| Super capacitor energy buffer system is widely used in electric vehicles. This system not only can provide instantaneous acceleration power and improve automobile performance, but also can absorb the braking energy of vehicle and improve the utilization rate of automobile energy. When the system is working periodically, irregular charging of battery can be avoided and the life of battery is prolonged. Bidirectional DC-DC converter(BDC) is the core of the super capacitor energy buffer system. This paper studies and designs the BDC of the super capacitor energy buffer system, which mainly included the following aspects.In order to select the topology of BDC, advantages and disadvantages of a variety of non-isolated bidirectional DC-DC topologies are analyzed based on practical parameters. By comparison, two kinds of schemes are obtained: hard-switching Buck/Boost converter and interleaved quasi-square wave soft-switching Buck/Boost converter. Finally, in the consideration of reliability and cost, hard-switching Buck/Boost is selected as the interface converter.The control scheme of the energy management system based on Buck/Boost converter is designed, in which Buck mode and Boost mode are corresponded to the charging and discharging of the super capacitor respectively. Besides, the control model of system is established and controllers are designed respectively for the buck and boost mode. The effectiveness of the control scheme is verified through the simulation.High reliability is required in the vehicle system. Therefore, the high power IGBT module is chosen carefully to improve the system reliability. Firstly, the losses calculation method of IGBT and diode are described in detail. In addition, the junction temperature of three different types of IGBT power modules are analyzed, then the prediction of device reliability is given. Finally, power module selection is done according to the prediction results.A 100 k W prototype is designed in the laboratory, and realizations of software and hardware are explained in detail. The correctness of the analysis and design is verified through the experiment. |
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