Multi-split system

Abstract

The invention discloses a multi-split air conditioning system. The method comprises the steps that the starting indoor unit load rate is determined; when the load rate of the started indoor unit is below the set load rate, the operation frequency of the compressor is controlled to be the first frequency; determining the exhaust pressure target value of the compressor as a first target exhaust pressure value, and controlling the gear or rotating speed of an outdoor fan to enable the exhaust pressure of the compressor to reach the first target exhaust pressure value or the threshold range of the first target exhaust pressure value; wherein the first target exhaust pressure value is a pressure value higher than the normal exhaust pressure value. When the load rate of the multi-split air conditioning system to the started indoor unit is low, the exhaust pressure of the compressor is improved, the pressure difference between the outdoor heat exchanger and the indoor expansion valve is increased, liquid refrigerants left at the bottom of the outdoor heat exchanger can be reduced, more refrigerants flow out of the outdoor heat exchanger to participate in refrigeration circulation, the actual refrigerant circulation amount of the multi-split air conditioning system is guaranteed, and the service life of the multi-split air conditioning system is prolonged. And the refrigerant at the inlet of the indoor unit is in a supercooling state, so that the refrigerant sound of the indoor unit when the load rate of the indoor unit is low during refrigeration starting is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of air conditioning, in particular to a multi-connected system. Background Art

[0002] The compressor frequency of the multi-split system is related to the load rate of the indoor unit. When the load rate of the indoor unit is low, the operating frequency adaptability of the compressor is reduced. However, under refrigeration conditions, when the compressor runs at a low frequency, the power provided by the compressor to the refrigerant for circulation is small. At the same time, due to gravity, liquid refrigerant will remain at the bottom of the outdoor heat exchanger. Therefore, the actual amount of refrigerant participating in the refrigeration cycle is insufficient, making the refrigerant at the inlet of the indoor unit in a two-phase state, resulting in high refrigerant noise at the indoor expansion valve.

[0003] The above information disclosed in the background technology is only used to increase the understanding of the background technology of the present application, and therefore, it may include information that does not constitute the prior art known to ordinary technicians in the field. Summary of the invention

[0004] The present invention proposes a multi-split system, which solves the problem of refrigerant noise in the indoor unit when the load rate of the indoor unit is small and the compressor is running at a low frequency under the refrigeration working condition of the existing multi-split system.

[0005] In order to achieve the above-mentioned purpose, the present invention adopts the following technical solutions:

[0006] A multi-connection system, comprising:

[0007] The outdoor unit includes a compressor, an outdoor heat exchanger and an outdoor fan;

[0008] An exhaust pressure detection module is used to detect the exhaust pressure of the compressor;

[0009] At least two indoor units, the multi-split system further comprises:

[0010] A control module configured to determine a load rate of a powered-on indoor unit;

[0011] When the load rate of the indoor unit is lower than the set load rate:

[0012] controlling the operating frequency of the compressor to be a first frequency;

[0013] Determine the exhaust pressure target value of the compressor as a first target exhaust pressure value, and control the gear position or speed of the outdoor fan so that the exhaust pressure of the compressor reaches the first target exhaust pressure value;

[0014] Among them, the first target exhaust pressure value is a value within the setting threshold range of the standard exhaust pressure value, and the standard exhaust pressure value corresponds to the exhaust pressure value under standard working conditions, when the indoor unit is fully open and the compressor operates at the second frequency; the first frequency is less than the second frequency.

[0015] The above technical solution has the following advantages or beneficial effects: the multi-split system includes an outdoor unit, at least two indoor units, a compressor exhaust pressure detection module and a control module, and the control module is configured to determine the load rate of the indoor unit when it is turned on; when the load rate of the indoor unit when it is turned on is below the set load rate: control the operating frequency of the compressor to be the first frequency; determine the exhaust pressure target value of the compressor to be the first target exhaust pressure value, and control the gear or speed of the outdoor fan so that the exhaust pressure of the compressor reaches the first target exhaust pressure value; wherein the first target exhaust pressure value is a value within the threshold range of the standard exhaust pressure value setting, and the standard exhaust pressure value is the exhaust pressure value corresponding to the standard working condition, the indoor unit is fully opened, and the compressor is operated at the second frequency; the first frequency is less than the second frequency. The multi-split system optimizes the exhaust pressure of the compressor when the load rate of the indoor unit when it is turned on is low: when the indoor load rate of the machine is below the set load rate and the compressor is operated at the first frequency, increase the exhaust pressure of the compressor to the exhaust pressure value corresponding to the standard working condition, the indoor unit is fully opened, and the compressor is operated at the second frequency, and increase the pressure difference between the outdoor heat exchanger and the indoor expansion valve. The large pressure difference can reduce the liquid refrigerant retained at the bottom of the outdoor heat exchanger. Under the action of the pressure difference, more refrigerant flows out of the outdoor heat exchanger to participate in the refrigeration cycle, ensuring the actual refrigerant circulation volume of the multi-split system and achieving a supercooled refrigerant at the inlet of the indoor unit, thereby reducing the refrigerant noise of the indoor unit when the indoor unit load rate is low when the refrigeration is turned on, thereby improving user comfort.

[0016] In some embodiments, the first frequency is a frequency within a threshold range of a lower limit value of a normal operating frequency range of the compressor;

[0017] The second frequency is a frequency within a threshold range of an upper limit value of a normal operating frequency range of the compressor.

[0018] The above technical solution has the following advantages or beneficial effects: the setting of the first frequency can ensure that the frequency is compatible with the load rate of the indoor unit when it is turned on, and the setting of the second frequency can ensure that the compressor exhaust pressure can completely avoid the indoor refrigerant sound.

[0019] In some embodiments, the multi-link system includes a storage module;

[0020] The storage module is used to store different first target exhaust pressure values ​​corresponding to different startup indoor unit load rate intervals, or to store the correlation between the startup indoor unit load rate and the first target exhaust pressure value;

[0021] The control module is configured to determine a first target exhaust pressure value according to the load rate of the indoor unit being powered on and the storage module.

[0022] The control module is configured to determine the start-up indoor unit load rate interval according to the start-up indoor unit load rate, and determine a first target exhaust pressure value corresponding to the start-up indoor unit load rate interval as the exhaust pressure target value of the compressor.

[0023] The control module is configured to determine the first target exhaust pressure value according to the correlation between the load rate of the indoor unit when it is turned on and the first target exhaust pressure value, and use the first target exhaust pressure value as the exhaust pressure target value of the compressor.

[0024] The above technical solution has the following advantages or beneficial effects: the first target exhaust pressure value of the multi-split system is not a fixed value, but is adjusted and determined according to the load rate of the indoor unit when it is turned on. The corresponding relationship between the load rate of the indoor unit when it is turned on and the first target exhaust pressure value for avoiding the indoor refrigerant sound is determined in advance. Therefore, the first target exhaust pressure value can be more accurately adapted to the load rate of the indoor unit when it is turned on, so that when the low load rate condition is met, any load rate of the indoor unit when it is turned on can better reduce the indoor refrigerant sound.

[0025] In some embodiments, the startup indoor unit load rate interval is negatively correlated with the first target exhaust pressure value, or the startup indoor unit load rate is negatively correlated with the first target exhaust pressure value.

[0026] The above technical solution has the following advantages or beneficial effects: when the load rate of the indoor unit of the multi-split system is low, the first target exhaust pressure value is large, and when the load rate of the indoor unit is high, the first target exhaust pressure value is small, so as to ensure that the indoor refrigerant noise can be better reduced at any load rate of the indoor unit, especially when the load rate of the indoor unit is low.

[0027] In some embodiments, the multi-link system includes:

[0028] A storage module, used to store different outdoor fan gears or speeds corresponding to a plurality of different first target exhaust pressure values, or to store an association between the first target exhaust pressure value and the outdoor fan gear or speed;

[0029] The control module is configured to determine the gear position or speed of the outdoor fan according to the first target exhaust pressure value and the storage module.

[0030] The control module is configured to determine the gear position or speed of the outdoor fan according to the correlation between the first target exhaust pressure value and the outdoor fan speed, and control the outdoor fan to operate at the above gear position or speed.

[0031] The above technical solution has the following advantages or beneficial effects: the multi-split system adjusts the compressor exhaust pressure by adjusting the outdoor fan gear or speed, and determines in advance the correspondence between the outdoor fan gear or speed and the first target exhaust pressure value. Therefore, the compressor exhaust pressure can quickly reach the required first target exhaust pressure value, avoiding the refrigerant sound of the indoor unit.

[0032] In some embodiments, the outdoor fan gear position or speed is negatively correlated with the first target exhaust pressure value.

[0033] The above technical solution has the following advantages or beneficial effects: when the first target exhaust pressure value is small, the outdoor fan gear or speed is large in the multi-split system, and when the first target exhaust pressure value is large, the outdoor fan gear or speed is small, so as to ensure that the compressor exhaust pressure quickly reaches the required first target exhaust pressure value.

[0034] In some embodiments, the control module is configured to control the operating frequency of the compressor to a frequency lower than the first frequency when the load rate of the indoor unit is lower than the set load rate.

[0035] The above technical solution has the following advantages or beneficial effects: the multi-split system can further reduce the operating frequency to be lower than the first frequency, and can better adapt to the low startup indoor unit load rate requirements by reducing the operating frequency.

[0036] In some embodiments, the first target exhaust pressure value is between the first exhaust pressure value and the second exhaust pressure value; the control module is configured such that during an increase in exhaust pressure, when the exhaust pressure is below the second exhaust pressure value, the operating frequency of the compressor is limited to above a third frequency, and when the exhaust pressure is above the second exhaust pressure value, the operating frequency of the compressor is limited to above the first frequency; during a decrease in exhaust pressure, when the exhaust pressure is above the first exhaust pressure value, the operating frequency of the compressor is limited to above the first frequency, and when the exhaust pressure is below the first exhaust pressure value, the operating frequency of the compressor is limited to above the third frequency; the third frequency < the first frequency.

[0037] The above technical solution has the following advantages or beneficial effects: associating the lower limit of the compressor operating frequency with the compressor exhaust pressure can ensure the reliability of the compressor drive, the noise of the compressor body and the piping stress problem, and setting the hysteresis between the first exhaust pressure and the second exhaust pressure can prevent frequency fluctuations.

[0038] In some embodiments, the indoor unit includes an indoor heat exchanger and an indoor expansion valve;

[0039] The system includes:

[0040] An exhaust temperature detection module is used to detect the exhaust temperature of the compressor;

[0041] Indoor temperature detection module, used to detect indoor temperature;

[0042] A set temperature acquisition module is used to obtain the set temperature;

[0043] The control module is configured to determine the target value of the indoor heat exchanger outlet superheat according to the exhaust temperature of the compressor, the difference between the indoor temperature and the set temperature, and control the opening of the indoor expansion valve so that the indoor heat exchanger outlet superheat reaches the indoor heat exchanger outlet superheat target value or the target value threshold range.

[0044] The above technical solution has the following advantages or beneficial effects: when the load rate of the indoor unit is below the set load rate, the opening of the indoor expansion valve first takes the superheat at the outlet of the indoor unit heat exchanger as the control target, taking into account the exhaust temperature, thereby ensuring that the refrigerant flow of the indoor unit matches the actual load rate of the indoor unit, avoiding the high refrigerant noise caused by the increase in the refrigerant flow. At the same time, taking into account the exhaust temperature, when the exhaust temperature is too high, the target value of the superheat at the outlet of the indoor unit heat exchanger will be reduced to reduce the compressor exhaust temperature and ensure the reliability of the unit operation.

[0045] In some embodiments, the indoor unit comprises:

[0046] Indoor heat exchanger temperature detection module, used to detect the outlet temperature and inlet temperature of the indoor heat exchanger;

[0047] The control module is configured to determine the current indoor heat exchanger outlet superheat based on the indoor heat exchanger outlet temperature and inlet temperature, determine that the difference between the current indoor heat exchanger outlet superheat and the indoor heat exchanger outlet superheat target value is a first difference, determine that the difference between the last indoor heat exchanger outlet superheat and the indoor heat exchanger outlet superheat target value is a second difference, and determine the opening adjustment value of the indoor expansion valve based on the first difference and the second difference.

[0048] The above technical solution has the following advantages or beneficial effects: determining the opening adjustment value of the indoor expansion valve to gradually adjust the opening of the indoor expansion valve.

[0049] In some embodiments, the control module is configured to obtain the minimum and maximum values ​​of the indoor heat exchanger inlet temperature, determine a correction coefficient based on the indoor heat exchanger inlet temperature, maximum and minimum values, and correct the opening adjustment value of the indoor expansion valve using the correction coefficient.

[0050] The above technical solution has the following advantages or beneficial effects: the correction coefficient is determined by the indoor heat exchanger inlet temperature, the minimum value and the maximum value of the indoor heat exchanger inlet temperature, and the opening adjustment value of the indoor expansion valve is corrected by the correction coefficient to further reduce the refrigerant noise and ensure the reliability of the unit operation.

[0051] After reading the specific embodiments of the present invention in conjunction with the accompanying drawings, other features and advantages of the present invention will become more clear. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0053] Figure 1 is a schematic diagram of a multi-link system according to an embodiment;

[0054] Figure 2 is a principle block diagram of a multi-connection system according to an embodiment;

[0055] Figure 3 is a flow chart of a multi-link system according to an embodiment;

[0056] Figure 4 is a principle block diagram of a multi-link system according to an embodiment;

[0057] Figure 5 is a flow chart of a multi-link system according to an embodiment;

[0058] Figure 6 A graph showing the correlation between the lower limit of the compressor operating frequency and the exhaust pressure of the multi-split system according to an embodiment;

[0059] Figure 7 is a flow chart of a multi-link system according to an embodiment;

[0060] Figure 8 is a principle block diagram of a multi-link system according to an embodiment;

[0061] Fig. 9 A flow chart of determining an indoor expansion valve opening adjustment value for a multi-split system according to an embodiment;

[0062] Fig.10 The present invention is a flow chart of determining a correction coefficient of an indoor expansion valve opening adjustment value for a multi-split system according to an embodiment.

[0063] In the figure,

[0064] 1. Compressor;

[0065] 2. Oil separator;

[0066] 3. Gas-liquid separator;

[0067] 4. Four-way valve;

[0068] 5. Outdoor heat exchanger;

[0069] 6. Outdoor fan;

[0070] 7. Outdoor expansion valve;

[0071] 9. Oil return capillary;

[0072] 1O, gas side stop valve;

[0073] 11. Liquid side stop valve;

[0074] 13. First indoor heat exchanger; 14. First indoor expansion valve; 15. First indoor fan;

[0075] 18. Second indoor heat exchanger; 19. Second indoor expansion valve; 20. Second indoor fan;

[0076] 23. nth indoor heat exchanger; 24. nth indoor expansion valve; 25. nth indoor fan. DETAILED DESCRIPTION

[0077] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0078] In the description of the present application, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0079] The terms "first", "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. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise specified, "plurality" means two or more.

[0080] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" 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 it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0081] In the present invention, unless otherwise clearly stipulated and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and 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" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0082] The disclosure below provides many different embodiments or examples to realize different structures of the present invention. In order to simplify the disclosure of the present invention, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present invention. In addition, the present invention can repeat reference numbers and / or reference letters in different examples, and this repetition is for the purpose of simplicity and clarity, which itself does not indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides various specific examples of processes and materials, but those of ordinary skill in the art can be aware of the application of other processes and / or the use of other materials.

[0083] The multi-split system provided in the present application performs a refrigeration cycle of an air conditioner by using a compressor, a condenser, a throttling device and an evaporator. The refrigeration cycle includes a series of processes involving compression, condensation, expansion and evaporation to cool or heat the indoor space.

[0084] The low-temperature and low-pressure refrigerant enters the compressor, which compresses it into high-temperature and high-pressure refrigerant gas and discharges the compressed refrigerant gas. The discharged refrigerant gas flows into the condenser. The condenser condenses the compressed refrigerant into a liquid phase, and the heat is released to the surrounding environment through the condensation process.

[0085] The throttling device expands the high-temperature and high-pressure liquid refrigerant condensed in the condenser into a low-pressure liquid refrigerant. The evaporator evaporates the refrigerant expanded in the throttling device and returns the refrigerant gas in a low-temperature and low-pressure state to the compressor. The evaporator can achieve a cooling effect by utilizing the latent heat of evaporation of the refrigerant to exchange heat with the material to be cooled. In the entire cycle, the air conditioner can adjust the temperature of the indoor space.

[0086] The outdoor unit of the multi-split system refers to the part of the refrigeration cycle including the compressor and the outdoor heat exchanger, and the throttling device is located in the outdoor unit.

[0087] The indoor unit of the multi-split system includes an indoor heat exchanger. The multi-split system includes at least two indoor units, and each indoor unit is provided with an indoor expansion valve. The capacity of the indoor unit is adjusted by adjusting the opening of the indoor expansion valve.

[0088] The indoor heat exchanger and the outdoor heat exchanger function as a condenser or an evaporator. When the indoor heat exchanger functions as a condenser, the air conditioner functions as a heater in a heating state, and when the indoor heat exchanger functions as an evaporator, the air conditioner functions as a cooler in a cooling state.

[0089] exist Figure 1 , Figure 2 In the example, the multi-split system includes an outdoor unit, at least two indoor units, a compressor exhaust pressure detection module and a control module.

[0090] The outdoor unit includes a compressor 1 , an outdoor heat exchanger 5 and an outdoor fan 6 .

[0091] The compressor exhaust pressure detection module is used to detect the exhaust pressure of the compressor.

[0092] Each indoor unit includes an indoor heat exchanger and an indoor expansion valve.

[0093] The control module is configured to determine the load rate of the indoor unit when it is turned on;

[0094] When the load rate of the indoor unit is lower than the set load rate:

[0095] controlling the operating frequency of the compressor to be a first frequency;

[0096] Determine the exhaust pressure target value of the compressor as a first target exhaust pressure value, and control the gear position or speed of the outdoor fan so that the exhaust pressure of the compressor reaches the first target exhaust pressure value;

[0097] Among them, the first target exhaust pressure value is a value within the setting threshold range of the standard exhaust pressure value, and the standard exhaust pressure value corresponds to the exhaust pressure value under standard working conditions, when the indoor unit is fully open and the compressor operates at the second frequency; the first frequency is less than the second frequency.

[0098] The standard operating conditions refer to the standard indoor temperature, outdoor temperature and indoor humidity conditions specified in the air-conditioning field.

[0099] Indoor 27 / 19, outdoor 35 / -, 27, 35 are dry bulb temperatures, 19 is wet bulb temperature, outdoor wet bulb temperature is not specified.

[0100] The multi-split system optimizes the compressor exhaust pressure when the load rate of the indoor unit is low: when the indoor load rate is below the set load rate and the compressor is running at the first frequency, the compressor exhaust pressure is increased to the exhaust pressure value corresponding to the standard working condition, the indoor unit is fully open, and the compressor is running at the second frequency. By increasing the exhaust pressure, the pressure difference between the outdoor heat exchanger and the indoor expansion valve is increased. A large pressure difference can reduce the liquid refrigerant retained at the bottom of the outdoor heat exchanger. Under the action of the pressure difference, more refrigerant flows out of the outdoor heat exchanger to participate in the refrigeration cycle, ensuring the actual refrigerant circulation volume of the multi-split system, and realizing that the refrigerant at the inlet of the indoor unit is in a supercooled state, thereby reducing the indoor unit refrigerant noise when the load rate of the indoor unit is low when the refrigeration is turned on, and improving user comfort.

[0101] exist Figure 1 In the example, the multi-split system includes an outdoor unit and one or more indoor units.

[0102] The outdoor unit includes a compressor 1, an oil separator 2, a gas-liquid separator 3, a four-way valve 4, an outdoor heat exchanger 5, an outdoor fan 6, an outdoor expansion valve 7, an oil return capillary 9, a gas-side stop valve 10, and a liquid-side stop valve 11.

[0103] The indoor unit 1 includes a first indoor heat exchanger 13 , a first indoor expansion valve 14 and a first indoor fan 15 .

[0104] The indoor unit 2 includes a second indoor heat exchanger 18 , a second indoor expansion valve 19 and a second indoor fan 20 .

[0105] The indoor unit n includes an nth indoor heat exchanger 23 , an nth indoor expansion valve 24 and an nth indoor fan 25 .

[0106] After the multi-split system is in the cooling mode and is turned on, the compressor 1 discharges high-temperature and high-pressure refrigerant gas, which flows through the oil separator 2 and then enters the outdoor heat exchanger 5 through the four-way valve 4. The lubricating oil separated in the oil separator 2 returns to the suction port of the compressor 1 through the oil return capillary 9. After being cooled by the outdoor heat exchanger 5, the refrigerant becomes a medium-temperature and high-pressure liquid, and then flows through the outdoor expansion valve 7 and the liquid-side stop valve 11, and is divided into n paths and flows into n indoor units respectively. The medium-temperature and high-pressure refrigerant liquid, after throttling through the expansion valve of the indoor unit in operation (such as the first indoor expansion valve 14 of the indoor unit 1, the second indoor expansion valve 19 of the indoor unit 2, and the nth indoor expansion valve 24 of the indoor unit n), forms a low-temperature and low-pressure two-phase refrigerant, and then flows into the indoor heat exchanger for evaporation and heat absorption to form a superheated refrigerant gas. Finally, it passes through the gas-side stop valve 10 and the four-way valve 4 and returns to the suction port of the compressor 1 to complete the refrigeration cycle.

[0107] In some embodiments, the load rate of the indoor units on (LR) = the total number of indoor units on / the number of outdoor units on.

[0108] In some embodiments, the load rate (LR) of the powered-on indoor unit = the capacity of the powered-on indoor unit / the capacity of the outdoor unit.

[0109] In some embodiments, the load ratio LR' is set to a value determined in advance through experiments.

[0110] In some embodiments, the first frequency is a frequency within a threshold range of a lower limit value of a normal compressor operating frequency range.

[0111] The first frequency is the lower limit threshold ±c of the normal operating frequency of the compressor, where c is a constant determined in advance.

[0112] The second frequency is a frequency within a threshold range of an upper limit value of a normal operating frequency range of the compressor.

[0113] The second frequency is the upper limit threshold value ±d of the normal operating frequency of the compressor, where d is a constant determined in advance.

[0114] The first frequency can make the compressor run at a low frequency. The setting of the first frequency can ensure that the frequency is compatible with the low startup indoor unit load rate. The setting of the second frequency can ensure that the compressor exhaust pressure can completely avoid indoor refrigerant noise. In some embodiments, the standard exhaust pressure value is e1, and the first target exhaust pressure value is e2, and e2 is a value within the threshold range set by e1, that is, e2 is a value within the range of e1±b.

[0115] The multi-connected air-conditioning system reduces the indoor refrigerant noise by optimizing the compressor discharge pressure under low load rate conditions. Under low load rate conditions, the compressor operating frequency is low, the refrigerant flow rate is small, the flow velocity is low, the kinetic energy is low, and the system discharge pressure is low. By adjusting the outdoor fan speed or gear to increase the compressor discharge pressure, the pressure difference between the outdoor heat exchanger and the indoor expansion valve is increased, and the liquid refrigerant remaining at the bottom of the outdoor heat exchanger is reduced. Under the action of the pressure difference, more refrigerant flows out of the outdoor heat exchanger to participate in the refrigeration cycle, ensuring the actual refrigerant circulation volume of the multi-connected air-conditioning system, and achieving a subcooled state of the refrigerant at the inlet of the indoor unit, thereby reducing the indoor refrigerant noise when the load rate of the indoor unit is low at the start of refrigeration.

[0116] Under low load rate conditions, the multi-connected air-conditioning system also causes a low refrigerant condensation temperature in the outdoor heat exchanger, a small heat exchange temperature difference with the environment, and a small heat exchange amount, resulting in no subcooling degree of the refrigerant at the inlet of the indoor unit. By adjusting the outdoor fan speed or gear to increase the compressor discharge pressure, the heat exchange amount between the refrigerant in the outdoor heat exchanger and the environment can also be increased. The state of the refrigerant at the inlet of the indoor unit changes from a two-phase state to a subcooled state, reducing the indoor refrigerant noise.

[0117] In some embodiments, when the ambient temperature is 35°C, the discharge pressure is 2.3 MPa, the corresponding saturation temperature is 39.7°C, and the heat exchange temperature difference between the refrigerant and the atmospheric environment is only 4.7°C; if the refrigerant discharge pressure is increased to 2.8 MPa, the corresponding saturation temperature is 47.66°C, the heat exchange temperature difference between the refrigerant and the atmospheric environment is increased to 12.66°C, the heat exchange amount is increased, the cooling effect of the refrigerant in the outdoor unit heat exchanger by the atmospheric environment is more obvious, the state of the refrigerant at the inlet of the indoor unit changes from a two-phase state to a subcooled state, reducing the indoor refrigerant noise.

[0118] In Figure 3 the example of

[0119] S1. Refrigeration starts.

[0120] S2. Determine the load rate LR of the indoor unit at startup.

[0121] S4. If LR < LR′, yes, go to step S4, otherwise, go to step S7.

[0122] S4. The operating frequency of the compressor is the first frequency.

[0123] S5. Determine that the target value of the compressor discharge pressure is the first target discharge pressure value.

[0124] S6. Control the outdoor fan speed or gear so that the compressor discharge pressure reaches the first target discharge pressure value or the threshold range of the first target discharge pressure value. Go to step S2.

[0125] S7. Enter normal refrigeration operation. Go to step S2.

[0126] exist Figure 4 In an example, the multi-connection system includes a storage module.

[0127] The storage module is used to store different first target exhaust pressure values ​​corresponding to different startup indoor unit load rate intervals.

[0128] The control module is configured to determine a first target exhaust pressure value according to the load rate of the indoor unit being powered on and the storage module.

[0129] The control module is configured to determine the start-up indoor unit load rate interval according to the start-up indoor unit load rate, and determine a first target exhaust pressure value corresponding to the start-up indoor unit load rate interval as the exhaust pressure target value of the compressor.

[0130] In some embodiments, the storage module stores different start-up indoor unit load rate intervals and first target exhaust pressure values ​​in a predetermined correspondence table, as shown in the following table:

[0131] Indoor unit load factor (LR) range when powered on Target exhaust pressure LR<LR 1% e21 LR 1%≤LR<LR 2% e22 LR 2%≤LR<LR 3% e23

[0132] Among them, e21≥e22≥e23.

[0133] In some embodiments, the storage module stores the correlation between the load rate of the powered-on indoor unit and the first target exhaust pressure value.

[0134] The control module is configured to determine a first target exhaust pressure value according to the load rate of the indoor unit being powered on and the storage module.

[0135] The control module is configured to determine the first target exhaust pressure value according to the correlation between the load rate of the indoor unit when it is turned on and the first target exhaust pressure value, and use the first target exhaust pressure value as the exhaust pressure target value of the compressor.

[0136] In some embodiments, the correlation between the load rate of the powered-on indoor unit and the first target exhaust pressure value is a pre-determined functional relationship.

[0137] The first target exhaust pressure value of the multi-split system is not a fixed value, but is adjusted and determined according to the load rate of the indoor unit when it is turned on. The corresponding relationship between the load rate of the indoor unit when it is turned on and the first target exhaust pressure value is determined in advance. Therefore, the first target exhaust pressure value can be more accurately adapted to the load rate of the indoor unit when it is turned on, so that when the low load rate conditions are met, any load rate of the indoor unit when it is turned on can better reduce the indoor refrigerant sound.

[0138] In some embodiments, the startup indoor unit load rate interval is negatively correlated with the first target exhaust pressure value; when the startup indoor unit load rate interval is a large value interval, the first target exhaust pressure value is small; when the startup indoor unit load rate interval is a small value interval, the first target exhaust pressure value is large.

[0139] In some embodiments, the load rate of the indoor unit at startup is negatively correlated with the first target exhaust pressure value; the smaller the load rate of the indoor unit at startup, the larger the first target exhaust pressure value; the larger the load rate of the indoor unit at startup, the smaller the first target exhaust pressure value.

[0140] The multi-connected air-conditioning system has a large first target exhaust pressure value when the load rate of the indoor unit at startup is low, and a small first target exhaust pressure value when the load rate of the indoor unit at startup is high, so as to ensure that the indoor refrigerant noise can be better reduced especially when the load rate of the indoor unit at startup is low.

[0141] In some embodiments, the storage module is used to store the outdoor fan gears or speeds corresponding to a number of different first target exhaust pressure values.

[0142] The control module is configured to determine the outdoor fan gears or speeds according to the first target exhaust pressure value and the storage module.

[0143] In some embodiments, the outdoor fan gears corresponding to the first target exhaust pressure value are shown in the following table:

[0144] The first target exhaust pressure value Outdoor fan position e21 Fo1 e22 Fo2 e23 Fo3

[0145] Wherein, Fo1 ≤ Fo2 ≤ Fo3.

[0146] In some embodiments, when LR 1% ≤ LR < LR 2%, the target exhaust pressure is e22 and the outdoor fan gear is Fo2. When LR = e22, the outdoor fan gear remains Fo2 unchanged. When LR < e22, the fan gear is reduced to Fo1. When LR > e22, the fan gear is increased to Fo3.

[0147] In some embodiments, the storage module is used to store the correlation between the first target exhaust pressure value and the outdoor fan gears or speeds.

[0148] The control module is configured to determine the outdoor fan gears or speeds according to the first target exhaust pressure value and the storage module.

[0149] The control module is configured to determine the outdoor fan gears or speeds according to the correlation between the first target exhaust pressure value and the outdoor fan speed, and control the outdoor fan to operate at the above gears or speeds.

[0150] The multi-connected air-conditioning system adjusts the compressor exhaust pressure by adjusting the outdoor fan gears or speeds, and determines the corresponding relationship between the outdoor fan gears or speeds and the first target exhaust pressure value in advance. Therefore, the compressor exhaust pressure can quickly reach the required first target exhaust pressure value, avoiding the generation of refrigerant noise in the indoor unit.

[0151] In some embodiments, the outdoor fan gear or speed is negatively correlated with the first target exhaust pressure value.

[0152] In the multi-connected air-conditioning system, when the first target exhaust pressure value is small, the outdoor fan gear or speed is large; when the first target exhaust pressure value is large, the outdoor fan gear or speed is small, so as to ensure that the compressor exhaust pressure quickly reaches the required first target exhaust pressure value.

[0153] In Figure 5 the example of

[0154] S1. Refrigeration starts.

[0155] S2. Determine the load ratio LR of the indoor units that are turned on.

[0156] S4. If LR < LR′, go to step S4; otherwise, go to step S7.

[0157] S4. The operating frequency of the compressor is the first frequency.

[0158] S5. Determine the first exhaust pressure target value of the compressor according to LR and the content stored in the storage module.

[0159] S6. Determine the gear or speed of the outdoor fan according to the first exhaust pressure target value of the compressor and the content stored in the storage module, and control the outdoor fan. Then go to step S2.

[0160] S7. Enter normal refrigeration operation. Then go to step S2.

[0161] In some embodiments, the control module is configured to control the operating frequency of the compressor to be a frequency lower than the first frequency when the load ratio of the indoor units that are turned on is below the set load ratio.

[0162] The multi-connected air-conditioning system can further reduce the operating frequency to be lower than the first frequency, so as to better adapt to the demand of the low load ratio of the indoor units that are turned on by reducing the operating frequency.

[0163] In some embodiments, the lower limit threshold of the normal operating frequency range of the compressor is a1.

[0164] When the compressor operates in a stable state, in order to ensure the refrigeration pull-down speed and take into account problems such as noise and piping vibration, a lower limit is set for the stable operating frequency, which is a1. When operating under low load ratio conditions, the compressor operates at the lower limit a1 of the operating frequency. When the load ratio is very small, the theoretically required frequency of the compressor is very small, but due to the limitation of the lower limit a1 of the operating frequency, the compressor can only operate at a frequency a1 greater than the theoretically required frequency. Therefore, the refrigerant flow rate is large, the refrigerant sound is high, and the energy consumption increases. Therefore, for the method of reducing the lower limit of the compressor operating frequency in the heat pump system, the lower limit of the compressor operating frequency is adjusted to a2, where a2 < a1.

[0165] After the lower limit of the compressor operating frequency is adjusted to a2, if the compressor discharge pressure is too high, there will be a risk of reduced reliability of the compressor drive, and the risks of problems such as compressor body noise and piping stress will increase. Therefore, when reducing the lower limit of the compressor operating frequency, it is necessary to associate it with the discharge pressure Pd. When the discharge pressure Pd is too high, the original lower limit of the operating frequency a1 is maintained.

[0166] In some embodiments, the first target discharge pressure value is between the first discharge pressure value Pd1 and the second discharge pressure value Pd2, where Pd1 < Pd2.

[0167] In Figure 6 the example of, the control module is configured such that during the process of increasing the discharge pressure, when the discharge pressure is below the second discharge pressure value Pd2, the operating frequency of the compressor is limited to be above the third frequency a2, and when the discharge pressure is above the second discharge pressure value Pd2, the operating frequency of the compressor is limited to be above the first frequency a1; during the process of decreasing the discharge pressure, when the discharge pressure is above the first discharge pressure value Pd1, the operating frequency of the compressor is limited to be above the first frequency a1, and when the discharge pressure is below the first discharge pressure value Pd1, the operating frequency of the compressor is limited to be above the third frequency a2.

[0168] Associating the lower limit of the compressor operating frequency with the compressor discharge pressure can ensure the reliability of the compressor drive, the noise of the compressor body, and the piping stress problems. Setting a dead band between the first discharge pressure and the second discharge pressure can prevent frequency fluctuations.

[0169] In Figure 7 the example of, the control method for the multi-connected air-conditioning system is as follows:

[0170] S1. Refrigeration starts.

[0171] S2. Determine the load ratio LR of the indoor unit that is turned on.

[0172] S4. If LR < LR′, then go to step S4; otherwise, go to step S12.

[0173] S4. The operating frequency of the compressor is the third frequency a2.

[0174] S5. Determine that the target value of the compressor discharge pressure is the first target discharge pressure value.

[0175] S6. Control the gear or speed of the outdoor fan so that the discharge pressure of the compressor reaches the first target discharge pressure value or the threshold range of the first target discharge pressure value.

[0176] S7. Detect the exhaust pressure of the compressor. During the process of the increase in the exhaust pressure of the compressor, proceed to step S8. During the process of the decrease in the exhaust pressure of the compressor, proceed to step S11.

[0177] S8. If the exhaust pressure Pd < Pd2, then proceed to step S9; otherwise, proceed to step S10.

[0178] S9. The operating frequency of the compressor is the third frequency a2. Proceed to step S2.

[0179] S10. The operating frequency of the compressor is the first frequency a1. Proceed to step S2.

[0180] S11. If the exhaust pressure Pd > Pd1, then proceed to step S10; otherwise, proceed to step S9.

[0181] S12. Enter the normal refrigeration operation. Proceed to step S2.

[0182] In some embodiments, the opening degree of the indoor expansion valve is controlled to avoid indoor refrigerant noise.

[0183] In the prior art, in the stable operation state of the multi-connected air-conditioning system under the refrigeration condition, in order to control the exhaust temperature Td of the compressor within the normal range, the opening degree of the indoor expansion valve is adjusted, and the exhaust temperature of the compressor is controlled by adjusting the refrigerant flow rate.

[0184] When the multi-connected air-conditioning system operates under the low load rate condition, the compressor operates at the first frequency. At this time, due to the oil return of the oil separator 2, the suction temperature of the compressor is increased compared with that at the liquid-side stop valve 11, and both the suction temperature and the suction superheat degree are increased, resulting in an increase in the exhaust temperature of the compressor. To ensure the stability of the exhaust temperature Td of the compressor, the opening degree of the indoor expansion valve is controlled to increase, the refrigerant flow rate is increased, and the refrigerant at the outlet of the indoor unit is not in the superheated state but in the two-phase state, so as to reduce the refrigerant temperature and the suction superheat degree at the suction port of the compressor, and further reduce the exhaust temperature Td of the compressor. In the existing control method, in order to keep the exhaust temperature Td of the compressor stable, the refrigerant at the outlet of the indoor unit heat exchanger is in the two-phase state, the refrigerant flow rate is increased, so that the actual refrigerant flow rate is greater than the theoretically required flow rate, aggravating the phenomenon of high refrigerant noise in the indoor unit. Therefore, a new control strategy for the indoor expansion valve is proposed, and the primary control target of the indoor expansion valve is changed from the exhaust temperature Td of the compressor to the superheat degree at the outlet of the indoor unit heat exchanger.

[0185] In Figure 8 the example of, the multi-connected air-conditioning system includes:

[0186] An exhaust temperature detection module for detecting the exhaust temperature Td of the compressor.

[0187] An indoor temperature detection module for detecting the indoor temperature.

[0188] The set temperature acquisition module is used to obtain the set temperature.

[0189] The control module is configured to determine the target value of the indoor heat exchanger outlet superheat according to the exhaust temperature of the compressor, the difference between the indoor temperature and the set temperature, and control the opening of the indoor expansion valve so that the indoor heat exchanger outlet superheat reaches the indoor heat exchanger outlet superheat target value or the target value threshold range.

[0190] When the load rate of the indoor unit is below the set load rate, the opening of the indoor expansion valve first takes the superheat at the outlet of the indoor unit heat exchanger as the control target, taking into account the exhaust temperature. Therefore, the refrigerant flow of the indoor unit is guaranteed to match the actual load rate of the indoor unit, avoiding the high refrigerant noise caused by the increase of the refrigerant flow. At the same time, the exhaust temperature is taken into account. When the exhaust temperature is too high, the target value of the superheat at the outlet of the indoor unit heat exchanger will be reduced to reduce the exhaust temperature of the compressor and ensure the reliability of the unit operation.

[0191] The indoor unit includes:

[0192] Indoor heat exchanger temperature detection module, used to detect the outlet temperature and inlet temperature of the indoor heat exchanger;

[0193] The control module is configured to determine the current indoor heat exchanger outlet superheat based on the indoor heat exchanger outlet temperature and inlet temperature, determine that the difference between the current indoor heat exchanger outlet superheat and the indoor heat exchanger outlet superheat target value is a first difference, determine that the difference between the last indoor heat exchanger outlet superheat and the indoor heat exchanger outlet superheat target value is a second difference, and determine the opening adjustment value of the indoor expansion valve based on the first difference and the second difference.

[0194] Determine the opening adjustment value of the indoor expansion valve to gradually adjust the opening of the indoor expansion valve.

[0195] The control module is configured to obtain the minimum and maximum values ​​of the indoor heat exchanger inlet temperature, determine a correction coefficient according to the indoor heat exchanger inlet temperature, the maximum and the minimum values, and correct the opening adjustment value of the indoor expansion valve by the correction coefficient.

[0196] The correction coefficient is determined by the indoor heat exchanger inlet temperature, the minimum value and the maximum value of the indoor heat exchanger inlet temperature. The opening adjustment value of the indoor expansion valve is corrected by the correction coefficient to further reduce the refrigerant noise and ensure the reliability of the unit operation.

[0197] In some embodiments, the indoor unit heat exchanger outlet superheat target value Shx is the difference between the indoor temperature and the set temperature. The exhaust temperature Td is related to the following table, where t1, t2, and t3 are The relevant empirical values, Tdm and Tdn are empirical values ​​related to the compressor exhaust temperature Td and the compressor reliability, where Tdm<Tdn, Shx (x=1, 2, . . . , 12) are empirical values.

[0198]

[0199] Indoor expansion valve opening adjustment value

[0200] In the formula, Among them, SH is the actual outlet superheat of the indoor unit heat exchanger, Shx is the target value of the outlet superheat of the indoor unit heat exchanger, The last calculated value.

[0201] The actual indoor unit heat exchanger outlet superheat SH is calculated as: the difference between the indoor heat exchanger refrigerant outlet temperature Tg and the indoor heat exchanger refrigerant inlet temperature Tl, SH = Tg-Tl.

[0202] A and B are coefficients respectively, and C is the coefficient related to the refrigerant outlet temperature Tg of the indoor heat exchanger and the refrigerant inlet temperature Tl of the indoor heat exchanger, which can be calculated as follows:

[0203] C=D*exp[1-(Tl-Tl_min) / (Tl_max-Tl_min)]+E.

[0204] Where Tl_min and Tl_max are the minimum and maximum values ​​of the refrigerant inlet temperature Tl of the indoor unit heat exchanger, respectively, and D and E are the fitting coefficients, respectively.

[0205] exist Fig. 9 In the example of , the process of determining the indoor expansion valve opening adjustment value is:

[0206] S1. Start.

[0207] S2. Obtain the set temperature, detect the exhaust temperature of the compressor, the indoor temperature, and detect the outlet temperature and inlet temperature of the indoor heat exchanger.

[0208] S3. Determine the current indoor heat exchanger outlet superheat according to the indoor heat exchanger outlet temperature and inlet temperature, and determine the indoor heat exchanger outlet superheat target value according to the compressor exhaust temperature, the difference between the indoor temperature and the set temperature.

[0209] S4. Determine that the difference between the current indoor heat exchanger outlet superheat and the indoor heat exchanger outlet superheat target value is a first difference, and determine that the difference between the last indoor heat exchanger outlet superheat and the indoor heat exchanger outlet superheat target value is a second difference.

[0210] S5. Determine an opening adjustment value of the indoor expansion valve according to the first difference and the second difference.

[0211] exist Fig.10 In the example, the process of determining the correction coefficient of the indoor expansion valve opening adjustment value is as follows:

[0212] S1. Start.

[0213] S2. Detect the inlet temperature of the indoor heat exchanger.

[0214] S3. Obtain the minimum and maximum values ​​of the indoor heat exchanger inlet temperature.

[0215] S4. Determine the correction factor based on the indoor heat exchanger inlet temperature, maximum value and minimum value.

[0216] When the multi-split system is running under low load rate conditions, the indoor heat exchanger outlet superheat is first used as the control target, taking into account the compressor exhaust temperature Td, thereby ensuring that the indoor unit refrigerant flow is a flow that matches the actual load and avoiding the high refrigerant noise caused by the increase in refrigerant flow. At the same time, taking into account Td, when the exhaust temperature Td is too high, the indoor heat exchanger outlet superheat target value will be reduced to reduce the compressor exhaust temperature Td and ensure the reliability of the unit operation.

[0217] In the description of the above embodiments, specific features, structures, materials or characteristics may be combined in a suitable manner in any one or more embodiments or examples.

[0218] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention 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 multi-link system, comprising: The outdoor unit includes a compressor, an outdoor heat exchanger and an outdoor fan; At least two indoor units; An exhaust pressure detection module is used to detect the exhaust pressure of the compressor; It is characterized by further comprising: A control module configured to determine a load rate of a powered-on indoor unit; When the load rate of the indoor unit is lower than the set load rate: controlling the operating frequency of the compressor to be a first frequency; Determine the exhaust pressure target value of the compressor as a first target exhaust pressure value, and control the gear position or speed of the outdoor fan so that the exhaust pressure of the compressor reaches the first target exhaust pressure value; Among them, the first target exhaust pressure value is a value within the setting threshold range of the standard exhaust pressure value, and the standard exhaust pressure value corresponds to the exhaust pressure value under standard working conditions, when the indoor unit is fully open and the compressor operates at the second frequency; the first frequency is less than the second frequency.

2. The multi-connection system according to claim 1, characterized in that: The first frequency is a frequency within a threshold range of a lower limit value of a normal operating frequency range of the compressor; The second frequency is a frequency within a threshold range of an upper limit value of a normal operating frequency range of the compressor.

3. The multi-connection system according to claim 1, characterized in that: The multi-connection system includes a storage module; The storage module is used to store different first target exhaust pressure values ​​corresponding to a number of different startup indoor unit load rate intervals, or to store the correlation between the startup indoor unit load rate and the first target exhaust pressure value; The control module is configured to determine a first target exhaust pressure value according to the load rate of the indoor unit being powered on and the storage module.

4. The multi-connection system according to claim 3, characterized in that: The startup indoor unit load rate interval is negatively correlated with the first target exhaust pressure value, or the startup indoor unit load rate is negatively correlated with the first target exhaust pressure value.

5. The multi-connection system according to claim 1, characterized in that: The multi-connection system comprises: A storage module, used to store different outdoor fan gears or speeds corresponding to different first target exhaust pressure values, or to store an association between the first target exhaust pressure value and the outdoor fan gear or speed; The control module is configured to determine the gear position or speed of the outdoor fan according to the first target exhaust pressure value and the storage module; The outdoor fan gear position or speed is negatively correlated with the first target exhaust pressure value.

6. The multi-connection system according to claim 1, characterized in that: The control module is configured to control the operating frequency of the compressor to be a frequency lower than the first frequency when the load rate of the indoor unit is lower than the set load rate.

7. The multi-connection system according to claim 6, characterized in that: The first target exhaust pressure value is between the first exhaust pressure value and the second exhaust pressure value; The control module is configured such that, during an increase in exhaust pressure, when the exhaust pressure is below a second exhaust pressure value, the operating frequency of the compressor is limited to above a third frequency, and when the exhaust pressure is above the second exhaust pressure value, the operating frequency of the compressor is limited to above the first frequency; during a decrease in exhaust pressure, when the exhaust pressure is above the first exhaust pressure value, the operating frequency of the compressor is limited to above the first frequency, and when the exhaust pressure is below the first exhaust pressure value, the operating frequency of the compressor is limited to above the third frequency; the third frequency < the first frequency.

8. The multi-connection system according to any one of claims 1 to 7, characterized in that: The indoor unit includes an indoor heat exchanger and an indoor expansion valve; The system includes: An exhaust temperature detection module is used to detect the exhaust temperature of the compressor; Indoor temperature detection module, used to detect indoor temperature; A set temperature acquisition module is used to obtain the set temperature; The control module is configured to determine the target value of the indoor heat exchanger outlet superheat according to the exhaust temperature of the compressor, the difference between the indoor temperature and the set temperature, and control the opening of the indoor expansion valve so that the indoor heat exchanger outlet superheat reaches the indoor heat exchanger outlet superheat target value or the target value threshold range.

9. The multi-connection system according to claim 8, characterized in that: The indoor unit comprises: Indoor heat exchanger temperature detection module, used to detect the outlet temperature and inlet temperature of the indoor heat exchanger; The control module is configured to determine the current indoor heat exchanger outlet superheat based on the indoor heat exchanger outlet temperature and inlet temperature, determine that the difference between the current indoor heat exchanger outlet superheat and the indoor heat exchanger outlet superheat target value is a first difference, determine that the difference between the last indoor heat exchanger outlet superheat and the indoor heat exchanger outlet superheat target value is a second difference, and determine the opening adjustment value of the indoor expansion valve based on the first difference and the second difference.

10. The multi-connection system according to claim 9, characterized in that: The control module is configured to obtain the minimum and maximum values ​​of the indoor heat exchanger inlet temperature, determine a correction coefficient according to the indoor heat exchanger inlet temperature, the maximum and the minimum values, and correct the opening adjustment value of the indoor expansion valve by the correction coefficient.

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