A method and system for estimating SOC of battery after aging based on actual vehicle operating conditions

Abstract

The embodiment of the present invention discloses a method and system for estimating the SOC of an aged battery based on actual vehicle working conditions; the current SOH value is determined by a table lookup method combined with a battery model in real time calculation; and the current battery capacity and the current battery internal resistance are obtained according to the current SOH value; the current SOC estimation value is obtained according to these calculations; and the difference between the cell terminal voltage estimation value and the actual cell terminal voltage value is obtained by using the battery model calculation formula, and the current SOC estimation value is adjusted in combination with the correction coefficient under the current working conditions to obtain the adjusted SOC value. The corresponding update of the parameters in each step of the embodiment of the present invention can improve the estimation accuracy of the SOC of the aged battery, thereby improving the user experience of the electric vehicle when used for a long time.

Description

Technical Field

[0001] The present invention relates to the field of electric vehicle battery management systems, and in particular to a method and system for estimating the SOC (state of charge) of an aged battery based on actual vehicle operating conditions. Background Art

[0002] The state of charge (SOC) of electric vehicles is closely related to the driving range and power of the whole vehicle, but SOC is an estimated value rather than a truly measurable physical quantity. At present, there are many methods for estimating SOC. In addition to the traditional ampere-hour integration method, there is also the extended Kalman filter algorithm (EKF) based on the equivalent circuit model. Although there are many algorithms for SOC estimation, they can only guarantee high-precision estimation on brand-new batteries. For aging batteries, the estimation accuracy of SOC faces great challenges. The reason is that when the battery ages, the capacity will decay and the internal resistance will increase. At the same time, the battery capacity and internal resistance cannot be measured in real time, so the accurate aging state of the battery cannot be obtained in real time. Since the estimation of SOC is closely related to the capacity and internal resistance, if the algorithm is still based on the calibration of new battery parameters, it cannot match the actual performance of the aged battery, resulting in a large error in the SOC estimation of the aged battery. The corresponding relationship between the cumulative charge and discharge capacity and the battery capacity obtained based on the battery cell test is only the average data of the battery test with limited data, and cannot truly reflect the aging state of the current battery cell.

[0003] In the prior art, the ampere-hour integration method for estimating SOC usually requires auxiliary open circuit voltage (OCV) correction to eliminate the influence of the ampere-hour integration cumulative error. However, this method also has shortcomings. The correction window is small, which makes the SOC change greatly each time it is corrected, which is not accurate enough and affects the driving experience. Summary of the invention

[0004] The technical problem to be solved by the present invention is that the present invention provides a method and system for estimating the SOC of a battery after aging based on actual vehicle operating conditions, which improves the accuracy of SOC estimation after battery aging, thereby improving the user experience of electric vehicles.

[0005] In order to solve the above technical problems, one aspect of the present invention provides a method for estimating the SOC of a battery after aging based on actual vehicle operating conditions, which comprises the following steps:

[0006] Step S10, querying a pre-calibrated cumulative discharge capacity-SOH comparison table according to the current cumulative discharge capacity of the battery to obtain a first SOH value (State Of Health, a percentage value) of the battery, and obtaining a second SOH value calculated according to the battery model, and determining the smaller of the first SOH value and the second SOH value as the current SOH value; and obtaining the current battery capacity and the current battery internal resistance according to the current SOH value;

[0007] Step S11, obtaining the SOC value of the previous cycle in the periodic sampling interval, and obtaining the current current value of the battery, and combining the current battery capacity to calculate the current SOC estimation value;

[0008] Step S12, using the current current value, the current battery internal resistance, and the current battery capacity, and obtaining an estimated value of the cell terminal voltage according to a battery model calculation formula;

[0009] Step S13: compare the estimated cell terminal voltage value with the actually measured cell terminal voltage value obtained by sampling, and adjust the current SOC estimated value in combination with the correction coefficient under the current working condition to obtain an adjusted SOC value.

[0010] The method further comprises: a step of calculating a second SOH value obtained according to the battery model, specifically comprising:

[0011] Under the DC charging condition, a charging period that meets the predetermined standard is selected to obtain a battery capacity change value dQ and an SOC change value dSOC, and a second SOH value is obtained and stored according to a ratio of the two;

[0012] Periodically detect and determine whether there is a newly calculated second SOH value in the previous cycle. If not, query the pre-calibrated cumulative discharge amount-SOH comparison table according to the current cumulative discharge amount to obtain the corresponding SOH value, and store the corresponding SOH value as the second SOH value.

[0013] Wherein, the step S10 further comprises:

[0014] According to the current SOH value, a pre-calibrated SOH-battery capacity-internal resistance correspondence table is queried to obtain the battery capacity and internal resistance values ​​corresponding to the current SOH value.

[0015] Wherein, the step S11 further comprises:

[0016] The current SOC estimate is calculated using the following formula:

[0017]

[0018] Among them, SOC0 is the SOC value calculated in the previous cycle, I is the current current value; dt is the sampling interval; C is the current battery capacity.

[0019] Wherein, the step S12 further comprises:

[0020] The estimated value of the cell terminal voltage U is calculated according to the following formula sim (t):

[0021]

[0022] Among them, OCV(t) is the current open circuit voltage, dt is the sampling interval, I(t) is the current total current in the battery model, R1, C1, are the resistance, capacitance, and current flowing through the resistance at the previous sampling moment of the first RC circuit in the battery model; R2, C1, are respectively the resistance, capacitance, and current flowing through the resistance at the previous sampling moment of the second RC circuit in the battery model.

[0023] Wherein, the step S13 further comprises:

[0024] The current SOC estimate is adjusted using the following formula based on the actual cell terminal voltage value and the correction coefficient under the current working condition to obtain the adjusted SOC value.

[0025] U Diff =U meas -U sim

[0026] △SOC=U Diff ×λ

[0027]

[0028] Among them, U meas is the measured cell terminal voltage value; λ is the preset correction coefficient under the current working condition, and its value range is between 0 and 1.

[0029] Among them, further include:

[0030] A predetermined number of new batteries of the same model are selected, and through test calibration, the corresponding relationship between battery capacity and temperature, the internal resistance information at different temperatures and currents, the OCV curve of the battery cell, the relationship between the cumulative discharge capacity and the battery cell capacity or SOH, and the relationship between the DC internal resistance and capacity of the aged battery cell at 50% and 100% SOC, respectively, are obtained.

[0031] The steps of selecting a charging period that meets a predetermined standard under a DC charging condition, obtaining a capacity change value dQ and an SOC change value dSOC, and obtaining and storing a second SOH value according to a ratio of the two are specifically as follows:

[0032] Before fast charging, keep the high voltage powered on, turn off all loads such as air conditioning and audio, let the vehicle stand for at least the first time, open the charging port and insert the fast charging gun; adjust the high voltage to the keyoff state, wait for at least the second time, and then start charging, obtain the voltage rebound curve of the second waiting time period, estimate the battery OCV based on the curve, and obtain the initial SOC1;

[0033] When the DC charging is fully charged, the battery management system delays the first time and then goes to sleep, obtains the voltage rebound curve of the battery after no current in the first time, estimates the OCV of the battery according to the curve, and obtains the ending SOC2; or when the DC charging is in the last stage in the keyoff state, the charging is exited, the battery management system delays the first time and then goes to sleep, obtains the voltage rebound curve of the battery without current in at least the second time period within the first time, estimates the OCV of the battery according to the curve, and obtains the ending SOC2;

[0034] Subtract the initial SOC1 from the final SOC2 to obtain dSOC;

[0035] The estimated battery capacity C is calculated using the following formula, and the second SOH value is obtained according to the battery capacity:

[0036] C=dQ / dSOC

[0037] Among them, dQ is the charging capacity of the charging condition.

[0038] Accordingly, another aspect of the present invention further provides a system for estimating the SOC of a battery after aging based on actual vehicle operating conditions, which comprises:

[0039] An SOH obtaining unit is used to query a pre-calibrated cumulative discharge amount-SOH comparison table according to the current cumulative discharge amount of the battery to obtain a first SOH value of the battery, and obtain a second SOH value calculated according to a battery model, and determine the smaller one of the first SOH value and the second SOH value as the current SOH value; and obtain the current battery capacity and the current battery internal resistance according to the current SOH value;

[0040] The SOC estimation value acquisition unit is used to obtain the SOC value of the previous cycle in the periodic sampling interval, the current current value of the battery, and calculate the current SOC estimation value in combination with the current battery capacity;

[0041] A voltage estimation value acquisition unit, used to obtain a cell terminal voltage estimation value according to a battery model calculation formula using the current current value, the current battery internal resistance, and the current battery capacity;

[0042] The SOC adjustment unit is used to compare the estimated value of the cell terminal voltage with the measured cell terminal voltage value obtained by sampling, and adjust the current SOC estimated value in combination with the correction coefficient under the current working condition to obtain an adjusted SOC value.

[0043] Among them, further include:

[0044] A second SOH value calculation unit is used to select a charging period that meets a predetermined standard under a DC charging condition, obtain a battery capacity change value dQ and an SOC change value dSOC, and obtain and store a second SOH value according to a ratio of the two;

[0045] The second SOH value updating unit is used to periodically detect and determine whether there is a newly calculated second SOH value in the previous cycle. If not, query the pre-calibrated cumulative discharge amount-SOH comparison table according to the current cumulative discharge amount to obtain the corresponding SOH value, and store the corresponding SOH value as the second SOH value.

[0046] The SOC estimation value acquisition unit specifically uses the following formula to calculate and obtain the current SOC estimation value:

[0047]

[0048] Among them, SOC0 is the SOC value calculated in the previous cycle, I is the current current value; dt is the sampling interval; C is the current battery capacity.

[0049] The voltage estimation value acquisition unit is specifically used to calculate and obtain the cell terminal voltage estimation value U according to the following formula: sim (t):

[0050]

[0051] Among them, OCV(t) is the current open circuit voltage, dt is the sampling interval, I(t) is the current total current in the battery model, R1, C1, are the resistance, capacitance, and current flowing through the resistance at the previous sampling moment of the first RC circuit in the battery model; R2, C1, are respectively the resistance, capacitance, and current flowing through the resistance at the previous sampling moment of the second RC circuit in the battery model.

[0052] The SOC adjustment unit is specifically used to obtain the measured cell terminal voltage value and the correction coefficient under the current working condition, and adjust the current SOC estimation value according to the following formula to obtain the adjusted SOC value:

[0053] U Diff =U meas -U sim

[0054] △SOC=U Diff ×λ

[0055]

[0056] Among them, U meas is the measured cell terminal voltage value; λ is the preset correction coefficient under the current working condition, and its value range is between 0 and 1.

[0057] Wherein, the second SOH value calculation unit further includes:

[0058] The initial SOC acquisition unit is used to keep the high voltage powered on before fast charging, turn off all loads such as air conditioning and audio, let the vehicle stand for at least a first time, open the charging port and insert the fast charging gun; adjust the high voltage to the keyoff state, wait for at least a second time, and then start charging, obtain the voltage rebound curve of the second waiting time period, estimate the OCV of the battery according to the curve, and obtain the initial SOC1;

[0059] The end SOC acquisition unit is used for when the DC charging is completed with full charge, the battery management system delays the first time and then sleeps, obtains the voltage rebound curve of the battery after no current in the first time, estimates the OCV of the battery according to the curve, and obtains the end SOC2; or when the DC charging is in the last stage in the keyoff state, the charging is exited, the battery management system delays the first time and then sleeps, obtains the voltage rebound curve under no current of at least the second time period within the first time, estimates the OCV of the battery according to the curve, and obtains the end SOC2;

[0060] An SOC difference calculation unit, configured to subtract the initial SOC1 from the final SOC2 to obtain dSOC;

[0061] The SOH value calculation unit is used to calculate the estimated battery capacity C by using the following formula, and obtain a second SOH value according to the battery capacity:

[0062] C=dQ / dSOC

[0063] Among them, dQ is the charging capacity of the charging condition.

[0064] The implementation of the embodiments of the present invention has the following beneficial effects:

[0065] The embodiment of the present invention provides a method and system for estimating the SOC of an aged battery based on actual vehicle operating conditions; the current SOH value is determined by a table lookup method combined with a battery model in real-time calculation; and the current battery capacity and the current battery internal resistance are obtained according to the current SOH value; the current SOC estimation value is obtained according to these calculations; and the difference between the estimated cell terminal voltage value and the measured cell terminal voltage value is obtained by using the calculation formula of the battery model, and the current SOC estimation value is adjusted in combination with the correction coefficient under the current operating conditions to obtain the adjusted SOC value. The corresponding update of the parameters in each step of the embodiment of the present invention can improve the estimation accuracy of the SOC of the aged battery, thereby improving the user experience of the electric vehicle when used for a long time. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, without paying creative labor, other drawings obtained based on these drawings still belong to the scope of the present invention.

[0067] Figure 1 A schematic diagram of the main process of an embodiment of a method for estimating the SOC of a battery after aging based on actual vehicle operating conditions provided by the present invention;

[0068] Figure 2 It is a structural schematic diagram of a battery model involved in the present invention;

[0069] Figure 3 for Figure 2 Schematic diagram of the current flowing through each resistor of the RC circuit;

[0070] Figure 4 A schematic diagram of the structure of an embodiment of a system for estimating the SOC of a battery after aging based on actual vehicle operating conditions provided by the present invention;

[0071] Figure 5 for Figure 4 Schematic diagram of the structure of the second SOH value calculation unit. DETAILED DESCRIPTION

[0072] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings.

[0073] like Figure 1FIG. 1 is a schematic diagram showing a main flow chart of an embodiment of a method for estimating the SOC of a battery after aging based on actual vehicle operating conditions provided by the present invention; and FIG. Figure 2 and Figure 3 As shown, in this embodiment, the SOC estimation method after battery aging based on actual vehicle operating conditions includes the following steps:

[0074] Step S10, querying a pre-calibrated cumulative discharge capacity-SOH comparison table according to the current cumulative discharge capacity of the battery to obtain a first SOH value of the battery, and obtaining a second SOH value calculated according to a battery model, and determining the smaller one of the first SOH value and the second SOH value as the current SOH value; and obtaining the current battery capacity and the current battery internal resistance according to the current SOH value;

[0075] It is understandable that before step S10, it is necessary to calibrate the new battery and store the calibration data. For example, in one example, it is necessary to select a predetermined number of new batteries of the same model, and obtain the corresponding relationship between the capacity and temperature in the battery through test calibration, the internal resistance information at different temperatures and currents, the OCV curve of the battery cell, the relationship between the cumulative discharge capacity and the battery cell capacity or SOH, the relationship between the DC internal resistance and the capacity of the aged battery cell at 50% and 100% SOC, and so on.

[0076] At the same time, it is necessary to calculate the second SOH value in advance according to the charging condition and the battery model. The step of calculating the second SOH value specifically includes:

[0077] Under the DC charging condition, a charging period that meets the predetermined standard is selected to obtain the battery capacity change value dQ and the SOC change value dSOC, and a second SOH value is obtained and stored according to the ratio of the two. In this step, in order to ensure the accuracy of SOH estimation, it is necessary to ensure that the charging temperature is in a suitable range, and the span of dSOC is large enough, usually greater than 70%.

[0078] Periodically (such as three months) detect and determine whether there is a newly calculated second SOH value in the previous cycle. If not, query the pre-calibrated cumulative discharge amount-SOH comparison table according to the current cumulative discharge amount to obtain the corresponding SOH value, and store the corresponding SOH value as the second SOH value.

[0079] More specifically, under the DC charging condition, the steps of selecting a charging period that meets a predetermined standard, obtaining a capacity change value dQ and an SOC change value dSOC, and obtaining and storing a second SOH value according to a ratio of the two are specifically as follows:

[0080] Before fast charging, keep the high voltage powered on, turn off all loads such as air conditioning and audio, let the vehicle stand for at least the first time (such as 2 minutes), open the charging port and insert the fast charging gun; adjust the high voltage to the keyoff state, and wait for at least the second time (such as 30 seconds), then start charging, obtain the voltage rebound curve of the second waiting time period (such as 30 seconds), estimate the battery OCV according to the curve, and obtain the initial SOC1;

[0081] When DC charging is fully charged, the battery management system delays the first time and then goes to sleep, obtains the voltage rebound curve of the battery after no current for the first time (such as 2 minutes), estimates the OCV of the battery according to the curve, and obtains the ending SOC2; or when the DC charging is in the last stage in the keyoff state, the charging is exited, the battery management system delays the first time (such as 2 minutes) and then goes to sleep, obtains the voltage rebound curve of the battery without current for at least a second time period (such as 30 seconds) within the first time (such as 2 minutes), estimates the OCV of the battery according to the curve, and obtains the ending SOC2;

[0082] Subtract the initial SOC1 from the final SOC2 to obtain dSOC;

[0083] The estimated battery capacity C is calculated using the following formula, and the second SOH value is obtained according to the battery capacity:

[0084] C=dQ / dSOC

[0085] Wherein, dQ is the charging capacity of the charging condition, and the second SOH value is obtained by dividing the capacity by the rated capacity of the new battery.

[0086] It is understandable that, in the embodiment of the present invention, the DC charging condition is selected to calculate the second SOH value for the following considerations:

[0087] The battery capacity is affected by the cell temperature and current. In order to ensure the comparability of the calculated capacity value and improve the accuracy of SOH estimation, a DC charging condition is selected. That is, in the embodiment of the present invention, the real-time estimation of SOH is activated only under the DC charging condition. This is because the DC charging current changes in a step-like manner, which is the only steady-state condition in the actual vehicle condition; on the other hand, due to the existence of the vehicle thermal management system, the battery is maintained in an ideal temperature range during DC charging. When the battery is in a low temperature environment, the heater will start to heat up the battery, and when the battery is running at a high temperature, the cooling system will lower the battery temperature. The working conditions are stable and the temperature is suitable. This is the most important reason for choosing DC charging as the working condition to start the SOH algorithm.

[0088] At the same time, for the value dSOC, because SOC is an estimated value, not a measured value, the estimation error of SOC will inevitably affect the result of capacity estimation. In the embodiment of the present invention, specific measures need to be adopted to ensure the accuracy of the initial SOC1 and the result SOC2 points of the dSOC calculation. In the embodiment of the present invention, in order to increase the frequency of algorithm activation, the algorithm needs to predict the terminal voltage OCV of the battery after the vehicle has been stationary for a short time. The key to predicting OCV is that when the current of the battery is removed, the voltage of the battery will gradually return to the static open circuit voltage. The test can be used to obtain in advance the relationship between the ratio of the terminal voltage to the open circuit voltage and time after the current is removed.

[0089] In some more specific examples, it is necessary to ensure that the temperature range of SOC2 is within 30℃-35℃. There is no temperature requirement for SOC1 because the charging capacity is most closely related to the temperature at the end. In addition, the interval between SOC2 and SOC1 is at least greater than 70%. The exact value of each battery cell needs to refer to the SOC-OCV curve to avoid the platform area in the curve. At the same time, when calculating, if it is found that the capacity drops too fast in a short period of time and exceeds the upper limit parameter in the battery management system, it is considered that the calculation result is unreliable and the value calculated this time is abandoned. If the capacity value calculated this time is higher than the previous value, the calculation result of this time is discarded; if there is no online estimated capacity value within 3 months, the SOH value estimated by the table lookup is used for forced update.

[0090] The step S10 further includes:

[0091] According to the current cumulative discharge amount of the battery, a pre-calibrated cumulative discharge amount-SOH comparison table is queried to obtain a first SOH value. Among them, the current cumulative discharge amount of the battery can be obtained in real time from the battery management system. Since the battery cell samples used for testing are limited when the cumulative discharge amount-SOH comparison table is calibrated, the data of the sample battery cells may differ from the battery cells actually used. In addition, the test conditions are single, and the test environment is always maintained at a constant temperature, which cannot match the complex environment of the whole vehicle. Therefore, the test results do not necessarily reflect the actual aging of the battery on the vehicle. Therefore, in the embodiments of the present invention, it is also necessary to combine the real-time estimated second SOH value to determine the current SOH value;

[0092] And after obtaining the current SOH value, a pre-calibrated SOH-battery capacity-internal resistance correspondence table is queried according to the current SOH value to obtain the battery capacity and internal resistance values ​​corresponding to the current SOH value.

[0093] Step S11, obtaining the SOC value of the previous cycle in the periodic sampling interval, and obtaining the current current value of the battery, and combining the current battery capacity to calculate the current SOC estimation value;

[0094] Wherein, the step S11 further comprises:

[0095] The current SOC estimate is calculated using the following formula:

[0096]

[0097] Among them, SOC0 is the SOC value calculated in the previous cycle, I is the current current value; dt is the sampling interval; C is the current battery capacity.

[0098] It is understandable that during the operation of the battery management system, the remaining battery capacity SOC is always calculated and reported to the vehicle system. It is one of the important input parameters of the vehicle control strategy. The parameters calibrated based on test data can ensure high-precision SOC calculation of new batteries. However, with the continuous use of the battery, the performance of the battery gradually deteriorates, the capacity decreases, and the internal resistance increases. In order to ensure that the SOC of the aged battery can still be accurately estimated, the parameters of the SOC calculation must be updated according to the aging status of the battery. For the SOC calculation of new and old batteries, the algorithm behind it will not change, only the parameters will be updated as the battery ages.

[0099] Step S12, using the current current value, the current battery internal resistance, and the current battery capacity, and obtaining an estimated value of the cell terminal voltage according to a battery model calculation formula;

[0100] Wherein, the step S12 further comprises:

[0101] The estimated value of the cell terminal voltage U is calculated according to the following formula sim (t):

[0102]

[0103] Among them, OCV(t) is the current open circuit voltage, dt is the sampling interval, I(t) is the current total current in the battery model, R1, C1, are the resistance, capacitance, and current flowing through the resistance at the previous sampling moment of the first RC circuit in the battery model; R2, C1, are respectively the resistance, capacitance, and current flowing through the resistance at the previous sampling moment of the second RC circuit in the battery model.

[0104] Combine the following Figure 2 and Figure 3 As shown, let's introduce how to calculate the estimated value of the cell terminal voltage U sim The process of obtaining the formula of (t):

[0105] exist Figure 3 According to Kirchhoff's law:

[0106] I R =II C

[0107] Where: I R is the current passing through the resistor R of the RC circuit; I C is the current passing through the capacitor C of the RC circuit; I is the total current. From the basic relationship between voltage, current and capacitance, we can know that:

[0108] dQ C =C × V C , dV C =dV R =R×dI R

[0109] Where: Q C is the charge of capacitor C; V C is the voltage of capacitor C; V R is the voltage of capacitor R; dI R is the change in current passing through resistor R,

[0110] From the above relationship, we can get:

[0111]

[0112] Therefore, according to the relationship of the circuit, it can be deduced that:

[0113] U sim =OCV-U0-U1-U2

[0114] U sim =OCV-I×R0-I1×R1-I2×R2

[0115]

[0116] Thus, the estimated value of the cell terminal voltage U obtained by estimating the circuit model can be calculated in real time. sim , where U sim Corresponds to Figure 2 U L , and OCV corresponds to Figure 2 U oc .

[0117] Step S13: compare the estimated cell terminal voltage value with the actually measured cell terminal voltage value obtained by sampling, and adjust the current SOC estimated value in combination with the correction coefficient under the current working condition to obtain an adjusted SOC value.

[0118] In a specific example, the step S13 further includes:

[0119] The current SOC estimate is adjusted using the following formula based on the actual cell terminal voltage value and the correction coefficient under the current working condition to obtain the adjusted SOC value.

[0120] U Diff =U meas -U sim

[0121] △SOC=U Diff ×λ

[0122]

[0123] Among them, U meas is the measured cell terminal voltage value; λ is the preset correction coefficient under the current working conditions, and its value range is between 0-1.

[0124] Among them, the setting of the correction coefficient λ is crucial. In some examples, λ can be automatically updated according to parameters such as sampling error; but considering that in engineering applications, in order to prevent the algorithm from running away, the correction parameter λ can be set to a manual assignment. More specifically, the value of the correction parameter λ is related to SOC, temperature, and operating conditions. The most important consideration is the accuracy of the battery model under different conditions. For example, when the characteristics of the battery model match the battery characteristics well (such as normal temperature and mild conditions), the value of λ is larger; and in conditions where the battery characteristics cannot be correctly reflected by the battery model (such as conditions corresponding to low temperature and low SOC areas), the value of λ is reduced.

[0125] like Figure 4 FIG. 1 is a schematic diagram showing a structure of an embodiment of a battery SOC estimation system after aging based on actual vehicle operating conditions provided by the present invention; and FIG. Figure 5 As shown, the SOC estimation system 1 for battery aging based on actual vehicle operating conditions includes:

[0126] The SOH obtaining unit 10 is used to query a pre-calibrated cumulative discharge amount-SOH comparison table according to the current cumulative discharge amount of the battery to obtain a first SOH value of the battery, and obtain a second SOH value calculated according to the battery model, and determine the smaller one of the first SOH value and the second SOH value as the current SOH value; and obtain the current battery capacity and the current battery internal resistance according to the current SOH value;

[0127] The SOC estimation value acquisition unit 11 is used to obtain the SOC value of the previous cycle in the periodic sampling interval, the current value of the battery, and the current battery capacity to calculate the current SOC estimation value;

[0128] The voltage estimation value acquisition unit 12 is used to obtain the estimated value of the cell terminal voltage according to the battery model calculation formula by using the current current value, the current battery internal resistance, and the current battery capacity;

[0129] The SOC adjustment unit 13 is used to compare the estimated value of the cell terminal voltage with the actually measured cell terminal voltage value obtained by sampling, and adjust the current SOC estimated value in combination with the correction coefficient under the current working condition to obtain an adjusted SOC value;

[0130] The second SOH value calculation unit 14 is used to select a charging period that meets a predetermined standard under a DC charging condition, obtain a battery capacity change value dQ and an SOC change value dSOC, and obtain and store a second SOH value according to a ratio between the two;

[0131] The second SOH value updating unit 15 is used to periodically detect and determine whether there is a newly calculated second SOH value in the previous cycle. If not, a pre-calibrated cumulative discharge amount-SOH comparison table is queried according to the current cumulative discharge amount to obtain a corresponding SOH value, and the corresponding SOH value is stored as the second SOH value.

[0132] More specifically, in one example, the SOC estimation value acquisition unit 11 specifically uses the following formula to calculate and obtain the current SOC estimation value:

[0133]

[0134] Among them, SOC0 is the SOC value calculated in the previous cycle, I is the current current value; dt is the sampling interval; C is the current battery capacity.

[0135] More specifically, in one example, the voltage estimation value acquisition unit 12 is specifically used to calculate and obtain the cell terminal voltage estimation value U according to the following formula: sim (t):

[0136]

[0137] Among them, OCV(t) is the current open circuit voltage, dt is the sampling interval, I(t) is the current total current in the battery model, R1, C1, are the resistance, capacitance, and current flowing through the resistance at the previous sampling moment of the first RC circuit in the battery model; R2, C1, are respectively the resistance, capacitance, and current flowing through the resistance at the previous sampling moment of the second RC circuit in the battery model.

[0138] More specifically, in one example, the SOC adjustment unit 13 is specifically used to obtain the measured cell terminal voltage value and the correction coefficient under the current working condition, and adjust the current SOC estimation value according to the following formula to obtain the adjusted SOC value:

[0139] U Diff =U meas -U sim

[0140] △SOC=U Diff ×λ

[0141]

[0142] Among them, U meas is the measured cell terminal voltage value; λ is the preset correction coefficient under the current working condition, and its value range is between 0 and 1.

[0143] Wherein, the second SOH value calculation unit 14 further includes:

[0144] The initial SOC acquisition unit 140 is used to keep the high voltage powered on before fast charging, turn off all loads such as air conditioning and audio, let the vehicle stand for at least a first time, open the charging port and insert the fast charging gun; adjust the high voltage to the keyoff state, wait for at least a second time, and then start charging, obtain the voltage rebound curve of the second waiting time period, estimate the OCV of the battery according to the curve, and obtain the initial SOC1;

[0145] The end SOC acquisition unit 141 is used for, when the DC charging is completed with full charge, the battery management system delays the first time and then sleeps, obtains the voltage rebound curve of the battery after no current in the first time, estimates the OCV of the battery according to the curve, and obtains the end SOC2; or when the DC charging is in the last stage in the keyoff state, the charging is exited, the battery management system delays the first time and then sleeps, obtains the voltage rebound curve under no current of at least the second time period within the first time, estimates the OCV of the battery according to the curve, and obtains the end SOC2;

[0146] An SOC difference calculation unit 142 is used to subtract the initial SOC1 from the final SOC2 to obtain dSOC;

[0147] The SOH value calculation unit 143 is used to calculate the estimated battery capacity C by using the following formula, and obtain a second SOH value according to the battery capacity:

[0148] C=dQ / dSOC

[0149] Among them, dQ is the charging capacity of the charging condition.

[0150] For more details, please refer to and combine the above Figures 1 to 3 The description is not given in detail here.

[0151] The implementation of the embodiments of the present invention has the following beneficial effects:

[0152] The embodiment of the present invention provides a method and system for estimating the SOC of an aged battery based on actual vehicle operating conditions; the current SOH value is determined by a table lookup method combined with a battery model in real-time calculation; and the current battery capacity and the current battery internal resistance are obtained according to the current SOH value; the current SOC estimation value is obtained according to these calculations; and the difference between the estimated cell terminal voltage value and the measured cell terminal voltage value is obtained by using the calculation formula of the battery model, and the current SOC estimation value is adjusted in combination with the correction coefficient under the current operating conditions to obtain the adjusted SOC value. The corresponding update of the parameters in each step of the embodiment of the present invention can improve the estimation accuracy of the SOC of the aged battery, thereby improving the user experience of the electric vehicle when used for a long time.

[0153] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, devices, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0154] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0155] The above disclosure is only a preferred embodiment of the present invention, which certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

1. A method for estimating the SOC of a battery after aging based on actual vehicle operating conditions, characterized in that: The steps include: Step S10, querying a pre-calibrated cumulative discharge capacity-SOH comparison table according to the current cumulative discharge capacity of the battery to obtain a first SOH value of the battery, and obtaining a second SOH value calculated according to the battery model, and determining the smaller of the first SOH value and the second SOH value as the current SOH value; And according to the current SOH value, obtain the current battery capacity and the current battery internal resistance; Step S11, obtaining the SOC value of the previous cycle in the periodic sampling interval, and obtaining the current current value of the battery, and combining the current battery capacity to calculate and obtain the current SOC estimation value; Step S12, using the current current value, the current battery internal resistance, and the current battery capacity to obtain an estimated value of the cell terminal voltage according to a battery model; Step S13: compare the estimated cell terminal voltage value with the actually measured cell terminal voltage value obtained by sampling, and adjust the current SOC estimated value in combination with the correction coefficient under the current working condition to obtain an adjusted SOC value.

2. The method according to claim 1, characterized in that Further including: The step of calculating the second SOH value obtained according to the battery model specifically includes: Under the DC charging condition, a charging period that meets a predetermined standard is selected to obtain a battery capacity change value dQ and an SOC change value dSOC, thereby obtaining and storing a second SOH value; Periodically detect and determine whether there is a newly calculated second SOH value in the previous cycle. If not, query the pre-calibrated cumulative discharge amount-SOH comparison table according to the current cumulative discharge amount to obtain the corresponding SOH value, and store the corresponding SOH value as the second SOH value.

3. The method according to claim 1, characterized in that The step S10 further comprises: According to the current SOH value, a pre-calibrated SOH-battery capacity-internal resistance correspondence table is queried to obtain the battery capacity and internal resistance values ​​corresponding to the current SOH value.

4. The method according to claim 1, characterized in that The step S11 further comprises: The current SOC estimate is calculated using the following formula: : Among them, SOC0 is the SOC value calculated in the previous cycle, I is the current current value; dt is the sampling interval; C is the current battery capacity.

5. The method according to claim 1, characterized in that The step S12 further comprises: The estimated value of the cell terminal voltage U is calculated according to the following formula sim (t): Among them, OCV(t) is the current open circuit voltage, dt is the sampling interval, I(t) is the current total current in the battery model, R1, C1, are the resistance, capacitance, and current flowing through the resistance at the previous sampling moment of the first RC circuit in the battery model; R2, C1, are respectively the resistance, capacitance, and current flowing through the resistance at the previous sampling moment of the second RC circuit in the battery model.

6. The method according to claim 5, characterized in that The step S13 further comprises: The current SOC estimate is adjusted using the following formula based on the actual cell terminal voltage value and the correction coefficient under the current working condition to obtain the adjusted SOC value. : U Diff =U meas -U sim (t) △SOC=U Diff ×λ Among them, U meas is the measured cell terminal voltage value; λ is the preset correction coefficient under the current working condition, and its value range is between 0 and 1.

7. The method according to claim 6, characterized in that Further including: A predetermined number of new batteries of the same model are selected, and through test calibration, the corresponding relationship between battery capacity and temperature, the internal resistance information at different temperatures and currents, the OCV curve of the battery cell, the relationship between the cumulative discharge capacity and the battery cell capacity or SOH, and the relationship between the DC internal resistance and capacity of the aged battery cell at 50% and 100% SOC, respectively, are obtained.

8. The method according to claim 2, characterized in that The steps of selecting a charging period that meets a predetermined standard under a DC charging condition, obtaining a battery capacity change value dQ and an SOC change value dSOC, and thereby obtaining and storing a second SOH value are specifically as follows: Before fast charging, keep the high voltage powered on, turn off the air conditioner, audio and other loads, let the vehicle stand still for at least the first time, open the charging port and insert the fast charging gun; put the high voltage in the keyoff state, wait for at least the second time, and then start charging, obtain the voltage rebound curve of the second waiting time period, estimate the battery OCV according to the voltage rebound curve of the second waiting time period, and obtain the initial SOC1; When the DC charging is fully charged, the battery management system delays the first time and then goes to sleep, obtains the voltage rebound curve of the battery after no current in the first time, estimates the OCV of the battery according to the voltage rebound curve of the battery after no current in the first time, and obtains the ending SOC2; or when the DC charging is in the last stage in the keyoff state, the charging is exited, the battery management system delays the first time and then goes to sleep, obtains the voltage rebound curve under no current of at least a second time period within the first time, estimates the OCV of the battery according to the voltage rebound curve under no current, and obtains the ending SOC2; Subtract the initial SOC1 from the final SOC2 to obtain dSOC; The estimated battery capacity C is calculated using the following formula, and the second SOH value is obtained according to the battery capacity: C=dQ / dSOC Among them, dQ is the charging capacity of the charging condition.

9. A battery SOC estimation system after aging based on actual vehicle operating conditions, characterized in that: include: An SOH obtaining unit, configured to obtain a first SOH value of the battery by querying a pre-calibrated cumulative discharge capacity-SOH comparison table according to the current cumulative discharge capacity of the battery, and obtain a second SOH value calculated according to the battery model, and determine the smaller of the first SOH value and the second SOH value as the current SOH value; And according to the current SOH value, obtain the current battery capacity and the current battery internal resistance; The SOC estimation value acquisition unit is used to obtain the SOC value of the previous cycle in the periodic sampling interval, the current current value of the battery, and calculate the current SOC estimation value in combination with the current battery capacity; A voltage estimation value acquisition unit, used to obtain a cell terminal voltage estimation value according to a battery model calculation formula using the current current value, the current battery internal resistance, and the current battery capacity; The SOC adjustment unit is used to compare the estimated value of the cell terminal voltage with the measured cell terminal voltage value obtained by sampling, and adjust the current SOC estimated value in combination with the correction coefficient under the current working condition to obtain an adjusted SOC value.

10. The system according to claim 9, characterized in that Further including: A second SOH value calculation unit is used to select a charging period that meets a predetermined standard under a DC charging condition, obtain a battery capacity change value dQ and an SOC change value dSOC, and obtain and store a second SOH value according to a ratio of the two; The second SOH value updating unit is used to periodically detect and determine whether there is a newly calculated second SOH value in the previous cycle. If not, query the pre-calibrated cumulative discharge amount-SOH comparison table according to the current cumulative discharge amount to obtain the corresponding SOH value, and store the corresponding SOH value as the second SOH value.

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