Novel bi-directional AC-DC converter for electrical vehicle battery testing

This paper develops a bi-directional converter for electrical vehicle battery testing that has fast dynamic response for meeting various battery test requirements. The proposed converter consists of two bi-directional stages, including a front end and second stage. The front end is a three-phase AC-DC converter under charging mode operation. It becomes a DC-AC converter that recovers energy. The second stage is a bi-directional DC-DC converter which simulates the charge and discharge battery behavior. A transient load compensator (TLC) is proposed to provide a fast dynamic response. This special feature reduces the DC-link voltage fluctuation and thereby avoids potential front stage current trip. Furthermore, this fast front end dynamic performance significantly improves the current tracking capability of the DC-DC converter, which simulates the battery charge and discharge behavior. The dynamic current battery behavior used in the EV can therefore be truly reflected by the presented battery simulator. These claims are fully confirmed by experimental results derived from a fully digitally controlled battery simulator for a 6kW/250V EV battery.