A hybrid time–frequency approach based fuzzy logic system for power island detection in grid connected distributed generation

Abstract

A new time–frequency approach for power island detection in distributed generation systems is presented in this paper, using a hybrid fast variant of the S-Transform (ST) algorithm and a fuzzy expert system. The fast S-Transform algorithm with different types of frequency scaling, band pass filtering and interpolation techniques, results in significantly reduced computational cost, than the conventional S-Transform approach. The relevant spectral features of negative sequence voltage and current signals obtained from the distributed generation (DG) system terminals are extracted from the time–frequency matrix, obtained through fast ST. These features are used as inputs to a fuzzy expert system (FES), to distinguish between an islanding or non-islanding event, over a variety of operating conditions of the DGs including the change of system configurations, power imbalance, etc. The accuracy and response time of this new approach is compared with several well-known techniques (including time–frequency transform based methods), by applying it on both standard and existing distribution networks.