The Key Technology Of The Super-capacitor And Research Of Its Application In Electric Vehicles

In the past decades,the demand for transportation by humans has been getting higher and higher.In all types of the vehicles,the most important thing is the automobile which also has largest quantity of owner.Since the reform and development in China,the economy has developed rapidly and it has become the world's largest automotive consumer market.The huge amount of petroleum resources has been consumed by the automobiles,which will lead to an intensification of the energy crisis due to highly depending on oil.Moreover,the traditional gasoline-powered vehicles have produced a large amount of emissions,which has brought about a tremendous adverse impact on the treatment of environmental pollution.For the sake of energy security and environmental protection,electric vehicles have become the target of the major industrial countries for the past ten years because they do not consume oil energy and zero emissions.However,there are also many factors that restrict the development of electric vehicles.From a technical perspective,the biggest bottleneck is the electricity energy storage system on-vehicle.Currently,no electricity energy storage source is able to compare with the traditional gasoline fuels in terms of comprehensive aspects of energy density,power density,cycle life,use cost and reliability.For a foreseeable longer period of time,it is difficult for a single energy storage source to make breakthrough progress on several key indicators at the same time.Therefore,it is generally believed that a composite storage energy source formed by the combination of lithium-ion power batteries which has high-energy-density and super-capacitors which has high-power-density is a very attractive option.The research on lithium-ion batteries is relatively abundant,but the research on vehicle-mounted supercapacitors is relatively scarce.This research focuses on the application and key technologies of supercapacitors in electric vehicles.The main existing modeling methods of supercapacitors are analyzed and a modeling method of the supercapacitor based on support vector machine is proposed.After fully examining the characteristics of the use environment of electric vehicles,the voltage equalization of the vehicle-mounted supercapacitors is analyzed.Then,a static voltage equalization strategy is designed,as well a dynamic voltage equalization circuit is proposed and a dynamic voltage equalization strategy is designed.The advantages of a supercapacitor are explored in this paper and a novel multi-level voltage pumping circuit structure based on supercapacitors is proposed.It can be used in special applications that require high voltage in electric vehicles.At last,based on the composite energy storage composed of super capacitors and batteries,the research on compound storage energy combined with the electric vehicle drive system is performed.In the research,the management strategy of the composite energy storage and the control strategy of the energy brake recovery are proposed.The above research contents are all combined with experiments.The experimental results show that the theoretical research is feasible and effective.The main research content of this thesis can be summarized as follows:1.Based on a detailed discussion of the structure of supercapacitors,several classical models are analyzed and compared with experimental tests.Then,a supercapacitor modeling method based on support vector machine is proposed completely combined with the characteristics of electric vehicles.The correctness of this method is proved by the experimental results.2.The research of the existing supercapacitor voltage-sharing circuit is reviewed and analyzed.Then,according to the characteristics of electric vehicles,an improved flying capacitor static voltage equalization circuit is selected for the vehicle-mounted supercapacitor-bank,and then a voltage-equalization strategy is proposed for the circuit.An experimental circuit for the voltage equalization circuit described above is made and a control program is designed.The experimental results show that the static voltage equalization circuit and the control strategy meet the demand of the application in electric vehicles.3.The supercapacitor-bank onboard is often in a relatively frequent charge and discharge state.In view of this,a new type of dynamic voltage equalization circuit is proposed and a dynamic voltage equalization strategy is designed.Simulation and experimental results show that the proposed voltage-equalization circuit and control strategy meet the predetermined requirements.4.In order to take advantages of the supercapacitor,such as rapid charge and discharge capability and high efficiency,a new multilevel pump-up circuit topology is proposed.This circuit can be used for special applications where high voltage is required under vehicle condition.Then,the operation and the working-modes of the circuit is analyzed.Principles and modes of operation are verified by simulations and experiments.5.Research on the application of composite energy storage consisting of supercapacitors and batteries in electric vehicles is carried out.Joint Modeling and Simulation of the composite energy is realized taking the characteristics of supercapacitors and batteries into consideration.Then,the management of composite energy storage and control strategy of the braking recovery is proposed.Based on the established model and basic working principle,a mathematical model is established,and then a Matlab/simulink simulation model is built.The operating characteristics of the system is studied and the proposed control strategy of braking recovery of the composite energy storage is verified.6.Based on the characteristics of the electric vehicle driving system and energy braking recovery,an experimental platform is built for the electric drive and braking system with the composite energy storage which is composed by supercapacitor and battery.Meanwhile,a control platform based on the STM32 controller and high-power drivers is designed and made.As a consequence,the proposed energy braking recovery strategy of the composite energy storage is verified by the experiment results.