Abstract
Energy-efficient train control (EETC) has been studied a lot over the last decades, because it contributes to cost savings and reduction of CO2 emissions. The aim of EETC is to minimize total traction energy consumption of a train run given the running time in the timetable. Most research is focused to apply mechanical braking on this problem. However, current trains are able to use regenerative braking, which leads to another optimal driving strategy compared to mechanical braking. Research on EETC with a realistic nonlinear bounded model for regenerative braking or a combination between regenerative and mechanical braking is limited. The aim of this paper is to compare the difference between the EETC with regenerative and/or mechanical braking. First, we derive the optimal control structure for the problems with different braking combinations. Second, we apply the pseudospectral method on different scenarios where we investigate the effect of varying speed limits and gradients on the different driving strategies. Results indicate that compared to pure mechanical braking, combined regenerative and mechanical braking leads to a driving strategy with higher energy savings, a lower optimal cruising speed, a shorter coasting phase and a higher speed at the beginning of the braking phase. In addition, a nonlinear bounded regenerative braking curve leads to a different driving strategy compared to a constant braking rate that is commonly used in literature. We show that regenerative braking at a constant braking rate overestimates the total energy savings.
Highlights
The topic of energy-efficient train control (EETC) or energy-efficient train trajectory optimization has been studied a lot in the literature during the last decades
We investigate combined nonlinear bounded regenerative and mechanical braking (RMeB, see Section 2.2), constant-bounded regenerative braking only (RB, see Section 2.3) and mechanical braking only (MeB, see Section 2.4)
This paper investigated the difference between mechanical and regenerative braking on the energy-efficient driving strategy using a multiple-phase pseudospectral optimal train control method for a single train
Summary
The topic of energy-efficient train control (EETC) or energy-efficient train trajectory optimization has been studied a lot in the literature during the last decades. The aim of EETC is to run a train with the least traction energy consumption. The train uses the available running time supplements in order to arrive exactly on-time (i.e. not too early and not too late) at the station. The minimum-time running can be computed by solving the minimum-time train control (MTTC) problem. Energy-efficient train driving is applied if the train is running punctual (Scheepmaker and Goverde, 2015). A comprehensive overview on the topic of energy-efficient train control can be found in Scheepmaker et al (2017) and Yang et al (2016)
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