An Electrolytic capacitor-less and single-stage controlled three-phase isolated battery charger with wide-range output voltage for EV applications

This paper presents a new electrolytic capacitorless and single-stage controlled three-phase battery charger with electrical isolation to provide wide-range output voltage for EV applications. To achieve this, a three-phase rectifier cascaded by a current-feed isolated converter is proposed to yield DC voltage output and eliminate the bulk electrolytic capacitor installed behind the rectifier. Therefore, the lifetime of charger can be dramatically extended. Moreover, a novel control method for the charger is developed to mitigate the current and voltage ripples for charging battery and improve power factor compared to conventional rectifier simultaneously by single-stage control. Due to ZCS and ZVS in light load and single stage switching architecture for the proposed charger, the efficiency can be increased. Experimental results derived from the DSP-based controlled charger will be presented. The charger rating is 4 kW and output voltage is from 50V to 400V. It will be shown that the output current and voltage ripples are reduced significantly without any electrolytic capacitor in the proposed charger. It will also be demonstrated that the efficiency and power factor are more than 0.94 even in 25% rated load from 300V to 400V output voltage. These experimental results therefore confirm the superb performance of the proposed topology and control techniques.