An inverse time overcurrent relay strategy for microgrids based on improved manta ray foraging optimization algorithm

Abstract When faults occur in microgrid lines, the large-scale integration of distributed energy resources and the switching between grid-connected and off-grid modes can lead to prolonged operation times of inverse-time overcurrent protection and the failure of coordinated protection at different levels. To address these issues, this paper proposes an improved protection scheme for inverse-time overcurrent protection based on the enhanced manta ray foraging optimization algorithm. The proposed scheme incorporates reverse learning and fractional-order calculus to enhance the performance of the MRFO algorithm. The optimized algorithm is applied to the coordinated setting of ITOCR parameters with the objectives of accelerating protection response and improving selectivity. The effectiveness of the proposed scheme is validated through extensive fault simulations in PSCAD/EMTDC under different operating modes, fault locations, and fault types. Simulation results show that the proposed scheme reduces the primary protection operating time by approximately 50% on average compared with the conventional ITOCR, while maintaining the coordination time interval within the required range of 0.2–0.5 s, demonstrating superior speed and coordination performance.