Cluster Based Optimal Relay Coordination Scheme for Efficient Protection of Multi-Microgrids

The growing popularity of multi-microgrids (MMGs) is driven by their enhanced reliability and resilience. However, efficient protection of MMGs is challenging due to changes in topology and fluctuations in short-circuit current levels across different configurations. This paper proposes a setting group based protection scheme using directional overcurrent relays (DOCRs) to provide adequate protection for MMGs. A matrix of fault currents is generated for each possible topology of microgrids to divide them into eight cluster groups. The relay coordination problem is formulated as a nonlinear programming problem. The relay settings are optimally determined using the function minimizer with linear and nonlinear constraints (fmincon) and genetic algorithm (GA) to minimize the total relay operating time, considering different IEC standard relay characteristics curves. The effectiveness of the proposed protection approach has been verified using an IEEE benchmark test system for MMGs.