Harmonic filter-based improved islanding detection technique for microgrid

Islanding detection in microgrid using harmonic filters connected at the distributed generation units (DGs) end has been described. Traditional islanding techniques related to impedance estimation suffer from poor detection accuracy due to false detection during load switching. In the proposed method, tuned filters connected at DG terminals are utilised for islanding detection in the microgrid. These filters can be connected at the DG end to reduce harmonic injection to the source end, besides helping the islanding detection through the proposed technique. The measured grid-side harmonic impedances at tuned frequency after the filter are used for islanding detection instead of the direct input harmonic impedance calculated in traditional techniques. The proposed method can overcome the difficulties of the existing impedance-based islanding detection techniques like larger non-detection zone (NDZ), false detection during load switching etc. The effectiveness of the proposed method is tested in a six bus microgrid system and comparison with other existing islanding detection techniques reveals the fact that the proposed method has much better performance in terms of improved detection accuracy, detection speed, and it also significantly reduces the NDZ.