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

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

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。

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.