Optimal integration location and sizing of renewable energy systems in AC railways for cost optimisation

This is the authors' abstract. We don't add key points for this paper.

This study presents a bi-level optimisation framework for the optimal integration of photovoltaic (PV) systems and energy storage systems (ESS) in AC railway traction power supply networks. The framework addresses two key objectives: determining the optimal capacities and selecting effective integration locations for PV and ESS to enhance energy efficiency and reduce operational costs. At the master level, a grid search explores combinations of PV and ESS sizes and locations, while the slave level employs a mixed-integer linear programming (MILP) model solved with CPLEX to optimise ESS charge/discharge operations under variable energy conditions. Case studies demonstrate that integrating a 10 MW PV system with a 1 MWh, 2 MW ESS can reduce daily operational costs by 30% (from £20k to £14k per day). The system shows resilience to short-term fluctuations in solar irradiance but exhibits higher sensitivity during extended low-irradiance periods. These findings highlight the importance of carefully balancing system configuration, operational strategies, and renewable energy variability. Overall, the proposed approach provides a structured methodology for achieving cost-effective and sustainable PV-ESS integration in railway electrification systems, supporting both economic and operational performance objectives.