The Design of Hybrid Energy Storage System for Hybrid Electric Vehicles.

In view of the problem of power batteries being frequently charged and discharged at large power in hybrid electric vehicle, the battery/ultra-capacitor hybrid energy storage system (B/UC HESS ) is adopted, which takes advantage of the high power characteristics of ultra-capacitor to improve the performance of storage system. In this paper, two schemes of B/UC HESS are studied: direct battery/ultra-capacitor parallel connection and active battery/ultra-capacitor parallel connection, in which the latter uses DC-DC convertor with zero current transition soft switching as interface to connect battery and ultra-capacitor. The dynamic model for the DC-DC convertor and the models for battery and ultra-capacitor are set up with Matlab simulink and a simulation is conducted with AVL Cruise. The results indicate that the direct parallel scheme doesn't take full use of the capability of ultra-capacitor, while with the active parallel scheme the peak current of battery lowers in pure electric driving and regenerative braking conditions, the variation range of battery end voltage reduces, with an energy efficiency 14. 92 % higher than that of sole battery energy storage system. In addition, its dynamic response performance also improves due to the use of fuzzy PID control algorithm. [ABSTRACT FROM AUTHOR]