Multi-connected system noise control method and device and multi-connected system

Abstract

The application provides a multi-connected system noise control method and device and a multi-connected system. The method comprises the following steps: obtaining the exhaust pressure corresponding saturated temperature and condensation temperature of each indoor unit, and calculating the difference between the saturated temperature and the condensation temperature of each indoor unit; the condensation temperature is the temperature collected by the liquid pipe temperature sensing package at the inlet of the electronic expansion valve; if the difference of all indoor units is greater than a first threshold value, the current opening degree of the electronic expansion valve of each indoor unit is maintained; if the difference of part of the indoor units is less than the first threshold value, the opening degree of the electronic expansion valve of the part of the indoor units is reduced so that the difference is greater than the first threshold value; if the opening degree of the electronic expansion valve of the part of the indoor units has been adjusted to the minimum opening degree, the opening degree of the electronic expansion valve of the part of the indoor units is increased so that the difference is less than a second threshold value; the second threshold value is less than the first threshold value. The embodiment of the application differentiates the control of the heating standby refrigerant state, thereby reducing the noise of the stopped indoor unit.

Description

Technical Field

[0001] This invention relates to the field of air conditioning noise reduction technology, and more specifically, to a noise control method, device, and multi-split air conditioning system. Background Technology

[0002] When a multi-split air conditioning system is in heating mode, the electronic expansion valve of the indoor unit in the off / standby state needs to maintain a certain small opening to allow refrigerant circulation, preventing liquid buildup in the indoor unit during shutdown and thus avoiding refrigerant shortage during system operation. However, refrigerant flow will generate flow noise, affecting the user experience. Summary of the Invention

[0003] To address the aforementioned problems, this invention provides a noise control method for a multi-split air conditioning system. The multi-split system includes multiple indoor units. The method includes: acquiring the saturation temperature and condensation temperature corresponding to the exhaust pressure of each indoor unit, and calculating the difference between the saturation temperature and the condensation temperature of each indoor unit; the condensation temperature is the temperature collected by the liquid pipe temperature sensor at the inlet of the electronic expansion valve; if the difference for all indoor units is greater than a first threshold, then maintaining the current opening of the electronic expansion valve of each indoor unit; if the difference for some indoor units is less than the first threshold, then reducing the opening of the electronic expansion valve of some indoor units to make the difference greater than the first threshold; if the opening of the electronic expansion valve of some indoor units has been adjusted to the minimum opening, then increasing the opening of the electronic expansion valve of some indoor units to make the difference less than a second threshold; the second threshold is less than the first threshold.

[0004] The noise control method for multi-split air conditioning systems provided in this invention determines the gas-liquid state of the refrigerant flowing through the electronic expansion valve by the difference between the exhaust pressure and the saturation temperature and the condensation temperature. The opening of the electronic expansion valve is controlled to decrease, thereby making the refrigerant fully liquid or to increase, thereby making the refrigerant fully gaseous. By differentially controlling the refrigerant state during heating standby, the noise of the indoor unit during shutdown is reduced.

[0005] Optionally, the method further includes: if the difference between all the indoor units is less than the first threshold, then determining the frequently used indoor units and the infrequently used indoor units based on the operating frequency and / or operating duration of each indoor unit; if the indoor unit is a frequently used indoor unit, then reducing the opening degree of the electronic expansion valve of the frequently used indoor unit to make the difference greater than the first threshold; if the indoor unit is an infrequently used indoor unit, then increasing the opening degree of the electronic expansion valve of the infrequently used indoor unit to make the difference less than the second threshold.

[0006] In this embodiment of the invention, if the difference between all indoor units is less than the first threshold, then the above indoor units need to be controlled differently to avoid reliability risks caused by all gas or all liquid refrigerant. For frequently used indoor units, the control target is all liquid control, and for infrequently used indoor units, the control target is switched to all gas control.

[0007] Optionally, determining the frequently used and infrequently used indoor units based on the operating time of each indoor unit includes: obtaining the average operating time of all indoor units; if the operating time of any indoor unit is greater than the average operating time, it is determined to be a frequently used indoor unit, otherwise it is determined to be an infrequently used indoor unit.

[0008] In this embodiment of the invention, by measuring the average operating time of all indoor units, indoor units with an operating time greater than the average operating time are identified as frequently used indoor units, and the rest are identified as infrequently used indoor units. This allows for an accurate calculation of whether an indoor unit is frequently used or not, thereby improving the effect of differentiated control.

[0009] Optionally, the method further includes: if the difference of all the indoor units is greater than a first threshold, then increasing the current opening of the electronic expansion valve of each indoor unit.

[0010] In this embodiment of the invention, the current opening degree of the electronic expansion valve of each indoor unit can be increased, thereby increasing the amount of refrigerant circulating in the shut-down indoor unit to a certain extent and reducing the risk of liquid accumulation in the indoor unit. After increasing the opening degree of the electronic expansion valve, the above difference may decrease to be equal to or less than the first threshold. In this case, it is necessary to further reduce the opening degree of the electronic expansion valve to maintain the subcooled state.

[0011] Optionally, the first threshold value ranges from 3 to 7.

[0012] Optionally, the value range of the second threshold is -2 to 1.

[0013] Optionally, the first threshold is 5 and the second threshold is 0.

[0014] The embodiments of the present invention provide the value range and typical value of each threshold, which can be used to achieve differentiated control of the refrigerant state during heating standby and reduce the noise of the indoor unit when it is stopped.

[0015] This invention provides a noise control device for a multi-split air conditioning system. The multi-split system includes multiple indoor units. The device includes: an acquisition module, used to acquire the saturation temperature and condensation temperature corresponding to the exhaust pressure of each indoor unit, and to calculate the difference between the saturation temperature and the condensation temperature of each indoor unit; the condensation temperature is the temperature collected by the liquid pipe temperature sensor at the inlet of the electronic expansion valve; and an adjustment module, used to: maintain the current opening degree of the electronic expansion valve of each indoor unit if the difference degree of all indoor units is greater than a first threshold; reduce the opening degree of the electronic expansion valve of some indoor units to make the difference greater than the first threshold if the difference degree of some indoor units is less than the first threshold; and increase the opening degree of the electronic expansion valve of some indoor units to make the difference less than a second threshold if the opening degree of the electronic expansion valve of some indoor units has been adjusted to the minimum opening degree; the second threshold is less than the first threshold.

[0016] This invention provides a multi-split air conditioning system, characterized in that the multi-split air conditioning system includes multiple indoor units and the aforementioned multi-split air conditioning system noise control device.

[0017] This invention provides a computer-readable storage medium storing a computer program, which is read and executed by a processor to implement the above-described method.

[0018] The noise control device and multi-split air conditioning system of the present invention can achieve the same technical effect as the noise control method of the multi-split air conditioning system described above. Attached Figure Description

[0019] Figure 1 This is a pressure-enthalpy diagram in an embodiment of the present invention;

[0020] Figure 2 This is a schematic flowchart of a noise control method for a multi-unit air conditioning system according to an embodiment of the present invention;

[0021] Figure 3 This is a schematic diagram of the structure of a noise control device for a multi-unit air conditioning system according to an embodiment of the present invention. Detailed Implementation

[0022] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0023] The noise mechanism analysis of this invention embodiment is as follows: The noise during heating shutdown is mainly generated by the refrigerant flowing through the electronic expansion valve of the indoor unit. Further analysis reveals that at the inlet of the electronic expansion valve, the refrigerant state is affected by factors such as control and pipeline pressure loss, resulting in different refrigerant states at the valve port, typically categorized into three states: fully liquid, gas-liquid mixture, and fully gaseous. Among these, the fully liquid stable flow generates relatively little noise; in the fully gaseous state, a stable annular flow is formed, and the liquid film adhering to the wall partially blocks the outward propagation of noise, resulting in less noise; in the gas-liquid mixture state, the refrigerant flow contains a large number of air bubbles, which impact the valve needle of the electronic expansion valve, and the air bubbles are crushed as they pass through the electronic expansion valve, generating discontinuous "gurgling" noise, which is one of the main complaints from users during heating standby.

[0024] This invention, in conjunction with the noise generation mechanism, reduces operating noise by differentially controlling the target supercooling.

[0025] The refrigerant status detection and judgment are as follows:

[0026] During heating, the indoor unit is the condenser side. The high-temperature, high-pressure gaseous refrigerant undergoes heat exchange and condenses into a medium-temperature, high-pressure liquid refrigerant. If condensation is insufficient, it will be a two-phase system consisting of a gaseous component and a liquid component. According to... Figure 1 As shown in the pressure-enthalpy diagram, when the temperature is to the left of the saturation line, it is undercooled and the refrigerant is in a completely liquid state; when the temperature is to the right of the saturation line, it is superheated and the refrigerant is in a completely gaseous state; the temperature between the saturation lines indicates a two-phase gas-liquid relationship. Figure 1 The two curves to the left and right are saturation lines. The area between the saturation lines is liquid, and the area outside is gaseous.

[0027] The formula for calculating saturation is: Exhaust pressure corresponding to saturation temperature - condensation temperature = 0.

[0028] In the formula: the exhaust pressure corresponds to the saturation temperature, which is the temperature converted from the pressure detected by the high-pressure pressure sensor (obtainable from the pressure-temperature comparison table); the condensation temperature is the temperature of the liquid tube sensing bulb at the inlet of the electronic expansion valve.

[0029] Therefore, the refrigerant state can be calculated from the saturated state:

[0030] 1) Fully liquid state: Exhaust pressure corresponds to saturation temperature - condensation temperature ≥ a

[0031] 2) All gaseous state: Exhaust pressure corresponds to saturation temperature - condensation temperature < c

[0032] 3) Gas-liquid mixture: c ≤ exhaust pressure corresponding to saturation temperature - condensation temperature < a

[0033] In the formula, the preferred value of a is 5, and the value ranges from 3 to 7. This value represents the pipeline pressure loss (due to the pressure loss of the connecting pipeline between the indoor and outdoor units. In order to ensure that the state entering the indoor unit is pure liquid, a certain degree of subcooling needs to be maintained); the preferred value of c is 0, and the value ranges from -2 to 1.

[0034] The noise of the electronic expansion valve depends on the state of the refrigerant, which in turn depends on the control of the subcooling at the inlet of the electronic expansion valve. If the subcooling is large, the refrigerant is in a liquid state; otherwise, it is in a gas-liquid mixture or a gaseous state.

[0035] The noise reduction control principle is as follows:

[0036] Since the indoor unit fan is off during shutdown, the condensation is achieved through natural convection heat transfer, and the condensation amount is constant under the same conditions. When the refrigerant flow rate is low, the heat transfer formula is as follows:

[0037] Q=(t1-t2)hA

[0038] Where Q is the heat, h is the overall heat transfer coefficient of the system, and A is the inner surface area of ​​the evaporator. t1 is the evaporator surface temperature, and t2 is the air temperature.

[0039] From the above formula, we can see that the heat transfer is constant. The outlet temperature of the indoor heat exchanger is determined based on the following formula:

[0040] Q = (t3 - t4)C V ρV

[0041] Among them, C V Let ρ be the constant-volume specific heat of the fluid inside the pipe, ρ be the fluid density, and V be the fluid volume in the evaporator. t3 is the inlet temperature, t4 is the outlet temperature; Derivation:

[0042]

[0043] According to the formula on the right, the smaller the volumetric flow rate, the smaller the subcooling. Conversely, the same amount of condensation will result in a larger temperature difference.

[0044] When the refrigerant flow rate is high, the same condensation volume will result in a smaller temperature difference. The refrigerant flow rate is regulated by an electronic expansion valve. Therefore, when the temperature difference is small, the electronic expansion valve can be closed to reduce the refrigerant flow rate and achieve a greater degree of subcooling (subcooling is the high-pressure saturation temperature minus the electronic expansion valve inlet temperature). However, due to the limited adjustment range of the valve body, in some scenarios (such as high-temperature heating), it is not possible to guarantee that all indoor units are in a subcooled state (i.e., fully liquid). Therefore, differentiated control of indoor units in different rooms is required.

[0045] Figure 2 A schematic flowchart of a noise control method for a multi-split air conditioning system according to an embodiment of the present invention is shown. The multi-split air conditioning system includes multiple indoor units, and the method includes the following steps:

[0046] S202, obtain the saturation temperature and condensation temperature corresponding to the exhaust pressure of each indoor unit, and calculate the difference between the saturation temperature and condensation temperature of each indoor unit.

[0047] The condensation temperature is the temperature collected by the liquid tube sensing bulb at the inlet of the electronic expansion valve.

[0048] In existing multi-split air conditioning systems, the high-pressure side is connected, resulting in pressure equilibrium (negligible pressure loss in the piping). Since the condensing temperature is located at the inlet of the electronic expansion valve, this embodiment uses both high-pressure and condensing temperature parameters for more accurate subcooling calculation. Existing technologies using coil temperature and exhaust temperature control schemes suffer from significantly increased calculation deviations and poor control performance because the coil temperature is higher than the pressure.

[0049] S204, if the difference between all indoor units is greater than the first threshold, then maintain the current opening of the electronic expansion valve of each indoor unit.

[0050] This indicates that all indoor units are in a sub-cooled state, with low noise, and can maintain the current control status.

[0051] Optionally, in the above situation, the current opening degree of the electronic expansion valve of each indoor unit can be increased, thereby increasing the amount of refrigerant circulating in the shut-down indoor unit to a certain extent and reducing the risk of liquid accumulation in the indoor unit. After increasing the opening degree of the electronic expansion valve, the above difference may decrease to be equal to or less than the first threshold. In this case, it is necessary to further reduce the opening degree of the electronic expansion valve to maintain the subcooled state.

[0052] S206, if the difference between some indoor units is less than the first threshold, then the opening of the electronic expansion valve of the aforementioned indoor units is reduced so that the difference is greater than the first threshold.

[0053] This indicates that the refrigerant in some indoor units is in a gas-liquid mixed state when it flows through the electronic expansion valve. Therefore, the opening of the electronic expansion valve can be reduced to make the refrigerant appear as a fully liquid state.

[0054] S208, if the opening degree of the electronic expansion valve of the above-mentioned indoor unit has been adjusted to the minimum opening degree, then the opening degree of the electronic expansion valve of the above-mentioned indoor unit is increased so that the difference is less than the second threshold.

[0055] If the opening of the electronic expansion valve of the aforementioned indoor unit is reduced to its adjustment limit and still cannot meet the requirements of a fully liquid state, it is necessary to control it to present a fully gaseous state. Based on this, the opening of the electronic expansion valve of the aforementioned indoor unit can be increased until the difference is less than the second threshold, thereby making the refrigerant present a fully gaseous state.

[0056] The noise control method for multi-split air conditioning systems provided in this invention determines the gas-liquid state of the refrigerant flowing through the electronic expansion valve by the difference between the exhaust pressure and the saturation temperature and the condensation temperature. The opening of the electronic expansion valve is controlled to decrease, thereby making the refrigerant fully liquid or to increase, thereby making the refrigerant fully gaseous. By differentially controlling the refrigerant state during heating standby, the noise of the indoor unit during shutdown is reduced.

[0057] Furthermore, if the differences in all indoor units are less than the first threshold, then differentiated control needs to be implemented for each indoor unit to avoid reliability risks caused by all-gas or all-liquid refrigerant. Based on this, the above method may also include the following steps:

[0058] If the difference between all indoor units is less than the first threshold, then the frequently used indoor units and infrequently used indoor units are determined based on the frequency and / or duration of each indoor unit's operation. Indoor units with higher operation frequency are determined to be frequently used indoor units, and those with longer operation duration are determined to be frequently used indoor units.

[0059] If the above-mentioned indoor unit is a frequently used indoor unit, the opening of the electronic expansion valve of the frequently used indoor unit will be reduced so that the difference is greater than the first threshold; if the above-mentioned indoor unit is a rarely used indoor unit, the opening of the electronic expansion valve of the rarely used indoor unit will be increased so that the difference is less than the second threshold.

[0060] For frequently used indoor units, the control objective is to use full liquid control; for infrequently used indoor units, the control objective is to switch to full gas control.

[0061] Optionally, frequently used and infrequently used indoor units can be determined based on the following method: obtaining the average operating time of all indoor units; if the operating time of any indoor unit is greater than the average operating time, it is determined to be a frequently used indoor unit; otherwise, it is determined to be an infrequently used indoor unit. By using the average operating time of all indoor units, indoor units with operating times greater than the average operating time are determined to be frequently used indoor units, and the rest are determined to be infrequently used indoor units, thereby accurately calculating whether an indoor unit is frequently used or not, and improving the effect of differentiated control.

[0062] Optionally, the value range of the first threshold is 3 to 7.

[0063] Optionally, the value range of the second threshold is -2 to 1.

[0064] For example, the first threshold is 5 and the second threshold is 0.

[0065] The following details the control logic for the opening degree of the electronic expansion valve in different states.

[0066] State 1: All indoor unit exhaust pressure corresponds to saturation temperature - condensation temperature ≥ a

[0067] Control action: At this time, it indicates that all indoor units are in a subcooled state with relatively low noise. The current control is maintained. That is, when the indoor unit exhaust pressure corresponds to the saturation temperature minus the condensing temperature > a, the opening of the indoor unit's electronic expansion valve increases, and vice versa.

[0068] State 2: The exhaust pressure of some indoor units corresponds to the saturation temperature minus the condensation temperature < a, and the opening of the electronic expansion valve of this part of the indoor unit is already at its minimum;

[0069] Control Actions: ① For indoor units where the exhaust pressure corresponds to saturation temperature - condensation temperature ≥ a, maintain normal control; ② For indoor units where the exhaust pressure corresponds to saturation temperature - condensation temperature < a, this indicates that the electronic expansion valve has reached its adjustment limit and still cannot meet the requirements of the fully liquid state. Therefore, the gas-liquid mixture state poses a high noise risk and needs to be adjusted to a fully gaseous state, as follows:

[0070] For indoor units with exhaust pressure corresponding to saturation temperature - condensation temperature < a, the target subcooling of the indoor unit changes from a to c. By controlling the entire gas state, the noise risk is reduced.

[0071] State 3: The exhaust pressure of all indoor units corresponds to the saturation temperature minus the condensation temperature < a, and the opening of the electronic expansion valve of the indoor unit is already at its minimum;

[0072] Control actions: At this time, based on usage habits, it is estimated which rooms are frequently used and which are infrequently used, usually based on the frequency of opening and the duration of opening.

[0073] Calculation method: If the average operating time of room h1 is greater than or equal to the average operating time of all rooms, it is considered a frequently used room; otherwise, it is considered an infrequently used room. Specifically, frequently used rooms are controlled under full liquid state; infrequently used rooms are controlled under full gaseous state.

[0074] The multi-split air conditioning noise control method provided in this embodiment of the invention reduces indoor unit noise during shutdown by differentially controlling the refrigerant state during heating standby; and avoids reliability risks caused by all-gas or all-liquid refrigerant control through differential control.

[0075] Figure 3 This diagram illustrates a structural schematic of a noise control device for a multi-split air conditioning system according to an embodiment of the present invention. The multi-split air conditioning system includes multiple indoor units, and the device includes:

[0076] The acquisition module 301 is used to acquire the saturation temperature and condensation temperature corresponding to the exhaust pressure of each indoor unit, and to calculate the difference between the saturation temperature and the condensation temperature of each indoor unit; the condensation temperature is the temperature collected by the liquid pipe temperature sensor at the inlet of the electronic expansion valve.

[0077] The adjustment module 302 is used to maintain the current opening degree of the electronic expansion valve of each indoor unit if the difference value of all indoor units is greater than the first threshold.

[0078] If the difference between some of the indoor units is less than the first threshold, then the opening of the electronic expansion valve of some of the indoor units is reduced so that the difference is greater than the first threshold.

[0079] If the opening degree of the electronic expansion valve of some of the indoor units has been adjusted to the minimum opening degree, the opening degree of the electronic expansion valve of some of the indoor units will be increased so that the difference is less than the second threshold; the second threshold is less than the first threshold.

[0080] The noise control device for multi-split air conditioning systems provided in this invention determines the gas-liquid state of the refrigerant flowing through the electronic expansion valve by the difference between the exhaust pressure and the saturation temperature and the condensation temperature. It controls the opening of the electronic expansion valve to decrease so that the refrigerant is in a fully liquid state or controls the opening of the electronic expansion valve to increase so that the refrigerant is in a fully gaseous state. By differentially controlling the refrigerant state during heating standby, the noise of the indoor unit when the system is off is reduced.

[0081] As a possible approach, the adjustment module is further configured to: if the difference between all the indoor units is less than the first threshold, determine the frequently used indoor unit and the infrequently used indoor unit based on the operating frequency and / or operating duration of each indoor unit; if the indoor unit is a frequently used indoor unit, reduce the opening of the electronic expansion valve of the frequently used indoor unit to make the difference greater than the first threshold; if the indoor unit is an infrequently used indoor unit, increase the opening of the electronic expansion valve of the infrequently used indoor unit to make the difference less than the second threshold.

[0082] As a possible approach, the adjustment module is further configured to: obtain the average operating time of all the indoor units; if the operating time of any indoor unit is greater than the average operating time, it is determined to be a frequently used indoor unit; otherwise, it is determined to be an infrequently used indoor unit.

[0083] As a possible approach, the adjustment module is further configured to: if the difference between all the indoor units is greater than a first threshold, increase the current opening of the electronic expansion valve of each indoor unit.

[0084] As a feasible approach, the first threshold value ranges from 3 to 7.

[0085] As a feasible approach, the second threshold can be in the range of -2 to 1.

[0086] As a feasible approach, the first threshold is set to 5, and the second threshold is set to 0.

[0087] This invention provides a multi-split air conditioning system, which includes multiple indoor units and a noise control device for the multi-split air conditioning system.

[0088] This invention also provides a computer-readable storage medium storing a computer program. When the computer program is read and executed by a processor, it implements the method provided in the above embodiments and achieves the same technical effect. To avoid repetition, further details are omitted here. The computer-readable storage medium may be a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0089] Of course, those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by computer-controlled devices. The program can be stored in a computer-readable storage medium. When the program is executed, it can include the processes of the above method embodiments. The storage medium can be a memory, a disk, an optical disk, etc.

[0090] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

[0091] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0092] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0093] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A noise control method for a multi-split air conditioning system, characterized in that, The multi-split air conditioning system includes multiple indoor units, and the method includes: Obtain the saturation temperature and condensation temperature corresponding to the exhaust pressure of each indoor unit, and calculate the difference between the saturation temperature and the condensation temperature of each indoor unit; the condensation temperature is the temperature collected by the liquid pipe temperature sensor at the inlet of the electronic expansion valve. If the difference value of all indoor units is greater than the first threshold, the current opening of the electronic expansion valve of each indoor unit is maintained; or, if the difference value of all indoor units is greater than the first threshold, the current opening of the electronic expansion valve of each indoor unit is increased, and then the opening of the electronic expansion valve is decreased to maintain the subcooling state. If the difference between some of the indoor units is less than the first threshold, then the opening of the electronic expansion valve of some of the indoor units is reduced so that the difference is greater than the first threshold. If the opening degree of the electronic expansion valve of some of the indoor units has been adjusted to the minimum opening degree, then the opening degree of the electronic expansion valve of some of the indoor units will be increased so that the difference is less than the second threshold; the second threshold is less than the first threshold. If the difference between all the indoor units is less than the first threshold, then the frequently used indoor units and the infrequently used indoor units are determined based on the frequency of operation and / or the duration of operation of each indoor unit. If the indoor unit is a commonly used indoor unit, then the opening of the electronic expansion valve of the commonly used indoor unit is reduced so that the difference is greater than the first threshold. If the indoor unit is a rarely used indoor unit, the opening of the electronic expansion valve of the rarely used indoor unit is increased so that the difference is less than the second threshold.

2. The method as described in claim 1, characterized in that, The step of determining frequently used and infrequently used indoor units based on the operating duration of each indoor unit includes: Obtain the average operating time of all the aforementioned indoor units; If the operating time of any of the indoor units is greater than the average operating time, it is determined to be a frequently used indoor unit; otherwise, it is determined to be an infrequently used indoor unit.

3. The method according to any one of claims 1-2, characterized in that, The first threshold value ranges from 3 to 7.

4. The method according to any one of claims 1-2, characterized in that, The second threshold value ranges from -2 to 1.

5. The method according to any one of claims 1-2, characterized in that, The first threshold is 5, and the second threshold is 0.

6. A noise control device for a multi-split air conditioning system, characterized in that, The method of any one of claims 1-5, wherein the multi-split air conditioning system comprises a plurality of indoor units, and the device comprises: The acquisition module is used to acquire the saturation temperature and condensation temperature corresponding to the exhaust pressure of each indoor unit, and to calculate the difference between the saturation temperature and the condensation temperature of each indoor unit; the condensation temperature is the temperature collected by the liquid pipe temperature sensor at the inlet of the electronic expansion valve. The adjustment module is configured to maintain the current opening of the electronic expansion valve of each indoor unit if the difference value of all indoor units is greater than the first threshold; or, if the difference value of all indoor units is greater than the first threshold, increase the current opening of the electronic expansion valve of each indoor unit and then decrease the opening of the electronic expansion valve to maintain the subcooling state. If the difference between some of the indoor units is less than the first threshold, then the opening of the electronic expansion valve of some of the indoor units is reduced so that the difference is greater than the first threshold. If the opening degree of the electronic expansion valve of some of the indoor units has been adjusted to the minimum opening degree, the opening degree of the electronic expansion valve of some of the indoor units will be increased so that the difference is less than the second threshold; the second threshold is less than the first threshold.

7. A multi-split air conditioning system, characterized in that, The multi-split air conditioning system includes multiple indoor units and a noise control device for the multi-split air conditioning system as described in claim 6.

8. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when read and executed by a processor, implements the method as described in any one of claims 1-5.

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