Optimal siting and sizing of renewable energy and energy storage of power grids in mountainous areas with the access of railway traction loads

The large-scale exploitation and utilization of renewable energy, such as solar and wind power, have become an inevitable trend in the evolution of modern power systems. Meanwhile, electrified railways are rapidly extending into remote mountainous areas. With the deep integration of renewable energy and railway transportation, the safe operation of power grids in mountainous areas faces substantial challenges due to the combined effects of the complex characteristics of sources and loads. Therefore, it is necessary to develop a siting and sizing method for renewable energy and energy storage that accounts for the influence of traction loads to improve the safety of power grids. To this end, this paper first proposes a power grid vulnerability assessment method that incorporates renewable energy, traction loads, and energy storage. Then, hybrid energy storage is introduced to mitigate frequent traction-load fluctuations, and the voltage stability at the point of interconnection of renewable energy stations is quantitatively analyzed. On this basis, a multi-objective planning model for the siting and sizing of renewable energy and energy storage is then established by considering both economic and vulnerability indices. Case studies based on an actual 130-node power grid of Southwest China demonstrate that the proposed method can effectively enhance the operational security margin of the power grid while reducing total system cost. The method also significantly mitigates power and voltage fluctuations caused by traction-load access, providing a theoretical basis for the coordinated planning of power grids and electrified railways.