A Robust Dynamic Compensator with Anti-windup Scheme for Grid-Interlinked Photovoltaic Inverter under Unbalanced Grid Voltages

In this paper, a robust dynamic compensator together with anti-windup scheme for a grid tied inverter with L filter is proposed to provide satisfactory tracking performance of the reference signal under control input saturation. The control implementation is performed in the αβ reference frame to make the systems output matches a sinusoidal reference signal with zero tracking error. The sinusoidal current references are calculated using the active power command, reactive power command, and sequence voltages to deal with both balanced and unbalanced grid voltages. The dynamic compensator has the property of a resonant action in that it ensures accurate tracking of sinusoidal references in the presence of sinusoidal disturbances with known frequency. With the resonant behavior of the feedback controller, considerable overshoot and settling time may occur in the transient response, particularly during control saturation. To compensate for the effect of control input saturation, the dynamic compensator was modified to include an anti-windup compensator. The role of the anti-windup scheme is to improve the quality of the transient behavior during control input saturation. Simulation tests were used to verify the suggested controller performance. The proposed composite controller demonstrated excellent tracking performance with a graceful degradation during control saturation under both balanced and unbalanced grid voltages.