Kercher, Michael and Yu, Wensong and Husain, Iqbal}, year={2021}, pages={2206–2210} }
 @article{husain_ozpineci_islam_gurpinar_su_yu_chowdhury_xue_rahman_sahu_2021, title={Electric Drive Technology Trends, Challenges, and Opportunities for Future Electric Vehicles}, volume={109}, ISSN={["1558-2256"]}, DOI={10.1109/JPROC.2020.3046112}, abstractNote={The transition to electric road transport technologies requires electric traction drive systems to offer improved performances and capabilities, such as fuel efficiency (in terms of MPGe, i.e., miles per gallon of gasoline-equivalent), extended range, and fast-charging options. The enhanced electrification and transformed mobility are translating to a demand for higher power and more efficient electric traction drive systems that lead to better fuel economy for a given battery charge. To accelerate the mass-market adoption of electrified transportation, the U.S. Department of Energy (DOE), in collaboration with the automotive industry, has announced the technical targets for light-duty electric vehicles (EVs) for 2025. This article discusses the electric drive technology trends for passenger electric and hybrid EVs with commercially available solutions in terms of materials, electric machine and inverter designs, maximum speed, component cooling, power density, and performance. The emerging materials and technologies for power electronics and electric motors are presented, identifying the challenges and opportunities for even more aggressive designs to meet the need for next-generation EVs. Some innovative drive and motor designs with the potential to meet the DOE 2025 targets are also discussed.}, number={6}, journal={PROCEEDINGS OF THE IEEE}, author={Husain, Iqbal and Ozpineci, Burak and Islam, Md Sariful and Gurpinar, Emre and Su, Gui-Jia and Yu, Wensong and Chowdhury, Shajjad and Xue, Lincoln and Rahman, Dhrubo and Sahu, Raj}, year={2021}, month={Jun}, pages={1039–1059} }
 @article{luo_awal_yu_husain_2021, title={FPGA-Based High-Bandwidth Motor Emulator for Interior Permanent Magnet Machine Utilizing SiC Power Converter}, volume={9}, ISSN={["2168-6785"]}, DOI={10.1109/JESTPE.2020.3015179}, abstractNote={A high-bandwidth (>20 kHz) motor emulator (ME) prototype for ac machines, utilizing field programmable gate array (FPGA)-based hybrid model predictive control (MPC) and a high fidelity motor model and implemented with a voltage source power converter, and fast-switching SiC devices, is presented in this article. The hybrid MPC incorporates a unique gate stitching modulation strategy that synchronizes the inverter switching state with the ME switching state for an accurate representation of the emulated motor currents in the physical inverter hardware output. The gate stitching MPC hybrid algorithm avoids the need for an excessively high switching frequency of the ME power converter. The developed high-bandwidth ME can emulate up to the switching ripple current of the inverter under test (IUT) where the current slope can change up to six times within one switching period when using space vector pulse width modulation (PWM). The FPGA-based fast iterating online motor model is another key component which along with the high-performance ME current regulation algorithm can accurately emulate the motor current. The bandwidth achieved far exceeds that of existing ME solutions that can only emulate fundamental current and only a few orders of harmonic content. The high bandwidth also allows the use of a small line inductor, which reduces the size and cost of the ME system. Simulation and experiment results are provided to the FPGA implementation and validate the high-bandwidth current emulating capability.}, number={4}, journal={IEEE JOURNAL OF EMERGING AND SELECTED TOPICS IN POWER ELECTRONICS}, author={Luo, Yukun and Awal, M. A. and Yu, Wensong and Husain, Iqbal}, year={2021}, month={Aug}, pages={4340–4353} }
 @article{awal_bipu_montes_feng_husain_yu_lukic_2020, title={Capacitor Voltage Balancing for Neutral Point Clamped Dual Active Bridge Converters}, volume={35}, ISSN={["1941-0107"]}, DOI={10.1109/TPEL.2020.2988272}, abstractNote={A capacitor voltage balancing method is proposed for a full-bridge neutral point diode clamped (NPC) dual-active bridge (DAB) converter. In existing literature, capacitor voltage balancing is achieved by actively selecting between the small voltage vectors, i.e., connecting either the upper or the lower capacitor on the dc bus to the transformer winding, on the basis of measured voltage mismatch. These balancing methods are dependent on the direction of power flow through the DAB converter. In this work, we propose a voltage balancing controller, which is independent of power flow direction and does not require adjustments of active voltage vectors through the modulator. Irrespective of the direction of transformer current, by dynamically shifting the switching instants of the inner switch pairs in the two NPC legs during the free-wheeling/zero voltage vector time, either of the two capacitors can be selectively charged without introducing any offsets in the voltage-second seen by the transformer. A simple bidirectional phase-shift modulator is designed to facilitate voltage balancing irrespective of power flow direction or mode of operation. The proposed method is highly and universally effective under any converter operating condition and was verified and demonstrated through analysis, simulation, and hardware experiments using a laboratory prototype.}, number={10}, journal={IEEE TRANSACTIONS ON POWER ELECTRONICS}, author={Awal, M. A. and Bipu, Md Rashed Hassan and Montes, Oscar Andres and Feng, Hao and Husain, Iqbal and Yu, Wensong and Lukic, Srdjan}, year={2020}, pages={11267–11276} }
 @article{moorthy_aberg_olimmah_yang_rahman_lemmon_yu_husain_2020, title={Estimation, Minimization, and Validation of Commutation Loop Inductance for a 135-kW SiC EV Traction Inverter}, volume={8}, ISSN={["2168-6785"]}, DOI={10.1109/JESTPE.2019.2952884}, abstractNote={With growing interests in low-inductance silicon carbide (SiC)-based power module packaging, it is vital to focus on system-level design aspects to facilitate easy integration of the modules and reap system-level benefits. To effectively utilize the low-inductance modules, busbar and interconnects should also be designed with low stray inductances. A holistic investigation of the flux path and flux cancellations in the module-busbar assembly, which can be treated as differentially coupled series inductors, is thus mandatory for a system-level design. This article presents a busbar design, which can be adopted to effectively integrate the CREE’s low-inductance 1.2-/1.7-kV SiC power modules. This article also proposes a novel measurement technique to measure the inductance of the module-busbar assembly as a whole rather than deducing it from individual components. The inductance of the overall commutation loop of the inverter that encompasses the SiC power module, interconnects, and printed circuit board (PCB) busbar has been estimated using finite-element analysis (FEA). Insights gained from FEA provided the guidelines to decide the placement of the decoupling capacitors in the busbar to minimize the overall commutation loop inductance from 12.8 to 7.4 nH, which resulted in a significant reduction in the device voltage overshoot. The simulation results have been validated through measurements using an impedance analyzer (ZA) with less than 5% difference between the extracted loop inductance from FEA and measurements. The busbar design study and the measurement technique discussed in this article can be easily extended to other power module packages. Finally, the 135-kW inverter has been compared to a similar high-power inverter utilizing a laminated busbar to highlight the performance of the former.}, number={1}, journal={IEEE JOURNAL OF EMERGING AND SELECTED TOPICS IN POWER ELECTRONICS}, author={Moorthy, Radha Sree Krishna and Aberg, Bryce and Olimmah, Marshal and Yang, Li and Rahman, Dhrubo and Lemmon, Andrew N. and Yu, Wensong and Husain, Iqbal}, year={2020}, month={Mar}, pages={286–297} }
 @article{awal_yu_husain_2020, title={Passivity-Based Predictive-Resonant Current Control for Resonance Damping in LCL-Equipped VSCs}, volume={56}, ISSN={["1939-9367"]}, DOI={10.1109/TIA.2019.2959594}, abstractNote={In this article, we propose a frequency-domain passivity-based damping controller combined with predictive current control for LCL-filter-equipped voltage source converters (VSCs) connected to an arbitrary ac network to achieve passive VSC input admittance almost up to the Nyquist frequency. The controller guarantees resonance damping in the corresponding frequency range irrespective of the network impedance seen by the VSC. Resonant current compensation is added to eliminate the steady-state tracking error and to achieve superior disturbance rejection. We have used impedance-based method for the analysis of harmonic resonance instabilities caused by current controllers. The developed passivity-based predictive-resonant current controller is analytically shown to stabilize interactions among multiparalleled VSCs. Resonance damping capability of the proposed method is validated through simulation and hardware experiments.}, number={2}, journal={IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS}, author={Awal, M. A. and Yu, Wensong and Husain, Iqbal}, year={2020}, pages={1702–1713} }
 @article{awal_yu_husain_yu_lukic_2020, title={Selective Harmonic Current Rejection for Virtual Oscillator Controlled Grid-Forming Voltage Source Converters}, volume={35}, ISSN={0885-8993 1941-0107}, url={http://dx.doi.org/10.1109/tpel.2020.2965880}, DOI={10.1109/tpel.2020.2965880}, abstractNote={Virtual oscillator control (VOC) is a nonlinear grid-forming controller that simultaneously achieves the functionality of output voltage control and primary control layers in a power electronics interfaced distributed generation (DG) unit. Unlike conventional phasor-based primary control methods such as the droop control and virtual synchronous machine control, VOC is a time-domain controller that can guarantee almost global asymptotic synchronization. However, the high-frequency dynamics has largely been ignored in the analysis of VOC in prior art; as a result, VOC-based DGs fail to suppress harmonic current in the presence of harmonic distortion in the network-side voltage. In this work, we demonstrate that frequency-domain method can be used for oscillator-based converters in the high-frequency range, specifically, for harmonic mitigation in the converter output current. We propose a virtual impedance-based selective harmonic current suppression method, and demonstrate that it is better to use the network-side current feedback rather than that of the converter-side current for VOC implementation with virtual impedance control. Established harmonic rejection strategies for grid-following and conventional grid-forming converters are compared with the proposed method for VOC. Through impedance-based analysis, we demonstrate that the proposed method augments the passivity range of the converter terminal response with a much simpler implementation. The proposed harmonic suppression strategy is validated through hardware experiments using a single-phase inverter prototype.}, number={8}, journal={IEEE Transactions on Power Electronics}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Awal, M A and Yu, Hui and Husain, Iqbal and Yu, Wensong and Lukic, Srdjan M.}, year={2020}, month={Aug}, pages={8805–8818} }
 @misc{satvik_yu_wang_chen_2020, title={Switched Capacitor Converter with Flexible Voltage Gain and 99.2% Efficiency Utilizing Autotransformer}, url={http://dx.doi.org/10.1109/ecce44975.2020.9235902}, DOI={10.1109/ecce44975.2020.9235902}, abstractNote={This paper presents a novel topology for bidirectional power transfer between an Energy Storage System and a DC Microgrid. The topology provides a cost-effective, high-efficiency approach to extend the voltage gain range of a switched capacitor converter with only addition of an autotransformer. The proposed non-isolated topology is derived from an isolated dual active bridge (DAB) converter. In which, the flexible voltage gain is realized by selecting of the turn's ratio of an autotransformer with bidirectional phase-shift modulation. A 30 kW prototype is designed, manufactured, and tested. It has verified the operating principle of the proposed converter with 99.2% peak measured power conversion efficiency.}, journal={2020 IEEE Energy Conversion Congress and Exposition (ECCE)}, publisher={IEEE}, author={Satvik and Yu, Wensong and Wang, Dakai and Chen, Siyuan}, year={2020}, month={Oct} }
 @misc{wang_yu_chen_philpott_2019, title={AC-DC Converter with Hybrid Three-Level and Two-Level Legs Using Space Vector Modulation for Medium-Voltage SST Applications}, url={http://dx.doi.org/10.1109/ecce.2019.8912588}, DOI={10.1109/ecce.2019.8912588}, abstractNote={This paper presents a single-phase five-level AC-DC converter with hybrid three-level and two-level legs using space vector modulation for medium-voltage SST application. The hybrid topology combines the low-loss Silicon Carbide (SiC) MOSFET and low-cost IGBT to solve the issues of severe switching-loss of semiconductors, unavailable medium-voltage SiC MOSFET, bulky volume of the inductor and high system cost under medium voltage. The converter reduces the number of active switches and transformers compared to the existing solutions. Moreover, a simple space vector modulation scheme which solves the zero-crossing distortion of presented topology is proposed and verified to realize the smooth transition between switch states for the hybrid topology using a digital signal processor (DSP) instead of FPGA. A 10 kW prototype has been built and verified the topology and modulation scheme.}, journal={2019 IEEE Energy Conversion Congress and Exposition (ECCE)}, publisher={IEEE}, author={Wang, Dakai and Yu, Wensong and Chen, Siyuan and Philpott, David}, year={2019}, month={Sep} }
 @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} }
 @misc{wang_yu_2019, title={Series Connection of SiC MOSFETs with Hybrid Active and Passive Clamping for Solid State Transformer Applications}, url={http://dx.doi.org/10.1109/wipda46397.2019.8998791}, DOI={10.1109/wipda46397.2019.8998791}, abstractNote={This paper presents a novel hybrid active and passive clamping technique for series-connected SiC MOSFETs with simple circuit structure and minimized power loss. Firstly, a dedicated switching pattern with predefined dead-time is proposed to keep the direction of current through flying capacitor unchanged under all conditions. Secondly, only single passive clamping device is in parallel connection with a small capacitor to clamp the voltages across all four SiC MOSFETs in a bridge leg within a few nanoseconds during high-speed dynamic switching transition of turn-on and turn-off. Then, the technology is extended to series-connection of n $n > 1)$ pieces of SiC MOSFETs in series per position in bridge structure using (n-1) clamping devices and capacitors. The hybrid clamping technique could be applied in any topologies including AC-DC and DC-DC. A 10 kW prototype has been built and verified the proposed topology and modulation scheme. The power loss on clamping device is negligible (0.02% of the output power). At the same time, the tested voltage stresses across all 1.7 kV SiC MOSFETs are less than 1.1 kV at 2 kV dc-link voltage.}, journal={2019 IEEE 7th Workshop on Wide Bandgap Power Devices and Applications (WiPDA)}, publisher={IEEE}, author={Wang, Dakai and Yu, Wensong}, year={2019}, month={Oct} }
 @inproceedings{aberg_moorthy_yang_yu_husain_2018, title={Estimation and minimization of power loop inductance in 135 kW SiC traction inverter}, DOI={10.1109/apec.2018.8341257}, abstractNote={The paper discusses the estimation and minimization of commutation loop inductance for a printed circuit board (PCB) busbar based 135 kW SiC inverter with a 1 kV DC link using finite element analysis (FEA) simulations. For the inductance estimation of the power module (Wolfspeed: HT-3231-R), PCB busbar, and customized interconnects constituting the commutation loop have been modelled accurately in Ansys Q3D Extractor. Based on the simulation results, subsequent modification to the original PCB busbar design has been proposed to lower the loop inductance. FEA simulation results have resulted in an optimized PCB busbar with lower commutation loop inductance, thereby limiting the device voltage spike well below its rated value. Loop inductance results from the Q3D simulation have been validated through double pulse tests (DPT) and the performance improvements achieved therefore have been highlighted.}, booktitle={Thirty-third annual ieee applied power electronics conference and exposition (apec 2018)}, author={Aberg, B. and Moorthy, R. S. K. and Yang, L. and Yu, Wensong and Husain, I.}, year={2018}, pages={1772–1777} }
 @article{song_zhang_liang_jiang_yu_2018, title={Fault-Tolerant Control for a Flexible Group Battery Energy Storage System Based on Cascaded Multilevel Converters}, volume={11}, ISSN={["1996-1073"]}, DOI={10.3390/en11010171}, abstractNote={A flexible group battery energy storage system (FGBESS) based on cascaded multilevel converters is attractive for renewable power generation applications because of its high modularity and high power quality. However, reliability is one of the most important issues and the system may suffer from great financial loss after fault occurs. In this paper, based on conventional fundamental phase shift compensation and third harmonic injection, a hybrid compensation fault-tolerant method is proposed to improve the post-fault performance in the FGBESS. By adjusting initial phase offset and amplitude of injected component, the optimal third harmonic injection is generated in an asymmetric system under each faulty operation. Meanwhile, the optimal redundancy solution under each fault condition is also elaborated comprehensively with a comparison of the presented three fault-tolerant strategies. This takes full advantage of battery utilization and minimizes the loss of energy capacity. Finally, the effectiveness and feasibility of the proposed methods are verified by results obtained from simulations and a 10 kW experimental platform.}, number={1}, journal={ENERGIES}, author={Song, Junhong and Zhang, Weige and Liang, Hui and Jiang, Jiuchun and Yu, Wensong}, year={2018}, month={Jan} }
 @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{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} }
 @inproceedings{yang_gao_yu_husain_2017, title={A geometrical linearization approach for salient-pole PMSM optimal voltage/current constrained control over whole speed range}, DOI={10.1109/ecce.2017.8095803}, abstractNote={Permanent Magnet Synchronous Machine (PMSM) torque control over a wide speed range is essentially an optimization problem that treats torque error minimization as the objective function with inverter voltage and current as constraints. It is usually time consuming and difficult to solve such optimization problem for closed-form solutions since torque, voltage and current equations are all non-linear in the problem. In this paper, a model linearization based approach is proposed to manage the calculation complexity for such non-linear optimization. By dividing the problem into two sub-optimizations and solving them sequentially, the calculation is simplified. By identifying different operating regions of the PMSM, the closed-form solutions can be obtained geometrically with model linearization, which further simplifies the optimization process. The proposed algorithm is implemented for PMSM current loop controller design; simulation results show a good performance of the controller.}, booktitle={2017 ieee energy conversion congress and exposition (ecce)}, author={Yang, L. and Gao, R. and Yu, Wensong and Husain, I.}, year={2017}, pages={350–356} }
 @article{peng_mackey_husain_huang_yu_lequesne_briggs_2017, title={Active Damping of Ultrafast Mechanical Switches for Hybrid AC and DC Circuit Breakers}, volume={53}, ISSN={["1939-9367"]}, DOI={10.1109/tia.2017.2740830}, abstractNote={An active damping method for Thomson coil actuated ultrafast mechanical switches is proposed, including its control. Ultrafast 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 15 kV/630 A/1 ms mechanical switch designed to enable the fast protection of medium voltage dc circuits is used as a testbed for the concept. The switch is based on the principle of repulsion forces (Thomson coil actuator). By energizing a second coil, higher opening speeds can be damped, resulting in 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.}, number={6}, journal={IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS}, author={Peng, Chang and Mackey, Landon and Husain, Iqbal and Huang, Alex Q. and Yu, Wensong and Lequesne, Bruno and Briggs, Roger}, year={2017}, pages={5354–5364} }
 @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{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} }
 @inproceedings{gao_yang_yu_husain_2017, title={Gate driver design for a high power density EV/HEV traction driveu using silicon carbide MOSFET six-pack power modules}, DOI={10.1109/ecce.2017.8096484}, abstractNote={Targeting the development of a silicon carbide (SiC) inverter for electric vehicle/hybrid electric vehicle (EV/HEV) applications, the design considerations of the gate driver for the adopted SiC metal-oxide-semiconductor field-transistor (MOSFET) power modules are presented. Given the system power density requirement, the gate driver design challenges for the commercial off-the-shelf (COTS) SiC modules are identified, analyzed, and tackled with proposed solutions. To accomplish such design with the constraint of limited layout space, a single chip MAX 13256 (3 mm×3 mm) enabled high frequency link based isolated bias supply structure is proposed for each six-pack module. Moreover, the gate driver design guidelines for module phase-leg parallel operation are introduced with a comparison study confirming the printed circuit board (PCB) layout effectiveness for electromagnetic interference (EMI) mitigation. Experimental validation is conducted on the traction inverter prototype.}, booktitle={2017 ieee energy conversion congress and exposition (ecce)}, author={Gao, R. and Yang, L. and Yu, Wensong and Husain, I.}, year={2017}, pages={2546–2551} }
 @inproceedings{awal_husain_yu_2017, title={Predictive current control for stabilizing power electronics based AC power systems}, DOI={10.1109/ecce.2017.8096792}, abstractNote={Frequency domain passivity theory is used to evaluate harmonic resonance instabilities in a system with multiple grid-tied voltage source converters (VSCs), and subsequently, a stabilizing controller using predictive current control (PCC) method is proposed to prevent such instabilities. The input admittance of VSCs using PCC can achieve passivity almost up to the Nyquist frequency. This research demonstrates that a very simple and easy implementation of PCC can extend the controller delay dependent stability range of converter side current control for VSCs equipped with LCL-filters up to that point. The alternative approaches achieved stability over similar frequency range by combining complicated active damping techniques with proportional-integral or proportional-resonant type controllers. The frequency domain analysis of the proposed PCC based method is validated via simulation and hardware experiments. The controller is experimentally shown to achieve stable operation irrespective of model imperfections.}, booktitle={2017 ieee energy conversion congress and exposition (ecce)}, author={Awal, M. A. and Husain, I. and Yu, Wensong}, year={2017}, pages={4634–4641} }
 @book{yu_2017, title={Solid State Transformer for Power Distribution Applications}, institution={United States Department of Energy}, author={Yu, W.}, year={2017}, month={Sep} }
 @inproceedings{srdic_liang_zhang_yu_lukic_2016, title={A SiC-based high-performance medium-voltage fast charger for plug-in electric vehicles}, DOI={10.1109/ecce.2016.7854777}, abstractNote={This paper presents an isolated medium-voltage, high-power-quality and high efficiency (over 96%), fast charger for plug-in electric vehicles. The proposed fully modular fast charger uses off-the-shelf Silicon Carbide (SiC) power devices to convert the rectified single-phase 2.4 kV medium-voltage input to variable dc output. The adopted input-series-output-parallel unidirectional topology enables converter scalability in both the input voltage and the output power. Using wide bandgap (WBG) power devices enables 9 times reduction in volume and 6 times reduction in weight, compared to the state-of-the-art fast chargers, while exceeding the efficiency of the state-of-the-art fast chargers by more than 1.5% Based on the system requirements, the appropriate converter topology was selected, its operation was simulated and validated by experiments on the developed fast charger prototype.}, booktitle={2016 ieee energy conversion congress and exposition (ecce)}, author={Srdic, S. and Liang, X. Y. and Zhang, C. and Yu, Wensong and Lukic, Srdjan}, year={2016} }
 @inproceedings{srdic_zhang_liang_yu_lukic_2016, title={A SiC-based power converter module for medium-voltage fast charger for plug-in electric vehicles}, DOI={10.1109/apec.2016.7468247}, abstractNote={This paper presents an isolated power converter module for medium-voltage (2.4 kV), high-power-quality (PF ≥ 0.98, current THD ≤ 2%), 50 kW fast charger for plug-in electric vehicles. The proposed high-efficiency (above 96%), and reduced-footprint converter module utilizes off-the-shelf Silicon Carbide (SiC) devices to step down the rectified single-phase medium-voltage input. The developed module can also serve as a building block for other medium voltage rectifier applications, including power supplies for data centers and other dc power distribution systems. Based on the system requirements, the appropriate unidirectional converter topology was selected, its operation was simulated and validated by experiments on the developed converter prototype.}, booktitle={Apec 2016 31st annual ieee applied power electronics conference and exposition}, author={Srdic, S. and Zhang, C. and Liang, X. Y. and Yu, Wensong and Lukic, Srdjan}, year={2016}, pages={2714–2719} }
 @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{morgan_xu_hopkins_husain_yu_2016, title={Decomposition and electro-physical model creation of the CREE 1200V, 50A 3-Ph SiC module}, url={https://www.lens.org/005-651-099-193-878}, DOI={10.1109/apec.2016.7468163}, abstractNote={The CREE 1200V/50A, 25mΩ 6-Pack SiC MOSFET module (CCS050M12CM2) is decomposed into a full 3D CAD model, and materials identified, for use in electrical circuit and multi-physics simulations. A reverse engineering technique is first developed, outlined, and then demonstrated on the CREE module. The ANSYS Q3D Extractor is applied to the 3D CAD model where electrical, lumped parameter, parasitic circuit elements are determined. The model is also analyzed with a multi-physics simulator to provide in-situ thermal maps of the baseplate surface for application scenarios, e.g. with a thermal interface material and pin fin heat sink to capture the thermal spreading from junction to case. The complete model is made open source and freely distributed for use by the reader.}, note={\urlhttps://ieeexplore.ieee.org/document/7468163 ; \urlhttps://works.bepress.com/kang-peng/10/download/ ; \urlhttps://works.bepress.com/kang-peng/10/}, booktitle={Apec 2016 31st annual ieee applied power electronics conference and exposition}, author={Morgan, A. J. and Xu, Y. and Hopkins, Douglas C and Husain, I. and Yu, Wensong}, year={2016}, pages={2141–2146} }
 @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{rahman_morgans_xu_gao_yu_hopkins_husain_2016, title={Design methodology for a planarized high power density EV/HEV traction drive using SiC power modules}, url={https://www.lens.org/036-754-675-774-950}, DOI={10.1109/ecce.2016.7855018}, abstractNote={This paper provides a methodology for overall system level design of a high-power density inverter to be used for EV/HEV traction drive applications. The system design is guided to accommodate off-the-shelf SiC power modules in a planar architecture that ensures proper electrical, thermal, and mechanical performances. Bi-directional interleaved DC-DC boost structure and a three-phase voltage source inverter (VSI) have been utilized with the primary focus on the size, weight and loss reduction of passive components. A stacked layer approach has been used for a unique PCB-based busbar, ultra-low profile gate driver, and controller board. This holistic design approach results in a highly compact traction drive inverter with power density of 12.1 kW/L that has lower volume and weight compared to the commercially available state-of-the-art power converter systems.}, note={\urlhttps://ieeexplore.ieee.org/document/7855018/}, booktitle={2016 ieee energy conversion congress and exposition (ecce)}, author={Rahman, D. and Morgans, A. J. and Xu, Y. and Gao, R. and Yu, Wensong and Hopkins, Douglas C and Husain, I.}, year={2016} }
 @inproceedings{xu_husain_west_yu_hopkins_2016, title={Development of an ultra-high density power chip on bus (PCoB) module}, url={https://www.lens.org/092-761-376-063-354}, DOI={10.1109/ecce.2016.7855040}, abstractNote={A traditional power module uses metal clad ceramic (e.g. DBC or DBA) bonded to a baseplate that creates a highly thermally resistive path, and wire bond interconnect that introduces substantial inductance and limits thermal management to single-sided cooling. This paper introduces a Power Chip on Bus (PCoB) power module approach that reduces parasitic inductance through an integrated power interconnect structure. The PCoB maximizes thermal performance by direct attaching power chips to the busbar, integrating the heatsink and busbar as one, and uses a dielectric fluid, such as air, for electrical isolation. This new power module topology features all planar interconnects and double-sided air cooling. Performance evaluations are carried out through comprehensive electrical and multi-physics simulation and thermal testing for a 1200V, 100A rated single-switch PCoB design. Fabrication and assembly processes are included. For the developed double-sided air-cooled module, 0.5°C/w thermal resistance and 8nH power loop parasitic inductance are achieved.}, note={\urlhttp://ieeexplore.ieee.org/document/7855040/}, booktitle={2016 ieee energy conversion congress and exposition (ecce)}, author={Xu, Y. and Husain, I. and West, H. and Yu, Wensong and Hopkins, Douglas C}, year={2016} }
 @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{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{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} }
 @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{gao_yang_yu_husain_2016, title={Single chip enabled high frequency link based isolated bias supply for silicon carbide MOSFET six-pack power module gate drives}, DOI={10.1109/ecce.2016.7855435}, abstractNote={Regarded as one of the most successful wide bandgap (WBG) devices, Silicon Carbide (SiC) metal-oxide-semiconductor field-transistors (MOSFETs) are being considered in an increasing number of power electronics applications. One of those applications is the hybrid and electric vehicle (HEV/EV) traction inverters where high-efficiency and high-power density is essential. From the system-level perspective, the gate driver circuit design for such device is challenging considering the device's fast switching speed and compact system structure. This paper presents a low profile (6 mm) isolated bias supply design using commercially available components for the SiC MOSFET modules targeting an HEV/EV traction inverter application. A single chip MAX 13256 (3 mm∗3 mm) is adopted to form the high-frequency link for entire power module gate drive supply. Distributed transformer strategy is highlighted to provide multiple isolated output and compact structure with minimized parasitic capacitance between all the isolation barriers. The featured low profile optimization reduces the parasitic parameters that might deteriorate the system performance for the fast switching WBG devices. Moreover, the open-loop high-frequency link architecture allows easy configuration for customized output voltage level, polarity and higher reliability. A prototype gate driver has been built for 1.2 kV, 50 A SiC six-pack MOSFET power module, and experimental results are presented.}, booktitle={2016 ieee energy conversion congress and exposition (ecce)}, author={Gao, R. and Yang, L. and Yu, Wensong and Husain, I.}, year={2016} }
 @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{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{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} }
 @article{ma_zheng_yu_lai_2015, title={A single-stage integrated bridgeless AC/DC converter for electrolytic capacitor-less LED lighting applications}, volume={43}, ISSN={0098-9886}, url={http://dx.doi.org/10.1002/CTA.1970}, DOI={10.1002/CTA.1970}, abstractNote={Summary}, number={6}, journal={International Journal of Circuit Theory and Applications}, publisher={Wiley}, author={Ma, Hongbo and Zheng, Cong and Yu, Wensong and Lai, Jih-Sheng Jason}, year={2015}, month={Jun}, pages={742–755} }
 @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{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} }
 @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{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{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{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{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{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{ma_lai_feng_yu_zheng_2013, title={A universal-input high-power-factor power supply without electrolytic capacitor for multiple lighting LED lamps}, volume={41}, ISSN={0098-9886}, url={http://dx.doi.org/10.1002/cta.816}, DOI={10.1002/cta.816}, abstractNote={SUMMARY}, number={5}, journal={International Journal of Circuit Theory and Applications}, publisher={Wiley}, author={Ma, Hongbo and Lai, Jih-Sheng Jason and Feng, Quanyuan and Yu, Wensong and Zheng, Cong}, year={2013}, month={May}, pages={514–534} }
 @article{york_yu_lai_2013, title={An Integrated Boost Resonant Converter for Photovoltaic Applications}, volume={28}, ISSN={0885-8993 1941-0107}, url={http://dx.doi.org/10.1109/tpel.2012.2207127}, DOI={10.1109/tpel.2012.2207127}, abstractNote={Effective photovoltaic power conditioning requires efficient power conversion and accurate maximum power point tracking to counteract the effects of panel mismatch, shading, and general variance in power output during a daily cycle. In this paper, the authors propose an integrated boost resonant converter with low component count, galvanic isolation, simple control, as well as high efficiency across a wide input and load range. Provided is a discussion of the converter synthesis, key operational features, converter design procedure, and loss analysis, as well as experimental verification by way of a 250-W prototype with a California Energy Commission efficiency of 96.8%.}, number={3}, journal={IEEE Transactions on Power Electronics}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={York, Ben and Yu, Wensong and Lai, Jih-Sheng}, year={2013}, month={Mar}, pages={1199–1207} }
 @article{ma_gu_feng_lai_zheng_yu_2013, title={Bridgeless electrolytic capacitor-less valley-fill AC/DC converter for offline Twin-Bus light-emitting diode lighting application}, volume={6}, ISSN={1755-4535 1755-4543}, url={http://dx.doi.org/10.1049/IET-PEL.2012.0708}, DOI={10.1049/IET-PEL.2012.0708}, abstractNote={To match the key features of light-emitting diode (LED) lighting source and further save power, LED lighting driver also requires long life, while maintaining high efficiency, high power factor, pulse-width modulation dimming and low cost. However, a typical LED lighting driver has the following drawbacks: (i) utilise bulky electrolytic capacitor as storage capacitor with short lifetime; (ii) employ a low-frequency diode bridge as the rectifier cell; and (iii) engage multiple stages cascade structure for multiple LED strings. To overcome the aforementioned shortages, this study proposed a bridgeless electrolytic capacitor-less AC/DC converter for offline LED lighting application. In the proposed converter, the conventional diode rectified bridge is replaced by Totem-pole bridgeless configuration for reducing the number of semiconductors in the line-current path. Meanwhile, the valley-fill circuit is introduced to further reduce the capacitor size. As comparison to its counterpart, the proposed circuit requires only one quarter of the capacitor energy when considering the energy amount (CV 2 ) as the capacitor sizing criterion. Furthermore, the isolation type of the studied circuit is compatible with Twin-Bus configuration for achieving higher overall system efficiency. Finally, the experimental results, taken from a laboratory prototype rated at 50 W, are presented to verify the effectiveness of the proposed converter.}, number={6}, journal={IET Power Electronics}, publisher={Institution of Engineering and Technology (IET)}, author={Ma, Hongbo and Gu, Bin and Feng, Quanyuan and Lai, Jih-Sheng (Jason) and Zheng, Cong and Yu, Wensong}, year={2013}, month={Jul}, pages={1132–1141} }
 @article{yu_lai_lai_wan_2012, title={Hybrid Resonant and PWM Converter With High Efficiency and Full Soft-Switching Range}, volume={27}, ISSN={0885-8993 1941-0107}, url={http://dx.doi.org/10.1109/tpel.2012.2192293}, DOI={10.1109/tpel.2012.2192293}, abstractNote={A novel soft-switching converter combining resonant half-bridge and phase-shifted pulsewidth modulation (PWM) full-bridge configuration is proposed to ensure the switches in the leading-leg operating at zero-voltage switching from true zero-load to full-load, and the switches in the lagging leg working at zero-current switching with minimum duty cycle loss and circulating conduction loss by significantly reducing leakage or series inductance. Experimental results of a 3.4-kW hardware prototype show that the circuit achieves true full-range soft switching with 98% peak efficiency. The hybrid resonant and PWM converter is attractive for electrical vehicle battery charger application.}, number={12}, journal={IEEE Transactions on Power Electronics}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Yu, Wensong and Lai, Jih-Sheng and Lai, Wei-Han and Wan, Hongmei}, year={2012}, month={Dec}, pages={4925–4933} }
 @article{yu_lai_ma_zheng_2011, title={High-Efficiency DC–DC Converter With Twin Bus for Dimmable LED Lighting}, volume={26}, ISSN={0885-8993 1941-0107}, url={http://dx.doi.org/10.1109/tpel.2011.2104368}, DOI={10.1109/tpel.2011.2104368}, abstractNote={An improved twin-bus converter using n + 1 active switches is proposed for the n-string LEDs to be dimmable from true zero to the rated current level. The n-switches that perform the current-loop regulation can operate at very high frequency because of significantly reduced voltage stresses, while achieving high efficiency over a wide load range. The dimming switch, however, can operate at a low frequency to ensure high-efficiency operation without light flicker. The detailed power stage operating principle and control scheme of the individual string current for the presented converter are described. Experimental results of a 3-string 50-W LED driver hardware prototype show that the independent string current can be regulated from zero to the desired 350 mA for dimming control. A peak efficiency of 98.3% was achieved with 1.08-MHz switching frequency.}, number={8}, journal={IEEE Transactions on Power Electronics}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Yu, Wensong and Lai, Jih-Sheng and Ma, Hongbo and Zheng, Cong}, year={2011}, month={Aug}, pages={2095–2100} }
 @article{yu_lai_qian_hutchens_2011, title={High-Efficiency MOSFET Inverter with H6-Type Configuration for Photovoltaic Nonisolated AC-Module Applications}, volume={26}, ISSN={0885-8993 1941-0107}, url={http://dx.doi.org/10.1109/tpel.2010.2071402}, DOI={10.1109/tpel.2010.2071402}, abstractNote={A novel, high-efficiency inverter using MOSFETs for all active switches is presented for photovoltaic, nonisolated, ac-module applications. The proposed H6-type configuration features high efficiency over a wide load range, low ground leakage current, no need for split capacitors, and low-output ac-current distortion. The detailed power stage operating principles, pulsewidth modulation scheme, associated multilevel bootstrap power supply, and integrated gate drivers for the proposed inverter are described. Experimental results of a 300 W hardware prototype show that not only are MOSFET body diode reverse-recovery and ground leakage current issues alleviated in the proposed inverter, but also that 98.3% maximum efficiency and 98.1% European Union efficiency of the dc-ac power train and the associated driver circuit are achieved.}, number={4}, journal={IEEE Transactions on Power Electronics}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Yu, Wensong and Lai, Jih-Sheng Jason and Qian, Hao and Hutchens, Christopher}, year={2011}, month={Apr}, pages={1253–1260} }
 @article{yu_lai_park_2010, title={An Improved Zero-Voltage Switching Inverter Using Two Coupled Magnetics in One Resonant Pole}, volume={25}, ISSN={0885-8993 1941-0107}, url={http://dx.doi.org/10.1109/tpel.2009.2030197}, DOI={10.1109/tpel.2009.2030197}, abstractNote={A novel soft-switching inverter using two small coupled magnetics in one resonant pole is proposed to ensure the main switches operating at zero-voltage switching from zero load to full load and the auxiliary switches at zero-current switching with load adaptability and small current stress. Since independent coupled magnetics structure avoids the unwanted magnetizing current freewheeling loop, the size of the coupled magnetics can be minimized with low magnetizing inductance, and the saturable inductor can be eliminated. Detailed circuit operation is described, and voltage-second balance condition of the magnetics is expressed mathematically. A 4-kW hardware prototype has been designed, fabricated, and tested to verify the validity of the novel circuit and the improved performance of the proposed soft-switching inverter. Experimental results show an excellent agreement with analytical results. Since the measured efficiency from 20% to 100% load consistently shows above 97.8% and peaks at 98.2%, the proposed inverter is very attractive for high-efficiency applications where energy saving is a major concern.}, number={4}, journal={IEEE Transactions on Power Electronics}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Yu, Wensong and Lai, Jih-Sheng and Park, Sung-Yeul}, year={2010}, month={Apr}, pages={952–961} }