Real-Time PHIL Platform for High-Fidelity Evaluation of Next-Generation Reversible DC Traction Substations

Efficient utilization of regenerative braking energy (RBE) in DC railway systems has received significant attention in recent years, driven by the growing demand for improved energy efficiency and reduced power quality degradation in traction infrastructures. Reversible substations have emerged as an effective solution to enable bidirectional power flow between railway networks and utility grids, thereby overcoming the inherent limitations of conventional unidirectional traction substations. Although active reversible traction substations (AR-TSSs) exhibit strong potential for recovering surplus RBE and enhancing grid interaction, their large power ratings, high development costs, and operational risks pose significant challenges to experimental validation and real-world deployment. To address these challenges, this paper proposes a real-time power-hardware-in-the-loop (PHIL) platform for the development and validation of AR-TSSs prior to field implementation. The proposed platform couples a high-fidelity real-time model of a DC railway system with physical bidirectional power converters, enabling realistic closed-loop emulation of traction motoring and regenerative braking operating modes under practical conditions. Two interleaved bidirectional converters sharing a common DC link are coordinated through an OPAL-RT 5707XG real-time simulator, allowing detailed investigation of bidirectional energy flow, converter dynamics, and control interactions in a real-time environment. The principal novelty of this work lies in the realization of a high-fidelity PHIL-based experimental framework that enables low-level, hardware-validated evaluation of interleaved PWM-based AR-TSS architecture. Unlike conventional offline simulations or controller-only test benches, the proposed platform offers a safe, cost-effective, and scalable solution for assessing large-power reversible traction substations while preserving system fidelity and real-time behavior. PHIL experimental results validate effective RBE recovery, power quality improvement, and coordinated control performance, thereby establishing a practical pathway for the design and optimization of next-generation reversible DC traction substations.