采用PI+重复控制的并网逆变器控制耦合机理及其抑制策略

Mechanism of the Control Coupling and Suppression Strategy Using PI and Repetitive Control in Grid-connected Inverters

对于并网逆变器系统而言,为了抑制并网电流谐波,提高稳态控制精度,常采用重复控制。单一的重复控制动态性能差,PI+重复控制由于动态性能好、稳态精度高而被广泛应用。然而,比例积分(proportional integral,PI)调节器和重复控制器之间存在控制耦合,在动态过程中使并网电流发生畸变。该文分析了控制耦合机理,提出一种基于改进型重复控制的并网逆变器控制方法,一方面利用零相位跟踪控制(zero phase error tracking control,ZPETC)改善了系统的动态性能;另一方面通过对指令信号的动态延迟处理,抑制了控制耦合。最后通过仿真和实验表明理论分析的正确性和控制策略的有效性。

For grid-connected inverter systems, the repetitive control is often adopted to suppress the grid current harmonics and improve the steady-state control accuracy. Dynamic performances of the single repetitive control are poor, and the proportional integral（PI） and repetitive control is widely used due to its fast dynamic process and high steady-state accuracy. However, there exists control coupling between two regulators, which causes distortion of grid currents when the system is in the dynamic process. The mechanism of control coupling was analyzed and a control strategy based on an improved repetitive control for grid-connected inverters was proposed in this paper. The improved repetitive control based on the zero phase error tracking control（ZPETC） can improve the dynamic performance of the system; while a dynamic delay process for the input signal can solve the control coupling problem. Finally, simulation and experiment results show that the theoretical analysis is correct and the proposed control scheme is effective.