A Double-Loop Robust Model Predictive Control for LCL-Type Grid-Connected Inverters

To suppress resonance and improve the stability of LCL-type grid-connected inverters effectively, this paper presents a double-loop robust model predictive control (MPC) method for LCL-type grid-connected inverters. The proposed control strategy consists of two parts: the inner loop finite control set model predictive control (FCS-MPC) for regulating inverter-side current and capacitor voltage, and the outer loop linear control for regulating grid-side current. It has the advantages of fast response speed and simple parameters design guidelines. To establish the relationship between the inner loop and outer loop, the describing function method is adopted to identify the frequency response function of the inner loop. The harmonics compensation and robustness against grid-side inductance variation are satisfied during the parameters design procedure. And simulation tests are conducted to prove the effectiveness of the proposed method.