| Nowadays,with the development of power electronics control technology and the continuous development of new batteries and power supply,electric vehicles have ushered in new opportunities for development because of the strict control of emissions and energy conservation.As the core of green transportation,the electric bus is the key to achieve energy saving,emission reduction and the diversification of traffic energy structure.However,as the core of electric bus,the battery has obvious shortcomings in the respects of specific energy,specific power,charging technology,service life,safety and cost.The HESS(hybrid energy storage system)consisted of battery and supercapacitor(SC)will make full use of the advantages of the two kinds of energy storage devices.The use of supercapacitor will protect the battery and avoid the battery charging and discharging in large current in order to extend the cycle life of battery and reduce the using cost.The reasonable power split control strategy is the key to ensure the efficiency of the HESS,and make full use of the advantages of the two energy sources.Therefore,the research on the optimal design and control of HESS for electric bus will be of great significance to the actual engineering research and the corresponding product development.In this paper,the configuration analysis,parameter matching and optimization of HESS are presented.In addition,the battery cycle life is predicted on the basis of completed energy management strategy.The main contents of this paper include the following aspects:(1)On the basis of the research object,and the current situation and problems of HESS are analyzed,referring to the domestic and foreign literatures.The research ideas will be determined according to the actual design needs of the electric bus,determine the specific research ideas.(2)The key components characteristics and topology of HESS are analyzed.The charging and discharging tests of the battery and the super capacitor are carried out and the efficiency of the DC/DC is tested.The dynamic model of battery and SC areselected and the parameters of the models are obtained.Then the dynamic model of battery and SC are established and simulated.A reasonable HESS topology is selected according to the analysis of the performance of different configurations.(3)According to the design demand of electric bus and cycle demand,the parameters of battery and SC are matched reasonably by using PE function and CPE function.The parameters of HESS are optimized for reducing the using cost of HESS.And ultimately the optimal parameters of SC are determined.(4)According to the demand power distribution of drive cycle,choosing average power of driving cycle as threshold,the rule-based control strategy for HESS is established.And the fuzzy logic control strategy for HESS is established by reasonably designing fuzzy controller,membership function and fuzzy control rules.(5)The control strategies of HESS are simulated and verified through Matlab/Simulink and the cycle life of the battery is predicted using battery capacity degradation model.According to the results,the superiority of the HESS is verified compared with the single battery configuration to prolong the service life of battery.Meantime,it is proved that the fuzzy logic control strategy is more reasonable than the rule-based control strategy for the power distribution between battery and SC.Comparing the total cost,the HESS of fuzzy logic control strategy will be more economical than the single battery configuration after 5 years using. |
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