Optimization-Based Adaptive Coordination of Directional Overcurrent Relays in Multi-DG Radial Distribution Systems

Abstract

The integration of Distributed Generation (DG) into radial distribution systems has introduced significant challenges to conventional protection schemes, particularly the coordination of Directional Overcurrent Relays (DOCRs). Bidirectional fault currents caused by DG penetration often result in miscoordination, non-selective tripping, and reduced reliability. This study develops and evaluates an adaptive protection framework using metaheuristic optimization techniques to enhance DOCR performance in DG-integrated networks. Two optimization methods, Particle Swarm Optimization (PSO) and the Coronavirus Optimization Algorithm (CVOA), were implemented in MATLAB/Simulink and applied to the IEEE 34-bus radial test system. The optimization problem was formulated to minimize relay operating times while satisfying coordination time interval (CTI) constraints. Simulation results show that DG integration significantly increases fault current magnitudes, compromising traditional relay settings. Optimization restored coordination, with CVOA achieving superior performance in terms of total operating time (4.72 s), reliability (σ = 0.07), and CTI margins (≥0.32 s), while PSO offered faster convergence and slightly lower computation time. These findings demonstrate that adaptive metaheuristic optimization can effectively address DG-induced protection challenges, with CVOA emerging as a robust solution for maintaining selectivity, reliability, and stability in modern radial distribution systems.