A new islanding detection method for grid-connected photovoltaic system based on harmonic impedance sequence component

In order to solve the problems of the existing islanding detection methods, the relationship between the structural features and fault characteristics of photovoltaic power generation system, and the difference between normal grid-connected operation and islanding operation are studied in this paper. According to the difference, a new principle about the anti-islanding protection is proposed, which is implemented by using impedance characteristic frequency sequence components and has no detecting blind area. The principle can quickly identify islanding state by detecting impedance component at the PCC point even in the case of single-phase and two-phase disconnection, and it can not affect the quality of power system. The simulation results show that this method can effectively detect the island and has no detection zones. And it's response is fast and has no impact on the power quality.