Electric energy saving in urban railways by using energy storage system and optimal speed profiles simultaneously

Energy crisis and environmental pollution are two important factors that have caused the operators and researchers to prioritize the reduction of energy consumption in transportation and especially in urban railway systems. Speed profile optimization could be effective in decreasing energy consumption. The use of energy storage systems (ESSs) can also help to increase energy efficiency by recovering regenerative braking energy. In this paper, the above two measures were used simultaneously. First, the total energy consumption and stationary energy storage capacity was determined for a network consisting of trains with normal speed. Then the amount of energy and ESS size required for trains with optimal speed profiles were calculated. It was shown that by using the optimum speed profiles, while achieving a significant increase in energy saving, the required ESS capacity is also reduced compared to the normal speed profile. By using the practical results extracted from line 1 of Mashhad urban railway, the real network simulation was performed. The simulation results showed a significant reduction in the total input energy and ESS capacity associated with the optimal speed profile mode, which can also lead to lower ESS costs.