| Power battery is the core of electric vehicle,with the hot development of electric vehicle,there will be a large number of power battery retirement in the future.In addition,the related performance of power batteries directly affects the normal operation of electric vehicles,so all power battery manufacturers should carry out charge and discharge tests before leaving the factory.In the process of charging and discharging test,in order to prevent the electric energy released by the power battery from being wasted,some enterprises use the retired power battery to make a simple energy storage device.In order to enrich the function of the energy storage device,this paper designs a constant current charge and discharge system which is applied to power battery constant current charge and discharge detection,so as to realize the combination of energy storage device and constant current charge and discharge system and deepen the internal energy cycle of enterprises.Based on the requirements of constant-current charge-discharge test and the requirements of energy storage device applied to decommissioning power battery,the principle and working characteristics of charge-discharge circuit and constant-current closed-loop control are analyzed to determine the overall framework of constant-current charge-discharge system.Through the battery charging and discharging experiment to determine the SOC-OCV curve of the battery so as to determine the simulation parameters,using Simulink software to build the simulation model and specify the control strategy,and through Matlab PID Tuner toolbox to optimize the PID module parameters involved in constant current control so as to avoid blind trial and error.The simulation results show that the system can realize constant current control and current jump according to the instructions when the energy storage device is charged,discharged and charged and discharged at the same time.The voltage and State of Charge(SOC)of the energy storage device change normally,which proves that the constant current charging and discharging system can achieve the expected function.After simulation verification,STM32F103ZET6 chip is used as the main control chip,and the acquisition board and the control module of the constant current charging and discharging system are designed.The acquisition board mainly includes isolation circuit,voltage acquisition circuit,current acquisition circuit and temperature acquisition circuit.Constant current control module mainly includes switch tube drive circuit,current sampling circuit and signal amplifier circuit.With the main control chip as the core,the acquisition board assists in collecting the battery status information of the energy storage device,and the constant current control module controls the current in the working process of the energy storage device to keep it relatively constant.On the basis of hardware circuit design,Keil5 software is used to write the control program of acquisition board and constant current control module and burn it into the main control chip.The control procedure of the acquisition board mainly consists of voltage and temperature collection command cycles based on Serial Peripheral Interface(SPI)communication,which,together with corresponding hardware circuits,accurately collects the data information of the batteries in the energy storage device.The constant current control program adopts the sliding average filtering algorithm to filter the amplified signal collected by hardware,which reduces the mean change caused by a single error.After filtering,Proportional Integral Derivative(PID)control algorithm outputs control wave of duty ratio change,and then controls switching tube of hardware circuit to achieve constant current control effect.In order to intuitively observe the state of the energy storage device and improve the function of the system,Labview is used to design the upper computer and the corresponding data frame format,which can collect,display and store the information of the working state of the energy storage device in the form of data and coordinate diagram.GA-BP(Genetic Algorithm-Back Propagation)neural network was written using Matlab,and the results were compared through data training in measuring SOCOCV.The results show that the error between the output results and experimental data after training is less than 4%,which can be used for SOC prediction of energy storage devices.The upper computer designed by Labview software calls the trained neural network through the module to estimate the SOC of the battery of the energy storage device.On the basis of hardware and software design,the acquisition board and constant-current control module are tested.The voltage measurement error of single battery of the acquisition board is less than 20 m V.The constant-current control module can make the current fluctuate in a controllable range and meet the design requirements.An experimental system of constantcurrent charging and discharging system was established.Through experimental verification of simulation conditions and data analysis and comparison,the current value of the energy storage device is relatively constant and can be jumped,and the voltage variation trend is consistent with the simulation results,which proves that the constant-current charging and discharging system can realize the constant-current charging and discharging function of the energy storage device to the power battery.Combined with the simulation results and experimental results,it is proved that the constant current charging and discharging system can assist the energy storage device to use the energy released during the discharge detection of the storage power battery for the next charge detection,which verifies the feasibility of the constant current charging and discharging system. |
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