Design of LCL filter for improving robustness of grid-connected voltage source inverter

In this paper, a design method of the LCL filter for the robustness of grid-connected voltage source inverter (VSI) is proposed in the case of the grid-side current feedback control. A stable region is investigated for the robust operation of VSI with regard to stability margins without a passive or an active damping. The proposed design method presents a means to place the resonance frequency in a proposed stable region, and considers the harmonic currents injected into the grid. Also, the grid impedance is considered for the system stability. The inverter-side inductance and the filter capacitance performs an important role in the proposed design method. A grid-connected VSI with filter parameters designed by the proposed design method is experimentally verified.