适用于模块化多电平变换器的改进调制策略研究

Research on improved modulation strategy for modular multilevel converter

在介绍模块化多电平变换器基本运行特性的基础上,分析了传统的最近电平逼近调制(Nearest Level Modulation,NLM)策略,针对传统的NLM调制提出一种优化改进策略,该策略能够将变换器的输出电平数由N+1提高至2N+1,有效降低变换器输出电压的谐波含量,提高变换器输出性能。同时,所提调制策略还能够降低子模块电容电压的波动,有利于延长电容器的使用寿命。最后,在PSCAD/EMTDC软件平台上建立了系统的详细仿真模型,验证了所提策略的有效性。

The basic operation characteristics of modular multilevel converter （MMC） were introduced. Then, the traditional nearest level modulation （NLM） strategy was analyzed. An optimized modulation strategy was proposed, which could improve the output voltage levels of MMC from N ＋ 1 to 2N ＋ 1, as a result, it could effectively reduce the harmonics content of the output voltages, and enhance the output performance of MMC. In addition, the investigated strategy could decrease the capacitor voltage fluctuation of sub-modules, which benefits to extend the life time of the capacitor. Finally, the detailed simulation model was built on PSCAD/EMTDC to verify the effectiveness the proposed strategy.