A New Method of Utilizing Ultra-Capacitor Energy Sources in Hybrid Electric Vehicles Over a Wide Speed Range

In previous research, the authors introduced a unique method to directly use an ultra-capacitor (UC) without using a dc/dc converter as the peak traction power source of the (hybrid) electric vehicles. That method works well in urban driving cycles where the motor speed is usually lower than half rated speed. Considerable energy efficiency improvement was achieved compared to conventional methods using a dc/dc converter as the UC interface. However, the acceleration and braking at higher speeds with only ultra-capacitor sources still require a dc/dc converter. In this paper, a new methodology is proposed to directly use UC to provide peak power up to the full vehicle speed. Two UC charging options are also proposed. The overall cost reduction compared to the previous methods is considerable. Detailed simulations verify the effectiveness of the proposed methodology. Lab validation is ongoing.