基于连续控制集模型预测控制的MMC桥臂电流控制策略

Arm Current Control Strategy of Modular Multilevel Converter Based on Continuous Control Set Model Predictive Control

模块化多电平变换器(MMC)的桥臂电流控制方法可同时实现交流侧电流控制和环流抑制。连续控制集模型预测控制(CCS-MPC)是一种时域内基于模型的最优控制方法,动态响应快,可以实现多频带复合信号的准确跟踪。提出一种基于CCS-MPC的桥臂电流控制方法,通过设计模型预测控制(MPC)控制器同时实现桥臂电流直流分量、基频交流分量的准确跟踪和倍频环流的抑制,克服了传统分频控制策略在暂态期间不同控制器相互影响的问题,无须对各个频率信号单独设计控制器,简化控制结构。在此基础上,提出了包含桥臂电流指令值计算、基于MPC的桥臂电流控制和子模块电容电压均压控制的MMC综合控制策略。最后,在MATLAB/Simulink中搭建三相MMC仿真模型,验证了所提控制策略的可行性和有效性。

The arm current control method for modular multilevel converter(MMC)can simultaneously accomplish AC-side current control and circulating current suppression control.Continuous control set-model predictive control(CCS-MPC)is an optimal control method based on system model in time domain.It has fast dynamic response and can accurately track multi-band compound signals.In this paper,an arm current control strategy based on CCS-MPC is presented.The designed model predictive control(MPC)controller can simultaneously realize the accurate tracking of DC component and fundamental-frequency AC component of bridge arm current,and suppress multiple-frequency circulating currents.The interaction problem between different bandwidth controllers during transient state of conventional arm current control is eliminated.Besides,there is no need to design a separate controller for each frequency signal,therefore the control structure is simplified.On this basis,a comprehensive control strategy of MMC is proposed,which includes reference value calculation of arm current,MPC based arm current control and balancing control of sub-module capacitor voltage.Finally,a three-phase MMC simulation model is built in MATLAB/Simulink to verify the feasibility and effectiveness of the proposed control strategy.