Electrochemical impedance spectroscopy-based method and system for inspecting power system battery pack

Abstract

The application provides a power system battery group inspection method based on electrochemical impedance spectroscopy, which comprises the following steps: obtaining a reference electrochemical impedance spectrum of a test battery in advance; selecting the same working condition and periodically measuring the electrochemical impedance spectrum of the test battery to obtain a test electrochemical impedance spectrum; and finally calculating the deviation degree of the electrochemical impedance spectrum and the reference electrochemical impedance spectrum, and judging the health condition of the test battery group through weighted calculation if the inconsistency degree of the electrochemical impedance spectrum of each battery is inconsistent. The application solves the technical problems of inaccurate evaluation of the available capacity and the remaining life of the battery and low effectiveness of the evaluation data.

Description

Technical Field

[0001] This invention relates to the field of digital operation and maintenance data processing for batteries, specifically to a method and system for inspecting power system battery banks based on electrochemical impedance spectroscopy. Background Technology

[0002] Battery banks are the power source of substations, responsible for providing electrical energy for the operation of the power system. As a core component of the DC system, their stable and reliable operation provides a safety guarantee for the operation of the substation. Due to the large workload of battery bank maintenance and the low degree of automation, especially the reliance on mobile maintenance equipment for manual capacity verification during capacity assessment, there are problems such as numerous and heavy pieces of equipment, complicated wiring, complex operation, and high risks. Battery bank maintenance has always been a difficult problem for operation and maintenance personnel.

[0003] Currently, in the digital operation and maintenance of batteries, time-series collected float charge voltage, float charge current, and internal resistance are used for battery monitoring and evaluation. This replaces repetitive and tedious manual labor, saving significant human resources and reducing costs for grassroots operation and maintenance units. Furthermore, the higher precision of intelligent systems has become a driving force for the rapid development of these units. However, time-series collected float charge voltage, float charge current, and internal resistance data are insufficient for a comprehensive assessment of battery status. Introducing frequency-domain-based electrochemical impedance spectroscopy (EIS) measurements can greatly enrich the evaluation dimensions of batteries. However, this historical data lacks algorithm-based data analysis and effective, convenient equipment operation and maintenance experience guidance, and cannot provide effective guidance for current and future DC power supply equipment operation and maintenance. This leads to an increasingly prominent contradiction between the heavy workload of statistical reporting and the shortage of operation and maintenance personnel. Therefore, developing a remote capacity health monitoring and analysis algorithm for lead-acid batteries based on EIS, float charge voltage, float charge current, and internal resistance is of great research significance.

[0004] The existing invention patent application document CN202310167013.7, entitled "Method and Apparatus for Inspection of Battery Packs in Power Systems Based on Electrochemical Impedance Spectroscopy", includes the following steps: obtaining the reference electrochemical impedance spectrum of the battery pack under test in advance, then selecting the same operating conditions and periodically measuring the electrochemical impedance spectrum of the battery pack under test to obtain the test electrochemical impedance spectrum; finally, calculating the deviation between the test electrochemical impedance spectrum and the reference electrochemical impedance spectrum to determine the health status of the battery pack under test. And the existing invention patent application document CN116224117A entitled "A Method for Diagnosing the Health Status of Lead-Acid Batteries Based on Electrochemical Impedance Spectroscopy", which includes the following steps: (1) obtaining the electrochemical impedance spectrum of the battery under test under different aging states using an EIS measurement device; (2) disassembling and analyzing the electrochemical impedance spectrum obtained in step (1) to obtain the changing trend of each part of the AC impedance of the battery under test under different aging states; (3) quantifying the correlation between the impedance change and capacity degradation of the battery under test according to the Pearson correlation coefficient, and selecting the imaginary part of the AC impedance as the basis for further analysis. (4) Linearly fit the imaginary part of the AC impedance at different frequency points with the battery health status, evaluate the goodness of fit according to the goodness of fit, select the best fitting frequency as the characteristic frequency, and obtain the health factor used to characterize the health status of the battery under test; (5) With the health factor obtained in step (4) as the independent variable and the health status of the battery under test as the dependent variable, establish a first-order linear estimation model, input the health factor, and output the ratio of the current output maximum capacity of the battery under test to the nominal capacity, i.e., the health status SOH. If SOH < 80%, it is judged that the battery under test is in an unhealthy state. The aforementioned prior art mainly focuses on the impedance spectrum change of the entire battery group, but in actual operation, the deterioration of a single battery often precedes the deterioration of the entire group, and the deterioration of a single battery will also accelerate the deterioration of the entire battery group. At the same time, the traditional battery health status assessment mainly relies on the time-series collected float charge voltage, float charge current, and internal resistance. Currently, relying solely on these time-domain data, it is impossible to accurately assess the current usable capacity and remaining life of the battery, and it is still necessary to rely on periodic capacity verification to determine the usable capacity of the battery.

[0005] In summary, existing technologies suffer from inaccurate assessments of battery usable capacity and remaining lifespan, as well as low validity of the assessment data. Summary of the Invention

[0006] The technical problem to be solved by this invention is: how to solve the technical problems of inaccurate assessment of the available capacity and remaining life of batteries and low validity of assessment data in the prior art.

[0007] This invention solves the above-mentioned technical problems by employing the following technical solution: A power system battery pack inspection method based on electrochemical impedance spectroscopy includes:

[0008] S1. Collect and calculate the impedance spectrum of the tested battery pack to obtain the reference electrochemical impedance spectrum of the tested battery pack.

[0009] S2. Under the same operating conditions, the test battery is subjected to electrochemical impedance spectroscopy measurement according to the preset cycle to obtain the test electrochemical impedance spectrum.

[0010] S3. Calculate the deviation between the tested electrochemical impedance spectrum and the reference electrochemical impedance spectrum, and the degree of inconsistency of the electrochemical impedance spectra of each battery. Perform weighted calculations based on the deviation and degree of inconsistency to determine the health status of the tested battery pack.

[0011] This invention determines the health status of the battery pack by obtaining the reference electrochemical impedance spectrum and the test electrochemical impedance spectrum of the tested battery, and calculating the deviation between the electrochemical impedance spectrum and the reference electrochemical impedance spectrum, which helps to improve the battery's power supply and safe and reliable operation.

[0012] In a more specific technical solution, in step S1, the positive and negative electrodes of the battery pack electrochemical impedance spectroscopy detection device are connected to the positive and negative electrodes of the battery pack under test, respectively, so as to collect and process the impedance spectrum of the battery pack under test and form a reference electrochemical impedance spectroscopy spectrum.

[0013] In a more specific technical solution, in step S1, the test frequency range for the tested battery pack includes: [0.01Hz, 7.8kHz].

[0014] In a more specific technical solution, step S2 includes:

[0015] S21. In accordance with the preset operation and maintenance procedures, before each test, compare the test temperatures to control the temperature difference within the preset range;

[0016] S22. Query the historical charging and discharging data of the battery pack monitoring device under test to avoid the routine maintenance equalization charging phase.

[0017] In a more specific technical solution, in step S22, the historical charge and discharge data of the battery pack monitoring device under test are queried to ensure that the operating conditions of the battery pack under test are consistent with the initial operating conditions.

[0018] This invention follows the operation and maintenance procedures for DC power supply devices in power systems. Before each test, the test temperature is compared and the temperature difference is controlled within a set range. Then, the historical charging and discharging data of the battery pack under test are queried to ensure that the operating conditions of the battery pack under test are consistent with the initial operating conditions, thus avoiding the equalization charging phase of routine maintenance.

[0019] In a more specific technical solution, step S3 includes:

[0020] S31. Calculate the impedance difference ΔZ1, ΔZ2, ΔZ3 between the test electrochemical impedance spectrum and the reference electrochemical impedance spectrum at a specific frequency point.

[0021] S32. The impedance differences ΔZ1, ΔZ2, and ΔZ3 are arithmetically averaged to obtain the relative reference electrochemical impedance spectrum deviation ΔZ(b) of each tested battery in the tested battery pack.

[0022] S33. Based on the relative deviation ΔZ(b) of the reference electrochemical impedance spectroscopy, for the impedance Z at a specific frequency in the reference electrochemical impedance spectroscopy... s1 Z s2 and Z s3 The arithmetic mean Z sa The deviation is calculated to obtain the deviation rate ΔZ(b). a :

[0023] S34. Calculate the average impedance spectrum data Zta1, Zta2, Zta3 at the characteristic frequency points of the impedance spectrum of each tested battery.

[0024] S35. The impedance measurement value Z of each tested battery in the tested battery pack at the characteristic frequency point. t1 Z t2 Z t3 The dispersion of the impedance mean is calculated to obtain the dispersion ΔZ(b). b ;

[0025] S36. Based on the detected electrochemical impedance spectroscopy, calculate the deviation ΔZ(b) and dispersion ΔZ(b) relative to the reference electrochemical impedance spectroscopy. b To determine the internal electrochemical characteristics of the tested battery pack, and thereby obtain data on the health status of the tested battery pack.

[0026] In a more specific technical solution, step S33 uses the following logic to calculate the deviation:

[0027] ΔZ(b) a =(ΔZ(b)-Z sa ) / Z sa ×100%.

[0028] In a more specific technical solution, in step S35, the following logic is used to calculate the dispersion to obtain the dispersion ΔZ(b). b :

[0029] ΔZ(b) n =(Z tn -Z tan ) / Z tan ×100%

[0030] n = 1, 2, 3...

[0031] ΔZ(b) b =∑|ΔZ(b) n |

[0032] In a more specific technical solution, in step S36, the relative reference electrochemical impedance spectral deviation ΔZ(b) and dispersion ΔZ(b) are calculated using the following logic. b :

[0033] ΔZ=k1×ΔZ(b) a +k2×ΔZ(b) b

[0034] In the formula, k1 and k2 are weights.

[0035] This invention introduces the concept of electrochemical impedance spectroscopy, expands the dimensions of battery monitoring data to multiple frequency domains, and extracts characteristic quantities related to the healthy life of the battery based on electrochemical impedance spectroscopy to complete the assessment of the healthy life of the battery, which can significantly improve the accuracy and effectiveness of battery assessment.

[0036] In a more specific technical solution, the power system battery pack inspection system includes:

[0037] The reference electrochemical impedance spectroscopy acquisition module is used to collect and calculate the impedance spectrum of the test battery pack, thereby obtaining the reference electrochemical impedance spectrum of the test battery pack.

[0038] The electrochemical impedance spectroscopy measurement module is used to perform electrochemical impedance spectroscopy measurements on the test battery under the same operating conditions and according to a preset cycle, and to obtain the test electrochemical impedance spectrum.

[0039] The battery pack health status assessment module is used to determine the deviation between the tested electrochemical impedance spectroscopy and the reference electrochemical impedance spectroscopy, as well as the degree of inconsistency of the electrochemical impedance spectra of each battery. Based on the deviation and inconsistency, a weighted calculation is performed to determine the health status of the tested battery pack. The battery pack health status assessment module is connected to the reference electrochemical impedance spectroscopy acquisition module and the electrochemical impedance spectroscopy measurement module.

[0040] Compared with the prior art, the present invention has the following advantages: by obtaining the reference electrochemical impedance spectrum and the test electrochemical impedance spectrum of the tested battery, and calculating the deviation between the electrochemical impedance spectrum and the reference electrochemical impedance spectrum, the present invention can determine the health status of the tested battery pack, which helps to improve the battery's power supply and safe and reliable operation.

[0041] This invention follows the operation and maintenance procedures for DC power supply devices in power systems. Before each test, the test temperature is compared and the temperature difference is controlled within a set range. Then, the historical charging and discharging data of the battery pack under test are queried to ensure that the operating conditions of the battery pack under test are consistent with the initial operating conditions, thus avoiding the equalization charging phase of routine maintenance.

[0042] This invention introduces the concept of electrochemical impedance spectroscopy, expands the dimensions of battery monitoring data to multiple frequency domains, and extracts characteristic quantities related to the healthy life of the battery based on electrochemical impedance spectroscopy to complete the assessment of the healthy life of the battery, which can significantly improve the accuracy and effectiveness of battery assessment.

[0043] This invention solves the technical problems of inaccurate assessment of battery usable capacity and remaining lifespan, and low validity of assessment data in the prior art. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the basic steps of the power system battery pack inspection method based on electrochemical impedance spectroscopy in Embodiment 1 of the present invention.

[0045] Figure 2 This is a schematic diagram illustrating the specific steps for obtaining and testing electrochemical impedance spectroscopy in Example 1 of the present invention;

[0046] Figure 3 This is a schematic diagram illustrating the specific steps for determining the health status of a battery pack in Embodiment 1 of the present invention. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of 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 some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0048] Example 1

[0049] like Figure 1 As shown, the power system battery pack inspection method based on electrochemical impedance spectroscopy provided by this invention includes the following basic steps:

[0050] S1. Obtain the reference electrochemical impedance spectrum of the battery under test in advance;

[0051] In this embodiment, in step S1 of pre-acquiring the reference electrochemical impedance spectrum of the test battery, the positive and negative electrodes of the battery pack electrochemical impedance spectrum detection device are electrically connected to the positive and negative electrodes of the test battery pack, respectively. The impedance spectrum of the test battery is collected and calculated by the acquisition main control board to form an electrochemical impedance detection spectrum.

[0052] In this embodiment, the reference electrochemical impedance spectroscopy of the individual battery cells in the test battery pack is obtained under conditions where the float charging time is sufficiently long. In this embodiment, after, for example, 2 to 3 discharge-float charging-equalizing charging processes, the float charging continues for, for example, 48 hours. The positive and negative terminals of the battery pack electrochemical impedance spectroscopy detection device are electrically connected to the positive and negative terminals of the test battery pack, respectively. In this embodiment, the test frequency can be within a range including, but not limited to, 0.01 Hz to 7.8 kHz, applied to the test battery. The impedance spectrum of the test battery is collected and calculated by the acquisition main control board to form an electrochemical impedance detection spectrum.

[0053] S2. Select the same operating conditions and periodically perform electrochemical impedance spectroscopy measurements on the tested battery to obtain the test electrochemical impedance spectrum.

[0054] In this embodiment, in step S2 of measuring the electrochemical impedance spectroscopy of the battery pack under test, the historical charge and discharge data of the battery pack monitoring device under test are queried to ensure that the operating conditions of the battery pack under test are consistent with the initial operating conditions, thus avoiding the equalization charging phase of routine maintenance.

[0055] like Figure 2 As shown, in this embodiment, step S2, which involves obtaining the electrochemical impedance spectroscopy spectrum, further includes the following specific steps:

[0056] S21. In accordance with the operation and maintenance procedures for DC power supply devices in power systems, compare the test temperatures before each test and control the temperature difference within the set range.

[0057] S22. Query the historical charging and discharging data of the battery pack under test monitoring device to ensure that the operating conditions of the battery pack under test are consistent with the initial operating conditions, and avoid the equalization charging phase of routine maintenance.

[0058] S3. Calculate the deviation of the electrochemical impedance spectrum from the reference electrochemical impedance spectrum and the degree of inconsistency of the electrochemical impedance spectra of each battery. After weighted calculation, the results are used to determine the health status of the tested battery pack.

[0059] In this embodiment, in step S3 of calculating the deviation between the test electrochemical impedance spectrum and the reference electrochemical impedance spectrum, the impedance deviation rate at a specific frequency is obtained by calculating the impedance difference between the test electrochemical impedance spectrum and the reference electrochemical impedance spectrum at a specific same frequency point, and the impedance dispersion is calculated.

[0060] like Figure 3 As shown, in this embodiment, step S3, which determines the health status of the battery pack, further includes the following specific steps:

[0061] S31. Calculate the impedance difference ΔZ1, ΔZ2, ΔZ3 between the test electrochemical impedance spectrum and the reference electrochemical impedance spectrum at a specific same frequency point; in this embodiment, the specific same frequency can be selected as, for example, 1KHz, 1Hz, and 0.1Hz.

[0062] S32. The impedance differences ΔZ1, ΔZ2, and ΔZ3 are arithmetically averaged to obtain the deviation ΔZ(b) of each battery in the battery pack relative to the reference electrochemical impedance spectrum.

[0063] S33. The impedance Z at a specific frequency in the reference electrochemical impedance spectrum is obtained by measuring the ΔZ(b) deviation of each cell. s1 Z s2 and Z s3 The arithmetic mean Z sa The deviation is calculated to obtain the deviation rate ΔZ(b). a :

[0064] ΔZ(b) a =(ΔZ(b)-Z sa ) / Z sa ×100%

[0065] S34. Calculate the average values ​​Zta1, Zta2, and Zta3 of the impedance spectrum data at the characteristic frequency points of the impedance spectrum of each battery. In this embodiment, the specific same frequency can be selected as, for example, 1KHz, 1Hz, and 0.1Hz.

[0066] S35. Measure the impedance Z of each battery in the battery pack at its characteristic frequency. t1 Z t2 Z t3 The dispersion ΔZ(b) is obtained by calculating the dispersion of the mean impedance. b In this embodiment, the specific same frequency can generally be selected as, for example, 1KHz, 1Hz, and 0.1Hz.

[0067] ΔZ(b) n =(Z tn -Z tan ) / Z tan ×100%

[0068] n = 1, 2, 3...

[0069] ΔZ(b) b =∑|ΔZ(b) n |

[0070] S36. The deviation and dispersion calculated based on the detected electrochemical impedance spectroscopy are used to determine the internal electrochemical characteristics of the tested battery pack, thereby completing the assessment of the health status of the tested battery pack:

[0071] ΔZ=k1×ΔZ(b) a +k2×ΔZ(b) b

[0072] Among them, k1 and k2 are weights, which can be adjusted according to the characteristics of different batteries. Generally, k1 = 0.5 and k2 = 0.5 are recommended.

[0073] In summary, this invention, by obtaining the reference electrochemical impedance spectroscopy and the test electrochemical impedance spectroscopy of the tested battery and calculating the deviation between the electrochemical impedance spectroscopy and the reference electrochemical impedance spectroscopy, determines the health status of the tested battery pack, which helps to improve the battery's power supply and safe and reliable operation.

[0074] This invention follows the operation and maintenance procedures for DC power supply devices in power systems. Before each test, the test temperature is compared and the temperature difference is controlled within a set range. Then, the historical charging and discharging data of the battery pack under test are queried to ensure that the operating conditions of the battery pack under test are consistent with the initial operating conditions, thus avoiding the equalization charging phase of routine maintenance.

[0075] This invention introduces the concept of electrochemical impedance spectroscopy, expands the dimensions of battery monitoring data to multiple frequency domains, and extracts characteristic quantities related to the healthy life of the battery based on electrochemical impedance spectroscopy to complete the assessment of the healthy life of the battery, which can significantly improve the accuracy and effectiveness of battery assessment.

[0076] This invention solves the technical problems of inaccurate assessment of battery usable capacity and remaining lifespan, and low validity of assessment data in the prior art.

[0077] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for inspecting power system battery packs based on electrochemical impedance spectroscopy, characterized in that, The method includes: S1. Collect and calculate the impedance spectrum of the tested battery pack to obtain the reference electrochemical impedance spectrum of the tested battery pack. S2. Under the same operating conditions, the test battery is subjected to electrochemical impedance spectroscopy measurement according to a preset cycle to obtain the test electrochemical impedance spectrum. S3. Calculate the deviation between the tested electrochemical impedance spectrum and the reference electrochemical impedance spectrum, and the degree of inconsistency of the electrochemical impedance spectra of each battery. Perform a weighted calculation based on the deviation and the degree of inconsistency to determine the health status of the tested battery pack. S3 includes: S31. Calculate the impedance difference ΔZ1, ΔZ2, ΔZ3 between the test electrochemical impedance spectrum and the reference electrochemical impedance spectrum at a specific frequency point. S32. The impedance differences ΔZ1, ΔZ2, and ΔZ3 are arithmetically averaged to obtain the relative reference electrochemical impedance spectrum deviation ΔZ(b) of each of the tested batteries in the tested battery pack. S33、According to the relative reference electrochemical impedance spectrum deviation ΔZ(b), the arithmetic mean value Z sa of the impedance Z s1 , Z s2 and Z s3 of the same specific frequency in the reference electrochemical impedance spectrum is calculated to obtain the deviation rate ΔZ(b) a : S34. Calculate the average values ​​Zta1, Zta2, and Zta3 of the impedance spectrum data at the characteristic frequency points of the impedance spectrum of each of the tested batteries. S35. Measure the impedance Z at the characteristic frequency point of each of the tested batteries in the tested battery pack. t1 Z t2 Z t3 The dispersion of the impedance mean is calculated to obtain the dispersion ΔZ(b). b ; In S35, the following logic is used to calculate the dispersion to obtain the dispersion ΔZ(b). b : ΔZ(b) n =(Z tn - Z tan ) / Z tan ×100% n=1、2、3 S36. Calculate the deviation rate ΔZ(b) based on the detected electrochemical impedance spectroscopy. a The dispersion ΔZ(b) b The purpose is to determine the internal electrochemical characteristics of the tested battery pack, thereby obtaining data on the health status of the tested battery pack.

2. The method for inspecting power system battery banks according to claim 1, characterized in that, In step S1, the positive and negative electrodes of the battery pack electrochemical impedance spectroscopy detection device are connected to the positive and negative electrodes of the battery pack under test, respectively, so as to collect and process the impedance spectrum of the battery pack under test and form the reference electrochemical impedance spectrum.

3. The method for inspecting power system battery banks according to claim 1, characterized in that, In step S1, the test frequency range for the tested battery pack includes: [0.01Hz, 7.8kHz].

4. The method for inspecting power system battery banks according to claim 1, characterized in that, Step S2 includes: S21. In accordance with the preset operation and maintenance procedures, before each test, compare the test temperatures to control the temperature difference within the preset range; S22. Query the historical charge and discharge data of the test battery pack monitoring device to avoid the routine maintenance equalization charging phase.

5. The method for inspecting power system battery banks according to claim 4, characterized in that, In step S22, the historical charge and discharge data of the battery pack monitoring device under test are queried to ensure that the operating conditions of the battery pack under test are consistent with the initial operating conditions.

6. The method for inspecting power system battery banks according to claim 1, characterized in that, In step S33, the deviation is calculated using the following logic: ΔZ(b) a =(ΔZ(b)- Z sa ) / Z sa ×100%。 7. The method for inspecting power system battery banks according to claim 1, characterized in that, In step S36, the deviation rate ΔZ(b) is calculated using the following logic. a The dispersion ΔZ(b) b : In the formula, k1 and k2 are weights.

8. A power system battery pack inspection system, used to perform the power system battery pack inspection method according to any one of claims 1 to 7, characterized in that, The system includes: The reference electrochemical impedance spectroscopy acquisition module is used to collect and calculate the impedance spectrum of the test battery pack, thereby obtaining the reference electrochemical impedance spectrum of the test battery pack. An electrochemical impedance spectroscopy (EIS) measurement module is used to perform EIS measurements on the tested battery under the same operating conditions and according to a preset cycle, and to obtain the test EIS spectrum. The battery pack health status assessment module is used to determine the deviation between the tested electrochemical impedance spectroscopy and the reference electrochemical impedance spectroscopy, and the degree of inconsistency of the electrochemical impedance spectra of each battery. Based on the deviation and the degree of inconsistency, a weighted calculation is performed to determine the health status of the tested battery pack. The battery pack health status assessment module is connected to the reference electrochemical impedance spectroscopy acquisition module and the electrochemical impedance spectroscopy measurement module.

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