A combined method for anti-islanding in PV inverters

This paper presents a combined method to detect islanding conditions. The method combines two approaches in a two stage process, and is based on the injection of reactive current as a disturbance to detect islanding. In the first stage, the method tests the voltage rate of change and the frequency rate of change. Once an islanding situation is presumed in the first stage, then in the second stage, a positive feedback scheme is enabled to confirm the islanding condition. This combined detection method is more effective and precise, avoids false tripping out by reducing the sensitivity to other perturbations, and avoids instabilities as the positive feedback is not connected all time. Simulations are presented to assess the performance of the proposed combined detection method.