Collaborative capacity planning of grounded and onboard energy storage for multi-substation rail transit systems considering photovoltaic uncertainty

The large-scale integration of distributed photovoltaic (PV) energy into traction substations can significantly promote the energy self-consistency and low-carbon transition of rail transit systems. However, the inherent PV fluctuations and the mismatch between PV generation and traction load at individual traction substations restrict the efficient operation of rail transit systems. To address these challenges, this study proposes a capacity planning method for energy storage systems (ESSs) in rail transit self-consistent energy systems. The method considers both ground-based hybrid ESSs (HESSs) and onboard energy storage (OBES) under multi-substation collaborative operation within a “source–grid–storage–train” architecture. First, the spatial-temporal characteristics of OBES are modeled by defining its physical location and energy states through a multi-layer spatiotemporal network. Second, a collaborative planning model is developed with the economic operation of the rail transit self-consistent energy system as the objective and system security constraints as boundaries, enabling coordinated configuration of ground-based HESS and OBES across multiple substations. This model incorporates the spatiotemporal energy transfer mechanism of OBES among substations, aiming to achieve a globally efficient utilization of distributed renewable energy and storage capacity within the rail transit system. Finally, based on actual data from the Baoshen Railway, the effectiveness of the proposed multi-substation collaborative HESS planning model under PV uncertainty is validated through simulation studies on MATLAB/Gurobi software.