CN114371418B - Incremental capacity curve determining method based on real vehicle charging data - Google Patents

Incremental capacity curve determining method based on real vehicle charging data Download PDF

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CN114371418B
CN114371418B CN202210016953.1A CN202210016953A CN114371418B CN 114371418 B CN114371418 B CN 114371418B CN 202210016953 A CN202210016953 A CN 202210016953A CN 114371418 B CN114371418 B CN 114371418B
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charging
capacity
voltage
segment
data
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CN114371418A (en
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王震坡
吴益忠
刘鹏
张照生
林倪
佘承其
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Beijing Institute of Technology BIT
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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
    • 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

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Charge And Discharge Circuits For Batteries Or The Like (AREA)
  • Secondary Cells (AREA)
  • Electric Propulsion And Braking For Vehicles (AREA)

Abstract

The invention provides a method for determining an increment capacity curve based on real-vehicle charging data, which utilizes a Hermite interpolation polynomial to fit a functional relation between capacity and voltage in each charging segment, can ensure accurate calculation of increment capacity curve characteristics, and simultaneously obviously reduces the demand on calculation resources, thereby being beneficial to promoting realization of real-time SOH estimation of a new energy automobile based on a remote big data platform and having a plurality of beneficial effects which are not possessed by the prior art.

Description

Incremental capacity curve determining method based on real vehicle charging data
Technical Field
The invention belongs to the technical field of health state estimation of a power battery of a new energy automobile, and particularly relates to a method for determining an incremental capacity curve based on real automobile charging data.
Background
For a pure electric new energy automobile, the power battery of the pure electric new energy automobile inevitably generates energy and power degradation in use, and accordingly, the driving range and the power performance are reduced. Therefore, how to implement accurate state of health (SOH) estimation of a power battery is of vital importance for efficient and safe operation of a vehicle. The analysis of the incremental capacity of a battery is an important implementation way in the field of SOH estimation of a power battery, and quantitative estimation of SOH is performed by acquiring characteristics such as peak height, position and area in an incremental capacity (INCREMENTAL CAPACITY, IC) curve. However, most IC curve determination and optimization methods are based only on low current fully charged laboratory data, while some laboratory environments can guarantee good control, but still differ greatly from the complex and varied actual operating environments of electric vehicles. For example, in the real world, the charging and discharging behavior of a vehicle is complex and diverse, and the charging process is highly discontinuous, rarely following a 0-100% full charge mode, as users most tend to begin charging before the battery is fully depleted in daily use. In some prior art based on real vehicle big data, the quality of data collected by the existing sensor and transmission equipment is even inferior to that of data obtained in laboratory environment, so that the corresponding IC curve determining method has the defects of parameter identification, high calculation cost, sensitivity to data noise and the like, and is difficult to be directly applied to a non-full charging scene in the real world.
Disclosure of Invention
In view of the above, the present invention provides a method for determining an incremental capacity curve based on real vehicle charging data, which specifically includes the following steps:
step one, uploading original data comprising current, voltage and time items in real vehicle operation to a big data platform by a vehicle-mounted remote terminal;
Secondly, the big data platform processes the received original data, extracts charging behavior data from the original data according to charging current and running speed, and cuts out a plurality of charging fragments with the same current in a certain time range;
step three, calculating the charging capacity in each charging segment, and combining the voltage and time items of each segment to form a group of ordered voltage and capacity sequences:
V＝[v1,v2,...,vk,vk+1,...,vn-1,vn]
Q＝[q1,q2,...,qk,qk+1,...,qn-1,qn]
Fitting a functional relation between the capacity and the voltage in each charging segment by using the ordered voltage and capacity sequence and using a Hermite interpolation polynomial;
Step five, deriving the functional relation obtained in the step four to obtain an incremental capacity curve corresponding to each charging segment; the foregoing steps are applied to all charging curves to obtain a complete incremental capacity curve change for the power cell.
Further, in the third step, the charging capacity is calculated by an ampere-hour integration method:
Wherein I is a charging current in a certain charging behavior, T is a charging time, and Q is a charging capacity.
Further, in step four, a hermite interpolation polynomial of the form is constructed for the voltage and capacity data in each charging segment:
Wherein,
Where n is the number of voltage or capacity data contained in each segment and q' i is the derivative of q i with respect to v i;
The following rules are respectively executed for the q' i:
① When i epsilon [1, n-1], the q' i is calculated specifically in the following form:
In the method, in the process of the invention,
hi＝vi+1-vi
The precondition for calculating q 'i by using the above formula is that the symbols of delta i and delta i-1 are the same, otherwise q' i must be set to 0;
② For q '0 and q' n, the following form is used for calculation, respectively:
The precondition for calculating q '0 by the above formula is that the symbols of delta 0 and delta 1 are the same, the precondition for calculating q' n is that the symbols of delta n-1 and delta n-2 are the same, otherwise, q '0 and q' n are set to 0 correspondingly.
The step adopts a piecewise interpolation polynomial, so that the defects of low vehicle data acquisition frequency and sparse data of the existing cloud platform can be overcome. For q i in the formula, the voltage and the capacity obtained based on the real sampling are calculated by adopting a first-order difference quotient and a weighted average method, and corresponding constraint is applied to the derivative q' i, so that more information in the original charging data is reserved, and further obtained incremental capacity curve can reflect the real state of health of the battery more.
Further, in step five, a capacity-voltage functional relationship q=f (v) is obtained for each charging segment by performing the following derivation:
The incremental capacity curve corresponding to the charging fragments can be obtained, and the incremental capacity change conditions corresponding to all the charging fragments can be reflected by further adopting the steps above for all the charging fragments.
According to the incremental capacity curve determining method based on the real-vehicle charging data, provided by the invention, the function relation between the capacity and the voltage in each charging segment is fitted by using the Hermite interpolation polynomial, so that the demand on calculation resources is obviously reduced while the accurate calculation of the incremental capacity curve characteristic can be ensured, the realization of real-time SOH estimation of a new energy vehicle based on a remote big data platform is facilitated, and a plurality of beneficial effects which are not possessed by the prior art are achieved.
Drawings
FIG. 1 is a schematic flow chart of a method according to the present invention;
Fig. 2 is an incremental capacity change for all charge segments obtained for a vehicle in an example according to the invention.
Detailed Description
The following description of the embodiments of the present invention will be made apparent and fully in view of the accompanying drawings, in which some, but not all embodiments of the invention are shown. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The method for determining the incremental capacity curve based on the real vehicle charging data provided by the invention, as shown in fig. 1, specifically comprises the following steps:
step one, uploading original data comprising current, voltage and time items in real vehicle operation to a big data platform by a vehicle-mounted remote terminal;
Secondly, the big data platform processes the received original data, extracts charging behavior data from the original data by taking charging current as a basis, and cuts out a plurality of charging fragments with the same current in a certain time range;
step three, calculating the charging capacity in each charging segment, and combining the voltage and time items of each segment to form a group of ordered voltage and capacity sequences:
V＝[v1,v2,...,vk,vk+1,...,vn-1,vn]
Q＝[q1,q2,...,qk,qk+1,...,qn-1,qn]
Fitting a functional relation between the capacity and the voltage in each charging segment by using the ordered voltage and capacity sequence and using a Hermite interpolation polynomial;
step five, deriving the functional relation obtained in the step four to obtain an incremental capacity curve corresponding to each charging segment; the foregoing steps are applied to all of the charged segments to obtain a change in the incremental capacity curve of the power cell over a range of time.
In a preferred embodiment of the present invention, the calculation of the filling capacity in step three specifically uses the ampere-hour integration method:
Wherein I is a charging current in a certain charging behavior, T is a charging time, and Q is a charging capacity.
It will be appreciated by those skilled in the art that this step may utilize a number of different ways in the art to calculate the fill volume.
Further, in step four, a hermite interpolation polynomial of the form is constructed for the voltage and capacity data in each charging segment:
Wherein,
Where n is the number of voltage or capacity data contained in each segment and q' i is the derivative of q i with respect to v i;
The following rules are respectively executed for the q' i:
① When i epsilon [1, n-1], the q' i is calculated specifically in the following form:
In the method, in the process of the invention,
hi＝vi+1-vi
The precondition for calculating q 'i by using the above formula is that the symbols of delta i and delta i-1 are the same, otherwise q' i must be set to 0;
② For q '0 and q' n, the following form is used for calculation, respectively:
The precondition for calculating q '0 by the above formula is that the symbols of delta 0 and delta 1 are the same, the precondition for calculating q' n is that the symbols of delta n-1 and delta n-2 are the same, otherwise, q '0 and q' n are set to 0 correspondingly.
In a preferred embodiment of the invention, the capacity-voltage function q=f (v) is obtained for each charging segment in step five by performing the following derivation:
Namely, the incremental capacity curve corresponding to the charging segments can be obtained, and the incremental capacity change conditions corresponding to all the charging segments are reflected. Fig. 2 shows a preferred example of the present invention, in which the corresponding incremental capacity curve is obtained for all the charging segments of a certain vehicle by the above method, and the change situation of the incremental capacity curve is comprehensively and clearly reflected with the continuous use and the increase of the accumulated mileage of the vehicle.
It should be understood that, the sequence number of each step in the embodiment of the present invention does not mean that the execution sequence of each process should be determined by the function and the internal logic of each process, and should not limit the implementation process of the embodiment of the present invention.
Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made therein without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims (4)

1. The incremental capacity curve determining method based on the real vehicle charging data is characterized by comprising the following steps of: the method specifically comprises the following steps:
step one, uploading original data comprising current, voltage and time items in real vehicle operation to a big data platform by a vehicle-mounted remote terminal;
Secondly, the big data platform processes the received original data, extracts charging behavior data from the original data according to charging current and running speed, and cuts out a plurality of charging fragments with the same current in a certain time range;
Step three, calculating the charging capacity in each charging segment, combining the voltage item and the time item in each segment to form a group of ordered voltage V and capacity Q sequences, wherein the sequence elements are n total voltage or capacity data:
V＝[v1,v2,...,vk,vk+1,...,vn-1,vn]
Q＝[q1,q2,...,qk,qk+1,...,qn-1,qn]
Fitting a functional relation between the capacity and the voltage in each charging segment by using the ordered voltage and capacity sequence and using a Hermite interpolation polynomial;
Step five, deriving the functional relation obtained in the step four to obtain an incremental capacity curve corresponding to each charging segment; the foregoing steps are applied to all charging segments to obtain the change in all incremental capacity curves of the power battery over a range of time.
2. The method of claim 1, wherein: and step three, calculating the filling capacity by adopting an ampere-hour integration method:
Wherein I is a charging current in a certain charging behavior, T is a charging time, and Q is a charging capacity.
3. The method of claim 1, wherein: in step four, a hermite interpolation polynomial of the following form is constructed for the voltage v i and capacity Q i data in each charging segment:
Wherein,
v∈[vi,vi+1](i＝0,1,2,...,n-1)
Where n is the number of voltage or capacity data contained in each segment, q' i is the derivative of the coefficient q i with respect to v i;
The following rules are respectively executed for the q' i:
① When i epsilon [1, n-1], the q' i is calculated specifically in the following form:
In the method, in the process of the invention,
hi＝vi+1-vi
The precondition for calculating q 'i by using the above formula is that the symbols of delta i and delta i-1 are the same, otherwise q' i must be set to 0;
② For q '0 and q' n, the following form is used for calculation, respectively:
The precondition for calculating q '0 by the above formula is that the symbols of delta 0 and delta 1 are the same, the precondition for calculating q' n is that the symbols of delta n-1 and delta n-2 are the same, otherwise, q '0 and q' n are set to 0 correspondingly.
4. The method of claim 1, wherein: in the fifth step, a function relationship q=f (v) of the capacity Q and the voltage v is obtained for each charging segment, by performing the following derivation:
and obtaining the increment capacity curves corresponding to all the charging fragments.
CN202210016953.1A 2022-01-07 2022-01-07 Incremental capacity curve determining method based on real vehicle charging data Active CN114371418B (en)

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CN115993538B (en) * 2023-02-01 2023-10-20 上海玫克生储能科技有限公司 Fitting method and device of battery capacity increment comprehensive curve and electronic equipment
CN116224128B (en) * 2023-05-06 2023-08-01 广汽埃安新能源汽车股份有限公司 Method and device for detecting capacity health state of battery

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