Lithium battery charge state correction method and related device

Abstract

The invention discloses a lithium battery state-of-charge correction method, which comprises the following steps: estimating a first SOC at a current moment based on an initial state-of-charge SOC and current information, and if a lithium battery is in a depolarization state, obtaining a change voltage of the lithium battery from the depolarization start to the current moment; according to the method and the device, the first SOC is determined according to the OCV and the SOC-OCV data table constructed in advance, the open-circuit voltage OCV of the lithium battery which is still in the depolarization state after the preset time length is predicted, then the second SOC is determined according to the OCV and the SOC-OCV data table constructed in advance, and the SOC obtained according to the OCV which is closer to the OCV when depolarization is completed is closer to the real SOC of the stage, so that the second SOC has higher precision compared with the SOC obtained according to the current OCV; and finally, taking a result closer to a true value in the first SOC and the second SOC as the SOC at the current moment, and correcting the SOC in the depolarization process, thereby effectively reducing a relatively large estimation error possibly caused by the initial SOC and a sampling error of a current sensor, and improving the calculation accuracy of the SOC when the lithium battery is in the depolarization stage.

Description

Technical Field

[0001] The present application relates to the field of lithium battery management, and specifically relates to a method for correcting the state of charge of a lithium battery and related devices. Background Art

[0002] Estimation of the state of charge (SOC) of a lithium battery can help extend the life of the lithium battery, optimize the performance of the lithium battery, improve safety, and enhance system reliability.

[0003] In related technologies, by combining the use of the ampere-hour integration method, terminal voltage correction, and open circuit voltage (OCV) correction technology, the SOC can be estimated. Among them, OCV correction refers to obtaining an accurate SOC by looking up the SOC-OCV data table through the open circuit voltage after the lithium battery has been static for a long time and reaches a fully relaxed state.

[0004] However, the conventional estimation method of SOC is affected by the current sensor error and the initial SOC error, and the error accumulates continuously over time. Moreover, when the potential of the lithium battery does not reach a fully stable state, that is, when the lithium battery is in the depolarization process, the OCV correction cannot be triggered, resulting in low accuracy of the SOC estimated by the conventional algorithm during the depolarization process. Summary of the Invention

[0005] In view of this, the present application provides a method for correcting the state of charge of a lithium battery and related devices. The present application can obtain a relatively accurate SOC of the lithium battery in the depolarization state through the changing voltage of the lithium battery, and then compare it with the first SOC estimated based on the initial SOC and current, and use the SOC close to the true value as the current SOC, realizing the SOC correction of the lithium battery in the depolarization state, effectively reducing the SOC estimation error caused by the initial SOC and current sensor sampling errors, and improving the estimation accuracy of the SOC.

[0006] To solve the above problems, the technical solution of the present application is as follows:

[0007] On the one hand, the present application provides a method for correcting the state of charge of a lithium battery, and the method includes:

[0008] Obtain the first SOC of the lithium battery at the current moment, where the first SOC is estimated based on the initial SOC and current of the lithium battery;

[0009] If the lithium battery is in the depolarization state, predict the open circuit voltage OCV of the lithium battery after a first preset duration according to the changing voltage of the lithium battery from the start of depolarization to the current moment, and the lithium battery is still in the depolarization state after the first preset duration;

[0010] Determine the second SOC of the lithium battery at the first preset time according to the OCV and the pre-constructed SOC-OCV data table;

[0011] Determine the result closer to the true value among the first SOC and the second SOC as the SOC at the current moment.

[0012] In a possible implementation manner, the predicting the open circuit voltage OCV of the lithium battery after the first preset time according to the changing voltage of the lithium battery from the start of depolarization to the current moment includes:

[0013] Obtain the duration of the lithium battery from the start of depolarization to the current moment and the changing voltage;

[0014] If the duration is greater than the second preset time, fit an exponential function according to the changing voltage of the lithium battery from the start of depolarization to the current moment;

[0015] Predict the OCV of the lithium battery after the first preset time according to the exponential function.

[0016] In a possible implementation manner, the determining the result closer to the true value among the first SOC and the second SOC as the SOC at the current moment includes:

[0017] Obtain the working condition of the lithium battery before the depolarization state;

[0018] If the working condition is discharging and the first SOC is less than the second SOC, use the second SOC as the SOC at the current moment;

[0019] If the working condition is charging and the first SOC is greater than the second SOC, use the first SOC as the SOC at the current moment.

[0020] In a possible implementation manner, the obtaining the first SOC of the lithium battery at the current moment includes:

[0021] Estimate the first SOC according to the ampere-hour integration method.

[0022] In a possible implementation manner, after obtaining the first SOC of the lithium battery at the current moment, the method further includes:

[0023] Correct the first SOC by at least one of the terminal voltage correction method and the OCV correction method.

[0024] In another aspect, the present application further provides a correction device for the state of charge of a lithium battery, and the device includes an acquisition unit, a prediction unit, a determination unit, and a correction unit:

[0025] The obtaining unit is used to obtain the first SOC of the lithium battery at the current moment, and the first SOC is estimated based on the initial SOC and current of the lithium battery;

[0026] The prediction unit is used to, if the lithium battery is in a depolarization state, predict the open circuit voltage OCV of the lithium battery after a first preset duration according to the changing voltage of the lithium battery from the start of depolarization to the current moment, and the lithium battery is still in a depolarization state after the first preset duration;

[0027] The determination unit is used to determine the second SOC of the lithium battery after a first preset duration according to the OCV and a pre-constructed SOC-OCV data table;

[0028] The correction unit is used to determine the result closer to the true value among the first SOC and the second SOC as the SOC at the current moment.

[0029] In a possible implementation manner, the prediction unit is specifically used for:

[0030] Obtain the duration of the lithium battery from the start of depolarization to the current moment and the changing voltage;

[0031] If the duration is greater than a second preset duration, fit an exponential function according to the changing voltage of the lithium battery from the start of depolarization to the current moment;

[0032] Predict the OCV of the lithium battery after a first preset duration according to the exponential function.

[0033] In a possible implementation manner, the correction unit is specifically used for:

[0034] Obtain the working condition of the lithium battery before the depolarization state;

[0035] If the working condition is discharging and the first SOC is less than the second SOC, use the second SOC as the SOC at the current moment;

[0036] If the working condition is charging and the first SOC is greater than the second SOC, use the first SOC as the SOC at the current moment.

[0037] In a possible implementation manner, the obtaining unit is specifically used for:

[0038] Estimate the first SOC according to the ampere-hour integration method.

[0039] In a possible implementation manner, the correction unit is further used for:

[0040] The first SOC is corrected by at least one of the terminal voltage correction method and the OCV correction method.

[0041] In another aspect, the present application also provides a computer device, including:

[0042] A memory for storing a computer program;

[0043] A processor for implementing the steps of the method for correcting the state of charge of the lithium battery as described above when executing the computer program.

[0044] In another aspect, the present application also provides a computer-readable medium, on which a computer program is stored, and when the computer program is processed and executed, the steps of the method for correcting the state of charge of the lithium battery as described above are implemented.

[0045] In another aspect, the present application also provides a computer program product including a computer program, which when running on a computer device causes the computer device to execute the method for correcting the state of charge of the lithium battery as described above.

[0046] The technical solution of the present application first obtains the first SOC of the lithium battery at the current moment based on the initial SOC and current of the lithium battery through a conventional estimation method, and determines the state of the lithium battery. If the lithium battery is in the state of returning to the equilibrium potential, that is, the depolarization state, the OCV of the lithium battery after the first preset duration is predicted according to the change voltage of the lithium battery from the start of depolarization to the current moment, where the setting of the first preset duration satisfies the following conditions: when the lithium battery is still in the depolarization state after the preset duration, since the OCV of the lithium battery gradually tends to be stable in the depolarization state, and the SOC obtained based on the more stable OCV can better represent the true SOC in the depolarization state, it can be known that the obtained second SOC has higher accuracy compared to the SOC found according to the OCV at the current moment. Thus, two SOC results are obtained at the current moment through the above two methods. Finally, the result closer to the true value among the first SOC and the second SOC is used as the SOC at the current moment, which can correct the SOC during the depolarization process, effectively reducing the large estimation error caused by the initial SOC and the sampling error of the current sensor, and further improving the accuracy of calculating the SOC. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings described below are only some embodiments recorded in the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0048] Figure 1 Schematic diagram of voltage change of a lithium battery provided by an embodiment of the present application;

[0049] Figure 2 Schematic flow chart of a method for correcting the state of charge of a lithium battery provided by an embodiment of the present application;

[0050] Figure 3 Schematic diagram of steps of a method for correcting the state of charge of a lithium battery provided by an embodiment of the present application;

[0051] Figure 4 Schematic diagram of a device for correcting the state of charge of a lithium battery provided by an embodiment of the present application. Detailed implementation manners

[0052] In order to enable those skilled in the art to better understand the solutions of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0053] As described in the background art, currently, most battery management systems (BMS) estimate the SOC of lithium batteries using conventional estimation methods, such as estimating the SOC by the ampere-hour integration method, and then correcting it through the terminal voltage correction method and the OCV correction method. However, the conventional estimation method is affected by the errors of the initial SOC and the current sensor sampling. Even if the initial SOC is relatively accurate, the current sampling error cannot be avoided and gradually accumulates over time, ultimately reducing the SOC estimation accuracy. Moreover, the triggering scenarios of the terminal voltage correction and the OCV correction methods are few. During the depolarization process of the battery, since the OCV of the lithium battery changes very slowly or hardly changes, the relationship between the SOC and the OCV is no longer significant, resulting in the inability to trigger the OCV correction. Therefore, the accuracy of the SOC obtained by the conventional estimation method during the depolarization stage is relatively low.

[0054] See Figure 1 As described, a schematic diagram of the voltage change of a lithium battery provided by the present application. The voltage change of the lithium battery has the following characteristics: when the lithium battery starts to discharge at a constant current from a static state (the lithium battery is in a polarized state), its voltage will first suddenly drop, then slowly drop, and finally reach a stable state. When the lithium battery returns from the constant current discharge state to a static state (the lithium battery is in a depolarized state), its voltage will first suddenly rise, then slowly rise, and finally reach a stable state. And so on, in combination with Figure 1, it can be known the voltage change of the lithium battery from being static to charging and from charging back to being static. When the current I is 0, the voltage Ut is called the open-circuit voltage. When I is not 0, Ut is called the terminal voltage.

[0055] Under normal circumstances, the depolarization process of the lithium battery, that is, from the terminal voltage to the open-circuit voltage OCV being completely stable, takes at least an hour-level time, and the lower the battery temperature, the longer the required time.

[0056] Therefore, the present application provides a method for correcting the state of charge of a lithium battery. First, based on the initial SOC and current information, a first SOC at the current moment is obtained through a conventional estimation method. When the lithium battery is in a depolarization state, the changing voltage of the lithium battery from the start of depolarization to the current moment is obtained, and the OCV of the lithium battery after a preset duration is predicted according to the changing voltage. The setting of the preset duration satisfies the following conditions: when the lithium battery is still in a depolarization state after the preset duration, then the second SOC is determined according to the OCV and the pre-constructed SOC-OCV data table. Since the SOC remains unchanged during the depolarization process until depolarization is completed, and the SOC obtained based on the OCV closer to the completion of depolarization is closer to the true SOC at this stage, it can be known that the second SOC has higher accuracy compared to the SOC obtained according to the current OCV. Thus, two SOC results are obtained at the current moment through the above two methods. Finally, the result closer to the true value among the first SOC and the second SOC is used as the SOC at the current moment, which can correct the SOC during the depolarization process, effectively reducing the large estimation error that may be caused by the initial SOC and the sampling error of the current sensor in the related art, and further improving the accuracy of calculating the SOC.

[0057] The method provided by the present application is applied to the field of lithium battery management, and can be specifically applied to the management of ternary nickel-cobalt-manganese batteries, lithium cobalt oxide batteries, lithium manganese oxide batteries, lithium iron phosphate manganese batteries, lithium titanate batteries, sodium-ion batteries, all-solid-state or semi-solid-state batteries.

[0058] See Figure 2 As shown, it is a schematic flowchart of a method for correcting the state of charge of a lithium battery provided by an embodiment of the present application. In this embodiment, a computer device can be used as an example for execution.

[0059] S101: Obtain the first SOC of the lithium battery at the current moment.

[0060] The first SOC is estimated based on the initial SOC and current of the lithium battery, is estimated according to conventional techniques, and is an uncorrected result.

[0061] Conventional techniques for estimating SOC, such as the ampere-hour integration method, Kalman Filter (KF) algorithm, Adaptive Extended Kalman Filter (AEKF) algorithm, Unscented Extended Kalman Filter (UEKF) algorithm, Double Kalman Filter (DKF), and multi-time scale filtering algorithm, etc. These conventional techniques are all affected by the errors of current sensors and the initial measured SOC error, and the errors will continuously accumulate over time, resulting in low estimation accuracy of SOC. It is necessary to combine other techniques to correct the estimated SOC to improve the accuracy of the obtained SOC.

[0062] S102: If the lithium battery is in a depolarized state, predict the open-circuit voltage OCV of the lithium battery after a first preset duration according to the changing voltage of the lithium battery from the start of depolarization to the current moment.

[0063] The changing voltage is used to identify the change of the voltage of the lithium battery from the start of depolarization to the current moment over time. This changing voltage can be divided into two parts, namely the ohmic voltage caused by the ohmic resistance and the polarization voltage / capacitance caused by the polarization resistance. Among them, the ohmic voltage changes at the moment when the lithium battery starts to depolarize, and the voltage changes during the subsequent depolarization process are all called polarization voltages. By monitoring with the BMS, it can be determined whether the lithium battery is in a depolarized state. Based on the above characteristics, according to the change of the voltage recorded by the lithium battery from the start of depolarization to the current moment, a network model can be constructed or data can be fitted to obtain a fitting curve to predict the OCV of the lithium battery still in a depolarized state at a future moment.

[0064] As an example, it is estimated that the depolarized state of the battery may last for 4 hours or longer. At the moment when the lithium battery starts to depolarize (the ohmic voltage Ur has disappeared), the terminal voltage is Ut. At the current moment, the depolarized state of the battery has lasted for 1 hour, and the polarization voltage is Up1. According to the change of the polarization voltage within 1 hour, the polarization voltage Up2 after another 2 hours or 2.5 hours can be predicted by fitting the data, and then the OCV can be determined according to the terminal voltage Ut and the polarization voltage Up2.

[0065] S103: Determine the second SOC of the lithium battery after a first preset duration according to the OCV and the pre-constructed SOC-OCV data table.

[0066] During the depolarization process, the voltage of the battery is constantly changing, but the SOC does not change. The OCV correction is usually performed when the OCV reaches a completely stable state, and the SOC is obtained by looking up the SOC-OCV data table at this time, which represents the true SOC during the depolarization process.

[0067] The SOC-OCV data table is obtained through off-line testing of charge and discharge experiments. In the pre-constructed SOC-OCV data table, as the OCV increases / decreases, the SOC continuously increases / decreases, and the voltage change of the lithium battery during the depolarization process has certain characteristics. Combining Figure 1 As shown, the voltage will suddenly drop / rise and then slowly drop / rise. Therefore, the closer it is to the time when the voltage is completely stable, the closer the SOC obtained according to the OCV at this time is to the true SOC during the depolarization process.

[0068] Therefore, the SOC determined according to the predicted OCV at the first preset duration represents the true SOC of the lithium battery during the depolarization stage better than the SOC determined according to the current OCV. Moreover, the SOC result can be obtained based on the OCV change information during the depolarization stage. This method is not affected by the initial SOC or the sampling error of the current sensor.

[0069] S104: Determine the result closer to the true value between the first SOC and the second SOC as the SOC at the current moment.

[0070] When the battery is in the depolarization state, two SOCs can be obtained at the current moment through two methods. The first SOC is affected by the initial SOC and the current, and the second SOC is predicted based on the voltage characteristics, and has less relationship with the battery capacity and temperature. When it is found that there are large errors in current sampling or the initial SOC, or the lithium battery is in an aging state, or under low-temperature conditions, it is considered that the second SOC is closer to the true value, and the second SOC is used as the SOC at the current moment. In other cases, it can still be considered that the first SOC is closer to the true value. Or, according to the working conditions of the lithium battery before entering the depolarization state, combined with the voltage change characteristics of the lithium battery, it can be determined which SOC is closer to the true SOC.

[0071] Therefore, since the SOC determined according to the OCV closer to the completion state of depolarization represents the true SOC during the depolarization state better, it can be known that the second SOC has higher accuracy than the SOC determined according to the current OCV. Thus, two SOC results are obtained at the current moment through the above two methods. Finally, the result closer to the true value between the first SOC and the second SOC is used as the SOC at the current moment, which can correct the SOC during the depolarization process, effectively reducing the large estimation error that may be caused by the initial SOC and the sampling error of the current sensor during the depolarization process, and further improving the accuracy of calculating the SOC.

[0072] In a possible implementation, step S102 can be implemented through the following steps:

[0073] A1: Obtain the duration from the start of depolarization of the lithium battery to the current moment and the changing voltage.

[0074] A2: If the duration is greater than the second preset duration, fit an exponential function based on the changing voltage of the lithium battery from the start of depolarization to the current moment.

[0075] A3: Predict the OCV of the lithium battery after the first preset duration according to the exponential function.

[0076] Combined Figure 1 As shown, at the moment when the lithium battery starts to enter the depolarization state, the Ohmic voltage will change sharply, and the changing voltage during the subsequent depolarization process is the polarization voltage. After the lithium battery enters the depolarization state, the curve of the polarization voltage is approximately an exponential function curve. By fitting the changing data of the polarization voltage within a few minutes after the lithium battery just enters the depolarization state with an exponential function, the prediction of the polarization voltage at a future time can be realized.

[0077] The fitted exponential function requires more fitting data to have a certain prediction accuracy. Through the BMS, the duration of the depolarization state of the lithium battery and the information of the changing voltage can be obtained. The second preset duration can be set to a few minutes, such as 3 minutes or 5 minutes, etc. If the lithium battery has entered the depolarization state for more than the second preset duration, fit the data information of the changing voltage obtained during this period with an exponential function, and predict the OCV of the lithium battery after the first preset duration based on the fitted exponential function.

[0078] Thus, by setting the second preset duration, the possibility of obtaining a second SOC with a large error based on less changing voltage data when the lithium battery just enters the depolarization state is avoided, the invalid comparison between the first SOC and the second SOC is avoided, thereby improving the calculation efficiency of the SOC, and based on the changing characteristics of the lithium battery voltage during the depolarization stage, the data information of the changing voltage is fitted with an exponential function, effectively improving the prediction efficiency.

[0079] In a possible implementation, step S104 is specifically implemented through the following steps:

[0080] B1: Obtain the working condition of the lithium battery before the depolarization state.

[0081] B2: If the working condition is discharging and the first SOC is less than the second SOC, use the second SOC as the SOC at the current moment.

[0082] B3: If the working condition is charging and the first SOC is greater than the second SOC, use the first SOC as the SOC at the current moment.

[0083] The operating conditions that cause the depolarization state of the lithium battery include charging or discharging. Combining Figure 1 with the voltage change characteristics in After the lithium battery discharges and enters the depolarization state, the voltage will steadily rise until it stabilizes. The SOC determined by the OCV when depolarization is completed is the true SOC of the polarization state. And according to the characteristics that SOC increases / decreases as OCV increases / decreases in the SOC-OCV data table, it can be determined that the second SOC is less than the true SOC in the depolarization state. After the lithium battery charges and enters the depolarization state, the voltage will steadily decline until it stabilizes. From this, it can be determined that the second SOC is greater than the true SOC in the depolarization state.

[0084] Through BMS monitoring, it can be determined whether the lithium battery is in a charging state or a discharging state before entering the depolarization state. If the lithium battery enters the depolarization state from the discharging state and the first SOC is less than the second SOC, it can be determined that the second SOC is closer to the true SOC, and the second SOC is used as the SOC at the current moment to correct the first SOC estimated according to the conventional method. Similarly, if the lithium battery enters the depolarization state from the charging state and the first SOC is greater than the second SOC, it can be determined that the first SOC is closer to the true SOC, and the first SOC is used as the SOC at the current moment to correct the first SOC.

[0085] As an example, when the lithium battery enters the depolarization state from the discharging state, at the moment when the lithium battery starts to depolarize (the Ohmic voltage Ur has disappeared), the terminal voltage is Ut. According to the change of the polarization voltage after the lithium battery enters the depolarization state, it is predicted that the polarization voltage is Up2 after the first preset time duration. Then the OCV after the first preset time duration is Uocv = Ut + Up2. Then, according to the pre-constructed SOC-OCV data table, the second SOC corresponding to this OCV is obtained. If the second SOC is 90% and the estimated first SOC is 80%, since 80% < 90%, the SOC at the current moment is corrected to 90%.

[0086] Therefore, by comparing the two SOC results obtained at the current moment according to the voltage change characteristics, the SOC at the current moment is corrected without considering whether the current or the initial SOC has errors or the influence of the temperature and state of the lithium battery on the performance of the lithium battery, which has higher efficiency. And compared with the method that needs to comprehensively consider many factors for SOC correction, the SOC determined according to the voltage change characteristics has higher accuracy, thus ensuring the reliability and safety of the lithium battery.

[0087] In a possible implementation manner, obtaining the first SOC of the lithium battery at the current moment includes:

[0088] Estimate the first SOC according to the ampere-hour integration method.

[0089] The calculation method of the ampere-hour integration method is simple, requires low computing resources, and has strong real-time performance. Estimating the SOC by the ampere-hour integration method effectively improves the efficiency of SOC estimation and correction.

[0090] In a possible implementation, after obtaining the first SOC of the lithium battery at the current moment, the method further includes:

[0091] Correct the first SOC by at least one of the terminal voltage correction method and the OCV correction method.

[0092] The terminal voltage correction mainly includes full charge correction (when the monomer voltage rises to a certain threshold during charging, the SOC is corrected to 100%), zero point / full discharge correction (when the monomer voltage drops to a certain threshold during discharge, the SOC is corrected to 0%). The OCV correction means that when the lithium battery completes the depolarization state, that is, when the OCV reaches complete stability, the true SOC at this moment is obtained by looking up the SOC-OCV data table of the OCV, and the SOC estimated at this moment is corrected.

[0093] The terminal voltage correction method, the OCV correction method, and the method for correcting the SOC during the depolarization process do not conflict. By combining multiple correction methods, the estimation error in different scenarios can be reduced, thereby effectively improving the estimation accuracy of the SOC.

[0094] For a clearer description of this lithium battery SOC correction method, see Figure 3 , which is a schematic diagram of the steps of a lithium battery state of charge correction method proposed in an embodiment of this application.

[0095] Step 1: Estimate the SOC result according to the ampere-hour integration method and record it as SOC_est.

[0096] Step 2: Determine whether the current of the lithium battery is almost 0 and has lasted for Δt time, or whether the vehicle has been dormant for Δt time and is in the just-woken state.

[0097] The conditions for triggering SOC correction are: one is that the current is almost 0 and has maintained this working condition for Δt time, where Δt can be a few minutes, such as 3 minutes, 5 minutes, 10 minutes, and the current range can be appropriately relaxed to ±1A, ±3A, or ±5A. At this time, the change in the ohmic voltage is almost 0, and the lithium battery is in the depolarization process; the other is that the whole vehicle has been dormant for a few minutes, but is currently in the just-woken state. When the whole vehicle is dormant, the current is almost 0, the change in the ohmic voltage is also almost 0, and the lithium battery must also be in the depolarization process.

[0098] Step 3: Determine whether the vehicle condition before the current almost zero current or before dormancy is charging or discharging.

[0099] If the current vehicle condition meets the condition of A2, determine whether the vehicle condition before the current almost zero current or before dormancy is charging or discharging. If the previous vehicle condition or the vehicle condition before dormancy is discharging, the voltage of the battery is in a continuous rising process; if the previous vehicle condition or the vehicle condition before dormancy is charging, the voltage of the battery is in a continuous falling process.

[0100] Step 4: Predict the OCV after a period of time and determine SOC_tab according to the SOC-OCV data table.

[0101] If the current vehicle condition meets the condition of A2, obtain the terminal voltage Ut (ohmic voltage Ur has been removed) when the lithium battery just enters the depolarization state. Assume that the depolarization voltage Up1 has been removed within △t in step A2, record the change of the depolarization voltage within △t, fit an exponential function based on the change data of the depolarization voltage within △t, and predict the depolarization voltage Up2 that is removed again when the voltage reaches complete stability, and obtain the predicted open-circuit voltage Uocv = Ut ± Up2. If the previous vehicle condition is discharging, use Uocv = Ut + Up2 to query the SOC-OCV data table to obtain SOC_tab1, and at this time SOC_tab1 will be slightly lower than the true SOC; if the previous vehicle condition is charging, use Uocv = Ut - Up2 to query the SOC-OCV data table to obtain SOC_tab2, and at this time SOC_tab2 will be slightly higher than the true SOC. In addition, if the condition of A2 is continuously met, continuously query the SOC-OCV data table to obtain SOC_tab, and the longer the duration, the closer SOC_tab is to the true SOC, and the better the correction effect.

[0102] Step 5: Compare SOC_tab with SOC_est and decide whether to perform correction according to the situation.

[0103] Compare SOC_tab with SOC_est estimated by ampere-hour integration. If the previous vehicle condition is discharging and SOC_est < SOC_tab, then let SOC_est = SOC_tab; if the previous vehicle condition is charging and SOC_est > SOC_tab, then let SOC_est = SOC_tab; in other cases, no correction is performed. In this way, the SOC estimation error of the ampere-hour integration method can be reduced to a certain extent.

[0104] Based on the above embodiments, the embodiments of the present application further provide a correction device for the state of charge of a lithium battery. Refer to Figure 4 As described, it is a schematic diagram of a correction device 400 for the state of charge of a lithium battery provided by the embodiments of the present application. The device includes an acquisition unit 401, a prediction unit 402, a determination unit 403, and a correction unit 404:

[0105] The obtaining unit is used to obtain the first SOC of the lithium battery at the current moment, and the first SOC is estimated based on the initial SOC and current of the lithium battery.

[0106] The prediction unit is used to, if the lithium battery is in a depolarization state, predict the open circuit voltage OCV of the lithium battery after a first preset time duration according to the changing voltage of the lithium battery from the start of depolarization to the current moment, and the lithium battery is still in a depolarization state after the first preset time duration.

[0107] The determining unit is used to determine the second SOC of the lithium battery after a first preset time duration according to the OCV and a pre-constructed SOC-OCV data table.

[0108] The calibration unit is used to determine the result closer to the true value among the first SOC and the second SOC as the SOC at the current moment.

[0109] Since the SOC determined according to the OCV closer to the depolarization completion state can better represent the true SOC in the depolarization state, it can be known that the second SOC has higher accuracy compared to the SOC determined according to the OCV at the current moment. Thus, two SOC results are obtained at the current moment through the above two methods, and finally the result closer to the true value among the first SOC and the second SOC is used as the SOC at the current moment, which can calibrate the SOC during the depolarization process, effectively reducing the large estimation error that may be caused by the initial SOC and current sensor sampling error during the depolarization process, and further improving the accuracy of calculating the SOC.

[0110] In a possible implementation manner, the prediction unit is specifically used for:

[0111] Obtain the time duration of the lithium battery from the start of depolarization to the current moment and the changing voltage;

[0112] If the time duration is greater than a second preset time duration, fit an exponential function according to the changing voltage of the lithium battery from the start of depolarization to the current moment;

[0113] Predict the OCV of the lithium battery after a first preset time duration according to the exponential function.

[0114] Thus, by setting the second preset time duration, the possibility of obtaining a second SOC with a large error based on less changing voltage data when the lithium battery just enters the depolarization state is avoided, and the invalid comparison between the first SOC and the second SOC is avoided, thereby improving the calculation efficiency of the SOC. And based on the changing characteristics of the lithium battery voltage during the depolarization stage, the data information of the changing voltage is fitted based on the exponential function, effectively improving the prediction efficiency.

[0115] In a possible implementation, the correction unit is specifically configured to:

[0116] Obtain the working condition before the depolarization state of the lithium battery;

[0117] If the working condition is discharging and the first SOC is less than the second SOC, use the second SOC as the SOC at the current moment;

[0118] If the working condition is charging and the first SOC is greater than the second SOC, use the first SOC as the SOC at the current moment.

[0119] Thus, by comparing the two SOC results obtained at the current moment according to the voltage change characteristics, the SOC at the current moment is corrected, without considering whether the current or the initial SOC has errors or the influence of the temperature and state of the lithium battery on the performance of the lithium battery, which has higher efficiency. And compared with the method that needs to comprehensively consider many factors for SOC correction, the SOC determined according to the voltage change characteristics has higher accuracy, thus ensuring the reliability and safety of the lithium battery.

[0120] In a possible implementation, the obtaining unit is specifically configured to:

[0121] Estimate the first SOC according to the ampere-hour integration method.

[0122] The ampere-hour integration method has a simple calculation method, low calculation resource requirements, and strong real-time performance. By estimating the SOC through the ampere-hour integration method, the efficiency of SOC estimation and correction is effectively improved.

[0123] In a possible implementation, the correction unit is further configured to:

[0124] Correct the first SOC by at least one of the terminal voltage correction method and the OCV correction method.

[0125] Thus, by combining multiple correction methods, the estimation error in different scenarios can be reduced, thereby effectively improving the estimation accuracy of the SOC.

[0126] Based on the above embodiments, an embodiment of the present application provides a computer device, including:

[0127] A memory for storing a computer program;

[0128] A processor for implementing the steps of the method for correcting the state of charge of the lithium battery as described above when executing the computer program.

[0129] Based on the above embodiments, an embodiment of the present application further provides a computer-readable medium, on which a computer program is stored, and when the computer program is processed and executed, the steps of the method for correcting the state of charge of the lithium battery as described above are implemented.

[0130] Based on the above embodiments, an embodiment of the present application further provides a computer program product including a computer program, which when running on a computer device, causes the computer device to execute the steps of the method for correcting the state of charge of the lithium battery as described above.

[0131] It should be noted that the various embodiments in this specification are described in a progressive manner, and the key point of each embodiment is to illustrate the differences from other embodiments. The same or similar parts among the various embodiments can be referred to each other. For the systems or devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple, and the relevant parts can be referred to the descriptions in the method part.

[0132] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for correcting the state of charge of a lithium battery, characterized in that: The method comprises: Obtaining a first SOC of the lithium battery at a current moment, where the first SOC is estimated based on an initial SOC and current of the lithium battery; If the lithium battery is in a depolarized state, predict the open circuit voltage (OCV) of the lithium battery after a first preset time period according to the voltage change of the lithium battery from the beginning of depolarization to the current moment, and the lithium battery is still in a depolarized state after the first preset time period; Determine a second SOC of the lithium battery after a first preset time period according to the OCV and a pre-constructed SOC-OCV data table; The one of the first SOC and the second SOC that is closer to the true value is determined as the SOC at the current moment.

2. The method according to claim 1, characterized in that The step of predicting the open circuit voltage OCV of the lithium battery after a first preset time period according to the voltage change of the lithium battery from the beginning of depolarization to the current moment includes: Obtaining the duration of the lithium battery from the start of depolarization to the current moment and the changed voltage; If the duration is greater than a second preset duration, fitting an exponential function according to the voltage change of the lithium battery from the beginning of depolarization to the current moment; The OCV of the lithium battery after a first preset time period is predicted according to the exponential function.

3. The method according to claim 2, characterized in that The determining the result of the first SOC and the second SOC which is closer to the true value as the SOC at the current moment includes: Obtaining the operating condition of the lithium battery before the depolarization state; If the operating condition is discharging, and the first SOC is less than the second SOC, the second SOC is used as the SOC at the current moment; If the operating condition is charging, and the first SOC is greater than the second SOC, the first SOC is used as the SOC at the current moment.

4. The method according to claim 1, characterized in that: The obtaining of the first SOC of the lithium battery at the current moment includes: The first SOC is estimated according to the ampere-hour integration method.

5. The method according to claim 1, characterized in that After obtaining the first SOC of the lithium battery at the current moment, the method further includes: The first SOC is corrected by at least one of a terminal voltage correction method and an OCV correction method.

6. A device for correcting the state of charge of a lithium battery, characterized in that: The device comprises an acquisition unit, a prediction unit, a determination unit and a correction unit: The acquisition unit is used to acquire a first SOC of the lithium battery at a current moment, where the first SOC is estimated based on an initial SOC and a current of the lithium battery; The prediction unit is used to predict the open circuit voltage OCV of the lithium battery after a first preset time period if the lithium battery is in a depolarized state, based on the voltage change of the lithium battery from the beginning of depolarization to the current moment, and the lithium battery is still in a depolarized state after the first preset time period; The determining unit is used to determine a second SOC of the lithium battery after a first preset time period according to the OCV and a pre-constructed SOC-OCV data table; The correction unit is used to determine the result of the first SOC and the second SOC that is closer to the true value as the SOC at the current moment.

7. The device according to claim 6, characterized in that The prediction unit is specifically used for: Obtaining the duration of the lithium battery from the start of depolarization to the current moment and the changed voltage; If the duration is greater than a second preset duration, fitting an exponential function according to the voltage change of the lithium battery from the beginning of depolarization to the current moment; The OCV of the lithium battery after a first preset time period is predicted according to the exponential function.

8. A computer device, characterized in that: The computer device comprises a processor and a memory: The memory is used to store computer programs; The processor is configured to execute the method according to any one of claims 1 to 5 according to the computer program.

9. A computer-readable storage medium, characterized in that: The computer-readable storage medium is used to store a computer program, and when the computer program is executed by a computer device, the method according to any one of claims 1 to 5 is implemented.

10. A computer program product comprising a computer program, which, when executed on a computer device, causes the computer device to execute the method according to any one of claims 1 to 5.

Images