CN111983469A - 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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- 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
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Abstract
The invention 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 invention aims at the problem that the safety of the battery cannot be quantitatively estimated and displayed in the prior art. The invention is based on the standard working voltage range and the voltage safety boundary B of the batteryUAnd obtaining the voltage safety coefficient S of the battery according to the battery voltage acquisition valueU(ii) a Safety temperature boundary B according to standard working temperature range of batteryTAnd obtaining the temperature safety coefficient S of the battery through the battery temperature acquisition valueT(ii) a According to SS＝ω1*SU+ω2*STEstimating the safety degree of the battery; the invention can intuitively estimate and display the safety process of the battery in real timeAnd the problem of safety judgment of the lithium power battery is solved.
Description
Technical Field
The invention relates to the field of battery safety degree judgment, in particular to a lithium battery safety degree estimation method and device based on a voltage safety boundary and a temperature safety boundary.
Background
With the increasingly rapid commercialization pace of electric vehicles in the global market, the demand for high-power and high-energy power batteries is rapidly increasing, and the safety of the batteries is receiving more and more attention. Particularly, in recent years, news about accidents such as spontaneous combustion and explosion of lithium batteries occurs, and the safety of lithium batteries is increasingly emphasized. At present, lithium batteries in China are still in the initial stage of technical research and development, and still have many problems in the aspect of safety.
The lithium ion battery is a complex electrochemical system, the failure mechanism of the battery is complex, and the failure mode of the battery is influenced by a plurality of factors, such as the ambient temperature, the discharge depth, the charge and discharge current and the like. Although the state parameters of the battery, such as voltage, current, temperature, etc., can be measured in real time, and the parameters of internal resistance, capacity, SOC, etc., can also be obtained by calculating the actual measurement parameters, the safety of the battery cannot be measured, and is a variable influenced by multiple factors at any time, and the guarantee of the safety is also a precondition for the normal application of the battery system. The problem of quantifying the safety of the battery also becomes a key point and a difficulty in the current battery application research and safety research. At present, domestic scholars are few in the aspect of quantitative research on battery safety, and mainly focus on the aspect of a battery fault diagnosis method. The failure diagnosis is to make a judgment on the failure problem only after the battery fails, and it cannot prevent the battery from failing. In fact, the composition of the battery fault is a gradually changing process, for example, the battery can be evaluated for safety in the using process of the battery, and a quantitative index is given, which plays an important role in preventing the battery accident and guaranteeing the life safety of a user. How to achieve real-time and accurate safety 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 invention provides a lithium battery safety degree estimation method and a lithium battery safety degree estimation 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 invention 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 margin B of a batteryUAnd temperature safety margin B of the batteryT；
Acquiring a battery voltage acquisition value and a battery temperature acquisition value in a time interval;
safety margin B based on the voltage of the batteryUObtaining the voltage safety coefficient S of the battery by the standard working voltage and the battery voltage acquisition valueU；
Safety margin B according to the temperature of the batteryTStandard working temperature and temperature safety coefficient S of battery obtained by battery temperature acquisition valueT；
According to SS＝ω1*SU+ω2*STEstimating the degree of battery safety, wherein SSAs a degree of safety of the battery, omega1And ω2Respectively, a weight coefficient of the battery voltage and a weight coefficient of the battery temperature.
Further, the voltage safety factor S of the batteryUComprises the following steps:
in the formula of USIs a standard operating voltage, BUTo a voltage safety margin, UiAnd acquiring a battery voltage value obtained for the ith time interval.
Further, the voltage safety margin BUThe determination method comprises the following steps:
collecting voltage boundary samples with SOH (state of charge) of [ 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 margin B estimated by the regression equationUThe value of (a) is,
being a vector coefficient, XiIs the support vector of the battery SOH and current multiplying power C sample, b is the parameter of regression equation, 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 CUThe value is obtained.
Further, the battery temperature safety coefficient STComprises the following steps:
in the formula, TsIs the standard working temperature, BTAnd T is a battery temperature acquisition value obtained in the ith time interval.
Further, the temperature safety boundary BTThe determination method comprises the following steps:
collecting temperature boundary samples with SOH (state of health) of [ 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 equationTThe value of (a) is,
is a vector coefficient, Y is a support vector of a battery SOH and current multiplying power C sample, C is a regression equation parameter, K (Y, Y)i) Is a kernel function;
will be described inInputting the training set into the regression equation, and calculating to obtain B under any SOH and current multiplying power CTThe value is obtained.
Further, the weight coefficient omega of the battery voltage1The acquisition method comprises the following steps:
obtaining a characteristic value F of the battery voltage safety coefficientuAnd the corresponding variable total variance d (u);
by passing
Obtaining the contribution rate sigma of the battery voltage varianceu；
The contribution rate sigma of the cell voltage varianceuObtaining the weight coefficient omega of the battery voltage after normalization1。
Further, the weight coefficient omega of the battery temperature2The acquisition method comprises the following steps:
obtaining the characteristic value F of the battery temperature safety systemtAnd the total variance d (t) of the corresponding variables;
by passing
Obtaining the contribution rate sigma of the temperature variance of the batteryt；
The contribution rate sigma of the battery temperature variancetObtaining the weight coefficient omega of the battery voltage after normalization2。
Furthermore, 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 battery or a chemical power supply.
The second aspect of the present invention provides a lithium battery safety degree estimation device based on a voltage safety boundary and a temperature safety boundary, comprising:
the voltage acquisition unit is used for acquiring the voltage of the battery 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 transmitting 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 the battery safety by using the lithium battery safety estimation method based on the voltage and temperature characteristics in the first aspect of the invention;
and the display unit is used for displaying the battery safety degree 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, averaging the voltage data of the residual battery to be used 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, averaging the temperature data of the residual battery to be used as a battery temperature acquisition value, and recording.
As described above, the method and apparatus for estimating the safety of a lithium battery based on voltage and temperature characteristics according to the present invention have the following effects:
1. the invention realizes real-time quantitative estimation and display of the safety degree of the battery, is applied to the estimation of the safety degree 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 pre-warned in real time in the prior art, and provides effective indexes for judging the safety degree of the battery in the use process.
2. The invention only uses two variables of voltage and temperature to estimate the safety of the battery, the two variables can more comprehensively reflect the working state of the battery, the acquisition is easy, the parameters are few, the model is simple, the calculation result can be conveniently updated, and the real-time performance is realized.
3. In the prior art, the research on the safety of the lithium power battery mainly researches the safety of the battery when the battery leaves a 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 under a working condition is relatively low, the battery has the conditions of aging and decline in the actual operation under the working condition, and a large number of practices and researches prove that the safety of the battery is gradually reduced 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 change of the safety of the battery caused by aging and recession in the circulating use process, so that the estimated SOS of the battery meets the working condition better.
4. The method adopts the SVR to determine the battery voltage safety boundary and the battery temperature safety boundary, the SVR has the advantages of small samples, high latitude calculation, high operation speed, no dimension disaster and small occupied system memory, and the real-time accurate estimation of the battery safety degree is realized.
5. The invention is suitable for estimating the safety degree of various batteries, has wide applicability and is easy to realize hardware circuits.
Drawings
FIG. 1 is a schematic block diagram of a battery safety estimation apparatus according to an embodiment of the present invention;
FIG. 2 is a flow chart of a method for estimating battery safety according to an embodiment of the present invention;
FIG. 3 shows the explosion test performed at 1C magnification, BUGraph as a function of SOH;
FIG. 4 shows the explosion test performed at 1C magnification, BTGraph as a function of SOH;
FIG. 5 is a contour plot of battery safety, battery voltage, and battery temperature for an embodiment of the present invention;
FIG. 6 is a contour plot of safety around standard voltage;
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. It is to be noted that the features in the following embodiments and examples may be combined with each other without conflict.
It should be noted that the drawings provided in the following embodiments are only for illustrating the basic idea of the present invention, and the drawings only show the components related to the present invention rather than the number, shape and size of the components in actual implementation, and the type, quantity and proportion of the components in actual implementation may be changed freely, and the layout of the components may be more complicated.
In the prior art, research related to battery safety mainly develops around fault diagnosis technologies, the methods are directed at diagnosing the cause of the battery fault after the battery fault occurs, the battery is improved according to the diagnosis result, the method cannot substantially prevent the battery fault from occurring, but in the use process of the battery, the fault behavior of the battery is a gradually changing process, and in many cases, the battery reaches an extreme aging condition of combustion and explosion when the battery fault behavior is not obviously shown, so that great loss is caused to personnel and property. Moreover, the battery is a lead-acid battery, a cadmium-nickel battery, a nickel-hydrogen battery, a lithium ion battery, a fuel cell, a solar battery or a chemical power source, the battery of this embodiment adopts a 3.7V/1250mAh ternary material 18650 type lithium ion battery, and the estimation device is shown in fig. 1 and includes:
the temperature acquisition unit 200 is used for acquiring battery temperature data in real time, and the temperature acquisition unit of the embodiment adopts a temperature sensor MAX 6613;
the voltage acquisition unit 300 is used for acquiring battery voltage data in real time, and the voltage acquisition unit in the embodiment is a sampling chip LTC 6802;
the battery is used as an electrochemical system, when the working states of the battery are different, the electrochemical reactions in the battery are different, in the prior art, some technical indexes are adopted as main parameters for measuring the performance of the battery, and generally comprise battery capacity, energy density, charging and discharging 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 current battery state most visually, the change of the two indexes can reflect the reaction abnormal degree of the battery to a great extent, and the data acquisition means of the two indexes are more mature, so that the temperature acquisition unit and the voltage acquisition unit are used for respectively acquiring the temperature information and the voltage information of the battery for subsequent calculation of the safety degree of the battery.
The communication unit 400 is used for sending the battery voltage collected by the voltage collection unit and the battery temperature collected by the temperature collection unit to the control unit, and the communication unit of the embodiment adopts a PCA82C250 standard external circuit;
a control unit 500 for respectively preprocessing the battery voltage and the battery temperature to obtain a battery voltage acquisition value and a battery temperature acquisition value, and performing SVR operation to obtain C, SOH and BU、BTThe regression relationship of (a) is used for calculating to obtain a battery safety degree value, in practical application, the control unit 500 may adopt an existing module to carry the battery health degree calculation program of the embodiment according to actual needs to realize calculation of the battery health degree, which is used for calculation of the health degree of the lithium power battery of the embodiment, so that the control unit 500 of the 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 can 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 Freescale series single chip microcomputer and the like, and the single chip microcomputer can be connected with a charging and discharging source in a serial port or bus mode.
The display unit 600 is used for displaying information such as battery safety information, voltage, current, alarm signals, discharge time, capacity and safety early warning information, the vehicle-mounted analog load LB-42KW-230VDC is adopted in the embodiment, the display unit CAN be a desktop computer, a notebook computer, an LED liquid crystal display screen, a UM12864 liquid crystal display screen and the like, and the display unit 600 and the control unit CAN select RS232, RS485 and 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 safety degree information obtained by estimation to the display unit 600 to display the health value of the battery.
The control unit 400 establishes a safety comparison table, which is composed of a plurality of safety intervals corresponding to the battery safety conditions at the current time.
The safety of the battery refers to that the battery does not burn, explode, generate toxic and harmful gases, and do not cause harm to users during the use process, and quantitatively describing the safety degree of the battery during the use process is called as the safety degree of the battery.
In this embodiment, the control unit 500 is configured to calculate the battery safety degree value, but in an actual application process, in order to make the user use the safety degree more intuitively and definitely, the control unit 500 is provided with a determination unit, the obtained safety degree value is matched with the safety interval to obtain the battery safety condition at the current moment, when the estimated safety degree value satisfies the safety degree interval, different warning information is provided, the determination unit determines the safety degree interval to which the current safety degree of the battery belongs, and then determines the battery state at the current moment, and the display unit 600 displays the safety degree value of the current battery and corresponding battery warning information in a percentage system manner. The segmentation of the present embodiment is as follows:
table 1 battery safety stage, safety range and warning information.
| Safe phase | Safety degree value range | Displaying early warning information |
| 1 | 0-20 | The battery reaches a |
| 2 | 20-40 | The battery reaches a |
| 3 | 40-60 | Potential danger exists in the |
| 4 | 60-80 | General state of the |
| 5 | 80-100 | Good battery state |
The method for segmenting the safety degree of the battery in the embodiment is characterized in that a large number of experiments of the battery and basic parameters of the battery are divided, the safety degree value of the battery in the embodiment is in a percentage system form, the safety degree value of the battery is divided into a plurality of intervals, when the safety degree value of the battery is located in the interval of [80,100], the battery is good at the moment and can be continuously used, when the safety degree value of the battery is located in the interval of [60,80 ], the battery state is general and needs to be slightly noticed by a user at the moment, when the safety degree value of the battery is located in the interval of [40, 60 ], the battery is potentially dangerous at the moment, the user needs to pay more attention in the using process, when the safety degree value of the battery is located in the interval of [20, 40 ], the battery reaches a dangerous degree at the moment, the use is stopped and the battery is replaced, when the safety degree value of the battery is, 20) in the interval, the surface battery reaches a serious danger degree, which indicates that a burning explosion condition occurs or the battery is easy to cause burning and explosion, and at the moment, the battery is disassembled and properly transferred by adopting an emergency treatment mode according to actual needs.
The method for estimating the safety degree of the lithium battery based on the voltage safety boundary and the temperature safety boundary in the embodiment specifically comprises the following steps:
s1, determining the voltage safety boundary B of the batteryUAnd temperature safety margin B of the batteryT；
S11, obtaining a voltage safety boundary BU；
S111, collecting voltage boundary samples with SOH (state of health) of [ 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 carried out under the conditions of current multiplying factors of 1C, 2C and 3C, respectively, and the SOH of the battery was [ 1%, 100% ]under each of the above current multiplying factors]Charging at constant current every 1% SOH until the battery burns, explodes or produces toxic gas, and recording the voltage as the voltage safety boundary B under the SOHUFurther, when the battery rate is 1C, 2C, or 3C, the SOH is [ 1%, 100%]Inner voltage safety boundary B at every 1%UThe data samples of (1). The explosion experiment under each current multiplying power totally 100 sample data, 80 of them are selected as training set, the other 20 are test set;
s112, calculating by using Support Vector Regression (SVR) to obtain a regression equation as follows:
wherein f (x) is the voltage safety margin B estimated by the regression equationUThe value of (a) is,
being a vector coefficient, XiIs the support vector of the battery SOH and current multiplying power C sample, b is the parameter of regression equation, K (X, X)i) As a kernel function, specifically:
wherein λ is a nuclear parameter;
s113, setting the voltage safety boundary BUInputting the value, multiplying power C and the training set of the battery health degree SOH into the regression equation for training, and establishing the battery health degree SOH, the current multiplying power C and the voltage safety boundary BUThe regression relationship of (2).
S12, acquiring temperature safety boundary BT；
S121, collecting temperature boundary samples with SOH (state of health) of [ 1%, 100% ] under different current multiplying powers, and dividing the samples into a training set and a testing set;
the battery explosion test was performed at current multiplying factors of 1C, 2C, and 3C. At each current rate, the SOH of the battery is 1%, 100%]Charging at constant current every 1% SOH until the battery burns, explodes or produces toxic gas, and recording the temperature as the temperature safety boundary B under the SOHTThe battery multiplying power is 1C, 2C and 3C, and the SOH is 1 percent, 100 percent]Inner temperature safety boundary B at intervals of 1%TThe data samples of (1). The explosion experiment under each multiplying power totally 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 as follows:
wherein f (y) is the temperature boundary B estimated by the regression equationTThe value of (a) is,
is a vector coefficient, Y is a support vector of a battery SOH and 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) described in this embodimenti) Is a polynomial kernel function, specifically:
where is the lambda kernel parameter.
S123, setting the temperature safety boundary BTInputting the value, multiplying power C and the training set of the battery health degree SOH into the regression equation for training, and establishing a battery health degree SOH, a current multiplying power C and a temperature safety boundary BTThe regression relationship of (2).
S2, collecting the voltage and temperature of the battery in real time;
in this embodiment, the frequency of collecting battery information by the temperature collecting unit 200 and the voltage collecting unit 300 is 10 ms/time, and the control unit 500 receives the collected original battery voltage information { u [ u ] through the communication unit 4001，u2…ul… and raw battery temperature information t1,t2…tl…}；
S3, obtaining accurate real-time voltage and temperature data through filtering, where the filtering method may be arithmetic mean filtering, moving average filtering, median average filtering, and various filtering methods based on digital signals, and the filtering method of this embodiment is: setting the fixed time interval as 100ms, removing the maximum value and the minimum value of the battery voltage acquired within the fixed time interval of 100ms, and averaging the voltage data of the residual battery to obtain a battery voltage acquisition value { U1, U2…Ui… }, and recording; will be fixed atRemoving the maximum value and the minimum value of the battery temperature collected in the time interval, and averaging the residual battery temperature data to obtain a battery temperature collection value { T }1，T2…Ti… }, and recording.
S4, collecting value of battery voltage and standard working voltage USMaking a comparison in conjunction with a voltage safety margin BUObtaining the voltage safety coefficient S of the batteryU：
In the formula of USIs a standard operating voltage, UiThe battery voltage acquisition value obtained for the ith time interval, BUThe voltage safety boundary is the voltage safety boundary value of the battery under the current SOH state. The voltage safety factor represents the current working state of the power battery, the minimum value is 0 under the normal working state of the battery, and the more the value is close 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 the temperature safety coefficient S of the battery by combining the temperature safety boundary to obtain the safety coefficient of the temperatureT；
In the formula, TsIs a standard working temperature, TiBattery temperature acquisition value, B, obtained for the ith time intervalTThe voltage safety boundary is the temperature safety boundary value of the battery under the current SOH state. The voltage safety factor represents the current working state of the power battery, the minimum value is 0 under the normal working state of the battery, and the more the value is close to 0, the more abnormal the working state of the battery is proved.
When any value of the voltage safety coefficient and the temperature safety coefficient of the battery is too low, the working state of the battery is very dangerous, so that the influence of the voltage safety coefficient and the temperature safety coefficient on the safety degree of the battery when the voltage safety coefficient and the temperature safety coefficient are too low is increased by adding a weight variable. According to the voltage safety coefficient and the temperature safety coefficient and the degree close to zero, the embodiment obtains the correlation between the current battery voltage safety coefficient and the temperature safety coefficient and the current battery safety degree by using a principal component analysis method. As shown in step S6 and step S7.
S6, obtaining weight coefficient omega of battery voltage1The method specifically comprises the following steps:
s61, acquiring the battery voltage safety coefficient data set { SU1，SU2Characteristic value F of …uAnd the corresponding variable total variance d (u);
s62, passing
Obtaining the contribution rate sigma of the battery voltage varianceu；
S63, calculating the contribution rate sigma of the battery voltage varianceuObtaining the weight coefficient omega of the battery voltage after normalization1。
S7, acquiring weight coefficient omega of battery temperature2The method specifically comprises the following steps:
s71, acquiring the battery temperature safety system data set { ST1，ST2Characteristic value F of …tAnd the total variance d (t) of the corresponding variables;
s72, passing
Obtaining the contribution rate sigma of the temperature variance of the batteryt；
S73, calculating the contribution rate sigma of the battery temperature variancetObtaining the weight coefficient omega of the battery voltage after normalization2。
S8, according to SS＝ω1*SU+ω2*STEstimating the degree of battery safety, wherein SSThe 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 analyzing the difference between the voltage and the temperature of the battery under the working condition and the standard value, the Ss is one percent under the ideal working state of the battery. Therefore, the more the value of the safety degree Ss of the power battery obtained through the test approaches to one hundred, the higher the safety of the battery at the moment is represented; the lower the value of the safety level Ss of the power cell is obtained, the higher the probability of the power cell module being dangerous under the condition is represented.
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 analyzing the difference between the voltage and the temperature of the battery under the working condition and the standard value, the Ss is one percent under the ideal working state of the battery. Therefore, the more the value of the safety degree Ss of the power battery obtained through the test approaches to one hundred, the higher the safety of the battery at the moment is represented; the lower the value of the safety level Ss of the power cell is obtained, the higher the probability of the power cell module being dangerous under the condition is represented.
S9, judging the numerical value of the current safety degree of the battery, further judging the current battery state, and displaying the safety degree numerical value of the current battery and corresponding battery early warning information in a percentage mode through the display unit 600;
contour lines drawn by the battery safety degree estimation result of the embodiment are shown in fig. 5 and fig. 6, in fig. 5, the abscissa is the battery voltage, the ordinate is the battery temperature, and the safety degrees under different voltages and temperatures are shown in the diagram in the form of contour line diagrams, wherein fig. 6 is a contour line diagram near the standard voltage, as can be seen from the diagram, the battery safety degree estimation device and method of the embodiment can accurately estimate the battery safety degree, and has high estimation precision and strong real-time performance.
The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.
Claims (10)
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: the method comprises the following steps:
determining a voltage safety margin B of a batteryUAnd temperature safety margin B of the batteryT；
Acquiring a battery voltage acquisition value and a battery temperature acquisition value in a time interval;
safety margin B based on the voltage of the batteryUObtaining the voltage safety coefficient S of the battery by the standard working voltage and the battery voltage acquisition valueU；
Safety margin B according to the temperature of the batteryTStandard working temperature and temperature safety coefficient S of battery obtained by battery temperature acquisition valueT；
According to SS＝ω1*SU+ω2*STEstimating the degree of battery safety, wherein SSAs a degree of safety of the battery, omega1And ω2Respectively, a weight coefficient of the battery voltage and a weight coefficient of the battery temperature.
2. The lithium battery safety degree estimation method based on the voltage safety boundary and the temperature safety boundary according to claim 1, characterized in that: voltage safety factor S of the batteryUComprises the following steps:
in the formula of USIs a standard operating voltage, BUTo a voltage safety margin, UiAnd acquiring a battery voltage value obtained for the ith time interval.
3. The method for estimating the safety degree of the lithium battery based on the voltage safety boundary and the temperature safety boundary as claimed in claim 1, wherein the method comprises the following steps:
the voltage safety margin BUThe determination method comprises the following steps:
collecting voltage boundary samples with SOH (state of charge) of [ 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 margin B estimated by the regression equationUThe value of (a) is,
being a vector coefficient, XiIs the support vector of the battery SOH and current multiplying power C sample, b is the parameter of regression equation, 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 CUThe value is obtained.
4. The lithium battery safety degree estimation method based on the voltage safety boundary and the temperature safety boundary according to claim 1, characterized in that:
battery temperature safety coefficient STComprises the following steps:
in the formula, TsIs the standard working temperature, BTAnd T is a battery temperature acquisition value obtained in the ith time interval.
5. The lithium battery safety degree estimation method based on the voltage safety boundary and the temperature safety boundary according to claim 1, characterized in that:
the temperature safety margin BTThe determination method comprises the following steps:
collecting temperature boundary samples with SOH (state of health) of [ 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 equationTValue of (a), betai-βi *Is a vector coefficient, Y is a support vector of a battery SOH and 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 B under any SOH and current multiplying power CTThe value is obtained.
6. The lithium battery safety degree estimation method based on the voltage safety boundary and the temperature safety boundary according to claim 1, characterized in that: weight coefficient ω of the battery voltage1The acquisition method comprises the following steps:
obtaining a characteristic value F of the battery voltage safety coefficientuAnd the corresponding variable total variance d (u);
by passing
Obtaining the contribution rate sigma of the battery voltage varianceu；
The contribution rate sigma of the cell voltage varianceuObtaining the weight coefficient omega of the battery voltage after normalization1。
7. The lithium battery safety degree estimation method based on the voltage safety boundary and the temperature safety boundary as claimed in claim 1, characterized in thatIn the following steps: weight coefficient ω of the battery temperature2The acquisition method comprises the following steps:
obtaining the characteristic value F of the battery temperature safety systemtAnd the total variance d (t) of the corresponding variables;
by passing
Obtaining the contribution rate sigma of the temperature variance of the batteryt；
The contribution rate sigma of the battery temperature variancetObtaining the weight coefficient omega of the battery voltage after normalization2。
8. The lithium battery safety degree estimation method based on the voltage safety boundary and the temperature safety boundary according to claim 1, characterized in that: 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 battery or a chemical power supply.
9. A lithium battery safety degree estimation device based on a voltage safety boundary and a temperature safety boundary is characterized in that: the method comprises the following steps:
the voltage acquisition unit is used for acquiring the voltage of the battery 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 transmitting 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 the battery safety by using the lithium battery safety estimation method based on the voltage and temperature characteristics according to claims 1-8;
and the display unit is used for displaying the battery safety degree information.
10. The lithium battery safety degree estimation apparatus based on the voltage safety margin and the temperature safety margin as set forth in claim 9, 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, averaging the voltage data of the residual battery to be used 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, averaging the temperature data of the residual battery to be used as a battery temperature acquisition value, and recording.
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