MOPSO/FDMT-based Pareto-optimal solution for coordination of overcurrent relays in interconnected networks and multi-DER microgrids

The minimisation of discrimination time between main and backup overcurrent (OC) relays is one of the most important issues in power system relays coordination. On account of the massive computation burden and complexities for determining power system breakpoint, the implementation of the previously reported OC protection methods in large interconnected networks is almost impossible or at least cumbersome. In this regard, a variety of optimisation algorithms have been presented for coordination between relays and finding optimal operation time (OT) of the protection system. The previously reported single-objective optimisation algorithms have some limitations/drawbacks regarding OT of relays and their coordination. In this study, a new multi-objective optimisation algorithm is presented for coordination of OC relays in interconnected networks, based on multi-objective particle swarm optimisation (MOPSO) and fuzzy decision-making tool (FDMT). Then, using some useful assumption and recommendations of IEC-6090 and fault calculations for the microgrids including distributed energy resources, the proposed method is generalised for OC relay coordination in microgrids. Finally, the proposed method has been successfully implemented on different test systems and the obtained results have been compared with other reported methods to prove accuracy, authenticity, and efficiency of the MOPSO/FDMT-based protection and relay coordination algorithm.