基于子模块组合的模块化多电平变换器简化空间矢量调制策略

调制策略对模块化多电平变换器MMC（modular multilevel converter）的稳定运行有着至关重要的作用。针对空间矢量调制SVM（space vector modulation）策略应用在MMC中存在计算复杂度高的问题，提出了一种简化的SVM控制策略。首先，将子模块分组构成子单元，使用三电平SVM对每一个子单元进行控制。其次，将相邻子单元的采样时间均匀地错开，以实现MMC多电平输出，降低输出电压和电流的谐波含量。最后，结合电容电压排序策略对子模块进行灵活控制，保证子模块电容电压的均衡。所提出的调制策略在子模块数量较多的MMC拓扑中实施简单，计算复杂度低，控制灵活性高。实验验证了所提方法的可行性和有效性。

Simplified Space Vector Modulation Strategy for Modular Multilevel Converter Based on Grouping Submodules

The modulation strategy plays a vital role in the stable operation of a modular multilevel converter(MMC). Aimed at the high computational complexity when applying the space vector modulation(SVM) strategy to the MMC, a simplified SVM control strategy is proposed in this paper. First, submodules(SMs) are grouped to form subunits, and the three-level SVM is exploited to control each subunit. Second, the sampling times of adjacent subunits are staggered evenly to achieve multi-level output from the MMC and reduce the harmonic content in output voltage and current. Finally, the capacitor voltage sorting strategy is combined to flexibly control the SMs, thus ensuring a balance between capacitor voltages of SMs. The modulation strategy proposed in this paper can be easily implemented in the topology of an MMC with more SMs, and it also has a low computational complexity and a high control flexibility. Experimental results verify the feasibility and effectiveness of the proposed method.