Voltage Quality of an AC Grid Supplying a Railway Power System with Energy Saving Strategy

Railway industry is experiencing a strong need of renewal and smart technology. Hence, advanced approaches are needed to improve efficiency and sustainability of railway operations. In urban contexts, the public railway sector is object of an inevitable process of revamping, which involves expectations of end-users, railway operators, local supply distributors or local authorities. This paper examines an urban railway power system, where a smart scenario is envisaged. Particularly, an Italian AC/DC railway power infrastructure is considered, and an energy efficiency strategy is assumed. Aim of the paper is to evaluate the voltage quality in the supplying distribution network for any operating conditions of the railway system. Also, the energy efficiency strategy is arranged to improve voltage quality. More specifically, the strategy exploits electrical energy storage systems recharged by regenerative braking of rolling stocks in order to increase efficiency of the whole system. Also, the storage system allows shaving the peak load demand aimed at improving the voltage quality. Numerical simulations are carried out, they provide power quality analysis by examining nodal voltages as a function of the efficiency measure. The behavior of the railway power system has been analyzed under different operating conditions.