基于环流注入的MMC电容电压平衡控制策略

针对模块化多电平变换器(MMC)存在的电容电压在不同工况下易出现波动的问题,设计了一种基于环流注入的MMC电容电压平衡控制策略,其中环流参考是基于桥臂电流瞬时值和对应调制信号获得的。相对于传统环流注入方案,新方案不需要确定输出电流的幅值和相位,具有一定的优势。此外,电容电压平衡控制方案中还设计了能够跟踪环流参考的闭环控制器。最后,搭建了5 kV·A级MMC样机开展了相关试验,试验结果验证了新型电容电压控制器的效果。

MMC Capacitor Voltage Balancing Control Strategy Based on Circulating Current Injection

To solve the problem that the capacitance voltage of the modular multilevel converter(MMC)tends to fluctuate under different operating conditions,an MMC capacitor voltage balancing control strategy based on circulating current injection was presented.The circulating current references were obtained from the instantaneous values of the arm current and corresponding modulation signal of the phase leg.Compared with the traditional circulation injection scheme,the new scheme did not need to determine the amplitude and phase of the output current and has certain advantages.In addition,a closed-loop controller capable of tracking the circulating reference was also designed in the capacitive voltage balance control scheme.Finally,a 5 kV·A MMC prototype was built to carry out relevant tests.The test results verify the effectiveness of the new capacitor voltage controller.