Peak Demand Cutting Strategy with an On-Board Energy Storage System in Mass Rapid Transit

An energy storage system (ESS) in electric railways can be installed on a train, at trackside, or at substations. The main purpose of the ESS application is to reduce energy demand and peak power with good voltage regulation. This paper presents a control strategy for efficient regenerative braking of a vehicle equipped with an on-board ESS (OBESS) and evaluates the effects on the energy consumption, voltage profile, and power drawn from substations and the OBESS during vehicle acceleration and braking. This proposed strategy is to store recovered braking energy into the OBESS and find appropriate positions to deliver its stored energy back in such a way that the peak demand of all the substations is cut. The Bangkok Transit System (BTS)-Sky Train Silom (Green) Line in Thailand is used as a case study. This system has a service distance of 13.649 km with 13 passenger stations and 7 traction substations. It employs 750-V DC rectifier substations to supply electric power through its 3rd rails. The results showed that the proposed strategy can cut the peak power at the substations approximately 75% and the overall energy consumption of the system can be reduced by 16%.