@article{dsouza_wang_cakir_baran_zhao_2021, title={Power Electronics Assisted Voltage Regulator: An Effective Solution for Mitigating Voltage Variations Caused by High Penetration PV on a Distribution System}, ISSN={["2329-5759"]}, DOI={10.1109/PEDG51384.2021.9494246}, abstractNote={The ever-increasing levels of distributed energy resources (DERs), especially solar photovoltaics (PV) tend to detrimentally affect the operation of the distribution systems on which they are installed, causing issues like voltage violations, excessive voltage regulator operations, voltage flicker, etc. Recent improvements in power electronics have led to an increase in the proliferation of power electronics based voltage regulators that are capable of fast voltage compensation. However, being a recent addition, very few studies exist that quantify the benefits of such devices on a distribution system. This work uses a case study to quantify the main benefits of a power electronics assisted voltage regulator (PEVR) in mitigating the impacts of high penetration PV using a supervisory control scheme for the PEVR. This study considers high resolution (1 second) PV and load profiles to capture the accurate operation of the step voltage regulator (SVR) and PEVR. The results from this case study highlight the effectiveness of a PEVR in mitigating excessive voltage variation and tap operations due to high penetration PV. The results also illustrate the trade-off between converter capacity and benefits.}, journal={2021 IEEE 12TH INTERNATIONAL SYMPOSIUM ON POWER ELECTRONICS FOR DISTRIBUTED GENERATION SYSTEMS (PEDG)}, author={DSouza, Keith and Wang, Yafeng and Cakir, Gokhan and Baran, Mesut and Zhao, Tiefu}, year={2021} }
 @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_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} }
 @article{bhattacharya_zhao_wang_dutta_baek_du_parkhideh_zhou_huang_2010, title={Design and Development of Generation-I Silicon based Solid State Transformer}, ISSN={["1048-2334"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77952195486&partnerID=MN8TOARS}, DOI={10.1109/apec.2010.5433455}, abstractNote={The Solid State Transformer (SST) is one of the key elements proposed in the National Science Foundation (NSF) Generation-III Engineering Research Center (ERC) “Future Renewable Electric Energy Delivery and Management” (FREEDM) Systems Center. The SST is used to enable active management of distributed renewable energy resources, energy storage devices and loads. In this paper, the Generation-I SST single-phase 20kVA, based on 6.5kV Si-IGBT is proposed for interface with 12kV distribution system voltage. The SST system design parameters, overall system efficiency, high frequency transformer design, dual active bridge converter, auxiliary power supply and gate drives are investigated. Design considerations and experimental results of the prototype SST are reported.}, journal={2010 TWENTY-FIFTH ANNUAL IEEE APPLIED POWER ELECTRONICS CONFERENCE AND EXPOSITION (APEC)}, author={Bhattacharya, Subhashish and Zhao, Tiefu and Wang, Gangyao and Dutta, Sumit and Baek, Seunghun and Du, Yu and Parkhideh, Babak and Zhou, Xiaohu and Huang, Alex Q.}, year={2010}, pages={1666–1673} }
 @article{zhao_wang_zeng_dutta_bhattacharya_huang_2010, title={Voltage and Power Balance Control for a Cascaded Multilevel Solid State Transformer}, ISSN={["1048-2334"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77952178838&partnerID=MN8TOARS}, DOI={10.1109/apec.2010.5433584}, abstractNote={In this paper, a 20kVA Solid State Transformer (SST) based on 6.5kV IGBT is proposed for interface with 7.2kV distribution system voltage. The proposed SST consists of a cascaded multilevel AC/DC rectifier stage, a Dual Active Bridge (DAB) converter stage with high frequency transformers and a DC/AC inverter stage. Based on the single phase d-q vector control, a novel control strategy is proposed to balance the rectifier capacitor voltages and the real power through the DAB parallel modules. Furthermore, the power constraints of the voltage balance control are analyzed. The SST switching model simulation demonstrates the effectiveness of the proposed voltage and power balance controller. A 3kW SST scale-down prototype is implemented. The experiment results verify the single phase d-q vector controller for the SST cascaded multilevel rectifier.}, journal={2010 TWENTY-FIFTH ANNUAL IEEE APPLIED POWER ELECTRONICS CONFERENCE AND EXPOSITION (APEC)}, author={Zhao, Tiefu and Wang, Gangyao and Zeng, Jie and Dutta, Sumit and Bhattacharya, Subhashish and Huang, Alex Q.}, year={2010}, pages={761–767} }
 @article{wang_zhou_li_zhao_huang_callanan_husna_agarwal_2009, title={10-kV SiC MOSFET-Based Boost Converter}, volume={45}, ISSN={["1939-9367"]}, DOI={10.1109/tia.2009.2031915}, abstractNote={10-kV silicon carbide (SiC) MOSFETs are currently being developed by a number of organizations in the U.S. with prospective applications in high-voltage and high-frequency power-electronic systems. The aim of this paper is to demonstrate the high-frequency and high-temperature capability of 10-kV SiC MOSFETs in the application of a dc/dc boost converter. In this study, 10-kV SiC MOSFET and junction barrier Schottky (JBS) diode were characterized and modeled in SPICE. Following this, a dc/dc boost converter based on a 10-kV 10-A MOSFET and a 10-kV 5-A JBS diode was designed and tested under continuous operation for frequencies up to 25 kHz. The boost converter had an output voltage of 4 kV, an output power of 4 kW, and operated with a junction temperature of 174degC for the SiC MOSFET. The fast-switching speed, low losses, and high-temperature operation capability of 10-kV SiC MOSFETs demonstrated in the dc/dc boost converter make them attractive for high-frequency and high-voltage power-conversion applications.}, number={6}, journal={IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS}, author={Wang, Jun and Zhou, Xiaohu and Li, Jun and Zhao, Tiefu and Huang, Alex Q. and Callanan, Robert and Husna, Fatima and Agarwal, Anant}, year={2009}, pages={2056–2063} }
 @inproceedings{zhao_zeng_bhattacharya_baran_huang_2009, title={An average model of solid state transformer for dynamic system simulation}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-71849090346&partnerID=MN8TOARS}, DOI={10.1109/pes.2009.5275542}, abstractNote={The Solid State Transformer (SST) is one of the key elements proposed in the National Science Foundation (NSF) Generation-III Engineering Research Center (ERC) “Future Renewable Electric Energy Delivery and Management” (FREEDM) Systems Center established in 2008. The SST is used to enable active management of distributed renewable energy resources, energy storage devices and loads. In this paper, a 20kVA solid state transformer based on 6.5kV IGBT is proposed for interface with 12kV distribution system voltage. The average model and control scheme of SST including AC/DC rectifier, Dual Active Bridge (DAB) converter and DC/AC inverter are developed to enable dynamic system level simulation. The developed average model is verified by comparing with the detailed switching model simulation. The dynamic system level SST simulation verifies the proposed controller and the corresponding average model illustrates the functionalities and advantages of the SST in FREEDM system.}, booktitle={2009 IEEE Power and Energy Society General Meeting, PES '09}, author={Zhao, T. and Zeng, J. and Bhattacharya, Subhashish and Baran, M.E. and Huang, A.Q.}, year={2009}, pages={1516–1523} }
 @inproceedings{zhao_wang_huang_agarwal_2007, title={Comparisons of SiC MOSFET and Si IGBT based motor drive systems}, ISBN={9781424412600}, DOI={10.1109/07ias.2007.51}, abstractNote={With the rapid development of silicon carbide (SiC) material quality, SiC power devices are gaining tremendous attentions in power electronics. In this paper, a SiC device based motor drive system is performed to provide a quantitative estimate of the system improvement. Two 60 kW motor drive systems based on SiC MOSFET/Schottky diode and Si IGBTs are designed. The power losses of the two inverters with sinusoidal pulse width modulation (SPWM) control are calculated analytically. By comparing the efficiencies, sizes and temperatures of the two designed systems, SiC device shows the superior advantages of smaller loss, better efficiency and smaller size in the same motor drive application.}, booktitle={Conference record of the 2007 IEEE Industry Applications Conference forty-second IAS annual meeting}, publisher={New York:  IEEE}, author={Zhao, T. F. and Wang, J. and Huang, A. Q. and Agarwal, A.}, year={2007}, pages={331–335} }