Parameter Matching And Power Split Strategy Of Hybrid Energy Storage System In Pure Electric Vehicle

With the problem of environment pollution and energy crisis highlights,the devlopement of pure electric vehicles is valued.As the main energy source of pure electric vehicle,power battery is still restricted by the problems of cost,cycle life,unable to balance energy density and power density.It is one of the key factors for the popularization of pure electric vehicles.In this paper,the pure electric vehicle with hybrid energy storage system?HESS?is taken as the subject investigated.In order to evaluate the application value of HESS and improve the power source economy in vehicle lifetime,the parameters matching and control strategy of HESS are studied.The researches are as follows:?1?The working characteristics of power battery,ultracapacitor?UC?and bidirectional DC/DC converter are analyzed.The configuration scheme of HESS is determined and the HESS simulation model including a semi empirical capacity degradation model for LiFePO₄ battery is established.?2?Under the premise of performance requirements for HESS with typical cycle conditions and taking UDDS as the basic working condition of parameter matching,a combined optimization method for parameter matching and control strategy of HESS is established.In this method,the number of single battery,the number of single UC and the rule-based control strategy threshold are taken as the optimization variables,and the power sources cost over vehicle lifetime is taken as the optimization objective.Besides,the application potential of HESS under different cycle conditions is discussed.?3?The shortcomings of commonly used fuzzy logic controller for HESS are analyzed and improved;The optimal control sequence of typical cycle conditions is obtained by using dynamic programming?DP?algorithm,and an adaptive rule control strategy is formulated based on extracted information;The feasibility of extreme learning machine?ELM?application in HESS power distribution is analyzed and an instantaneous power allocation strategy based on ELM is proposed.In this method,the ELM model is trained by DP optimal control sequence based on the correlation analysis and mean impact value?MIV?screening of input variables.Then,the three kinds of control strategies above are compared with the rule-based control strategy.?4?As the general application of navigation system in automobile,a cycle condition including traffic congestion and road slope information is constructed to design auxiliary controller.The auxiliary controller first judge the future speed trend based on K-means and traffic congestion information,followed by combining with future road slope information,and then output power correction factor of UC by fuzzy logic controller.When the traffic information is not available,the instantaneous power allocation strategy based on the current power demand is adopted;when the traffic information can be obtained,the instantaneous power allocation strategy based on current power demand is used as the main controller,and the fuzzy logic controller is used as the auxiliary controller to optimize the power distribution coefficient of UC.