Study On The Parametric Design And Control Strategy Of Hybrid Power System For Hybrid Electric Vehicle

Energy source shortage and enviroment pollution arising from automobile industry have been given more and more attention all over the world . Development of new type motor vehicle with low energy consumption and emmission is being under-way by automobile industry and research institude , which is encouraged by government policy . Hybrid electric vehicles are born , which can combine the goodness of traditional combustion vehicles and electric vehicles , and can achieve the goal of low energy consumption and ultra-low emmissions , which make it to become the hot point for the development of global electric vehicle , and tend to be the trend.In the past few years , The supercapacitors, however new, are an attractive option in hybrid vehicles due to their high power density and long lifetime , and are very suitable for the high power need like acceleration ,brake or mountain climbing of the vehicle.Hybrid system composed of batteies and supercapacitors could combine the high power density of supercapacitors and the high energy of convenient batteries . supercapacitors are used to provide the essentially high peak power demaned by the vehicle , while the batteries are uesfull to charge the supercapacitors when they discharged , the hybrid batteries/supercapacitors power system could reduce the volume of the batteries used in this system,meanwhile the life time of the hybrid system can also be longer than ever.This paper modeled the hybrid power system composed of batteries and supercapacitors with Matlab/Simulink after researching the characteristic of them ,and searched out the influence on their performance. Designed the control strategy of the hybrid power system ,and tested the system under pulse-power duty,and made the conclusion of the parallel combinations system exhibited good pulse power performance. In order to exerting the push and pull ability of the supercapacitors,desiged the controll strategy according to the need of vehicle. Optimized the parameters in the hybrid system based on the overall energy ,power ,weight and cost constrains . Selected the parellel small car and using the Advances vehicle simulator(Advisor) to test the economic and dynamical performance. From the results of these simulates comparing with the batteries alone, could conclude that: the vehicles which applied the hybrid power system could achieve higher fuel economy than batteries alone,even the maximum speed and the the biggest acceleration aslo could be a little bigger. The reason should be that ,firstly, thanks for the control strategy ,the overall efficiency of the hybrid power system was higher than the Ni-H2 or the Pb-acid batteries alone . secondly, the hybrid system could be more powerful for regenerating the braking energy. But another conclusion could be made from this paper was that the enhancement of the fuel economy was highly dependent on the simulation drive cycles. Through analysis and caculation it is proved that the hybrid power system which applied the same number and smaller in Ah.capacity of batteries could reduce the cost more than 50%, weight could aslo drop a lot. Besides these hybrid system could resolve the problem of start in cold temperature and transient response of the hybrid electric vehicles. Based on the research of conventional hybrid electric system , this thesis has settled the foudation for the model designing and parametric and control strategy of the batteries/supercapacitors hybrid power system . After learning the very soft characteristics of the supercapacitors , this thesis also research the methods to control the current stream in/out the supercapacitors and how to design the cupercapacitors' controller. The principle presented , the conclusion drew here and the control strategy require to be improved by research and experiments.