Improved Model Predictive Control of Three-level Voltage Source Converter

Abstract

Abstract—In conventional model predictive control, 27 switching states for three-level power converters are evaluated online, and the state in which the cost function is the smallest will be applied in the next sampling period. The amount of calculation, however, is too high, and it may cause too high of a jump for the phase voltage or line voltage in the AC side of the three-level converter, which means that each switching action causes voltage variation to exceed U_dc/2. To solve these problems, an improved model predictive method is proposed in this article. The proposed method only needs a subset of all the three-level states, which is obtained by adding and subtracting two-level state groups in the current switching state, for prediction and optimization. The high jump of the AC-side voltage is effectively avoided, and computational effort is greatly reduced. In addition, reduced switching frequency is obtained. The experiments are carried out by the two methods, and the results verify the correctness and feasibility of the proposed control strategy.

Keywords:

• amplitude jump
• model current predictive control
• neutral-point voltage balance
• state switch
• three-level converter

Additional information

Notes on contributors

Tingna Shi

Tingna Shi received the B. S. and M. S. degrees from Zhejiang University, China, in 1991 and 1996 respectively, and the Ph.D. degree from Tianjin University, China, in 2009. She is currently a professor in the School of Electrical Engineering and Automation, Tianjin University, China. Her current research interests include electrical machines and their control systems, power electronics, and electric drives.

Ce Zhang

Ce Zhang received the B. S. degree from Central South University, China, in 2010, and the M. S. degree from Tianjin University, China, in 2012. He is currently an assistant engineer in the Tianjin Design and Research Institute of Electric Drive CO.LTD, China. His current research interests include electrical machines and their control systems, power electronics.

Qiang Geng

Qiang Geng received the B. S., M. S., and Ph.D. degrees from Tianjin University, China, in 2000, 2006, and 2011, respectively. Presently, he is a Lecturer in the School of Electrical Engineering and Automation, Tianjin Polytechnic University, China. His research interests include electrical machines and their control systems and power electronics.

Changliang Xia

Changliang Xia received the B. S. degree from Tianjin University, China, in 1990, and the M. S. and Ph.D. degrees from Zhejiang University, China, in 1993 and 1995 respectively, all in electrical engineering. He is currently a Professor in the School of Electrical Engineering and Automation, Tianjin University, and also in Tianjin Key Laboratory of Advanced Technology of Electrical Engineering and Energy, Tianjin Polytechnic University. He is an IET Fellow and IEEE Senior Member. His research interests include electrical machines and their control systems, power electronics, and control of wind generators.