阅读说明：本技术 一种多联机系统的控制方法 (control method of multi-split system ) 是由 李君飞 于 2019-09-12 设计创作，主要内容包括：本发明多联机系统的控制方法,多联机系统包括室外机和多个室内机,室外机包括压缩机、控制阀及室外换热器,室内机包括室内制冷剂支路,多个室内制冷剂支路相互并联,室内制冷剂支路包括室内换热器和电子膨胀阀,电子膨胀阀位于室内换热器与室外换热器之间的连接管道上,控制阀用于控制压缩机排气口与室内制冷剂支路连通、压缩机吸气口与室外换热器连通,部分室内机的安装位置低于其他室内机的安装位置,包括以下步骤：多个室内机进行制热运行、且多个室内换热器的过冷度中最大值小于或等于预设最大过冷度时,根据多联机系统控制参数,调控相应的室内机中电子膨胀阀的开度,以调控相应的室内机的过冷度；控制参数包括多个室内机的温度状态参数。(The invention relates to a control method of a multi-split system, wherein the multi-split system comprises an outdoor unit and a plurality of indoor units, the outdoor unit comprises a compressor, a control valve and an outdoor heat exchanger, the indoor units comprise indoor refrigerant branches, the indoor refrigerant branches are connected in parallel, each indoor refrigerant branch comprises an indoor heat exchanger and an electronic expansion valve, the electronic expansion valves are positioned on a connecting pipeline between the indoor heat exchangers and the outdoor heat exchangers, the control valve is used for controlling the communication between the exhaust port of the compressor and the indoor refrigerant branches and the communication between the suction port of the compressor and the outdoor heat exchangers, and the installation positions of part of the indoor units are lower than the installation positions: when the indoor units perform heating operation and the maximum value in the supercooling degrees of the indoor heat exchangers is less than or equal to the preset maximum supercooling degree, regulating and controlling the opening of an electronic expansion valve in the corresponding indoor unit according to the control parameters of the multi-split system so as to regulate and control the supercooling degree of the corresponding indoor unit; the control parameters comprise temperature state parameters of a plurality of indoor units.)

1. A control method of a multi-split system comprises an outdoor unit and a plurality of indoor units, wherein the outdoor unit comprises a compressor, a control valve and outdoor heat exchangers, each indoor unit comprises an indoor refrigerant branch connected with the outdoor heat exchanger in series, the indoor refrigerant branches are connected in parallel, each indoor refrigerant branch comprises an indoor heat exchanger and an electronic expansion valve which are connected with each other in series, the electronic expansion valve is arranged on a connecting pipeline between the indoor heat exchanger and the outdoor heat exchanger, the control valve is used for controlling an exhaust port of the compressor to be communicated with the outdoor heat exchanger, an air suction port of the compressor to be communicated with the indoor refrigerant branch, or controlling an exhaust port of the compressor to be communicated with the indoor refrigerant branch and an air suction port of the compressor to be communicated with the outdoor heat exchanger, the installation positions of part of the indoor units are lower than the installation positions of other indoor units, and the control method is characterized by comprising the following steps:

when the indoor units are in heating operation and the maximum value of the supercooling degrees of the indoor heat exchangers is less than or equal to the preset maximum supercooling degree, regulating and controlling the opening of the electronic expansion valve in the corresponding indoor unit according to the control parameters of the multi-split system so as to regulate and control the supercooling degree of the corresponding indoor unit;

The control parameters comprise temperature state parameters of the indoor units.

2. The method for controlling a multi-split system as claimed in claim 1, wherein the temperature state parameter of the indoor unit is an outlet air temperature of the indoor unit or a refrigerant temperature in a pipe between an indoor heat exchanger of the indoor unit and the electronic expansion valve.

3. The method for controlling a multi-split system according to claim 2, wherein when the temperature state parameter of the indoor unit is an outlet air temperature of the indoor unit, the controlling an opening degree of an electronic expansion valve in the corresponding indoor unit according to the control parameter of the multi-split system to control a supercooling degree of the corresponding indoor unit specifically comprises:

A first acquisition step: acquiring the air outlet temperatures of a plurality of indoor units;

A first calculation step: calculating a first difference value between the maximum value and the minimum value in the outlet air temperatures;

A first regulation step: when the first difference value is larger than or equal to a first preset outlet air temperature difference threshold value, reducing the opening degree of an electronic expansion valve in the indoor unit corresponding to the maximum value so as to increase the supercooling degree of the corresponding indoor heat exchanger, or increasing the opening degree of the electronic expansion valve in the indoor unit corresponding to the minimum value so as to decrease the supercooling degree of the corresponding indoor heat exchanger; and when the first difference value is smaller than the first preset outlet air temperature difference threshold value, keeping the opening degree of the electronic expansion valves in the indoor units.

4. The method for controlling a multi-split system as set forth in claim 3, further comprising, at the first regulating step:

A first circulation step: and returning to the first acquisition step after the first preset time.

5. the method for controlling a multi-split system according to claim 3, wherein the first controlling step specifically includes:

When the first difference value is greater than or equal to the first preset outlet air temperature difference threshold value and smaller than a second preset outlet air temperature difference threshold value, reducing the opening degree of an electronic expansion valve in the indoor unit corresponding to the maximum value so as to adjust the supercooling degree of the corresponding indoor heat exchanger to increase the first preset supercooling degree on the basis of the current supercooling degree;

When the first difference value is greater than or equal to the second preset outlet air temperature difference threshold value and smaller than a third preset outlet air temperature difference threshold value, reducing the opening degree of an electronic expansion valve in the indoor unit corresponding to the maximum value so as to adjust the supercooling degree of the corresponding indoor heat exchanger to increase the second preset supercooling degree on the basis of the current supercooling degree;

When the first difference value is larger than or equal to the third preset outlet air temperature difference threshold value, reducing the opening degree of an electronic expansion valve in the indoor unit corresponding to the maximum value so as to adjust the supercooling degree of the corresponding indoor heat exchanger to increase the third preset supercooling degree on the basis of the current supercooling degree;

The first preset supercooling degree is smaller than the second preset supercooling degree, and the second preset supercooling degree is smaller than the third preset supercooling degree.

6. The method as claimed in claim 2, wherein the control parameter further includes a number of matching values of the indoor units when the temperature state parameter of the indoor units is a refrigerant temperature in a pipe between an indoor heat exchanger of the indoor unit and the electronic expansion valve.

7. The method for controlling a multi-split system according to claim 6, wherein the controlling the opening degree of the electronic expansion valve in the corresponding indoor unit according to the control parameter of the multi-split system to control the supercooling degree of the corresponding indoor unit specifically comprises:

A second acquisition step: acquiring the temperature of refrigerant in pipelines between indoor heat exchangers and the electronic expansion valves in a plurality of indoor units and the matching value of the plurality of indoor units;

a second calculation step: calculating a second difference value between a maximum value and a minimum value in the plurality of refrigerant temperatures and a matching difference value between the indoor unit corresponding to the maximum value and the indoor unit corresponding to the minimum value;

a second regulation and control step: when the matching difference value is smaller than or equal to a preset matching difference value and the second difference value is larger than a first preset refrigerant temperature difference threshold value, or the matching difference value is larger than a preset matching difference value and the second difference value is larger than a second preset refrigerant temperature difference threshold value, reducing the opening degree of an electronic expansion valve in the indoor unit corresponding to the maximum value to increase the supercooling degree of the indoor heat exchanger, or increasing the opening degree of an electronic expansion valve in the indoor unit corresponding to the minimum value to decrease the supercooling degree of the indoor heat exchanger;

And when the matching difference value is smaller than or equal to a preset matching difference value, and the second difference value is smaller than or equal to the first preset refrigerant temperature difference threshold value, or the matching difference value is larger than the preset matching difference value, and the second difference value is smaller than or equal to the second preset refrigerant temperature difference threshold value, keeping the opening degrees of the electronic expansion valves in the indoor units.

8. The method for controlling a multi-split system as set forth in claim 7, further comprising, after the second regulating step:

a second circulation step: and after second preset time, returning to the second acquisition step.

9. The method for controlling a multi-split system according to claim 8, wherein the second controlling step specifically includes:

When the matching difference value is smaller than or equal to a preset matching difference value, the second difference value is larger than a first preset refrigerant temperature difference threshold value and is smaller than or equal to a third preset refrigerant temperature difference threshold value, reducing the opening degree of an electronic expansion valve in the indoor unit corresponding to the maximum value so as to adjust the supercooling degree of the corresponding indoor heat exchanger to increase the first preset supercooling degree on the basis of the current supercooling degree;

When the matching difference value is smaller than or equal to a preset matching difference value, and the second difference value is larger than the third preset refrigerant temperature difference threshold value, reducing the opening degree of an electronic expansion valve in the indoor unit corresponding to the maximum value so as to adjust the supercooling degree of the corresponding indoor heat exchanger to increase a second preset supercooling degree on the basis of the current supercooling degree;

Wherein the first preset supercooling degree is smaller than the second preset supercooling degree.

10. The method for controlling a multi-split system according to claim 8, wherein the second controlling step specifically includes:

When the matching difference value is larger than a preset matching difference value, the second difference value is larger than the second preset refrigerant temperature difference threshold value and is smaller than or equal to a fourth preset refrigerant temperature difference threshold value, reducing the opening degree of an electronic expansion valve in the indoor unit corresponding to the maximum value so as to adjust the supercooling degree of the corresponding indoor heat exchanger to increase a first preset supercooling degree on the basis of the current supercooling degree;

When the matching difference value is larger than a preset matching difference value and the second difference value is larger than a fourth preset refrigerant temperature difference threshold value, reducing the opening degree of an electronic expansion valve in the indoor unit corresponding to the maximum value so as to adjust the supercooling degree of the corresponding indoor heat exchanger to increase a second preset supercooling degree on the basis of the current supercooling degree;

Wherein the first preset supercooling degree is smaller than the second preset supercooling degree.

11. the method for controlling a multi-split system according to claim 5, 9 or 10, wherein the decreasing the opening degree of an electronic expansion valve in an indoor unit corresponding to the maximum value to adjust the supercooling degree of the corresponding indoor heat exchanger to increase the first preset supercooling degree on the basis of the current supercooling degree specifically comprises:

When the sum of the current supercooling degree of the indoor heat exchanger corresponding to the maximum value and a first preset supercooling degree is smaller than or equal to the preset maximum supercooling degree, reducing the opening degree of an electronic expansion valve in the indoor unit corresponding to the maximum value so as to adjust the supercooling degree of the corresponding indoor heat exchanger to increase the first preset supercooling degree on the basis of the current supercooling degree;

And when the sum of the current supercooling degree of the indoor heat exchanger corresponding to the maximum value and a first preset supercooling degree is greater than the preset maximum supercooling degree, reducing the opening degree of an electronic expansion valve in the indoor unit corresponding to the maximum value so as to adjust the supercooling degree of the corresponding indoor heat exchanger to the preset maximum supercooling degree.

Technical Field

The invention relates to the technical field of multi-split air conditioner control, in particular to a control method of a multi-split air conditioner system.

Background

Along with the expansion of the multi-split air conditioner market, the demand of users on multi-split air conditioners is more and more, particularly, the demand of indoor units in the multi-split air conditioners crossing multiple floors is more and more prominent, and the height difference between the indoor unit at the highest position and the indoor unit at the lowest position is even up to 10 m.

the multi-split system includes an outdoor unit and a plurality of indoor units, and refrigerant pressure losses between the indoor units on different floors can be roughly classified into the following three types: (1) pressure drop delta P caused by self gravity of refrigerant₁I.e. Δ P₁Rho is the fluid density, and h is the height difference of the two indoor units; (2) pressure loss delta P caused by friction between refrigerant fluid flowing along refrigerant connecting pipe in multi-split system and inner wall of pipeline₂I.e. Δ P₂fLG/de ρ, where f is the coefficient of friction, L is the length of the pipe, G is the mass flow rate of the refrigerant fluid, and de is the equivalent diameter of the pipe; (3) pressure loss due to changes in fluid density of refrigerant and velocity of refrigerant, i.e. Δ P₃＝G²[(1-x₂)/ρ(1-a₂)+x₂ ²/ρa₂-(1-x₁)²/ρ(1-a₁)-x₁ ²/ρa₁]in the formula x₁Is the gas content, x, of the two-phase flow in the liquid pipe of the first indoor unit₂Is the gas content of the two-phase fluid in the liquid pipe of the second indoor unit, a₁Is the void fraction of the two-phase flow in the first indoor unit, a₂The void fraction of the two-phase flow in the second indoor unit (the first indoor unit and the second indoor unit are located in different layers). In summary, the total pressure loss of the refrigerant between the indoor units on different floors is Δ P ═ Δ P₁+ΔP₂+ΔP₃Because the difference between the outdoor unit and the indoor unit of the multi-split air conditioner generally meets the installation requirement, and the indoor heat exchanger has certain supercooling degree, the liquid pipe of the indoor unit does not have two-phase fluid, namely delta P₃Is 0, so the total pressure loss of the refrigerant is mainly delta P₁and Δ P₂And (4) causing. When a plurality of indoor units in the multi-split air-conditioning system are in heating operation, the refrigerant gas needs to overcome resistance and flow towards the indoor refrigerant branch at a lower position, delta P₁The pressure loss is large, the outlet air temperature difference among a plurality of indoor units is large, and the use comfort of users is affected.

Disclosure of Invention

The invention provides a control method of a multi-split air conditioner system, which is used for solving the problem of large air outlet temperature difference of indoor units caused by large installation fall of a plurality of indoor units in the multi-split air conditioner system.

In order to achieve the purpose, the invention adopts the following technical scheme:

The invention provides a control method of a multi-split system, the multi-split system comprises an outdoor unit and a plurality of indoor units, the outdoor unit comprises a compressor, a control valve and an outdoor heat exchanger, each indoor unit comprises an indoor refrigerant branch connected with the outdoor heat exchanger in series, the indoor refrigerant branches are connected in parallel, each indoor refrigerant branch comprises an indoor heat exchanger and an electronic expansion valve which are connected in series, the electronic expansion valve is positioned on a connecting pipeline between the indoor heat exchanger and the outdoor heat exchanger, the control valve is used for controlling an exhaust port of the compressor to be communicated with the outdoor heat exchanger, an air suction port of the compressor to be communicated with the indoor refrigerant branch, or controlling an exhaust port of the compressor to be communicated with the indoor refrigerant branch and an air suction port of the compressor to be communicated with the outdoor heat exchanger, the installation positions of part of the indoor units are lower than the installation positions of other indoor units, and the control method comprises the following steps: when the indoor units are in heating operation and the maximum value of the supercooling degrees of the indoor heat exchangers is less than or equal to the preset maximum supercooling degree, regulating and controlling the opening of the electronic expansion valve in the corresponding indoor unit according to the control parameters of the multi-split system so as to regulate and control the supercooling degree of the corresponding indoor unit; the control parameters comprise temperature state parameters of the indoor units.

The control method of the multi-split air conditioner system provided by the invention is characterized in that the installation positions of part of indoor units in the multi-split air conditioner system are lower than the installation positions of other indoor units, when a plurality of indoor units perform heating operation and the maximum value in the supercooling degrees of a plurality of indoor heat exchangers is less than or equal to the preset maximum supercooling degree, the air outlet temperature difference conditions of the indoor units in the multi-split air conditioner system can be known according to the temperature state parameters of the indoor units, and when the temperature state parameters of the indoor units indicate that the air outlet temperature difference of the indoor units is smaller, the opening degree of electronic expansion valves in the indoor units can be maintained; when the temperature state parameters of the indoor units indicate that the air outlet temperature difference of the indoor units is large, the opening degree of the electronic expansion valve in the corresponding indoor unit can be adjusted to change the supercooling degree of the corresponding indoor unit, so that the flow of the refrigerant in the corresponding indoor unit is controlled, the heat exchange between the refrigerant in the indoor heat exchanger and indoor air is changed, the air outlet temperature of the indoor unit is adjusted, and the indoor units are guaranteed not to have large temperature difference.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a schematic connection diagram of a multi-split system;

Fig. 2 is a schematic connection diagram of a multi-split system according to an embodiment of the invention;

Fig. 3 is a first control flowchart of a control method of a multi-split system according to an embodiment of the present invention;

Fig. 4 is a flowchart illustrating a first control procedure of a control method of a multi-split system according to an embodiment of the present invention;

Fig. 5 is a schematic control flow diagram of a second control method of a multi-split system according to an embodiment of the invention;

Fig. 6 is a flowchart illustrating a second control procedure of a control method of a multi-split system according to an embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; may be a mechanical connection; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

In the description of the present invention, "and/or" is only one kind of association relationship describing an association object, and means that there may be three kinds of relationships, for example, a and/or B, and may mean: a exists alone, A and B exist simultaneously, and B exists alone. In addition, the character "/" herein generally indicates that the former and latter related objects are in an "or" relationship.

the supercooling degree means a difference that the temperature of a refrigerant condensed at a certain pressure is lower than the saturation temperature at the corresponding pressure.

Referring to fig. 1, the multi-split system includes an outdoor unit and four indoor units, wherein a number 1 indoor unit and a number 2 indoor unit of the four indoor units are located on a first floor, a number 3 indoor unit and a number 4 indoor unit of the four indoor units are located on a second floor, and the first floor is higher than the second floor. Testing different heating operation combinations (one indoor unit heats, two indoor units simultaneously heats, three indoor units simultaneously heats and four indoor units simultaneously heats) of the multi-split air-conditioning system, wherein the difference H between the first floor and the second floor is 0m, 4m and 6.5m respectively, and the outlet air temperature difference To under different differences is obtained_dThe changes in (A) are shown in the following table:

table 1 table of experimental results of outlet air temperature varying with drop

H(m)	0	4	6.5
				Tod(℃)	0	4.7	5.2

As can be seen from table 1, as the drop height between the indoor units increases, the outlet air temperature difference between the indoor units also increases, which affects the comfort of the user.

Referring to fig. 2 and 4, a method for controlling a multi-split system according to an embodiment of the present invention includes an outdoor unit 100 and a plurality of indoor units 200, the outdoor unit 100 includes a compressor 101, a control valve 102, and outdoor heat exchangers 103, each of the indoor units 200 includes an indoor refrigerant branch 210 in which the outdoor heat exchangers 103 are connected in series, the plurality of indoor refrigerant branches 210 are connected in parallel, each of the indoor refrigerant branches 210 includes an indoor heat exchanger 201 and an electronic expansion valve 202 in which the electronic expansion valve 202 is disposed in a connection pipe between the indoor heat exchanger 201 and the outdoor heat exchanger 103, the control valve 102 is configured to control an exhaust port of the compressor 101 to communicate with the outdoor heat exchanger 103, a suction port of the compressor 101 to communicate with the indoor refrigerant branch 210, or an exhaust port of the compressor 101 to communicate with the indoor refrigerant branch 210, and a suction port of the compressor 101 to, the installation positions of some indoor units 200 are lower than the installation positions of other indoor units 200, and the control method comprises the following steps:

When the plurality of indoor units 200 perform a heating operation and the supercooling degrees of the plurality of indoor heat exchangers 201 are the maximum value SC_w(max) is less than or equal to a preset maximum supercooling degree SC_maxoMeanwhile, according to the control parameters of the multi-split system, the opening degree of the electronic expansion valve 202 in the corresponding indoor unit 200 is regulated and controlled to regulate and control the correspondingThe supercooling degree of the indoor unit 200 of (a); the control parameters include temperature state parameters of the indoor units 200.

Whether the indoor unit 200 is in a heating operation state or not can be known from the current position of the valve element in the control valve 102, a pipe between the indoor heat exchanger 201 and the electronic expansion valve 202 of the indoor unit 200 is called a liquid pipe, and a liquid pipe temperature sensor 203 (which may be another temperature detection device) and a pressure sensor are installed in the liquid pipe. When the multi-split system heats, the liquid pipe temperature sensor 203 can detect the temperature value of the refrigerant liquid flowing out of the indoor heat exchanger 201, the pressure sensor can detect the pressure value of the refrigerant liquid flowing out of the indoor heat exchanger 201, the saturation temperature corresponding to the pressure value can be obtained through table lookup, and the supercooling degree of the indoor heat exchanger 201 can be obtained through calculating the difference value between the temperature value and the saturation temperature. The temperature state parameters of the indoor units 200 can be obtained according to temperature detection devices at corresponding positions of the indoor units 200, and the temperature detection devices can be temperature sensors. The multiple on-line system further includes a controller or a control module, where the controller may be specially used for controlling the opening degree of the electronic expansion valve 202, or the control module is a control module in a general controller of the multiple on-line system, and the control module is used for regulating and controlling the opening degree of the electronic expansion valve 202.

the control method of the multi-split air conditioner system provided by the invention is characterized in that the installation position of part of indoor units 200 in the multi-split air conditioner system is lower than the installation positions of other indoor units 200, when a plurality of indoor units 200 are in heating operation and the maximum value of the supercooling degrees of a plurality of indoor heat exchangers 201 is less than or equal to the preset maximum supercooling degree, the air outlet temperature difference of the plurality of indoor units 200 in the multi-split air conditioner system can be known according to the temperature state parameters of the plurality of indoor units 200, and when the temperature state parameters of the plurality of indoor units 200 indicate that the air outlet temperature difference of the indoor units 200 is smaller, the opening degree of electronic expansion valves 202 in the plurality of indoor units 200 can be maintained; when the temperature state parameters of the indoor units 200 indicate that the outlet air temperature difference of the indoor units 200 is large, the opening degree of the electronic expansion valve 202 in the corresponding indoor unit 200 can be adjusted to change the supercooling degree of the corresponding indoor unit 200, so that the flow of the refrigerant in the corresponding indoor unit 200 is controlled, the heat exchange between the refrigerant in the indoor heat exchanger 201 and the indoor air is changed, the outlet air temperature of the indoor unit is adjusted, and the indoor units 200 are ensured not to have large temperature difference.

Further, the temperature state parameter of the indoor unit 200 may be the outlet air temperature To of the indoor unit 200, or may be the refrigerant temperature Tl in the pipe between the indoor heat exchanger 201 and the electronic expansion valve 202 of the indoor unit 200. An air outlet temperature sensor is installed at an air outlet of the indoor unit 200 and used for detecting the temperature at the air outlet of the indoor unit 200; the liquid pipe temperature sensor 203 is installed in the liquid pipe to detect the temperature of the refrigerant in the liquid pipe. The control method of the embodiment of the invention can intuitively know the difference between the outlet air temperatures of the indoor units 200 by detecting the outlet air temperatures of the indoor units 200, or indirectly know the difference between the outlet air temperatures of the indoor units 200 by detecting the temperature of the refrigerant in the liquid pipe. The latter is suitable for the working condition of the indoor unit 200 without the air outlet temperature sensor, and does not need to modify the existing indoor unit 200 and add a detection device.

In some embodiments, referring to fig. 3, when the temperature state parameter of the indoor unit 200 is the outlet air temperature of the indoor unit 200, the adjusting the opening degree of the electronic expansion valve 202 in the corresponding indoor unit 200 according to the control parameter of the multi-split air-conditioning system to adjust the supercooling degree of the corresponding indoor unit 200 specifically includes:

first acquisition step S110: the outlet air temperature To of the indoor units 200 is obtained. The controller or the master controller obtains the outlet air temperature To of the indoor unit 200 from the outlet air temperature sensor.

First calculation step S120: calculating the maximum value To of the multiple outlet air temperatures_maxAnd minimum value To_minfirst difference To between_d(i) In that respect The controller or the master controller further comprises a calculation module, and the calculation module is used for calculating the maximum value To in the plurality of outlet air temperatures_maxAnd minimum value To_minFirst difference To between_d(i)。

a first conditioning step S130: when the first difference To_d(i) Is greater than or equal To a first preset outlet air temperature difference threshold To_d1When the temperature of the indoor heat exchanger 201 in the indoor unit 200 is higher than the temperature of the electronic expansion valve 202 in the indoor unit 200, the opening degree of the electronic expansion valve 202 in the indoor unit 200 corresponding to the maximum value is increased, or the opening degree of the electronic expansion valve 202 in the indoor unit 200 corresponding to the minimum value is increased, so that the supercooling degree of the indoor heat exchanger 201 in the indoor unit 200 is increased; when the first difference To_d(i) Is less than a first preset outlet air temperature difference threshold To_d1At this time, the opening degree of the electronic expansion valve 202 in the plurality of indoor units 200 is maintained.

When the first difference To_d(i) Is greater than or equal To a first preset outlet air temperature difference threshold To_d1When the temperature difference is too large, the controller can increase the supercooling degree of the indoor heat exchanger 201 in the indoor unit 200 by reducing the opening degree of the electronic expansion valve 202 in the indoor unit 200 corresponding to the maximum value of the outlet air temperature, so that the flow speed of the refrigerant in the indoor heat exchanger 201 in the indoor unit 200 is increased, the heat exchange time between the indoor air and the indoor heat exchanger 201 is short, the outlet air temperature of the indoor unit 200 is reduced, and the maximum temperature difference of the outlet air temperatures of the indoor units 200 is reduced; or the controller can reduce the supercooling degree of the indoor heat exchanger 201 in the indoor unit 200 by increasing the opening degree of the electronic expansion valve 202 of the indoor unit 200 corresponding to the minimum value of the outlet air temperature, and reduce the flow rate of the refrigerant in the indoor heat exchanger 201 in the indoor unit 200, so that the heat exchange time between the indoor air and the indoor heat exchanger 201 is longer, the outlet air temperature of the indoor unit 200 is increased, and the temperature difference of the maximum outlet air temperature of the indoor units 200 is reduced. When the first difference To_d(i) is less than a first preset outlet air temperature difference threshold To_d1In the multi-split system, the maximum temperature difference between the outlet air temperatures of the indoor units 200 is small, and the multi-split system does not need to adjust the outlet air temperatures of the indoor units 200.

Considering that the indoor unit 200 with the minimum outlet air temperature is the minimum value among the indoor units 200, the electronic expansion valve 202 therein is adjusted, and the flow rate of the refrigerant is adjusted slowly because the output power of the compressor 101 itself is small. Therefore, in the embodiment of the present invention, when the temperature difference value of the indoor unit 200 is large, the opening degree of the electronic expansion valve 202 in the indoor unit 200 corresponding to the maximum value is decreased to increase the supercooling degree of the indoor heat exchanger 201 in the indoor unit 200, and usually, the matching value of the indoor unit 200 corresponding to the maximum value is the maximum value among the plurality of indoor units 200, and the opening degree of the electronic expansion valve 202 in the indoor unit 200 corresponding to the maximum outlet air temperature value is decreased, so that the flow rate change of the refrigerant in the indoor unit is large, and the outlet air temperature adjustment speed of the indoor unit 200 is high.

For the multi-split air-conditioning system, when the outlet air temperature of part of the indoor units 200 is too high and the outlet air temperature of part of the indoor units 200 is too low, after the multi-split air-conditioning system performs the first regulation and control step once, only the outlet air temperature of the indoor unit 200 corresponding To the maximum value or the minimum value of the outlet air temperatures is regulated, and for the regulated multi-split air-conditioning system, if the outlet air temperatures of a plurality of indoor units 200 are obtained again and the first difference To is calculated_d(i) The first difference may still be large. Therefore, in other embodiments, the above control method further comprises:

First loop step S140: after a first predetermined time t₁and then returning to the first acquisition step.

The controller or the master controller further includes a timing module, and the timing module is configured to record a duration t for adjusting or maintaining the opening degree of the electronic expansion valve 202. The opening degree of the electronic expansion valve 202 is regulated once, and the duration t reaches a first preset time t₁Then, the controller returns To execute the first obtaining step, if the first difference To recalculated by the adjusted multi-split air-conditioning system_d(i) is still greater than the first preset outlet air temperature difference threshold To_d1The above-mentioned first obtaining step To the first circulation step are repeated one or more times until the adjusted first difference To is obtained_d(i) Are all smaller than a first preset outlet air temperature difference threshold To_d1Therefore, the temperature difference value of the outlet air temperature of the indoor units 200 is small, and the comfort level of a user is good.

Further, referring to fig. 4, the first adjusting and controlling step specifically includes:

When the first difference To_d(i) Is greater than or equal To a first preset outlet air temperature difference threshold To_d1And is less than the second preset outlet air temperature difference threshold To_d2At this time, the opening degree of the electronic expansion valve 202 of the indoor unit 200 corresponding to the maximum value is decreased to adjust the supercooling degree SC of the corresponding indoor heat exchanger 201_m(i) Adjusted to the current supercooling degree SC_w(i) on the basis of increasing the first preset supercooling degree SC₁。

When the first difference To_d(i) Is greater than or equal To a second preset outlet air temperature difference threshold To_d2And is less than the third preset outlet air temperature difference threshold To_d3At this time, the opening degree of the electronic expansion valve 202 of the indoor unit 200 corresponding to the maximum value is decreased to adjust the supercooling degree SC of the corresponding indoor heat exchanger 201_m(i) Adjusted to the current supercooling degree SC_w(i) On the basis of the first preset supercooling degree SC₂。

when the first difference To_d(i) Is greater than or equal To a third preset outlet air temperature difference threshold To_d3At this time, the opening degree of the electronic expansion valve 202 in the indoor unit 200 corresponding to the maximum value is decreased to adjust the supercooling degree SC of the corresponding indoor heat exchanger 201_m(i) Adjusted to the current supercooling degree SC_w(i) On the basis of the third preset supercooling degree SC₃。

Wherein the first predetermined supercooling degree SC₁less than a second predetermined supercooling degree SC₂Second predetermined supercooling degree SC₂Less than a third predetermined supercooling degree SC₃。

the control method of the embodiment of the invention is based on the first difference To_d(i) Within different air outlet temperature difference ranges, the opening degree of the electronic expansion valve 202 in the indoor unit 200 corresponding To the maximum value is adjusted To increase the supercooling degree of the corresponding indoor heat exchanger 201 by different supercooling degrees on the basis of the current supercooling degree, that is, if the first difference To is greater than the first threshold_d(i) if the first difference is larger than or equal to the third preset outlet air temperature difference threshold, increasing the supercooling degree of the corresponding indoor heat exchanger 201 by a larger supercooling degree on the basis of the current supercooling degree; if the first difference To_d(i) if the air temperature is smaller (if the first difference is greater than or equal to the first preset air outlet temperature difference threshold and smaller than the second preset air outlet temperature difference threshold), the supercooling degree of the corresponding indoor heat exchanger 201 is increased by a smaller supercooling degree on the basis of the current supercooling degree, so that the air temperature of the indoor units 200 is increasedThe degree can be adjusted accurately and quickly.

Considering that the temperature of the refrigerant in the liquid pipe can only indirectly reflect the air-out temperature of the indoor unit 200, according to the temperature of the refrigerant in the liquid pipe, the opening of the corresponding electronic expansion valve 202 is adjusted and controlled, which is prone to generate a large deviation, and thus the adjustment speed is too slow, in some embodiments, when the temperature state parameter of the indoor unit 200 is the temperature of the refrigerant in the pipe between the indoor heat exchanger 201 of the indoor unit 200 and the electronic expansion valve 202, the control parameter further includes the matching value of the indoor unit 200, that is, according to the matching values of the plurality of indoor units 200 and the temperature of the refrigerant in the pipe between the indoor heat exchanger 201 of the indoor unit 200 and the electronic expansion valve 202, the opening of the corresponding electronic expansion valve 202 is adjusted and controlled, so as to adjust and control the supercooling degree of the corresponding indoor heat exchanger 201. For the multi-split air conditioner with a large matching difference value of the indoor units 200, the control method is adopted, and the air outlet temperature of the indoor units is adjusted at a high speed.

Further, referring to fig. 5, the adjusting and controlling the opening degree of the electronic expansion valve 202 in the corresponding indoor unit 200 according to the control parameter of the multi-split air conditioning system to adjust and control the supercooling degree of the corresponding indoor unit 200 specifically includes:

Second acquisition step S210: obtaining the refrigerant temperature Tl in the pipeline between the indoor heat exchanger 201 and the electronic expansion valve 202 in the indoor units 200 and the matching value P of the indoor units 200_o. The controller or the master controller further includes a storage module, and the storage module stores the matching value of the indoor unit 200.

Second calculation step S220: calculating a maximum value Tl of a plurality of refrigerant temperatures_maxAnd the minimum value Tl_minSecond difference value Tl_d(j) And the difference P between the number of matches between the indoor unit 200 corresponding to the maximum value and the indoor unit 200 corresponding to the minimum value_o(j) In that respect The calculating module of the controller or the master controller calculates the second difference Tl_d(j) And a match difference value P_o(j)。

Second conditioning step S230: when the difference value P of the number of matches_o(j) Less than or equal to a predetermined difference P_ocAnd the second difference valueTl_d(j) Is greater than a first preset refrigerant temperature difference threshold Tl_d1Or a match difference P_o(j) Greater than a predetermined match difference value P_ocand the second difference Tl_d(j) Greater than a second preset refrigerant temperature difference threshold Tl_d2At this time, the opening degree of the electronic expansion valve 202 in the indoor unit 200 corresponding to the maximum value is decreased to increase the supercooling degree of the indoor heat exchanger 201, or the opening degree of the electronic expansion valve 202 in the indoor unit 200 corresponding to the minimum value is increased to decrease the supercooling degree of the indoor heat exchanger 201. When the above-mentioned match difference value P_o(j) Less than or equal to a predetermined difference P_ocAnd the second difference Tl_d(j) Less than or equal to the first preset refrigerant temperature difference threshold Tl_d1Or a match difference P_o(j) Greater than a predetermined match difference value P_ocAnd the second difference value P_o(j) Less than or equal to a second preset refrigerant temperature difference threshold Tl_d2At this time, the opening degree of the electronic expansion valve 202 in the plurality of indoor units 200 is maintained.

The above-mentioned current number difference P_o(j) Less than or equal to a predetermined difference P_ocAnd the second difference Tl_d(j) Is greater than a first preset refrigerant temperature difference threshold Tl_d1Or a match difference P_o(j) Greater than a predetermined match difference value P_ocAnd the second difference Tl_d(j) Greater than a second preset refrigerant temperature difference threshold Tl_d2when the temperature difference indicates that the maximum value of the outlet air temperatures of the indoor units 200 in the multi-split system is too large, the opening degree of the electronic expansion valve 202 in the indoor unit 200 corresponding to the maximum value of the refrigerant temperature is reduced by the controller, so that the supercooling degree of the indoor heat exchanger 201 in the indoor unit 200 is increased, the flow speed of the refrigerant in the indoor heat exchanger 201 in the indoor unit 200 is increased, the heat exchange time between the indoor air and the indoor heat exchanger 201 is short, the outlet air temperature of the indoor unit 200 is reduced, and the temperature difference of the maximum outlet air temperatures of the indoor units 200 is reduced; or the controller increases the opening degree of the electronic expansion valve 202 in the indoor unit 200 corresponding to the minimum temperature value of the refrigerator to reduce the supercooling degree of the indoor heat exchanger 201 in the indoor unit 200 and reduce the flow rate of the refrigerant in the indoor heat exchanger 201 in the indoor unit 200, so that the heat exchange time between the indoor air and the indoor heat exchanger 201 is longer, thereby improving the indoor unit 200thereby reducing the temperature difference of the maximum outlet air temperature of the indoor units 200. When the difference value P of the number of matches_o(j) less than or equal to a predetermined difference P_ocand the second difference Tl_d(j) Less than or equal to the first preset refrigerant temperature difference threshold Tl_d1Or a match difference P_o(j) Greater than a predetermined match difference value P_ocAnd the second difference value P_o(j) Less than or equal to a second preset refrigerant temperature difference threshold Tl_d2In the multi-split system, the maximum value of the outlet air temperatures of the indoor units 200 is small, and the multi-split system does not need to adjust the outlet air temperatures of the indoor units 200.

Similarly, for the control method for regulating and controlling the opening degree of the electronic expansion valve 202 in the corresponding indoor unit 200 by using the refrigerant temperature of the liquid pipe and the matching value of the indoor unit 200, preferably, in the embodiment of the present invention, when the temperature difference value of the indoor unit 200 is large, the opening degree of the electronic expansion valve 202 in the indoor unit 200 corresponding to the maximum refrigerant temperature value is adjusted to increase the supercooling degree of the indoor heat exchanger 201 in the indoor unit 200, because the matching value of the indoor unit 200 corresponding to the normal maximum refrigerant temperature value is the maximum value among the plurality of indoor units 200, the opening degree of the electronic expansion valve 202 in the indoor unit 200 corresponding to the maximum refrigerant temperature value is reduced, the flow velocity of the refrigerant in the indoor unit changes greatly, and the speed of adjusting the outlet air temperature of the indoor unit 200 is high.

If the refrigerant temperature of part of the indoor units 200 in the multi-split air-conditioning system is too high and the refrigerant temperature of part of the indoor units 200 in the multi-split air-conditioning system is too low, after the multi-split air-conditioning system sequentially reaches the second regulation and control step, only the outlet air temperature of the indoor unit 200 corresponding to the maximum value or the minimum value in the refrigerant temperatures is regulated, and if the regulated multi-split air-conditioning system is subjected to reacquisition of the refrigerant temperatures of the liquid pipes in the indoor units 200 and calculation of a second difference value Tl_d(j) The second difference may still be large. Accordingly, in some embodiments, the control method further comprises:

Second loop step S240: after a second preset time t₂And then returning to the second acquisition step.

The timing module in the controller or the master controller is used for recordingThe duration t for which the opening degree of the electronic expansion valve 202 is adjusted or maintained is recorded. The opening degree of the electronic expansion valve 202 is regulated once, and the duration t reaches a second preset time t₂Then, the controller returns to the second obtaining step, and if the second difference Tl recalculated by the adjusted multi-split system is larger than the first difference, the controller returns to the second obtaining step_d(j) Is still greater than the first preset refrigerant temperature difference threshold Tl_d1And the difference value P of the number of matches_o(j) Less than or equal to a predetermined difference P_ocOr the second difference Tl_d(j) Is still greater than the second preset refrigerant temperature difference threshold Tl_d2And the difference value P of the number of matches_o(j) Greater than a predetermined match difference value P_ocThe above-mentioned cycle from the second acquisition step to the second cycle step is performed one or more times again until the adjusted second difference Tl is reached_d(j) less than or equal to the first preset refrigerant temperature difference threshold Tl_d1And the difference value P of the number of matches_o(j) Less than or equal to a predetermined difference P_ocOr the second difference Tl_d(j) Less than or equal to a second preset refrigerant temperature difference threshold Tl_d2And the difference value P of the number of matches_o(j) Greater than a predetermined match difference value P_ocThe temperature difference value of the air outlet temperature of the indoor units 200 is small, and the comfort level of a user is good.

Of course, in practical applications, the above control method is performed continuously and cyclically, and even if the opening degree of any one electronic expansion valve 202 does not need to be adjusted due to the temperature difference of the liquid pipes in the plurality of indoor units 200 within a short period of time, after a certain period of time (for example, the outlet air temperature of the indoor units 200 is adjusted during the period of time), the opening degree of one or more electronic expansion valves 202 may need to be adjusted again due to the temperature difference of the refrigerant in the liquid pipes in the plurality of indoor units 200. In addition, the first preset time t₁And a second preset time t₂May all be 15 minutes.

It should be noted that the second adjusting and controlling step specifically includes:

When the difference value P of the number of matches_o(j) Less than or equal to a predetermined difference P_ocThe second difference Tl_d(j) Is greater than a first preset refrigerant temperature difference threshold Tl_d1And is less than or equal to a third preset refrigerant temperature difference threshold valueTl_d3At this time, the opening degree of the electronic expansion valve 202 of the indoor unit 200 corresponding to the maximum value is decreased to adjust the supercooling degree SC of the corresponding indoor heat exchanger 201_m(j) Adjusted to the current supercooling degree SC_w(j) On the basis of increasing the first preset supercooling degree SC₁。

When the difference value P of the number of matches_o(j) Less than or equal to a predetermined difference P_ocThe second difference Tl_d(j) Greater than a third preset refrigerant temperature difference threshold Tl_d3At this time, the opening degree of the electronic expansion valve 202 in the indoor unit 200 corresponding to the maximum value is decreased to adjust the degree of supercooling SC of the indoor heat exchanger 201_m(j) adjusted to the current supercooling degree SC_w(j) On the basis of the first preset supercooling degree SC₂。

Wherein the first predetermined supercooling degree SC₁Less than a second predetermined supercooling degree SC₂。

The control method of the embodiment of the invention executes the steps to the matching difference value P_o(j) Less than or equal to a predetermined difference P_ocBased on the second difference Tl_d(j) within different refrigerant temperature difference ranges, the opening degree of the electronic expansion valve 202 in the indoor unit 200 corresponding to the maximum value is adjusted to increase the supercooling degree of the corresponding indoor heat exchanger 201 by different supercooling degrees on the basis of the current supercooling degree, that is, if the second difference value Tl is greater_d(j) If the second difference is larger than or equal to the third preset refrigerant temperature difference threshold value, increasing the supercooling degree of the corresponding indoor heat exchanger 201 by a larger supercooling degree on the basis of the current supercooling degree; if the second difference Tl_d(j) And if the second difference value is smaller (if the second difference value is larger than the first preset refrigerant temperature difference threshold value and smaller than or equal to the third preset refrigerant temperature difference threshold value), the supercooling degree of the corresponding indoor heat exchanger 201 is increased by a smaller supercooling degree on the basis of the current supercooling degree, so that the outlet air temperature of the indoor units 200 can be accurately and quickly adjusted.

Similarly, in some embodiments, referring to fig. 6, the second adjusting and controlling step specifically includes:

when the difference value P of the number of matches_o(j) Greater than a predetermined match difference value P_ocThe second difference Tl_d(j) Greater than the secondSetting a temperature difference threshold Tl of the refrigerant_d2And is less than or equal to a fourth preset refrigerant temperature difference threshold Tl_d4At this time, the opening degree of the electronic expansion valve 202 in the indoor unit 200 corresponding to the maximum value is decreased to correspond to the supercooling degree SC of the indoor heat exchanger 201_m(j) Adjusted to the current supercooling degree SC_w(j) On the basis of increasing the first preset supercooling degree SC₁。

When the difference value P of the number of matches_o(j) Greater than a predetermined match difference value P_ocThe second difference Tl_d(j) Is greater than a fourth preset refrigerant temperature difference threshold Tl_d4At this time, the opening degree of the electronic expansion valve 202 in the indoor unit 200 corresponding to the maximum value is decreased to correspond to the supercooling degree SC of the indoor heat exchanger 201_m(j) Adjusted to the current supercooling degree SC_w(j) on the basis of the first preset supercooling degree SC₂。

wherein the first predetermined supercooling degree SC₁Less than a second predetermined supercooling degree SC₂。

The control method of the embodiment of the invention executes the steps to the matching difference value P_o(j) Greater than a predetermined match difference value P_ocBased on the second difference Tl_d(j) Within different refrigerant temperature difference ranges, the opening degree of the electronic expansion valve 202 in the indoor unit 200 corresponding to the maximum value is adjusted to increase the supercooling degree of the corresponding indoor heat exchanger 201 by different supercooling degrees on the basis of the current supercooling degree, that is, if the second difference value Tl is_d(j) If the second difference is larger than or equal to the fourth preset refrigerant temperature difference threshold value, increasing the supercooling degree of the corresponding indoor heat exchanger 201 by a larger supercooling degree on the basis of the current supercooling degree; if the second difference Tl_d(j) The supercooling degree of the corresponding indoor heat exchanger 201 is increased by a small supercooling degree on the basis of the current supercooling degree (if the second difference value is greater than the second preset refrigerant temperature difference threshold value and less than or equal to the fourth preset refrigerant temperature difference threshold value), so that the outlet air temperature of the indoor units 200 can be accurately and quickly adjusted.

In addition, the above-mentioned decreasing the opening degree of the electronic expansion valve in the indoor unit corresponding to the maximum value to adjust the supercooling degree of the corresponding indoor heat exchanger to increase the first preset supercooling degree on the basis of the current supercooling degree, and the sum of the current supercooling degree of the indoor heat exchanger corresponding to the maximum value and the first preset supercooling degree may be greater than the preset maximum supercooling degree, so, with reference to fig. 4 and 6, the decreasing the opening degree of the electronic expansion valve in the indoor unit corresponding to the maximum value to adjust the supercooling degree of the corresponding indoor heat exchanger to increase the first preset supercooling degree on the basis of the current supercooling degree specifically includes:

When the current supercooling degree of the indoor heat exchanger corresponding to the maximum value and the first preset supercooling degree SC₁The sum of the sub-cooling degrees is less than or equal to the preset maximum sub-cooling degree SC_maxoThen, the opening degree of the electronic expansion valve in the indoor unit corresponding to the maximum value is reduced so as to adjust the supercooling degree of the corresponding indoor heat exchanger to increase the first preset supercooling degree SC on the basis of the current supercooling degree₁；

When the current supercooling degree of the indoor heat exchanger corresponding to the maximum value and the first preset supercooling degree SC₁the sum is greater than the preset maximum supercooling degree SC_maxoThen, the opening degree of the electronic expansion valve in the indoor unit corresponding to the maximum value is reduced so as to adjust the supercooling degree of the corresponding indoor heat exchanger to the preset maximum supercooling degree SC_maxo。

According to the control method provided by the embodiment of the invention, through the control steps, the supercooling degree of the indoor heat exchanger in the multi-split air-conditioning system is ensured not to be too large. And in the same way, the opening degree of the electronic expansion valve in the indoor unit corresponding to the maximum value is reduced so as to adjust the supercooling degree of the corresponding indoor heat exchanger to increase a second preset supercooling degree or a third preset supercooling degree on the basis of the current supercooling degree, and the control steps are also adopted.

The above decreasing the opening degree of the electronic expansion valve 202 in the indoor unit 200 corresponding to the maximum value to adjust the supercooling degree of the corresponding indoor heat exchanger 201 to increase the first preset supercooling degree on the basis of the current supercooling degree specifically includes:

Step S301: and adjusting the opening degree of the electronic expansion valve 202 in the indoor unit 200 corresponding to the maximum value according to the current supercooling degree of the indoor heat exchanger 201 corresponding to the maximum value.

step S302: and after a third preset time, re-acquiring the current supercooling degree of the indoor heat exchanger 201 corresponding to the maximum value.

Step S303: and if the current supercooling degree of the indoor heat exchanger 201 corresponding to the maximum value is smaller than or larger than the first preset supercooling degree, returning to the step S301. If the current supercooling degree of the currently corresponding indoor heat exchanger 201 is equal to the first preset supercooling degree, the opening degree of the electronic expansion valve 202 in the indoor unit 200 corresponding to the maximum value is maintained.

In summary, the adjusting of the opening degree of the electronic expansion valve 202 adjusts the supercooling degree of the corresponding indoor heat exchanger 201 to increase the first preset supercooling degree on the basis of the current supercooling degree as a feedback control process. The control process of adjusting the opening degree of the electronic expansion valve 202 to increase the supercooling degree of the corresponding indoor heat exchanger 201 to the second preset supercooling degree, or the third preset supercooling degree, or the preset maximum supercooling degree based on the current supercooling degree is the same as the control process described above.

Fig. 2 shows a specific multi-split system, which includes an outdoor unit and two outdoor units, the outdoor unit 100 includes a compressor 101, a control valve 102 (a four-way valve in the figure) and an outdoor heat exchanger 103, an oil separator 104, a discharge pressure sensor 105, a discharge pressure switch 106 and a discharge check valve 107 are sequentially connected in series between a discharge port of the compressor 101 and the control valve 102, an inspection valve 108 is connected in series between the control valve 103 and the outdoor heat exchanger 103, a blower fan 109 is installed at the outdoor heat exchanger 103, the outdoor heat exchanger 103 includes a first heat exchange pipe and a second heat exchange pipe, the first heat exchange pipe is disposed near one side of the inspection valve 108, a flow divider 110, a first filter 111, a first expansion valve 112 and a second filter 113 are connected in series between the first heat exchange pipe and the second heat exchange pipe, two indoor units 200 are installed at different floors, each indoor unit 200 includes an indoor refrigerant branch 210 connected in series, the indoor refrigerant branch 210 comprises an indoor heat exchanger 201 and an electronic expansion valve 202 which are connected in series, the electronic expansion valve 202 is positioned on a connecting pipeline between the indoor heat exchanger 201 and the outdoor heat exchanger 103, a refrigerant heat dissipation assembly 114 and a liquid side stop valve 115 are installed between a second heat exchange pipe of the outdoor heat exchanger 103 and the electronic expansion valve 202, a liquid pipe temperature sensor 203 is installed on a pipeline between the electronic expansion valve 202 and the indoor heat exchanger 201, one end of the indoor heat exchanger 201 is connected with a control valve 102, an air side stop valve 116 is installed on a pipeline between the indoor heat exchanger 201 and the electronic expansion valve 202, a third filter 117, a gas-liquid separator 118 and a suction pressure switch 119 are installed on a pipeline between the control valve 102 and a suction port of the compressor 101, a balance pressure branch is arranged between a discharge port of the compressor 101 and an inlet of the gas-liquid separator, The bypass capillary 120 is disposed near an inlet of the gas-liquid separator 118, an oil return branch is disposed between an oil return port of the oil separator 104 and the inlet of the gas-liquid separator 118, the oil return branch includes an oil return capillary 123 and a fifth filter 124 connected in series, and the oil return capillary 123 is disposed near the inlet of the gas-liquid separator 118. The multi-split system shown in fig. 2 can be controlled by the above control method to ensure that the outlet air temperature difference of the two indoor units is small (in the figure, the solid long arrow indicates the flowing direction of the refrigeration cycle refrigerant, and the dotted long arrow indicates the flowing method of the heating cycle refrigerant).

In the description herein, particular features, structures, materials, or characteristics may be combined in any suitable manner in any one or more embodiments or examples.

The above description is only for the specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.