A hybrid GA — Interval linear programming implementation for microgrid relay coordination considering different fault locations

This paper proposes hybrid Genetic Algorithm (GA) — Interval Linear Programming (ILP) approach to optimal relay coordination problem for microgrids. Relay coordination in microgrids is complex because of varied and bidirectional fault currents because of the existence of Distributed Generation (DG). Overcurrent relays are the feasible and economic choice of protection for meshed distribution systems. The coordinated relay settings must account for various possible fault scenarios in both grid connected and isolated microgrid modes of operation. Inadequate fault current levels from grid connected to the isolated mode are the major cause of protection miscoordination. This paper systematically formulates the relay coordination problem for microgrids as a linear interval optimization problem and introduces a new method of solution using hybrid GA — ILP method. The challenge in using GA to find the optimum in less number of iterations and the feasibility of ILP method to include various fault scenarios as “uncertain but bounded” intervals are combined to find the optimal overcurrent relay settings. The results show the effectiveness of proposed method. The programming is done using optimization tool box available in Matlab.