Method, system, medium and equipment for detecting consistency of internal resistance of lithium battery

Abstract

The invention discloses a method, a system, a medium and equipment for detecting lithium battery internal resistance consistency, in the method, a to-be-detected lithium battery module is connected to # imgabs 0 # frequency superposed low-voltage power supply to measure a time domain reflection signal, and # imgabs 1 # is a natural number; fourier transform is carried out on the time domain reflection signal to obtain a frequency domain reflection coefficient spectrum, and a part corresponding to a measuring point frequency is cut out; performing inverse Fourier transform on the frequency domain reflection coefficient spectrum to obtain time domain impedance distribution, and taking a real part; respectively executing the above steps on the lithium battery module which is confirmed to be intact and the lithium battery module to be tested and has the same scale, comparing the difference of time domain impedance distribution of the lithium battery module and the lithium battery module to be tested with the impedance of the intact lithium battery module to obtain a normalized difference value, and comparing the normalized difference value with a preset threshold value; if the normalized difference value is larger than a preset threshold value, it is judged that the lithium battery module to be detected breaks down; and if the normalized difference value is not greater than the preset threshold value, judging that the lithium battery module to be detected does not have a fault.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery internal resistance detection, and in particular to a method, system, medium and equipment for detecting the consistency of lithium battery internal resistance. Background Art

[0002] With the continuous expansion of new energy application scenarios, energy storage systems occupy an important position in modern power systems and smart grids. In energy storage lithium battery modules, repeated charging and discharging will cause battery aging, resulting in increased internal resistance and reduced capacity. The decline in battery performance sometimes brings reliability problems and leads to safety accidents.

[0003] The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Summary of the invention

[0004] The present invention provides a method, system, medium and device for detecting the consistency of lithium battery internal resistance. A low-voltage signal with multiple frequencies superimposed is injected into a battery module. By detecting the reflected signal, the frequency and time domain impedance distribution in the module can be obtained, and the module containing degraded batteries can be detected. The problem of detecting the consistency of lithium battery module internal resistance is solved. The phenomenon of inconsistent internal resistance is amplified by time-frequency domain conversion, and the detection accuracy of lithium battery modules with different rated parameters and different connection forms is relatively high.

[0005] A method for detecting the consistency of internal resistance of a lithium battery includes:

[0006] Step 1: Connect the lithium battery module to be tested The time domain reflection signal is measured by a low voltage power supply with frequency superposition. is a natural number;

[0007] Step 2, performing Fourier transform on the time domain reflection signal to obtain a frequency domain reflection coefficient spectrum, and cutting out a portion corresponding to the measurement point frequency;

[0008] Step 3, performing an inverse Fourier transform on the frequency domain reflection coefficient spectrum to obtain a time domain impedance distribution, and taking the real part;

[0009] Step 4, performing steps 1 to 3 on the lithium battery module confirmed to be intact and the lithium battery module to be tested of the same scale, respectively, comparing the difference in the time domain impedance distribution between the two with the impedance of the intact lithium battery module to obtain a normalized difference and comparing it with a predetermined threshold;

[0010] Step 5: If the normalized difference is greater than a predetermined threshold, it is determined that the lithium battery module to be tested is faulty; if the normalized difference is not greater than the predetermined threshold, it is determined that the lithium battery module to be tested is not faulty.

[0011] In the method for detecting the consistency of the internal resistance of a lithium battery, the voltage waveform of the low-voltage power supply is ,in is the voltage amplitude constant, The voltage waveform of the low voltage power supply should be The maximum value does not harm the normal operation of the lithium battery module. is the measurement point frequency, .

[0012] In the method for detecting the consistency of internal resistance of a lithium battery, the time domain reflection signal includes a voltage reflection waveform, and the expression of the voltage reflection waveform is: ,in is the frequency The reflection coefficient under .

[0013] In the method for detecting the consistency of internal resistance of a lithium battery, the frequency domain reflection coefficient spectrum is obtained by Fourier transform , cut off and take out part.

[0014] In the method for detecting the consistency of the internal resistance of a lithium battery, the time domain impedance distribution includes a time domain reflection coefficient spectrum obtained by taking the real part of the inverse Fourier transform, which is , read the reflection coefficient of a good lithium battery module at the maximum reflection coefficient point And the reflection coefficient of the lithium battery module to be tested , the normalized difference of the lithium battery module to be tested is .

[0015] In the method for detecting the consistency of the internal resistance of a lithium battery, the predetermined threshold is 0.005.

[0016] In the method for detecting the consistency of internal resistance of a lithium battery, the lithium battery module includes lithium batteries connected in series and parallel.

[0017] A system for detecting the consistency of internal resistance of a lithium battery comprises:

[0018] k low-voltage power supplies with superimposed frequencies;

[0019] A measuring unit, which is used to measure a lithium battery module to be tested that is connected to a low-voltage power supply with k frequencies superimposed to obtain a time domain reflection signal;

[0020] A Fourier transform unit, which is used to perform Fourier transform on the time domain reflection signal to obtain a frequency domain reflection coefficient spectrum and cut out a part corresponding to the measurement point frequency;

[0021] An inverse Fourier transform unit, which is used to perform an inverse Fourier transform on the frequency domain reflection coefficient spectrum to obtain a time domain impedance distribution and take the real part;

[0022] A comparison unit, which is used to compare the difference in time domain impedance distribution between the lithium battery module confirmed to be intact and the lithium battery module to be tested of the same scale with the impedance of the intact lithium battery module to obtain a normalized difference and compare it with a predetermined threshold;

[0023] The judgment unit is used to judge that the lithium battery module to be tested has failed if the normalized difference is greater than a predetermined threshold value; and judge that the lithium battery module to be tested has not failed if the normalized difference is not greater than the predetermined threshold value.

[0024] A computer storage medium includes computer instructions, which, when executed on a computer, cause the computer to execute the method described.

[0025] An electronic device, comprising:

[0026] A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein:

[0027] When the processor executes the program, the method described is implemented.

[0028] Compared with the prior art, the present invention has the following advantages: the present invention measures the time-domain reflection waveform of the lithium battery module, obtains the frequency-domain reflection coefficient spectrum by Fourier transform, obtains the time-domain impedance spectrum of the module by inverse Fourier transform after truncation, and can detect the aged battery in the module by comparing the time-domain impedance spectrum. The problem of detecting the consistency of the internal resistance of the lithium battery module is solved, the phenomenon of inconsistent internal resistance is amplified by time-frequency domain conversion, and the detection accuracy of lithium battery modules with different rated parameters and different connection forms is relatively high. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] By reading the detailed description of the preferred specific embodiments below, various other advantages and benefits of the present invention will become clear to those of ordinary skill in the art. The drawings in the specification are only for the purpose of illustrating the preferred embodiments and are not considered to be limitations of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative work. Moreover, the same reference numerals are used to represent the same components throughout the drawings.

[0030] In the attached picture:

[0031] Figure 1 It is a flow chart of the method for detecting the consistency of the internal resistance of lithium batteries;

[0032] Figure 2 It is a simulated multi-frequency superimposed low-voltage power supply waveform diagram;

[0033] Figure 3 It is a schematic diagram of the battery pack structure;

[0034] FIG4(a) and FIG4(b) are schematic diagrams of the time-frequency domain reflection coefficient spectrum of battery packs of different aging degrees. FIG4(a) is the absolute value of the frequency domain reflection coefficient spectrum, and FIG4(b) is the real part of the time domain reflection coefficient spectrum.

[0035] The present invention is further explained below in conjunction with the accompanying drawings and embodiments. DETAILED DESCRIPTION

[0036] The specific embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the specific embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0037] It should be noted that certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that technicians may use different nouns to refer to the same component. This specification and claims do not use the difference in nouns as a way to distinguish components, but use the difference in the functions of the components as the criterion for distinction. As mentioned throughout the specification and claims, "including" or "comprising" is an open term, so it should be interpreted as "including but not limited to". The subsequent description of the specification is a preferred embodiment of the present invention, but the description is based on the general principles of the specification and is not intended to limit the scope of the present invention. The scope of protection of the present invention shall be determined by the attached claims.

[0038] To facilitate understanding of the embodiments of the present invention, further explanation will be given below by taking specific embodiments as examples in conjunction with the accompanying drawings, and each of the accompanying drawings does not constitute a limitation on the embodiments of the present invention.

[0039] like Figure 1 As shown in FIG4( b ), the method for detecting the consistency of the internal resistance of a lithium battery includes the following steps:

[0040] Step 1: Connect the lithium battery module to be tested The time domain reflection signal is measured by a low voltage power supply with frequency superposition. is a natural number;

[0041] Step 2, performing Fourier transform on the time domain reflection signal to obtain a frequency domain reflection coefficient spectrum, and cutting out a portion corresponding to the measurement point frequency;

[0042] Step 3, performing an inverse Fourier transform on the frequency domain reflection coefficient spectrum to obtain a time domain impedance distribution, and taking the real part;

[0043] Step 4, performing steps 1 to 3 on the lithium battery module confirmed to be intact and the lithium battery module to be tested of the same scale, respectively, comparing the difference in the time domain impedance distribution between the two with the impedance of the intact lithium battery module to obtain a normalized difference and comparing it with a predetermined threshold;

[0044] Step 5: If the normalized difference is greater than a predetermined threshold, it is determined that the lithium battery module to be tested is faulty; if the normalized difference is not greater than the predetermined threshold, it is determined that the lithium battery module to be tested is not faulty.

[0045] In a preferred embodiment of the method for detecting the consistency of internal resistance of a lithium battery, the voltage waveform of the low-voltage power supply is ,in is the voltage amplitude constant, The voltage waveform of the low voltage power supply should be The maximum value does not harm the normal operation of the lithium battery module. is the measurement point frequency, .

[0046] In a preferred embodiment of the method for detecting the consistency of internal resistance of a lithium battery, the time domain reflection signal includes a voltage reflection waveform, and the expression of the voltage reflection waveform is: ,in is the frequency The reflection coefficient under .

[0047] In a preferred embodiment of the method for detecting the consistency of internal resistance of a lithium battery, the frequency domain reflection coefficient spectrum is obtained by Fourier transform , cut off and take out part.

[0048] In a preferred embodiment of the method for detecting the consistency of internal resistance of a lithium battery, the time domain impedance distribution includes a time domain reflection coefficient spectrum obtained by taking the real part of the inverse Fourier transform, which is , read the reflection coefficient of a good lithium battery module at the maximum reflection coefficient point And the reflection coefficient of the lithium battery module to be tested , the normalized difference of the lithium battery module to be tested is .

[0049] In a preferred implementation of the method for detecting the consistency of internal resistance of a lithium battery, the predetermined threshold is 0.005.

[0050] In a preferred embodiment of the method for detecting the consistency of internal resistance of a lithium battery, the lithium battery module includes lithium batteries connected in series and parallel.

[0051] A system for detecting the consistency of internal resistance of a lithium battery comprises:

[0052] A low voltage power supply with superimposed frequencies;

[0053] Measuring unit, which is used to measure access A lithium battery module to be tested with a low-voltage power supply with frequency superposition to measure the time domain reflection signal;

[0054] A Fourier transform unit, which is used to perform Fourier transform on the time domain reflection signal to obtain a frequency domain reflection coefficient spectrum and cut out a part corresponding to the measurement point frequency;

[0055] An inverse Fourier transform unit, which is used to perform an inverse Fourier transform on the frequency domain reflection coefficient spectrum to obtain a time domain impedance distribution and take the real part;

[0056] A comparison unit, which is used to compare the difference in time domain impedance distribution between the lithium battery module confirmed to be intact and the lithium battery module to be tested of the same scale with the impedance of the intact lithium battery module to obtain a normalized difference and compare it with a predetermined threshold;

[0057] The judgment unit is used to judge that the lithium battery module to be tested has failed if the normalized difference is greater than a predetermined threshold value; and judge that the lithium battery module to be tested has not failed if the normalized difference is not greater than the predetermined threshold value.

[0058] A computer storage medium includes computer instructions, which, when executed on a computer, cause the computer to execute the method described.

[0059] An electronic device, comprising:

[0060] A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein:

[0061] When the processor executes the program, the method described is implemented.

[0062] In one embodiment, a method for detecting the consistency of internal resistance of a lithium battery using time-frequency domain impedance spectrum conversion includes the following steps:

[0063] Access A low-voltage power supply with superimposed frequencies, whose voltage waveform is ,in is the voltage amplitude constant. The determination of this constant must ensure The maximum value does not harm the normal operation of the battery pack. is the measurement point frequency, . Measure the voltage reflection waveform, the expression of the reflected voltage is ,in is the frequency The reflection coefficient under the condition of Fourier transform is performed on the time domain waveform to obtain the frequency domain reflection coefficient spectrum , cut off and take out , and perform an inverse Fourier transform to obtain the real part to obtain the time domain reflection coefficient spectrum , read the reflection coefficient of the standard module at the maximum reflection coefficient point And the reflection coefficient of the module to be tested , compare the difference between the two with the standard module reflection coefficient, and get the normalized difference ,like If the ratio is greater than the threshold of 0.005, it can be used as a criterion for the presence of deteriorated batteries in the module. For battery modules with the same structure, the larger the ratio, the more damaged batteries there are, or the more serious the battery damage.

[0064] Example 1

[0065] The second-order differential equivalent circuit simulation is used to simulate the lithium battery. First, five batteries are connected in parallel, and then five groups of parallel batteries are connected in series, for a total of 25 batteries. Figure 3 As shown. The standard internal resistance of the battery is set to 2mΩ, the internal resistance of the slightly aged battery is set to 10mΩ, and the internal resistance of the severely aged battery is set to 20mΩ. The voltage amplitude constant of the connected voltage source , measuring point frequency (Hz), , its waveform is as follows Figure 2 The terminal impedance is a 2mΩ resistor and a 1μF capacitor in parallel. The structure of the battery pack is as follows: Figure 3 As shown in FIG. 4 , in addition to the standard module, four battery groups containing degraded batteries are set up, represented by Roman numerals Ⅱ, Ⅲ, Ⅳ, and Ⅴ, respectively. Battery group Ⅱ places a slightly aged battery at position 1; battery group Ⅲ places a severely aged battery at position 1; battery group Ⅳ places a slightly aged battery at position 1 and a severely aged battery at position 2; battery group Ⅴ places a slightly aged battery at position 1 and a severely aged battery at position 11. The frequency domain reflection coefficient spectrum image of the five groups is shown in FIG. 4 (a) and the time domain reflection coefficient spectrum image is shown in FIG. 4 (b), and the normalized difference of the reflection coefficient is shown in Table 1.

[0066] Table 1 Normalized difference of real part of time domain reflection coefficient of battery packs with different damage degrees

[0067]

[0068] Using the time-frequency domain impedance spectrum conversion method, it was found that the above four types of modules containing aged batteries were all damaged, and the test results were correct.

[0069] Although the embodiments of the present invention are described above in conjunction with the accompanying drawings, the present invention is not limited to the above specific embodiments and application fields, and the above specific embodiments are only illustrative and instructive, rather than restrictive. A person of ordinary skill in the art can also make many forms under the guidance of this specification and without departing from the scope of protection of the claims of the present invention, all of which belong to the protection of the present invention.

Claims

1. A method for detecting the consistency of internal resistance of a lithium battery, characterized in that: The method comprises the following steps: Step 1: Connect the lithium battery module to be tested The time domain reflection signal is measured by a low voltage power supply with frequency superposition. is a natural number; Step 2, performing Fourier transform on the time domain reflection signal to obtain a frequency domain reflection coefficient spectrum, and cutting out a portion corresponding to the measurement point frequency; Step 3, performing an inverse Fourier transform on the frequency domain reflection coefficient spectrum to obtain a time domain impedance distribution, and taking the real part; Step 4, performing steps 1 to 3 on the lithium battery module confirmed to be intact and the lithium battery module to be tested of the same scale, respectively, comparing the difference in the time domain impedance distribution between the two with the impedance of the intact lithium battery module to obtain a normalized difference and comparing it with a predetermined threshold; Step 5: If the normalized difference is greater than a predetermined threshold, it is determined that the lithium battery module to be tested is faulty; if the normalized difference is not greater than the predetermined threshold, it is determined that the lithium battery module to be tested is not faulty.

2. A method for detecting the consistency of internal resistance of a lithium battery according to claim 1, characterized in that: Preferably, the voltage waveform of the low voltage power supply is ,in is the voltage amplitude constant, The voltage waveform of the low voltage power supply should be The maximum value does not harm the normal operation of the lithium battery module. is the measurement point frequency, .

3. A method for detecting the consistency of internal resistance of a lithium battery according to claim 2, characterized in that: The time domain reflection signal includes a voltage reflection waveform, and the expression of the voltage reflection waveform is: ,in is the frequency The reflection coefficient under .

4. A method for detecting the consistency of internal resistance of a lithium battery according to claim 3, characterized in that: The frequency domain reflection coefficient spectrum is obtained by Fourier transform , cut off and take out part.

5. A method for detecting the consistency of internal resistance of a lithium battery according to claim 4, characterized in that: The time domain impedance distribution includes the time domain reflection coefficient spectrum obtained by taking the real part of the inverse Fourier transform, which is , read the reflection coefficient of a good lithium battery module at the maximum reflection coefficient point And the reflection coefficient of the lithium battery module to be tested , the normalized difference of the lithium battery module to be tested is .

6. A method for detecting the consistency of internal resistance of a lithium battery according to claim 1, characterized in that: The predetermined threshold is 0.

005.

7. A method for detecting the consistency of internal resistance of a lithium battery according to claim 1, characterized in that: The lithium battery module includes lithium batteries connected in series and parallel.

8. A system for detecting the consistency of internal resistance of a lithium battery, characterized in that: These include, k low-voltage power supplies with superimposed frequencies; A measuring unit, which is used to measure a lithium battery module to be tested that is connected to a low-voltage power supply with k frequencies superimposed to obtain a time domain reflection signal; A Fourier transform unit, which is used to perform Fourier transform on the time domain reflection signal to obtain a frequency domain reflection coefficient spectrum and cut out a part corresponding to the measurement point frequency; An inverse Fourier transform unit, which is used to perform an inverse Fourier transform on the frequency domain reflection coefficient spectrum to obtain a time domain impedance distribution and take the real part; A comparison unit, which is used to compare the difference in time domain impedance distribution between the lithium battery module confirmed to be intact and the lithium battery module to be tested of the same scale with the impedance of the intact lithium battery module to obtain a normalized difference and compare it with a predetermined threshold; The judgment unit is used to judge that the lithium battery module to be tested has failed if the normalized difference is greater than a predetermined threshold value; and judge that the lithium battery module to be tested has not failed if the normalized difference is not greater than the predetermined threshold value.

9. A computer storage medium, characterized in that: The storage medium includes computer instructions, which, when executed on a computer, enable the computer to execute the method according to any one of claims 1 to 7.

10. An electronic device, characterized in that: The electronic device comprises: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the program, the method according to any one of claims 1 to 7 is implemented.

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