A Passive Islanding Detection Method for Grid-Connected Renewable Generation System

This study proposes an islanding detection method for use of grid-connected inverter of renewable generation system. The proposed method is based on an index: the change of power factor (COPF). When an inverter is grid-connected, the COPF is lower than the threshold values. In contrast, as an islanding occurs, the COPF becomes much higher than the threshold value. Detection systems monitor the terminal voltage and load current at the grid-connected point to calculate COPF, and issue an operating signal when the value of COPF exceeds a given threshold. In this study, experiments are conducted to illustrate the principles of the proposed technique for a prototype grid-connected inverter. The test results show that the proposed method is reliable, economical, and easy to implement for islanding detection of grid-connected inverter.