Efficiency Comparison of Discharge Strategies of Mobile Supercapacitor Energy Storage System for Public Electric Transport

This paper analyses and compares three discharge strategies for a mobile supercapacitor energy storage system of public electric transport – trolleybus. Within each strategy, the trolleybus traction drive is supplied with power from both overhead DC catenary and supercapacitors during the entire acceleration mode. According to the simulation results, these strategies are nearly equivalent in terms of efficiency when comparing the total energy consumptions of the catenary supply substation. On the other hand, it was found that strategies or cases where supercapacitors get discharged before the end of the acceleration mode should be avoided because during this phase the drive consumes the highest power due to which also overhead transmission losses are higher thus resulting up to 5% reduction in efficiency of supercapacitor energy storage system using.