The sub-module(SM) capacitor voltage balancing problem of modular multilevel converters(MMC) is one of the technical difficulties demanding prompt solution in the MMC engineering application.In contrast to the traditional voltage balancing method which uses the sorting results of SM capacitor voltages according to the direction of the arm current,two improved and optimized method is proposed for current modulation strategy whose output is current reference's specified value and voltage modulation strategy whose output is voltage reference's specified value.Meanwhile,the relationship between the current and the phase current of the bridge is derived.The optimized voltage balancing method has realized reduction of the number of current sensors and improvement of the capacitor voltage stability.Similar to the traditional method,this method is suitable for a variety of modulation strategies.The model of MMC with four SMs is realized by experimental platform,with both correctness and effectiveness of the proposed method verified by experimental results.%模块化多电平变换器(MMC)的子模块电容电压均衡问题是工程应用急需解决的难点之一.传统排序均压控制算法,存在需多个电流传感器的问题,推导了桥臂电流与相电流的关系,分别针对电压型与电流型调制策略提出了两种新的子模块电容电压均衡控制策略.该方法不仅降低了电流传感器的数目,而且能有效维持子模块电容电压的稳定,适用于多种调制策略.最后,通过搭建5电平的MMC实验平台,对提出的控制策略进行了验证,实验结果证明了提出的子模块稳压控制策略的正确性和有效性.
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