Electro-thermal simulation combined use method of battery system

Abstract

The invention discloses a battery system electro-thermal simulation combined use method. The method comprises the following steps: simplifying an established battery system simulation model comprising a battery, a busbar and a thermal management system; carrying out grid division on the simplified battery system simulation model; building a battery system electric model by using the Fluent software battery model, and respectively performing electric heating simulation on the busbar and thermal simulation on the battery by using the battery model and the thermal model; and setting a thermal management boundary condition, and carrying out flow field and temperature field coupling calculation to obtain temperature rise and temperature difference of the battery and the busbar in a set working condition under a transient working condition / a steady working condition and thermal distribution of a complete battery system including the busbar and the battery. According to the method, heat production and heat dissipation are carried out at the same time in simulation, real temperature rise data of the battery and the busbar under the thermal management condition are obtained, busbar heat production is accurately calculated, the busbar and the battery are not split, heat conduction of the surrounding environment is avoided, and busbar temperature rise and temperature difference and the cooling system heat dissipation effect are rapidly evaluated.

Description

Technical Field

[0001] The present invention relates to the technical field of battery system electrothermal simulation, and in particular to a method for combining electrothermal simulation with battery system. Background Art

[0002] Good thermal design and thermal management of the battery system are crucial for the battery to operate in the optimal operating range. In the early design stage without physical objects, simulation technology is an important means to verify the thermal management design solution.

[0003] The existing battery system thermal design and thermal management technologies only explore simulation methods for heat generation and heat dissipation of the battery itself, or only simulate the bus overcurrent and only calculate the bus temperature rise without including the battery temperature rise. The simulation method considering the battery and bus requires support from HPPC (Hybrid Pulse Power Characteristic) or rate discharge data, which requires a lot of testing resources.

[0004] For example, a new project is to carry out thermal design and thermal simulation of the battery system when there is no rate discharge data or HPPC test data for the single cell. Without complete data, the MSMD battery model in the Fluent software cannot be used. Therefore, the traditional method is to remove the bus, retain only the battery and thermal management system, and give the battery a heat generation power for simulation. This can only obtain the temperature rise and temperature difference of the battery. For the bus, according to the resistance formula R = resistivity * length / cross-sectional area, the resistance value of the bus is calculated, and then according to the heat generation power P = current square * R, the temperature rise of the bus is calculated. Since most buses are irregular in shape, and the bus current path cannot be simply expressed by the length value, the resistance formula cannot accurately obtain the resistance, so the given bus heat generation power needs to be repeatedly adjusted after verification with the experiment before it can be applied. The above-mentioned method of simulating the battery and the bus separately separates the heat conduction between the battery and the bus, and can only reflect the temperature rise of the battery itself and the temperature rise of the bus itself. If a cooling system is being simulated at the same time, the cooling conditions of the bus cannot be set in the simulation, which is also the reason why the bus temperature is inaccurate when simply simulating it. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings and defects of the prior art and to provide a method for combining electric and thermal simulation of a battery system. The method is a simulation method that combines the electric and thermal simulation of the bus with the thermal simulation of the battery. The method can quickly obtain the temperature rise and temperature difference of the battery and the bus, and the heat dissipation effect of the cooling system, so as to evaluate the thermal performance of the battery module or system.

[0006] A method for combining electric and thermal simulation of a battery system, comprising:

[0007] Simplify the established battery system simulation model including battery, bus and thermal management system;

[0008] Divide the simplified battery system simulation model network;

[0009] Use the Fluent software battery model to build the battery system electrical model, and then use the battery model and thermal model to perform electrical and thermal simulation on the bus and thermal simulation on the battery respectively;

[0010] Set thermal management boundary conditions, perform coupled calculations of flow field and temperature field, and obtain the temperature rise and temperature difference of the battery and bus under set conditions under transient / steady-state conditions, as well as the thermal distribution of the complete battery system including the bus and batteries.

[0011] The shape and size of the busbar and the battery in the battery system simulation model are consistent with the shape and size of the busbar and the battery of the battery pack to be simulated and tested.

[0012] The simplification of the established battery system simulation model including the battery, bus and thermal management system is to retain only the model components that affect the heat dissipation of the battery system in the battery system simulation model.

[0013] The steps for simplifying the battery system simulation model include:

[0014] Determine the type of cooling system for the battery system;

[0015] The battery system simulation model is simplified according to the type of cooling system, the model components that affect the heat dissipation of the battery system are retained, and the remaining model components are deleted.

[0016] In the electrothermal simulation of the busbar, after inputting the corresponding parameters of the current working condition, only the heat generated by the busbar through which the current passes is calculated.

[0017] When simulating the battery system, all batteries in the battery system and all buses through which the current passes are included in the calculation range; and the current forms a complete path, so that the current is connected from the total positive to the total negative.

[0018] Among them, when the electric and thermal simulation calculation of the battery system bus is performed, when selecting the equivalent model parameters, if there is battery rate discharge data, the data fitting parameters corresponding to the battery rate discharge data are selected, otherwise the software default equivalent model recognition parameters are selected.

[0019] In the battery thermal simulation calculation of the battery system, the battery heat generation is calculated by inputting a given heat generation power.

[0020] The heat generation power of the battery is a preset fixed value, heat generation power data that changes according to the battery state of charge SOC and temperature, and heat generation power data that changes with time and is set according to simulation working conditions.

[0021] Wherein, when the battery system adopts an air cooling system, the thermal management boundary conditions include setting the air inlet as a pressure inlet, setting the PQ curve of the fan at the fan position, and setting the outlet as a pressure outlet.

[0022] The simulation method of the present invention combines the electrothermal simulation of the bus with the thermal simulation of the battery, generates and dissipates heat simultaneously during the simulation process, and obtains real temperature rise data of the battery and the bus with both heat dissipation and heat generation under thermal management. The heat generation of the bus can be accurately calculated without separating the heat conduction between the bus and the battery and the surrounding environment, the temperature rise and temperature difference of the bus, and the heat dissipation effect of the cooling system can be quickly evaluated, and the rationality of the arrangement of the temperature sampling points can be judged, which plays a positive role in accelerating project development.

[0023] The simulation model of the present invention retains all factors that affect the temperature and retains the geometric details of the bus and the battery as much as possible, so the bus current path is consistent with the actual object. By setting the correct material resistivity, the heat generation and temperature rise of the bus can be accurately calculated; at the same time, the heat conduction of the bus and the surrounding environment and the battery is calculated simultaneously, thereby obtaining the heat generation and heat dissipation simulation results consistent with the real system.

[0024] Through simulation, combined with the flow field simulation results of the thermal management system, the thermal distribution of the complete battery system including the bus and battery can be obtained after coupling the thermal field and flow field, achieving multiple goals, including evaluating the heat dissipation effect of the cooling system design, judging the bus current capacity, and the rationality of the temperature sampling point setting. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a flow chart of a method for combining electric and thermal simulation of a battery system according to an embodiment of the present invention.

[0026] Figure 2 Schematic diagram of a simplified simulation model of an air-cooled battery system according to an embodiment of the present invention.

[0027] Figure 3 It is a schematic diagram of a grid diagram corresponding to a simulation model processed in a simulation of an embodiment of the present invention.

[0028] Figure 4 It is a cloud diagram of flow velocity distribution in a battery system obtained after simulation processing of an embodiment of the present invention.

[0029] Figure 5 It is a battery (module) temperature cloud diagram obtained after simulation processing of an embodiment of the present invention.

[0030] Figure 6 It is a busbar temperature cloud diagram obtained after simulation processing of an embodiment of the present invention. DETAILED DESCRIPTION

[0031] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0032] See also Figure 1 As shown, the method for combining electric and thermal simulation of a battery system according to an embodiment of the present invention is a method for simulating a battery and a bus at the same time, comprising the steps of:

[0033] S1. Simplify the established battery system simulation model including battery, bus and thermal management system;

[0034] S2. Divide the simplified battery system simulation model network;

[0035] S3. Use Fluent software battery model to build a battery system electrical model, and then use the battery model and thermal model to perform electrical and thermal simulation on the bus and thermal simulation on the battery (i.e., the battery module composed of battery cells);

[0036] S4 sets the thermal management boundary conditions, performs coupled calculations of the flow field and temperature field, obtains the temperature rise and temperature difference of the battery and bus under the set working conditions under transient / steady-state conditions, and obtains the thermal distribution of the complete battery system including the bus and batteries.

[0037] The battery system simulation model is a three-dimensional model made by engineering and technical personnel using drawing tools, including all system components. For the busbar electrothermal simulation and battery thermal simulation, some components are unnecessary and need to be simplified, such as the BMS circuit board, some screws and nuts, etc., which need to be deleted, while the battery and busbar do not need to be particularly simplified. When simplifying, the model must ensure the current path, that is, the correct current direction, to ensure the current is connected from the total positive to the total negative. For the temperature rise of the busbar that needs to be paid attention to, its key features must be kept unchanged when simplifying the model, so as to ensure that the overcurrent capacity and contact area remain unchanged. At this stage, the products all arrange the temperature sampling points on the busbar. If you want to grasp the busbar temperature rise or whether the temperature sampling points are arranged reasonably through simulation, you need to obtain the battery and busbar temperatures through simulation.

[0038] Therefore, in this application, after establishing a complete battery system simulation model, in the Fluent software, before performing meshing and building the battery system electrical model, the battery system simulation model is simplified through pre-processing simplification steps, and only the model components that affect the heat dissipation of the battery system are retained in the battery system simulation model.

[0039] Among them, the steps of pre-processing and simplifying the battery system simulation model include: determining the type of the cooling system of the battery system; simplifying the battery system simulation model according to the type of the cooling system, retaining the model components that affect the heat dissipation of the battery system, and deleting the remaining model components.

[0040] Specifically, for example, if the battery system adopts an air cooling system, all components that affect the temperature need to be retained, such as battery packs, busbars, end plates, fans, air ducts, etc. If the battery system adopts a liquid cooling system, the battery packs, busbars, end plates, support beams, thermal conductive adhesives, cold plates or boxes, coolants, etc. can be retained. If the battery system adopts immersion liquid cooling, the battery packs, busbars, end plates, flow channels, coolants, etc. can be retained. Figure 1 It is a simplified simulation model of an air-cooled battery system, with an air inlet on the left and a fan on the right to draw air out. The battery system is simplified into a rectangular block, and the busbars are connected in series and parallel to achieve the total output of 2P12S. Figure 2 It is the grid map corresponding to the simulation model to be simulated.

[0041] In the present application, the electrical model is used to automatically identify the model by the battery model (Battery model) of the Fluent software after specifying the battery and the overcurrent bus, the total positive and total negative ports of the current. The model is a battery pack that includes several parallel and several series forms, and clearly defines the path through which the current of the battery system flows from the total positive to the total negative.

[0042] Figure 2 This is a simplified battery system simulation model of an air-cooled battery system, with an air inlet on the left and a fan on the right to draw air out. The battery system is simplified into a rectangular parallelepiped, and the busbars are connected in series and parallel to achieve the total output of 2P12S. Figure 3 This is the grid diagram corresponding to the simplified battery system simulation model.

[0043] Preferably, the shape and size of the bus and the battery in the simplified battery system simulation model are consistent with the shape and size of the bus and the battery of the battery pack to be simulated and tested.

[0044] In the present invention, the simulation is performed using the battery model of the Fluent software. The battery model has three types of models that can perform electrothermal simulation of batteries or battery systems: the NTGK model (which requires input of the battery's rate discharge data), the ECM model (which requires input of the battery's HPPC charge and discharge data), and the P2D model (which requires input of the battery's electrochemical parameters).

[0045] In the present invention, there is no need for battery rate discharge data or complete HPPC test data, nor electrochemical parameters. Battery thermal simulation only needs to provide a heat generation power, which is a thermal model simulation, busbar electrothermal simulation, and is implemented using a battery model (Battery model); the two parts are combined, and the simulation data of the two parts are added to obtain the key data such as the complete temperature rise and temperature difference of the battery system, which is used to evaluate the cooling system design.

[0046] In the electrothermal simulation of the bus, after inputting the corresponding parameters of the current condition, only the heat generated by the bus through which the current passes is calculated. In the simulation of the battery system, all batteries of the battery system and all buses through which the current passes are included in the calculation range; and the current forms a complete path, so that the current is connected from the total positive to the total negative.

[0047] Among them, when the electric and thermal simulation calculation of the battery system bus is performed, when selecting the equivalent model parameters, if there is battery rate discharge data, the data fitting parameters corresponding to the battery rate discharge data are selected, otherwise the software default equivalent model recognition parameters are selected.

[0048] In the battery system battery thermal simulation calculation, the battery heat generation is calculated by inputting a given heat generation power. The heat generation power of the battery is a preset fixed value, heat generation power data that changes according to the battery state of charge SOC and temperature, and heat generation power data that changes with time according to the simulation working conditions.

[0049] Wherein, when the battery system adopts an air cooling system, the thermal management boundary conditions include setting the air inlet as a pressure inlet, setting the PQ curve of the fan at the fan position, and setting the outlet as a pressure outlet.

[0050] Specifically, in the Fluent software, the simulation parameters are set and the simulation process is performed through the following steps:

[0051] 1. First, on the activation interface of the corresponding module of the battery model, in the battery model, use the MSMD module or Circuit Network in its Solution Method; select NTGK Empirical Model in its E-Chemistry Models, that is, select the first-order empirical model of the battery; in its EnergySource Options, only check Enable Joule Heat in Passive Zones, that is, only calculate the heat generated by the bus part through which the current passes; normally input the rated current of the battery, and in its Solution option, set appropriate parameters according to the operating conditions to be calculated, which can be the charge and discharge rate, or the charge and discharge current or power.

[0052] 2. In the Battery model, in the ConductionZone setting, select all batteries in Active Components and all buses through which current flows in Passive Components. Make sure that all buses to be calculated are selected in Passive Components.

[0053] 3. On the interface of the specified total positive and total negative of the battery model, to ensure the complete path of the current, select a face of the total negative output end in the Negative Tab and a face of the total positive output end in the Positive Tab.

[0054] 4. On the interface for setting equivalent model parameters of the battery model, in the ModelParameters setting, if there is rate discharge data for the corresponding battery, the corresponding data fitting parameters can be used; if there is no rate discharge data, the software default equivalent model parameters can be used to ensure that the simulation calculation can proceed smoothly.

[0055] 5. In Fluent software, use the Cell Zone Conditions of its thermal model to set the heat generation of the battery. The heat generation unit is W / m 3 The heat generation power of the battery can be a fixed value, or a data table that changes according to SOC and temperature, or heat generation power data that changes over time according to working conditions.

[0056] 6. In the Fluent software, set the thermal management boundary conditions of the battery system, set the air inlet to the pressure inlet, set the fan position to the PQ curve of the fan, and set the outlet to the pressure outlet. After the thermal management boundary conditions of the battery system are set, the temperature rise and temperature difference of the set working conditions can be obtained under transient or steady-state conditions.

[0057] The present invention combines the battery model (Battery model) of Fluent software and the thermal model (setting energy items in the Cell Zone) to calculate the heat generated by the batteries and buses of the battery module or battery system, and simultaneously obtains the temperature rise and temperature difference of the battery and the bus, which are used to evaluate the thermal management design effect, solving the problem of simultaneously obtaining the temperature rise and temperature difference of the battery and the bus in the absence of battery rate data or HPPC test data.

[0058] In a simulation example, the simulation is performed under the condition of an initial temperature of 25°C, 1CP charging for 3600s, and fan cooling. The simulation flow field results are as follows: Figure 3 , the battery and busbar are cooled. The temperature field results are shown in Figure 4 and Figure 5 , and the temperature of the battery and the bus are obtained at the same time.

[0059] The basic principles and main features of the present invention and the advantages of the present invention are shown and described above. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention.

[0060] Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is therefore intended that all changes falling within the meaning and range of equivalent elements of the claims are included in the present invention.

[0061] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for combining electric and thermal simulation of a battery system, characterized in that: Includes steps: Simplify the established battery system simulation model including battery, bus and thermal management system; Divide the simplified battery system simulation model network; Use the Fluent software battery model to build the battery system electrical model, and then use the battery model and thermal model to perform electrical and thermal simulation on the bus and thermal simulation on the battery respectively; Set thermal management boundary conditions, perform coupled calculations of flow field and temperature field, and obtain the temperature rise and temperature difference of the battery and bus under set conditions under transient / steady-state conditions, as well as the thermal distribution of the complete battery system including the bus and batteries.

2. The method for combining electric and thermal simulation of a battery system according to claim 1, characterized in that: The shape and size of the busbars and batteries in the battery system simulation model are consistent with the shape and size of the busbars and batteries of the battery pack to be simulated and tested.

3. The method for combining electric and thermal simulation of a battery system according to claim 1, characterized in that: The simplification of the established battery system simulation model including the battery, the bus and the thermal management system is to retain only the model components that affect the heat dissipation of the battery system in the battery system simulation model.

4. The method for combining electric and thermal simulation of a battery system according to claim 3, characterized in that: The steps to simplify the battery system simulation model include: Determine the type of cooling system for the battery system; The battery system simulation model is simplified according to the type of cooling system, the model components that affect the heat dissipation of the battery system are retained, and the remaining model components are deleted.

5. The method for combining electric and thermal simulation of a battery system according to claim 1, characterized in that: In the electrothermal simulation of the busbar, after inputting the corresponding parameters of the current working condition, only the heat generated by the busbar through which the current passes is calculated.

6. The method for combining electric and thermal simulation of a battery system according to claim 1, characterized in that: When simulating a battery system, all batteries in the battery system and all buses through which the current passes are included in the calculation scope; and the current forms a complete path, connecting the current from the total positive to the total negative.

7. The method for combining electric and thermal simulation of a battery system according to claim 1, characterized in that: When performing the electrothermal simulation calculation of the battery system bus, when selecting the equivalent model parameters, if there is battery rate discharge data, select the data fitting parameters corresponding to the battery rate discharge data, otherwise select the software default equivalent model recognition parameters.

8. The method for combining electric and thermal simulation of a battery system according to claim 1, characterized in that: In the battery thermal simulation calculation of the battery system, the battery heat generation is calculated by inputting a given heat generation power.

9. The method for combining electric and thermal simulation of a battery system according to claim 8, characterized in that: The heat generation power of the battery is one of a preset fixed value, heat generation power data that changes according to the battery state of charge SOC and temperature, and heat generation power data that changes with time and is set according to a simulation working condition.

10. The method for combining electric and thermal simulation of a battery system according to claim 1, characterized in that: When the battery system adopts an air cooling system, the thermal management boundary conditions include setting the air inlet as a pressure inlet, setting the PQ curve of the fan at the fan position, and setting the outlet as a pressure outlet.

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