An Improved Control Strategy of Power Fluctuation and Current Suppression for Grid-connected Photovoltaic Inverter Under Unbalanced Fault Condition

Three-phase grid-connected photovoltaic inverter will cause active and reactive power fluctuations, produce apparent harmonic currents, and increase peak current under unbalance voltage faults condition. In this paper, the power control of photovoltaic inverter under unbalanced fault condition is studied, and an advanced control strategy which can restrain the fluctuation of active power, reactive power, output harmonic currents and peak current is proposed. By adding several adjusting parameters based on the existing reference current algorithm, the relationships between harmonic current, power fluctuations, peak current and parameters are analyzed, and the determination principle of adjusting parameters and the power-limited measures are proposed. The simulation models in PSCAD/EMTDC have been built to validate the accuracy of proposed control strategy.