WO2020143193A1 - Method, device, and computer-readable storage medium for estimating charge state of battery - Google Patents

Abstract

Provided are a method, a device, and computer-readable storage medium for estimating the charge state of a battery, wherein the method includes: in response to the current operating condition being a matching operating condition, identifying the parameter value of the first-order RC equivalent circuit model of the power battery online, and obtaining the charge state estimated by the model on the basis of the parameter value (100); estimating the charge state of the power battery using the ampere-hour integration method (200); and on the basis of the relationship between the charge state estimated by the model and the charge state of the power battery estimated by using the ampere-hour integration method, correcting the charge state of the power battery estimated by using the ampere-hour integration method (300). The technical solution for estimating the charge state of the battery proposed in the embodiment uses the parameter value of the specific operating condition to realize the accumulated error correction of the ampere-hour integration, eliminating the accumulated error of long-term operation in the prior ampere-hour integration method, avoiding the situation that online identifying parameter of the device under complex operating condition may cause large errors or even divergence and error correction.

Description

Method, equipment and computer-readable storage medium for estimating battery state of charge Technical field

The invention belongs to the technical field of power batteries, and in particular relates to a method, equipment and computer-readable storage medium for estimating the state of charge of a battery.

Background technique

With the current development of the new energy industry, pure electric vehicles are becoming more and more popular, and people's requirements for the performance, function, and safety of electric vehicles are constantly increasing. Power batteries are the core components of electric vehicles, and the battery management system BMS that manages power batteries is becoming increasingly demanding. The state-of-charge SOC reflects the remaining capacity state of the power battery. The accuracy of the battery management system BMS estimation of the power battery SOC is of great significance for improving the safety and reliability of the battery, improving the battery energy utilization rate, and extending the battery life.

The estimation methods of state of charge SOC mainly include ampere-hour integration method, open circuit voltage (OCV) method, Kalman filter method and neural network method. Among them, the ampere-hour integration method is the most important method for current electric vehicle applications due to its low cost and convenient measurement. However, its accuracy is greatly affected by the initial SOC and current sampling accuracy, and the accumulated error for long-term operation cannot be eliminated. The open circuit voltage method is only applicable to the long-term stationary working conditions of the vehicle, and is usually combined with the ampere-hour integration method to modify the initial SOC, but it still cannot solve the cumulative error of the ampere-hour integration discharge process. The Kalman filter algorithm is mainly based on the recursive calculation of the battery equivalent circuit model, which requires high model parameter accuracy and a large amount of calculation. In practical applications, certain working conditions are easily divergent.

Therefore, it is necessary to study the technical solution to eliminate the cumulative error existing in the ampere-hour integration method.

Summary of the invention

In order to solve the technical problem of the cumulative error existing in the ampere-hour integration method, the embodiments of the present invention provide a method, device and computer-readable storage medium for estimating the state of charge of the battery, which can effectively eliminate the long-term existence of the ampere-hour integration method Accumulated running error.

In the first aspect of the present invention, a method for estimating the state of charge of the battery is proposed. The method includes:

In response to the current operating condition being a matching operating condition, the parameter value of the first-order RC equivalent circuit model of the power battery is identified online, and based on the parameter value, the estimated state of charge of the model is obtained; wherein, the matching operating condition represents the current The actual working condition parameter value of the working condition matches the preset parameter value;

Estimate the state of charge of the power battery using the ampere-hour integration method; and

Based on the relationship between the state-of-charge estimated by the model and the state-of-charge estimated by the ampere-hour integration method, the state-of-charge of the power battery estimated by the ampere-hour integration method is corrected.

In some embodiments of the first aspect, the obtaining the state of charge estimated by the model includes: based on the parameter value, obtaining the polarization voltage and the ohmic voltage of the power battery under the matching operating conditions, and calculating the corresponding Open circuit voltage, according to the calculated open circuit voltage through the relationship table formed by the open circuit voltage and the state of charge, to find the corresponding state of charge as the estimated state of charge of the model;

The estimation of the state-of-charge of the power battery using the ampere-hour integration method includes: estimating the state-of-charge of the power battery at the current time using the ampere-hour integration method based on the working condition parameter value obtained in real time at the current time; and

The modification of the state of charge of the power battery estimated by the ampere-hour integration method includes: in response to the difference between the state of charge at the current moment and the state of charge estimated by the model exceeding the designed error value Using the difference as feedback, the state of charge of the power battery estimated by the ampere-hour integration method is corrected.

In some embodiments of the first aspect, the method further includes:

Obtain the current value of the power battery in the first time period in real time, and determine the current working condition of the power battery;

Comparing the current value of the first time period with the pre-calibrated operating current curve under the current operating conditions, and judging the similarity between the current value of the first time period and the pre-calibrated operating current curve ;as well as

In response to the similarity being within the threshold range, it is determined that the current operating condition belongs to the matching operating condition.

In some embodiments of the first aspect, the method further includes:

In response to the current working condition belonging to the matching working condition, the current value and the voltage value of the power battery belonging to the matching working condition in the second time period are acquired in real time, based on the current value and the voltage value of the power battery in the second time period, Online identification of the parameter value of the first-order RC equivalent circuit model under the current working condition; the second time period coincides with the first time period or is a different time period.

In some embodiments of the first aspect, the method further includes:

Obtain the current value and voltage value of the power battery at the current time in real time, and obtain the polarization voltage and the ohmic voltage of the power battery under the matching operating conditions according to the current value and the voltage value at the current time and the parameter value, and according to the basis Erhoff's law, calculate the corresponding open circuit voltage, and find the corresponding state of charge in the relationship table between the open circuit voltage and the state of charge according to the calculated open circuit voltage, as the state of charge estimated by the model; at the same time, according to the The current value and initial state of charge of the current moment, using the ampere-hour integration method, to estimate the state of charge of the power battery at the current moment;

In response to the difference between the state-of-charge at the current moment and the state-of-charge estimated by the model exceeding the designed error value, the difference is used as feedback to evaluate the power battery’s Correct the state of charge.

In some embodiments of the first aspect, the modification of the state of charge of the power battery estimated by the ampere-hour integration method includes:

An ampere-hour integration correction factor is introduced into the ampere-hour integration method, and the ampere-hour integration correction factor is related to the relationship; based on the ampere-hour integration correction factor, the charge of the power battery estimated by the ampere-hour integration method is corrected status.

In some embodiments of the first aspect, wherein the relationship between the state-of-charge estimated by the model and the state-of-charge estimated by the ampere-hour integration method is the state-of-charge estimated by the model And the difference between estimating the state of charge of the power battery using the ampere-hour integration method;

The relationship between the state-of-charge estimated based on the model and the state-of-charge estimated using the ampere-hour integration method to modify the state-of-charge of the power battery estimated using the ampere-hour integration method includes:

Obtain the current value of the power battery in real time, use the ampere-hour integration method to estimate the state of charge of the power battery based on the current value and the initial state of charge, and use it as the reference state of charge;

Obtain the current ampere-hour integration correction coefficient at the current time, and adjust the current current value using the current-time ampere-hour integration correction coefficient as a multiple; according to the adjusted current current value and initial state of charge, use the ampere-hour integration method, Estimate the state of charge of the power battery and use it as the current state of charge;

In response to that the difference between the current state of charge and the reference state of charge is not within an error range compared to the difference, the step of returning to the real-time acquisition of the current value of the power battery is continued until all The difference between the current state of charge and the reference state of charge is within the error range compared to the difference.

In some embodiments of the first aspect, the obtaining the current-time integral correction factor includes: obtaining the current-time integral correction factor based on the user experience adjustment coefficient; the user experience adjustment coefficient characterizes user expectations How fast the state of charge changes;

The method further includes: in response to the user changing the user experience adjustment coefficient, re-acquiring the current time ampere point correction coefficient.

In a second aspect of the present invention, a device for estimating the state of charge of a battery is provided, including: a processor; and a memory storing instructions that when executed by the processor cause the device to perform according to the present invention The method described in the first aspect.

In a third aspect of the present invention, a computer-readable storage medium is provided which stores machine-readable instructions, which when executed by the machine causes the machine to execute the description according to the first aspect of the invention method.

Beneficial effect of the present invention: The technical solution for estimating the state of charge of the battery proposed by the embodiment of the present invention is mainly based on the ampere-hour integration method, and at the same time, combined with the fusion algorithm based on the first-order RC equivalent circuit model of the power battery to identify the parameters online, using The relationship between the two corrects the state of charge of the power battery estimated by the ampere-hour integration method, which not only takes advantage of the high accuracy of the SOC calculated by the ampere-hour integration method in a short time, but also makes full use of the first-order The RC equivalent circuit model has the characteristics of higher SOC estimation accuracy for certain specific working conditions, thereby realizing the correction of the cumulative error of ampere-hour integration, eliminating the accumulated error of long-term operation existing in the existing ampere-hour integration method, and avoiding the equipment (For example, vehicles) Online identification of parameters under complex operating conditions may cause large errors or even divergence, resulting in erroneous corrections.

BRIEF DESCRIPTION

FIG. 1 shows a flowchart of a method for estimating the state of charge of a battery according to an embodiment of the present invention;

2 shows a schematic structural diagram of a first-order RC equivalent circuit model according to an embodiment of the present invention;

3 shows a schematic diagram of a current value and a pre-calibrated operating current curve according to an embodiment of the present invention;

4 shows an exemplary diagram of a U _OCV -SOC table according to an embodiment of the invention;

5 shows a flowchart of a method for estimating the state of charge of a battery according to another embodiment of the present invention;

6 shows a flowchart of a method for estimating the state of charge of a battery according to yet another embodiment of the present invention;

7 shows a flowchart of a method for estimating the state of charge of a battery according to yet another embodiment of the present invention;

8 shows a flowchart of a method for obtaining a state of charge of a power battery at a current time in a method for estimating a state of charge of a battery according to still another embodiment of the present invention;

9 shows a schematic diagram of actual current in different SOC segments of a real vehicle NEDC operating condition in a method for estimating a state of charge of a battery according to still another embodiment of the present invention;

10 shows an exemplary diagram of ohmic internal resistances of different SOC segments identified under NEDC operating conditions in a method for estimating the state of charge of a battery according to still another embodiment of the present invention;

11 shows an example diagram of the ohmic internal resistance and polarization internal resistance of different SOC segments identified under NEDC operating conditions in a method for estimating the state of charge of a battery according to still another embodiment of the present invention;

12 shows an exemplary diagram of the polarization capacitances of different SOC segments identified under NEDC operating conditions in a method for estimating the state of charge of a battery according to still another embodiment of the present invention;

13 shows an example diagram of online estimation of polarization voltages of different SOC segments under NEDC operating conditions in a method for estimating the state of charge of a battery according to still another embodiment of the present invention;

14 shows a comparison diagram between an open-circuit voltage calculated online at different SOC segments and an actual voltage under NEDC operating conditions in a method for estimating the state of charge of a battery according to yet another embodiment of the present invention;

FIG. 15 shows the state of charge SOC1 estimated according to the ampere-hour integration method and the state of charge SOC2 estimated according to the first-order RC equivalent circuit model in the method of estimating the state of charge of the battery according to still another embodiment of the present invention. Example diagram of

FIG. 16 shows a flowchart of a method for estimating the state of charge of a battery according to another embodiment of the present invention.

detailed description

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail in conjunction with specific embodiments and with reference to the accompanying drawings. However, those skilled in the art know that the present invention is not limited to the drawings and the following embodiments.

An embodiment of the present invention provides a method for estimating the state of charge (SOC) of a battery, including:

In step 100, in response to the current operating condition being a matching operating condition, the parameter value of the first-order RC equivalent circuit model of the power battery is identified online, and based on the parameter value, the state of charge estimated by the model is obtained; wherein, the Matching working condition means that the actual working condition parameter value of the current working condition matches the preset parameter value.

Since this embodiment performs online identification of the first-order RC equivalent circuit model online identification parameter values under matching working conditions, it is possible to avoid the divergence of the battery model in the Kalman filter method from the source, and the calculation accuracy is greatly deviated under individual working conditions Improve the accuracy of the identification results.

In this embodiment, the working condition parameter value includes at least a power battery voltage value and a power battery current value. In one embodiment, the working condition parameter value further includes the current power-on time and the previous power-off time used to characterize the resting time of the power battery. In another embodiment, the working condition parameter value may further include the latest state-of-charge value stored at the previous power-up. It should also be understood that the working condition parameter value may also include other working condition parameter values that are favorable for estimating the state of charge of the battery. In one embodiment, the battery management system (BMS) has voltage and current sampling functions. The voltage value of the power battery and the current value of the power battery can be collected in real time by a battery management system (BMS).

In addition, in some embodiments, in step 100, a battery management system (BMS) or other collection device may be used to collect the voltage and current values of the power battery during a period of time (such as 1 minute or half a minute) under matching conditions, Online identification of the parameter values of the first-order RC equivalent circuit model under the matching conditions. The period of time can be selected according to the user's driving habits and driving route, combined with actual operating conditions, so that the current value collected during the period of time is more similar to the pre-calibrated operating condition current curve, and can effectively avoid Karl The divergence of the Mann filter method under certain operating conditions further improves the accuracy of the identification results.

In one embodiment, the first-order RC equivalent circuit model can use the Thevenin model, as shown in FIG. 2, including the open circuit voltage U _OCV , the ohmic internal resistance R _{0 in} series with the open circuit voltage, and the polarization internal resistance R ₁ and The first-order RC structure formed by the parallel connection of the polarization capacitor C ₁ ; the first-order RC structure is connected in series with the open circuit voltage U _OCV and the ohmic internal resistance R ₀ . The parameters of the first-order RC equivalent circuit model include the ohmic internal resistance R ₀ , the polarization internal resistance R _1, and the polarization capacitance C ₁ in the first-order RC equivalent circuit model. The voltage across the first-order RC structure is called the polarization voltage U _P , and the voltage across the ohmic internal resistance R ₀ is called the ohmic voltage U _0. According to the first-order RC equivalent circuit model and Kirchhoff’s law, the open circuit voltage U _OCV It is equal to the sum of the ohmic voltage U ₀ , the polarization voltage U _P and the acquired voltage value V.

Further, in step 100, based on the parameter values of the first-order RC equivalent circuit model identified online under the matching conditions, the polarization voltage and ohmic voltage of the power battery under the matching conditions are obtained, and then according to the real-time Obtain the voltage value, calculate the corresponding open circuit voltage, and find the corresponding load according to the calculated open circuit voltage through the relationship table between the open circuit voltage and the state of charge (that is, U _OCV -SOC table, or OCV-SOC table) The state of charge is the state of charge estimated by the model. In the embodiment, based on the parameter values of the first-order RC equivalent circuit model identified online under the matching operating conditions, the polarization voltage and the ohmic voltage of the power battery under the matching operating conditions are obtained by calculation Open circuit voltage, so there is no need to recalculate the open circuit voltage using least squares vector machine and other methods, which can greatly reduce the amount of calculation.

In addition, in this embodiment, an estimation method such as Kalman filtering method and least square method can be used to online identify the parameter value of the first-order RC equivalent circuit model under the matching condition.

The estimation can also be further performed by using a recursive least squares method with forgetting factors.

In some application scenarios, before step 100, a device (eg, a vehicle) where the power battery is located is powered on, and the battery management system (BMS) included in the device performs a self-test after the device is powered on. In one embodiment, when the self-test result is normal, the battery management system (BMS) obtains the operating parameter value of the power battery.

In an embodiment, determining whether the current operating condition is a matching operating condition may include: matching the current value of the power battery included in the real-time acquired operating parameter value with the pre-calibrated operating current curve, and determining the real-time acquired current value and The similarity of the pre-calibrated operating condition current curve; in response to the similarity being within the threshold, the corresponding operating condition belongs to the matching operating condition, otherwise it does not. The judgment operation may be completed by a battery management system (BMS). For example, the coordinate values and corresponding working conditions of the pre-calibrated operating condition current curve are stored in the form of a table in the Flash memory of the battery management system (BMS). The battery management system (BMS) collects in real time a period of time under an actual operating condition Current value, the collected current value is stored in an array, the current value stored in the array and the pre-calibrated working condition current curve stored in the Flash memory are coordinated under the working condition that matches the actual working condition In contrast, when the difference between the two is within the threshold range, the actual operating conditions belong to the matching operating conditions, and vice versa do not. Figure 3 shows a schematic diagram of the current value under actual working conditions and the pre-calibrated working condition current curve. The dotted line in the figure represents the pre-calibrated working condition current curve, and the solid line represents the curve formed by the current value obtained under actual working conditions. It can be intuitively understood from the figure that in the areas of uphill deceleration conditions, areas of waiting conditions and areas of constant speed conditions, the obtained current value has a high similarity to the pre-calibrated condition current curve. The applicant found through verification tests that, under the situation shown in the figure, the matching working conditions include: deceleration uphill conditions, waiting conditions and uniform speed conditions.

In step 200, the ampere-hour integration method is used to estimate the state of charge of the power battery.

In one embodiment, according to the initial state of charge of the power battery and the current value of the power battery obtained in real time at the current time, an ampere-hour integration method is used to estimate the state of charge of the power battery at the current time. Further, in an embodiment, the initial state of charge of the power battery can be obtained by determining whether the time interval between the current power-on time and the previous power-off time exceeds a preset value, if the time If the interval exceeds the preset value, the corresponding state of charge is searched in the relationship table (ie, U _OCV -SOC table) composed of the open circuit voltage and the state of charge according to the voltage value included in the obtained working condition parameter value of the power battery, As the initial state of charge of the power battery; if the time interval does not exceed the preset value, the acquired latest state of charge value stored at the previous power-on is used as the initial state of charge of the power battery. Figure 4 shows an example of a U _OCV -SOC table. By knowing the U _OCV -SOC table, the corresponding state of charge can be queried.

And in step 300, based on the relationship between the state of charge estimated by the model and the state of charge estimation of the power battery using the ampere-hour integration method, the state of charge of the power battery estimated by the ampere-hour integration method is performed. Fix.

In one embodiment, the relationship is the difference between the state-of-charge estimated by the model and the state-of-charge estimated by the ampere-hour integration method. The step 300 may include: in response to the difference between the state-of-charge at the current moment and the state-of-charge estimated by the model exceeding the designed error value, using the difference as feedback to estimate the ampere-hour integration method The state of charge of the power battery is corrected. In this embodiment, the designed error value can be set according to different operating conditions. For example, in the uphill deceleration mode, the designed error value can be selected in the range of 1 to 3%; in the waiting mode, the designed error value can be selected in the range of 3 to 5%. In the uniform speed mode, the design The error value can be selected from 6 to 14%. It can be understood that the design error value can be designed according to factors such as the power battery and actual working conditions. The embodiment provides constraint conditions for the correction operation in combination with the working conditions, that is, the difference between the state of charge at the current moment and the state of charge estimated by the model exceeds the design error value before correction is made, which can avoid the The cumulative error within the tolerable range is corrected to reduce the amount of calculation and improve practicality. In addition, in the embodiment, the error value of the design can be adjusted within the engineering allowable range to meet the user's different accuracy requirements.

Further, in an embodiment, when correcting the state-of-charge of the power battery estimated by the ampere-hour integration method, an ampere-hour integration correction coefficient can be introduced into the ampere-hour integration method, and the ampere-hour integration correction coefficient represents the correction speed Generally speaking, the larger the ampere-hour integral correction coefficient, the faster the correction speed. The magnitude of the ampere-hour integral correction coefficient is constrained by the relationship (in some embodiments, the relationship is a difference). Based on the ampere-hour integration correction factor, correcting the state of charge of the power battery estimated by the ampere-hour integration method can effectively control the speed of the correction speed, and can satisfy the experience of different users. In some embodiments, the ampere-hour integral correction coefficient may be designed as a function of the difference, and the functional relationship is selected based on factors such as actual operating conditions of a specific device (such as a specific vehicle model), user experience, and other factors. For example, if the difference is 5%, when the actual operating conditions are uphill deceleration conditions, assuming that the user prefers a smoother experience, the ampere-hour integral correction factor can be selected to be 1%, and the adoption of slow correction The state of charge of the power battery estimated by the ampere-hour integration method; assuming that the user preference is normal, the ampere-hour integration correction factor can be selected to be 2%.

In one embodiment, in response to the difference between the state of charge at the current moment and the state of charge estimated by the model does not exceed the designed error value, the charge of the power battery estimated by the ampere-hour integration method The status is corrected.

It should be understood that after the correction of the state of charge of the power battery estimated by the ampere-hour integration method is completed, when the conditions of the matching operating conditions are met again, the parameter values of the first-order RC equivalent circuit model can be identified online again, or When the current working condition has not changed, the parameter value of the model identified online last time can be directly used for the next correction operation.

In one embodiment, the correction operation may be implemented by a battery management system (BMS).

The method for estimating the state of charge of the battery provided by the embodiment of the present invention is to satisfy the matching test condition after verification and testing as a prerequisite for correction. In the estimation, the ampere-hour integration method is mainly used, and the first-order RC based on the power battery is combined. The fusion algorithm of the online identification parameters of the equivalent circuit model under matching working conditions, the relationship between the two is used to modify the state of charge of the power battery estimated by the ampere-hour integration method, which not only plays the ampere-hour integration method in a short time The advantage of the calculated SOC accuracy is high, and the first-order RC equivalent circuit model is fully utilized to estimate the high accuracy of the SOC in certain specific conditions (ie, matching conditions), thereby realizing the correction of the cumulative error of the ampere-hour integration. It eliminates the accumulated error of long-term operation existing in the existing safety integration method, and avoids the situation that the equipment (such as the vehicle) online identification parameters under complex working conditions may cause large errors or even divergence, resulting in erroneous correction, ensuring identification The accuracy of the results is small, and the calculation amount is small, and the calculation accuracy is high.

In order to more clearly explain the correction scheme provided by the embodiment of the present invention, the method for estimating the state of charge of the battery provided by the embodiment of the present invention will be further described by way of example. In the following embodiments, although the implementation process is described based on a specific order, the implementation process is not limited to the specific order described, different steps can be performed in parallel, or in the reverse order, these feasible solutions are all Within the protection scope of the present invention.

Example 1:

In the first embodiment, before the parameter value of the first-order RC equivalent circuit model is estimated, the matching condition is judged. Specifically, the method for estimating the state of charge of the battery proposed in this embodiment, as shown in FIG. 5, includes:

Obtain the current value of the power battery in the first time period in real time, and determine the current operating condition of the power battery, and compare the current value of the first time period with the pre-calibrated operating current curve under the current operating condition A comparison is made to determine the similarity between the current value of the first time period and the pre-calibrated operating current curve; in response to the similarity being within the threshold, the current operating condition is determined to be a matching operating condition;

In response to the current working condition belonging to the matching working condition, the current value and the voltage value of the power battery belonging to the matching working condition in the second time period are acquired in real time, based on the current value and the voltage value of the power battery in the second time period, Online identification of the parameter values of the first-order RC equivalent circuit model under the current operating conditions;

Obtain the current value and voltage value of the power battery at the current time in real time, and obtain the polarization voltage and the ohmic voltage of the power battery under the matching operating conditions according to the current value and the voltage value at the current time and the parameter value, and according to the basis Erhoff's law, calculate the corresponding open circuit voltage, and find the corresponding state of charge in the relationship table between the open circuit voltage and the state of charge according to the calculated open circuit voltage, as the state of charge estimated by the model; at the same time, according to the The current value and initial state of charge of the current moment, using the ampere-hour integration method, to estimate the state of charge of the power battery at the current moment;

In response to the difference between the state-of-charge at the current moment and the state-of-charge estimated by the model exceeding the designed error value, the difference is used as feedback to evaluate the power battery’s Correct the state of charge.

In this embodiment 1, the first time period is verified to test whether the current working condition belongs to the matching working condition, and the parameters of the first-order RC equivalent circuit model are further identified online during the second time period belonging to the matching working condition. The value can avoid the situation of the Kalman filter method, the battery model divergence, and the calculation accuracy are greatly deviated under individual working conditions, and improve the accuracy of the online identification results. In addition, when the current working conditions are relatively stable, the current value and voltage value obtained in real time in the first time period can also be directly used for online identification of the first-order RC equivalent circuit model parameter values; even the first The current value acquired in real time in the time period or the second time period estimates the state of charge at the current moment.

Example 2:

This embodiment, based on the foregoing embodiment, introduces an ampere-hour integral correction coefficient when correcting the estimated state of charge of the power battery, and the ampere-hour integral correction coefficient is related to the relationship. In this embodiment, The relationship is a difference. Take the difference as the cumulative error of ampere-hour integration.

The method for estimating the state of charge of the battery proposed in this embodiment, as shown in FIG. 6, on the basis of the embodiment 1, the difference is used as feedback to estimate the charge of the power battery using the ampere-hour integration method. The status is revised, including:

Obtain the current value of the power battery in real time, use the ampere-hour integration method to estimate the state of charge of the power battery based on the current value and the initial state of charge, and use it as the reference state of charge;

Obtain the current ampere-hour integration correction coefficient at the current time, and adjust the current current value using the current-time ampere-hour integration correction coefficient as a multiple; according to the adjusted current current value and initial state of charge, use the ampere-hour integration method, Estimate the state of charge of the power battery and use it as the current state of charge;

In response to that the difference between the current state of charge and the reference state of charge is not within an error range compared to the difference, the step of returning to the real-time acquisition of the current value of the power battery is continued until all The difference between the current state of charge and the reference state of charge is within the error range compared to the difference.

Wherein, the error range is set by the user, or adopts a system preset value.

In an embodiment, the ampere-hour integral correction factor can be selected based on the current operating condition, current value, and the difference. Generally, it is necessary to ensure that the difference between the current state of charge and the reference state of charge is not Exceed the difference. In the case where the ampere-hour integral correction coefficient remains unchanged, the larger the current value, the larger the amount of correction of the state of charge, then the difference between the current state of charge and the reference state of charge approaches The faster the speed is at or equal to the difference.

In this embodiment, the ampere-hour integration correction coefficient (that is, the queried ampere-hour integration correction factor as a multiple is used to adjust the current current value) is further introduced into the ampere-hour integration method, and combined with the actual operating conditions and actual current value It can even be combined with user experience to obtain the timing integral correction coefficient, which not only realizes the correction of accumulated error of ampere-hour integration, eliminates the accumulated error of long-term operation existing in the existing ampere-hour integration method, can effectively control the correction speed, and satisfies users Experience.

Example 3:

In the third embodiment, based on the foregoing embodiment, the ampere-hour integral correction coefficient is additionally selected based on user experience.

The method for estimating the state of charge of the battery proposed in this embodiment, as shown in FIG. 7, on the basis of Embodiment 1, the difference is used as feedback to estimate the charge of the power battery using the ampere-hour integration method. The status is revised, including:

Obtain the current value of the power battery in real time, and use the ampere-hour integration method to estimate the state of charge of the power battery based on the current value and the initial state of charge, and use it as the reference state of charge;

Based on the user experience adjustment coefficient, obtain the current ampere-hour integration correction factor at the current time, and adjust the current current value using the current-time ampere-hour integration correction factor as a multiple; according to the adjusted current current value and initial state of charge, Use the ampere-hour integration method to estimate the state of charge of the power battery and use it as the current state of charge;

In response to that the difference between the current state of charge and the reference state of charge is not within an error range compared to the difference, the step of returning to the real-time acquisition of the current value of the power battery is continued until all The difference between the current state of charge and the reference state of charge is within an error range compared to the difference.

Wherein, the error range is set by the user, or adopts a system preset value.

The user experience adjustment coefficient represents the degree of change in the state of charge expected by the user, and the number can be used to indicate the user experience adjustment coefficient. It can be agreed that the smaller the number, the slower the user's expected state of charge change; the larger the number, the user The faster the desired state of charge changes. Of course, the degree of speed can also be defined in the expressions of fast, medium, and slow, or in other expressions. It can be understood that if the user experience adjustment coefficient is to be maintained, then when the current value becomes smaller, the current-hour integration correction coefficient at the current moment will become larger.

In an embodiment, the user may change the user experience adjustment coefficient, and when it is detected that the user changes the user experience adjustment coefficient, the ampere-time integral correction coefficient at the current time is re-acquired.

This embodiment not only realizes the correction of accumulated error of ampere-hour integration, eliminates the accumulated error of long-term operation existing in the existing ampere-hour integration method, can effectively control the correction speed, and satisfies the user experience.

Example 4:

In this embodiment, a recursive least squares method with a forgetting factor is used to online identify the parameter value of the first-order RC equivalent circuit model. For the state of charge estimated by the acquisition model in the foregoing embodiment, for example, the following method may be used, and reference may be made to FIG. 8:

According to the first-order RC equivalent circuit model, the expression of open circuit voltage U _OCV can be obtained from Kirchhoff's law,

U _OCV = V+I*R ₀ +U _p ,

Among them, V represents the voltage value of the power battery at the current moment, I represents the current value of the power battery at the current moment, R ₀ represents the ohmic internal resistance in the first-order RC equivalent circuit model, and U _P represents the first-order RC equivalent circuit model The voltage at both ends of the first-order RC structure formed by the parallel connection of the polarization internal resistance R _{1 of the} power battery and the polarization capacitance C _{1 of the} power battery, or called the polarization voltage;

Convert the expression of open circuit voltage U _OCV into the transfer function G(s),

Among them, s represents Laplace operator;

Then further discretize the transfer function G(s) to obtain the discretized function V(k),

V(k)=(1-θ ₁ )*U _ocv (k)+θ ₁ *V(k-1)+θ ₂ *I(k)+θ ₃ *I(k-1),

Among them, θ ₁ , θ ₂ , θ ₃ are the coefficients, k represents the current moment, k-1 represents the last moment, U _ocv (k) represents the open-circuit voltage at the current moment, and V(k-1) represents the last moment The collected voltage value, I(k) represents the current value at the current moment, and I(k-1) represents the current value at the previous moment;

Convert the discretized function V(k) to the least squares equation:

V(k)=θ(k)*φ(k),

Among them, θ(k) represents the state matrix, and φ(k) represents the system matrix:

φ(k)=[1V(k-1)I(k)I(k-1)],,

θ(k)=[(1-θ ₁ )*U _ocv (k) θ ₁ θ ₂ θ ₃ ]';

Calculate the gain K,

K=P _k-1 *φ(k-1)/(φ′(k-1)*P _k-1 *φ(k-1)+λ),

In the formula, P _k-1 is the estimated covariance at the last moment, where P ₀ is a given value, λ is the forgetting factor, and the value range is 0.95 to 1. In an embodiment, the forgetting factor may be 0.98.

Update covariance:

P _k = (IK*φ'(k))*P _k-1 /λ,

Identification parameter θ(k):

θ(k)=θ(k-1)+K*(V-φ’(k)*θ(k-1)),

By separating the identified parameter θ(k), the parameters of the first-order RC equivalent circuit model can be obtained:

Estimate the polarization voltage U _Pk :

Among them, Δt represents the sampling interval;

Calculate the open circuit voltage U _OCV :

U _ocv (k)=V(k)+I _k *R _p +Up _k ;

According to the calculated open circuit voltage U _OCV , query the U _OCV -SOC table to obtain the state of charge SOC2 estimated by the model.

This embodiment is based on the first-order RC equivalent circuit model and realizes the online identification of the parameters according to the online operating conditions. Figure 9 shows the NEC (New European Driving Cycle, or the new standard European cycle) of different SOC segments. Test) Schematic diagram of actual vehicle current under operating conditions; Figure 10 shows examples of ohmic internal resistance and polarization internal resistance identified in different SOC segments under NEDC operating conditions; Figure 11 shows different SOC segments identified under NEDC operating conditions Examples of ohmic internal resistance and polarization internal resistance, the dotted line in the figure indicates the polarization internal resistance, and the solid line indicates the ohmic internal resistance; Figure 12 shows an example of the polarization capacitance of different SOC segments identified under NEDC operating conditions; then According to the zero state and zero input response of the first-order RC circuit, the current polarization of the power battery can be calculated online. Refer to the polarization voltage U _P calculated online for different SOC segments under the NEDC operating condition shown in FIG. 13; electromotive force of the battery current, in order to achieve real-time estimate can stand when not long battery open circuit voltage at the current time, Figure 14 shows the line after elimination of the estimated polarization SOC NEDC, under various sections of the open circuit voltage U _ocv It can be understood from the _graph of the actual voltage that the deviation between the open-circuit voltage U _ocv estimated online and the actual voltage after the polarization is eliminated is the _sum of the polarization voltage U _Pk and the ohmic voltage (I*R ₀ ), and thus can The state-of-charge SOC2 at the current moment is estimated. Figure 15 shows the state-of-charge SOC1 estimated by the ampere-hour integration method for NEDC and the current state-of-charge SOC2 estimated by the first-order RC equivalent circuit model. The value range of SOC may be 0-100%, and the different SOC segments here represent a certain segment within the entire value range of 0-100%.

This embodiment uses the least square method to estimate the state of charge SOC2 at the current time for the collected voltage and current values, which is different from the conventional real-time online continuous estimation, but selects the actual working condition and the preset working condition (select the most commonly used Operating conditions) Identify parameters online under similar matching operating conditions. The parameters in the first-order RC equivalent circuit model (such as the forgetting factor) are also pre-matched with the actual operating conditions, thereby realizing the recursive process from offline data to online data . It avoids the problem of the identification data divergence when the input voltage and current conditions are complicated by the conventional online identification method, while retaining the advantages of the ampere-hour integration method and the higher accuracy of the SOC calculation in a short time. It can realize the real-time online calibration of the accumulated error existing in the ampere-hour integration method.

Example 5:

This embodiment takes the power battery as the power battery of the vehicle as an example, and further describes the method for estimating the state of charge of the battery provided by the embodiment of the present invention.

The method for estimating the state of charge of the battery proposed in this embodiment is shown in FIG. 16, and the method includes:

At S1, the vehicle is powered on, and if the battery management system (BMS) is powered on, the self-test is normal. If the self-test is normal, continue to collect the power battery voltage value and power battery current value in real time, and obtain the power battery last power-on The latest stored state-of-charge value, the current power-on time and the previous power-off time; after the battery management system (BMS) is high-voltage, in response to judging that the current working condition is a matching working condition, perform subsequent operations (subsequent operations The description order does not represent the execution order of the operations);

In S2, the static time of the power battery is calculated according to the current power-on time and the previous power-off time, and it is determined whether the power battery's static time exceeds the preset value t1, if the power battery's static time exceeds the preset value t1, query the U _OCV -SOC table based on the real-time collected voltage value, and obtain the corresponding state of charge as the initial state of charge of the power battery SOC_int, otherwise, the latest state of charge value stored in the previous power battery will be obtained , As the initial state of charge of the power battery SOC_int;

At S3, the ampere-hour integration method is used to continuously estimate the state of charge of the power battery SOC1 in real time,

SOC1=SOC_int-∫Idt/Cp,

The estimated state of charge SOC1 of the power battery is taken as the current state of charge, where SOC_int represents the initial state of charge of the power battery, I represents the current value collected in real time at the current time, and Cp is the current battery capacity;

At S4, the voltage and current values within a period of time (for example, 1 minute) are collected, the parameter value of the first-order RC equivalent circuit model is identified using a recursive least squares method with forgetting factors, and then the power is calculated according to Kirchhoff's law The open circuit voltage U _{OCV of the} battery at the current moment,

U _OCV = V+I*R ₀ +U _p ,

Among them, V represents the voltage value of the power battery at the current moment, I represents the current value of the power battery at the current moment, R ₀ represents the ohmic internal resistance in the first-order RC equivalent circuit model, and UC represents the first-order RC equivalent circuit model The voltage across the first-order RC structure formed by the parallel connection of the polarization internal resistance R _{1 of the} power battery and the polarization capacitance C _{1 of the} power battery, or called the polarization voltage; according to the calculated open circuit voltage U _OCV , query U _OCV -SOC table, get the state of charge SOC2 estimated by the model;

At S5, based on the state-of-charge SOC1 of the power battery at the current moment and the state-of-charge SOC2 estimated by the model, the deviation ΔSOC0 of the two is calculated,

ΔSOC0=SOC1-SOC2,

And record the deviation value ΔSOC0;

In S6, in response to the deviation value ΔSOC0 exceeding the designed error value, the deviation value ΔSOC0 is used as the accumulated error of the ampere-hour integration, and is used as feedback to the subsequent state of charge of the power battery estimated by the ampere-hour integration method SOC to amend;

In one embodiment, the calibration method can be corrected by the state of charge estimated at each sampling time of the ampere-hour integration or the amount of change in the state of charge estimated at each sampling time, and the correction speed depends on the ampere-hour integration correction coefficient The size of Ki, where the ampere-hour integral correction coefficient Ki = Fun (ΔSOC0), is a function of the deviation value ΔSOC0. Usually Fun(ΔSOC0) is selected based on the actual working conditions of specific vehicle models, user experience and other factors;

At S7, it is determined whether the absolute value of the ampere-hour correction amount corrected by the ampere-hour integration correction coefficient Ki at the current time |∫I*(1-Ki)dt/Cp| exceeds the absolute value of the ampere-hour integration cumulative error ΔSOC0, if If it exceeds, the correction is completed until the next working condition meets the revised conditions (for example, matching working condition, the deviation value exceeds the designed error value).

This embodiment takes a specific application scenario as an example to describe the method for estimating the state of charge of the battery. The method for estimating the state of charge of the battery proposed in this embodiment combines the first order based on the power battery through the ampere-hour integration method The fusion algorithm of RC equivalent circuit model online identification parameters not only takes advantage of the high accuracy of the SOC calculated by the ampere-hour integration method in a short time, but also makes full use of some specific tools suitable for the first-order RC equivalent circuit model It has the characteristics of high SOC estimation accuracy, thereby realizing the correction of accumulated error of ampere-hour integration, eliminating the accumulated error of long-term operation existing in the existing ampere-hour integration method, and avoiding the possibility of online identification of parameters under complex operating conditions. Large error or even divergence leads to the situation of erroneous correction.

An embodiment of the present invention further proposes a device for estimating the state of charge of a battery, including a processor and a memory storing instructions that, when executed by the processor, cause the electronic device to perform actions to implement the present invention. Any of the methods described in the examples.

Embodiments of the present invention also provide a computer-readable storage medium that stores machine-readable instructions, which when executed by a machine, causes the machine to perform any method described according to the embodiments of the present invention.

Those skilled in the art can understand that the logic and/or steps represented in the flowchart or described in other ways here, for example, can be regarded as a sequenced list of executable instructions for implementing logical functions, which can be specifically implemented in In any computer-readable medium for use by an instruction execution system, device, or device (such as a computer-based system, a system including a processor, or other system that can fetch and execute instructions from the instruction execution system, device, or device), or Used in conjunction with these instruction execution systems, devices, or equipment. For the purposes of this specification, a "computer-readable medium" may be any device that can contain, store, communicate, propagate, or transmit a program for use by or in connection with an instruction execution system, apparatus, or device.

More specific examples of computer-readable media (non-exhaustive list) include the following: electrical connections (electronic devices) with one or more wires, portable computer cartridges (magnetic devices), random access memory (RAM), Read only memory (ROM), erasable and editable read only memory (EPROM or flash memory), fiber optic devices, and portable compact disk read only memory (CDROM). In addition, the computer-readable medium may even be paper or other suitable medium on which the program can be printed, because, for example, by optically scanning the paper or other medium, followed by editing, interpretation, or other appropriate if necessary Process to obtain the program electronically and then store it in computer memory.

It should be understood that each part of the present invention may be implemented by hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods may be implemented with software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: a logic gate circuit for implementing a logic function on a data signal Discrete logic circuits, dedicated integrated circuits with appropriate combinational logic gates, programmable gate arrays (PGA), field programmable gate arrays (FPGA), etc.

In the description of this specification, the term "including" and its various variations may be understood as open-ended terms, which means "including but not limited to." The term "based on" may be understood as "based at least in part on." The term "one embodiment" may be understood as "at least one embodiment". The term "another embodiment" may be understood as "at least one other embodiment". The descriptions of the terms "one embodiment", "another embodiment", "some embodiments", "examples", "specific examples" or "some examples" mean specific features and structures described in conjunction with the embodiment or example , Materials or features are included in at least one embodiment or example of the present invention. In this specification, the schematic expression of the above term does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

In the above, the embodiment of the present invention has been described. However, the present invention is not limited to the above-mentioned embodiment. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims (10)

1. A method for estimating the state of charge of a battery, which is characterized by including:

   In response to the current operating condition being a matching operating condition, the parameter value of the first-order RC equivalent circuit model of the power battery is identified online, and based on the parameter value, the estimated state of charge of the model is obtained; wherein, the matching operating condition represents the current The actual working condition parameter value of the working condition matches the preset parameter value;

   Estimate the state of charge of the power battery using the ampere-hour integration method; and

   Based on the relationship between the state-of-charge estimated by the model and the state-of-charge estimated by the ampere-hour integration method, the state-of-charge of the power battery estimated by the ampere-hour integration method is corrected.
2. The method according to claim 1, wherein the obtaining the state of charge estimated by the model comprises: obtaining the polarization voltage and the ohmic voltage of the power battery under the matching operating condition based on the parameter value, and calculating Corresponding open circuit voltage, according to the calculated open circuit voltage through the relationship table formed by the open circuit voltage and the state of charge, to find the corresponding state of charge as the estimated state of charge of the model;

   The estimation of the state-of-charge of the power battery using the ampere-hour integration method includes: estimating the state-of-charge of the power battery at the current time using the ampere-hour integration method based on the working condition parameter value obtained in real time at the current time; and

   The modification of the state of charge of the power battery estimated by the ampere-hour integration method includes: in response to the difference between the state of charge at the current moment and the state of charge estimated by the model exceeding the designed error value Using the difference as feedback, the state of charge of the power battery estimated by the ampere-hour integration method is corrected.
3. The method according to claim 1, wherein the method further comprises:

   Obtain the current value of the power battery in the first time period in real time, and determine the current working condition of the power battery;

   Comparing the current value of the first time period with the pre-calibrated operating current curve under the current operating conditions, and judging the similarity between the current value of the first time period and the pre-calibrated operating current curve ;as well as

   In response to the similarity being within the threshold range, it is determined that the current operating condition belongs to the matching operating condition.
4. The method according to claim 3, wherein the method further comprises:

   In response to the current working condition belonging to the matching working condition, the current value and the voltage value of the power battery belonging to the matching working condition in the second time period are acquired in real time, based on the current value and the voltage value of the power battery in the second time period, Online identification of the parameter value of the first-order RC equivalent circuit model under the current working condition; the second time period coincides with the first time period or is a different time period.
5. The method according to claim 4, wherein the method further comprises:

   Obtain the current value and voltage value of the power battery at the current time in real time, and obtain the polarization voltage and the ohmic voltage of the power battery under the matching operating conditions according to the current value and the voltage value at the current time and the parameter value, and according to the basis Erhoff's law, calculate the corresponding open circuit voltage, and find the corresponding state of charge in the relationship table between the open circuit voltage and the state of charge according to the calculated open circuit voltage, as the state of charge estimated by the model; at the same time, according to the The current value and initial state of charge of the current moment, using the ampere-hour integration method, to estimate the state of charge of the power battery at the current moment;

   In response to the difference between the state-of-charge at the current moment and the state-of-charge estimated by the model exceeding the designed error value, the difference is used as feedback to evaluate the power battery’s Correct the state of charge.
6. The method according to claim 1, wherein the correction of the state of charge of the power battery estimated by the ampere-hour integration method includes:

   An ampere-hour integration correction factor is introduced into the ampere-hour integration method, and the ampere-hour integration correction factor is related to the relationship; based on the ampere-hour integration correction factor, the charge of the power battery estimated by the ampere-hour integration method is corrected status.
7. The method according to claim 6, wherein the relationship between the state-of-charge estimated by the model and the state-of-charge estimated by the ampere-hour integration method is the estimated charge by the model The difference between the state of charge and the state of charge estimation of the power battery using the ampere-hour integration method;

   The relationship between the state-of-charge estimated based on the model and the state-of-charge estimated using the ampere-hour integration method to modify the state-of-charge of the power battery estimated using the ampere-hour integration method includes:

   Obtain the current value of the power battery in real time, use the ampere-hour integration method to estimate the state of charge of the power battery based on the current value and the initial state of charge, and use it as the reference state of charge;

   Obtain the current ampere-hour integration correction coefficient at the current time, and adjust the current current value using the current-time ampere-hour integration correction coefficient as a multiple; according to the adjusted current current value and initial state of charge, use the ampere-hour integration method Estimate the state of charge of the power battery and use it as the current state of charge;

   In response to that the difference between the current state of charge and the reference state of charge is not within an error range compared to the difference, the step of returning to the real-time acquisition of the current value of the power battery is continued until all The difference between the current state of charge and the reference state of charge is within the error range compared to the difference.
8. The method according to claim 7, wherein the obtaining of the current-time integral correction coefficient comprises: obtaining the current-time integral correction coefficient based on the user experience adjustment coefficient; the user experience adjustment coefficient characterization The degree of change of the state of charge expected by the user;

   The method further includes: in response to the user changing the user experience adjustment coefficient, re-acquiring the current time ampere point correction coefficient.
9. A device for estimating the state of charge of a battery is characterized by including:

   Processor; and

   A memory storing instructions that when executed by the processor causes the device to perform the method according to any one of claims 1 to 8.
10. A computer-readable storage medium, characterized in that it stores machine-readable instructions, which when executed by the machine causes the machine to perform the method according to any one of claims 1 to 8. .

Images