基于二自由度内模控制的LCL并网逆变器控制策略

并网逆变器需要具有极高的功率因数和极低的输出电流总谐波失真,在并网逆变系统中,对高频谐波的抑制效果显著,但由于其内部滤波器为一个三阶低阻尼系统,自身容易出现谐振。针对LCL型滤波器自身存在的谐振现象,提出一种基于二自由度内模控制的LCL并网逆变器控制策略来抑制其谐振尖峰,该控制器仅有两个可调参数,通过参数整定,所设计的控制器可同时具备良好的对给定信号的跟随性能和抑制干扰特性。该方法不需要增加额外传感器,系统成本较低。最后在Matlab/Simulink仿真平台上搭建LCL并网逆变器系统仿真模型,对两种控制策略进行仿真。仿真结果证明,采用二自由度内模控制策略时并网电流em_g总谐波畸变率只有1.4%,远低于国家标准5%,且具有良好的跟随性能,提高了系统的鲁棒性。

LCL Grid-connected Inverter Control Strategy Based on Two-degree-of-freedom Internal Model Control

The grid-connected inverter is required to have extremely high power factor and extremely low total harmonic distortion of output current. In the grid-connected inverter system, the LCL filter can suppress the high-frequency harmonics. However, the LCL filter is a low-damping three-order system, and easy to resonate. In this paper, a control strategy of LCL grid-connected inverter based on two-degree-of-freedom (2DOF) internal model control (IMC) is proposed to suppress the resonant peak of LCL. The controller has only two tunable parameters. By means of tuning parameters,the designed controller has the good performances on tracking the set value and suppressing the disturbance. No additional sensors are needed to be equipped and the system cost is reduced. Finally, the simulation model of LCL grid-connected inverter system is built on Matlab / Simulink platform, and the two control strategies are simulated and compared. The simulation results show that the total harmonic distortion of the grid current em_g is only 1.4%, which is far lower than the national standard of 5% with good tracking performance and improves the robustness of the system.