Control method and control device of multi-split air conditioner and multi-split air conditioner

Abstract

The invention relates to the technical field of air conditioners, and provides a control method and device of a multi-split air conditioner and the multi-split air conditioner, the control method of the multi-split air conditioner comprises a starting stage, in the starting stage, the outdoor environment temperature, the bottom oil temperature of a gas-liquid separator, the suction temperature of a compressor and the load rate of the multi-split air conditioner are obtained; the state of an electromagnetic valve is controlled according to the outdoor environment temperature, the bottom oil temperature and the suction temperature, and the state of an electronic expansion valve is controlled according to the load rate, the bottom oil temperature and the suction temperature; wherein the state of the electromagnetic valve comprises opening and closing, and the state of the electronic expansion valve comprises initial opening and opening adjustment. When the multi-split air conditioner is in a severe working condition or a low refrigerant utilization rate stage, part of lubricating oil at the bottom of the gas-liquid separator can flow back into the compressor by controlling the states of the electromagnetic valve and the electronic expansion valve, space is provided for the gas-liquid separator to store refrigerants, and the liquid impact phenomenon caused when the liquid refrigerants enter the compressor is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of air conditioners, and in particular to a control method, a control device and a multi-connected air conditioner for a multi-connected air conditioner. Background Art

[0002] Due to the characteristics that the number of indoor and outdoor units and the output capacity of a multi-connected air conditioner can be freely adjusted according to requirements, multi-connected air conditioners have been widely used nowadays. As the core component of a multi-connected air conditioner, the compressor is very vulnerable to system liquid return, which may cause damage to the compressor. In related technologies, a capillary tube is added to connect the bottom of the gas-liquid separator to the compressor suction pipe in a multi-connected system, and it is kept open during system operation and standby states, so that the lubricating oil deposited at the bottom of the gas-liquid separator can flow back into the compressor along the compressor suction pipe. However, during the start-up stage and the operation stage under harsh working conditions of the multi-connected air conditioner, a large amount of refrigerant in the system accumulates in the gas-liquid separator due to insufficient circulation. When there is a large amount of refrigerant, the deposited liquid refrigerant will flow back into the compressor along the suction pipe, and long-term operation under liquid hammer conditions is likely to cause damage to the compressor. Summary of the Invention

[0003] The present invention aims to solve at least one of the technical problems existing in the related technologies. For this purpose, the present invention provides a control method for a multi-connected air conditioner. When the multi-connected air conditioner is in a harsh working condition or a low refrigerant utilization rate stage, by controlling the states of the solenoid valve and the electronic expansion valve, part of the lubricating oil at the bottom of the gas-liquid separator can be refluxed into the compressor, providing a storage space for storing refrigerant in the gas-liquid separator, preventing the refrigerant in the gas-liquid separator from entering the compressor, and avoiding the occurrence of compressor liquid hammer phenomenon.

[0004] The present invention also provides a control device for a multi-connected air conditioner.

[0005] The present invention also provides a multi-connected air conditioner.

[0006] According to the control method for a multi-connected air conditioner provided by the first aspect embodiment of the present invention, the bottom of the gas-liquid separator is communicated with the suction port of the compressor through a drain pipe. The drain pipe is provided with a valve group composed of a solenoid valve and an electronic expansion valve in parallel. A first temperature sensor is provided upstream of the valve group, and a second temperature sensor is provided downstream of the valve group. The control method includes a start-up stage. During the start-up stage:

[0007] Obtain the outdoor ambient temperature, the bottom oil temperature of the gas-liquid separator, the suction temperature of the compressor, and the load rate of the multi-connected air conditioner;

[0008] Control the state of the solenoid valve according to the outdoor ambient temperature, the bottom oil temperature, and the suction temperature, and control the state of the electronic expansion valve according to the load rate, the bottom oil temperature, and the suction temperature; wherein, the state of the solenoid valve includes open and closed, and the state of the electronic expansion valve includes an initial opening degree and an opening degree adjustment.

[0009] According to an embodiment of the present invention, the step of controlling the state of the solenoid valve according to the outdoor ambient temperature, the bottom oil temperature, and the suction temperature specifically includes:

[0010] When the outdoor ambient temperature is less than or equal to the low temperature threshold, control the solenoid valve to be normally closed;

[0011] When the outdoor ambient temperature is greater than the low temperature threshold, control the solenoid valve to close, and after a first preset duration, control the state of the solenoid valve every first period based on the bottom oil temperature and the suction temperature.

[0012] According to an embodiment of the present invention, the step of controlling the state of the solenoid valve based on the bottom oil temperature and the suction temperature specifically includes:

[0013] When the temperature difference between the bottom oil temperature and the suction temperature is greater than or equal to a first temperature difference, control the solenoid valve to open;

[0014] When the temperature difference between the bottom oil temperature and the suction temperature is less than the first temperature difference, control the solenoid valve to close.

[0015] According to an embodiment of the present invention, the step of controlling the state of the electronic expansion valve according to the load rate, the bottom oil temperature, and the suction temperature specifically includes:

[0016] Adjust the opening degree of the electronic expansion valve to the initial startup opening degree according to the load rate, and adjust the opening degree of the electronic expansion valve every second period based on the bottom oil temperature and the suction temperature.

[0017] According to an embodiment of the present invention, after the startup stage, there is also an operation stage. In the operation stage:

[0018] Obtain the operation mode of the multi-connected air conditioner, and control the state of the solenoid valve according to the operation mode, the bottom oil temperature, and the suction temperature, and control the state of the electronic expansion valve according to the operation mode, the load rate, the outdoor ambient temperature, the bottom oil temperature, and the suction temperature.

[0019] According to an embodiment of the present invention, the step of controlling the state of the solenoid valve according to the operation mode, the bottom oil temperature, and the suction temperature specifically includes:

[0020] Determine a second temperature difference according to the operating mode;

[0021] When the temperature difference between the bottom oil temperature and the suction temperature is greater than or equal to the second temperature difference, control the solenoid valve to open;

[0022] When the temperature difference between the bottom oil temperature and the suction temperature is less than the second temperature difference and the duration is greater than a second preset duration, control the solenoid valve to close.

[0023] According to an embodiment of the present invention, the step of controlling the state of the electronic expansion valve according to the operating mode, the load rate, the outdoor ambient temperature, the bottom oil temperature, and the suction temperature specifically includes:

[0024] Determine an initial opening degree correspondence according to the operating mode, and determine the initial operating opening degree of the electronic expansion valve according to the load rate and the initial opening degree correspondence;

[0025] Adjust the opening degree of the electronic expansion valve based on the outdoor ambient temperature, the bottom oil temperature, and the suction temperature every third period.

[0026] According to an embodiment of the present invention, the step of determining the initial operating opening degree of the electronic expansion valve according to the load rate and the initial opening degree correspondence specifically includes:

[0027] When the load rate is lower than a first load rate, the initial operating opening degree is a first initial operating opening degree;

[0028] When the load rate is between the first load rate and a second load rate, the initial operating opening degree is a second initial operating opening degree;

[0029] When the load rate is greater than the second load rate, the initial operating opening degree is a third initial operating opening degree;

[0030] Wherein, the first load rate and the second load rate increase in sequence, and the first initial operating opening degree, the second initial operating opening degree, and the third initial operating opening degree increase in sequence.

[0031] According to a control device for a multi-connected air conditioner provided by a second aspect embodiment of the present invention, it includes:

[0032] An acquisition module for acquiring the outdoor ambient temperature, the bottom oil temperature of the gas-liquid separator, the suction temperature of the compressor, and the load rate of the multi-connected air conditioner;

[0033] A control module is configured to control the state of a solenoid valve based on the outdoor ambient temperature, the bottom oil temperature, and the suction temperature, and control the state of an electronic expansion valve based on the load rate, the bottom oil temperature, and the suction temperature; wherein, the state of the solenoid valve includes open and closed, and the state of the electronic expansion valve includes an initial opening degree and an opening degree adjustment.

[0034] The multi-connected air conditioner according to the third aspect embodiment of the present invention includes a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the program, the steps of the control method of the multi-connected air conditioner according to the first aspect embodiment of the present invention are implemented.

[0035] One or more of the above technical solutions in the present invention have at least one of the following technical effects:

[0036] According to the control method of the multi-connected air conditioner provided by the embodiment of the present invention, the bottom of the gas-liquid separator is connected to the suction port of the compressor through a drain pipe. The drain pipe is provided with a valve group composed of a parallel connection of a solenoid valve and an electronic expansion valve. A first temperature sensor is provided upstream of the valve group for detecting the bottom oil temperature of the gas-liquid separator. A second temperature sensor is provided downstream of the valve group for detecting the suction temperature of the compressor. The control method of the multi-connected air conditioner includes a startup stage. In the startup stage: obtain the outdoor ambient temperature, the bottom oil temperature of the gas-liquid separator, the suction temperature of the compressor, and the load rate of the multi-connected air conditioner; control the state of the solenoid valve based on the outdoor ambient temperature, the bottom oil temperature, and the suction temperature, and control the state of the electronic expansion valve based on the load rate, the bottom oil temperature, and the suction temperature; wherein, the state of the solenoid valve includes open and closed, and the state of the electronic expansion valve includes an initial opening degree and an opening degree adjustment. In the case of the multi-connected air conditioner in a harsh working condition or a low refrigerant utilization rate stage, by controlling the states of the solenoid valve and the electronic expansion valve, a part of the lubricating oil at the bottom of the gas-liquid separator can be returned to the compressor, providing a storage space for storing refrigerant in the gas-liquid separator, avoiding the refrigerant in the gas-liquid separator from entering the compressor, and avoiding the occurrence of compressor liquid hammer phenomenon. Description of the Drawings

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the following will briefly introduce the drawings required for use in the description of the embodiments or related technologies. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0038] Figure 1 It is a schematic structural diagram of the multi-connected air conditioner provided by the embodiment of the present invention;

[0039] Figure 2 Flow chart of the control method for a multi-connected air conditioner provided by an embodiment of the present invention;

[0040] Figure 3 Schematic structural diagram of the control device for a multi-connected air conditioner provided by an embodiment of the present invention;

[0041] Figure 4 Schematic structural diagram of the electronic device of a multi-connected air conditioner provided by an embodiment of the present invention.

[0042] Reference numerals:

[0043] 10. Compressor; 11. Outdoor heat exchanger; 12. Indoor heat exchanger; 13. Four-way valve; 14. Gas-liquid separator; 20. Drainage pipeline; 21. Solenoid valve; 22. Electronic expansion valve; 23. First temperature sensor; 24. Second temperature sensor;

[0044] 301. Acquisition module; 302. Control module. Detailed implementation manners

[0045] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions in the present invention will be clearly described below with reference to the accompanying drawings in the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without creative efforts shall fall within the protection scope of the present invention.

[0046] In the description of the embodiments of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the embodiments of the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the embodiments of the present invention. In addition, the terms "first", "second", and "third" are only used for descriptive purposes and should not be construed as indicating or implying relative importance.

[0047] In the description of the embodiments of the present invention, it should be noted that unless otherwise clearly defined and limited, the terms "connected" and "coupled" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific circumstances.

[0048] In the embodiments of the present invention, unless otherwise clearly specified or limited, the first feature being "on" or "under" the second feature may mean that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature may mean that the first feature is directly above or obliquely above the second feature, or merely indicates that the horizontal height of the first feature is higher than that of the second feature. The first feature being "under", "below" and "beneath" the second feature may mean that the first feature is directly below or obliquely below the second feature, or merely indicates that the horizontal height of the first feature is less than that of the second feature.

[0049] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the embodiments 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, without contradiction, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0050] In the related art, a multi-connected air conditioner system connects the bottom of the gas-liquid separator to the compressor suction pipe by adding a capillary tube, which is kept open during the operation and standby states of the system, so that the lubricating oil deposited at the bottom of the gas-liquid separator can flow back into the compressor along the compressor suction pipe. However, during the startup stage and the operation stage under harsh conditions of the multi-connected air conditioner, a large amount of refrigerant in the system accumulates in the gas-liquid separator due to insufficient circulation. When there is a large amount of refrigerant, the deposited liquid refrigerant will flow back into the compressor along the suction pipe, and the compressor is easily damaged by long-term liquid slugging operation.

[0051] The multi-connected air conditioner involved in the present invention includes multiple indoor units and / or multiple outdoor units. When multiple indoor units and / or multiple outdoor units work simultaneously, the refrigerant demand is relatively large. During the startup stage, under extremely harsh conditions, when some indoor units or some outdoor units are working, the refrigerant demand decreases. Therefore, it is necessary to temporarily store the excess refrigerant. Please refer to Figure 1, in the embodiment of the present invention, an indoor heat exchanger and an outdoor heat exchanger are used to illustrate the connection relationship of the refrigerant circulation circuit. The multi-connected air conditioner includes a compressor 10, an outdoor heat exchanger 11, an indoor heat exchanger 12, a throttle valve, a gas-liquid separator 14, and a four-way valve 13. The compressor 10, the outdoor heat exchanger 11, the indoor heat exchanger 12, and the throttle valve are connected through refrigerant pipelines to form a refrigerant circulation circuit. The four-way valve 13 is arranged on the refrigerant circulation circuit and is used to adjust the flow direction of the refrigerant, thereby adjusting the operating mode of the multi-connected air conditioner. A gas-liquid separator 14 is arranged upstream of the suction port of the compressor 10. The gas-liquid separator 14 includes an air inlet and an air outlet. The air inlet is communicated with the return pipe of the refrigerant circulation circuit, and the air outlet is communicated with the suction port of the compressor 10 through a refrigerant pipeline. If the gas pipe contains liquid refrigerant or there is a large amount of liquid refrigerant in the refrigerant circulation circuit, the liquid refrigerant will be stored in the gas-liquid separator 14 to avoid entering the suction port of the compressor 10.

[0052] In the multi-connected air conditioner provided by the embodiment of the present invention, please refer to Figure 1, a liquid drain pipe 20 is provided at the bottom of the gas-liquid separator 14, and the other end of the liquid drain pipe 20 communicates with the suction port of the compressor 10. A valve group is provided on the liquid drain pipe 20. The valve group includes a solenoid valve 21 and an electronic expansion valve 22 connected in parallel. The lubricating oil in the gas-liquid separator 14 can flow into the suction port of the compressor 10 along the solenoid valve 21 or along the electronic expansion valve 22. A first temperature sensor 23 and a second temperature sensor 24 are also provided on the liquid drain pipe 20. The first temperature sensor 23 is located upstream of the valve group and is used to detect the oil temperature at the bottom of the gas-liquid separator 14. The second temperature sensor 24 is located downstream of the valve group and is used to detect the suction temperature of the compressor 10. The refrigerant pipeline at the outlet of the gas-liquid separator 14 communicates with the pipeline between the valve group and the first temperature sensor 23. When there is liquid refrigerant or a large amount of liquid refrigerant in the gas-liquid separator 14, the liquid refrigerant level in the gas-liquid separator 14 rises, and the temperature of the refrigerant flowing into the suction port of the compressor 10 along the outlet of the gas-liquid separator 14 is close to the liquid refrigerant temperature. At this time, the bottom oil temperature and the suction temperature have a small difference; when there is no liquid refrigerant or a small amount of liquid refrigerant in the gas-liquid separator 14, the temperature of the refrigerant flowing into the suction port of the compressor 10 along the outlet of the gas-liquid separator 14 has a large difference from the liquid refrigerant temperature. At this time, the bottom oil temperature and the suction temperature have a large difference. According to the above principle, the refrigerant state and the refrigerant amount in the gas-liquid separator 14 can be determined. If the multi-split air conditioner is in a harsh working condition or a low refrigerant utilization rate stage, the liquid refrigerant has the possibility of flowing into the suction port of the compressor 10 along the outlet of the gas-liquid separator 14, increasing the risk of liquid slugging. The control method of the multi-split air conditioner provided by the embodiment of the present invention adjusts the capacity of the refrigerant accumulated in the gas-liquid separator 14 by controlling the states of the solenoid valve 21 and the electronic expansion valve 22 during the start-up stage and the harsh working condition operation stage of the multi-split air conditioner, avoiding the occurrence of liquid slugging phenomenon in the compressor 10.

[0053] According to the control method of the multi-split air conditioner provided by the first aspect embodiment of the present invention, please refer to Figure 2 , the control method of the multi-split air conditioner includes a start-up stage. In the start-up stage:

[0054] S100. Obtain the outdoor ambient temperature, the oil temperature at the bottom of the gas-liquid separator, the suction temperature of the compressor, and the load rate of the multi-split air conditioner.

[0055] It can be understood that the outdoor ambient temperature can be obtained by the temperature sensor installed on the outdoor unit or by an independent outdoor temperature sensor, and the temperature sensor is electrically connected to the controller of the multi-connected air conditioner. During the startup phase, the multi-connected air conditioner first operates in the cooling mode, or executes the previously determined cooling mode during the startup phase. If the outdoor ambient temperature is low at this time, there is a situation of low-temperature cooling. At this time, the utilization rate of the refrigerant is low, which belongs to an extremely harsh working condition. Therefore, it is necessary to judge whether there is such an extreme working condition according to the outdoor ambient temperature. At the same time, the temperature difference between the bottom oil temperature of the gas-liquid separator and the suction temperature of the compressor can reflect whether there is liquid refrigerant or the amount of liquid refrigerant inside the gas-liquid separator, and can feedback the possibility of liquid refrigerant entering the suction port of the compressor. Furthermore, the load rate of the multi-connected air conditioner refers to the ratio of the capacity of the indoor units in the working state to the total capacity of the indoor units. For example, the load rates are 25%, 50%, 60%, 70%, 100%, etc. The lower the load rate of the multi-connected air conditioner, the lower the utilization rate of the refrigerant in the refrigerant circulation circuit, the more liquid refrigerant stored in the gas-liquid separator, and the greater the possibility of liquid refrigerant entering the suction port of the compressor.

[0056] S110. Control the state of the solenoid valve according to the outdoor ambient temperature, the bottom oil temperature and the suction temperature, and control the state of the electronic expansion valve according to the load rate, the bottom oil temperature and the suction temperature; wherein, the state of the solenoid valve includes open and closed, and the state of the electronic expansion valve includes the initial opening and the opening adjustment.

[0057] In step S110, when controlling the state of the solenoid valve according to the outdoor ambient temperature, the bottom oil temperature and the suction temperature, when the multi-connected air conditioner is in the extreme working condition of low-temperature cooling or there is more liquid refrigerant in the gas-liquid separator, control the solenoid valve to close. If the solenoid valve is opened at this time, a large amount of liquid refrigerant and lubricating oil will enter the suction port of the compressor together; in non-extreme low-temperature cooling working conditions, it is necessary to control the on-off of the solenoid valve according to the liquid refrigerant situation in the gas-liquid separator. During the startup phase, if the load rate is low, the amount of liquid refrigerant in the gas-liquid separator is large, and the initial startup opening of the electronic expansion valve should not be opened too large to avoid liquid refrigerant and lubricating oil entering the suction port of the compressor together. Subsequently, the opening of the electronic expansion valve can be further adjusted based on the liquid refrigerant situation in the gas-liquid separator. When the amount of liquid refrigerant is large, it is necessary to avoid liquid refrigerant entering the suction port. When the amount of liquid refrigerant decreases or does not exist, the electronic expansion valve can be closed to make the gas-liquid separator and the compressor operate normally.

[0058] When the multi-connected air conditioner is in a harsh working condition or a low refrigerant utilization rate stage, by controlling the states of the solenoid valve and the electronic expansion valve, part of the lubricating oil at the bottom of the gas-liquid separator can be returned to the compressor, providing a storage space for the gas-liquid separator to store refrigerant, avoiding the refrigerant in the gas-liquid separator from entering the compressor, and avoiding the occurrence of compressor liquid hammer phenomenon.

[0059] In some embodiments, the step of controlling the state of the solenoid valve according to the outdoor ambient temperature, the bottom oil temperature, and the suction temperature specifically includes:

[0060] S111. When the outdoor ambient temperature is less than or equal to the low temperature threshold, control the solenoid valve to be normally closed.

[0061] It can be understood that the low temperature threshold is used to define whether the multi-split air conditioner is in a low temperature environment. For example, the low temperature threshold is 15 °C. If the multi-split air conditioner is in an extreme working condition of low temperature refrigeration, there is a relatively large amount of refrigerant in the gas-liquid separator. Control the solenoid valve to close to prevent liquid refrigerant and lubricating oil from entering the suction port of the compressor together and avoid the occurrence of liquid hammer phenomenon.

[0062] S112. When the outdoor ambient temperature is greater than the low temperature threshold, control the solenoid valve to close, and after the first preset duration, control the state of the solenoid valve every first period based on the bottom oil temperature and the suction temperature.

[0063] In step S112, when the outdoor ambient temperature is greater than the low temperature threshold, the multi-split air conditioner is not in the low temperature refrigeration working condition, but at this time the multi-split air conditioner is still in the starting stage, the refrigerant utilization rate is low, and there is still a relatively large amount of liquid refrigerant in the gas-liquid separator. The solenoid valve needs to be in the closed state. After the multi-split air conditioner operates for the first preset duration, for example, after 3 minutes, determine the liquid refrigerant situation in the gas-liquid separator based on the bottom oil temperature and the suction temperature, and then control the on-off state of the solenoid valve.

[0064] In some embodiments, the step of controlling the state of the solenoid valve based on the bottom oil temperature and the suction temperature specifically includes:

[0065] S1121. When the temperature difference between the bottom oil temperature and the suction temperature is greater than or equal to the first temperature difference, control the solenoid valve to open.

[0066] In step S1121, when the temperature difference between the bottom oil temperature of the gas-liquid separator and the suction temperature of the compressor is greater than or equal to the first temperature difference, for example, -2 °C, it indicates that the temperature of the refrigerant entering the suction port of the compressor along the outlet of the gas-liquid separator is relatively low. At this time, there is liquid refrigerant or a relatively large amount of liquid refrigerant in the gas-liquid separator, and the liquid refrigerant may enter the suction port of the compressor along the outlet. Therefore, it is necessary to control the solenoid valve to open, introduce part of the lubricating oil into the suction port of the compressor, create some space for the refrigerant, increase the refrigerant storage capacity of the gas-liquid separator, and avoid the occurrence of liquid hammer phenomenon in the compressor.

[0067] S1122. When the temperature difference between the bottom oil temperature and the suction temperature is less than the first temperature difference, control the solenoid valve to close.

[0068] In step S1122, when the temperature difference between the bottom oil temperature of the gas-liquid separator and the suction temperature of the compressor is less than the first temperature difference, it indicates that the refrigerant temperature entering the suction port of the compressor along the outlet of the gas-liquid separator is relatively high (higher than the bottom liquid oil temperature / bottom liquid refrigerant temperature). At this time, there is no liquid refrigerant or the reserve of liquid refrigerant in the gas-liquid separator is small, and the liquid refrigerant will not enter the suction port of the compressor along the outlet. At this time, the solenoid valve is controlled to close, and the compressor will not experience liquid slugging.

[0069] In some embodiments, the step of controlling the state of the electronic expansion valve according to the load rate, the bottom oil temperature, and the suction temperature specifically includes:

[0070] S113. Adjust the opening degree of the electronic expansion valve to the initial startup opening degree according to the load rate, and adjust the opening degree of the electronic expansion valve every second period based on the bottom oil temperature and the suction temperature.

[0071] In step S113, during the startup stage of the multi-connected air conditioner, the load rate is directly related to the utilization rate of the refrigerant in the refrigerant circulation loop. If the load rate is low at the startup moment, there is a large amount of liquid refrigerant in the gas-liquid separator. At this time, the opening degree of the electronic expansion valve should not be adjusted too large to avoid the liquid refrigerant entering the suction port of the compressor together with the lubricating oil. There is a positive correlation between the load rate and the initial startup opening degree. Subsequently, as the compressor operates, some refrigerant participates in the refrigerant circulation, and then the opening degree of the electronic expansion valve is adjusted once every second period, such as 20 seconds.

[0072] For example: when the load rate is lower than 25%, the initial startup opening degree of the electronic expansion valve is 15% pls; when the load rate is lower than 50%, the valve opening degree of the electronic expansion valve is 12% pls; when the load rate is higher than 50%, the valve opening degree of the electronic expansion valve is 6% pls.

[0073] Let Temp1 be the bottom oil temperature of the gas-liquid separator and Temp2 be the suction temperature of the compressor, then a determination is made every 20 s:

[0074] 1) When Temp1 - Temp2 ≥ -2°C, the valve opening degree is not adjusted;

[0075] 2) When Temp1 - Temp2 < -2°C, the valve opening degree is reduced by 20% pls on the current basis, and the minimum opening degree of the electronic expansion valve can be reduced to 0.

[0076] According to an embodiment of the present invention, after the startup stage, there is also an operation stage. In the operation stage:

[0077] S130. Obtain the operating mode of the multi-connected air conditioner, control the state of the solenoid valve according to the operating mode, bottom oil temperature, and suction temperature, and control the state of the electronic expansion valve according to the operating mode, load rate, outdoor ambient temperature, bottom oil temperature, and suction temperature.

[0078] It can be understood that during the operation stage, the multi-connected air conditioner includes at least a cooling mode and a heating mode. There are certain differences in the control logics for the solenoid valve and the electronic expansion valve under different operating modes. For example, in the cooling mode and the heating mode, there are differences in the temperature difference used to determine whether there is liquid refrigerant in the gas-liquid separator, and there are also differences in the initial opening degree of the electronic expansion valve. In the embodiments of the present invention, for different operating modes of the multi-connected air conditioner, based on the refrigerant situation in the gas-liquid separator, the states of the solenoid valve and the electronic expansion valve are respectively controlled to prevent liquid refrigerant from entering the suction port of the compressor.

[0079] In some embodiments, the step of controlling the state of the solenoid valve according to the operating mode, bottom oil temperature, and suction temperature specifically includes:

[0080] S131. Determine the second temperature difference according to the operating mode.

[0081] It can be understood that the second temperature difference is used to reflect the temperature difference between the bottom oil temperature / liquid refrigerant temperature and the suction temperature when there is liquid refrigerant in the gas-liquid separator and the amount of liquid refrigerant is relatively large. Taking the second temperature difference as the boundary, it reflects the possibility of liquid refrigerant entering the suction port of the compressor. There is heat exchange between the refrigerant pipeline from the outlet of the gas-liquid separator to the suction port of the compressor and the outside world. In the cooling mode and the heating mode, they respectively correspond to a relatively high outdoor environment and a relatively low outdoor environment. Therefore, the second temperature difference may be different. For example, in the cooling mode, the second temperature difference is -2 °C; in the heating mode, the second temperature difference is 0 °C.

[0082] S132. When the temperature difference between the bottom oil temperature and the suction temperature is greater than or equal to the second temperature difference, control the solenoid valve to open.

[0083] In step S132, if the temperature difference between the bottom oil temperature and the suction temperature is greater than or equal to the second temperature difference, it means that the suction temperature is relatively close to the bottom oil temperature / liquid refrigerant temperature, and the possibility of liquid refrigerant entering the suction port of the compressor along the outlet is increasing. At this time, control the solenoid valve to open, and introduce part of the lubricating oil into the suction port of the compressor to make some space for the refrigerant.

[0084] S133. When the temperature difference between the bottom oil temperature and the suction temperature is less than the second temperature difference and the continuous duration is greater than the second preset duration, control the solenoid valve to close.

[0085] In step S133, if the temperature difference between the bottom oil temperature and the suction temperature is less than the second temperature difference, it indicates that the temperature difference between the suction temperature and the bottom oil temperature / liquid refrigerant temperature is large, and the possibility of the liquid refrigerant entering the suction port of the compressor along the outlet is small. At this time, the solenoid valve is controlled to close, and it is not necessary to discharge part of the lubricating oil.

[0086] Let Temp1 be the bottom oil temperature of the gas-liquid separator and Temp2 be the suction temperature of the compressor. Then in the refrigeration mode:

[0087] (1) When Temp1 - Temp2 ≥ -2°C, the solenoid valve opens;

[0088] (2) When Temp1 - Temp2 < -2°C and the duration exceeds 1 minute, the solenoid valve closes.

[0089] In the heating mode:

[0090] (1) When Temp1 - Temp2 ≥ 0°C, the solenoid valve opens;

[0091] (2) When Temp1 - Temp2 < 0°C and the duration exceeds 1 minute, the solenoid valve closes.

[0092] In some embodiments, the step of controlling the state of the electronic expansion valve according to the operating mode, load rate, outdoor ambient temperature, bottom oil temperature, and suction temperature specifically includes:

[0093] S134. Determine the initial opening degree correspondence according to the operating mode, and determine the initial operating opening degree of the electronic expansion valve according to the load rate and the initial opening degree correspondence.

[0094] It can be understood that in the heating mode and the refrigeration mode, the outdoor ambient temperature is different, the heat exchange efficiency of the refrigerant pipeline and the gas-liquid separator with the air is different, and the state of the liquid refrigerant in the gas-liquid separator will also be affected. Therefore, the initial opening degree correspondence can be determined according to the operating mode, and then the initial operating opening degree of the electronic expansion valve can be determined according to the load rate and the initial opening degree correspondence.

[0095] S135. Adjust the opening degree of the electronic expansion valve based on the outdoor ambient temperature, bottom oil temperature, and suction temperature every third period.

[0096] It can be understood that in the operation stage, it is still necessary to avoid extreme working conditions, such as low-temperature refrigeration working conditions. Therefore, the outdoor ambient temperature is added as an environmental parameter. In the refrigeration mode, there are different valve opening degree adjustment strategies based on different outdoor ambient temperatures.

[0097] When Tao > 15°C:

[0098] (1) When Temp1 - Temp2 > 0°C, the valve opening of the electronic expansion valve remains unchanged;

[0099] (2) When -2°C < Temp1 - Temp2 < 0°C, the valve opening of the electronic expansion valve is reduced by 5% based on the original;

[0100] (3) When Temp1 - Temp2 < -2°C, the valve opening of the electronic expansion valve is reduced by 8% based on the original.

[0101] When Tao ≤ 15°C:

[0102] (1) Temp1 - Temp2 > -1°C, the valve opening of the electronic expansion valve remains unchanged;

[0103] (2) Temp1 - Temp2 < -1°C, the valve opening of the electronic expansion valve is reduced by 10% based on the original.

[0104] In some embodiments, the step of determining the initial operating opening of the electronic expansion valve according to the load rate and the corresponding relationship of the initial opening specifically includes:

[0105] S1341. When the load rate is lower than the first load rate, the initial operating opening is the first initial operating opening.

[0106] S1342. When the load rate is between the first load rate and the second load rate, the initial operating opening is the second initial operating opening.

[0107] S1343. When the load rate is higher than the second load rate, the initial operating opening is the third initial operating opening.

[0108] Wherein, the first load rate and the second load rate increase in sequence, and the first initial operating opening, the second initial operating opening, and the third initial operating opening increase in sequence.

[0109] For example: In the refrigeration mode, the electronic expansion valve executes the initial operating opening: when the load rate is lower than 25%, the valve opening of the electronic expansion valve is 20% pls; when the load rate is lower than 50%, the valve opening of the electronic expansion valve is 30% pls; when the load rate is higher than 50%, the valve opening of the electronic expansion valve is 50% pls.

[0110] In the heating mode, the electronic expansion valve executes the initial operating opening: when the load rate is lower than 25%, the valve opening of the electronic expansion valve is 30% pls; when the load rate is lower than 50%, the valve opening of the electronic expansion valve is 40% pls; when the load rate is higher than 50%, the valve opening of the electronic expansion valve is 50% pls.

[0111] According to the control device of the multi-connected air conditioner provided by the second aspect embodiment of the present invention, please refer to Figure 3 , including:

[0112] An acquisition module 301 is configured to acquire the outdoor ambient temperature, the bottom oil temperature of the gas-liquid separator, the suction temperature of the compressor, and the load rate of the multi-split air conditioner.

[0113] A control module 302 is configured to control the state of the solenoid valve according to the outdoor ambient temperature, the bottom oil temperature, and the suction temperature, and control the state of the electronic expansion valve according to the load rate, the bottom oil temperature, and the suction temperature; wherein, the state of the solenoid valve includes open and closed, and the state of the electronic expansion valve includes an initial opening and an opening adjustment.

[0114] It should be noted that the above steps S100 to S130, as well as other steps, are only for convenience of description and do not constitute a timing limitation on the steps in the control method of the multi-split air conditioner. Moreover, some content is described in detail in the control method of the multi-split air conditioner provided in the first aspect embodiment, and all the content in the control method of the multi-split air conditioner is also applicable to the control device of the multi-split air conditioner provided in the second aspect embodiment. Therefore, in order to avoid repetition, it is not described in detail in the control device of the multi-split air conditioner provided in the second aspect embodiment. Similarly, the content in the above two aspect embodiments can be used to explain the content of all subsequent aspect embodiments. Therefore, the repeated content is not described in the subsequent embodiments. According to the control device of the multi-split air conditioner provided by the embodiment of the present invention, its technical effect corresponds to the technical effect of the above control method of the multi-split air conditioner, and will not be elaborated here.

[0115] According to a multi-split air conditioner provided by the third aspect embodiment of the present invention, it includes a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the program, it implements the steps of the control method of the multi-split air conditioner provided by the first aspect embodiment of the present invention.

[0116] Figure 4Schematic diagram of the physical structure of an electronic device of a multi-connected air conditioner is illustrated. The electronic device may include: a processor 810, a communications interface 820, a memory 830, and a communication bus 840. Among them, the processor 810, the communication interface 820, and the memory 830 complete communication with each other through the communication bus 840. The processor 810 can call the logical instructions in the memory 830 to execute the control method of the multi-connected air conditioner. The method includes: obtaining the outdoor ambient temperature, the bottom oil temperature of the gas-liquid separator, the suction temperature of the compressor, and the load rate of the multi-connected air conditioner; controlling the state of the solenoid valve according to the outdoor ambient temperature, the bottom oil temperature, and the suction temperature, and controlling the state of the electronic expansion valve according to the load rate, the bottom oil temperature, and the suction temperature; wherein, the state of the solenoid valve includes open and closed, and the state of the electronic expansion valve includes the initial opening degree and the opening degree adjustment.

[0117] In addition, when the logical instructions in the above-mentioned memory 830 are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on such an understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or a part of this technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in various embodiments of the present invention. The foregoing storage medium includes: various media such as USB flash drives, mobile hard disks, read-only memories (ROM, Read-Only Memory), random access memories (RAM, Random Access Memory), magnetic disks, or optical discs that can store program codes.

[0118] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place, or may be distributed to multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment. Those of ordinary skill in the art can understand and implement it without creative labor.

[0119] Through the description of the above embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus a necessary general hardware platform, and of course, it can also be implemented by hardware. Based on such an understanding, the essence of the above technical solution, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to enable a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0120] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A control method for a multi-connected air conditioner, characterized in that, the bottom of the gas-liquid separator is connected to the suction port of the compressor through a drain pipe, and the drain pipe is provided with a valve group composed of a solenoid valve and an electronic expansion valve in parallel. A first temperature sensor is provided upstream of the valve group, and a second temperature sensor is provided downstream of the valve group. The control method includes a startup stage, and in the startup stage: Obtain the outdoor ambient temperature, the bottom oil temperature of the gas-liquid separator, the suction temperature of the compressor, and the load rate of the multi-connected air conditioner; Control the state of the solenoid valve according to the outdoor ambient temperature, the bottom oil temperature, and the suction temperature, and control the state of the electronic expansion valve according to the load rate, the bottom oil temperature, and the suction temperature; wherein, the state of the solenoid valve includes open and closed, and the state of the electronic expansion valve includes an initial opening and an opening adjustment.

2. The control method for a multi-connected air conditioner according to claim 1, characterized in that, the step of controlling the state of the solenoid valve according to the outdoor ambient temperature, the bottom oil temperature, and the suction temperature specifically includes: When the outdoor ambient temperature is less than or equal to a low temperature threshold, control the solenoid valve to be normally closed; When the outdoor ambient temperature is greater than the low temperature threshold, control the solenoid valve to close, and after a first preset duration, control the state of the solenoid valve every first period based on the bottom oil temperature and the suction temperature.

3. The control method for a multi-connected air conditioner according to claim 2, characterized in that, the step of controlling the state of the solenoid valve based on the bottom oil temperature and the suction temperature specifically includes: When the temperature difference between the bottom oil temperature and the suction temperature is greater than or equal to a first temperature difference, control the solenoid valve to open; When the temperature difference between the bottom oil temperature and the suction temperature is less than the first temperature difference, control the solenoid valve to close.

4. The control method for a multi-connected air conditioner according to any one of claims 1 to 3, characterized in that, the step of controlling the state of the electronic expansion valve according to the load rate, the bottom oil temperature, and the suction temperature specifically includes: Adjust the opening of the electronic expansion valve to an initial startup opening according to the load rate, and adjust the opening of the electronic expansion valve every second period based on the bottom oil temperature and the suction temperature.

5. The control method for a multi-connected air conditioner according to claim 4, characterized in that, after the startup stage, there is also an operation stage, and in the operation stage: Obtain the operation mode of the multi-connected air conditioner, and control the state of the solenoid valve according to the operation mode, the bottom oil temperature, and the suction temperature, and control the state of the electronic expansion valve according to the operation mode, the load rate, the outdoor ambient temperature, the bottom oil temperature, and the suction temperature.

6. The control method for a multi-connected air conditioner according to claim 5, characterized in that, the step of controlling the state of the solenoid valve according to the operation mode, the bottom oil temperature, and the suction temperature specifically includes: Determine a second temperature difference according to the operation mode; When the temperature difference between the bottom oil temperature and the suction temperature is greater than or equal to the second temperature difference, control the solenoid valve to open; When the temperature difference between the bottom oil temperature and the suction temperature is less than the second temperature difference and the duration is greater than the second preset duration, control the solenoid valve to close.

7. The control method of the multi-connected air conditioner according to claim 5, characterized in that the step of controlling the state of the electronic expansion valve according to the operating mode, the load rate, the outdoor ambient temperature, the bottom oil temperature and the suction temperature specifically includes: Determine the initial opening degree correspondence according to the operating mode, and determine the initial operating opening degree of the electronic expansion valve according to the load rate and the initial opening degree correspondence; Adjust the opening degree of the electronic expansion valve based on the outdoor ambient temperature, the bottom oil temperature and the suction temperature every third period.

8. The control method of the multi-connected air conditioner according to claim 7, characterized in that the step of determining the initial operating opening degree of the electronic expansion valve according to the load rate and the initial opening degree correspondence specifically includes: When the load rate is lower than the first load rate, the initial operating opening degree is the first initial operating opening degree; When the load rate is between the first load rate and the second load rate, the initial operating opening degree is the second initial operating opening degree; When the load rate is greater than the second load rate, the initial operating opening degree is the third initial operating opening degree; wherein, the first load rate and the second load rate increase in sequence, and the first initial operating opening degree, the second initial operating opening degree, and the third initial operating opening degree increase in sequence.

9. A control device for a multi-connected air conditioner, characterized in that it includes: An acquisition module for acquiring the outdoor ambient temperature, the bottom oil temperature of the gas-liquid separator, the suction temperature of the compressor, and the load rate of the multi-connected air conditioner; A control module for controlling the state of the solenoid valve according to the outdoor ambient temperature, the bottom oil temperature and the suction temperature, and controlling the state of the electronic expansion valve according to the load rate, the bottom oil temperature and the suction temperature; wherein, the state of the solenoid valve includes opening and closing, and the state of the electronic expansion valve includes an initial opening degree and an opening degree adjustment.

10. A multi-connected air conditioner includes a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that when the processor executes the program, it implements the steps of the control method of the multi-connected air conditioner according to any one of claims 1 to 8.

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