Energy evaluation of the power network of a DC railway system with regenerating trains

Regenerating trains are now in common use on many DC fed railway systems, and train operating companies are able to get a discount on their energy costs if regeneration is active. The electrical energy consumption in a DC system is significant, and a comprehensive understanding of how regeneration affects the overall system energy consumption has not been developed. This study presents a simulation method in which a multi-train analysis is used to determine the system energy consumption with and without regeneration in operation, as well as the impact on the system energy consumption of different headways. The results are used to determine a full 'energy audit' of the system based on the data of the Beijing Yizhuang subway line. This includes the energy supplied by the substations, the energy wasted in the power transmission network, the energy used by the train in traction and regenerated by braking trains. The initial results show that regenerating trains have a significantly lower substation demand, but slightly more energy is lost within the network. The results also indicate that, the available regenerative energy and total substation demand vary with different timetables, and there is a 27% difference between the best and worst headways.