Review of the Key Technologies and Development of Flywheel Energy Storage in Urban Rail Transit

Abstract The continuous expansion of the scale of global urban rail transit (URT) network has led to the aggravation of traction energy consumption and the utilization of regenerative braking energy (RBE). Applying energy storage technology in URT can enhance the stability of traction power supply system (TPSS), absorb RBE, reduce traction energy consumption, and bring an opportunity to access new energy. This paper focuses on the flywheel energy storage system (FESS). First, the basic working principle and basic structure combined with the application summary of FESS in URT are analyzed in detail. Second, the technical breakthroughs of flywheel devices that need further improvement are illustrated in terms of rotor, bearing, and converter. Then common energy management and control methods of single flywheel device and flywheel array are summarized and compared. Finally, from the aspects of high-performance development of flywheel unit as well as intelligent energy management of FESS, the future development of FESS is put forward, which provides a reference for the standardization, high efficiency, and simplicity of FESS in URT.