Low-temperature refrigeration control method for commercial vehicle battery thermal management system

Abstract

The invention relates to a low-temperature refrigeration control method of a commercial vehicle battery heat management system, which belongs to the field of new energy vehicle battery management and comprises a heating band preheating function, a fan low-temperature control function and a compressor rotating speed control function. The fan rotating speed is associated with the system pressure and the compressor exhaust temperature, it is guaranteed that the system pressure and temperature are always kept within a reasonable range during low-temperature refrigeration, the refrigeration efficiency and energy efficiency are maximized, meanwhile, the rotating speed is increased in a staged mode when the compressor is started, it is guaranteed that the rotating speed of the compressor is slowly and stably increased in the low-temperature environment, and the risks of low-temperature starting overload and starting failure are avoided; the three functions are closely matched, so that the battery thermal management system is stable, reliable, low in failure rate and suitable for being used and popularized in new energy commercial vehicles when the battery thermal management system operates at low temperature.

Description

Technical Field

[0001] The present invention relates to the technical field of thermal management of new energy vehicle batteries, and in particular to a low-temperature refrigeration control method for a commercial vehicle battery thermal management system. Background Art

[0002] The core task of an electric vehicle's battery thermal management system (TMS) is to monitor and regulate the temperature of the vehicle's batteries, ensuring they remain within the optimal operating range. This optimal operating temperature is crucial for the proper functioning of an electric vehicle's battery pack, electronic control system, and motor. At this optimal operating temperature, the battery's charge level, health, and capacity degradation are slowed. The basic operating principle of a TMS is to utilize sensors to monitor the temperature and pressure of various components in real time. The control system analyzes this data according to pre-set strategies and controls the coolant circulation system and air conditioning system accordingly, ensuring efficient heat transfer and a comfortable cabin environment. This is crucial to the safety and performance of electric vehicles.

[0003] In recent years, with the development of new energy, new energy commercial vehicles have been used more and more widely. Commercial vehicles such as mining trucks have harsh and complex operating conditions. In low-temperature conditions, such as in cold northern regions, the ambient temperature is extremely low, often below -20°C, causing TMS low-temperature refrigeration to face many problems.

[0004] To ensure the normal operation of the TMS low-temperature refrigeration function, some patents have proposed adding a heating belt and connecting an air-cooled radiator in parallel on the TMS antifreeze side. However, commercial vehicles have limited space and are highly price-conscious. Air-cooled radiators are large and increase costs, so commercial vehicles rarely use the solution of connecting an air-cooled radiator in parallel on the TMS antifreeze side. In addition, although some patents have added a heating belt, the power of the heating belt is too small or the heating is insufficient, resulting in the risk of damage to the compressor during TMS low-temperature refrigeration. In addition, the existing technology rarely involves the optimization control of the fan and the control and adjustment of the compressor speed when studying TMS low-temperature refrigeration. As a result, during TMS low-temperature refrigeration, the fan is turned on too early or the speed is too high, resulting in large fluctuations in the high and low pressures on the refrigerant side of the battery thermal management system, system instability, poor cooling effect, or overload and startup failure of the compressor at low temperature.

[0005] For example, patent CN106705362A discloses a low-temperature refrigeration control method, which belongs to the field of air conditioning and involves the control of fan speed and compressor speed at low temperatures. However, in this patent, the compressor does not work below -3°C and cannot adapt to the operating conditions of commercial vehicles with ambient temperatures as low as -20°C. In addition, in this patent, the external fan must be turned on as long as the compressor is running, which will cause large fluctuations in the high and low pressures of the system at extremely low ambient temperatures and poor compressor cooling effect. In addition, the fan speed is related to the compressor speed, which may cause low system pressure at low temperatures and high system pressure at high temperatures, and there is a risk of unstable system pressure.

[0006] Therefore, it is very necessary to optimize the thermal management control of new energy commercial vehicles under low temperature conditions. Summary of the Invention

[0007] In response to the shortcomings of the existing technology, the present invention proposes a low-temperature refrigeration control method for a commercial vehicle battery thermal management system. Through the rational coordination of low-temperature operation control of the fan, staged speed increase of the compressor when starting, and heating belt preheating function, the system is guaranteed to be stable and reliable with a low failure rate when the TMS operates at low temperatures.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is: A low-temperature cooling control method for a commercial vehicle battery thermal management system (TMS) includes a heater belt preheating function, a fan low-temperature control function, and a compressor speed control function. When the system is in non-cooling mode and the ambient temperature is low, the heater belt preheating function is activated, and the preheating set temperature is detected in real time during preheating to ensure sufficient, effective, and safe preheating. During low-temperature cooling, the fan low-temperature control function is activated to timely and effectively adjust the fan speed based on the system high-pressure pressure and system high-pressure temperature to ensure system pressure stability. During cooling, the compressor speed control function is activated, first activating the preheating function, and then increasing and controlling the compressor speed in stages to ensure normal startup and stable operation of the compressor under low-temperature conditions.

[0009] Furthermore, the ambient temperature for starting preheating is set to △T1, the temperature for actively stopping the heating belt is set to △T, and the ambient temperature for calling the fan low-temperature control function is set to △T2. The calling conditions of each function are as follows: when the TMS is in non-cooling mode, if the current ambient temperature is less than △T1 and the temperature at the joint between the current heating belt and the compressor casing is less than △T, the TMS controller turns on the heating belt preheating function; when the TMS is in cooling mode and the current ambient temperature is less than △T2, the TMS controller calls the fan low-temperature control function, otherwise it calls the fan normal control function; when the TMS is in cooling mode, the TMS controller turns on the compressor speed control function, otherwise the function is turned off.

[0010] Furthermore, the control process of the heating belt preheating function is as follows: when the system is in non-cooling mode, if the current ambient temperature is less than △T1 and the temperature at the joint between the heating belt and the compressor housing is less than △T, TMS turns on the heating belt preheating function; when the temperature at the joint between the heating belt and the compressor housing is greater than or equal to △T or the current ambient temperature is greater than or equal to △T1, TMS stops the heating belt preheating function.

[0011] Furthermore, the ambient temperature for calling the fan low-temperature control function is set to △T2, the fan low-temperature opening pressure point is △P, the fan low-temperature opening temperature point is △T3, the fan normal opening pressure point is △P1, and the fan normal opening temperature point is △T4. The control process of the fan low-temperature control function is: when TMS is in cooling mode: TMS detects the current ambient temperature T1 and compares it with △T2: if T1<△T2, call the fan low-temperature control function, specifically: when the compressor high-pressure pressure P<△P and the compressor exhaust temperature T2<△T3, the fan does not turn on; when △P≤P≤△P1 or △T3≤T2≤△T4, the fan runs at a low speed; when P>△P1 or T2>△T4 or T1≥△T2, call the fan normal control function, and the fan is linearly adjusted to the maximum speed.

[0012] Furthermore, the control flow of the fan normal control function is as follows: when the ambient temperature is greater than △T2, before the liquid cooling unit turns on the compressor, the fan runs at a minimum speed of 30% for 10 seconds. After the compressor turns on, the fan speed is associated with the current system high pressure and exhaust temperature: When the high pressure is greater than 15 bar or the exhaust temperature is greater than 80°C, the fan runs at 100% speed; When the high pressure is less than 5 bar or the exhaust temperature is less than 40°C, the fan runs at 30% speed; When 15bar≥high pressure≥5bar and 80℃≥exhaust temperature≥40℃, the fan speed is adjusted linearly.

[0013] Furthermore, the control process of the compressor speed control function is as follows: when TMS is in cooling mode: if the current ambient temperature is lower than the preheating ambient temperature of the heating belt △T1, and the temperature T2 at the joint between the heating belt and the compressor shell is lower than △T, the heating belt preheating function is called, and the compressor stops waiting for preheating; if the current ambient temperature is greater than or equal to △T1, or the temperature T2 at the joint between the heating belt and the compressor shell is greater than △T, the compressor starts running, and within the cooling time t<30 seconds, the compressor runs at the minimum speed; within the range of 30 seconds ≤ t<60 seconds, the compressor speed is increased by 1500rps compared to the minimum speed; when t>60 seconds, the compressor speed is linked to the current outlet water temperature.

[0014] Furthermore, the compressor speed is related to the current outlet water temperature, specifically: When the outlet water temperature is ≥ target temperature + 3°C, the compressor runs at the maximum speed SpeedMax; When target temperature + 3°C > outlet water temperature ≥ target temperature + 1°C, the compressor runs at SpeedMax-1000; When target temperature +1℃>outlet water temperature ≥target temperature -1℃, the compressor speed PID is adjusted to stabilize the outlet water temperature within the target temperature range; Target temperature -1℃>outlet water temperature ≥target temperature -3℃, the compressor runs at minimum speed; If the outlet water temperature is less than the target temperature -3°C, the compressor will stop.

[0015] Furthermore, the maximum speed of the compressor SpeedMax is set according to the ambient temperature, specifically: When the ambient temperature is >50°C, the maximum speed of the compressor is SpeedMax=4000rps; 50℃≥ambient temperature>40℃, the maximum speed of the compressor is SpeedMax=5000rps; 40℃≥ambient temperature>10℃, the maximum speed of the compressor is SpeedMax=6000rps; 10℃≥ambient temperature>-10℃, the maximum speed of the compressor is SpeedMax=5000rps; -10℃≥ambient temperature>-30℃, the maximum speed of the compressor is SpeedMax=4000rps.

[0016] Furthermore, the minimum speed of the compressor is 2000 rps.

[0017] Furthermore, the fan low temperature control function is called and the ambient temperature ΔT2 is 10°C.

[0018] Beneficial effects: The low-temperature refrigeration control method of the commercial vehicle battery thermal management system of the present invention has a heating belt preheating function, a fan low-temperature control function, and a compressor control function. The three functions work closely together to compensate for the problems of the prior art when the compressor is started at a low temperature, such as unstable system refrigerant pressure, excessive speed when the compressor is started, insufficient heating of the heating belt, etc., which lead to a high failure rate when the TMS is running at a low temperature. Through the reasonable coordination of functions such as the fan low-temperature operation control, the staged increase in the speed of the compressor when starting, and the heating belt preheating function, the system is guaranteed to be stable and reliable with a low failure rate when the TMS is running at a low temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Functional block diagram of the TMS system low-temperature operation scheme; Figure 2 Control flow chart of the heating zone prediction function; Figure 3 Control flow chart of fan low temperature control function; Figure 4 Control flow chart of the compressor speed control function. DETAILED DESCRIPTION

[0020] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0021] like Figure 1 As shown, a low-temperature refrigeration control method for a commercial vehicle battery thermal management system is applied to the battery thermal management system of a new energy commercial vehicle. It is suitable for environments with extremely low operating temperatures, often below -20°C. The battery thermal management system corresponding to this control method includes a heating belt preheating detection function module, a fan low-temperature control function module, and a compressor speed control function module.

[0022] The heating belt preheating function module is mainly composed of a heating belt and a temperature collector. The heating belt is 24V / 90W, which ensures fast and sufficient preheating. The temperature collector detects the heating temperature of the heating belt in real time. When the heating temperature is too high, the preheating is stopped to ensure that the heating belt preheating function is timely, effective, safe and reliable.

[0023] The fan low-temperature control module adjusts the fan speed promptly and effectively according to the system high-pressure pressure and system high-pressure temperature, thereby ensuring that the system pressure and temperature are always kept within a reasonable range during TMS low-temperature cooling, ensuring the maximum cooling efficiency and energy efficiency of the TMS.

[0024] The compressor control module, TMS, starts the preheating function when cooling at low temperatures. After the preheating is completed, the speed of the compressor is controlled in stages to ensure that the speed of the compressor increases slowly and steadily in a low-temperature environment, avoiding the risk of overload and startup failure when starting at low temperatures.

[0025] The low-temperature refrigeration control method of the battery thermal management system of a new energy commercial vehicle in this embodiment includes a heating belt preheating function, a fan low-temperature control function, and a compressor speed control function. When the TMS is in non-refrigeration mode under a low-temperature environment, the heating belt preheating mode is turned on to ensure that the compressor is fully preheated when it starts, and the compressor starts stably and reliably; when the TMS is in cooling mode under a low-temperature environment, the fan low-temperature control function and the compressor speed control function are called, and the two functions are closely coordinated to ensure that the compressor can start and run stably under low-temperature conditions of the TMS, the system pressure is stable, and the cooling effect is good; through the close coordination of the three functions, the problems of the high failure rate of the TMS during low-temperature operation caused by unstable system refrigerant pressure, excessive speed of the compressor when starting, insufficient heating of the heating belt, etc. when the compressor is started at low temperature in the prior art are compensated.

[0026] In order to facilitate a clear explanation of each functional process, some temperature or pressure values are first defined. The preheating start-up ambient temperature is set to △T1, the heating belt active stop temperature is △T, the ambient temperature for calling the fan low-temperature control function is △T2, the fan low-temperature start-up pressure point is △P, the fan low-temperature start-up temperature point is △T3, the fan normal start-up pressure point is △P1, and the fan normal start-up temperature point is △T4.

[0027] When performing low-temperature refrigeration control, the calling conditions of the three functions are as follows: when the TMS is in non-cooling mode, if the current ambient temperature is lower than the preheating ambient temperature △T1 and the temperature at the joint between the current heating belt and the compressor casing is lower than the active stop temperature △T of the heating belt, the TMS controller turns on the heating belt preheating function; when the TMS is in cooling mode and the current ambient temperature is lower than △T2, the TMS controller calls the fan low-temperature control function (i.e., the fan low-temperature control function), otherwise it calls the fan normal control function; when the TMS is in cooling mode, the TMS controller turns on the compressor speed control function, otherwise the function is turned off.

[0028] Among them, Figure 2 As shown in FIG, the control flow of the heating belt preheating detection function is as follows: after the system is powered on, when the TMS is in non-cooling mode, if the current ambient temperature is less than the preheating start ambient temperature △T1, and the temperature at the joint between the heating belt and the compressor housing is less than the heating belt active stop temperature △T, the TMS starts the heating belt preheating function; when the temperature at the joint between the heating belt and the compressor housing is greater than or equal to △T or the current ambient temperature is greater than or equal to △T1, the TMS stops the heating belt preheating function. The flow chart is as follows Figure 2 shown.

[0029] The flow chart of the fan low temperature control function is as follows Figure 3 As shown, the specific process is: when TMS is in cooling mode: TMS detects the current ambient temperature T1 and compares it with the ambient temperature △T2 of the fan low temperature control function: if T1<△T2, call the fan low temperature control function, specifically: when the compressor high pressure pressure P<fan low temperature opening pressure point △P and the compressor exhaust temperature T2<fan low temperature opening temperature point △T3, the fan does not turn on; when the compressor high pressure pressure P is between the fan low temperature opening pressure point △P and the fan normal opening pressure point △P1, or the fan low temperature control function is called and the ambient temperature △T2 is between the fan low temperature opening temperature point △T3 and the fan normal opening temperature point △T4, that is: △P≤P≤△P1 or △T3≤T2≤△T4, the fan runs at a low speed; when P>△P1 or T2>△T4 or T1≥△T2, call the fan normal control function, and the fan is linearly adjusted to the maximum speed.

[0030] Among them, the specific control process of the fan normal control function is as follows: When the ambient temperature is greater than △T2 (10°C), the fan of the liquid cooling unit runs at a minimum speed of 30% for 10 seconds before the compressor is turned on. After the compressor is turned on, the fan speed is related to the current system high pressure and exhaust temperature: When the high pressure is greater than 15 bar or the exhaust temperature is greater than 80°C, the fan runs at 100% speed; When the high pressure is less than 5 bar or the exhaust temperature is less than 40°C, the fan runs at 30% speed; When the high pressure is 15 bar or higher and the exhaust temperature is 80°C or higher and 40°C or higher, the fan speed is adjusted linearly.

[0031] The flow chart of the compressor speed control function is as follows Figure 4 As shown, the control process is: when TMS is in cooling mode: if the current ambient temperature is greater than or equal to the heating belt preheating ambient temperature △T1, the compressor starts running, and within the running time t<30 seconds, the compressor runs at a minimum speed of 2000rps; within the range of 30 seconds<t<60 seconds, the compressor runs at 3500rps; when t>60 seconds, the compressor speed is associated with the current outlet water temperature; if the current ambient temperature is lower than the heating belt preheating ambient temperature △T1, it is necessary to further determine whether the temperature T2 at the joint between the heating belt and the compressor casing is greater than △T. If T2<△T, the heating belt preheating function is turned on, and the compressor stops and waits for the preheating to be completed before starting again. If T2≥△T, the compressor runs at a minimum speed of 2000rps within the running time t<30 seconds; within the range of 30 seconds<t<60 seconds, the compressor runs at 3500rps; when t>60 seconds, the compressor speed is associated with the current outlet water temperature.

[0032] When the compressor is turned on, when t>60 seconds, the compressor speed is linked to the current outlet water temperature. Specifically: when the outlet water temperature ≥ target temperature + 3°C, the compressor runs at the maximum speed SpeedMax; When target temperature + 3°C > outlet water temperature ≥ target temperature + 1°C, the compressor runs at SpeedMax-1000; When target temperature +1℃>outlet water temperature ≥target temperature -1℃, the compressor speed PID is adjusted to stabilize the outlet water temperature within the target temperature range; If the target temperature -1°C > the outlet water temperature ≥ the target temperature -3°C, the compressor will run at a minimum speed of 2000rps. If the outlet water temperature is less than the target temperature -3°C, the compressor will stop.

[0033] The maximum speed of the compressor SpeedMax is not a fixed value, but varies according to the ambient temperature, as follows: When the ambient temperature is >50°C, the maximum speed of the compressor is SpeedMax=4000rps; 50℃≥ambient temperature>40℃, the maximum speed of the compressor is SpeedMax=5000rps; 40℃≥ambient temperature>10℃, the maximum speed of the compressor is SpeedMax=6000rps; 10℃≥ambient temperature>-10℃, the maximum speed of the compressor is SpeedMax=5000rps; -10℃≥ambient temperature>-30℃, the maximum speed of the compressor is SpeedMax=4000rps.

[0034] The control method of the present invention optimizes the low-temperature cooling function of the battery thermal management system. Through the preheating detection function of the heating belt, it ensures sufficient preheating of the compressor in a low-temperature environment, avoiding the risk of compressor damage caused by insufficient preheating. In the low-temperature cooling mode, the compressor speed is increased in stages through staged speed control, avoiding startup overload and startup failure problems when the compressor is started at low temperature, and the compressor speed is related to the outlet water temperature. At the same time, during low-temperature operation, by increasing the low-temperature speed control of the fan, it is avoided that the high and low pressure fluctuations on the refrigerant side of the battery thermal management system are large due to the fan starting too early or the speed is too high, the system is unstable, the cooling effect is poor, and other problems.

[0035] The control method of the present invention is simple, ingenious and easy to implement. It ensures that the system is stable and reliable with a low failure rate when the TMS operates at low temperatures. Compared with the existing technology, this solution can achieve normal operation of the compressor and stable system pressure at an ambient temperature above -20°C. There is no need to connect an air-cooled radiator in parallel on the refrigerant side, which effectively saves space and is low in cost. It is particularly suitable for use and promotion in new energy commercial vehicles.

[0036] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with the present profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical content disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A low-temperature refrigeration control method for a commercial vehicle battery thermal management system, characterized in that: The battery thermal management system (TMS) includes a heater belt preheating function, a fan low-temperature control function, and a compressor speed control function. When the system is in non-cooling mode and the ambient temperature is low, the heater belt preheating function is turned on, and the preheating set temperature is detected in real time during preheating to ensure that the preheating is sufficient, effective, and safe; during low-temperature cooling, the fan low-temperature control function is called to adjust the fan speed in a timely and effective manner according to the system high-pressure pressure and system high-pressure temperature to ensure system pressure stability; during cooling, the compressor speed control function is called, the preheating function is turned on first, and then the compressor speed is increased and controlled in stages to ensure that the compressor starts normally and runs stably under low-temperature conditions.

2. A low-temperature refrigeration control method for a commercial vehicle battery thermal management system according to claim 1, characterized in that: Set the preheating start ambient temperature to △T1, the heating belt active stop temperature to △T, and the fan low temperature control function calling ambient temperature to △T2. The calling conditions of each function are: when TMS is in non-cooling mode, if the current ambient temperature is less than △T1 and the current temperature of the heating belt and the compressor casing is less than △T, the TMS controller turns on the heating belt preheating function; when TMS is in cooling mode and the current ambient temperature is less than △T2, the TMS controller calls the fan low temperature control function, otherwise it calls the fan normal control function; when TMS is in cooling mode, the TMS controller turns on the compressor speed control function, otherwise the function is turned off.

3. The low-temperature refrigeration control method for a commercial vehicle battery thermal management system according to claim 2, characterized in that: The control process of the heating belt preheating function is as follows: when the system is in non-cooling mode, if the current ambient temperature is less than △T1 and the temperature at the joint between the heating belt and the compressor housing is less than △T, TMS starts the heating belt preheating function; when the temperature at the joint between the heating belt and the compressor housing is greater than or equal to △T or the current ambient temperature is greater than or equal to △T1, TMS stops the heating belt preheating function.

4. The low-temperature refrigeration control method for a commercial vehicle battery thermal management system according to claim 2, characterized in that: Set the ambient temperature for calling the fan low temperature control function to △T2, the fan low temperature opening pressure point to △P, the fan low temperature opening temperature point to △T3, the fan normal opening pressure point to △P1, and the fan normal opening temperature point to △T4. The control flow of the fan low temperature control function is as follows: When TMS is in cooling mode: TMS detects the current ambient temperature T1 and compares it with △T2: If T1 < △T2, call the fan low temperature control function, specifically: when the compressor high pressure P < △P and the compressor exhaust temperature T2 < △T3, the fan does not turn on; when △P ≤ P ≤ △P1 or △T3 ≤ T2 ≤ △T4, the fan runs at a low speed; when P > △P1 or T2 > △T4 or T1 ≥ △T2, call the fan normal control function and the fan is linearly adjusted to the maximum speed.

5. The low-temperature refrigeration control method for a commercial vehicle battery thermal management system according to claim 4, characterized in that: The control flow of the fan normal control function is as follows: when the ambient temperature is greater than △T2, before the liquid cooling unit turns on the compressor, the fan runs at a minimum speed of 30% for 10 seconds. After the compressor turns on, the fan speed is linked to the current system high pressure and exhaust temperature: When the high pressure is greater than 15 bar or the exhaust temperature is greater than 80°C, the fan runs at 100% speed; When the high pressure is less than 5 bar or the exhaust temperature is less than 40°C, the fan runs at 30% speed; When 15bar≥high pressure≥5bar and 80℃≥exhaust temperature≥40℃, the fan speed is adjusted linearly.

6. The low-temperature refrigeration control method for a commercial vehicle battery thermal management system according to claim 2, characterized in that: The control flow of the compressor speed control function is as follows: when TMS is in cooling mode: if the current ambient temperature is lower than the preheating ambient temperature of the heating belt △T1, and the temperature T2 at the joint between the heating belt and the compressor shell is lower than △T, the heating belt preheating function is called, and the compressor stops waiting for preheating; if the current ambient temperature is greater than or equal to △T1, or the temperature T2 at the joint between the heating belt and the compressor shell is greater than △T, the compressor starts running. During the cooling time t<30 seconds, the compressor runs at the minimum speed; within the range of 30 seconds ≤ t<60 seconds, the compressor speed is increased by 1500rps compared to the minimum speed; when t>60 seconds, the compressor speed is linked to the current outlet water temperature.

7. The low-temperature refrigeration control method for a commercial vehicle battery thermal management system according to claim 6, characterized in that: The compressor speed is related to the current outlet water temperature, specifically: When the outlet water temperature is ≥ target temperature + 3°C, the compressor runs at the maximum speed SpeedMax; When target temperature + 3°C > outlet water temperature ≥ target temperature + 1°C, the compressor runs at SpeedMax-1000; When target temperature +1℃>outlet water temperature ≥target temperature -1℃, the compressor speed PID is adjusted to stabilize the outlet water temperature within the target temperature range; Target temperature -1℃>outlet water temperature ≥target temperature -3℃, the compressor runs at minimum speed; If the outlet water temperature is less than the target temperature -3°C, the compressor will stop.

8. The low-temperature refrigeration control method for a commercial vehicle battery thermal management system according to claim 7, characterized in that: The maximum speed of the compressor SpeedMax is set according to the ambient temperature, specifically: When the ambient temperature is >50°C, the maximum speed of the compressor is SpeedMax=4000rps; 50℃≥ambient temperature>40℃, the maximum speed of the compressor is SpeedMax=5000rps; 40℃≥ambient temperature>10℃, the maximum speed of the compressor is SpeedMax=6000rps; 10℃≥ambient temperature>-10℃, the maximum speed of the compressor is SpeedMax=5000rps; -10℃≥ambient temperature>-30℃, the maximum speed of the compressor is SpeedMax=4000rps.

9. A low-temperature refrigeration control method for a commercial vehicle battery thermal management system according to claim 6 or 7, characterized in that: The minimum compressor speed is 2000rps.

10. A low-temperature refrigeration control method for a commercial vehicle battery thermal management system according to any one of claims 2 to 6, characterized in that: Call the fan low temperature control function when the ambient temperature △T2 is 10℃.

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