Islanding detection is one of critical technologies for the stable and reliable operation of distributed photovoltaic grid generation system. However

the traditional active island detection method is difficult to balance the accuracy of detection and power quality. The influence of load characteristic for islanding detection is analyzed carefully

and an active frequency shift islanding detection technology is proposed based on the load impedance angle for the grid on/off inverter. The disturbance of the injected current is changed according to the load impedance angle

which improves the detection efficiency for single inverter and multi-inverters

and eliminates the non-detection zones. Besides

a segmented improvement method of the proposed detection is adopted to mitigate the grid current distortion caused by the nonlinear factor in practical application

which improves the power quality of the system. Finally

simulation and experimental results both verify the effectiveness and feasibility of the proposed method.