An Improved Active Frequency Drift Anti-islanding Detection Method

Grid connected photovoltaic systems have been paid more and more attention by people. The problem of antiislanding is a key problem that threatens the secure operation of distributed generation (DG) system, so the system must have the function of timely detecting islanding. The traditional active frequency drift ( AFD) method is not fast enough, and the total harmonic distortion (THD) is large, which greatly affect the output current quality. Hence, an improved active frequency drift detection method based on changing chopping factor ( cf) is proposed in view of the above shortcomings of the traditional AFD method. In this method, the detection time is shortened, THD is reduced. The effectiveness and superiority of the proposed method are verified by theoretical analysis and Matlab/Simulink simulation.