A Robust Feedback Repetitive Control for Inverters with LLCL Filter Connected to Weak Grid

A robust controller design based on state feedback control with repetitive control is proposed in this paper to ensure both steady state performance and dynamic performances of grid-connected inverters with LLCL filter. The state feedback control with Proportional Resonant (PR) designed by linear matrix inequalities can both ensure stability and the dynamic responses for grid impedance uncertainty and variation, while the repetitive control can improve the harmonic suppression, thus improve the steady state tracking accuracy. The simulation and experimental results for a three-phase grid-connected inverter verified the effectiveness and superiority of the proposed control method.