Speed-based supercapacitor state of charge tracker for light railway vehicles

The paper suggests a supercapacitor control for light railway vehicles based on the tracking of the actual train speed. Different configurations in terms of storage capacity and braking resistance power are presented and compared. The proposed control algorithm evaluates analytically the supercapacitor reference current on the basis of the actual train kinetic energy, taking properly into account the efficiencies of the different subsystems. Therefore, on the basis of the size selected for the storage device, the control is capable of recovering the electrical energy during the braking of the train for recharging completely the supercapacitor units and dissipating the extra energy on the braking resistor. Realistic railway vehicle operations are presented by means of numerical simulations referring to different configurations of storage device and braking resistors. The results obtained show that the control is very effective in all the cases considered and that the final choice of the storage size is a trade-off between energy saving and equipment cost.