Utilization of proportional filter capacitor voltage feedforward to realize active damping for digitally-controlled grid-tied inverter operating under wide grid impedance variation

Many active damping (AD) techniques have been proposed to deal with current oscillation in grid-tied voltage source inverter with an LCL filter. Among them, the proportional-capacitor-voltage-feedforward (PCVFF) has been found to be an effective way. However, there is a lack of detailed modeling, design, and analysis of the PCVFF. This paper will elucidate the characteristics of the PCVFF AD scheme by using the virtual impedance model, analyze the dynamic characteristics under wide grid impedance variation, and give a step-by-step controller design procedure for the proportional-resonant-plus-harmonic-compensation (PR+HC)-based grid current controller with the PCVFF AD. The control method has been applied to a 3kW, 220V, 50Hz prototype. The steady-state and transient performances of the inverter under a wide variation of the grid inductance from 0.0025 pu to 0.15 pu will be studied and evaluated.