Evaluation of an isolated and modular Bi-directional Power Converter for Charging Battery/Ultra-Capacitors for EV

The energy transformation/storage and energy revolution of renewable energy, distributed generation, and other clean energy as the main energy development goals getting more and more attention from the academic world and industry. Thus, a suitable power converter should be proposed to adapt to this trend. Due to its modular symmetrical structure, high power density, zero-voltage-switching (ZVS), bi-directional energy transmission ability and simple Phase-Shift (PS) control, and other inherent advantages [1], the Dual Active Bridge (DAB) topology has been the most widely bi-directional converter discussed since it was proposed. This paper presents the single-phase shift (SPS) control, double-phase shift (DPS) control of the DAB converter, and non-ZVS and ZVS performance. Also, the components selection was included, and their efficiency was calculated using the embedded loss model. The coulomb counting SOC estimation was also included to monitor the SOC of a battery. To reach a higher output power capability, modular Input-Series/Output-Parallel (ISOP) was applied. A three-stage converter, 20KW each producing 60KW, has an efficiency of more than 97% at rated power. Efficiency results under different load conditions are also included and analyzed in this paper.