A New Harmonic-based Protection structure for Meshed Microgrids

This paper presents a novel harmonic-based overcurrent relay which detects and isolates three-phase faults in a meshed microgrid. The harmonic signals are generated by two Distributed Generators (DGs) which each of them communicate with its adjacent DG. In the first step, a set of features are extracted from DG output signal and then fed to a Support Vector Machine (SVM) to detect occurrence of fault. Once the fault is detected, based on minimum voltage measured by DG, two closest DGs will recognize and these two DGs inject two distinct harmonics to activate harmonic-based relays. As each set of relays located at either beginning or end of each section is activated by current with specific frequency, these relays behave like directional relays without using voltage transformers. As a result, the proposed method is cost-effective solution. The optimum Time Dial Settings (TDSs) of these relays are obtained by solving a coordination problem with Particle Swarm Optimization (PSO) algorithm. Real-time results are taken by OPAL-RT to show the effectiveness of the proposed method for two different locations of fault in a meshed microgrid.