A 20kW Three Phase Off-Board Charging System with Multiple Outputs for Wide Variety of EVs

For wide variety of EVs, there is a need to provide multiple charging points as per charging standards. This paper gives a solution for off-board charging system design. The charging system uses three different isolated DC-DC converters as per their charging rates for different charging terminals whereas all converters sharing single DC-link. The three phase AC to DC power conversion is made through a Vienna rectifier, which maintains both DC link voltage and PFC (Power Factor Correction). For super-fast charging (250-450V charging range), a DAB (Dual Active Bridge) DC-DC converter (15kW) is used. For fast charging (250-500V), a reconfigurable-type isolated resonant DC-DC converter (3.5 kW) is used while for e-moped charging, a half bridge isolated LLC converter (1.5kW) is used. For all isolated DC-DC converters, turn ratio of HF isolation transformer is decided to make sure that during whole charging range, the peak series inductor current is not increasing too much for maintaining minimum level of current stress during whole charging range at each charging port. The Vienna converter is controlled through digital DQ control approach while DAB is controlled through SPS control and half bridge converter is controlled through frequency modulation approach. Simulated results are presented in different charging modes.