CN112433170B - Method for identifying parameter difference of single batteries of series battery pack - Google Patents
Method for identifying parameter difference of single batteries of series battery pack Download PDFInfo
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- CN112433170B CN112433170B CN202011092297.0A CN202011092297A CN112433170B CN 112433170 B CN112433170 B CN 112433170B CN 202011092297 A CN202011092297 A CN 202011092297A CN 112433170 B CN112433170 B CN 112433170B
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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]
- G01R31/396—Acquisition or processing of data for testing or for monitoring individual cells or groups of cells within a battery
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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
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Abstract
The invention belongs to the technical field of battery parameter identification, and relates to a method for identifying parameter difference of single batteries of a series battery packd(ii) a And setting a proportionality coefficient T according to the charging multiplying power and the sampling time interval of the battery packr(ii) a Then calculate TdAnd TrThe ratio R is used as the initial SOC of the battery monomer in the charging process; and finally, calculating the single SOC difference condition reflecting the SOC consistency of the battery pack according to the charging initial SOC of each single battery. The method realizes the estimation of the charging initial SOC of each battery monomer in the series battery pack and the consistency of the SOC of the battery pack, and has higher precision and efficiency.
Description
Technical Field
The invention belongs to the technical field of battery parameter identification, and relates to a method for identifying parameter difference of single batteries of a series battery pack.
Background
The available capacity of the battery pack is directly restricted by the inconsistency of the state of charge (SOC) of the single batteries in the battery pack, the energy utilization rate of the battery pack is rapidly reduced along with the expansion of the SOC inconsistency, and the influence effect of the available capacity of the battery pack on the available capacity of the battery pack is more obvious than the battery capacity decline caused by the aging of the battery. The SOC of the lithium ion battery is used as an important battery pack consistency parameter, and has important guiding significance for balancing and maintaining the battery pack. Therefore, the method has important significance on the SOC consistency of the battery pack, namely the estimation of the SOC of the battery pack single body.
Currently, SOC estimation methods can be divided into off-line and on-line methods according to aging, and the specific methods mainly include ampere-hour integration, kalman filtering, machine learning, and the like, and all of the above methods have their own advantages and disadvantages. For a power driving system, such as an electric automobile and the like, generally adopted online or offline battery pack single SOC estimation methods all depend on dynamic working conditions, the adaptability of the SOC estimation methods to the working conditions of constant current, constant power and the like is poor, and estimation errors are large; for the energy storage system, the SOC estimation of the battery pack monomer still adopts the most basic ampere-hour integration method with voltage correction, and the estimation precision is extremely low.
Disclosure of Invention
The invention provides and realizes an initial SOC estimation method for a series battery pack monomer. The method adopts stable charging data of the series battery pack as input, takes the recorded initial OCV curve of the single battery of the series battery pack as a reference, considers the operating conditions of the power driving system and the energy storage system, and realizes that the initial charging SOC of each single battery in the series battery pack can be determined only by partial charging curve of the series battery pack.
The technical scheme of the invention comprises the following implementation steps:
a method for identifying parameter differences of series battery pack monomers comprises the following steps:
step 1: taking a complete Open Circuit Voltage (OCV) curve of the battery cells of the series battery as a reference curve of the method, which is called as a reference curve for short;
step 2: taking the primary constant-current charging data of the series battery pack as an analysis object, and selecting a charging voltage curve of one battery monomer for analysis, namely the charging curve;
and step 3: carrying out forward difference operation on the reference curve and the charging curve to obtain voltage difference curves of the two curves, and calculating similarity and matching relation of the two voltage difference curves by adopting a Dynamic Time Warping (DTW) algorithm to obtain corresponding relation of data points on the two voltage difference curves; the corresponding relationship of the data points is as follows: "one-to-one correspondence" or "one-to-many";
and 4, step 4: screening out the data points with the correspondence relationship of one to one correspondence, and calculating the average value T of the difference of index values between all the data points with the correspondence relationship of one to one correspondenced；
And 5: setting a proportionality coefficient T according to the charging multiplying power and the sampling time interval of the series battery packr；
Step 6: calculating the average value T of the difference between the index valuesdAnd the proportionality coefficient TrThe ratio R of (A) is calculated by the following formula (1),
wherein, R is the initial SOC of the battery monomer in the charging process;
and 7: selecting other battery monomers in the series battery pack, and repeating the steps 2-6 until all the battery monomers are calculated to obtain the initial SOC of all the battery monomers in the series battery pack in the charging process;
and 8: and calculating the single SOC difference condition reflecting the SOC consistency of the series battery pack according to the charging initial SOC of each single battery.
On the basis of the technical scheme, the open-circuit voltage curve in the step 1 is provided or tested by a battery factory before the batteries are delivered or grouped.
On the basis of the technical scheme, the open-circuit voltage curve is mapped to the conditions of charging multiplying power and sampling frequency corresponding to the charging working condition of the series battery pack.
On the basis of the technical scheme, the DOD of the constant-current charging in the step 2 is more than 20%.
Based on the technical scheme, the method comprises the following stepsThe scale factor T in step 5rAnd setting the SOC increment corresponding to each sampling point on the reference curve.
On the basis of the above technical solution, the proportionality coefficient T in step 5rThe method comprises the following steps:
assuming that the charging rate of the reference curve of the series battery pack is m C and the sampling time interval is n s; the proportionality coefficient TrCalculated according to the following formula (2),
the invention has the following beneficial technical effects:
the method is based on a dynamic time warping algorithm, the charging data of the series battery pack is analyzed and processed, and the charging initial SOC (namely the charging initial SOC) of each battery monomer in the series battery pack and the SOC consistency of the series battery pack are estimated by comparing the OCV curve of the battery with the charging voltage curve of the battery monomer. The method has higher precision and efficiency, and under the condition that the difference of the SOC of the monomers is 15 percent and the difference of the capacity of the monomers is +/-4 percent, the data of any initial SOC of 0-80 percent is analyzed, and the estimation error of the initial SOC is-2 percent to +3 percent.
Drawings
The invention has the following drawings:
fig. 1 is a flow chart of a method for obtaining initial SOC of a battery cell during charging.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings.
As shown in fig. 1, the technical solution of the present invention is implemented as follows:
step 1: taking a complete Open Circuit Voltage (OCV) curve of the battery cells of the series battery as a reference curve of the method, which is hereinafter referred to as a reference curve;
typically, the open circuit voltage curve of a battery may be provided or tested by a battery factory before the battery is shipped or grouped. The single batteries in the same series battery pack are generally the same batch of batteries, and the batteries need to be screened more strictly before being grouped, so that only the open-circuit voltage curve of one single battery in the series battery pack is needed.
The battery open circuit voltage curve needs to be mapped to the conditions of charging multiplying power, sampling frequency and the like corresponding to the charging working condition of the series battery pack. Setting a measurement interval of 5% SOC according to a common HPPC test, obtaining OCV data with 21 data points of SOC respectively being 0, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% and 100%, and mapping the OCV data to the same conditions as the charging data of the series battery pack by a linear or non-linear interpolation method (for example, the magnitude of the charging current of the actual series battery pack is used as a charging rate of 1C, and the actual data sampling time interval is used as a data time interval).
Step 2: taking the primary constant-current charging data of the series battery pack as an analysis object, selecting a charging voltage curve (namely a constant-current charging voltage curve) of one battery monomer for analysis, and hereinafter referred to as a charging curve;
the constant-current charging section of the series battery pack is required to have a certain length in time, if the DOD of the constant-current charging section is mapped to an actual SOC interval and the DOD is required to be greater than 20%, if the charging time is too short, the information provided by the data is insufficient, so that the error of the estimation result of the algorithm (namely the method of the invention) is greatly increased, and even estimation cannot be performed.
And step 3: forward difference operation (namely difference operation on a time scale) is carried out on the reference curve and the charging curve to obtain a voltage difference curve of the two curves, and similarity and matching relation calculation is carried out on the two voltage difference curves by adopting a Dynamic Time Warping (DTW) algorithm to obtain corresponding relation (namely data point correlation relation) of data points on the two voltage difference curves. The correspondence of data points can be divided into two categories: "one-to-one correspondence" or "one-to-many".
The dynamic time warping algorithm is a mature curve similarity evaluation algorithm, and can conveniently map data points on one curve to another curve, namely, the corresponding relation of the data points on the two curves can be obtained through calculation, and the similar section of the part of curve on the other curve can be obtained according to the corresponding relation of the data points of a continuous section. Because the integrality of the two curves analyzed by the dynamic time warping algorithm is different, the actual detail characteristics of the curve shapes are also different, and the matching relation of points on the curves can be established by the algorithm according to the principle that the cumulative distance is shortest in the automatic curve matching process. Because the data points of the two curves are different in quantity, if all the data points have corresponding matching points, part of the data points need to establish corresponding relations with a plurality of data points, and therefore two corresponding relations of one-to-one correspondence and one-to-many correspondence appear.
And 4, step 4: screening out the data points with the corresponding relationship of one-to-one correspondence, and calculating the average value T of the differences of the index values between all the data points with the corresponding relationshipd；
According to the characteristics of the dynamic time warping algorithm, the one-to-one correspondence of the data points of the two curves is considered that the two curve segments only have a translation relationship, namely, the two curve segments are caused by the SOC difference of the two curves; the "one-to-many" data points are considered to have a scaling relationship, i.e., caused by curve capacity differences.
And 5: setting a proportionality coefficient T according to the charging multiplying power and the sampling time interval of the series battery packr；
The setting principle of the proportionality coefficient is set according to the SOC increment corresponding to each sampling point of the reference curve. For example, if the reference curve is a charge rate of 1C and the sampling time interval is 1s, 3600 data points are counted in the reference curve, and each 36 data points represent 1% SOC, so the proportionality coefficient T isrSet to 36.
Step 6: calculating the average value T of the difference between the index valuesdAnd the proportionality coefficient TrThe ratio R of (A) is calculated by the following formula (1),
wherein, R is the initial SOC of the battery monomer in the charging process;
and 7: selecting other battery monomers in the series battery pack, and repeating the steps 2-6 until all the battery monomers are calculated, so that the initial SOC of all the battery monomers in the series battery pack in the charging process can be obtained;
and 8: according to the initial charging SOC of each single battery, the single SOC difference condition reflecting the SOC consistency of the series battery pack can be calculated.
The method is based on a dynamic time warping algorithm, the charging data of the series battery pack is analyzed and processed, and the charging initial SOC of each battery monomer in the series battery pack and the SOC consistency of the series battery pack are estimated by comparing the OCV curve of the battery with the charging voltage curve of the battery monomer. The method has higher precision and efficiency, and under the condition that the difference of the SOC of the monomers is 15 percent and the difference of the capacity of the monomers is +/-4 percent, the data of any initial SOC of 0-80 percent is analyzed, and the estimation error of the initial SOC is-2 percent to +3 percent.
It is obvious that the above description is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and it is intended that any person skilled in the art who is skilled in the art will appreciate that other variations or modifications based on the above description are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Those not described in detail in this specification are within the knowledge of those skilled in the art.
Claims (6)
1. A method for identifying parameter differences of single batteries of series battery packs is characterized by comprising the following steps:
step 1: taking a complete open-circuit voltage curve of a battery monomer of the series battery pack as a reference curve of the method, which is called the reference curve for short;
step 2: taking the primary constant-current charging data of the series battery pack as an analysis object, and selecting a charging voltage curve of one battery monomer for analysis, namely a charging curve;
and step 3: carrying out forward difference operation on the reference curve and the charging curve to obtain a voltage difference curve of the two curves, and calculating similarity and matching relation of the two voltage difference curves by adopting a dynamic time warping algorithm to obtain corresponding relation of data points on the two voltage difference curves; the corresponding relationship of the data points is as follows: one-to-one or one-to-many;
and 4, step 4: screening out the data points with the corresponding relationship as one-to-one correspondence, and calculating the average value T of the difference of the index values between all the data points with the one-to-one correspondenced；
And 5: setting a proportionality coefficient T according to the charging multiplying power and the sampling time interval of the series battery packr；
Step 6: calculating the average value T of the difference between the index valuesdAnd the proportionality coefficient TrThe ratio R of (A) is calculated by the following formula (1),
wherein, R is the initial SOC of the battery monomer in the charging process;
and 7: selecting other battery monomers in the series battery pack, and repeating the steps 2-6 until all the battery monomers are calculated to obtain the initial SOC of all the battery monomers in the series battery pack in the charging process;
and 8: and calculating the single SOC difference condition reflecting the SOC consistency of the series battery pack according to the charging initial SOC of each single battery.
2. The method for identifying the difference in the parameters of the series battery cells as claimed in claim 1, wherein: and 1, providing or testing the open-circuit voltage curve by a battery factory before the battery leaves a factory or is grouped.
3. The method for identifying the difference in the parameters of the series battery cells as claimed in claim 1 or 2, wherein: and mapping the open-circuit voltage curve to the conditions of charging multiplying power and sampling frequency corresponding to the charging working condition of the series battery pack.
4. The method for identifying the difference in the parameters of the series battery cells as claimed in claim 1, wherein: and 2, the DOD of the constant current charging is more than 20%.
5. The method for identifying the difference in the parameters of the series battery cells as claimed in claim 1, wherein: the proportionality coefficient T in step 5rAnd setting the SOC increment corresponding to each sampling point on the reference curve.
6. The method for identifying differences in parameters of series-connected battery cells as claimed in claim 1 or 5, wherein: the proportionality coefficient T in step 5rThe method comprises the following steps:
assuming that the charging multiplying power of a reference curve of the series battery pack is mC and the sampling time interval is ns; the proportionality coefficient TrCalculated according to the following formula (2),
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| CN113466696A (en) * | 2021-05-17 | 2021-10-01 | 北京交通大学 | Battery pack monomer state estimation method based on voltage curve transformation |
| CN113625176B (en) * | 2021-08-02 | 2024-02-09 | 合肥国轩高科动力能源有限公司 | Lithium ion battery module SOC difference calculation method and equipment |
| CN113740754B (en) * | 2021-09-06 | 2023-10-13 | 北京西清能源科技有限公司 | Method and system for detecting inconsistency of battery pack |
| CN114114039B (en) * | 2021-12-06 | 2023-10-03 | 湖北亿纬动力有限公司 | Method and device for evaluating consistency of single battery cells of battery system |
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