Real-time Power Flow Control Strategy for Electric Railway FTSSs Integrated with PVs and ESSs

Flexible traction substations (FTSSs) integrating power converters, solar photovoltaics (PVs), and energy storage systems (ESSs) are beneficial for electric railways (ERs) evolving toward a sustainable and efficient system. However, traction load and PV generation are uncertain and fluctuating, unfavorable to efficient PV energy consumption in ERs. Thus, this paper proposes a power flow control strategy for FTSSs. First, a real-time power flow optimization method is proposed to calculate the output power references of the back-to-back converter (BTBC) and ESS. It aims for efficient regenerative braking energy and PV energy utilization and negative sequence current suppression. Then, a model predictive power control (MPPC) scheme is designed for BTBC to track output power and DC-bus voltage references quickly and accurately. It includes a revised dynamic reference generation method and a model-based double-line frequency ripple (DLFR) filter. Meanwhile, an MPPC scheme for a bidirectional DC-DC converter is designed to regulate output power of ESS, which realizes accurate power reference tracking and smooth operational mode transition. Finally, the validity of the proposed strategy is confirmed through simulations and experiments.