| Energy storage systems of electric vehicles are key technologies which decide and limit the development and application of electric vehicles. With good characteristics, batteries are often used as power sources of electric vehicles. But the characteristics of battery also have obvious limitations, such as the limitation of power density. When EV fast start, accelerate or climb, battery is discharged in high-current, and when EV brake or slow down, battery is charged in high-current. These situations may damage the battery and reduce battery's lifespan. To meet requirements of EV's power performance, this paper design EV auxiliary power system which is consisting of super capacitor and Bi-DC/DC converter,and it can be applied to make up for the limitations of battery.Firstly, this paper find corresponding needs of electric vehicle auxiliary power system according to the needs of electric vehicles. Power compensation and regenerative braking energy recovery are two main functions of electric vehicle auxiliary power system. The control strategies of the EV auxiliary power system which is focus on the control method of Bi-DC/DC converter and mode-switching strategies of Bi-DC/DC is designed.Then the closed-loop parameters of Bi-DC/DC converter in Boost mode and Buck mode are designed.Finally, experimental is done with a 5kW Bi-DC/DC converter of EV auxiliary power system. Experimental results demonstrate the effectiveness of the proposed strategies. |
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