基于CPS-SPWM调制方法的MMC-HVDC输电系统冗余保护策略研究

子模块故障是模块化多电平换流器高压直流输电(MMC-HVDC)系统最常见故障之一。为保证子模块故障后MMC-HVDC系统能够稳定工作,本文首先对子模块故障后桥臂电流、桥臂间环流及直流侧电流的影响进行数学分析,确定了MMC子模块容错方案;然后将子模块冗余控制与带有电容均压控制和环流抑制控制的载波相移脉宽调制(CPS-SPWM)方法相结合,设计了基于电容电压平衡控制CPS-SPWM的冗余保护策略;最后在PSCAD/EMTDC中搭建双端10电平的MMCHVDC输电系统模型。通过对模型进行稳态仿真以及子模块故障时的暂态对比仿真,验证了本文所提出的冗余保护策略的正确性和有效性。

Redundancy protection strategy research of MMC-HVDC transmission system based on CPS-SPWM modulation method

The sub?module failure is one of the most common faults in modular multilevel converter HVDC trans?mission systems. In order to ensure the MMC?HVDC system can work steadily when the sub?module was failure, the following steps are needed to be done. Firstly, a mathematical analysis for the influence of bridge arm current, circulation current and it’ s DC side current is made under the sub?module fault, so that the sub?module fault?toler?ant scheme is determined. Then, the sub?module redundancy control is combined with the CPS?SPWM modulation method which contains capacitor voltage balance control and circulation inhibitory control. The redundancy protec?tion strategy is designed which is based on the CPS?SPWM modulation method with capacitor voltage balance control method. Finally, a two?terminal 10?level MMC?HVDC transmission system model is established in PSCAD/EMT?DC. Through the steady state simulation and the comparison of sub?module fault transient simulation, the correct?ness and validity of redundancy protection strategy which is proposed in this paper are verified.