Study on dual-loop grid current control scheme for grid-connected inverter with an LCL-filter

Grid connected inverter can attenuate high frequency harmonics effectively through an LCL filter which has potential benefits for the inverter to get higher harmonic performance with lower switching frequency and less inductance in contrast with L filter. However, LCL filter is a third order system without damping and easy to resonate. In order to eliminate resonance and improve the system stability, dual-loop control strategy with grid current and capacitor current feedback is proposed in this paper, where inner capacitor current regulation is adopted for active damping. System modeling and stability analysis is presented. The simulation and experiment results prove that the dual-loop current control strategy for the grid-connected inverter with LCL filter is feasible and the controller performance is good.