Novel optimal control strategy for power fluctuation and current harmonic suppression of a three-phase photovoltaic inverter under unbalanced grid faults

Summary Under unbalanced grid faults, the output currents of a photovoltaic (PV) system injected into the grid lose their sinusoidal and balanced appearance. The interaction between such unbalanced currents and voltages leads to fluctuations in active and reactive powers. This study investigates the instantaneous output power characteristics of a PV inverter and its flexible power control strategy under unbalanced grid faults. A new optimal parameter model of power control is established to generate minimal integrated power fluctuations under the constraint of harmonic distortion in the output current. Finally, the optimal power control of the PV inverter based on dead beat current tracking is realized. The feasibility of the proposed control strategy is verified with the power system transient software PSCAD/EMTDC. Copyright © 2015 John Wiley & Sons, Ltd.