Abstract:Islanding detection is a necessary function of photovoltaic grid-connected power generation system, which requires to be characterized with such features as rapidity, accuracy, stability and safe detection. The current active island detection method exhibits such flaws as the necessity to introduce harmonic interference, a tendency to cause power quality deterioration, a slow detection speed of passive detection method with a large blind area of detection which can easily lead to islanding detection failure and other issues. In view of these existing problems, a proposal has thus been made of a low distortion current perturbation method to shift the current frequency by changing the current phase instead of the traditional active frequency offset method (AFD) which injects the perturbed current directly. The combination of passive detection method and low distortion current disturbance method can effectively achieve a faster detection speed, reduce harmonic interference and essentially improve the power quality of power grid. The simulation results in Matlab verify the effectiveness of the hybrid method.