Air conditioning system and control method thereof

Abstract

The invention relates to the technical field of air conditioners, particularly provides an air conditioning system and a control method thereof, and aims to solve the problem that a compressor of an existing air conditioning system is lack of lubricating oil just after being started. In order to achieve the purpose, the air conditioning system comprises a compressor and an oil storage tank, an oil outlet of the oil storage tank is connected to an air suction port of the compressor through a pipeline, an oil return valve is arranged on the pipeline, and after the air conditioning system is started, the oil return valve is opened to supplement oil to the compressor, so that the phenomenon of oil shortage of the compressor is avoided, and the service life of the compressor is prolonged. And the compressor is prevented from being damaged due to oil shortage.

Description

Technical Field

[0001] The present invention relates to the technical field of air conditioners, and particularly provides an air conditioning system and a control method therefor. Background Art

[0002] Due to the characteristics that the number of indoor and outdoor units and the output capacity of multi-connected air conditioners can be freely adjusted according to requirements, multi-connected air conditioners have been widely used nowadays. The pain points of existing multi-connected air conditioners are as follows:

[0003] First, when the outdoor ambient temperature is relatively low, the compressor takes a long time to reach the required discharge superheat degree. During this period, most of the lubricating oil inside the compressor will be carried to various parts of the system along with the discharged refrigerant, and the small amount of lubricating oil returning to the compressor cannot ensure the normal working conditions of the compressor.

[0004] Second, after the defrosting of the multi-connected air conditioner system is completed, the four-way valve commutation causes a large amount of refrigerant to accumulate on the suction side of the compressor, and the lubricating oil is diluted and carried into the system along with the suction of the compressor. These situations will all pose a risk of damage to the compressor.

[0005] Therefore, there is an urgent need in the related art for an air conditioning system and a control method therefor to solve the above technical problems. Summary of the Invention

[0006] The present invention aims to solve the above technical problems, that is, to solve the problem that the compressor of the existing air conditioning system lacks lubricating oil after just starting up.

[0007] In a first aspect, the present invention provides an air conditioning system, which includes a compressor and an oil storage tank. The oil outlet of the oil storage tank is connected to the suction port of the compressor through a pipeline, and an oil return valve is provided on the pipeline. After the air conditioning system is started, the oil return valve is opened to replenish oil for the compressor.

[0008] In a specific embodiment of the control method of the above air conditioning system, it further includes a gas-liquid separator. Its first outlet is connected to the suction port of the compressor through a first pipeline, and its second outlet is connected to the oil inlet of the oil storage tank through a second pipeline. An oil inlet valve is provided on the second pipeline to control whether to fill the oil storage tank with oil.

[0009] In a second aspect, the present invention provides a control method for an air conditioning system as described above. The control method includes the following steps:

[0010] After the air conditioning system is started, according to the target working mode, running time of the air conditioning system, and the discharge superheat degree of the compressor, determine the opening degree of the oil return valve and the working mode of the air conditioning system.

[0011] In the specific implementation of the control method of the above air conditioning system, "determining the opening degree of the oil return valve and the working mode of the air conditioning system according to the target working mode, running time of the air conditioning system, and the exhaust superheat degree of the compressor" includes:

[0012] When the air conditioning system is in the cooling mode and after running for a first preset duration in the cooling mode, open the oil return valve to replenish oil to the compressor.

[0013] In the specific implementation of the control method of the above air conditioning system, "determining the opening degree of the oil return valve and the working mode of the air conditioning system according to the target working mode, running time of the air conditioning system, and the exhaust superheat degree of the compressor" further includes:

[0014] When the air conditioning system is in the cooling mode and after the exhaust superheat degree of the compressor rises by a first preset value, close the oil return valve.

[0015] In the specific implementation of the control method of the above air conditioning system, "determining the opening degree of the oil return valve and the working mode of the air conditioning system according to the target working mode, running time of the air conditioning system, and the exhaust superheat degree of the compressor" includes:

[0016] After the air conditioning system is started, first run in the cooling mode for a second preset duration, then switch to the heating mode, and open the oil return valve to replenish oil to the compressor.

[0017] In the specific implementation of the control method of the above air conditioning system, "determining the opening degree of the oil return valve and the working mode of the air conditioning system according to the target working mode, running time of the air conditioning system, and the exhaust superheat degree of the compressor" further includes:

[0018] When the air conditioning system is in the heating mode and after the exhaust superheat degree of the compressor rises by a second preset value, close the oil return valve.

[0019] In the specific implementation of the control method of the above air conditioning system, "determining the opening degree of the oil return valve and the working mode of the air conditioning system according to the target working mode, running time of the air conditioning system, and the exhaust superheat degree of the compressor" includes:

[0020] When the air conditioning system needs to switch from the defrosting mode to the heating mode, after the air conditioning system completes defrosting, switch to the heating mode, and after running for a third preset duration, open the oil return valve to replenish oil to the compressor.

[0021] In the specific implementation of the control method of the above air-conditioning system, "determining the opening degree of the oil return valve and the working mode of the air-conditioning system according to the target working mode, operating time of the air-conditioning system, and the exhaust superheat degree of the compressor" further includes:

[0022] When the air-conditioning system is in the heating mode and the exhaust superheat degree of the compressor rises by a third preset value, the oil return valve is closed.

[0023] In the specific implementation of the control method of the above air-conditioning system, the first preset duration, the second preset duration, and the third preset duration are calculated and obtained according to actual machine experiments and / or the digital model of the air-conditioning system.

[0024] In the specific implementation of the control method of the above air-conditioning system, the first preset value, the second preset value, and the third preset value are calculated and obtained according to actual machine experiments and / or the digital model of the air-conditioning system.

[0025] In the case of adopting the above technical solution, the air-conditioning system of the present invention includes a compressor and an oil storage tank. The oil outlet of the oil storage tank is connected to the suction port of the compressor through a pipeline, and an oil return valve is provided on the pipeline. After the air-conditioning system is started, the oil return valve is opened to supply oil to the compressor, avoiding the phenomenon of oil shortage in the compressor and ensuring that the compressor will not be damaged due to oil shortage.

[0026] Specifically, after each mode runs for a period of time, the oil return valve is opened. When the air-conditioning system is just started, it is actually a liquid compression process. At this time, most of the oil in the oil storage tank will be discharged back into the air-conditioning system along with the refrigerant, and the lubricating oil cannot stay at the compressor, that is, it cannot play the role of lubricating the compressor. If the oil return valve is opened at the beginning, the effect on lubricating the compressor is very small. Therefore, it is selected to make the air-conditioning system run for a period of time before opening the oil return valve. At this time, the compressor discharges high-temperature and high-pressure gas, and the lubricating oil will not flow away in large quantities with the refrigerant, only a small part will flow away, which can ensure the lubrication effect of the compressor. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The following describes the preferred embodiments of the present invention with reference to the drawings. In the drawings:

[0028] Figure 1 is a schematic structural diagram of the air-conditioning system provided by the present invention;

[0029] Figure 2 is a flowchart of the control method of the air-conditioning system provided by the present invention.

[0030] LIST OF REFERENCE NUMERALS:

[0031] 1. Compressor; 2. Oil separator; 3. Outdoor heat exchanger; 4. Indoor heat exchanger; 5. Gas-liquid separator; 6. Oil storage tank; 61. Oil inlet valve; 62. Oil return valve; 7. Four-way valve. Specific embodiments

[0032] The following describes the preferred embodiments of the present invention with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the protection scope of the present invention.

[0033] It should be noted that in the description of the present invention, the terms indicating directions or positional relationships such as "upper", "lower", "left", "right", "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings. This is only for convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be construed as a limitation of the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0034] In addition, it should also be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "installation", "setting", "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected, or indirectly connected through an intermediate medium, and can also be the communication inside two elements. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0035] Due to the characteristics that the number of indoor and outdoor units and the output capacity of the multi-connected air conditioner can be freely adjusted according to needs, it has been widely used nowadays. As the core component of the air conditioner, the compressor is very vulnerable to the influence of system liquid return and insufficient lubricating oil inside the compressor, resulting in damage to the compressor. In order to solve the problem that the compressor in the existing air conditioner system lacks lubricating oil after just starting.

[0036] As Figure 1 shown, this embodiment discloses an air conditioner system, which includes a compressor 1, an oil storage tank 6, a gas-liquid separator 5, an oil separator 2, an indoor heat exchanger 4, an outdoor heat exchanger 3 and a four-way valve 7.

[0037] Among them, the inlet of the gas-liquid separator 5 is connected to the first interface of the four-way valve 7, and the first outlet of the gas-liquid separator 5 is connected to the suction side of the compressor 1 through the first pipeline. The second outlet of the gas-liquid separator 5 is connected to the oil inlet of the oil storage tank 6 through the second pipeline, and an oil inlet valve 61 is provided on the second pipeline. The oil inlet valve 61 is used to control whether the oil storage tank 6 returns oil; that is, it specifically controls whether the hydraulic oil flowing in the air-conditioning system is recovered into the oil storage tank 6. The oil outlet of the oil storage tank 6 is connected to the suction port of the compressor 1 through the third pipeline, and a return oil valve 62 is provided on the third pipeline; the return oil valve 62 is used to determine whether the hydraulic oil in the oil storage tank 6 flows to the compressor 1 to supplement the compressor 1. The second outlet of the gas-liquid separator 5 is also connected to the suction port of the compressor 1 through the fourth pipeline, and a capillary tube is provided on the fourth pipeline. The capillary tube is used to control the flow rate of the refrigerant flowing to the compressor 1. The gas-liquid separator 5 is used to separate the refluxed liquid refrigerant and gas refrigerant, and cool and liquefy the gas refrigerant with the liquid refrigerant.

[0038] The intake side of the oil separator 2 is connected to the exhaust port of the compressor 1, and the outlet of the oil separator 2 is connected to the second interface of the four-way valve 7 through a pipeline. The oil return port of the oil separator 2 is connected to the suction side of the compressor 1, so that the hydraulic oil separated by the oil separator 2 can be absorbed into the compressor 1 to lubricate the compressor 1; the oil separator 2 can make the refrigerant discharged without passing through the indoor heat exchanger and the outdoor heat exchanger 3 circulate and flow back to the compressor 1 to ensure the lubrication of the compressor 1.

[0039] The outdoor heat exchanger 3 is connected to the third interface of the four-way valve 7. The outdoor heat exchanger 3 is connected to the indoor heat exchanger 4 through the fifth pipeline, and an electronic expansion valve is provided on the fifth pipeline to adjust the refrigerant flow rate to control the heating capacity and cooling capacity of the indoor heat exchanger 4. The indoor heat exchanger 4 is connected to the fourth interface of the four-way valve 7. The four-way valve 7 is used to control the working mode of the air-conditioning system, and specifically can control the air-conditioning system to switch between the refrigeration mode and the heating mode. Among them, the indoor heat exchanger 4 can specifically be multiple, and multiple indoor heat exchangers 4 are arranged in parallel, and each indoor heat exchanger 4 corresponds to an electronic expansion valve. Among them, the outdoor heat exchanger 3 is multiple, and multiple outdoor heat exchangers 3 are arranged in parallel.

[0040] In the refrigeration mode, the second interface of the four-way valve 7 is connected to the third interface, and the first interface is connected to the fourth interface. After the high-temperature and high-pressure refrigerant flows out of the compressor 1, it flows through the oil separator 2 and the four-way valve 7 to the outdoor heat exchanger 3 to release heat, so that the refrigerant changes from gaseous to liquid; then it flows to the indoor heat exchanger 4 for heat exchange, and the liquid refrigerant absorbs heat to cool the indoor; the refrigerant absorbs heat and changes into gaseous refrigerant; then it flows back to the compressor 1 through the gas-liquid separator 5 for compression.

[0041] In the heating mode, the second port of the four-way valve 7 is connected to the fourth port, and the first port is connected to the third port. After the high-temperature and high-pressure refrigerant flows out of the compressor 1, it flows through the oil separator 2 and the four-way valve 7 to the indoor heat exchanger 4 for heat release, causing the refrigerant to change from a gaseous state to a liquid state. The heat released by the refrigerant heats the indoor space; then it flows to the outdoor heat exchanger 3 for heat exchange, and the refrigerant absorbs heat and changes into a gaseous refrigerant; then it flows back to the compressor 1 through the gas-liquid separator 5 for compression.

[0042] In the defrosting mode, the second port of the four-way valve 7 is connected to the third port, and the first port is connected to the fourth port. After the high-temperature and high-pressure refrigerant flows out of the compressor 1, it flows through the oil separator 2 and the four-way valve 7 to the outdoor heat exchanger 3 for heat release, causing the refrigerant to change from a gaseous state to a liquid state; heat release at the outdoor heat exchanger 3 can melt the frost on the surface of the outdoor heat exchanger 3 for defrosting. The refrigerant flowing out of the outdoor heat exchanger 3 flows to the indoor heat exchanger 4 for heat exchange, and the refrigerant absorbs heat and changes into a gaseous refrigerant, and then flows back to the compressor 1 through the gas-liquid separator 5 for compression.

[0043] The air-conditioning system further includes a control module, which is configured to be able to execute the control method of the air-conditioning system.

[0044] Both the four-way valve 7 and the compressor 1 are communicatively connected to the control module. The control module can control the state of the four-way valve 7 to control the working mode of the air-conditioning system. Moreover, the control module also controls the frequency of the compressor 1 to control the cooling power and heating power of the air-conditioning system.

[0045] As Figure 2 shown, the control method of the air-conditioning system includes the following steps:

[0046] S1. After the air-conditioning system is started, obtain the target working mode, running time of the air-conditioning system, and the exhaust superheat degree of the compressor 1;

[0047] S2. Determine the opening degree of the oil return valve 62 and the working mode of the air-conditioning system according to the target working mode, running time of the air-conditioning system, and the exhaust superheat degree of the compressor 1.

[0048] Among them, "determine the opening degree of the oil return valve 62 and the working mode of the air-conditioning system according to the target working mode, running time of the air-conditioning system, and the exhaust superheat degree of the compressor 1" includes:

[0049] When the air conditioning system needs to operate in the cooling mode, the air conditioning system starts in the cooling mode. After running for a first preset duration, the oil return valve 62 is opened to replenish oil to the compressor 1. When the outside ambient temperature is relatively low, the air conditioning system actually undergoes a liquid compression process at startup. At this time, most of the oil in the oil storage tank 6 will be discharged back into the air conditioning system along with the refrigerant again, and it is impossible to keep the lubricating oil at the compressor 1, that is, it cannot play the role of lubricating the compressor 1. If the oil return valve 62 is opened at the beginning, the effect on lubricating the compressor 1 is very small. Therefore, it is selected to first make the air conditioning system run for the first preset duration, and then open the oil return valve 62. At this time, the gas discharged from the compressor 1 is high-temperature and high-pressure gas, and the lubricating oil will not flow away in large quantities along with the refrigerant. Only a small part flows away, which can ensure the lubrication effect of the compressor 1. The first preset duration is obtained by calculation based on actual machine experiments and / or the digital model of the air conditioning system; in this embodiment, it is preferably obtained by conducting experiments on the actual machine, and the first preset duration corresponding to each refrigeration power needs to be determined separately.

[0050] Among them, "determining the opening degree of the oil return valve 62 and the working mode of the air conditioning system according to the target working mode, operating time of the air conditioning system, and the exhaust superheat degree of the compressor 1" further includes:

[0051] When the air conditioning system is in the cooling mode and the exhaust superheat degree of the compressor 1 rises by a first preset value, the oil return valve 62 is closed. That is, after the air conditioning system operates for a period of time, the exhaust superheat degree will increase. The first preset value is obtained by calculation based on actual machine experiments and / or the digital model of the air conditioning system; in this embodiment, preferably, it is obtained by actual machine experiments, and the first preset value corresponding to each refrigeration power needs to be determined separately, and the corresponding first preset value also needs to be obtained at each initial exhaust superheat degree.

[0052] When the air conditioning system needs to operate in the cooling mode, the air conditioning system first starts in the cooling mode. After running for a first preset duration, the oil return valve 62 is opened to replenish oil to the compressor 1; and the air conditioning system continues to operate in the cooling mode. When the exhaust superheat degree of the compressor 1 rises by a first preset value, the oil return valve 62 is closed (at this time, the compressor 1 is no longer short of lubricating oil); then the air conditioning system continues to operate in the cooling mode.

[0053] "Determining the opening degree of the oil return valve 62 and the working mode of the air conditioning system according to the target working mode, operating time of the air conditioning system, and the exhaust superheat degree of the compressor 1" includes:

[0054] When the air - conditioning system needs to operate in the heating mode, the air - conditioning system first starts in the cooling mode and runs for a second preset duration, then switches to the heating mode and opens the oil return valve 62 to replenish oil for the compressor 1. Generally, the heating mode is only turned on when the indoor and outdoor temperatures are relatively low to raise the indoor temperature. When the external ambient temperature is low, the air - conditioning system actually undergoes a liquid compression process at startup. At this time, most of the oil in the oil storage tank 6 will be discharged back into the air - conditioning system along with the refrigerant again, and it is impossible to keep the lubricating oil at the compressor 1, that is, it cannot play the role of lubricating the compressor 1. If the oil return valve 62 is opened at the beginning, the lubricating effect on the compressor 1 is very little. Therefore, it is chosen to first make the air - conditioning system operate in the cooling mode for the second preset duration, and then open the oil return valve 62. At this time, the compressor 1 discharges high - temperature and high - pressure gas, and only a small part of the lubricating oil will flow away with the refrigerant, and most of it will not. This can ensure the lubricating effect of the compressor 1. The second preset duration is obtained by calculation based on actual machine experiments and / or the digital model of the air - conditioning system; in this embodiment, it is preferably obtained by conducting experiments on the actual machine, and the second preset duration corresponding to each heating power needs to be determined separately.

[0055] "Determining the opening degree of the oil return valve 62 and the operating mode of the air - conditioning system according to the target operating mode, operating time of the air - conditioning system, and the exhaust superheat degree of the compressor 1" further includes:

[0056] When the air - conditioning system is in the heating mode and the exhaust superheat degree of the compressor 1 rises by a second preset value, the oil return valve 62 is closed. After the air - conditioning system operates for a period of time, the exhaust superheat degree will increase. The second preset value is obtained by calculation based on actual machine experiments and / or the digital model of the air - conditioning system; in this embodiment, preferably, it is obtained by actual machine experiments, and the second preset value corresponding to each cooling power needs to be determined separately, and the corresponding second preset value also needs to be obtained at each initial exhaust superheat degree. When the air - conditioning system needs to operate in the cooling mode, the air - conditioning system first starts in the cooling mode and runs for a second preset duration, then switches to the heating mode and opens the oil return valve 62 to replenish oil for the compressor 1; and the air - conditioning system continues to operate in the heating mode, and when the exhaust superheat degree of the compressor 1 rises by the second preset value, the oil return valve 62 is closed (at this time, the compressor 1 no longer lacks lubricating oil); then the air - conditioning system continues to operate in the heating mode.

[0057] "Determining the opening degree of the oil return valve 62 and the operating mode of the air - conditioning system according to the target operating mode, operating time of the air - conditioning system, and the exhaust superheat degree of the compressor 1" includes:

[0058] When the air - conditioning system needs to switch from the defrosting mode to the heating mode, after the air - conditioning system completes defrosting, it switches to the heating mode and runs for a third preset duration, then opens the oil return valve 62 to replenish oil for the compressor 1.

[0059] The defrosting mode generally runs after the heating mode has been operating for a period of time. The heating mode generally operates when the indoor and outdoor temperatures are relatively low to raise the indoor temperature. The essence of the defrosting mode of the air-conditioning system is the same as that of the cooling mode, that is, the high-temperature and high-pressure refrigerant flowing out of the compressor 1 flows to the outdoor heat exchanger 3, then flows to the indoor heat exchanger 4 for heat exchange, and then flows back to the compressor 1. When the defrosting mode is completed, that is, when the air-conditioning system meets the defrosting completion condition. When the external ambient temperature is relatively low, when the air-conditioning system is just switched to the heating mode, it is actually a liquid compression process. At this time, most of the oil in the oil storage tank 6 will be discharged back into the air-conditioning system along with the refrigerant again, and the lubricating oil cannot stay at the compressor 1, that is, it cannot play the role of lubricating the compressor 1. If the oil return valve 62 is opened at the beginning, the effect on lubricating the compressor 1 is very small. Therefore, it is selected to first make the air-conditioning system operate in the heating mode for a third preset duration, and then open the oil return valve 62. At this time, the gas discharged from the compressor 1 is high-temperature and high-pressure, and the lubricating oil will not flow away in large quantities with the refrigerant, and only a small part flows away, which can ensure the lubricating effect of the compressor 1. The third preset duration is obtained by calculation according to actual machine experiments and / or the digital model of the air-conditioning system; in this embodiment, it is preferably obtained by conducting experiments on the actual machine.

[0060] "Determining the opening degree of the oil return valve 62 and the operating mode of the air-conditioning system according to the target operating mode, operating time of the air-conditioning system, and the exhaust superheat degree of the compressor 1" further includes:

[0061] After the air-conditioning system is switched to the heating mode and the exhaust superheat degree of the compressor 1 rises by a third preset value, the oil return valve 62 is closed. After the air-conditioning system operates in the heating mode for a period of time, the exhaust superheat degree will increase. The third preset value is obtained by calculation according to actual machine experiments and / or the digital model of the air-conditioning system; in this embodiment, it is preferably obtained by actual machine experiments, and the third preset value corresponding to each heating power when switching from the defrosting mode to the heating mode needs to be determined separately, and the corresponding third preset value also needs to be obtained at each initial exhaust superheat degree. When the air-conditioning system needs to be switched from the defrosting mode to the heating mode, after switching to the heating mode and operating for a third preset duration, the oil return valve 62 is opened to replenish oil to the compressor 1; and the air-conditioning system continues to operate in the heating mode, and when the exhaust superheat degree of the compressor 1 rises by a third preset value, the oil return valve 62 is closed (at this time, the compressor 1 is no longer lacking lubricating oil); then the air-conditioning system continues to operate in the heating mode.

[0062] So far, the technical solution of the present invention has been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the protection scope of the present invention.

Claims

1. An air conditioning system, characterized in that, The air conditioning system includes a compressor (1) and an oil storage tank (6). The oil outlet of the oil storage tank (6) is connected to the suction port of the compressor (1) through a pipeline, and an oil return valve (62) is arranged on the pipeline. After the air conditioning system is started, the oil return valve (62) is opened to supply oil to the compressor.

2. The air conditioning system according to claim 1, wherein It further includes a gas-liquid separator. Its first outlet is connected to the suction port of the compressor through a first pipeline, and its second outlet is connected to the oil inlet of the oil storage tank (6) through a second pipeline. An oil inlet valve (61) is arranged on the second pipeline to control whether to fill the oil storage tank (6) with oil.

3. A control method for an air conditioning system as claimed in claim 1 or 2, characterized in that, The control method includes the following steps: After the air conditioning system is started, according to the target working mode, running time of the air conditioning system, and the exhaust superheat degree of the compressor (1), determine the opening degree of the oil return valve (62) and the working mode of the air conditioning system.

4. The control method of the air conditioning system according to claim 3, characterized in that, "According to the target working mode, running time of the air conditioning system, and the exhaust superheat degree of the compressor (1), determine the opening degree of the oil return valve (62) and the working mode of the air conditioning system" includes: When the air conditioning system needs to operate in the cooling mode, the air conditioning system starts in the cooling mode and, after running for a first preset duration in the cooling mode, opens the oil return valve (62) to supply oil to the compressor (1).

5. The control method of the air conditioning system according to claim 4, characterized in that "According to the target working mode, running time of the air conditioning system, and the exhaust superheat degree of the compressor (1), determine the opening degree of the oil return valve (62) and the working mode of the air conditioning system" further includes: When the air conditioning system is in the cooling mode and the exhaust superheat degree of the compressor (1) rises by a first preset value, close the oil return valve (62).

6. The control method of the air conditioning system according to claim 5, characterized in that, "According to the target working mode, running time of the air conditioning system, and the exhaust superheat degree of the compressor (1), determine the opening degree of the oil return valve (62) and the working mode of the air conditioning system" includes: When the air conditioning system needs to operate in the heating mode, the air conditioning system first starts in the cooling mode, runs for a second preset duration, then switches to the heating mode, and opens the oil return valve (62) to supply oil to the compressor (1).

7. The control method of the air conditioning system according to claim 6, characterized in that, "According to the target working mode, running time of the air conditioning system, and the exhaust superheat degree of the compressor (1), determine the opening degree of the oil return valve (62) and the working mode of the air conditioning system" further includes: When the air conditioning system is in the heating mode and the exhaust superheat degree of the compressor (1) rises by a second preset value, close the oil return valve (62).

8. The control method of the air conditioning system according to claim 7, characterized in that, "According to the target working mode, running time of the air conditioning system, and the exhaust superheat degree of the compressor (1), determine the opening degree of the oil return valve (62) and the working mode of the air conditioning system" includes: When the air conditioning system needs to switch from the defrosting mode to the heating mode, after the air conditioning system completes defrosting, it switches to the heating mode, and after running for a third preset duration, opens the oil return valve (62) to supply oil to the compressor (1).

9. The control method of the air conditioning system according to claim 8, characterized in that, "Determining the opening degree of the oil return valve (62) and the operating mode of the air conditioning system according to the target operating mode, operating time of the air conditioning system, and the superheat degree of the exhaust gas of the compressor (1)" further includes: When the air conditioning system is in the heating mode and the superheat degree of the exhaust gas of the compressor (1) rises by a third preset value, the oil return valve (62) is closed.

10. The control method of the air conditioning system according to claim 9, wherein, The first preset duration, the second preset duration, and the third preset duration are calculated and obtained according to actual machine experiments and / or the digital model of the air conditioning system.

11. The control method of the air conditioning system according to claim 9, characterized in that, The first preset value, the second preset value, and the third preset value are calculated and obtained according to actual machine experiments and / or the digital model of the air conditioning system.

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