Sizing and energy management of on-board hybrid energy storage systems in urban rail transit

Currently, lithium batteries are characterized by higher energy density but they require an accurate charge and discharge profile to increase its lifetime, and it is not easily to be obtained feeding urban railway systems. On the other hand, supercapacitors are powerful components, which can deliver very high power pulse for both traction and braking phases. The hybridization of these energy storage systems allows obtaining the advantages of the two different technologies improving overall performance but it needs an accurate sizing and energy management. This paper describes a methodology for designing hybrid energy storage systems (ESS) for urban railway applications integrating lithium batteries and supercapacitors. The sizing procedure takes into the account both the energy management strategy and power limitations of the two storage technologies. The effectiveness of the hybrid ESS is shown on a real case study presenting catenary-less zones. The encouraging results are presented and discussed.