电网不平衡下模块化多电平整流器控制策略

Control Strategy of Modular Multilevel Rectifier Under an Unbalanced Grid Condition

为解决目前电网不平衡下模块化多电平整流器存在负序电流以及电压二次谐波影响系统稳定性的问题,在传统单一正序电流内环控制方法存在有功功率扰动大、整流器直流侧电压存在二次谐波问题的基础上,提出了一种基于信号延时法和双电流内环控制结合的控制策略。该策略以电流指令算法为基础,对电流的正、负序分量进行分离并计算,采用PI调节器,实现对正、负序电流的无静差控制,也可以有效降低有功功率p(ωt)的扰动,有效抑制整流器直流侧电压的二次谐波。仿真实验结果表明,该控制策略具有较好的抑制效果。

Aiming at solving the problems of negative sequence current and voltage second harmonic in modular multilevel rectifier affect system stability under an unbalanced power grid voltage condition, a control strategy has thus been proposed based on the combination of signal delay method and dual current inner loop control, taking into consideration the large active power disturbance and the second harmonic found in the DC side voltage of the rectifier. Based on the current instruction algorithm, the positive and negative sequence components of current can be separated and calculated. By using PI regulator, no static error control of positive and negative sequence current can be achieved, thus effectively reducing the disturbance of active power p(ωt) and restraining the second harmonic of DC side voltage of the rectifier. The simulation results show that the proposed control strategy exhibits a favorable suppression effect.