Recovery of Train Braking Energy in 3 kV DC Railway Systems: a case of study

Today, in the railway sector there is considerable interest in studying the best ways for recovering the electrical energy resulting from train braking as it may allow significant energy saving and better management of the railways grid voltage. This paper presents the results of a feasibility study that has been developed in order to sizing both power electronics and energy storage system that could be arranged in the railways AC/DC substations for recovering the train braking energy in 3 kV DC railway systems. Based on the evaluation of the recoverable energy during one day of operation in a given railway station, the paper discusses a suitable configuration for a braking energy recovery system that could be used to feed two associated electrical utilities, such as an electric vehicles charging station and the electrical distribution circuits of the railway station. According to available experimental data concerning the braking transient of a number of train arrangements, a suitable mathematical model in Matlab has been developed by taking into account the overall train traffic in a given mid-size railway station, so as to estimate the recoverable energy during 24 hours traffic operation. Then, the results of this study have been considered as input for developing the technical specification of both the power electronic converter and the battery energy storage that would be used to arrange the envisaged system for recovering energy from train braking transients.