采用重复控制的LCL型并网逆变器单闭环电流控制

A Single-loop Current Control Method for LCL-filtered Grid-connected Inverters Based on the Repetitive Controller

提出一种应用重复控制器的单闭环电流控制。重复控制器能提高并网电流质量,然而其常用多环结构来保证稳定性,这就需要增加额外传感器。而针对LCL型滤波器,其常用的超前补偿和二阶滤波器使系统相频特性变得复杂,参数的稳定范围常不能定量计算,参数设计具有一定的试探性。文中所提控制方法可以解决以上问题。通过分析频率特性得到重复控制器的稳定边界,同时针对LCL型并网逆变器的特点,使用一阶补偿器替代传统的超前补偿,并使用陷波器组来消除系统谐振峰并提供足够的高频衰减。这种结构能使重复控制系统获得更高的低频谐波增益,并具有良好的电网阻抗鲁棒性,且实现容易。仿真和实验结果验证了提出控制方法的有效性。

A single-loop current control based on the repetitive controller was proposed. The repetitive controller can suppress the disturbances from grid, which can improve the quality of injected current. However, a multi-loop structure with the extra sensors is usually needed to ensure the system stability. And for the LCL filter, the phase advanced factor and the second-order low-pass filter, used in repetitive controller system, will cause the phase characteristics more complex. Thus, the control parameters cannot be gotten from the quantitative design. To cope with these problems, the frequency response analysis of repetitive controller was introduced to acquire the stable margin of controller. For the LCL based inverter, a first-order compensator is applied to replace the traditional phase advanced factor. And a bank of notch filters is employed to eliminate the resonant peak and provide the sufficient damping. This control structure can obtain a higher gain in low frequency range, and acquire a good robustness to grid impedance with the easy implementation. Simulation and experimental results verify the effectiveness of the proposed control method.