A method for obtaining an equivalent circuit model of a lithium battery and a related device

Abstract

The present invention relates to the field of lithium battery technology, and in particular to a method for acquiring an equivalent circuit model of a lithium battery, a method for estimating the SOC of a lithium battery, an electronic device and a storage medium. The equivalent circuit model includes equivalent circuit models in two states: one is a first equivalent circuit model in a current excitation state, and the other is a second equivalent circuit model in a non-current excitation state; the first equivalent circuit model includes a first parameter; the second equivalent circuit model includes a second parameter; the first parameter is different from the second parameter. The method for acquiring an equivalent circuit model of a lithium battery fully considers the influence of different current excitation states, and can accurately acquire the parameters of the equivalent circuit model according to different current excitation states, so that when the corresponding equivalent circuit model is used to estimate the SOC value of the lithium battery, the accuracy of estimating the SOC value of the lithium battery can be improved, and an accurate SOC value can be obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium batteries, and in particular to a method for acquiring an equivalent circuit model of a lithium battery, a method for estimating the SOC of a lithium battery, an electronic device and a storage medium. Background Art

[0002] The state of charge (SOC) is an important parameter of lithium batteries. Generally, the SOC is estimated through parameters such as voltage, current and temperature, thereby completing functions such as battery charge and discharge control and thermal management.

[0003] In practical applications, it is difficult to achieve accurate online estimation of SOC due to various factors. Currently, the commonly used SOC estimation methods include three categories: traditional methods, model-based methods and intelligent algorithms. Among them, there are two types of models established by the model-based method, one is the electrochemical model and the other is the equivalent circuit model. The equivalent circuit model includes the Rint model, the Thevenin model, the second-order RC model, the PNGV model, the GNL model, etc. Among them, the second-order RC equivalent circuit model (ie, the improved Thevenin model) is the most widely used. However, the existing equivalent circuit model cannot obtain accurate parameters, resulting in low estimation accuracy of the SOC value of the lithium battery and an inability to obtain a more accurate SOC value. Summary of the invention

[0004] In view of this, an embodiment of the present invention provides a method for obtaining an equivalent circuit model of a lithium battery, a method for estimating the SOC of a lithium battery, an electronic device and a storage medium. The method for obtaining an equivalent circuit model of a lithium battery fully considers the influence of different current excitation states, and can accurately obtain parameters of the equivalent circuit model according to different current excitation states. Therefore, when the corresponding equivalent circuit model is used to estimate the SOC value of the lithium battery, the accuracy of estimating the SOC value of the lithium battery can be improved, and an accurate SOC value can be obtained.

[0005] To solve the above technical problems, the embodiments of the present invention provide the following technical solutions:

[0006] In a first aspect, an embodiment of the present invention provides a method for obtaining an equivalent circuit model of a lithium battery, wherein the equivalent circuit model includes equivalent circuit models in two states: one is a first equivalent circuit model in a current excitation state, and the other is a second equivalent circuit model in a non-current excitation state; the first equivalent circuit model includes a first parameter, and the second equivalent circuit model includes a second parameter, and the first parameter is different from the second parameter;

[0007] The method comprises:

[0008] Based on the first equivalent circuit model, a first relational expression for the battery terminal voltage is established, wherein the first relational expression includes the first parameter; based on the second equivalent circuit model, a second relational expression for the battery terminal voltage is established, wherein the second relational expression includes the second parameter;

[0009] Acquire first test data of charging or discharging of the battery under set experimental conditions, the first test data including: test time and battery SOC, current and terminal voltage corresponding to the test time; acquire second test data of the battery under set experimental conditions and in a static state, the second test data including: test time and battery SOC, current and terminal voltage corresponding to the test time; the set experimental conditions are fixed battery temperature and charge and discharge current;

[0010] Obtaining an open circuit voltage characteristic curve of the battery, wherein the open circuit voltage characteristic curve is a curve of a relationship between an open circuit voltage of the battery and a battery SOC at a specific battery temperature;

[0011] According to the battery SOC and battery temperature in the first test data and the second test data, and in accordance with the open circuit voltage characteristic curve, obtaining the open circuit voltage corresponding to the SOC of each battery;

[0012] The first test data and the corresponding open circuit voltage are input into a first relational expression, and the second test data and the corresponding open circuit voltage are input into a second relational expression, and a first parameter and a second parameter are obtained through an identification algorithm.

[0013] In some embodiments, the equivalent circuit model is a second-order RC model including two states;

[0014] The first equivalent circuit model in the current excitation state includes: a first ohmic internal resistance, a first polarization resistance, a second polarization resistance, a first polarization capacitance, a second polarization capacitance and an open circuit voltage;

[0015] The second-order RC model in a non-current excitation state includes: a second ohmic internal resistance, a first bipolarization resistor, a second bipolarization resistor, a first bipolarization capacitor, a second bipolarization capacitor and an open circuit voltage.

[0016] In some embodiments, the first relationship is:

[0017]

[0018]

[0019]

[0020] The second relation is:

[0021]

[0022]

[0023]

[0024] in, is the open circuit voltage of lithium battery, is the terminal voltage of the lithium battery; It is the working current of lithium battery when charging and discharging. is the ohmic internal resistance of the lithium battery under current excitation, is the electrochemical polarization voltage of the lithium battery under current excitation, , They are the polarization internal resistance and electrochemical polarization capacitance of lithium batteries under current excitation. is the concentration difference polarization voltage of the lithium battery under current excitation, , They are respectively the polarization internal resistance and concentration difference polarization capacitance of lithium battery under current excitation; is the ohmic internal resistance of the lithium battery in the state of no current excitation, is the electrochemical polarization voltage of the lithium battery in the state of no current excitation, , They are the polarization internal resistance and electrochemical polarization capacitance of lithium battery in the state of no current excitation, is the concentration difference polarization voltage of the lithium battery in the state of no current excitation, , They are respectively the polarization internal resistance and concentration difference polarization capacitance of lithium battery in the state of no current excitation, and Indicates time.

[0025] In some embodiments, the equivalent circuit model is a Thevenin model including two states;

[0026] The first equivalent circuit model in the current excitation state includes: a first ohmic internal resistance, a first polarization resistance, a first polarization capacitance and an open circuit voltage;

[0027] The second equivalent circuit model in the no-current excitation state includes: a second ohmic internal resistance, a second polarization resistance, a second polarization capacitance and an open circuit voltage.

[0028] In some embodiments, the first relationship is:

[0029]

[0030]

[0031] The second relation is:

[0032]

[0033]

[0034] in, is the open circuit voltage of lithium battery, is the terminal voltage of the lithium battery; It is the working current of lithium battery when charging and discharging. is the ohmic internal resistance of the lithium battery under current excitation, is the polarization voltage of the lithium battery under current excitation, , They are respectively the polarization internal resistance and polarization capacitance of lithium battery under current excitation; is the ohmic internal resistance of the lithium battery in the state of no current excitation, is the polarization voltage of the lithium battery in the state of no current excitation, , They are respectively the polarization internal resistance and polarization capacitance of lithium battery in the state of no current excitation, and Indicates time.

[0035] In some embodiments, the equivalent circuit model is a PNGV model including two states;

[0036] The first equivalent circuit model in the current excitation state includes: an equivalent capacitor, a first ohmic internal resistance, a first polarization resistor, a first polarization capacitor and an open circuit voltage;

[0037] The second equivalent circuit model in the no-current excitation state includes: an equivalent capacitor, a second ohmic internal resistance, a second polarization resistor, a second polarization capacitor and an open circuit voltage.

[0038] In some embodiments, the first relationship is:

[0039]

[0040]

[0041]

[0042] The second relation is:

[0043]

[0044]

[0045]

[0046] in, is the open circuit voltage of lithium battery, is the terminal voltage of the lithium battery, It is the working current of lithium battery when charging and discharging. is the equivalent capacitance of the lithium battery, is the equivalent voltage of lithium battery; is the ohmic internal resistance of the lithium battery under current excitation, is the polarization voltage of the lithium battery under current excitation, , They are respectively the polarization internal resistance and polarization capacitance of lithium battery under current excitation; is the ohmic internal resistance of the lithium battery in the state of no current excitation, is the polarization voltage of the lithium battery in the state of no current excitation, , They are respectively the polarization internal resistance and polarization capacitance of lithium battery in the state of no current excitation, and Indicates time.

[0047] In some embodiments, the equivalent circuit model is a GNL model including two states;

[0048] The first equivalent circuit model in the current excitation state includes: an equivalent capacitor, a first ohmic internal resistance, a first polarization resistor, a second polarization resistor, a first polarization capacitor, a second polarization capacitor and an open circuit voltage;

[0049] The second equivalent circuit model in the non-current excitation state includes: an equivalent capacitor, a second ohmic internal resistance, a first bipolarization resistor, a second bipolarization resistor, a first bipolarization capacitor, a second bipolarization capacitor and an open circuit voltage.

[0050] In some embodiments, the first relationship is:

[0051]

[0052]

[0053]

[0054]

[0055]

[0056] The second relation is:

[0057]

[0058]

[0059]

[0060]

[0061]

[0062]

[0063] in, is the open circuit voltage of lithium battery, is the terminal voltage of the lithium battery, It is the working current of lithium battery when charging and discharging. is the self-discharge current, is the self-discharge resistance, is the equivalent capacitance of the lithium battery, is the equivalent voltage of lithium battery; is the ohmic internal resistance of the lithium battery under current excitation, is the electrochemical polarization voltage of the lithium battery under current excitation, , They are the polarization internal resistance and electrochemical polarization capacitance of lithium batteries under current excitation. is the concentration difference polarization voltage of the lithium battery under current excitation, , They are respectively the polarization internal resistance and concentration difference polarization capacitance of lithium battery under current excitation; is the ohmic internal resistance of the lithium battery in the state of no current excitation, is the electrochemical polarization voltage of the lithium battery in the state of no current excitation, , They are the polarization internal resistance and electrochemical polarization capacitance of lithium battery in the state of no current excitation, is the concentration difference polarization voltage of the lithium battery in the state of no current excitation, , They are respectively the polarization internal resistance and concentration difference polarization capacitance of lithium battery in the state of no current excitation, and Indicates time.

[0064] In some embodiments, the first test data and the second test data are obtained through a hybrid power pulse characteristic test.

[0065] In some embodiments, the open circuit voltage characteristic curve is obtained through a mixed power pulse characteristic test or an open circuit voltage test.

[0066] In some embodiments, fitting is performed by one of a least squares algorithm, an iterative least squares algorithm, a recursive least squares algorithm, a recursive augmented least squares algorithm, and a recursive least squares algorithm with a forgetting factor to obtain the first parameter and the second parameter.

[0067] In some embodiments, different set experimental conditions are changed to obtain the first parameter and the second parameter under different working conditions, and the set experimental conditions include at least one of battery temperature, current magnitude, and current direction.

[0068] In a second aspect, an embodiment of the present invention provides a SOC estimation method for a lithium battery, which performs SOC estimation based on an equivalent circuit model of the lithium battery, wherein the equivalent circuit model of the lithium battery is obtained by using any of the equivalent circuit model acquisition methods for a lithium battery proposed in the first aspect.

[0069] In a third aspect, an embodiment of the present invention provides an electronic device, including:

[0070] A processor and a memory communicatively connected to the processor;

[0071] The memory stores computer program instructions executable by the processor, and when the computer program instructions are called by the processor, the processor executes the SOC estimation method for a lithium battery proposed in the second aspect.

[0072] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium, on which is stored computer program instructions executable by a processor, and when the computer program instructions are called by the processor, the processor executes the SOC estimation method for a lithium battery proposed in the second aspect.

[0073] Beneficial effects of the embodiments of the present invention: Different from the prior art, the equivalent circuit model acquisition method of the lithium battery provided by the embodiments of the present invention includes equivalent circuit models in two states: one is a first equivalent circuit model in a current excitation state, and the other is a second equivalent circuit model in a non-current excitation state; the first equivalent circuit model includes a first parameter; the second equivalent circuit model includes a second parameter; the first parameter is different from the second parameter; the method includes: based on the first equivalent circuit model, establishing a first relationship for the battery terminal voltage, the first relationship includes the first parameter; based on the second equivalent circuit model, establishing a second relationship for the battery terminal voltage, the second relationship includes the second parameter; obtaining first test data of charging or discharging of the battery under set experimental conditions, the first test data includes: test time and test time corresponding to The battery SOC, current and terminal voltage are obtained; the second test data of the battery under the set experimental conditions and in a static state is obtained, the second test data including: the test time and the battery SOC, current and terminal voltage corresponding to the test time; the experimental conditions are set to a fixed battery temperature and charge and discharge current; the open circuit voltage characteristic curve of the battery is obtained, the open circuit voltage characteristic curve is a relationship curve between the open circuit voltage of the battery and the battery SOC at a specific battery temperature; according to the battery SOC and battery temperature in the first test data and the second test data, the open circuit voltage corresponding to each battery SOC is obtained according to the open circuit voltage characteristic curve; the first test data and the corresponding open circuit voltage are input into the first relationship, the second test data and the corresponding open circuit voltage are input into the second relationship, and the first parameter and the second parameter are obtained through the identification algorithm.

[0074] The method for obtaining an equivalent circuit model of a lithium battery provided in an embodiment of the present invention fully considers the influence of different current excitation states, and can accurately obtain the parameters of the equivalent circuit model according to different current excitation states. Therefore, when the corresponding equivalent circuit model is used to estimate the SOC value of the lithium battery, the accuracy of estimating the SOC value of the lithium battery can be improved, and an accurate SOC value can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0075] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art description. Obviously, the drawings described below only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope of protection. For those of ordinary skill in the art, other related drawings can also be obtained based on these drawings without creative work.

[0076] Figure 1 It is a structural schematic diagram of a second-order RC equivalent circuit model of a battery in the prior art;

[0077] Figure 2is the voltage response curve of the battery during each pulse in the HPPC test;

[0078] Figure 3 is a structural schematic diagram of a second-order RC equivalent circuit model of a battery in Embodiment 1 of the present invention;

[0079] Figure 4 is a structural schematic diagram of the Thevenin equivalent circuit model of the battery in the second embodiment of the present invention;

[0080] Figure 5 It is a structural schematic diagram of the PNGV model equivalent circuit model of the battery in the third embodiment of the present invention;

[0081] Figure 6 Schematic diagram of the structure of the GNL model equivalent circuit model of the battery in the fourth embodiment of the present invention;

[0082] Figure 7 It is a schematic diagram of the structure of an electronic device provided in Embodiment 6 of the present invention. DETAILED DESCRIPTION

[0083] In order to make the purpose and advantages of the embodiments of the present invention easier to understand, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The detailed description of the embodiments of the present invention in the drawings below does not limit the scope of protection claimed by the present invention, but only represents the selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0084] It should be noted that, if no conflict is constituted, the various technical features involved in the embodiments of the present invention described below can be combined with each other, and are all within the scope of protection of the present invention. In addition, although the functional modules are divided in the device or structural schematic diagram, and the logical order is shown in the flow chart, in some cases, the steps shown or described can be performed in a different order than the module division in the device, or in a different order than in the flow chart. In addition, the "first", "second", "third" and other similar expressions used herein do not limit the data and execution order, but are only for the purpose of convenience of explanation and to distinguish between the same or similar items with basically the same functions and effects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features.

[0085] Unless otherwise defined, the technical terms and scientific terms used in this specification have the same meanings as those generally understood by those of ordinary skill in the art of the present invention. The terms used in this specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. It should be understood that the term "and / or" used in this specification includes any and all combinations of one or more of the related listed items.

[0086] The battery equivalent circuit model is designed to simulate the electrical characteristics of the battery by simplifying the circuit, so as to facilitate the analysis and prediction of battery performance. These models can help us understand the behavior of the battery in different operating scenarios, such as key indicators such as voltage, current, output power and efficiency. Common battery equivalent circuit models include the Rint model (internal resistance model), the Thevenin model (Thevenin model, also known as the first-order RC model), the second-order RC model, the PNGV model (New Generation Vehicle Partner Program model), the GNL model (nonlinear equivalent model), etc. Among them, the second-order RC model can better balance the model accuracy and model complexity, and has won wide recognition and adoption in the industry, becoming the preferred solution in the field of battery management system (BMS) design and performance optimization.

[0087] See also Figure 1 , Figure 1 The schematic diagram of the structure of a typical second-order RC model 100 in the prior art includes: an ohmic internal resistance , the first polarization resistance , the second polarization resistance , first polarization capacitor , the second polarization capacitor and open circuit voltage Specifically, the first polarization resistance Electrochemical polarization internal resistance , the second polarization resistance is the concentration polarization internal resistance , first polarization capacitor Electrochemical polarization capacitance , the second polarization capacitor is the concentration polarization capacitance .

[0088] Open Circuit Voltage (OCV) is the core part of the model. The open circuit voltage of a battery refers to the voltage across the battery when the battery is not connected to any external load, that is, in an open circuit state. In this state, no current flows inside the battery, so the open circuit voltage directly reflects the electrochemical potential difference of the battery under static conditions and is not affected by internal resistance.

[0089] Battery terminal voltage It is the actual output voltage of the model after considering the influence of the battery internal resistance and load. It refers to the voltage measured between the positive and negative electrodes of the battery when the battery bears the load, that is, under normal working conditions. Due to the resistance inside the battery, when current passes through, this part of the resistance will cause a voltage drop, making the actual terminal voltage lower than the open circuit voltage. The change of battery terminal voltage is restricted by many factors, including the state of charge (SOC), operating temperature and discharge rate.

[0090] The parameter that can be directly measured in the second-order RC model in the experiment is usually the current flowing through the battery and terminal voltage , while other resistance and capacitance parameters (ohm internal resistance , the first polarization resistance , the second polarization resistance , first polarization capacitor , the second polarization capacitor ) cannot be directly tested, so parameter identification is required.

[0091] The identification of resistance and capacitance components in a battery model usually involves a series of experiments. Common experimental methods include the following:

[0092] 1) Constant current charge and discharge test: Charge and discharge the battery at a constant current and record the voltage change over time. By analyzing the charge and discharge curves, the battery's ohmic internal resistance and electrochemical polarization resistance can be estimated.

[0093] 2) Pulse test: Apply a short current pulse to the battery and measure the instantaneous change in voltage before and after the pulse. This method can be used to estimate the dynamic internal resistance of the battery, including fast and slow response RC links.

[0094] 3) AC impedance spectroscopy: Apply a small amplitude AC signal (usually at the millivolt level) and measure the impedance of the battery over a wide frequency range. It can provide impedance information of the battery at different time scales, thereby identifying the parameters of the RC link.

[0095] 4) Step response test: Apply a step change in voltage or current to observe the dynamic response of the battery voltage. The step response can reveal the transient characteristics of the battery and help identify the RC time constant.

[0096] 5) Hybrid Pulse Power Characterization (HPPC) test: As a comprehensive dynamic test method, especially combining the features of pulse test and step response test, it includes a series of pulse charge and discharge of the battery at different states of charge (SOC) of the battery, while also considering the regeneration ability of the battery, providing a more comprehensive view of battery performance.

[0097] In the HPPC test, the battery goes through the following steps: 1) charging to a full state; 2) discharging to a specific state of charge; 3) a period of rest to allow the battery to reach thermal equilibrium; 4) applying a series of current pulses, usually including smaller pulses and larger pulses, to simulate the transient working conditions of the battery in actual applications; 5) recording the voltage response curve during each pulse; 6) performing regenerative charging, that is, applying reverse pulses to evaluate the battery's energy recovery capability.

[0098] The voltage response curve during each pulse is as follows Figure 2 As shown, it mainly includes 4 sections:

[0099] AB segment: voltage jump segment when current is loaded; BC segment: voltage slowly changes segment after current is loaded; CD segment: voltage jump segment after current is unloaded; DE segment: voltage slowly changes segment after current is unloaded. In the prior art, parameters are usually obtained through AB segment and CD segment. When the current changes suddenly (AB and CD segments), the voltage at both ends of the lithium battery will drop and rise suddenly, but at this moment, no polarization effect will occur inside the current, so and There will be no change at this moment, so the voltage drop at the battery terminal when the current appears and disappears can be used to calculate the ohmic internal resistance. , which is expressed as the following formula:

[0100] Formula (1)

[0101] In the prior art, the test data of the DE segment is subsequently obtained. * (Tau1) and * (Tau2), obtained through the test data of the BC segment and .

[0102] However, since the current state of the AB and BC segments is different from that of the CD and DE segments, the current of the AB and CD segments is Usually they are not the same value, but the existing technology is equivalent to taking the average value of the AB segment and the CD segment and assigning it to , so a large error is introduced in the early stage of fitting; similarly, the prior art * Assigned to the BC segment * , parameter identification is performed based on the premise that the two are equal. Although the error of the voltage fitting result of the DE segment is small, the error of the voltage fitting result of the BC segment is large. In actual use, accurate fitting results are usually required in the BC segment. The prior art uses the same set of model parameters for the AC segment and the CE segment with different current excitation states, resulting in a large difference between the fitting results and the actual voltage measurement results of the HPPC experiment in the full SOC segment, and also a large difference between the voltage measurement results during constant current charging and discharging. The reason is that the prior art does not fully consider the influence of different current excitation states. Therefore, when the same set of parameter identification results is applied to different current excitation states, there is a large error in the voltage fitting results, especially when applied to battery voltage estimation at low current. When further applied to battery SOC estimation, accurate estimation values ​​cannot be obtained.

[0103] Example 1 (Second-order RC model in two states)

[0104] The embodiment of the present application fully considers the influence of different current excitation states and provides a method for obtaining an equivalent circuit model of a lithium battery, in which the original equivalent circuit model is improved into an equivalent circuit model with two states, one is an equivalent circuit model with current excitation state, and the other is an equivalent circuit model without current excitation state, and the parameters of the equivalent circuit models in the two states are set separately.

[0105] Take the second-order RC model as an example, Figure 3 As shown, the second-order RC model 200 includes two state models: a state with current excitation and a state without current excitation. The model 201 with current excitation includes: a first ohmic internal resistance , the first polarization resistance , the second polarization resistance , the first polarization capacitor , Second polarization capacitor and open circuit voltage ; Model 202 in the non-current excitation state, including: a second ohm internal resistance , the first two polarization resistor , the second polarization resistor , the first two polarization capacitors , the second polarization capacitor and open circuit voltage .

[0106] By setting a set of parameters for the equivalent circuit models in the two states respectively and identifying these two sets of parameters, the behavior of the battery under different temperatures, different SOCs, different current sizes and different charging and discharging directions can be accurately simulated.

[0107] Based on the above two-state second-order RC model, the battery terminal voltage The discretization relationship can be expressed as follows:

[0108] For the state model with current excitation (AC segment), the terminal voltage The first relation is:

[0109] Formula (2)

[0110] Formula (3)

[0111] Formula (4)

[0112] For the state model without current excitation (CE segment), the terminal voltage The second relation is:

[0113] Formula (5)

[0114] Formula (6)

[0115] Formula (7)

[0116] in, is the open circuit voltage of lithium battery, is the terminal voltage of the lithium battery; It is the working current of lithium battery when charging and discharging. is the ohmic internal resistance of the lithium battery under current excitation, is the electrochemical polarization voltage of the lithium battery under current excitation, , They are the polarization internal resistance and electrochemical polarization capacitance of lithium batteries under current excitation. is the concentration difference polarization voltage of the lithium battery under current excitation, , They are respectively the polarization internal resistance and concentration difference polarization capacitance of lithium battery under current excitation; is the ohmic internal resistance of the lithium battery in the state of no current excitation, is the electrochemical polarization voltage of the lithium battery in the state of no current excitation, , They are the polarization internal resistance and electrochemical polarization capacitance of lithium battery in the state of no current excitation, is the concentration difference polarization voltage of the lithium battery in the state of no current excitation, , They are respectively the polarization internal resistance and concentration difference polarization capacitance of lithium battery in the state of no current excitation, and Indicates time.

[0117] The two sets of parameters are identified, and under set experimental conditions (fixed battery temperature and charge / discharge current), the battery test data (battery SOC, terminal voltage, charge / discharge current, etc.) are obtained through experiments. The experiments used can be constant current charge and discharge test, pulse test, AC impedance spectrum, step response test, etc. In this embodiment, HPPC test is preferably used.

[0118] To perform HPPC test on the battery, first set the experimental conditions, such as battery temperature of 25℃ and discharge current of 1C ("C" refers to the rated capacity of the battery. For example, if a 100Ah battery is charged at 1C, the charging current is 100A). Before the test, adjust the battery state of charge to 100%, and then record the battery SOC and terminal voltage according to the following steps. , Current Changes over time.

[0119] The specific process information is as follows:

[0120]

[0121] In the above process step information, the discharge interval step is 5% SOC, and the standing time is 60 minutes. It can be adjusted according to actual conditions, for example: the discharge interval step is 2% SOC, 3% SOC, 10% SOC, etc., and the standing time is 1.5h, 2h, etc.

[0122] The test data of discharge under the set experimental conditions as above is taken as the first test data; the test data under the set experimental conditions and in a static state is taken as the second test data.

[0123] In addition, the open circuit voltage characteristic curve of the battery is obtained. The open circuit voltage characteristic curve is a table showing the relationship between the open circuit voltage of the battery and the battery SOC and the battery temperature. One way is to obtain it by using the test data of the HPPC test as above. The open circuit voltage is the voltage of the battery at point E during each pulse, that is, the voltage before the next round of discharge after each 60 minutes of rest. The HPPC test as above can only obtain the open circuit voltage at each discharge interval step (that is: the corresponding open circuit voltage at SOC=100%, 95%, 90%, ..., 10%, 5%, 0%), so another way can be used, that is, to test the open circuit voltage of the battery to obtain more accurate and more open circuit voltage experimental data (such as: the corresponding open circuit voltage at SOC=100%, 99%, 98%, ..., 3%, 2%, 1%, 0%).

[0124] According to the battery SOC and battery temperature in the first test data and the second test data, the open circuit voltage corresponding to each battery at a specific SOC and temperature can be obtained according to the open circuit voltage characteristic curve.

[0125] According to the two states of current excitation (AC segment) and no current excitation (CE segment), the first test data and the corresponding open circuit voltage are input into the first terminal voltage relation of formula (2)-formula (4), and the second test data and the corresponding open circuit voltage are input into the second terminal voltage relation of formula (5)-formula (7). The above terminal voltage relation is fitted with the actual test data to obtain the parameter values ​​in the relation.

[0126] Terminal voltage for two-state model The relationship and the corresponding sampling data are used to start the identification algorithm for parameter identification. The identification algorithms include the least squares algorithm, the maximum likelihood function method, the iterative least squares algorithm, the recursive least squares algorithm, the recursive augmented least squares algorithm, the recursive least squares algorithm with the forgetting factor, etc.

[0127] In this embodiment, the nlinfit function in MATLAB is used to perform parameter identification. nlinfit is a function in MATLAB that is used to perform nonlinear least squares regression, which is used to fit data points to a nonlinear mathematical model and minimize the residual sum of squares by adjusting the model parameters. nlinfit uses an iterative algorithm (usually the Loewenberg-Marquardt algorithm) to find the best parameter estimates.

[0128] The initial values ​​of the parameters in the terminal voltage relationship can be determined based on historical experience data or literature data. It is worth noting that the identification of the first parameter and the second parameter does not necessarily mean that all individual parameters are identified independently, but a combination of multiple parameters can be identified. For example, , , and No independent identification is performed, but * and * For example, in some embodiments, the initial value of the parameter in the terminal voltage relationship is set to [ , , , , , , , ]=[0.01, 0.01, 0.01, 0.01, 50, 100, 100, 500], where = * , = * , = * , = * According to the experimental data, the terminal voltage relationship is iteratively calculated using an identification algorithm (the parameter value is continuously changed based on the initial value), and the parameter corresponding to the minimum error between the terminal voltage estimate and the actual value is taken as the result of parameter identification.

[0129] The parameter identification results of the second-order RC model under different SOC states at a specific discharge current (1C) and a specific battery temperature (25°C) are shown in Table 1.

[0130] Table 1 Model parameter identification results (battery temperature 25°C, discharge current 1C)

[0131]

[0132] Subsequently, different set experimental conditions (including at least one of battery temperature, current magnitude, and current direction) are changed, and the above experiments and parameter identification methods are repeated to obtain the first parameters and the second parameters of the second-order RC model under different operating conditions (different temperatures, different current directions, different current magnitudes, and different SOC states).

[0133] When other conditions remain unchanged, only the current of the battery is changed. , and This is a parameter without current excitation, so it is not affected by current changes. Therefore, after fixing this parameter, you only need to identify , , , and .

[0134] By only changing the discharge current, the second-order RC model parameter identification results under different SOC states are shown in Table 2.

[0135] Table 2 Model parameter identification results (battery temperature 25°C, discharge current 0.5C)

[0136]

[0137] Example 2 (Thevenin model with two states)

[0138] This embodiment takes the Thevenin model as an example and improves the original equivalent circuit model into an equivalent circuit model with two states, one is an equivalent circuit model with current excitation, and the other is an equivalent circuit model without current excitation. The parameters of the equivalent circuit models in the two states are set separately.

[0139] like Figure 4 As shown, the Thevenin model 300 includes two state models: a state with current excitation and a state without current excitation. The model 301 with current excitation includes: a first ohmic internal resistance , the first polarization resistance , first polarization capacitor and open circuit voltage ; Model 302 in the non-current excitation state, including: a second ohm internal resistance , the second polarization resistance , the second polarization capacitor and open circuit voltage .

[0140] Based on the above two-state Thevenin model, the battery terminal voltage The discretization relationship can be expressed as follows:

[0141] For the state model with current excitation (AC segment), the terminal voltage The first relation is:

[0142] Formula (8)

[0143] Formula (9)

[0144] For the state model without current excitation (CE segment), the terminal voltage The second relation is:

[0145] Formula (10)

[0146] Formula (11)

[0147] in, is the open circuit voltage of lithium battery, is the terminal voltage of the lithium battery; It is the working current of lithium battery when charging and discharging. is the ohmic internal resistance of the lithium battery under current excitation, is the polarization voltage of the lithium battery under current excitation, , They are respectively the polarization internal resistance and polarization capacitance of lithium battery under current excitation; is the ohmic internal resistance of the lithium battery in the state of no current excitation, is the polarization voltage of the lithium battery in the state of no current excitation, , They are respectively the polarization internal resistance and polarization capacitance of lithium battery in the state of no current excitation, and Indicates time.

[0148] Similarly, these two sets of parameters are identified, and under set experimental conditions (fixed battery temperature and charge and discharge current), the battery test data (battery SOC, terminal voltage, current, etc.) are obtained through experiments. The charge and discharge test data are used as the first test data, and the static test data are used as the second test data.

[0149] In addition, the open circuit voltage characteristic curve of the battery is obtained. According to the battery SOC and battery temperature in the first test data and the second test data, the open circuit voltage corresponding to each battery at a specific SOC and temperature can be obtained according to the open circuit voltage characteristic curve.

[0150] The test data of the battery (terminal voltage, open circuit voltage, current, temperature, SOC, etc.) are obtained through experiments, and the relationship formula (Formula 8-11) derived from the above theory is fitted with the actual test data to obtain the parameter values ​​in the relationship formula. The experiments used can be constant current charge and discharge test, pulse test, AC impedance spectrum, step response test, etc. This embodiment preferably uses HPPC test. The steps and process are similar to those of Example 1, except that the relationship formula is different.

[0151] Finally, the Thevenin model parameter identification result table under different operating conditions (different temperatures, different current directions, different current magnitudes, and different SOC states) is obtained.

[0152] Example 3 (PNGV model in two states)

[0153] This embodiment takes the PNGV model as an example and improves the original equivalent circuit model into an equivalent circuit model with two states, one is an equivalent circuit model with current excitation, and the other is an equivalent circuit model without current excitation. The parameters of the equivalent circuit models in the two states are set separately.

[0154] like Figure 5 As shown, the PNGV model 400 includes two state models: a state with current excitation and a state without current excitation. The model 401 with current excitation includes: an equivalent capacitor , the first ohm internal resistance , the first polarization resistance , first polarization capacitor and open circuit voltage ; Model 402 of the no current excitation state, including: equivalent capacitance , the second ohm internal resistance , the second polarization resistance , the second polarization capacitor and open circuit voltage .

[0155] Based on the above two-state PNGV model, the battery terminal voltage The discretization relationship can be expressed as follows:

[0156] For the state model with current excitation (AC segment), the terminal voltage The first relation is:

[0157] Formula (12)

[0158] Formula (13)

[0159] Formula (14)

[0160] For the state model without current excitation (CE segment), the terminal voltage The second relation is:

[0161] Formula (15)

[0162] Formula (16)

[0163] Formula (17)

[0164] in, is the open circuit voltage of lithium battery, is the terminal voltage of the lithium battery, It is the working current of lithium battery when charging and discharging. is the equivalent capacitance of the lithium battery, is the equivalent voltage of lithium battery; is the ohmic internal resistance of the lithium battery under current excitation, is the polarization voltage of the lithium battery under current excitation, , They are respectively the polarization internal resistance and polarization capacitance of lithium battery under current excitation; is the ohmic internal resistance of the lithium battery in the state of no current excitation, is the polarization voltage of the lithium battery in the state of no current excitation, , They are respectively the polarization internal resistance and polarization capacitance of lithium battery in the state of no current excitation, and Indicates time.

[0165] Similarly, these two sets of parameters are identified, and the test data of the battery (terminal voltage, open circuit voltage, current, temperature, SOC, etc.) is obtained through experiments. The relationship equations (Formulas 12-17) derived from the above theory are fitted with the actual test data to obtain the parameter values ​​in the relationship equations. The experiments used can be constant current charge and discharge tests, pulse tests, AC impedance spectroscopy, step response tests, etc. This embodiment preferably uses HPPC testing. The steps and processes are similar to those of Example 1, except that the relationship equations are different.

[0166] Finally, the PNGV model parameter identification result table under different operating conditions (different temperatures, different current directions, different current magnitudes, and different SOC states) is obtained.

[0167] Example 4 (GNL model in two states)

[0168] This embodiment takes the GNL model as an example and improves the original equivalent circuit model into an equivalent circuit model with two states, one is an equivalent circuit model with current excitation, and the other is an equivalent circuit model without current excitation. The parameters of the equivalent circuit models in the two states are set separately.

[0169] like Figure 6 As shown, the GNL model 500 includes two state models: a state with current excitation and a state without current excitation. The model 501 with current excitation includes: an equivalent capacitor , Self-discharge resistance 、First ohm internal resistance , the first polarization resistance , the second polarization resistance , the first polarization capacitor , Second polarization capacitor and open circuit voltage ; Model 502 of the non-current excitation state, including: equivalent capacitance , Self-discharge resistance 、Second ohm internal resistance , the first two polarization resistor , the second polarization resistor , the first two polarization capacitors , the second polarization capacitor and open circuit voltage .

[0170] Based on the above two-state GNL model, the battery terminal voltage The discretization relationship can be expressed as follows:

[0171] For the state model with current excitation and current not equal to 0, the terminal voltage The first relation is:

[0172] Formula (18)

[0173] Formula (19)

[0174] Formula (20)

[0175] Formula (21)

[0176] Formula (22)

[0177] For the state model without current excitation (CE segment), the terminal voltage The second relation is:

[0178] Formula (23)

[0179] Formula (24)

[0180] Formula (25)

[0181] Formula (26)

[0182] Formula (27)

[0183] Formula (28)

[0184] in, is the open circuit voltage of lithium battery, is the terminal voltage of the lithium battery, It is the working current of lithium battery when charging and discharging. is the self-discharge current, is the self-discharge resistance, is the equivalent capacitance of the lithium battery, is the equivalent voltage of lithium battery; is the ohmic internal resistance of the lithium battery under current excitation, is the electrochemical polarization voltage of the lithium battery under current excitation, , They are the polarization internal resistance and electrochemical polarization capacitance of lithium batteries under current excitation. is the concentration difference polarization voltage of the lithium battery under current excitation, , They are respectively the polarization internal resistance and concentration difference polarization capacitance of lithium battery under current excitation; is the ohmic internal resistance of the lithium battery in the state of no current excitation, is the electrochemical polarization voltage of the lithium battery in the state of no current excitation, , They are the polarization internal resistance and electrochemical polarization capacitance of lithium battery in the state of no current excitation, is the concentration difference polarization voltage of the lithium battery in the state of no current excitation, , They are respectively the polarization internal resistance and concentration difference polarization capacitance of lithium battery in the state of no current excitation, and Indicates time.

[0185] Similarly, these two sets of parameters are identified, and the test data of the battery (terminal voltage, open circuit voltage, current, temperature, SOC, etc.) is obtained through experiments. The relationship equations (Formulas 18-28) derived from the above theory are fitted with the actual test data to obtain the parameter values ​​in the relationship equations. The experiments used can be constant current charge and discharge tests, pulse tests, AC impedance spectroscopy, step response tests, etc. This embodiment preferably uses HPPC testing. The steps and processes are similar to those of Example 1, except that the relationship equations are different.

[0186] Finally, the GNL model parameter identification result table under different working conditions (different temperatures, different current directions, different current magnitudes, and different SOC states) is obtained.

[0187] In summary, the equivalent circuit model acquisition method of the lithium battery provided in the embodiment of the present invention comprises equivalent circuit models in two states: one is a first equivalent circuit model in a current excitation state, and the other is a second equivalent circuit model in a non-current excitation state; the first equivalent circuit model comprises a first parameter; the second equivalent circuit model comprises a second parameter; the first parameter is different from the second parameter; the method comprises: based on the first equivalent circuit model, establishing a first relationship for the battery terminal voltage, the first relationship comprises the first parameter; based on the second equivalent circuit model, establishing a second relationship for the battery terminal voltage, the second relationship comprises the second parameter; obtaining first test data of charging or discharging of the battery under set experimental conditions, the first test data comprising: test time and battery SOC corresponding to the test time , current and terminal voltage; obtain second test data of the battery under set experimental conditions and in a static state, the second test data including: test time and battery SOC, current and terminal voltage corresponding to the test time; set the experimental conditions to a fixed battery temperature and charge and discharge current; obtain the open circuit voltage characteristic curve of the battery, the open circuit voltage characteristic curve is a relationship curve between the open circuit voltage and the battery SOC of the battery at a specific battery temperature; according to the battery SOC and battery temperature in the first test data and the second test data, obtain the open circuit voltage corresponding to each battery SOC according to the open circuit voltage characteristic curve; input the first test data and the corresponding open circuit voltage into the first relationship, input the second test data and the corresponding open circuit voltage into the second relationship, and obtain the first parameter and the second parameter through the identification algorithm.

[0188] The method for obtaining an equivalent circuit model of a lithium battery provided in an embodiment of the present invention fully considers the influence of different current excitation states, and can accurately obtain the parameters of the equivalent circuit model according to different current excitation states. Therefore, when the corresponding equivalent circuit model is used to estimate the SOC value of the lithium battery, the accuracy of estimating the SOC value of the lithium battery can be improved, and an accurate SOC value can be obtained.

[0189] Embodiment 5

[0190] By using the equivalent circuit models and the identified parameters of the above embodiments 1 to 4, combined with the existing model-based SOC estimation method for lithium batteries, the SOC of the battery can be further estimated.

[0191] The battery state (current, temperature, etc. and known open-circuit voltage) obtained by real-time sampling in actual working conditions and the model parameters after parameter identification are input into the corresponding battery equivalent circuit model, and the model estimated voltage of the battery can be obtained according to the terminal voltage relationship; wherein, the battery state is judged whether there is current excitation or not according to the battery state. If there is current excitation (usually the battery is charged or discharged), the battery state is input into the first equivalent circuit model; if there is no current excitation (usually the battery is at rest or fully charged), the battery state is input into the second equivalent circuit model.

[0192] According to the model-estimated voltage, combined with the real voltage obtained by real-time sampling, the estimated SOC under the current working condition can be obtained through the model-based SOC estimation algorithm. The model-based SOC estimation algorithms mainly include Kalman filter algorithm, particle filter algorithm, sliding film observer method, HIF algorithm and various composite algorithms. The specific algorithm implementation will not be described in detail.

[0193] In this embodiment, by using an equivalent circuit model including different current excitation states to estimate the SOC of the lithium battery, the accuracy of estimating the SOC value of the lithium battery can be improved and an accurate SOC value can be obtained.

[0194] Embodiment 6

[0195] This embodiment provides an electronic device. Figure 7 , Figure 7 A schematic structural diagram of an electronic device 700 provided in some embodiments of the present invention is shown.

[0196] For example, Figure 7 As shown, the electronic device 700 includes at least one processor 710 and a memory 720 ( Figure 7 In the example of a bus system connection and a processor, the components in the electronic device 700 are coupled together through the bus system 730, and the bus system 730 is used to realize the connection and communication between these components. It is easy to understand that the bus system 730 includes not only a data bus, but also a power bus, a control bus, and a status signal bus. However, for the sake of clarity and brevity, the following description is omitted. Figure 7 In FIG. 7 , various buses are labeled as bus system 730. Those skilled in the art will appreciate that Figure 7 The structure shown in the embodiment is only for illustration and does not impose any limitation on the structure of the electronic device 700. For example, the electronic device 700 may also include Figure 7 More or fewer components as shown, or with Figure 7 Different configurations are shown.

[0197] Specifically, the processor 710 is used to provide computing and control capabilities to control the electronic device 700 to perform corresponding tasks. For example, the electronic device 700 is controlled to perform the steps in any possible implementation of the SOC estimation method for a lithium battery provided in Embodiment 5 of the present invention. Those skilled in the art will appreciate that the processor 210 may be a general-purpose processor, including a central processing unit (CPU), a network processor (NP), etc.; it may also be a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components.

[0198] The memory 720, as a non-transitory computer-readable storage medium, can be used to store non-transitory software programs, non-transitory computer executable programs, instructions and modules, for example, programs, instructions and modules corresponding to the SOC estimation method of the lithium battery in the embodiment of the present invention. In some embodiments, the memory 720 may include a storage program area and a storage data area, and the storage program area may store an operating system, an application required for at least one function; the storage data area may store data created according to the use of the processor 710, etc. The processor 710 executes various functional applications and data processing of the electronic device 700 by running the non-transitory software programs, instructions and modules stored in the memory 720 to implement the steps in any possible implementation of the SOC estimation method of the lithium battery provided in the fifth embodiment of the present invention. In some embodiments, the memory 720 may include a high-speed random access memory and may also include a non-transitory memory. For example, at least one disk storage device, a flash memory device or other non-transitory solid-state storage device. In some embodiments, the memory 720 may also include a memory remotely arranged relative to the processor 710, and these remote memories may be connected to the processor 710 via a network. It is understood that examples of the above-mentioned network include but are not limited to the Internet, an intranet, a local area network, a mobile communication network and a combination thereof.

[0199] It is easy to understand that the implementation and execution subject of the SOC estimation method of the lithium battery provided in the embodiment of the present invention can be any suitable type of electronic device with certain computing and control capabilities. In some possible implementations, the SOC estimation method of the lithium battery provided in the embodiment of the present invention can be implemented by a processor calling a computer program instruction stored in a memory.

[0200] An embodiment of the present invention also provides a computer-readable storage medium, on which computer program instructions executable by a processor are stored. When the computer program instructions are called by the processor, the processor executes the SOC estimation method for a lithium battery provided in the embodiment of the present invention, or executes the steps in any possible implementation manner of the SOC estimation method for a lithium battery provided in the embodiment of the present invention.

[0201] In some embodiments, the storage medium may be a flash memory, a hard disk, an optical disk, a register, a magnetic surface storage, a removable disk, a CD-ROM, a random access memory (RAM), a read-only memory (ROM), an electrically programmable ROM, and an electrically erasable programmable ROM, or any other form of storage medium known in the technical field, or may be various devices including one or any combination of the above storage media.

[0202] In some embodiments, computer program instructions may be in the form of a program, software, software module, script or code, written in any form of programming language (including compiled or interpreted languages, or declarative or procedural languages), and may be deployed in any form, including as a stand-alone program or as a module, component, subroutine or other unit suitable for use in a computing environment.

[0203] As an example, computer program instructions may, but need not, correspond to a file in a file system, may be stored as part of a file storing other programs or data, such as in one or more scripts in a HyperText Markup Language (HTML) document, in a single file dedicated to the program in question, or in multiple coordinated files (e.g., files storing one or more modules, subroutines, or code portions).

[0204] As an example, the computer program instructions may be deployed to be executed on a computing device (including devices such as smart terminals and servers), or on multiple computing devices located at one location, or on multiple computing devices distributed at multiple locations and interconnected by a communication network. It is easy to understand that all or part of the steps of the method described in the embodiments provided by the present invention above can be directly implemented using electronic hardware or processor executable computer program instructions, or a combination of the two.

[0205] Those skilled in the art will appreciate that the embodiments provided by the present invention are only illustrative, and the order of writing the steps in the method of the embodiment does not mean a strict execution order and does not constitute any limitation on the implementation process. The order can be adjusted, merged and deleted according to actual needs, and the modules or sub-modules, units or sub-units in the device or system of the embodiment can be merged, divided and deleted according to actual needs. For example, the division of units is only a logical function division, and there can be other division methods in actual implementation. For another example, multiple units or components can be combined or integrated into another device, or some features can be ignored or not executed.

[0206] Through the description of the above implementation methods, those skilled in the art can clearly understand that each implementation method can be implemented by means of software plus a general hardware platform, and of course can also be implemented by hardware. Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment method can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. The storage medium can be a disk, an optical disk, a read-only memory (ROM) or a random access memory (RAM), etc.

[0207] It should be noted that the above embodiments are intended to illustrate the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the content of the present invention and implement it accordingly, and cannot be used to limit the scope of protection of the present invention. Ordinary technicians in this field can understand that all or part of the processes of the above embodiments can be implemented according to the technical solutions recorded in the embodiments of the present invention, or some of the technical features can be equivalently replaced. It can be understood that these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and should be regarded as equal changes and modifications based on the embodiments of the present invention, and should all fall within the scope of the claims of the present invention.

Claims

1. A method for obtaining an equivalent circuit model of a lithium battery, characterized in that: The equivalent circuit model includes equivalent circuit models in two states: one is a first equivalent circuit model in a current excitation state, and the other is a second equivalent circuit model in a non-current excitation state; the first equivalent circuit model includes a first parameter, and the second equivalent circuit model includes a second parameter, and the first parameter is different from the second parameter; The method comprises: Based on the first equivalent circuit model, a first relational expression for the battery terminal voltage is established, wherein the first relational expression includes the first parameter; based on the second equivalent circuit model, a second relational expression for the battery terminal voltage is established, wherein the second relational expression includes the second parameter; Acquire first test data of charging or discharging of the battery under set experimental conditions, the first test data including: test time and battery SOC, current and terminal voltage corresponding to the test time; acquire second test data of the battery under set experimental conditions and in a static state, the second test data including: test time and battery SOC, current and terminal voltage corresponding to the test time; the set experimental conditions are fixed battery temperature and charge and discharge current; Obtaining an open circuit voltage characteristic curve of the battery, wherein the open circuit voltage characteristic curve is a curve of a relationship between an open circuit voltage of the battery and a battery SOC at a specific battery temperature; According to the battery SOC and battery temperature in the first test data and the second test data, and in accordance with the open circuit voltage characteristic curve, obtaining the open circuit voltage corresponding to the SOC of each battery; The first test data and the corresponding open circuit voltage are input into a first relational expression, and the second test data and the corresponding open circuit voltage are input into a second relational expression, and a first parameter and a second parameter are obtained through an identification algorithm.

2. The method according to claim 1, characterized in that The equivalent circuit model is a second-order RC model including two states; The first equivalent circuit model in the current excitation state includes: a first ohmic internal resistance, a first polarization resistance, a second polarization resistance, a first polarization capacitance, a second polarization capacitance and an open circuit voltage; The second-order RC model in a non-current excitation state includes: a second ohmic internal resistance, a first bipolarization resistor, a second bipolarization resistor, a first bipolarization capacitor, a second bipolarization capacitor and an open circuit voltage.

3. The method according to claim 2, characterized in that The first relation is: The second relation is: in, is the open circuit voltage of lithium battery, is the terminal voltage of the lithium battery; It is the working current of lithium battery when charging and discharging. is the ohmic internal resistance of the lithium battery under current excitation, is the electrochemical polarization voltage of the lithium battery under current excitation, , They are the polarization internal resistance and electrochemical polarization capacitance of lithium batteries under current excitation. is the concentration difference polarization voltage of the lithium battery under current excitation, , They are respectively the polarization internal resistance and concentration difference polarization capacitance of lithium battery under current excitation; is the ohmic internal resistance of the lithium battery in the state of no current excitation, is the electrochemical polarization voltage of the lithium battery in the state of no current excitation, , They are the polarization internal resistance and electrochemical polarization capacitance of lithium battery in the state of no current excitation, is the concentration difference polarization voltage of the lithium battery in the state of no current excitation, , They are respectively the polarization internal resistance and concentration difference polarization capacitance of lithium battery in the state of no current excitation, and Indicates time.

4. The method according to claim 1, characterized in that The equivalent circuit model is a Thevenin model including two states; The first equivalent circuit model in the current excitation state includes: a first ohmic internal resistance, a first polarization resistance, a first polarization capacitance and an open circuit voltage; The second equivalent circuit model in the no-current excitation state includes: a second ohmic internal resistance, a second polarization resistance, a second polarization capacitance and an open circuit voltage.

5. The method according to claim 4, characterized in that The first relation is: The second relation is: in, is the open circuit voltage of lithium battery, is the terminal voltage of the lithium battery; It is the working current of lithium battery when charging and discharging. is the ohmic internal resistance of the lithium battery under current excitation, is the polarization voltage of the lithium battery under current excitation, , They are respectively the polarization internal resistance and polarization capacitance of lithium battery under current excitation; is the ohmic internal resistance of the lithium battery in the state of no current excitation, is the polarization voltage of the lithium battery in the state of no current excitation, , They are the polarization internal resistance and polarization capacitance of lithium battery in the state of no current excitation, and Indicates time.

6. The method according to claim 1, characterized in that The equivalent circuit model is a PNGV model including two states; The first equivalent circuit model in the current excitation state includes: an equivalent capacitor, a first ohmic internal resistance, a first polarization resistor, a first polarization capacitor and an open circuit voltage; The second equivalent circuit model in the non-current excitation state includes: an equivalent capacitor, a second ohmic internal resistance, a second polarization resistor, a second polarization capacitor and an open circuit voltage.

7. The method according to claim 6, characterized in that The first relation is: The second relation is: in, is the open circuit voltage of lithium battery, is the terminal voltage of the lithium battery, It is the working current of lithium battery when charging and discharging. is the equivalent capacitance of the lithium battery, is the equivalent voltage of lithium battery; is the ohmic internal resistance of the lithium battery under current excitation, is the polarization voltage of the lithium battery under current excitation, , They are respectively the polarization internal resistance and polarization capacitance of lithium battery under current excitation; is the ohmic internal resistance of the lithium battery in the state of no current excitation, is the polarization voltage of the lithium battery in the state of no current excitation, , They are the polarization internal resistance and polarization capacitance of lithium battery in the state of no current excitation, and Indicates time.

8. The method according to claim 1, characterized in that The equivalent circuit model is a GNL model including two states; The first equivalent circuit model in the current excitation state includes: an equivalent capacitor, a first ohmic internal resistance, a first polarization resistor, a second polarization resistor, a first polarization capacitor, a second polarization capacitor and an open circuit voltage; The second equivalent circuit model in the non-current excitation state includes: an equivalent capacitor, a second ohmic internal resistance, a first bipolarization resistor, a second bipolarization resistor, a first bipolarization capacitor, a second bipolarization capacitor and an open circuit voltage.

9. The method according to claim 8, characterized in that The first relation is: The second relation is: in, is the open circuit voltage of lithium battery, is the terminal voltage of the lithium battery, It is the working current of lithium battery when charging and discharging. is the self-discharge current, is the self-discharge resistance, is the equivalent capacitance of the lithium battery, is the equivalent voltage of lithium battery; is the ohmic internal resistance of the lithium battery under current excitation, is the electrochemical polarization voltage of the lithium battery under current excitation, , They are the polarization internal resistance and electrochemical polarization capacitance of lithium batteries under current excitation. is the concentration difference polarization voltage of the lithium battery under current excitation, , They are respectively the polarization internal resistance and concentration difference polarization capacitance of lithium battery under current excitation; is the ohmic internal resistance of the lithium battery in the state of no current excitation, is the electrochemical polarization voltage of the lithium battery in the state of no current excitation, , They are the polarization internal resistance and electrochemical polarization capacitance of lithium battery in the state of no current excitation, is the concentration difference polarization voltage of the lithium battery in the state of no current excitation, , They are respectively the polarization internal resistance and concentration difference polarization capacitance of lithium battery in the state of no current excitation, and Indicates time.

10. The method according to claim 1, characterized in that The first test data and the second test data are obtained through a mixed power pulse characteristic test.

11. The method according to claim 1, characterized in that The open circuit voltage characteristic curve is obtained by a mixed power pulse characteristic test or an open circuit voltage test.

12. The method according to claim 1, characterized in that The first parameter and the second parameter are obtained by fitting through one of the least squares algorithm, iterative least squares algorithm, recursive least squares algorithm, recursive augmented least squares algorithm, and recursive least squares algorithm with forgetting factor.

13. The method according to claim 1, characterized in that Different set experimental conditions are changed to obtain the first parameter and the second parameter under different working conditions, and the set experimental conditions include at least one of battery temperature, current magnitude and current direction.

14. A method for estimating the SOC of a lithium battery, characterized in that: SOC estimation is performed based on an equivalent circuit model of a lithium battery, wherein the equivalent circuit model of the lithium battery is obtained by using the method for obtaining an equivalent circuit model of a lithium battery as described in any one of claims 1 to 13.

15. An electronic device, characterized in that: include: A processor and a memory communicatively connected to the processor; The memory stores computer program instructions executable by the processor, and when the computer program instructions are called by the processor, the processor executes the SOC estimation method for a lithium battery as claimed in claim 14.

16. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer program instructions executable by a processor, and when the computer program instructions are called by the processor, the processor executes the SOC estimation method for a lithium battery as described in claim 14.

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