A Passive Islanding Detection Technique for Grid-Connected Photovoltaic Inverters

One of the problem associated with grid connected distribution generator is islanding, which occurs when a disconnected distribution generator is energized unintentionally. If islanding is not detected quickly it could pose a serious threat to the distribution generator and to the personnel working. The islanding methods that are available use system parameter to distinguish between islanding and non-islanding condition. This paper presents a passive islanding detection method based on the difference of ripple content of voltage at the point of common coupling during non-islanding and islanding period. Islanding is detected whenever the ripple content of the voltage at point of common coupling breaches the set threshold level for fixed period of time. This method distinguishes the islanding condition from the other grid disturbances efficiently and detects whenever an islanding occurs. The various islanding and non-islanding condition were simulated to test the working of this method. It was inferred that the proposed method did not exhibit any non-detection zone and was able to detect all types of islanding cases within 300ms of the allowed delay time.Theoretical analysis and simulation results are presented to validate the proposed method.