Applying hybrid PSO to optimize directional overcurrent relay coordination in variable network topologies

In power systems,determining the values of time dial setting (tds) and the plug setting (ps) for directional overcurrent relays (docrs) is an extremely constrained optimization problem that has been previously described and solved as a nonlinear programming problem. optimization coordination problems of near-end faults and far-end faults occurring simultaneously in circuits with various topologies,including fixed and variable network topologies,are considered in this study. the aim of this study was to apply the nelder-mead (nm) simplex search method and particle swarm optimization (pso) to solve this optimization problem. the proposed nm-pso method has the advantage of nm algorithm,with a quicker movement toward optimal solution,as well as the advantage of pso algorithm in the ability to obtain globally optimal solution. neither a conventional pso nor the proposed nm-pso method is capable of dealing with constrained optimization problems. therefore,we use the gradient-based repair method embedded in a conventional pso and the proposed nm-pso. this study used an ieee 8-bus test system as a case study to compare the convergence performance of the proposed nm-pso method and a conventional pso approach. the results demonstrate that a robust and optimal solution can be obtained efficiently by implementing the proposal. © 2013 ming-ta yang and an liu.