Resonance Suppression Scheme in Single-Phase Grid 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 connected 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, since the resonance phenomenon is a critical issue in this case, a new control method using the proportional and resonant (PR) controllers is proposed to damp out the resonance. The simulation results have verified the effectiveness of the proposed control algorithm for a single-phase grid inverter.