A Virtual Phase Current Regulation Strategy to Mitigate Reactive Power Oscillation for Three-Phase Grid-Tied Inverter under Unbalanced Voltages

A three-phase, three-wire grid-tied inverter, when operating under unbalanced voltages with traditional control strategies, inevitably injects the reactive power oscillating at twice the utility frequency. To mitigate or eliminate the reactive power oscillation, this paper proposes a virtual phase current regulation (VPCR) based strategy that is effective and easy to implement by incorporating a current feedback gain. The VPCR-based mitigation strategy can be activated in either the sagging or normal phases, with the former showing better performance, as demonstrated by the modeling of instantaneous power theory under the VPCR strategy. Subsequently, the proposed strategy is implemented in the simulation, effectively validating the proposed concepts and analysis.