CN107991623A - It is a kind of to consider temperature and the battery ampere-hour integration SOC methods of estimation of degree of aging - Google Patents

Abstract

The invention discloses a method for estimating battery ampere-hour integral SOC considering temperature and aging degree. Effect of aging degree Correct the maximum available capacity of the battery to obtain the correction coefficient of the maximum available capacity affected by the aging degree; according to the obtained correction coefficient, the current sensor detects and saves the measured battery charge and discharge current i _bat in real time, and integrates it through the ampere-hour The basic algorithm obtains the change of battery SOC at different temperatures and aging degrees, that is, the corrected SOC estimation expression. Considering the influence of battery temperature and aging degree on SOC, the initial value of battery SOC can be accurately estimated, and at the same time, the cumulative error problem existing in the ampere-hour integration method is solved, and the SOC estimation accuracy of the ampere-hour integration method is improved.

Description

A battery ampere-hour integral SOC estimation method considering temperature and aging degree

technical field

The invention relates to the technical field of power batteries, in particular to a battery ampere-hour integral SOC estimation method considering temperature and aging degree.

Background technique

At present, lithium-ion power batteries have become one of the most attractive rechargeable batteries for electric vehicles due to their advantages such as high energy density, low self-discharge rate, no memory effect and high monomer voltage. As the core of electric vehicles, power batteries are currently the key factors restricting the scale development of electric vehicles. Different from traditional fuel vehicles, the energy of electric vehicles comes from the power battery, and the power battery and its management system are crucial to the power, safe operation and economic performance of the vehicle.

The state of charge (SOC) of the battery is a very important parameter index during the operation of electric vehicles. It is an important basis for judging the remaining battery power, preventing battery overcharge and overdischarge, and judging whether it needs to be balanced to improve battery performance. , is also one of the key technologies that the battery management system needs to solve. Similar to the oil gauge of a traditional fuel car, the battery SOC reflects the remaining power of the battery. However, different from the remaining fuel detection method of traditional fuel vehicles, the remaining power of the battery cannot be directly measured by sensors. It must be measured through some other measurable physical quantities (such as battery terminal voltage, charging and discharging current, battery temperature, etc.) and corresponding algorithms. indirect estimate.

The existing SOC estimation methods mainly include discharge method, open circuit voltage method, electrochemical impedance method, ampere-hour integration method, neural network method, Kalman filter method, etc. The problems of various algorithms are as follows:

The SOC estimation of the discharge method is more accurate, but requires a large amount of experimental data, and does not meet the online estimation requirements of electric vehicles in actual driving, so it is difficult to apply in practice; the SOC estimation effect of the open circuit voltage method is better at the beginning and end of charging and discharging, but The error is large in the process of charging and discharging, and because the open circuit voltage needs to be estimated, the battery pack needs to be left for a long time, which is in contradiction with the application of electric vehicles, and is rarely used alone in practice; the electrochemical impedance method is used when the battery power is low or relatively low. When it is high, the SOC estimation is more accurate, but when the power is in the middle section, the SOC estimation is inaccurate due to the small change in AC impedance, and the impedance is greatly affected by the initial power, temperature, aging degree, etc., making it difficult to estimate, and it is also difficult to achieve on hardware , which is rarely used in practical applications; the neural network method requires a large amount of data for training, and is easily affected by the training data and training methods, and the processing process is relatively complicated; the Kalman filter method is currently a more researched algorithm. There are many studies on optimization algorithms, but the neural network and Kalman filter methods are difficult to set up in the system, and the cost is very high when they are applied in the battery management system. The method is simple, practical and effective, and is currently the most commonly used SOC estimation algorithm for electric vehicle applications. The ampere-hour integration method calculates the state of charge of the battery by integrating the battery current with time. This method has a certain accuracy for calculating the amount of electricity discharged by the battery. However, the chemical reaction process inside the battery charge and discharge is very complicated, and the battery SOC is easily affected by many factors such as temperature, aging degree (cycle number), current rate, self-discharge, etc., making it very difficult to accurately estimate the SOC of the power battery. challenging. At present, the ampere-hour integration method has not yet solved the problem of accurately estimating the battery's initial SOC, because once the ambient temperature changes, the battery's available capacity and initial SOC will change. In addition, inaccurate current measurement in the current integration method will also cause SOC calculation errors, and the errors are cumulative and will gradually increase with time.

To sum up, in the prior art, there is still no effective solution to the problem of accurate estimation of the SOC of the power battery.

Contents of the invention

In order to solve the deficiencies of the prior art, the present invention provides a method for estimating battery ampere-hour integral SOC considering temperature and aging degree, which takes into account the influence of battery temperature and aging degree on SOC, and can estimate battery SOC more accurately The initial value, and solve the cumulative error problem existing in the ampere-hour integration method, and improve the SOC estimation accuracy of the ampere-hour integration method.

A battery ampere-hour integral SOC estimation method considering temperature and aging degree, comprising:

Considering the temperature and aging degree, the initial value of the battery is corrected to obtain the correction coefficient that the initial value of the battery SOC is affected by the temperature and aging degree;

Considering the influence of the aging degree, the maximum available capacity of the battery is corrected to obtain the correction coefficient that the maximum available capacity is affected by the aging degree;

According to the obtained correction coefficient, the current sensor detects and saves the measured battery charge and discharge current i _bat in real time, and through the basic algorithm of ampere-hour integration, the change of the battery SOC at different temperatures and aging degrees is obtained, that is, the corrected SOC estimate expression.

Further, when correcting the initial value of the battery in consideration of the temperature and aging degree, the battery management system obtains the battery temperature and the number of charging and discharging cycles of the battery, that is, the aging degree in real time, and recalculates the initial SOC of the battery according to the correction algorithm, which can be It is denoted as γSOC ₀ , where γ represents the correction coefficient for the initial value of battery SOC affected by temperature and aging degree, and γSOC ₀ is the initial value of battery SOC when considering the influence of temperature and aging degree.

Further, when correcting the maximum available capacity of the battery considering the influence of the aging degree, according to the relationship between the maximum available capacity of the battery and the aging degree, that is, the number of charge and discharge cycles, the number of charge and discharge cycles obtained in real time by the battery management system, and Recalculate the maximum available capacity of the battery according to the revised algorithm, which can be recorded as μ _N C _max , where μ _N represents the correction coefficient of the maximum available capacity affected by the aging degree, and μ _N C _max is the maximum battery capacity under different aging degrees, that is, the number of cycles. available capacity.

Further, the above battery ampere-hour integral SOC estimation method considering the temperature and aging degree, wherein the initial value of the battery SOC SOC ₀ itself needs to be corrected regularly, which means that when the battery needs to be reset to the initial value of the battery SOC periodically or after a period of time One correction.

Further, the correction method for the initial value of the battery SOC is as follows: when the battery voltage reaches the charging cut-off voltage and is close to the fully charged state, the initial value of the battery SOC is corrected according to the measured relationship between the open circuit voltage and the SOC.

Further, the above battery ampere-hour integral SOC estimation method considering the temperature and aging degree needs to select multiple groups of power battery cells of the same batch before correcting the initial value of the battery, and part of them is used for the correction experiment that the maximum available capacity is affected by the aging degree , part of which is used for the correction experiment that the initial value of battery SOC is affected by temperature and aging degree; select battery charging and discharging equipment with high current control accuracy, temperature control box with appropriate temperature accuracy and range, and high-precision current sensor.

Further, when the initial value of the battery is corrected considering the temperature and aging degree, the specific process is:

Select a part of the power battery monomer, and charge it with a constant current at room temperature to restore the power battery to a fully charged state;

Then, conduct constant current discharge experiments on the power battery to obtain the maximum available capacity of the power battery, and select the maximum available capacity C _max of the first full charge as a benchmark;

Then, the battery is subjected to a charge-discharge cycle aging test under a constant current until the maximum available capacity of the battery is only a set percentage of the initial maximum available capacity. At this time, the battery life is considered to have terminated, and the correction of the maximum available capacity affected by the aging degree is obtained. coefficient where N represents the number of cycles.

Further, the number of cycles is determined according to the actual number of cycle life of the battery and the required estimation accuracy.

Further, when considering the influence of the aging degree to correct the maximum available capacity of the battery, the specific process is:

Set the test temperature range and temperature change step;

At different temperatures, carry out constant current charging on some of the selected power battery cells to restore the power battery to a fully charged state;

Carry out current constant current discharge experiment on the power battery to obtain the maximum available capacity of the power battery;

Carry out charge-discharge cycle aging experiments on the battery under constant current until the maximum available capacity of the battery is only the set percentage of the initial maximum available capacity. At this time, the battery life is considered to have terminated, and the maximum available capacity at room temperature is selected as the benchmark. At different temperatures T°C and different cycle times N, the correction coefficient of the initial value of battery SOC affected by temperature and aging degree can be obtained

Further, the above battery ampere-hour integral SOC estimation method considering the temperature and aging degree is applied to the battery management system.

Compared with prior art, the beneficial effect of the present invention is:

(1) A battery ampere-hour integral SOC estimation method that considers temperature and aging degree proposed by the present invention obtains a correction factor that considers temperature and aging degree of maximum available capacity affected by aging degree The correction coefficient of the influence is optimized for the ampere-hour integral method, which is simple, reliable and easy to implement.

(2) A battery SOC estimation method of the present invention considers the influence of battery temperature and aging degree on SOC, can accurately estimate the initial value of battery SOC, solves the cumulative error problem existing in the ampere-hour integral method at the same time, and improves the ampere-hour Integral SOC estimation accuracy.

(3) The present invention provides a more accurate battery SOC estimation method for the battery management system, and provides a basic guarantee for safe, reasonable and efficient use of power batteries.

Description of drawings

The accompanying drawings constituting a part of the present application are used to provide further understanding of the present application, and the schematic embodiments and descriptions of the present application are used to explain the present application, and do not constitute improper limitations to the present application.

FIG. 1 is a schematic diagram of a battery SOC estimation method considering temperature and aging degree according to the present invention.

Detailed ways

It should be pointed out that the following detailed description is exemplary and intended to provide further explanation to the present application. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

It should be noted that the terminology used here is only for describing specific implementations, and is not intended to limit the exemplary implementations according to the present application. As used herein, unless the context clearly dictates otherwise, the singular is intended to include the plural, and it should also be understood that when the terms "comprising" and/or "comprising" are used in this specification, they mean There are features, steps, operations, means, components and/or combinations thereof.

As introduced in the background technology, the existing ampere-hour integration method in the prior art to estimate battery SOC does not consider the influence of factors such as temperature and aging degree, and the estimation accuracy is limited. In order to solve the above technical problems, this application proposes a A battery ampere-hour integral SOC estimation method considering temperature and aging degree.

In a typical implementation of the present application, as shown in FIG. 1 , a battery ampere-hour integral SOC estimation method considering temperature and aging degree is provided. The battery ampere-hour integral SOC estimation method considering temperature and aging degree The method includes a step of correcting the initial value of battery SOC considering the temperature and aging degree, and a step of correcting the maximum available capacity of the battery considering the influence of the aging degree. According to the correction coefficient obtained in the above steps, the basic algorithm of the ampere-hour integration method is used to estimate the battery SOC.

Among them, regarding the battery SOC, it refers to the percentage of the battery's remaining power and the maximum available capacity, where the battery's remaining power refers to the total power released from the current state of the battery to the fully discharged state; the maximum available capacity refers to the battery from full to full The total amount of electricity released during the process of discharging with a sufficiently small current to the fully discharged state, this value has nothing to do with the temperature, but only with the design capacity and aging degree of the battery. The battery SOC can be expressed as:

Among them, C _rem and C _max respectively represent the remaining power and the maximum available capacity of the battery;

The ampere-hour integration method refers to calculating the SOC of the battery by integrating the battery current with time. The basic principle is:

Among them, SOC ₀ represents the initial value of the battery SOC, and i _bat represents the charging and discharging current of the battery.

The battery SOC initial value SOC ₀ refers to the battery SOC value at the initial moment when the battery starts charging and discharging.

The battery SOC initial value correction considering the temperature and aging degree refers to obtaining the battery temperature and the number of charging and discharging cycles (aging degree) of the battery in real time through the battery management system, and recalculating the initial SOC of the battery according to the correction algorithm, which can be recorded as γSOC ₀ , where γ represents the correction coefficient for the initial value of battery SOC affected by temperature and aging degree, and γSOC ₀ is the initial value of battery SOC when considering the influence of temperature and aging degree.

The correction of the maximum available capacity of the battery considering the influence of the aging degree refers to the number of charge and discharge cycles obtained in real time through the battery management system according to the relationship between the maximum available capacity of the battery and the degree of aging (number of charge and discharge cycles), and recalculated according to the correction algorithm The maximum available capacity of the battery can be recorded as μ _N C _max , where μ _N represents the correction coefficient of the maximum available capacity affected by the aging degree, and μ _N C _max is the maximum available capacity of the battery under different aging degrees (number of cycles);

A battery SOC estimation method considering temperature and aging degree can be expressed as;

In yet another embodiment of the present application, applying the above concept to realize a method for estimating battery SOC considering temperature and aging degree includes the following steps:

Step 1: Select multiple groups of power battery cells of the same batch, one part is used for the correction experiment that the maximum usable capacity is affected by the aging degree, and the other part is used for the correction experiment that the initial value of the battery SOC is affected by the temperature and aging degree; select the current control accuracy Higher battery charging and discharging equipment, selection of temperature control boxes with appropriate temperature accuracy and range, and selection of high-precision current sensors to reduce current measurement errors and cumulative errors of ampere-hour integration;

Step 2: Select a part of the power battery monomer, and charge it with a constant current at a normal temperature of 25°C to restore the power battery to a fully charged state; then, conduct a constant-current discharge experiment with a sufficiently small current on the power battery to obtain a power battery The maximum available capacity of the battery, and select the maximum available capacity _Cmax of the first full charge as a benchmark; then, the battery is subjected to a charge-discharge cycle aging test at a constant current of 1C until the maximum available capacity of the battery is only 80% of the initial maximum available capacity At this point, it can be considered that the battery life has expired, and the correction coefficient for the maximum available capacity affected by the aging degree can be obtained Where N represents the number of cycles, since the value of C _max (N) has a small variation with the number of cycles, it can be simplified into a segmented form, namely

The specific segmentation values of the above-mentioned cycle number N of 300 and 600 are not fixed, but may be determined according to specific conditions such as the actual number of cycle life of the battery and the required estimation accuracy;

Step 3: Design the appropriate test temperature range and temperature change step, and then, at different temperatures, charge the selected power battery cells with constant current to restore the power battery to a fully charged state; then, charge the power battery The battery is subjected to a small enough current constant current discharge experiment to obtain the maximum available capacity of the power battery, and then the battery is subjected to a charge-discharge cycle aging test at a constant current of 1C until the maximum available capacity of the battery is only 80% of the initial maximum available capacity. , at this point, it can be considered that the battery life has expired, and the maximum available capacity at room temperature 25°C is selected as the benchmark. At this time, it can be obtained in

Correction coefficient for the initial value of battery SOC affected by temperature and aging degree at different temperatures T°C and different cycle times N

Step 4: According to the correction coefficient obtained in Step 2 and Step 3, the battery charging and discharging current i _bat measured in real time is detected and saved by the high-precision current sensor, and the battery is obtained at different temperatures and aging degrees through the basic algorithm of ampere-hour integration. The change of battery SOC, that is, the corrected SOC estimation expression

In yet another implementation example of the present invention, if the current measurement is inaccurate, it will cause SOC calculation errors, and the errors are cumulative and will gradually increase with time. value to correct. The calibration method is when the battery needs to re-calibrate the initial value of the battery SOC periodically or after a period of time. The calibration can be performed when the battery is about to be fully charged, that is, when the battery voltage reaches 98% of the charge cut-off voltage (also known as the charge cut-off voltage). At this time, the battery voltage will reach the charging cut-off voltage. A change in battery SOC corresponds to a large change in battery open circuit voltage, and the calibration accuracy is high. At the same time, because the charging current is small enough, the influence of ohmic resistance voltage drop and polarization voltage can be ignored. At this time The battery voltage is basically equal to the open circuit voltage of the battery; according to the battery data measured by the open circuit voltage method in the early stage, mainly the corresponding relationship between the open circuit voltage and SOC measured in the experiment, the current battery SOC value is corrected by the table look-up method according to the current battery voltage , obviously, the more and more detailed the data measured and stored in the early stage, the more accurate the SOC correction will be. Through the above, the initial battery SOC value can be corrected more accurately.

In another typical implementation manner of the present application, a battery management system is disclosed. The battery management system uses the above battery SOC estimation method considering temperature and aging degree to estimate the battery SOC. The battery management system estimates the battery SOC more accurately, which provides a basic guarantee for the safe, reasonable and efficient use of power batteries.

The above descriptions are only preferred embodiments of the present application, and are not intended to limit the present application. For those skilled in the art, there may be various modifications and changes in the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of this application shall be included within the protection scope of this application.

Claims (10)

1. a kind of consider temperature and the battery ampere-hour integration SOC methods of estimation of degree of aging, it is characterized in that, including：

Consider that temperature and degree of aging are corrected the initial value of battery and obtain battery SOC initial value by temperature and degree of aging The correction coefficient of influence；

Consider that degree of aging influences to be corrected the maximum available of battery and obtain maximum available by degree of aging shadow Loud correction coefficient；

According to obtained correction coefficient, the battery charging and discharging electric current i measured is detected and preserved in real time by current sensor_bat, lead to Ampere-hour integration rudimentary algorithm is crossed, the situation of change of battery battery SOC under different temperatures and degree of aging is obtained, that is, corrects SOC estimates expression formula.

2. a kind of battery ampere-hour for considering temperature and degree of aging as claimed in claim 1 integrates SOC methods of estimation, its feature It is that when the consideration temperature and degree of aging are corrected the initial value of battery, electricity is obtained by battery management system in real time Pond temperature and the charge and discharge cycles of battery number, that is, degree of aging, and the initial SOC of battery is recalculated according to correction algorithm, can To be denoted as γ SOC₀, wherein, γ represents the correction coefficient that battery SOC initial value is influenced by temperature and degree of aging, γ SOC₀It is exactly Consider battery SOC initial value when temperature and degree of aging influence.

3. a kind of battery ampere-hour for considering temperature and degree of aging as claimed in claim 1 integrates SOC methods of estimation, its feature Be, it is described when considering that degree of aging influences to be corrected the maximum available of battery, according to battery maximum available with Relation between degree of aging, that is, charge and discharge cycles number, the charge and discharge cycles number obtained in real time by battery management system, And the maximum available of battery is recalculated according to correction algorithm, μ can be denoted as_NC_max, wherein, μ_NRepresent maximum available The correction coefficient influenced by degree of aging, μ_NC_maxIt is exactly the battery maximum available under different degree of aging i.e. cycle-indexes.

4. a kind of battery ampere-hour for considering temperature and degree of aging as claimed in claim 1 integrates SOC methods of estimation, its feature It is the battery ampere-hour integration SOC methods of estimation of above-mentioned consideration temperature and degree of aging, wherein, battery SOC initial value SOC₀Itself Regular calibration is needed, is referred to when battery needs are regular or once corrected being done again to battery SOC initial value after a period of time.

5. a kind of battery ampere-hour for considering temperature and degree of aging as claimed in claim 4 integrates SOC methods of estimation, its feature It is described to be corrected to battery SOC initial value, bearing calibration：Cell voltage is up to charge cutoff voltage, close to fully charged shape During state, according to the open-circuit voltage and the relation curve of SOC measured, battery SOC initial value is corrected.

6. a kind of battery ampere-hour for considering temperature and degree of aging as claimed in claim 1 integrates SOC methods of estimation, its feature It is that the battery ampere-hour integration SOC methods of estimation of above-mentioned consideration temperature and degree of aging need before the initial value of correction battery Choose multigroup real for the correction that maximum available is influenced by degree of aging with a batch of power battery monomer, a part Test, a part is used for the correction experiment that battery SOC initial value is influenced by temperature and degree of aging；Select current control accuracy higher Battery charging and discharging equipment, temperature accuracy and the suitable temperature control box of scope and high-precision current sensor.

7. a kind of battery ampere-hour for considering temperature and degree of aging as claimed in claim 1 or 2 integrates SOC methods of estimation, its It is characterized in, when the consideration temperature and degree of aging are corrected the initial value of battery, detailed process is：

A part of power battery monomer is chosen, at normal temperatures, constant-current charge is carried out, power battery is returned to fully charged shape State；

Then, electric current constant-current discharge experiment is carried out to power battery, obtains the maximum available of power battery, and select first The secondary maximum available C being full of_maxAs benchmark；

Then, charge and discharge cycles senile experiment is carried out to battery under continuous current, until battery maximum available is only first Untill the setting percentage of beginning maximum available, think that battery life has terminated at this time, obtain maximum available by old The correction coefficient that change degree influencesWherein N represents cycle-index.

8. a kind of battery ampere-hour for considering temperature and degree of aging as claimed in claim 7 integrates SOC methods of estimation, its feature It is that the cycle-index is depending on the actual cycle service life number of battery and the estimated accuracy of requirement.

9. the battery ampere-hour integration SOC methods of estimation of a kind of consideration temperature and degree of aging as described in claim 1 or 3, its It is characterized in, when the consideration degree of aging influences to be corrected the maximum available of battery, detailed process is：

Set Range of measuring temp and temperature change step-length；

At different temperatures, to the partial power battery cell of selection, constant-current charge is carried out, returns to power battery fully charged State；

Electric current constant-current discharge experiment is carried out to power battery, obtains the maximum available of power battery；

Charge and discharge cycles senile experiment is carried out to battery under continuous current, until battery maximum available only has initial maximum Maximum available when untill the setting percentage of active volume, thinking that battery life has terminated at this time, and selecting room temperature As benchmark, at this point it is possible to obtain under T DEG C of different temperatures, different cycle-index N, battery SOC initial value is by temperature and aging The correction coefficient that degree influences

10. a kind of battery ampere-hour for considering temperature and degree of aging as claimed in claim 1 integrates SOC methods of estimation, it is special Sign is that the battery ampere-hour integration SOC methods of estimation of the consideration temperature and degree of aging are applied to battery management system.