Adaptive Control Method for Cooling Water Pump of Electric Vehicle Thermal Management System

Abstract

The present invention relates to an adaptive control method for a cooling water pump of an electric vehicle thermal management system, and belongs to the technical field of thermal management systems for automobiles. The thermal management system model includes a battery heat generation model and a battery thermal management model. The battery heat generation model includes a heat generation rate model of the battery under different working conditions. The battery thermal management model is a closed thermal management system formed by a battery cold plate, a water pump, a radiator, and connecting pipes. The operation steps are as follows: based on the full factorial experimental design method, the influence of the water pump flow is simulated, and the difference in battery termination temperature under the combined effect of flow and battery initial temperature at different vehicle speeds is analyzed; the optimal flow distribution diagram is obtained by statistics, and a water pump adaptive control strategy is designed; and simulation verification is carried out under NEDC and WLTC working conditions respectively. By comparing the battery temperature under the flow of other control strategies, the effectiveness of the flow control strategy is proved.

Description

Technical Field

[0001] The present invention belongs to the technical field of automobile thermal management systems, and in particular is a method for adaptively controlling a cooling water pump of an electric vehicle thermal management system. Background Art

[0002] New energy vehicles have entered the stage of large-scale industrialization. However, battery performance is significantly affected by temperature. The optimal operating temperature for batteries is a narrow range of 20-40°C, severely impacting vehicle performance. The 2022 Automotive Technology Trends Report released by the China Society of Automotive Engineers (SAE) indicates that intelligent thermal management technology can significantly improve the adaptability of new energy vehicles to ambient temperatures. The application of intelligent thermal management technology effectively supports new energy vehicles, even enabling operation in temperatures as low as -30°C, significantly resolving the current pain points facing new energy vehicles.

[0003] The use of liquid-cooled battery thermal management has the advantages of high thermal conductivity, fast cooling speed, and good heat dissipation effect, so it has been widely used. The control of the electronic water pump of the liquid cooling system of new energy vehicles is generally relatively simple. For example, Wang Chunli adopted a control method of continuous operation at the maximum opening; Liu Weidong and Xia Yingqi adopted high-speed and low-speed control, with the battery pack water temperature as the control target, and the actual control parameters were obtained through actual vehicle calibration. Jiang Feng considered the impact of water pump energy consumption, and pointed out that when designing the thermal management control strategy, controlling the water temperature too high or too low will lead to an increase in thermal management energy consumption, and there is an optimal solution for controlling the water temperature; and proposed to judge the pros and cons of the strategy based on three dimensions: thermal management energy consumption, constant temperature ratio, and temperature drop rate, but the specific control method was not discussed in detail. Summary of the Invention

[0004] In order to improve the control effect of the battery thermal management system without significantly increasing energy consumption, the present invention provides a design method for an adaptive control strategy of a cooling water pump of a thermal management system of an electric vehicle.

[0005] The present invention simulates the influence of water pump flow rate based on the full-factor experimental design method, analyzes the differences in battery termination temperature under the combined effects of flow rate and initial battery temperature at different vehicle speeds, obtains the optimal flow distribution diagram statistically, and designs an adaptive water pump control strategy. The flow control strategy of the present invention is verified by simulation under NEDC and WLTC operating conditions, and the effectiveness of the battery temperature under flow rates of other control strategies is demonstrated.

[0006] The adaptive control method for the cooling water pump of the electric vehicle thermal management system described in the present invention relies on a thermal management system model. The thermal management system model includes a battery heat generation model and a battery thermal management model. The battery heat generation model includes a heat generation rate model of the battery under different operating conditions. The battery thermal management model is a closed thermal management system formed by a battery cold plate, a water pump, a radiator, and connecting pipes. The control operation steps are as follows:

[0007] (1) Use AMESim software to build battery heat generation model and battery thermal management model;

[0008] (2) Conduct full factorial experimental design. In order to systematically study the effects of the initial battery temperature and different water pump flow rates on the cooling effect of the battery liquid cooling system, this paper considers using the full factorial experimental design method to simulate and analyze the battery liquid cooling system at different vehicle speeds.

[0009] (3) According to the experimental combination designed according to the full factorial experimental design method, the simulation model built in step 1 is used to conduct simulation tests one by one and record the termination temperature of the battery;

[0010] (4) Obtaining the optimal flow distribution diagram, taking the lowest temperature point at the battery termination moment recorded in step 3 as the optimal flow point, summarizing the simulation results, and counting the optimal flow points corresponding to different vehicle speeds and different battery initial temperatures to obtain the distribution diagram of the optimal flow of the liquid cooling system water pump;

[0011] (5) Determine the adaptive control strategy for the water pump flow, convert the data in the optimal flow distribution diagram into an interpolation table, and use the interpolation method to set the water pump flow parameters in the model. When the pure electric vehicle is running, the water pump flow will be obtained in real time through interpolation according to the operating status of the vehicle and the changes in battery temperature. In this way, an adaptive flow control strategy for the battery thermal management system is constructed, which can adjust the flow in real time according to the battery temperature and driving speed.

[0012] Based on the battery thermal management model and a full-factorial experimental design approach, the impact of water pump flow was simulated. The differences in battery termination temperature under the combined effects of flow and initial battery temperature at different vehicle speeds were analyzed. The optimal flow distribution was statistically derived, and the data in this diagram was converted into an interpolation table to design an adaptive water pump control strategy. This overall implementation of adaptive control of the battery thermal management water pump significantly improves the efficiency of the battery thermal management system, reduces the misjudgment rate caused by system defects, enables real-time adjustment of the water pump flow, and improves the quality of the thermal management system.

[0013] In the step (1), the battery thermal management model is designed based on the process in which the battery heat is transferred to the coolant through the battery cold plate, the water pump transfers the coolant in the battery cold plate to the radiator, the coolant heat is transferred to the air in the radiator, and the cooled coolant returns to the battery cold plate to continue to take away the heat from the battery, and finally the thermal management model is built.

[0014] In step (2), the full factorial design means that all levels of all factors and all their combinations are tested at least once. This process is equivalent to enumerating every possible situation.

[0015] The present invention aims to improve the control effect of the battery thermal management system without significantly increasing energy consumption. The ultimate goal is to maintain the battery temperature within an appropriate range, so the battery temperature at the initial moment is used as one of the factors.

[0016] The faster the car travels, the more power the motor requires. If the power consumption of other components remains unchanged, more power consumption will directly lead to more heat generated by the battery, so vehicle speed is one of the factors.

[0017] For the water pump, increasing the flow rate output, while keeping the power consumption of other components constant, will result in an increase in the total power consumption of the battery, which will increase the heat generated by the battery. However, for the same water pump, providing a higher flow rate, the greater the flow entering the liquid cooling system, the more heat the coolant will remove, which means the water pump consumes more power from the battery and, at the same time, the heat generated by the battery will increase. From a global perspective, the flow rate provided by the water pump to the liquid cooling system is not necessarily better. The lower the flow rate, the more heat generated by the battery will accumulate, and the higher the battery temperature will be. The higher the flow rate, the faster the coolant removes heat, but at the same time, the heat generated by the battery will also increase. Therefore, when exploring the cooling effect of the liquid cooling system on the battery, it is important to consider controlling the water pump flow rate, so the water pump flow rate is one of the factors.

[0018] It can be seen that vehicle speed, flow rate, and initial battery temperature all have a significant impact on the battery thermal management effect. At different vehicle speeds and initial temperatures, the optimal flow rate is different, that is, the optimal flow point is also different. Therefore, in step (3), the present invention takes the three factors of battery initial temperature, water pump flow rate, and vehicle speed, selects multiple battery temperatures as the initial battery temperature for simulation, controls the water pump to enter the liquid cooling system at a fixed flow rate, selects different water pump flow rates, and drives at different constant vehicle speeds during simulation. Simulate each combination separately, and calculate the battery temperature at the end of the simulation for each combination.

[0019] The optimal flow distribution diagram in the step (4) can obtain the optimal flow point in each combination through the above step (3), thereby drawing the optimal flow distribution diagram. However, considering that the ambient temperature and the actual battery temperature during actual operation may differ from the ambient temperature set in the simulation and the initial battery temperature, the present invention defines the temperature difference between the battery temperature and the ambient temperature, and converts the above optimal flow distribution into the optimal flow distribution of the temperature difference and the vehicle speed.

[0020] In the step (5), the data in the optimal flow distribution diagram is converted into an interpolation table, and the water pump flow parameters in the model are set using the interpolation method. When the pure electric vehicle is running, the water pump flow rate will be obtained in real time through interpolation according to the operating status of the vehicle and the change of battery temperature. The specific process is:

[0021] (5.1) Calculate the temperature difference between the battery temperature and the ambient temperature;

[0022] (5.2) Substitute the current vehicle speed and temperature difference into the interpolation table represented by the formula to calculate the optimal flow rate;

[0023] (5.3) Control the water pump according to the optimal flow rate.

[0024] At this point, an adaptive flow control strategy for the battery thermal management system has been constructed, which can adjust the flow in real time according to the battery temperature and driving speed.

[0025] The beneficial technical effects of the present invention are embodied in the following aspects:

[0026] (1) Optimal battery temperature control can be achieved. Since the invention is based on flow distribution table data for optimal heat dissipation performance of the battery under various operating conditions and ambient temperatures, adaptive control based on the table can well meet the optimal temperature control target of the battery.

[0027] (2) Compared with the constant flow control method, this invention can adaptively adjust the water pump flow according to the vehicle speed and temperature, thereby ensuring that the battery meets the heat dissipation requirements while obtaining the lowest water pump energy consumption, thereby effectively saving the energy consumption of the entire vehicle and improving the driving range. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of battery liquid cooling according to the present invention;

[0029] Figure 2 A battery liquid cooling system model established for the present invention;

[0030] Figure 3 The simulation results of the full factorial test at different vehicle speeds of an embodiment of the present invention are shown;

[0031] Figure 4This is the optimal flow distribution diagram of the present invention;

[0032] Figure 5 The optimal flow distribution diagram based on temperature difference and vehicle speed of the present invention;

[0033] Figure 6 This is the water pump flow adaptive control strategy of the present invention. DETAILED DESCRIPTION

[0034] The embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0035] like Figure 1 and Figure 2 As shown, the battery liquid cooling system model includes a whole vehicle model, a battery heat transfer model, a battery thermal management system model and an auxiliary electrical appliance model. The electric vehicle thermal management system cooling water pump adaptive control strategy design method described in the present invention relies on the thermal management system model. The thermal management system model includes a battery heat generation model and a battery thermal management model. The battery heat generation model includes a heat generation rate model of the battery under different working conditions. The battery thermal management model is a closed thermal management system formed by a battery cold plate, a water pump, a radiator and connecting pipes.

[0036] The method for designing an adaptive control strategy for a cooling water pump of an electric vehicle thermal management system according to the present invention comprises the following steps: step (1): using AMESim software to construct a battery heat generation model and a battery thermal management model;

[0037] Step (2): Conduct a full factorial experimental design. In order to systematically study the effects of the initial battery temperature and different water pump flow rates on the cooling effect of the battery liquid cooling system, this paper considers using the full factorial experimental design method to simulate and analyze the battery liquid cooling system at different vehicle speeds.

[0038] Step (3): According to the experimental combination designed according to the full factorial experimental design method, the simulation model built in step 1 is used to conduct simulation experiments one by one and record the termination temperature of the battery;

[0039] Step (4): Obtain the optimal flow distribution diagram, take the lowest temperature point of the battery at the end of step (3) as the optimal flow point, summarize the simulation results, and count the optimal flow points corresponding to different vehicle speeds and different battery initial temperatures to obtain the distribution diagram of the optimal flow of the liquid cooling system water pump;

[0040] Step (5): Determine the water pump flow adaptive control strategy, convert the data in the optimal flow distribution diagram into an interpolation table, and use the interpolation method to set the water pump flow parameters in the model. When the pure electric vehicle is running, the water pump flow will be obtained in real time through interpolation according to the vehicle's operating status and the change of battery temperature. In this way, an adaptive flow control strategy for the battery thermal management system is constructed, which can adjust the flow in real time according to the battery temperature and driving speed.

[0041] A thermal management model was established using software, and the impact of water pump flow was simulated using a full-factorial design of experiments. The differences in battery termination temperature under the combined effects of flow and initial battery temperature at different vehicle speeds were analyzed. The optimal flow distribution was statistically derived, and the data in this diagram was converted into an interpolation table to design an adaptive water pump control strategy. This overall implementation of adaptive control of the battery thermal management water pump significantly improved the efficiency of the battery thermal management system, reduced the misjudgment rate caused by system defects, enabled real-time adjustment of the water pump flow, and enhanced the quality of the thermal management system.

[0042] The thermal management model in step 1 described in the present invention is designed based on the process in which battery heat is transferred to the coolant through the battery cold plate, a water pump transfers the coolant in the battery cold plate to the radiator, the heat of the coolant is transferred to the air in the radiator, and the cooled coolant returns to the battery cold plate to continue to remove the heat from the battery, ultimately building a thermal management model.

[0043] The full factorial experimental design in step 2 is a full factorial design that involves testing all levels of all factors and all their combinations at least once. This process is equivalent to enumerating every possible situation.

[0044] The present invention aims to improve the control effect of the battery thermal management system without significantly increasing energy consumption. The ultimate goal is to maintain the battery temperature within an appropriate range, so the battery temperature at the initial moment needs to be set.

[0045] The faster the car travels, the more power the motor requires. If the power consumption of other components remains constant, more power consumption will directly lead to more heat generation in the battery, so the speed needs to be set.

[0046] For the water pump, increasing the flow output will increase the total power consumption of the battery while the power consumption of other components remains unchanged, which will increase the heat generated by the battery. However, for the same water pump, providing a larger flow, the greater the flow entering the liquid cooling system, the more heat the coolant will take away, which means that the water pump consumes more power from the battery, and at the same time, the heat generated by the battery will increase; from a global perspective, the flow provided by the water pump to the liquid cooling system is not the greater the better, nor is it the smaller the better; the smaller the flow, the heat generated by the battery will accumulate, and the higher the battery temperature; the larger the flow, although the speed at which the coolant takes away heat will increase, but at the same time, the heat generated by the battery will also increase. Therefore, when exploring the cooling effect of the liquid cooling system on the battery, it is necessary to consider controlling the flow of the water pump.

[0047] like Figure 3 As shown, it is known that vehicle speed, flow rate and initial battery temperature all have a significant impact on the thermal management effect of the battery. At different vehicle speeds and initial temperatures, the optimal flow rate is different, that is, the optimal flow point is also different. Therefore, in the present invention, the initial battery temperature, water pump flow rate and vehicle speed are taken as three factors, and four battery temperatures of 30°C, 32°C, 35°C and 40°C are selected as the initial battery temperatures for simulation. By controlling the water pumps, they all enter the liquid cooling system at a fixed flow rate. There are 16 water pump flow rate options, namely 1L / min, 2L / min, 4L / min, 6L / min, 8L / min, 10L / min, 12L / min, 14L / min, 16L / min, 18L / min, 2 0L / min, 22L / min, 24L / min, 26L / min, 28L / min, 30L / min. The simulation was carried out at a constant speed. There were 14 speed options: 0km / h, 10km / h, 20km / h, 30km / h, 40km / h, 50km / h, 60km / h, 70km / h, 80km / h, 90km / h, 100km / h, 110km / h, 120km / h, and 130km / h. Each combination was simulated separately, and the battery temperature at the end of the simulation was calculated for each combination.

[0048] like Figure 4 and Figure 5 As shown, the optimal flow distribution diagram in step 4 can be obtained through step 3 to obtain the optimal flow point in each combination, thereby drawing the optimal flow distribution diagram. However, considering that the ambient temperature and the actual battery temperature during actual operation may differ from the ambient temperature and the initial battery temperature set in the simulation, the present invention defines the temperature difference between the battery temperature and the ambient temperature, and converts the above-mentioned optimal flow distribution into the optimal flow distribution of the temperature difference and the vehicle speed.

[0049] like Figure 6As shown, in step 5, the data in the optimal flow distribution diagram is converted into an interpolation table, and the water pump flow parameters in the model are set using the interpolation method. When the pure electric vehicle is running, the water pump flow rate will be obtained in real time through interpolation according to the operating status of the vehicle and the change of battery temperature. The specific process is:

[0050] 1. Calculate the temperature difference between the battery temperature and the ambient temperature;

[0051] 2. Substitute the current vehicle speed and temperature difference into the interpolation table represented by the formula to calculate the optimal flow rate;

[0052] 3. Control the water pump according to the optimal flow rate.

[0053] At this point, an adaptive flow control strategy for the battery thermal management system has been constructed, which can adjust the flow in real time according to the battery temperature and driving speed.

[0054] To sum up, the present invention is reasonably designed and realizes adaptive control of the battery thermal management water pump as a whole, thereby improving the efficiency of the battery thermal management system, adjusting the water pump flow in real time, improving the quality of the thermal management system, and ensuring that the power battery operates within a suitable temperature range, thereby alleviating the mileage anxiety of electric vehicles to a certain extent.

Claims

1. An adaptive control method for the cooling water pump of an electric vehicle thermal management system is based on a thermal management system model. The thermal management system model includes a battery heat generation model and a battery thermal management model. The battery heat generation model includes a heat generation rate model of the battery under different operating conditions. The battery thermal management model is a closed thermal management system formed by a battery cold plate, a water pump, a radiator, and connecting pipes. The steps are as follows: (1) Use AMESim software to build a battery heat generation model and a battery thermal management model; the battery thermal management model is designed based on the process that the battery heat is transferred to the coolant through the battery cold plate, the water pump transfers the coolant in the battery cold plate to the radiator, the coolant heat in the radiator is transferred to the air, and the cooled coolant returns to the battery cold plate to continue to take away the heat of the battery, and finally builds a thermal management model; (2) Conduct a full factorial experimental design. In order to systematically study the effects of the initial battery temperature and different water pump flow rates on the cooling effect of the battery liquid cooling system, a full factorial experimental design method is used to simulate and analyze the battery liquid cooling system at different vehicle speeds. (3) According to the experimental combination designed according to the full factorial experimental design method, the simulation model built in step (1) is used to conduct simulation tests one by one and record the termination temperature of the battery; (4) Obtain the optimal flow distribution diagram, take the lowest temperature point of the battery at the end of step (3) as the optimal flow point, summarize the simulation results, and count the optimal flow points corresponding to different vehicle speeds and different battery initial temperatures to obtain the distribution diagram of the optimal flow of the liquid cooling system water pump; (5) Determine the adaptive control strategy for the water pump flow, convert the data in the optimal flow distribution diagram into an interpolation table, and use the interpolation method to set the water pump flow parameters in the model. When the pure electric vehicle is running, the water pump flow will be obtained in real time through interpolation according to the vehicle's operating status and the change of battery temperature, realizing the adaptive flow control of the battery thermal management system that adjusts the flow in real time according to the battery temperature and driving speed.

2. The method for adaptively controlling a cooling water pump of a thermal management system of an electric vehicle according to claim 1, characterized in that: In step (1), based on the battery thermal management model and the full factorial experimental design method, the influence of the water pump flow rate is simulated, the difference in battery termination temperature under the combined effect of flow rate and battery initial temperature at different vehicle speeds is analyzed, and the optimal flow distribution diagram is obtained statistically. The data in the diagram is converted into an interpolation table, and the water pump adaptive control strategy is designed; the battery thermal management water pump adaptive control is realized as a whole.

3. The method for adaptively controlling a cooling water pump of a thermal management system of an electric vehicle according to claim 1, characterized in that: In step (2), full factorial experimental design means that all levels of all factors and all their combinations are tested at least once. This process is equivalent to enumerating every possible situation.

4. The method for adaptively controlling a cooling water pump of a thermal management system of an electric vehicle according to claim 1, characterized in that: In step (3), the three factors of battery initial temperature, water pump flow rate and vehicle speed are taken, and multiple battery temperatures are selected as the initial battery temperature of the simulation. By controlling the water pump to enter the liquid cooling system at a fixed flow rate, different water pump flow rates are selected, and the vehicle is driven at different constant speeds during the simulation; each combination is simulated separately, and the battery temperature at the end of the simulation for each combination is counted.

5. The method for adaptively controlling a cooling water pump of a thermal management system of an electric vehicle according to claim 1, characterized in that: In step (4), the optimal flow point for each combination is obtained through step (3), and the optimal flow distribution diagram is drawn. The temperature difference between the battery temperature and the ambient temperature is defined, and the above optimal flow distribution is converted into the optimal flow distribution of temperature difference and vehicle speed.

6. The method for adaptively controlling a cooling water pump of a thermal management system of an electric vehicle according to claim 1, characterized in that: In step (5), the data in the optimal flow distribution diagram is converted into an interpolation table, and the water pump flow parameters in the model are set using the interpolation method. When the pure electric vehicle is running, the water pump flow rate will be obtained in real time through interpolation according to the operating status of the vehicle and the change of battery temperature. The specific process is: (5.1) Calculate the temperature difference between the battery temperature and the ambient temperature; (5.2) Substitute the current vehicle speed and temperature difference into the interpolation table represented by the formula to calculate the optimal flow rate; (5.3) Control the water pump according to the optimal flow rate.

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