中文摘要：

为解决模块化多电平换流器（MMC）在采用载波移相调制时的电容电压平衡问题，提出一种基于载波交换的平衡方法。该方法位于调制层．不改变子模块的调制波，既不影响输出电压波形．也不会产生额外的开关损耗。首先详述了MMC的拓扑结构、工作原理以及调制方式；分析了开关状态交换时可能会出现的4种情况．分别是存在上升沿时桥臂电流大于0或小于0和存在下降沿时桥臂电流大于0或小于0；给出了具体的电容电压平衡方法及流程图。实验结果表明．所提方法可快速有效地将桥臂的电容电压集中在参考值附近．且各路电压之间无大幅波动．具有很好的平衡效果。

英文摘要：

A method based on carrier exchange is proposed to balance the capacitor voltage of MMC （Modular Multilevel Converter） adopting carrier phase-shift PWM method, which, located at the modulation layer and without additional switching loss,neither changes the modulation signal of sub- module nor influences the output voltage waveform. The topology,operating principle and modulation strategy of MMC are discussed in detail. Four situations that may happen during the state switchover are analyzed：the bridge arm current is positive or negative and there is a rising or failing edge. The specific capacitor voltage balancing method and its flowchart are given. Experimental results show that, the dispersive capacitor voltages of bridge arms are balanced quickly and effectively around the reference voltage without large fluctuations ,verifying the better balancing effect of the proposed method.exchange; voltage control; electric converters