Simulation And Experimental Research On Cycle Condition Of Electric Vehicle Based On Series Composite Power Supply

In recent years,electric vehicles have become an important direction in the development of the automotive industry.However,due to the limitation of battery technology,the problem of the driving range of electric vehicles has always been a major problem that restricts the development of electric vehicles.Regenerative braking technology is a key technology to improve the driving range of the car.The supercapacitor which is combined with the electric vehicle power battery to form a composite power source has the characteristics of fast charging speed and high power.In the composite power system,the super capacitor is used as an energy storage device for recovering and storing braking energy,and also as an auxiliary power source to participate in the driving process,drives the motor with auxiliary power battery,avoiding the high power charging and discharging of the power battery,and protecting the battery to prolong its service life.Select the main and auxiliary power supply,the main power supply uses lithium battery and the auxiliary power supply uses super capacitor.According to the connection mode of the battery and super capacitor,whether to use the active module,four composite power supply topologies are proposed.After comprehensive consideration,select passive connection as a system structure.The composite structure is designed to regenerate the electric vehicle regenerative braking system.The various components in the system structure are described,and the control of the recovered current is studied.In the MATLAB/Simulink platform,the battery in the SimPowerSystems is used to build a battery based on the designed passive series hybrid power supply structure—the super-capacitor composite power electric vehicle dynamic energy consumption model.The model input is ECE urban working speed,and the model is input speed curve.Run,observe the changes of battery and super capacitor voltage,drive current and recovery current,calculate the energy consumption,and analyze the mileage contribution rate of the composite power system.In the braking process,the model determines the duty ratio of the brake control signal according to the speed difference between the actual vehicle speed and the required vehicle speed to control the working state of the rectifier bridge module,and performs braking test at different decelerations to observe the change of the average recovered current.Can verify the feasibility of the constant current braking strategy.Analyze the main implementation functions of the control system,design the regenerative braking system controller with Atmega8 as the core,and specifically introduce the functions to be realized by each module.The regenerative braking experiment was carried out.The initial braking speed was 40 km/h,the initial voltage of the capacitor was 1 V,and the duty ratio of the brake control signal was 50%,70% and 100 %.On this basis,the constant current control brake test,in order to facilitate the control during the experiment,according to the rectification voltage and the super capacitor terminal voltage continuously change the duty cycle to ensure the constant recovery current,so as to achieve the purpose of controlling the brake deceleration.Set up the gantry for the composite power drive experiment.The composite power drive experiment shows that the series composite power supply can apply the stored energy in the super capacitor to the driving process,reducing the energy output of the battery and improving the battery efficiency.According to the results of the ECE urban working conditions,the contribution rate of the driving range can reach 11 %.