An Islanding Detection Algorithm for Inverter-Based Distributed Generation Based on Reactive Power Control

For the inverter-based distributed generation (DG) under constant power control, this paper analyzes the relationship between the active/reactive power mismatch and frequency deviation, respectively, during islanding and finds that the frequency variation trends caused by active and reactive power mismatches may be opposite. In order to eliminate the nondetection zone (NDZ) and detect islanding rapidly, an innovative islanding detection algorithm is presented based on a reactive power control strategy. The strategy provides the reactive power reference for the DG to guarantee the consistency of the frequency variation trends caused by both active and reactive power mismatches, thus accelerating the islanding detection speed. In addition, the introduction of the voltage variation into the proposed reactive power control strategy can regulate voltage dynamically in grid-connected mode and further shorten the islanding detection time as well. According to the antiislanding test system in the IEEE Std. 929-2000 and IEEE Std. 1547-2003, several case studies are carried out in the power systems computer-aided design/EMTDC environment. The simulation results show that the proposed algorithm has the zero NDZ property and can detect islanding rapidly. Moreover, the algorithm also performs effectively for load imbalance conditions as well as for the system with multiple DGs.