High Efficiency Energy Conversion System for Decreaces in Electric Vehicle Battery Terminal Voltage

Abstract

The powertrain of electric vehicles in the market has a problem in that its performance degrades because of fluctuations in battery voltage. In order to solve this problem, this paper proposes an energy conversion system to boost a part of the electric vehicle battery voltage. This system consists of the existing electric vehicle powertrain and a bi-directional isolated DC-DC converter called the dual active bridge (DAB). This system is able to compensate for battery voltage drops with high efficiency by using a small capacity DAB converter. In addition, a control method for the DAB converter is proposed. This control method achieves a better response to the transient state than conventional methods. The validity of the proposed system and its control method are confirmed by simulation and experiments. A high efficiency of about 99% is obtained from the experimental system prototype.