CN116680938B

CN116680938B - Modeling method and system for lithium battery electric heating coupling model

Info

Publication number: CN116680938B
Application number: CN202310973111.XA
Authority: CN
Inventors: 张雯丽; 文灿辉; 徐美双; 欧周权; 周汩; 张志浩
Original assignee: Tongda Electromagnetic Energy Co ltd
Current assignee: Tongda Electromagnetic Energy Co ltd
Priority date: 2023-08-04
Filing date: 2023-08-04
Publication date: 2023-10-20
Anticipated expiration: 2043-08-04
Also published as: CN116680938A

Abstract

The application provides a modeling method and a system of a lithium battery electric heating coupling model, wherein the method comprises the following steps: according to the actually measured open-circuit voltage data of the lithium battery, the current stored electric quantity of the lithium battery is taken as an independent variable, and the open-circuit voltage of the lithium battery is taken as a dependent variable, so that a dynamic model of the open-circuit voltage of the lithium battery is constructed; according to the internal resistance loss power of the lithium battery, the thermal resistance and the hot melting of the lithium battery, a Foster equivalent temperature rise model is adopted to construct a lithium battery dynamic temperature rise model; according to the actually measured internal resistance value of the lithium battery under the preset working condition, the lithium battery temperature, the charge load and the discharge multiplying power are taken as independent variables, and the lithium battery discharge internal resistance value is taken as a dependent variable, so that a lithium battery discharge internal resistance electrothermal coupling model is constructed; and establishing a lithium battery electrothermal coupling model according to the lithium battery open-circuit voltage dynamic model, the lithium battery dynamic temperature rise model and the lithium battery discharge internal resistance electrothermal coupling model. The application can improve the accuracy of simulation research of the electric heating coupling model of the lithium battery.

Description

Modeling method and system for lithium battery electric heating coupling model

Technical Field

The application relates to the technical field of energy storage, in particular to a modeling method and a modeling system of a lithium battery electric heating coupling model.

Background

The lithium ion battery has the characteristics of higher energy density and power density, high charge and discharge efficiency, long service life, low self-discharge rate, environmental friendliness and the like, and is widely applied to an energy storage system of an electric automobile. At present, the modeling of lithium batteries of most application platforms such as electric automobiles adopts rough equivalent models, such as an internal resistance equivalent model, a Thevenin equivalent model, a second-order RC equivalent circuit model and the like. The model cannot accurately represent the change of key parameters such as voltage, internal resistance, temperature and the like of the lithium battery in the charging and discharging process, cannot finely represent the multi-physical coupling characteristic of the lithium battery in the simulation process of researching the energy storage control strategy of the lithium battery of the electric automobile, and cannot effectively perform capacity configuration, determination of the use boundary and formulation of the control strategy of the battery.

Therefore, how to improve the accuracy of simulation research of the electrothermal coupling model of the lithium battery is a technical problem to be solved urgently by those skilled in the art.

Disclosure of Invention

In order to solve the technical problems, the application provides a modeling method of a lithium battery electric heating coupling model, which can improve the accuracy of simulation research of the lithium battery electric heating coupling model. The application also provides a modeling system of the lithium battery electric heating coupling model, which has the same technical effect.

The first object of the application is to provide a modeling method of a lithium battery electrothermal coupling model.

The first object of the present application is achieved by the following technical solutions:

a modeling method of a lithium battery electrothermal coupling model comprises the following steps:

obtaining actual measurement open-circuit voltage data of a lithium battery, and constructing a lithium battery open-circuit voltage dynamic model by taking the current storage electric quantity of the lithium battery as an independent variable and the open-circuit voltage of the lithium battery as a dependent variable according to the actual measurement open-circuit voltage data;

according to the internal resistance loss power of the lithium battery, the thermal resistance and the hot melting of the lithium battery, a Foster equivalent temperature rise model is adopted to construct a lithium battery dynamic temperature rise model;

obtaining an actually measured internal resistance value of the lithium battery under a preset working condition, and constructing a lithium battery discharge internal resistance electrothermal coupling model by taking the lithium battery temperature, the charge load and the discharge multiplying power as independent variables and taking the lithium battery discharge internal resistance value as a dependent variable according to the actually measured internal resistance value;

and establishing a lithium battery electrothermal coupling model according to the lithium battery open-circuit voltage dynamic model, the lithium battery dynamic temperature rise model and the lithium battery discharge internal resistance electrothermal coupling model.

Preferably, in the modeling method of the electrothermal coupling model of a lithium battery, the obtaining measured open-circuit voltage data of the lithium battery, according to the measured open-circuit voltage data, taking the current stored electric quantity of the lithium battery as an independent variable and taking the open-circuit voltage of the lithium battery as a dependent variable, and constructing the open-circuit voltage dynamic model of the lithium battery includes:

Construction of the current stored power of lithium batteriesInitial charge to lithium cell +.>And lithium battery charge-discharge current->The relation expression of the ampere-hour accumulation number of the formula is as follows:

；

let the total stored electricity of the lithium battery energy storage beThe current stored electric quantity of the lithium battery is +.>And carrying out per unit calculation to obtain the current state of charge (SOC) of the lithium battery, wherein the expression is as follows:

；

acquiring a first actually measured open circuit voltage of the lithium battery when the lithium battery is in a full state, namely the current state of charge (SOC) of the lithium battery is 1；

According to the first measured open circuit voltageAnd the current state of charge SOC, with lithium battery open circuit voltage +.>As a dependent variable, a lithium battery open-circuit voltage dynamic model is constructed, and the expression is as follows:

；

in the method, in the process of the invention,representing the voltage drop coefficient.

Preferably, in the modeling method of the electrothermal coupling model of a lithium battery, the voltage drop coefficient is calculated by the following steps:

acquiring the lowest usable state of charge of the lithium battery, namely that the current state of charge (SOC) of the lithium battery is a preset valueAt this time, the second measured open circuit voltage of the lithium battery +.>；

According to the second measured open circuit voltageAnd a first measured open circuit voltage->Calculating to obtain the voltage drop coefficient +.>The calculation formula is as follows:

；

in the method, in the process of the invention,。

preferably, in the modeling method of the electrothermal coupling model of a lithium battery, the modeling method of constructing a dynamic temperature rise model of the lithium battery by adopting a Foster equivalent temperature rise model according to internal resistance loss power of the lithium battery, thermal resistance and hot melting of the lithium battery includes:

Loss of power according to internal resistance of lithium batteryCorresponding current source->Thermal resistance of lithium cell>Corresponding resistorHeat-dissolving of lithium cell>Corresponding capacitance->Adopts Foster equivalent temperatureAnd (3) lifting the model, and constructing a dynamic temperature rise model of the lithium battery, wherein the expression is as follows:

；

in the method, in the process of the invention,temperature value representing lithium battery, +.>Indicating the initial temperature of the lithium battery, +.>Indicating the temperature of the environment and,represents the mass of the lithium battery in +.>，/>The unit of the hot melt of the lithium battery is +.>Capacitance->，Representing capacitance +.>Is>For +.>Voltage value of the same value, +.>Represents the thermal resistance of the lithium battery in +.>Resistance->，/>Indicating the initial temperature of the lithium battery +.>A corresponding voltage source.

Preferably, in the modeling method of the electrothermal coupling model of a lithium battery, the obtaining an actually measured internal resistance value of the lithium battery under a preset working condition, and according to the actually measured internal resistance value, using a lithium battery temperature, a charge load and a discharge rate as independent variables, and using a lithium battery discharge internal resistance value as a dependent variable, constructing the electrothermal coupling model of the lithium battery discharge internal resistance includes:

acquiring first actually measured internal resistance values of the discharge internal resistances of a plurality of groups of lithium batteries under the environmental conditions that the temperature T is 35 ℃, and under various charge loads SOC and various discharge multiplying powers BL through tests;

Obtaining the internal resistance of the first lithium battery under the current working condition by fitting according to the first actually measured internal resistance valueThe expression is as follows:

；

in the formula, SOC represents the charge load of the current working condition, and BL represents the discharge multiplying power of the current working condition;

acquiring second actually measured internal resistance values of the discharge internal resistances of a plurality of groups of lithium batteries under the environmental conditions of various temperatures T measured through tests under the working condition that the charge load SOC is 0.5 and the discharge multiplying power BL is 50C;

obtaining the current working condition through fitting according to the second actually measured internal resistance valueSecond lithium battery internal resistance of (2)The expression is as follows:

；

in the method, in the process of the invention,a temperature representative of the current environmental condition;

according to the internal resistance of the first lithium batteryAnd second lithium battery internal resistance->And constructing a lithium battery discharge internal resistance electrothermal coupling model by taking a lithium battery discharge internal resistance value as a dependent variable, wherein the expression is as follows:

；

in the method, in the process of the invention,represents the discharge internal resistance value of the lithium battery, +.>Indicating the rated discharge internal resistance of the lithium battery.

Preferably, in the modeling method of the lithium battery electrothermal coupling model, the establishing a lithium battery electrothermal coupling model according to the lithium battery open-circuit voltage dynamic model, the lithium battery dynamic temperature rise model and the lithium battery discharge internal resistance electrothermal coupling model includes:

And taking the lithium battery temperature, the charge load and the discharge multiplying power as input variables of the lithium battery discharge internal resistance electrothermal coupling model, calculating to obtain a lithium battery discharge internal resistance value, and taking the lithium battery discharge internal resistance value as input variables of the lithium battery open-circuit voltage dynamic model and the lithium battery dynamic temperature rise model to establish the lithium battery electrothermal coupling model.

The second object of the application is to provide a modeling system of the lithium battery electrothermal coupling model.

The second object of the present application is achieved by the following technical solutions:

a modeling system for a lithium battery electrothermal coupling model, comprising:

the first construction unit is used for acquiring actual measurement open-circuit voltage data of the lithium battery, and constructing a lithium battery open-circuit voltage dynamic model by taking the current storage electric quantity of the lithium battery as an independent variable and taking the open-circuit voltage of the lithium battery as an independent variable according to the actual measurement open-circuit voltage data;

the second construction unit is used for constructing a dynamic temperature rise model of the lithium battery by adopting a Foster equivalent temperature rise model according to the internal resistance loss power of the lithium battery, the thermal resistance and the hot melting of the lithium battery;

the third construction unit is used for obtaining an actually measured internal resistance value of the lithium battery under a preset working condition, and constructing a lithium battery discharge internal resistance electrothermal coupling model by taking the lithium battery temperature, the charge load and the discharge multiplying power as independent variables and taking the lithium battery discharge internal resistance value as a dependent variable according to the actually measured internal resistance value;

The establishing unit is used for establishing a lithium battery electric heating coupling model according to the lithium battery open-circuit voltage dynamic model, the lithium battery dynamic temperature rise model and the lithium battery discharge internal resistance electric heating coupling model.

Preferably, in the modeling system of the electrothermal coupling model of a lithium battery, the first construction unit is configured to, when executing the obtaining actual measurement open-circuit voltage data of the lithium battery, take a current stored electric quantity of the lithium battery as an independent variable and take an open-circuit voltage of the lithium battery as a dependent variable, construct an open-circuit voltage dynamic model of the lithium battery according to the actual measurement open-circuit voltage data, specifically:

；

According to the first measured open circuit voltageAnd the current state of charge SOC, with lithium battery open circuit voltage +. >As a dependent variable, a lithium battery open-circuit voltage dynamic model is constructed, and the expression is as follows:

；

in the method, in the process of the invention,representing the voltage drop coefficient;

the first construction unit is further configured to calculate the voltage drop coefficient, where the first construction unit is specifically configured to:

；

in the method, in the process of the invention,。

preferably, in the modeling system of the electrothermal coupling model of a lithium battery, the second construction unit is specifically configured to, when executing the modeling system of the electrothermal coupling model of a lithium battery by adopting a Foster equivalent temperature rise model according to the internal resistance loss power of the lithium battery, the thermal resistance and the hot melting of the lithium battery, construct a dynamic temperature rise model of the lithium battery:

loss of power according to internal resistance of lithium batteryCorresponding current source->Thermal resistance of lithium cell>Corresponding resistorHeat-dissolving of lithium cell>Corresponding capacitance->And constructing a dynamic temperature rise model of the lithium battery by adopting a Foster equivalent temperature rise model, wherein the expression is as follows:

；

Preferably, in the modeling system of the electrothermal coupling model of a lithium battery, the third construction unit is configured to, when executing the obtaining an actually measured internal resistance value of the lithium battery under a preset working condition, and taking a lithium battery temperature, a charge load and a discharge rate as independent variables and a lithium battery discharge internal resistance value as dependent variables, construct the electrothermal coupling model of the lithium battery discharge internal resistance, according to the actually measured internal resistance value, specifically:

；

obtaining the internal resistance of the second lithium battery under the current working condition by fitting according to the second actually measured internal resistance valueThe expression is as follows:

；

According to the technical scheme, the change of multiple physical characteristics of the lithium battery is accurately represented by constructing the lithium battery open-circuit voltage dynamic model, the lithium battery dynamic temperature rise model and the lithium battery discharge internal resistance electrothermal coupling model, and the change characteristics of the voltage, the internal resistance and the temperature of the lithium battery in the charge and discharge process are accurately described; and further, according to the lithium battery open-circuit voltage dynamic model, the lithium battery dynamic temperature rise model and the lithium battery discharge internal resistance electrothermal coupling model, establishing a lithium battery electrothermal coupling model, and improving the accuracy of simulation research of the lithium battery electrothermal coupling model. In addition, the technical scheme has the advantages of generalization and simplification, and has important significance in making a battery model closer to reality, making the model accurate degree higher, further researching a control strategy of a lithium battery and the like. In conclusion, the technical scheme can improve the accuracy of simulation research of the electric heating coupling model of the lithium battery.

Drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings that are required to be used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments described in the present application, and other drawings may be obtained according to the drawings without inventive effort to those skilled in the art.

FIG. 1 is a schematic flow chart of a modeling method of a lithium battery electrothermal coupling model in an embodiment of the application;

fig. 2 is a schematic diagram of a Foster equivalent model of a lithium battery in an embodiment of the application;

FIG. 3 is a schematic diagram of the test results of the internal resistance of the lithium battery with respect to the variation of SOC and discharge current under the environmental condition of 35 ℃ in the embodiment of the application;

FIG. 4 is a schematic diagram of the test results of the internal resistance of the lithium battery with respect to the temperature change under the working conditions of 50% SOC and 50C discharge rate in the embodiment of the application;

fig. 5 is a schematic structural diagram of a modeling system of a lithium battery electrothermal coupling model according to an embodiment of the application.

Detailed Description

In order to enable those skilled in the art to better understand the technical solutions of the present application, the technical solutions of the embodiments of the present application will be clearly and completely described below, and it is obvious that the described embodiments are only some embodiments of the present application, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.

In the embodiments provided in the present application, it should be understood that the disclosed method and system may be implemented in other manners. The system embodiments described below are merely illustrative, and for example, the division of units and modules is merely a logical function division, and other divisions may be implemented in practice such as: multiple units or modules may be combined or may be integrated into another system, or some features may be omitted, or not performed. In addition, the various components shown or discussed may be coupled or directly coupled or communicatively coupled to each other via some interface, whether indirectly coupled or communicatively coupled to devices or modules, whether electrically, mechanically, or otherwise.

In addition, each functional unit in each embodiment of the present application may be integrated in one processor, or each unit may be separately used as one device, or two or more units may be integrated in one device; the functional units in the embodiments of the present application may be implemented in hardware, or may be implemented in a form of hardware plus a software functional unit.

Those of ordinary skill in the art will appreciate that: all or part of the steps of implementing the method embodiments described below may be performed by program instructions and associated hardware, and the foregoing program instructions may be stored in a computer readable storage medium, which when executed, perform steps comprising the method embodiments described below; and the aforementioned storage medium includes: a mobile storage device, a Read Only Memory (ROM), a magnetic disk or an optical disk, or the like, which can store program codes.

It should be appreciated that the use of "systems," "devices," "units," and/or "modules" in this disclosure is but one way to distinguish between different components, elements, parts, portions, or assemblies at different levels. However, if other words can achieve the same purpose, the word can be replaced by other expressions.

Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the present application, the meaning of "a plurality" or "a number" means two or more, unless specifically defined otherwise.

If a flowchart is used in the present application, the flowchart is used to describe the operations performed by a system according to an embodiment of the present application. It should be appreciated that the preceding or following operations are not necessarily performed in order precisely. Rather, the steps may be processed in reverse order or simultaneously. Also, other operations may be added to or removed from these processes.

It should also be noted that, in this document, terms such as "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that an article or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such article or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in an article or apparatus that comprises such element.

The embodiment of the application is written in a progressive manner.

As shown in fig. 1, an embodiment of the present application provides a modeling method for a lithium battery electrothermal coupling model, including:

s101, obtaining actual measurement open-circuit voltage data of a lithium battery, and constructing a lithium battery open-circuit voltage dynamic model by taking the current storage electric quantity of the lithium battery as an independent variable and the open-circuit voltage of the lithium battery as a dependent variable according to the actual measurement open-circuit voltage data;

in S101, specifically, an initial model may be constructed by performing mathematical derivation according to the current stored power of the lithium battery and the open-circuit voltage of the lithium battery, and parameters in the initial model may be derived according to the measured open-circuit voltage data of the lithium battery, so as to finally obtain a dynamic model of the open-circuit voltage of the lithium battery.

S102, constructing a dynamic temperature rise model of the lithium battery by adopting a Foster equivalent temperature rise model according to the internal resistance loss power of the lithium battery, the thermal resistance and the hot melting of the lithium battery;

in S102, specifically, referring to fig. 2, a schematic diagram of a Foster equivalent temperature rise model may be further referred to, and according to the internal resistance loss power of the lithium battery and its equivalent thermal resistance and thermal melting coefficient, a Foster equivalent temperature rise model is adopted to construct a dynamic temperature rise model of the lithium battery.

S103, obtaining an actually measured internal resistance value of the lithium battery under a preset working condition, and constructing a lithium battery discharge internal resistance electrothermal coupling model by taking the lithium battery temperature, the charge load and the discharge multiplying power as independent variables and taking the lithium battery discharge internal resistance value as a dependent variable according to the actually measured internal resistance value;

in S103, specifically, the preset working condition may be a standard discharging working condition of the lithium battery, and through a test of the standard working condition, characteristic data, that is, an actually measured internal resistance value, of the lithium battery may be obtained; according to the derivation of the mathematical relationship of the lithium battery discharge internal resistance with respect to the lithium battery temperature, the charge load SOC and the charge-discharge multiplying power multi-factor coupling, a data model of the lithium battery discharge internal resistance multi-physical characteristic coupling can be constructed, the actually measured internal resistance value is further substituted into the data model to be fitted, and finally the lithium battery discharge internal resistance electrothermal coupling model is obtained.

S104, establishing a lithium battery electrothermal coupling model according to the lithium battery open-circuit voltage dynamic model, the lithium battery dynamic temperature rise model and the lithium battery discharge internal resistance electrothermal coupling model.

In S104, specifically, based on the above-constructed open-circuit voltage dynamic model, lithium battery dynamic temperature rise model and lithium battery discharge internal resistance electrothermal coupling model, the lithium battery electrothermal coupling model may be built in a simulink simulation platform. One implementation manner of the method specifically comprises the following steps: and taking the lithium battery temperature, the charge load and the discharge multiplying power as input variables of a lithium battery discharge internal resistance electrothermal coupling model, calculating to obtain a lithium battery discharge internal resistance value, and taking the lithium battery discharge internal resistance value as input variables of a lithium battery open circuit voltage dynamic model and a lithium battery dynamic temperature rise model to establish the lithium battery electrothermal coupling model. Other construction modes can be reasonably adopted for the lithium battery electric heating coupling model, and the application is not limited to the construction modes.

At present, the modeling of lithium batteries of most application platforms such as electric automobiles adopts rough equivalent models, such as an internal resistance equivalent model, a Thevenin equivalent model, a second-order RC equivalent circuit model and the like. The model cannot accurately represent the change of key parameters such as voltage, internal resistance, temperature and the like of the lithium battery in the charging and discharging process, cannot finely represent the multi-physical coupling characteristic of the lithium battery in the simulation process of researching the energy storage control strategy of the lithium battery of the electric automobile, and cannot effectively perform capacity configuration, determination of the use boundary and formulation of the control strategy of the battery.

According to the embodiment, the change of multiple physical characteristics of the lithium battery is accurately represented by constructing the lithium battery open-circuit voltage dynamic model, the lithium battery dynamic temperature rise model and the lithium battery discharge internal resistance electrothermal coupling model, and the change characteristics of the voltage, the internal resistance and the temperature of the lithium battery in the charge and discharge process are accurately described; and further, according to the lithium battery open-circuit voltage dynamic model, the lithium battery dynamic temperature rise model and the lithium battery discharge internal resistance electrothermal coupling model, establishing a lithium battery electrothermal coupling model, and improving the accuracy of simulation research of the lithium battery electrothermal coupling model. In addition, the embodiment has the advantages of generalization and simplification, and has important significance in making a battery model closer to reality, making the model accurate degree higher, further researching a control strategy of a lithium battery and the like. In summary, the above embodiment can improve the accuracy of simulation research on the electrothermal coupling model of the lithium battery.

In other embodiments of the present application, obtaining measured open-circuit voltage data of a lithium battery, and according to the measured open-circuit voltage data, using a current stored electric quantity of the lithium battery as an independent variable and using an open-circuit voltage of the lithium battery as an independent variable, one implementation manner of the step of constructing an open-circuit voltage dynamic model of the lithium battery includes:

S201, constructing current storage capacity of lithium batteryInitial charge to lithium cell +.>And lithium battery charge-discharge currentThe relation expression of the ampere-hour accumulation number of the formula is as follows:

；

in the method, in the process of the invention,indicating the current stored charge of the lithium battery,/->Indicating the initial charge of the lithium battery, +.>Representing the charge and discharge current of the lithium battery;

s202, setting the total stored energy of the lithium battery asThe current stored electric quantity of the lithium battery is +.>Performing per unit calculation to obtain the current state of charge (SOC) of the lithium battery,the expression is as follows:

；

in theoretical analysis and calculation, a per unit value or a relative value is often sampled to represent the magnitude of each physical quantity, for example, a state quantity voltage, current, power, rotation speed, time or frequency, resistance, inductance, and the like are all represented by relative values, and in particular, the per unit calculation is to divide an actual value of a physical quantity by a selected same unit value, which is called a reference value, and the process is called per unit. In the step, the total stored energy of the lithium battery is taken asFor the reference value, the current stored electric quantity of the lithium battery is +.>And carrying out per unit calculation to obtain the current state of charge (SOC) of the lithium battery.

S203, acquiring a first actually measured open circuit voltage of the lithium battery when the lithium battery is in a full state, namely the current state of charge (SOC) of the lithium battery is 1 ；

Wherein the first measured open circuit voltageThe lithium battery can be obtained through test when the lithium battery is in a full charge state, namely the current charge state SOC of the lithium battery is 1. It may also be obtained directly by other means, to which the application is not limited.

S204, according to the first actual measured open circuit voltageAnd the current state of charge SOC, with lithium battery open circuit voltage +.>Construction of lithium battery open-circuit voltage dynamics as dependent variablesThe model is represented as follows:

；

in the method, in the process of the application,representing the voltage drop coefficient.

In some embodiments, the voltage drop coefficientThe method can be calculated by the following steps:

s205, acquiring the lowest usable state of charge of the lithium battery, namely that the current state of charge (SOC) of the lithium battery is a preset valueAt this time, the second measured open circuit voltage of the lithium battery +.>；

Wherein the preset valueMay be determined based on the range of least usable charge for a particular type of lithium battery. For example, if the available SOC range of the lithium battery is 0.25-1, the preset value +.>Taking 0.25; further obtaining the second actually measured open circuit voltage detected by the test when the lithium battery is in the lowest usable state of charge, namely the current state of charge SOC of the lithium battery is 0.25>To the voltage drop coefficient of the lithium battery open-circuit voltage dynamic model +. >And (5) performing measurement and calculation.

S206, according to the second actual measurement of the open circuit voltageAnd a first measured open circuit voltage->Calculating to obtain the voltage drop coefficientThe calculation formula is as follows:

；

in the method, in the process of the application,。

in a specific embodiment, the preset valueTaking 0.25 as an example, the voltage drop coefficient +.>The calculation formula of (2) is as follows:

in this embodiment, an initial model is constructed based on the mathematical relationship derivation of the ampere-hour cumulative number of the charging and discharging current of the lithium battery, the current storage electric quantity of the lithium battery and the open-circuit voltage of the lithium battery, key parameters in the initial model are derived according to the open-circuit voltage test data of the lithium battery, and finally an open-circuit voltage dynamic model of the lithium battery is obtained, so that the change characteristic of the voltage of the lithium battery in the charging and discharging process can be more accurately carved out, and the accuracy of simulation research of the electric heating coupling model of the lithium battery is further improved.

In other embodiments of the present application, one implementation manner of the step of constructing a dynamic temperature rise model of a lithium battery by adopting a Foster equivalent temperature rise model according to the internal resistance loss power of the lithium battery, the thermal resistance and the hot melting of the lithium battery includes:

s301, power is lost according to internal resistance of the lithium batteryCorresponding current source->Thermal resistance of lithium cell>Corresponding resistance->Heat-dissolving of lithium cell >Corresponding capacitance->And constructing a dynamic temperature rise model of the lithium battery by adopting a Foster equivalent temperature rise model, wherein the expression is as follows:

；

in the method, in the process of the application,temperature value representing lithium battery, +.>Indicating the initial temperature of the lithium battery, +.>Indicating the temperature of the environment and,represents the mass of the lithium battery in +.>，/>The unit of the hot melt of the lithium battery is +.>Capacitance->，Representing capacitance +.>Is>For +.>Voltage value of the same value, +.>Represents the thermal resistance of the lithium battery in +.>Resistance->，/>Indicating the initial temperature of the lithium battery +.>A corresponding voltage source.

In the embodiment, according to the internal resistance loss of the lithium battery and the thermal resistance hot melting value of the lithium battery, a Foster equivalent loop is adopted to construct a dynamic temperature rise model of the lithium battery, so that the temperature change characteristic of the lithium battery in the charge and discharge process can be more accurately carved out, and the accuracy of simulation research of the electric heating coupling model of the lithium battery is further improved.

In other embodiments of the present application, one implementation manner of the steps of obtaining an actually measured internal resistance value of a lithium battery under a preset working condition, and constructing a lithium battery discharge internal resistance electrothermal coupling model according to the actually measured internal resistance value, using a lithium battery temperature, a charge load and a discharge rate as independent variables, and using a lithium battery discharge internal resistance value as a dependent variable includes:

S401, acquiring first actually measured internal resistance values of the discharge internal resistances of a plurality of groups of lithium batteries under the environment condition that the temperature T is 35 ℃ and under the conditions of various charge loads SOC and various discharge multiplying powers BL through tests;

specifically, under the environmental condition of 35 ℃, the first measured internal resistance values of the discharge internal resistances of a plurality of groups of lithium batteries are measured through tests under different charge loads SOC and different discharge multiplying powers BL, and the test results are shown in figure 3; the first measured internal resistance value may also be directly obtained by other means, and the present application is not limited thereto.

S402, obtaining the internal resistance of the first lithium battery under the current working condition through fitting according to the first actually measured internal resistance valueThe expression is as follows:

；

s403, obtaining second actually measured internal resistance values of the discharge internal resistances of a plurality of groups of lithium batteries under the environmental conditions of various temperatures T measured through tests under the working condition that the charge load SOC is 0.5 and the discharge multiplying power BL is 50C;

specifically, under the working condition that the charge load SOC is 0.5 and the discharge multiplying power BL is 50C, the second actually measured internal resistance values of the discharge internal resistances of the plurality of groups of batteries are measured under the environmental conditions of different temperatures T through tests, and the test results are shown in fig. 4; the second measured internal resistance value may also be obtained directly by other means, which the present application is not limited to.

S404, obtaining the internal resistance of the second lithium battery under the current working condition through fitting according to the second actually measured internal resistance valueExpression ofThe formula is as follows:

；

in the method, in the process of the invention,a temperature representative of the current environmental condition; it should be noted that the first lithium battery internal resistance +.>And constructing a second lithium battery internal resistance +.>The execution order of (c) may be interchanged or may be executed simultaneously, which does not affect the implementation of the present embodiment.

S405, according to the internal resistance of the first lithium batteryAnd second lithium battery internal resistance->And constructing a lithium battery discharge internal resistance electrothermal coupling model by taking a lithium battery discharge internal resistance value as a dependent variable, wherein the expression is as follows:

；

In the embodiment, considering that the internal resistance of the lithium battery is a variable related to the coupling of multiple physical characteristics of the temperature, the SOC and the charge-discharge multiplying power of the lithium battery, according to the actually measured internal resistance value of the lithium battery under various standard discharge working conditions, a lithium battery discharge internal resistance electrothermal coupling model is constructed in a data fitting mode, and the change characteristic of the internal resistance of the lithium battery in the charge-discharge process can be more accurately carved out, so that the accuracy of simulation research of the lithium battery electrothermal coupling model is further improved.

In a specific embodiment, based on the above-mentioned lithium battery open-circuit voltage dynamic model constructed in S201-S206, the above-mentioned lithium battery dynamic temperature rise model constructed in S301, and the above-mentioned lithium battery discharge internal resistance electrothermal coupling model constructed in S401-S405, one implementation manner of the lithium battery electrothermal coupling model is constructed in a simulink simulation platform, and specifically includes:

s501, adopting a Subsystem module of a simulink simulation platform as a lithium battery generalized simulation module, and setting mask parameters of the lithium battery generalized simulation module;

specifically, the mask parameter is set to include a first measured open circuit voltage of the lithium battery corresponding to the state of charge of the lithium battery being full, i.e., the current state of charge SOC of the lithium battery being 1Rated discharge internal resistance of lithium battery>Rated internal charging resistance of lithium battery>Ambient temperature->Initial temperature of lithium cell->Lithium battery energy storage total storage electric quantity>Initial charge of lithium battery->A second measured open circuit voltage +.2 for a lithium battery corresponding to 0.25SOC (the lithium battery is in the lowest state of charge that can be used, i.e., the current state of charge of the lithium battery is at SOC 0.25)>Series number of cells->And parallel number->Lithium battery mass->Hot melt of lithium cell>Thermal resistance of lithium cell >；

The Subsystem (Subsystem) module of the simulink simulation platform combines some basic modules and signal connection lines thereof into a large module, shields the internal structure, and only hierarchically divides the output number of people outside. Creating a model using a subsystem module has the following advantages: the number of modules displayed in the model window can be reduced, so that the appearance structure of the model is clearer, and a user conceals custom or complex logic in the subsystem, thereby enhancing the readability of the model; on the basis of simplifying the appearance structure diagram of the model, the functional relation among the modules is maintained, so that the modules with specific functions can have independent attributes; a hierarchical block diagram may be built in which a hierarchy is built within a Subsystem module, where the hierarchy is the parent of the internal module.

S502, building 3 subsystems modules, namely a primary loop module of the lithium battery, a temperature rise calculation module and a battery discharge internal resistance calculation module, in the subsystems modules built in the S501;

s503, in the primary circuit module of the lithium battery established in the S502, a primary circuit of the lithium battery is established by adopting a basic module of simulink such as a voltage source module, a current source module, a resistor, an inductor, a diode and a voltage and current sampling module; meanwhile, according to the mathematical expression involved in S201-S206, a basic module of simulink such as an integrating module, an addition and subtraction module, a multiplication module and a Function module is adopted to build an open-circuit voltage model of the lithium battery;

Wherein, MATLAB functions can be implemented into the simulink model using the Function module to deploy and embed the code into the processor.

S504, in a temperature rise calculation module established in S502, a basic module of simulink such as a voltage source module, a resistor, a capacitor, a voltage measurement module, a multiplication module and an addition module is adopted, and a dynamic temperature rise model of the lithium battery is established according to the mathematical expression involved in S301;

s505, in a discharge internal resistance calculation module established in S502, a 2-dimensional Lookup Table module is adopted to fit the change relation (namely the mathematical expression in S402) of the discharge internal resistances of a plurality of groups of lithium batteries under different charge loads SOC and different discharge multiplying powers BL at the environmental temperature of 35 ℃ according to test data; fitting a relation (namely a mathematical expression in S404) of discharge internal resistances of a plurality of groups of lithium batteries along with temperature change under the working conditions that the charge load SOC is 0.5 and the discharge multiplying power BL is 50C by adopting a 1-dimensional Lookup Table module according to test data; multiplying the fitting result by a sine multiplication module according to the mathematical expression in S405 to obtain a lithium battery discharge internal resistance value, namely completing the construction of a lithium battery discharge internal resistance electrothermal coupling model;

the Lookup Table module is also called a Lookup Table module, and nonlinear modeling is performed by using the modules in the Lookup Tables library. The look-up table module uses the data array to map the input values to the output values, solving for an approximate mathematical function.

S506, determining input and output signals and connection relations of the models according to the lithium battery open-circuit voltage dynamic model, the lithium battery dynamic temperature rise model and the lithium battery discharge internal resistance electric heating coupling model constructed in the S503-S505;

specifically, the input variable of the primary loop module of the lithium battery is set as the discharge internal resistance value of the lithium battery output by the battery discharge internal resistance calculation modulePrimary circuit of lithium batteryThe output variable of the module is set as the charge and discharge current of the battery anode and cathode and the lithium battery>Current state of charge SOC of lithium battery, lithium battery open circuit voltage +.>；

Setting the input variable of the temperature rise calculation module as the lithium battery discharge internal resistance value output by the battery discharge internal resistance calculation moduleAnd rated internal charging resistance of lithium battery +.>Charging and discharging current of lithium battery>Setting the output variable of the temperature rise calculation module as the temperature value of the lithium battery +.>And internal resistance loss power of lithium battery->；

Setting the input variable of the discharge internal resistance calculation module as the charge load SOC and the charge-discharge current of the lithium batteryTemperature value of lithium battery +.>Setting the output variable of the battery discharge internal resistance calculation module to be the calculated lithium battery discharge internal resistance value +.>. And determining the signal connection relation among the modules according to the relation of the input and output variables of the modules.

S507, determining input and output variables of the lithium battery generalized simulation module constructed in the S501, wherein the input variables are the anode and the cathode of the battery, and the output variables are the open-circuit voltage of the lithium batteryCurrent state of charge SOC of lithium battery, internal resistance loss power of lithium battery +.>Temperature value of lithium cell->Charging and discharging current of lithium battery>Lithium battery discharge internal resistance value +.>Thus, the establishment of the lithium battery electrothermal coupling model is completed on the simulink simulation platform.

In the implementation, the lithium battery electric heating coupling model is built in the simulink simulation platform based on the lithium battery open-circuit voltage dynamic model constructed in the S201-S206, the lithium battery dynamic temperature rise model constructed in the S301 and the lithium battery discharge internal resistance electric heating coupling model constructed in the S401-S405, so that the advantages of generalization and simplification are achieved, the battery model is closer to reality, the accuracy of the model is higher, and the method has important significance for further researching the control strategy and the like of the lithium battery.

As shown in fig. 5, in another embodiment of the present application, there is also provided a modeling system of a lithium battery electrothermal coupling model, including:

the first construction unit 10 is configured to obtain measured open-circuit voltage data of the lithium battery, and construct a dynamic model of the open-circuit voltage of the lithium battery according to the measured open-circuit voltage data, with the current stored electric quantity of the lithium battery as an independent variable and the open-circuit voltage of the lithium battery as a dependent variable;

The second construction unit 11 is configured to construct a dynamic temperature rise model of the lithium battery by adopting a Foster equivalent temperature rise model according to the internal resistance loss power of the lithium battery, the thermal resistance and the hot melting of the lithium battery;

the third construction unit 12 is configured to obtain an actually measured internal resistance value of the lithium battery under a preset working condition, and construct a lithium battery discharge internal resistance electrothermal coupling model according to the actually measured internal resistance value, with a lithium battery temperature, a charge load and a discharge rate as independent variables and with a lithium battery discharge internal resistance value as a dependent variable;

and the establishing unit 13 is used for establishing a lithium battery electric heating coupling model according to the lithium battery open-circuit voltage dynamic model, the lithium battery dynamic temperature rise model and the lithium battery discharge internal resistance electric heating coupling model.

In other embodiments of the present application, when the first construction unit 10 performs obtaining the measured open-circuit voltage data of the lithium battery, and uses the current stored electricity of the lithium battery as an independent variable and the open-circuit voltage of the lithium battery as a dependent variable according to the measured open-circuit voltage data, the first construction unit is specifically configured to:

；

in the method, in the process of the application,representing the voltage drop coefficient;

the first building unit 10 is further configured to calculate a voltage drop coefficient, where the first building unit 10 is specifically configured to, when performing the calculation of the voltage drop coefficient:

；

in the method, in the process of the application,。

in other embodiments of the present application, the second construction unit 11 is specifically configured to, when performing construction of a dynamic temperature rise model of a lithium battery using a Foster equivalent temperature rise model according to internal resistance loss power of the lithium battery, thermal resistance of the lithium battery, and hot melting:

；

In other embodiments of the present application, the third construction unit 12 is configured to obtain an actually measured internal resistance value of the lithium battery under a preset working condition, and construct a lithium battery discharge internal resistance electrothermal coupling model according to the actually measured internal resistance value, with a lithium battery temperature, a charge load, and a discharge rate as independent variables, and with a lithium battery discharge internal resistance value as dependent variables, where the third construction unit is specifically configured to:

；

in the method, in the process of the application,a temperature representative of the current environmental condition;

according to the internal resistance of the first lithium batteryAnd second lithium battery internal resistance->And constructing a lithium battery discharge internal resistance electrothermal coupling model by taking a lithium battery discharge internal resistance value as a dependent variable, wherein the expression is as follows: />

；

In the method, in the process of the application,represents the discharge internal resistance value of the lithium battery, +.>Indicating the rated discharge internal resistance of the lithium battery.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. The modeling method of the lithium battery electrothermal coupling model is characterized by comprising the following steps of:

establishing a lithium battery electrothermal coupling model according to the lithium battery open-circuit voltage dynamic model, the lithium battery dynamic temperature rise model and the lithium battery discharge internal resistance electrothermal coupling model;

the method for obtaining the actually measured open-circuit voltage data of the lithium battery, taking the current stored electric quantity of the lithium battery as an independent variable and the open-circuit voltage of the lithium battery as an independent variable according to the actually measured open-circuit voltage data, and constructing the open-circuit voltage dynamic model of the lithium battery comprises the following steps:

；

the voltage drop coefficient is calculated by the following steps:

；

in the method, in the process of the invention,；

the method for establishing the lithium battery electric heating coupling model comprises the steps of:

2. The method as claimed in claim 1, wherein the constructing a dynamic temperature rise model of the lithium battery by using a Foster equivalent temperature rise model according to the internal resistance loss power of the lithium battery, the thermal resistance of the lithium battery and the hot melting comprises:

loss of power according to internal resistance of lithium batteryCorresponding current source->Thermal resistance of lithium cell>Corresponding resistance->Heat-dissolving of lithium cell>Corresponding capacitance->And constructing a dynamic temperature rise model of the lithium battery by adopting a Foster equivalent temperature rise model, wherein the expression is as follows:

；

in the method, in the process of the invention,temperature value representing lithium battery, +.>Indicating the initial temperature of the lithium battery, +.>Indicating ambient temperature, ++>Represents the mass of the lithium battery in +.>，/>The unit of the hot melt of the lithium battery is +.>Capacitance->，/>Representing capacitance +.>Is>For +.>Voltage value of the same value, +. >Represents the thermal resistance of a lithium battery in units ofResistance->，/>Indicating the initial temperature of the lithium battery +.>A corresponding voltage source.

3. The method of claim 1, wherein the obtaining the measured internal resistance value of the lithium battery under the preset working condition, and constructing the lithium battery discharge internal resistance electrothermal coupling model according to the measured internal resistance value, with the lithium battery temperature, the charge load and the discharge multiplying power as independent variables and with the lithium battery discharge internal resistance value as dependent variables, comprises:

；

acquiring various temperatures through tests under the working condition that the charge load SOC is 0.5 and the discharge multiplying power BL is 50CTA second measured internal resistance value of the discharge internal resistances of the plurality of groups of lithium batteries;

obtaining the internal resistance of the second lithium battery under the current working condition by fitting according to the second actually measured internal resistance value The expression is as follows:

；

according to the internal resistance of the first lithium batteryAnd second lithium battery internal resistance->Constructing lithium battery discharge internal resistance by taking lithium battery discharge internal resistance value as dependent variableThe thermal coupling model has the expression:

；

4. A modeling system for a model of a lithium battery electrothermal coupling, comprising:

The building unit is used for building a lithium battery electric heating coupling model according to the lithium battery open-circuit voltage dynamic model, the lithium battery dynamic temperature rise model and the lithium battery discharge internal resistance electric heating coupling model;

the first construction unit is configured to, when executing the obtaining of the actually measured open circuit voltage data of the lithium battery, take the current stored electric quantity of the lithium battery as an independent variable and take the open circuit voltage of the lithium battery as a dependent variable, construct a dynamic model of the open circuit voltage of the lithium battery according to the actually measured open circuit voltage data, and specifically:

；

in the method, in the process of the invention,；

the establishing unit is specifically configured to, when executing the establishing a lithium battery electrothermal coupling model according to the lithium battery open-circuit voltage dynamic model, the lithium battery dynamic temperature rise model and the lithium battery discharge internal resistance electrothermal coupling model:

5. The system as claimed in claim 4, wherein the second construction unit, when performing the construction of the dynamic temperature rise model of the lithium battery using the Foster equivalent temperature rise model according to the internal resistance loss power of the lithium battery, the thermal resistance and the hot melting of the lithium battery, is specifically configured to:

；

in the method, in the process of the invention,temperature value representing lithium battery, +.>Indicating the initial temperature of the lithium battery, +.>Indicating ambient temperature, ++>Represents the mass of the lithium battery in +.>，/>The unit of the hot melt of the lithium battery is +.>Capacitance->，/>Representing capacitance +.>Is>For +.>Numerical phaseThe same voltage value, ">Represents the thermal resistance of a lithium battery in units ofResistance->，/>Indicating the initial temperature of the lithium battery +.>A corresponding voltage source.

6. The system as claimed in claim 4, wherein the third construction unit is configured to, when executing the obtaining an actually measured internal resistance value of the lithium battery under the preset working condition, construct a lithium battery discharge internal resistance electrothermal coupling model according to the actually measured internal resistance value, with a lithium battery temperature, a charge load, and a discharge rate as independent variables, and with a lithium battery discharge internal resistance value as a dependent variable:

；