Coordinated Operation Strategy for Islanding Protection and Low Voltage Ride-through of Grid-connected Photovoltaic System Based on Harmonic Characteristics

To tackle the operation conflict between the islanding protection and the low voltage ride-through (LVRT) of the grid-connected photovoltaic (PV) system, a coordinated operation strategy based on harmonic characteristics is proposed. The harmonic voltage variation characteristics before and after the occurrence of the islanding are analyzed. And the harmonic voltage threshold is calculated explicitly, based on which the islanding phenomenon and the voltage transient perturbation are differentiated, so as to coordinate the functions of the islanding protection and LVRT of the grid-connected PV system. Simulation results show the feasibility and effectiveness of the proposed strategy.