Hybrid fuzzy anti-islanding for grid-connected and islanding operation in distributed generation systems

This study proposes a method for islanding detection in distributed generation systems, namely, hybrid fuzzy positive feedback (PF). The aim is to reduce the injection of disturbances during the grid-connected operation from the anti-islanding methods, particularly at the instant of load connection and, do not require adjustment of the PF gain and frequency filters. This method is designed from fuzzy inference rules and the frequency and voltage inputs are also taken into account in the design procedure. Since the classical active methods do not identify if the voltage variation arises from the islanding condition or from a power quality issue in the grid, the fuzzy PF enables the proposed methods to differentiate the islanding condition from other grid events. In contrast to classical methods that have a fixed PF gain, a dynamic fuzzy PF gain is obtained by means of the fuzzy inference rules. The classical active technique is compared with the proposed approach in terms of detection time and injected disturbances during the grid-connected operation. The simulation and experimental results are presented to demonstrate the effectiveness of the proposed approach.