模块化多电平变换器改进型环流抑制方法

An Improved Method of Circulating Current Suppression for Modular Multilevel Converter

这里首先分析了载波移相脉宽调制(CPS-PWM)策略下广泛应用于模块化多电平变换器(MMC)的平均电容电压控制模型及其优缺点,在此基础上提出了一种改进型环流抑制方案,新方案采用了原模型中的外环桥臂电压均衡控制,并同时在内环环流控制中加入了环流的直流分量提取环节以及基于准比例谐振的二倍频谐波分量消除环节。针对所提出的改进抑制方案并综合考虑稳定裕度和稳态精度等条件,给出了离散域下控制器关键参数设计方法。最后,在搭建的三相MMC样机上分别对改进前后的控制方案进行了对比实验,充分验证了所提方案的有效性以及参数设计的合理性。

First,the average capacitance voltage control model widely used in modular multilevel converters(MMC) with carrier phase-shifting pulse width modulation(CPS-PWM) and its advantages and disadvantages are analyzed.On this basis,an improved loop current suppression scheme is proposed.The new scheme adopted the voltage equalization control of the outer loop bridge arm in the original model,and added the DC component extraction of the loop current and the harmonic component elimination of the double frequency based on quasi-proportional resonance to the inner loop current control.According to the proposed improved suppression scheme and considering the stability margin and steady-state accuracy conditions,the design method of the key parameters of the controller is given in discrete domain.Finally,the control schemes before and after the improvement are compared on the built three-phase MMC prototype,which fully verify the effectiveness of the proposed scheme and the rationality of the parameter design.