Auxiliary battery-based substations (ABSs) can enhance conventional railway feeder systems. In particular, ABSs make DC feeders located in areas far from the AC grid, able to power high-performance passenger and freight trains and store their braking energy. The paper proposes a techno-economic method to define size, position along the track, and control parameters of an ABS, with the goal to minimize the annual cost of energy (ACOE). Our approach takes into account the replacements of battery modules within the ABS expected lifetime in order to reduce costs. Numerical simulations are carried out assuming a new generation high-performance train on a real Italian 3 kV DC railway system equipped with one ABS. Although in some cases ABSs are already cheaper solutions compared to new traditional substations, the proposed sizing method allows obtaining a further reduction in the ABS cost.

In this paper, we investigate the design of stationary ESSs based on supercapacitors (SCs) for metro network (MN). We implement a simulation tool in order to estimate the power flow among the metro vehicles and the ESSs through the MN. A new formulation of the ESSs siting and sizing optimisation problem is proposed and solved using particle swarm algorithm. The optimisation process minimises the energy supplied by the electrical substations and the whole ESSs capacity taking into the electrical line constraints in the metro network simulator. Several simulations are performed in order to design the number, the position along the track and the required capacity of the SCs. Using commercially available modules, a realistic design solution is compared with the theoretical one obtained by solving the optimisation algorithm. Finally, we estimate the energy delivered from the electric substations and the energy saved using the real ESSs configuration.

Power systems are facing increasing strain due to the worldwide diffusion of electric vehicles (EVs). The need for charging stations (CSs) for battery electric vehicles (BEVs) in urban and private parking areas (PAs) is becoming a relevant issue. In this scenario, the use of energy storage systems (ESSs) could be an effective solution to reduce the peak power request by CSs in PAs to the grid. Moreover, II-Life battery modules are a potential approach for cutting costs and implementing sustainable solutions. We propose a method to size ESSs coupled to CSs by using II-Life battery modules. Our methodology is based on the estimation of the residual cycles and the decrease in the supplied power due to the battery aging for defining the number of EV battery packs required for an ESS use case. Then, economic evaluations are presented to compare II-Life with the equivalent I-Life storage system.

The calculation of optimal driving speed profiles for metro vehicles that improve energy saving and, thus, reduce costs, are investigated. The optimization problem is solved in two different steps: in the first one, a Dynamic Programming Optimization (DPO) algorithm (including slopes and curves effects) is used to find a set of pseudo-optimal speed cycles; the objective is to minimize the electrical energy used for traction subject to constraints such as travel time, trip distance, acceleration limits, etc. In the second optimization step, the speed profiles set are evaluated in a simulation tool implemented to estimate the power flow among vehicles through the metro network. A test campaign monitoring the saved energy and main electric variables have been implemented and the presented results showing the effectiveness of the performance of the proposed optimization algorithm.

Currently, lithium batteries are characterized by higher energy density but they require an accurate charge and discharge profile to increase its lifetime, and it is not easily to be obtained feeding urban railway systems. On the other hand, supercapacitors are powerful components, which can deliver very high power pulse for both traction and braking phases. The hybridization of these energy storage systems allows obtaining the advantages of the two different technologies improving overall performance but it needs an accurate sizing and energy management. This paper describes a methodology for designing hybrid energy storage systems (ESS) for urban railway applications integrating lithium batteries and supercapacitors. The sizing procedure takes into the account both the energy management strategy and power limitations of the two storage technologies. The effectiveness of the hybrid ESS is shown on a real case study presenting catenary-less zones. The encouraging results are presented and discussed.