This paper provides an optimal approach to denote the location and size of ESSs (energy storage systems) with the intention of reliability improvement in radial electrical distribution networks. The proposed optimal ESSs planning is addressed as a minimization problem which aims at minimizing the cost of ENS (energy not supplied) as well as ESSs costs at the same time, subject to safe operation of the network; where, the safe operation is guaranteed through satisfying security constraints such as voltage and line-flows limits. The minimization problem is mathematically formulated as a mixed-integer nonlinear programming and solved by PSO (particle swarm optimization) algorithm. A comprehensive sensitivity analysis is carried out on the results such as ESSs numbers, ESSs cost and reliability parameters. Simulation results demonstrate the viability of the proposed method in the real networks. Results also indicate the positive impact of ESSs on the network reliability. The proposed ESSs planning significantly reduces the ENS of the network and can be employed to deal with low reliability issues in the real networks.
