Key Technologies For Electric Vehicles

The key technology in hybrid power system of electric vehicle was researched in this paper. The hybrid power system constituted by the battery and the ultracapacitor can combine the advantage of the high energy density of battery and the high power density of ultracapacitor. Ultracapacitor can provide strong current when electric vehicle is starting, accelerating and mountain climbing in order to avoid the strong current discharge which can destroy the battery and to extend battery life. The feedback of strong current can be absorbed by the ultracapacitor when electric vehicle is mountain climbing-down or braking in order to implement the energy recovery and protect the battery from the impact of the strong current. The research in this paper can be used as the initial exploration of solving power technology of electric vehicle.First, the characteristics of components of the hybrid power system were researched. On the basis of predominating the characteristics of battery, ultracapacitor and bidirection--al DC/DC converter, the structure characteristics and work patterns of the system were determined. Second, the models of components of the system were respectively established using appropriate method of modeling and the models were packed as separate modules with the idea of using module in order to apply to the models of the system. Third, a cycle of road and vehicle parameters were determined and the appropriate matching parameters were selected. According to control objective of the system, the control strategy of the systems was constituted. The single battery power system and hybrid power system were simulated in a cycle of road using Matlab/simulink in order to study the effect of the ultracapacitor "clipped peak and filled channel" for the battery. From the results of these simulations, ultracapacitor can provide energy when electric vehicle is accelerating and recover energy when electric vehicle is braking. So it can protect the battery according to avoiding the strong current charge and discharge of battery and it also can effectively extend the electric vehicle continued driving mileages. At last, according to the design requirements of bidirectional DC/DC converter, the bidirectional DC/DC converter was designed using Protel and simulated using Matlab/Simulink. The simulation results show the correctness of theoretical calculation. And the converter was manufactured in order to apply to experiment bench in hybrid power system.