Power battery system heating / cooling scheme rapid evaluation method and medium

Abstract

The application discloses a kind of power battery system heating / cooling scheme rapid evaluation method and medium.The method can include: according to the heat generation power of cell soc and temperature matrix by table lookup and calculation;Based on the heat generation power of cell, the heat production rate of power battery is calculated;Determine the cooling water temperature;According to the heat production rate of power battery, cooling water temperature and the temperature matrix of last iteration, two-dimensional heat conduction differential equation is solved, the temperature matrix of this iteration is obtained, and the cell soc of this iteration is calculated;According to the cell soc of this iteration, determine whether to end iteration, if end, output calculation result and evaluate.The application improves the evaluation accuracy and efficiency of power battery thermal management scheme, effectively avoids the related problems such as project delay, cost increase caused by battery thermal management scheme evaluation accuracy.

Description

Technical Field

[0001] This invention relates to the field of batteries, and more specifically, to a method and medium for rapid evaluation of heating / cooling schemes for power battery systems. Background Technology

[0002] Currently, in the process of matching battery cooling systems, the required cooling power of the battery system is evaluated using the fast charging equivalent rate and the fixed cell internal resistance ohmic thermal properties. This method has the following disadvantages: 1. The internal resistance of a battery cell changes continuously with temperature and state of charge (SOC). Using a fixed internal resistance to assess the cooling power required for the cell will inevitably lead to a large deviation. If the internal resistance is too small, the estimated cooling power required for the cell will be too low, resulting in overheating of the battery in the later stages of the project, failing to meet project targets, impacting the project, and increasing project costs. If the internal resistance is too large, the estimated cooling power will be too conservative, leading to over-powered components such as compressors, condensers, evaporators, chillers, and fans selected for the vehicle, increasing overall vehicle costs and energy consumption.

[0003] 2. Using the equivalent rate assessment cannot obtain the temperature rise curve throughout the entire fast charging process, which cannot effectively support the fast charging time assessment and affects the achievement of key indicators in the later stages.

[0004] 3. The temperature used in calculating the required cooling power using the equivalent ratio and fixed internal resistance method is the average temperature of the battery cell. However, in the actual heat conduction process, there is a temperature gradient inside the battery cell. In the actual fast charging process of a vehicle, the temperature used in the map is the highest temperature (high temperature) or the lowest temperature (low temperature). Using the average temperature cannot effectively represent the actual working state of the battery cell, resulting in a large deviation in the evaluation results.

[0005] 4. The effects of battery water temperature, flow rate, and battery operating temperature are not considered. The system relies more on experience-based judgment. If the maximum allowable operating temperature of the battery changes, the cooling power of the cold plate itself cannot be effectively assessed, which poses a challenge to the entire thermal management system.

[0006] 5. In order to obtain a more accurate assessment of cooling power, the entire fast charging process is divided into multiple segments according to the SoC. For each segment, an equivalent multiplier and a fixed internal resistance are adopted. The accuracy of the cooling power obtained by this method is improved, but it still cannot meet the current requirements and the workload increases significantly.

[0007] Therefore, it is necessary to develop a rapid evaluation method and medium for heating / cooling schemes of power battery systems.

[0008] The information disclosed in the background section of this invention is intended only to enhance the understanding of the general background of this invention and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art. Summary of the Invention

[0009] This invention proposes a rapid evaluation method and medium for heating / cooling schemes of power battery systems. Starting from basic theory, it combines the fast-charging map lookup method and internal resistance change trend during actual fast charging of power batteries. The current change and internal resistance change are obtained by looking up tables. Furthermore, the three-dimensional heat transfer model of the battery cell is simplified to a two-dimensional model calculation through dimensional analysis. The two-dimensional model is then embedded into the one-dimensional calculation, effectively solving all the problems of the currently used cooling power evaluation methods. Moreover, the model can support the preliminary evaluation of thermal management strategies. Before three-dimensional simulation, the thermal management parameter table can be developed using this model, which can greatly save the time of three-dimensional simulation evaluation of the rationality of thermal management strategies and improve work efficiency.

[0010] In a first aspect, embodiments of this disclosure provide a method for rapid evaluation of heating / cooling schemes for power battery systems, including: The heating power of the battery cell is obtained by looking up a table and calculating based on the cell's SOC and temperature matrix. Calculate the heat generation rate of the power battery based on the cell heating power; Determine the cooling water temperature; The two-dimensional thermal conductivity differential equation is solved based on the power battery heat generation rate, cooling water temperature, and temperature matrix of the previous iteration to obtain the temperature matrix of the current iteration, and the cell SOC of the current iteration is calculated. The iteration should be terminated based on the cell SOC of this iteration. If terminated, the calculation results should be output and evaluated.

[0011] Preferably, the cell heating power is obtained by looking up a table and calculating based on the cell's state of charge (SOC) and temperature matrix, including: Based on the cell's state of charge (SOC) and temperature matrix, the cell current and internal resistance are obtained by looking up the table model using the current and internal resistance matrices, and then the cell's heating power is calculated.

[0012] Preferably, calculating the heat generation rate of the power battery based on the cell's heating power includes: Based on the cell heating power, the volumetric heat generation rate is simplified to the point mass heat generation rate using dimensional analysis, and the point mass heat generation rate is taken as the power battery heat generation rate.

[0013] Preferably, determining the cooling water temperature includes: Calculate the outlet water temperature of the power battery based on the heat exchange of the cold plate and the inlet water temperature of the power battery from the previous iteration. The battery thermal management strategy determines whether it is in a cooling state. If it is not in a cooling state, the power battery outlet water temperature is used as the cooling water temperature. If it is in a cooling state, the power battery inlet water temperature for this iteration is calculated based on the set cooling power and the power battery outlet water temperature. The higher of the power battery inlet water temperature and the required cooling temperature is taken as the cooling water temperature.

[0014] Preferably, the heat exchange capacity of the cold plate is:

[0015] in, For heat exchange of cold plates, R0 is the contact area between the liquid cooling system and the battery cell, and T is the thermal resistance between the liquid cooling system and the battery cell. cell This refers to the temperature at the contact surface between the battery cell and the liquid cooling system. The inlet water temperature of the power battery. This refers to the outlet water temperature of the power battery.

[0016] Preferably, the outlet water temperature of the power battery is:

[0017] in, For the specific heat capacity of the battery cell, M For cell quality and, △ T This refers to the temperature rise of the battery cell over a given period of time. For the heat dissipation of the power battery, This generates heat for the battery system.

[0018] Preferably, the inlet water temperature of the power battery is:

[0019] in, P For cooling capacity, Let m be the specific heat capacity of the fluid in the liquid cooling system, and m be the mass flow rate of the liquid cooling system.

[0020] Preferably, the calculation results include current, cell SOC, temperature matrix, and cell heating power.

[0021] Preferably, it further includes: If the iteration is not terminated, the cell SOC and temperature matrix obtained in this iteration will be used as the input for the next iteration, and the above steps will be repeated.

[0022] Secondly, embodiments of this disclosure also provide a computer-readable storage medium storing a computer program that, when executed by a processor, implements the aforementioned rapid evaluation method for heating / cooling schemes of a power battery system.

[0023] Its beneficial effects are as follows: This invention simplifies a three-dimensional numerical calculation model into a two-dimensional numerical calculation model using dimensional analysis, and then embeds the two-dimensional numerical calculation into the one-dimensional numerical calculation process. This improves the accuracy and efficiency of evaluating power battery thermal management solutions, effectively avoiding problems such as project delays and increased costs due to inaccurate evaluation of battery thermal management solutions. Furthermore, this model can quickly determine thermal management strategies, reducing the time spent on subsequent three-dimensional numerical calculations, improving work efficiency, and lowering R&D costs.

[0024] The methods and apparatus of the present invention have other features and advantages that will be apparent from or will be set forth in detail in the accompanying drawings and following detailed description, which together serve to explain the particular principles of the invention. Attached Figure Description

[0025] The above and other objects, features and advantages of the present invention will become more apparent from the more detailed description of exemplary embodiments of the invention in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same parts.

[0026] Figure 1 A flowchart illustrating the steps of a rapid evaluation method for heating / cooling schemes of a power battery system according to an embodiment of the present invention is shown. Detailed Implementation

[0027] Preferred embodiments of the invention will now be described in more detail. While preferred embodiments of the invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0028] To facilitate understanding of the solutions and effects of the embodiments of the present invention, two specific application examples are given below. Those skilled in the art should understand that these examples are merely for the purpose of understanding the present invention, and any specific details therein are not intended to limit the present invention in any way.

[0029] Example 1

[0030] Figure 1 A flowchart illustrating the steps of a rapid evaluation method for heating / cooling schemes of a power battery system according to an embodiment of the present invention is shown.

[0031] like Figure 1 As shown, the rapid evaluation method for the heating / cooling scheme of this power battery system includes:

[0032] Step 101: Obtain the cell heating power by looking up a table and calculating based on the cell's SOC and temperature matrix; Step 102: Calculate the heat generation rate of the power battery based on the cell heating power; Step 103: Determine the cooling water temperature; Step 104: Solve the two-dimensional thermal conductivity differential equation based on the power battery heat generation rate, cooling water temperature and the temperature matrix of the previous iteration to obtain the temperature matrix of the current iteration, and calculate the cell SOC of the current iteration. Step 105: Determine whether to end the iteration based on the cell SOC of this iteration. If it ends, output the calculation results and perform an evaluation.

[0033] In one example, the cell heating power is obtained through table lookup and calculation based on the cell's SOC and temperature matrix, including: Based on the cell's state of charge (SOC) and temperature matrix, the cell current and internal resistance are obtained by looking up the table model using the current and internal resistance matrices, and then the cell's heating power is calculated.

[0034] In one example, calculating the heat generation rate of a power battery based on the cell's heat output includes: Based on the cell heating power, the volumetric heat generation rate is simplified to the point mass heat generation rate using dimensional analysis, and the point mass heat generation rate is taken as the power battery heat generation rate.

[0035] In one example, determining the cooling water temperature includes: Calculate the outlet water temperature of the power battery based on the heat exchange of the cold plate and the inlet water temperature of the power battery from the previous iteration. The battery thermal management strategy determines whether it is in a cooling state. If it is not in a cooling state, the power battery outlet water temperature is used as the cooling water temperature. If it is in a cooling state, the power battery inlet water temperature for this iteration is calculated based on the set cooling power and the power battery outlet water temperature. The higher of the power battery inlet water temperature and the required cooling temperature is taken as the cooling water temperature.

[0036] In one example, the heat exchange capacity of the cold plate is:

[0037] in, For heat exchange of cold plates, R0 is the contact area between the liquid cooling system and the battery cell, and T is the thermal resistance between the liquid cooling system and the battery cell. cell This refers to the temperature at the contact surface between the battery cell and the liquid cooling system. The inlet water temperature of the power battery. This refers to the outlet water temperature of the power battery.

[0038] In one example, the outlet water temperature of the power battery is:

[0039] in, For the specific heat capacity of the battery cell, M For cell quality and, △ T This refers to the temperature rise of the battery cell over a given period of time. For the heat dissipation of the power battery, This generates heat for the battery system.

[0040] In one example, the inlet water temperature of the power battery is:

[0041] in, P For cooling capacity, Let m be the specific heat capacity of the fluid in the liquid cooling system, and m be the mass flow rate of the liquid cooling system.

[0042] In one example, the calculation results include current, cell SOC, temperature matrix, and cell heating power.

[0043] In one example, it also includes: If the iteration is not terminated, the cell SOC and temperature matrix obtained in this iteration will be used as the input for the next iteration, and the above steps will be repeated.

[0044] Specifically, the rapid evaluation method for heating / cooling schemes of a power battery system according to the present invention includes the following steps: S1: Set the initial values ​​for fast charging of the power battery, including initial SOC, temperature, cooling power, initial cell temperature matrix and other related parameters. Refer to Table 1 for specific parameter inputs.

[0045] Table 1

[0046] S2: Based on the cell's state of charge (SOC) and temperature, the cell's current and internal resistance parameters are obtained by looking up a table model using the current and internal resistance matrix, and then the cell's heating power is calculated. Here, we take current and internal resistance as an example. Any other methods used to obtain the cell's heating power and their inclusion in this logic for calculation are within the scope of this invention.

[0047] S3: Based on the cell heating power, the volumetric heat generation rate is simplified to the point mass heat generation rate by using the dimensional analysis method and the battery state at this time, which is then used as the power battery heat generation rate.

[0048] S4: Using the cold plate heat transfer rate Q2 calculated in the previous iteration and the inlet water temperature, obtain the power battery outlet water temperature for this iteration; where the cold plate heat transfer rate is:

[0049] In the formula: The contact area between the liquid cooling system and the battery cell is in meters (m). 2 R0 is the thermal resistance between the liquid cooling system and the battery cell, m2 K / W; T cell Temperature of the contact surface between the battery cell and the liquid cooling system, in K; The inlet water temperature of the power battery, in K; The outlet water temperature of the power battery is measured in K.

[0050] The outlet water temperature of the power battery is:

[0051] in, For the specific heat capacity of the battery cell, M For cell quality and, △ T This refers to the temperature rise of the battery cell over a given period of time. For the heat dissipation of the power battery, , For the heat generated by the battery system, , Ambient temperature, unit: K; Average cell temperature, unit: K; The sum of the areas of the battery module excluding the contact surface with the cold plate, in meters. 2 ; Equivalent heat transfer coefficient, unit: J / (K) m 2 ).

[0052] The battery thermal management strategy determines whether it is in a cooling state. If it is not in a cooling state, the outlet water temperature of the power battery is used as the cooling water temperature. If the battery is in a cooling state, the inlet water temperature of the power battery for this iteration is calculated based on the set cooling power and outlet water temperature.

[0053] in, P Cooling power, W. ; Specific heat capacity of the fluid in the liquid cooling system, J / (kg) K); m is the mass flow rate of the liquid cooling system, in kg / s; The inlet water temperature of the power battery, in K; The outlet water temperature of the power battery is measured in K.

[0054] The inlet water temperature of the power battery is compared with the required cooling temperature. If the inlet water temperature of the power battery is higher than the required cooling temperature, the inlet water temperature of the power battery is used as the cooling water temperature; if the inlet water temperature of the power battery is lower than the required cooling temperature, the required cooling temperature is used as the cooling water temperature.

[0055] S5: Determine the nodes for the two-dimensional numerical calculation (region discretization). During discretization, the Fourier convergence criterion must be fully considered to ensure the convergence of the results. Use the heat generation rate, cooling water temperature, and the cell temperature matrix from the previous iteration as the initial values ​​for the temperature field iteration in the two-dimensional numerical calculation, and solve the two-dimensional thermal conductivity differential equation. If this is the first calculation, use the initial cell temperature as the input. After the two-dimensional numerical calculation meets the convergence condition, output the temperature matrix for this iteration. Calculate the cell SOC value for this iteration using the power battery SOC time accumulation model.

[0056] S6: Determine whether the set cutoff condition has been met based on the cell SOC value obtained in this iteration. If yes, output the calculation results and evaluate them. The calculation results include current, cell SOC, temperature matrix, and cell heating power. Determine whether the requirements are met based on the calculation results. If no, use the cell SOC and temperature matrix obtained in this iteration as the input for the next iteration and repeat steps S2 to S5 until the SOC reaches the set cutoff condition.

[0057] Example 2

[0058] This disclosure provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the rapid evaluation method for heating / cooling schemes of a power battery system.

[0059] A computer-readable storage medium according to embodiments of the present disclosure stores non-transitory computer-readable instructions. When these non-transitory computer-readable instructions are executed by a processor, all or part of the steps of the methods described in the foregoing embodiments of the present disclosure are performed.

[0060] The aforementioned computer-readable storage media include, but are not limited to: optical storage media (e.g., CD-ROM and DVD), magneto-optical storage media (e.g., MO), magnetic storage media (e.g., magnetic tape or portable hard drive), media with built-in rewritable non-volatile memory (e.g., memory card), and media with built-in ROM (e.g., ROM cartridge).

[0061] Those skilled in the art should understand that the above description of the embodiments of the present invention is only intended to illustrate the beneficial effects of the embodiments of the present invention, and is not intended to limit the embodiments of the present invention to any of the examples given.

[0062] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A rapid evaluation method for heating / cooling schemes of power battery systems, characterized in that, include: The heating power of the battery cell is obtained by looking up a table and calculating based on the cell's SOC and temperature matrix. Calculate the heat generation rate of the power battery based on the cell heating power; Determine the cooling water temperature; The two-dimensional thermal conductivity differential equation is solved based on the power battery heat generation rate, cooling water temperature, and temperature matrix of the previous iteration to obtain the temperature matrix of the current iteration, and the cell SOC of the current iteration is calculated. The iteration should be terminated based on the cell SOC of this iteration. If terminated, the calculation results should be output and evaluated.

2. The rapid evaluation method for heating / cooling schemes of power battery systems according to claim 1, wherein, The cell heating power is obtained through table lookup and calculation based on the cell's SOC and temperature matrix, including: Based on the cell's state of charge (SOC) and temperature matrix, the cell current and internal resistance are obtained by looking up the table model using the current and internal resistance matrices, and then the cell's heating power is calculated.

3. The rapid evaluation method for heating / cooling schemes of power battery systems according to claim 1, wherein, The calculation of the heat generation rate of a power battery based on the cell's heating power includes: Based on the cell heating power, the volumetric heat generation rate is simplified to the point mass heat generation rate using dimensional analysis, and the point mass heat generation rate is taken as the power battery heat generation rate.

4. The rapid evaluation method for heating / cooling schemes of power battery systems according to claim 1, wherein, Determining the cooling water temperature includes: Calculate the outlet water temperature of the power battery based on the heat exchange of the cold plate and the inlet water temperature of the power battery from the previous iteration. The battery thermal management strategy determines whether it is in a cooling state. If it is not in a cooling state, the power battery outlet water temperature is used as the cooling water temperature. If it is in a cooling state, the power battery inlet water temperature for this iteration is calculated based on the set cooling power and the power battery outlet water temperature. The higher of the power battery inlet water temperature and the required cooling temperature is taken as the cooling water temperature.

5. The rapid evaluation method for heating / cooling schemes of power battery systems according to claim 4, wherein, The heat exchange capacity of the cold plate is: in, For heat exchange of cold plates, R0 is the contact area between the liquid cooling system and the battery cell, and T is the thermal resistance between the liquid cooling system and the battery cell. cell This refers to the temperature at the contact surface between the battery cell and the liquid cooling system. The inlet water temperature of the power battery. This refers to the outlet water temperature of the power battery.

6. The rapid evaluation method for heating / cooling schemes of power battery systems according to claim 5, wherein, The outlet water temperature of the power battery is: in, For the specific heat capacity of the battery cell, M For cell quality and, △ T This refers to the temperature rise of the battery cell over a given period of time. For the heat dissipation of the power battery, This generates heat for the battery system.

7. The rapid evaluation method for heating / cooling schemes of power battery systems according to claim 6, wherein, The inlet water temperature of the power battery is: in, P For cooling capacity, Let m be the specific heat capacity of the fluid in the liquid cooling system, and m be the mass flow rate of the liquid cooling system.

8. The rapid evaluation method for heating / cooling schemes of power battery systems according to claim 1, wherein, The calculation results include current, cell SOC, temperature matrix, and cell heating power.

9. The rapid evaluation method for heating / cooling schemes of power battery systems according to claim 1, wherein, Also includes: If the iteration is not terminated, the cell SOC and temperature matrix obtained in this iteration will be used as the input for the next iteration, and the above steps will be repeated.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the rapid evaluation method for heating / cooling schemes of a power battery system as described in any one of claims 1-9.

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