Parameter Optimization of DOCR and FCL in Microgrids Based on Grey Wolf Optimizer

The operating time of directional overcurrent relays (DOCRs) can be reduced, while protection coordination is achieved, by setting the time dial setting (TDS) and pickup current of DOCRs. However, in the microgrids, the dual operating modes (grid-connected and islanded) and the introduction of distributed generations (DGs) bring some problems to coordination of DOCRs, due to changes in short-circuit levels. To limit the fault current levels and the effects of DGs on protection coordination, fault current limiters (FCLs) have been proposed. This paper employs grey wolf optimizer (GWO) to optimize the setting parameters of DOCRs and the values of FCLs not only in microgrids’ two operating modes, but also under two different kinds of protection coordination schemes. The comparison between optimized results obtained by five algorithms demonstrates the outstanding performance of GWO in low dimensional optimization problems and its potential for improvement.