Estimation optimization method, battery system, and nonvolatile storage medium

Abstract

The application provides an estimation optimization method, a battery system and a nonvolatile storage medium, comprising: obtaining self-discharge rates of a first system battery and a second system battery at different SOC and different temperatures respectively, obtaining storage working conditions of the first system battery and the second system battery to calculate a first self-discharge amount of the first system battery and a second self-discharge amount of the second system battery respectively; comparing the first self-discharge amount with the second self-discharge amount; and discharging the system battery with the smaller self-discharge amount among the first self-discharge amount and the second self-discharge amount according to the comparison result of the first self-discharge amount and the second self-discharge amount to balance the first self-discharge amount and the second self-discharge amount. The technical scheme provided by the application can solve the technical problem of poor SOC estimation accuracy of the hybrid system in the prior art.

Description

Technical Field

[0001] This invention relates to the field of SOC estimation technology for hybrid systems, and more specifically, to an estimation optimization method, a battery system, and a non-volatile storage medium. Background Technology

[0002] Currently, with the large-scale application of lithium batteries, especially the vigorous promotion of new energy vehicles, users have increasingly higher requirements for battery performance. The power batteries used in electric vehicles are mainly divided into lithium iron phosphate (LFP) batteries and ternary lithium batteries (NCM). To combine the safety advantages of LFP batteries with the energy density and temperature performance advantages of ternary lithium batteries, hybrid battery systems have been developed in recent years. These systems combine LFP and NCM batteries within a single battery system, allowing them to function together.

[0003] However, since there are two or more cell systems in the hybrid system, the OCV curves of different material systems, the SOC window, the decay rate and self-discharge rate are different, which makes SOC estimation difficult. Moreover, the difference in decay rate and self-discharge rate between different cell systems makes the accuracy of SOC estimation poor. Summary of the Invention

[0004] The main objective of this invention is to provide an estimation optimization method, a battery system, and a non-volatile storage medium to solve the technical problem of poor SOC estimation accuracy in existing hybrid systems.

[0005] To achieve the above objectives, according to one aspect of the present invention, a method for estimating and optimizing the state of charge (SOC) of a battery system is provided. The battery system includes at least a first battery cell and a second battery cell. The estimation and optimization method is used to optimize the estimation of the SOC of the battery system. The optimization method includes: obtaining the self-discharge rates of the first battery cell and the second battery cell at different SOCs and different temperatures; obtaining the storage conditions of the first battery cell and the second battery cell to calculate the first self-discharge amount of the first battery cell and the second self-discharge amount of the second battery cell, respectively; comparing the first self-discharge amount with the second self-discharge amount; and discharging the battery cell with the smaller self-discharge amount among the first and second self-discharge amounts to balance the first and second self-discharge amounts.

[0006] Furthermore, discharging the battery system with the smaller self-discharge among the first and second self-discharge amounts includes: calculating the self-discharge difference between the first and second self-discharge amounts; and controlling the battery system with the smaller self-discharge amount among the first and second self-discharge amounts to discharge based on the self-discharge difference.

[0007] Furthermore, obtaining the self-discharge rate of the first battery system includes: selecting temperature values ​​T1, T2, ..., T based on the storage temperature range and SOC range of the first battery system. m And SOC values ​​SOC1, SOC2, ..., SOC n The first system battery was stored under different temperatures and different SOC states, and the self-discharge amount at each state after a specified time was tested. The self-discharge rate at different temperatures and different SOC states was calculated based on the self-discharge amount at the specified time to obtain the self-discharge rate matrix.

[0008] Furthermore, the self-discharge amount of each state at a specified time is tested, including: using the BMS to wake up at regular intervals and detect the SOC state, storage temperature and storage time of the first system battery in order to calculate the self-discharge amount of the first system battery.

[0009] Furthermore, the optimization method also includes: using the SOHA of the first system battery and the SOHB of the second system battery to correct the SOCB of the second system battery.

[0010] Furthermore, the SOCB of the second system battery is corrected using the SOHA of the first system battery and the SOHB of the second system battery, including: calculating the corrected SOCB of the second system battery according to the correction formula, which is:

[0011]

[0012] ,in, This represents the initial SOC of the second battery system at the start of the calculation. This indicates the initial SOC of the first battery system at the start of the calculation. This refers to the initial capacity of the first-stage battery system. This refers to the initial capacity of the second-system battery.

[0013] Furthermore, before correcting the SOCB of the second system battery using the SOHA of the first system battery and the SOHB of the second system battery, the optimization method also includes: establishing a SOOH mapping relationship between the SOHA of the first system battery and the SOHB of the second system battery. B =f(SOH) A );use The SOHA of the first battery system is calculated using the method described above, and the SOHB of the second battery system is calculated based on the mapping relationship described above.

[0014] According to another aspect of the present invention, a battery system is provided, the battery system including a first battery cell and a second battery cell, the battery system further including: an acquisition module configured to acquire the self-discharge rate of the first battery cell and the second battery cell at different SOCs and different temperatures, and to acquire the storage conditions of the first battery cell and the second battery cell to calculate the first self-discharge amount of the first battery cell and the second self-discharge amount of the second battery cell respectively; a comparison module configured to compare the first self-discharge amount and the second self-discharge amount; and an balancing module configured to discharge the battery cell with the smaller self-discharge amount among the first self-discharge amount and the second self-discharge amount according to the comparison result of the first self-discharge amount and the second self-discharge amount, so as to balance the first self-discharge amount and the second self-discharge amount.

[0015] Furthermore, one of the first-system battery and the second-system battery is a lithium iron phosphate battery, and the other of the first-system battery and the second-system battery is a ternary battery.

[0016] According to another aspect of the present invention, a non-volatile storage medium is provided, the non-volatile storage medium including a program that employs the estimation and optimization method provided above.

[0017] By applying the technical solution of this invention, the difference in usable capacity between batteries with different material systems can be eliminated to a certain extent, thereby facilitating the improvement of the estimation accuracy of SOC and realizing a self-discharge difference equalization mechanism to eliminate the difference in usable capacity caused by the difference in self-discharge between different material systems. Attached Figure Description

[0018] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0019] Figure 1 A flowchart illustrating the estimation method provided according to an embodiment of the present invention is shown. Detailed Implementation

[0020] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0021] like Figure 1As shown, Embodiment 1 of the present invention provides a method for estimating and optimizing the State of Charge (SOC) of a battery system. The battery system includes at least a first battery cell and a second battery cell. The estimation and optimization method is used to optimize the estimation of the SOC of the battery system. The optimization method includes: obtaining the self-discharge rates of the first battery cell and the second battery cell at different SOCs and different temperatures; obtaining the storage conditions of the first battery cell and the second battery cell to calculate the first self-discharge amount of the first battery cell and the second self-discharge amount of the second battery cell respectively; comparing the first self-discharge amount and the second self-discharge amount; and discharging the battery cell with the smaller self-discharge amount among the first and second self-discharge amounts to balance the first and second self-discharge amounts.

[0022] Specifically, in the SOC estimation of a hybrid system, an SOC mapping relationship is established between the first-system battery and the second-system battery, and another SOC mapping relationship is established between the second-system battery and the battery system. This is to adjust for the imbalance in the SOC usage range caused by the different decay rates between the first-system battery and the second-system battery. Since the self-discharge characteristics of batteries with different material systems are not the same, and this difference increases cumulatively over time, existing estimation methods generally ignore this difference. However, the method in this embodiment can, to a certain extent, eliminate the difference in usable capacity between batteries with different material systems, thereby improving the accuracy of SOC estimation. The above method can be understood as a self-discharge difference balancing mechanism to eliminate the difference in usable capacity caused by the difference in self-discharge between different material systems.

[0023] Specifically, discharging the battery system with the smaller self-discharge among the first and second self-discharge quantities includes: calculating the self-discharge difference between the first and second self-discharge quantities; and controlling the battery system with the smaller self-discharge quantity to discharge based on the self-discharge difference. This method facilitates effective balancing of the first and second self-discharge quantities, ensuring they are equal in magnitude, thereby improving the accuracy of SOC estimation.

[0024] In this embodiment, obtaining the self-discharge rate of the first battery system includes: selecting temperature values ​​T1, T2, ..., T based on the storage temperature range and SOC range of the first battery system. m And SOC values ​​SOC1, SOC2, ..., SOC nThe first battery system was stored and tested at different temperatures and SOC states, and the self-discharge rate at each state after a specified time was measured. The self-discharge rate at different temperatures and SOC states was calculated based on the self-discharge rate at the specified time to obtain a self-discharge rate matrix. This method allows for the rapid and accurate acquisition of the self-discharge rate of the first battery system. The self-discharge rate of the second battery system was obtained in the same way as that of the first battery system.

[0025] Specifically, the self-discharge rate at each state after a specified time is tested, including: using the BMS to periodically wake up and detect the SOC state, storage temperature, and storage time of the first battery system to calculate the self-discharge rate of the first battery system. This method facilitates accurate calculation of the self-discharge rate of the first battery system. The self-discharge rate of the second battery system is calculated using the same method as that of the first battery system.

[0026] In this embodiment, the optimization method further includes: utilizing the SOH of the first system battery. A SOH of the second system battery B SOC of the second-system battery B Corrections are made. This method takes into account the impact of different decay rates on the estimation accuracy of SOC, thus facilitating an effective improvement in the estimation accuracy of SOC.

[0027] Specifically, utilizing the SOH of the first system battery A SOH of the second system battery B SOC of the second-system battery B The corrections include: calculating the corrected SOC of the second battery system according to the correction formula. B The corrected formula is:

[0028]

[0029] ,in, This represents the initial SOC of the second battery system at the start of the calculation. This indicates the initial SOC of the first battery system at the start of the calculation. This refers to the initial capacity of the first-stage battery system. This refers to the initial capacity of the second-system battery. Using this calculation method allows for effective adjustments to the second-system battery to improve its State of Charge (SOC). B The accuracy of the estimate.

[0030] In this embodiment, the SOH of the first system battery is utilized. A SOH of the second system battery B SOC of the second-system battery BBefore making corrections, the optimization method also includes: establishing the SOH of the first system battery. A Second system battery SOH B The mapping relationship between SOH and SOC B =f(SOH) A );use The method for calculating the SOH of the first system battery A And calculate the SOH of the second system battery based on the above mapping relationship. B Using this method, a mapping relationship is established between the first-system battery and the second-system battery, and the SOH is improved. B The accuracy.

[0031] The optimization method in this embodiment is also applicable to hybrid systems with more than two material systems.

[0032] Specifically, the self-discharge difference equalization mechanism is implemented as follows: A self-discharge decay calculation module is introduced into the SOC estimation algorithm. Using the self-discharge rate of the battery system under different SOC and temperature storage conditions, the self-discharge amount of the battery system is calculated based on the storage conditions. Then, the self-discharge amounts of different battery systems (which may include the first and second battery systems) are subtracted to obtain the self-discharge difference. The BMS system uses an equalization device to discharge the battery system with the lower self-discharge, ensuring the discharge amount equals the self-discharge difference, thus maintaining equal usable capacity among different battery systems. This reduces the SOC estimation error of the hybrid system.

[0033] Specifically, the SOC error caused by differences in decay rates between different material systems can be eliminated by the following method: First, establish the SOH mapping relationship between different material systems through laboratory testing. B =f(SOH) A Then use The method is used to calculate the SOH of system A, and then the SOH of system B. Finally, the SOH data is used to correct the SOC of the target battery.

[0034] The optimization method in this embodiment specifically includes the following:

[0035] (1): Obtain the self-discharge rate of batteries with different material systems.

[0036] a. The self-discharge rate of a battery system is a function of the battery materials, state of charge (SOC), storage temperature, and storage time. When the battery materials are fixed, the self-discharge rate is a function of SOC, storage temperature, and storage time. R SD = f(SOC, T, t), where R SCThis refers to the self-discharge rate, measured in 1% SOC / day; T refers to the battery storage temperature, measured in °C; and t refers to the storage time, measured in days. This ternary function, the decay rate, can be obtained through orthogonal experimental testing. Assuming the hybrid system uses both LFP (which can correspond to one of the first and second battery systems) and NCM (which can correspond to the other of the first and second battery systems) systems, the self-discharge rates of the two systems are Ri and Rc, respectively. SD_L and R SD_N .

[0037] Depending on battery characteristics, even with the same SOC and storage temperature, different storage times will result in different self-discharge rates R. SD Generally, they differ. For ease of engineering use, the storage time is determined to be N times the BMS wake-up time, where N ≤ 100. A suggested R... SD The acquisition method is as follows:

[0038] ① Select a series of temperature values ​​T1, T2, ..., T based on the battery storage temperature range and SOC range. m And SOC values ​​SOC1, SOC2, ..., SOC n .

[0039] ② The battery was stored under corresponding temperature and SOC conditions, and the test results were taken for each state to reach a specified time N×t. wakeup The self-discharge amount at (BMS wake-up time) is shown in Table 1:

[0040] Table 1 shows the storage time as N×t. wakeup Self-discharge

[0041]

[0042] ③ Calculate the self-discharge rate R under each state. SD =C SD ÷(N×t wakeup The self-discharge rate matrix was obtained, as shown in Table 2.

[0043] Table 2 shows the storage time as N×t. wakeup self-release rate

[0044]

[0045] (2): Obtain the SOH relationship of batteries with different material systems.

[0046] Through laboratory testing, the SOH mapping relationship between different material systems was established. B =f(SOH) A Then use The method is used to calculate the SOH of system A, and then to calculate the SOH of system B.

[0047] (3): Calculate the self-discharge and the difference in self-discharge of batteries with different material systems.

[0048] a. BMS timed wake-up to calculate self-discharge. The BMS timed wake-up detects the SOC state, storage temperature, and storage time of the battery system, and calculates the self-discharge of different battery systems. C SD =C initial ×SOH×R SD ×t. Where C SD It is the self-discharge capacity of the battery system, C initial This refers to the initial capacity of the battery system, SOH refers to the state of health of the battery system, and t refers to the storage time of the battery system. Assuming the hybrid system uses two battery systems, A (corresponding to the first system) and B (corresponding to the second system), then the two self-discharge rates are C... SD_A (corresponding to the first self-discharge of the first battery system) and C SD_B (This corresponds to the second self-discharge of the second system battery).

[0049] b. Calculate the difference in self-discharge capacity between batteries of different systems. ΔC SD =C SD_A -C SD_B The unit is Ah.

[0050] (4): Analysis of the differences and errors in self-discharge of batteries with different material systems balanced by BMS.

[0051] After calculating the difference in self-discharge capacity ΔC SD Afterwards, the BMS activates its balancing function to discharge the battery with low self-discharge material system until the discharge capacity equals ΔC. SD This ensures that the usable capacity is the same across different battery systems. Based on the premise that system A and system B batteries have the same discharge capacity, the SOC... B and SOC A The relationship is as follows:

[0052]

[0053] Among them, SOC B SOC represents the SOC of system B. A Indicates the SOC of system A. This represents the actual capacity of system A. This represents the actual capacity of system B. This represents the initial SOC of system B at the start of the calculation. This represents the initial state of charge (SOC) of system A at the start of the calculation. ΔCSD The difference lies in the amount of self-discharge.

[0054] Specifically, after equilibrium is reached, the formula above... It is 0.

[0055] Assuming system A battery is 100Ah with NCM material and system B battery is 110Ah with LFP material, typically at 100% SOC, 25℃, and stored for 30 days, the self-discharge of LFP is 1%, and that of NCM is 1.5%. In other words, without correcting for self-discharge error (and without using an equalization system), the estimated error for a cumulative resting time of one month will increase to 0.36%, and the error for a cumulative resting time of ten months will increase to 3.6%.

[0056] (5): Correcting SOC using SOH data B .

[0057] because Therefore, after considering the SOH correction, SOC B The calculation formula has been changed to the following:

[0058]

[0059] in This represents the initial SOC of system B at the start of the calculation. This indicates the initial SOC of system A at the start of the calculation. This refers to the initial capacity of the A-system battery. This refers to the initial capacity of the B-system battery. As can be seen from the formula above, with the increase of SOH... B As the self-discharge rate decreases, the error caused by self-discharge also increases.

[0060] Embodiment 2 of the present invention provides a battery system, comprising a first battery cell and a second battery cell. The battery system further includes an acquisition module, a comparison module, and an balancing module. The acquisition module is configured to acquire the self-discharge rates of the first and second battery cells at different SOCs and temperatures, and to acquire the storage conditions of the first and second battery cells to calculate the first self-discharge amount of the first battery cell and the second self-discharge amount of the second battery cell, respectively. The comparison module is configured to compare the first and second self-discharge amounts. The balancing module is configured to discharge the battery cell with the smaller self-discharge amount based on the comparison result of the first and second self-discharge amounts, thereby balancing the first and second self-discharge amounts.

[0061] Specifically, in this embodiment, one of the first system battery and the second system battery is a lithium iron phosphate battery, and the other of the first system battery and the second system battery is a ternary battery.

[0062] Embodiment 3 of the present invention provides a non-volatile storage medium, which includes a program that uses the estimation and optimization method provided in Embodiment 1 above.

[0063] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects: a self-discharge difference estimation method is proposed; a self-discharge difference calculation model is introduced into the SOC estimation model; a self-discharge difference balancing method is designed in the hybrid system; and the SOC estimation error caused by the self-discharge difference between batteries of different material systems in the hybrid system can be eliminated in a timely manner, thereby improving the SOC estimation accuracy.

[0064] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0065] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of this application. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following drawings denote similar items; therefore, once an item is defined in one drawing, it need not be further discussed in subsequent drawings.

[0066] In the description of this application, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is usually based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this application and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this application; the directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0067] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0068] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be construed as limiting the scope of protection of this application.

[0069] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for estimating and optimizing the state of charge (SOC) of a battery system, characterized in that, The battery system includes at least a first-cell battery and a second-cell battery; The estimation optimization method is used to optimize the estimation of the state of charge (SOC) of the battery system, and the optimization method includes: The self-discharge rates of the first battery system and the second battery system at different SOCs and different temperatures are obtained, and the storage conditions of the first battery system and the second battery system are obtained to calculate the first self-discharge of the first battery system and the second self-discharge of the second battery system, respectively. Compare the first self-discharge amount with the second self-discharge amount; Based on the comparison results of the first self-discharge and the second self-discharge, the battery system with the smaller self-discharge between the first self-discharge and the second self-discharge is discharged to balance the first self-discharge and the second self-discharge. The optimization method further includes: utilizing the SOH of the first system battery. A and the SOH of the second system battery B SOC of the second system battery B Make corrections; Utilizing the SOH of the first system battery A and the SOH of the second system battery B SOC of the second system battery B Make corrections, including: The corrected SOC of the second battery system was calculated according to the corrected formula. B The corrected formula is: ,in, This indicates the initial SOC of the second system battery at the start of the calculation. This indicates the initial SOC of the first system battery at the start of the calculation. This refers to the initial capacity of the first battery system. This refers to the initial capacity of the second battery system, ΔC. SD The difference lies in the self-discharge capacity between batteries of different systems. , This represents the first self-discharge capacity of the first-system battery. This is the second self-discharge quantity of the second system battery.

2. The method for estimating and optimizing the state of charge (SOC) of a battery system according to claim 1, characterized in that, Discharging the battery system with the smaller self-discharge value among the first and second self-discharge values ​​includes: Calculate the difference between the first self-discharge and the second self-discharge; The battery system with the smaller self-discharge value between the first self-discharge value and the second self-discharge value discharges according to the difference in self-discharge value.

3. The method for estimating and optimizing the state of charge (SOC) of a battery system according to claim 1, characterized in that, Obtaining the self-discharge rate of the first battery system includes: The temperature value is selected based on the storage temperature range and SOC range of the first system battery. , ,…, and SOC value , ,…, ; The first system battery was stored under different temperatures and different SOC states, and the self-discharge amount of each state after a specified time was tested. The self-discharge rate is calculated based on the self-discharge amount at the specified time under different temperatures and different SOC states to obtain a self-discharge rate matrix.

4. The method for estimating and optimizing the state of charge (SOC) of a battery system according to claim 3, characterized in that, Test the self-discharge amount at a specified time in each state, including: The BMS is used to periodically wake up and detect the SOC state, storage temperature and storage time of the first battery system in order to calculate the self-discharge of the first battery system.

5. The method for estimating and optimizing the state of charge (SOC) of a battery system according to claim 1, characterized in that, Utilizing the SOH of the first system battery A and the SOH of the second system battery B SOC of the second system battery B Before making the correction, the optimization method further includes: Establish the SOH of the first system battery A and the SOH of the second system battery B SOH mapping relationship between ; use The method for calculating the SOH of the first system battery A And calculate the SOH of the second system battery based on the above mapping relationship. B .

6. A battery system, characterized in that, The state-of-charge (SOC) estimation and optimization method for a battery system according to any one of claims 1 to 5 is applicable to the battery system, the battery system comprising a first battery cell and a second battery cell, and the battery system further comprising: The acquisition module is configured to acquire the self-discharge rates of the first system battery and the second system battery at different SOCs and different temperatures, and to acquire the storage conditions of the first system battery and the second system battery to calculate the first self-discharge amount of the first system battery and the second self-discharge amount of the second system battery, respectively. The comparison module is configured to compare the first self-discharge amount with the second self-discharge amount; The balancing module is configured to discharge the battery system with the smaller self-discharge between the first self-discharge and the second self-discharge based on the comparison result of the first self-discharge and the second self-discharge, so as to balance the first self-discharge and the second self-discharge.

7. The battery system according to claim 6, characterized in that, One of the first battery system and the second battery system is a lithium iron phosphate battery system, and the other of the first battery system and the second battery system is a ternary battery system.

8. A non-volatile storage medium, characterized in that, The non-volatile storage medium includes a program that employs the estimation optimization method described in any one of claims 1 to 5.

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