Frequency Drift Anti-islanding Method with low harmonic components

摘要

PURPOSE: A method for detecting islanding is provided to rapidly detect the islanding using a correlation index according to frequency variation and to improve the quality of electricity by reducing total harmonic distortion. CONSTITUTION: System voltage at a distributed power system interconnection spot and the data of an inverter output current and inverter output voltage are obtained. Zero-crossing of the inverter output voltage is adjusted by sampling the data. The output current in which frequency is changed is inserted in a zero-crossing state. A correlation index of frequency variation is calculated using the amount of change of frequency of the inverter output current and the amount of change of chopping fraction. Islanding is detected by comparing the correlation index and a boundary value of the correlation index.