Evaluation of AFD islanding detection methods based on NDZs described in power mismatch space

Islanding detection and anti-islanding protection are the essential functions of the gird-connected inverter in DG systems. The active frequency drift (AFD) method is an effective islanding detection technology. In this paper, AFD methods are studied analytically. the boundaries of the non-detection zones which demonstrates the effectiveness of the methods is then obtained. For comparing with the passive islanding detection methods, the non-detection zones of the AFD methods are represented in a power mismatch space (DeltaP versus DeltaQ). Finally, the analysis of the NDZs of the system with AFD is verified with simulation results.