A control strategy of grid-connected photovoltaic inverter under unbalanced voltage conditions

The ride-through operation of photovoltaic inverter will produce apparent harmonic currents, cause active and reactive power fluctuations as well as DC voltage fluctuation under unbalance voltage faults. This paper studied on the power control of photovoltaic inverter under unbalanced faults, and proposed an improved control strategy which can restrain the fluctuation of active power, reactive power and output current harmonics. Adding several adjusting parameters based on the existing reference current algorithm, the relationships between harmonic current, power fluctuations and parameters are analyzed. The simulation models in PSCAD/EMTDC have been established with the proportional-resonant (PR) controller used to obtain a better dynamic performance, and the effectiveness of the proposed control strategies are demonstrated by satisfactory simulation results.