A lithium battery impedance spectrum rapid testing method based on optimized binary sequence

Abstract

The application discloses a kind of lithium battery impedance spectrum fast test method based on optimization binary sequence, comprising: initialization parameter;According to the length of binary sequence, period, harmonic amplitude and harmonic phase angle, calculate the discretization sequence: according to the discretization sequence calculation binary sequence;The complex frequency domain coefficient of binary sequence is calculated by Fourier transform, including complex frequency domain amplitude and complex frequency domain phase angle;After replacing complex frequency domain phase angle with harmonic phase angle, judge whether complex frequency domain amplitude meets accuracy requirement, if meet, then the corresponding binary sequence is designated as optimization sequence and with current signal form to battery injection optimization binary sequence, collect battery terminal voltage and current in the process of optimization binary sequence injection, and calculate the impedance of battery at different frequencies, otherwise recalculate the discretization sequence.The application does not need complex hardware design, can quickly and accurately measure battery impedance, test result is not easy to deviate, applicable to various application scenarios.

Description

Technical Field

[0001] This invention belongs to the field of power lithium battery state monitoring technology, specifically relating to a rapid method for testing the impedance spectrum of lithium batteries based on optimized binary sequences. Background Technology

[0002] Lithium-ion batteries possess advantages such as high power energy density, long cycle life, and no memory effect, attracting widespread attention and research in energy storage power stations, electric vehicles, and electronic devices. To ensure the safe and stable operation of batteries, a battery management system is needed to monitor their state. Battery impedance is closely related to the battery's state of charge, health, and faults. Electrochemical impedance spectroscopy (EIS) provides a wealth of information, enabling real-time estimation of the battery's state and fault diagnosis, provided that appropriate measurement methods are used to obtain the battery impedance in real time.

[0003] Traditional testing methods obtain the wideband impedance of lithium batteries using sinusoidal frequency sweep signals, which can provide relatively accurate impedance measurement results, but requires a long measurement time. Using superimposed sinusoidal signals allows for simultaneous measurement of impedance at different frequencies, significantly shortening the impedance spectrum testing time; however, generating this signal requires complex hardware design and involves large signal amplitudes. Step signal impedance spectrum measurement is easy to implement, but the signal power spectrum is non-uniform, making it unsuitable for obtaining complete impedance spectrum information. Therefore, currently, there is still a lack of effective and reliable methods for online measurement of wideband battery impedance. The design of excitation signals needs further improvement, and the accuracy and stability of battery impedance acquisition still need further enhancement. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a rapid method for testing the impedance spectrum of lithium batteries based on optimized binary sequences, addressing the shortcomings of the prior art.

[0005] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows:

[0006] A rapid method for measuring the impedance spectrum of lithium-ion batteries based on optimized binary sequences, comprising:

[0007] Step 1: Initialize the length, period, harmonic amplitude, and harmonic phase angle of the binary sequence;

[0008] Step 2: Calculate the discretized sequence based on the length, period, harmonic amplitude, and harmonic phase angle of the binary sequence:

[0009] Step 3: Calculate the binary sequence based on the discretized sequence obtained in Step 2;

[0010] Step 4: Calculate the complex frequency domain coefficients of the binary sequence using Fourier transform, including the complex frequency domain amplitude and the complex frequency domain phase angle;

[0011] Step 5: After replacing the complex frequency domain phase angle with the harmonic phase angle, determine whether the complex frequency domain amplitude meets the accuracy requirements. If it does, specify the corresponding binary sequence as the optimized sequence and execute step 6; otherwise, return to step 2.

[0012] Step 6: Inject an optimized binary sequence into the battery in the form of a current signal;

[0013] Step 7: Collect the battery terminal voltage and current during the optimized binary sequence injection process, and calculate the battery impedance at different frequencies.

[0014] To optimize the above technical solution, the specific measures also include:

[0015] Step 2 above calculates the discretized sequence d using the inverse Fourier transform. n As shown below:

[0016]

[0017] Where j represents the imaginary unit, k represents the harmonic index, and n represents the discretized sequence d. n The serial number;

[0018] N is the length of the binary sequence, C d (k) represents the harmonic amplitude.

[0019] Step 3 above uses the following formula to calculate the binary sequence.

[0020]

[0021] Where, d n is the discretized sequence number, and N is the length of the binary sequence.

[0022] Step 4 above calculates the binary sequence using Fourier transform. The complex frequency domain coefficients are shown below.

[0023]

[0024] in, for The amplitude in the complex frequency domain, for The phase angle in the complex frequency domain, where N is the length of the binary sequence.

[0025] Step 6 above injects an optimized binary sequence into the battery in the form of a current signal through the battery management system.

[0026] Step 7 above uses the battery management system to collect and optimize the battery terminal voltage and current during the binary sequence injection process.

[0027] The impedance of the battery at different frequencies, as described in step 7 above, is calculated using the following formula:

[0028]

[0029] Where f represents the impedance frequency, V(f) and I(f) represent the battery impedance, voltage harmonics, and current harmonics at frequency f, respectively.

[0030] The present invention has the following beneficial effects:

[0031] This invention relates to a rapid lithium-ion battery impedance spectrum testing method based on an optimized binary sequence. It involves optimizing the generation of the binary sequence and impedance measurement. Through an iterative algorithm, a binary sequence with the optimal power spectrum can be generated. Compared to traditional impedance measurement schemes, this invention does not require complex hardware design, offering the advantage of low cost. It can quickly and accurately measure battery impedance, and the test results are less prone to deviation. Furthermore, the optimized binary sequence proposed in this invention has a high signal-to-noise ratio and sufficient stability, making it suitable for various application scenarios. Attached Figure Description

[0032] Figure 1 The flowchart shows a rapid method for testing the impedance spectrum of lithium batteries based on optimized binary sequences.

[0033] Figure 2 The graph shows the broadband impedance measurement results at an ambient temperature of 25℃ and a state of charge of 20%.

[0034] Figure 3 The graph shows the broadband impedance measurement results at an ambient temperature of 25℃ and a state of charge of 50%.

[0035] Figure 4 The graph shows the broadband impedance measurement results at an ambient temperature of 25℃ and a state of charge of 80%.

[0036] Figure 5 The graph shows the broadband impedance measurement results at an ambient temperature of 15℃ and a state of charge of 50%.

[0037] Figure 6 The graph shows the broadband impedance measurement results at an ambient temperature of 35℃ and a state of charge of 50%. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0039] Although the steps in this invention are arranged by reference numerals, this is not intended to limit the order of the steps. Unless the order of the steps is explicitly stated or the execution of a step requires other steps as a basis, the relative order of the steps can be adjusted. It is understood that the term "and / or" as used herein refers to and covers any and all possible combinations of one or more of the associated listed items.

[0040] like Figure 1 As shown, this invention provides a rapid method for testing the impedance spectrum of lithium batteries based on optimized binary sequences, involving optimized binary sequence generation and impedance measurement, including the following steps:

[0041] Step 1: Initialize the length, period, harmonic amplitude, and harmonic phase angle of the binary sequence;

[0042] Initialize the length N, period T, and harmonic amplitude C of the binary sequence. d (k), harmonic phase angle φ d (k).

[0043] Step 2: Based on the length of the binary sequence, the harmonic amplitude, and the harmonic phase angle, calculate the discretized sequence using the inverse Fourier transform:

[0044] The discretized sequence d is calculated using the inverse Fourier transform. n As shown below

[0045]

[0046] Where j represents the imaginary unit, k represents the harmonic index, and n represents the discretized sequence d. n The serial number;

[0047] N is the length of the binary sequence, C d (k) represents the harmonic amplitude;

[0048] Step 3: Calculate the binary sequence based on the discretized sequence;

[0049] Calculate binary sequence As shown below,

[0050]

[0051] Step 4: Calculate the complex frequency domain coefficients of the binary sequence using Fourier transform, including the complex frequency domain amplitude and the complex frequency domain phase angle;

[0052] Calculating binary sequences using Fourier transform The complex frequency domain coefficients are shown below.

[0053]

[0054] in, for The amplitude in the complex frequency domain, for The phase angle in the complex frequency domain.

[0055] Step 5: After replacing the complex frequency domain phase angle with the harmonic phase angle, determine whether the complex frequency domain amplitude meets the accuracy requirements. If it does, specify the corresponding binary sequence as the optimized sequence and execute step 6; otherwise, return to step 2.

[0056] That is, the phase angle in the complex frequency domain Replace with harmonic phase angle φ d (k).

[0057] If the amplitude in the complex frequency domain To meet the accuracy requirements, Specify the optimized sequence and proceed to step 6; otherwise, return to step 2.

[0058] Step 6: Inject an optimized binary sequence into the battery in the form of a current signal through the battery management system.

[0059] Step 7: Collect and optimize the battery terminal voltage and current during the binary sequence injection process through the battery management system, and calculate the battery impedance at different frequencies, as shown below.

[0060]

[0061] Where f represents the impedance frequency, V(f) and I(f) represent the battery impedance, voltage harmonics, and current harmonics at frequency f, respectively.

[0062] Example 1

[0063] The selected battery is an 18650 cylindrical lithium iron phosphate battery with a rated capacity of 1.5Ah and a rated voltage of 3.6V. Key steps in optimizing binary sequence generation and impedance measurement include: parameter initialization, sequence optimization, signal injection, and impedance calculation.

[0064] like Figure 1 As shown, the length, period, and harmonic amplitude and phase angle of the binary sequence are first initialized. Then, the amplitude and phase angle of the time-domain discretized sequence, the binary sequence, and the complex frequency domain of the binary sequence are calculated respectively. Based on this, the complex frequency domain phase angle is designated as the harmonic phase angle. It is determined whether the complex frequency domain amplitude meets the accuracy requirements. If not, the binary sequence is optimized through iterative steps. If the accuracy requirements are met, the optimized binary sequence is injected into the battery as a current signal through the battery management system. Finally, current and voltage data are collected and the battery impedance at different frequencies is calculated.

[0065] The key aspects of the present invention will be described one by one below through examples.

[0066] 1. Parameter initialization

[0067] Initialize the length N, period T, and harmonic amplitude C of the binary sequence. d (k), harmonic phase angle φ d (k).

[0068] In this embodiment, the length N of the binary sequence is 16000 bits, the period T is 10 seconds, and the harmonic amplitude C is specified. d (k) is 0.183A, and the specified harmonic phase angle is 0°.

[0069] 2. Sequence optimization

[0070] (1) Calculate the time-domain discretized sequence d using the inverse Fourier transform. n As shown below

[0071]

[0072] Where j represents the imaginary unit, k represents the harmonic index, and n represents the discretized sequence d. n The serial number.

[0073] (2) Calculate binary sequence As shown below,

[0074]

[0075] (3) Calculate using Fourier transform The complex frequency domain coefficients are shown below.

[0076]

[0077] in for The amplitude in the complex frequency domain, for The phase angle in the complex frequency domain.

[0078] (4) Phase angle in the complex frequency domain Specify as harmonic phase angle φ d (k).

[0079] If the amplitude in the complex frequency domain To meet the accuracy requirements, Specify as the optimized sequence, otherwise return (1).

[0080] 3. Signal Injection

[0081] An optimized binary sequence is injected into the battery in the form of a current signal through the battery management system.

[0082] 4. Impedance Calculation

[0083] The battery terminal voltage and current are collected and optimized during the binary sequence injection process through the battery management system, and the battery impedance at different frequencies is calculated, as shown below.

[0084]

[0085] Where f represents the impedance frequency. V(f) and I(f) represent the battery impedance, voltage harmonics, and current harmonics at frequency f, respectively.

[0086] Battery impedance measurement experimental results are as follows Figures 2-6 As shown; among them, the broadband impedance measurement results Figure 2 Corresponding to an ambient temperature of 25℃ and a state of charge of 20%; broadband impedance measurement results Figure 3 Corresponding to an ambient temperature of 25℃ and a state of charge of 50%; broadband impedance measurement results Figure 4 Corresponding to an ambient temperature of 25℃ and a state of charge of 80%; broadband impedance measurement results. Figure 5 Corresponding to an ambient temperature of 15℃ and a state of charge of 50%. Wideband impedance measurement results. Figure 6 This corresponds to an ambient temperature of 35℃ and a state of charge of 50%.

[0087] As demonstrated by the results of the embodiments, the binary sequence with the optimal power spectrum optimized by the iterative algorithm of this invention, compared to traditional impedance measurement schemes, does not require complex hardware design, has the advantage of low cost, and can quickly and accurately measure battery impedance with less susceptibility to deviation in test results. Furthermore, the optimized binary sequence proposed in this invention has a high signal-to-noise ratio and sufficient stability, making it suitable for various application scenarios.

[0088] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0089] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A rapid method for testing the impedance spectrum of lithium batteries based on optimized binary sequences, characterized in that, include: Step 1: Initialize the length, period, harmonic amplitude, and harmonic phase angle of the binary sequence; Step 2: Calculate the discretized sequence based on the length, period, harmonic amplitude, and harmonic phase angle of the binary sequence: Step 3: Calculate the binary sequence based on the discretized sequence obtained in Step 2; Step 4: Calculate the complex frequency domain coefficients of the binary sequence using Fourier transform, including the complex frequency domain amplitude and the complex frequency domain phase angle; Step 5: After replacing the complex frequency domain phase angle with the harmonic phase angle, determine whether the complex frequency domain amplitude meets the preset accuracy requirements. If it does, specify the corresponding binary sequence as the optimized sequence and execute step 6; otherwise, return to step 2. Step 6: Inject an optimized binary sequence into the battery in the form of a current signal; Step 7: Collect the battery terminal voltage and current during the optimized binary sequence injection process, and calculate the battery impedance at different frequencies.

2. The rapid method for testing the impedance spectrum of lithium batteries based on optimized binary sequences according to claim 1, characterized in that, Step 2 calculates the discretized sequence d using the inverse Fourier transform. n As shown below: Where j represents the imaginary unit, k represents the harmonic index, and n represents the discretized sequence d. n The serial number; N is the length of the binary sequence, |C d (k)| represents the harmonic amplitude, φ d (k) is the harmonic phase angle.

3. The rapid method for testing the impedance spectrum of lithium batteries based on optimized binary sequences according to claim 1, characterized in that, Step 3 uses the following formula to calculate the binary sequence. Where, d n is the discretized sequence number, and N is the length of the binary sequence.

4. The rapid method for testing the impedance spectrum of lithium batteries based on optimized binary sequences according to claim 1, characterized in that, Step 4 calculates the binary sequence using Fourier transform. The complex frequency domain coefficients are shown below. in, for The amplitude in the complex frequency domain, for The phase angle in the complex frequency domain, where N is the length of the binary sequence.

5. The rapid method for testing the impedance spectrum of lithium batteries based on optimized binary sequences according to claim 1, characterized in that, Step 6 involves injecting an optimized binary sequence into the battery in the form of a current signal through the battery management system.

6. The rapid method for testing the impedance spectrum of lithium batteries based on optimized binary sequences according to claim 1, characterized in that, Step 7 involves collecting and optimizing the battery terminal voltage and current during the binary sequence injection process through the battery management system.

7. The rapid method for testing the impedance spectrum of lithium batteries based on optimized binary sequences according to claim 1, characterized in that, The impedance of the battery at different frequencies, as described in step 7, is calculated using the following formula: Where f represents the impedance frequency, V(f) and I(f) represent the battery impedance, voltage harmonics, and current harmonics at frequency f, respectively.

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