Application study of six-point frequency measurement method in islanding detection

Considering the fact that the precision of frequency measurement of zero-crossing method and PLL(phase locked loop) method in the islanding detection of grid-connected PV(photo voltaic) generation system is influenced by the noise interference nearby zero crossing point of grid-connected side signal to be measured, this paper studies principle of six-point frequency measurement method and proposes a improved six point frequency measurement method. With optimal detection point interval and frequency outlier elimination, the improved six-point frequency measurement method can avoid island misjudgment although grid-connected side signal to be measured is interfered by the noise and improve power system operation reliability. The simulation results show the correctness of this study.