Research And Realization Of Bi-Directional DC/DC Control Strategy For Micro Hybrid Vehicle

With the intensification of urbanization,the number of cars has increased,and a large number of automobile exhaust emissions have aggravated the urban air pollution.Hybrid technology has passed the start-up period,began to enter the mature stage,is the most effective new energy vehicle technology solutions,and is a bridge linking the traditional and future technology.In the hybrid electric vehicle,the micro hybrid electric vehicle has the advantages of simple technology,low technology cost and good technical ability.Bi-directional DC/DC converter is a key component in the micro hybrid electric vehicle,which can realize the bidirectional flow of electric energy.But there is little research on the control of the bi-directional DC/DC converter for the 12+48V micro hybrid vehicle.This paper mainly aimed at the problem of the difficulty of the bus voltage stability caused by the frequent start and stop of the car and the load fluctuation of the micro hybrid electric vehicle with DC/DC.The main research of this paper is as follows:Firstly,it introduces the research status of hybrid vehicles at home and abroad,analyzes the 12+48V mild hybrid system research,comparison and analysis of the control strategy of bidirectional DC/DC different and the present development situation,and introduces several kinds of nonlinear DC/DC control bidirectional control method.According to the requirement of mild hybrid electric vehicle,a kind of Buck/Boost synchronous rectifier topology is proposed,and the working principle of the converter is analyzed in detail.On the basis of the design requirements,the parameters of the main circuit are designed,and the protection logic of the system is analyzed in detail.Secondly,The detailed analysis of the 12V+48V power system of mixed light,according to the analysis of various working modes,put forward a mathematical model with the traditional bi-directional DC/DC converter;combined with the actual working conditions and the mathematical model of bidirectional DC/DC converter and mild hybrid electric vehicle,clear in different modes of bidirectional DC/DC converter control target.A sliding mode controller is designed,and the principle of the sliding mode controller is analyzed in detail.On the basis of the design of sliding mode controller is improved,the introduction of adaptive control,sliding mode to solve the existing conditions required may not meet;or sliding mode controller is designed for dynamic instability problems.The design process of the adaptive sliding mode controller is summarized,and the simulation of the adaptive sliding mode controller is given.Finally,according to the summary of the design process to make the experimental prototype,set up the physical experiment platform,carried out the experimental verification.