基于Y-MMC的柔性低频输电控制策略

Flexible low frequency transmission control strategy based on Y-MMC

采用传统矢量控制的Y型模块化多电平换流器(Y-MMC),存在控制结构复杂、参数整定困难等缺点。针对上述问题,采用模型预测控制方法对Y-MMC进行控制器设计,提出一种适用于柔性低频输电的分层协调控制策略。建立各桥臂开关状态组合下的预测模型,实现内环电流控制和电容电压均衡控制。采用分层优化思想建立直流电容电压跟踪、交流电流跟踪和开关频率优化的逐级评估系统。结合稳态逆模型和比例积分控制实现了功率换流站的功率控制和电压频率换流站的低频电压控制。通过MATLAB/Simulink对双端低频输电系统进行仿真,结果验证了所提控制方案在多种工况下的正确性和有效性。相较于传统的矢量控制,该策略简化了控制器设计,加快了响应速度。

Modular multilevel converter in Y configuration(Y-MMC)using traditional vector control has dis⁃advantages such as complex control structure and difficult parameter tuning.To address the above issues,the model predictive control method is adopted to design the controller of Y-MMC,and a hierarchical and coordinated control strategy for flexible low frequency transmission is proposed.A prediction model for the combination of the switch states of each arm bridge is established to achieve the inner loop current and capacitor voltage balanced control.The hierarchical optimization idea is used to establish a hierarchical evaluation system for DC capacitor voltage tracking,AC current tracking,and switch frequency optimization.The power output control of active and reactive power converter station and the low-frequency AC voltage control of voltage and frequency converter station are realized by the steady state inverse model and pro⁃portional-integral control.The correctness and effectiveness of the proposed control scheme of the two-terminal low-frequency transmission system under various conditions are verified by MATLAB/Simulink simulation.Compared to traditional vector control,this strategy simplifies the controller design and improves the response speed.