Battery thermal management system and control method and device of compressor in battery thermal management system

Abstract

The invention belongs to the technical field of battery thermal management systems, and particularly relates to a battery thermal management system and a control method and device of a compressor in the battery thermal management system. The method comprises the steps that in the operation process of a compressor in a refrigerant circulation loop of the battery thermal management system, when the actual water outlet temperature between a water outlet of a heat exchanger in a water circulation loop of the battery thermal management system and a water inlet of a battery pack is reduced to the difference between the actual water outlet temperature and a target water outlet temperature which is smaller than or equal to a first set temperature difference; and controlling the compressor to decelerate. As the actual outlet water temperature is close to the temperature of the battery pack at the moment, even if the compressor runs at a reduced speed and the refrigerating capacity is reduced, the cooling of the battery pack is not influenced, and the refrigerating effect of the battery heat management system is not influenced; therefore, according to the control method of the compressor in the battery thermal management system, the refrigeration effect is guaranteed, and the energy consumption of the compressor is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery thermal management systems, and in particular relates to a battery thermal management system and a control method and device for a compressor therein. Background Art

[0002] The main function of the battery thermal management system is to respond to the cooling of the battery, cool the battery system, and make the battery system work within a suitable temperature range (usually 20-35°C). Since the battery generates a lot of heat during operation, in order to ensure that it works within a suitable temperature range, higher requirements are placed on the cooling capacity of the battery thermal management system. In the cooling mode of the battery thermal management system, the main working components are compressors, fans, and water pumps. Generally, the rated power of the compressor configured for the vehicle-mounted battery cooling system is between 2000W and 8000W, and the rated power of the compressor configured for the energy storage battery cooling system is between 750W and 25000W; from the above data, the power consumption of the compressor is very large.

[0003] The control method of the compressor of the battery thermal management system in the prior art is mostly to adjust the speed of the compressor in different gears according to the battery temperature, the circulating water temperature, etc. in the cooling mode. However, the compressor needs to keep running throughout the cooling mode, so the compressor needs to continuously consume electricity, resulting in high energy consumption of the entire battery thermal management system. Summary of the invention

[0004] The object of the present invention is to provide a battery thermal management system and a control method and device for a compressor therein, so as to solve the technical problem of high energy consumption of the compressor of the battery thermal management system in the prior art.

[0005] In order to solve the above technical problems, the present invention provides a control method for a compressor in a battery thermal management system, the method comprising: during the operation of the compressor in the refrigerant circulation loop of the battery thermal management system, when the actual water outlet temperature between the water outlet of the heat exchanger and the water inlet of the battery pack in the water circulation loop of the battery thermal management system drops to a point where the difference between the actual water outlet temperature and the target water outlet temperature is less than or equal to a first set temperature difference, the compressor is controlled to start decelerating, and after decelerating to a third set speed, the compressor is controlled to operate at the third set speed.

[0006] Furthermore, when the difference between the target water outlet temperature and the actual water outlet temperature between the water outlet of the heat exchanger and the water inlet of the battery pack in the water circulation loop of the battery thermal management system is greater than or equal to the second set temperature difference, the compressor is controlled to stop running.

[0007] Furthermore, if after the compressor runs at the third set speed for a set time, the difference between the target outlet water temperature and the actual outlet water temperature is not greater than or equal to the second set temperature difference, the compressor is controlled to start accelerating until the compressor speed reaches the second set speed and no longer accelerates or the difference between the target outlet water temperature and the actual outlet water temperature is greater than or equal to the second set temperature difference and no longer accelerates; the second set speed is greater than the third set speed.

[0008] Further, the process of controlling the compressor to stop operation includes: if the compressor speed is greater than the maximum speed that can directly stop the compressor, first controlling the compressor to decelerate, and when the compressor speed is reduced to the maximum speed that can directly stop the compressor, controlling the compressor to stop, otherwise controlling the compressor to stop directly; The third set rotation speed is less than or equal to the maximum rotation speed that can directly stop the compressor.

[0009] Furthermore, after the compressor in the refrigerant circulation loop of the battery thermal management system is started, the compressor first accelerates to a first set speed according to a first set speed change rate, and then accelerates to a second set speed according to a second set speed change rate, and the second set speed change rate is less than the first set speed change rate; the first set speed is a speed used to prevent the compressor speed from increasing too fast, and the second set speed is a speed used to make the compressor run at a larger cooling capacity.

[0010] Furthermore, after the compressor stops running, if the battery management system is still in the cooling mode, the compressor restarts when the difference between the actual outlet water temperature and the target outlet water temperature is greater than the third set temperature difference.

[0011] Furthermore, when the compressor is accelerated, the rotation speed of the compressor increases linearly.

[0012] Furthermore, when the compressor decelerates, the rotation speed of the compressor decreases linearly.

[0013] The present invention is a pioneering invention, and its beneficial effects are as follows: the control method of the compressor in the battery thermal management system of the present invention proposes a technical solution for controlling the compressor according to the actual water outlet temperature and the target water outlet temperature between the water outlet of the heat exchanger and the water inlet of the battery pack in the water circulation loop of the battery thermal management system. When the actual water outlet temperature between the water outlet of the heat exchanger and the water inlet of the battery pack in the water circulation loop of the battery thermal management system is reduced to the difference between the actual water outlet temperature and the target water outlet temperature is equal to or less than the first set temperature difference, the compressor is controlled to start decelerating. Since the actual water outlet temperature is close to the battery pack temperature at this time, even if the compressor runs at a reduced speed and the cooling capacity is reduced, it has little effect on the cooling of the battery pack and will not affect the cooling effect of the battery thermal management system. Therefore, the control method of the compressor in the battery thermal management system of the present invention not only ensures the cooling effect but also reduces the energy consumption of the compressor.

[0014] To solve the above technical problems, the present invention further provides a compressor control device, including a processor, which implements the method steps described in the method for controlling a compressor in a battery thermal management system of the present invention when executing a computer program.

[0015] The present invention is a pioneering invention, and its beneficial effects are the same as those of the method for controlling a compressor in a battery thermal management system of the present invention, and will not be described in detail here.

[0016] In order to solve the above technical problems, the present invention also provides a battery thermal management system, including a water circulation loop, a refrigerant loop and a compressor control device; the water circulation loop is used to cool the battery system and a water pump is provided in the water circulation loop, and a compressor is provided in the refrigerant loop; the water circulation loop and the refrigerant loop perform heat exchange through a heat exchanger; the compressor control device includes a processor, and the processor implements the method steps described in the method for controlling the compressor in the battery thermal management system of the present invention when executing a computer program.

[0017] The present invention is a pioneering invention, and its beneficial effects are the same as those of the method for controlling a compressor in a battery thermal management system of the present invention, and will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a schematic diagram of the structure of a battery thermal management system of a system embodiment of the present invention; Figure 2 is a compressor speed variation diagram in one case of a system embodiment of the present invention; Figure 3 4 is a compressor speed variation diagram under another situation of the system embodiment of the present invention. DETAILED DESCRIPTION

[0019] A battery thermal management system and a control method and device for the compressor therein of the present invention propose a technical solution for controlling the compressor according to the actual outlet water temperature and the target outlet water temperature between the water outlet of the heat exchanger and the water inlet of the battery pack in the water circulation loop of the battery thermal management system. When the actual outlet water temperature between the water outlet of the heat exchanger and the water inlet of the battery pack in the water circulation loop of the battery thermal management system is reduced to the point where the difference between the actual outlet water temperature and the target outlet water temperature is equal to or less than the first set temperature difference, the compressor is controlled to start decelerating. Since the actual outlet water temperature is close to the battery pack temperature at this time, even if the compressor runs at a reduced speed and the cooling capacity is reduced, it has little effect on the cooling of the battery pack and will not affect the cooling effect of the battery thermal management system. Therefore, the control method of the compressor in the battery thermal management system of the present invention not only ensures the cooling effect but also reduces the energy consumption of the compressor.

[0020] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0021] System Example: The structure of the battery thermal management system TMS of this embodiment is as follows: Figure 1 As shown, it includes a battery system (battery pack in the figure), a water circulation circuit, a refrigerant circuit and a compressor control device; the water circulation circuit is used to cool the battery system; the water circulation circuit and the refrigerant circuit exchange heat through a heat exchanger, and the water circulation pipeline mainly includes a water pump, a PTC heater, a water outlet temperature sensor T1, etc.; the refrigerant pipeline mainly includes a compressor, a condenser, a low-pressure pressure sensor P1, a high-pressure pressure sensor P2, a low-pressure charging valve V1, a high-pressure charging valve V2, an exhaust temperature sensor T3 and an expansion valve TXV and other components.

[0022] The compressor only works in the cooling mode of the thermal management system, and when the battery thermal management unit is cooling, the main working electrical components include fans, water pumps, etc. The rated power of the compressor configured in the general vehicle battery cooling system is between 2000W and 8000W, and the rated power of the compressor configured in the energy storage battery cooling system is between 750W and 25000W; from the above data, the power consumption of the compressor is very large, so under the premise of meeting the battery cooling requirements, giving the compressor a more reasonable operation logic can save the power consumption of the compressor and achieve the purpose of energy saving.

[0023] The battery thermal management system of the present invention further includes a compressor controller, which includes a processor. The processor implements the following compressor control method when executing a computer program.

[0024] like Figure 2 and Figure 3 As shown, the control method of the compressor in the battery thermal management system of the present invention includes: 1. After the compressor is started, it begins to accelerate according to the first set speed change rate, and the compressor speed is rapidly increased to the first set speed of 3000rpm; the first set speed is used to prevent the compressor speed from increasing too fast.

[0025] 2. When the speed of the compressor is increased to the first set speed, it starts to accelerate at the second set speed change rate of 600rpm / min until the compressor speed increases to the second set speed of 5500rpm, then it stops accelerating and continues to run at the second set speed of 5500rpm. The second set speed is a speed for making the compressor run at a larger cooling capacity. The larger the compressor speed, the larger the cooling capacity. In this embodiment, the second set speed is the maximum speed of the compressor. The second set speed change rate is less than the first set speed change rate.

[0026] 3. When the difference between the actual outlet water temperature and the target outlet water temperature is less than or equal to the first set temperature difference of 3°C (corresponding to Figure 2 and Figure 3 At time T1 in FIG. 1 ), the vehicle starts to decelerate at a third set speed change rate of 1000 rpm / min, and decelerates to a third set speed of 2000 rpm. The third set speed is a relatively low speed, and the third set speed is less than the second set speed.

[0027] In this embodiment, the third set speed is less than or equal to the maximum speed at which the compressor can stop directly. The third set speed is the speed at which the compressor can stop directly, which facilitates the rapid shutdown of the compressor and has a certain protective effect on the compressor.

[0028] According to Fourier's law, the amount of heat conducted per unit time increases as the temperature difference increases. Therefore, in the later stage of refrigeration, as the temperature difference between the water temperature and the battery temperature decreases, the heat transfer efficiency gradually decreases. Therefore, in the later stage, the refrigeration capacity does not contribute much to the heat exchange rate, and the compressor speed can be appropriately reduced. Therefore, in this embodiment, when the difference between the actual outlet water temperature and the target outlet water temperature is less than or equal to the first set temperature difference of 3°C, the compressor speed is reduced to reduce the energy consumption of the compressor, and reducing the speed at this time will not have much impact on the refrigeration effect.

[0029] 4. When the compressor is at the third set speed of 2000rpm, the difference between the target outlet water temperature and the actual outlet water temperature is greater than the second set temperature difference of 4℃ (corresponding to Figure 2 At time t3, the compressor stops running; otherwise, the compressor continues to run at the third set speed of 2000 rpm.

[0030] At this time, the actual water outlet temperature is already much lower than the target water outlet temperature. Since the compressor speed does not contribute much to the heat exchange rate, there is no need to lower the water outlet temperature. In addition, the circulating water at this time is sufficient to cool the battery pack within a certain period of time. Therefore, when this situation occurs, the present invention directly controls the compressor to stop running, which can effectively reduce the energy consumption of the compressor.

[0031] 5. When the compressor runs continuously for 5 minutes at the third set speed of 2000 rpm, if the difference between the target outlet water temperature and the actual outlet water temperature is still not greater than or equal to the second set temperature difference, the compressor will re-accelerate (corresponding to Figure 3 When re-accelerating, the compressor gradually increases the speed according to the fourth set speed change rate of 300 rpm / min to improve the cooling capacity of the thermal management system until the compressor speed reaches the second set speed and no longer accelerates, or the difference between the target outlet water temperature and the actual outlet water temperature is greater than or equal to the second set temperature difference, and the compressor stops running.

[0032] In this embodiment, the process of controlling the compressor to stop running includes: if the speed of the compressor is greater than the maximum speed at which it can be directly stopped, it is necessary to decelerate first, and then stop after decelerating to the maximum speed at which it can be directly stopped; if the speed of the compressor is less than or equal to the maximum speed at which it can be directly stopped, it can be directly stopped. This shutdown method can protect the compressor, prevent the compressor from directly shutting down when the speed is high, and increase the service life of the compressor. Among them, stopping operation means that the compressor is finally shut down through a certain control strategy.

[0033] This step is executed repeatedly during the temperature adjustment process until the difference between the target outlet water temperature and the actual outlet water temperature is greater than the second set temperature difference of 4°C, and the compressor stops running.

[0034] At the third set speed, if the difference between the target outlet water temperature and the actual outlet water temperature is not greater than or equal to the second set temperature difference, the compressor will continue to run. If the difference between the target outlet water temperature and the actual outlet water temperature is not greater than or equal to the second set temperature difference after the set time, it means that the compressor cannot meet the cooling demand of the battery thermal management system at the third set speed. At this time, the compressor speed should be increased again to meet the cooling demand of the battery thermal management system. After increasing the compressor speed, if the difference between the target outlet water temperature and the actual outlet water temperature is greater than or equal to the second set temperature difference, the compressor still needs to be controlled to stop running.

[0035] 6. If the battery thermal management system TMS does not receive other mode instructions sent by the battery management system BMS, the compressor remains stopped until the difference between the actual outlet water temperature and the target outlet water temperature is greater than the third set temperature difference of 1°C, and then the compressor restarts. The third set temperature difference is a small value. When the actual outlet water temperature is slightly greater than the target outlet water temperature, the compressor can be restarted.

[0036] After the compressor is restarted, continue to control the compressor according to the above control method.

[0037] When the compressor stops running, but the battery thermal management system is still in cooling mode, and the actual water outlet temperature is greater than the target water outlet temperature and the temperature difference between the two is higher than a certain value, the compressor needs to be restarted to ensure the cooling effect.

[0038] As other implementations, each set temperature difference, rotation speed and speed change rate can be set according to actual use requirements.

[0039] Method Example: The specific process, steps and principles of the method for controlling a compressor in a battery thermal management system of the present invention have been described in detail in the system embodiment, and will not be described in detail in this embodiment.

[0040] Compressor control device embodiment: A compressor control device of the present invention includes a processor, and the processor implements the steps of the control method of the compressor in the battery thermal management system as described in the system embodiment when executing a computer program. The specific process, principle and beneficial effects of the method have been described in detail in the system embodiment, and will not be repeated in this embodiment.

[0041] The processor may be a microprocessor MCU, a programmable logic device FPGA or other processing device.

[0042] A battery thermal management system and a control method and device for a compressor therein of the present invention start to reduce the speed of the compressor when the actual outlet water temperature between the water outlet of the heat exchanger and the water inlet of the battery pack is reduced to a value close to the target outlet water temperature. Since the actual outlet water temperature is close to the battery pack temperature at this time, even if the compressor is running at a reduced speed and the cooling capacity is reduced, the cooling of the battery pack is not greatly affected, which can not only ensure the cooling effect of the battery thermal management system but also reduce the energy consumption of the compressor. Furthermore, the present invention runs for a set time at a first set speed. If the actual outlet water temperature is still greater than the target outlet water temperature after the set time, it means that the first set speed cannot meet the cooling requirement. At this time, the present invention meets the cooling requirement of the battery thermal management system by increasing the speed of the compressor. Furthermore, in the battery thermal management system of the present invention, when the actual outlet water temperature is less than the target outlet water temperature, the compressor is controlled to stop running. Further. The control method for the compressor in the battery thermal management system of the present invention starts to increase the speed of the compressor when the compressor speed cannot meet the cooling requirement, that is, when the actual outlet water temperature is higher than the target outlet water temperature, so as to meet the requirements of the battery thermal management system.

Claims

1. A method for controlling a compressor in a battery thermal management system, characterized in that: The method includes: during the operation of the compressor in the refrigerant circulation loop of the battery thermal management system, when the actual water outlet temperature between the water outlet of the heat exchanger and the water inlet of the battery pack in the water circulation loop of the battery thermal management system drops to a point where the difference between the actual water outlet temperature and the target water outlet temperature is less than or equal to a first set temperature difference, the compressor is controlled to start decelerating, and after decelerating to a third set speed, the compressor is controlled to operate at the third set speed.

2. The method for controlling a compressor in a battery thermal management system according to claim 1, characterized in that: When the difference between the target water outlet temperature and the actual water outlet temperature between the water outlet of the heat exchanger and the water inlet of the battery pack in the water circulation loop of the battery thermal management system is greater than or equal to the second set temperature difference, the compressor is controlled to stop running.

3. The method for controlling a compressor in a battery thermal management system according to claim 2, characterized in that: If the difference between the target outlet water temperature and the actual outlet water temperature is not greater than or equal to the second set temperature difference after the compressor runs at the third set speed for the set time, the compressor is controlled to start accelerating until the compressor speed reaches the second set speed and no longer accelerates or the difference between the target outlet water temperature and the actual outlet water temperature is greater than or equal to the second set temperature difference and no longer accelerates; The second set speed is greater than the third set speed.

4. The method for controlling a compressor in a battery thermal management system according to claim 2 or 3, characterized in that: The process of controlling the compressor to stop running includes: if the compressor speed is greater than the maximum speed that can directly stop the compressor, first control the compressor to slow down, and when the compressor speed is reduced to the maximum speed that can directly stop the compressor, control the compressor to stop, otherwise control the compressor to stop directly; The third set rotation speed is less than or equal to the maximum rotation speed that can directly stop the compressor.

5. The method for controlling a compressor in a battery thermal management system according to claim 2 or 3, characterized in that: After the compressor in the refrigerant circulation loop of the battery thermal management system is started, the compressor first accelerates to a first set speed according to a first set speed change rate, and then accelerates to a second set speed according to a second set speed change rate, and the second set speed change rate is less than the first set speed change rate; the first set speed is a speed used to prevent the compressor speed from increasing too fast, and the second set speed is a speed used to make the compressor run at a larger cooling capacity.

6. The method for controlling a compressor in a battery thermal management system according to claim 2 or 3, characterized in that: After the compressor stops running, if the battery management system is still in the cooling mode, the compressor restarts when the difference between the actual outlet water temperature and the target outlet water temperature is greater than the third set temperature difference.

7. The method for controlling a compressor in a battery thermal management system according to claim 3, characterized in that: When the compressor accelerates, the speed of the compressor increases linearly.

8. The method for controlling a compressor in a battery thermal management system according to any one of claims 1 to 3, characterized in that: When the compressor decelerates, the speed of the compressor decreases linearly.

9. A compressor control device, comprising a processor, characterized in that: The processor implements the steps of the method for controlling a compressor in a battery thermal management system according to any one of claims 1 to 8 when executing the computer program.

10. A battery thermal management system, comprising a water circulation loop, a refrigerant loop and a compressor control device; the water circulation loop is used to cool the battery system and a water pump is provided in the water circulation loop, and a compressor is provided in the refrigerant loop; the water circulation loop and the refrigerant loop perform heat exchange through a heat exchanger; the compressor control device comprises a processor, characterized in that, The processor implements the steps of the method for controlling a compressor in a battery thermal management system according to any one of claims 1 to 8 when executing the computer program.

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