Models for Evaluating Energy Savings Achieved by Energy Storage System in Urban Railway

Energy storage systems (ESSs) that reuse the braking energy of trains have been installed in Korean urban railway systems, but the energy savings achieved by the ESSs vary among the systems: Urban railway systems operating with a longer train headway show greater ESS energy savings. This paper proposes a simulation-based approach to evaluate the ESS energy savings, providing the simulation model of an ESS, a DC feeding system of urban railway, and train power that fluctuates continuously while the train travels from station to station. In a simulated case study of an ESS in an urban railway system, the ESS energy savings rate increases from 6.2 % to 13.4 % when the train headway increases from 2.5 min to 7 min. These results indicate that the ESS energy savings increase in direct proportion to the train headway, thus the effect of train headway on the ESS energy savings should be considered when an ESS is introduced in an urban railway system. The proposed simulation-based approach can be applied to a feasibility study of ESS applications to urban railway systems