高压直流输电系统中模块化多电平换流器的重复预测控制

Repeat Predictive Control of Modular Multilevel Converter in High Voltage Direct Current System

模块化多电平换流器(modular multilevel converter,MMC)是高压直流输电(high voltage direct current,HVDC)系统中最具潜力的拓扑结构之一。针对MMC中存在的直流侧电容电压平衡及桥臂间的环流问题,提出了一种基于重复控制原理的模型预测控制策略,通过求解一个最优化问题,得到每个MMC单元中最佳的开关状态,来抑制循环电流,并实现MMC单元的电容电压平衡。最后,在Matlab/Simulink中对五电平背靠背MMC-HVDC的重复预测控制进行性能评估。仿真结果表明,基于重复预测控制策略的MMC-HVDC系统运行更理想,实现过程容易且简单。

The modular multilevel converter（MMC） is one of the most potential converter topologies in high-voltage direct current（HVDC） transmission system. According to the equalizing voltages of DC capacitor in MMC and the circulating currents of converter arms, the paper proposed a model predictive control（MPC） strategy based on the principle of repetitive control. The best switching states of each MMC unit can be obtained by solving an optimization problem,which can eliminate the circulating currents and achieve the voltage balance of DC capacitor. Finally, the performance of the proposed MPC strategy for five-level back-to-back MMC-HVDC system model was evaluated by Matlab/Simulink software. The simulation results demonstrate that the MMC-HVDC system based on repetitive control of MPC strategy operates better and the implementation process is easy and simple.