Metro trains equipped onboard with supercapacitors: A control technique for energy saving

The paper suggests a control technique for improving energy saving in metropolitan trains equipped by onboard supercapacitors. On the basis of the typical duty-cycle of a metro-train, the supercapacitor system has been sized with reference to an energetic criterion that tries to limit overhead line current and, consequently, voltage drop at the train pantograph. The control algorithm is then based on a changeover scheme that properly manage the charge and discharge of supercapacitors in order to keep constant the line current during acceleration, coasting and braking of the train. Experimental results on a scale model, reproducing forces and inertias of a real railroad vehicle, validate completely both the sizing procedure and the control technique proposed.