T型H桥级联多电平变换器的改进型脉宽调制策略

针对T型H桥级联变换器的拓扑结构及其调制策略进行分析和研究,提出了基于载波移相脉宽调制(CPS-PWM)的改进型调制策略。以单极倍频CPS-PWM所得的虚拟五电平波形作为T型H桥的输出目标,结合T型H桥变换器输出不同电平时的开关模式,遵循"改变最少个数开关管状态来实现输出电平改变"原则,逆向推导T型H桥变换器的PWM信号,并在此基础上给出基于T型H桥单元级联多电平变换器的调制策略。搭建了基于T型H桥级联的单相静止同步补偿器(STATCOM)样机,分析了T型H桥上、下电容均压策略,最后通过仿真和实验结果验证所提调制策略以及电容均压策略的正确性和可行性。

Improved Phase Width Modulation Strategy for T-type H-bridge Based Cascaded Multilevel Converter

The cascaded multilevel converter is widely employed in medium/high voltage and high power electronic applications for its small harmonic components of output voltage and convenient modulation. In this paper, the operation principle of a T-type H-bridge topology is investigated in detail, and a carrier phase shifted pulse width modulation(CPS-PWM)based control method for this topology is proposed. By taking a virtual five-level waveform achieved with uni-polar double frequency CPS-PWM as the output objective, PWM signals of the T-type H-bridge can be obtained by reverse derivation according to its switching modes. Besides, a control method for T-type H-bridge based cascaded multilevel converter is introduced. A single-phase T-type H-bridge cascaded static synchronous compensator(STATCOM)prototype is built, and the DC-link voltage balancing control scheme is analyzed. Finally, the correctness and feasibility of the proposed modulation method and control strategy for T-type H-bridge based cascaded multilevel converter is verified by simulation and experimental results. This work is supported by National Natural Science Foundation of China(No. 51177147)and Zhejiang Key Science and Technology Innovation Group Program(No. 2010R50021).