Measurement-Based Assessment of Tram-to-Vehicle Energy Recovery at the Caio Mario DC Tram Substation

Regenerative braking energy (RBE) in diode-fed DC tram networks may be curtailed when the available electrical demand is insufficient. This paper presents a measurement-based case study of the Caio Mario 600 V DC tram substation in Turin, Italy, and an idealized simulation-based assessment of electric vehicle charging equipment (EVCE) as an energy sink. Feeder-current and dc-link voltage measurements from two tram regions are used to quantify traction energy consumption and regenerative energy injected into the dc-link. An EV charging experiment demonstrates operation from the tram dc-link, with charging power limited to approximately 15 kW by the connected vehicle. The measured charging power includes energy supplied by both regenerative braking and the substation rectifier, depending on the instantaneous operating conditions. A Simulation X model representing the substation configuration is driven by the measured Reg02 current profile to assess idealized absorption limits of 40 kW and 150 kW. Over the investigated 5000 s interval, the estimated captured energy is 3.17 kWh and 5.79 kWh, respectively, corresponding to 45.42% and 82.95% of the 6.98 kWh of regenerative energy measured at the Reg02 feeder. These results are conditional estimates for the imposed profile, assuming continuous charging availability and neglecting conversion and feeder losses. They do not quantify additional recovery from onboard braking resistors or the net energy savings of the complete tram network. The study provides a site-specific assessment of the influence of charging power capacity on regenerative energy capture.