EIS rapid detection method and system for equal-amplitude broadband excitation signals

Abstract

The invention relates to the field of energy storage battery rapid detection, and provides an EIS rapid detection method for an equal-amplitude broadband excitation signal, and the method comprises the steps: calculating the frequency and amplitude of each order of sub-square waves based on the Fourier transform characteristic between a square wave signal and a sinusoidal signal, and building a compensation sub-square wave parameter matrix; a constant-amplitude broadband excitation signal EABE is constructed; building an equivalent circuit model detection simulation platform of the energy storage battery by adopting Simulink; injecting the equal-amplitude broadband excitation signal into the equivalent circuit model to obtain a corresponding broadband response signal; converting an equal-amplitude broadband excitation signal and a response signal obtained in the detection process into a frequency domain through fast Fourier transform; and analyzing the frequency domain information of the excitation and response signals, and calculating to obtain the EIS in the target frequency. According to the method, the rapidity and the accuracy of the EIS detection method are improved.

Description

Technical Field

[0001] The invention relates to the field of rapid detection of energy storage batteries, and in particular to a rapid detection method of electrochemical impedance spectroscopy based on a broadband excitation signal and a system thereof. Background Art

[0002] With the full development of new energy power, electrochemical energy storage systems are widely used in power grid peak and valley regulation, safe and stable operation, and backup power supply. Among them, the state detection of energy storage batteries is an important reference standard for the safe and efficient operation of energy storage systems. However, the battery state depends on a series of complex electrochemical reaction states inside it, and ordinary current and voltage detection methods are difficult to quickly reflect the true state of the battery. Electrochemical impedance spectroscopy (EIS) detection is a non-invasive measurement technology that applies small-amplitude sinusoidal interference signals of different frequencies to the electrochemical system. It can decompose complex electrochemical processes into a series of basic processes based on different relaxation times and is widely used in battery electrochemical research. Compared with the voltage and current curve detection process of complete charge and discharge, the EIS detection of batteries is relatively time-saving. However, the current EIS measurement of batteries generally adopts the sweep frequency method, that is, the single-frequency sinusoidal excitation signals of different frequencies are injected at intervals through the electrochemical workstation in sequence. This detection method has the advantages of good scale and high accuracy, but because the excitation signal of each frequency point needs to be injected into the battery in sequence, the cumulative detection time is long. The rapid detection technology of EIS is also one of the research focuses.

[0003] The broadband excitation detection method is one of the research focuses of EIS rapid detection. The Journal of Electrotechnical Engineering paper "Online Identification Method of Low-Frequency Band of Electrochemical Impedance Spectroscopy of Lithium-Ion Batteries Based on Step Wave" fits the approximate sinusoidal AC signal in the low-frequency domain based on the step wave to realize the online identification of low-frequency EIS. However, due to the limitation of the EIS frequency domain, only part of the electrochemical state information of the battery can be obtained, which is difficult to fully reflect the battery state. The Power Grid Technology paper "Broadband Signal Estimation Algorithm Based on Variational Mode Decomposition" extracts the waveform information of multiple modal components from the broadband signal through the variational mode decomposition method, and then converts the signal time domain information into frequency domain information for research. However, the modal components decomposed by this method will have modal aliasing, and the broadband signal cannot be completely decomposed according to the frequency point scale. Summary of the invention

[0004] The technical problem to be solved by the present invention is to improve the efficiency and detection accuracy of the EIS detection method.

[0005] The present invention solves the above technical problems through the following technical means:

[0006] The present invention provides an EIS rapid detection method of an equal amplitude broadband excitation signal (EABE), comprising the following steps:

[0007] S1. Based on the Fourier transform characteristics between the square wave signal and the sine signal, the frequency and amplitude of each order of sub-square waves are calculated, and a compensation sub-square wave parameter matrix is ​​established;

[0008] S2, constructing an equal-amplitude broadband excitation signal EABE;

[0009] S3. Use Simulink to build an equivalent circuit model detection simulation platform for energy storage batteries;

[0010] S4, injecting a broadband excitation signal of equal amplitude into the equivalent circuit model to obtain a corresponding broadband response signal; converting the broadband excitation signal and response signal of equal amplitude obtained in the detection process into the frequency domain by fast Fourier transform;

[0011] S5. Analyze the frequency domain information of the excitation and response signals, and calculate and obtain the EIS within the target frequency.

[0012] Furthermore, the Fourier transform characteristics between the square wave signal and the sine signal in step S1 are specifically:

[0013] Fast Fourier transform converts time domain signals into frequency domain for analysis, which fully reflects the complex internal electrochemical processes of the battery at different relaxation times;

[0014] The FFT of a periodic function is as follows

[0015]

[0016] Among them, f(t) is the periodic signal function, a0 is the DC amplitude information, ω=2πf is the angular frequency, a n and b n is the amplitude information corresponding to each frequency component nωt;

[0017] From equation (1), it can be concluded that any periodic signal can be transformed into a series of sine and cosine signals through Fourier transform, and any periodic signal can also be formed by superimposing a series of sine and cosine signals with different frequencies and amplitudes;

[0018] The FFT of a square wave signal is as follows

[0019]

[0020] Among them, g(t) is the square wave signal function, a is the square wave amplitude, and ω is the signal angular frequency;

[0021] From formula (2), it can be seen that the amplitude of each frequency component of the square wave signal after FFT transformation changes regularly. The equal-amplitude broadband signal can be obtained by compensating and superimposing the amplitude-frequency change law.

[0022] Furthermore, the frequency and amplitude of each order of sub-square waves are calculated in step S1 to establish a compensation sub-square wave parameter matrix, which is specifically:

[0023] The compensation sub-square wave amplitude parameter matrix is ​​as follows:

[0024]

[0025] Among them, A is the harmonic amplitude coefficient matrix of the fundamental frequency square wave, E is the unit matrix, and B is the amplitude parameter matrix of each order compensation square wave;

[0026] The compensation sub-square wave frequency parameter matrix is ​​as follows:

[0027]

[0028] Among them, F is the frequency parameter matrix of each compensation sub-square wave, C is the harmonic order of the square wave of each frequency order, and n is the frequency domain order.

[0029] Furthermore, the step S2 of constructing the equal-amplitude broadband excitation signal is specifically as follows:

[0030] Based on equations (3) and (4), the amplitude and frequency parameter matrix of each order of sub-square waves in the frequency domain are obtained by extended calculation, and a sequence of sub-square waves is generated in sequence, and the sequence of sub-square waves is superimposed into a synthetic signal, namely, the equal-amplitude broadband excitation signal EABE.

[0031] Furthermore, the step S3 is specifically as follows:

[0032] First, construct the impedance calculation formula of the equivalent circuit model

[0033]

[0034] Where: ω = 2πf is the angular velocity at each frequency point, Z(ω) is the impedance at each frequency point, L is the inherent inductive effect inside the battery and the equivalent inductance of the electrochemical interface, R s is the electrolyte resistance, R SEI is the equivalent resistance of SEI film, C SEI is the SEI film equivalent capacitance, R CT1 is the charge transfer equivalent internal resistance of the electrode material, C DL1 is the charge transfer equivalent capacitance of the electrode material, R CT2 is the ion diffusion equivalent resistance, C DL2 is the ion diffusion equivalent capacitance;

[0035] Then, the real part, imaginary part and frequency information of the impedance at each frequency point of the EIS are substituted into equation (5), and a series of equations are constructed based on the impedance information at each frequency point, and then the approximate parameters of R, L, and C are identified to determine the equivalent circuit model to be tested.

[0036] Furthermore, the calculation to obtain the EIS within the target frequency in step S5 is specifically as follows:

[0037] The impedance information in the target frequency domain is obtained by calculating equations (6)-(9), as follows

[0038]

[0039] Z′=|Z|×cosθ (7)

[0040] Z″=|Z|×sinθ (8)

[0041]

[0042] Where: U and I are the voltage amplitude and current amplitude at each frequency point respectively, θ U ,θ I are the voltage phase and current phase at each frequency point, Z is the impedance at each frequency point, |Z| is the impedance amplitude, θ is the impedance phase, Z′ is the real part of the impedance, Z″ is the imaginary part of the impedance, and e is a natural constant.

[0043] The present invention also provides an EIS rapid detection system for a constant amplitude broadband excitation signal. The system adopts the above method when running, and includes the following modules:

[0044] A parameter matrix building module is used to calculate the frequency and amplitude of each order of sub-square waves based on the Fourier transform characteristics between the square wave signal and the sine signal, and to establish a compensation sub-square wave parameter matrix;

[0045] Excitation signal construction module, constructing equal amplitude broadband excitation signal EABE;

[0046] Model building module, used to build an equivalent circuit model detection simulation platform for energy storage batteries using Simulink;

[0047] The detection module is used to inject the equal-amplitude broadband excitation current signal into the equivalent circuit model to obtain the corresponding broadband response voltage signal; the equal-amplitude broadband excitation signal and response signal obtained in the detection process are converted into the frequency domain by fast Fourier transform;

[0048] The output module is used to analyze the frequency domain information of the excitation and response signals and calculate the EIS within the target frequency.

[0049] Furthermore, the parameter matrix building module includes the following units:

[0050] The amplitude parameter matrix construction unit is used to construct the compensation sub-square wave amplitude parameter matrix. The formula used is:

[0051]

[0052] Among them, A is the harmonic amplitude coefficient matrix of the fundamental frequency square wave, E is the unit matrix, and B is the amplitude parameter matrix of each order compensation square wave.

[0053] The frequency parameter matrix construction unit is used to construct the compensation sub-square wave amplitude frequency parameter matrix, and the formula used is:

[0054]

[0055] Among them, F is the frequency parameter matrix of each compensation sub-square wave, C is the harmonic order of the square wave of each frequency order, and n is the frequency domain order.

[0056] Furthermore, the specific operation mode of the excitation signal construction module is:

[0057] Based on equations (3) and (4), the amplitude and frequency parameter matrix of each order of sub-square waves in the frequency domain are obtained by extended calculation, and a sequence of sub-square waves is generated in sequence, and the sequence of sub-square waves is superimposed into a synthetic signal, namely, the equal-amplitude broadband excitation signal EABE.

[0058] Furthermore, the calculation of the output module to obtain the EIS within the target frequency is specifically performed as follows:

[0059] The impedance information in the target frequency domain is obtained by calculating equations (6)-(9), as follows

[0060]

[0061] Z′=|Z|×cosθ (7)

[0062] Z″=|Z|×sinθ (8)

[0063]

[0064] Where: U and I are the voltage amplitude and current amplitude at each frequency point respectively, θ U ,θ I are the voltage phase and current phase at each frequency point, Z is the impedance at each frequency point, |Z| is the impedance amplitude, θ is the impedance phase, Z′ is the real part of the impedance, Z′′ is the imaginary part of the impedance, and e is a natural constant.

[0065] The advantages of the present invention are:

[0066] (1) The present invention obtains the frequencies of the various orders of compensation sub-square waves and the amplitude parameter matrix required for the equal-amplitude wide-band excitation signal through the Fourier transform relationship between the square wave and the sine wave, and the parameter matrix can be flexibly adjusted according to the target amplitude and target frequency domain to achieve the equal-amplitude wide-band signal fitting under different requirements.

[0067] (2) The equal-amplitude broadband signal fitting method provided by the present invention can be implemented through basic square wave or pulse fitting, which reduces the hardware and computing power requirements of the experimental equipment and reduces the cost and application threshold of EIS rapid detection equipment.

[0068] (3) The present invention adopts an equal-amplitude broadband signal detection method, which can compress all frequency signals in the target frequency domain into a low-frequency excitation cycle, so as to obtain amplitude-frequency and phase-frequency information in the full frequency domain with a single excitation, thereby realizing rapid EIS detection.

[0069] (4) The equal-amplitude broadband signal adopted in the present invention can evenly distribute the detection excitation stress at each frequency point in the target frequency domain after FFT transformation, effectively improving the measurement deviation caused by the superimposed resonance difference and improving the broadband detection EIS accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Figure 1 Schematic diagram of the steps of the EIS rapid detection method of the equal-amplitude broadband excitation signal according to an embodiment of the present invention;

[0071] Figure 2 A schematic diagram of an equivalent circuit model established based on a simulation test experiment according to an embodiment of the present invention;

[0072] Figure 3 It is a schematic diagram of comparing amplitude-frequency information based on a single-frequency square wave, a synthetic square wave and a constant-amplitude broadband excitation signal according to an embodiment of the present invention;

[0073] Figure 4 It is a comparative schematic diagram of EIS results obtained based on the sweep frequency method, synthetic square wave and equal amplitude broadband excitation detection method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0074] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0075] Example 1

[0076] This embodiment provides a method for rapid EIS detection of a constant amplitude broadband excitation signal, such as Figure 1 As shown, the following steps are included:

[0077] S1. Based on the Fourier transform characteristics between the square wave signal and the sine signal, the frequency and amplitude of each order of sub-square waves are calculated, and a compensation sub-square wave parameter matrix is ​​established;

[0078] Fast Fourier transform converts time domain signals into frequency domain for analysis, which fully reflects the complex internal electrochemical processes of the battery at different relaxation times;

[0079] The FFT of a periodic function is as follows

[0080]

[0081] Among them, f(t) is the periodic signal function, a0 is the DC amplitude information, ω=2πf is the angular frequency, a n and b n is the amplitude information corresponding to each frequency component nωt;

[0082] From equation (1), it can be concluded that any periodic signal can be transformed into a series of sine and cosine signals through Fourier transform, and any periodic signal can also be formed by superimposing a series of sine and cosine signals with different frequencies and amplitudes;

[0083] The Fourier transform relationship between square wave signal and sine signal is expressed as

[0084]

[0085] Where: g(t) is the square wave signal function; a is the square wave amplitude; ω is the signal angular frequency.

[0086] From equation (2), the amplitude of each frequency component of the square wave signal after FFT transformation changes regularly. Based on the frequency domain amplitude change law, equal-amplitude broadband signal fitting can be performed. For example, for a sinusoidal fundamental AC signal with an amplitude of 1A and a frequency of 0.1Hz, equation (1) shows that the corresponding frequency is 0.1Hz and the amplitude is The square wave signal of the fundamental frequency square wave. The corresponding amplitudes of the 1st, 3rd, 5th, 7th, and 9th harmonics after FFT decomposition are 1A, Etc. Based on this rule, equal-amplitude broadband signals can be superimposed. Taking equal-amplitude broadband signals as the target, the frequency, amplitude and other parameters of each order square wave are calculated to establish a parameter matrix; the specific process is:

[0087] Compensation superposition is performed in sequence according to the FFT transformation relationship between square waves and sine waves. The key is to determine the amplitude and frequency information parameter matrix of each superimposed sub-square wave. On this basis, the required frequency point information in the target frequency domain can be superimposed into an excitation cycle. Here, the combination process of equal-amplitude broadband signals in the frequency domain scale of 0.1-1.1Hz is taken as an example. The sub-square wave parameter matrix is ​​expressed as follows:

[0088]

[0089] Among them, A is the harmonic amplitude coefficient matrix of the fundamental frequency square wave, E is the unit matrix, and B is the amplitude coefficient matrix of the compensation square waves of each order from 0.1 to 1.1 Hz.

[0090] It is worth noting that in the calculation process of the compensation square wave amplitude coefficient, the compensation resonance situation should be considered. For example, when calculating the amplitude coefficient of the 0.9Hz compensation square wave, the ninth harmonic component of the fundamental wave and the third harmonic component of the 0.3Hz compensation square wave will appear at the 0.9Hz frequency point at the same time, and should be included in the compensation calculation process. The basic square wave that is easier to implement using the detection device is arranged and combined based on the compensation amplitude coefficient provided by the parameter matrix B and the corresponding frequency coefficient provided by the parameter matrix F, so as to obtain an EABE signal with relatively consistent stress in the frequency domain within the range of 0.1-1.1Hz. In particular, this method can be further extended to any set target frequency domain. In addition, it should be noted that with the expansion of the target frequency domain, the order of the compensation square wave and the scale of the parameter matrix will also expand accordingly, and a large number of compensation resonance situations will also appear, which need to be eliminated through coefficient calculation, so as to obtain a more accurate EABE signal.

[0091] In order to make full use of the high-order harmonic components of each order of sub-square waves and avoid harmonic interference of non-target frequency points, this embodiment clarifies the optimal selection strategy for each frequency point in the frequency domain based on the FFT transformation characteristics, and the frequency parameters are expressed as equation (4).

[0092]

[0093] Among them, F is the frequency parameter matrix of each compensation sub-square wave, C = [1 3 5 7 9] is the harmonic order of the square wave of each frequency order, and n is the frequency domain order.

[0094] The waveform fitting method and sub-square wave parameter matrix calculation method can compress the signal of any frequency domain target range into a single low-frequency cycle and maintain a relatively consistent frequency domain detection stress.

[0095] S2, constructing an equal-amplitude broadband excitation signal EABE; the specific process is:

[0096] Based on equations (3) and (4), the amplitude and frequency parameter matrix of each order of sub-square waves in the frequency domain are obtained by extended calculation, and a sequence of sub-square waves is generated in sequence, and the sequence of sub-square waves is superimposed into a synthetic signal, namely, the equal-amplitude broadband excitation signal EABE.

[0097] S3. Use Simulink to build an equivalent circuit model detection simulation platform for energy storage batteries. The equivalent circuit model uses circuit elements to measure and extract EIS data and Nyquist plot trends from chemical energy storage batteries, thereby characterizing the complex chemical processes inside the battery. The impedance spectra in different frequency domains characterize the complex electrochemical reaction processes inside the battery. In the high-frequency range, the inherent inductive effect inside the battery and the capacitive characteristic impedance of the electrochemical interface are represented by the inductive element L. At this time, the polarization process is dominant, and the electrolyte resistance is represented by R. s Indicates that the cross impedance exists in this frequency domain; when the frequency drops to the medium and high frequency domain, the impedance spectrum usually characterizes the solid electrolyte interface process of the battery. At this time, the impedance presents resistance and capacitance, with R SEI / / C SEI The frequency is further reduced to the medium frequency range, which characterizes the charge transfer process of the battery. At this time, the impedance still shows resistance and capacitance, with R CT / / C DL Indicates the charge transfer internal resistance of the electrode material. The impedance in the low-frequency range represents the lithium ion diffusion resistance. The impedance spectrum is usually close to a straight line curve, which characterizes the charge transfer and ion diffusion process in the battery. It can be fitted with multiple R / / C elements. The equivalent circuit model of multi-order R / / C elements has good fitting accuracy, but the number of parameters and identification calculations also increase accordingly.

[0098] This embodiment presents the measurement results of a third-order equivalent circuit model. Figure 2 As shown, the specific steps are:

[0099] First, construct the impedance calculation formula of the equivalent circuit model

[0100]

[0101] Where: ω = 2πf is the angular velocity at each frequency point, Z(ω) is the impedance at each frequency point, L is the inherent inductive effect inside the battery and the equivalent inductance of the electrochemical interface, R s is the electrolyte resistance, R SEI is the equivalent resistance of SEI film, C SEI is the SEI film equivalent capacitance, R CT1 is the charge transfer equivalent internal resistance of the electrode material, C DL1 is the charge transfer equivalent capacitance of the electrode material, R CT2 is the ion diffusion equivalent resistance, C DL2 is the ion diffusion equivalent capacitance;

[0102] Then, the real part, imaginary part and frequency information of the impedance at each frequency point of the EIS are substituted into equation (5), and a series of equations are constructed based on the impedance information at each frequency point, and then the approximate parameters of R, L, and C are identified to determine the equivalent circuit model to be tested.

[0103] S4, inject the equal-amplitude broadband excitation signal into the equivalent circuit model to obtain the corresponding broadband response signal; convert the equal-amplitude broadband excitation signal and response signal obtained in the detection process into the frequency domain through fast Fourier transform. The specific process is:

[0104] Based on the extended calculation of equations (3) and (4) in step S1, the amplitude and frequency information matrix of each order square wave in the frequency domain of 0.1Hz-999.99Hz can be obtained. The EABE excitation signal is superimposed by the square wave arrangement and combination. After the FFT transformation of equation (1), the broadband excitation amplitude and frequency information can be obtained. Figure 3 As shown, the amplitude-frequency information of three broadband excitation signals, among which, the amplitude of the signal component of the 0.1Hz single-frequency square wave amplitude-frequency information in the range of 900-1000Hz is almost zero, which is the same as the background noise amplitude. The amplitude of the signal component of the synthetic square wave broadband signal at the 900.1Hz frequency point is 0.1416A, which has greatly improved the high-frequency signal-to-noise ratio compared with the single-frequency square wave, and to a certain extent solves the problem that the single-frequency square wave detection still requires multiple excitations; however, in the full frequency domain scale, the amplitude of the signal component of each frequency point of the synthetic square wave detection method is gradually attenuated from low frequency to high frequency. Compared with the above two excitation methods, the amplitude-frequency information of the equal-amplitude broadband excitation signal EABE described in this embodiment has an amplitude of 0.98A-1.012A at the required frequency point in the full frequency domain, and the amplitude fluctuates within 2%, which proves that the equal-amplitude broadband excitation signal can carry the equal-amplitude signal of any target frequency domain within one excitation cycle, and the uniform amplitude in the frequency domain can provide uniform detection stress for EIS detection. By measuring the sample to be tested with this broadband AC current detection signal, the corresponding broadband voltage response signal can be obtained. The excitation and response signals can be transformed into the frequency domain through FFT to obtain the corresponding amplitude-frequency and phase-frequency information. The frequency domain relationship between the excitation and response signals will reflect a richer electrochemical state as the frequency decreases, providing technical support for battery status detection.

[0105] S5. Calculate and obtain the EIS within the target frequency by analyzing the frequency domain information of the excitation and response. The specific process is:

[0106] The impedance information calculation process in the target frequency domain is expressed as

[0107]

[0108] Z′=|Z|×cosθ (7)

[0109] Z″=|Z|×sinθ (8)

[0110]

[0111] Where: U and I are the voltage amplitude and current amplitude at each frequency point respectively, θ U ,θI are the voltage phase and current phase at each frequency point, Z is the impedance at each frequency point, |Z| is the impedance amplitude, θ is the impedance phase, Z′ is the real part of the impedance, Z″ is the imaginary part of the impedance, and e is a natural constant.

[0112] like Figure 4 As shown, the results of frequency sweep detection, synthetic square wave detection and EABE detection are compared. Taking the EIS results of frequency sweep detection as a reference, it can be seen that in the frequency domain of 1Hz-1000Hz, the EIS trends of the two broadband detection methods, synthetic square wave and EABE, are basically the same, while the real part of the impedance of the synthetic square wave detection EIS in the range of 0.1Hz-1.1Hz will have a jump difference. This difference is due to the superposition mechanism of the synthetic square wave. There is a significant stress difference between the amplitude of the component that is attenuated in the high-frequency region and the amplitude of the component that is rapidly pulled up at the compensation resonance frequency point. The resonance accumulation effect of this detection stress difference will affect the EIS detection result. The EABE detection method proposed in this embodiment can evenly distribute the detection excitation stress at each frequency point in the target frequency domain, effectively improving the measurement deviation caused by the superimposed resonance difference. As shown in Table 1, the error comparison of EIS results between broadband detection and swept frequency detection shows that compared with the synthetic square wave detection method, the EABE method reduces the real part error of impedance by 0.02618% and the imaginary part error of impedance by 0.01384%, which verifies that the accuracy of EIS results measured by the EABE detection method has been further improved.

[0113] Table 1 Broadband detection EIS error

[0114]

[0115] The time required for the three detection methods is further statistically shown in Table 2

[0116] Table 2 Comparison of detection time

[0117]

[0118] It can be seen that, in the same impedance point number and measurement frequency domain, compared with the sweep frequency detection method, the broadband excitation detection method can compress the detection time by 66.426%, which verifies the rapidity of the detection method used in this embodiment.

[0119] Through the above technical scheme, the EIS rapid detection method of the equal-amplitude broadband excitation signal provided by the present invention, and the broadband fitting method provided are based on square waves or pulses, which reduces the difficulty of fitting equal-amplitude broadband signals. In addition, the parameter matrix of the provided sub-square wave can be flexibly applied to the frequency domain and amplitude requirements of each detection target. This method can compress all frequency signals in the target frequency domain into a low-frequency excitation cycle, so as to obtain the amplitude-frequency and phase-frequency information in the full frequency domain scale with a single excitation, and realize EIS rapid detection. At the same time, the equal-amplitude broadband signal adopted in this embodiment can evenly distribute the detection excitation stress at each frequency point in the target frequency domain after FFT transformation, so as to improve the measurement deviation caused by the superimposed resonance difference and improve the EIS accuracy of broadband detection.

[0120] Example 2

[0121] It should be further explained that, based on the same inventive concept, the present invention also provides an EIS rapid detection system for a constant amplitude broadband excitation signal. When the system is running, the method described in Example 1 is executed, including the following modules:

[0122] A parameter matrix building module is used to calculate the frequency and amplitude of each order of sub-square waves based on the Fourier transform characteristics between the square wave signal and the sine signal, and to establish a compensation sub-square wave parameter matrix;

[0123] Excitation signal construction module, constructing equal amplitude broadband excitation signal EABE;

[0124] Model building module, used to build an equivalent circuit model detection simulation platform for energy storage batteries using Simulink;

[0125] The detection module is used to inject the equal-amplitude broadband excitation current signal into the equivalent circuit model to obtain the corresponding broadband response voltage signal; the equal-amplitude broadband excitation signal and response signal obtained in the detection process are converted into the frequency domain by fast Fourier transform;

[0126] The output module is used to analyze the frequency domain information of the excitation and response signals and calculate the EIS within the target frequency.

[0127] The parameter matrix building module includes the following units:

[0128] The amplitude parameter matrix construction unit is used to construct the compensation sub-square wave amplitude parameter matrix. The formula used is:

[0129]

[0130] Among them, A is the harmonic amplitude coefficient matrix of the fundamental frequency square wave, E is the unit matrix, and B is the amplitude parameter matrix of each order compensation square wave.

[0131] The frequency parameter matrix construction unit is used to construct the compensation sub-square wave amplitude frequency parameter matrix, and the formula used is:

[0132]

[0133] Among them, F is the frequency parameter matrix of each compensation sub-square wave, C is the harmonic order of the square wave of each frequency order, and n is the frequency domain order.

[0134] The specific operation mode of the excitation signal construction module is:

[0135] Based on equations (3) and (4), the amplitude and frequency parameter matrix of each order of sub-square waves in the frequency domain are obtained by extended calculation, and a sequence of sub-square waves is generated in sequence, and the sequence of sub-square waves is superimposed into a synthetic signal, namely, the equal-amplitude broadband excitation signal EABE.

[0136] The calculation described in the output module obtains the EIS within the target frequency in the following manner:

[0137] The impedance information in the target frequency domain is obtained by calculating equations (6)-(9), as follows

[0138]

[0139] Z′=|Z|×cosθ (7)

[0140] Z″=|Z|×sinθ (8)

[0141]

[0142] Where: U and I are the voltage amplitude and current amplitude at each frequency point respectively, θ U ,θ I are the voltage phase and current phase at each frequency point, Z is the impedance at each frequency point, |Z| is the impedance amplitude, θ is the impedance phase, Z′ is the real part of the impedance, Z″ is the imaginary part of the impedance, and e is a natural constant.

[0143] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. The EIS rapid detection method of equal amplitude broadband excitation signal is characterized by: The following steps are involved: S1. Based on the Fourier transform characteristics between the square wave signal and the sine signal, the frequency and amplitude of each order of sub-square waves are calculated, and a compensation sub-square wave parameter matrix is ​​established; S2, constructing an equal-amplitude broadband excitation signal EABE; S3. Use Simulink to build an equivalent circuit model detection simulation platform for energy storage batteries; S4, injecting a broadband excitation signal of equal amplitude into the equivalent circuit model to obtain a corresponding broadband response signal; converting the broadband excitation signal and response signal of equal amplitude obtained in the detection process into the frequency domain by fast Fourier transform; S5. Analyze the frequency domain information of the excitation and response signals, and calculate and obtain the EIS within the target frequency.

2. The EIS rapid detection method of the equal-amplitude broadband excitation signal according to claim 1 is characterized in that: The Fourier transform characteristics between the square wave signal and the sine signal in step S1 are specifically: Fast Fourier transform converts time domain signals into frequency domain for analysis, which fully reflects the complex internal electrochemical processes of the battery at different relaxation times; The FFT of a periodic function is as follows Among them, f(t) is the periodic signal function, a0 is the DC amplitude information, ω=2πf is the angular frequency, a n and b n is the amplitude information corresponding to each frequency component nωt; From equation (1), it can be concluded that any periodic signal can be transformed into a series of sine and cosine signals through Fourier transform, and any periodic signal can also be formed by superimposing a series of sine and cosine signals with different frequencies and amplitudes; The FFT of a square wave signal is as follows Among them, g(t) is the square wave signal function, a is the square wave amplitude, and ω is the signal angular frequency; From formula (2), it can be seen that the amplitude of each frequency component of the square wave signal after FFT transformation changes regularly. The equal-amplitude broadband signal can be obtained by compensating and superimposing the amplitude-frequency change law.

3. The EIS rapid detection method of the equal-amplitude broadband excitation signal according to claim 2 is characterized in that: The frequency and amplitude of each order of sub-square waves are calculated in step S1 to establish a compensation sub-square wave parameter matrix, which is specifically: The compensation sub-square wave amplitude parameter matrix is ​​as follows: Among them, A is the harmonic amplitude coefficient matrix of the fundamental frequency square wave, E is the unit matrix, and B is the amplitude parameter matrix of each order compensation square wave; The compensation sub-square wave frequency parameter matrix is ​​as follows: Among them, F is the frequency parameter matrix of each compensation sub-square wave, C is the harmonic order of the square wave of each frequency order, and n is the frequency domain order.

4. The EIS rapid detection method of the equal-amplitude broadband excitation signal according to claim 3 is characterized in that: The step S2 of constructing a constant amplitude broadband excitation signal is specifically as follows: Based on equations (3) and (4), the amplitude and frequency parameter matrix of each order of sub-square waves in the frequency domain are obtained by extended calculation, and a sequence of sub-square waves is generated in sequence, and the sequence of sub-square waves is superimposed into a synthetic signal, namely, the equal-amplitude broadband excitation signal EABE.

5. The EIS rapid detection method of the equal-amplitude broadband excitation signal according to claim 1, characterized in that: The step S3 is specifically as follows: First, construct the impedance calculation formula of the equivalent circuit model Where: ω = 2πf is the angular velocity at each frequency point, Z(ω) is the impedance at each frequency point, L is the inherent inductive effect inside the battery and the equivalent inductance of the electrochemical interface, R s is the electrolyte resistance, R SEI is the equivalent resistance of SEI film, C SEI is the SEI film equivalent capacitance, R CT1 is the equivalent internal resistance of the electrode material for charge transfer, C DL1 is the charge transfer equivalent capacitance of the electrode material, R CT2 is the ion diffusion equivalent resistance, C DL2 is the ion diffusion equivalent capacitance; Then, the real part, imaginary part and frequency information of the impedance at each frequency point of the EIS are substituted into equation (5), and a series of equations are constructed based on the impedance information at each frequency point, and then the approximate parameters of R, L, and C are identified to determine the equivalent circuit model to be tested.

6. The EIS rapid detection method of the equal-amplitude broadband excitation signal according to claim 5, characterized in that: The calculation to obtain the EIS within the target frequency in step S5 is specifically as follows: The impedance information in the target frequency domain is obtained by calculating equations (6)-(9), as follows Z′=|Z|×cosθ (7) Z″=|Z|×sinθ (8) Where: U and I are the voltage amplitude and current amplitude at each frequency point respectively, θ U ,θ I are the voltage phase and current phase at each frequency point, Z is the impedance at each frequency point, |Z| is the impedance amplitude, θ is the impedance phase, Z′ is the real part of the impedance, Z″ is the imaginary part of the impedance, and e is a natural constant.

7. The EIS rapid detection system of equal amplitude and broadband excitation signal is characterized by: The system adopts the method described in any one of claims 1 to 6 when running, and includes the following modules: A parameter matrix building module is used to calculate the frequency and amplitude of each order of sub-square waves based on the Fourier transform characteristics between the square wave signal and the sine signal, and to establish a compensation sub-square wave parameter matrix; Excitation signal construction module, constructing equal amplitude broadband excitation signal EABE; Model building module, used to build an equivalent circuit model detection simulation platform for energy storage batteries using Simulink; The detection module is used to inject the equal-amplitude broadband excitation current signal into the equivalent circuit model to obtain the corresponding broadband response voltage signal; the equal-amplitude broadband excitation signal and response signal obtained in the detection process are converted into the frequency domain by fast Fourier transform; The output module is used to analyze the frequency domain information of the excitation and response signals and calculate the EIS within the target frequency.

8. The EIS rapid detection system of the equal-amplitude broadband excitation signal according to claim 7, characterized in that: The parameter matrix building module includes the following units: The amplitude parameter matrix construction unit is used to construct the compensation sub-square wave amplitude parameter matrix. The formula used is: Among them, A is the harmonic amplitude coefficient matrix of the fundamental frequency square wave, E is the unit matrix, and B is the amplitude parameter matrix of each order compensation square wave; The frequency parameter matrix construction unit is used to construct the compensation sub-square wave amplitude frequency parameter matrix, and the formula used is: Among them, F is the frequency parameter matrix of each compensation sub-square wave, C is the harmonic order of the square wave of each frequency order, and n is the frequency domain order.

9. The EIS rapid detection system of the equal-amplitude broadband excitation signal according to claim 8, characterized in that: The specific operation mode of the excitation signal construction module is: Based on equations (3) and (4), the amplitude and frequency parameter matrix of each order of sub-square waves in the frequency domain are obtained by extended calculation, and a sequence of sub-square waves is generated in sequence, and the sequence of sub-square waves is superimposed into a synthetic signal, namely, the equal-amplitude broadband excitation signal EABE.

10. The EIS rapid detection system of the equal-amplitude broadband excitation signal according to claim 9, characterized in that: The calculation described in the output module obtains the EIS within the target frequency in the following manner: The impedance information in the target frequency domain is obtained by calculating equations (6)-(9), as follows Z′=|Z|×cosθ (7) Z″=|Z|×sinθ (8) Where: U and I are the voltage amplitude and current amplitude at each frequency point respectively, θ U ,θ I are the voltage phase and current phase at each frequency point, Z is the impedance at each frequency point, |Z| is the impedance amplitude, θ is the impedance phase, Z′ is the real part of the impedance, Z″ is the imaginary part of the impedance, and e is a natural constant.

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