Unintentional islanding phenomenon has been one of the most important problems of gridconnected photovoltaic inverters. To prevent this phenomenon

all kinds of anti-islanding methods have been discussed. This paper presents a combined active islanding detection method

which consists of active frequency drift method and automatic phase-shift method. The traditional active anti-islanding methods of grid-connected PV inverters bear nondetection zone possibilities for certain paralleled RLC loads. The combined method shows islanding detection ability effectively

and it can eliminate nondetection zones even in the worst case conditions. Simulation in different load conditions is performed for verification.