Integration of E-bus Opportunity Chargers to the Voltage-Stabilized DC Railway Grid

Abstract

Because the transportation industry accounts for approximately a quarter of worldwide energy-related direct CO2 emissions and is a substantial contributor to air pollution, green and low-emission modes of transportation have received widespread attention. This paper investigates the deployment of a railway DC grid to feed electric bus (E-bus) opportunity charging stations by considering the real data of line in Zara street in Milan city as a real case study. A smart voltage stabilizer is studied and modeled for this system to overcome the issue of voltage fluctuation produced by trams’ acceleration and braking and consequently maximize opportunity charging stations’ performance. This approach has several advantages, including creating a set of lower-cost E-bus charging stations by making use of the existing traction DC grid and its equipment, regulating the DC grid’s voltage and maximizing the performance of chargers, and making use of regenerative braking energy (RBE) of trams instead of dissipation by braking resistors. The proposed stabilizing controlling system is aimed at keeping the voltage in a predefined bandwidth (550-630V DC). In MATLAB/Simulink, the performance of such a system is simulated and evaluated throughout the time it takes a tram to travel between two stops.