Failure mechanism study of conventional active methods based on inverter disturbances and a novel islanding detection method

This paper analyzes the failure mechanism of the typical active islanding detection method (f-Q feedback islanding detection method) under multi-inverter distributed generation (DG) system circumstances. When disturbances produced by each inverter almost counteract each other or the reactive power variation of local load matches the reactive power disturbance, the f-Q feedback detection method will be malfunction. A novel active islanding detection method suitable for both single-DG and multi-DG system is put forward in this paper. It is based on impedance estimation and applies an external centralized disturbance algorithm to avoid mutual interferences of multi-supply disturbance signals. The method has high accuracy of detection and a high detection speed.