Study On Modeling,Energy Control Strategy And Performance Of Hybrid Power System For Electric Vehicle

Due to the lower power density,lower charge and discharge capacity and aging at high temperature,the performance of electric vehicles(EVs)with lithium battery power system is difficult to meet the requirements.A hybrid power system(HPS)combining lithium batteries with higher power pensity and supercapacitors(SCs)with stronger charging and discharging capacity is an effective way to improve the performance of EVs.The paper studies the modeling,energy control strategy,performance and optimization of the HPS.The main research contents and conclusions are as follows.Because the simulation of the EV with the lithium battery and the SC HPS can not be carried out in the ADVISOR software,the simulation model of the EV with the lithium battery and the SC HPS is constructed after the ADVISOR software is developed secondly.Based on the test data,the lithium battery model,the SC model,the motor model and the DC/DC converter model are established respectively.The simulation model of the HPS has good engineering application value.In view of the high peak to average power ratio of the EVs,a power follower energy control strategy for the HPS is proposed.The basic characteristics of the strategy are that the lithium battery pack provides the basic power and charges the SC group.The SC group provides high power assistance in the acceleration of the EVs and reclaims the braking energy during the braking of the EVs.The simulation results under five typical operating conditions show that the energy control strategy is suitable for the lithium battery semi-active structure HPS.Compared with the fuzzy control energy management strategy,the performances of the EVs are slightly improved.The direct comparison method can not reflect the relationship between the parameters of the configuration of the HPS and the parameters of the energy control strategy and the performances of the EV,the performance research method based on the sensitivity analysis is proposed.The relationship between the series number of lithium batteries,the number of SCs in series,the number of SCs in parallel,the capacity coefficient of the lithium battery,the capacity coefficient of the SC and the SC charging power and the maximum speed of the EV,the acceleration time from zero to one hundred kilometer per hour and the energy consumption of a hundred kilometers are studied by the single factor variation method.The conclusions provide a basis for the performance optimization design of the EV with HPS.In view of the problem that the performances of the EVs are less considered in the optimization target,a method of joint simulation and optimization of the genetic algorithm and ADVISOR software based on multi objective function is proposed.The multi-objective functions,including the maximum speed of the EV,the acceleration time from zero to one hundred kilometer per hour,the energy consumption of 100 kilometers,the driving range and the life cycle cost of the HPS are constructed.The single performance and comprehensive performance of lithium battery EVs and HPS EVs are compared.The five parameters of the capacity coefficient of lithium battery,the series number of lithium batteries,the series number of SCs,the number of SCs in parallel and the charging power of the SC are optimized to improve the comprehensive performance of the EV.A HPS experiment platform based on the lithium battery semi-active HPS is constructed.The simulation model of the HPS,the power following energy control strategy and the effectiveness of the performance analysis method based on the sensitivity of the EV are verified.To sum up,this paper studies the modeling,power following energy control strategy,performance and optimization of the HPS for EV and compares the performance with the lithium battery EV.The research conclusion is of certain significance to the design of the HPS of the EV.