Performance analysis of Q-f droop anti-islanding protection in the presence of mixed types of DG

This paper analyses the performance of a Q-f droop based anti-islanding protection (AIP) scheme when the islanded circuit contains both inverter based DG and directly connected synchronous generator (SG) based DG. It is found that the performance of the AIP method is significantly degraded when SG is present in the island. This is because frequency cannot be directly manipulated by injecting reactive power when SG is present. However, feeding reactive power still indirectly affects frequency and the Q-f droop based AIP scheme thus still facilitates islanding detection. The simulation results aim to bring awareness to which extent the presence of SG degrades the performance of the Q-f droop based AIP.