新型模块化多电平变流器容错运行策略

Novel Fault-tolerant Operation Strategy for Modular Multilevel Converter

为了解决模块化多电平变流器(MMC)在部分子模块故障时,因系统处于不对称运行状态而造成输出电流畸变、电容电压纹波较大、直流电流波动过大等问题,提高系统容错运行能力,本文提出了一种新型MMC容错运行策略,针对不同范围的调制比,对调制波进行相应调整。同时在载波移相调制基础上,提出一种利用当前关断模块替换故障模块导通的调制策略,并给出相应的优化方法,来增大桥臂正常模块平均导通时间,维持桥臂能量不变,减小桥臂间的不对称性。在MATLAB/Simulink上进行了仿真和实验验证。结果表明,本文提出的容错运行策略能够改善MMC故障运行时的输出波形,减小畸变率,提高了MMC的故障穿越能力,有利于MMC系统的稳定可靠运行。

In order to solve the problems of modular muhilevel converter （MMC） under sub-module fault, such as current distortion, larger capacitive voltage ripple and too-large DC current fluctuation, a novel fault-tolerant operation strategy for MMC is presented in this paper to improve the fault-tolerant operation capability of the system. According to different ranges of modulation ratio, the modulation wave is adjusted appropriately. Furthermore, a modulation strategy is put forward on the basis of carrier phase-shift modulation （CPSM） , which replaces the fault modules with current shutdown modules, and the corresponding optimization method is also given. In this way, the average switching-on time of normal module in bridges is prolonged, the bridge energy is kept unchanged and the asymmetry of bridges is reduced. The simulation and experimental verifications in MATLAB/Simulink are realized, and results show that the proposed fault-tolerant operation strategy can improve the output waveforms of MMC under fault, reduce the distortion rate and increase the fault ride-through capability of MMC, which is helpful to the stable and reliable operation of MMC system.