Research On Energy Management Strategy Of Pure Electric Vehicle Based On DC/DC Converter

With the worsening of environmental problems and the shortage of energy,the traditional internal combustion engine vehicles have been unable to meet the requirements of the current economic development.Therefore,the development of electric vehicles will be the tendency of future,among several models of electric vehicles in current research,pure electric vehicles with zero pollution,low noise and other advantages of talent shows itself the future direction of the development of electric vehicles.Now the pure electric vehicles on the market use battery as its single energy source in general,however,as the driving energy,the battery has the defects such as low specific power,frequent high current charging and discharging may affect the battery life and so on,it would cause the problem of vehicle dynamic performance,and then the use of super capacitor of high specific power as the auxiliary power supply of composite power electric vehicle came into being.This paper takes composite power system of power battery and ultra-capacitor as the research object,give full play to the advantages of the two,to solve the problem of a single energy source electric vehicles based on the research of energy management control strategy.In this paper,the characteristics of two kinds of basic energy sources,which are composed of composite power source,are analyzed in detail,it is concluded that the high current charge discharge capability of lithium-ion battery is poor,which is suitable for working in small current range,and the super capacitor can carry out fast charging and discharging in large current;then lead to the bi-directional DC/DC converter by the different characteristics of two,and select the suitable high power bi-directional full bridge DC/DC converter topology,then analyse its operate mode by combine with the working pattern of composite power system;then,the basic structure of the composite power supply system is determined,and the key components of the system such as lithium-ion battery,super capacitor and DC/DC converter are simulated;Based on the above analysis,combined with different working modes of electric vehicles,two kinds of energy management control strategies based on logic threshold and fuzzy logic are designed to realize the power allocation of the composite power supply;the vehicle simulation software ADVISOR has been made a second developed,a new pure electric vehicle model has been built according to the dual energy source mode established previously,two kinds of control strategies are simulated under the condition of UDDS and SC03 working condition,through the comparison and analysis of the simulation results,it is concluded that the fuzzy control strategy can make use of energy more efficiently than the logic threshold control,and extend driving range.Finally,in order to overcome the limitation of fuzzy control rules based on artificial experience,an intelligent optimization algorithm--genetic algorithm,is introduced,the fuzzy rules of fuzzy control strategy for composite power electric vehicle are optimized based on the energy consumption of pure electric vehicle,the simulation results show that the energy consumption of the optimized vehicle is significantly lower than that before optimization.