A Star-Connected Railway Energy Router and its Control Strategy for new Energy Integration Into AC Traction Substation

For back-to-back railway energy routers (BTB-RER), renewable energy utilization, regenerative braking energy (RBE) recycling, and traction inter-phase power balance are all achieved through two back-to-back (BTB) inverters, resulting in high hardware capacity requirements and system costs. This paper proposes a novel star-connected structure of an interphase-bridging inverter (IBI) and BTB inverters. This star-connected structure leverages not only the advantage of the smaller hardware rating of IBI but also the flexible controllability of BTB inverters, thereby reducing system costs while realizing similar functionality. Firstly, the power transfer principles and operational modes of the star-connected structure are analyzed to reveal the power complementarity relationship between the IBI and the BTB inverters. Subsequently, in response to the characteristics of multi-functionality and multi-directional energy flow, a power optimization control strategy is proposed to maximize the utilization of photovoltaic (PV) and RBE while enhancing power quality as much as possible. Finally, the superiority of the proposed star-connected structure is validated via hardware-in-the-loop experiments, and the measured data shows a 15% reduction in both inverter and transformer capacity requirements.