New Islanding Detection for Grid-connected PV Generation System Based on the Voltage Harmonic Sequence Components

The islanding problem in grid-connected photoltaics system and traditional islanding detecting method are studied in this paper. Based on the technology of passive islanding detection, a new method of islanding detection is proposed which is implemented by using the voltage harmonic sequence component. According to the principle that the power quality of inverter-side is unequal to power quality of the grid-side at PCC point, the characteristic harmonic frequency sequence components of voltage can be extracted by FFT at PCC when islanding state is occurring. Theoretically, non-detection zone can be thoroughly eliminated by the extraction and recognition of microscopic variables. Simulation model of grid-connected PV generation system is established in PSCAD/EMTDC, and algorithm is carried out by MTALB. The simulation results show that the method is effective and fast. The method proposed has high response speed and no influence on the power quality of the system.