Island detection method based on combination of phase mutation and active frequency drift

The invention discloses an island detection method based on the combination of phase mutation and active frequency drift, and belongs to the field of anti-islanding protection of large-scale new energy centralized grid connection. The island detection method based on the combination of phase mutation and active frequency drift comprises the steps that (1) the phase difference delta phi between grid connection output current of an inverter and voltage of a public coupling point and the frequency f of the voltage of the public coupling point are detected; (2) whether the delta phi is larger than phi is judged, if yes, the step (5) is executed, and if not, the step (1) is executed again; whether the f is smaller than fmin or larger than fmax is judged, if yes, the step (5) is executed, and if not, the step (3) is executed; (3) frequency disturbance is added to the grid connection output current of the inverter through the active frequency drift technology in every period, and the frequency f' of the voltage of the public coupling point is detected; (4) whether the f' is larger than the fmax is judged, if yes, the step (5) is executed, and if not, the step (1) is executed again; (5) an island protection action is adopted. The island detection method based on the combination of phase mutation and active frequency drift resolves the problem that a single passive detection method fails under the condition of a resistance-similar load, has no detection blind area, and can effectively detect an island.