A Study on DC-DC Battery Charger Employing Bus Converter for Electric Vehicles by Jung, Kwang-Soon Department of Secured Smart Electric Vehicle Engineering Graduate School, Kookmin University Seoul, Korea-버스 컨버터를 적용한 전기자동차용DC-DC 배터리 충전기에 관한 연구

A Study on DC-DC Battery Charger Employing Bus Converter for Electric Vehicles by Jung, Kwang-Soon Department of Secured Smart Electric Vehicle Engineering Graduate School, Kookmin University Seoul, Korea -

버스 컨버터를 적용한 전기자동차용DC-DC 배터리 충전기에 관한 연구

Doctor of Engineerintg Reques

 ABSTRACT

 Recently, it has become an important issue to solve the environmental pollution problem caused by exhaust gas in the automobile industry. Also, a lot of researches are proceeding to develop eco-friendly vehicles such as electric vehicles. Basically, electric vehicles are equipped with batteries and various types of battery chargers. Among the battery chargers, the DC-DC battery charger is powered from the high-voltage battery for motor drive and charges the low-voltage battery for driving electrical components. The 3.5kW DC-DC battery charger could be developed with a phase-shift full-bridge converter. However, a conventional phase-shift full-bridge converter has low performance, which is resulted from both low effective duty ratio and low transformer turn ratio, when designed as a battery charger with a wide input/output voltage range. To overcome these drawbacks, this paper suggests DC-DC battery charger employing bus converter for electric vehicles. The proposed DC-DC battery consists of the bus converter and the pre-regulator. The bus converter produces constant input/ output voltage conversion ratio, and the pre-regulator controls the output of the bus converter by providing a variable link voltage to the bus converter. The bus converter adopts the two-transformer full-bridge converter with active clamp circuit, which operates constantly with a maximum duty ratio of 0.5. The two-transformer full-bridge converter simplifies the secondary-side circuit, since two series-connected transformers replace output inductor. Also, the two transformers can be integrated, which provides efficient device placement solution. The bus converter eliminates conduction loss caused by the circulating current and achieves ZVS for the full-bridge inverter easily without commutating inductor. In addition, the bus converter achieves excellent ripple cancellation effects and small output current ripple. The bus converter can adopt SR switches with low Rds.on and reduce conduction loss on SR switches, since the bus converter minimizes voltage stress across SR switches. Therefore, the bus converter is very suitable for high output current applications. The proposed step-up/step-down converter is derived from a two-switch buck-boost converter operating the boost leg with a constant duty ratio of 0.5. The proposed step-up/step-down converter can share switches with the bus converter. Also, the proposed converter has low current ripple by using coupled inductor. The proposed DC-DC battery charger employs the bus converter and the proposed step-up/step-down converter as the preregulator. The proposed battery charger realizes high power density by sharing switches. Also, the control of the proposed DC-DC battery charger is simple because the battery charger adopts PWM control. In this paper, the operation principle of the proposed battery charger is explained and verified by experimental results with 3.5kW prototype. The proposed DC-DC battery charger achieves high efficiency. The maximum measured efficiency is 96.25%. 

 Key Words : Electric Vehicle, Battery Charger, Bus Converter, Full-Bridge Converter, Two Transformer, Pre-Regulator, Coupled inductor

ORIGINAL LINK: http://www.riss.kr/search/detail/DetailView.do?p_mat_type=be54d9b8bc7cdb09&control_no=c7106ade01d21f03ffe0bdc3ef48d419

LINK: http://www.mediafire.com/file/l31m31y3kwwlm1l/A_Study_on_DC-DC_Battery_Charger_Employing_Bus_Converter.pdf/file