CN111337843B - Generation method of power battery differential capacitor and capacity estimation method and system - Google Patents
Generation method of power battery differential capacitor and capacity estimation method and system Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 73
- 239000003990 capacitor Substances 0.000 title claims abstract description 17
- 238000001453 impedance spectrum Methods 0.000 claims abstract description 52
- 230000005284 excitation Effects 0.000 claims abstract description 47
- 238000012360 testing method Methods 0.000 claims description 54
- 238000001514 detection method Methods 0.000 claims description 33
- 238000004364 calculation method Methods 0.000 claims description 27
- 238000012512 characterization method Methods 0.000 claims description 8
- 239000011159 matrix material Substances 0.000 claims description 6
- 238000004458 analytical method Methods 0.000 claims description 3
- 238000007599 discharging Methods 0.000 abstract description 4
- 238000005265 energy consumption Methods 0.000 abstract description 4
- 238000011156 evaluation Methods 0.000 abstract description 4
- 238000010586 diagram Methods 0.000 description 4
- 238000012545 processing Methods 0.000 description 3
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 2
- 229910001416 lithium ion Inorganic materials 0.000 description 2
- 230000002238 attenuated effect Effects 0.000 description 1
- 238000000157 electrochemical-induced impedance spectroscopy Methods 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
- G01R31/385—Arrangements for measuring battery or accumulator variables
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
- G01R31/385—Arrangements for measuring battery or accumulator variables
- G01R31/387—Determining ampere-hour charge capacity or SoC
- G01R31/388—Determining ampere-hour charge capacity or SoC involving voltage measurements
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
- G01R31/389—Measuring internal impedance, internal conductance or related variables
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
- G01R31/392—Determining battery ageing or deterioration, e.g. state of health
Abstract
The application relates to a power battery differential capacitor generation method, a capacity estimation method and a capacity estimation system. The method for generating the differential capacitor of the power battery comprises the following steps: providing a sample power cell; acquiring impedance data of a sample power battery under different frequency excitations; constructing an electrochemical impedance spectrum of the sample power battery according to impedance data of the sample power battery under different frequencies; and calculating the differential capacitance of the sample power battery based on a regularization method according to the electrochemical impedance spectrum of the sample power battery. The application provides a method for quickly and accurately acquiring a differential capacitor of a power battery. The application also provides a power battery capacity estimation method, which can quickly and accurately estimate the capacity of the power battery to be tested. The power battery capacity estimation method depends on the electrochemical impedance spectrum of the power battery, has the characteristics of accurate and rapid evaluation and the like, and avoids the problems of time consumption, energy consumption and the like caused by long-time charging and discharging of the power battery.
Description
Technical Field
The application relates to the field of new energy automobiles, in particular to a power battery differential capacitor generation method, a power battery differential capacitor capacity estimation method and a power battery differential capacitor capacity estimation system.
Background
Power batteries are important energy sources, especially lithium ion batteries. During the use of the power battery, the battery capacity changes, and the battery capacity needs to be frequently estimated to evaluate the battery health state or predict the battery residual life.
The traditional battery capacity estimation method needs to perform full charge test, full discharge test or periodic charge and discharge test on the battery, is long in time consumption, and cannot meet the requirement of rapid estimation of the capacity of the power battery in actual engineering.
Disclosure of Invention
Therefore, it is necessary to provide a method for generating a differential capacitance of a power battery, a method for estimating the capacity of the power battery, and a system for estimating the capacity of the power battery, in order to solve the problem that the battery capacity of the power battery cannot be rapidly estimated in the conventional scheme.
A method for generating a power battery differential capacitor comprises the following steps:
providing a sample power cell;
acquiring impedance data of the sample power battery under different frequency excitations;
constructing an electrochemical impedance spectrum of the sample power cell according to the impedance data of the sample power cell under different frequencies;
and calculating the differential capacitance of the sample power battery based on a regularization method according to the electrochemical impedance spectrum of the sample power battery.
In one embodiment, the specific step of acquiring impedance data of the sample power battery under excitation of different frequencies includes:
using voltage excitation equipment to generate a first test frequency sine wave to excite the sample power battery, and recording a first detection voltage, wherein the first test frequency is the highest test frequency in sine wave frequencies;
detecting the current of the sample power battery in the voltage excitation process by using a current detection device, and recording a first detection current;
calculating the first detection voltage and the first detection current by using impedance spectrum calculation equipment to obtain impedance of the first test frequency;
adjusting the frequency of a sine wave excited by the voltage, exciting the sample power battery at a second test frequency, recording a second detection voltage, detecting and recording a second detection current, and calculating the impedance of the second test frequency;
and adjusting the sine wave frequency of voltage excitation again, and exciting the sample power battery at the Nth test frequency until the Nth test frequency is the lowest test frequency in the sine wave frequencies, wherein N is a positive integer and is greater than or equal to 3.
In one embodiment, the step of obtaining the impedance of the first test frequency by performing calculation processing on the first detection voltage and the first detection current by using an impedance spectrum calculation device includes:
providing different test sine frequencies, and calculating the complex impedance of the current frequency by adopting the following formula at each test sine frequency:
in the formula, ωiIs the current frequency; vsin (ω)it) is voltage excitation device data; isin (omega)it + phi) is current acquisition device data, Z (omega)i) A complex impedance calculated for that frequency;
when ω isiTesting all the calculated Z (omega) from the highest frequency to the lowest frequencyi) Namely the impedance spectrum of the battery to be tested is marked as Z (omega);
the combination of all frequency complex impedances is the impedance data of the sample power cell under different frequency excitation, Z (omega) is the complex impedance which simultaneously comprises a real part and an imaginary part, so that the complex impedance can be written into a form of adding the real part and the imaginary part,
Z＝ZRe+jZIm
wherein Z isReIs the real part impedance value; zImIs the imaginary impedance value; j is an imaginary number.
In one embodiment, the step of calculating the differential capacitance of the sample power cell based on the regularization method comprises:
the regularization method calculation is performed using the following formula:
wherein, CDCIs the differential capacitance of the sample power cell; j (x) is a minimization objective function; Ω is a frequency matrix; rohmOhmic internal resistance; a' is an impedance real part characterization coefficient; a' is an impedance imaginary part characterization coefficient; x is an impedance characterization parameter; λ is a regularization coefficient; m is a regularization matrix.
In one embodiment, the range of the frequency to be measured is 2kHz to 2mHz when the sample power battery is excited by impedance data under different frequencies.
In one embodiment, when the sample power battery is excited by different frequencies, the frequency point of the frequency to be measured is logarithmically and linearly divided.
A power battery capacity estimation method, comprising:
s10, providing a sample power battery, wherein the capacity of the sample power battery is a first capacity;
s20, acquiring impedance data of the sample power battery with the first capacity under excitation of different frequencies;
s30, constructing an electrochemical impedance spectrum of the sample power cell of the first capacity from the impedance data of the sample power cell of the first capacity at different frequencies;
s40, calculating the differential capacitance of the sample power battery with the first capacity based on a regularization method according to the electrochemical impedance spectrum of the sample power battery with the first capacity;
s50, attenuating the capacity of the sample power battery to a second capacity, and executing the steps S20-S40 by taking the sample power battery with the second capacity as a collection and analysis object so as to obtain the differential capacitance of the sample power battery with the second capacity;
s60, repeating the step of S50 to obtain a differential capacitance of the sample power cell of a third capacity, a differential capacitance of the sample power cell of a fourth capacity … a differential capacitance of the sample power cell of an mth capacity, M being a positive integer;
s70, establishing a differential capacitance-capacity database of the sample power battery according to the differential capacitances of the sample power battery with different capacities obtained in the step S60;
s80, providing a power battery to be tested, and obtaining the differential capacitance of the power battery to be tested according to any one of the power battery differential capacitance generation methods;
and S90, searching the capacity of the power battery to be tested from the differential capacitance-capacity database of the sample power battery according to the differential capacitance of the power battery to be tested.
In one embodiment, the differential capacitance-capacity database of the sample power cell comprises a two-dimensional look-up table or interpolation function.
In one embodiment, the differential capacitance-capacity database of the sample power cell is an interpolation function, and the expression of the interpolation function is:
Q＝a1 exp(b1·CDC)+a2 exp(b2·CDC)
wherein a is1，a2，b1，b2Are interpolation coefficients, Q is the capacity of the sample power battery, CDCIs the differential capacitance of the sample power cell.
A power battery capacity estimation system, comprising:
the impedance data acquisition module is used for acquiring impedance data of the sample power battery under different testing capacities and different frequency excitations;
the electrochemical impedance spectrum acquisition module is connected with the impedance data acquisition module and used for constructing electrochemical impedance spectra of the sample power battery under different test capacities;
the differential capacitance calculation module is connected with the electrochemical impedance spectrum acquisition module and is used for calculating the differential capacitance of the sample power battery under different capacities based on a regularization method;
the differential capacitance-capacity database acquisition module of the power battery is connected with the differential capacitance calculation module and is used for generating a database in the form of a two-dimensional lookup table or an interpolation function according to different differential capacitance values of the sample power battery under different capacities; and
and the power battery capacity estimation and search module is connected with the differential capacitance calculation module and used for acquiring the differential capacitance of the power battery to be tested and searching the capacity of the power battery to be tested corresponding to the differential capacitance of the power battery to be tested in a differential capacitance-capacity database of the power battery.
In one embodiment, the impedance data acquisition system comprises:
the voltage excitation equipment is connected with the sample power battery or the power battery to be tested;
the current detection equipment is connected with the sample power battery or the power battery to be tested;
and the impedance spectrum calculation device is respectively connected with the voltage excitation device and the current detection device and is used for acquiring voltage data and current data of the sample power battery or the power battery to be tested.
The application provides a power battery differential capacitor generation method, a capacity estimation method and a capacity estimation system. The generation method of the power battery differential capacitor comprises the following steps: providing a sample power cell; acquiring impedance data of the sample power battery under different frequency excitations; constructing an electrochemical impedance spectrum of the sample power cell according to the impedance data of the sample power cell under different frequencies; and calculating the differential capacitance of the sample power battery based on a regularization method according to the electrochemical impedance spectrum of the sample power battery. The application provides a method for quickly and accurately acquiring a differential capacitor of a power battery. The application also provides a power battery capacity estimation method, which can quickly and accurately estimate the capacity of the power battery to be tested. The power battery capacity estimation method depends on the electrochemical impedance spectrum of the power battery, has the characteristics of accurate and rapid evaluation and the like, and avoids the problems of time consumption, energy consumption and the like caused by long-time charging and discharging of the power battery.
Drawings
Fig. 1 is a schematic flow chart of a method for generating a differential capacitor of a power battery according to an embodiment of the present application;
FIG. 2 is a schematic flow chart of a power battery capacity estimation method provided in an embodiment of the present application;
FIG. 3 is a method for measuring and calculating impedance data under different frequency excitations of a power battery according to an embodiment of the present application;
FIG. 4 is a power cell electrochemical impedance spectrum constructed based on power cell impedance data in one embodiment of the present application;
FIG. 5 is a schematic diagram of differential capacitance values of power cells of different capacities according to an embodiment of the present application;
fig. 6 is a schematic diagram of an impedance data acquisition system provided in an embodiment of the present application.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.
Referring to fig. 1, the present application provides a method for generating a differential capacitor of a power battery, including:
and S100, providing a sample power battery. The sample power battery in the step can be a lithium ion power battery of any manufacturer and any model.
And S200, acquiring impedance data of the sample power battery under different frequency excitations. In this step, the impedance data under different frequency excitations may be different types of frequency excitations, or the same type of frequency excitations of different sizes. Specific impedance data may be referenced to the data curve shown in fig. 3.
S300, constructing an electrochemical impedance spectrum of the sample power battery according to the impedance data of the sample power battery under different frequencies. In this step, the impedance data at different frequencies are summarized to obtain an electrochemical impedance spectrum. Specifically, the electrochemical impedance spectrum of the sample power cell can be referred to the electrochemical impedance spectrum shown in fig. 4. FIG. 4 is the electrochemical impedance spectrum information of the sample power cell, the frequency to be tested is 2 kHz-2 mHz (milli-Hz), and the frequency point is logarithmic linear frequency division. Frequency data is not contained in fig. 4 because the power cell impedance spectrum convention is increasing in frequency from right to left.
S400, calculating the differential capacitance of the sample power battery based on a regularization method according to the electrochemical impedance spectrum of the sample power battery. In the step, the differential capacitance of the sample power battery is obtained based on the electrochemical impedance spectrum obtained in the step. Different differential capacitance values can be obtained for different sample power batteries, and in particular, the differential capacitance value diagram of the power battery with different capacities shown in fig. 5 can be referred to.
In this embodiment, the electrochemical impedance spectrum of the sample power cell may be constructed by collecting impedance data of the sample power cell under excitation of different frequencies. And finally obtaining the differential capacitance of the sample power battery based on a regularization method according to the electrochemical impedance spectrum of the sample power battery. When the capacity of the power battery needs to be estimated, the sample power batteries with the same model can be selected in advance, and the differential capacitance of the sample power batteries with the same model can be calculated under different battery capacities. The selection process of the specific different battery capacities can be set by referring to empirical values or technicians according to needs. The method for generating the power battery differential capacitor in the embodiment can guide the setting and implementation of the power battery capacity estimation method.
In one embodiment, the specific step of acquiring impedance data of the sample power battery under excitation of different frequencies includes:
and using a voltage excitation device to generate a first test frequency sine wave to excite the sample power battery, and recording a first detection voltage, wherein the first test frequency is the highest test frequency in the sine wave frequencies.
And detecting the current of the sample power battery in the voltage excitation process by using a current detection device, and recording a first detection current.
And calculating the first detection voltage and the first detection current by using impedance spectrum calculation equipment to obtain the impedance of the first test frequency.
And adjusting the frequency of a sine wave excited by the voltage, exciting the sample power battery at a second test frequency, recording a second detection voltage, detecting and recording a second detection current, and calculating the impedance of the second test frequency.
And adjusting the sine wave frequency of voltage excitation again, and exciting the sample power battery at the Nth test frequency until the Nth test frequency is the lowest test frequency in the sine wave frequencies, wherein N is a positive integer and is greater than or equal to 3.
In this embodiment, the experimental steps may be set in a manner of referring to the connection mode of the impedance data acquisition system provided in fig. 6. Finally, acquiring impedance data of the sample power battery under different frequency excitations as shown in figure 3.
In one embodiment, the step of obtaining the impedance of the first test frequency by performing calculation processing on the first detection voltage and the first detection current by using an impedance spectrum calculation device includes:
providing different test sine frequencies, and calculating the complex impedance of the current frequency by adopting the following formula at each test sine frequency:
in the formula, ωiIs the current frequency; vsin (ω)it) is voltage excitation device data; isin (omega)it + phi) is current acquisition device data, Z (omega)i) A complex impedance calculated for that frequency;
when ω isiFrom the highest frequency to the lowest frequencyRate, all Z (ω) calculated by testi) Namely the impedance spectrum of the battery to be tested is marked as Z (omega);
the combination of all frequency complex impedances is the impedance data of the sample power cell under different frequency excitation, Z (omega) is the complex impedance which simultaneously comprises a real part and an imaginary part, so that the complex impedance can be written into a form of adding the real part and the imaginary part,
Z＝ZRe+jZIm
wherein Z isReIs the real part impedance value; zImIs the imaginary impedance value; j is an imaginary number.
In this embodiment, it may be limited that the impedance data acquisition system may directly obtain a final impedance spectrum calculation result, and the calculation method is point-by-point calculation, that is, the current frequency complex impedance is calculated at each test sinusoidal frequency, and a combination of all the frequency complex impedances is the impedance spectrum of the battery to be tested, and the complex impedance Z (ω) at one sinusoidal frequency.
In one embodiment, the step of calculating the differential capacitance of the sample power cell based on the regularization method comprises:
the regularization method calculation is performed using the following formula:
wherein, CDCIs the differential capacitance of the sample power cell; j (x) is a minimization objective function; Ω is a frequency matrix; rohmOhmic internal resistance; a' is an impedance real part characterization coefficient; a' is an impedance imaginary part characterization coefficient; x is an impedance characterization parameter; λ is a regularization coefficient; m is a regularization matrix.
In this embodiment, a calculation process for calculating the differential capacitance of the sample power battery based on the regularization method is shown in detail, and of course, other calculation formulas may also be adopted in the calculation process for the differential capacitance of the sample power battery, and the differential capacitance of the sample power battery may also be obtained, and no specific limitation is made again.
In one embodiment, the range of frequencies to be measured is 2kHz to 2mHz when the sample power cell is excited at different frequencies for impedance data. In this embodiment, the selection of the frequency range to be tested can realize the integrity test of the impedance data of the sample power battery, so that the obtained data of the differential capacitor is more reliable.
In one embodiment, when the sample power battery is excited by different frequencies, the frequency point of the frequency to be measured is logarithmically and linearly divided. In this embodiment, the selection of the frequency point of the frequency to be measured may also be implemented by using other frequency division modes. The frequency points are selected primarily to derive impedance data for different frequency excitations.
Referring to fig. 2, the present application provides a power battery capacity estimation method. The power battery capacity estimation method includes:
and S10, providing a sample power battery, wherein the capacity of the sample power battery is the first capacity.
And S20, acquiring impedance data of the sample power battery with the first capacity under excitation of different frequencies.
S30, constructing an electrochemical impedance spectrum of the sample power cell of the first capacity from the impedance data of the sample power cell of the first capacity at different frequencies.
And S40, calculating the differential capacitance of the sample power battery with the first capacity based on a regularization method according to the electrochemical impedance spectrum of the sample power battery with the first capacity.
S50, the capacity of the sample power battery is attenuated to a second capacity, and the steps S20-S40 are executed by taking the sample power battery with the second capacity as a collection and analysis object, so as to obtain the differential capacitance of the sample power battery with the second capacity.
And S60, repeating the step S50 to obtain a differential capacitance of the sample power battery with a third capacity and a differential capacitance of the sample power battery with a fourth capacity …, wherein M is a positive integer.
And S70, establishing a differential capacitance-capacity database of the sample power battery according to the differential capacitances of the sample power battery with different capacities obtained in the step S60.
S80, providing a power battery to be tested, and obtaining the differential capacitance of the power battery to be tested according to the power battery differential capacitance generating method. The model of the power battery to be tested is the same as that of the sample power battery.
And S90, searching the capacity of the power battery to be tested from the differential capacitance-capacity database of the sample power battery according to the differential capacitance of the power battery to be tested.
In the present embodiment, a power battery capacity estimation method is provided. The power battery capacity estimation method comprises the method for acquiring the differential capacitance of the power battery. And acquiring the differential capacitance of the sample power battery by adopting the differential capacitance method of the power battery. And further establishing a differential capacitance-capacity database of the sample power battery. And after the differential capacitance of the power battery to be tested is obtained, searching the capacity of the power battery to be tested from the differential capacitance-capacity database of the sample power battery. The power battery capacity estimation method can quickly and accurately estimate the capacity of the power battery to be tested. The power battery capacity estimation method depends on the electrochemical impedance spectrum of the power battery, has the characteristics of accurate and rapid evaluation and the like, and avoids the problems of time consumption, energy consumption and the like caused by long-time charging and discharging of the power battery.
In one embodiment, the differential capacitance-capacity database of the sample power cell comprises a two-dimensional look-up table or interpolation function.
For example, in this embodiment, a two-dimensional lookup table in the power battery capacity estimation method is provided as follows:
| CDC(105F) | 1.80 | 1.33 | 1.12 | 0.928 | 0.857 | 0.785 | 0.673 |
| Q(Ah) | 24.2 | 22.6 | 22.0 | 21.1 | 20.1 | 19.3 | 15.5 |
q in the two-dimensional lookup table is the capacity of the power battery; cDCIs the differential capacitance of the power battery.
In one embodiment, the differential capacitance-capacity database of the sample power cell is an interpolation function, and the expression of the interpolation function is:
Q＝a1 exp(b1·CDC)+a2 exp(b2·CDC)
wherein a is1，a2，b1，b2Are interpolation coefficients, Q is the capacity of the sample power battery, CDCIs the differential capacitance of the sample power cell. In this embodiment, please show the interpolation resultSee fig. 5.
The present application further provides a power battery capacity estimation system, including: the device comprises an impedance data acquisition module, an electrochemical impedance spectrum acquisition module, a differential capacitance calculation module, a differential capacitance-capacity database acquisition module of the power battery and a power battery capacity estimation and search module.
And the impedance data acquisition module is used for acquiring impedance data of the sample power battery under different test capacities and different frequency excitations.
The electrochemical impedance spectrum acquisition module is connected with the impedance data acquisition module and used for constructing the electrochemical impedance spectrum of the sample power battery under different test capacities.
The differential capacitance calculation module is connected with the electrochemical impedance spectrum acquisition module, and calculates the differential capacitance of the sample power battery under different capacities based on a regularization method.
And the differential capacitance-capacity database acquisition module of the power battery is connected with the differential capacitance calculation module and is used for generating a database in the form of a two-dimensional lookup table or an interpolation function according to different differential capacitance values of the sample power battery under different capacities.
The power battery capacity estimation searching module is connected with the differential capacitance calculating module and used for obtaining the differential capacitance of the power battery to be tested and searching the capacity of the power battery to be tested corresponding to the differential capacitance of the power battery to be tested in a differential capacitance-capacity database of the power battery.
In this embodiment, a power battery capacity estimation system is provided, which can quickly and accurately estimate the capacity of a power battery to be tested. The power battery capacity estimation system depends on the electrochemical impedance spectrum of the power battery, has the characteristics of accurate and rapid evaluation and the like, and avoids the problems of time consumption, energy consumption and the like caused by long-time charging and discharging of the power battery.
In one embodiment, please refer to fig. 6, which provides a specific structure of the impedance data acquisition system. The impedance data acquisition system includes: the device comprises a voltage excitation device, a current detection device and an impedance spectrum calculation device.
The voltage excitation device is connected with the sample power battery or the power battery to be tested.
The current detection equipment is connected with the sample power battery or the power battery to be tested.
The impedance spectrum calculation device is respectively connected with the voltage excitation device and the current detection device and is used for acquiring voltage data and current data of the sample power battery or the power battery to be tested.
In this embodiment, the impedance data acquisition system can accurately detect the voltage data and the current data of the sample power battery or the power battery to be tested.
In a particular embodiment, the data acquisition system is defined as an electrochemical impedance spectroscopy data acquisition system. The device comprises a voltage excitation device, a current detection device and an impedance spectrum calculation device, and the schematic diagram is shown at the end of text. Impedance spectroscopy data is defined as impedance data over a range of frequencies (e.g., 2kHz to 2 mHz). The impedance data measuring method comprises the following specific steps
1) Exciting the battery to be tested by using a voltage excitation device to generate a sine wave with the highest test frequency required by an impedance spectrum;
2) detecting the battery current in the voltage excitation process by using current detection equipment;
3) processing the voltage obtained by the voltage excitation device and the current obtained by the current detection device by using impedance spectrum calculation equipment to obtain the impedance of the frequency point;
4) and reducing the frequency of the sine wave of the voltage excitation, and repeating the steps 1) -3) until the frequency of the sine wave is reduced to the required minimum test frequency.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (6)
1. A method for generating a power battery differential capacitor is characterized by comprising the following steps:
providing a sample power cell;
acquiring impedance data of the sample power battery under different frequency excitations;
constructing an electrochemical impedance spectrum of the sample power cell according to the impedance data of the sample power cell under different frequencies;
calculating the differential capacitance of the sample power battery based on a regularization method according to the electrochemical impedance spectrum of the sample power battery;
the specific steps of collecting the impedance data of the sample power battery under the excitation of different frequencies comprise:
using voltage excitation equipment to generate a first test frequency sine wave to excite the sample power battery, and recording a first detection voltage, wherein the first test frequency is the highest test frequency in sine wave frequencies;
detecting the current of the sample power battery in the voltage excitation process by using a current detection device, and recording a first detection current;
calculating the first detection voltage and the first detection current by using impedance spectrum calculation equipment to obtain impedance of the first test frequency;
adjusting the frequency of a sine wave excited by the voltage, exciting the sample power battery at a second test frequency, recording a second detection voltage, detecting and recording a second detection current, and calculating the impedance of the second test frequency;
adjusting the sine wave frequency of voltage excitation again, and exciting the sample power battery at an Nth test frequency until the Nth test frequency is the lowest test frequency in the sine wave frequencies, wherein N is a positive integer and is greater than or equal to 3;
the impedance at the current test frequency is calculated using the following formula:
in the formula, ωiIs the current test frequency; vsin (ω)it) is voltage excitation device data; isin (omega)it + phi) is current sensing device data, Z (omega)i) Calculating an impedance for the test frequency;
when ω isiAll Z (omega) calculated from the highest test frequency to the lowest test frequency are testedi) Namely the impedance spectrum of the battery to be tested is marked as Z (omega);
all frequency impedance combinations are impedance data of the sample power cell under excitation of different test frequencies, Z (omega) is complex impedance which simultaneously comprises a real part and an imaginary part, so that the impedance data can be written in a form of adding the real part and the imaginary part,
Z(ω)＝ZRe+jZIm
wherein Z isReIs the real part impedance value; zImIs the imaginary impedance value; j is an imaginary number;
the step of calculating the differential capacitance of the sample power battery based on the regularization method comprises the following steps:
the regularization method calculation is performed using the following formula:
wherein, CDCIs the differential capacitance of the sample power cell; j (x) is a minimization objective function; Ω is a frequency matrix; rohmOhmic internal resistance; a' is an impedance real part characterization coefficient; a' is an impedance imaginary part characterization coefficient; x isAn impedance characterizing parameter; λ is a regularization coefficient; m is a regularization matrix.
2. The method for generating the power battery differential capacitance according to claim 1, wherein when impedance data of the sample power battery under different frequency excitation is collected, a test frequency range is 2kHz to 2 mHz.
3. The method for generating the power battery differential capacitance according to claim 2, wherein when the impedance data of the sample power battery under different frequency excitations are collected, the frequency point of the test frequency is obtained by logarithmic linear frequency division.
4. A power battery capacity estimation method, characterized by comprising:
s10, providing a sample power battery, wherein the capacity of the sample power battery is a first capacity;
s20, acquiring impedance data of the sample power battery with the first capacity under excitation of different frequencies;
s30, constructing an electrochemical impedance spectrum of the sample power cell of the first capacity from the impedance data of the sample power cell of the first capacity at different frequencies;
s40, calculating the differential capacitance of the sample power battery with the first capacity based on a regularization method according to the electrochemical impedance spectrum of the sample power battery with the first capacity;
s50, attenuating the capacity of the sample power battery to a second capacity, and executing the steps S20-S40 by taking the sample power battery with the second capacity as a collection and analysis object so as to obtain the differential capacitance of the sample power battery with the second capacity;
s60, repeating the step of S50 to obtain a differential capacitance of the sample power cell of a third capacity, a differential capacitance of the sample power cell of a fourth capacity … a differential capacitance of the sample power cell of an mth capacity, M being a positive integer;
s70, establishing a differential capacitance-capacity database of the sample power battery according to the differential capacitances of the sample power battery with different capacities obtained in the step S60;
s80, providing a power battery to be tested, and obtaining the differential capacitance of the power battery to be tested according to the power battery differential capacitance generation method of any one of claims 1-3;
and S90, searching the capacity of the power battery to be tested from the differential capacitance-capacity database of the sample power battery according to the differential capacitance of the power battery to be tested.
5. The power battery capacity estimation method of claim 4, wherein the differential capacitance-capacity database of sample power batteries comprises a two-dimensional look-up table or an interpolation function.
6. The power battery capacity estimation method of claim 5, wherein the differential capacitance-capacity database of the sample power battery is an interpolation function, and the expression of the interpolation function is:
wherein a is1，a2，b1，b2Are all the interpolation coefficients of the image data,Qis the capacity of the sample power cell, CDCIs the differential capacitance of the sample power cell.
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