@article{zhu_wang_huang_booth_zhang_2019, title={7.2-kV Single-Stage Solid-State Transformer Based on the Current-Fed Series Resonant Converter and 15-kV SiC MOSFETs}, volume={34}, ISSN={["1941-0107"]}, DOI={10.1109/TPEL.2018.2829174}, abstractNote={This paper proposes a novel two-level single-stage direct ac–ac converter for realizing a 7.2-kV medium-voltage (MV) solid-state transformer (SST) based on 15-kV SiC mosfets. A new current-fed series resonant converter (CFSRC) topology is proposed to address major challenges in MV ac–ac converters such as achieving zero-voltage switching (ZVS) for the MV mosfets across wide voltage and load ranges and minimizing system capacitance. The topology is analyzed with both time-domain analysis and first harmonic approximation to provide useful equations for circuit design. Constant deadtime strategy is adopted, allowing partial ZVS to occur at low-voltage (LV) levels. ZVS behavior over wide voltage range is investigated, and calculation of the associated loss from partial ZVS is presented. System parameters are optimized based on the tradeoff between conduction loss and switching loss. The 15-kV mosfet has been tested continuously at a park voltage of 10 kV and 37 kHz, indicating stable device operation and an extremely high voltage × frequency figure of merit. Moreover, inherent cycle-by-cycle current limiting in the proposed CFSRC under output short-circuit circumstance is realized by paralleling diodes to the LV resonant capacitors. Without employing any additional current sensors, the input and circulating currents are limited to a safe range automatically when the short-circuit occurs. This paper presents detailed short-circuit protection operating principles and peak resonant current equation to aid the design of the resonant tank. A full-scale and compact SST that converts 7.2 kV ac to 240 V ac is developed to verify the theoretical analysis. This is the highest reported voltage rating for two-level-based power converters without device series connection. ZVS is verified and achieved over wide voltage and load ranges with a peak efficiency of 97.8%. A short-circuit experiment is conducted at 3-kV peak voltage to verify the analysis. Experimental results closely match the theoretical analysis.}, number={2}, journal={IEEE TRANSACTIONS ON POWER ELECTRONICS}, author={Zhu, Qianlai and Wang, Li and Huang, Alex Q. and Booth, Kristen and Zhang, Liqi}, year={2019}, month={Feb}, pages={1099–1112} }
 @inproceedings{song_huang_liu_zhang_2016, title={1200v/200a freedm-pair: loss and cost reduction analysis}, DOI={10.1109/wipda.2016.7799928}, abstractNote={FREEDM-Pair is an innovative power semiconductor switch which reduces the loss and cost through the hybrid integration of a Si IGBT and a SiC MOSFET. During the turn-off of the FREEDM-Pair, the Si IGBT is turned off first under ZVS condition and after a carefully selected delay time, the Si MOSFET is turn-off. In this way, the IGBT's turn-off loss is significantly reduced due to the ZVS turn-off condition. During the delay time, the current will be carried by the MOSFET only. During the turn-on, the SiC MOSFET and the IGBT can be turned on at the same time. Due to faster turn-on speed of the MOSFET, the IGBT is also turned on under the ZVS condition. Another advantage of the FREEDM-Pair is the better conduction characteristics compared to the Si IGBT by combining both the unipolar and bipolar devices' advantages in current conduction. Therefore the FREEDM-Pair provides an ideal option to realize the tradeoff between the cost and performance, and can be applied to main stream applications which currently use IGBT. Previously, the 6.5-kV FREEDM-Pairs results have been published and analyzed. In this paper, loss and cost reduction of a 1200V/200A FREEDM-Pair is presented and analyzed for the first time.}, booktitle={2016 IEEE 4th Workshop on Wide Bandgap Power Devices and Applications (wipda)}, author={Song, X. Q. and Huang, A. Q. and Liu, P. K. and Zhang, L. Q.}, year={2016}, pages={152–157} }
 @inproceedings{song_huang_zhang_liu_ni_2016, title={15kV/40A FREEDM super-cascode: A cost effective SiC high voltage and high frequency power switch}, DOI={10.1109/ecce.2016.7854643}, abstractNote={High voltage wide bandgap (WBG) semiconductor devices like the 15kV SiC MOSFET have attracted great attentions because of its potential applications in high voltage and high frequency power converters. However, these devices are not commercially available at the moment and their high cost due to expensive material growth and fabrication may limit their widespread adoption in the future. In this paper, a 15kV/40A three terminal power switch, the FREEDM Super-Cascode, is reported for the first time which is based on series connection of 1.2kV SiC power devices. The design and operation principle of the FREEDM Super-Cascode are introduced and the performance including the static blocking capability, conduction characteristics over a wide range of temperatures, and dynamic switching performances are analyzed. In addition, the thermal resistance of the FREEDM Super-Cascode is measured and the power dissipation capability is projected. The FREEDM Super-Cascode costs only one third of the estimated high voltage SiC MOSFETs, and will facilitate early applications of SiC in very high voltage and high frequency power converters.}, booktitle={2016 ieee energy conversion congress and exposition (ecce)}, author={Song, X. Q. and Huang, A. Q. and Zhang, L. Q. and Liu, P. K. and Ni, X. J.}, year={2016} }
 @inproceedings{guo_liu_yu_zhang_huang_2016, title={Analysis and loss comparison of megahertz high voltage isolated dc/dc converters utilizing integrated sic mosfet module}, DOI={10.1109/wipda.2016.7799955}, abstractNote={Silicon Carbide (SiC) MOSFETs are being increasingly utilized in medium and high power electronics converters (>1 kW) because of the significantly lower switching and conduction losses when compared with conventional power switches such as the Si IGBT. SiC MOSFET based converters operating at high frequency can achieve high efficiency and high power density at the same time. Minimum switching loss can be achieved in the SiC MOSFET with carefully designed gate driving condition and DC link layout, such as the integrated SiC MOSFET module discussed in this paper. Multi-megahertz switching frequency could be realized by the proposed SiC MOSFET module with proper soft switching topology. This paper analyzes three isolated DC/DC converters, namely the asymmetrical half bridge converter, phase shift full bridge converter, and LLC resonant converter. The loss model of the SiC MOSFET is developed and utilized in the analysis. Comparisons are carried out from the device loss and soft switching requirement point of view. The LLC resonant converter is deemed more suitable for multi-megahertz application. A 4.5 kW 1.2 MHz LLC resonant converter prototype is developed and it demonstrates a peak efficiency of 97% at 4 kW.}, booktitle={2016 IEEE 4th Workshop on Wide Bandgap Power Devices and Applications (wipda)}, author={Guo, S. X. and Liu, P. K. and Yu, R. Y. and Zhang, L. Q. and Huang, A. Q.}, year={2016}, pages={291–296} }
 @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{liu_zhang_huang_guo_lei_2016, title={High bandwidth current sensing of sic mosfet with a si current mirror}, DOI={10.1109/wipda.2016.7799937}, abstractNote={SiC Intelligent Power Module (IPM) with high bandwidth integrated current sensors is a future trend to improve the device protection capability and chip utilization. In this work, an integrated current sensing scheme for Silicon Carbide (SiC) MOSFET power module using a Si MOSFET current mirror is proposed, analyzed and tested. The use of Si MOSFET not only lowers the overall cost, but compensates the temperature variation as well. The influence of device mismatching on sensing accuracy are discussed. Optimal selection and trade-off of sensing resistor value are calculated. Discrete device circuit and conceptual DBC-based module are tested to verify the scheme's feasibility and performance. The results show good steady state accuracy and high bandwidth performance.}, booktitle={2016 IEEE 4th Workshop on Wide Bandgap Power Devices and Applications (wipda)}, author={Liu, P. K. and Zhang, L. Q. and Huang, A. Q. and Guo, S. X. and Lei, Y.}, year={2016}, pages={200–203} }
 @inproceedings{song_huang_peng_zhang_2016, title={Improved 6.5kV FREEMD-pair based on SiC JFET and Si IGBT}, DOI={10.1109/apec.2016.7467883}, abstractNote={The newly proposed FREEDM-Pair is an ideal and economical solution to address high cost issue in high power SiC power devices. The FREEDM-Pair, in which a Si IGBT and a SiC JFET are connected in parallel, combines the advantages of SiC JFET's low switching losses and Si IGBT's superior forward conduction characteristics. One issue of the JFET based FREEDM-Pair is the incompatible gate drive voltage for the SiC JFET and Si IGBT which complicates the gate driver design and increases the total cost. Also, the high voltage SiC JBS reverse diode in FREEDM-Pair is indispensable for the reverse current conduction, leading to higher cost and larger package size. To address these issues, an improved FREEDM-Pair is proposed in this paper, in which the SiC JBS diode is eliminated and the normally-off SiC JFET is operated in cascode configuration to unify the gate driver voltage level and speed up the switching of the JFET. The design and operation of improved FREEDM-Pair is elaborated and experimental results verified its advantages. Also, the affordable cost demonstrates that this promising concept is an ideal step to introduce high voltage SiC power devices.}, booktitle={Apec 2016 31st annual ieee applied power electronics conference and exposition}, author={Song, X. Q. and Huang, A. Q. and Peng, C. and Zhang, L. Q.}, year={2016}, pages={269–275} }
 @inproceedings{zhu_wang_zhang_yu_huang_2016, title={Improved medium voltage AC-DC rectifier based on 10kV SiC MOSFET for solid state transformer (SST) application}, DOI={10.1109/apec.2016.7468196}, abstractNote={An improved bidirectional medium voltage AC-DC converter based on 10kV silicon carbide (SiC) MOSFETs for SST (Solid State Transformer) application is presented in this paper. Avalanche breakdown of the reverse blocking silicon diode and bridge arm shoot-through problems in traditional high voltage bridge-type AC-DC converters are solved. Shoot-through currents are limited to low di/dt events that are readily controlled, allowing zero dead-time operation. The reverse recovery dissipation of the SiC MOSFET is eliminated because no freewheeling current will flow through the body diode. This increases the efficiency as well as the reliability of the SiC MOSFET. Detailed power stage operating principles and energy transfer mechanism are described. A unique customized 10kV SiC MOSFET/JBS diode power module is developed and tested, which further reduces parasitic parameters and simplifies converter wire connection. This topology is therefore a very good choice for median voltage applications.}, booktitle={Apec 2016 31st annual ieee applied power electronics conference and exposition}, author={Zhu, Q. L. and Wang, L. and Zhang, L. Q. and Yu, Wensong and Huang, A. Q.}, year={2016}, pages={2365–2369} }
 @inproceedings{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{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{huang_song_zhang_2015, title={6.5 kV Si/SiC hybrid power module: An ideal next step?}, DOI={10.1109/iwipp.2015.7295979}, abstractNote={Silicon carbide (SiC) power switches such as JFET or MOSFET have demonstrated their superior advantages over silicon (Si) power devices such as IGBT, especially in terms of significantly reduced switching losses. A major issue facing large scale adoption of SiC power devices is still the much higher cost. This paper proposes that Si/SiC hybrid power module (HPM) should be a natural next step moving forward for high voltage applications to address the cost issue. In the proposed Si/SiC HPM, a SiC JFET is connected in parallel with Si IGBT to combine the advantages of both IGBT and JFET. A 6.5 kV HPM is developed based on Si IGBT and SiC JFET as an example to demonstrate its superior cost/performance. The switching loss can be reduced by more than 70% at a cost of about 70% higher compared to Si IGBT. This work is especially essential for high voltage applications such as medium voltage motor drive, FACTS and HVDC systems.}, booktitle={2015 IEEE International Workshop on Integrated Power Packaging (IWIPP)}, author={Huang, A. Q. and Song, X. Q. and Zhang, L. Q.}, year={2015}, pages={64–67} }
 @inproceedings{song_huang_ni_zhang_2015, title={Comparative evaluation of 6kV Si and SiC power devices for medium voltage power flectronics applications}, DOI={10.1109/wipda.2015.7369289}, abstractNote={In order to better assist researchers to select the appropriate power device for medium voltage power electronics applications, this paper presents a comparative evaluation on three typical 6kV level Si and SiC power devices, including 6.5kV/25A Si IGBT from ABB, 6.5kV/15A normally off SiC JFET from USCi and a FREEDM System Center developed 6kV/26A SiC series-connected JFET. The 6.5kV Si IGBT and 6.5kV SiC JFET are packaged in the same module to minimize the effect of different parasitic inductance on the comparison. The 6kV SiC series-connected JFET is developed based on one 1.2kV SiC MOSFET from Cree and four 1.2kV SiC JFETs from Infineon, in this paper, named FREEDM Super-Cascode. A short introduction on the three selected devices are first given, then their forward conduction and switching performances are compared. Also, some additional features are discussed and compared, including the device size, cost, gate driver circuit complexity.}, booktitle={WiPDA 2015 3rd IEEE Workshop on Wide Bandgap Power Devices and Applications}, author={Song, X. Q. and Huang, A. Q. and Ni, X. J. and Zhang, L. Q.}, year={2015}, pages={160–165} }