A combined islanding detection algorithm for grid connected multiple microgrids for enhanced microgrid utilisation

There is an abundant interest in microgrids due to its innate ability to operate in either utility connected or isolated mode. The existing conventional methods disconnect the individual distributed generators on loss of utility. In this work, a combined islanding detection algorithm at the point of common coupling (PCC) of the whole microgrid is proposed. It detects islanding using islanding detection monitoring factor, rate of change of inverse hyperbolic cosecant function, and voltage at the PCC as the islanding detection elements with the help of phasor measurement units. On detection of islanding event, the whole microgrid is transferred to autonomous mode. Moreover, any fault in the microgrid side which may isolate the distributed generator is detected using dilation and erosion mathematical morphological operators. The algorithm estimates the probability of power balance and probability of islanding duration at the control centre for events within the microgrid. The decision for islanded operation or disconnecting the distributed generator is communicated based on this. The proposed method is tested on a microgrid test system and verified on a section of the realistic local feeder of the Indian utility system. The simulation results indicate that the developed algorithm is quick, reliable, and secure in discriminating between the islanding and nonislanding scenarios for the various cases during both import and export conditions with an accuracy of 100%. It eliminates the nondetection zone completely even during zero power mismatch conditions. With the proposed method, any unnecessary distributed generator outage can be avoided enhancing the microgrid utilisation.