Observer-based active damping for grid-connected converters with LCL filter

In this paper an add-on control method is proposed to damp oscillations in the LCL filter of a grid-connected converter. An observer is used to estimate the capacitor current, and successively, a conventional active damping technique is applied. Since the capacitor current is estimated from already available measurements, the proposed active damping method does not need an extra current sensor for the capacitor current. Model analysis and simulation validate the effectiveness of the proposed control method.