辅加逼近的MMC抑制电容电压波动

Suppression of capacitor voltage fluctuation by auxiliary approximation for MMC

子模块电容电压的均衡是模块化多电平换流器MMC控制的重中之重。应用于等级较高的MMC子模块数多,频繁投切造成的开关损耗可观。为此,提出分组设限电压均衡控制策略。即使电平不变时,越限电压的子模块也要投切,均衡电容电压。通过分组能增加模块保持原有状态的能力,降低开关损耗。引入补偿模块PC,使得输出直流电压逼近参考值,支撑直流电压的同时有效地抑制了环流。在Matlab/Simulink中搭建模型进行仿真实验,仿真实验结果验证了所提方法的有效性和正确性。

The capacitor voltage balancing of the sub-module is the most important part of the(MMC)control of the modularized multilevel converter(MMC).It has large number of sub-modules that applied high voltage grade engineering.The switching loss caused by frequent switching is considerable.Therefore,a control strategy of grouping and setting the upper and lower limit voltage balancing is proposed in this paper.Even if the level is constant,the sub modules beyond the limiting voltage should be switched for balancing capacitance voltage.In order to reduce switching loss,the ability to maintain the original state of the sub-module is increased by grouping.In order to make the output DC voltage approach the reference value,the compensation module PC is introduced.It can support DC voltage and suppress circulation effectively.Finally,the MMC-HVDC model is built in Matlab/Simulink.Simulation and experimental results show the effectiveness of the proposed control strategy.