DAB Converter with Trapezoidal Wave Heating Capability for Lithium-Ion Battery of Electric Vehicles

Abstract

Lithium-ion batteries (LIBs) in electric vehicles at low temperatures need to be adequately heated to prevent a decrease in a cruising distance. Internal ac heating techniques with high heating efficiency have been proposed. However, conventional internal ac heating techniques face various challenges, such as increased system complexity and cost, a long heating time due to a low rms value of triangular or sinusoidal current waves, and large inductor size. This paper proposes a dual active bridge (DAB) converter with trapezoidal wave heating capability. The proposed converter is derived from integrating a DAB converter and ac heating inverter, achieving the simplified system and reduced cost. In addition, since the proposed PWM control generates the trapezoidal current wave at a high switching frequency, the shortened heating time and the inductor miniaturization are feasible. Experimental results demonstrated that in addition to the bidirectional power flow, the proposed converter could heat up the LIB from-10°C to 0°C in four minutes thanks to the trapezoidal wave, halving the heating time compared to the conventional sinusoidal wave.