Estimation method of state of charge of power battery and storage medium

Abstract

The invention provides a method for estimating the state of charge of a power battery and a storage medium. The method comprises the following steps: acquiring a target open-circuit voltage value of the power battery; inputting the target open-circuit voltage value into a pre-created fitting function to obtain a corresponding charge state, output by the fitting function, of the power battery under the target open-circuit voltage value; wherein the fitting function is fitted according to the relationship between the open-circuit voltage and the state of charge of the power battery. The method is used for improving the accuracy of SOC estimation.

Description

Technical Field

[0001] The present application relates to the field of vehicle technology, and in particular to a method for estimating a state of charge of a power battery and a storage medium. Background Art

[0002] In order to improve the utilization rate of lithium-ion batteries and ensure the safe operation of electric vehicles, the battery management system must obtain accurate battery state of charge (SOC) data. SOC represents the ratio of the remaining capacity of a battery after it has been used for a period of time or has been left unused for a long time to the rated capacity, usually expressed as a percentage. The size of SOC cannot be measured directly and is easily affected by factors such as the battery's operating current, voltage, and temperature. Therefore, accurate estimation of SOC is an issue that needs to be addressed urgently. Summary of the invention

[0003] The purpose of the embodiments of the present application is to provide a method for estimating the state of charge of a power battery and a storage medium, so as to improve the accuracy of SOC estimation.

[0004] In a first aspect, the present invention provides a method for estimating the state of charge of a power battery, the method comprising:

[0005] Obtain the target open circuit voltage value of the power battery;

[0006] The target open circuit voltage value is input into a pre-created fitting function to obtain the charge state of the power battery corresponding to the target open circuit voltage value output by the fitting function;

[0007] The fitting function is fitted based on the relationship between the open circuit voltage and the state of charge of the power battery.

[0008] In an alternative embodiment, the fitting function is created in the following manner:

[0009] Based on the internal resistance model of the power battery, determine the state space equation corresponding to the charge state of the power battery during the charging and discharging process;

[0010] Based on the derivation results of the state space equation, determine the formula type of the fitting function;

[0011] Collecting multiple groups of data pairs of the power battery, each data pair including a sample state of charge of the power battery and a corresponding sample open circuit voltage value;

[0012] Fitting is performed based on multiple sets of data pairs to obtain a fitting function, wherein the fitting function includes multiple monomials of different orders and a constant term.

[0013] In an optional embodiment, it also includes:

[0014] The fitting function is error checked. If the fitting function does not meet the error requirement, the number of items in the fitting function is adjusted, and the fitting function is obtained by refitting.

[0015] In an optional embodiment, the internal resistance model includes an internal resistance, a polarization resistance, a discharge resistance, a charging resistance, a polarization capacitor, a first diode and a second diode, and a power supply.

[0016] The first connection end of the internal resistance model is connected to the cathode of the first diode, the anode of the first diode is connected to the first end of the discharge resistor, the second end of the discharge resistor is connected to the anode of the power supply, the cathode of the power supply is connected to the first end of the internal resistance resistor, the second end of the internal resistance resistor is connected to the first end of the polarization internal resistance, and the second end of the polarization internal resistance is connected to the second connection end of the internal resistance model;

[0017] The first end of the charging resistor is connected to the second end of the discharging resistor, the second end of the charging resistor is connected to the positive electrode of the second diode, and the negative electrode of the second diode is connected to the first connection end of the internal resistance model;

[0018] The polarization capacitor is connected in parallel with the polarization resistor.

[0019] In a second aspect, the present invention provides a device for estimating the state of charge of a power battery, the device comprising:

[0020] An acquisition module, used to obtain a target open circuit voltage value of a power battery;

[0021] A calculation module, used for inputting the target open circuit voltage value into a pre-created fitting function to obtain the charge state of the power battery corresponding to the target open circuit voltage value output by the fitting function;

[0022] The fitting function is fitted based on the relationship between the open circuit voltage and the state of charge of the power battery.

[0023] In an optional embodiment, a fitting module is further included, which is used to create a fitting function in the following manner:

[0024] Based on the internal resistance model of the power battery, determine the state space equation corresponding to the charge state of the power battery during the charging and discharging process;

[0025] Based on the derivation results of the state space equation, determine the formula type of the fitting function;

[0026] Collecting multiple groups of data pairs of the power battery, each data pair including a sample state of charge of the power battery and a corresponding sample open circuit voltage value;

[0027] Fitting is performed based on multiple sets of data pairs to obtain a fitting function, wherein the fitting function includes multiple monomials of different orders and a constant term.

[0028] In an optional implementation, a verification module is further included for performing error verification on the fitting function. If the fitting function does not meet the error requirement, the number of items in the fitting function is adjusted, and the fitting function is re-fitted.

[0029] In an optional embodiment, the internal resistance model includes an internal resistance, a polarization resistance, a discharge resistance, a charging resistance, a polarization capacitor, a first diode and a second diode, and a power supply.

[0030] The first connection end of the internal resistance model is connected to the cathode of the first diode, the anode of the first diode is connected to the first end of the discharge resistor, the second end of the discharge resistor is connected to the anode of the power supply, the cathode of the power supply is connected to the first end of the internal resistance resistor, the second end of the internal resistance resistor is connected to the first end of the polarization internal resistance, and the second end of the polarization internal resistance is connected to the second connection end of the internal resistance model;

[0031] The first end of the charging resistor is connected to the second end of the discharging resistor, the second end of the charging resistor is connected to the positive electrode of the second diode, and the negative electrode of the second diode is connected to the first connection end of the internal resistance model;

[0032] The polarization capacitor is connected in parallel with the polarization resistor.

[0033] In a third aspect, the present invention provides an electronic device, comprising: a processor, a memory and a bus, the memory storing machine-readable instructions executable by the processor, and when the electronic device is running, the processor and the memory communicate through the bus, and the processor executes the machine-readable instructions to perform the steps of the method for estimating the state of charge of a power battery in any of the aforementioned embodiments.

[0034] In a fourth aspect, the present invention provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the steps of the method for estimating the state of charge of a power battery in any of the aforementioned embodiments are executed.

[0035] The present application provides a method for estimating the state of charge of a power battery and a storage medium, the method comprising obtaining a target open circuit voltage value of the power battery; inputting the target open circuit voltage value into a pre-created fitting function to obtain the state of charge of the power battery corresponding to the target open circuit voltage value output by the fitting function; wherein the fitting function is fitted according to the relationship between the open circuit voltage and the state of charge of the power battery. By establishing a fitting function between the open circuit voltage and the state of charge, the state of charge is estimated, thereby improving the accuracy of the state of charge estimation. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0037] Figure 1 A flow chart of a method for estimating the state of charge of a power battery provided in an embodiment of the present application;

[0038] Figure 2 A flowchart of the steps for generating a fitting function provided in an embodiment of the present application;

[0039] Figure 3 An internal resistance model of a power battery provided in an embodiment of the present application;

[0040] Figure 4 A voltage variation curve diagram provided in an embodiment of the present application;

[0041] Figure 5 A current variation curve diagram provided in an embodiment of the present application;

[0042] Figure 6 A voltage pulse curve diagram provided in an embodiment of the present application;

[0043] Figure 7 A structural diagram of a device for estimating the state of charge of a power battery provided in an embodiment of the present application;

[0044] Figure 8 A schematic diagram of the structure of an electronic device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0045] First, the applicable scenarios of the present application are explained. The technical solution of the present application is applicable to SOC estimation of power batteries.

[0046] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application.

[0047] Figure 1 A flow chart of a method for estimating the state of charge of a power battery provided in an embodiment of the present application. Figure 1 As shown, the method for estimating the state of charge of a power battery provided in the present application includes:

[0048] S11. Obtain a target open circuit voltage value of the power battery.

[0049] The target open circuit voltage value here can be specified and needs to be within a reasonable range.

[0050] S12: input the target open circuit voltage value into a pre-created fitting function to obtain the charge state of the power battery output by the fitting function at the target open circuit voltage value.

[0051] The fitting function is fitted according to the relationship between the open circuit voltage and the state of charge of the power battery.

[0052] The fitting function here has been fully verified and can be used to predict the SOC of the power battery at a specific open circuit voltage value. For example, the target open circuit voltage value obtained in step S1 is input into this function to calculate the corresponding SOC, thereby improving the accuracy of SOC estimation.

[0053] like Figure 2 As shown, in one embodiment of the present application, the fitting function can be created in the following manner:

[0054] S21. Based on the internal resistance model of the power battery, determine the state space equation corresponding to the charge state of the power battery during the charging and discharging process.

[0055] like Figure 3 As shown, the internal resistance model includes an internal resistance, a polarization resistance, a discharge resistance, a charging resistance, a polarization capacitor, a first diode, a second diode, and a power supply.

[0056] Among them, the first connection end of the internal resistance model is connected to the cathode of the first diode, the anode of the first diode is connected to the first end of the discharge resistor, the second end of the discharge resistor is connected to the anode of the power supply, the negative electrode of the power supply is connected to the first end of the internal resistance resistor, the second end of the internal resistance resistor is connected to the first end of the polarization internal resistance, and the second end of the polarization internal resistance is connected to the second connection end of the internal resistance model; the first end of the charging resistor is connected to the second end of the discharge resistor, the second end of the charging resistor is connected to the anode of the second diode, and the cathode of the second diode is connected to the first connection end of the internal resistance model; the polarization capacitor is connected in parallel with the polarization resistor.

[0057] Figure 3 Middle,U oc is the open circuit voltage, R0 represents the ohmic internal resistance, R p Represents polarization internal resistance, C p Represents polarized capacitance, R d is the discharge resistance, R c is the charging resistance, U L Indicates terminal voltage, I L (t) is the total circuit current, I cp (t) is the current flowing through the polarization capacitor C p The current, U cp (t) is the polarization capacitance C p The voltage across both ends.

[0058] The internal resistance model takes polarization reactions into account and has better battery dynamic simulation characteristics. At the same time, the change of battery internal resistance during charging and discharging is simulated through charging and discharging resistance, which has better battery dynamic simulation characteristics and makes the equivalent circuit model closer to the actual working conditions of the battery.

[0059] Among them, R cd (t) represents the internal resistance R during charging and discharging d and R c When in the discharge process, R cd (t) = R d ; When in the charging process, R c =R cd (t). According to Kirchhoff's law, the state space equation is constructed:

[0060] I L (t)·[R0+R cd (t)]+U cp (t) = U oc -U L

[0061]

[0062] Assuming the voltage Ucp(t) across the polarized capacitor Cp in the equivalent circuit model as the state variable, the state equation can be obtained after sorting:

[0063]

[0064] According to the definition of SOC:

[0065]

[0066] E m (t) = f[SOC(t)],

[0067] Where SOC(t) represents the SOC at time t, η is the charge and discharge efficiency, Q0 represents the rated capacity, and f[SOC(t)] is the function of the battery open circuit voltage (OCV) with respect to SOC.

[0068] S22. Determine a formula type of a fitting function based on the derivation result of the state-space equation.

[0069] After deriving the state space equation, it can be determined that the relationship between the open circuit voltage and the state of charge of the power battery can be fitted by a polynomial function.

[0070] S23. Collect multiple groups of data pairs of the power battery, each data pair including a sample state of charge of the power battery and a corresponding sample open circuit voltage value.

[0071] In a specific embodiment of the present application, a ternary material 18650 lithium-ion battery can be selected as an example, and the parameters of the power battery are shown in Table 1.

[0072] Table 1 Parameters of ternary material 18650 lithium-ion battery

[0073]

[0074] The SOC and OCV data of the power battery can be collected to form a data pair.

[0075] S24. Perform fitting based on the multiple data sets to obtain the fitting function, wherein the fitting function includes multiple monomials of different degrees and a constant term.

[0076] Taking the aforementioned power battery as an example, curve fitting can be performed through mathematical analysis software (Matlab, etc.) to obtain the fitting function of SOC-OCV:

[0077] U oc (SOC)=2.641+1.714·x-3.512·x 2 +5.708 x 3 -5.068 x 4 +1.867 x 5

[0078] Among them, U oc (SOC) is the open circuit voltage of the battery; x is the state of charge of the battery.

[0079] Furthermore, the error of the fitting formula can be verified.

[0080] S25, performing an error check on the fitting function. If the fitting function does not meet the error requirement, returning to step S22 to adjust the number of items of the fitting function, and refitting to obtain the fitting function.

[0081] Here we can identify the relevant parameters R0, Rp, Cp, Rc, and Rd of the above model. At room temperature of 25°C, HPPC test was performed on 18650 lithium-ion batteries with a capacity of 3.2A·h. The charging and discharging currents are generally maintained at around 1C (3.2A), the instantaneous maximum charging current can reach around 4C (12.8A), and the instantaneous maximum discharging current can reach around 5C (16A). Data is collected every 500ms. The voltage change curve is as follows: Figure 4 The current change curve is shown in Figure 5As shown. Select the voltage pulse curve of any SOC for analysis, such as Figure 6 shown.

[0082] Depend on Figure 6 It can be seen that the AB segment is the voltage of the battery in a static state, that is, the electromotive force E of the battery m The BC segment indicates that the terminal voltage of the battery drops sharply due to the ohmic internal resistance R0 under the excitation of the discharge pulse current. Assuming that the current pulse is I, the ohmic internal resistance R0 can be obtained as:

[0083]

[0084] The difference in internal resistance during charge and discharge can be obtained by removing the common ohmic internal resistance. Figure 5 As shown in the figure, segment DE indicates that after the pulse discharge ends, the battery terminal voltage rises rapidly due to the characteristics of the ohmic internal resistance. Combined with the acquisition of the ohmic internal resistance R0, the discharge internal resistance R d for:

[0085]

[0086] The IJ segment indicates the instantaneous rapid drop in the battery terminal voltage due to the characteristics of the ohmic internal resistance after the pulse charging is completed. Combined with the acquisition of the ohmic internal resistance R0, the charging internal resistance R c for:

[0087]

[0088] In the CD segment, due to the polarization effect, the terminal voltage of the battery drops slowly after a rapid drop. In the EF segment, the battery is at rest, and the voltage rebounds under the influence of the RC loop. During the entire pulse discharge process, the state of the polarized RC loop can be regarded as a zero-state response, from which we can know:

[0089]

[0090] Where τ = R p C p , represents the time constant.

[0091] When the polarization internal resistance R is known p Based on this, the polarization capacitance C p for:

[0092]

[0093] The least squares algorithm is used to identify and update the parameters of the model. The identification results are shown in Table 2.

[0094] Table 2 Battery parameter identification results

[0095]

[0096] Combining the advantages of Sage-Husa noise estimator and AUKF algorithm (Adaptive unscented Kalman filter, referred to as AUKF algorithm), an improved adaptive algorithm, SH-AUKF algorithm, is proposed. Finally, the Monte Carlo method (MC method) is introduced to perform repeated estimation sampling to obtain an approximate estimate of SOC.

[0097] While correcting the covariance matrices Qk and Rk in real time, the noise kq in the state equation and the noise kr in the measurement equation are also updated and adjusted in real time to enhance the tracking effect of time-varying noise. The algorithm flow of SH-AUKF is as follows:

[0098] The first step is to calculate the noise q in the state equation k The average value of:

[0099]

[0100] The second step is to calculate the covariance of the noise in the state equation

[0101]

[0102] The third step is to calculate the noise r in the measurement equation. k The average value of:

[0103]

[0104] Step 4: Calculate the covariance of the noise in the measurement equation

[0105]

[0106] The above Replace the corresponding noise matrix in the UKF algorithm.

[0107] The state equation of the battery is:

[0108]

[0109] U L (k) = f[SOC(k)]-[R L +R cd (t)]·I L (k)-U cp (k)+v(k).

[0110] In the formula, k represents each moment, [SOC(k), U cp (k)] T are the state variables of the state equation, I(k)L is the total current in the circuit, U(k)L is the terminal voltage, ()1ωk and ()2ωk represent process noise, and v(k) represents measurement noise.

[0111] Among them, after adding the system process noise and measurement noise, the state equation and measurement equation of the nonlinear battery dynamic system model can be expressed as:

[0112] x k =f(x k-1 ,u k )+ω k =A k ·x k +B k ·u k +ω k ,

[0113] y k =g(x k ,u k )+v k =f[SOC(k)]-[R L +R cd (t)]·u k -U cp (k)+v(k),

[0114] Among them, yk is the observed variable of the system, uk is the input variable of the system, f is the state function of the system, g is the observation function of the system, ωk is the process noise of the system, vk is the measurement noise of the system, ωk and vk are both Gaussian white noise with zero mean, and their variances are Qk and Rk respectively.

[0115] like Figure 7 As shown, based on the same inventive concept, an embodiment of the present application further provides a device 70 for estimating the state of charge of a power battery, the device comprising:

[0116] An acquisition module 710 is used to acquire a target open circuit voltage value of a power battery;

[0117] The calculation module 720 is used to input the target open circuit voltage value into a pre-created fitting function to obtain the charge state of the power battery corresponding to the target open circuit voltage value output by the fitting function;

[0118] The fitting function is fitted based on the relationship between the open circuit voltage and the state of charge of the power battery.

[0119] In a preferred embodiment, a fitting module 730 is further included, which is used to create a fitting function in the following manner:

[0120] Based on the internal resistance model of the power battery, a state-space equation corresponding to the state of charge of the power battery during the charging and discharging process is determined; based on the derivation result of the state-space equation, the formula type of the fitting function is determined; multiple groups of data pairs of the power battery are collected, each data pair includes a sample state of charge of the power battery and a corresponding sample open-circuit voltage value; fitting is performed based on the multiple groups of data pairs to obtain a fitting function, wherein the fitting function includes multiple monomials of different orders and constant terms.

[0121] In a preferred embodiment, a verification module 740 is further included to perform error verification on the fitting function. If the fitting function does not meet the error requirement, the number of items of the fitting function is adjusted, and the fitting function is re-fitted.

[0122] In a preferred embodiment, the internal resistance model includes an internal resistance resistor, a polarization resistor, a discharge resistor, a charging resistor, a polarization capacitor, a first diode, a second diode, and a power supply, wherein the first connection end of the internal resistance model is connected to the negative electrode of the first diode, the positive electrode of the first diode is connected to the first end of the discharge resistor, the second end of the discharge resistor is connected to the positive electrode of the power supply, the negative electrode of the power supply is connected to the first end of the internal resistance resistor, the second end of the internal resistance resistor is connected to the first end of the polarization internal resistance, and the second end of the polarization internal resistance is connected to the second connection end of the internal resistance model; the first end of the charging resistor is connected to the second end of the discharge resistor, the second end of the charging resistor is connected to the positive electrode of the second diode, and the negative electrode of the second diode is connected to the first connection end of the internal resistance model; the polarization capacitor is connected in parallel with the polarization resistor.

[0123] See also Figure 8 , Figure 8 This is a schematic diagram of the structure of an electronic device provided in an embodiment of the present application. Figure 8 As shown in , the electronic device 800 includes a processor 810 , a memory 820 and a bus 830 .

[0124] The memory 820 stores machine-readable instructions executable by the processor 810. When the electronic device 800 is running, the processor 810 communicates with the memory 820 via a bus 830. When the machine-readable instructions are executed by the processor 810, the steps of a method for estimating the state of charge of a power battery in the above-mentioned method embodiment can be executed. The specific implementation method can be found in the method embodiment, which will not be repeated here.

[0125] An embodiment of the present application also provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of a method for estimating the state of charge of a power battery in the above method embodiment can be executed. The specific implementation method can be found in the method embodiment, which will not be repeated here.

[0126] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0127] In the embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. The device embodiments described above are merely schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some communication interfaces, and the indirect coupling or communication connection of the devices or units can be electrical, mechanical or other forms.

[0128] In addition, the units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0129] Furthermore, the functional modules in the various embodiments of the present application may be integrated together to form an independent part, or each module may exist separately, or two or more modules may be integrated to form an independent part.

[0130] It should be noted that if the function is implemented in the form of a software function module and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application can essentially be embodied in the form of a software product, or the part that contributes to the prior art or the part of the technical solution. The computer software product is stored in a storage medium, including a number of instructions to enable a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM) random access memory (RAM), disk or optical disk, and other media that can store program codes.

[0131] In this document, relational terms such as first and second, etc. are used merely to distinguish one entity or operation from another entity or operation, but do not necessarily require or imply any such actual relationship or order between these entities or operations.

[0132] The above description is only an embodiment of the present application and is not intended to limit the protection scope of the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for estimating the state of charge of a power battery, characterized in that: The method comprises: Obtaining a target open circuit voltage value of the power battery; Inputting the target open circuit voltage value into a pre-created fitting function to obtain a state of charge of the power battery output by the fitting function at the target open circuit voltage value; The fitting function is fitted according to the relationship between the open circuit voltage and the state of charge of the power battery.

2. The method according to claim 1, characterized in that The fitting function is created in the following way: Based on the internal resistance model of the power battery, determine the state space equation corresponding to the charge state of the power battery during the charging and discharging process; Determining a formula type of a fitting function based on a derivation result of the state-space equation; Collecting multiple groups of data pairs of the power battery, each data pair including a sample state of charge of the power battery and a corresponding sample open circuit voltage value; Fitting is performed based on the multiple sets of data to obtain the fitting function, wherein the fitting function includes multiple monomials of different orders and a constant term.

3. The method according to claim 2, characterized in that Also includes: An error check is performed on the fitting function. If the fitting function does not meet the error requirement, the number of items of the fitting function is adjusted, and the fitting function is re-fitted to obtain the fitting function.

4. The method according to claim 2, characterized in that: The internal resistance model includes an internal resistance, a polarization resistance, a discharge resistance, a charging resistance, a polarization capacitor, a first diode, a second diode, and a power supply. The first connection end of the internal resistance model is connected to the cathode of the first diode, the anode of the first diode is connected to the first end of the discharge resistor, the second end of the discharge resistor is connected to the anode of the power supply, the cathode of the power supply is connected to the first end of the internal resistance resistor, the second end of the internal resistance resistor is connected to the first end of the polarization internal resistance, and the second end of the polarization internal resistance is connected to the second connection end of the internal resistance model; The first end of the charging resistor is connected to the second end of the discharging resistor, the second end of the charging resistor is connected to the positive electrode of the second diode, and the negative electrode of the second diode is connected to the first connection end of the internal resistance model; The polarization capacitor is connected in parallel with the polarization resistor.

5. A device for estimating the state of charge of a power battery, characterized in that: The device comprises: An acquisition module, used to obtain a target open circuit voltage value of a power battery; A calculation module, used for inputting the target open circuit voltage value into a pre-created fitting function to obtain a state of charge corresponding to the power battery under the target open circuit voltage value output by the fitting function; The fitting function is fitted according to the relationship between the open circuit voltage and the state of charge of the power battery.

6. The device according to claim 5, characterized in that A fitting module is also included for creating the fitting function in the following manner: Based on the internal resistance model of the power battery, determine the state space equation corresponding to the charge state of the power battery during the charging and discharging process; Determining a formula type of a fitting function based on a derivation result of the state-space equation; Collecting multiple groups of data pairs of the power battery, each data pair including a sample state of charge of the power battery and a corresponding sample open circuit voltage value; Fitting is performed based on the multiple sets of data to obtain the fitting function, wherein the fitting function includes multiple monomials of different orders and a constant term.

7. The device according to claim 5, characterized in that It also includes a verification module for performing error verification on the fitting function. If the fitting function does not meet the error requirement, the number of items in the fitting function is adjusted, and the fitting function is re-fitted.

8. The device according to claim 6, characterized in that The internal resistance model includes an internal resistance, a polarization resistance, a discharge resistance, a charging resistance, a polarization capacitor, a first diode, a second diode, and a power supply. The first connection end of the internal resistance model is connected to the cathode of the first diode, the anode of the first diode is connected to the first end of the discharge resistor, the second end of the discharge resistor is connected to the anode of the power supply, the cathode of the power supply is connected to the first end of the internal resistance resistor, the second end of the internal resistance resistor is connected to the first end of the polarization internal resistance, and the second end of the polarization internal resistance is connected to the second connection end of the internal resistance model; The first end of the charging resistor is connected to the second end of the discharging resistor, the second end of the charging resistor is connected to the positive electrode of the second diode, and the negative electrode of the second diode is connected to the first connection end of the internal resistance model; The polarization capacitor is connected in parallel with the polarization resistor.

9. An electronic device, characterized in that: include: A processor, a memory and a bus, wherein the memory stores machine-readable instructions executable by the processor, and when the electronic device is running, the processor communicates with the memory via the bus, and the processor executes the machine-readable instructions to perform the steps of the method for estimating the state of charge of the power battery as described in any one of claims 1 to 4.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the method for estimating the state of charge of the power battery as claimed in any one of claims 1 to 4 are executed.

Images