Application of a Three-Level NPC Inverter

IEEE TRANSACTIONS ON POWER ELECTRONICS, VOL. 21, NO. 2, MARCH 2006

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Application of a Three-level NPC Inverter as a Three-Phase Four-Wire Power Quality Compensator by Generalized 3DSVM
Ning-Yi Dai, Student Member, IEEE, Man-Chung Wong, Member, IEEE, and Ying-Duo Han, Senior Member, IEEE
Abstract—A two-level four-leg inverter has been developed for the three-phase four-wire power quality compensators. When it is applied to medium and large capacity compensators, the voltage stress across each switch is so high that the corresponding causes large electromagnetic interference. The multilevel voltage source inverter topologies are good substitutes, since they can reduce voltage stress and improves output harmonic contents. The existing three-level neutral point clamped (NPC) inverter in threephase three-wire systems can be used in three-phase four-wire systems also, because the split dc capacitors provide a neutral connection. This paper presents a comparison study between the threelevel four-leg NPC inverter and the three-level NPC inverter. A fast and generalized applicable three-dimensional space vector modulation (3DSVM) is proposed for controlling a three-level NPC inverter in a three-phase four-wire system. The zero-sequence component of each vector is considered in order to implement the neutral current compensation. Both simulation and experimental results are given to show the effectiveness of the proposed 3DSVM control strategy. Comparisons with the - -0 hysteresis control strategy are also achieved. Index Terms—Three-dimensional space vector modulation (3DSVM), power quality, three-level neutral point clamped (NPC) inverter, three-phase four-wire system.

I. INTRODUCTION

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UE to the development of the “custom power” concept, three-phase four-wire systems will play a very important role in the distribution site. In past research, there are mainly two ways to provide neutral current compensation by two-level voltage-source inverters (VSIs): 1)

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Adams, “Harmonics and reactive power compensation based on the generalized instantaneous reactive power theory for three-phase four-wire systems,” IEEE Trans. Power Electron., vol. 13, no. 1, pp. 1174–1181, Jan. 2003. 2 Man-Chung Wong (M’03) was born in Hong Kong in 1969. He received the B.Sc. and M.Sc degrees in electrical and electronics engineering from the University of Macau, Macau, China, in 1993 and 1997, respectively, and the Ph.D. degree from the Tsinghua University, Beijing, China, in 2003. He became a Lecturer in the Department of Electrical and Electronics Engineering, University of Macau, in 1998. He has been an Assistant Professor at the University of Macau since 2003. His research interests are FACTS and DFACTS, power quality, custom power, and PWM. Dr. Wong received the Young Scientist Award from the “Instituto Internacional De Macau” in 2000 and the Young Scholar Award from the University of Macau in 2001. Ning-Yi Dai (S’04) was born in Nanjing, China, in 1979. She received the B.Sc. degree in electrical engineering from Southeast University, Nanjing, in 2001 and the M.Sc. degree in electrical and electronics engineering from the University of Macau, Macau, China, in 2004 where she is currently pursuing the Ph.D. degree. Her research interests are power quality, active power filters, and PWM. Ying-Duo Han (SM’95) was born in Shenyang, Liaoning province, China, in 1938. He received the B.S. and M.S. degrees from the Electrical Engineering Department, Tsinghua University, Beijing, China, in 1962 and 1965, respectively, and the Ph.D. degree from Erlangen-Nuerenberg University, Nuerenberg, Germany. He is a Professor in the Electrical Engineering Department, Tsinghua University, and he was the Vice-Chairman and Chairman of the Electrical Engineering Department, from 1986 to 1995. Since 1989, he has been the head of Power Electronics Research Center, Tsinghua University. He is a Visiting Professor at the University of Macau, Macau, China. He has published two books and more than 100 papers. He has been engaged for more than 30 years in education and research work on electric power systems and the automation field. In recent years, he has engaged in FACTS and DFACTS, intelligent control, regional stability control, new dynamic security estimation, and control based on GPS. Dr. Han received four State-level prizes, and six first and second ranked Province-level and Ministry-level prizes. He is a Member of the Chinese Academy of Engineering.