Multiobjective Optimization of Layout and Characteristics of Bidirectional Converter in Metro Traction Substation

Enhancing the stability and energy efficiency of metro power supply systems through advanced traction technologies and upgraded infrastructure represents a critical pathway toward sustainable urban rail transit. Current systems face challenges of catenary voltage fluctuation, which compromise operational safety and stability, alongside high energy consumption that undermines economic performance. Bidirectional converter (BC)-equipped traction substations offer a promising solution by stabilizing grid voltage and recovering regenerative braking energy, yet their efficacy hinges on optimal deployment and tuning. This study presents an integrated optimization framework for the siting and droop characteristics of BCs retrofitted from existing rectifier substations. A dynamic power flow computation platform is developed to simulate multi-train operations under heterogeneous traction power supply conditions, enabling the accurate calculation of system-level electrical behavior. Based on this, a multi-objective optimization model is formulated to minimize the number of BC deployments, the maximum contact line voltage deviation, and the total energy consumption. An enhanced multi-objective whale optimization algorithm incorporating an adaptive elite evolutionary strategy is proposed to efficiently solve the resulting high-dimensional, non-convex problem. Based on the data of Wuxi Metro Line 1, numerical experiments demonstrate that the optimized BC configuration (deploying 8 BCs) reduces peak voltage fluctuation by 33.9% and system-wide energy consumption by 11.5%, while yielding a 7.4% reduction in overall costs considering investment expenses. The proposed methodology provides a systematic and economically viable approach to significantly enhancing the safety and energy efficiency of metro power-train integrated systems.