Research on Improved Synchronized Carrier Based PWM for Three-Level Neutral Point Clamped Converter under Low Carrier Ratio
Gao Zhan1,2, Li Yaohua1,2, Ge Qiongxuan1, Zhao Lu1, Zhang Bo1
1. Key Laboratory of Power Electronics and Electric Drive Institute of Electrical Engineering Chinese Academy of Sciences Beijing 100190 China; 2. University of Chinese Academy of Sciences Beijing 100049 China
Abstract:When the three-level converter is applied to traction drive system of high power motor, synchronized modulation is usually used under low carrier ratio to optimize harmonic performance. Synchronized carrier based PWM (SCBPWM) is simple to calculate, but the carrier ratio must be an odd integer multiple of 3 to ensure synchronization, three-phase symmetry and half-wave symmetry, and it cannot enter the square wave modulation. In order to overcome the shortcomings of SCBPWM, this paper firstly studies the phase voltage waveforms of two SVPWM switching sequences under different carrier ratios, and then proposes an improved SCBPWM (ISCBPWM) based on modulation wave equivalence, which can realize synchronized modulation when the carrier ratio is an odd and an even integer multiples of 3, respectively. By calculating the switching angle online, the ISCBPWM can enter the square wave modulation. On this basis, the performance of ISCBPWM is analyzed and the modulation strategy based on ISCBPWM in full speed range is designed. Finally, the simulation and experimental results show that compared with the traditional SCBPWM, ISCBPWM has more suitable synchronous segments and higher DC voltage utilization. It can realize synchronous modulation at any integer multiple carrier ratio of 3 and enter the square wave modulation, and its implementation is very convenient.
高瞻, 李耀华, 葛琼璇, 赵鲁, 张波. 低载波比下三电平中点钳位变流器改进型同步载波脉宽调制策略研究[J]. 电工技术学报, 2020, 35(18): 3894-3907.
Gao Zhan, Li Yaohua, Ge Qiongxuan, Zhao Lu, Zhang Bo. Research on Improved Synchronized Carrier Based PWM for Three-Level Neutral Point Clamped Converter under Low Carrier Ratio. Transactions of China Electrotechnical Society, 2020, 35(18): 3894-3907.
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