EIS rapid detection method and system for constant amplitude and broadband excitation signal

Abstract

The present invention relates to the field of rapid detection of energy storage batteries and provides an EIS rapid detection method using a constant-amplitude, wide-band excitation signal. The method comprises: calculating the frequency and amplitude of each order of sub-square waves based on the Fourier transform characteristics between a square wave signal and a sinusoidal signal, and establishing a compensation sub-square wave parameter matrix; constructing a constant-amplitude, wide-band excitation signal EABE; using Simulink to build an equivalent circuit model detection simulation platform for energy storage batteries; injecting the constant-amplitude, wide-band excitation signal into the equivalent circuit model to obtain a corresponding wide-band response signal; converting the constant-amplitude, wide-band excitation signal and response signal obtained during the detection process to the frequency domain through a fast Fourier transform; analyzing the frequency domain information of the excitation and response signals to calculate and obtain the EIS within the target frequency. The above method improves the speed and accuracy of the EIS detection method.

Description

Technical Field

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

[0002] With the rapid development of renewable energy, electrochemical energy storage systems are widely used for peak and valley regulation of power grids, safe and stable operation, and backup power supply. Among these applications, monitoring the status of energy storage batteries is a crucial benchmark for the safe and efficient operation of energy storage systems. However, battery status depends on a complex series of internal electrochemical reactions, making conventional current and voltage detection methods incapable of quickly reflecting the battery's true state. Electrochemical impedance spectroscopy (EIS) is a non-invasive measurement technique that applies small-amplitude sinusoidal interference signals of varying frequencies to an electrochemical system. This technique can decompose complex electrochemical processes into a series of fundamental processes with varying relaxation times, making it widely used in battery electrochemical research. Compared to measuring voltage and current curves during a complete charge and discharge cycle, battery EIS measurements are relatively time-efficient. However, current battery EIS measurements generally employ a swept frequency method, in which a single-frequency sinusoidal excitation signal of varying frequencies is sequentially injected through an electrochemical workstation. While this method offers advantages such as good scalability and high accuracy, it requires sequential injection of the excitation signal at each frequency point, resulting in a long cumulative detection time. Rapid EIS detection techniques are also a research focus.

[0003] Broadband excitation detection methods are a key research area for rapid EIS detection. The Journal of Electrotechnical Engineering paper, "A Low-Frequency Online Identification Method for Lithium-Ion Battery Electrochemical Impedance Spectroscopy Based on Step Waves," uses step waves to fit an approximately sinusoidal AC signal in the low-frequency domain to achieve online low-frequency EIS identification. However, due to the limitations of the EIS frequency domain, only partial electrochemical state information can be obtained, making it difficult to fully reflect the battery's state. The Power Grid Technology paper, "A Broadband Signal Estimation Algorithm Based on Variational Modal Decomposition," uses variational modal decomposition to extract waveform information of multiple modal components from a broadband signal, then converts the signal's time-domain information into frequency-domain information for further research. However, this method decomposes modal components that exhibit modal aliasing, failing to fully decompose the broadband signal at the frequency 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 using an equal amplitude broadband excitation (EABE) signal, 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 the sub-square wave are calculated, and the compensation sub-square wave parameter matrix is ​​established;

[0008] S2, constructing a constant 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 constant-amplitude broadband excitation signal into the equivalent circuit model to obtain a corresponding broadband response signal; converting the constant-amplitude broadband excitation signal and response signal obtained during the detection process into the frequency domain through 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, comprehensively reflecting 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 formula (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] Where 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 the sub-square wave are calculated in step S1 to establish a compensation sub-square wave parameter matrix, 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 constant-amplitude broadband excitation signal is specifically as follows:

[0030] Based on equations (3) and (4), the amplitude and frequency parameter matrices 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 equivalent circuit model impedance calculation formula

[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 equivalent capacitance of the SEI film, 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 EIS are substituted into equation (5). 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 measured.

[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 in operation and includes the following modules:

[0044] A parameter matrix construction 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 a constant-amplitude broadband excitation current signal into the equivalent circuit model to obtain a corresponding broadband response voltage signal; the constant-amplitude broadband excitation signal and response signal obtained during the detection process are converted into the frequency domain through 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 construction 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 matrices 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 output module calculates and obtains the EIS within the target frequency in the following manner:

[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 broadband excitation signal through the Fourier transform relationship between the square wave and the sine wave. The parameter matrix can be flexibly adjusted according to the target amplitude and target frequency domain to achieve equal-amplitude broadband 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 a constant-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 used 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 for a constant-amplitude broadband excitation signal according to an embodiment of the present invention;

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

[0072] Figure 3 Schematic diagram showing comparison of 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 Schematic diagram comparing EIS results obtained using the frequency sweep method, synthetic square wave method, and constant-amplitude broadband excitation detection method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0074] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall 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 the sub-square wave are calculated, and the compensation sub-square wave parameter matrix is ​​established;

[0078] Fast Fourier transform converts time domain signals into frequency domain for analysis, comprehensively reflecting 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 formula (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] According to formula (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, the 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, according to formula (1), the corresponding frequency is 0.1Hz and the amplitude is The square wave signal of the fundamental frequency square wave. After FFT decomposition, the corresponding amplitudes of the 1st, 3rd, 5th, 7th, and 9th harmonics are 1A, Etc. Based on this rule, we can perform equal-amplitude broadband signal superposition. Taking equal-amplitude broadband signal as the target, we calculate the frequency, amplitude and other parameters of each order square wave and establish a parameter matrix. The specific process is as follows:

[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 one excitation cycle. Here, the process of combining equal-amplitude broadband signals in the 0.1-1.1Hz frequency domain is taken as an example. The sub-square wave parameter matrix is ​​expressed as follows:

[0088]

[0089] Among them, A is the amplitude coefficient matrix of each harmonic of the fundamental frequency square wave, E is the unit matrix, and B is the amplitude coefficient matrix of each order compensation square wave 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. By using the basic square wave that is easier to implement using the detection device, the compensation amplitude coefficient provided by the parameter matrix B and the corresponding frequency coefficient provided by the parameter matrix F are arranged and combined 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 at the same time, a large number of compensation resonance situations will appear, which need to be eliminated through coefficient calculation 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. The frequency parameters are expressed as shown in 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] This 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 period and maintain relatively consistent frequency domain detection stress.

[0095] S2. Construct an equal-amplitude broadband excitation signal EABE. The specific process is as follows:

[0096] Based on equations (3) and (4), the amplitude and frequency parameter matrices 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 equivalently 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 mid-frequency range to characterize the charge transfer process of the battery. At this time, the impedance still presents resistance and capacitance, with R CT / / C DL This represents the charge transfer internal resistance of the electrode material. The impedance in the low-frequency range represents the resistance to lithium-ion diffusion. The impedance spectrum typically forms a nearly linear curve, characterizing the charge transfer and ion diffusion processes within the battery. Multiple R / / C elements can be used to fit the equivalent circuit model. Multi-order R / / C elements provide better fitting accuracy, but the number of parameters and identification computational complexity also increase.

[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 equivalent circuit model impedance calculation formula

[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 equivalent capacitance of the SEI film, 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 EIS are substituted into equation (5). 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 measured.

[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 during 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 obtained by combining and superimposing the square waves. 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 the three broadband excitation signals is shown. Among them, the amplitude of the signal component of the 0.1Hz single-frequency square wave amplitude-frequency information in the 900-1000Hz range is almost zero, which is the same as the noise floor 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 to the single-frequency square wave, and to some extent solves the problem that single-frequency square wave detection still requires multiple excitations. However, in the full frequency domain, the amplitude of the signal component at each frequency point of the synthetic square wave detection method shows a gradient attenuation 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 is within 0.98A-1.012A at the required frequency point in the full frequency domain, and the amplitude fluctuates within 2%. This proves that the equal-amplitude broadband excitation signal can carry equal-amplitude signals of any target frequency domain within one excitation cycle. 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 are 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. By analyzing the frequency domain information of the excitation and response, calculate and obtain the EIS within the target frequency. The specific process is:

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

[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 1Hz-1000Hz frequency domain, 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 attenuates in the high-frequency region and the amplitude of the component that is rapidly pulled up at the compensation resonant 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 the impedance by 0.02618%, and the imaginary part error of the impedance by 0.01384%. This verifies that the accuracy of the EIS results measured by the EABE detection method has been further improved.

[0113] Table 1 Broadband 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 number of impedance points and measurement frequency domain, the broadband excitation detection method can shorten the detection time by 66.426% compared with the swept frequency detection method, which verifies the rapidity of the detection method used in this embodiment.

[0119] Through the above technical solutions, the present invention provides an EIS rapid detection method for an equal-amplitude broadband excitation signal, and the broadband fitting method provided is based on a square wave or pulse, 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 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, thereby improving the measurement deviation caused by the superimposed resonance difference and improving 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 with a constant-amplitude broadband excitation signal. When the system is running, the method described in Example 1 is executed, and the system includes the following modules:

[0122] A parameter matrix construction 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 a constant-amplitude broadband excitation current signal into the equivalent circuit model to obtain a corresponding broadband response voltage signal; the constant-amplitude broadband excitation signal and response signal obtained during the detection process are converted into the frequency domain through 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 matrices 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 as follows:

[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 they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. 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 various embodiments of the present invention.

Claims

1. The EIS rapid detection method of the constant 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 the sub-square wave are calculated, and the compensation sub-square wave parameter matrix is ​​established; The compensation sub-square wave amplitude parameter matrix is ​​as follows: （3） in, A is the harmonic amplitude coefficient matrix of the fundamental frequency square wave, E is the identity matrix, B is the parameter matrix of each order compensation square wave amplitude; The compensation sub-square wave frequency parameter matrix is ​​as follows: （4） in, F is the frequency parameter matrix of each compensation sub-square wave, is the harmonic order of the square wave at each frequency order of magnitude, n is the frequency domain magnitude; S2. Construct an equal-amplitude broadband excitation signal EABE; specifically: 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; S3. Use Simulink to build an equivalent circuit model detection simulation platform for energy storage batteries; S4, injecting a constant-amplitude broadband excitation signal into the equivalent circuit model to obtain a corresponding broadband response signal; converting the constant-amplitude broadband excitation signal and response signal obtained during the detection process into the frequency domain through 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 a constant-amplitude broadband excitation signal according to claim 1, 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, comprehensively reflecting the complex internal electrochemical processes of the battery at different relaxation times; The FFT of a periodic function is as follows （1） in, is a periodic signal function, is the DC amplitude information, is the angular frequency, and For each frequency component Corresponding amplitude information; 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 （2） in, is a square wave signal function, is the square wave amplitude, is the signal angular frequency; From formula (2), it can be seen that the amplitudes of the frequency components of the square wave signal after FFT transformation change 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 a constant-amplitude broadband excitation signal according to claim 1, characterized in that: The step S3 is specifically as follows: First, construct the equivalent circuit model impedance calculation formula Z （5） in: is the angular velocity corresponding to each frequency point, Z The impedance corresponding to each frequency point is: 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 the SEI film, C SEI is the equivalent capacitance of the SEI film, 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; Then, the real part, imaginary part and frequency information of the impedance at each frequency point of EIS are substituted into equation (5), and a series of equations are constructed based on the impedance information at each frequency point to identify each R, L, C Approximate parameters to determine the equivalent circuit model to be tested.

4. The EIS rapid detection method of a constant-amplitude broadband excitation signal according to claim 3, 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 （6） （7） （8） （9） in: U 、 I are the voltage amplitude and current amplitude at each frequency point respectively, 、 are the voltage phase and current phase at each frequency point respectively, is the impedance at each frequency point, is the impedance amplitude, is the impedance phase, is the real part of impedance, is the imaginary part of impedance, e is a natural constant.

5. EIS rapid detection system with constant amplitude and broadband excitation signal, characterized by: The system adopts the method according to any one of claims 1 to 4 when running, and includes the following modules: A parameter matrix construction 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; 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: （3） in, A is the harmonic amplitude coefficient matrix of the fundamental frequency square wave, E is the identity matrix, B is the parameter matrix of each order compensation square wave amplitude; The frequency parameter matrix construction unit is used to construct the compensation sub-square wave amplitude frequency parameter matrix, and the formula used is: （4） in, F is the frequency parameter matrix of each compensation sub-square wave, is the harmonic order of the square wave at each frequency order of magnitude, n is the frequency domain magnitude; The excitation signal construction module constructs the equal-amplitude broadband excitation signal EABE; the specific operation mode is 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; 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 a constant-amplitude broadband excitation current signal into the equivalent circuit model to obtain a corresponding broadband response voltage signal; the constant-amplitude broadband excitation signal and response signal obtained during the detection process are converted into the frequency domain through 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.

6. The EIS rapid detection system of the constant amplitude broadband excitation signal according to claim 5, characterized in that: The calculation described in the output module obtains the EIS within the target frequency as follows: The impedance information in the target frequency domain is obtained by calculating equations (6)-(9), as follows （6） （7） （8） （9） in: U 、 I are the voltage amplitude and current amplitude at each frequency point respectively, 、 are the voltage phase and current phase at each frequency point respectively, is the impedance at each frequency point, is the impedance amplitude, is the impedance phase, is the real part of impedance, is the imaginary part of impedance, e is a natural constant.

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