模块化多电平换流器电容电压均衡控制策略研究

模块化多电平换流器(MMC)中各个子模块的电容电压均衡问题亟待解决。在分析MMC拓扑结构及其工作原理的基础上,结合载波移相调制方法,提出了一种基于PI控制器的电压均衡控制策略。该策略包括平衡电容电压和抑制桥臂环流两部分,通过调整调制信号的波形,进而改变各个电容的充放电时间,使电容电压保持一致并跟踪其给定值。该控制策略无需对所测得的电容电压进行排序,减少了IGBT的开关频率,大大降低了系统损耗。最后,在Matlab/Simulink仿真平台上对MMC系统进行验证,结果表明控制策略正确有效。

Research on Strategy for Capacitor Voltage Balancing of Modular Multilevel Converter

In modular multilevel converter, the balancing of capacitor voltage in each modular is urgent to be solved. On the basis of analyzing the topology and operation principle of MMC, a strategy based on PI controllers for capacitor voltage balancing is proposed in this paper by using carrier phase-shifting SPWM. The aim of control strategy is to balance capacitor voltage and to control loop bridge-arm current. By adjusting the waveform of the modulation signal, the charge/discharge time of each capacitor is modified in order to make capacitor voltage keep consistent and track the given value. No need of sequencing measured capacitor voltage, the control strategy decrease switching frequency of IGBT and system loss. In the end, the MMC system is verified on Matlab /Simulink simulation platform, and the results show that the control strategy is correct and effective.