@article{acharya_she_todorovic_datta_mandrusiak_2019, title={Thermal Performance Evaluation of a 1.7-kV, 450-A SiC-MOSFET Based Modular Three-Phase Power Block With Wide Fundamental Frequency Operations}, volume={55}, ISSN={["1939-9367"]}, url={https://doi.org/10.1109/TIA.2018.2879028}, DOI={10.1109/TIA.2018.2879028}, abstractNote={To accelerate wide industry adoption of Silicon Carbide (SiC) based technology, a three-phase two-level inverter based power block is designed with the latest generation high performance 1.7 kV/450 A SiC-mosfet module from General Electric. The designed power block is expected to replace the currently standardized 1.7 kV/450 A Silicon (Si) insulated gate bipolar transistor (IGBT) based three-phase power block. Power converters face thermal challenges when subjected to very low fundamental frequency operations (below 10 Hz). This is particularly relevant in the wind power applications. At low operating fundamental frequencies, the junction temperature of the power device experiences high peak-to-peak ripple, which degrades the reliability of the power modules significantly. This paper presents the thermal performance of the designed power block and draws comparisons with a similar rated Si-IGBT module based power blocks, especially at low output fundamental frequency operations. Key performance indices, including power rating curves at different switching frequencies and power factors; temperature ripple at different fundamental frequencies, are examined. Simulation and experimental results are provided to validate the claims. The results indicate that the SiC-mosfet module based power block can be a promising replacement for the Si-IGBT based power block especially in applications where wide range of fundamental frequency operations are needed.}, number={2}, journal={IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Acharya, Sayan and She, Xu and Todorovic, Maja Harfman and Datta, Rajib and Mandrusiak, Gary}, year={2019}, pages={1795–1806} }
 @article{liao_zhang_yang_zheng_she_2014, title={A cloud and evidential reasoning integrated model for insulation condition assessment of high voltage transformers}, volume={24}, number={7}, journal={International Transactions on Electrical Energy Systems}, author={Liao, R. J. and Zhang, Y. Y. and Yang, L. J. and Zheng, H. B. and She, X.}, year={2014}, pages={913–926} }
 @article{she_huang_ni_2014, title={Current Sensorless Power Balance Strategy for DC/DC Converters in a Cascaded Multilevel Converter Based Solid State Transformer}, volume={29}, ISSN={["1941-0107"]}, DOI={10.1109/tpel.2013.2256149}, abstractNote={This letter proposes a current sensorless controller for balancing the power in the dc/dc stage of a cascaded multilevel converter based solid state transformer. It is revealed that the equalization of the active power component of duty cycles in the cascaded multilevel rectifier stage can be a good indicator of power balance in the dc/dc stage. Additionally, the power balance of the dc/dc stage can guarantee the voltage balance in the rectifier stage if the differences among the power devices are negligible. Based on this principle, a novel power balance controller without sensing any current in the dc/dc stage is proposed. In the end, experimental results in a seven-level three-stage solid state transformer are provided for verifying the proposed method.}, number={1}, journal={IEEE TRANSACTIONS ON POWER ELECTRONICS}, author={She, Xu and Huang, Alex Q. and Ni, Xijun}, year={2014}, month={Jan}, pages={17–22} }
 @article{she_yu_wang_huang_2014, title={Design and Demonstration of a 3.6-kV-120-V/10-kVA Solid-State Transformer for Smart Grid Application}, volume={29}, ISSN={["1941-0107"]}, DOI={10.1109/tpel.2013.2293471}, abstractNote={Solid-state transformer (SST) has been regarded as one of the most important emerging technologies for traction system and smart grid application. This paper presents the system design and performance demonstration of a high-voltage SST lab prototype that works as the active grid interface in smart grid architecture. Specifically, the designs of the key components of the system, including both power stage and controller platform, are presented. In addition, the advanced control system is developed to achieve high-performance operation. Furthermore, integration issues of SST with dc microgrid are presented. Lastly, tests under different scenarios are conducted to verify the following advanced features of the presented SST technology: 1) VAR compensation; 2) voltage regulation; 3) source voltage sag operation; and 4) microgrid integration.}, number={8}, journal={IEEE TRANSACTIONS ON POWER ELECTRONICS}, author={She, Xu and Yu, Xunwei and Wang, Fei and Huang, Alex Q.}, year={2014}, month={Aug}, pages={3982–3996} }
 @article{yu_she_zhou_huang_2014, title={Power Management for DC Microgrid Enabled by Solid-State Transformer}, volume={5}, ISSN={["1949-3061"]}, DOI={10.1109/tsg.2013.2277977}, abstractNote={A novel distributed power management scheme is proposed in this paper for a DC microgrid system, which is enabled by Solid-State transformer (SST). The proposed system includes distributed renewable energy resource (DRER) and distributed energy storage device (DESD). The proposed distributed control algorithm, which only relies on the local information and guarantees full utilization of each module in the system based on their characteristics, is applied to both SST and DC microgrid. To this end, a simulation platform is developed in MATLAB/Simulink, in which Photovoltaic (PV), fuel cell and battery are selected as the typical DRERs and DESD, respectively. Lastly, several typical case studies are carried out and the simulation results verify the proposed distributed power management.}, number={2}, journal={IEEE TRANSACTIONS ON SMART GRID}, author={Yu, Xunwei and She, Xu and Zhou, Xiaohu and Huang, Alex. Q.}, year={2014}, month={Mar}, pages={954–965} }
 @inproceedings{she_huang_ni_2013, title={A cost effective power sharing strategy for a cascaded multilevel converter based Solid state transformer}, DOI={10.1109/ecce.2013.6646725}, abstractNote={This paper proposes a power sharing strategy for DC/DC stage of a cascaded multilevel converter based solid state transformer. It is revealed that the equalization of the active power component of duty cycles in the cascaded multilevel rectifier stage can be a good indicator of power balance in the DC/DC stage. Additionally, the power balance of the DC/DC stage can guarantee the voltage balance in the rectifier stage if the differences among the power devices are negligible. Based on this principle, a novel power balance controller without sensing any current in the DC/DC stage is proposed. Both simulation and experimental results in a seven-level three-stage solid state transformer are provided for verifying the proposed method.}, booktitle={2013 ieee energy conversion congress and exposition (ecce)}, author={She, X. and Huang, A. Q. and Ni, X. J.}, year={2013}, pages={372–379} }
 @inproceedings{yu_she_huang_2013, title={Hierarchical power management for DC microgrid in islanding mode and solid state transformer enabled mode}, DOI={10.1109/iecon.2013.6699381}, abstractNote={A hierarchical power management scheme is proposed in this paper for a typical DC Microgrid. Different from other Microgrids, the DC Microgrid can interface to the distribution system by Solid-State transformer (SST). The hierarchical power management strategy includes three control levels: 1) primary control for DC Microgrid to implement distributed operation 2) secondary control for the DC Microgrid bus voltage recovery to achieve seamless mode switch 3) tertiary control to manage the battery charge and discharge. The DC Microgrid can operate in islanding mode, including the individual control for distributed renewable energy source (DRER) and distributed energy storage device (DESD). In addition, the DC microgrid can operate in SST-enabled mode to interface to the distribution system. The DC Micorgrid can seamlessly switch between islanding mode and SST-enable mode. The consideration of state of charge (SOC) for battery is also involved into the tertiary control. To this end, a lab test-bed is constructed to verify the system performance. Lastly, several typical case studies are carried out and the experimental results verify the proposed power management strategy.}, booktitle={39th annual conference of the ieee industrial electronics society (iecon 2013)}, author={Yu, X. W. and She, X. and Huang, A.}, year={2013}, pages={1656–1661} }
 @inproceedings{yu_she_ni_wang_huang_2013, title={Power management strategy for DC microgrid interfaced to distribution system based on solid state transformer}, DOI={10.1109/ecce.2013.6647394}, abstractNote={A typical DC microgrid, which can be enabled by Solid State Transformer (SST), is investigated in this paper. One unidirectional DC/DC converter for photovoltaic (PV), one bidirectional DC/DC converters for battery, and a SST based on distribution system level, are included in the proposed DC microgrid system. In order to manage the system operation, a distributed power management strategy is proposed. In the proposed control algorithm, not only the DC microgrid system can interface to the distribution system, but each module in the system can be distributed based on its own characteristics. Experimental results verify that the proposed power management strategy can be applied to a DC microgrid stably and achieve good performance.}, booktitle={2013 ieee energy conversion congress and exposition (ecce)}, author={Yu, X. W. and She, X. and Ni, X. J. and Wang, G. Y. and Huang, A.}, year={2013}, pages={5131–5136} }
 @inproceedings{she_huang_ni_burgos_2012, title={AC Circulating Currents Suppression in Modular Multilevel Converter}, DOI={10.1109/iecon.2012.6388809}, abstractNote={Modular multilevel converter is a next generation multilevel converters for medium to high voltage conversion applications, such as medium voltage motor drive and high voltage direct current transmission. One potential issue of this type of converter is the AC circulating current, which increases the current stress and brings additional conduction loss to the system. This paper proposes modified control architecture for modular multilevel converters, aiming at suppressing the AC components in the circulating current. Specifically, a proportional-resonant type minor loop is incorporated to regulate the most AC components of the circulating current to zero in addition to the DC regulation loop. The proposed minor loop can also be applied to single phase MMC, which is not available in previous methods. Simulation results for a three-phase MMC operating as an inverter are provided to demonstrate the feasibility of the proposed method.}, booktitle={38th annual conference on ieee industrial electronics society (iecon 2012)}, author={She, X. and Huang, A. and Ni, X. J. and Burgos, R.}, year={2012}, pages={191–196} }
 @inproceedings{she_huang_2012, title={Circulating Current Control of Double-Star Chopper-Cell Modular Multilevel Converter for HVDC System}, DOI={10.1109/iecon.2012.6388594}, abstractNote={Modular multilevel converter is regarded as a promising technology in high voltage application, such as off-shore wind farm system. This paper proposes control technique for modular multilevel converters, aiming at suppressing the AC components in the circulating current. Specifically, an additional proportional-resonant control loop is designed to regulate the AC component of the circulating current to zero. The proposed method can effectively suppress the AC circulating current even in the unbalanced/fault condition. Simulation results for a 10MVA, 25KV DC system are provided to demonstrate the feasibility of the proposed method.}, booktitle={38th annual conference on ieee industrial electronics society (iecon 2012)}, author={She, X. and Huang, A.}, year={2012}, pages={1234–1239} }
 @article{she_huang_zhao_wang_2012, title={Coupling Effect Reduction of a Voltage-Balancing Controller in Single-Phase Cascaded Multilevel Converters}, volume={27}, ISSN={["1941-0107"]}, DOI={10.1109/tpel.2012.2186615}, abstractNote={This paper presents a new voltage-balancing controller for cascaded multilevel converters, especially for single-phase cascaded multilevel converters. It proposes a control algorithm that devotes itself not only to balancing the floating dc capacitors but also to eliminating the coupling effect between the voltage-balancing controller and the original system controller (controller without additional voltage-balancing controllers). Specifically, the average model in the d-q coordinate frame is derived and the control law is established. Then, the coupling effect between the voltage-balancing controller and the original system controller is identified and a new expression for duty cycle modification is proposed thus to eliminate the effect. Furthermore, this paper gives the design considerations of the pro- posed method, including the derivation of key transfer functions and effective voltage-balancing area, for the completeness of the discussion. Moreover, the reference generation techniques of the voltage-balancing controller are also discussed. This paper investigates the voltage imbalance in the soft-start process caused by an unsuitable reference, and presents a simple modified reference generation solution. Finally, both simulation and experimental results verify the performance of the proposed control system.}, number={8}, journal={IEEE TRANSACTIONS ON POWER ELECTRONICS}, author={She, Xu and Huang, Alex Q. and Zhao, Tiefu and Wang, Gangyao}, year={2012}, month={Aug}, pages={3530–3543} }
 @inproceedings{wang_huang_wang_she_burgos_2012, title={Feed-forward control of solid state transformer}, DOI={10.1109/apec.2012.6165964}, abstractNote={The solid state transformer (SST) can be viewed as an energy router for electricity in an analogous way to what network routers are for information. The SST impact on the system can be hence paramount, especially in terms of stability since it is essentially an active closed-loop regulated power converter. Within the SST itself however, with its different ac-dc, dc-dc and dc-ac stages, stability is also crucial, as it is well understood that for cascaded converter systems the interaction between stages is the cause of instability from a small-signal perspective. This paper represents an initial quest into the SST stability study, exploring two feed-forward control schemes for the ac-dc and dc-dc converter stages. Simulation and experimental results with a 7.2 kV ac 400 V dc, 20 kW laboratory prototype are presented for validation purposes.}, booktitle={2012 twenty-seventh annual ieee applied power electronics conference and exposition (apec)}, author={Wang, F. and Huang, A. and Wang, G. Y. and She, X. and Burgos, R.}, year={2012}, pages={1153–1158} }
 @inproceedings{wang_she_wang_huang_burgos_2012, title={Parallel operation of solid state transformer}, booktitle={2012 IEEE Energy Conversion Congress and Exposition (ECCE)}, author={Wang, F. and She, X. and Wang, G. Y. and Huang, A. and Burgos, R.}, year={2012}, pages={1433–1438} }
 @inproceedings{she_burgos_wang_wang_huang_2012, title={Review of solid state transformer in the distribution system: From components to field application}, DOI={10.1109/ecce.2012.6342269}, abstractNote={The emergence of high power converters makes the modern power grid more active than it was before. One of the research directions in this area is the solid state transformer, which aims at replacing the traditional 50/60 Hz power transformer by means of high frequency isolated AC/AC solid state conversion techniques. This paper presents a systematical technology review essential for the development of solid state transformer in the distribution system, especially focusing on the following four areas: high voltage and high frequency power devices, high power and high frequency transformers, AC/AC converter topologies, and applications of solid state transformer in the distribution system. For each category, the state-of-art technologies are reviewed and possible research directions are presented. It is concluded that the solid state transformer is an emerging technology for the modernization of the future smart grid.}, booktitle={2012 IEEE Energy Conversion Congress and Exposition (ECCE)}, author={She, X. and Burgos, R. and Wang, G. Y. and Wang, F. and Huang, A. Q.}, year={2012}, pages={4077–4084} }
 @inproceedings{she_wang_burgos_huang_2012, title={Solid state transformer interfaced wind energy system with integrated active power transfer, reactive power compensation and voltage conversion functions}, DOI={10.1109/ecce.2012.6342508}, abstractNote={As the power of wind energy system increases, the control of their active and reactive power becomes increasingly more important from a system standpoint given that these are typical frequency and voltage control parameters. In this paper a family of wind energy systems with integrated active power transfer, reactive power compensation and voltage-conversion functionality is proposed. The proposed wind energy systems using solid state transformer (SST) can effectively suppress the voltage fluctuation caused by the transient nature of wind energy without additional reactive power compensator and as such may enable the large penetration of wind farm (WF) into the distribution system. To this end, a simulation study for WF driven by squirrel-cage induction generators is presented to verify the effectiveness of the proposed system. In addition, a modular type high voltage and high power three-phase SST topology is presented for the proposed system, and its basic building block, which is a single-phase SST, is analyzed. The function of SST in the presented wind energy system is verified in a single-phase laboratory prototype with scaled down experiments.}, booktitle={2012 IEEE Energy Conversion Congress and Exposition (ECCE)}, author={She, X. and Wang, F. and Burgos, R. and Huang, A. Q.}, year={2012}, pages={3140–3147} }
 @inproceedings{she_huang_wang_zhao_wang_yao_2011, title={A new voltage-balancing controller in cascaded multilevel converters}, DOI={10.1109/ecce.2011.6063766}, abstractNote={Voltage-balancing controller in cascaded multilevel converters has been discussed extensively in previous literatures where several effective methods have been proposed. The coupling effect between a voltage-balancing controller and the original system controller is however not addressed comprehensively. This paper proposes a new voltage-balancing controller for single-phase cascaded multilevel converters in a d-q coordinate. The theoretical finding shows that the proposed method can effectively eliminate the coupling between two controllers in both steady and dynamic state. Simulation and experimental results validate the proposed method.}, booktitle={2011 IEEE Energy Conversion Congress and Exposition (ECCE)}, author={She, X. and Huang, A. Q. and Wang, G. Y. and Zhao, T. F. and Wang, F. and Yao, W. X.}, year={2011}, pages={177–184} }
 @inproceedings{wang_she_wang_kadavelugu_zhao_huang_yao_2011, title={Comparisons of different control strategies for 20kVA solid state transformer}, DOI={10.1109/ecce.2011.6064196}, abstractNote={This paper presents and compares different control strategies for 20kVA silicon IGBT based solid state transformer (SST). The SST has a cascaded seven level rectifier stage, three output parallel Dual Active Bridge (DAB) DC/DC stage and an inverter stage. The voltage of the three high voltage capacitors must be balanced for the safe operation of the IGBTs, however, the mismatch of power devices parameters and variance of high frequency transformer leakage inductance of the DAB stage will cause voltage unbalance for these capacitors as well as the power unbalance of the three output parallel DAB stages. This paper analyzed these effects and discussed the limitations and merits for several different control strategies. The newly proposed control strategy for the SST has been determined as the most suitable strategy in terms of performance and simplicity. Simulation and experiment results are presented to validate the analysis.}, booktitle={2011 IEEE Energy Conversion Congress and Exposition (ECCE)}, author={Wang, G. Y. and She, X. and Wang, F. and Kadavelugu, A. and Zhao, T. F. and Huang, A. and Yao, W. X.}, year={2011}, pages={3173–3178} }
 @inproceedings{wang_baek_elliott_kadavelugu_wang_she_dutta_liu_zhao_yao_et al._2011, title={Design and hardware implementation of Gen-1 silicon based solid state transformer}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-79955785263&partnerID=MN8TOARS}, DOI={10.1109/apec.2011.5744766}, abstractNote={This paper presents the design and hardware implementation and testing of 20kVA Gen-1 silicon based solid state transformer (SST), the high input voltage and high voltage isolation requirement are two major concerns for the SST design. So a 6.5kV 25A dual IGBT module has been customized packaged specially for this high voltage low current application, and an optically coupled high voltage sensor and IGBT gate driver has been designed in order to fulfill the high voltage isolation requirement. This paper also discusses the auxiliary power supply structure and thermal management for the SST power stage.}, booktitle={Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC}, author={Wang, G. and Baek, S. and Elliott, J. and Kadavelugu, A. and Wang, F. and She, X. and Dutta, S. and Liu, Y. and Zhao, T. and Yao, W. and et al.}, year={2011}, pages={1344–1349} }
 @inproceedings{she_lukic_huang_bhattacharya_baran_2011, title={Performance evaluation of solid state transformer based microgrid in FREEDM systems}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-79955771308&partnerID=MN8TOARS}, DOI={10.1109/apec.2011.5744594}, abstractNote={A new concept of solid state transformer based microgrid system is presented in this paper. By utilizing 400V DC bus generated from Gen-I solid state transformer proposed by FREEDM systems center, integration issues of DC microgrid and solid state transformer are analyzed. Zonal DC microgrid concept is applied to this novel system with the consideration of burden minimization to the existing AC grid. The future grid architecture is described by using this solid state transformer based integrated microgrid system.}, booktitle={Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC}, author={She, X. and Lukic, Srdjan and Huang, A.Q. and Bhattacharya, Subhashish and Baran, M.}, year={2011}, pages={182–188} }