Research On Optimal Control Of Electric Vehicle Power Supply System

With the development of the science and technology and the improvement of social and economic level,people’s living standard has also been greatly improved.In the meanwhile,the automobile industry has been developing rapidly,and the number of cars purchased has been increasing year by year.However,the consequent impact is that the society not only faces the energy crisis,but also causes a series of environmental problems,such as air pollution caused by exhaust gas,environmental noise pollution and so on.In order to alleviate these problems,various countries begin to conduct research on electric vehicles.The automobile industry is transforming from internal combustion engine vehicles to electric vehicles gradually.Coupled with domestic and foreign policy support,electric vehicles will usher in an era of rapid development.As a single energy source of electric vehicles,the power density of battery is small,which cannot meet the instantaneous high-power demand during the operation of the electric vehicle.The storage energy of battery is limited,which leads to the shorter mileage of vehicle and frequent charge and discharge.However,the damage of frequent charge and discharge to battery is great,which leads to the limited life of battery.The electric vehicle power supply has a short life and a short range,which seriously limits the development of electric vehicle research.In order to solve this problem,the paper uses super capacitor as auxiliary power supply,which is connected with battery in parallel to form a compound power supply of electric vehicle,and drives the electric vehicle together.The main contents include:(1)Describes the working principle and charging/discharging characteristics of the key components of the composite power supply system battery,super capacitor and the working principle of the DC/DC converter.The battery has a higher energy density,and the super capacitor has a higher power density.Combining the two to work together as a power supply for electric vehicles can complement each other’s advantages and make electric vehicles operate more efficiently.(2)Introduced several connection methods commonly used in electric vehicle power supply systems,including passive,semi-active,and active composite power supply topologies,and their respective advantages and disadvantages.Choose semi-active and active compound power supply for comparative study.(3)The five basic operating modes of electric vehicles and the energy flow in each operating mode are analyzed in detail.When the electric vehicle is driven to run,there are three working modes of the composite power supply: the battery provides driving power alone,the super capacitor provides driving power alone,and the battery-super capacitor provides driving power together.When the electric vehicle is running in the braking state,there are two working modes of the composite power supply: the supercapacitor recovers the braking energy and the energy consumption resistor consumes the braking energy.(4)Based on the research of the electric vehicle composite power supply system,a hybrid control strategy based on the change of demand power during operation is proposed,so as to more rationally allocate energy,make dynamic adjustments in time,and better adapt to the work of electric vehicles Changes in patterns.Under the MATLAB/simulink simulation environment,the simulation model of the electric vehicle composite power supply is built and the proposed control strategy is simulated and verified.