Reliability-Oriented Optimal Planning of Photovoltaic Distributed Generation and Energy Storage in Radial Distribution Networks

• A reliability-oriented planning framework is developed for radial distribution networks • Multiple planning scenarios were validated on IEEE 33-bus and IEEE 69-bus systems • The full-hybrid case reduced loss of load probability from 0.080 to 0.040 • System average interruption duration decreased from 5.5 h to 3.2 h • Coordinated planning improved voltage profile and reduced feeder power losses Increasing deployment of PV-based distributed generation (DG) and energy storage systems (ESS) can improve the efficiency and resilience of distribution networks, but improper allocation may aggravate voltage deviation and reliability problems. This paper proposes an Enhanced Walrus Optimization (EWO)-based framework for the optimal placement and sizing of photovoltaic distributed generation (PV-DG) and energy storage systems (ESS) in radial distribution networks. The proposed formulation simultaneously addresses active power-loss reduction, voltage profile improvement and reliability enhancement by jointly considering the loss of load probability (LOLP) and the system average interruption duration index (SAIDI). The proposed metaheuristic optimization method is validated on the IEEE 33-bus and IEEE 69-bus systems under base, PV-only, semi-hybrid, and full-hybrid planning scenarios. For the IEEE 33-bus system, the best full-hybrid case reduces active power loss from 0.2025 MW to 0.0451 MW, lowers LOLP from 0.080 to 0.040, decreases SAIDI from 5.5 h to 3.2 h, and improves the weak-bus voltage profile by up to 9.99%. For the IEEE 69-bus system, the full-hybrid case likewise provides the best overall performance, reducing power loss to 78.73 kW while improving both voltage behavior and reliability indices. A comparative analysis further indicates that the proposed EWO yields the best final solution quality among the tested metaheuristics for the studied planning problem. Overall, the results confirm that coordinated hybrid PV-DG/ESS planning offers a technically effective and practically relevant approach to enhancing radial distribution system reliability.