A control method to improve the efficiency of a soft- switching non-isolated bidirectional DC-DC converter for hybrid and plug-in electric vehicle applications

Hybrid energy storage system (HESS) can be adopted in hybrid, plug-in hybrid, and pure electric vehicles (HEV, PHEV, and EV), where a bidirectional DC-DC converter (BDC) is used to connect batteries and ultra-capacitors. The efficiency improvement of the BDC is beneficial to increase the efficiency viability of HESS. Due to ZVS, high efficiency can be obtained at heavy load operations while the efficiency is low at light load operations mainly because of the conduction losses of the auxiliary circuits. These losses A control method to improve the efficiency 67 can be reduced by optimising the switching frequency. The relationship of efficiency and switching frequency are presented and discussed. A scaled-down 1 kW BDC prototype is built to verify the feasibility of the efficiency improvement. With the aim of achieving ZVS conditions and variable frequency control, the implementing method is proposed. The simulated results are also presented, which can validate the feasibility of the proposed control method. (2014) 'A control method to improve the efficiency of a soft-switching non-isolated bidirectional DC-DC converter for hybrid and plug-in electric vehicle applications', Int. research interests include soft-switching technologies of dc-dc converters, hybrid energy storage systems (HESS), vehicle controllers, battery management systems (BMS), and on-board chargers. Control Technology. His research interests include the control of automotive electronics, electric vehicles, especially the research and development of hybrid electric vehicles. 68 L. Jiang et al.