Impedance Spectrum Measurement And Model Parameter Identification Of Single-flow Zinc-nickel Battery

Single-Flow Zinc-Nickel Battery is a new type of energy storage device.It has the advantages of low cost,large energy storage capacity and long cycle life,and has broad prospects in the field of energy storage.Electrochemical Impedance Spectroscopy(EIS)covers a wide range of frequencies and contains rich impedance information,which provides a strong basis for battery modeling and analysis.In this thesis,to obtain impedance spectra and impedance parameters of the single-flow zinc-nickel battery,a single-flow zinc-nickel battery impedance spectroscopy measurement platform based on STM32 was designed,and an improved whale optimization algorithm was proposed to identify the battery impedance model parameters.The thesis analyzed the All-Phase FFT(APFFT)method to estimate the amplitude ratio and phase difference of two sinusoidal signals at the same frequency.Combined with the principle of frequency domain impedance spectrum measurement,the impedance spectrum measurement scheme of singleflow nickel-zinc battery was determined,and the corresponding impedance spectrum measurement platform was designed.The measurement platform taked STM32 controller as the core,used AD9833 to generate a sine wave signal with set frequency,and injected current excitation into the battery to be tested after V/I conversion by constant current meter.Timer interrupt was used to control the sampling rate of AD7606.The APFFT algorithm was integrated on the STM32 controller,and realized use APFFT analysis of current and voltage signals in the controller chip,which can calculate out the battery impedance measurements of certain frequency point.Automatic sweep frequency measurement of battery EIS was achieved by looking up a table,and the measurement data is sent to the master computer through the serial port for storage.The functions of filter amplifier circuit and galvanostat were tested on the impedance spectrum measurement platform of single-flow nickel-zinc battery.The EIS of RC equivalent circuit and single-flow nickel-zinc battery were measured,and the measurement results were compared with professional instrument of frequency response analyzer.The result of measurement platform measured the EIS of single-flow nickel-zinc battery showed that,the error of impedance amplitude measurement is less than 5%,and the error of phase angle measurement is less than 1.2°.The single-flow nickel-zinc battery was charged and discharged by Neware charge and discharge tester,and the EIS data of the battery under a different state of charge(SOC)were obtained through the measurement platform.To solve the problem of building an equivalent circuit model by fitting the EIS data,this thesis used the Distribution of Relaxation Times(DRT)method to analyze the EIS of single flow nickel-zinc battery and established the fourth-order RC impedance equivalent circuit model of the single-flow nickel-zinc battery.An improved whale optimization algorithm was proposed to identify the parameters of impedance equivalent circuit model.Based on the measured EIS data of the battery,the improved whale optimization algorithm was used to identify the model parameters of the battery under different SOC.The experimental results show that the average relative error of the real part of the impedance is less than2%,and the average relative error of the imaginary part is less than 10%.