Optimal protection coordination for directional overcurrent relays in radial distribution networks with inverter-based distributed energy resources

The optimal setting of directional overcurrent relays ensures the reliable protection and fast fault clearance of radial distribution networks. However, the increasing proliferation of inverter-based distributed energy resources can result in protection coordination failure or high operating times of directional overcurrent relays in radial distribution networks. This paper investigates the adverse impacts of grid-connected inverter-based distributed energy resources that adopt the active/reactive power control strategy on the protection speed, sensitivity and selectivity of directional overcurrent relays in radial distribution networks. A multi-objective optimal protection coordination model is formulated, which incorporates the protection performance of directional overcurrent relays, operation conditions and economics that result from the inverter-based distributed energy resources and power grids. The Pareto-front of the proposed optimal protection coordination problem is obtained by the improved multi-objective particle swarm optimization, where a time–space section evaluation utilizes the K-means clustering method to improve the computational efficiency. Furthermore, an analytic hierarchy process and criteria importance through intercrieria correlation weights-based technique for order preference by similarity to ideal solution algorithm is proposed to determine the optimal directional overcurrent relay settings. The developed coordinated framework is applied to a radial distribution network with inverter-based distributed energy resources in MATLAB and PSCAD/EMTDC simulation. The comparative analysis is provided and the effectiveness of the proposed scheme is validated through extensive case studies.