Energy-efficient train control including regenerative braking with catenary efficiency

Train operating companies try to reduce energy consumption. One of the measures taken by them is energy-efficient train control or EETC, in which the traction energy consumption of a train is minimized. Most research on this topic focuses on EETC without regenerative braking. However, modern rolling stock may have the ability to apply regenerative braking instead of mechanical braking in order to re-use braking energy, which changes the optimal solution to the EETC problem. Therefore, this paper presents a model that determines EETC with regenerative braking including the efficiency at the catenary system for main line passenger trains. We apply a Gauss Pseudospectral Method to solve the optimal train control problem, and tested the model in a Dutch case study with different scenarios (flat track and fixed speed limit). Regenerative braking leads to a lower optimal cruising speed, later coasting, and earlier braking at a higher speed to generate energy. For lower running time supplements or smaller speed limits the speed profiles become more similar, although EETC with regenerative braking will always regenerate energy in the final braking regime. Thus, EETC regenerative braking is more energy-efficient than EETC with mechanical braking, even considering the transmission losses over the catenary system.