A SOC calibration method based on voltage acquisition error margin

Abstract

This invention discloses a State of Charge (SOC) calibration method based on voltage acquisition error margin. First, it determines whether the battery has been in a long-term static state. Calculations are performed for different states, and if the SOC is greater than a certain value and less than a certain value, the current SOC is within the allowable error range, therefore no SOC correction is needed, and the system returns to the static battery assessment. If the SOC is less than a certain value, the current SOC is significantly low, so the SOC is corrected upwards, and the system returns to the static battery assessment. If the SOC is greater than a certain value, the current SOC is significantly high, so the SOC is corrected downwards, and the system returns to the static battery assessment. This method can correct the SOC to a reasonable range when it significantly deviates from the allowable estimation error, thereby improving the SOC estimation accuracy.

Description

Technical Field

[0001] This invention belongs to the field of voltage acquisition error value calibration technology, specifically a SOC calibration method based on voltage acquisition error margin. Background Technology

[0002] The State of Charge (SOC) of a lithium battery is a crucial parameter characterizing its remaining energy, significantly impacting users' assessment of a device's or vehicle's range. However, SOC is not a parameter that can be directly measured. First, battery parameters need to be measured, and then these parameters need to be calculated to obtain the SOC. Therefore, the accuracy of battery parameter measurements directly affects the accuracy of SOC estimation. Among these parameters, battery voltage is a critical one affecting the accuracy of SOC estimation.

[0003] The accuracy of SOC estimation for lithium batteries significantly impacts users' judgment of the vehicle's or device's range. Inaccurate SOC estimation can be caused by various factors, including low accuracy of voltage sensor data acquisition. To address this issue, this invention proposes an SOC calibration method based on voltage acquisition error margin. When the SOC deviates significantly from the allowable estimation error, it corrects the SOC to a reasonable range, thereby improving SOC estimation accuracy. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, this invention provides a SOC calibration method based on voltage acquisition error margin, solving the problem of inaccurate SOC estimation caused by voltage acquisition errors. Higher voltage sensor measurement accuracy leads to higher SOC estimation accuracy, but also significantly increases overall cost. Therefore, in practical engineering applications, the battery voltage acquired by the voltage sensor often has a certain deviation. To maximize the estimation accuracy of lithium battery SOC, this patent proposes an SOC calibration method based on voltage acquisition error margin. This method can correct the SOC to a reasonable range when it significantly deviates from the allowable estimation error, thereby improving SOC estimation accuracy.

[0005] The aforementioned SOC calibration method based on voltage acquisition error margin includes the following steps:

[0006] S1 determines whether the battery has been left idle for a long time;

[0007] If the battery does not meet the resting conditions, S2 will calculate using the ampere-hour integration algorithm. and update the SOC to Then return to the static judgment;

[0008] If the battery meets the resting conditions, S3 will collect the battery voltage V and utilize the previously measured voltage collection error. Calculate the allowable upper bias voltage. and down bias voltage ;

[0009]

[0010]

[0011] S4 is based on the upper bias voltage and down bias voltage The upper limit of SOC is calculated using the OCV lookup table method. and allowable lower limit ;

[0012]

[0013]

[0014] S5 determines the current SOC and and Relationship;

[0015] S6 If SOC is greater than And SOC is less than This indicates that the current SOC is within the allowable error range, therefore no correction is needed for the SOC, and the system returns to the battery rest judgment.

[0016] S7 If SOC is less than This indicates that the current SOC is significantly low, therefore the SOC will be adjusted upwards. It then returns to the battery resting state for judgment;

[0017] S8 If SOC is greater than This indicates that the current SOC is significantly too high, therefore the SOC will be adjusted downwards. It then returns a judgment on battery rest.

[0018] Furthermore, in step S2, the ampere-hour integration algorithm is as follows:

[0019]

[0020] in Indicates the initial ; express Current at any given moment; This indicates the battery capacity.

[0021] Furthermore, in step S4, the OCV lookup table method is as follows:

[0022]

[0023] in This indicates the battery's open-circuit voltage, which is the stable voltage of the battery after it has been left undisturbed for a long time.

[0024] Furthermore, step S9 involves comparing the theoretical values;

[0025] The S91 fully charges the battery to 100% SOC.

[0026] The S92 uses high-precision testing equipment to perform discharge tests on the battery, collecting and recording key data during the test process; the battery BMS simultaneously collects key data, performs calculations, and records the key data and calculation results.

[0027] The S93 exports data recorded by both the high-precision testing equipment and the BMS for calculation, processing, and comparison.

[0028] Furthermore, step S92 includes:

[0029] S92.1, with a preset current value Perform a discharge test on the battery until the preset stopping conditions are met. ;

[0030] S92.2, pause discharge to allow the battery to enter a resting state and continue... Duration;

[0031] S92.3, continue with the preset current value. Perform a discharge test on the battery until the preset stopping conditions are met. ;

[0032] S92.4, with a preset current value Perform a discharge test on the battery until the preset stopping conditions are met. ;

[0033] S92.5, the stopping condition is met. The test is over.

[0034] Compared with the prior art, the present invention has the following advantages:

[0035] When the State of Charge (SOC) deviates significantly from the allowable estimation error, the SOC is corrected to a reasonable range, thereby improving the SOC estimation accuracy. Through comparative calculations, the SOC calibration method based on voltage acquisition error margin proposed in this patent can reduce the average SOC deviation by 64.9% after triggering the SOC calibration condition, greatly improving the SOC estimation accuracy. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the invention;

[0037] Figure 2 This is a line graph showing the relationship between SOC value and time in a specific embodiment;

[0038] Figure 3 This is a line graph showing the relationship between SOC deviation and time in a specific embodiment. Detailed Implementation

[0039] The invention will now be further described with reference to the accompanying drawings.

[0040] like Figure 1 As shown, a SOC calibration method based on voltage acquisition error margin includes the following steps:

[0041] S1 determines whether the battery has been left idle for a long time;

[0042] If the battery does not meet the resting conditions, S2 will calculate using the ampere-hour integration algorithm. and update the SOC to Then return to the static judgment;

[0043] If the battery meets the resting conditions, S3 will collect the battery voltage V and utilize the previously measured voltage collection error. Calculate the allowable upper bias voltage. and down bias voltage ;

[0044]

[0045]

[0046] S4 is based on the upper bias voltage and down bias voltage The upper limit of SOC is calculated using the OCV lookup table method. and allowable lower limit ;

[0047]

[0048]

[0049] S5 determines the current SOC and and Relationship;

[0050] S6 If SOC is greater than And SOC is less than This indicates that the current SOC is within the allowable error range, therefore no correction is needed for the SOC, and the system returns to the battery rest judgment.

[0051] S7 If SOC is less than This indicates that the current SOC is significantly low, therefore the SOC will be adjusted upwards. It then returns to the battery resting state for judgment;

[0052] S8 If SOC is greater than This indicates that the current SOC is significantly too high, therefore the SOC will be adjusted downwards. It then returns a judgment on battery rest.

[0053] In step S2, the ampere-hour integration algorithm is as follows:

[0054]

[0055] in Indicates the initial ; express Current at any given moment; This indicates the battery capacity.

[0056] In step S4, the OCV lookup table method is as follows:

[0057]

[0058] in This indicates the battery's open-circuit voltage, which is the stable voltage of the battery after it has been left undisturbed for a long time.

[0059] Combination Figure 2-3 Specifically, the test involves comparing theoretical values ​​with theoretical values, and the test steps are as follows:

[0060] Step 1: Fully charge the battery to SOC=100%;

[0061] Step 2: Use high-precision testing equipment to perform a discharge test on the battery, collect and record key data during the test; the battery BMS simultaneously collects key data, performs calculations, and records the key data and calculation results.

[0062] Step 3: Export the data recorded by both the high-precision testing equipment and the BMS, and perform calculations and comparisons.

[0063] Step 2 is further divided into the following steps:

[0064] Step 2.1, using a preset current value Perform a discharge test on the battery until the preset stopping conditions are met. ;

[0065] Step 2.2: Pause the discharge process to allow the battery to enter a resting state, and continue... Duration;

[0066] Step 2.3, continue with the preset current value. Perform a discharge test on the battery until the preset stopping conditions are met. ;

[0067] Step 2.4, using a preset current value Perform a discharge test on the battery until the preset stopping conditions are met. ;

[0068] Step 2.5, stopping condition is met. The test is over.

[0069] Through comparative calculations, the SOC calibration method based on voltage acquisition error margin proposed in this patent can reduce the average SOC deviation by 64.9% after triggering the SOC calibration conditions, which greatly improves the estimation accuracy of SOC.

[0070] Due to factors such as sensor acquisition accuracy or the presence of undetectable additional power consumption current in the system, the deviation between the calculated SOC and the actual SOC gradually increases over time. When the SOC correction conditions proposed in this invention are met, the SOC is corrected towards the true value, reducing the error between the two.

[0071] By determining whether the battery has been idle for an extended period, the State of Charge (SOC) estimation is divided into two modes. When the battery has not been idle for an extended period, the ampere-hour integration method is used to estimate the battery's SOC; when the battery has been idle for an extended period, the OCV lookup table method is used for SOC correction. These two methods are combined based on the determination of whether the battery has been idle for an extended period, resulting in higher SOC estimation accuracy than using a single method.

[0072] By introducing the influence of voltage sensor acquisition error and combining it with the currently acquired battery voltage, the battery voltage range within the allowable error range is defined.

[0073] Based on the allowable battery voltage range, the permissible SOC range is calculated using the OCV lookup table method. If the current SOC is outside the permissible range, it is corrected to the corresponding range boundary value.

[0074] The method of this invention corrects the SOC to a reasonable range when the SOC deviates significantly from the allowable estimation error, thereby improving the accuracy of SOC estimation.

Claims

1. A SOC calibration method based on voltage acquisition error margin, characterized in that, Comprising the following steps: S1 Determine whether the battery has been standing for a long time; S2 If the battery does not meet the static condition, calculate by ampere-hour integration algorithm SOC Ah and update the SOC as SOC Ah and then return to the static condition judgment again; S3 If the battery meets the static condition, collect the battery voltage V , and collect the error of the voltage by using the voltage measured in advance , calculate the allowed upper deviation voltage V up and the lower deviation voltage V down ; ， ；； S4 upper limit of SOC allowable according to upper bias voltage V up and lower bias voltage V down , SOC is calculated by OCV lookup table method SOC up and lower limit of allowable SOC down : SOC up = f ( V up )， SOC down = f ( V down )； S5 determines the relationship between the current SOC and SOC up and SOC down the target SOC. S6 If SOC is greater than SOC down , and SOC is less than SOC up , it indicates that the current SOC is within the allowable error range, so there is no need to correct the SOC, and return to the battery resting judgment; S7 If SOC is less than SOC down , it means that the current SOC is significantly low, so the SOC is corrected upward to SOC down , and the battery resting judgment is returned. S8 If SOC is greater than SOC up , it indicates that the current SOC is significantly high, so the SOC is corrected downward to SOC up , and the battery resting judgment is returned. S9 Compare with the theoretical value; S91 Charge the battery to SOC = 100%; S92 Use the test equipment to discharge the battery, collect and record the key data during the test process; The battery BMS also collects key data for calculation, and records the key data and calculation results; S92.1 with a pre-set current value I 1 Discharge test is performed on the battery until a pre-set stop condition is met C 1; S92.2 Suspend discharging, make the battery enter the standing state, and continue for T duration; S92.3 continue with the pre-set current value I 1 discharge test is performed on the battery until a pre-set stop condition is met C 2; S92.4 at a pre-set current value I 2 The battery is discharged until a pre-set stop condition is met C 3; S92.5 stop condition met C 3, test end; S93 Export the data recorded by the test equipment and the BMS, and perform calculation processing and comparison.

2. The SOC calibration method based on voltage collection error margin according to claim 1, characterized in that, In step S2, the ampere-hour integral algorithm is: ， wherein, SOC 0 represents an initial SOC; I(t) represents a current at time t; C represents a battery capacity.

3. The SOC calibration method based on voltage collection error margin of claim 1, wherein, In step S4, the OCV lookup table method is: SOC ocv = f ( V oc )， wherein, V oc represents the open circuit voltage of the battery.

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