Battery/ultra-capacitor Hybrid Energy Storage System Used in HEV

It has been shown that none of any energy sources which own high specific energy or high specific power, but not both, can solely fulfil all the demands of hybrid electric vehicle (HEV) in some circumstances. In this paper a simulation model for battery/ultra-capacitor hybrid energy storage system (B/UC HESS) was presented by Matlab/Simulink. Based on the model a low-pass filtering control strategy which adopts ultra-capacitor as load leveling device was developed with a goal of improving battery life. The simulation results under different urban driving cycles show the validity of the model. The peak charge/discharge currents are smoothed effectively, which benefits the battery lifetime improvement. The experiment results also show that the buffering effect of ultracapacitor has optimized the charging and discharging processes of Ni-MH battery considerably.