Design of LCL filter using feedforward controller for grid-connected inverter

This article presents a new approach that provides scaling the LCL-filter inductances based on the harmonic analysis of the filter output current. The approach considers the filter design together with the inverter control, both together, improving the system stability and the dynamic response. The model and general guidelines for selecting the filter parameters, taking into account the variation of the grid equivalent inductor, are presented. The proposed control system makes use of a simple PI since the feed-forward controller removes from the feedback controller the control on the grid current and eliminates the need of synchronization procedure. Simulation tests with a 15 kW three-phase VSI in series with an LCL filter have proved the effectiveness of the proposed approach.