An Optimal Unbalanced and Reactive Current Compensation Strategy for PV Inverter

The increasing presence of unbalanced loads and distributed energy resources (DERs) in low-voltage distribution networks has led to significant phase current unbalance, adversely impacting power quality, system efficiency, and equipment reliability. While existing mitigation approaches often involve high costs, additional equipment, or computational complexity. To address these challenges without introducing new hardware, this paper investigates the use of existing photovoltaic (PV) inverters for three-phase unbalance compensation. Two implementation scenarios are considered: one utilizing external computing resources and another relying solely on the PV inverter's embedded digital signal processor (DSP). In the optimal scenario, an external solver computes the negative-sequence and reactive current reference values via a Lagrange optimization algorithm, whereas in the DSP-based scenario, a simplified real-time control algorithm is employed to ensure compensation within each phase's current limit. The proposed method includes an optimal negative sequence current compensation strategy and a reactive current compensation scheme, both constrained by current limits of the inverter capacity. Simulation results validate the effectiveness of the proposed method.