Compressor liquid return control method and compressor liquid return control system

Abstract

This application discloses a compressor liquid return control method and a compressor liquid return control system. The compressor liquid return control method of this application is applied to an air conditioning unit, which includes a compressor and a fan. The compressor liquid return control method includes: acquiring the compressor's operating frequency, the fan speed, and the air conditioning unit's high-pressure and low-pressure operating values ​​at a preset cycle; determining whether liquid return exists in the compressor based on the operating frequency, fan speed, high-pressure, and low-pressure operating values; and providing protective control to the compressor when liquid return exists. Thus, without adding other modules, it can accurately determine whether liquid return exists in the compressor, reducing costs. Furthermore, it can provide protective control to the compressor, effectively reducing damage caused by liquid return and improving the reliability of the air conditioning unit.

Description

Technical Field

[0001] This application relates to the field of air conditioning technology, and in particular to a compressor liquid return control method and a compressor liquid return control system. Background Technology

[0002] Due to numerous influencing factors such as the operating status, system control, and on-site installation of air conditioning units, compressor liquid return frequently occurs. As the core component of an air conditioning unit, compressor failure due to liquid return directly impacts the reliable operation of the unit. Therefore, accurately determining whether liquid return is occurring in the compressor is a pressing issue that needs to be addressed. Summary of the Invention

[0003] This application provides a compressor liquid return control method, control device, control system, and computer-readable storage medium to solve at least one of the aforementioned technical problems.

[0004] The compressor liquid return control method of this application is applied to an air conditioning unit, which includes a compressor and a fan. The compressor liquid return control method includes:

[0005] The operating frequency of the compressor, the fan speed of the fan, and the high-pressure and low-pressure operating of the air conditioning unit are obtained at a preset cycle.

[0006] The presence of liquid return in the compressor is determined based on the operating frequency, the fan speed, the high operating pressure, and the low operating pressure.

[0007] When liquid return occurs in the compressor, protective control is implemented for the compressor.

[0008] In some embodiments, the fan includes an outdoor fan and an indoor fan, and the fan speed of the fan is obtained at a preset period, including:

[0009] When the air conditioning unit is operating in cooling mode, the first fan speed of the outdoor fan is obtained at the preset cycle and used as the fan speed.

[0010] When the air conditioning unit is operating in heating mode, the second fan speed of the indoor fan is obtained at the preset cycle and used as the fan speed.

[0011] In some embodiments, the air conditioning unit includes a first pressure sensor and a second pressure sensor. The first pressure sensor is disposed at the discharge end of the compressor, and the second pressure sensor is disposed at the suction end of the compressor. The air conditioning unit acquires its operating high pressure and operating low pressure at preset intervals, including:

[0012] The operating high pressure of the air conditioning unit is obtained through the first pressure sensor at the preset cycle;

[0013] The operating low pressure of the air conditioning unit is obtained through the second pressure sensor at the preset cycle.

[0014] In some embodiments, determining whether the compressor experiences liquid return based on the operating frequency, the fan speed, the high operating pressure, and the low operating pressure includes:

[0015] Calculate the difference between the operating frequency obtained at the current moment and the operating frequency obtained at the previous moment to obtain the frequency difference;

[0016] Calculate the difference between the fan speed obtained at the current moment and the fan speed obtained at the previous moment to obtain the speed difference;

[0017] Calculate the difference between the operating high pressure obtained at the current moment and the operating high pressure obtained at the previous moment to obtain the high pressure difference value;

[0018] Calculate the difference between the operating low pressure obtained at the current moment and the operating low pressure obtained at the previous moment to obtain the low pressure difference value;

[0019] The presence of liquid return in the compressor is determined based on the frequency difference, the speed difference, the high pressure difference, and the low pressure difference.

[0020] In some embodiments, determining whether the compressor experiences liquid return based on the frequency difference, the speed difference, the high-pressure difference, and the low-pressure difference includes:

[0021] If, in a series of predetermined preset cycles, the frequency difference is zero, the speed difference is less than a preset speed difference, the high pressure difference is greater than or equal to a first pressure difference, and the low pressure difference is greater than or equal to a second pressure difference, it is determined that the compressor has a liquid return phenomenon.

[0022] When the frequency difference is not zero, and / or the speed difference is greater than or equal to a preset speed difference, and / or the high pressure difference is less than a first pressure difference, and / or the low pressure difference is less than a second pressure difference, it is determined that the compressor does not have a liquid return phenomenon.

[0023] In some embodiments, the air conditioning unit further includes an expansion valve connected to the fan, and the protection control of the compressor when liquid return occurs includes:

[0024] When liquid return occurs in the compressor, the compressor is protected by adjusting the opening degree of the expansion valve, the superheat of the compressor, and the operating frequency.

[0025] In some embodiments, when liquid return occurs in the compressor, the protective control of the compressor by adjusting the opening degree of the expansion valve, the superheat of the compressor, and the operating frequency includes:

[0026] When liquid return occurs in the compressor, the opening of the expansion valve is reduced to increase the discharge superheat and suction superheat of the compressor, and the process returns to the step of obtaining the operating frequency of the compressor, the fan speed of the fan, and the operating high pressure and operating low pressure of the air conditioning unit at a preset cycle, so as to determine again whether liquid return occurs in the compressor.

[0027] When it is determined again that the compressor has a liquid return phenomenon, it is determined whether the opening degree of the expansion valve is equal to the preset opening degree;

[0028] When the opening degree of the expansion valve is not equal to the preset opening degree, return to reducing the opening degree of the expansion valve to achieve the step of increasing the discharge superheat and suction superheat of the compressor;

[0029] When the opening degree of the expansion valve is equal to the preset opening degree, the operating frequency is reduced;

[0030] Determine whether unit protection needs to be activated based on the reduced operating frequency.

[0031] In some embodiments, after determining again whether the compressor experiences liquid return, the compressor liquid return control method further includes:

[0032] When there is no liquid return phenomenon in the compressor, the compressor is controlled to maintain the current exhaust superheat and intake superheat.

[0033] In some implementations, determining whether to activate unit protection based on the reduced operating frequency includes:

[0034] Determine whether the reduced operating frequency is equal to the frequency threshold;

[0035] When the reduced operating frequency is less than or equal to the frequency threshold, the operating frequency is maintained at the frequency threshold, and the unit protection is activated.

[0036] When the reduced operating frequency is greater than the frequency threshold, the process returns to the step of obtaining the compressor's operating frequency, the fan speed, and the air conditioning unit's high-pressure and low-pressure operating values ​​at a preset cycle, in order to determine again whether the compressor has a liquid return phenomenon.

[0037] If it is determined again that the compressor has liquid return, return to the step of reducing the operating frequency;

[0038] When there is no liquid return phenomenon in the compressor, the compressor is controlled to maintain the current operating frequency, the exhaust superheat and the intake superheat.

[0039] The compressor liquid return control device according to the embodiments of this application is applied to an air conditioning unit, the air conditioning unit including a compressor and a fan, and the compressor liquid return control device includes:

[0040] The acquisition module is used to acquire the operating frequency of the compressor, the fan speed of the fan, and the operating high pressure and operating low pressure of the air conditioning unit at a preset period.

[0041] The judgment module is used to determine whether the compressor has a liquid return phenomenon based on the operating frequency, the fan speed, the operating high pressure, and the operating low pressure.

[0042] The control module is used to protect the compressor when liquid return occurs.

[0043] The compressor liquid return control system of this application includes one or more processors and a memory. The memory stores a computer program. When the computer program is executed by the processor, it implements the compressor liquid return control method of any of the above embodiments.

[0044] The computer-readable storage medium of the present application embodiment stores a computer program thereon, which, when executed by a processor, implements the compressor liquid return control method of any of the above embodiments.

[0045] The compressor liquid return control method, control device, control system, and computer-readable storage medium of this application acquire the compressor's operating frequency, fan speed, and the air conditioning unit's high-pressure and low-pressure operating values ​​at preset intervals. Based on the operating frequency, fan speed, high-pressure, and low-pressure operating values, it determines whether liquid return is occurring in the compressor. Multiple parameters are combined for a comprehensive judgment, and when liquid return is detected, protective control is implemented on the compressor. This eliminates the need for additional modules, accurately determining whether liquid return is occurring in the compressor, resulting in low cost. Furthermore, it provides protective control for the compressor, effectively reducing damage caused by liquid return and improving the reliability of the air conditioning unit.

[0046] Additional aspects and advantages of embodiments of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of embodiments of this application. Attached Figure Description

[0047] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, wherein:

[0048] Figure 1 This is a flowchart illustrating a compressor liquid return control method according to certain embodiments of this application;

[0049] Figure 2 This is a schematic diagram of the structure of an air conditioning unit according to certain embodiments of this application;

[0050] Figure 3 This is a flowchart illustrating a compressor liquid return control method according to certain embodiments of this application;

[0051] Figure 4 This is a flowchart illustrating a compressor liquid return control method according to certain embodiments of this application;

[0052] Figure 5 This is a flowchart illustrating a compressor liquid return control method according to certain embodiments of this application;

[0053] Figure 6 This is a flowchart illustrating a compressor liquid return control method according to certain embodiments of this application;

[0054] Figure 7 This is a flowchart illustrating a compressor liquid return control method according to certain embodiments of this application;

[0055] Figure 8 This is a schematic diagram of the process for protecting and controlling an air conditioning unit according to certain embodiments of this application;

[0056] Figure 9This is a flowchart illustrating a compressor liquid return control method according to certain embodiments of this application;

[0057] Figure 10 This is a flowchart illustrating a compressor liquid return control method according to certain embodiments of this application;

[0058] Figure 11 This is a flowchart illustrating a compressor liquid return control method according to certain embodiments of this application;

[0059] Figure 12 This is a schematic diagram of a compressor liquid return control device according to certain embodiments of this application;

[0060] Figure 13 This is a schematic diagram of the compressor liquid return control system according to certain embodiments of this application;

[0061] Figure 14 This is a schematic diagram illustrating the connection state between a computer-readable storage medium and a processor according to certain embodiments of this application.

[0062] Explanation of reference numerals in the attached figures:

[0063] Air conditioning unit 100, compressor 10, fan 20, outdoor fan 21, indoor fan 22, first pressure sensor 31, second pressure sensor 32, expansion valve 40, first expansion valve 41, second expansion valve 42, four-way valve 50, outdoor heat exchanger 61, indoor heat exchanger 62, gas-liquid separator 70, compressor liquid return control device 200, acquisition module 210, judgment module 220, control module 230, compressor liquid return control system 300, processor 310, memory 320, computer-readable storage medium 400, computer program 410, processor 420. Detailed Implementation

[0064] The embodiments of this application will be further described below with reference to the accompanying drawings. The same or similar reference numerals in the drawings denote the same or similar elements or elements having the same or similar functions throughout. Furthermore, the embodiments of this application described below with reference to the accompanying drawings are exemplary and are only used to explain the embodiments of this application, and should not be construed as limiting this application.

[0065] Please see Figure 1 and Figure 2 This application provides a compressor 10 liquid return control method, applied to an air conditioning unit 100. The air conditioning unit 100 includes a compressor 10 and a fan 20, and the compressor 10 liquid return control method includes:

[0066] 010: Obtain the operating frequency of compressor 10, the fan speed of fan 20, and the high-pressure and low-pressure operating of air conditioning unit 100 at a preset cycle;

[0067] 020: Determine whether compressor 10 has liquid return based on operating frequency, fan speed, high operating pressure, and low operating pressure;

[0068] 030: When there is liquid return in compressor 10, protect compressor 10 by controlling it.

[0069] In the compressor 10 liquid return control method of this application embodiment, the operating frequency of the compressor 10, the fan speed of the fan 20, and the operating high pressure and low pressure of the air conditioning unit 100 are acquired at a preset period to determine whether liquid return occurs in the compressor 10. Multiple parameters are combined for joint judgment, and when liquid return occurs in the compressor 10, protective control is implemented for the compressor 10. Thus, without adding other modules, it can accurately determine whether liquid return occurs in the compressor 10, resulting in low cost. Furthermore, it can also provide protective control for the compressor 10, effectively reducing damage caused by liquid return and improving the reliability of the air conditioning unit 100.

[0070] Specifically, the air conditioning unit 100 includes a compressor 10 and a fan 20. The compressor 10 is used to draw in low-temperature, low-pressure refrigerant and convert it into high-temperature, high-pressure refrigerant for discharge. In this embodiment, the compressor 10 is a rolling rotor compressor. The fan 20 is used to realize the circulation and transfer of air between the air conditioning unit 100 and the external environment.

[0071] The system acquires the operating frequency of compressor 10, the fan speed of fan 20, and the high and low operating pressures of air conditioning unit 100 at preset intervals. The preset interval can be set to 5-10 minutes, and can be adjusted according to actual needs. For example, the preset interval can be set to 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, 10 minutes, or any number of minutes within 5-10 minutes. The operating frequency of compressor 10 can be read directly from compressor 10, and the fan speed of fan 20 can be read directly from fan 20. The high operating pressure of air conditioning unit 100 is the pressure at the discharge end of compressor 10, and the low operating pressure is the pressure at the suction end of compressor 10. Both the high and low operating pressures can be acquired through the pressure sensors configured within air conditioning unit 100 itself.

[0072] It should be noted that the rotary compressor does not have an intake valve at the suction end; it relies on direct airflow for compression (the low-pressure area and high-pressure area are isolated by vanes inside the compression chamber). Therefore, if there is a small amount of liquid return or liquid in the pump oil system, compression becomes impossible, and the pressure inside the compression chamber increases dramatically. The high-pressure area of ​​the rotary compressor, isolated by valves, has an internal pressure relief design. The timing when the compressor 10 stops compression varies with the pressure in the exhaust pipe; intermittent or small amounts of liquid return will also cause pressure changes. Therefore, the periodic fluctuations in the high-pressure and low-pressure operating conditions of the air conditioning unit 100 can be used as one of the criteria for determining whether liquid is returning to the compressor 10.

[0073] As described above, the presence of liquid return in compressor 10 can be determined based on changes in operating frequency, fan speed, and fluctuations in high and low operating pressures. When liquid return is detected in compressor 10, protective controls are implemented to minimize damage caused by the return.

[0074] In related technologies, to prevent liquid return from the compressor 10, the exhaust superheat and intake superheat of the compressor 10 are controlled within a certain range during air conditioner operation to reduce the probability of liquid return. However, this method cannot completely prevent liquid return from the compressor 10, and it cannot accurately determine whether liquid return is occurring in the compressor 10.

[0075] In other related technologies, the presence of liquid return in compressor 10 is determined based on its operating power, operating frequency, and outdoor ambient temperature. However, due to the influence of on-site power supply and voltage fluctuations, power calculation or acquisition requires an additional power acquisition module, which is costly. Furthermore, since power fluctuation deviations are generally small, and wear and tear on the compressor 10 itself can also cause power fluctuations, there is a certain possibility of misjudgment.

[0076] In this embodiment, multiple parameters related to liquid return in the compressor 10 are considered. The operating frequency of the compressor 10, the fan speed of the fan 20, and the high and low operating pressures of the air conditioning unit 100 are acquired at preset intervals. Based on the operating frequency, fan speed, high and low operating pressures, it is determined whether liquid return occurs in the compressor 10. A combined judgment is made based on multiple parameters, and protective control is implemented on the compressor 10 when liquid return is detected. Thus, without adding other modules, it can accurately determine whether liquid return occurs in the compressor 10, reducing costs. Furthermore, it can provide protective control for the compressor 10, effectively reducing damage caused by liquid return and improving the reliability of the air conditioning unit 100.

[0077] Please see Figure 2 and Figure 3In some embodiments, the fan 20 includes an outdoor fan 21 and an indoor fan 22. Obtaining the fan speed (i.e., 010) of the fan 20 at a preset period includes:

[0078] 011: When the air conditioning unit 100 is working in cooling mode, the first fan speed of the outdoor fan 21 is obtained at a preset cycle and used as the fan speed;

[0079] 012: When the air conditioning unit 100 is operating in heating mode, the second fan speed of the indoor fan 22 is obtained at a preset cycle and used as the fan speed.

[0080] Specifically, the fan 20 includes an outdoor fan 21 and an indoor fan 22. The air conditioning unit 100 also includes a four-way valve 50, an outdoor heat exchanger 61, an indoor heat exchanger 62, and a gas-liquid separator 70. The outdoor fan 21 is connected to the outdoor heat exchanger 61, and the indoor fan 22 is connected to the indoor heat exchanger 62.

[0081] When the air conditioning unit 100 is operating in cooling mode, such as Figure 2 As shown, the four-way valve 50 connects the compressor 10 to the outdoor heat exchanger 61, and the indoor heat exchanger 62 to the gas-liquid separator 70. The high-temperature, high-pressure gaseous refrigerant discharged from the compressor 10 flows through the four-way valve 50 to the outdoor heat exchanger 61, where it exchanges heat with the outdoor air via the outdoor fan 21. The high-temperature, high-pressure gaseous refrigerant is then converted into a medium-temperature, high-pressure liquid refrigerant, which flows back to the indoor heat exchanger 62. The medium-temperature, high-pressure liquid refrigerant exchanges heat with the indoor air in the indoor heat exchanger 62 via the indoor fan 22, evaporating into a low-temperature, low-pressure gaseous refrigerant. This gaseous refrigerant then flows through the four-way valve 50 to the gas-liquid separator 70, where it undergoes gas-liquid separation before returning to the compressor 10.

[0082] When the air conditioning unit 100 is operating in heating mode, the four-way valve 50 connects the compressor 10 to the indoor heat exchanger 62, and the outdoor heat exchanger 61 to the gas-liquid separator 70. The high-temperature, high-pressure gaseous refrigerant discharged from the compressor 10 flows through the four-way valve 50 to the indoor heat exchanger 62, where it exchanges heat with the indoor air via the indoor fan 22. The high-temperature, high-pressure gaseous refrigerant is then converted into a medium-temperature, high-pressure liquid refrigerant, which flows to the outdoor heat exchanger 61. The medium-temperature, high-pressure liquid refrigerant exchanges heat with the outdoor air via the outdoor fan 21 in the outdoor heat exchanger 61, evaporating into a low-temperature, low-pressure gaseous refrigerant. This gaseous refrigerant then flows through the four-way valve 50 to the gas-liquid separator 70, where it undergoes gas-liquid separation before returning to the compressor 10.

[0083] Please see Figure 2 and Figure 4In some embodiments, the air conditioning unit 100 includes a first pressure sensor 31 and a second pressure sensor 32. The first pressure sensor 31 is disposed at the discharge end of the compressor 10, and the second pressure sensor 32 is disposed at the suction end of the compressor 10. Acquiring the operating high pressure and operating low pressure (i.e., 010) of the air conditioning unit 100 at preset intervals includes:

[0084] 013: The operating high pressure of the air conditioning unit 100 is obtained through the first pressure sensor 31 at a preset cycle;

[0085] 014: The operating low pressure of the air conditioning unit 100 is obtained by the second pressure sensor 32 at a preset cycle.

[0086] Specifically, the air conditioning unit 100 includes a first pressure sensor 31 and a second pressure sensor 32. The first pressure sensor 31 is located at the discharge end of the compressor 10, between the compressor 10 and the four-way valve 50. The compressor 10 discharges high-temperature, high-pressure gaseous refrigerant; therefore, the high-pressure operating pressure of the air conditioning unit 100 can be obtained at preset intervals using the first pressure sensor 31. The second pressure sensor 32 is located at the suction end of the compressor 10, between the four-way valve 50 and the gas-liquid separator 70. The compressor 10 draws in low-temperature, low-pressure gaseous refrigerant; therefore, the low-pressure operating pressure of the air conditioning unit 100 can be obtained at preset intervals using the second pressure sensor 32.

[0087] In related technologies, the multi-directional index of compressor 10 is calculated by acquiring parameters such as return gas temperature, discharge temperature, return gas pressure, and discharge pressure to determine whether compressor 10 is experiencing liquid return. This method requires multiple detection sensors, including return gas temperature sensor, discharge temperature sensor, return gas pressure sensor, and discharge pressure sensor, resulting in high costs. Furthermore, while the temperature and pressure of refrigerant in the two-phase region correspond, the return gas process is superheated and lacks pressure values. Temperature alone cannot accurately indicate whether the actual refrigerant is humid air or experiencing liquid return, especially in heating mode, where the return gas temperature is often lower than the outdoor coil temperature. Therefore, this method cannot determine whether compressor 10 is experiencing liquid return.

[0088] In this embodiment, the operating high pressure and operating low pressure are obtained by the first pressure sensor 31 and the second pressure sensor 32 configured on the air conditioning unit 100, respectively. The operating frequency and fan speed of the compressor 10 can be obtained by direct reading. In this way, without adding other modules, it is possible to accurately determine whether there is liquid return in the compressor 10, which is low cost.

[0089] Please see Figure 2 and Figure 5In some embodiments, determining whether compressor 10 experiences liquid return (i.e., 020) based on operating frequency, fan speed, high operating pressure, and low operating pressure includes:

[0090] 021: Calculate the difference between the operating frequency acquired at the current moment and the operating frequency acquired at the previous moment to obtain the frequency difference;

[0091] 022: Calculate the difference between the fan speed obtained at the current moment and the fan speed obtained at the previous moment to obtain the speed difference;

[0092] 023: Calculate the difference between the operating high pressure obtained at the current moment and the operating high pressure obtained at the previous moment to obtain the high pressure difference;

[0093] 024: Calculate the difference between the operating low pressure obtained at the current moment and the operating low pressure obtained at the previous moment to obtain the low pressure difference value;

[0094] 025: Determine whether compressor 10 has liquid return phenomenon based on frequency difference, speed difference, high pressure difference and low pressure difference.

[0095] Specifically, the operating frequency of compressor 10, the fan speed of fan 20, and the operating high pressure and operating low pressure of air conditioning unit 100 are acquired at preset intervals. Each time an acquisition is made, the difference between the operating frequency acquired at the current moment and the operating frequency acquired at the previous moment is calculated to obtain the frequency difference; the difference between the fan speed acquired at the current moment and the fan speed acquired at the previous moment is calculated to obtain the speed difference; the difference between the operating high pressure acquired at the current moment and the operating high pressure acquired at the previous moment is calculated to obtain the high pressure difference; and the difference between the operating low pressure acquired at the current moment and the operating low pressure acquired at the previous moment is calculated to obtain the low pressure difference.

[0096] Frequency difference, speed difference, high pressure difference, and low pressure difference characterize the operating frequency of compressor 10, the fan speed of fan 20, and the changes in operating high pressure and operating low pressure of air conditioning unit 100 within a preset cycle. Based on the frequency difference, speed difference, high pressure difference, and low pressure difference, it can be determined whether compressor 10 has a liquid return phenomenon.

[0097] Please see Figure 2 and Figure 6 In some embodiments, determining whether compressor 10 experiences liquid return (i.e., 020) based on frequency difference, speed difference, high-pressure difference, and low-pressure difference includes:

[0098] 026: If, within a series of predetermined preset cycles, the frequency difference is zero, the speed difference is less than the preset speed difference, the high pressure difference is greater than or equal to the first pressure difference, and the low pressure difference is greater than or equal to the second pressure difference, it is determined that the compressor 10 has a liquid return phenomenon.

[0099] 027: When the frequency difference is not zero, and / or the speed difference is greater than or equal to the preset speed difference, and / or the high pressure difference is less than the first pressure difference, and / or the low pressure difference is less than the second pressure difference, it is determined that the compressor 10 does not have a liquid return phenomenon.

[0100] Specifically, the preset cycle can be set to 3-5 preset cycles. For example, if the preset cycle is set to 3 preset cycles, and the frequency difference is zero, the speed difference is less than the preset speed difference, the high pressure difference is greater than or equal to the first pressure difference, and the low pressure difference is greater than or equal to the second pressure difference in 3 consecutive preset cycles, it is determined that the compressor 10 has a liquid return phenomenon.

[0101] The preset speed difference can be set between 60-100 rpm, and the specific value can be set according to the actual situation. For example, the preset difference can be set to any value between 60 rpm, 65 rpm, 70 rpm, 75 rpm, 80 rpm, 85 rpm, 90 rpm, 95 rpm, 100 rpm, or 60-100 rpm.

[0102] The first pressure differential value can be set between 0.8 and 1.5 Bar, and the specific value can also be set according to the actual situation. For example, the first pressure differential value can be set to 0.8 Bar, 0.9 Bar, 1.0 Bar, 1.1 Bar, 1.2 Bar, 1.3 Bar, 1.4 Bar, 1.5 Bar or any value between 0.8 and 1.5 Bar.

[0103] The second pressure differential value can be set between 0.5 and 1.0 Bar, and the specific value can also be set according to the actual situation. For example, the second pressure differential value can be set to 0.5 Bar, 0.6 Bar, 0.7 Bar, 0.8 Bar, 0.9 Bar, 1.0 Bar, or any value between 0.5 and 1.0 Bar.

[0104] In addition, when compressor 10 returns liquid, it will cause an increase in the fluctuation of operating high pressure and operating low pressure. Therefore, if the high pressure difference of air conditioning unit 100 is greater than or equal to the first pressure difference and the low pressure difference is greater than or equal to the second pressure difference, it indicates that compressor 10 may be experiencing liquid return.

[0105] Combining the above four parameters, a joint judgment is made on the liquid return phenomenon of compressor 10. If, in a series of predetermined preset cycles, the frequency difference is zero, the speed difference is less than the preset speed difference, the high pressure difference is greater than or equal to the first pressure difference, and the low pressure difference is greater than or equal to the second pressure difference, then it is determined that compressor 10 has a liquid return phenomenon.

[0106] It should be noted that if any one of the above four conditions is not met within a consecutive predetermined number of preset cycles, that is, when the frequency difference is not zero, and / or the speed difference is greater than or equal to the preset speed difference, and / or the high pressure difference is less than the first pressure difference, and / or the low pressure difference is less than the second pressure difference, it is determined that the compressor 10 does not have a liquid return phenomenon.

[0107] Then, the preset cycle is recounted until all four conditions are met simultaneously within a predetermined number of consecutive preset cycles. This allows for accurate assessment of the compressor's liquid return phenomenon, reducing the probability of misjudgment.

[0108] Please see Figure 2 , Figure 7 and Figure 8 In some embodiments, the air conditioning unit 100 further includes an expansion valve 40 connected to the fan 20. When liquid return occurs in the compressor 10, protective control (i.e., 030) is performed on the compressor 10, including:

[0109] 031: When there is liquid return in compressor 10, the compressor 10 is protected by adjusting the opening degree of expansion valve 40, the overheating degree of compressor 10 and the operating frequency.

[0110] Specifically, the air conditioning unit 100 also includes an expansion valve 40, which comprises a first expansion valve 41 and a second expansion valve 42. The first expansion valve 41 is connected to the outdoor fan 21 and functions as a throttling valve when the air conditioning unit 100 is operating in cooling mode. The second expansion valve 42 is connected to the indoor fan 22 and functions as a throttling valve when the air conditioning unit 100 is operating in heating mode. When liquid return occurs in the compressor 10, the compressor 10 can be protected by adjusting the opening degree of the expansion valve 40, the superheat of the compressor 10, and the operating frequency.

[0111] It should be noted that the air conditioning unit 100 adjusts the control of different expansion valves 40 when operating in different modes. When the air conditioning unit 100 is operating in cooling mode, the opening of the second expansion valve is adjusted; when the air conditioning unit 100 is operating in heating mode, the opening of the first expansion valve 41 is adjusted.

[0112] Please see Figure 2 , Figure 8 and Figure 9 In some embodiments, when liquid return occurs in the compressor 10, the compressor 10 is protected by adjusting the superheat of the compressor 10, the opening degree of the expansion valve 40, and the operating frequency (i.e., 031), including:

[0113] 0311: When there is liquid return in compressor 10, reduce the opening of expansion valve 40 to increase the discharge superheat and suction superheat of compressor 10, and return to the steps of obtaining the operating frequency of compressor 10, fan speed of fan 20, and operating high pressure and operating low pressure of air conditioning unit 100 at a preset cycle, so as to determine again whether there is liquid return in compressor 10.

[0114] 0312: When it is determined again that there is liquid return in compressor 10, determine whether the opening degree of expansion valve 40 is equal to the preset opening degree;

[0115] 0313: When the opening degree of expansion valve 40 is not equal to the preset opening degree, return to the step of reducing the opening degree of expansion valve 40 to increase the discharge superheat and suction superheat of compressor 10.

[0116] 0314: When the opening degree of expansion valve 40 is equal to the preset opening degree, reduce the operating frequency;

[0117] 0315: Determine whether the unit protection needs to be activated based on the reduced operating frequency.

[0118] Specifically, when there is liquid return in the compressor 10, the expansion valve 40 that needs to be adjusted is determined according to the working mode of the air conditioning unit 100. The opening of the expansion valve 40 is reduced. The reduction can be 40-80 steps, and the specific number of steps can be set according to the actual situation. For example, the reduction can be 40, 45, 50, 55, 60, 65, 70, 75, 80 steps or any number of steps between 40 and 80.

[0119] Taking the air conditioning unit 100 operating in cooling mode as an example, the opening of the second expansion valve 42 is reduced, which correspondingly reduces the amount of liquid refrigerant entering the indoor heat exchanger 62. This allows the liquid refrigerant in the indoor heat exchanger 62 to evaporate more fully, reducing the possibility of continued evaporation of the liquid refrigerant in the suction pipe of the compressor 10. Therefore, the refrigerant temperature in the suction pipe will rise, i.e., the suction temperature will rise, thereby increasing the suction superheat.

[0120] Since reducing the opening of the second expansion valve 42 increases the intake temperature, and the intake temperature is a direct precursor to the exhaust temperature, the exhaust temperature will also rise, thereby increasing the exhaust superheat.

[0121] After increasing the exhaust superheat and intake superheat of compressor 10, the process returns to the step of obtaining the operating frequency of compressor 10, the fan speed of fan 20, and the operating high pressure and operating low pressure of air conditioning unit 100 at a preset cycle (i.e., 010) to determine again whether compressor 10 has liquid return phenomenon.

[0122] If the compressor 10 is again found to have liquid return, it indicates that further protection control of the air conditioning unit 100 is required. Since the opening of the expansion valve 40 has already been reduced, it is necessary to first determine whether the opening of the expansion valve 40 is equal to the preset opening to determine whether the opening of the expansion valve 40 can be further reduced. The preset opening can be set to the minimum allowable opening of the expansion valve 40, and the range of the minimum opening is 40-50 steps. For example, the preset opening can be set to 40 steps, 42 steps, 44 steps, 46 steps, 48 ​​steps, 50 steps, or any number of steps between 40 and 50.

[0123] When the opening of the expansion valve 40 is not equal to the preset opening, it indicates that protection control can be performed by continuing to reduce the opening of the expansion valve 40. Therefore, the process returns to the step of reducing the opening of the expansion valve 40 to increase the exhaust superheat and intake superheat of the compressor 10 (i.e., 0311).

[0124] When the opening degree of expansion valve 40 is equal to the preset opening degree, it means that the opening degree of expansion valve 40 cannot be further reduced. At this time, the air conditioning unit 100 can be protected by reducing the operating frequency of compressor 10. The operating frequency of compressor 10 can be reduced to a preset frequency, which can be set to 8-20Hz. The specific frequency can be set according to the actual situation. For example, the preset frequency can be set to 8Hz, 10Hz, 12Hz, 14Hz, 16Hz, 18Hz, 20Hz, or any frequency between 8-20Hz. After reducing the operating frequency of compressor 10, it is determined whether the unit protection needs to be activated based on the reduced operating frequency.

[0125] Please see Figure 2 , Figure 8 and Figure 10 In some embodiments, after determining again whether there is liquid return in the compressor 10 (i.e., 0311), the liquid return control method for the compressor 10 further includes:

[0126] 0316: When there is no liquid return phenomenon in compressor 10, control compressor 10 to maintain the current discharge superheat and suction superheat.

[0127] Specifically, after re-evaluating whether there is liquid return in compressor 10, if it is determined that there is no liquid return in compressor 10, it indicates that reducing the opening of expansion valve 40 has effectively solved the liquid return problem in compressor 10. At this time, compressor 10 is controlled to maintain the current discharge superheat and suction superheat, which are the discharge superheat and suction superheat increased by reducing the opening of expansion valve 40.

[0128] Please see Figure 2 , Figure 8 and Figure 11 In some implementations, determining whether to activate unit protection (i.e., 0315) based on the reduced operating frequency includes:

[0129] 03151: Determine whether the reduced operating frequency is equal to the frequency threshold;

[0130] 03152: When the reduced operating frequency is less than or equal to the frequency threshold, maintain the frequency threshold operation and activate the unit protection.

[0131] 03153: When the reduced operating frequency is greater than the frequency threshold, return to the step of obtaining the operating frequency of compressor 10, the fan speed of fan 20, and the operating high pressure and operating low pressure of air conditioning unit 100 at a preset cycle, so as to determine again whether compressor 10 has liquid return phenomenon.

[0132] 03154: If it is determined again that there is liquid return in compressor 10, return to the step of reducing the operating frequency;

[0133] 03155: When there is no liquid return phenomenon in compressor 10, control compressor 10 to maintain the current operating frequency, exhaust superheat and suction superheat.

[0134] Specifically, after reducing the operating frequency of compressor 10, it is determined whether the reduced operating frequency is equal to a frequency threshold. The frequency threshold can be set as the minimum allowable operating frequency of compressor 10. The minimum operating frequency range is 10-20Hz. For example, the frequency threshold can be set to any frequency between 10Hz, 12Hz, 14Hz, 16Hz, 18Hz, 20Hz, or 10-20Hz.

[0135] When the reduced operating frequency is less than or equal to the frequency threshold, the compressor 10 cannot operate at the reduced operating frequency, but liquid return still occurs in the compressor 10. At this time, the unit protection is activated, which includes stopping the operation of the air conditioning unit 100, issuing a fault alarm signal, and sending fault information to the customer.

[0136] If the reduced operating frequency exceeds the frequency threshold, the process returns to the step of acquiring the operating frequency of compressor 10, the fan speed of fan 20, and the high-pressure and low-pressure operating pressures of air conditioning unit 100 at a preset cycle to re-determine whether compressor 10 experiences liquid return. If liquid return is again detected in compressor 10, it indicates that further protection control of air conditioning unit 100 is required. At this point, the expansion valve 40 is already at its minimum opening; therefore, the process returns to the step of reducing the operating frequency.

[0137] When there is no liquid return in compressor 10, it means that reducing the operating frequency effectively solves the problem of liquid return in compressor 10 and controls compressor 10 to maintain the current operating frequency.

[0138] Please see Figure 2 and Figure 12 This application also provides a compressor 10 liquid return control device 200, applied to an air conditioning unit 100. The air conditioning unit 100 includes a compressor 10 and a fan 20. The compressor 10 liquid return control device 200 includes an acquisition module 210, a judgment module 220, and a control module 230. The acquisition module 210 is used to acquire the operating frequency of the compressor 10, the fan speed of the fan 20, and the high-pressure and low-pressure operating pressure of the air conditioning unit 100 at preset intervals. The judgment module 220 is used to determine whether liquid return occurs in the compressor 10 based on the operating frequency, fan speed, high-pressure operating pressure, and low-pressure operating pressure. The control module 230 is used to perform protective control on the compressor 10 when liquid return occurs.

[0139] In some embodiments, the fan 20 includes an outdoor fan 21 and an indoor fan 22. The acquisition module 210 is specifically used to acquire the first fan speed of the outdoor fan 21 at a preset period when the air conditioning unit 100 is operating in cooling mode, and to acquire the second fan speed of the indoor fan 22 at a preset period when the air conditioning unit 100 is operating in heating mode, and to acquire the second fan speed of the indoor fan 22 at a preset period, and to acquire the second fan speed of the indoor fan 22, and to acquire the second fan speed of the indoor fan 22, and to acquire the second fan speed of the indoor fan 22, when the air conditioning unit 100 is operating in heating mode.

[0140] In some embodiments, the air conditioning unit 100 includes a first pressure sensor 31 and a second pressure sensor 32. The first pressure sensor 31 is disposed at the discharge end of the compressor 10, and the second pressure sensor 32 is disposed at the suction end of the compressor 10. The acquisition module 210 is specifically used to acquire the operating high pressure of the air conditioning unit 100 at a preset period using the first pressure sensor 31; and to acquire the operating low pressure of the air conditioning unit 100 at a preset period using the second pressure sensor 32.

[0141] In some implementations, the determination module 220 is specifically used to calculate the difference between the operating frequency acquired at the current moment and the operating frequency acquired at the previous moment, to obtain a frequency difference; calculate the difference between the fan speed acquired at the current moment and the fan speed acquired at the previous moment, to obtain a speed difference; calculate the difference between the operating high pressure acquired at the current moment and the operating high pressure acquired at the previous moment, to obtain a high pressure difference; calculate the difference between the operating low pressure acquired at the current moment and the operating low pressure acquired at the previous moment, to obtain a low pressure difference; and determine whether the compressor 10 has a liquid return phenomenon based on the frequency difference, speed difference, high pressure difference, and low pressure difference.

[0142] In some embodiments, the determination module 220 is specifically used to determine that the compressor 10 has a liquid return phenomenon when the frequency difference is zero, the speed difference is less than the preset speed difference, the high pressure difference is greater than or equal to the first pressure difference, and the low pressure difference is greater than or equal to the second pressure difference in a consecutive predetermined number of preset cycles; and to determine that the compressor 10 does not have a liquid return phenomenon when the frequency difference is not zero, and / or the speed difference is greater than or equal to the preset speed difference, and / or the high pressure difference is less than the first pressure difference, and / or the low pressure difference is less than the second pressure difference.

[0143] In some embodiments, the air conditioning unit 100 further includes an expansion valve 40 connected to the fan 20. Specifically, the control module 230 is used to protect the compressor 10 by correcting and controlling its superheat, the opening degree of the expansion valve 40, and its operating frequency when liquid return occurs.

[0144] In some embodiments, the control module 230 is specifically used to, when liquid return occurs in the compressor 10, reduce the opening of the expansion valve 40 to increase the discharge superheat and suction superheat of the compressor 10, and return to the step of acquiring the operating frequency of the compressor 10, the fan speed of the fan 20, and the operating high pressure and operating low pressure of the air conditioning unit 100 at a preset cycle, so as to determine again whether liquid return occurs in the compressor 10; when liquid return occurs in the compressor 10 again, determine whether the opening of the expansion valve 40 is equal to the preset opening; when the opening of the expansion valve 40 is not equal to the preset opening, return to the step of reducing the opening of the expansion valve 40 to increase the discharge superheat and suction superheat of the compressor 10; when the opening of the expansion valve 40 is equal to the preset opening, reduce the operating frequency; and determine whether the unit protection needs to be activated based on the reduced operating frequency.

[0145] In some embodiments, after determining again whether there is liquid return in the compressor 10, the control module 230 is also used to control the compressor 10 to maintain the current exhaust superheat and intake superheat when there is no liquid return in the compressor 10.

[0146] In some implementations, the control module 230 is specifically used to determine whether the reduced operating frequency is equal to the frequency threshold; when the reduced operating frequency is less than or equal to the frequency threshold, the unit protection is activated; when the reduced operating frequency is greater than the frequency threshold, the process returns to the step of obtaining the operating frequency of the compressor 10, the fan speed of the fan 20, and the operating high pressure and operating low pressure of the air conditioning unit 100 at a preset cycle, so as to determine again whether there is liquid return in the compressor 10; when it is determined again that there is liquid return in the compressor 10, the process returns to the step of reducing the operating frequency; when there is no liquid return in the compressor 10, the compressor 10 is controlled to maintain the current operating frequency, exhaust superheat and suction superheat.

[0147] It should be noted that the explanation of the compressor 10 liquid return control method in the foregoing embodiments also applies to the compressor 10 liquid return control device 200 in the embodiments of this application, and will not be elaborated here.

[0148] Please see Figure 13 This application also provides a compressor 10 liquid return control system 300, which includes one or more processors 310 and a memory 320. The memory 320 stores a computer program. When the computer program is executed by the processor 310, the compressor 10 liquid return control method of any of the above embodiments is implemented.

[0149] For example, when the computer program is executed by the processor 310, the following method for controlling the return liquid of the compressor 10 is implemented:

[0150] 010: Obtain the operating frequency of compressor 10, the fan speed of fan 20, and the high-pressure and low-pressure operating of air conditioning unit 100 at a preset cycle;

[0151] 020: Determine whether compressor 10 has liquid return based on operating frequency, fan speed, high operating pressure, and low operating pressure;

[0152] 030: When there is liquid return in compressor 10, protect compressor 10 by controlling it.

[0153] For example, when the computer program is executed by the processor 310, the following method for controlling the return liquid of the compressor 10 is implemented:

[0154] 011: When the air conditioning unit 100 is working in cooling mode, the first fan speed of the outdoor fan 21 is obtained at a preset cycle and used as the fan speed;

[0155] 012: When the air conditioning unit 100 is operating in heating mode, the second fan speed of the indoor fan 22 is obtained at a preset cycle and used as the fan speed.

[0156] It should be noted that the explanations and descriptions of the compressor 10 liquid return control method and compressor 10 liquid return control device 200 in the foregoing embodiments also apply to the compressor 10 liquid return control system 300 in the embodiments of this application, and will not be elaborated here.

[0157] Please see Figure 14 This application also provides a computer-readable storage medium 400 storing a computer program 410, which, when executed by a processor 420, implements the compressor 10 liquid return control method of any of the above embodiments.

[0158] For example, when computer program 410 is executed by processor 420, the following compressor 10 liquid return control method is implemented:

[0159] 010: Obtain the operating frequency of compressor 10, the fan speed of fan 20, and the high-pressure and low-pressure operating of air conditioning unit 100 at a preset cycle;

[0160] 020: Determine whether compressor 10 has liquid return based on operating frequency, fan speed, high operating pressure, and low operating pressure;

[0161] 030: When there is liquid return in compressor 10, protect compressor 10 by controlling it.

[0162] For example, when computer program 410 is executed by processor 420, the following method for controlling the return liquid of compressor 10 is implemented:

[0163] 011: When the air conditioning unit 100 is working in cooling mode, the first fan speed of the outdoor fan 21 is obtained at a preset cycle and used as the fan speed;

[0164] 012: When the air conditioning unit 100 is operating in heating mode, the second fan speed of the indoor fan 22 is obtained at a preset cycle and used as the fan speed.

[0165] It should be noted that the explanations and descriptions of the compressor 10 liquid return control method and compressor 10 liquid return control device 200 in the foregoing embodiments also apply to the computer-readable storage medium 400 of the embodiments of this application, and will not be elaborated here.

[0166] In summary, the compressor 10 liquid return control method, control device 200, control system 300, and computer-readable storage medium 400 of this application acquire the operating frequency of the compressor 10, the fan speed of the fan 20, and the high-pressure and low-pressure operating pressures of the air conditioning unit 100 at preset intervals. Based on the operating frequency, fan speed, high-pressure, and low-pressure operating pressures, it is determined whether liquid return occurs in the compressor 10. Multiple parameters are combined for a joint judgment, and when liquid return occurs, protective control is implemented on the compressor 10. Thus, without adding other modules, it can accurately determine whether liquid return occurs in the compressor 10, reducing costs. Furthermore, it can protect the compressor 10, effectively reducing damage caused by liquid return and improving the reliability of the air conditioning unit 100.

[0167] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0168] Any process or method described in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing a particular logical function or process, and the scope of the preferred embodiments of this application includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the function involved, as will be understood by those skilled in the art to which embodiments of this application pertain.

[0169] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable storage medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, a computer-readable storage medium can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable storage media include: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and programmable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Alternatively, the computer-readable storage medium could be paper or other suitable media on which the program can be printed, since the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in a computer memory.

[0170] It should be understood that various parts of this application can be implemented using hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented using software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0171] Those skilled in the art will understand that all or part of the steps of the methods in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, it includes one or a combination of the steps of the method embodiments. Furthermore, the functional units in the various embodiments of this application can be integrated into a processing module, or each unit can exist physically separately, or two or more units can be integrated into a module. The integrated module can be implemented in hardware or as a software functional module. If the integrated module is implemented as a software functional module and sold or used as an independent product, it can also be stored in a computer-readable storage medium. The storage medium mentioned above can be a read-only memory, a disk, or an optical disk, etc.

[0172] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. A compressor liquid return control method, characterized in that, Applied to air conditioning units, the air conditioning unit includes a compressor and a fan, the fan includes an outdoor fan and an indoor fan, and the compressor liquid return control method includes: The operating frequency of the compressor, the fan speed of the fan, and the high-pressure and low-pressure operating of the air conditioning unit are obtained at a preset cycle. The presence of liquid return in the compressor is determined based on the operating frequency, the fan speed, the high operating pressure, and the low operating pressure. When liquid return occurs in the compressor, protective control is implemented for the compressor. The step of determining whether the compressor experiences liquid return based on the operating frequency, the fan speed, the high operating pressure, and the low operating pressure includes: Calculate the difference between the operating frequency obtained at the current moment and the operating frequency obtained at the previous moment to obtain the frequency difference; Calculate the difference between the fan speed obtained at the current moment and the fan speed obtained at the previous moment to obtain the speed difference; Calculate the difference between the operating high pressure obtained at the current moment and the operating high pressure obtained at the previous moment to obtain the high pressure difference value; Calculate the difference between the operating low pressure obtained at the current moment and the operating low pressure obtained at the previous moment to obtain the low pressure difference value; The presence of liquid return in the compressor is determined based on the frequency difference, the speed difference, the high pressure difference, and the low pressure difference. The step of determining whether the compressor experiences liquid return based on the frequency difference, the speed difference, the high-pressure difference, and the low-pressure difference includes: If, in a series of predetermined preset cycles, the frequency difference is zero, the speed difference is less than a preset speed difference, the high pressure difference is greater than or equal to a first pressure difference, and the low pressure difference is greater than or equal to a second pressure difference, it is determined that the compressor has a liquid return phenomenon.

2. The compressor liquid return control method according to claim 1, characterized in that, The fan speed of the blower is obtained at a preset period, including: When the air conditioning unit is operating in cooling mode, the first fan speed of the outdoor fan is obtained at the preset cycle and used as the fan speed. When the air conditioning unit is operating in heating mode, the second fan speed of the indoor fan is obtained at the preset cycle and used as the fan speed.

3. The compressor liquid return control method according to claim 1, characterized in that, The air conditioning unit includes a first pressure sensor and a second pressure sensor. The first pressure sensor is located at the discharge end of the compressor, and the second pressure sensor is located at the suction end of the compressor. It acquires the operating high pressure and operating low pressure of the air conditioning unit at preset intervals, including: The operating high pressure of the air conditioning unit is obtained through the first pressure sensor at the preset cycle; The operating low pressure of the air conditioning unit is obtained through the second pressure sensor at the preset cycle.

4. The compressor liquid return control method according to claim 1, characterized in that, The step of determining whether the compressor experiences liquid return based on the frequency difference, the speed difference, the high-pressure difference, and the low-pressure difference includes: When the frequency difference is not zero, and / or the speed difference is greater than or equal to a preset speed difference, and / or the high pressure difference is less than a first pressure difference, and / or the low pressure difference is less than a second pressure difference, it is determined that the compressor does not have a liquid return phenomenon.

5. The compressor liquid return control method according to claim 1, characterized in that, The air conditioning unit also includes an expansion valve connected to the fan. The protection control for the compressor when liquid return occurs includes: When liquid return occurs in the compressor, the compressor is protected by adjusting the opening degree of the expansion valve, the superheat of the compressor, and the operating frequency.

6. The compressor liquid return control method according to claim 5, characterized in that, When liquid return occurs in the compressor, the compressor is protected by adjusting the opening degree of the expansion valve, the superheat of the compressor, and the operating frequency, including: When liquid return occurs in the compressor, the opening of the expansion valve is reduced to increase the discharge superheat and suction superheat of the compressor, and the process returns to the step of obtaining the operating frequency of the compressor, the fan speed of the fan, and the operating high pressure and operating low pressure of the air conditioning unit at a preset cycle, so as to determine again whether liquid return occurs in the compressor. When it is determined again that the compressor has a liquid return phenomenon, it is determined whether the opening degree of the expansion valve is equal to the preset opening degree; When the opening degree of the expansion valve is not equal to the preset opening degree, return to the step of reducing the opening degree of the expansion valve to increase the discharge superheat and suction superheat of the compressor; When the opening degree of the expansion valve is equal to the preset opening degree, the operating frequency is reduced; Determine whether unit protection needs to be activated based on the reduced operating frequency.

7. The compressor liquid return control method according to claim 6, characterized in that, After determining again whether the compressor experiences liquid return, the compressor liquid return control method further includes: When there is no liquid return phenomenon in the compressor, the compressor is controlled to maintain the current exhaust superheat and intake superheat.

8. The compressor liquid return control method according to claim 6, characterized in that, The step of determining whether to activate unit protection based on the reduced operating frequency includes: Determine whether the reduced operating frequency is equal to the frequency threshold; When the reduced operating frequency is less than or equal to the frequency threshold, the operating frequency is maintained at the frequency threshold, and the unit protection is activated. When the reduced operating frequency is greater than the frequency threshold, the process returns to the step of obtaining the compressor's operating frequency, the fan speed, and the air conditioning unit's high-pressure and low-pressure operating values ​​at a preset cycle, in order to determine again whether the compressor has a liquid return phenomenon. If it is determined again that the compressor has liquid return, return to the step of reducing the operating frequency; When there is no liquid return phenomenon in the compressor, the compressor is controlled to maintain the current operating frequency, the exhaust superheat and the intake superheat.

9. A compressor liquid return control system, characterized in that, The compressor liquid return control system includes one or more processors and a memory, the memory storing a computer program, which, when executed by the processor, implements the compressor liquid return control method according to any one of claims 1-8.

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