Experimental Verification of Dual Active Bridge Converter to Integrate AC Heating Inverter for Lithium-Ion Batteries in Electric Vehicles

Abstract

Lithium-ion batteries in electric vehicles must be adequately heated at low temperatures to prevent the decrease in discharge capacity. Therefore, ac heating techniques that use the Joule heat generated by the internal resistance of batteries have been proposed. Although these techniques achieve higher heating efficiency and uniform heating, they require an ac heating inverter to produce ac current, resulting in increased system complexity and cost. In this study, a dual active bridge converter that integrates an inverter for ac heating in electric vehicles is proposed. The proposed converter is derived by sharing two legs of both converters, thus achieving a simplified system and low cost. This converter operates either in the ac heating or power transfer mode. These modes operate at different switching frequencies and are independent of each other. Experimental results of a prototype for a 12-cell battery demonstrated that in addition to the bidirectional power flow, the proposed converter can heat up the 12-cell battery from -11°C to 0°C within 10min.