Variable window hysteresis control strategy for ultra-capacitor configured energy storage system in electric vehicles

Ultra-capacitors are known to absorb and deliver large amount of energy for a short period of time. This property has made them ideal components to be used in conjunction with batteries. Hence a hybrid energy storage system comprising of ultra-capacitor and battery offer many advantages. There are many ways in which the hybrid energy storage system can be configured in electric vehicles. In this paper a configuration wherein the ultra-capacitor is interfaced with the battery through a bi-directional converter is chosen for the simulation study which mainly focuses on strategies to maintain the capacitor voltage within a hysteresis band and the influence of the band on the energy absorbed/delivered. Also the detailed simulation results pertaining to various discussed strategies have been tabulated to aid sizing of ultra-capacitor for meeting the load energy requirements.