CN116685853A - Method for determining direct current discharge resistance and maximum discharge power and battery management system - Google Patents
Method for determining direct current discharge resistance and maximum discharge power and battery management system 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
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
Abstract
The application relates to a method for determining the DC discharge resistance of a battery, comprising: acquiring working condition data of a battery in a specified health condition interval, wherein the working condition data comprises the temperature, the state of charge, the current and the voltage of the battery, and the specified health condition interval is a health condition interval corresponding to the latest health condition point of a data table which is specified for updating the direct current discharge resistor and is experienced; determining a data table of a direct current discharge resistance of the battery in the appointed health state interval according to the working condition data of the battery in the appointed health state interval; acquiring the current temperature and the current state of charge of the battery; and determining the direct current discharge resistance of the battery according to the data table of the direct current discharge resistance in the appointed health state interval, the current temperature and the current state of charge. The application also relates to a method for determining the maximum discharge power of a battery and a battery management system.
Description
The present application relates to the field of battery technologies, and in particular, to a method for determining a dc discharge resistance of a battery, a method for determining a maximum discharge power of the battery, and a battery management system.
With the development of new energy technology, more and more fields adopt batteries as power. The battery is widely applied to the fields of new energy automobiles, consumer electronics, energy storage systems and the like due to the advantages of high energy density, recycling charge, safety, environmental protection and the like.
The power supply capability of the battery directly affects the performance of the electric equipment, and in order to exert the performance of the battery to the greatest extent and protect the battery from over-discharge, the maximum available power of the battery needs to be estimated.
Disclosure of Invention
In view of the above, the present application proposes a method for determining a dc discharge resistance of a battery, a method for determining a maximum discharge power of a battery, and a battery management system.
To this end, a first aspect of the application provides a method for determining a direct current discharge resistance of a battery, wherein the method comprises:
acquiring working condition data of the battery in a specified health condition interval, wherein the working condition data comprise the temperature, the state of charge, the current, the voltage and the health condition of the battery, and the specified health condition interval is a health condition interval corresponding to the latest health condition point of a data table which is specified to update the direct current discharge resistor and is experienced;
determining a data table of a direct current discharge resistance of the battery in the specified health state interval according to the working condition data of the battery in the specified health state interval;
Acquiring the current temperature and the current state of charge of the battery; and
and determining the direct current discharge resistance of the battery according to the data table of the direct current discharge resistance in the specified health state interval, the current temperature and the current state of charge.
In an embodiment of the application, the dc resistance of the battery is determined by obtaining a data table of dc resistance of the latest state of health interval and based on the data table of dc resistance and the current temperature and state of charge. According to the embodiment, the data table of the direct current discharge resistor is obtained in the whole life cycle of the battery, so that the accuracy of the determined direct current discharge resistor is ensured.
In the embodiment of the present application, the "direct current discharge resistance" refers to the resistance of the battery at the time of direct current discharge, not the stationary internal resistance of the battery.
In some embodiments of the application, the data table for determining the dc discharge resistance of the battery over the specified state of health interval comprises:
screening out data fragments meeting preset working conditions from the working condition data in the specified health state interval;
when the current of the data point in the data segment is in a preset current interval, updating the data table of the discharge current and the voltage difference according to the dissimilarity between the data of the data point and the data of the corresponding position of the data point in the data table of the discharge current and the voltage difference;
When the data of the corresponding position meets the preset sufficient condition, calculating the direct current discharge resistance of the battery at the corresponding position according to the linear fitting relation of the discharge current and the voltage difference; and
and according to whether the working condition covered by the calculated direct current discharge resistor meets the preset data sufficiency condition and the health state of the data point, completing a data table of the direct current discharge resistor of the battery in the specified health state interval.
In an embodiment of the present application, the "corresponding position" is a table position corresponding to the state of charge (SOC) and temperature of a data point in a data table of discharge current and voltage difference. In the embodiment of the application, the data in the data table of the direct current discharge resistance of the battery is ensured to be closest to the current parameter condition of the battery by updating the two-dimensional data table of the discharge current and the voltage difference based on the temperature and the charge state and periodically updating the data table of the direct current discharge resistance.
In some embodiments of the present application, the preset operating conditions include a rest period requiring a current draw of less than or equal to 0.05C and a duration of greater than or equal to 30 seconds, and a pulse period requiring an average current draw of greater than or equal to 0.2C, a state of charge of greater than or equal to 30%, and a duration of greater than or equal to 2 seconds. In some embodiments of the application, after determining that the operating condition data meets the requirements of the stationary phase, it is determined whether the operating condition data meets the requirements of the pulse phase.
When measuring the data sheet of the direct current discharge resistance under different SOCs and temperatures on line, the battery needs to be firstly stood for a period of time, then discharged for a period of time with constant current, then the voltage difference between the end time of the stood period and the end time of the constant current discharge is measured, and the direct current discharge resistance is measured by using the voltage difference and the current of the constant current discharge. However, under the working condition that electric equipment such as an electric automobile and the like actually operates, standing and constant current conditions of off-line measurement are almost impossible to occur, so that the working condition is relaxed to the requirements of the standing section and the pulse section to screen available data.
In some embodiments of the present application, a data table for determining the dc discharge resistance of a battery over the specified state of health interval includes the steps of:
when the current in the pulse section of the data segment does not meet the quasi-constant current condition, the current in the pulse section of the data segment is converted into an equivalent constant current. In some embodiments of the application, the quasi-constant current condition is that the current ripple does not exceed ±7%, preferably ±5%. The lower the current fluctuation in the quasi-constant current condition is, the more accurate the obtained data is; however, when the current ripple is too low, there will be insufficient data to meet the requirements of the preset operating conditions, and therefore, in the most preferred embodiment, the quasi-constant current condition is set to ±5%.
In embodiments of the present application, the current of the pulse segment may occur in several cases: monotonically increasing, monotonically decreasing, constant current or quasi-constant current, monotonically increasing first then constant current or quasi-constant current, monotonically decreasing first then constant current or quasi-constant current, etc., after converting the non-constant current into an equivalent constant current, the equivalent constant current can be utilized to calculate the direct current discharge resistance.
In some embodiments of the application, the equivalent constant current is calculated according to the following formulas (1) and (2):
wherein I is eq Represents an equivalent constant current, w (t) represents a weight function, I (t) represents a discharge current at a sampling time point, t end The end time of the pulse segment is represented, n is a positive integer, and n is more than or equal to 2 and less than or equal to 6.
In some embodiments of the present application, the preset current interval includes three current intervals, a first current interval of the three current intervals is between 0.05 times and 0.2 times of a maximum discharge current, a second current interval of the three current intervals is between 0.2 times and 0.4 times of the maximum discharge current, and a third current interval of the three current intervals is between 0.4 times and 0.8 times of the maximum discharge current, and the maximum discharge current is a maximum current allowed by the battery with rated capacity to discharge under a temperature and a state of charge corresponding to a working condition of the data point. In the embodiment of the present application, as described before, it is necessary to determine whether the current of the data points in the data segment is within a preset plurality of current intervals, ensure that the data of the discharge current and the voltage difference is within a linear range, and hope that the current is distributed in each current interval, so as to obtain a linear fitting curve with higher availability.
In some embodiments of the application, when the capacity of the battery at the data point is attenuated by a preset percentage relative to the rated capacity of the battery, a data table of discharge current and voltage difference is emptied or a new data table is provided to store data of discharge current and voltage difference. In some embodiments of the application, a new two-dimensional data table of discharge current and voltage difference based on temperature and state of charge is stored and a data table of direct current discharge resistance is updated every time the capacity of the battery decays by 5%. In this embodiment, a capacity fade of 5% of the battery represents a large change in the internal parameters of the battery, so a new discharge current and voltage difference are used to calculate the dc discharge resistance which also changes significantly. In the embodiment of the two-dimensional data table for clearing the discharging current and the voltage difference, the two-dimensional data table for clearing the discharging current and the voltage difference is based on the consideration of saving the system memory or the limited system memory, and when the system memory is enough or not considered, all the original two-dimensional data tables for clearing the discharging current and the voltage difference can be reserved and the new two-dimensional data table is used for storing the data of the discharging current and the voltage difference.
In some embodiments of the present application, a data table for determining the dc discharge resistance of a battery over the specified state of health interval includes the steps of:
When the data of the data point and the data of the corresponding position are not mutually different:
taking the average value of the voltage difference between the voltage at the end time of the standing segment in the data segment and the voltage of the data point and the voltage difference between the corresponding position and the data of the data point, and replacing the voltage difference between the corresponding position and the data of the data point; and is also provided with
The current of the data point and the current of the data of the corresponding position and the data of the data point which are not mutually different are averaged to replace the current of the data point of the corresponding position which are not mutually different.
In such an embodiment, the voltage difference and current are averaged when there is no variability, so that the data for the corresponding location reduces error by updating to more nearly the actual value.
In some embodiments of the present application, a data table for determining the dc discharge resistance of a battery over the specified state of health interval includes the steps of:
when the data of the data point and the data of the corresponding position have dissimilarity, a data table of the discharge current and the voltage difference is updated according to the relation between the data of the data point and the data of the corresponding position in the preset current interval, wherein the preset current interval comprises a plurality of current intervals.
In such an embodiment, the distribution of data stored in the two-dimensional data table of the discharge current and the voltage difference may be controlled so that the availability of the linear fitting curve of the discharge current and the voltage difference is higher, by updating the two-dimensional data table of the discharge current and the voltage difference according to the relationship between the data of the data point and the data of the corresponding position within the preset plurality of current intervals.
In some embodiments of the application, the criterion for determining that the data of the data point and the data of the corresponding location are mutually different is that the current of the data point fluctuates more than 5% up and down relative to the current of a location in a two-dimensional data table of discharge current and voltage difference that fluctuates within 1 ℃ up and down the temperature of the data point and within 2% up and down the state of charge.
In the embodiment of the present application, updating the two-dimensional data table based on the discharge current and the voltage difference of the temperature and the state of charge is desirable to fill each cell in the two-dimensional data table, however, the measured data cannot completely correspond to the SOC and the temperature point of the table position in the two-dimensional data table, so it is necessary to judge in which cell of the two-dimensional data table this measured data falls according to the dissimilarity judgment criterion. If the data is stored in the cell in which the measurement data is located, then no dissimilarity is considered, and if the data is not stored in the cell in which the measurement data is located, then dissimilarity is considered.
In some embodiments of the present application, the step of updating the data table of the discharge current and the voltage difference according to the relationship between the data of the data point and the data of the corresponding position in the preset current interval includes:
comparing squares of correlation coefficients of linear fitting of the data of the corresponding position to the discharge current and the voltage difference before and after replacing the data of the current interval in which the data point is located in the corresponding position with the data of the data point when the data of the corresponding position is distributed in all the plurality of current intervals;
when the square of the correlation coefficient of the data using the data point is larger, the data of the data point is stored in a data table of the discharge current and the voltage difference.
In embodiments of the present application, by retaining the data for which the square of the correlation coefficient is larger, the error in the linear fit to the voltage difference and current is made smaller. In some embodiments of the present application, the correlation coefficient R may be calculated according to the following equation (3):
wherein Cov (X, Y) is the covariance of X and Y, var [ X ] is the variance of X, var [ Y ] is the variance of Y, and R ranges from-1 to +1. Thus, the square of the correlation coefficient can be expressed by the following equation (4):
wherein, Is the average value of X and is,is the average value of Y. In an embodiment of the application, X corresponds to a current value and Y corresponds to a voltage difference.
In some embodiments of the present application, the step of updating the data table of the discharge current and the voltage difference according to the relationship between the data of the data point and the data of the corresponding position in the preset current interval includes:
judging whether the data of the corresponding position has a value in the current interval of the current of the data point when the data of the corresponding position is not distributed in all the current intervals;
when the data at the corresponding position has no value in the current interval in which the current of the data point is located, the data of the data point is stored in a data table of discharge current and voltage difference.
In some embodiments of the present application, the step of updating the data table of the discharge current and the voltage difference according to the relationship between the data of the data point and the data of the corresponding position in the preset current interval includes:
judging whether the data of the data point is credible or not when the data of the corresponding position has a value in a current interval where the current of the data point is located; and
when the data of the data point is authentic:
when the current of the data point is in the current interval with the smallest current value in the current intervals, storing the data of the current of the data point and the smaller current value in the current interval with the smallest current value in the current intervals in the corresponding position in a data table of discharge current and voltage difference;
When the current of the data point is not in the current section with the smallest current value in the plurality of current sections, the data of the current value of the data point and the current value of the corresponding position in the current section with the current of the data point are stored in a data table of discharge current and voltage difference.
In some embodiments of the present application, the preset current interval includes three current intervals, a first current interval of the three current intervals is between 0.05 and 0.2 times of a maximum discharge current, a second current interval of the three current intervals is between 0.2 and 0.4 times of the maximum discharge current, a third current interval of the three current intervals is between 0.4 and 0.8 times of the maximum discharge current, and the maximum discharge current is a maximum current allowed by a battery having a rated capacity to discharge at a temperature and a state of charge corresponding to a working condition of the data point;
when the data of the data point is authentic:
when the current of the data point is in the first current interval, storing the data of the current of the data point and the current value of the corresponding position smaller in the current of the first current interval in a data sheet of discharge current and voltage difference;
When the current of the data point is in the second current interval or the third current interval, the data of the current value of the current of the data point and the current of the corresponding position in the current interval of the current of the data point are stored in a data table of discharge current and voltage difference.
In the embodiment of the application, whether the data is credible or not is judged, so that the data accords with the change rule, and the condition of jumping points in a data table is avoided. In addition, by reserving smaller current in the first current interval and reserving larger current in the second current interval and the third current interval, the currents are respectively closer to two ends and distributed more uniformly, and therefore a linear fitting curve with higher usability can be obtained.
In a specific embodiment of the present application, the data credibility determination principle of the data points includes:
when the current of the data point is larger than the current of the data at the corresponding position in the current interval of the current of the data point, the voltage difference of the data point is larger than the voltage difference of the data at the corresponding position in the current interval of the current of the data point; and
the resistance of the data point does not fluctuate more than 20% relative to the resistance of the data at the corresponding location in the current interval in which the current of the data point is located, wherein the resistance of the data point is equal to the voltage difference of the data point divided by the current, and the resistance of the data at the corresponding location in the current interval in which the current of the data point is located is equal to the voltage difference of the data at the corresponding location in the current interval in which the current of the data point is located divided by the current.
Based on system memory considerations, in a preferred embodiment of the present application, the operating condition data of the battery is the operating condition data of the two cells with the lowest states of charge and voltages in the battery. However, it should be understood that the operating condition data of the battery may include not only two representative cells, but also all of the cells in the battery, regardless of the system memory.
In some embodiments of the application, the voltage difference for the data point is equal to the voltage at the end of the rest segment in the data segment minus the voltage for the data point; and is also provided with
The current of this data point is the absolute value of the discharge current of the battery.
In an embodiment of the application, since the screened data segment is in discharge, the voltage of the battery is continuously reduced so that the voltage difference of the data points is a positive value. In addition, although in the Battery Management System (BMS), the charging current sign is +, and the discharging current sign is-; however, in the embodiment of the present application, the absolute value of the discharge current is taken as the current value of the data point, that is, the current values stored in the data table of the discharge current and the voltage difference are both positive values, and the currents compared with each other are both positive values. Therefore, both the current value and the voltage difference calculated for the above formulas (3) and (4) are positive values.
In some embodiments of the present application, the preset current interval includes a plurality of current intervals, and the preset sufficient condition includes:
the data of the corresponding position in the data table of the discharge current and the voltage difference are distributed in the plurality of current intervals; and
the square of the correlation coefficient of the linear fit of the discharge current and the voltage difference at the corresponding position in the data table of the discharge current and the voltage difference is greater than or equal to 0.95.
In the embodiment of the application, by the preset sufficient condition, it is ensured that the current and voltage difference data for calculating the direct current discharge resistance are grouped, the linear fitting can be performed, and the error of the linear fitting is sufficiently small.
In other embodiments of the present application, the predetermined sufficiency conditions include:
the minimum current at the corresponding position in the data table of the discharge current and the voltage difference is between 0.05 times and 0.2 times of the maximum discharge current at the corresponding position;
a current change step at the corresponding position in the data table of the discharge current and the voltage difference is between 0.15 times and 0.3 times of the maximum discharge current at the corresponding position; and
the square of the correlation coefficient of the linear fitting of the current and the voltage difference at the corresponding position in the data table of the discharge current and the voltage difference is more than or equal to 0.95;
Wherein the maximum discharge current of the corresponding location is the maximum current allowed by the discharge of the battery having rated capacity at the temperature and state of charge of the corresponding location.
In some embodiments of the application, the step of calculating the dc discharge resistance of the battery at the corresponding location based on a linear fit relationship of the discharge current and the voltage difference comprises:
performing linear fitting on the discharge current and the voltage difference at the corresponding position to obtain the slope and the pitch of a fitted voltage difference-current curve;
obtaining the open-circuit voltage of the corresponding position according to the charge state-open-circuit voltage curve of the battery and the charge state of the corresponding position;
subtracting the cut-off voltage of the battery from the open-circuit voltage of the corresponding position to obtain a first maximum voltage difference of the corresponding position;
obtaining a first maximum discharge current according to the fitted voltage difference-current curve and the first maximum voltage difference;
selecting the minimum value of the first maximum discharge current and the second maximum discharge current as a third maximum discharge current, wherein the second maximum discharge current is the discharge current limited by the mechanical part of the battery;
obtaining a second maximum voltage difference according to the fitted voltage difference-current curve and the third maximum discharge current; and
And dividing the second maximum voltage difference by the third maximum discharge current to obtain a direct current discharge resistance of the battery at the corresponding position.
In an embodiment of the present application, the first maximum voltage difference Δu is calculated according to the following equation (5) max ：
ΔU max ＝OCV-U Cut-off (5)
Wherein OCV is the open circuit voltage of the corresponding position，U Cut-off Is the cut-off voltage of the battery. Then, a first maximum voltage difference DeltaU is determined according to a fitted voltage difference-current curve obtained when the discharge current and the voltage difference are linearly fitted or when the correlation coefficient of the linear fitting is calculated before max Corresponding first maximum current I max0 ：
Where k is the slope of the fitted voltage-current curve and b is the pitch of the fitted voltage-current curve. Since the maximum discharge current allowed by the battery is limited not only by the cut-off voltage but also by the mechanical member, the maximum discharge current actually allowed by the battery is determined according to the following formula (7):
I’ max ＝min(I max0 ，I max1 ) (7)
wherein I' max Is the maximum discharge current actually allowed by the battery, namely the third maximum discharge current; i max1 Is the maximum discharge current limited by the off-voltage, i.e. the second maximum discharge current. In determining the maximum discharge current I 'actually allowed by the battery' max Then, based on the fitted voltage-current curve obtained when the discharge current and the voltage difference are linearly fitted or when the correlation coefficient of the linear fitting is calculated before, I 'is determined' max The corresponding maximum voltage difference, i.e. the second maximum voltage difference DeltaU' max ：
ΔU′ max ＝k*I′ max +b (8)。
Finally, the dc discharge resistance DCR is calculated according to the following formula (9):
DCR＝ΔU′ max /I′ max (9)。
in some embodiments of the present application, when the calculated working condition covered by the dc discharge resistor satisfies a preset data sufficiency condition, the data table of the discharge current and the voltage difference is complemented according to existing data in the data table of the discharge current and the voltage difference, and the data table of the dc discharge resistor of the battery in the above specified health state interval is complemented according to a linear fitting relation of the discharge current and the voltage difference based on the data in the data table of the complemented discharge current and the voltage difference.
In some embodiments of the present application, the preset data sufficiency condition includes the calculated dc discharge resistance coverage conditions meeting the following requirements:
the temperature of the covering comprises at least three groups of temperatures between-20 and 25 ℃, and each group of temperature interval in the at least three groups of temperatures is greater than or equal to 10 ℃;
the temperature of the covering comprises at least two groups of temperatures between 25 and 55 ℃, and each group of temperature interval in the at least two groups of temperatures is greater than or equal to 10 ℃; and
The covered states of charge comprises at least two groups of states of charge between 30% and 100%, and the interval between each group of states of charge in the at least two groups of states of charge is greater than or equal to 20%.
In the embodiment of the application, by the preset data sufficiency condition, the data stored in the data table of the discharge current and the voltage difference is ensured to be sufficiently large, so that all the data in the data table of the discharge current and the voltage difference can be complemented by a linear interpolation method or the like.
In some embodiments of the present application, the step of supplementing the data sheet for the discharge current and the voltage difference according to existing data in the data sheet for the discharge current and the voltage difference comprises:
performing linear fitting on the current and the voltage difference of the existing temperature and the state of charge, and complementing the voltage difference of the existing temperature and the state of charge in the preset current interval according to a fitted delta U-I curve;
linearly interpolating the state of charge at 30% to 100% based on the voltage differences of the known temperature, state of charge and current to complement the voltage differences of the state of charge at 30% to 100%; and
linear fitting is performed on lnΔU and 1/T according to the voltage differences of known temperature, state of charge and current, where T is in Kelvin, and the voltage differences between-25 to 25 ℃ and between 25 to 55 ℃ are interpolated according to the fitted lnΔU-1/T curve.
In some embodiments of the present application, a data table for determining the dc discharge resistance of a battery over the specified state of health interval includes the steps of:
when the working condition covered by the calculated direct current discharge resistor does not meet the preset data sufficiency condition, judging whether the capacity of the battery at the data point is attenuated by a preset percentage relative to the rated capacity of the battery;
when the capacity of the data point of the battery is attenuated by a preset percentage relative to the rated capacity of the battery, the direct current discharge resistance in the state of charge is calculated according to the maximum increase rate of the calculated direct current discharge resistance at the same temperature relative to the direct current discharge resistance in the data table of the prior direct current discharge resistance so as to complement the direct current discharge resistance in different temperatures and states of charge.
In the embodiment of the application, when the data is insufficient, judging whether the capacity of the battery is attenuated by the percentage of forced updating, and if the capacity is not attenuated by the preset percentage, continuing to supplement the data; if the preset percentage is attenuated, the data is supplemented according to the growth law. The implementation scheme ensures that the data accords with the change rule, and avoids the condition of jumping points in the data table.
A second aspect of the present application provides a battery management system, wherein the battery management system is configured to determine a direct current discharge resistance of a battery, the battery management system comprising:
at least one processor; and
a memory coupled to the at least one processor;
wherein the memory stores instructions that, when executed by the at least one processor, cause the at least one processor to perform the method for determining the dc discharge resistance of a battery as described in the first aspect.
A third aspect of the application provides a method for determining a maximum discharge power of a battery, wherein the method comprises:
acquiring working condition data of the battery in a specified health condition interval, wherein the working condition data comprise the temperature, the state of charge, the current, the voltage and the health condition of the battery, and the specified health condition interval is a health condition interval corresponding to the latest health condition point of a data table which is specified to update the maximum discharge power and is experienced;
determining a data table of maximum discharge power of the battery in the specified health state interval according to the working condition data of the battery in the specified health state interval;
Acquiring the current temperature and the current state of charge of the battery; and
and determining the maximum discharge power of the battery according to the data table of the maximum discharge power in the specified health state interval, the current temperature and the current state of charge.
In an embodiment of the application, the maximum discharge power of the battery is determined by obtaining a data table of maximum discharge power of the latest state of health section and based on the data table of maximum discharge power and the current temperature and state of charge. According to the embodiment, the data table of the maximum discharge power is obtained in the full life cycle of the battery, the direct current discharge resistance and the maximum discharge power of the battery can be calculated according to the real-time working condition in the full life cycle, the accuracy of the determined maximum discharge power is further ensured, the performance of the battery is brought into full play, and meanwhile, the driving safety and the driving dynamics are improved.
In some embodiments of the application, the data table for determining the maximum discharge power of the battery within the specified state of health interval comprises:
screening out data segments meeting preset working conditions from the working condition data in the specified health state interval;
when the current of the data point in the data segment is in a preset current interval, updating the data table of the discharge current and the voltage difference according to the dissimilarity between the data of the data point and the data of the corresponding position of the data point in the data table of the discharge current and the voltage difference;
When the data of the corresponding position meets the preset sufficient condition, calculating the maximum discharge power of the battery at the corresponding position according to the linear fitting relation of the discharge current and the voltage difference; and
and according to whether the working condition covered by the calculated maximum discharge power meets the preset data sufficiency condition and the health state of the data point, completing a data table of the maximum discharge power of the battery in the specified health state interval.
In an embodiment of the present application, by updating the two-dimensional data table of the discharge current and the voltage difference based on the temperature and the state of charge, the data table of the maximum discharge power is updated periodically, and it is ensured that the data in the data table of the maximum discharge power of the battery is closest to the current parameter condition of the battery.
In some embodiments of the present application, the preset operating conditions include a rest period requiring a current draw of less than or equal to 0.05C and a duration of greater than or equal to 30 seconds, and a pulse period requiring an average current draw of greater than or equal to 0.2C, a state of charge of greater than or equal to 30%, and a duration of greater than or equal to 2 seconds. In some embodiments of the application, after determining that the operating condition data meets the requirements of the stationary phase, it is determined whether the operating condition data meets the requirements of the pulse phase.
When measuring the data sheet of the direct current discharge resistance under different SOCs and temperatures on line, the battery needs to be firstly stood for a period of time, then discharged for a period of time with constant current, then the voltage difference between the end time of the stood period and the end time of the constant current discharge is measured, and the direct current discharge resistance is measured by using the voltage difference and the current of the constant current discharge. However, under the working condition that electric equipment such as an electric automobile and the like actually operates, standing and constant current conditions of off-line measurement are almost impossible to occur, so that the working condition is relaxed to the requirements of the standing section and the pulse section to screen available data.
In some embodiments of the present application, the data table for determining the maximum discharge power of the battery within the above specified state of health interval comprises the steps of:
when the current in the pulse section of the data segment does not meet the quasi-constant current condition, the current in the pulse section of the data segment is converted into an equivalent constant current. In some embodiments of the application, the quasi-constant current condition is that the current ripple does not exceed ±7%, preferably ±5%. The lower the current fluctuation in the quasi-constant current condition is, the more accurate the obtained data is; however, when the current ripple is too low, there will not be enough data to meet the requirements of the preset operating conditions. Thus, in embodiments of the present application, the limit of current ripple for quasi-constant current conditions is not lower than no more than ±2%; in the most preferred embodiment, quasi-constant current conditions are set to + -5%.
In embodiments of the present application, the current of the pulse segment may occur in several cases: monotonically increasing, monotonically decreasing, constant current or quasi-constant current, first monotonically increasing and then constant current or quasi-constant current, first monotonically decreasing and then constant current or quasi-constant current, etc., after converting the non-constant current into an equivalent constant current, the equivalent constant current can be utilized to calculate the maximum discharge power.
In some embodiments of the application, the equivalent constant current is calculated according to formulas (1) and (2) above.
In some embodiments of the present application, the preset current interval includes three current intervals, a first current interval of the three current intervals is between 0.05 times and 0.2 times of a maximum discharge current, a second current interval of the three current intervals is between 0.2 times and 0.4 times of the maximum discharge current, and a third current interval of the three current intervals is between 0.4 times and 0.8 times of the maximum discharge current, and the maximum discharge current is a maximum current allowed by a battery with rated capacity to discharge at a temperature and a state of charge corresponding to a working condition of the data point. In the embodiment of the present application, as described before, it is necessary to determine whether the current of the data points in the data segment is within a preset plurality of current intervals, ensure that the data of the discharge current and the voltage difference is within a linear range, and hope that the current is distributed in each current interval, so as to obtain a linear fitting curve with higher availability.
In some embodiments of the application, when the capacity of the battery at the data point is attenuated by a preset percentage relative to the rated capacity of the battery, a data table of discharge current and voltage difference is emptied or a new data table is provided to store data of discharge current and voltage difference. In some embodiments of the application, a new two-dimensional data table of discharge current and voltage difference based on temperature and state of charge is stored and a data table of maximum discharge power is updated every time the capacity of the battery decays by 5%. In this embodiment, a capacity fade of 5% of the battery represents a large change in the internal parameters of the battery, so a new discharge current and voltage difference are used to calculate the maximum discharge power that also changes significantly. In the embodiment of the two-dimensional data table for clearing the discharging current and the voltage difference, the two-dimensional data table for clearing the discharging current and the voltage difference is based on the consideration of saving the system memory or the limited system memory, and when the system memory is enough or not considered, all the original two-dimensional data tables for clearing the discharging current and the voltage difference can be reserved and the new two-dimensional data table is used for storing the data of the discharging current and the voltage difference.
In some embodiments of the present application, the data table for determining the maximum discharge power of the battery within the above specified state of health interval comprises the steps of:
When the data of the data point and the data of the corresponding position are not mutually different:
taking the average value of the voltage difference between the voltage at the end time of the standing segment in the data segment and the voltage of the data point and the voltage difference between the corresponding position and the data of the data point, and replacing the voltage difference between the corresponding position and the data of the data point; and is also provided with
The current of the data point and the current of the data of the corresponding position and the data of the data point which are not mutually different are averaged to replace the current of the data point of the corresponding position which are not mutually different.
In such an embodiment, the voltage difference and current are averaged when there is no variability, so that the data for the corresponding location reduces error by updating to more nearly the actual value.
In some embodiments of the present application, the data table for determining the maximum discharge power of the battery within the above specified state of health interval comprises the steps of:
when the data of the data point and the data of the corresponding position have dissimilarity, a data table of the discharge current and the voltage difference is updated according to the relation between the data of the data point and the data of the corresponding position in the preset current interval, wherein the preset current interval comprises a plurality of current intervals.
In such an embodiment, the distribution of data stored in the two-dimensional data table of the discharge current and the voltage difference may be controlled so that the availability of the linear fitting curve of the discharge current and the voltage difference is higher, by updating the two-dimensional data table of the discharge current and the voltage difference according to the relationship between the data of the data point and the data of the corresponding position within the preset plurality of current intervals.
In some embodiments of the application, the criterion for determining that the data of the data point and the data of the corresponding location are mutually different is that the current of the data point fluctuates more than 5% up and down relative to the current of a location in a two-dimensional data table of discharge current and voltage difference that fluctuates within 1 ℃ up and down the temperature of the data point and within 2% up and down the state of charge.
In the embodiment of the present application, updating the two-dimensional data table based on the discharge current and the voltage difference of the temperature and the state of charge is desirable to fill each cell in the two-dimensional data table, however, the measured data cannot completely correspond to the SOC and the temperature point of the table position in the two-dimensional data table, so it is necessary to judge in which cell of the two-dimensional data table this measured data falls according to the dissimilarity judgment criterion. If the data is stored in the cell in which the measurement data is located, then no dissimilarity is considered, and if the data is not stored in the cell in which the measurement data is located, then dissimilarity is considered.
In some embodiments of the present application, the step of updating the data table of the discharge current and the voltage difference according to the relationship between the data of the data point and the data of the corresponding position in the preset current interval includes:
comparing squares of correlation coefficients of linear fitting of the data of the corresponding position to the discharge current and the voltage difference before and after replacing the data of the current interval in which the data point is located in the corresponding position with the data of the data point when the data of the corresponding position is distributed in all the plurality of current intervals;
when the square of the correlation coefficient of the data using the data point is larger, the data of the data point is stored in a data table of the discharge current and the voltage difference.
In embodiments of the present application, by retaining the data for which the square of the correlation coefficient is larger, the error in the linear fit to the voltage difference and current is made smaller. In some embodiments of the present application, the correlation coefficient R may be calculated according to the above formula (3), and the square of the correlation coefficient may be represented by the above formula (4).
In some embodiments of the present application, the step of updating the data table of the discharge current and the voltage difference according to the relationship between the data of the data point and the data of the corresponding position in the preset current interval includes:
Judging whether the data of the corresponding position has a value in the current interval of the current of the data point when the data of the corresponding position is not distributed in all the current intervals;
when the data at the corresponding position has no value in the current interval in which the current of the data point is located, the data of the data point is stored in a data table of discharge current and voltage difference.
In some embodiments of the present application, the step of updating the data table of the discharge current and the voltage difference according to the relationship between the data of the data point and the data of the corresponding position in the preset current interval includes:
judging whether the data of the data point is credible or not when the data of the corresponding position has a value in a current interval where the current of the data point is located; and
when the data of the data point is authentic:
when the current of the data point is in the current interval with the smallest current value in the current intervals, storing the data of the current of the data point and the smaller current value in the current interval with the smallest current value in the current intervals in the corresponding position in a data table of discharge current and voltage difference;
when the current of the data point is not in the current section with the smallest current value in the plurality of current sections, the data of the current value of the data point and the current value of the corresponding position in the current section with the current of the data point are stored in a data table of discharge current and voltage difference.
In some embodiments of the present application, the preset current interval includes three current intervals, a first current interval of the three current intervals is between 0.05 and 0.2 times of a maximum discharge current, a second current interval of the three current intervals is between 0.2 and 0.4 times of the maximum discharge current, a third current interval of the three current intervals is between 0.4 and 0.8 times of the maximum discharge current, and the maximum discharge current is a maximum current allowed by a battery having a rated capacity to discharge at a temperature and a state of charge corresponding to a working condition of the data point;
when the data of the data point is authentic:
when the current of the data point is in the first current interval, storing the data of the current of the data point and the current value of the corresponding position smaller in the current of the first current interval in a data sheet of discharge current and voltage difference;
when the current of the data point is in the second current interval or the third current interval, the data of the current value of the current of the data point and the current of the corresponding position in the current interval of the current of the data point are stored in a data table of discharge current and voltage difference.
In the embodiment of the application, whether the data is credible or not is judged, so that the data accords with the change rule, and the condition of jumping points in a data table is avoided. In addition, by reserving smaller current in the first current interval and reserving larger current in the second current interval and the third current interval, the currents are respectively closer to two ends and distributed more uniformly, and therefore a linear fitting curve with higher usability can be obtained.
In a specific embodiment of the present application, the data credibility determination principle of the data points includes:
when the current of the data point is larger than the current of the data at the corresponding position in the current interval of the current of the data point, the voltage difference of the data point is larger than the voltage difference of the data at the corresponding position in the current interval of the current of the data point; and
the resistance of the data point does not fluctuate more than 20% relative to the resistance of the data at the corresponding location in the current interval in which the current of the data point is located, wherein the resistance of the data point is equal to the voltage difference of the data point divided by the current, and the resistance of the data at the corresponding location in the current interval in which the current of the data point is located is equal to the voltage difference of the data at the corresponding location in the current interval in which the current of the data point is located divided by the current.
Based on system memory considerations, in a preferred embodiment of the present application, the operating condition data of the battery is the operating condition data of the two cells with the lowest states of charge and voltages in the battery. However, it should be understood that the operating condition data of the battery may include not only two representative cells, but also all of the cells in the battery, regardless of the system memory.
In some embodiments of the application, the voltage difference for the data point is equal to the voltage at the end of the rest segment in the data segment minus the voltage for the data point; and is also provided with
The current of this data point is the absolute value of the discharge current of the battery.
In an embodiment of the application, since the screened data segment is in discharge, the voltage of the battery is continuously reduced so that the voltage difference of the data points is a positive value. In addition, although in the Battery Management System (BMS), the charging current sign is +, and the discharging current sign is-; however, in the embodiment of the present application, the absolute value of the discharge current is taken as the current value of the data point, that is, the current values stored in the data table of the discharge current and the voltage difference are both positive values, and the currents compared with each other are both positive values.
In some embodiments of the present application, the preset current interval includes a plurality of current intervals, and the preset sufficient condition includes:
The data of the corresponding position in the data table of the discharge current and the voltage difference are distributed in the plurality of current intervals; and
the square of the correlation coefficient of the linear fit of the discharge current and the voltage difference at the corresponding position in the data table of the discharge current and the voltage difference is greater than or equal to 0.95.
In the embodiment of the present application, by the preset sufficient condition, it is ensured that the current and voltage difference data for calculating the maximum discharge power are grouped, the linear fitting can be performed, and the error of the linear fitting is sufficiently small.
In other embodiments of the present application, the predetermined sufficiency conditions include:
the minimum current at the corresponding position in the data table of the discharge current and the voltage difference is between 0.05 times and 0.2 times of the maximum discharge current at the corresponding position;
a current change step at the corresponding position in the data table of the discharge current and the voltage difference is between 0.15 times and 0.3 times of the maximum discharge current at the corresponding position; and
the square of the correlation coefficient of the linear fitting of the current and the voltage difference at the corresponding position in the data table of the discharge current and the voltage difference is more than or equal to 0.95;
wherein the maximum discharge current of the corresponding location is the maximum current allowed by the discharge of the battery having rated capacity at the temperature and state of charge of the corresponding location.
In some embodiments of the application, the step of calculating the maximum discharge power of the battery at the corresponding location based on a linear fit relationship of the discharge current and the voltage difference comprises:
performing linear fitting on the discharge current and the voltage difference at the corresponding position to obtain the slope and the pitch of a fitted voltage difference-current curve;
obtaining the open-circuit voltage of the corresponding position according to the charge state-open-circuit voltage curve of the battery and the charge state of the corresponding position;
subtracting the cut-off voltage of the battery from the open-circuit voltage of the corresponding position to obtain a first maximum voltage difference of the corresponding position;
obtaining a first maximum discharge current according to the fitted voltage difference-current curve and the first maximum voltage difference;
selecting the minimum value of the first maximum discharge current and the second maximum discharge current as a third maximum discharge current, wherein the second maximum discharge current is the discharge current limited by the mechanical part of the battery;
obtaining a second maximum voltage difference according to the fitted voltage difference-current curve and the third maximum discharge current;
dividing the second maximum voltage difference by the third maximum discharge current to obtain a direct current discharge resistance of the battery at the corresponding position;
Subtracting the product of the direct current discharge resistor at the corresponding position and the third maximum discharge current from the open circuit voltage at the corresponding position to obtain the maximum power supply voltage of the battery at the corresponding position; and
and multiplying the third maximum discharge current at the corresponding position by the maximum power supply voltage to obtain the maximum discharge power at the corresponding position.
In an embodiment of the present application, the first maximum voltage difference ΔU is calculated according to the above equation (5) max . Then, a first maximum voltage difference DeltaU is determined according to a fitted voltage difference-current curve obtained when the discharge current and the voltage difference are linearly fitted or when the correlation coefficient of the linear fitting is calculated before max Corresponding first maximum current I max0 . Since the maximum discharge current allowed by the battery is limited not only by the cut-off voltage but also by the mechanical parts, the maximum discharge current I actually allowed by the battery is determined according to the above formula (7) ’ max I.e. a third maximum discharge current; i max1 Is the maximum discharge current limited by the off-voltage, i.e. the second maximum discharge current. In determining the maximum discharge current I 'actually allowed by the battery' max Then, based on the fitted voltage-current curve obtained when the discharge current and the voltage difference are linearly fitted or when the correlation coefficient of the linear fitting is calculated before, the method is accurate Set I' max The corresponding maximum voltage difference, i.e. the second maximum voltage difference DeltaU' max . Next, the dc discharge resistance DCR is calculated according to the above formula (9). Finally, the maximum discharge power P of the battery at the corresponding position is calculated according to the following formula (10) max ：
P max ＝(OCV-I′ max *DCR)*I′ max (10)。
In some embodiments of the present application, when the calculated working condition of the maximum discharge power coverage satisfies a preset data sufficiency condition, the data table of the discharge current and the voltage difference is complemented according to existing data in the data table of the discharge current and the voltage difference, and the data table of the maximum discharge power of the battery in the above specified health state interval is complemented according to a linear fitting relation of the discharge current and the voltage difference based on data in the data table of the complemented discharge current and the voltage difference.
In some embodiments of the present application, the preset data sufficiency condition includes the condition that the calculated maximum discharge power coverage meets the following requirements:
the temperature of the covering comprises at least three groups of temperatures between-20 and 25 ℃, and each group of temperature interval in the at least three groups of temperatures is greater than or equal to 10 ℃;
the temperature of the covering comprises at least two groups of temperatures between 25 and 55 ℃, and each group of temperature interval in the at least two groups of temperatures is greater than or equal to 10 ℃; and
The covered states of charge comprises at least two groups of states of charge between 30% and 100%, and the interval between each group of states of charge in the at least two groups of states of charge is greater than or equal to 20%.
In the embodiment of the application, by the preset data sufficiency condition, the data stored in the data table of the discharge current and the voltage difference is ensured to be sufficiently large, so that all the data in the data table of the discharge current and the voltage difference can be complemented by a linear interpolation method or the like.
In some embodiments of the present application, the step of supplementing the data sheet for the discharge current and the voltage difference according to existing data in the data sheet for the discharge current and the voltage difference comprises:
performing linear fitting on the current and the voltage difference of the existing temperature and the state of charge, and complementing the voltage difference of the existing temperature and the state of charge in the preset current interval according to a fitted delta U-I curve;
linearly interpolating the state of charge at 30% to 100% based on the voltage differences of the known temperature, state of charge and current to complement the voltage differences of the state of charge at 30% to 100%; and
linear fitting is performed on lnΔU and 1/T according to the voltage differences of known temperature, state of charge and current, where T is in Kelvin, and the voltage differences between-25 to 25 ℃ and between 25 to 55 ℃ are interpolated according to the fitted lnΔU-1/T curve.
In some embodiments of the present application, the data table for determining the maximum discharge power of the battery within the above specified state of health interval comprises the steps of:
when the working condition of the calculated maximum discharge power coverage does not meet the preset data sufficiency condition, judging whether the capacity of the battery at the data point is attenuated by a preset percentage relative to the rated capacity of the battery;
when the capacity of the data point is attenuated by a preset percentage relative to the rated capacity of the battery, the maximum discharge power of the missing charge state is calculated according to the maximum attenuation rate of the calculated maximum discharge power at the same temperature relative to the maximum discharge power in the data table of the previous maximum discharge power so as to complement the maximum discharge power of different temperatures and charge states.
In the embodiment of the application, when the data is insufficient, judging whether the capacity of the battery is attenuated by the percentage of forced updating, and if the capacity is not attenuated by the preset percentage, continuing to supplement the data; if the preset percentage is attenuated, the data is supplemented according to the attenuation law of the maximum discharge power. The implementation scheme ensures that the data accords with the change rule, and avoids the condition of jumping points in the data table.
In some embodiments of the application, the data table of the maximum discharge power of the battery is updated at the same time as the data table of the direct current discharge resistance of the battery is updated.
A fourth aspect of the present application provides a battery management system configured to determine a maximum discharge power of a battery, the battery management system comprising:
at least one processor; and
a memory coupled to the at least one processor;
wherein the memory stores instructions that, when executed by the at least one processor, cause the at least one processor to perform the method for determining the maximum discharge power of a battery as described in the third aspect above.
In order to more clearly illustrate the technical solutions of the present application, the drawings that are needed in the examples of the present application will be briefly described below, it being obvious that the drawings described below are only some embodiments of the present application, and that other drawings may be obtained according to the drawings without inventive effort for a person skilled in the art. In the drawings:
fig. 1 illustrates a flowchart of a method for determining a dc discharge resistance of a battery according to one embodiment of the present application;
FIG. 2a illustrates a flow chart of a method of determining a data table of a DC discharge resistance of a battery according to one embodiment of the application;
FIG. 2b illustrates a flowchart of a method of updating a data table of discharge currents and voltage differences according to the dissimilarity between data, according to one embodiment of the present application;
FIG. 2c illustrates a flowchart of a method of calculating a DC discharge resistance of a battery at a corresponding location based on a linear fit of a discharge current and a voltage difference, according to one embodiment of the application;
FIG. 3 illustrates a flow chart of a method for determining a maximum discharge power of a battery according to one embodiment of the application;
FIG. 4a illustrates a flow chart of a method of determining a data table of maximum discharge power of a battery according to one embodiment of the application;
FIG. 4b illustrates a flowchart of a method of calculating a maximum discharge power of a battery at a corresponding location according to a linear fit relationship of discharge current and voltage difference, according to one embodiment of the present application; and
fig. 5 is a schematic diagram of a battery management system according to an embodiment of the present application.
Embodiments of the present application will be described in detail below with reference to the accompanying drawings. The following embodiments are only for more clearly illustrating the technical aspects of the present application, and thus are merely examples, not to limit the scope of 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; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application; the terms "comprising" and "having" and any variations thereof in the description of the application and the claims and the description of the drawings above are intended to cover a non-exclusive inclusion.
In the description of embodiments of the present application, the technical terms "first" and "second" and the like are used merely to distinguish between different objects and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated, a particular order or a primary or secondary relationship.
Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein may be combined with other embodiments.
In the description of embodiments of the present application, the term "and/or" is merely an association relationship describing an association object, meaning that three relationships may exist, e.g., a and/or B, may represent: there are three cases, a, B, a and B simultaneously. In addition, the character "/" herein generally indicates that the front and rear associated objects are an "or" relationship. In the description of embodiments of the present application, the term "plurality" refers to two or more (including two) unless specifically defined otherwise.
If steps are recited in order in the present specification or claims, this does not necessarily mean that the embodiments or aspects are limited to the recited order. Rather, it is conceivable that the steps are also performed in a different order or in parallel with each other, unless one is built on top of the other, which absolutely requires that the built-up steps be performed later (which will however become clear in the individual case). Thus, the order stated may be a preferred embodiment.
Currently, batteries are widely used not only in energy storage power supply systems such as hydraulic power, thermal power, wind power and solar power stations, but also in electric vehicles such as electric bicycles, electric motorcycles and electric automobiles, as well as in a plurality of fields such as military equipment and aerospace. With the continuous expansion of the battery application field, the market demand thereof is also continuously expanding.
The present inventors have found in practice that a conventional method of obtaining the maximum available power of a battery looks up a stored data table of discharge power according to SOC and battery temperature, obtains a target output power, and then adjusts the maximum available power according to a voltage deviation of the lowest cell voltage from a cutoff voltage or a coefficient related to a state of health (SOH). However, on the one hand, a jump may occur in the temperature or SOC dimension in the data table of the discharge power stored in advance, i.e., a certain power value in the data table differs too far from the power value of the front-rear temperature or front-rear SOC, not conforming to the power change law, because it is not verified whether the measured voltage data are reasonable or not, and thus the maximum available power thus obtained is invalid. On the other hand, adjusting the maximum available power with only a single point voltage or SOH-related coefficient is only a rough estimate and does not accurately reflect the state of the performance parameters of the battery at the current SOH.
In order to accurately reflect the state of the performance parameter of the battery under the current SOH, the inventors contemplate updating the data table of the discharge power at regular time so as to reflect the state of the performance parameter of the battery under the current SOH relatively accurately. Furthermore, in order to guarantee the availability of the maximum available power, the inventors contemplate a series of filtering and preprocessing of the raw data obtained before storing it in the data table, so that the data stored in the data table is rational and reliable.
Fig. 1 illustrates a flow chart of a method 100 for determining a dc discharge resistance of a battery according to one embodiment of the application. As shown in fig. 1, in step 102, operating condition data of the battery in a specified state of health section is obtained, where the operating condition data includes a temperature, a state of charge, a current, a voltage, and a state of health of the battery, and the specified state of health section is a state of health section corresponding to a latest state of health point of a data table that has been experienced by the battery and is specified to update the dc discharge resistance. Then, in step 104, a data table of the internal resistance of the dc discharge of the battery in the specified health status interval is determined according to the working condition data in the specified health status interval. At step 106, the current temperature and current state of charge of the battery are obtained. In step 108, the dc resistance of the battery is determined based on the data table of the dc resistance in the specified health status interval, the current temperature and the current state of charge. In other words, the corresponding direct current discharge resistor of the current temperature and the state of charge in the data table of the direct current discharge resistor is searched.
The method 100 for determining the dc resistance of the battery shown in fig. 1 continuously updates the data table of the dc resistance during the whole life cycle of the battery, thereby ensuring the accuracy of the determined dc resistance.
Fig. 2a illustrates a flow chart of a method 200a of determining a data table of a dc discharge resistance of a battery according to one embodiment of the application. As shown in fig. 2a, in step 202, data segments satisfying a preset operating condition are screened out from operating condition data within a specified health state interval. In some embodiments of the application, the preset operating conditions include a rest period requiring a current draw of less than or equal to 0.05C for a duration of greater than or equal to 30 seconds, and a pulse period requiring an average current draw of greater than or equal to 0.2C, a state of charge of greater than or equal to 30%, and a duration of greater than or equal to 2 seconds. In a preferred embodiment of the present application, after judging that the condition data meets the requirement of the stationary phase, it is further judged whether the condition data meets the requirement of the pulse phase. In the embodiment of the application, the discharge current and the voltage difference are ensured to be in a linear interval through the preset working condition, so that the direct current discharge resistance calculated according to the linear fitting relation of the discharge current and the voltage difference is relatively reliable. After screening out the data segments meeting the preset working conditions, judging whether the pulse segments in the data segments are quasi-constant current or not, and in step 204.
If the pulse segment does not meet the quasi-constant current condition, the current in the pulse segment is converted to an equivalent constant current, step 206. In some embodiments of the application, the quasi-constant current condition is that the current ripple does not exceed ±7%, preferably ±5%. Furthermore, in some embodiments of the present application, an equivalent constant current is calculated according to formulas (1) and (2) above. After converting the current to an equivalent constant current, in step 208, it is determined whether the current of the data point in the data segment is within a preset current interval. If the pulse segment satisfies the quasi-constant current condition, the step 208 is directly entered without constant current conversion. In some embodiments of the application, the preset current interval is between 0.05 and 0.8 times the maximum discharge current, which is the maximum current allowed for the discharge of a battery having rated capacity at the temperature and state of charge corresponding to the operating conditions of the data points. In some embodiments of the present application, the preset current interval includes three current intervals, a first current interval of the three current intervals is between 0.05 and 0.2 times of a maximum discharge current, a second current interval of the three current intervals is between 0.2 and 0.4 times of the maximum discharge current, and a third current interval of the three current intervals is between 0.4 and 0.8 times of the maximum discharge current, the maximum discharge current being a maximum current allowed for the battery having a rated capacity to discharge under a temperature and a state of charge corresponding to a condition of the data point. In the embodiment of the present application, as described above, it is necessary to determine whether the current of the data points in the data segment is within a preset current interval, and ensure that the data of the current and the voltage difference is within a linear range, so as to obtain a linear fitting curve with higher availability.
If the current of the data point is within the preset current interval, updating the data table of the discharge current and the voltage difference according to the dissimilarity between the data of the data point and the data of the corresponding position of the data point in the data table of the discharge current and the voltage difference, step 210; otherwise, returning to step 202, working condition data of the next data point is obtained.
After updating the data table of the discharge current and the voltage difference, in step 212, it is determined whether the data of the corresponding position in the data table of the discharge current and the voltage difference satisfies a preset sufficient condition to determine whether the linear fitting of the discharge current and the voltage difference can be performed according to the data of the corresponding position. In some embodiments of the application, the preset sufficiency conditions include: the currents at corresponding positions in the two-dimensional data table of the discharge current and the voltage difference are distributed in a plurality of preset current intervals; and the square R of the correlation coefficient of the linear fitting of the current I and the voltage difference DeltaU at the corresponding position in the two-dimensional data table of the discharge current and the voltage difference 2 Greater than or equal to 0.95. By the preset sufficient conditions, the grouping of the current and voltage difference data for calculating the direct current discharge resistor is ensured, the linear fitting can be performed, and the error of the linear fitting is small enough.
When the preset sufficient condition is met, calculating the direct current discharge resistance of the battery at the corresponding position according to the linear fitting relation of the discharge current and the voltage difference, and step 214; otherwise, returning to step 202, working condition data of the next data point is obtained. Next, in step 216, it is determined whether the calculated working condition covered by the dc discharging resistor meets the preset data sufficiency condition, so as to determine whether all the data in the data table of the discharging current and the voltage difference can be reasonably complemented according to the existing data in the data table of the discharging current and the voltage difference. In some embodiments of the present application, the preset data sufficiency condition includes the calculated dc discharge resistance coverage conditions meeting the following requirements: the temperature of the covering comprises at least three groups of temperatures between-20 and 25 ℃, and each group of temperature interval in the at least three groups of temperatures is greater than or equal to 10 ℃; the temperature of the covering comprises at least two groups of temperatures between 25 and 55 ℃, and each group of temperature interval in the at least two groups of temperatures is greater than or equal to 10 ℃; and the covered states of charge comprises at least two groups of states of charge between 30% and 100%, each group of states of charge in the at least two groups of states of charge being spaced by greater than or equal to 20%. By the preset data sufficiency condition, the data stored in the data table of the discharge current and the voltage difference is ensured to be enough, so that all the data in the data table of the discharge current and the voltage difference can be complemented by a linear interpolation method and the like.
If the preset data sufficiency condition is met, the data table of the discharge current and the voltage difference is complemented according to the existing data in the data table of the discharge current and the voltage difference, and the data table of the direct current discharge resistor is complemented according to the linear fitting relation of the discharge current and the voltage difference based on the data in the complemented data table, step 218. The data table of the discharge current and the voltage difference is completed by interpolation, so that the data in the data table of the discharge current and the voltage difference accords with the change rule, and jump points cannot occur; accordingly, the data table of the dc discharge resistance and the data table of the maximum discharge power determined later do not show jump points.
In some embodiments of the application, first, a linear fit is made to the discharge current and voltage difference for a known temperature and state of charge, and the voltage difference for the existing temperature and state of charge over a preset number of current intervals is complemented according to the fitted ΔU-I curve. For example, table 1 below illustrates a data table of discharge currents and voltage differences for known temperatures and known states of charge. According to 30% SOC in Table 1 and 0.05 x I at-20 DEG C max 、0.25*I max 、0.45*I max The known DeltaU in (2) is used for acquiring a DeltaU-I curve of 30 percent of SOC at minus 20 ℃ and obtaining DeltaU under the current loss multiplying power according to the curve, thus reciprocally complementing each temperature Δu for different discharge rates.
TABLE 1
Then, based on the voltage differences of the known temperature, state of charge and current, linear interpolation is performed at 30% to 100% state of charge to complement the voltage differences at 30% to 100% state of charge. For example, table 2 below illustrates a data table of discharge current and voltage difference for known temperatures. According to-20 ℃ and 0.05 x i in table 2 max Known delta U of different SOCs at discharge multiplying power, obtaining temperature of minus 20 ℃ and 0.05 x I max Is interpolated from the linear curve of DeltaU-SOC at-20deg.C and 0.05 x I max Delta U under the missing SOC is recovered, and delta U of different SOCs under each temperature and discharge multiplying power is recovered.
TABLE 2
Finally, a linear fit is made to lnΔU and 1/T, where T is in Kelvin, based on the voltage differences of known temperature, state of charge and current, and the voltage differences between-25 to 25℃and between 25 to 55℃are interpolated from the fitted lnΔU-1/T curve. For example, table 3 below illustrates a data table of discharge current and voltage differences for known states of charge. According to SOC1 and 0.05 x I in Table 3 max Known delta U of different temperatures at discharge multiplying power, obtaining SOC1 and 0.05 x I max A linear curve of lnΔU-1/T, T in Kelvin, and interpolating and complementing SOC1 and 0.05 x I according to the linear curve max Missing at timeDelta U at temperature, delta U at different temperatures under each charge state and discharge multiplying power are complemented in a reciprocating manner.
TABLE 3 Table 3
If the calculated condition covered by the dc discharge resistor does not meet the preset data sufficiency condition, step 220 is entered to determine if the capacity fade of the battery has reached a preset percentage. If the capacity of the battery is not attenuated by the preset percentage, returning to step 202, and acquiring working condition data of the next data point. If the capacity of the battery decays by a preset percentage, the dc resistance DCR of the existing data point is updated and the data table of the dc resistance is completed according to the growth law of the dc resistance DCR, step 222. In some embodiments of the application, whenever the capacity of the battery decays by 5%, i.e. Δsoh >5%, meaning that the internal parameters of the battery have changed significantly, a new two-dimensional table of discharge currents and voltage differences based on temperature and state of charge needs to be stored and the data table of dc discharge resistance updated. In other words, when the capacity of the battery is 95%, 90%, 85%, 80%, etc., the data table of the dc discharge resistance is forcedly updated by complementing the data table of the dc discharge resistance according to the growth rule of the DCR. In some embodiments of the present application, the dc resistance of the missing state of charge is calculated to complement the dc resistance data table according to the calculated maximum rate of increase of the dc resistance at the same temperature relative to the dc resistance in the previous data table.
Fig. 2b illustrates a flowchart of a method 200b of updating a data table of discharge currents and voltage differences according to the dissimilarity between data, according to one embodiment of the present application. As shown in fig. 2b, in step 2102, it is determined whether the data of the data point and the data of the corresponding position in the data table of the discharge current and the voltage difference have the variability. In some embodiments of the application, the criterion for determining that the data of the data point is mutually different from the data of the corresponding location is that the current of the data point fluctuates more than 5% up and down relative to the current of the location within 1 ℃ up and down the temperature of the data point and within 2% up and down the state of charge of the data table of the discharge current and the voltage difference. It should be appreciated that the measured data may not correspond exactly to the SOC and temperature points of the table locations in the two-dimensional table, so it is necessary to determine in which cell of the data table this measured data falls according to a dissimilarity criterion. In some embodiments of the application, the measurement data is considered to be of no dissimilarity if the data is already stored in the cell in which it is located, and of dissimilarity if the data is not already stored in the cell in which it is located.
If the data of the data point and the data of the corresponding position are not mutually different, the voltage difference DeltaU' of the voltage of the data point subtracted by the voltage of the data point at the ending moment of the standing segment in the data segment and the voltage difference DeltaU of the corresponding position are averaged to replace the voltage difference of the corresponding position, and the equivalent constant current Ieq of the data point and the current I of the corresponding position are averaged to replace the current of the corresponding position, step 2104. Then, step 2116 is entered to store the current I and the voltage difference Δu in the two-dimensional table as described above according to different temperatures and SOCs.
If the data of the data point and the data of the corresponding position have different values, it is determined whether the data of the corresponding position has values in a plurality of preset current intervals, step 2106.
If the data of the corresponding position has values in a plurality of preset current intervals, calculating the square R of the correlation coefficient of the linear fit of the data of the corresponding position to the discharge current and the voltage difference before and after using the data of the data point to replace the data of the current interval in which the data point of the corresponding position is located 2 And retain R 2 Larger data, step 2108. Then, step 2116 is entered to store the current I and the voltage difference Δu in the two-dimensional table as described above according to different temperatures and SOCs. By retaining the data with a larger square of the correlation coefficient, the error of the linear fit to the current and voltage differences is made smaller. In some embodiments of the present application, the square of the correlation coefficient may be calculated according to the above equation (3) and equation (4)。
If the data of the corresponding position does not have values in all the preset current intervals, judging whether the data of the corresponding position has values in the current interval where the current of the data point is located, and step 2110.
If the data for the corresponding location has no value in the current interval in which the current of the data point is located, then step 2116 is entered, storing the current I and the voltage difference ΔU. If the data at the corresponding position has a value in the current interval where the current of the data point is located, step 2112 is entered, and in step 2112, it is determined whether the data of the data point is authentic. In some embodiments of the application, the decision principle for data trustworthiness of the data points includes: when the current of the data point is larger than the current of the data at the corresponding position in the current interval of the current of the data point, the voltage difference of the data point is larger than the voltage difference of the data at the corresponding position in the current interval of the current of the data point; and the resistance of the data point does not fluctuate by more than 20% relative to the resistance of the data at the corresponding position in the current interval in which the current of the data point is located, wherein the resistance of the data point is equal to the voltage difference of the data point divided by the discharge current, and the resistance of the data at the corresponding position in the current interval in which the current of the data point is located is equal to the voltage difference of the data at the corresponding position in the current interval in which the current of the data point is located divided by the discharge current. In the embodiment of the application, the data can be ensured to accord with the change rule through the data credibility judgment principle, and the condition of jumping points in a data table is avoided.
If the data of the data point is not trusted, the data of the data point is not stored, and the step 202 is returned to obtain the working condition data of the next data point. If the data of the data point is authentic, step 2114 is entered, wherein when the current of the data point is in the first current interval I1, the data of the current of the data point and the smaller data of the corresponding position in the current of the first current interval I1 are retained; when the current of the data point is in the second current interval I2 or the third current interval I3, the data of the current of the data point and the larger data in the corresponding position in the current of the corresponding second current interval I2 or the third current interval I3 are reserved. The operation in step 2114 retains the current closer to the two ends, resulting in a more uniform current distribution, and thus a more usable linear fit curve can be obtained. After step 2114, step 2116 is entered to store the current I and the voltage difference Δu.
In the embodiment of the application, the data table of the discharge current and the voltage difference is updated according to the dissimilarity, so that the distribution of data stored in the data table of the discharge current and the voltage difference can be controlled, the availability of a linear fitting curve of the discharge current and the voltage difference is higher, and the direct current discharge resistance is calculated according to the linear fitting relation of the discharge current and the voltage difference.
Fig. 2c illustrates a flow chart of a method 200c for calculating a dc discharge resistance of a battery at a corresponding location based on a linear fit of a discharge current and a voltage difference, according to one embodiment of the application. As shown in fig. 2c, in step 2142, the discharge current and the voltage difference at the corresponding position are linearly fitted to obtain the slope k and the pitch b of the fitted voltage difference-current curve; in step 2144, the open circuit voltage OCV at the corresponding position is obtained according to the state of charge-open circuit voltage curve of the battery and the SOC of the corresponding position; at step 2146, the open circuit voltage OCV at the corresponding position is subtracted by the cutoff voltage U of the battery Cut-off Obtaining a first maximum voltage difference DeltaU of the corresponding position max The method comprises the steps of carrying out a first treatment on the surface of the In step 2148, the first maximum voltage difference DeltaU is found max The corresponding discharge current in the fitted voltage-current curve is taken as the first maximum discharge current I max0 The method comprises the steps of carrying out a first treatment on the surface of the Then, in step 2150, a first maximum discharge current I is selected max0 And a second maximum discharge current I max1 As the minimum value of the maximum discharge current I 'practically allowed by the battery' max Wherein the second maximum discharge current I max1 Is the mechanical part-limited discharge current of the battery; in step 2152, the actual maximum discharge current I 'of the battery is looked up' max The corresponding voltage difference in the fitted voltage difference-current curve is taken as the second maximum voltage difference DeltaU' max The method comprises the steps of carrying out a first treatment on the surface of the Finally, in step 2154, a second maximum voltage difference ΔU' max Divided by the maximum discharge current I 'actually allowed by the battery' max Obtaining a batteryAnd a direct current discharge resistor DCR at the corresponding position. Briefly, as described above, the dc discharge resistance DCR of the corresponding position is calculated according to the above formulas (5) - (9).
Fig. 3 illustrates a flowchart of a method 300 for determining a maximum discharge power of a battery according to one embodiment of the application. As shown in fig. 3, in step 302, operating condition data of the battery in a specified state of health interval is obtained, where the operating condition data includes a temperature, a state of charge, a current, a voltage, and a state of health of the battery, and the specified state of health interval is a state of health interval corresponding to a latest state of health point of a data table that has been experienced by the battery and is specified to update a maximum discharge power. In some embodiments of the application, the latest state of health point of the data table that the battery has experienced that is designated for updating the direct current discharge resistance is the latest state of health point of the data table that the battery has experienced that is designated for updating the maximum discharge power. Then, in step 304, a data table of maximum discharge power of the battery in the specified health status section is determined according to the working condition data in the specified health status section. At step 306, the current temperature and current state of charge of the battery are obtained. In step 308, the maximum discharge power of the battery is determined based on the data table of the maximum discharge power in the above specified health status section and the current temperature and the current state of charge. In other words, the maximum discharge power corresponding to the current temperature and state of charge in the data table of the maximum discharge power is searched.
The method 300 for determining the maximum discharge power of the battery shown in fig. 3 continuously updates the data table of the maximum discharge power in the whole life cycle of the battery, thereby ensuring the accuracy of the determined maximum discharge power, enabling the performance of the battery to be exerted to the maximum, and improving the driving safety and the driving dynamics.
Fig. 4a illustrates a flow chart of a method 400a of determining a data table of a dc discharge resistance of a battery according to one embodiment of the application. The method illustrated in fig. 4a is similar to the method illustrated in fig. 2a, and like parts are not described again. In FIG. 4a, at step 414, the battery is calculated from the linear fit of the discharge current and the voltage differenceMaximum discharge power at the corresponding position; in step 416, the data table of the maximum discharge power of the battery in the specified health status interval is completed according to whether the calculated working condition of the maximum discharge power coverage meets the preset data sufficiency condition and the health status of the data point. In some embodiments of the present application, the preset data sufficiency condition satisfied by the working condition of the calculated maximum discharge power coverage is the same as the preset data sufficiency condition satisfied by the working condition of the calculated direct current discharge resistance coverage. Further, at step 418, the data table of discharge current and voltage difference is completed according to existing data in the data table of discharge current and voltage difference, and the data table of maximum discharge power is completed according to a linear fit relationship of discharge current and voltage difference based on data in the completed data table; at step 422, the maximum discharge power P of the existing data point is updated max And in accordance with the maximum discharge power P max The decay law of (2) complements the data table of maximum discharge power. In some embodiments of the present application, the maximum discharge power of the missing state of charge is calculated to complement the data table of maximum discharge power according to the maximum decay value of the calculated maximum discharge power at the same temperature relative to the maximum discharge power in the previous data table.
Fig. 4b illustrates a flowchart of a method 400b for calculating a maximum discharge power of a battery at a corresponding location based on a linear fit relationship of discharge current and voltage difference, according to one embodiment of the application. The method 400b of calculating the maximum discharge power illustrated in fig. 4b is similar to the method 300c of calculating the dc discharge resistance illustrated in fig. 3 c. The method 400b is different in that, after the dc discharge resistance is calculated in step 4154, in step 4156, the open circuit voltage OCV of the corresponding position is subtracted by the dc discharge resistance DCR of the corresponding position and the maximum discharge current I 'actually allowed by the battery' max Obtaining the maximum supply voltage U of the battery at the corresponding position S And the maximum discharge current I 'actually allowed by the battery at the corresponding position is calculated' max Multiplying the maximum supply voltage U S Obtaining the maximum discharge power P of the corresponding position max . In other words, as described above, the maximum discharge power P is calculated according to the above formula (10) max 。
Referring to fig. 5, according to the same inventive concept, a battery management system 500 is further provided in an embodiment of the present application, including: at least one processor 501; and a memory 502 communicatively coupled to the processor 501; the memory 502 stores instructions executable by the processor, which when executed by the processor 501, cause the processor 501 to perform the method for determining the dc discharge resistance of a battery and/or the method for determining the maximum discharge power of a battery provided by embodiments of the present application.
Wherein the processor 501 and the memory 502 are electrically connected directly or indirectly to enable transmission or interaction of data. For example, electrical connections may be made between these elements through one or more communication buses or signal buses. The method for correcting the state of charge of the battery comprises at least one software functional module which can be stored in the memory 502 in the form of software or firmware (firmware).
The processor 501 may be an integrated circuit chip having signal processing capabilities. The processor 501 may be a general purpose processor including a central processing unit (Central Processing Unit, CPU), a network processor (Network Processor, NP), etc.; but may be a digital signal processor, an application specific integrated circuit, an off-the-shelf programmable gate array or other programmable logic device, a discrete gate or transistor logic device, or a discrete hardware component. Which may implement or perform the disclosed methods, steps, and logic blocks in embodiments of the application. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like.
The memory 502 may store various software programs and modules, such as program instructions/modules corresponding to the method for determining a dc discharge resistance of a battery and/or the method and apparatus for determining a maximum discharge power of a battery provided by embodiments of the present application. The processor 501 executes various functional applications and data processing, i.e., implements the methods of embodiments of the present application, by running software programs and modules stored in the memory 502.
Memory 502 may include, but is not limited to, random access Memory (Random Access Memory, RAM), read Only Memory (ROM), programmable Read Only Memory (Programmable Read-Only Memory, PROM), erasable Read Only Memory (Erasable Programmable Read-Only Memory, EPROM), electrically erasable Read Only Memory (Electric Erasable Programmable Read-Only Memory, EEPROM), and the like.
The embodiments and specific examples of the foregoing method for determining the dc discharge resistance of the battery and the method for determining the maximum discharge power of the battery are equally applicable to the battery management system 500 shown in fig. 5, and the detailed description of the method for determining the dc discharge resistance of the battery and the method for determining the maximum discharge power of the battery, which are described above, will be apparent to those skilled in the art, so that the implementation method of the battery management system 500 in fig. 5 will not be described in detail herein for brevity of description.
In addition, the application also provides a device, which comprises: a battery; and a battery management system as shown in fig. 5. The battery may be used as a power source for the device and may also be used as an energy storage unit for the device. The device may be, but is not limited to, a mobile device (e.g., a cell phone, a notebook computer, etc.), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a watercraft, a satellite, an energy storage system, etc. The device may select the battery according to its use requirements.
While the application has been described with reference to a preferred embodiment, various modifications may be made and equivalents may be substituted for elements thereof without departing from the scope of the application. In particular, the technical features mentioned in the respective embodiments may be combined in any manner as long as there is no structural conflict. The present application is not limited to the specific embodiments disclosed herein, but encompasses all technical solutions falling within the scope of the claims.
Claims (40)
- A method for determining a dc discharge resistance of a battery, the method comprising:Acquiring working condition data of the battery in a specified health condition interval, wherein the working condition data comprise the temperature, the state of charge, the current, the voltage and the health condition of the battery, and the specified health condition interval is a health condition interval corresponding to the latest health condition point of a data table which is specified to update the direct current discharge resistance and is experienced;determining a data table of a direct current discharge resistance of the battery in the appointed health state interval according to the working condition data of the battery in the appointed health state interval;acquiring the current temperature and the current state of charge of the battery; andand determining the direct current discharge resistance of the battery according to the data table of the direct current discharge resistance in the appointed health state interval, the current temperature and the current state of charge.
- The method of claim 1, wherein determining a data table of dc discharge resistances of the battery over the specified state of health interval comprises:screening out data fragments meeting preset working conditions from the working condition data in the specified health state interval;when the current of the data point in the data segment is in a preset current interval, updating a data table of the discharge current and the voltage difference according to the dissimilarity between the data of the data point and the data of the corresponding position of the data point in the data table of the discharge current and the voltage difference;When the data of the corresponding position meets the preset sufficient condition, calculating the direct current discharge resistance of the battery at the corresponding position according to the linear fitting relation of the discharge current and the voltage difference; andand according to the calculated working condition covered by the direct current discharge resistor, whether the working condition covered by the direct current discharge resistor meets the preset data sufficiency condition and the health state of the data points, completing a data table of the direct current discharge resistor of the battery in the appointed health state interval.
- The method of claim 2, wherein determining a data table of dc discharge resistances of the battery over the specified state of health interval comprises the steps of:and when the current in the pulse section of the data segment does not meet the quasi-constant current condition, converting the current of the data segment in the pulse section into an equivalent constant current.
- A method according to claim 3, characterized in that the equivalent constant current is calculated according to the following formula:wherein I is eq Represents an equivalent constant current, w (t) represents a weight function, I (t) represents a discharge current at a sampling time point, t end And the ending time of the pulse segment is represented, n is a positive integer, and n is more than or equal to 2 and less than or equal to 6.
- The method according to any one of claims 2 to 4, wherein the preset current interval comprises three current intervals, a first current interval of the three current intervals is between 0.05 and 0.2 times a maximum discharge current, a second current interval of the three current intervals is between 0.2 and 0.4 times the maximum discharge current, and a third current interval of the three current intervals is between 0.4 and 0.8 times the maximum discharge current, the maximum discharge current being a maximum current allowed for the battery to discharge under conditions corresponding to the data points under conditions of temperature and state of charge.
- The method according to any one of claims 2 to 5, wherein the data table determining the dc discharge resistance of the battery in the specified state of health interval comprises the steps of:when the data of the data point and the data of the corresponding position are not mutually different:taking the average value of the voltage difference between the voltage at the end time of the standing segment in the data segment and the voltage of the data point and the voltage difference between the corresponding position and the data of the data point, which are not mutually different, to replace the voltage difference between the corresponding position and the data of the data point; and is also provided withAnd taking the average value of the current of the data point and the current of the data which does not have the dissimilarity between the corresponding position and the data of the data point to replace the current of the data which does not have the dissimilarity between the corresponding position and the data of the data point.
- The method according to any one of claims 2 to 6, wherein the data table determining the dc discharge resistance of the battery in the specified state of health interval comprises the steps of:and when the data of the data points and the data of the corresponding positions have dissimilarity, updating a data table of discharge current and voltage difference according to the relation between the data of the data points and the data of the corresponding positions in the preset current interval, wherein the preset current interval comprises a plurality of current intervals.
- The method of claim 7, wherein updating the data table of discharge current and voltage difference according to the relationship between the data of the data point and the data of the corresponding location within the preset current interval comprises:comparing squares of correlation coefficients of linear fitting of the data of the corresponding positions to discharge current and voltage difference before and after replacing the data of the current interval in which the data point of the corresponding positions is located with the data of the data point when the data of the corresponding positions are distributed in the plurality of current intervals;when the square of the correlation coefficient of the data point is larger, the data of the data point is stored in a data table of the discharge current and the voltage difference.
- The method according to claim 7 or 8, wherein the step of updating a data table of discharge current and voltage difference according to the relation between the data of the data point and the data of the corresponding position within the preset current interval comprises:judging whether the data of the corresponding position has a value in a current interval in which the current of the data point is located when the data of the corresponding position is not distributed in all the current intervals;And when the data of the corresponding position has no value in the current interval of the current of the data point, storing the data of the data point in a data table of discharge current and voltage difference.
- The method of claim 9, wherein updating the data table of discharge current and voltage difference according to the relationship between the data of the data point and the data of the corresponding location within the preset current interval comprises:judging whether the data of the data point is credible or not when the data of the corresponding position has a value in a current interval where the current of the data point is located; andwhen the data of the data point is authentic:when the current of the data point is in the current interval with the smallest current value in the current intervals, storing the data of the current of the data point and the smaller current value in the current of the current interval with the smallest current value in the current intervals in the corresponding position in a data table of discharge current and voltage difference;and when the current of the data point is not in the current interval with the smallest current value in the current intervals, storing the data of the current value of the data point and the current value of the corresponding position in the current interval with the current of the data point in a data table of discharge current and voltage difference.
- The method of claim 9, wherein the preset current interval comprises three current intervals, a first current interval of the three current intervals is between 0.05 and 0.2 times a maximum discharge current, a second current interval of the three current intervals is between 0.2 and 0.4 times the maximum discharge current, and a third current interval of the three current intervals is between 0.4 and 0.8 times the maximum discharge current, the maximum discharge current being a maximum current allowed for the battery having a rated capacity to discharge at a temperature and charge state corresponding to a condition of the data point;when the data of the data point is authentic:when the current of the data point is in the first current interval, storing the data of the current of the data point and the current value of the corresponding position smaller in the current of the first current interval in a data table of discharge current and voltage difference;and when the current of the data point is in the second current region or the third current region, storing the data of the current value, which is larger in the current of the current region of the data point, of the current of the corresponding position in the current region of the data point in a data table of discharge current and voltage difference.
- The method according to claim 10 or 11, wherein the data credibility determination principle of the data points comprises:when the current of the data point is larger than the current of the data at the corresponding position in the current interval of the current of the data point, the voltage difference of the data point is larger than the voltage difference of the data at the corresponding position in the current interval of the current of the data point; andthe resistance of the data point does not fluctuate by more than 20% relative to the resistance of the data at the corresponding position in the current interval where the current of the data point is located, wherein the resistance of the data point is equal to the voltage difference of the data point divided by the current, and the resistance of the data at the corresponding position in the current interval where the current of the data point is located is equal to the voltage difference of the data at the corresponding position in the current interval where the current of the data point is located divided by the current.
- The method of any one of claims 2 to 12, wherein the voltage difference of the data points is equal to the voltage at the end of a stationary segment in the data segment minus the voltage of the data points; and is also provided withThe current of the data point is the absolute value of the discharge current of the battery.
- The method according to any one of claims 2 to 13, wherein the preset current interval comprises a plurality of current intervals, and the preset sufficiency condition comprises:the data of the corresponding positions in the data table of the discharge current and the voltage difference are distributed in the plurality of current intervals; andthe square of the correlation coefficient of the linear fitting of the discharge current and the voltage difference at the corresponding position in the data table of the discharge current and the voltage difference is greater than or equal to 0.95.
- The method according to any one of claims 2 to 14, wherein the step of calculating the dc discharge resistance of the battery at the corresponding location from a linear fit of the discharge current and the voltage difference comprises:performing linear fitting on the discharge current and the voltage difference at the corresponding positions to obtain the slope and the pitch of a fitted voltage difference-current curve;obtaining an open-circuit voltage of the corresponding position according to the state-of-charge-open-circuit voltage curve of the battery and the state-of-charge of the corresponding position;subtracting the cut-off voltage of the battery from the open-circuit voltage of the corresponding position to obtain a first maximum voltage difference of the corresponding position;Obtaining a first maximum discharge current according to the fitted voltage difference-current curve and the first maximum voltage difference;selecting the minimum value of the first maximum discharge current and the second maximum discharge current as a third maximum discharge current, wherein the second maximum discharge current is the discharge current limited by the mechanical part of the battery;obtaining a second maximum voltage difference according to the fitted voltage difference-current curve and the third maximum discharge current; andand dividing the second maximum voltage difference by the third maximum discharge current to obtain the direct current discharge resistance of the battery at the corresponding position.
- The method according to any one of claims 2 to 15, wherein when the calculated condition of direct current discharge resistance coverage satisfies a preset data sufficiency condition, the data table of discharge current and voltage difference is complemented according to existing data in the data table of discharge current and voltage difference, and the data table of direct current discharge resistance of the battery in the specified health state interval is complemented according to a linear fitting relationship of discharge current and voltage difference based on data in the data table of complemented discharge current and voltage difference.
- The method according to any one of claims 2 to 16, wherein the preset data sufficiency condition includes a calculated dc discharge resistance coverage condition satisfying the following requirements:the covered temperature comprises at least three sets of temperatures between-20 and 25 ℃, each set of temperature intervals of the at least three sets of temperatures being greater than or equal to 10 ℃;the covered temperature comprises at least two sets of temperatures between 25 and 55 ℃, each set of the at least two sets of temperatures being spaced apart by greater than or equal to 10 ℃; andthe covered states of charge comprise at least two sets of states of charge between 30% and 100%, each set of states of charge in the at least two sets of states of charge having a state of charge interval greater than or equal to 20%.
- The method according to any one of claims 2 to 17, wherein the step of supplementing the data table of discharge current and voltage difference according to existing data in the data table of discharge current and voltage difference comprises:performing linear fitting on the current and the voltage difference of the existing temperature and the state of charge, and complementing the voltage difference of the existing temperature and the state of charge in the preset current interval according to a fitted delta U-I curve;linearly interpolating the state of charge at 30% to 100% based on the voltage differences of the known temperature, state of charge and current to complement the voltage differences of the state of charge at 30% to 100%; andLinear fitting is performed on lnΔU and 1/T according to the voltage differences of known temperature, state of charge and current, where T is in Kelvin, and the voltage differences between-25 to 25 ℃ and between 25 to 55 ℃ are interpolated according to the fitted lnΔU-1/T curve.
- The method according to any one of claims 2 to 18, wherein the data table determining the dc discharge resistance of the battery in the specified state of health interval comprises the steps of:when the working condition covered by the calculated direct current discharge resistor does not meet the preset data sufficiency condition, judging whether the capacity of the battery at the data point is attenuated by a preset percentage relative to the rated capacity of the battery;and when the capacity of the data point of the battery is attenuated by a preset percentage relative to the rated capacity of the battery, calculating the direct current discharge resistance of the missing charge state according to the maximum growth rate of the calculated direct current discharge resistance at the same temperature relative to the direct current discharge resistance in the data table of the direct current discharge resistance of the previous health state section of the appointed health state section so as to complement the direct current discharge resistances of different temperatures and charge states.
- A battery management system configured to determine a dc discharge resistance of a battery, the battery management system comprising:at least one processor; anda memory coupled to the at least one processor;wherein the memory stores instructions that, when executed by the at least one processor, cause the at least one processor to perform the method for determining the direct current discharge resistance of a battery of any one of claims 1 to 19.
- A method for determining a maximum discharge power of a battery, the method comprising:acquiring working condition data of the battery in a specified health condition interval, wherein the working condition data comprises the temperature, the state of charge, the current, the voltage and the health condition of the battery, and the specified health condition interval is a health condition interval corresponding to the latest health condition point of a data table which is specified to update the maximum discharge power and is experienced;determining a data table of maximum discharge power of the battery in the appointed health state interval according to the working condition data of the battery in the appointed health state interval;Acquiring the current temperature and the current state of charge of the battery; andand determining the maximum discharge power of the battery according to the data table of the maximum discharge power in the specified health state interval, the current temperature and the current state of charge.
- The method of claim 21, wherein determining a data table of maximum discharge power of the battery over the specified state of health interval comprises:screening out data fragments meeting preset working conditions from the working condition data in the specified health state interval;when the current of the data point in the data segment is in a preset current interval, updating a data table of the discharge current and the voltage difference according to the dissimilarity between the data of the data point and the data of the corresponding position of the data point in the data table of the discharge current and the voltage difference;when the data of the corresponding position meets the preset sufficient condition, calculating the maximum discharge power of the battery at the corresponding position according to the linear fitting relation of the discharge current and the voltage difference; andand according to whether the working condition covered by the calculated maximum discharge power meets the preset data sufficiency condition and the health state of the data points, completing a data table of the maximum discharge power of the battery in the appointed health state interval.
- The method of claim 22, wherein determining a data table of maximum discharge power of the battery within the specified state of health interval comprises the steps of:and when the current in the pulse section of the data segment does not meet the quasi-constant current condition, converting the current of the data segment in the pulse section into an equivalent constant current.
- The method of claim 23, wherein the equivalent constant current is calculated according to the formula:wherein I is eq Represents an equivalent constant current, w (t) represents a weight function, I (t) represents a discharge current at a sampling time point, t end Representation houseThe end time of the pulse segment is n is a positive integer, and n is more than or equal to 2 and less than or equal to 6.
- The method of any one of claims 22 to 24, wherein the preset current interval comprises three current intervals, a first one of the three current intervals being between 0.05 and 0.2 times a maximum discharge current, a second one of the three current intervals being between 0.2 and 0.4 times the maximum discharge current, a third one of the three current intervals being between 0.4 and 0.8 times the maximum discharge current, the maximum discharge current being a maximum current allowed for discharge of the battery having a rated capacity at a temperature and state of charge corresponding to a condition of the data point.
- The method according to any one of claims 22 to 25, wherein the data table determining the maximum discharge power of the battery within the specified state of health interval comprises the steps of:when the data of the data point and the data of the corresponding position are not mutually different:taking the average value of the voltage difference between the voltage at the end time of the standing segment in the data segment and the voltage of the data point and the voltage difference between the corresponding position and the data of the data point, which are not mutually different, to replace the voltage difference between the corresponding position and the data of the data point; and is also provided withAnd taking the average value of the current of the data point and the current of the data which does not have the dissimilarity between the corresponding position and the data of the data point to replace the current of the data which does not have the dissimilarity between the corresponding position and the data of the data point.
- The method according to any one of claims 22 to 26, wherein the data table determining the maximum discharge power of the battery within the specified state of health interval comprises the steps of:and when the data of the data points and the data of the corresponding positions have dissimilarity, updating a data table of discharge current and voltage difference according to the relation between the data of the data points and the data of the corresponding positions in the preset current interval, wherein the preset current interval comprises a plurality of current intervals.
- The method of claim 27, wherein updating the data table of discharge current and voltage difference according to the relationship between the data of the data point and the data of the corresponding location within the preset current interval comprises:comparing squares of correlation coefficients of linear fitting of the data of the corresponding positions to discharge current and voltage difference before and after replacing the data of the current interval in which the data point of the corresponding positions is located with the data of the data point when the data of the corresponding positions are distributed in the plurality of current intervals;when the square of the correlation coefficient of the data point is larger, the data of the data point is stored in a data table of the discharge current and the voltage difference.
- The method according to claim 27 or 28, wherein the step of updating a data table of discharge current and voltage difference according to the relation between the data of the data point and the data of the corresponding position within the preset current interval comprises:judging whether the data of the corresponding position has a value in a current interval in which the current of the data point is located when the data of the corresponding position is not distributed in all the current intervals;And when the data of the corresponding position has no value in the current interval of the current of the data point, storing the data of the data point in a data table of discharge current and voltage difference.
- The method of claim 29, wherein updating the data table of discharge current and voltage differences based on the relationship between the data of the data points and the data of the corresponding locations over the preset current interval comprises:judging whether the data of the data point is credible or not when the data of the corresponding position has a value in a current interval where the current of the data point is located; andwhen the data of the data point is authentic:when the current of the data point is in the current interval with the smallest current value in the current intervals, storing the data of the current of the data point and the smaller current value in the current of the current interval with the smallest current value in the current intervals in the corresponding position in a data table of discharge current and voltage difference;and when the current of the data point is not in the current interval with the smallest current value in the current intervals, storing the data of the current value of the data point and the current value of the corresponding position in the current interval with the current of the data point in a data table of discharge current and voltage difference.
- The method of claim 29, wherein the preset current interval comprises three current intervals, a first current interval of the three current intervals being between 0.05 and 0.2 times a maximum discharge current, a second current interval of the three current intervals being between 0.2 and 0.4 times the maximum discharge current, a third current interval of the three current intervals being between 0.4 and 0.8 times the maximum discharge current, the maximum discharge current being a maximum current allowed for the battery having a rated capacity to discharge at a temperature and state of charge corresponding to a condition of the data point;when the data of the data point is authentic:when the current of the data point is in the first current interval, storing the data of the current of the data point and the current value of the corresponding position smaller in the current of the first current interval in a data table of discharge current and voltage difference;and when the current of the data point is in the second current region or the third current region, storing the data of the current value, which is larger in the current of the current region of the data point, of the current of the corresponding position in the current region of the data point in a data table of discharge current and voltage difference.
- The method of claim 30 or 31, wherein the data credibility criteria of the data points include:when the current of the data point is larger than the current of the data at the corresponding position in the current interval of the current of the data point, the voltage difference of the data point is larger than the voltage difference of the data at the corresponding position in the current interval of the current of the data point; andthe resistance of the data point does not fluctuate by more than 20% relative to the resistance of the data at the corresponding position in the current interval where the current of the data point is located, wherein the resistance of the data point is equal to the voltage difference of the data point divided by the current, and the resistance of the data at the corresponding position in the current interval where the current of the data point is located is equal to the voltage difference of the data at the corresponding position in the current interval where the current of the data point is located divided by the current.
- The method of any one of claims 22 to 32, wherein the voltage difference of the data points is equal to the voltage at the end of a stationary segment in the data segment minus the voltage of the data points; and is also provided withThe current of the data point is the absolute value of the discharge current of the battery.
- The method according to any one of claims 22 to 33, wherein the preset current interval comprises a plurality of current intervals, and the preset sufficiency condition comprises:the data of the corresponding positions in the data table of the discharge current and the voltage difference are distributed in the plurality of current intervals; andthe square of the correlation coefficient of the linear fitting of the discharge current and the voltage difference at the corresponding position in the data table of the discharge current and the voltage difference is greater than or equal to 0.95.
- The method of any one of claims 22 to 34, wherein the step of calculating the maximum discharge power of the battery at the corresponding location from a linear fit relationship of discharge current and voltage difference comprises:performing linear fitting on the discharge current and the voltage difference at the corresponding positions to obtain the slope and the pitch of a fitted voltage difference-current curve;obtaining an open-circuit voltage of the corresponding position according to the state-of-charge-open-circuit voltage curve of the battery and the state-of-charge of the corresponding position;subtracting the cut-off voltage of the battery from the open-circuit voltage of the corresponding position to obtain a first maximum voltage difference of the corresponding position;Obtaining a first maximum discharge current according to the fitted voltage difference-current curve and the first maximum voltage difference;selecting the minimum value of the first maximum discharge current and the second maximum discharge current as a third maximum discharge current, wherein the second maximum discharge current is the discharge current limited by the mechanical part of the battery;obtaining a second maximum voltage difference according to the fitted voltage difference-current curve and the third maximum discharge current;dividing the second maximum voltage difference by the third maximum discharge current to obtain a direct current discharge resistance of the battery at the corresponding position;subtracting the product of the direct current discharge resistor at the corresponding position and the third maximum discharge current from the open circuit voltage at the corresponding position to obtain the maximum power supply voltage of the battery at the corresponding position; andand multiplying the third maximum discharge current of the corresponding position by the maximum power supply voltage to obtain the maximum discharge power of the corresponding position.
- The method according to any one of claims 22 to 35, wherein when the calculated condition of maximum discharge power coverage satisfies a preset data sufficiency condition, the data table of discharge current and voltage difference is complemented according to existing data in the data table of discharge current and voltage difference, and the data table of maximum discharge power of the battery in the specified state of health interval is complemented according to a linear fitting relationship of discharge current and voltage difference based on data in the data table of complemented discharge current and voltage difference.
- The method according to any one of claims 22 to 36, wherein the preset data sufficiency condition includes a condition that the calculated maximum discharge power coverage satisfies the following requirements:the covered temperature comprises at least three sets of temperatures between-20 and 25 ℃, each set of temperature intervals of the at least three sets of temperatures being greater than or equal to 10 ℃;the covered temperature comprises at least two sets of temperatures between 25 and 55 ℃, each set of the at least two sets of temperatures being spaced apart by greater than or equal to 10 ℃; andthe covered states of charge comprise at least two sets of states of charge between 30% and 100%, each set of states of charge in the at least two sets of states of charge having a state of charge interval greater than or equal to 20%.
- The method according to any one of claims 22 to 37, wherein the step of supplementing the data table of discharge current and voltage difference according to existing data in the data table of discharge current and voltage difference comprises:performing linear fitting on the current and the voltage difference of the existing temperature and the state of charge, and complementing the voltage difference of the existing temperature and the state of charge in the preset current interval according to a fitted delta U-I curve;linearly interpolating the state of charge at 30% to 100% based on the voltage differences of the known temperature, state of charge and current to complement the voltage differences of the state of charge at 30% to 100%; andLinear fitting is performed on lnΔU and 1/T according to the voltage differences of known temperature, state of charge and current, where T is in Kelvin, and the voltage differences between-25 to 25 ℃ and between 25 to 55 ℃ are interpolated according to the fitted lnΔU-1/T curve.
- The method according to any one of claims 22 to 38, wherein the data table determining the maximum discharge power of the battery within the specified state of health interval comprises the steps of:when the working condition of the calculated maximum discharge power coverage does not meet the preset data sufficiency condition, judging whether the capacity of the battery at the data point is attenuated by a preset percentage relative to the rated capacity of the battery;and when the capacity of the data point of the battery is attenuated by a preset percentage relative to the rated capacity of the battery, calculating the maximum discharge power of the missing charge state according to the maximum attenuation rate of the calculated maximum discharge power at the same temperature relative to the maximum discharge power in the data table of the previous maximum discharge power so as to complement the maximum discharge power of different temperatures and charge states.
- A battery management system configured to determine a maximum discharge power of a battery, the battery management system comprising:At least one processor; anda memory coupled to the at least one processor;wherein the memory stores instructions that, when executed by the at least one processor, cause the at least one processor to perform the method for determining the maximum discharge power of a battery of any of claims 21 to 39.
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| PCT/CN2021/129543 WO2023082046A1 (en) | 2021-11-09 | 2021-11-09 | Method for determining direct-current discharge resistance, method for determining maximum discharge power, and battery management system |
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| KR101147202B1 (en) * | 2010-10-13 | 2012-05-25 | 삼성에스디아이 주식회사 | Power storage apparatus |
| US9147910B2 (en) * | 2011-12-28 | 2015-09-29 | General Electric Company | Method and system for controlling energy storage device |
| CN105242217B (en) * | 2015-09-21 | 2019-01-01 | 郑州宇通客车股份有限公司 | A kind of power-supply system current limit calculation method |
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