Abstarct: Abstract Nowadays, the ever-increasing population growth and subsequently the rapid increase in electric energy demand has turned the attention of power network planners to renewable energy sources (RESs) such as wind and solar as an alternative to fossil fuel-baxsed sources. However, the inherent characteristics of these sources, i.e. their intermittent and non-dispatchable output power, affect the power network performance, especially the reliability. Therefore, several solutions have been proposed to meet the mentioned challenge, among which, energy storage systems (ESSs) are known as an efficient solution. Among the various energy storage technologies, battery energy storage systems (BESSs) due to its affordability and high adaptability to wind-solar renewable sources, and hydrogen energy storage systems (HESSs) due to its high energy density and low leakage rate have become attractive technologies in power distribution networks. Therefore, in this thesis, a cost-oriented planning model baxsed on reliability is developed to optimal allocation of hydrogen-battery energy storages systems and wind-solar renewable sources, taking into account the urban development hurdles such as the lack of sufficient land availability. The proposed model considers not only the investment and operation costs related to the wind-solar renewable sources as well as HESSs and BESSs, but also examines the customer outage costs as a reliability index. At the same time, operational and planning restrictions of distributed energy sources (DERs), available land, Kirchhoff laws, voltage limit and capital expenditure budget are considered as model constraints. As the resultant optimization problem formulation has a non-convex mixed-integer nonlinear structure, a genetic algorithm is widely employed to obtain the final optimal solution and followed by a Monte Carlo simulation method is apllied to handle non-deterministic characteristics pertaining to the output powers of wind-solar renewable sources. The effectiveness of the proposed model is verified through simulation results on a part of the power distribution network of Tehran metropolis.