A soc correction method for frequent uphill and downhill working conditions

Abstract

The application discloses a SOC correction method for frequent uphill and downhill working conditions, which realizes accurate correction of the SOC of a power battery by combining charge and discharge dynamic calibration and full charge calibration. The steps are as follows: display SOC values at a current temperature are calculated according to SOC capacity hidden values and algorithm estimated values; for a long uphill section, discharge dynamic calibration is performed according to the difference between a current ratio, a minimum single battery voltage, a display SOC value and a target discharge correction value; for a long downhill section, the battery is feedback charged, feedback charging does not perform charge dynamic calibration, and the SOC is limited to a full charge waiting value and below; when the battery needs to be charged due to power shortage, charge dynamic calibration is performed according to the difference between a current ratio, a maximum single battery voltage, a target charge correction value and a display SOC value; when the battery is in a charging state, the maximum single battery voltage is greater than or equal to a full charge cutoff voltage for a full charge duration, and the absolute value of a charging current is less than or equal to a current overcurrent alarm value, and the battery is subjected to full charge calibration.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium batteries, and particularly relates to a SOC correction method for frequent uphill and downhill working conditions. BACKGROUND

[0002] The frequent uphill and downhill working condition refers to a continuous long uphill and a continuous long downhill in the driving process of a vehicle, which is relatively common in mountainous and hilly areas in China, and is also the working condition of a golf cart. On a long downhill road section, a power battery vehicle does not need to step on the accelerator, and can obtain a large acceleration by inertia. When the vehicle is downhill, the brake feedbacks, the energy recovery system recovers energy to reversely charge the vehicle, and when the high SOC state feedbacks, the vehicle can even be almost full. On a long uphill road section, the battery will be discharged with a large current because high power is needed to climb the hill, and the SOC decreases greatly. The frequent uphill and downhill working condition can cause the SOC value to be too high after feedback charging on a downhill, and further cause inaccurate SOC. In winter, the battery cannot discharge the rated capacity because of low temperature, which also causes inaccurate SOC calculation. Accurate calculation of the SOC is related to the use efficiency of the power battery vehicle, can avoid vehicle power loss, and can improve user comfort.

[0003] Common SOC correction methods for the frequent uphill and downhill working condition in engineering include the ampere-hour integration method and the open-circuit voltage method. The ampere-hour integration method calculates the net capacity flowing into the battery by integrating the current with respect to time, and calculates the SOC according to the net flow divided by the rated capacity. However, the SOC error will become larger and larger with time because of the error in current sampling. The open-circuit voltage method corrects the SOC according to the OCV-SOC curve of the battery after the battery is static for a period of time and is powered on. However, the battery may have few opportunities to be static in actual use, and the open-circuit voltage method cannot be performed during work, so that the SOC cannot be corrected in time. SUMMARY

[0004] In order to make up for the deficiencies of the prior art, the application provides a SOC correction method for a frequent uphill and downhill working condition, which adopts a SOC capacity hiding method based on temperature, combines dynamic calibration and full charge calibration during charging and discharging, and accurately corrects the SOC of the power battery, so as to solve the problem of inaccurate SOC caused by frequent feedback charging in the frequent uphill and downhill working condition.

[0005] The technical problem solved by the application can be solved by the following technical scheme.

[0006] The SOC correction method for the frequent uphill and downhill working condition comprises the following steps.

[0007] S1, obtain SOC capacity hidden value SOC_Hide at different temperatures through temperature lookup table, and calculate display SOC value SOC_Disp according to SOC_Hide and SOC_Pre estimated by algorithm, i.e. SOC at current temperature;

[0008] S2, for long uphill road section, perform discharge dynamic calibration according to the difference between current rate Crate_dis, minimum single cell voltage Vmin, display SOC value SOC_Disp and target discharge correction value SOCthr_Dis;

[0009] S3, for long downhill road section, the battery will be feedback charged, feedback charging does not perform charging dynamic calibration, and SOC is limited to SOC full charging waiting value SOC_LIMIT and below;

[0010] S4, when the battery needs to be charged due to power loss, perform charging dynamic calibration according to the difference between current rate Crate_chg, maximum single cell voltage Vmax, target charging correction value SOCthr_Chg and display SOC value SOC_Disp;

[0011] S5, when the battery is in a charging state, maximum single cell voltage Vmax≥full charging cutoff voltage V_Fullchg for full charging duration Fullchg_Time, and charging current absolute value Cur_Chg≤current overcurrent alarm value Cur_Over, perform full charging calibration on the battery, and calibrate SOC to 100%.

[0012] Further, the SOC capacity hiding process in step S1 is as follows:

[0013] S11, when the temperature is low, the discharge cannot discharge the rated capacity at normal temperature due to the characteristics of the battery cell, the lower the temperature, the more capacity cannot be discharged, and the corresponding SOC capacity hidden value SOC_Hide is larger;

[0014] S12, discharge capacity test is carried out at different temperatures to obtain SOC capacity hidden value SOC_Hide table related to temperature Temp, and SOC_Hide corresponding to current temperature Temp is obtained by linear interpolation of temperature lookup table;

[0015] S13, calculate display SOC value SOC_Disp according to SOC_Hide and SOC_Pre estimated by algorithm, i.e. SOC at current temperature, and the specific calculation formula is:

[0016]

[0017] Wherein, SOC_Disp is the output display SOC value, SOC_Pre is the SOC value estimated by the algorithm, and SOC_Hide is the SOC capacity hidden value, all of which are calculated in %.

[0018] Further, in the step S13, when the SOC_Pre estimated by the algorithm is less than or equal to the SOC capacity hidden value SOC_Hide, the display SOC value SOC_Disp is 0%; when the SOC_Pre estimated by the algorithm is greater than or equal to 100%, the display SOC value SOC_Disp is 100%.

[0019] Further, in the step S2, the process of discharging dynamic calibration is as follows:

[0020] S21, for long uphill road sections, the battery discharge current is large, and the large current will rapidly pull down the single cell voltage, so dynamic calibration should not be performed at this time, and dynamic calibration should be performed at the end of discharge when the current is moderate, that is, the discharge current Cur_Dis should be greater than the current zero drift value CurDrift, and at the same time Cur_Dis should be less than the current rate Crate_dis, wherein the current rate Crate_dis is obtained by dividing the discharge current Cur_Dis by the rated capacity Q of the battery, when the step S21 is satisfied, the step S22 is executed;

[0021] S22, when the temperature is low, rely on the SOC capacity hidden value SOC_Hide for calibration, when the minimum single cell temperature Tmin is greater than the temperature threshold T_MIN, perform discharging dynamic calibration, when the step S22 is satisfied, the step S23 is executed;

[0022] S23, when the steps S21 and S22 are satisfied, at the same time, the minimum single cell voltage Vmin is less than or equal to the discharge voltage threshold V_MIN_Dis for a duration Dur_Time, and the display SOC-target discharge correction value SOCthr_Dis is greater than or equal to the discharge SOC difference value SOC_Diff_Dis, perform discharging dynamic calibration;

[0023] S24, when the steps S21, S22 or S23 are not satisfied, do not perform discharging dynamic calibration.

[0024] Further, in the step S23, when the target discharge correction value SOCthr_Dis is greater than 0%, the SOC is corrected to SOCthr_Dis+SOC_Diff_Dis at a correction rate Crt_rate1; when the target discharge correction value SOCthr_Dis is 0%, that is, the battery power is about to be exhausted, the SOC is corrected to 0% at a correction rate Crt_rate2, wherein Crt_rate2>Crt_rate1.

[0025] Further, in the step S3, the feedback charging is limited as follows: for a long downhill section, the battery performs feedback charging when the brake is pressed, and only ampere-hour integration is performed during feedback charging, without charging dynamic calibration; during feedback charging on a long downhill, the SOC rises due to brake feedback kinetic energy recovery, rather than the actual charging state, and there is a false high SOC, so the feedback charging SOC cannot be calibrated to 100%; when the feedback SOC exceeds the SOC full charging waiting value SOC_LIMIT, the battery SOC is limited to the SOC full charging waiting value SOC_LIMIT, where SOC_LIMIT<100%.

[0026] Further, in the step S4, the charging dynamic calibration process is as follows:

[0027] S41, when the battery needs to be charged due to power loss, too large a charging current will rapidly raise the single cell voltage, and dynamic calibration is not suitable at this time, and dynamic calibration should be performed on the end of charging when the current is moderate, that is, the absolute value of the charging current Cur_Chg should be greater than the current zero drift value CurDrift, and the absolute value of the charging current Cur_Chg should be less than the current rate Crate_chg, where the current rate Crate_chg is obtained by dividing the absolute value of the charging current Cur_Chg by the rated capacity Q of the battery, and when the step S41 is satisfied, the step S42 is executed;

[0028] S42, when the temperature is low, the discharge cut-off voltage of the battery is low, and the corresponding charging voltage threshold V_MAX_Chg is also low;

[0029] S43, when the battery is in a charging state, the highest single cell voltage Vmax is greater than the charging voltage threshold V_MAX_Chg for a duration of Dur_Time, and the target charging correction value SOCthr_Chg-displayed SOC is greater than the charging SOC difference SOC_Diff_Chg, the charging dynamic calibration is executed, and the SOC is corrected to SOCthr_Chg-SOC_Diff_Chg at a correction rate Crt_rate3, where SOCthr_Chg<100%;

[0030] S44, when the steps S41 or S43 are not satisfied, the charging dynamic calibration is not executed.

[0031] Further, in the step S42, the charging voltage threshold V_MAX_Chg is selected according to the following rules: when the lowest single cell temperature Tmin is less than or equal to the temperature threshold T_MIN, V_MAX_Chg=low voltage threshold V_MAX_Low; and when the lowest single cell temperature Tmin is greater than the temperature threshold T_MIN, V_MAX_Chg=high voltage threshold V_MAX_High.

[0032] Further, the step S5, the full charge calibration process is as follows:

[0033] S51, when the maximum monomer voltage Vmax≥ full charge cut-off voltage V_Fullchg, the timer Count starts counting;

[0034] S52, when the timer Count≥ full charge duration Fullchg_Time, the battery is in a charging state and the charging current absolute value Cur_Chg≤ current overcurrent alarm value Cur_Over, the battery is calibrated for full charge, and the SOC is calibrated to 100%;

[0035] S53, when the timer Count≥ full charge duration Fullchg_Time, the battery is in a charging state and the charging current absolute value Cur_Chg> current overcurrent alarm value Cur_Over, no full charge calibration is performed, and the SOC is limited to the SOC full charge waiting value SOC_LIMIT;

[0036] S54, when the timer Count≥ full charge duration Fullchg_Time, the battery is in a charging state and there is a discharge current, no full charge calibration and SOC limitation is performed, and the display SOC value is output;

[0037] S55, when 0< timer Count< full charge duration Fullchg_Time and the battery is in a charging state, no full charge calibration is performed, and the SOC is limited to the SOC full charge waiting value SOC_LIMIT;

[0038] S56, when the above S52, S53, S54, S55 are not met, no full charge calibration and SOC limitation is performed, and the display SOC value is output.

[0039] Compared with the prior art, the present application has the following advantages: the method of the present application adopts SOC capacity hiding method based on temperature, combines charging and discharging dynamic calibration and full charge calibration, and realizes accurate correction of the SOC of the power battery; based on the difference between the current rate, dynamic voltage, display SOC and target correction value, the SOC is corrected, which is not affected by the current sampling accuracy, and overcomes the cumulative error problem of the ampere-hour integral method; the SOC can be corrected in real time when the vehicle is working, without the need to place the battery, and the dependence of the open circuit voltage method on the static state is solved. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 The flowchart of the method of the present application. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be further described in detail below in combination with the drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0042] As shown in the figure, a frequently uphill and downhill working condition SOC correction method comprises the following steps: Figure 1

[0043] Step 1: Obtain the SOC capacity hidden value SOC_Hide at different temperatures through temperature table lookup, and calculate the display SOC value SOC_Disp according to SOC_Hide and the algorithm estimated SOC_Pre, i.e. the SOC at the current temperature.

[0044] Among them, the process of SOC capacity hiding is as follows:

[0045] (1) When the temperature is low, the discharge cannot discharge the rated capacity at normal temperature due to the characteristics of the battery cell, the lower the temperature, the more capacity cannot be discharged, and the corresponding SOC capacity hidden value SOC_Hide is larger;

[0046] (2) Discharge capacity test is carried out at different temperatures to obtain the SOC capacity hidden value SOC_Hide table related to temperature Temp, and the current temperature Temp corresponding SOC_Hide is obtained by linear interpolation of temperature to search the SOC_Hide table;

[0047] (3) Calculate the display SOC value SOC_Disp according to SOC_Hide and the algorithm estimated SOC_Pre, i.e. the SOC at the current temperature, the specific calculation formula is:

[0048]

[0049] Among them, SOC_Disp is the output display SOC value, SOC_Pre is the algorithm estimated SOC value, SOC_Hide is the SOC capacity hidden value, and the above SOC is calculated with %. When the algorithm estimated SOC_Pre≤SOC capacity hidden value SOC_Hide, the display SOC value SOC_Disp is 0%; When the algorithm estimated SOC_Pre≥100%, the display SOC value SOC_Disp is 100%.

[0050] ​In a specific embodiment, the temperature matrix Temp_Table = [-20, -10, 0, 10, 25]℃, the SOC capacity hidden value table SOC_Hide_Table = [20, 15, 10, 5, 0]%, the current temperature Temp = -15℃, and the algorithm-estimated SOC_Pre = 80%. By searching the SOC capacity hidden value table SOC_Hide_Table according to the current temperature Temp, the SOC_Hide corresponding to -15℃ is 17.5%, and the display SOC value SOC_Disp is calculated according to formula (1) to be (80%-17.5%) / (100%-17.5%) = 75.8%, that is, the SOC at the current -15℃.

[0051] Step 2, for a long uphill road section, a discharge dynamic calibration is performed according to the difference between the current rate Crate_dis, the minimum single cell voltage Vmin, the display SOC value SOC_Disp, and the target discharge correction value SOCthr_Dis.

[0052] The process of the discharge dynamic calibration of the present application is as follows:

[0053] (1) For a long uphill road section, the battery discharge current is large, and a large current will rapidly lower the single cell voltage. At this time, dynamic calibration should not be performed, and dynamic calibration should be performed at the end of discharge when the current is moderate, that is, the discharge current Cur_Dis should be greater than the current zero drift value CurDrift, and at the same time Cur_Dis should be less than the current rate Crate_dis, wherein the current rate Crate_dis is obtained by dividing the discharge current Cur_Dis by the rated capacity Q of the battery. When step (1) is satisfied, step (2) is continued.

[0054] (2) When the temperature is low, calibration is performed by relying on the SOC capacity hidden value SOC_Hide. When the minimum single cell temperature Tmin is greater than the temperature threshold T_MIN, discharge dynamic calibration is performed. When step (2) is satisfied, step (3) is continued.

[0055] (3) When steps (1) and (2) are satisfied, and the minimum single cell voltage Vmin is less than or equal to the discharge voltage threshold V_MIN_Dis for a duration Dur_Time, and the display SOC-target discharge correction value SOCthr_Dis is greater than or equal to the discharge SOC difference SOC_Diff_Dis, discharge dynamic calibration is performed. When the target discharge correction value SOCthr_Dis is greater than 0%, the SOC is corrected to SOCthr_Dis+SOC_Diff_Dis at a correction rate Crt_rate1. When the target discharge correction value SOCthr_Dis is 0%, that is, the battery power is about to be exhausted, the SOC is corrected to 0% at a correction rate Crt_rate2, wherein Crt_rate2>Crt_rate1.

[0056] (4) When steps (1), (2) or (3) are not met, no discharge dynamic calibration is performed.

[0057] It can be seen that for a long uphill section, when the current zero drift value CurDrift < discharge current Cur_Dis < current rate Crate_dis, the minimum cell temperature Tmin > temperature threshold T_MIN, the minimum cell voltage Vmin ≤ discharge voltage threshold V_MIN_Dis for a duration of Dur_Time, and the display SOC - target discharge correction value SOCthr_Dis ≥ discharge SOC difference SOC_Diff_Dis, discharge dynamic calibration is performed.

[0058] In a specific embodiment, if the discharge current Cur_Dis = 20 A, the battery rated capacity Q = 200 Ah, the current zero drift value CurDrift = 1 A, the current rate Crate_dis = 0.2 C, the minimum cell temperature Tmin = 10 °C, the temperature threshold T_MIN = 0 °C, the minimum cell voltage Vmin = 2.9 V, the discharge voltage threshold V_MIN_Dis = 3.0 V, the duration threshold Dur_Time = 5 min, the actual Vmin is lower than 3.0 V for 10 min, the display SOC value SOC_Disp = 30%, the target discharge correction value SOCthr_Dis = 10%, and the discharge SOC difference SOC_Diff_Dis = 5%, the correction rate Crt_rate1 = 0.05% / s, and the correction rate Crt_rate2 = 0.1% / s:

[0059] Then the current rate corresponding to the discharge current 20 A = discharge current Cur_Dis / battery rated capacity Q = 20 / 200 C = 0.1 C < current rate Crate_dis = 0.2 C, discharge current Cur_Dis = 20 A > current zero drift value CurDrift = 1 A, continue to the next step; the minimum cell temperature Tmin = 10 °C > temperature threshold T_MIN = 0 °C, continue to the next step; the actual minimum cell voltage Vmin = 2.9 V ≤ discharge voltage threshold V_MIN_Dis = 3.0 V for 10 min > duration threshold Dur_Time = 5 min, display SOC - target discharge correction value SOCthr_Dis = 30% - 10% = 20% ≥ discharge SOC difference SOC_Diff_Dis = 5%, so discharge dynamic calibration is performed; since the target discharge correction value SOCthr_Dis = 10% > 0%, the SOC is corrected from 30% to SOCthr_Dis + SOC_Diff_Dis = 10% + 5% = 15% at a correction rate Crt_rate1 = 0.05% / s.

[0060] Step 3, for long downhill road section, the battery will be fed back to charge, feedback charging does not perform charging dynamic calibration, SOC is limited to SOC full charge waiting value SOC_LIMIT and below.

[0061] Feedback charging limit: for long downhill road section, the battery will be fed back to charge when braking, only ampere-hour integration is performed during feedback charging, no charging dynamic calibration is performed; during long downhill feedback charging, SOC increases due to brake feedback kinetic energy recovery, not actual charging state, there is a false SOC high situation, so feedback charging SOC cannot be calibrated to 100%; when feedback SOC exceeds SOC full charge waiting value SOC_LIMIT, the battery SOC is limited to SOC full charge waiting value SOC_LIMIT, wherein SOC_LIMIT < 100%.

[0062] Step 4, when the battery needs to be charged due to power loss, charging dynamic calibration is performed according to the difference between the current rate Crate_chg, the maximum single cell voltage Vmax, the target charging correction value SOCthr_Chg and the display SOC value SOC_Disp.

[0063] Specifically, the process of charging dynamic calibration is as follows:

[0064] (1) When the battery needs to be charged due to power loss, too large charging current will quickly raise the single cell voltage, at which time it is not suitable to perform charging dynamic calibration, and dynamic calibration should be performed at the end of charging when the current is moderate, that is, the absolute value of charging current Cur_Chg should be greater than current zero drift value CurDrift, and the absolute value of charging current Cur_Chg should be less than current rate Crate_chg, wherein the current rate Crate_chg is obtained by dividing the absolute value of charging current Cur_Chg by the rated capacity Q of the battery, when step (1) is satisfied, the next step is continued;

[0065] (2) When the temperature is low, the discharge cut-off voltage of the battery is low, and its corresponding charging voltage threshold V_MAX_Chg is also low. The selection rule of charging voltage threshold V_MAX_Chg is: when the minimum single cell temperature Tmin is less than or equal to temperature threshold T_MIN, V_MAX_Chg = low voltage threshold V_MAX_Low; when the minimum single cell temperature Tmin is greater than temperature threshold T_MIN, V_MAX_Chg = high voltage threshold V_MAX_High.

[0066] (3) When the battery is in charging state, the maximum cell voltage Vmax > the charging voltage threshold V_MAX_Chg for more than Dur_Time, the target charging correction value SOCthr_Chg - the display SOC ≥ the charging SOC difference SOC_Diff_Chg, the charging dynamic calibration is performed to correct the SOC to SOCthr_Chg - SOC_Diff_Chg at the correction rate Crt_rate3, wherein SOCthr_Chg < 100%;

[0067] (4) When the steps (1) or (3) are not met, the charging dynamic calibration is not performed.

[0068] In a specific embodiment, for example, the charging current absolute value Cur_Chg = 10A, the battery rated capacity Q = 200Ah, the current zero drift value CurDrift = 1A, the current rate Crate_chg = 0.1C, the minimum cell temperature Tmin = -10℃, the temperature threshold T_MIN = 0℃, the low voltage threshold V_MAX_Low = 3.5V, the high voltage threshold V_MAX_High = 3.53V, the battery is in charging state, the maximum cell voltage Vmax = 3.52V, the duration threshold Dur_Time = 5min, the actual Vmax is higher than 3.5V for 10min, the display SOC value SOC_Disp = 60%, the target charging correction value SOCthr_Chg = 80%, the charging SOC difference SOC_Diff_Chg = 3%, and the correction rate Crt_rate3 = 0.01% / s:

[0069] According to the above steps, the charging current absolute value 10A corresponds to the current rate = the charging current absolute value Cur_Chg / the battery rated capacity Q = 10 / 200C = 0.05C < the current rate Crate_chg = 0.1C, the charging current absolute value Cur_Chg = 10A > the current zero drift value CurDrift = 1A, the next step is continued; the minimum cell temperature Tmin = -10℃ ≤ the temperature threshold T_MIN = 0℃, so the charging voltage threshold V_MAX_Chg = the low voltage threshold V_MAX_Low = 3.5V, the next step is continued; the battery is in charging state, the maximum cell voltage Vmax = 3.52V > the charging voltage threshold V_MAX_Chg = 3.5V for 10min > the duration threshold Dur_Time = 5min, the target charging correction value SOCthr_Chg - the display SOC = 80%-60% = 20% ≥ the charging SOC difference SOC_Diff_Chg = 3%, so the charging dynamic calibration is performed to correct the SOC from 60% to SOCthr_Chg - SOC_Diff_Chg = 80%-3% = 77% at the correction rate Crt_rate3 = 0.01% / s.

[0070] Step 5, when the battery is in a charging state, the maximum single cell voltage Vmax≥ full charge cut-off voltage V_Fullchg for a full charge duration Fullchg_Time, and the absolute value of the charging current Cur_Chg≤ current overcurrent alarm value Cur_Over, the battery is full charged calibration, the SOC is calibrated to 100%.

[0071] Specifically, the process of full charge calibration is as follows:

[0072] (1) When the maximum single cell voltage Vmax≥ full charge cut-off voltage V_Fullchg, the timer Count starts counting;

[0073] (2) When the timer Count≥ full charge duration Fullchg_Time, the battery is in a charging (on-board slow charging or fast charging machine) state and the absolute value of the charging current Cur_Chg≤ current overcurrent alarm value Cur_Over, the battery is full charged calibration, the SOC is calibrated to 100%;

[0074] (3) When the timer Count≥ full charge duration Fullchg_Time, the battery is in a charging (on-board slow charging or fast charging machine) state and the absolute value of the charging current Cur_Chg> current overcurrent alarm value Cur_Over, no full charge calibration is performed, and the SOC is limited to the SOC full charge waiting value SOC_LIMIT;

[0075] (4) When the timer Count≥ full charge duration Fullchg_Time, the battery is in a charging (on-board slow charging or fast charging machine) state and there is a discharge current, no full charge calibration and SOC limitation is performed, and the display SOC value is output;

[0076] (5) When 0< timer Count< full charge duration Fullchg_Time and the battery is in a charging state, no full charge calibration is performed, and the SOC is limited to the SOC full charge waiting value SOC_LIMIT;

[0077] (6) When the above steps (2), (3), (4), (5) are not met, no full charge calibration and SOC limitation is performed, and the display SOC value is output.

[0078] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for correcting State of Charge (SOC) under frequent uphill and downhill conditions, characterized in that, Includes the following steps: S1. Obtain the hidden SOC capacity value SOC_Hide at different temperatures by looking up the temperature table. Calculate and display the SOC value SOC_Disp based on SOC_Hide and the SOC_Pre estimated by the algorithm, which is the SOC at the current temperature. S2. For long uphill sections, perform dynamic discharge calibration based on the difference between the current ratio Crate_dis, the lowest single-cell voltage Vmin, the displayed SOC value SOC_Disp, and the target discharge correction value SOCthr_Dis. S3. For long downhill sections, the battery will perform regenerative charging. Regenerative charging does not perform dynamic charging calibration, and the SOC is limited to the SOC_LIMIT value at or below the full charge waiting value. S4. When the battery is low on charge and needs to be charged, perform dynamic charging calibration based on the difference between the current ratio Crate_chg, the highest single-cell voltage Vmax, the target charging correction value SOCthr_Chg, and the displayed SOC value SOC_Disp. S5. When the battery is in the charging state, the highest single cell voltage Vmax ≥ full charge cutoff voltage V_Fullchg, the continuous full charge duration Fullchg_Time, and the absolute value of the charging current Cur_Chg ≤ the current overcurrent alarm value Cur_Over, perform full charge calibration on the battery and calibrate the SOC to 100%.

2. The SOC correction method for frequent uphill and downhill driving conditions according to claim 1, characterized in that, The process of hiding the SOC capacity in step S1 is as follows: S11. At low temperatures, due to the characteristics of the battery cell, the discharge cannot reach the rated capacity at room temperature. The lower the temperature, the more capacity cannot be discharged, and the larger the corresponding SOC capacity hidden value SOC_Hide. S12. Conduct discharge capacity tests at different temperatures, obtain the SOC_Hide table related to temperature Temp, and look up the SOC_Hide table through linear temperature interpolation to obtain the SOC_Hide corresponding to the current temperature Temp. S13. Calculate and display the SOC value SOC_Disp based on SOC_Hide and the SOC_Pre estimated by the algorithm. This is the SOC at the current temperature. The specific calculation formula is as follows: Wherein, SOC_Disp is the output displayed SOC value, SOC_Pre is the SOC value estimated by the algorithm, and SOC_Hide is the hidden SOC capacity value. All SOC values ​​are calculated with percentages.

3. The SOC correction method for frequent uphill and downhill driving conditions according to claim 2, characterized in that, In step S13, when the SOC_Pre estimated by the algorithm is less than or equal to the SOC capacity hiding value SOC_Hide, the SOC value SOC_Disp is displayed as 0%; when the SOC_Pre estimated by the algorithm is greater than or equal to 100%, the SOC value SOC_Disp is displayed as 100%.

4. The SOC correction method for frequent uphill and downhill driving conditions according to claim 2, characterized in that, In step S2, the discharge dynamic calibration process is as follows: S21. For long uphill sections, the battery discharge current is large. The large current will rapidly pull down the individual cell voltage. At this time, dynamic calibration is not advisable. Dynamic calibration should be performed at the end of the discharge when the current is moderate. That is, the discharge current Cur_Dis should be greater than the current zero drift value CurDrift, and at the same time, Cur_Dis should be less than the current ratio Crate_dis. The current ratio Crate_dis is obtained by quotienting the discharge current Cur_Dis and the battery rated capacity Q. When step S21 is satisfied, continue to step S22. S22. When the temperature is low, calibration is performed based on the SOC capacity hidden value SOC_Hide. When the lowest single cell temperature Tmin > temperature threshold T_MIN, discharge dynamic calibration is performed. When step S22 is satisfied, continue to step S23. S23. When steps S21 and S22 are satisfied, and the minimum single-cell voltage Vmin ≤ discharge voltage threshold V_MIN_Dis duration Dur_Time is greater than or equal to the display SOC - target discharge correction value SOCthr_Dis ≥ discharge SOC difference SOC_Diff_Dis, then perform discharge dynamic calibration. S24. If steps S21, S22 or S23 are not met, dynamic discharge calibration is not performed.

5. The SOC correction method for frequent uphill and downhill driving conditions according to claim 4, characterized in that, In step S23, when the target discharge correction value SOCthr_Dis > 0%, the SOC is corrected to SOCthr_Dis + SOC_Diff_Dis at the correction rate Crt_rate1; when the target discharge correction value SOCthr_Dis = 0%, that is, the battery is about to be depleted, the SOC is corrected to 0% at the correction rate Crt_rate2, where Crt_rate2 > Crt_rate1.

6. The SOC correction method for frequent uphill and downhill driving conditions according to claim 1, characterized in that, In step S3, the regenerative charging is limited as follows: For long downhill sections, the battery will perform regenerative charging when braking. During regenerative charging, only ampere-hour integration is performed, and no dynamic charging calibration is performed. During long downhill regenerative charging, the SOC increases due to the recovery of kinetic energy from braking, not due to the actual charging state. There is a situation where the virtual SOC is too high, so the regenerative charging SOC cannot be calibrated to 100%. When the regenerative SOC exceeds the SOC waiting value for full charge, SOC_LIMIT, the battery SOC is limited to the SOC waiting value for full charge, where SOC_LIMIT < 100%.

7. The SOC correction method for frequent uphill and downhill driving conditions according to claim 1, characterized in that, In step S4, the dynamic charging calibration process is as follows: S41. When the battery is depleted and needs to be charged, an excessively large charging current will rapidly increase the individual cell voltage. At this time, dynamic charging calibration should not be performed. Dynamic calibration should be performed at the end of the charging process when the current is moderate. That is, the absolute value of the charging current Cur_Chg should be greater than the current zero drift value CurDrift, and the absolute value of the charging current Cur_Chg should be less than the current ratio Crate_chg. The current ratio Crate_chg is obtained by quotienting the absolute value of the charging current Cur_Chg and the rated capacity Q of the battery. When step S41 is satisfied, continue to step S42. S42. When the temperature is low, the battery's discharge cutoff voltage is low, and its corresponding charging voltage threshold V_MAX_Chg is also low. S43. When the battery is in a charging state, the highest single cell voltage Vmax > the charging voltage threshold V_MAX_Chg for more than Dur_Time, and the target charging correction value SOCthr_Chg - the displayed SOC ≥ the charging SOC difference SOC_Diff_Chg, perform dynamic charging calibration and correct the SOC to SOCthr_Chg - SOC_Diff_Chg at the correction rate Crt_rate3, where SOCthr_Chg < 100%. S44. If step S41 or S43 is not satisfied, dynamic charging calibration will not be performed.

8. The SOC correction method for frequent uphill and downhill driving conditions according to claim 7, characterized in that, In step S42, the charging voltage threshold V_MAX_Chg is selected according to the following rules: when the lowest single-cell temperature Tmin ≤ temperature threshold T_MIN, V_MAX_Chg = low voltage threshold V_MAX_Low; when the lowest single-cell temperature Tmin > temperature threshold T_MIN, V_MAX_Chg = high voltage threshold V_MAX_High.

9. The SOC correction method for frequent uphill and downhill driving conditions according to claim 1, characterized in that, In step S5, the full charge calibration process is as follows: S51. When the highest single-cell voltage Vmax ≥ the full-charge cutoff voltage V_Fullchg, the timer Count starts counting. S52. When the timer Count ≥ Full charge duration Fullchg_Time, the battery is in a charging state and the absolute value of the charging current Cur_Chg ≤ the current overcurrent alarm value Cur_Over, perform full charge calibration on the battery and calibrate the SOC to 100%. S53. When the timer Count ≥ Full charge duration Fullchg_Time, the battery is in a charging state and the absolute value of the charging current Cur_Chg > the current overcurrent alarm value Cur_Over, full charge calibration is not performed, and the SOC is limited to the SOC full charge waiting value SOC_LIMIT. S54. When the timer Count ≥ Full charge duration Fullchg_Time, the battery is in a charging state and has a discharge current, full charge calibration and SOC limit are not performed, and the SOC value is displayed on the output. S55. When 0 < Timer Count < Full charge duration Fullchg_Time and the battery is in a charging state, full charge calibration is not performed, and the SOC is limited to the SOC full charge waiting value SOC_LIMIT. S56. If none of the above conditions S52, S53, S54, and S55 are met, full charge calibration and SOC limit are not performed, and the SOC value is displayed on the output.

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