Energy storage systems to exploit regenerative braking in DC railway systems: Different approaches to improve efficiency of modern high-speed trains

Abstract

The growing attention to environmental sustainability of transport systems made necessary to investigate the possibility of energy optimization even in sectors typically characterized by an already high level of sustainability, as in particular the railway system. One of the most promising opportunity is the optimization of the braking energy recovery, which has been already considered in tramway systems, while it is traditionally overlooked for high-speed railway systems. In this research work, the authors have developed two simulation models able to reproduce the behavior of high-speed trains when entering in a railway node, and to analyze the impact of regenerative braking in DC railway systems, including usage of energy storage systems. These models, developed respectively in the Matlab-Simscape environment and in the open source Modelica language, have been experimentally validated considering an Italian high-speed train. After validation, the authors have performed a feasibility analysis considering the use of stationary and on-board storage systems, also by taking into account capital costs of the investment and annual energy saving, to evaluate costeffectiveness of the different solutions. The analysis has shown the possibility to improve the efficiency of high-speed railway systems, by improving braking energy recovery through the installation of such storage systems.

A Dual-Objective Substation Energy Consumption Optimization Problem in Subway Systems

“…Although timetable optimization is seldom considered in these studies, the modelling method of ESS is referable to our work. Ceraolo et al [11] develop models to analyze the impact of regenerative braking in high-speed railway systems, where ESS is used. Feasibility of using wayside and on-board ESS is analyzed, respectively.…”

“…Nevertheless, besides timetable optimization, this paper mainly focuses on the optimization of WESS configuration in a subway system, i.e., to determine the capacity of the WESS in each electrical supply interval. Thus, the control strategies of WESS are reasonably simplified as in [11,29]. For example, we assume that each WESS can only be in a charging, discharging or idle state at a time, the abnormal case that charging and discharging commands are simultaneously sent to a ESS is not considered.…”

“…Note that, according to [11,29], the maximum charging and discharging power of WESS are both variables changing with its state-of-charge, as shown in Figure 5. The horizontal axes are state-of-charge, and the vertical axes are maximum charging/discharging power of a WESS.…”

“…Thus, with regenerative braking systems being widely applied in subway systems, optimizing Regenerative Energy Utilization (REU) has become a hot topic in recent years [8]. Generally, there are three ways to do so [9][10][11][12].…”

“…Thus, the surplus regenerative energy can be used by other electricity facilities outside of a subway system. However, this is not yet diffused, as it needs to modify the substations greatly, which is complex and comes with high costs [11].…”