采用电抗子模块分段投切的模块化多电平换流器降电容方法

模块化多电平换流器(MMC)子模块电容的电容电压波动使得电容值难以降低,阻碍了MMC换流阀轻型化的发展。在考虑了2次和4次相间环流的基础上,分析了子模块电容电压与桥臂电流相互影响的机理。为了降低子模块电容电压的波动水平,提出了一种以子模块形式分段投切桥臂电抗器的降容方法。分析了子模块电容电压波动的产生机理,分析了电抗子模块分段投切降容方法的原理,并设计了相应的控制策略。最后,在PSCAD/EMTDC仿真环境下搭建了双端基于MMC的高压直流(MMC-HVDC)模型,验证了所提降容策略的有效性,并与现有的环流抑制策略进行了对比分析。

Capacitance Reduction Methods for Modular Multilevel Converter by Dynamically Switching Reactor Submodule

The fluctuation of the capacitor voltage of the modular multilevel converter(MMC)sub-module capacitor makes it difficult to reduce the capacitance value, which hinders the development of the light-weight MMC converter valve. Based on the consideration of the second and fourth inter-phase circulation, this paper analyzes the mechanism of interaction effect between that the sub-module capacitance voltage and the bridge arm current. In order to reduce the fluctuation level of the sub-module capacitor voltage, a control method for switching the bridge reactor in the form of submodule is proposed. The mechanism of capacitor voltage fluctuation of sub-module is analyzed. The principle of the reactor sub-module switching method is analyzed, and the control strategy of the method is designed. Finally, a two-terminal MMC based high-voltage direct current(MMC-HVDC)model is built under the PSCAD/EMTDC simulation environment to verify the effectiveness of the strategy proposed and compared with the existing circulation suppression strategy.