CN112147513A - Power battery SOC multidimensional calibration method - Google Patents

Abstract

The invention discloses a power battery SOC multidimensional calibration method, which comprises the steps of electrifying a power battery; reading initial data; calculating according to the initial data to obtain a table lookup SOC, and further calculating a real SOC; calculating the current battery health degree SOH of the battery according to the accumulated charge-discharge energy, and then calculating the current capacity of the power battery system; calculating a dynamic SOC and carrying out dynamic SOC following calibration; and (3) performing full charge or full discharge calibration and calibration by combining a monomer voltage limit value calibration and a current reduction strategy at the charge and discharge tail end of the power battery system, and finally outputting the calibrated real SOC of the battery system. The method adopts an ampere-hour integral method to calculate the discharging SOC of the power battery, and combines an aging calibration method, a static voltage method table look-up calibration method, a dynamic SOC following calibration method and a terminal monomer voltage limit value calibration and current reduction strategy combination method to carry out multi-dimensional calibration on the real SOC of the power battery, so that the SOC estimation accuracy is improved.

Description

A multi-dimensional calibration method for power battery SOC

technical field

The invention relates to the technical field of battery management, in particular to a multi-dimensional calibration method for the SOC of a power battery.

Background technique

Since the beginning of the 21st century, the excessive use and development of petroleum and derivative products has made the relationship between environmental pollution and energy utilization unbalanced, which has caused serious negative impacts on society. There is an urgent need for a technical solution to optimize the supply-side energy structure and improve environmental pollution. In this environment, electric vehicles have become the mainstream choice around the world.

Due to the complexity of the current internal state and external use of the battery (PACK), the SOC (State of Charge) of the battery cannot be directly measured, and can only be estimated through other characterization parameters of the battery, which cannot be avoided in the estimation process. error occurs. The size of the error directly affects the use state and service life of the power battery.

SUMMARY OF THE INVENTION

Purpose of the invention: Aiming at the defect of large SOC estimation error of the battery system in the prior art, the present invention discloses a multi-dimensional calibration method for the SOC of a power battery, which combines the aging calibration method, the static voltage method look-up table calibration method, the dynamic SOC follow-up calibration method and the The multi-dimensional calibration of the real SOC of the power battery is carried out by combining the terminal cell voltage limit value calibration and the downflow strategy.

Technical scheme: In order to achieve the above technical purpose, the present invention adopts the following technical scheme.

A multi-dimensional calibration method for a power battery SOC, comprising the following steps:

S1: The power battery is powered on;

S2: Read initial data: read clock information, display SOC, inspect battery temperature T, accumulated charge and discharge energy, power battery system nominal capacity C _rated , battery current and cell voltage;

S3: Calculation of dynamic parameters of the power battery system: Calculate the look-up table SOC according to the inspection battery temperature and cell voltage, calculate and obtain the real SOC according to the look-up table SOC combined with the conditional look-up table method; calculate the current battery health of the battery according to the accumulated charge and discharge energy SOH, calculate the current capacity of the power battery system according to the SOH;

S4: Dynamic SOC calculation: Calculate the discharge energy according to the ampere-hour integration method, and calculate the real-time dynamic SOC during the discharge process in combination with the current battery health SOH and the real SOC, and the dynamic SOC is the real SOC;

S5: Dynamic SOC following calibration: determine whether the difference between the real SOC and the displayed SOC is less than the threshold value, if so, the dynamic SOC following is allowed to be set to 0, and the dynamic SOC following calibration is not performed, if not, the dynamic SOC following is allowed to be set to 1, Perform SOC dynamic follow calibration correction during discharge;

S6: Synergy between terminal extreme value calibration and current reduction strategy: at the end of the charging and discharging of the power battery system, combined with the cell voltage limit value calibration and the current reduction strategy, the real SOC and displayed SOC of the power battery system are fully charged or fully discharged. Outputs the true SOC of the calibrated battery system.

Preferably, the calculation formula of the current battery health SOH of the battery and the current capacity of the power battery system in the S3 is:

C _real =C _rated *SOH

Among them, N _rated is the nominal dischargeable times of the battery system, Q _total is the cumulative discharge energy of the battery system, Q _rated is the characteristic parameter of the battery system itself, U _bat is the total battery voltage, and I is the battery during the charging and discharging process of the battery. Current, C _real is the current capacity of the power battery system, C _rated is the nominal capacity of the power battery system

Preferably, the process of obtaining the look-up table SOC according to the inspection of the battery temperature and the cell voltage in S3 and calculating and obtaining the real SOC according to the look-up table SOC combined with the condition look-up table method is the process of performing the table look-up calibration by the static voltage method; the The specific process of the static voltage method for look-up table calibration is as follows:

S31, battery inspection: obtain inspection battery temperature T, cell voltage V _cell , battery current I during battery charging and discharging;

S32. Obtain the look-up table SOC: obtain the look-up table SOC through the look-up table according to the current inspection battery temperature T and the cell voltage V _cell ;

S33, the static voltage method is used to perform table lookup calibration: according to the sleep duration of the power battery system and the state of the battery, combined with the lookup table SOC calculation to obtain the current real SOC, that is, SOC _real .

Preferably, the specific process of obtaining the current real SOC according to the sleep duration of the battery system and the state of the battery combined with the look-up table SOC calculation in S33 is as follows:

S331, determine whether the sleep duration is not less than 3 hours or the battery current I is in a continuous state of I<5A and the duration is not less than 3 hours, if yes, then SOC _real = lookup table SOC at this time; if not, go to step S332;

S332, determine whether the sleep duration is within the interval of 1 hour to 3 hours or the duration of the battery current I in the continuous I<5A state is within the interval of 1 hour to 3 hours, if not, proceed to step S333; if so, further determine the inequality |SOC _out -1.1*Look up table SOC|-|SOC _out -0.9*Look up table SOC|>0 is true, if yes, then SOC _real =1.1*Look up table SOC; if not, SOC _real =0.9*Look up table SOC; where SOC _out is the display SOC;

S333. At this time, the sleep duration does not exceed 1 hour or the battery current I is in the state of I<5A for less than 1 hour, then SOC _real =SOC _out .

Preferably, the dynamic SOC calculation formula in S4 is:

C _real =C _rated *SOH

Among them, I is the current during the charging and discharging of the battery, C _use is the capacity used in the charging and discharging of the battery, C _rated is the nominal capacity of the battery system, C _real is the current capacity of the battery system, SOH is the battery health, and in the formula The SOC is the dynamic SOC, where the dynamic SOC is the real SOC.

Preferably, the specific judgment process of the dynamic SOC following calibration in S5 is:

S51. Obtain the real SOC and the displayed SOC, and calculate the difference between the two;

S52. If |real SOC-display SOC|<α%, the dynamic SOC follow-up is allowed to be set to 0, that is, dynamic follow-up is not allowed; if |true SOC-display SOC| Allows dynamic follow-up calibration during discharge; where α is the first threshold.

Preferably, the S52 performs dynamic follow-up during the discharge process, and the specific process of the calibration is as follows:

S521. When the dynamic follow-up allowable value is set to 1, the dynamic follow-up during the discharge process is turned on;

S522. Set when the displayed SOC drops by β%, the real SOC equals the displayed SOC, and calculates the real-time displayed SOC according to the displayed initial value SOC, the real initial value SOC and the discharge power, and the real-time displayed SOC is the real value after the dynamic follow calibration SOC; where β is the second threshold.

Preferably, in the S522, the specific calculation process of displaying the SOC in real time is:

SOC _{display/initial} -SOC _identical = β

Among them, β is the second threshold, SOC _{display/initial} is the initial value of SOC, that is, the displayed SOC value read from the memory at the moment of power-on; SOC _identical is the SOC when calibrated to the same state; SOC _real/initial is the real initial value The value SOC, that is, the real SOC obtained by the table look-up method in step S3; C _interval is the discharge capacity when calibrated to a consistent state SOC; C _use is the capacity used in battery charging and discharging, and _SOC display is the real-time display SOC.

Preferably, the specific process of S6 calibrating the real SOC at the end of charging and discharging in combination with the cell voltage limit value calibration method and the current reduction strategy is as follows:

S61. The specific process of SOC calibration at the discharge end is as follows: according to the characteristics of the single cell, combined with the discharge MAP, the output current of the current limit is performed at the end until the voltage of the discharge single cell is the lowest limit, and the real SOC and the displayed SOC are forced to be calibrated to 0 %;

S62. The specific process of the SOC standard at the charging end is as follows: according to the characteristics of the single cell, combined with the current reduction spring to slightly reduce the current to charge until the cell voltage reaches the highest limit, the real SOC and the displayed SOC are forcibly calibrated to 100%.

Beneficial effects: the present invention adopts the ampere-hour integration method to calculate the real value discharge SOC of the power battery, and combines the aging (SOH) calibration method, the static voltage method look-up table calibration method, the dynamic SOC follow-up calibration method, and the terminal cell voltage limit value and current drop. The strategy collaborative calibration method performs multi-dimensional calibration on the real SOC of the power battery to improve the accuracy of SOC estimation.

Description of drawings

Fig. 1 is the general method flow chart of the present invention;

Fig. 2 is the static voltage method look-up table calibration flow chart of the present invention;

Fig. 3 is a flow chart of a SOC update process of the present invention;

Fig. 4 is the SOC display initial value > SOC real initial value & discharge condition SOC tracking relationship diagram;

Figure 5 is a graph showing the initial value of SOC display > the real initial value of SOC & the SOC tracking relationship under charging conditions;

Figure 6 is a graph showing the initial value of SOC display < the real initial value of SOC & the SOC tracking relationship under discharge conditions;

FIG. 7 is a graph showing the SOC display initial value < SOC real initial value & charging condition SOC tracking relationship.

Detailed ways

The multi-dimensional calibration method for the SOC of a power battery according to the present invention will be further described and explained below with reference to the accompanying drawings.

As shown in FIG. 1, a multi-dimensional calibration method of power battery SOC includes the following steps:

Step 1. Power on the power battery;

Step 2: Read initial data: read clock information, display SOC, inspect battery temperature T, accumulated charge and discharge energy, power battery system nominal capacity C _rated , battery current and cell voltage;

Step 3: Calculation of dynamic parameters of the power battery system: Calculate and obtain the look-up table SOC according to the inspection battery temperature and cell voltage, and calculate and obtain the real SOC according to the look-up table SOC combined with the conditional look-up table method, and calculate the current battery health of the battery according to the accumulated charge and discharge energy. The current capacity of the power battery system is calculated according to the SOH. The specific process is as follows:

1. Look up the table SOC is obtained by looking up the OCV table.

2. The real SOC is calculated by logically judging the table SOC and the display SOC, as shown in Figure 2, and the specific implementation is as follows:

Use the static voltage method for table look-up calibration: as shown in Figure 2, calculate and obtain the current real SOC according to the sleep duration range and the state of the battery, namely SOC _real ,

Step 1), judging whether the sleep duration is not less than 3 hours, or the battery current I is in a continuous I<5A state for a duration of not less than 3 hours, if so, then the calculation formula of SOC _real at this time is: SOC _real = look-up table SOC; If not, go to step 2);

Step 2), determine whether the dormancy duration is within the interval of 1 hour to 3 hours, or the duration of the battery current I in the continuous I<5A state is within the interval of 1 hour to 3 hours, if not, enter step 3); if so, then It is further judged whether formula (1) is established. If yes, then the calculation formula of SOC _real at this time is: SOC _real = 1.1* look-up table SOC; if not, SOC _real = 0.9* look-up table SOC; formula (1) is:

|SOC _out -1.1*Lookup table SOC|-|SOC _out -0.9*Lookup table SOC|＞0 (1)

Among them, SOC _out is the display SOC;

Step 3), at this time, the sleep duration is less than 1 hour, or the battery current I is in the state of I<5A and the duration is less than 1 hour, then the calculation formula of SOC _real is: SOC _real =SOC _out ;

3. SOH calculation:

Among them, N _rated is the nominal discharge times of the battery system, which is determined by the characteristics of the power battery system itself. The value of N _rated given by the power battery manufacturer is generally between 1500-3500; Q _total is the cumulative discharge energy of the battery system, The battery is calculated and obtained in real time during the use process, and Q _rated is the characteristic parameter of the battery system itself, which is given by the battery production and design manufacturer;

4. Calculation of cumulative discharge energy of battery system:

Among them, U _bat is the total voltage of the battery, which is detected by the BMS; I is the battery current during the charging and discharging process of the battery;

5. Calculation of the current capacity of the power battery system:

C _real =C _rated *SOH (4) where C _real is the current capacity of the power battery system.

Step 4. Dynamic SOC calculation: Calculate the discharge energy according to the ampere-hour integration method, and then calculate the real-time SOC during the discharge process in combination with the current battery health SOH and the real SOC, and the real-time SOC is the real SOC. Calculated as follows:

C _real = C _rated *SOH (6)

Among them: I is the battery current during the battery charging and discharging process, C _use is the capacity used during the battery discharging process, C _rated is the nominal capacity of the battery system, and C _real is the current power battery system capacity.

Step 5: Judging whether the SOC is dynamically following, and whether the dynamic following is turned on: as shown in Figure 3, determine whether the formula (8) is established, if not, enter the dynamic SOC following state, and the dynamic SOC following is allowed to be set to 1, then once During the SOC update process, the SOC _real is calibrated by combining the terminal cell voltage limit value calibration method; if so, the dynamic SOC following state is not entered, and the dynamic SOC following is allowed to be set to 0; the formula (2) is between the SOC _eal and the displayed value SOC _out The error calculation of the formula (8) is as follows:

|SOC _real -SOC _out |＜α% (8)

Formula (8) is a judging formula for determining whether the difference between the real SOC, ie, SOC _real , and the displayed SOC, ie, SOC _out , is less than the first threshold; where α is the first threshold, and the first threshold here is 2%.

Dynamic SOC follow-on: When the dynamic follow-up allowable value is set to 1, the dynamic follow-up of the discharge process is turned on; when the displayed SOC drops by β%, the real SOC equals the displayed SOC. According to the displayed initial value SOC, the real initial value SOC and the discharge power, The real-time displayed SOC is calculated, and the real-time displayed SOC is the real SOC after the dynamic follow calibration; β is the second threshold. The calculation process of the real-time display SOC, that is, the calculation formula of the calibration of the real SOC is as follows:

SOC _{display/initial} -SOC _identical = β (9)

Among them, β is the second threshold, SOC _{display/initial} is the initial SOC display, that is, the SOC _out value read from the memory at the moment of power-on; SOC _identical is the SOC when it is calibrated to the same state, and this scheme is set to display the initial value SOC When the second threshold β is lowered, it is estimated that the real SOC is consistent with the real-time display SOC; SOC _real/initial is the real initial value SOC after static calibration, that is, the real SOC obtained by the look-up table method in step S3; C _interval is the calibration to the consistent state The discharge capacity at SOC is calculated from the above formula; C _use is the capacity used in battery charging and discharging, SOC _display is the real-time display SOC, and the real-time display SOC is the real SOC after dynamic tracking calibration.

Step 6. Synergy between terminal extreme value calibration and current reduction strategy: at the end of the charging and discharging of the power battery system, combine the cell voltage limit value calibration and the current reduction strategy to perform full charge or full discharge calibration calibration for the real SOC and displayed SOC of the power battery system. The final output is the real SOC of the battery system after calibration.

Step 6.1. The SOC calibration at the discharge end is coordinated by the cell voltage limit state combined with the current limit: the specific process of the discharge end SOC calibration is: according to the characteristics of the single cell, combined with the discharge MAP, the end of the current limit output current, until the discharge Cell voltage minimum limit, SOC is forced to calibrate to 0%.

Step 6.2. The SOC at the charging end is calibrated by the cell voltage limit state combined with the current reduction strategy. The specific process of SOC calibration at the charging end is: according to the characteristics of the single cell, combined with the current reduction strategy, the current is reduced to charge until the cell voltage reaches the highest limit, the SOC is forced to calibrate to 100%.

The invention adopts the ampere-hour integration method to calculate the real SOC of the power battery, and combines the aging calibration method, the static voltage method look-up table calibration method, the dynamic SOC follow-up calibration method, and the terminal cell voltage limit value and the down-current strategy collaborative calibration method to the power battery. The real SOC is calibrated in multiple dimensions to improve the accuracy of SOC estimation.

In the dynamic follow calibration, the relationship between the displayed SOC and the real SOC is shown in Figure 4 to Figure 7:

Figure 4 is a diagram showing the initial value SOC>real initial value SOC&discharge condition SOC tracking relationship, the purpose is to reflect at the moment of power-on, display SOC>true SOC and under discharge condition, the real SOC after calibration and the real SOC without calibration follower relationship.

Figure 5. Display the initial value SOC>real initial value SOC&Charging condition SOC tracking relationship diagram, the purpose is to reflect at the moment of power-on, display SOC>true SOC and under charging condition, the real SOC after calibration and the real SOC without calibration follower relationship.

Figure 6 shows the following relationship diagram of initial value SOC < real initial value SOC & discharge condition SOC, the purpose is to reflect at the moment of power-on, display SOC < real SOC and under discharge condition, the real SOC after calibration and the real SOC without calibration follower relationship.

Fig. 7 shows the following relationship diagram of initial value SOC<true initial value SOC&charging condition SOC. The purpose is to reflect the following relationship between the calibrated real SOC and the uncalibrated real SOC at the moment of power-on, displaying SOC < real SOC and under charging conditions.

In Fig. 4 to Fig. 7, the value of uncalibrated display SOC is the estimated SOC discharge without calibration in theory, the value of uncalibrated real SOC is the estimated real SOC discharge without calibration in theory, and the value of real SOC after calibration is the estimated SOC discharge in theory. is the theoretically calibrated SOC discharge estimate.

The above is only the preferred embodiment of the present invention, it should be pointed out: for those skilled in the art, under the premise of not departing from the principle of the present invention, several improvements and modifications can also be made, and these improvements and modifications are also It should be regarded as the protection scope of the present invention.

Claims (9)

1. a power battery SOC multi-dimensional calibration method, is characterized in that, comprises the following steps: S1: The power battery is powered on; S2: Read initial data: read clock information, display SOC, inspect battery temperature T, accumulated charge and discharge energy, power battery system nominal capacity C _rated , battery current and cell voltage; S3: Calculation of dynamic parameters of the power battery system: Calculate the look-up table SOC according to the inspection battery temperature and cell voltage, calculate and obtain the real SOC according to the look-up table SOC combined with the conditional look-up table method; calculate the current battery health of the battery according to the accumulated charge and discharge energy SOH, calculate the current capacity of the power battery system according to the SOH; S4: Dynamic SOC calculation: Calculate the discharge energy according to the ampere-hour integration method, and calculate the real-time dynamic SOC during the discharge process in combination with the current battery health SOH and the real SOC, and the dynamic SOC is the real SOC; S5: Dynamic SOC following calibration: determine whether the difference between the real SOC and the displayed SOC is less than the threshold value, if so, the dynamic SOC following is allowed to be set to 0, and the dynamic SOC following calibration is not performed, if not, the dynamic SOC following is allowed to be set to 1, Perform SOC dynamic follow calibration correction during discharge; S6: Synergy between terminal extreme value calibration and current reduction strategy: at the end of the charging and discharging of the power battery system, combined with the cell voltage limit value calibration and the current reduction strategy, the real SOC and displayed SOC of the power battery system are fully charged or fully discharged. Outputs the true SOC of the calibrated battery system. 2. The method for multi-dimensional calibration of power battery SOC according to claim 1, wherein the calculation formula of the current battery health degree SOH of the battery and the current capacity of the power battery system in the S3 is:

C _real =C _rated *SOH Among them, N _rated is the nominal dischargeable times of the battery system, Q _total is the cumulative discharge energy of the battery system, Q _rated is the characteristic parameter of the battery system itself, U _bat is the total battery voltage, and I is the battery during the charging and discharging process of the battery. Current, C _real is the current capacity of the power battery system, and C _rated is the nominal capacity of the power battery system. 3 . The method for multi-dimensional calibration of power battery SOC according to claim 1 , wherein in S3 , a look-up table SOC is calculated and obtained according to the inspection battery temperature and cell voltage, and a look-up table SOC is obtained according to the look-up table SOC combination condition. 4 . The process of calculating and obtaining the real SOC is the process of table look-up calibration using the static voltage method; the specific process of performing the table look-up calibration using the static voltage method is as follows: S31, battery inspection: obtain inspection battery temperature T, cell voltage V _cell , battery current I during battery charging and discharging; S32. Obtain the look-up table SOC: obtain the look-up table SOC through the look-up table according to the current inspection battery temperature T and the cell voltage V _cell ; S33, the static voltage method is used to perform table lookup calibration: according to the sleep duration of the power battery system and the state of the battery, combined with the lookup table SOC calculation to obtain the current real SOC, that is, SOC _real . 4. The method for multi-dimensional calibration of power battery SOC according to claim 3, wherein in S33, the specific process of obtaining the current real SOC is calculated according to the dormancy duration of the battery system and the state of the battery combined with the look-up table SOC calculation for: S331, determine whether the sleep duration is not less than 3 hours or the battery current I is in a continuous state of I<5A and the duration is not less than 3 hours, if yes, then SOC _real = lookup table SOC at this time; if not, go to step S332; S332, determine whether the sleep duration is within the interval of 1 hour to 3 hours or the duration of the battery current I in the continuous I<5A state is within the interval of 1 hour to 3 hours, if not, proceed to step S333; if so, further determine the inequality |SOC _out -1.1*Look up table SOC|-|SOC _out -0.9*Look up table SOC|>0 is true, if yes, then SOC _real =1.1*Look up table SOC; if not, SOC _real =0.9*Look up table SOC; where SOC _out is the display SOC; S333. At this time, the sleep duration does not exceed 1 hour or the battery current I is in the state of I<5A for less than 1 hour, then SOC _real =SOC _out . 5. The method for multi-dimensional calibration of power battery SOC according to claim 1, wherein the dynamic SOC calculation formula in S4 is:

C _real =C _rated *SOH

Among them, I is the current during the charging and discharging of the battery, C _use is the capacity used in the charging and discharging of the battery, C _rated is the nominal capacity of the battery system, C _real is the current capacity of the battery system, SOH is the battery health, and in the formula The SOC is the dynamic SOC, where the dynamic SOC is the real SOC. 6. A power battery SOC multi-dimensional calibration method according to claim 1, wherein the specific judgment process of the dynamic SOC follow-up calibration in the S5 is: S51. Obtain the real SOC and the displayed SOC, and calculate the difference between the two; S52. If |real SOC-display SOC|<α%, the dynamic SOC follow-up is allowed to be set to 0, that is, dynamic follow-up is not allowed; if |true SOC-display SOC| Allows dynamic follow-up calibration during discharge; where α is the first threshold. 7. The method for multi-dimensional calibration of the SOC of a power battery according to claim 6, wherein the S52 performs dynamic follow-up during the discharge process, and the specific process of the calibration is: S521. When the dynamic follow-up allowable value is set to 1, the dynamic follow-up during the discharge process is turned on; S522. Set when the displayed SOC drops by β%, the real SOC equals the displayed SOC, and calculates the real-time displayed SOC according to the displayed initial value SOC, the real initial value SOC and the discharge power, and the real-time displayed SOC is the real value after the dynamic follow calibration SOC; where β is the second threshold. 8. The method for multi-dimensional calibration of the SOC of a power battery according to claim 7, wherein in the S522, the specific calculation process of displaying the SOC in real time is: SOC _{display/initial} -SOC _identical = β

Among them, β is the second threshold, SOC _{display/initial} is the initial value of SOC, that is, the value of the displayed SOC read from the memory at the moment of power-on; SOC _identical is the real SOC when it is calibrated to the consistent state, and the real SOC is in the consistent state. = Display SOC; SOC _real/initial is the real initial value SOC, that is, the real SOC obtained by the table look-up method in step S3; C _interval is the discharge capacity when the SOC is calibrated to a consistent state; C _use is the capacity used in battery charging and discharging , SOC _display is the real-time display SOC. 9 . The multi-dimensional calibration method for power battery SOC according to claim 1 , wherein the S6 is a specific process of calibrating the real SOC at the end of charging and discharging in combination with a cell voltage limit value calibration method and a current reduction strategy. 10 . for: S61. SOC calibration at the discharge end: According to the characteristics of the single cell, combined with the discharge MAP, the output current of the current limit is performed at the end until the voltage of the discharge single cell is the lowest limit, and the real SOC and the displayed SOC are forced to be calibrated to 0%; S62. The specific process of SOC calibration at the charging end is: according to the characteristics of the single cell, combined with the current reduction strategy, the current is reduced to charge until the cell voltage reaches the highest limit, and the real SOC and the displayed SOC are forcibly calibrated to 100%.

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