Department of Computer, Control and Management Engineering

The paper reports a methodology to define the optimal sizing and positioning of energy storage system (ESS) in a railway line, based on supercapacitors technologies and accounting for economic benefits. The problem of the optimal siting and sizing of an ESS is addressed by a bi-objective nonlinear mathematical model involving only discrete variables. A novelty is considering the siting ESS on wayside, imposing the constraint of siting in correspondence with the electrical substations. This reduces the possible choices for siting and it is advantageous in the real case both for cost and for management. The Pareto frontiers are obtained by a fully enumerative algorithm which is viable when the problem has a small dimension. The feasible solutions have been analyzed from an economic point of view, taken into account the least part energy to be taken from the primary network, on the basis of the purchase price of energy. A real Italian underground railway line, using a standard working day timetable, has been simulated using a simulation toolbox in order to estimate the power flow between the trains. Real energy storage systems, available on market, have been considered in the simulation. Analyzing a good Pareto solution, we got that the installation of 4 storage systems allows an energetic saving of 1730 kWh, equivalent to about 11% of profit each year for the case study.