Stability Analysis and Comprehensive Design of Grid-tied Inverter with Active Damped LCL Filter

Abstract

This paper proposes a comprehensive design strategy for an LCL filter and controller parameters of an active damped LCL filter which has low inverter-side inductance in a grid-tied inverter. Design methods of a current controller and an active damping gain become more challenging because grid impedance affects the stability when the inverter-side inductance is low. First, a maximum damping gain range is derived to achieve a virtual positive damping resistor with cutoff frequency of high-pass-filter (HPF) and the LCL resonance frequency. Next, the practical implementation solutions are discussed based on the proposed design procedure. The detailed design strategy is exhibited with the design procedure and the design example. The validity of the theoretical analysis is demonstrated by a 1-kW prototype with or without the designed active damping. The grid current THD below 1.2% is maintained over the grid impedance range from 0% to 10%.