A novel hybrid active anti-islanding method for multi-converter fed distributed generation systems

This paper presents a novel active anti-islanding detection scheme for the three phase grid-connected converters. The proposed hybrid method works based on the combination of Positive Feedback Frequency Shift (PFFS) and Reactive Power Variation (RPV) methods, and therefore it combines the features of both methods. Unlike the RPV scheme, this method is capable of synchronizing all power converters with each other in a distributed generation (DG) system. Therefore, it can effectively detect islanding when the DG system has multiple renewable energy sources interfaced to the system by multiple converters. The proposed method can also be combined with other active methods, such as the active frequency drift method. This minimizes the power quality degradation since the scheme is called upon only when 0.1Hz deviation in the grid frequency is detected. Moreover, unlike other positive feedback methods, this scheme has little impact on the stability of the DG system, since the positive feedback reference is only limited to ± 0.5% of the converter generated power. The performance of the proposed method is verified by simulation and experiments.