CN110826023A - Method for improving resolution of running data of battery system - Google Patents

Method for improving resolution of running data of battery system Download PDF

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CN110826023A
CN110826023A CN201911105046.9A CN201911105046A CN110826023A CN 110826023 A CN110826023 A CN 110826023A CN 201911105046 A CN201911105046 A CN 201911105046A CN 110826023 A CN110826023 A CN 110826023A
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voltage
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battery charging
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叶健诚
俞波
董晨
张伟
叶建德
杨洪涛
蔡小辰
张娅楠
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NARI Group Corp
State Grid Electric Power Research Institute
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Abstract

The invention discloses a method for improving the resolution of running data of a battery system. The invention can restore the original data with low voltage resolution and large recording time interval to the high-resolution data with higher voltage resolution and smaller time interval, thereby providing support for the subsequent data analysis.

Description

Method for improving resolution of running data of battery system
Technical Field
The invention relates to the technical field of electric power information processing, in particular to a method for improving the resolution of running data of a battery system.
Background
With the continuous development of lithium battery technology and related battery management technology, the application of lithium ion batteries in energy storage systems is also gradually popularized. Meanwhile, with the rise of big data of the internet, the analysis and prediction of the running state and the health state of the battery system through the running data of the energy storage system become relevant research hotspots. The state also sets a battery management system of an energy storage power station in a relevant standard specification, and for example, the national standard GBT34131-2017 explicitly sets the recording precision and time interval of parameters such as current, voltage and temperature of the battery management system of the energy storage power station.
In order to meet corresponding energy and power requirements, the energy storage system adopts a large number of battery cells which are connected in series and in parallel to form a group, and in order to ensure the stability of the energy storage system, a design that the maximum energy and power are higher than the requirements is usually adopted. Therefore, the generated battery operation data is usually very huge, and therefore, the bandwidth and flow occupied by data uploading, the data storage space and the like are greatly required. Generally, for economic reasons, uploading data takes the form of decreasing data resolution or increasing data time interval or both. While this approach can significantly reduce the cost of energy storage power plants in terms of operational data logging, the analysis of the data creates challenges. Due to the fact that partial battery data analysis methods such as a capacity increment analysis method and the like require high data resolution, low-resolution data cannot be analyzed or result errors are large, and therefore evaluation of the state of the battery system is affected.
Disclosure of Invention
The invention aims to provide a method for improving the resolution of the running data of a battery system, which can improve the resolution of the running data of an energy storage system with low voltage resolution and wide sampling interval.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows;
a method for improving the resolution of battery system operation data comprises the following steps:
acquiring original data of a battery system; the original data comprises voltage data of the battery monomer and voltage data recording time;
determining a fitting function for fitting a battery charging curve according to an electrochemical system of a battery from which original data is derived;
fitting the original data by adopting the determined fitting function to obtain a fitted voltage sequence and a battery charging curve;
and correcting the battery charging curve obtained after fitting to obtain a battery charging curve with improved resolution.
Further, the acquiring raw data of the battery system includes:
the method comprises the following steps that a data acquisition device samples battery system operation data according to a certain sampling interval;
and acquiring the operation original data of the battery system from the data acquisition equipment.
Further, the determining a form for fitting a battery charging curve based on the electrochemical system of the cell from which the raw data was derived includes:
and determining a fitting function for fitting a battery charging curve according to a battery cathode material system.
Further, in the above-mentioned case,
for the battery anode material system which is lithium iron phosphate, a double-exponential function is adopted;
and for the battery anode material system, the ternary positive electrode material system adopts an exponential and polynomial form.
Further, the fitting the raw data by using the determined fitting function includes:
using voltage data recording time as independent variableThe battery voltage being a dependent variable
Figure 183692DEST_PATH_IMAGE002
Adopt the bestFitting the battery charging data by the small two multiplication to obtain undetermined coefficients of a fitting function, and substituting the undetermined coefficients into the fitting function;
and calculating a corresponding battery voltage sequence under the time sequence with the interval of 1s as an increment by utilizing the fitting function, and recording as the fitted voltage sequence.
Further, the correcting the battery charging curve obtained after fitting includes:
filtering and interpolating the original data;
extracting time points corresponding to the voltage platform area from the filtered and interpolated original data;
replacing the voltage of the voltage platform area at the corresponding time point of the voltage platform area with the voltage of the corresponding time point in the fitted voltage sequence for integration;
and optimizing the integrated battery charging curve by adopting a sliding window.
Further, the filtering and interpolating the raw data includes:
filtering the original data by adopting a moving average method;
after filtering, a cubic spline interpolation method of shape maintenance is adopted, and the battery voltage value corresponding to each second within 10 seconds of data record interval is calculated through interpolation.
Further, the optimizing the integrated battery charging curve by using a sliding window includes:
establishing a sliding window with 3 points for the voltage platform area, sequencing the 3 points in the sliding window from small to large and replacing original numerical values to ensure that the voltage of the voltage platform area is monotonically increased.
The invention has the following beneficial effects:
the invention can restore the original data with low voltage resolution and large recording time interval to the high-resolution data with higher voltage resolution and smaller time interval, thereby providing support for the subsequent data analysis.
Drawings
FIG. 1 is a graph comparing a recovered voltage curve to a high resolution voltage curve in an embodiment of the present invention;
FIG. 2 is a graph illustrating error between a recovered voltage curve and a high resolution curve in an embodiment of the present invention;
FIG. 3 illustrates a data capacity delta curve after recovery in an embodiment of the present invention;
FIG. 4 is a graph of data voltage increment after recovery according to an embodiment of the present invention.
Detailed Description
The invention is further described below. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.
In the embodiment of the invention, the battery system is selected to be a ternary positive electrode/graphite negative electrode (in an electrochemical system of the battery, the positive electrode system is ternary, and the negative electrode system is graphite), and two sets of data acquisition equipment are adopted for data acquisition during experiments. Wherein, the set of equipment sets the voltage resolution to be 1mV and the sampling interval to be 1 s; the other set of equipment sets the voltage resolution to be 10mV and the sampling interval to be 10s according to the resolution of the returned data of the common energy storage system. The method of the invention is used for improving the resolution of the low-resolution data and comparing the low-resolution data with the high-resolution data.
The data resolution improvement process mainly comprises the following steps:
step 1: raw data of the battery system is acquired from the data acquisition device. The raw data includes time (unit: second) of data recording and voltage data (unit: volt) of the battery cell.
Step 2: the form used to fit the battery charge curve is determined based on the electrochemical system of the cell from which the raw data was derived.
For lithium ion batteries of different electrochemical systems, fitting original data by respectively adopting a double exponential function form and an exponential function and polynomial form.
The form of the bi-exponential function is as follows:
Figure DEST_PATH_IMAGE003
，
wherein the content of the first and second substances,
Figure 223061DEST_PATH_IMAGE001
is the independent variable of the number of the variable,
Figure 180652DEST_PATH_IMAGE002
as a function of the amount of the dependent variable,、
Figure DEST_PATH_IMAGE005
、
Figure 424738DEST_PATH_IMAGE006
、
Figure DEST_PATH_IMAGE007
is the undetermined coefficient.
Exponential function plus polynomial form such as exponential function plus first order polynomial:
Figure 775954DEST_PATH_IMAGE008
，
wherein the content of the first and second substances,
Figure 955262DEST_PATH_IMAGE001
is the independent variable of the number of the variable,
Figure 512994DEST_PATH_IMAGE002
as a function of the amount of the dependent variable,
Figure 422044DEST_PATH_IMAGE004
、、
Figure DEST_PATH_IMAGE009
、is the undetermined coefficient.
The fitting process is as follows:
with time as an independent variable
Figure 892843DEST_PATH_IMAGE001
The battery voltage being a dependent variable
Figure 46612DEST_PATH_IMAGE002
Fitting the battery charging data by adopting the most common least square method to obtain coefficients to be determined in two forms, namely obtaining a battery monomer time-voltage curve formula corresponding to a function form;
the corresponding cell voltage sequence in the time series with 1s as interval increment is further calculated and is marked as the fitted voltage sequence.
The choice of the form of the fitting equation depends primarily on the battery positive electrode material system. When the anode system is lithium iron phosphate, a double-exponential function is preferably adopted in consideration of a relatively flat voltage platform; when the anode system is ternary, because there is a stage of voltage end rising steadily, it adopts exponential and polynomial form.
And step 3: aiming at the battery charging curve obtained after fitting, under the condition of keeping monotonicity of the curve, the details of the curve part are modified to be more fit with the characteristics of the battery charging curve of the original electrochemical system.
Because the formula form used for fitting cannot completely reflect the chemical phase change process in the lithium battery charging process, the battery charging curve obtained after fitting needs to be subjected to detail modification.
The data compression uploading usually adopts a truncation mode, so that the original data is filtered and interpolated, the voltage change condition of a voltage platform area is extracted, the voltage change condition and a fitting curve are integrated and synthesized, then the overall curve is optimized, and the monotonicity of the numerical value is ensured.
In the embodiment of the invention, the original data is filtered by adopting a moving average method, and then a cubic spline interpolation method with a shape kept is adopted to calculate the battery voltage value corresponding to each second within the data recording interval of 10 seconds by interpolation.
In the embodiment of the invention, the voltage change condition of the voltage platform area is extracted by limiting the voltage range,
if the voltage platform area range of the lithium iron phosphate battery is about 3.2V-3.4V, the time point corresponding to the voltage platform area range is obtained, and then the voltage of the voltage platform area at the time point is replaced by the voltage value of the corresponding time point in the fitted voltage sequence, so that the integrated synthesis of the voltage change condition of the platform area and the fitted curve is realized.
The method for optimizing the overall curve comprises the following steps:
the fitting result has been defined to be monotonically increasing according to the selection of the fitting function, so that only the curve of the voltage plateau needs to be optimized.
Establishing a sliding window of 3 points, and processing the data of the voltage platform area, wherein the specific method is that 3 points in the sliding window are sequenced from small to large and replace the original numerical value, thereby realizing the monotone increasing of the voltage value of the platform area.
The voltage curve with improved resolution can be obtained through the three steps.
The invention can be used for lithium ion batteries of various common electrochemical systems, such as: lithium iron phosphate batteries, ternary batteries, and the like. According to an electrochemical system of the lithium ion battery, a phase change reaction principle in the charging and discharging process, the data recording characteristics of the applied battery management system, a data truncation mode in the data uploading process and the like, the characteristics of an original battery voltage curve are restored by adopting a data curve fitting mode, so that the data resolution is improved.
Fig. 1 to 4 show a specific embodiment of the method of the present invention, and fig. 1 shows that the data after curve precision recovery by the method of the present invention has a good goodness of fit with the data directly measured by the high precision sampling device. The error is shown in FIG. 2, and the absolute error of the plateau region (the portion between two gray vertical lines in FIG. 2) can be less than 2mV and the relative error can be less than 0.1%. The low-error voltage data of the platform area can be used for further analysis of the battery, common analysis comprises capacity increment analysis and voltage difference analysis, and a capacity increment curve and a voltage difference curve extracted from the data after the accuracy is recovered by the method are shown in fig. 3 and 4, and both show smoother shapes, and each characteristic shape on the curve is obvious and can be used for correlation analysis.
The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.

Claims (8)

1. A method for improving the resolution of battery system operation data is characterized by comprising the following steps:
acquiring original data of a battery system; the original data comprises voltage data of the battery monomer and voltage data recording time;
determining a fitting function for fitting a battery charging curve according to an electrochemical system of a battery from which original data is derived;
fitting the original data by adopting the determined fitting function to obtain a fitted voltage sequence and a battery charging curve;
and correcting the battery charging curve obtained after fitting to obtain a battery charging curve with improved resolution.
2. The method according to claim 1, wherein the obtaining raw data of the battery system comprises:
the method comprises the following steps that a data acquisition device samples battery system operation data according to a certain sampling interval;
and acquiring the operation original data of the battery system from the data acquisition equipment.
3. The method of claim 1, wherein determining the form for fitting the battery charging curve based on the electrochemical system of the cell from which the raw data was derived comprises:
and determining a fitting function for fitting a battery charging curve according to a battery cathode material system.
4. The method of claim 3, wherein the resolution of the operation data of the battery system is increased,
for the battery anode material system which is lithium iron phosphate, a double-exponential function is adopted;
and for the battery anode material system, the ternary positive electrode material system adopts an exponential and polynomial form.
5. The method of claim 4, wherein fitting the raw data with the determined fitting function comprises:
using voltage data recording time as independent variableThe battery voltage being a dependent variable
Figure 753613DEST_PATH_IMAGE002
Fitting the battery charging data by adopting a least square method to obtain undetermined coefficients of a fitting function, and substituting the undetermined coefficients into the fitting function;
and calculating a corresponding battery voltage sequence under the time sequence with the interval of 1s as an increment by utilizing the fitting function, and recording as the fitted voltage sequence.
6. The method according to claim 1, wherein the step of correcting the fitted battery charging curve includes:
filtering and interpolating the original data;
extracting time points corresponding to the voltage platform area from the filtered and interpolated original data;
replacing the voltage of the voltage platform area at the corresponding time point of the voltage platform area with the voltage of the corresponding time point in the fitted voltage sequence for integration;
and optimizing the integrated battery charging curve by adopting a sliding window.
7. The method of claim 6, wherein the filtering and interpolating the raw data comprises:
filtering the original data by adopting a moving average method;
after filtering, a cubic spline interpolation method of shape maintenance is adopted, and the battery voltage value corresponding to each second within 10 seconds of data record interval is calculated through interpolation.
8. The method of claim 6, wherein the optimizing the integrated battery charging curve by using a sliding window comprises:
establishing a sliding window with 3 points for the voltage platform area, sequencing the 3 points in the sliding window from small to large and replacing original numerical values to ensure that the voltage of the voltage platform area is monotonically increased.
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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113391220A (en) * 2020-03-12 2021-09-14 郑州深澜动力科技有限公司 Method and device for judging attenuation source of lithium ion battery

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CN108732508A (en) * 2018-05-23 2018-11-02 北京航空航天大学 A kind of real-time estimation method of capacity of lithium ion battery
CN109870655A (en) * 2019-03-26 2019-06-11 上海工程技术大学 A kind of evaluation method for lithium battery SOC
CN110031770A (en) * 2019-04-29 2019-07-19 上海玫克生储能科技有限公司 A method of quickly obtaining all cell capacities in battery pack
CN110208704A (en) * 2019-04-29 2019-09-06 北京航空航天大学 A kind of lithium battery modeling method and system based on voltage delay effect

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Publication number Priority date Publication date Assignee Title
CN103801521A (en) * 2014-01-28 2014-05-21 国家电网公司 Sorting method of secondary batteries
CN105070964A (en) * 2015-06-23 2015-11-18 常州市武进红光无线电有限公司 Lithium ion battery optimization charging technology based on charging voltage curve fixation control
CN108732508A (en) * 2018-05-23 2018-11-02 北京航空航天大学 A kind of real-time estimation method of capacity of lithium ion battery
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113391220A (en) * 2020-03-12 2021-09-14 郑州深澜动力科技有限公司 Method and device for judging attenuation source of lithium ion battery
CN113391220B (en) * 2020-03-12 2023-10-13 郑州深澜动力科技有限公司 Lithium ion battery attenuation source judging method and device

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