A soc dynamic estimation correction method for ternary lithium battery electric vehicles

Abstract

The application discloses a kind of ternary lithium battery electric vehicle SOC dynamic estimation correction methods, comprising: step S1, static correction: step S2, charging end correction;Step S3, discharge end correction.The application is in view of the problem that current BMS residual capacity estimation exists inherent error, and a phased SOC correction scheme is proposed, and the SOC estimation is carried out using ampere-hour integration method combined with differentiated correction strategy, and there is no SOC jump in the process of charging and discharging, and the correction function is activated in the vehicle starting stage, which can effectively correct SOC estimation error, and improve user experience.

Description

Technical Field

[0001] This invention relates to a lithium battery system, and more specifically, to a dynamic estimation and correction method for the state of charge (SOC) of a ternary lithium battery electric vehicle. Background Technology

[0002] During the operation of electric vehicles, the State of Charge (SOC) cannot be corrected in real time during the discharge phase due to interference from multiple sources, and the Battery Management System (BMS) will always have a certain deviation in its estimation of the remaining power. Summary of the Invention

[0003] Therefore, it is necessary to provide a dynamic estimation and correction method for the SOC of ternary lithium battery electric vehicles to address the above-mentioned technical problems.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A method for dynamically estimating and correcting the state of charge (SOC) of a ternary lithium battery electric vehicle, characterized by comprising: Step S1, Static Correction: Step S2, end-of-charge correction; Step S3: Correction of the discharge end.

[0005] In a preferred embodiment of the present invention, in step S1, The correction function is activated when the vehicle is powered on and started, and the SOC is not allowed to jump during charging and discharging. The logical SOC display rule is: 0% of the logical SOC corresponds to 5% of the actual SOC, and 100% of the logical SOC corresponds to 95% of the actual SOC.

[0006] As a preferred embodiment of the present invention, When the battery is powered off and left to stand for at least 1 hour and the highest voltage of a single cell is not higher than 4.15V, the SOC correction is completed by querying the open circuit voltage (OCV) table based on the lowest voltage of the single cell. The temperature parameter in the OCV correction table is selected as the lowest value among all collected temperatures. The correction rate is determined by the difference between the logical SOC display value and the actual SOC. The larger the difference, the faster the correction rate. When the vehicle is in a power-off parking state and the resting time is not less than 7 days, after power is restored, the SOC is corrected by querying the OCV table based on the lowest voltage of the individual unit. Under this condition, the actual SOC is directly updated to the table lookup value, and the logical SOC is updated to the corresponding calculated value. The entire correction process must be completed before the high voltage is powered on. When the SOC calibration conditions are not met, the system reads the SOC value stored in the previous loop, and both the actual SOC and the logical SOC remain unchanged.

[0007] In a preferred embodiment of the present invention, in step S2, When the highest voltage of a single cell is not lower than 4.13V and the current SOC is not higher than 95%, the actual SOC is set to 90%, and the logic SOC is updated to the calculated value according to the SOC correction rate rule. When the average battery voltage is not lower than 4.14V, the SOC is not higher than 99%, and the charging current is greater than 2A, the actual SOC is set to 95%, and the logical SOC is updated to 99% according to the SOC correction rate rule. If the SOC reaches 100% early during charging, but the cutoff voltage of the individual cell does not reach 4.15V, the logic SOC will remain at 99%. The logic SOC will be set to 100% when the three conditions are met simultaneously: the internal charging end flag is set, the highest voltage of the individual cell is not lower than 4.15V, and the charging gun remains connected.

[0008] In a preferred embodiment of the present invention, in step S3, When the lowest single-cell voltage is lower than the single-cell voltage level 1 alarm threshold and the logic SOC value is higher than the SOC level 1 alarm threshold, the actual SOC is set to 9.5%, and the logic SOC is pulled down to the SOC level 1 alarm threshold. When the lowest single-cell voltage is lower than the single-cell voltage level 2 alarm threshold, the actual SOC is set to 5%, and the logic SOC is pulled down to 0.

[0009] In a preferred embodiment of the present invention, the correction rate rule is defined as follows: the real SOC is defined as A, the logic SOC as B, and the standard integration rate is proportional to the current; Under charging conditions: When A < 95%: If AB > 30%, the correction rate is 0.1 times the standard integral rate; if 30% ≥ AB > 20%, the correction rate is 0.2 times the standard integral rate; if 20% ≥ AB > 10%, the correction rate is 0.4 times the standard integral rate; if 10% ≥ AB > 1%, the correction rate is 0.6 times the standard integral rate; if AB ≤ 1%, the standard integral rate is used; when it is necessary to directly pull up to 100%, the correction rate is 0.4% / s; for other charging conditions: if BA > 30%, the correction rate is 0.1% / s; if 30% ≥ BA > 20%, the correction rate is 0.1% / 4s; if 20% ≥ BA > 10%, the correction rate is 0.1% / 6s; if 10% ≥ BA > 1%, the correction rate is 0.1% / 10s; if BA ≤ 1%, the standard integral rate is used.

[0010] In a preferred embodiment of the present invention, the correction rate rule is defined as follows: the real SOC is defined as A, the logic SOC as B, and the standard integration rate is proportional to the current; Under discharge conditions: When A>5%: If BA>30%, the correction rate is 0.1 times the standard integral rate; if 30%≥BA>20%, the correction rate is 0.2 times the standard integral rate; if 20%≥BA>10%, the correction rate is 0.4 times the standard integral rate; if 10%≥BA>1%, the correction rate is 0.6 times the standard integral rate; if BA≤1%, the standard integral rate is used; when the discharge needs to be directly pulled down to 0%, the correction rate is the current current divided by the rated capacity per second, with an upper limit of 0.4% / s; for other discharge conditions: if AB>30%, the correction rate is 2 times the standard integral rate; if 30%≥AB>20%, the correction rate is 1.8 times the standard integral rate; if 20%≥AB>10%, the correction rate is 1.6 times the standard integral rate; if 10%≥AB>1%, the correction rate is 1.4 times the standard integral rate; if AB≤1%, the standard integral rate is used.

[0011] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a dynamic SOC estimation and correction method for ternary lithium battery electric vehicles. Addressing the inherent error in current BMS remaining power estimation, this invention proposes a phased SOC correction scheme. It employs an ampere-hour integral method combined with a differentiated correction strategy for SOC estimation, ensuring no SOC jumps during charging and discharging. The correction function is activated during vehicle startup, effectively correcting SOC estimation errors while improving the user experience. Detailed Implementation

[0012] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention.

[0013] The proposed method for dynamic estimation and correction of electric vehicle SOC in this invention employs an ampere-hour integral method combined with a correction strategy to estimate SOC. No SOC jumps are permitted during charging and discharging. The correction function is activated upon vehicle startup.

[0014] Where: Cm is the actual maximum usable capacity of the battery; Cx is the current usable capacity of the battery; η1 is the lower limit of the actual SOC usable ratio; η2 is the upper limit of the actual SOC usable ratio.

[0015] The dynamic estimation and correction method for the state of charge (SOC) of the ternary lithium battery electric vehicle includes: Step S1, static correction; Step S2, correction at the end of charging; Step S3, correction at the end of discharging.

[0016] In step S1, when the battery is powered off and left to stand for ≥1 hour and the highest voltage of a single cell is ≤4.15V (charging cutoff voltage, which can be calibrated and set by the host computer), the SOC correction is completed by querying the OCV table based on the lowest voltage of the single cell. The temperature parameter in the OCV table is selected as the lowest value among all collected temperatures. The correction rate is divided according to the difference between the logical SOC display value and the actual SOC. The larger the difference, the faster the correction rate. See the SOC correction rate requirements below for specific rules. When the vehicle is in a power-off parking state and the inactivity time is ≥7 days, after power is restored, the SOC correction is completed by querying the standard OCV table based on the lowest voltage of the single unit. Under this condition, the actual SOC is directly updated to the table lookup value, and the logical SOC is updated to the corresponding calculated value. The entire correction process must be completed before high voltage power is applied. When the SOC calibration conditions are not met, the system reads the SOC value stored in the previous loop, and both the actual SOC and the logical SOC remain unchanged.

[0017] In step S2, End-of-charge correction function: When the highest single-cell voltage is ≥4.13V (which can be set by the host computer calibration) and SOC is ≤95%, the actual SOC is set to 90%, and the logic SOC is updated to the calculated value according to the SOC correction rate requirement. When the average voltage is ≥4.14V (which can be calibrated and set via the host computer), the SOC is ≤99%, and the charging current is >2A, the actual SOC is set to 95%, and the logic SOC is updated to 99% according to the SOC correction rate requirement. If the SOC reaches 100% before the charging process, but the cutoff voltage of the individual cell does not reach 4.15V (charging cutoff voltage, which can be calibrated and set by the host computer), the logic SOC will remain at 99%. The logic SOC will be set to 100% when the three conditions are met simultaneously: the internal charging end flag is set, the highest voltage of the individual cell is ≥4.15V (charging cutoff voltage, which can be calibrated and set by the host computer), and the charging gun remains connected.

[0018] In step S3, Discharge end correction function: When the lowest single-cell voltage is lower than the single-cell voltage level 1 alarm threshold (3.2V, which can be set by the host computer) and the logic SOC value is higher than the SOC level 1 alarm threshold (5%), the actual SOC is set to 9.5%, and the logic SOC is pulled down to the SOC level 1 alarm threshold (5%). When the lowest individual cell voltage is lower than the individual cell voltage level 2 alarm threshold (3.1V, which can be set by the host computer calibration), the actual SOC is set to 5%, and the logic SOC is pulled down to 0.

[0019] The SOC correction rate rule of this invention is as follows: Definition: A is the true SOC value, B is the logic SOC value corresponding to the true SOC value, and the standard integration rate is proportional to the current.

[0020] In step S2, the charging condition (current < 0) is as follows: ① When A < 95%: If AB > 30%, the correction rate is 0.1 times the standard integration rate; if 30% ≥ AB > 20%, the correction rate is 0.2 times the standard integration rate; if 20% ≥ AB > 10%, the correction rate is 0.4 times the standard integration rate; if 10% ≥ AB > 1%, the correction rate is 0.6 times the standard integration rate; if AB ≤ 1%, the standard integration rate is used. ② When it is necessary to directly pull up to 100%, the correction rate is 0.4% / s; ③ For other charging conditions, the correction rate rules are as follows: If BA > 30%, the correction rate is 0.1% / s; if 30% ≥ BA > 20%, the correction rate is 0.1% / 4s; if 20% ≥ BA > 10%, the correction rate is 0.1% / 6s; if 10% ≥ BA > 1%, the correction rate is 0.1% / 10s; if BA ≤ 1%, the standard integration rate is used.

[0021] In step S3, the discharge condition (current > 0) is as follows: ① When A > 5%: If BA > 30%, the correction rate is 0.1 times the standard integration rate; if 30% ≥ BA > 20%, the correction rate is 0.2 times the standard integration rate; if 20% ≥ BA > 10%, the correction rate is 0.4 times the standard integration rate; if 10% ≥ BA > 1%, the correction rate is 0.6 times the standard integration rate; if BA ≤ 1%, the standard integration rate is used. ② When the discharge needs to be directly pulled down to 0%, the correction rate is (current current / rated capacity) / s, with an upper limit of 0.4% / s; ③ For other discharge conditions, the correction rate rules are as follows: If AB > 30%, the correction rate is 2 times the standard integration rate; if 30% ≥ AB > 20%, the correction rate is 1.8 times the standard integration rate; if 20% ≥ AB > 10%, the correction rate is 1.6 times the standard integration rate; if 10% ≥ AB > 1%, the correction rate is 1.4 times the standard integration rate; if AB ≤ 1%, the standard integration rate is used.

[0022] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for dynamically estimating and correcting the state of charge (SOC) of a ternary lithium battery electric vehicle, characterized in that, include: Step S1, Static Correction: Step S2, end-of-charge correction; Step S3: Correction of the discharge end.

2. The method for dynamic estimation and correction of the state of charge (SOC) of ternary lithium battery electric vehicles according to claim 1, characterized in that, In step S1, The correction function is activated when the vehicle is powered on and started, and the SOC is not allowed to jump during charging and discharging. The logical SOC display rule is: 0% of the logical SOC corresponds to 5% of the actual SOC, and 100% of the logical SOC corresponds to 95% of the actual SOC.

3. The method for dynamic estimation and correction of the state of charge (SOC) of ternary lithium battery electric vehicles according to claim 2, characterized in that, When the battery is powered off and left to stand for at least 1 hour and the highest voltage of a single cell is not higher than 4.15V, the SOC correction is completed by querying the open circuit voltage (OCV) table based on the lowest voltage of the single cell. The temperature parameter in the OCV correction table is selected as the lowest value among all collected temperatures. The correction rate is determined by the difference between the logical SOC display value and the actual SOC. The larger the difference, the faster the correction rate. When the vehicle is in a power-off parking state and the resting time is not less than 7 days, after power is restored, the SOC is corrected by querying the OCV table based on the lowest voltage of the individual unit. Under this condition, the actual SOC is directly updated to the table lookup value, and the logical SOC is updated to the corresponding calculated value. The entire correction process must be completed before the high voltage is powered on. When the SOC calibration conditions are not met, the system reads the SOC value stored in the previous loop, and both the actual SOC and the logical SOC remain unchanged.

4. The method for dynamic estimation and correction of the state of charge (SOC) of ternary lithium battery electric vehicles according to claim 1, characterized in that, In step S2, When the highest voltage of a single cell is not lower than 4.13V and the current SOC is not higher than 95%, the actual SOC is set to 90%, and the logic SOC is updated to the calculated value according to the SOC correction rate rule. When the average battery voltage is not lower than 4.14V, the SOC is not higher than 99%, and the charging current is greater than 2A, the actual SOC is set to 95%, and the logical SOC is updated to 99% according to the SOC correction rate rule. If the SOC reaches 100% early during charging, but the cutoff voltage of the individual cell does not reach 4.15V, the logic SOC will remain at 99%. The logic SOC will be set to 100% when the three conditions are met simultaneously: the internal charging end flag is set, the highest voltage of the individual cell is not lower than 4.15V, and the charging gun remains connected.

5. The method for dynamic estimation and correction of the state of charge (SOC) of a ternary lithium battery electric vehicle according to claim 1, characterized in that, In step S3, When the lowest single-cell voltage is lower than the single-cell voltage level 1 alarm threshold and the logic SOC value is higher than the SOC level 1 alarm threshold, the actual SOC is set to 9.5%, and the logic SOC is pulled down to the SOC level 1 alarm threshold. When the lowest single-cell voltage is lower than the single-cell voltage level 2 alarm threshold, the actual SOC is set to 5%, and the logical SOC is pulled down to 0.

6. The method for dynamic estimation and correction of the state of charge (SOC) of ternary lithium battery electric vehicles according to claim 4, characterized in that, The corrected rate rule is defined as follows: the real SOC is defined as A, the logic SOC as B, and the standard integration rate is proportional to the current. Under charging conditions: When A < 95%: If AB > 30%, the correction rate is 0.1 times the standard integral rate; if 30% ≥ AB > 20%, the correction rate is 0.2 times the standard integral rate; if 20% ≥ AB > 10%, the correction rate is 0.4 times the standard integral rate; if 10% ≥ AB > 1%, the correction rate is 0.6 times the standard integral rate; if AB ≤ 1%, the standard integral rate is used; when it is necessary to directly pull up to 100%, the correction rate is 0.4% / s; for other charging conditions: if BA > 30%, the correction rate is 0.1% / s; if 30% ≥ BA > 20%, the correction rate is 0.1% / 4s; if 20% ≥ BA > 10%, the correction rate is 0.1% / 6s; if 10% ≥ BA > 1%, the correction rate is 0.1% / 10s; if BA ≤ 1%, the standard integral rate is used.

7. The method for dynamic estimation and correction of the state of charge (SOC) of ternary lithium battery electric vehicles according to claim 5, characterized in that, The corrected rate rule is defined as follows: the real SOC is defined as A, the logic SOC as B, and the standard integration rate is proportional to the current. Under discharge conditions: When A>5%: If BA>30%, the correction rate is 0.1 times the standard integral rate; if 30%≥BA>20%, the correction rate is 0.2 times the standard integral rate; if 20%≥BA>10%, the correction rate is 0.4 times the standard integral rate; if 10%≥BA>1%, the correction rate is 0.6 times the standard integral rate; if BA≤1%, the standard integral rate is used; when the discharge needs to be directly pulled down to 0%, the correction rate is the current current divided by the rated capacity per second, with an upper limit of 0.4% / s; for other discharge conditions: if AB>30%, the correction rate is 2 times the standard integral rate; if 30%≥AB>20%, the correction rate is 1.8 times the standard integral rate; if 20%≥AB>10%, the correction rate is 1.6 times the standard integral rate; if 10%≥AB>1%, the correction rate is 1.4 times the standard integral rate; if AB≤1%, the standard integral rate is used.

Images