Modified Q-f droop curve method for islanding detection with zero non-detection zone

In this paper, a modified Q-f droop curve method for the inverter-based distributed generator is proposed. The proposed method has merits such as detecting islanding with zero non-detection zone, negligible effects on power quality, and simple implementation. A new parameter is embedded in the reactive power reference to accelerate the frequency deviation at the point of common coupling until the islanding is detected. Therefore, a passive under/over frequency relay will be simply sufficient to detect islanding within the permissible limit. The proposed method is modelled with a computer-aided design SIMULINK/MATLAB environment. The proposed method is analyzed for operation with unity and non-unity power factors. The performance is validated for various loading quality factors with a negligible change in detection time. In addition, it is confirmed that the proposed system is stable under unbalanced loading and switching conditions. The proper operation of the proposed islanding detection method under multi distributed generators connection is validated. The results of the hardware experimentations are presented to confirm the proposed method analysis and simulations.