An Anti-Islanding Technique for Grid-Connected DG and Multi DG System

Islanding is a major problem that is related to a grid connected distribution generator. During islanding the distribution generator gets disconnected from the grid while still being energized. It should be detected as fast as possible in order to prevent the distribution generator from getting damaged or to ensure the safety of the personnel working. The islanding detection makes use of system parameter to detect islanding at the time of occurrence. In this paper a passive islanding detection method based on ripple content of voltage at the point of common coupling is being used to differentiate between islanding and non-islanding conditions. A threshold level is set upon the ripple content of voltage at the point of common coupling and islanding is detected whenever the threshold level is exceeded for some certain period of time. This method effectively distinguishes the islanding condition from other non-islanding condition and detects the islanding condition efficiently. The working of this method is being ensured by simulating a variety of islanding and non-islanding condition. No non-detection zone was shown by this method and islanding conditions were detected within 150ms of the allowed delay time. Theoretical analysis and simulation results are presented to validate the proposed method.