Power lithium battery thermal model construction method and system

Abstract

The invention provides a power lithium battery thermal model construction method and system, and the method comprises the steps: constructing a battery heat generation model based on battery parameters; based on the cooling system parameter set, a convective heat transfer coefficient is calculated, and a battery heat dissipation model is constructed; based on the battery parameters, the battery heat generation model and the battery heat dissipation model, obtaining a single battery module heat model; constructing a single battery simulation model, setting a simulation parameter set, and obtaining a plurality of discharge thermal characteristic simulation results; updating the single battery module thermal model into an updated single battery module thermal model; and obtaining the battery module thermal model of the battery pack based on the arrangement condition of the battery pack and the updated single battery module thermal model. By adopting the method, the thermal model of the battery module of the battery pack has better applicability and accuracy.

Description

Technical Field

[0001] This invention relates to the field of new energy battery technology, and in particular to a method and system for constructing thermal models of power lithium batteries. Background Technology

[0002] As power battery technology continues to develop, the energy density of batteries increases, and the heat generated per unit volume also increases, causing the temperature to rise rapidly. This has a negative impact on the usable capacity and lifespan of power batteries.

[0003] Therefore, thermal management of power batteries in new energy vehicles is crucial. Establishing a battery thermal model is the foundation for analyzing factors affecting battery heating and designing battery temperature control and cooling strategies. Design-oriented battery thermal models typically employ methods based on internal mechanisms, combined with electrochemistry, to study heat generation and transfer laws and internal temperature distribution. However, these models have high computational complexity and are difficult to apply to practical temperature control. Control-oriented thermal models, on the other hand, suffer from simplification, insufficient applicability, and inadequate accuracy.

[0004] Existing control-oriented thermal models are typically based on cylindrical or prismatic single-cell lithium batteries, and their accuracy is verified by obtaining experimental data through testing under various operating conditions. However, these testing conditions usually employ typical real-vehicle driving conditions, placing the battery in a constant temperature chamber or at ambient temperature. In existing new energy vehicles, the battery pack arrangement and cooling system settings vary depending on the vehicle configuration. Current technologies lack consideration for cooling systems and battery pack arrangement, resulting in low practicality, limited applicability, and insufficient accuracy. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a method and system for constructing thermal models of power lithium batteries. This invention establishes a single-cell battery module thermal model capable of outputting ideal battery temperatures by incorporating specific parameters of the cooling system. Then, it updates the single-cell battery module thermal model by considering factors such as uneven battery temperature distribution through simulation. Finally, it establishes a battery pack module thermal model by considering the specific arrangement of the battery pack. This invention aims to solve the technical problem in existing control-oriented battery thermal models that insufficiently consider the heat dissipation system and battery pack arrangement, resulting in a limited applicability and low accuracy of the thermal models.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution: The method for constructing a thermal model for power lithium batteries includes the following steps: Obtain battery parameters, and based on the battery parameters, construct a battery heat generation model with charging and discharging current as the input variable; Obtain the cooling system parameter set, calculate the convective heat transfer coefficient based on the cooling system parameter set, and construct a battery heat dissipation model with coolant flow rate as the input variable based on the convective heat transfer coefficient. Based on the battery parameters, the battery heat generation model, and the battery heat dissipation model, a single-cell battery module thermal model is obtained to output the ideal battery temperature. A single-cell battery simulation model is constructed. Based on rapid acceleration, hill climbing, and high-speed driving conditions, a set of simulation parameters is set. Based on the single-cell battery simulation model, the set of simulation parameters, and the convective heat transfer coefficient, several simulation results of discharge thermal characteristics are obtained. Based on several simulation results of the discharge thermal characteristics, the thermal model of the single battery module is updated to the updated single battery module thermal model to output the actual battery temperature. Obtain the battery pack arrangement information, and based on the battery pack arrangement information and the updated individual battery module thermal model, obtain the battery pack module thermal model.

[0007] Compared with the prior art, the beneficial effects of the present invention are as follows: By obtaining the cooling system parameter set, the convective heat transfer coefficient that is more in line with the actual heat dissipation is calculated in a targeted manner, and the battery heat dissipation function that takes into account the liquid cooling heat dissipation factor is obtained. Furthermore, the thermal model of the single battery module is obtained. Compared with the traditional single battery thermal model, the single battery module thermal model incorporates the liquid cooling module, which improves the applicability of the thermal model. By setting the simulation parameter set through various operating conditions and the convective heat transfer coefficient corresponding to the liquid cooling system, multiple simulation results of the discharge thermal characteristics are simulated based on different battery model points. The thermal model of the module composed of the liquid cooling system and the single battery with ideal uniform temperature is corrected. The updated single battery module thermal model takes into account the problem that the non-uniformity of the temperature distribution of the single battery changes due to different discharge rates under different operating conditions, which further leads to changes in the actual battery temperature, thus further improving the accuracy of the thermal model. Since the heat dissipation effect of each single battery is different under the same cooling system parameters due to different battery arrangement methods, the battery module thermal model obtained by combining the battery arrangement has better applicability and accuracy.

[0008] Furthermore, the battery parameters include several fitting coefficients for the relationship between battery internal resistance and battery temperature, and the battery open-circuit voltage. The battery heat generation function is:

[0009] in, Indicates the battery's heat generation value. Indicates the charging and discharging current. , , This represents the fitting coefficient indicating the relationship between battery internal resistance and battery temperature. Indicates the ideal battery temperature. Indicates the battery open-circuit voltage. It represents the entropy heat coefficient.

[0010] Furthermore, the cooling system parameter set includes coolant density, coolant flow rate, coolant dynamic viscosity, coolant thermal conductivity, and equivalent diameter of the cooling pipes. The step of calculating the convective heat transfer coefficient based on the cooling system parameter set includes: The Reynolds number is obtained based on the coolant density, the coolant flow rate, the coolant dynamic viscosity, and the equivalent diameter of the cooling pipe. Based on the set of cooling system parameters, the coolant flow characteristics are determined, and the Nusselt number is obtained based on the coolant flow characteristics and the Reynolds number. The convective heat transfer coefficient is calculated based on the thermal conductivity of the coolant, the equivalent diameter of the cooling pipe, and the Nusselt number.

[0011] Furthermore, the battery heat dissipation function is:

[0012] in, Indicates the battery's heat dissipation value. Indicates the density of the coolant. Representing Prandtl numbers, Indicates the thermal conductivity of the coolant. Indicates the dynamic viscosity of the coolant. Indicates the equivalent diameter of the cooling pipe. This indicates the contact area between the battery and the coolant. Indicates the ideal battery temperature. Indicates the coolant temperature. This indicates the coolant flow rate.

[0013] Furthermore, the battery parameters also include the battery specific heat capacity and battery mass, and the thermal model of the single-cell battery module is as follows:

[0014] in, express The derivative, Indicates the ideal battery temperature. Indicates the battery's heat generation value. Indicates the battery's heat dissipation value. Indicates the battery's specific heat capacity. Indicates battery quality.

[0015] Furthermore, the step of setting the simulation parameter set according to the rapid acceleration condition, the climbing condition, and the high-speed driving condition includes: Based on the rapid acceleration condition, a first discharge rate is determined, and based on the first discharge rate, a first subset of simulation parameters is set. Based on the climbing conditions, a second discharge rate is determined, and based on the second discharge rate, a second subset of simulation parameters is set. Based on the high-speed driving conditions, a third discharge rate is determined, and based on the third discharge rate, a third subset of simulation parameters is set. The first subset of simulation parameters, the second subset of simulation parameters, and the third subset of simulation parameters constitute a simulation parameter set.

[0016] Furthermore, the step of obtaining several discharge thermal characteristic simulation results based on the single-cell simulation model, the simulation parameter set, and the convective heat transfer coefficient includes: Based on the single-cell simulation model, several single-cell locations are determined; Based on the single-cell simulation model, the simulation parameter set and the convective heat transfer coefficient are used to simulate discharge in the simulation software to obtain several discharge thermal characteristic simulation results corresponding to several single-cell locations. Each single-cell location corresponds to three discharge thermal characteristic simulation results.

[0017] Furthermore, the step of updating the thermal model of the single-cell battery module based on several simulation results of the discharge thermal characteristics includes: Based on several simulation results of the aforementioned discharge thermal characteristics, a set of correction coefficients is obtained; Based on the set of correction coefficients, the thermal model of the single-cell battery module is updated to an updated thermal model of the single-cell battery module.

[0018] Furthermore, the step of obtaining the battery pack module thermal model based on the battery pack arrangement and the updated individual battery module thermal model includes: Based on the battery pack arrangement, the individual battery module located near the cooling pipe inlet in the battery pack is selected as the starting battery module, the thermal model of the starting battery module is set as the thermal model of the updated individual battery module, and the coolant temperature corresponding to the starting battery module is set as the coolant inlet temperature. Select the single battery module near the outlet of the cooling pipe in the battery pack as the end battery module, and set the coolant temperature corresponding to the end battery module as the coolant outlet temperature. Based on the number of batteries in the battery pack arrangement, the actual number of times the battery temperature of the last battery module increases relative to the starting battery module is determined, and the number of times the coolant outlet temperature increases relative to the coolant inlet temperature is determined. Based on the updated battery module thermal model, the battery module incremental thermal model of several individual battery modules arranged sequentially in the battery pack is obtained, and a battery pack battery module thermal model is formed with charging and discharging current, coolant flow rate, coolant inlet temperature, and coolant outlet temperature as input variables.

[0019] A power lithium battery thermal model construction system, employing the power lithium battery thermal model construction method described in the above technical solution, the system comprising: The heat generation calculation module is used to obtain battery parameters and, based on the battery parameters, construct a battery heat generation model with charging and discharging current as the input variable. The heat dissipation calculation module is used to obtain the cooling system parameter set, calculate the convective heat transfer coefficient based on the cooling system parameter set, and construct a battery heat dissipation model with the coolant flow rate as the input variable based on the convective heat transfer coefficient. A single-unit module is used to obtain a single-unit battery module thermal model based on the battery parameters, the battery heat generation model, and the battery heat dissipation model, so as to output the ideal battery temperature; The simulation module is used to construct a single-cell battery simulation model. Based on rapid acceleration, hill climbing, and high-speed driving conditions, a set of simulation parameters is set. Based on the single-cell battery simulation model, the set of simulation parameters, and the convective heat transfer coefficient, several simulation results of discharge thermal characteristics are obtained. The update module is used to update the thermal model of the single cell module to an updated single cell module thermal model based on several simulation results of the discharge thermal characteristics, so as to output the actual battery temperature. The arrangement module is used to obtain the battery pack arrangement and, based on the battery pack arrangement and the updated individual battery module thermal model, obtain the battery pack module thermal model. Attached Figure Description

[0020] Figure 1 This is a flowchart of the method for constructing a thermal model of a power lithium battery in the first embodiment of the present invention; Figure 2 This is a structural block diagram of the power lithium battery thermal model construction system in the second embodiment of the present invention; The following detailed description, in conjunction with the accompanying drawings, will further illustrate the present invention. Detailed Implementation

[0021] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Several embodiments of the invention are illustrated in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

[0022] It should be noted that when a component is said to be "fixed to" another component, it can be directly on the other component or there may be an intervening component. When a component is said to be "connected to" another component, it can be directly connected to the other component or there may be an intervening component. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0024] Please see Figure 1 The method for constructing a thermal model of a power lithium battery in the first embodiment of the present invention includes the following steps: Step S10: Obtain battery parameters, and based on the battery parameters, construct a battery heat generation model with charging and discharging current as the input variable; The battery parameters include several fitting coefficients for the relationship between battery internal resistance and battery temperature, and the battery open-circuit voltage. The battery heat generation function is:

[0025] in, Indicates the battery's heat generation value. Indicates the charging and discharging current. , , This represents the fitting coefficient indicating the relationship between battery internal resistance and battery temperature. Indicates the ideal battery temperature. Indicates the battery open-circuit voltage. It represents the entropy heat coefficient.

[0026] Preferably, a second-order fit is performed between the battery internal resistance and the battery temperature to obtain several fitting coefficients. The battery internal resistance can be tested under different ambient temperatures by building a battery testing platform. The battery testing platform uses a constant temperature and humidity chamber, a charge / discharge machine, and a temperature sensor. The internal resistance of the battery during the pulse charge / discharge test can be obtained by dividing the voltage variable during pulse discharge by the charge / discharge current adjusted by the charge / discharge machine. Similarly, the battery is discharged using the battery testing platform, and the change in open-circuit voltage with battery temperature is recorded. The entropy-thermal coefficient can be obtained by taking the partial derivative of the battery open-circuit voltage with respect to the ideal battery temperature value.

[0027] Step S20: Obtain the cooling system parameter set, calculate the convective heat transfer coefficient based on the cooling system parameter set, and construct a battery heat dissipation model with coolant flow rate as the input variable based on the convective heat transfer coefficient. By obtaining the set of parameters of the cooling system, the convective heat transfer coefficient that is more in line with the actual heat dissipation situation is calculated in a targeted manner, and the battery heat dissipation function that takes into account the liquid cooling heat dissipation factor is obtained.

[0028] The cooling system parameter set includes coolant density, coolant flow rate, coolant dynamic viscosity, coolant thermal conductivity, and equivalent diameter of the cooling pipes. The battery heat dissipation function is:

[0029] in, Indicates the battery's heat dissipation value. Indicates the density of the coolant. Representing Prandtl numbers, Indicates the thermal conductivity of the coolant. Indicates the dynamic viscosity of the coolant. Indicates the equivalent diameter of the cooling pipe. This indicates the contact area between the battery and the coolant. Indicates the ideal battery temperature. Indicates the coolant temperature. This indicates the coolant flow rate.

[0030] Step S20 includes: S210: The Reynolds number is obtained based on the coolant density, the coolant flow rate, the coolant dynamic viscosity, and the equivalent diameter of the cooling pipe; The Reynolds number is a dimensionless parameter characterizing fluid flow. It is obtained by multiplying the coolant density, the coolant flow rate, and the equivalent diameter of the cooling pipe, and then dividing by the dynamic viscosity of the coolant.

[0031] S220: Determine the coolant flow characteristics based on the cooling system parameter set, and obtain the Nusselt number based on the coolant flow characteristics and the Reynolds number; Preferably, since the cooling system uses liquid cooling and is a forced convection cooling system, the flow characteristics of the coolant are determined to be turbulent based on the cooling system parameter set. Therefore, the relationship between the Nusselt number and the Reynolds number is determined according to the Dittus-Boelter correlation. Specifically, the coefficients in the Dittus-Boelter correlation, the exponent of the Reynolds number, the Prandtl number, and the exponent of the Prandtl number are determined to establish the relationship between the Nusselt number and the Reynolds number. The Nusselt number can then be further calculated from the Reynolds number.

[0032] S230: Calculate the convective heat transfer coefficient based on the thermal conductivity of the coolant, the equivalent diameter of the cooling pipe, and the Nusselt number.

[0033] Preferably, the equivalent diameter of the cooling pipe is calculated based on the inlet length and inlet width of the cooling pipe, and the convective heat transfer coefficient is obtained by multiplying the Nusselt number and the thermal conductivity of the coolant and dividing by the equivalent diameter of the cooling pipe.

[0034] Step S30: Based on the battery parameters, the battery heat generation model, and the battery heat dissipation model, obtain the thermal model of the single battery module to output the ideal battery temperature; The battery parameters also include the battery specific heat capacity and battery mass. The thermal model of the single battery module is as follows:

[0035] in, express The derivative, Indicates the ideal battery temperature. Indicates the battery's heat generation value. Indicates the battery's heat dissipation value. Indicates the battery's specific heat capacity. Indicates battery quality.

[0036] Preferably, the thermal model of the single-cell battery module is derived by assuming that the battery temperature is uniform, and the ideal battery temperature is derived by ignoring the difference between the battery surface temperature and the cell temperature. The battery parameters also include the battery specific heat capacity and the battery mass. The battery specific heat capacity can be calculated based on the specific heat capacity and corresponding mass of the materials of each part of the battery.

[0037] Step S40: Construct a single-cell battery simulation model, set a simulation parameter set according to the rapid acceleration condition, the hill climbing condition and the high-speed driving condition, and obtain several discharge thermal characteristic simulation results based on the single-cell battery simulation model, the simulation parameter set and the convective heat transfer coefficient. The rapid acceleration, hill climbing, and high-speed driving conditions are important operating conditions affecting battery heating in new energy vehicles. The discharge rate varies under different conditions. In common single-cell lithium batteries, the heat generation rate per unit volume of the tabs is higher than that of the cell. When the overall temperature of the tabs is higher than that of the cell, the tabs will continuously heat the cell, leading to uneven temperature distribution. Especially as the operating conditions become more extreme and the discharge rate increases, the difference between the heat generation of the tabs and the heat generation of the cell becomes more obvious. Therefore, conducting simulation experiments to obtain simulation results of the discharge thermal characteristics corresponding to several temperature measurement points is beneficial for correcting the thermal model of the liquid cooling system and the module composed of single-cell batteries with ideal uniform temperature.

[0038] Step S40 includes: S410: Determine the first discharge rate based on the rapid acceleration condition, and set the first subset of simulation parameters based on the first discharge rate; S420: Determine the second discharge rate based on the climbing condition, and set the second set of simulation parameters based on the second discharge rate; S430: Determine the third discharge rate based on the high-speed driving conditions, and set the third simulation parameter subset based on the third discharge rate; S440: The first subset of simulation parameters, the second subset of simulation parameters, and the third subset of simulation parameters constitute a simulation parameter set.

[0039] Preferably, the first discharge rate is 2C, the second discharge rate is 1.5C, and the third discharge rate is 1C. The simulation parameter set also includes the discharge time and battery ambient temperature corresponding to different discharge rates, and the battery ambient temperature is set according to the liquid cooling system.

[0040] S450: Based on the single-cell simulation model, determine several single-cell locations; S460: Based on the single cell simulation model, the simulation parameter set and the convective heat transfer coefficient are used to simulate discharge in the simulation software to obtain several discharge thermal characteristic simulation results corresponding to several single cell locations. One single cell location corresponds to three discharge thermal characteristic simulation results.

[0041] Preferably, three cell locations are determined: the tab, the middle of the cell, and the bottom of the cell. For each cell location, discharge thermal characteristic curves at three discharge rates are obtained through simulation, which serve as the three corresponding discharge thermal characteristic simulation results. The cell wall temperature characteristics are taken into account, and the internal temperature of the cell is analyzed by combining the discharge thermal characteristic results with the entropy thermal coefficient.

[0042] Step S50: Based on several simulation results of the discharge thermal characteristics, update the thermal model of the single cell module to the updated thermal model of the single cell module, so as to output the actual battery temperature; Step S50 includes: S510: Based on several simulation results of the aforementioned discharge thermal characteristics, obtain a set of correction coefficients; S520: Based on the correction coefficient group, update the thermal model of the single cell module to the updated thermal model of the single cell module.

[0043] Understandably, based on different battery model points, multiple simulation results of the discharge thermal characteristics are generated. The thermal model of the module composed of the liquid cooling system and the single battery with ideal uniform temperature is corrected. The updated single battery module thermal model takes into account the problem that the non-uniformity of the temperature distribution of the single battery changes due to different discharge rates under different operating conditions, which further leads to changes in the actual battery temperature. This is beneficial to improving the accuracy of the thermal model.

[0044] Step S60: Obtain the battery pack arrangement and, based on the battery pack arrangement and the updated individual battery module thermal model, obtain the battery pack module thermal model.

[0045] Preferably, the battery pack in this embodiment includes 6 individual battery modules connected in series, and the 6 individual battery modules are arranged in a row.

[0046] Step S60 includes: S610: Based on the battery pack arrangement, select the single battery module near the cooling pipe inlet in the battery pack as the starting battery module, set the thermal model of the starting battery module as the thermal model of the updated single battery module, and set the coolant temperature corresponding to the starting battery module as the coolant inlet temperature. Preferably, the single-cell battery module closest to the inlet of the cooling pipe is selected as the starting battery module, and the thermal model of the starting battery module is the thermal model of the updated single-cell battery module, which includes the starting battery and part of the coolant for cooling the starting battery.

[0047] S620: Select the single battery module near the outlet of the cooling pipe in the battery pack as the end battery module, and set the coolant temperature corresponding to the end battery module as the coolant outlet temperature. S630: Based on the number of batteries in the battery pack arrangement, determine the actual number of times the battery temperature of the last battery module increases relative to the starting battery module, and determine the number of times the coolant outlet temperature increases relative to the coolant inlet temperature. Based on the updated battery module thermal model, obtain the battery module incremental thermal model of several individual battery modules arranged sequentially in the battery pack, and form a battery pack battery module thermal model with charging and discharging current, coolant flow rate, coolant inlet temperature and coolant outlet temperature as input variables.

[0048] Preferably, based on the coolant inlet temperature and the coolant outlet temperature, the total heat absorbed by the coolant in the cooling system can be calculated, and this heat is equal to the total heat dissipated by the multiple batteries in the battery pack. Based on the coolant temperature at the starting battery module and the coolant temperature at the next battery module starting from the starting battery module, the heat dissipated by the starting battery module can be calculated. The battery temperature between adjacent battery modules is considered to increase at a constant rate, and the coolant temperature between adjacent battery modules is also considered to increase at a constant rate. In the battery pack containing 6 batteries, the actual number of battery temperature increases and the number of coolant temperature increases are both 5. This can be understood as... Based on the updated battery module thermal model, the calculation of coolant inlet temperature and coolant outlet temperature is added. Combined with the battery pack arrangement, the thermal model of each individual battery module in the battery pack, except for the initial battery module, can be calculated. The input variables of the incremental battery module thermal model are the same as those of the updated battery module thermal model, which are the charging and discharging current and the coolant flow rate. The thermal models of all individual battery modules in the battery pack constitute the battery pack module thermal model. By fully considering the battery pack arrangement, the resulting battery pack module thermal model has better applicability and accuracy.

[0049] Please see Figure 2 The power lithium battery thermal model construction system in the second embodiment of the present invention is applied to the power lithium battery thermal model construction method described in the first embodiment above. The system includes: The heat generation calculation module 10 is used to acquire battery parameters and, based on the battery parameters, construct a battery heat generation model with charging and discharging current as the input variable. The battery parameters include several fitting coefficients for the relationship between battery internal resistance and battery temperature, and the battery open-circuit voltage. The battery heat generation function is:

[0050] in, Indicates the battery's heat generation value. Indicates the charging and discharging current. , , This represents the fitting coefficient indicating the relationship between battery internal resistance and battery temperature. Indicates the ideal battery temperature. Indicates the battery open-circuit voltage. It represents the entropy heat coefficient.

[0051] The heat dissipation calculation module 20 is used to obtain the cooling system parameter set, calculate the convective heat transfer coefficient based on the cooling system parameter set, and construct a battery heat dissipation model with the coolant flow rate as the input variable based on the convective heat transfer coefficient. The cooling system parameter set includes coolant density, coolant flow rate, coolant dynamic viscosity, coolant thermal conductivity, and equivalent diameter of the cooling pipes. The battery heat dissipation function is:

[0052] in, Indicates the battery's heat dissipation value. Indicates the density of the coolant. Representing Prandtl numbers, Indicates the thermal conductivity of the coolant. Indicates the dynamic viscosity of the coolant. Indicates the equivalent diameter of the cooling pipe. This indicates the contact area between the battery and the coolant. Indicates the ideal battery temperature. Indicates the coolant temperature. This indicates the coolant flow rate.

[0053] The heat dissipation calculation module 20 includes: The first unit is used to obtain the Reynolds number based on the coolant density, the coolant flow rate, the coolant dynamic viscosity, and the equivalent diameter of the cooling pipe; The second unit is used to determine the coolant flow characteristics based on the cooling system parameter set, so as to obtain the Nusselt number based on the coolant flow characteristics and the Reynolds number; The third unit is used to calculate the convective heat transfer coefficient based on the thermal conductivity of the coolant, the equivalent diameter of the cooling pipe, and the Nusselt number.

[0054] The single-unit module 30 is used to obtain a single-unit battery module thermal model based on the battery parameters, the battery heat generation model and the battery heat dissipation model, so as to output the ideal battery temperature; The battery parameters also include the battery specific heat capacity and battery mass. The thermal model of the single battery module is as follows:

[0055] in, express The derivative, Indicates the ideal battery temperature. Indicates the battery's heat generation value. Indicates the battery's heat dissipation value. Indicates the battery's specific heat capacity. Indicates battery quality.

[0056] The simulation module 40 is used to construct a single-cell battery simulation model. Based on the rapid acceleration condition, the hill climbing condition, and the high-speed driving condition, a set of simulation parameters is set. Based on the single-cell battery simulation model, the set of simulation parameters, and the convective heat transfer coefficient, several simulation results of discharge thermal characteristics are obtained. The simulation module 40 includes: The fourth unit is used to determine the first discharge rate based on the rapid acceleration condition, and to set the first set of simulation parameters based on the first discharge rate. The fifth unit is used to determine the second discharge rate based on the climbing conditions, and to set the second set of simulation parameters based on the second discharge rate; The sixth unit is used to determine the third discharge rate based on the high-speed driving conditions, and to set the third set of simulation parameters based on the third discharge rate; The seventh unit is used to form a simulation parameter set by the first simulation parameter subset, the second simulation parameter subset, and the third simulation parameter subset.

[0057] The eighth unit is used to determine several individual battery locations based on the single-cell simulation model. The ninth unit is used to simulate discharge in simulation software based on the single cell simulation model, using the simulation parameter set and the convective heat transfer coefficient, to obtain several discharge thermal characteristic simulation results corresponding to several single cell locations, with one single cell location corresponding to three discharge thermal characteristic simulation results.

[0058] The update module 50 is used to update the thermal model of the single cell module to an updated single cell module thermal model based on several simulation results of the discharge thermal characteristics, so as to output the actual battery temperature. The update module 50 includes: The tenth unit is used to obtain a set of correction coefficients based on several simulation results of the aforementioned discharge thermal characteristics; The eleventh unit is used to update the thermal model of the single-cell battery module to an updated thermal model of the single-cell battery module based on the set of correction coefficients.

[0059] Arrangement module 60 is used to obtain the battery pack arrangement and, based on the battery pack arrangement and the updated individual battery module thermal model, obtain the battery pack module thermal model.

[0060] The arrangement module 60 includes: The twelfth unit is used to select the single battery module near the inlet of the cooling pipe in the battery pack as the starting battery module based on the battery pack arrangement, set the thermal model of the starting battery module as the thermal model of the updated single battery module, and set the coolant temperature corresponding to the starting battery module as the coolant inlet temperature. The thirteenth unit is used to select the single battery module near the outlet of the cooling pipe in the battery pack as the end battery module, and set the coolant temperature corresponding to the end battery module as the coolant outlet temperature. The fourteenth unit is used to determine the actual number of times the battery temperature of the last battery module increases relative to the starting battery module, and the number of times the coolant outlet temperature increases relative to the coolant inlet temperature, based on the number of batteries in the battery pack arrangement. Based on the updated battery module thermal model, a battery module incremental thermal model of several individual battery modules arranged sequentially in the battery pack is obtained, and a battery pack battery module thermal model is formed with charging and discharging current, coolant flow rate, coolant inlet temperature and coolant outlet temperature as input variables.

[0061] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0062] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for constructing a thermal model for a power lithium battery, characterized in that, Includes the following steps: Obtain battery parameters, and based on the battery parameters, construct a battery heat generation model with charging and discharging current as the input variable; Obtain the cooling system parameter set, calculate the convective heat transfer coefficient based on the cooling system parameter set, and construct a battery heat dissipation model with coolant flow rate as the input variable based on the convective heat transfer coefficient. Based on the battery parameters, the battery heat generation model, and the battery heat dissipation model, a single-cell battery module thermal model is obtained to output the ideal battery temperature. A single-cell battery simulation model is constructed. Based on rapid acceleration, hill climbing, and high-speed driving conditions, a set of simulation parameters is set. Based on the single-cell battery simulation model, the set of simulation parameters, and the convective heat transfer coefficient, several simulation results of discharge thermal characteristics are obtained. Based on several simulation results of the discharge thermal characteristics, the thermal model of the single battery module is updated to the updated single battery module thermal model to output the actual battery temperature. Obtain the battery pack arrangement information, and based on the battery pack arrangement information and the updated individual battery module thermal model, obtain the battery pack module thermal model.

2. The method for constructing a thermal model of a power lithium battery according to claim 1, characterized in that, The battery parameters include several fitting coefficients for the relationship between battery internal resistance and battery temperature, and the battery open-circuit voltage. The battery heat generation function is: in, Indicates the battery's heat generation value. Indicates the charging and discharging current. , , This represents the fitting coefficient indicating the relationship between battery internal resistance and battery temperature. Indicates the ideal battery temperature. Indicates the battery open-circuit voltage. It represents the entropy heat coefficient.

3. The method for constructing a thermal model of a power lithium battery according to claim 2, characterized in that, The cooling system parameter set includes coolant density, coolant flow rate, coolant dynamic viscosity, coolant thermal conductivity, and equivalent diameter of cooling pipes. The step of calculating the convective heat transfer coefficient based on the cooling system parameter set includes: The Reynolds number is obtained based on the coolant density, the coolant flow rate, the coolant dynamic viscosity, and the equivalent diameter of the cooling pipe. Based on the set of cooling system parameters, the coolant flow characteristics are determined, and the Nusselt number is obtained based on the coolant flow characteristics and the Reynolds number. The convective heat transfer coefficient is calculated based on the thermal conductivity of the coolant, the equivalent diameter of the cooling pipe, and the Nusselt number.

4. The method for constructing a thermal model of a power lithium battery according to claim 3, characterized in that, The battery heat dissipation function is: in, Indicates the battery's heat dissipation value. Indicates the density of the coolant. Representing Prandtl numbers, Indicates the thermal conductivity of the coolant. Indicates the dynamic viscosity of the coolant. Indicates the equivalent diameter of the cooling pipe. This indicates the contact area between the battery and the coolant. Indicates the ideal battery temperature. Indicates the coolant temperature. This indicates the coolant flow rate.

5. The method for constructing a thermal model of a power lithium battery according to claim 4, characterized in that, The battery parameters also include the battery specific heat capacity and battery mass. The thermal model of the single battery module is as follows: in, express The derivative, Indicates the ideal battery temperature. Indicates the battery's heat generation value. Indicates the battery's heat dissipation value. Indicates the battery's specific heat capacity. Indicates battery quality.

6. The method for constructing a thermal model of a power lithium battery according to claim 1, characterized in that, The steps for setting the simulation parameter set based on rapid acceleration, hill climbing, and high-speed driving conditions include: Based on the rapid acceleration condition, a first discharge rate is determined, and based on the first discharge rate, a first subset of simulation parameters is set. Based on the climbing conditions, a second discharge rate is determined, and based on the second discharge rate, a second subset of simulation parameters is set. Based on the high-speed driving conditions, a third discharge rate is determined, and based on the third discharge rate, a third subset of simulation parameters is set. The first subset of simulation parameters, the second subset of simulation parameters, and the third subset of simulation parameters constitute a simulation parameter set.

7. The method for constructing a thermal model of a power lithium battery according to claim 1, characterized in that, The step of obtaining several discharge thermal characteristic simulation results based on the single-cell simulation model, the simulation parameter set, and the convective heat transfer coefficient includes: Based on the single-cell simulation model, several single-cell locations are determined; Based on the single-cell simulation model, the simulation parameter set and the convective heat transfer coefficient are used to simulate discharge in the simulation software to obtain several discharge thermal characteristic simulation results corresponding to several single-cell locations. Each single-cell location corresponds to three discharge thermal characteristic simulation results.

8. The method for constructing a thermal model of a power lithium battery according to claim 1, characterized in that, The step of updating the thermal model of the single-cell battery module based on several simulation results of the discharge thermal characteristics includes: Based on several simulation results of the aforementioned discharge thermal characteristics, a set of correction coefficients is obtained; Based on the set of correction coefficients, the thermal model of the single-cell battery module is updated to an updated thermal model of the single-cell battery module.

9. The method for constructing a thermal model of a power lithium battery according to claim 5, characterized in that, The step of obtaining the battery pack module thermal model based on the battery pack arrangement and the updated individual battery module thermal model includes: Based on the battery pack arrangement, the individual battery module located near the cooling pipe inlet in the battery pack is selected as the starting battery module, the thermal model of the starting battery module is set as the thermal model of the updated individual battery module, and the coolant temperature corresponding to the starting battery module is set as the coolant inlet temperature. Select the single battery module near the outlet of the cooling pipe in the battery pack as the end battery module, and set the coolant temperature corresponding to the end battery module as the coolant outlet temperature. Based on the number of batteries in the battery pack arrangement, the actual number of times the battery temperature of the last battery module increases relative to the starting battery module is determined, and the number of times the coolant outlet temperature increases relative to the coolant inlet temperature is determined. Based on the updated battery module thermal model, the battery module incremental thermal model of several individual battery modules arranged sequentially in the battery pack is obtained, and a battery pack battery module thermal model is formed with charging and discharging current, coolant flow rate, coolant inlet temperature, and coolant outlet temperature as input variables.

10. A power lithium battery thermal model construction system, employing the power lithium battery thermal model construction method as described in any one of claims 1 to 9, characterized in that, The system includes: The heat generation calculation module is used to obtain battery parameters and, based on the battery parameters, construct a battery heat generation model with charging and discharging current as the input variable. The heat dissipation calculation module is used to obtain the cooling system parameter set, calculate the convective heat transfer coefficient based on the cooling system parameter set, and construct a battery heat dissipation model with the coolant flow rate as the input variable based on the convective heat transfer coefficient. A single-unit module is used to obtain a single-unit battery module thermal model based on the battery parameters, the battery heat generation model, and the battery heat dissipation model, so as to output the ideal battery temperature; The simulation module is used to construct a single-cell battery simulation model. Based on rapid acceleration, hill climbing, and high-speed driving conditions, a set of simulation parameters is set. Based on the single-cell battery simulation model, the set of simulation parameters, and the convective heat transfer coefficient, several simulation results of discharge thermal characteristics are obtained. The update module is used to update the thermal model of the single cell module to an updated single cell module thermal model based on several simulation results of the discharge thermal characteristics, so as to output the actual battery temperature. The arrangement module is used to obtain the battery pack arrangement and, based on the battery pack arrangement and the updated individual battery module thermal model, obtain the battery pack module thermal model.

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