| Recent advancements in ultra-capacitor technologies have enabled them to be applicable in high-power energy storage systems for electric and hybrid electric vehicular powertrains. By integrating ultra-capacitors with batteries in hybrid energy storage systems, it is possible to achieve higher instantaneous charge and discharge rates, while at the same time reducing the size and improving the life cycle of the battery. Therefore, hybrid energy storage systems are of significant importance for electric, hybrid electric, and plug-in hybrid electric vehicles.;In this dissertation, a new battery/ultra-capacitor hybrid energy storage system is proposed. Compared to the conventional design, which requires a full-size DC/DC converter to interface between the ultra-capacitor and the battery/DC link, the new design uses a much smaller DC/DC converter to maintain the voltage of the ultra-capacitor at a value higher than the battery voltage. The battery will only provide power directly when the ultra-capacitor voltage drops below the battery voltage. Therefore, a relatively constant load profile is created for the battery. In addition, the battery is not used to harvest energy from the regenerative braking. Thus, the battery is isolated from random charges, which will increase the life of the battery. The proposed hybrid energy storage system configuration has been verified through extensive simulations and experiments. |
