CN111983469B - Lithium battery safety degree estimation method and device based on voltage safety boundary and temperature safety boundary - Google Patents
Lithium battery safety degree estimation method and device based on voltage safety boundary and temperature safety boundary Download PDFInfo
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- CN111983469B CN111983469B CN202010857326.1A CN202010857326A CN111983469B CN 111983469 B CN111983469 B CN 111983469B CN 202010857326 A CN202010857326 A CN 202010857326A CN 111983469 B CN111983469 B CN 111983469B
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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]
- G01R31/367—Software therefor, e.g. for battery testing using modelling or look-up tables
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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]
- G01R31/392—Determining battery ageing or deterioration, e.g. state of health
Abstract
The application discloses a lithium battery safety degree estimation method and device based on a voltage safety boundary and a temperature safety boundary, and belongs to the field of battery safety. The application aims at the problem that the prior art cannot quantitatively evaluate and display the safety of the battery. The application is based on the standard working voltage range and the voltage safety boundary B of the battery U And the voltage safety coefficient S of the battery U The method comprises the steps of carrying out a first treatment on the surface of the According to the standard operating temperature range of the battery, temperature safety boundary B T And the temperature safety coefficient S of the battery T The method comprises the steps of carrying out a first treatment on the surface of the According to S S ＝ω 1 *S U +ω 2 *S T Estimating the safety degree of the battery; the application can intuitively estimate and display the safety degree of the battery in real time, and solves the problem of judging the safety of the lithium power battery.
Description
Technical Field
The application relates to the field of battery safety judgment, in particular to a lithium battery safety estimation method and device based on a voltage safety boundary and a temperature safety boundary.
Background
With the increasing pace of commercialization of electric vehicles in the global market, the demand for high-power and high-energy power batteries is rapidly increasing, and the safety of batteries is also receiving more and more attention. In particular, in recent years, the safety of lithium batteries has been increasingly emphasized because of the occurrence of accidents such as spontaneous combustion and explosion of lithium batteries. At present, the lithium battery in China is still in an initial stage in the technical development level, and a plurality of problems still exist in the aspect of safety.
Lithium ion batteries are a complex electrochemical system, and the failure mechanism of the battery is complex, and the failure mode is affected by a plurality of factors, such as the ambient temperature, the depth of discharge, the charge-discharge current and the like. Although the state parameters of the battery such as voltage, current, temperature and the like can be measured in real time, the parameters such as internal resistance, capacity, SOC and the like can also be obtained by calculation through actual measurement parameters, the safety of the battery cannot be measured, the safety is a variable quantity influenced by multiple factors at any time, and the safety guarantee is also a precondition for the normal application of a battery system. The problem of quantifying the safety of batteries is also an important point and difficulty in the current research of battery application and safety research. Domestic scholars are less in battery safety quantitative research at present, and mainly focus on a battery fault diagnosis method. The fault diagnosis makes a judgment on the fault problem only after the battery fails, and cannot prevent the occurrence of the battery fault. In practice, the formation of battery faults is a gradual change process, such as safety evaluation of the battery during the use process of the battery, and quantitative indexes are given, which plays an important role in preventing battery accidents and guaranteeing life safety of users. How to achieve real-time and accurate safe estimation is always a bottleneck problem in the design process of the lithium ion power battery pack.
Disclosure of Invention
In order to solve the problems, the application provides a lithium battery safety degree estimation method and device based on a voltage safety boundary and a temperature safety boundary, which can intuitively estimate and display the safety degree of a battery in real time and solve the problem of safety judgment of a lithium power battery.
The application provides a lithium battery safety degree estimation method based on a voltage safety boundary and a temperature safety boundary, which comprises the following steps:
determining a voltage safety boundary B of a battery U And a battery temperature safety boundary B T ；
Acquiring a battery voltage acquisition value and a battery temperature acquisition value in a time interval;
according to the voltage safety boundary B of the battery U Standard operating voltage and the battery voltage acquisition value, the voltage safety coefficient S of the battery U ；
Safety margin B according to the temperature of the battery T Standard operating temperature and temperature safety coefficient S of the battery T ；
According to S S ＝ω 1 *S U +ω 2 *S T Estimating the safety of the battery, wherein S S Omega is the safety of the battery 1 And omega 2 The weight coefficient of the battery voltage and the weight coefficient of the battery temperature, respectively.
Further, the voltage safety factor S of the battery U The method comprises the following steps:
in U S For standard working voltage, B U For voltage safety margin, U i The battery voltage acquisition value obtained for the i-th time interval.
Further, the voltage safety boundary B U The determining method of (1) comprises the following steps:
collecting voltage boundary samples of SOH (solid oxide) belonging to [1%,100% ] under different current multiplying powers, and dividing the samples into a training set and a testing set;
establishing a support vector regression equation:
wherein f (x) is the voltage safety boundary B estimated by the regression equation U Is a function of the number of (c),as vector coefficients, X i Support vector for SOH and current multiplying power C sample of battery, b is regression equation parameter, K (X, X i ) Is a kernel function;
inputting the training set into the regression equation to obtain B under any SOH and current multiplying power C U Values.
Further, the battery temperature safety coefficient S T The method comprises the following steps:
wherein T is s For standard working temperature, B T And T is a battery temperature acquisition value obtained at the ith time interval for a temperature safety boundary.
Further, the temperature safety boundary B T The determining method of (1) comprises the following steps:
collecting temperature boundary samples of SOH (solid oxide) belonging to [1%,100% ] under different current multiplying powers, and dividing the samples into a training set and a testing set;
establishing a support vector regression equation:
wherein f (y) is the temperature boundary B estimated by the regression equation T Is a function of the number of (c),is a vector coefficient, Y is a support vector of a battery SOH and a current multiplying power C sample, C is a regression equation parameter, K (Y, Y) i ) Is a kernel function;
inputting the training set into the regression equation, and calculating to obtain any SOH and B under current multiplying power C T Values.
Further, the weight coefficient omega of the battery voltage 1 The acquisition method of (1) comprises the following steps:
acquiring a characteristic value F of the battery voltage safety coefficient u And a corresponding variable total variance D (u);
by passing throughObtaining a contribution rate sigma of the battery voltage variance u ；
Contribution rate sigma of cell voltage variance u After normalization, the weight coefficient omega of the battery voltage is obtained 1 。
Further, the weight coefficient omega of the battery temperature 2 The acquisition method of (1) comprises the following steps:
acquiring a characteristic value F of the battery temperature safety system t And the total variance D (t) of the corresponding variables;
by passing throughContribution rate sigma of battery temperature variance t ；
Contribution rate sigma of the battery temperature variance t After normalization, the weight coefficient omega of the battery voltage is obtained 2 。
Further, the battery is a single battery or a battery pack formed by connecting batteries in series and parallel; the battery is a lead-acid battery, a cadmium-nickel battery, a nickel-hydrogen battery, a lithium ion battery, a fuel cell, a solar cell or a chemical power supply.
A second aspect of the present application provides a lithium battery safety degree estimating apparatus based on a voltage safety boundary and a temperature safety boundary, comprising:
the voltage acquisition unit is used for acquiring the battery voltage in real time;
the temperature acquisition unit is used for acquiring the temperature of the battery in real time;
the communication unit is used for sending the battery voltage acquired by the voltage acquisition unit and the battery temperature acquired by the temperature acquisition unit to the control unit;
the control unit is used for respectively preprocessing the battery voltage and the battery temperature to obtain a battery voltage acquisition value and a battery temperature acquisition value, and calculating to obtain the battery safety by using the lithium battery safety estimation method based on the voltage and the temperature characteristics according to the first aspect of the application;
and the display unit is used for displaying the battery safety information.
Further, the preprocessing process of the control unit comprises the following steps:
setting a fixed time interval, removing the maximum value and the minimum value of the battery voltage acquired in the fixed time interval, taking the average value of the residual battery voltage data as a battery voltage acquisition value, recording, removing the maximum value and the minimum value of the battery temperature acquired in the fixed time interval, taking the average value of the residual battery temperature data as a battery temperature acquisition value, and recording.
As described above, the method and the device for estimating the safety of the lithium battery based on the voltage and temperature characteristics provided by the application have the following effects:
1. the application realizes real-time quantitative estimation and display of the safety of the battery, is applied to the evaluation of the safety of various batteries in various states in the use process of the battery, solves the technical bottleneck problem that the safety of the battery cannot be early-warned in real time in the prior art, and provides a validity index for the judgment of the safety degree of the battery in the use process.
2. The application only uses two variables of voltage and temperature to estimate the safety of the battery, the two variables can reflect the working state of the battery more comprehensively, the acquisition is easy, the parameters are less, the model is simple, the calculation result can be updated conveniently, and the application has real-time property.
3. The research on the safety of the lithium power battery in the prior art mainly researches the safety of the battery when the battery leaves the factory, the safety evaluation of the battery takes the safety index of the battery when the battery leaves the factory as a main reference condition, the safety of the battery under the condition of recycling is relatively less, and the battery has the conditions of aging and degradation in the actual operation of the working condition, and a great amount of practices and researches prove that the safety of the battery gradually decreases along with recycling. As the SOH of the battery decreases, the tolerance of the battery to electrical abuse also gradually decreases; the voltage safety boundary and the temperature safety boundary can quantitatively reflect the safety change of the battery caused by aging and fading in the process of recycling the battery, so that the estimated SOS of the battery meets the working condition.
4. The application adopts SVR to determine the battery voltage safety boundary and the battery temperature safety boundary, the SVR has the advantages of small sample and high latitude calculation, high calculation speed, no dimension disaster, and small occupied system memory, and realizes the real-time accurate estimation of the battery safety.
5. The application is suitable for the safety evaluation of various batteries, and has wide applicability and easy realization of hardware circuits.
Drawings
FIG. 1 is a schematic block diagram of a battery safety level estimation device according to an embodiment of the present application;
FIG. 2 is a flowchart of a battery safety evaluation method according to an embodiment of the present application;
FIG. 3 is a schematic diagram showing an explosion experiment performed at a 1C magnification in the present application, B U SOH change graph;
FIG. 4 shows an explosion experiment performed at a 1C magnification in the present application, B T SOH change graph;
FIG. 5 is a graph of battery safety, battery voltage, and battery temperature contours for an embodiment of the present application;
FIG. 6 is a safety contour plot around standard voltage;
Detailed Description
Other advantages and effects of the present application will become apparent to those skilled in the art from the following disclosure, which describes the embodiments of the present application with reference to specific examples. The application may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present application. It should be noted that the following embodiments and features in the embodiments may be combined with each other without conflict.
It should be noted that the illustrations provided in the following embodiments merely illustrate the basic concept of the present application by way of illustration, and only the components related to the present application are shown in the illustrations, not according to the number, shape and size of the components in actual implementation, and the form, number and proportion of each component in actual implementation may be arbitrarily changed, and the layout of the components may be more complex.
In the prior art, researches related to battery safety are mainly developed around fault diagnosis technologies, the methods aim at diagnosing the cause of the fault of a battery after the fault of the battery, and the battery is improved according to the diagnosis result, so that the method cannot substantially prevent the fault of the battery, but the fault behavior of the battery is a gradual change process in the use process of the battery, and in many cases, the battery reaches the extreme aging condition of combustion explosion when the fault behavior of the battery is not obviously shown, so that great losses are caused to personnel and property, and the embodiment provides a lithium battery safety degree estimating device based on a voltage safety boundary and a temperature safety boundary. And, the battery is a lead-acid battery, a cadmium-nickel battery, a nickel-hydrogen battery, a lithium ion battery, a fuel cell, a solar cell or a chemical power supply, and the battery in this embodiment adopts a 3.7V/1250mAh ternary material 18650 type lithium ion battery, and the estimation device is as shown in fig. 1, and includes:
the temperature acquisition unit 200 is configured to acquire battery temperature data in real time, where the temperature acquisition unit in this embodiment adopts a temperature sensor MAX6613;
the voltage acquisition unit 300 is configured to acquire battery voltage data in real time, and the voltage acquisition unit in this embodiment is a sampling chip LTC6802;
when the working states of the battery are different, the electrochemical reactions inside the battery are different, and some technical indexes are adopted in the prior art as main parameters for measuring the performance quality of the battery, wherein the main parameters generally comprise battery capacity, energy density, charge-discharge multiplying power, voltage service life, internal resistance, self-discharge and working temperature, but in the working process of the battery, the battery temperature and voltage can reflect the battery state at the moment most intuitively, the change of the two indexes can reflect the abnormal reaction degree of the battery to a great extent, and the two index data acquisition means are more mature, so that the temperature information and the voltage information of the battery are respectively acquired by using the temperature acquisition unit and the voltage acquisition unit for subsequent battery safety calculation.
The communication unit 400 sends the battery voltage acquired by the voltage acquisition unit and the battery temperature acquired by the temperature acquisition unit to the control unit, and the communication unit in the embodiment adopts a PCA82C250 standard external circuit;
the control unit 500 performs pretreatment on the battery voltage and the battery temperature to obtain a battery voltage acquisition value and a battery temperature acquisition value, and performs SVR operation to obtain C, SOH and B U 、B T In practical application, the control unit 500 may adopt an existing module to carry a battery health degree calculation program according to actual needs, so as to implement calculation of the battery health degree, and the control unit 500 of the present embodiment is used for calculation of the health degree of the lithium power battery, so that the control unit 500 of the present embodiment adopts a domestic EVBCM-8133 battery management main control module, and the domestic EVBCM-8133 battery management main control module and the communication unit 400 establish communication connection in a CAN bus communication manner;
in practical application, the control unit may be an MSP430 single-chip microcomputer, a 51 single-chip microcomputer, a DSP, a TMS single-chip microcomputer, an STM32 single-chip microcomputer, a PIC single-chip microcomputer, an AVR single-chip microcomputer, an STC single-chip microcomputer, a freeboard serial single-chip microcomputer, etc. to control the charge and discharge of the battery charge and discharge source, and the single-chip microcomputer may be connected with the charge and discharge source through a serial port or a bus.
The display unit 600 is configured to display information such as battery safety information, voltage, current, alarm signals, discharge time, capacity, safety early warning information, etc., in this embodiment, a vehicle-mounted analog load LB-42KW-230VDC is adopted, the display unit may be a desktop computer, a notebook computer, an LED liquid crystal display, a UM12864 liquid crystal display, etc., and the display unit 600 and the control unit may select RS232, RS485, RS422 serial communication interfaces or ethernet transmission or CAN bus transmission.
As shown in fig. 1, the temperature acquisition unit 200 and the voltage acquisition unit 300 are respectively connected to the battery 100, the output ends of the temperature acquisition unit 200 and the voltage acquisition unit 300 are connected to the control unit 400 through the communication unit 400, and the control unit 400 sends the estimated safety information to the display unit 600 to display the health value of the battery.
The control unit 400 establishes a safety degree comparison table, wherein the safety degree comparison table is composed of a plurality of safety intervals, and the safety intervals correspond to the battery safety condition at the current moment.
The safety of the battery refers to the safety degree of the battery, which is quantitatively described as the safety degree of the battery, wherein the battery is not burnt, exploded, poisonous and harmful gases are not generated and the safety degree is not harmful to a user in the use process.
In the embodiment, the control unit 500 is configured to calculate the battery safety value, but in order to make the user use the battery safety more intuitively and definitely in the practical application process, the control unit 500 is configured with a judging unit to match the obtained safety value with the safety interval to obtain the battery safety condition at the current moment, when the estimated safety value meets the safety interval, different early warning information is provided, the judging unit judges the safety interval to which the current safety of the battery belongs, further judges the battery state at the moment, and displays the safety value of the current battery and the corresponding battery early warning information in a percentage mode through the display unit 600. The segmentation of this embodiment is as follows:
table 1 battery safety stage, safety range and early warning information.
| Safety stage | Safety degree value range | Displaying early warning information |
| 1 | 0-20 | The battery reaches a serious danger level |
| 2 | 20-40 | Battery deviceTo the extent of danger |
| 3 | 40-60 | The potential danger exists in the battery |
| 4 | 60-80 | Battery status is generally |
| 5 | 80-100 | The battery state is good |
According to the safety degree segmentation method, a large number of experiments of the battery and basic parameters of the battery are divided, the safety degree of the battery in the embodiment is divided into a plurality of sections, when the safety degree of the battery is located in the section [80,100], the battery is good in shape and can be used continuously, when the safety degree of the battery is located in the section [60,80 ], the battery state is generally indicated, a user needs to pay attention slightly, when the safety degree of the battery is located in the section [40, 60 ], the battery is indicated to have potential danger, the user needs to pay attention in the use process, when the safety degree of the battery is located in the section [20, 40), the battery reaches the dangerous degree, the use is stopped and the battery is replaced, when the safety degree of the battery is located in the section [0,20 ], the surface battery reaches the serious dangerous degree, the combustion explosion condition is indicated to appear or the combustion and explosion are extremely easy to cause, and the battery is detached and is transferred in an emergency treatment mode according to practical needs.
The lithium battery safety degree estimation method based on the voltage safety boundary and the temperature safety boundary specifically comprises the following steps:
s1, determiningVoltage safety margin B of constant cell U And a battery temperature safety boundary B T ；
S11, acquiring a voltage safety boundary B U ；
S111, collecting voltage boundary samples of SOH (solid oxide) belonging to [1%,100% ] under different current multiplying powers, and dividing the samples into a training set and a testing set;
in this example, the battery explosion test was performed under the conditions of current rates of 1C, 2C and 3C, respectively, and SOH of the battery was [1%,100 ]]In the process, constant current charging is carried out every 1% of SOH until the battery burns, explodes or toxic gas appears, and the voltage at the moment is recorded as a voltage safety boundary B under the SOH U Further, under the condition of obtaining the battery multiplying power of 1C, 2C and 3C, SOH is 1%,100%]Voltage safety margin B at every 1% U Is a data sample of (a). The explosion experiment under each current multiplying power comprises 100 sample data, wherein 80 data are selected as training sets, and the rest 20 data are selected as test sets;
s112, calculating by using Support Vector Regression (SVR) to obtain a regression equation as follows:
where f (x) is the voltage safety boundary B estimated by the regression equation U Is a function of the number of (c),as vector coefficients, X i Support vector for SOH and current multiplying power C sample of battery, b is regression equation parameter, K (X, X i ) Is a kernel function, specifically:
wherein λ is a kernel parameter;
s113, setting the voltage safety boundary B U Training set of numerical value, multiplying power C and battery health SOHInputting the regression equation for training, and establishing a battery health degree SOH, a current multiplying power C and a voltage safety boundary B U Is a regression relationship of (a).
S12, acquiring a temperature safety boundary B T ；
S121, collecting temperature boundary samples of SOH (solid oxide) belonging to [1%,100% ] under different current multiplying powers, and dividing the samples into a training set and a testing set;
and carrying out a battery explosion experiment under the condition that the current multiplying power is 1C, 2C and 3C. At each of the above current ratios, the SOH of the battery was 1%,100%]In the process, constant current charging is carried out every 1% SOH until the battery burns, explodes or toxic gas appears, and the temperature at the moment is recorded as a temperature safety boundary B under the SOH T The battery multiplying power is 1C, 2C and 3C, SOH is 1%,100%]Inner temperature safety boundary B at every 1% T Is a data sample of (a). The explosion experiment under each multiplying power comprises 100 sample data, wherein 80 data are sample training sets, and 20 data are test sets;
s122, calculating by using SVR to obtain a regression equation:
wherein f (y) is the temperature boundary B estimated by the regression equation T Is a function of the number of (c),is a vector coefficient, Y is a support vector of a battery SOH and a current multiplying power C sample, C is a regression equation parameter, K (Y, Y) i ) Is a kernel function;
the kernel function K (Y, Y i ) Is a polynomial kernel function, which is specifically:
where is the lambda kernel parameter.
S123, the temperature safety edgeBoundary B T The training set of the numerical value, the multiplying power C and the battery health degree SOH is input into the regression equation for training, and the battery health degree SOH, the current multiplying power C and the temperature safety boundary B are established T Is a regression relationship of (a).
S2, collecting the battery voltage and the battery temperature in real time;
the acquisition frequency of the battery information by the temperature acquisition unit 200 and the voltage acquisition remote 300 of the embodiment is 10 ms/time, and the control unit 500 receives the acquired original battery voltage information { u } through the communication unit 400 1 ，u 2 …u l … and raw cell temperature information { t } 1 ,t 2 …t l …}；
S3, obtaining accurate real-time voltage and temperature data through filtering, wherein the filtering method can be an arithmetic average filtering method, a moving average filtering method, a median average filtering method and various filtering methods based on digital signals, and the filtering method in the embodiment is as follows: setting the fixed time interval as 100ms, removing the maximum value and the minimum value of the battery voltage acquired in the fixed time interval of 100ms, taking the average value of the residual battery voltage data as the battery voltage acquisition value { U1, U } 2 …U i … }, and recording; removing the maximum value and the minimum value of the battery temperature acquired in a fixed time interval, and taking the average value of the residual battery temperature data as a battery temperature acquisition value { T } 1 ，T 2 …T i … }, and recorded.
S4, acquiring the battery voltage and the standard working voltage U S Comparing, incorporating voltage safety margin B U Obtaining the voltage safety coefficient S of the battery U ：
In U S For standard working voltage, U i Battery voltage acquisition value B for the i-th time interval U The voltage safety boundary is the voltage safety boundary value of the battery in the current SOH state. Voltage safetyThe full coefficient characterizes the current working state of the power battery, the minimum value is 0 in the normal working state of the battery, and the closer the value is to 0, the more abnormal the working state of the battery is proved.
S5, comparing the battery temperature acquisition value with a standard working temperature, and obtaining a temperature safety coefficient by combining a temperature safety boundary to obtain a temperature safety coefficient S of the battery T ；
Wherein T is s At standard working temperature, T i Battery temperature acquisition value B for the i-th time interval T The voltage safety boundary is the temperature safety boundary value of the battery in the current SOH state. The voltage safety coefficient characterizes the current working state of the power battery, the minimum value is 0 in the normal working state of the battery, and the closer the value is to 0, the more abnormal the working state of the battery is proved.
When any one of the voltage safety coefficient and the temperature safety coefficient of the battery is too low, the working state of the battery is dangerous, so that the influence of the voltage safety coefficient and the temperature safety coefficient on the safety of the battery is increased by adding a weight variable. According to the voltage safety coefficient and the temperature safety coefficient, the correlation between the current battery voltage safety coefficient and the current battery safety degree is obtained by using a principal component analysis method according to the degree of the voltage safety coefficient and the temperature safety coefficient approaching zero. Specifically, the method is shown in step S6 and step S7.
S6, obtaining the weight coefficient omega of the battery voltage 1 The method specifically comprises the following steps:
s61, acquiring the battery voltage safety coefficient data set { S } U1 ，S U2 Eigenvalue F of … } u And a corresponding variable total variance D (u);
s62, throughObtaining a contribution rate sigma of the battery voltage variance u ；
S63, the contribution rate sigma of the battery voltage variance is calculated u After normalization, the weight coefficient omega of the battery voltage is obtained 1 。
S7, obtaining a weight coefficient omega of the battery temperature 2 The method specifically comprises the following steps:
s71, acquiring the battery temperature safety system data set { S } T1 ，S T2 Eigenvalue F of … } t And the total variance D (t) of the corresponding variables;
s72, throughContribution rate sigma of battery temperature variance t ；
S73, the contribution rate sigma of the battery temperature variance is calculated t After normalization, the weight coefficient omega of the battery voltage is obtained 2 。
S8, according to S S ＝ω 1 *S U +ω 2 *S T Estimating the safety of the battery, wherein S S Is the safety of the battery.
In practical application, different standard voltages and standard temperatures are adopted for different power battery systems, and different voltage and temperature thresholds are selected according to different batteries, so that more effective battery safety can be obtained. By adopting the analysis of the difference between the voltage, the temperature and the standard value under the working condition of the battery, ss is one percent under the ideal working condition of the battery. Therefore, the closer to one hundred the value of the power battery safety Ss obtained by the test, the higher the safety of the battery at this time is characterized; the lower the value of the resulting power battery safety Ss, the higher the likelihood of a hazard occurring in this power battery module under such conditions.
In practical application, different standard voltages and standard temperatures are adopted for different power battery systems, and different voltage and temperature thresholds are selected according to different batteries, so that more effective battery safety can be obtained. By adopting the analysis of the difference between the voltage, the temperature and the standard value under the working condition of the battery, ss is one percent under the ideal working condition of the battery. Therefore, the closer to one hundred the value of the power battery safety Ss obtained by the test, the higher the safety of the battery at this time is characterized; the lower the value of the resulting power battery safety Ss, the higher the likelihood of a hazard occurring in this power battery module under such conditions.
S9, judging the value of the current safety degree of the battery, further judging the state of the battery at the moment, and displaying the safety degree value of the current battery and corresponding battery early warning information in a percentage mode through a display unit 600;
the contour lines drawn by the battery safety degree estimation result in this embodiment are shown in fig. 5 and 6, in fig. 5, the abscissa represents the battery voltage, the ordinate represents the battery temperature, and the safety degrees at different voltages and temperatures are shown in the form of contour lines, wherein fig. 6 is a contour line diagram near the standard voltage, and as can be seen from the figure, the battery safety degree estimation device and method in this embodiment can accurately estimate the battery safety degree, and has high estimation precision and strong real-time performance.
The above embodiments are merely illustrative of the principles of the present application and its effectiveness, and are not intended to limit the application. Modifications and variations may be made to the above-described embodiments by those skilled in the art without departing from the spirit and scope of the application. Accordingly, it is intended that all equivalent modifications and variations of the application be covered by the claims, which are within the ordinary skill of the art, be within the spirit and scope of the present disclosure.
Claims (8)
1. A lithium battery safety degree estimation method based on a voltage safety boundary and a temperature safety boundary is characterized by comprising the following steps of: the method comprises the following steps:
determining a voltage safety boundary B of a battery U And a battery temperature safety boundary B T ；
Acquiring a battery voltage acquisition value and a battery temperature acquisition value in a time interval;
according to the voltage safety boundary B of the battery U Standard operating voltage and the battery voltage acquisition value, the voltage safety coefficient S of the battery U ；
Safety margin B according to the temperature of the battery T Standard operating temperature and temperature safety coefficient S of the battery T ；
According to S S ＝ω 1 *S U +ω 2 *S T Estimating the safety of the battery, wherein S S Omega is the safety of the battery 1 And omega 2 The weight coefficient of the battery voltage and the weight coefficient of the battery temperature are respectively;
the voltage safety factor S of the battery U The method comprises the following steps:
in U S For standard working voltage, B U For voltage safety margin, U i Acquiring a battery voltage acquisition value for the ith time interval;
battery temperature safety coefficient S T The method comprises the following steps:
wherein T is s For standard working temperature, B T T is the temperature safety boundary i The battery temperature acquisition value obtained for the i-th time interval.
2. The lithium battery safety evaluation method based on the voltage safety boundary and the temperature safety boundary according to claim 1, wherein:
said voltage safety margin B U The determining method of (1) comprises the following steps:
collecting voltage boundary samples of SOH (solid oxide) belonging to [1%,100% ] under different current multiplying powers, and dividing the samples into a training set and a testing set;
establishing a support vector regression equation:
wherein f (x) is the voltage safety boundary B estimated by the regression equation U Is a function of the number of (c),as vector coefficients, X i Support vector for SOH and current multiplying power C sample of battery, b is regression equation parameter, K (X, X i ) Is a kernel function;
inputting the training set into the regression equation to obtain B under any SOH and current multiplying power C U Values.
3. The lithium battery safety evaluation method based on the voltage safety boundary and the temperature safety boundary according to claim 1, wherein:
said temperature safety boundary B T The determining method of (1) comprises the following steps:
collecting temperature boundary samples of SOH (solid oxide) belonging to [1%,100% ] under different current multiplying powers, and dividing the samples into a training set and a testing set;
establishing a support vector regression equation:
wherein f (y) is the temperature boundary B estimated by the regression equation T Is a function of the number of (c),as vector coefficients, Y i Support vector for SOH and current multiplying power C sample of battery, C is regression equation parameter, K (Y, Y i ) Is a kernel function;
inputting the training set into the regression equation, and calculating to obtain any SOH and B under current multiplying power C T Values.
4. According to claimThe lithium battery safety degree estimation method based on the voltage safety boundary and the temperature safety boundary as claimed in claim 1, wherein the method is characterized in that: weight coefficient omega of the battery voltage 1 The acquisition method of (1) comprises the following steps:
acquiring a characteristic value F of the battery voltage safety coefficient u And a corresponding variable total variance D (u);
by passing throughObtaining a contribution rate sigma of the battery voltage variance u ；
Contribution rate sigma of cell voltage variance u After normalization, the weight coefficient omega of the battery voltage is obtained 1 。
5. The lithium battery safety evaluation method based on the voltage safety boundary and the temperature safety boundary according to claim 1, wherein: weight coefficient omega of the battery temperature 2 The acquisition method of (1) comprises the following steps:
acquiring a characteristic value F of the battery temperature safety system t And the total variance D (t) of the corresponding variables;
by passing throughContribution rate sigma of battery temperature variance t ；
Contribution rate sigma of the battery temperature variance t After normalization, the weight coefficient omega of the battery temperature is obtained 2 。
6. The lithium battery safety evaluation method based on the voltage safety boundary and the temperature safety boundary according to claim 1, wherein: the battery is a battery pack formed by single batteries or batteries connected in series and parallel; the battery is a lead-acid battery, a cadmium-nickel battery, a nickel-hydrogen battery, a lithium ion battery, a fuel cell, a solar cell or a chemical power supply.
7. A lithium battery safety degree estimation device based on a voltage safety boundary and a temperature safety boundary is characterized in that: comprising the following steps:
the voltage acquisition unit is used for acquiring the battery voltage in real time;
the temperature acquisition unit is used for acquiring the temperature of the battery in real time;
the communication unit is used for sending the battery voltage acquired by the voltage acquisition unit and the battery temperature acquired by the temperature acquisition unit to the control unit;
the control unit is used for respectively preprocessing the battery voltage and the battery temperature to obtain a battery voltage acquisition value and a battery temperature acquisition value, and calculating to obtain the battery safety by using the lithium battery safety degree estimation method based on the voltage safety boundary and the temperature safety boundary according to any one of claims 1-6;
and the display unit is used for displaying the battery safety information.
8. The lithium battery safety degree estimating apparatus based on a voltage safety boundary and a temperature safety boundary according to claim 7, wherein: the pretreatment process of the control unit comprises the following steps:
setting a fixed time interval, removing the maximum value and the minimum value of the battery voltage acquired in the fixed time interval, taking the average value of the residual battery voltage data as a battery voltage acquisition value, recording, removing the maximum value and the minimum value of the battery temperature acquired in the fixed time interval, taking the average value of the residual battery temperature data as a battery temperature acquisition value, and recording.
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