Method for improving oil return of compressor, oil return system and compressor

Abstract

The invention provides a method for improving oil return of a compressor, an oil return system and the compressor, the method for improving the oil return of the compressor is achieved through the oil return system in the compressor, and the oil return system comprises a closed oil return unit connected between an oil separator and the compressor; the method comprises the following steps: acquiring the running state of the compressor; the capacity requirements q of all indoor units and the maximum refrigerating capacity Q in the current environment are calculated; judging whether a high-frequency oil return condition or a low-frequency oil return condition is met or not based on the obtained running state of the compressor in combination with the size relation between q / Q and a preset proportion; and when the high-frequency oil return condition or the low-frequency oil return condition is met, the closed oil return unit is controlled to be started so as to carry out high-frequency or low-frequency oil return treatment. The system is provided with a double-loop oil return system, logic judgment is carried out through system parameters, oil return is carried out in time, long-term operation of a unit during oil shortage and abrasion of a cylinder body are avoided, and the operation reliability of the compressor is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of compressors, and in particular to a method for improving oil return of a compressor, an oil return system and a compressor. Background Art

[0002] like Figure 1 As shown, in the field of air conditioning technology, after the mixture of refrigerant and oil from the compressor 1 enters the oil separator 2, the oil is separated, and the refrigerant enters the outdoor heat exchanger in an oil-free state. The separated oil returns to the compressor 1 through the capillary line 4. The capillary line 4 in the existing air conditioner is a single return oil line. Since the length of the capillary line 4 is fixed, the return oil amount of the compressor 1 is constant regardless of whether the compressor 1 is running at a low frequency or a high frequency. This easily leads to the difficulty of oil return of the compressor 1 during low-frequency operation, and the excessive oil discharge of the compressor 1 during high-frequency operation, resulting in oil shortage.

[0003] The applicant has discovered that the prior art has at least the following technical problems: the fixed return oil volume of the single oil return pipeline in the air conditioner in the prior art easily leads to a technical problem of oil shortage in the compressor, and no effective solution has been proposed so far. Summary of the invention

[0004] The object of the present invention is to provide a method for improving the oil return of a compressor, an oil return system and a compressor, so as to solve the technical problem in the prior art that the oil return amount of the compressor cannot be adjusted according to high and low frequency operation, which easily leads to oil return difficulties or oil shortage.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a method for improving oil return of a compressor, which is implemented by using an oil return system in the compressor, wherein the oil return system includes a closed oil return unit connected between an oil separator and the compressor; the method includes the following steps:

[0007] Get the compressor operating status;

[0008] Calculate the capacity requirements q of all indoor units and the maximum cooling capacity Q in the current environment;

[0009] Based on the acquired compressor operating status and the relationship between q / Q and the preset ratio, it is determined whether the high-frequency oil return condition or the low-frequency oil return condition is met;

[0010] When the high-frequency oil return condition or the low-frequency oil return condition is met, the opening of the closed oil return unit is controlled to perform high-frequency or low-frequency oil return processing.

[0011] The method for improving the oil return of the compressor of the present invention makes logical judgment through system parameters and returns oil in time, thereby avoiding long-term operation of the unit when lacking oil and wearing of the cylinder body. The new structure and new control method are helpful to improve the operating reliability of the compressor.

[0012] As a further improvement of the present invention, the capacity requirements q of all indoor units are calculated according to the following formula:

[0013] q = ∑ cmt0; where: t0 = t 设定 -t 目标 , c is the specific heat capacity of the corresponding refrigerant, m is the mass of the refrigerant passing through a single radiator, cmt0 is the capacity requirement of a single indoor unit; q is the sum of the capacity requirements of all indoor units.

[0014] As a further improvement of the present invention, the maximum refrigeration capacity Q under the current environment is calculated according to the following formula:

[0015] Q = kn (azt); where k is the compressor refrigeration coefficient, n is the number of compressors, a is the refrigeration capacity of a single compressor, z is the ambient temperature correction coefficient, and t is the ambient temperature.

[0016] As a further improvement of the present invention, the method of determining whether the high-frequency oil return condition or the low-frequency oil return condition is met based on the acquired compressor operating state and the relationship between q / Q and a preset ratio includes:

[0017] When the compressor is in low-frequency operation, compare whether q / Q is less than a preset ratio A;

[0018] When q / Q is less than the preset ratio A, it is determined that the low-frequency oil return condition is met;

[0019] When the compressor is in high-frequency operation, compare whether q / Q is greater than a preset ratio B;

[0020] When q / Q is greater than the preset ratio B, it is determined that the high-frequency oil return condition is met.

[0021] As a further improvement of the present invention, the control of opening of the closed oil return unit to perform high-frequency or low-frequency oil return processing includes:

[0022] When the low-frequency oil return conditions are met, the closed oil return unit is controlled to open and low-frequency oil return is performed;

[0023] After the first set time of low-frequency oil return is completed, the closed oil return unit is controlled to close, and the unit enters normal logic operation;

[0024] After the conventional logic runs for the second set time, the current compressor operating frequency is obtained;

[0025] When the compressor operating frequency is ≤ the first set frequency, the closed oil return unit is controlled to open for low-frequency oil return again; after the first set time of low-frequency oil return again is completed, the closed oil return unit is controlled to close, and the unit enters normal logic operation;

[0026] When the compressor operating frequency is greater than the first set frequency, the comparison is returned to see whether q / Q is less than the preset ratio A.

[0027] As a further improvement of the present invention, the control of opening of the closed oil return unit to perform high-frequency or low-frequency oil return processing includes:

[0028] When the high-frequency oil return conditions are met, the closed oil return unit is controlled to open for high-frequency oil return;

[0029] After the third setting time of high-frequency oil return is completed, the closed oil return unit is controlled to be closed, and the unit enters normal logic operation;

[0030] After the conventional logic runs for the second set time, the current compressor operating frequency is obtained;

[0031] When the compressor operating frequency is ≥ the second set frequency, the closed oil return unit is controlled to open for high-frequency oil return again; after completing the third set time of high-frequency oil return again, the closed oil return unit is controlled to close, and the unit enters normal logic operation;

[0032] When the compressor operating frequency is less than the second set frequency, the comparison returns to see whether q / Q is greater than the preset ratio B.

[0033] As a further improvement of the present invention, before obtaining the compressor operating status, the method further includes: waiting for the compressor to operate for a fourth set time.

[0034] As a further improvement of the present invention, the preset ratio A is 20%, and the preset ratio B is 80%.

[0035] As a further improvement of the present invention, the first set time is 45 minutes.

[0036] As a further improvement of the present invention, the second set time is 2 hours.

[0037] As a further improvement of the present invention, the first set frequency is 30 Hz.

[0038] As a further improvement of the present invention, the second set frequency is 70 Hz.

[0039] As a further improvement of the present invention, the third set time is 30 minutes.

[0040] The present invention provides an oil return system for executing the method, wherein the oil return system comprises a closed oil return unit connected between an oil separator and a compressor.

[0041] As a further improvement of the present invention, the closed oil return unit includes a closed oil return pipe, an oil return pipe solenoid valve or an electronic expansion valve; one end of the closed oil return pipe is connected to the oil separator, and the other end is connected to the oil pool at the bottom of the compressor; the oil return pipe solenoid valve or the electronic expansion valve is installed on the closed oil return pipe; or, the closed oil return unit includes a capillary line, one end of the capillary line is connected to the oil separator, and the other end is connected to the oil pool at the bottom of the compressor.

[0042] The present invention provides a compressor, comprising the oil return system.

[0043] The compressor of the present invention has a dual-circuit oil return system, which makes logical judgments through system parameters and returns oil in time, thus solving the problem of difficult oil return under low-frequency conditions. At high frequencies, the amount of oil leakage is large, and the refrigerant is made more uniform during the evaporation process, thereby improving the utilization rate of the heat exchanger and solving the technical problem in the prior art that the single return oil pipeline in the air conditioner has a fixed return oil volume, which easily leads to oil shortage in the compressor. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0045] Figure 1 It is a structural schematic diagram of an oil return system in a compressor in the prior art;

[0046] Figure 2 It is a structural schematic diagram of the oil return system in the compressor of the present invention;

[0047] Figure 3 is a control flow chart of a method for improving oil return of a compressor according to the present invention;

[0048] Figure 4 It is an oil return logic diagram during low frequency operation in the method for improving oil return of a compressor of the present invention;

[0049] Figure 5 It is an oil return logic diagram during high frequency operation in the method for improving oil return of a compressor of the present invention.

[0050] In the figure, 1 is the compressor; 2 is the oil separator; 3 is the gas-liquid separator; 4 is the capillary pipeline; 5 is the closed oil separator return pipe; 6 is the return valve of the return oil pipe. DETAILED DESCRIPTION

[0051] To make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described in detail below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0052] like Figure 3 As shown, the present invention provides a method for improving the oil return of a compressor, which is implemented by using an oil return system in the compressor, wherein the oil return system includes a closed oil return unit connected between an oil separator and the compressor; the method includes the following steps:

[0053] Step S1, obtaining the operating state of the compressor; the operating state of the compressor includes a low-frequency state and a high-frequency state;

[0054] Considering the possibility of fluctuations in the initial operating parameters of the compressor, before obtaining the operating status of the compressor and after the compressor is turned on, the process also includes waiting for the compressor to run for a fourth set time.

[0055] In this embodiment, the fourth set time may be 60 minutes, that is, the compressor operation status is obtained after the compressor is started and operated for 60 minutes;

[0056] Step S2: Calculate the capacity requirements q of all indoor units and the maximum cooling capacity Q under the current environment; wherein:

[0057] The capacity requirement q of all indoor units is calculated according to the following formula:

[0058] q = ∑ cmt0; where: t0 = t 设定 -t 目标 , c is the specific heat capacity of the corresponding refrigerant, m is the mass of the refrigerant passing through a single radiator, cmt0 is the capacity requirement of a single indoor unit; q is the sum of the capacity requirements of all indoor units.

[0059] The maximum cooling capacity Q under the current environment is calculated according to the following formula:

[0060] Q = kn (azt); where k is the compressor refrigeration coefficient, n is the number of compressors, a is the refrigeration capacity of a single compressor, z is the ambient temperature correction coefficient, and t is the ambient temperature.

[0061] Step S3: Based on the acquired compressor operating state and in combination with the relationship between q / Q and a preset ratio, determine whether a high-frequency oil return condition or a low-frequency oil return condition is met;

[0062] Specifically, as an optional implementation of the present invention:

[0063] 1. When the compressor is in low-frequency operation, compare whether q / Q is less than the preset ratio A; when q / Q is less than the preset ratio A, it is determined that the low-frequency oil return condition is met;

[0064] 2. When the compressor is in high-frequency operation, compare whether q / Q is greater than the preset ratio B; when q / Q is greater than the preset ratio B, it is determined that the high-frequency oil return condition is met.

[0065] Step S4: When the high-frequency oil return condition or the low-frequency oil return condition is met, the closed oil return unit is controlled to be opened to perform high-frequency or low-frequency oil return processing.

[0066] Further, the opening of the closed oil return unit is controlled to perform low-frequency oil return processing, including:

[0067] When the low-frequency oil return conditions are met, the closed oil return unit is controlled to open and low-frequency oil return is performed;

[0068] After the first set time of low-frequency oil return is completed, the closed oil return unit is controlled to be closed, and the unit enters normal logic operation; after the second set time of normal logic operation, the current compressor operating frequency is obtained;

[0069] When the compressor operating frequency is ≤ the first set frequency, the closed oil return unit is controlled to open for low-frequency oil return again; after the first set time of low-frequency oil return is completed, the closed oil return unit is controlled to close, and the unit enters normal logic operation; then the above normal logic operation is repeated for the second set time, and the current compressor operating frequency and subsequent steps are obtained;

[0070] When the compressor operating frequency is greater than the first set frequency, the comparison is returned to see whether q / Q is less than a preset ratio A. The corresponding subsequent steps are executed according to the comparison result.

[0071] Furthermore, the opening of the closed oil return unit is controlled to perform high-frequency oil return processing, including:

[0072] When the high-frequency oil return conditions are met, the closed oil return unit is controlled to open for high-frequency oil return;

[0073] After the third setting time of high-frequency oil return is completed, the closed oil return unit is controlled to be closed, and the unit enters normal logic operation;

[0074] After the conventional logic runs for the second set time, the current compressor operating frequency is obtained;

[0075] When the compressor operating frequency is ≥ the second set frequency, the closed oil return unit is controlled to open for high-frequency oil return again; after the third set time of high-frequency oil return is completed, the closed oil return unit is controlled to close, and the unit enters normal logic operation; then the above normal logic operation is repeated for the second set time to obtain the current compressor operating frequency and subsequent steps;

[0076] When the compressor operating frequency is less than the second set frequency, the comparison is returned to see whether q / Q is greater than a preset ratio B. The corresponding subsequent steps are executed according to the comparison result.

[0077] In this embodiment, the preset ratio A is 20%, the preset ratio B is 80%, the first setting time is 45 minutes, the second setting time is 2 hours, the first setting frequency is 30HZ, the second setting frequency is 70HZ, and the third setting time is 30 minutes.

[0078] It should be noted here that since the closed oil return unit includes a closed oil return pipe and an oil return pipe solenoid valve, or a closed oil return pipe and an electronic expansion valve, or a capillary pipeline; there are three embodiments, and the control processes of the three embodiments are slightly different. When the oil return pipe solenoid valve is used, since the oil return pipe solenoid valve only has an on-off function, there is only an opening and closing control process, that is, oil return and oil return stop control; the electronic expansion valve can adjust the opening, that is, on the basis of realizing oil return control, the return oil amount can also be controlled; and the capillary pipeline has the characteristic of adjusting the oil return speed, and the length of the capillary pipeline is fixed, and there is no need to perform other control steps.

[0079] The method for improving the oil return of the compressor of the present invention makes logical judgment through system parameters and returns oil in time, thereby avoiding long-term operation of the unit when lacking oil and wearing of the cylinder body. The new structure and new control method are helpful to improve the operating reliability of the compressor.

[0080] Embodiment 1:

[0081] In this embodiment, the present invention proposes a novel oil return control method for an oil return system in a compressor, which avoids the long-term operation of the unit when it is short of oil and wears the cylinder body, thereby helping to improve the operating reliability of the compressor.

[0082] In the refrigeration system, most of the compressor oil return systems use open oil return units, which rely on the system suction to drive the lubricating oil back to the compressor oil pool, and transport the lubricating oil to the compression chamber for lubrication through pressure difference, oil pump, etc. Since this method requires the oil to go through a set of cycles before it can enter the compression chamber, there is a delay, which leads to oil shortage in the compressor. Therefore, the compressor structure is adjusted, and a closed oil return pipe and an oil return pipe solenoid valve are added. The oil in the oil separator directly enters the compression chamber to achieve a large amount of oil pumping effect.

[0083] The specific control methods are as follows:

[0084] When the compressor is in low-frequency operation, after the refrigeration system is turned on, the normal startup control logic of the unit is executed and it runs stably for 60 minutes;

[0085] (1) Calculate the capacity requirements of all indoor units q(q = ∑ cmt0(t0 = t 设定 -t 目标 , c: specific heat capacity of corresponding refrigerant, m: mass of refrigerant passing through a single radiator, calculate and sum the required capacities of all indoor units;

[0086] (2) Calculate the maximum refrigeration capacity Q under the current environment (calculate the maximum refrigeration capacity Q under the current environment = kn(azt), where k is the compressor refrigeration coefficient; n is the number of compressors, a is the refrigeration capacity of a single compressor; z is the ambient temperature correction coefficient; t is the ambient temperature);

[0087] (3) Determine whether q / Q is less than A;

[0088] (4) If it is less than A, the oil return pipe solenoid valve, capillary line or electronic expansion valve is opened to perform auxiliary oil return action. If it is greater than A, the unit's conventional logic control operation is executed; (the oil return pipe solenoid valve only has an on-off function, the capillary line can be fixed in length and slowly adjusted, and it is not necessary to execute all logical relationships; the electronic expansion valve can be adjusted according to the suction superheat. When the suction superheat is -5℃ to -2℃, 70% of the electronic expansion valve is opened; when it is -2℃ to 0℃, 50% is opened; when it is 0℃ to 5℃, 30% is opened; when it is >5℃, the electronic expansion valve is closed. The calculation formula for suction superheat is: suction superheat = suction pipe temperature - saturated steam temperature)

[0089] (5) After the oil return pipe solenoid valve is opened and operated for 45 minutes, the oil return pipe solenoid valve is closed;

[0090] (6) The unit starts normal logic control operation;

[0091] (7) After the unit has been running for 2 hours, determine the current compressor operating frequency;

[0092] (8) If it is greater than 30Hz, the unit will operate according to the normal logic control procedure;

[0093] (9) If it is less than 30 Hz, the oil return solenoid valve is opened and step (5) is executed.

[0094] It should be noted that A can be between 5-30%. When the capacity is low, that is, below the range A (5% to 30%), the compressor oil return power is insufficient, and an auxiliary oil return part needs to be added. The closed oil return system acts as one of the auxiliary oil returns.

[0095] Embodiment 2:

[0096] When the compressor is in low-frequency operation, after the refrigeration system is turned on, the normal startup control logic of the unit is executed and it runs stably for 60 minutes;

[0097] (1) Calculate the capacity requirements of all indoor units q(q = cmt0(t0 = t 设定 -t 目标 , c: specific heat capacity of corresponding refrigerant, m: mass of refrigerant passing through a single radiator);

[0098] (2) Calculate the maximum refrigeration capacity Q under the current environment (calculate the maximum refrigeration capacity Q under the current environment = k(azt), where k is the compressor refrigeration coefficient; a is the refrigeration capacity of a single compressor; z is the ambient temperature correction coefficient; t is the ambient temperature);

[0099] (3) Determine whether q / Q is greater than B;

[0100] (4) If it is greater than B, the return oil pipe solenoid valve, capillary tube or electronic expansion valve is opened to perform auxiliary oil return action. If it is less than B, the unit's conventional logic control operation is executed (the return oil pipe solenoid valve only has an on-off function; the capillary tube has a fixed length and is slowly adjusted, and does not need to execute all logical relationships; the electronic expansion valve can be adjusted according to the suction superheat. When the suction superheat is -5℃ to -2℃, the electronic expansion valve is opened by 70%, -2 to 0℃, 50%, 0 to 5℃, 30%, and >5℃, the electronic expansion valve is closed. The suction superheat calculation formula is: suction superheat = suction pipe temperature - saturated steam temperature);

[0101] (5) After the oil return pipe solenoid valve is opened and operated for 30 minutes, the oil return pipe solenoid valve is closed;

[0102] (6) The unit starts normal logic control operation;

[0103] (7) After the unit has been running for 2 hours, determine the current compressor operating frequency;

[0104] (8) If it is greater than 70Hz, the unit will operate according to the normal logic control procedure;

[0105] (9) If it is less than 70 Hz, the oil return solenoid valve is opened and (5) is executed.

[0106] It should be noted that B can be between 80% and 100%: when the capacity demand is greater than B (80% to 100%), the compressor oil return power is indeed sufficient, but the oil discharge rate is also high, so when the load is high, it will also be necessary to open the auxiliary oil return circuit.

[0107] The present invention provides an oil return system for executing a method, wherein the oil return system comprises a closed oil return unit connected between an oil separator and a compressor.

[0108] As a further improvement of the present invention, the closed oil return unit includes a closed oil return pipe, an oil return pipe solenoid valve, ； One end of the closed oil separator return pipe is connected to the oil separator, and the other end is connected to the oil pool at the bottom of the compressor; the return pipe solenoid valve is installed on the closed oil separator return pipe.

[0109] As another improvement of the present invention, the closed oil return unit includes a closed oil return pipe and an electronic expansion valve; one end of the closed oil return pipe is connected to the oil separator, and the other end is connected to the oil pool at the bottom of the compressor; the electronic expansion valve is installed on the closed oil return pipe.

[0110] As a third improvement of the present invention, the closed oil return unit includes a capillary pipe, one end of the capillary pipe is connected to the oil separator, and the other end is connected to the oil pool at the bottom of the compressor.

[0111] The present invention provides a compressor, comprising the above-mentioned oil return system.

[0112] The compressor of the present invention has a dual-circuit oil return system, which makes logical judgments through system parameters and returns oil in time, thus solving the problem of difficult oil return under low-frequency conditions. At high frequencies, the amount of oil leakage is large, and the refrigerant is made more uniform during the evaporation process, thereby improving the utilization rate of the heat exchanger and solving the technical problem in the prior art that the single return oil pipeline in the air conditioner has a fixed return oil volume, which easily leads to oil shortage in the compressor.

[0113] First of all, it should be explained here that “inward” refers to the direction toward the center of the accommodating space, and “outward” refers to the direction away from the center of the accommodating space.

[0114] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate directions or positional relationships based on the attached Figure 1 The orientation or positional relationship shown is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0115] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0116] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like 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 a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0117] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0118] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0119] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for improving oil return of a compressor, characterized in that: The method is implemented by using an oil return system in a compressor, wherein the oil return system includes a closed oil return unit connected between an oil separator and the compressor; the method includes the following steps: Get the compressor operating status; Calculate the capacity requirements q of all indoor units and the maximum cooling capacity Q in the current environment; Based on the acquired compressor operating status and the relationship between q / Q and the preset ratio, it is determined whether the high-frequency oil return condition or the low-frequency oil return condition is met; When the high-frequency oil return condition or the low-frequency oil return condition is met, the opening of the closed oil return unit is controlled to perform high-frequency or low-frequency oil return processing.

2. The method according to claim 1, characterized in that The capacity requirement q of all indoor units is calculated according to the following formula: q = ∑ cmt0; where: t0 = t 设定 -t 目标 , c is the specific heat capacity of the corresponding refrigerant, m is the mass of the refrigerant passing through a single radiator, cmt0 is the capacity requirement of a single indoor unit; q is the sum of the capacity requirements of all indoor units.

3. The method according to claim 1, characterized in that The maximum cooling capacity Q under the current environment is calculated according to the following formula: Q = kn (azt); where k is the compressor refrigeration coefficient, n is the number of compressors, a is the refrigeration capacity of a single compressor, z is the ambient temperature correction coefficient, and t is the ambient temperature.

4. The method according to claim 1, characterized in that: The method of determining whether a high-frequency oil return condition or a low-frequency oil return condition is met based on the acquired compressor operation state and in combination with the size relationship between q / Q and a preset ratio includes: When the compressor is in low-frequency operation, compare whether q / Q is less than a preset ratio A; When q / Q is less than the preset ratio A, it is determined that the low-frequency oil return condition is met; When the compressor is in high-frequency operation, compare whether q / Q is greater than a preset ratio B; When q / Q is greater than the preset ratio B, it is determined that the high-frequency oil return condition is met.

5. The method according to claim 1, characterized in that The control of opening of the closed oil return unit to perform high-frequency or low-frequency oil return processing includes: When the low-frequency oil return conditions are met, the closed oil return unit is controlled to open and low-frequency oil return is performed; After the first set time of low-frequency oil return is completed, the closed oil return unit is controlled to close, and the unit enters normal logic operation; After the conventional logic runs for the second set time, the current compressor operating frequency is obtained; When the compressor operating frequency is ≤ the first set frequency, the closed oil return unit is controlled to open for low-frequency oil return again; after the first set time of low-frequency oil return again is completed, the closed oil return unit is controlled to close, and the unit enters normal logic operation; When the compressor operating frequency is greater than the first set frequency, the comparison is returned to see whether q / Q is less than the preset ratio A.

6. The method according to claim 1, characterized in that The control of opening of the closed oil return unit to perform high-frequency or low-frequency oil return processing includes: When the high-frequency oil return conditions are met, the closed oil return unit is controlled to open for high-frequency oil return; After the third setting time of high-frequency oil return is completed, the closed oil return unit is controlled to be closed, and the unit enters normal logic operation; After the conventional logic runs for the second set time, the current compressor operating frequency is obtained; When the compressor operating frequency is ≥ the second set frequency, the closed oil return unit is controlled to open for high-frequency oil return again; after completing the third set time of high-frequency oil return again, the closed oil return unit is controlled to close, and the unit enters normal logic operation; When the compressor operating frequency is less than the second set frequency, the comparison returns to see whether q / Q is greater than the preset ratio B.

7. The method according to claim 1, characterized in that Before obtaining the compressor operation status, the method further includes: waiting for the compressor to operate for a fourth set time.

8. The method according to claim 4, characterized in that The preset ratio A is 20%, and the preset ratio B is 80%.

9. An oil return system, characterized in that: Used to perform the method according to any one of claims 1 to 8, the oil return system comprises a closed oil return unit connected between the oil separator and the compressor.

10. The oil return system according to claim 9, characterized in that: The closed oil return unit includes a closed oil return pipe, an oil return pipe solenoid valve or an electronic expansion valve; one end of the closed oil return pipe is connected to the oil separator, and the other end is connected to the oil pool at the bottom of the compressor; the oil return pipe solenoid valve or the electronic expansion valve is installed on the closed oil return pipe; or, the closed oil return unit includes a capillary pipe, one end of the capillary pipe is connected to the oil separator, and the other end is connected to the oil pool at the bottom of the compressor.

11. A compressor, characterized in that: Comprising an oil return system as described in any one of claims 9-10.

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