模块化多电平型换流器电容电压二倍频波动抑制策略研究

摘要

Study on the subject of suppressing the capacitor voltage fluctuation of modular multilevel converter (MMC) is scarce, thus this paper proposes a control strategy for suppressing the double fundamental frequency fluctuation of capacitor voltage of MMC. The sum of capacitor voltages of phase unit reflects the double fundamental frequency fluctuation of submodule capacitor voltage, so the strategy uses double fundamental frequency negative sequence rotational frame to decompose the capacitor voltages of three phase units to dq0 components. An additional controller is designed to control the dq0 components, which suppresses the double fundamental frequency fluctuation of capacitor voltage of submodules. The MMC simulation model containing the additional controller is established based on the Matlab/Simulink. The results show that the phase capacitor voltages controller can suppress the double fundamental frequency fluctuation of submodule capacitor voltage efficiently without increasing the submodule capacitance. It is also shown that this additional controller doesn’t affect the AC voltage and current output by external MMC.%针对当前关于抑制模块化多电平型换流器(Modular Multilevel Converter,MMC)直流电容电压波动的研究较少被涉及，提出了一种用于抑制MMC电容电压二倍频波动的控制策略。由于相单元电容电压之和反映了子模块电容电压的二倍频波动，所以采用二倍频负序旋转坐标变换将换流器三个相单元分别的电容电压之和分解为dq0轴分量，并设计了相应的附加控制器用于分别控制相单元电容电压之和的dq0轴分量，从而抑制了子模块电容电压的二倍频波动。最后通过Matlab/Simulink搭建了包含该附加控制器的MMC仿真模型，结果证明所提出的控制策略可以在不增大子模块电容值的情况下，有效地抑制子模块电容电压的二倍频波动，同时不会对MMC外部输出的交流电压和电流产生不良影响。