Supercapacitor state of charge control based on changeover finite state controller for metro-train applications

The paper deals with the control of onboard storage devices with supercapacitors for urban railway trains. The practical utilization of supercapacitors requires suitable power converters for the regulation of power flows between the catenary and the electrical drives of the power-train. These converters operate in DC current and have to be bi-directional in order to allow the charge and discharge of supercapacitors. The mathematical model of the whole electrical drive has been developed and the main features of the control strategy have been presented. The control is capable of limiting the peak currents of the contact line and recovering partially the kinetic energy of the train during the braking periods. Simulations prove that the suggested control strategy is very effective for both purposes. Experimental tests made on a scaled prototype, representing the translating masses of a train, fully confirm the results of the simulations.