Regenerative Braking Energy Recovery Of Variable Composite Power Supply Based On Series Parallel Structure

During the process of regenerative braking energy recovery of power batteries,there are overcharging and discharging,which affects the service life of the power batteries,and there are problems such as low energy recovery rate,high maintenance and replacement costs.In response to these issues,the topology structure of the composite power supply composed of supercapacitors and power batteries is improved to bear the ultimate power of overcharging and discharging,and to protect the battery.Conduct technical research on the regenerative braking energy recovery system based on composite power sources to improve the energy recovery rate.The main tasks are as follows:(1)Taking the series parallel variable composite power supply structure as the research object,analyze and match the characteristics of each part,determine the circuit current flow,and improve the working mode.Establish a regenerative braking energy recovery model based on this structure,propose a technical method for regenerative braking energy recovery with target current constant value control,and optimize it.When different duty cycles are output,the regenerative braking intensity is different.This openloop control method is simple,and the braking current will decrease as the duty cycle decreases;Based on PID,the closed-loop control of the constant current of the supercapacitor load is carried out,with the duty cycle changing according to the vehicle speed and supercapacitor load voltage output,and the braking current remains unchanged.Simulate and analyze the control strategy results on the MATLAB/Simulink platform,and verify the feasibility of the technical methods.(2)Based on STM32,the hardware and software of the controller are designed to output different duty cycles for different regenerative braking intensities.The initial speed is 45km/h and the controller begins to decelerate.The controller switches the composite power supply working mode according to the brake pedal position sensor signal and speed signal.Under different regenerative braking intensities,the deceleration of vehicle operation is also different,and braking is effective.In regenerative braking energy recovery tests with constant control of different target currents,the duty cycle is variable,and the larger the target current,the greater the energy recovery rate,reaching a maximum of 51.6%.The optimization control strategy is evident through experimental verification.(3)Build a testing platform,install passive components such as auxiliary power supercapacitors and diodes,transistors and rectifiers,and control them through regenerative braking energy recovery controllers.Conduct performance tests on the charging and discharging characteristics of supercapacitors,regenerative braking energy recovery voltage,rectifier thyristors,diodes,and other additional components to ensure the smooth completion of regenerative braking energy recovery.Afterwards,a driving test was conducted to compare the time taken by the motor controller to control the motor to accelerate to the same vehicle speed under different driving voltages,using supercapacitor assisted power supply and battery independent power supply.The experimental results showed that the larger the driving voltage,the shorter the acceleration time,and the more obvious the switching point between supercapacitor assisted power supply and battery independent power supply.After the supercapacitor was depleted,there was no loss of battery power.Research has shown that the improved series parallel structure variable composite power supply protection battery fully utilizes the advantages of supercapacitors,has a reasonable structure,simple control,obvious optimization effect of control strategy,and improved energy recovery rate;When driving,the acceleration time is significantly improved,and the auxiliary power supply supercapacitor has no loss on the main power supply,fully utilizing the recovered energy.