Resonance Suppression Based on PR Control for Single-Phase Grid-Connected Inverters With $LLCL$ Filters

This paper proposes a novel resonance suppression scheme for a single-phase grid inverter with the LLCL filters. In the structure of the LLCL filters, a small inductor is added in series with the capacitor in the conventional LCL filters to make zero impedance at the switching frequency, by which the grid-side inductor filter can be reduced remarkably. However, a resonance phenomenon is still a critical issue in this system. Therefore, an active damping method based on the proportional and resonant controllers is proposed to suppress the resonance. In addition, the stability is analyzed for the feasibility of the proposed algorithm. Finally, the simulation and experimental results have verified the control algorithm for a single-phase grid inverter.