Speed-Based State-of-Charge Tracking Control for Metro Trains With Onboard Supercapacitors

This paper suggests a novel energy management control algorithm for metro trains based on speed measurement and acceleration estimation. The aim of the control is to recover in a supercapacitor (SC) storage device the maximum energy regenerated during train electrical braking and to limit the contact line peak current. The energy management control is integrated with the motor drive control, since discharge and charge of SC are connected to motoring and braking operations of the train. The algorithm is based on two nested loops on voltage and current of SC. The voltage and current references are calculated on the basis of the estimation of the train inertial force and acceleration, taking into account the power losses of the system. A simplified mathematical model of the whole electrical drive has been developed and the main features of the control strategy have been presented. Numerical simulations show the efficacy of suggested control and the energy saving obtained for metro trains. Experimental tests made on an electromechanical simulator fully confirm theoretical results.