Battery impedance spectrum detection system and method

Abstract

The invention relates to a battery impedance spectroscopy detection system and method. According to the invention, the multi-frequency-point mixed current signal is adopted as the excitation current to be injected into the to-be-detected battery pack, so that impedance spectrum information of multiple frequency points can be obtained, and the EIS detection efficiency is improved; deriving first data by modeling and testing an equivalent circuit model of the battery pack to be tested and determining an initial value of the equivalent circuit, by converting at least one initial value using a preset conversion coefficient, and calculating a first voltage value based on the first data; the method includes obtaining a first voltage value, obtaining voltage amplitude information by exciting the battery pack, comparing the first voltage value with the voltage amplitude information and correcting a conversion coefficient based on a comparison result, calculating a final parameter value based on the corrected conversion coefficient, and instructing to obtain an impedance spectrum value of the battery pack to be measured by applying the final parameter value to the equivalent circuit. Thus, reassembly is facilitated and cost is reduced by performing non-destructive measurement without disassembling the battery into battery cells.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a battery impedance spectrum detection system and method. Background Art

[0002] Electrochemical impedance spectroscopy (EIS) is a very important method in electrochemical testing technology and an important means to study electrode process dynamics and surface phenomena. Electrochemical impedance spectroscopy has been widely used in the field of electrochemical energy, such as fuel cells, supercapacitors, etc. EIS is used to detect the impedance of the battery pack, analyze the battery pack power (status of charge-SOC), health (status of health-SoH) and temperature information, and improve the safety of battery use. The existing EIS detection generally uses a single-frequency excitation current source to inject current into the battery and then detect the voltage component, but each round of acquisition can only obtain impedance information of one frequency. If the impedance spectrum of multiple frequencies is to be collected, it will take a long time and be inefficient because the frequency detection is performed in sequence. In addition, in the prior art, when measuring the impedance spectrum of the battery pack, the EIS device for detecting the impedance of the battery pack generally disassembles the battery pack into single cells for measurement, but when the battery pack is disassembled into single cells, the welding part of the single cell lead will be damaged, and there is a disadvantage that it is difficult to reassemble after measurement. Summary of the invention

[0003] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a battery impedance spectrum detection system and method, which can solve the problem of low EIS detection efficiency. By modeling an equivalent circuit model (ECM) and correcting the measured impedance spectrum to estimate the impedance spectrum value of the detection battery pack, non-destructive measurement can be performed, greatly reducing the detection cost.

[0004] To solve the above technical problems, according to the first aspect of this article, the present invention provides a battery impedance spectrum detection system, including a signal generation module, an excitation module, a signal recognition module, a filtering module, a battery pack to be tested, and an analysis module; The signal generating module is coupled to the excitation module and is configured to generate a multi-frequency mixed current signal and send it to the excitation module; The excitation module is coupled to the battery pack to be tested, and is configured to generate an excitation current after receiving the mixed current signal, and send the excitation current to the battery pack to be tested; The signal recognition module is coupled to the battery pack to be tested and is configured to obtain a multi-frequency voltage signal after the excitation current acts on the battery pack to be tested; The filtering module is coupled to the signal identification module and is configured to set parallel filtering channels having the same number as the multiple frequency points to extract the voltage amplitude information of the multiple frequency points; The analysis module is coupled to the filtering module, and is configured to calculate the impedance spectrum value of the battery pack to be tested based on the voltage amplitude information and the equivalent circuit model.

[0005] In one embodiment of the present invention, the excitation module includes a digital-to-analog converter, a loop amplifier and a complementary current mirror; the digital-to-analog converter is coupled to the loop amplifier, and is configured to convert the received multi-frequency mixed current signal from the digital domain into a current domain signal; the loop amplifier is coupled to the complementary current mirror, and is configured to amplify the current domain signal; the complementary current mirror is coupled to the battery group to be tested, and is configured to copy the amplified current domain signal and inject it into the battery group to be tested.

[0006] In one embodiment of the present invention, the signal identification module includes an input stage circuit, an output stage circuit, a DC component servo loop, and an analog-to-digital converter; the input stage circuit is coupled to the DC component servo loop, which is configured to convert a voltage signal into a current signal; the DC component servo loop is configured to remove the DC component of the current signal; the output stage circuit is coupled to the DC component servo loop, which is configured to amplify the current signal after the DC component is removed and convert the amplified current signal into a voltage signal; the analog-to-digital converter is coupled to the output stage circuit, which is configured to sample the voltage signal to obtain a voltage signal with multiple frequency points.

[0007] In one embodiment of the present invention, the calculating the impedance spectrum value of the battery pack to be tested based on the voltage amplitude information and the equivalent circuit model includes: firstly modeling the equivalent circuit model, and the modeling function is as follows: Wherein, R0: electrolyte resistance; R1: resistance of EIS device; R2: resistance of solid electrolyte interphase layer; R3: charge transfer resistance; L1: line inductance of EIS device; C2: capacitance of solid electrolyte interphase layer; C3: capacitance in electrode and electrolytic double layer; t: time; K: constant; W: Warburg impedance coefficient; U(t) and I(t) are real-time voltage and current, respectively.

[0008] In one embodiment of the present invention, the calculation of the impedance spectrum value of the battery pack to be tested based on the voltage amplitude information and the equivalent circuit model includes: determining an initial value of the equivalent circuit model; converting the initial value into a first data through a conversion coefficient, and calculating a first voltage value based on the first data; comparing the voltage amplitude information and the first voltage value, and correcting the conversion coefficient according to the comparison result; calculating a final parameter value according to the corrected conversion coefficient; and obtaining the impedance spectrum value of the battery pack to be tested by inputting the final parameter value into the equivalent circuit model.

[0009] In order to solve the above technical problems, according to the second aspect of this document, the present invention provides a battery impedance spectrum detection method, which is applied to the above battery impedance spectrum detection system, comprising: Generate a multi-frequency mixed current signal; generate an excitation current after receiving the mixed current signal; obtain a multi-frequency voltage signal after the excitation current acts on the battery pack to be tested; set parallel filter channels with the same number as the multi-frequency points to extract the voltage amplitude information of the multi-frequency points; calculate the impedance spectrum value of the battery pack to be tested based on the voltage amplitude information and the equivalent circuit model. The specific steps of the detection method are consistent with the above and will not be repeated one by one.

[0010] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: by adopting a multi-frequency mixed current signal as the excitation current injected into the battery pack to be tested, the impedance spectrum information of multiple frequency points can be obtained, thereby improving the EIS detection efficiency; at the same time, the DC component servo loop in the signal recognition module removes the DC component of the collected voltage signal, thereby improving the test accuracy; in addition, parallel filtering channels with the same number as the frequency points are set in the filtering module to extract the voltage amplitude information of the multiple frequency points, thereby improving the processing speed.

[0011] The present invention models an equivalent circuit model of a battery pack to be tested and determines an initial value of the equivalent circuit, converts at least one initial value using a preset conversion coefficient to derive first data and calculates a first voltage value based on the first data; obtains voltage amplitude information by exciting the battery pack, compares the first voltage value and the voltage amplitude information and corrects the conversion coefficient based on the comparison result, calculates a final parameter value based on the corrected conversion coefficient, and indicates to obtain an impedance spectrum value of the battery pack to be tested by applying the final parameter value to the equivalent circuit. This facilitates reassembly and reduces costs by performing non-destructive measurement without disassembling the battery into battery cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a schematic diagram of a battery impedance spectrum detection system of the present invention; Figure 2 It is a schematic diagram of an excitation module in a battery impedance spectrum detection system of the present invention; Figure 3 It is a schematic diagram of a signal recognition module in a battery impedance spectrum detection system of the present invention; Figure 4 is the equivalent circuit model in the present invention; Figure 5 It is a flow chart of the battery impedance spectrum detection method of the present invention. DETAILED DESCRIPTION

[0013] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation mode, structure, characteristics and effects of the present invention are described in detail below in combination with the accompanying drawings and preferred embodiments.

[0014] In order to make the purpose, technical solutions and advantages of the embodiments of this article clearer, the technical solutions in the embodiments of this article will be clearly and completely described below in conjunction with the drawings in the embodiments of this article. Obviously, the described embodiments are part of the embodiments of this article, not all of the embodiments. Based on the embodiments in this article, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this article. It should be noted that the embodiments in this article and the features in the embodiments can be combined with each other arbitrarily unless there is a conflict. Unless the context clearly requires, the words "including", "comprising" and other similar words in the entire specification and claims should be interpreted as including. In order to better understand the first specific embodiment of the present invention, such as Figure 1 As shown, the present invention provides a battery impedance spectrum detection system, including a signal generation module, an excitation module, a signal recognition module, a filtering module, a battery pack to be tested, and an analysis module; the signal generation module is coupled to the excitation module, and is configured to generate a multi-frequency mixed current signal and send it to the excitation module.

[0015] Specifically, the present invention first uses a multi-frequency mixed sine wave generating circuit to generate a multi-frequency mixed control signal of the required EIS bandwidth, and uses the control signal to inject into a current source to generate a multi-frequency point mixed current signal. The detection speed can be accelerated by injecting the generated multi-frequency mixed current.

[0016] The excitation module is coupled to the battery pack to be tested, and is configured to generate an excitation current after receiving the mixed current signal, and send the excitation current to the battery pack to be tested.

[0017] In a preferred embodiment, another specific embodiment of the present invention is as follows: Figure 2As shown, the excitation module includes a digital-to-analog converter, a loop amplifier and a complementary current mirror; the digital-to-analog converter is coupled to the loop amplifier, and is configured to convert the received multi-frequency mixed current signal from the digital domain into a current domain signal; the loop amplifier is coupled to the complementary current mirror, and is configured to amplify the current domain signal; the complementary current mirror is coupled to the battery pack to be tested, and is configured to replicate the amplified current domain signal and inject it into the battery pack to be tested. The excitation module can simultaneously inject current into multiple battery cells connected in series, ensuring that the voltage of multiple battery cells is read in parallel.

[0018] Specifically, the current signal is used as an EIS detection excitation source and injected into the battery pack to be tested to generate a small signal voltage related to the impedance, which is convenient for subsequent further detection.

[0019] The signal identification module is coupled to the battery pack to be tested, and is configured to obtain a multi-frequency voltage signal after the excitation current acts on the battery pack to be tested.

[0020] In a preferred embodiment, another specific embodiment of the present invention is as follows: Figure 3 As shown, the signal identification module includes an input stage circuit, an output stage circuit, a DC component servo loop, and an analog-to-digital converter; the input stage circuit is coupled to the DC component servo loop, which is configured to convert a voltage signal into a current signal; the DC component servo loop is configured to remove the DC component of the current signal; the output stage circuit is coupled to the DC component servo loop, which is configured to amplify the current signal after the DC component is removed, and convert the amplified current signal into a voltage signal; the analog-to-digital converter is coupled to the output stage circuit, which is configured to sample the voltage signal to obtain a voltage signal with multiple frequency points.

[0021] Since there is an interfering voltage DC component when detecting the voltage component, the impedance amplitude of the voltage component will be inaccurately analyzed. The present invention adopts a DC component servo loop to effectively remove the interfering component, amplify the small signal component, increase the effective use range of the analog-to-digital conversion frequency, and improve the detection accuracy.

[0022] The filtering module is coupled to the signal identification module and is configured to set parallel filtering channels with the same number as the multiple frequency points to extract the voltage amplitude information of the multiple frequency points. The use of parallel filtering channels can speed up the detection speed.

[0023] The analysis module is coupled to the filtering module, and is configured to calculate the impedance spectrum value of the battery pack to be tested based on the voltage amplitude information and the equivalent circuit model.

[0024] In a preferred embodiment, another specific embodiment of the present invention is as follows: Figure 4As shown, the battery impedance model is a combination of a resistor R, a capacitor C, an inductor L, and a phase element CPE. Specifically, it can be represented by a combination of at least one parameter of resistors R0, R1, R2, R3, capacitors C2, C3, and inductor L1.

[0025] In a preferred embodiment, the equivalent circuit model is modeled, and the modeling function is as follows: R0: electrolyte resistance; R1: resistance of the EIS device; R2: resistance of the solid electrolyte interphase layer; R3: charge transfer resistance; L1: line inductance of the EIS device; C2: capacitance of the solid electrolyte interphase layer; C3: capacitance in the electrode and electrolytic double layer; t: time; K: constant; W: Warburg impedance coefficient; U(t) and I(t) are the real-time voltage and current, respectively.

[0026] In a preferred embodiment, calculating the impedance spectrum value of the battery pack to be tested includes: determining an initial value of the equivalent circuit model; Specifically, an initial value of at least one of resistance, capacitance, inductance, and CPE in the battery equivalent circuit model as shown in Table 1 is determined.

[0027] Table 1 Initial values ​​of parameters of equivalent circuit model parameter Initial Value R0 0.0058 R1 0.24 R2 0.00168 R3 0.0028 L1 C2 4.203 C3 30.58 The initial value is converted by a conversion coefficient to obtain first data, and a first voltage value is calculated based on the first data.

[0028] Specifically, the initial value is divided by a conversion coefficient n to obtain the first data. The conversion coefficient n may be a constant for converting the initial value obtained from the battery pack into the number of batteries.

[0029] According to one embodiment, the initial value of the conversion coefficient n may be defined based on the number of batteries included in the battery pack. For example, as shown in Table 2, some initial values ​​of the conversion coefficient n may be defined based on the number of batteries included in the battery pack (50 battery cells). Since the inductor L1 and the capacitors C2 and C3 have little effect on the change in the value of the impedance R, the conversion coefficient may not be defined.

[0030] Table 2 Initial values ​​of parameters of equivalent circuit model parameter Initial Value Conversion Factor First Data R0 0.0058 20.25 0.00028642 R1 0.24 18 0.013 R2 0.00168 18 0.000093 R3 0.0028 18 0.000156 L1 -- C2 4.203 -- 4.203 C3 30.58 -- 30.58 Specifically, the first voltage value is calculated by multiplying the internal resistance value of the battery by the current value based on a function of the equivalent circuit model.

[0031] In a preferred embodiment, the calculating the impedance spectrum value of the battery pack to be tested based on the voltage amplitude information and the equivalent circuit model includes: comparing the voltage amplitude information and the first voltage value, and correcting a conversion coefficient according to the comparison result.

[0032] Specifically, the correction conversion coefficient can minimize the difference between the first voltage value of the battery and the voltage amplitude information to calculate a more accurate battery cell. Therefore, the initial value of the conversion coefficient cannot be an accurate value at first. The initial value of the conversion coefficient can be input by an administrator or a preset value corresponding to the number of batteries.

[0033] Specifically, in one embodiment, a final parameter value is calculated according to the corrected conversion coefficient; and the impedance spectrum value of the battery pack to be tested is obtained by inputting the final parameter value into the equivalent circuit model.

[0034] A fifth specific embodiment of the present invention is as follows Figure 5 As shown, the present invention proposes a battery impedance spectrum detection method, which is applied to the above-mentioned battery impedance spectrum detection system, comprising: 101: Generate a multi-frequency mixed current signal; 102: Generate an excitation current after receiving the mixed current signal; 103: obtaining a multi-frequency voltage signal after the excitation current acts on the battery pack to be tested; 104: Setting the same number of parallel filtering channels as the multiple frequency points to extract voltage amplitude information of the multiple frequency points; 105: Calculate an impedance spectrum value of the battery pack to be tested based on the voltage amplitude information and the equivalent circuit model.

[0035] In a preferred embodiment, the calculation of the impedance spectrum value of the battery pack to be tested based on the voltage amplitude information and the equivalent circuit model includes: firstly modeling the equivalent circuit model, and the modeling function is as follows: R0: electrolyte resistance; R1: resistance of the EIS setup; R2: resistance of the solid electrolyte interphase layer; R3: charge transfer resistance; L1: line inductance of the EIS device; C2: capacitance of the solid electrolyte interphase layer; C3: capacitance in the electrode and electrolytic double layer; t: time; K: constant; W: Warburg impedance coefficient, U(t) and I(t) are the real-time voltage and current respectively.

[0036] In a preferred embodiment, the calculating the impedance spectrum value of the battery pack to be tested based on the voltage amplitude information and the equivalent circuit model includes: determining an initial value of the equivalent circuit model; The initial value is converted by a conversion coefficient to obtain first data, and a first voltage value is calculated based on the first data.

[0037] In a preferred embodiment, the calculating the impedance spectrum value of the battery pack to be tested based on the voltage amplitude information and the equivalent circuit model includes: Compare the voltage amplitude information with the first voltage value, and correct the conversion coefficient according to the comparison result: Calculate the final parameter value based on the corrected conversion factor; The impedance spectrum value of the battery pack to be tested is obtained by inputting the final parameter value into the equivalent circuit model.

[0038] The present invention adopts a multi-frequency mixed current signal as an excitation current to inject into the battery pack to be tested, so that impedance spectrum information of multiple frequency points can be obtained, thereby improving the efficiency of EIS detection; at the same time, the DC component servo loop in the signal identification module removes the DC component of the collected voltage signal, thereby improving the accuracy of the test; in addition, the filter module is provided with parallel filter channels with the same number of frequency points to extract the voltage amplitude information of the multiple frequency points, thereby improving the processing speed. By modeling the equivalent circuit model of the battery pack to be tested and determining the initial value of the equivalent circuit, first data is derived by converting at least one initial value using a preset conversion coefficient and a first voltage value is calculated based on the first data; voltage amplitude information is obtained by exciting the battery pack, the first voltage value and the voltage amplitude information are compared and the conversion coefficient is corrected based on the comparison result, the final parameter value is calculated based on the corrected conversion coefficient, and the impedance spectrum value of the battery pack to be tested is obtained by applying the final parameter value to the equivalent circuit. This facilitates reassembly and reduces costs by performing non-destructive measurement without disassembling the battery into battery cells.

[0039] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A battery impedance spectrum detection system, characterized in that: It includes a signal generation module, an excitation module, a signal recognition module, a filtering module, a battery pack to be tested, and an analysis module; The signal generating module is coupled to the excitation module and is configured to generate a multi-frequency mixed current signal and send it to the excitation module; The excitation module is coupled to the battery pack to be tested, and is configured to generate an excitation current after receiving the mixed current signal, and send the excitation current to the battery pack to be tested; The signal recognition module is coupled to the battery pack to be tested and is configured to obtain a multi-frequency voltage signal after the excitation current acts on the battery pack to be tested; The filtering module is coupled to the signal identification module and is configured to set parallel filtering channels having the same number as the multiple frequency points to extract the voltage amplitude information of the multiple frequency points; The analysis module is coupled to the filtering module, and is configured to calculate the impedance spectrum value of the battery pack to be tested based on the voltage amplitude information and the equivalent circuit model.

2. A battery impedance spectrum detection system according to claim 1, characterized in that: The excitation module includes a digital-to-analog converter, a loop amplifier and a complementary current mirror; the digital-to-analog converter is coupled to the loop amplifier and is configured to convert the received multi-frequency mixed current signal from the digital domain into a current domain signal; the loop amplifier is coupled to the complementary current mirror and is configured to amplify the current domain signal; The complementary current mirror is coupled to the battery pack under test and is configured to replicate the amplified current domain signal and then inject it into the battery pack under test.

3. A battery impedance spectrum detection system according to claim 1, characterized in that: The signal identification module includes an input stage circuit, an output stage circuit, a DC component servo loop, and an analog-to-digital converter; the input stage circuit is coupled to the DC component servo loop, which is configured to convert a voltage signal into a current signal; the DC component servo loop is configured to remove the DC component of the current signal; the output stage circuit is coupled to the DC component servo loop, which is configured to amplify the current signal after the DC component is removed and convert the amplified current signal into a voltage signal; the analog-to-digital converter is coupled to the output stage circuit, which is configured to sample the voltage signal to obtain a voltage signal with multiple frequency points.

4. A battery impedance spectrum detection system according to claim 1, characterized in that: The calculating the impedance spectrum value of the battery pack to be tested based on the voltage amplitude information and the equivalent circuit model includes: firstly modeling the equivalent circuit model, and the modeling function is as follows: Wherein, R0: electrolyte resistance; R1: resistance of EIS device; R2: resistance of solid electrolyte interphase layer; R3: charge transfer resistance; L1: line inductance of EIS device; C2: capacitance of solid electrolyte interphase layer; C3: capacitance in electrode and electrolytic double layer; t: time; K: constant; W: Warburg impedance coefficient; U(t) and I(t) are real-time voltage and current, respectively.

5. A battery impedance spectrum detection system according to claim 4, characterized in that: The calculating the impedance spectrum value of the battery pack to be tested based on the voltage amplitude information and the equivalent circuit model includes: determining an initial value of the equivalent circuit model; The initial value is converted by a conversion coefficient to obtain first data, and a first voltage value is calculated based on the first data.

6. A battery impedance spectrum detection system according to claim 5, characterized in that: The calculating the impedance spectrum value of the battery pack to be tested based on the voltage amplitude information and the equivalent circuit model includes: Compare the voltage amplitude information with the first voltage value, and correct the conversion coefficient according to the comparison result: Calculate the final parameter value based on the corrected conversion factor; The impedance spectrum value of the battery pack to be tested is obtained by inputting the final parameter value into the equivalent circuit model.

7. A battery impedance spectrum detection method, applied to the battery impedance spectrum detection system according to any one of claims 1 to 6, comprising: Generate multi-frequency mixed current signal; generating an excitation current after receiving the mixed current signal; The excitation current acts on the battery pack to be tested to obtain a multi-frequency voltage signal; Setting the same number of parallel filtering channels as the multiple frequency points to extract the voltage amplitude information of the multiple frequency points; Based on the voltage amplitude information and the equivalent circuit model, an impedance spectrum value of the battery pack to be tested is calculated.

8. A battery impedance spectrum detection method according to claim 7, characterized in that: The calculating the impedance spectrum value of the battery pack to be tested based on the voltage amplitude information and the equivalent circuit model includes: firstly modeling the equivalent circuit model, and the modeling function is as follows: Wherein, R0: electrolyte resistance; R1: resistance of EIS device; R2: resistance of solid electrolyte interphase layer; R3: charge transfer resistance; L1: line inductance of EIS device; C2: capacitance of solid electrolyte interphase layer; C3: capacitance in electrode and electrolytic double layer; t: time; K: constant; W: Warburg impedance coefficient; U(t) and I(t) are real-time voltage and current, respectively.

9. A battery impedance spectrum detection method according to claim 8, characterized in that: The calculating the impedance spectrum value of the battery pack to be tested based on the voltage amplitude information and the equivalent circuit model includes: determining an initial value of the equivalent circuit model; The initial value is converted by a conversion coefficient to obtain first data, and a first voltage value is calculated based on the first data.

10. A battery impedance spectrum detection method according to claim 9, characterized in that: The calculating the impedance spectrum value of the battery pack to be tested based on the voltage amplitude information and the equivalent circuit model includes: Compare the voltage amplitude information with the first voltage value, and correct the conversion coefficient according to the comparison result: Calculate the final parameter value based on the corrected conversion factor; The impedance spectrum value of the battery pack to be tested is obtained by inputting the final parameter value into the equivalent circuit model.

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