Air conditioning system

Abstract

Air conditioning system, comprising: an outdoor unit having a compressor and a first heat exchanger, a plurality of air handling units having a fan and a second heat exchanger, an expansion valve and a control unit arranged correspondingly; the air conditioning system has a refrigerant circuit in which a compressor, a first heat exchanger, an expansion valve and a second heat exchanger are connected in sequence to circulate refrigerant; wherein at least one air handling unit has a capacity smaller than that of a standard air handling unit; in the start-up stage of the cooling mode, when the capacity of the air handling unit that receives the start-up instruction and the capacity ratio to the total capacity respectively satisfy the corresponding low-capacity condition and low-capacity ratio condition at the same time, the control unit generates an opening correction value proportional to the preset initial opening value according to the preset initial opening value, and uses the sum of the opening correction value and the initial opening value to generate a target opening value to control the actual opening of the expansion valve corresponding to the air handling unit that meets the low-capacity condition in the start-up stage. The present invention can effectively reduce the noise in the start-up stage.

Description

Technical Field

[0001] The present invention relates to the technical field of air conditioning, and particularly to an air conditioning system. Background Art

[0002] A multi-connected air conditioner is a complex cycle system composed of one or more outdoor units and several indoor units. When there are many indoor units, the installation conditions, the environments where they are located, and their usage characteristics are different for each indoor unit. During the refrigeration operation, usually the same target superheat is used to control the opening degrees of the electronic expansion valves of all indoor units. However, if the opening degrees of the electronic expansion valves of multiple indoor units are controlled according to the same target value when the indoor units are turned on, it will cause some indoor units to not be able to efficiently exert their refrigeration performance, and in severe cases, it will lead to uneven distribution of the refrigerant in the system and a decrease in the overall efficiency of the unit.

[0003] To solve the above problems, Chinese Patent Application (Publication No. CN110579064A) discloses a "Control Method and Device for Electronic Expansion Valve during Refrigeration Operation of Multi-Connected Air Conditioner", and specifically discloses: "Obtain the current temperature difference of each indoor unit currently in the on state and the initial superheat preset by the outdoor unit, and calculate the target superheat of the corresponding indoor unit according to the current temperature difference and the initial superheat; the current temperature difference is the difference between the return air temperature of the current indoor unit and the preset reference temperature; determine the current superheat according to the difference between the outlet temperature and the inlet temperature of the heat exchanger in the indoor units currently in the on state obtained, and adjust the opening degree of the electronic expansion valve of the corresponding indoor unit according to the difference between the current superheat and the target superheat." And specifically discloses: "The working process of the multi-connected air conditioner includes four processes, namely: startup operation, stable operation, special timing operation, and shutdown operation; among them, the special timing operation includes room number switching and oil return control", and, during the startup operation stage, control the electronic expansion valve corresponding to the current indoor unit according to the initial valve opening degree; during the stable operation stage, correct the initial superheat according to the sine function; during the oil return control, control the opening degree of the electronic expansion valve of the indoor unit currently in the off state to be the oil return opening degree preset by the outdoor unit, and control the opening degree of the electronic expansion valve of the indoor unit currently in the on state to remain unchanged. During the room number switching, provide a new initial value of the target superheat according to the change rate of the on / off capacity. The above control method can ensure the best distribution of the refrigerant in the unit system.

[0004] However, some multi-connected air conditioners tend to be designed with indoor units having a smaller capacity, which makes the diameter of the electronic expansion valve smaller. This results in the setting of a fixed opening degree (such as the initial valve opening degree described in the above comparative document) during the startup operation stage, which will cause refrigerant flow noise in the small-capacity indoor units and reduce the user experience.

[0005] The above information disclosed in this background art is only used to increase the understanding of the background art of this application. Therefore, it may include prior art that is not known to those of ordinary skill in the art. Summary of the Invention

[0006] In view of the problems pointed out in the background art, an air conditioning system is provided.

[0007] In a first aspect, the air conditioning system includes: at least one outdoor unit having a compressor and a first heat exchanger; a plurality of air handling units having a fan and a second heat exchanger; an expansion valve corresponding to the air handling unit; and a control unit; the air conditioning system has a refrigerant circuit, and the refrigerant circuit sequentially connects the compressor, the first heat exchanger, the expansion valve, and the second heat exchanger to circulate the refrigerant.

[0008] In some embodiments of the present application, the capacity of at least one air handling unit is less than the capacity of a standard air handling unit; in the cooling mode, during the startup stage, when the capacity of the air handling unit receiving the startup instruction and the capacity ratio of the capacity of the air handling unit receiving the startup instruction to the total capacity of all air handling units receiving the startup instruction respectively satisfy the corresponding low-capacity conditions and low-capacity ratio conditions, the control unit generates an opening correction value proportional to the initial opening value according to the preset initial opening value, and uses the sum of the opening correction value and the initial opening value to generate a target opening value to control the actual opening of the expansion valve corresponding to the air handling unit that meets the low-capacity conditions during the startup stage. Through the opening correction value proportional to the preset opening value, the expansion valve corresponding to the small-capacity air handling unit in the air conditioning system can have an appropriate opening during the startup stage, avoiding an obvious refrigerant flow sound in the indoor unit due to too small a valve opening during the startup stage, and at the same time avoiding too large a valve opening, serious liquid return in the air conditioning system, and a long adjustment system time for the air conditioning system.

[0009] In some alternative embodiments of the present application, the control unit switches from the first stable operation stage to the room number switching stage after at least one air handling unit receives a startup instruction or a shutdown instruction different from the current operating state.

[0010] In some alternative embodiments of the present application, during the room number switching stage, when the front-back capacity ratio between the total capacity of the air handling units that are in the startup state after the room number is reduced and switched and the total capacity of the air handling units that are in the startup state before the switch satisfies the switching capacity condition, the control unit performs a valve closing control on the expansion valve corresponding to the air handling unit receiving the shutdown instruction.

[0011] In some alternative embodiments of the present application, during the room number switching stage, when the ratio of the total capacity of the air handling units that are in the on state after the room number decreases and switches and the total capacity of the air handling units that are in the on state before the switch does not meet the switching capacity condition, but the exhaust superheat does not meet the low exhaust superheat condition, the control unit keeps the valve opening degree of the expansion valve corresponding to the air handling unit receiving the shutdown instruction unchanged until the exhaust superheat meets the low exhaust superheat condition, and then performs a valve closing control on the expansion valve corresponding to the air handling unit receiving the shutdown instruction to prevent entering the anti-freezing protection.

[0012] In some alternative embodiments of the present application, after the valve closing control is completed, the control unit controls to first enter the second stable operation stage and then enter the first stable operation stage.

[0013] In some alternative embodiments of the present application, the control unit adjusts such that the first calculation frequency of obtaining the calculated opening degree of the expansion valve in the second stable operation stage is higher than the second calculation frequency of obtaining the calculated opening degree of the expansion valve in the first stable operation stage, and after continuously calculating and adjusting the opening degree of the expansion valve several times according to the first calculation frequency, the second stable operation stage ends, and then enters the first stable operation stage.

[0014] In some alternative embodiments of the present application, the calculated opening degree is obtained according to the target superheat of the air handling unit.

[0015] In some alternative embodiments of the present application, during the first stable operation stage and / or the second stable operation stage, when the real-time return air temperature of the air handling unit is higher than the corresponding set temperature of the unit preset room temperature cooling curve, the control unit adjusts and increases the calculated opening degree of the expansion valve corresponding to the air handling unit; when the real-time return air temperature of the air handling unit is lower than the corresponding set temperature of the unit preset room temperature cooling curve, the control unit adjusts and decreases the calculated opening degree of the expansion valve corresponding to the air handling unit; when the real-time return air temperature of the air handling unit matches the corresponding set temperature of the unit preset room temperature cooling curve, the control unit keeps the calculated opening degree of the expansion valve corresponding to the air handling unit unchanged.

[0016] In some alternative embodiments of the present application, during the first stable operation stage, when the control unit performs oil return control and the difference between the liquid pipe temperature of the liquid pipe located upstream of the expansion valve corresponding to the air handling unit in the on state and the saturation temperature obtained according to the valve front pressure of the expansion valve meets the set valve adjustment condition in the oil return stage, the control unit performs the valve adjustment control in the oil return stage, and adjusts and decreases the calculated opening degree of the expansion valve corresponding to the air handling unit until the set oil return valve adjustment cycle ends or the expansion valve opening degree has been adjusted to the set minimum opening degree.

[0017] In some alternative embodiments of the present application, when the set oil return valve adjustment period ends and the opening degree of the expansion valve is not the set minimum opening degree, the control unit executes the oil return stage valve adjustment control again until the difference between the liquid pipe temperature of the liquid pipe upstream of the expansion valve corresponding to the air handling unit in the on state and the saturation temperature obtained based on the pressure before the expansion valve no longer satisfies the set oil return stage valve adjustment condition, at which point the oil return stage valve adjustment control ends, and the oil return control is maintained until the set time point is reached, and the first stable operation stage is restored.

[0018] In some alternative embodiments of the present application, when the number of air handling units in the on state is multiple, the control unit executes the oil return stage valve adjustment control when the difference between the maximum liquid pipe temperature of the liquid pipe upstream of the expansion valve corresponding to the air handling unit in the on state and the saturation temperature obtained based on the pressure before the expansion valve satisfies the set oil return stage valve adjustment condition.

[0019] In a second aspect, the present application provides an air conditioning system. In the refrigeration mode, during the room number switching stage, when the number of rooms decreases and the capacity ratio of the air handling units in the on state after switching to the air handling units in the on state before switching meets the switching capacity condition, the control unit executes a valve closing control on the expansion valve corresponding to the air handling unit that receives the shutdown instruction; or when the number of rooms decreases and the capacity ratio of the air handling units in the on state after switching to the air handling units in the on state before switching does not meet the switching capacity condition but the exhaust superheat degree meets the low exhaust superheat degree condition, the valve opening degree of the expansion valve corresponding to the air handling unit that receives the shutdown instruction is maintained unchanged until the exhaust superheat degree meets the low exhaust superheat degree condition, at which point the control unit executes a valve closing control on the expansion valve corresponding to the air handling unit that receives the shutdown instruction.

[0020] In a third aspect, the present application provides an air conditioning system. In the refrigeration mode, during the stable operation stage, when the real-time return air temperature of the air handling unit is higher than the corresponding set temperature of the unit's preset room temperature cooling curve, the control unit adjusts and increases the calculated opening degree of the expansion valve corresponding to the air handling unit; when the real-time return air temperature of the air handling unit is lower than the corresponding set temperature of the unit's preset room temperature cooling curve, the control unit adjusts and decreases the calculated opening degree of the expansion valve corresponding to the air handling unit; when the real-time return air temperature of the air handling unit matches the corresponding set temperature of the unit's preset room temperature cooling curve, the control unit maintains the calculated opening degree of the expansion valve corresponding to the air handling unit unchanged; the calculated opening degree is obtained based on the target superheat degree of the air handling unit.

[0021] In some alternative embodiments, during the stable operation phase, when the difference between the liquid pipe temperature of the liquid pipe upstream of the expansion valve corresponding to the air handling unit in the powered-on state and the saturation temperature obtained based on the pressure before the expansion valve satisfies the set valve adjustment condition for the oil return phase, the control unit performs the valve adjustment control for the oil return phase, and adjusts and reduces the calculated opening degree of the expansion valve corresponding to the air handling unit until the end of the set oil return valve adjustment period or the expansion valve opening degree has been adjusted to the set minimum opening degree; when the set oil return valve adjustment period ends and the expansion valve opening degree is not the set minimum opening degree, the control unit performs the valve adjustment control for the oil return phase again until the difference between the liquid pipe temperature of the liquid pipe upstream of the expansion valve corresponding to the air handling unit in the powered-on state and the saturation temperature obtained based on the pressure before the expansion valve no longer satisfies the set valve adjustment condition for the oil return phase, the valve adjustment control for the oil return phase ends, and the oil return control is maintained until the set time point is reached, and the stable operation phase is restored.

[0022] Compared with the prior art, the advantages and positive effects of the present invention are as follows: The air conditioning system provided by this application has better stability and user comfort, the small-capacity indoor unit has low noise, shorter oil return time, more uniform refrigerant distribution, and improved refrigeration capacity.

[0023] After reading the specific embodiments of the present invention in conjunction with the drawings, other features and advantages of the present invention will become clearer. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0025] Figure 1 is a schematic structural diagram according to some embodiments of the present invention;

[0026] Figure 2 is a flowchart according to some embodiments of the present invention;

[0027] Figure 3 The shown table represents a set of optional low-capacity conditions and low-capacity ratio conditions;

[0028] Figure 4 is a flowchart according to some embodiments of the present invention;

[0029] Figure 5 is a flowchart according to some embodiments of the present invention;

[0030] Figure 6 is a flowchart according to some embodiments of the present invention;

[0031] Figure 7 is a flowchart according to some embodiments of the present invention;

[0032] Figure 8 is an example of a preset room temperature cooling curve;

[0033] Figure 9 is a flowchart according to some embodiments of the present invention;

[0034] Figure 10 is a flowchart according to some embodiments of the present invention;

[0035] Figure 11 is a flowchart according to some embodiments of the present invention;

[0036] Figure 12 is a flowchart according to some embodiments of the present invention;

[0037] Figure 13 is a flowchart according to some embodiments of the present invention. Detailed implementation manners

[0038] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0039] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present application.

[0040] The terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present application, unless otherwise specified, the meaning of "plurality" is two or more.

[0041] In the description of the present application, it should be noted that, unless otherwise clearly specified and defined, the terms "installed", "connected" and "coupled" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected, or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0042] In the present invention, unless otherwise clearly specified and defined, the first feature being "on" or "under" the second feature may include the direct contact between the first and second features, or may include the situation where the first and second features are not in direct contact but in contact through other features therebetween. Moreover, the first feature being "above", "over" and "on top of" the second feature includes that the first feature is directly above and obliquely above the second feature, or merely means that the horizontal height of the first feature is higher than that of the second feature. The first feature being "under", "below" and "beneath" the second feature includes that the first feature is directly below and obliquely below the second feature, or merely means that the horizontal height of the first feature is lower than that of the second feature.

[0043] The following disclosure provides many different embodiments or examples for implementing different structures of the present invention. To simplify the disclosure of the present invention, components and settings of specific examples are described below. Of course, they are merely examples and are not intended to limit the present invention. In addition, the present invention may repeat reference numerals and / or reference letters in different examples. This repetition is for the purpose of simplification and clarity, and does not itself indicate the relationship between various embodiments and / or settings discussed. In addition, the present invention provides examples of various specific processes and materials, but those of ordinary skill in the art may be aware of the application of other processes and / or the use of other materials.

[0044] Figure 1 It is a structural diagram of the air-conditioning system 100 related to the first embodiment.

[0045] Figure 1 In the figure, the solid arrow F indicates the flow direction of the refrigerant in the refrigeration mode. The flow direction of the refrigerant during the heating operation is not marked in the present application.

[0046] The air-conditioning system 100 is a system that executes the refrigeration cycle of the air-conditioning system 100 by using a compressor 12, a condenser, a throttling device, and an evaporator. The refrigeration cycle includes a series of processes involving compression, condensation, expansion, and evaporation to cool or heat an indoor space.

[0047] From a principle perspective, a low-temperature and low-pressure refrigerant enters the compressor 12, and the compressor 12 compresses it into a refrigerant gas in a high-temperature and high-pressure state and discharges the compressed refrigerant gas. The discharged refrigerant gas flows into the condenser. The condenser condenses the compressed refrigerant into a liquid phase, and heat is released to the surrounding environment through the condensation process.

[0048] The throttling device expands the high-temperature and high-pressure liquid-phase refrigerant formed by condensation in the condenser into a low-pressure liquid-phase refrigerant. The evaporator evaporates the refrigerant expanded in the throttling device and returns the refrigerant gas in a low-temperature and low-pressure state to the compressor 12. The evaporator can achieve a refrigeration effect by using the latent heat of evaporation of the refrigerant to exchange heat with the material to be cooled. Throughout the cycle, the air-conditioning system 100 can adjust the temperature of the indoor space.

[0049] The outdoor unit 10 of the air-conditioning system 100 refers to the part of the refrigeration cycle including the compressor 12 and the outdoor heat exchanger (the first heat exchanger 14). The air handling unit of the air-conditioning system 100 (as shown in Figure 1 24, 32, 40, 48, 56) is placed in the air-conditioned room and is also called the indoor unit, including the indoor heat exchanger (the second heat exchanger, as shown in Figure 1 26, 34, 42, 50, 58), and the throttling device can be provided in the indoor unit and the outdoor unit 10. For example, in this embodiment, each air handling unit is provided with an expansion valve (as shown in Figure 1 30, 38, 46, 54, 62), and at the same time, an outdoor expansion valve 22 can be provided in the outdoor unit 10.

[0050] The indoor heat exchanger and the outdoor heat exchanger are used as condensers or evaporators. When the indoor heat exchanger is used as a condenser, the air-conditioning system 100 is used as a heater in the heating mode. When the indoor heat exchanger is used as an evaporator, the air-conditioning system 100 is used as a cooler in the cooling mode.

[0051] In an alternative embodiment, one or more compressors 12 can be provided in each outdoor unit 10, and alternating current is supplied to the operating compressor 12 through a frequency conversion device. When the output frequency of the frequency conversion device changes, the rotational speed of the compressor 12 changes, achieving different air-conditioning capacities.

[0052] An outdoor unit 10 is also provided with an outdoor fan 20 and a four-way valve 18. In addition, other conventional components such as a gas-liquid separator 16, a capillary tube, and an oil separator can also be provided. The gas-liquid separator 16 is a shell-shaped component for separating the refrigerant into gas and liquid, and is usually provided on the suction side of the compressor 12. The first heat exchanger 14 is configured to exchange heat between the refrigerant flowing through its internal heat exchange pipeline and the air (or other medium) guided by the outdoor fan 20. The outdoor fan 20 can be an axial flow fan, a cross-flow fan, or other optional fan forms, and is usually provided near the first heat exchanger 14. The four-way valve 18 is a valve for switching the refrigerant flow direction according to the operation mode of the air conditioning system 100. That is, in the cooling mode, the discharge side of the compressor 12 is connected to one end of the first heat exchanger 14 through pipelines such as the four-way valve 18, and the suction side of the compressor 12 is connected to one end of the second heat exchanger through pipelines such as the four-way valve 18. Thus, the first heat exchanger 14 functions as a condenser, and the second heat exchanger functions as an evaporator. Similarly, in the heating mode, the discharge side of the compressor 12 is connected to one end of the second heat exchanger through the four-way valve 18 and pipelines, and the suction side of the compressor 12 is connected to one side of the first heat exchanger 14 through pipelines such as the four-way valve 18. Thus, the second heat exchanger functions as a condenser, and the first heat exchanger 14 functions as an evaporator. The refrigerant circuit of the air conditioning system 100 is sequentially connected to the compressor 12, the first heat exchanger 14, the expansion valve, and the second heat exchanger to circulate the refrigerant.

[0053] The expansion valve corresponding to the air handling unit (indoor unit) and the outdoor expansion valve 22 are both valves for reducing the pressure of the refrigerant flowing into the valve body itself, and are provided on the pipeline through which the liquid refrigerant or the gas-liquid two-phase refrigerant flows.

[0054] The oil separator is used to separate the lubricating oil in the refrigerant discharged by the compressor 12, and is usually provided on the discharge side of the compressor 12. The lubricating oil separated by the oil separator can be guided to the gas-liquid separator 16 through a pipeline. A one-way valve can also be provided to guide the separated refrigerant to the four-way valve 18.

[0055] An outdoor control circuit is provided in the outdoor unit 10. The outdoor control circuit is usually arranged in an electrical box with good sealing performance. The outdoor control circuit includes components such as a processor, a storage unit, an input / output interface, a communication interface, etc. The processor can be a dedicated processor, a central processing unit (CPU), etc. The processor can access the storage unit to execute instructions or application programs stored in the storage unit to implement related functions. The storage unit can include volatile memory and / or non-volatile memory. The input / output interface can be communicatively connected to various sensors arranged in the outdoor unit 10 to receive the detection values of various sensors arranged in the outdoor unit 10. The sensors include, but are not limited to, an outdoor temperature sensor, a temperature sensor on the suction side of the compressor 12, a temperature sensor on the discharge side, and a pressure sensor on the discharge side, etc. The input / output interface can be communicatively connected to devices such as a frequency conversion module, the compressor 12, the outdoor fan 20, the four-way valve 18, the outdoor expansion valve 22, etc. to output control instructions generated by the processor to them. The communication interface can support different wireless communication protocols, such as WiFi, Bluetooth, near field communication, NB-IoT, etc. to be communicatively connected to other electronic devices, including but not limited to cloud servers, computers (upper computers), smart phones, tablets, PDAs, intelligent control tooling, wearable devices, in-vehicle devices, and so on.

[0056] In an alternative embodiment, the air conditioning system 100 can include multiple outdoor units 10. Each outdoor unit 10 can work independently or can be configured to work in groups, such as two outdoor units 10 as a group, four outdoor units 10 as a group, and so on. Each or each group of outdoor units 10 is provided with a corresponding air handling unit.

[0057] The air handling unit is an indoor unit of the air conditioning system 100.

[0058] In an alternative embodiment, the air handling unit can adopt an independent air supply structure, such as a wall-mounted air supply structure, a floor-standing air supply structure, a duct-type air supply structure, or an air supply structure embedded in the ceiling, etc. The air supply structure includes a housing, the housing has an air return opening for sucking air, and an air supply opening for sending the heat-exchanged air into the air-conditioned room. A fan and a second heat exchanger are arranged in the housing. The fan is arranged near the second heat exchanger.

[0059] The expansion valve corresponding to the air handling unit is used to decompress the refrigerant flowing through itself while adjusting the circulation flow rate of the refrigerant.

[0060] In an alternative embodiment, the air handling unit is correspondingly provided with a wired controller, and the wired controller is fixedly installed on the wall of the air-conditioned room. An operation interface for inputting the set temperature and operation mode and a display interface for displaying the real-time temperature of the air-conditioned room and the operation state of the air conditioning system 100 are arranged on the wired controller.

[0061] In an alternative embodiment, a remote controller is correspondingly provided for the air handling unit. The remote controller is communicatively connected to the air handling unit. The remote controller is provided with keys for inputting the set temperature and the operating mode, as well as a display interface for displaying the real-time temperature of the air-conditioned room and the operating state of the air-conditioning system 100.

[0062] In an alternative embodiment, a mobile control terminal is correspondingly provided for the air handling unit. The mobile control terminal is communicatively connected to the air handling unit. The mobile control terminal has an application interface through which the set temperature and the operating mode can be input and the real-time temperature or the operating state of the air-conditioned room can be displayed.

[0063] In an alternative embodiment, the mobile control terminal can be a computer, a tablet computer, a smart phone, a wearable device, etc.

[0064] An indoor unit control circuit is provided in the air handling unit. The indoor unit control circuit preferably is provided with an indoor controller. The indoor controller is configured to drive the fan to work, display various parameters on the display panel, perform human-computer interaction, receive and process the sampling signals of various sensors, and implement necessary communication functions.

[0065] The indoor unit control circuit also includes electrical components such as a storage unit, a processor, an input / output interface, a communication interface, etc.

[0066] The storage unit can include a volatile memory and / or a non-volatile memory. The storage unit is configured to store instructions or data associated with at least one component of the indoor unit, such as storing application programs. Exemplarily, the application program can be to adjust the temperature of the air-conditioned room by different speed levels of the fan.

[0067] The indoor processor can be a dedicated processor, a central processing unit (CPU), etc. The indoor processor can access the storage unit to execute the instructions stored in the storage unit to implement related functions.

[0068] The input / output interface can be communicatively connected to various sensors provided in the air handling unit to receive the detection values of various sensors provided in the air handling unit. The sensors include but are not limited to an air temperature sensor provided at the air return opening, a humidity sensor provided at the air return opening, an air temperature sensor provided at the air supply opening, a refrigerant temperature sensor provided at the inlet end of the second heat exchanger, a refrigerant temperature sensor provided at the outlet end of the second heat exchanger, etc. The input / output interface can be a serial communication interface. The input / output interface can also be communicatively connected to components such as an indicator light, a buzzer, a stepping motor, etc. to output control instructions thereto. The stepping motor can be a driving component of the air deflector.

[0069] The communication interface can be a software interface that supports different wireless communication protocols, such as WiFi, Bluetooth, etc.

[0070] A power supply circuit is usually provided on the indoor unit control circuit to supply 12V and 5V voltages.

[0071] The control circuit of the outdoor unit 10 is communicatively connected to the control circuit of the indoor unit. In some alternative embodiments of the present application, the control circuit of the outdoor unit 10 and the control circuit of the indoor unit jointly serve as the control unit 64 to execute the control of the air conditioning system 100.

[0072] The plurality of air handling units have different capacities, and at least one air handling unit has a capacity less than that of the standard handling unit. In the present application, the capacity is in units of KW (kilowatt) or HP (horsepower), and the two can be converted. The capacity of the standard air handling unit is 1.8KW or 1.5KW. The capacity represents the heat exchange performance of the air handling unit, and can also be understood as the cooling capacity of the air handling unit. As Figure 1 shown, it is assumed that the air conditioning system 100 includes an outdoor unit 10 with a capacity of 2.5HP, and is equipped with 5 air handling units, namely I1: 0.8HP, I2: 0.6HP, I3: 0.6HP, I4: 0.4HP, I5: 0.2HP.

[0073] Figure 2 A flowchart showing the processing executed by the control unit 64. It should be noted that Figure 2 the shown process can be carried out in the test mode of the air conditioning system 100, or can also be carried out during the normal use process of the air conditioning system 100.

[0074] In step S101, the air conditioning system 100 enters the startup stage in the cooling mode.

[0075] In step S102, the control unit 64 reads the switch states of all the air handling units, that is, reads whether each air handling unit has received a startup instruction generated by a wired controller, a remote controller or a mobile control terminal with control authority. The capacity of the air handling unit that has received the startup instruction can be represented as A j , where j represents the ordinal number of the air handling unit, and j is a positive integer.

[0076] In step S103, the control unit 64 determines whether the capacity of the air handling unit that has received the startup instruction meets the low-capacity condition. The low-capacity condition is set according to the small-capacity air handling units that are prone to generating noise. In some alternative embodiments, the low-capacity condition is set to the capacity of the air handling unit being less than 0.5KW. In other alternative embodiments, the low-capacity condition can also be set to the capacity of the air handling unit being less than 0.5HP.

[0077] In step S104, when the capacity of the air handling unit that receives the power-on instruction meets the low-capacity condition, the control unit 64 further determines whether the capacity ratio of the capacity of the air handling unit that receives the power-on instruction and the total capacity of all air handling units that receive the power-on instruction meets the low-capacity ratio condition. The capacity ratio can be expressed as C j ,∑ k A thon (k) represents the total capacity of all air handling units that receive the power-on instruction. The capacity ratio is the ratio of the capacity of the air handling unit that receives the power-on instruction to the total capacity of all air handling units that receive the power-on instruction.

[0078]

[0079] In step S105, when the capacity ratio of the capacity of the air handling unit that receives the power-on instruction and the total capacity of all air handling units that receive the power-on instruction meets the low-capacity ratio condition, a preset initial opening value EVI j is called. The preset initial opening value EVI j is the opening calculated according to the indoor environmental temperature of the air-conditioned room. Calculating the preset initial opening value EVI j from the indoor environmental temperature of the air-conditioned room can adopt the algorithms disclosed in the prior art, which is not the focus of the protection of the present invention and will not be elaborated here.

[0080] In step S106, the control unit 64 generates an opening correction value proportional to the initial opening value. The opening correction value can be expressed as ΔEVI j , that is, ΔEVI j =EVI j ×S, where S is a proportionality coefficient, a constant set and stored in advance.

[0081] In step S107, the control unit 64 uses the opening correction value ΔEVI j and the initial opening value EVI j to generate a target opening value EVI 初j to control the actual opening of the expansion valve corresponding to the air handling unit that meets the low-capacity condition during the startup phase, that is,

[0082] EVI 初j =EVI j +ΔEVI j .

[0083] In step S108, when the capacity of the air handling unit that receives the power-on instruction does not meet the low-capacity condition, a preset initial opening value EVI j is called to control the actual opening of the expansion valve corresponding to the air handling unit that receives the power-on instruction during the startup phase.

[0084] In step S109, when the capacity of the air handling unit receiving the power-on command meets the low-capacity condition but the capacity ratio of the air handling unit receiving the power-on command and the total capacity of all air handling units receiving the power-on command does not meet the low-capacity ratio condition, the control unit 64 calls the preset initial opening value EVIj to control the actual opening of the expansion valve corresponding to the air handling unit receiving the power-on command during the power-on startup phase.

[0085] According to the first embodiment described above, by using an opening correction value that is proportional to a preset opening value, the expansion valves corresponding to the small-capacity air handling units in the air-conditioning system 100 can have an appropriate opening during the startup phase, thereby avoiding the valve opening being too small during the startup phase, which may result in obvious refrigerant flow noise in the indoor unit, and also avoiding the valve opening being too large, which may result in serious liquid return in the air-conditioning system 100 and a long time for the air-conditioning system 100 to adjust the system.

[0086] Figure 3 The table shown shows a set of optional low capacity conditions and low capacity ratio conditions: when the capacity of the air handling unit receiving the startup command is less than 0.5HP and the capacity Ai of the air handling unit receiving the startup command and the total capacity of all air handling units receiving the startup command ∑ k A thon (k) capacity ratio C j When the proportional coefficient S is 1, ΔEVI is EVI j , EVI 初j 2EVI j , that is, the opening of the expansion valve corresponding to the small-capacity air handling unit is doubled, avoiding the occurrence of noise during the startup phase. This control method is particularly suitable for indoor units with a single unit capacity of less than 0.5HP.

[0087] Assume that the control unit 64 obtains the three indoor units of I3, I4 and I5 that receive the power-on command. At this time, A4 and A5 meet the low capacity condition, and C4 and C5 meet the low capacity ratio condition. Assume that EVI4 corresponding to I4 is 167pls, and EVI5 corresponding to I5 is 83pls, and S=1, then the corresponding ΔEVI4 is 167pls, and ΔEVI5 is 83pls. EVI 初4 334pls, EVI 初5 The air handling unit with small capacity will not produce large flow noise during the startup phase.

[0088] Figure 4 A flowchart showing the processing performed by the control unit 64 in some optional embodiments of the present application.

[0089] In step S10, the control unit 64 executes the startup phase. For the specific process of the startup phase control, please refer to the above text and will not be elaborated here.

[0090] In step S21, after the control unit 64 finishes executing the startup phase, it controls the air conditioning system 100 to enter the first stable operation phase. The opening degree is obtained and calculated according to the target superheat degree of each air handling unit in the working state, and the corresponding expansion valve is controlled to operate according to the calculated opening degree. The target superheat degree can be the exhaust superheat degree, the suction superheat degree, the superheat degree at the outlet of the second heat exchanger, etc. The algorithm for obtaining the calculated opening degree can adopt the algorithms disclosed in the prior art, which is not the focus of the protection of the present invention and will not be elaborated here.

[0091] In step S22, the control unit 64 reads and determines whether at least one air handling unit has received a startup instruction different from the current operating state.

[0092] In step S23, the control unit 64 reads and determines whether at least one air handling unit has received a shutdown instruction different from the current operating state.

[0093] In step S30, when at least one air handling unit has received a startup instruction different from the current operating state or at least one air handling unit has received a shutdown instruction different from the current operating state, the control unit 64 switches to the room number switching phase.

[0094] In step S301, the control unit 64 determines whether the number of rooms decreases, that is, whether the number of air handling units in the startup state relative to the first stable operation phase decreases. If the number of air handling units receiving startup instructions different from the current operating state is the same as the number of air handling units receiving shutdown instructions different from the current operating state, it does not belong to the situation defined in this step.

[0095] In step S302, the control unit 64 determines whether the switching capacity condition is met, that is, whether the ratio of the total capacity of the air handling units in the startup state after switching to the total capacity of the air handling units in the startup state before switching meets the switching capacity condition. The ratio of the total capacity before and after can be represented by K, represents the total capacity of the air handling units in the startup state before switching, represents the total capacity of the air handling units in the startup state after switching. The ratio of the total capacity before and after is the ratio of the total capacity of the air handling units in the startup state after switching to the total capacity of the air handling units in the startup state before switching.

[0096]

[0097] When the set front-back capacity ratio K is greater than K1, it is determined that the switching capacity condition is satisfied. K1 is preferably a constant stored in advance, such as 0.5.

[0098] In step S303, the control unit 64 performs valve closing control when the switching capacity condition is satisfied.

[0099] In step S304, the control unit 64 performs control to calculate the opening degree under the condition that the number of rooms does not decrease, that is, the first stable control stage remains unchanged.

[0100] Figure 5 A flowchart showing the processing performed by the control unit 64 in some alternative embodiments of the present application.

[0101] Compared with Figure 4 the shown process, Figure 5 the difference is that in step S302, when the control unit 64 determines that the front-back capacity ratio between the total capacity of the air handling units in the on state after switching and the total capacity of the air handling units in the on state before switching does not satisfy the switching capacity condition (K ≤ K1), it executes the steps in step S304. The control unit 64 determines whether the exhaust superheat degree satisfies the low exhaust superheat degree condition. If the low exhaust superheat degree condition is satisfied, the control process of step S303 is also executed to perform valve closing control. If the control unit 64 determines that the low exhaust superheat degree condition is not satisfied, then in step S305, the opening degree of the expansion valve corresponding to the air handling unit receiving the shutdown instruction is kept unchanged until the exhaust superheat degree satisfies the low exhaust superheat degree condition, and then valve closing control is performed on the expansion valve of the air handling unit receiving the shutdown instruction.

[0102] The low exhaust superheat degree condition can be set as Tdsh < Tc, where Tdsh is the actually estimated exhaust superheat degree and Tc is a preset fixed value. Tc can be optionally set to 20°C.

[0103] Exemplarily, when the control unit 64 enters the room number switching stage and the number of rooms decreases, assuming the front-back capacity ratio K = 0.8 or the front-back capacity ratio is K = 0.4 (K ≤ K1), and Tdsh = 18°C (Tdsh < Tc), valve closing control needs to be performed at this time. When the front-back capacity ratio is K = 0.3 (K ≤ K1) and Tdsh = 25°C (Tdsh ≥ Tc), it proves that the unit capacity is well exerted at this time and there is no reliability risk. At this time, the valve is not adjusted until Tdsh is less than 20°C and then adjusted.

[0104] Figure 5The flow shown can prevent the valve opening adjustment speed from being faster than the frequency reduction speed of the compressor 12, and avoid the air-conditioning system 100 entering the anti-freezing protection under conditions such as the upper and lower limits of the refrigeration temperature and the mid-stage of refrigeration. When the number of rooms decreases, the exhaust superheat degree is used to determine whether there is a risk of liquid return in the system. When the exhaust superheat degree is relatively large, it indicates that there is no risk of liquid return in the system. To prevent the system from entering the anti-freezing state, the expansion valve does not act. During this process, the compressor 12 will first reduce its frequency, and the exhaust superheat degree will decrease accordingly. When the exhaust superheat degree drops below Tc, it indicates that there may be a risk of liquid return in the system, and then the valve closing control is performed, which can effectively solve the problem of the air-conditioning system 100 entering the anti-freezing state when switching with the reduction of the number of low-temperature refrigeration rooms.

[0105] Figure 6 It is a schematic diagram showing each process stage of the processing executed by the control unit 64 in some alternative embodiments of the present application. In the case where there is a room number switching stage, the startup stage (as shown in step S10), the first stable operation stage (as shown in step S21), and the room number switching stage (as shown in step S30) are sequentially performed.

[0106] In the embodiment as Figure 6 shown, after the execution of the valve closing control ends, the control unit 64 controls to first enter the second stable operation stage (as shown in step S22), and then enter the first stable operation stage (as shown in step S21). The control unit 64 adjusts so that the first calculation frequency for obtaining the calculated opening degree of the expansion valve in the second stable operation stage is higher than the second calculation frequency for obtaining the calculated opening degree of the expansion valve in the first stable operation stage, and after continuously calculating and adjusting the opening degree of the expansion valve several times according to the first calculation frequency, the second stable operation stage ends, and then the first stable operation stage is entered.

[0107] For example, in the first stable operation stage, the calculated opening degree of the expansion valve is obtained every T seconds (T = 60, 120...), and in the second stable operation stage, the calculated opening degree of the expansion valve is obtained every T1 seconds (T1 = 15, 30...). After continuously obtaining, calculating, and adjusting N times (N = 2, 3..., optionally set to 5), the first calculation frequency for obtaining the calculated opening degree of the expansion valve is restored, that is, the control in the first stable operation stage. In the second stable operation stage, there are more adjustment points for the expansion valve, and the situation of sudden changes in the expansion valve opening degree is significantly reduced, and the system is more stable during the switching process.

[0108] In the first stable operation stage, the second stable operation stage, or both the first stable operation stage and the second stable operation stage, some embodiments of the present application also add a load correction step. Taking the first stable operation stage as an example, after entering the first stable operation stage, the control unit 64 is configured to execute the process as Figure 7 shown.

[0109] In step S201, the control unit 64 obtains the return air temperature and relative humidity of the return air outlet, and obtains the air enthalpy value h of the return air outlet based on the return air temperature and the relative humidity of the return air outlet ai_0 .

[0110] In step S202, the control unit 64 obtains the supply air temperature and relative humidity of the supply air outlet (by default, it is close to the saturated state, 95% in the cooling mode), and obtains the air enthalpy value h of the supply air outlet based on the supply air temperature and the relative humidity of the supply air outlet ao_0 .

[0111] In step S203, the control unit 64 obtains the real-time air volume G of the fan ij_0 .

[0112] In step S204, the control unit 64 calculates the unit capacity Q0 of the air conditioning system 100

[0113] Q0 = G ij_0 (h ai_0 - h ao_0 )

[0114] In step S205, after setting the test duration (for example, 1 to 2 minutes), the control unit 64 obtains the return air temperature and relative humidity of the return air outlet again, and obtains the air enthalpy value h of the return air outlet based on the return air temperature and the relative humidity of the return air outlet ai_1 ;

[0115] In step S206, the supply air temperature and relative humidity of the supply air outlet are obtained again, and the air enthalpy value h of the supply air outlet is obtained based on the supply air temperature and the relative humidity of the supply air outlet ao_1 .

[0116] In step S207, the control unit 64 obtains the real-time air volume G of the fan again ij_1 .

[0117] In step S208, the control unit 64 calculates the unit capacity Q1 of the air conditioning system 100

[0118] Q1 = G ij_1 (h ai_1 - h ao_1 )

[0119] In step S209, the control unit 64 calculates the temperature change value ΔT of the air-conditioned room within the set load adjustment duration according to the difference in unit capacity for the set test duration. The calculation of the temperature change value ΔT of the air-conditioned room within the set load adjustment duration according to the difference in unit capacity for the set test duration adopts an algorithm disclosed in the prior art and will not be elaborated here. For example, the cooling load of the air-conditioned room is calculated based on the difference between the real-time temperature and the target temperature, and the total time for adjusting the cooling load of the air-conditioned room is calculated based on the unit capacity for the set test duration, and further the temperature change value ΔT of the air-conditioned room within the set load adjustment duration is deduced.

[0120] In step S210, after the load adjustment duration ends, the control unit 64 acquires the return air temperature at the return air outlet again, and calculates the temperature difference between the return air temperature at the start time and the end time of the load adjustment duration.

[0121] In steps S211 to S216, if the temperature difference is lower than the temperature change value ΔT, it indicates that the unit capacity is insufficiently exerted, and the control unit 64 executes the control of adjusting and increasing the calculated opening degree of the expansion valve corresponding to the air handling unit; if the temperature difference is higher than the temperature change value ΔT, the control of adjusting and decreasing the calculated opening degree of the expansion valve corresponding to the air handling unit is executed; if the temperature difference is equal to the temperature change value ΔT or matches the temperature change value ΔT (for example, ΔT ± 1 °C), the calculated opening degree of the expansion valve corresponding to the air handling unit remains unchanged.

[0122] As Figure 8 shown, in some optional embodiments of the present application, a room temperature cooling curve is fitted according to the unit capacity. In the first stable operation stage and / or the second stable operation stage, when the real-time return air temperature of the air handling unit is higher than the corresponding set temperature of the unit preset room temperature cooling curve, the control unit 64 adjusts and increases the calculated opening degree of the expansion valve corresponding to the air handling unit; when the real-time return air temperature of the air handling unit is lower than the corresponding set temperature of the unit preset room temperature cooling curve, the control unit 64 adjusts and decreases the calculated opening degree of the expansion valve corresponding to the air handling unit; when the real-time return air temperature of the air handling unit matches the corresponding set temperature of the unit preset room temperature cooling curve, the calculated opening degree of the expansion valve corresponding to the air handling unit remains unchanged. Assume that when the load adjustment duration (5 minutes) ends, the return air temperature at the return air outlet drops by 1 °C, and the unit preset room temperature cooling curve drops by 3 °C during this period. At this time, the return air temperature is higher than the corresponding set temperature of the unit preset room temperature cooling curve. At this time, the capacity of the air conditioning system 100 is insufficiently exerted, and the control unit 64 determines that load correction needs to be performed. The control unit 64 executes the frequency increase of the compressor 12 and adjusts and increases the control of the calculated opening degree of the expansion valve corresponding to the air handling unit.

[0123] Figure 9A flowchart showing the processing executed by the control unit 64 in some alternative embodiments of the present application.

[0124] In step S401, the control unit 64 performs the first stable operation stage control. The control unit 64 can enter the oil return control according to the oil return control conditions set based on the compressor operation frequency and operation time, and execute the following control after entering the oil return control.

[0125] In step S402, the control unit 64 determines whether the difference between the liquid pipe temperature of the liquid pipe upstream of the expansion valve corresponding to the air handling unit in the startup state and the saturation temperature obtained based on the pressure before the expansion valve satisfies the set valve adjustment condition for the oil return stage. Exemplarily, the set valve adjustment condition for the oil return stage is set such that the difference between the liquid pipe temperature of the liquid pipe upstream of the expansion valve corresponding to the air handling unit in the startup state and the saturation temperature obtained based on the pressure before the expansion valve is less than the set temperature difference. At this time, the air conditioning system 100 needs to reduce the valve opening and increase the subcooling degree before the valve. For example, the liquid pipe temperature is 41°C, the pressure before the valve is 2.4 MPa, the saturation temperature T_sat corresponding to the pressure before the valve is 41.1°C, and the set temperature difference is 3°C. At this time, the difference between the liquid pipe temperature of the liquid pipe upstream of the expansion valve and the saturation temperature obtained based on the pressure before the expansion valve is 0.1°C, which is less than the set temperature difference of 3°C, satisfying the set valve adjustment condition for the oil return stage.

[0126] In step S403, when the set valve adjustment condition for the oil return stage is satisfied, the control unit 64 performs the oil return stage valve adjustment control to adjust and reduce the calculated opening of the expansion valve corresponding to the air handling unit. The reduced expansion valve opening can be adjusted according to the subcooling degree target value.

[0127] In step S404, the control unit 64 determines whether the set oil return valve adjustment cycle has ended.

[0128] In step S405, after the set oil return valve adjustment cycle ends, the control unit 64 determines whether the expansion valve opening is the set minimum opening.

[0129] In step S406, when the expansion valve opening is not the set minimum opening, the control unit 64 determines again whether the set valve adjustment condition for the oil return stage is satisfied. When the set valve adjustment condition for the oil return stage is satisfied again, the control unit 64 adjusts and reduces the calculated opening of the expansion valve corresponding to the air handling unit again until the difference between the liquid pipe temperature of the liquid pipe upstream of the expansion valve corresponding to the air handling unit in the startup state and the saturation temperature obtained based on the pressure before the expansion valve no longer satisfies the set valve adjustment condition for the oil return stage, and the oil return stage valve adjustment control ends (as shown in step S407), and the oil return control is maintained until the set time point is reached, and the first stable operation stage is restored (as shown in step S408). The set time point can be 1 minute after the oil return control is executed.

[0130] When the set oil return regulating valve period has not ended but the expansion valve opening is the set minimum opening, the control unit 64 maintains the expansion valve opening at the set minimum opening unchanged until the difference between the liquid pipe temperature of the liquid pipe upstream of the expansion valve corresponding to the air handling unit in the startup state and the saturation temperature obtained based on the pressure in front of the expansion valve no longer satisfies the set oil return stage regulating condition, or maintains the oil return control until the set time point is reached. The set minimum opening can ensure that the lubricating oil discharged from the compressor 12 can smoothly return to the compressor 12. The set minimum opening can be 8%.

[0131] When the number of air handling units in the startup state is multiple, the control unit 64 performs the oil return stage regulating control when the difference between the maximum liquid pipe temperature of the liquid pipe upstream of the expansion valve corresponding to the air handling unit in the startup state and the saturation temperature obtained based on the pressure in front of the expansion valve satisfies the set oil return stage regulating condition.

[0132] Another aspect of the present application provides an air conditioning system 100, specifically improving the room number switching stage, Figure 10 FIG. is a control flowchart of the control unit 64 in the improved room number switching stage, specifically including: in the refrigeration mode, during the room number switching stage, when the number of rooms decreases and the capacity ratio of the air handling unit in the startup state after switching to the air handling unit in the startup state before switching satisfies the switching capacity condition, the control unit 64 performs a valve closing control on the expansion valve corresponding to the air handling unit receiving the shutdown instruction.

[0133] Figure 11 FIG. is another control flowchart of the control unit 64 in the improved room number switching stage, specifically including that in the refrigeration mode, during the room number switching stage, when the number of rooms decreases and the capacity ratio of the air handling unit in the startup state after switching to the air handling unit in the startup state before switching does not satisfy the switching capacity condition but the exhaust superheat satisfies the low exhaust superheat condition, the control unit 64 maintains the valve opening of the expansion valve corresponding to the air handling unit receiving the shutdown instruction unchanged until the exhaust superheat satisfies the low exhaust superheat condition, and then performs a valve closing control on the expansion valve corresponding to the air handling unit receiving the shutdown instruction.

[0134] Another aspect of the present application provides an air conditioning system 100, specifically improving the stable operation stage, Figure 12It is a control flow chart of the control unit 64 in the stable control stage. In the refrigeration mode, during the stable operation stage, when the real-time return air temperature of the air handling unit is higher than the corresponding set temperature of the unit's preset room temperature cooling curve, the control unit 64 adjusts and increases the calculated opening of the expansion valve corresponding to the air handling unit; when the real-time return air temperature of the air handling unit is lower than the corresponding set temperature of the unit's preset room temperature cooling curve, the control unit 64 adjusts and decreases the calculated opening of the expansion valve corresponding to the air handling unit; when the real-time return air temperature of the air handling unit matches the corresponding set temperature of the unit's preset room temperature cooling curve, the control unit 64 keeps the calculated opening of the expansion valve corresponding to the air handling unit unchanged; the calculated opening is obtained according to the target superheat of the air handling unit.

[0135] Figure 13 It is a control flow chart of the control unit 64 in the stable control stage. During the stable operation stage, when the difference between the liquid pipe temperature of the liquid pipe located upstream of the expansion valve corresponding to the air handling unit in the on state and the saturation temperature obtained according to the valve front pressure of the expansion valve meets the set valve adjustment condition in the oil return stage, the control unit 64 executes the valve adjustment control in the oil return stage, adjusts and decreases the calculated opening of the expansion valve corresponding to the air handling unit until the set oil return valve adjustment cycle ends or the expansion valve opening has been adjusted to the set minimum opening; when the set oil return valve adjustment cycle ends and the expansion valve opening is not the set minimum opening, the control unit 64 executes the valve adjustment control in the oil return stage again until the difference between the liquid pipe temperature of the liquid pipe located upstream of the expansion valve corresponding to the air handling unit in the on state and the saturation temperature obtained according to the valve front pressure of the expansion valve no longer meets the set valve adjustment condition in the oil return stage, the valve adjustment control in the oil return stage ends, and the oil return control is maintained until the set time point is reached, and the stable operation stage is restored.

[0136] In the description of the above embodiments, the specific features, structures, materials or characteristics can be combined in a suitable manner in any one or more embodiments or examples.

[0137] The above is only the specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. An air conditioning system, comprising: At least one outdoor unit having a compressor and a first heat exchanger; Multiple air handling units having a fan and a second heat exchanger; An expansion valve correspondingly arranged with the air handling unit; and A control unit; The air conditioning system has a refrigerant circuit, and the refrigerant circuit sequentially connects the compressor, the first heat exchanger, the expansion valve, and the second heat exchanger to circulate the refrigerant; It is characterized in that the capacity of at least one air handling unit is less than the capacity of a standard air handling unit; in the cooling mode, during the startup stage, when the capacity of the air handling unit that receives the startup instruction meets the low-capacity condition, and at the same time the capacity ratio meets the low-capacity ratio condition, the control unit generates an opening correction value proportional to the preset initial opening value according to the preset initial opening value, and uses the sum of the opening correction value and the initial opening value to generate a target opening value to control the actual opening of the expansion valve corresponding to the air handling unit that meets the low-capacity condition during the startup stage; wherein, the capacity ratio is the ratio of the capacity of the air handling unit that receives the startup instruction to the total capacity of all air handling units that receive the startup instruction; When the capacity of the air handling unit that receives the startup instruction does not meet the low-capacity condition, the control unit calls the preset initial opening value to control the actual opening of the expansion valve corresponding to the air handling unit that receives the startup instruction during the startup stage; When the capacity of the air handling unit that receives the startup instruction meets the low-capacity condition but the capacity ratio of the capacity of the air handling unit that receives the startup instruction and the total capacity of all air handling units that receive the startup instruction does not meet the low-capacity ratio condition, the control unit calls the preset initial opening value to control the actual opening of the expansion valve corresponding to the air handling unit that receives the startup instruction during the startup stage.

2. The air conditioning system according to claim 1, characterized in that After at least one air handling unit receives a startup instruction or a shutdown instruction different from the current operating state, the control unit switches from the first stable operation stage to the room number switching stage; During the room number switching stage, when the number of rooms decreases and the front and rear capacity ratios meet the switching capacity condition, the control unit performs a valve closing control on the expansion valve corresponding to the air handling unit that receives the shutdown instruction; wherein the front and rear capacity ratio is the ratio of the total capacity of the air handling units that are in the startup state after switching and the total capacity of the air handling units that are in the startup state before switching.

3. The air conditioning system according to claim 1, characterized in that After at least one air handling unit receives a startup instruction or a shutdown instruction different from the current operating state, the control unit switches from the first stable operation stage to the room number switching stage; During the room number switching stage, when the number of rooms decreases, and the front-to-back capacity ratio does not meet the switching capacity condition but the exhaust superheat does not meet the low exhaust superheat condition, the control unit keeps the valve opening degree of the expansion valve corresponding to the air handling unit receiving the shutdown instruction unchanged until the exhaust superheat meets the low exhaust superheat condition, and then performs valve closing control on the expansion valve corresponding to the air handling unit receiving the shutdown instruction; wherein the front-to-back capacity ratio is the ratio between the total capacity of the air handling units in the on state after switching and the total capacity of the air handling units in the on state before switching.

4. The air conditioning system according to claim 2 or 3, characterized in that After the execution of the valve closing control ends, the control unit controls to first enter the second stable operation stage and then enter the first stable operation stage; The control unit adjusts so that the first calculation frequency of obtaining the calculated opening degree of the expansion valve in the second stable operation stage is higher than the second calculation frequency of obtaining the calculated opening degree of the expansion valve in the first stable operation stage, and after continuously calculating and adjusting the opening degree of the expansion valve several times according to the first calculation frequency, the second stable operation stage ends, and then the first stable operation stage is entered; the calculated opening degree is obtained according to the target superheat of the air handling unit.

5. The air conditioning system according to claim 4, characterized in that In the first stable operation stage and / or the second stable operation stage, when the real-time return air temperature of the air handling unit is higher than the corresponding set temperature of the unit preset room temperature cooling curve, the control unit adjusts and increases the calculated opening degree of the expansion valve corresponding to the air handling unit; when the real-time return air temperature of the air handling unit is lower than the corresponding set temperature of the unit preset room temperature cooling curve, the control unit adjusts and decreases the calculated opening degree of the expansion valve corresponding to the air handling unit; when the real-time return air temperature of the air handling unit matches the corresponding set temperature of the unit preset room temperature cooling curve, the control unit keeps the calculated opening degree of the expansion valve corresponding to the air handling unit unchanged.

6. The air conditioning system according to claim 5, characterized in that In the first stable operation stage, when the control unit performs oil return control, and when the difference between the liquid pipe temperature and the saturation temperature obtained according to the valve front pressure of the expansion valve meets the set valve adjustment condition in the oil return stage, the control unit performs valve adjustment control in the oil return stage, adjusts and decreases the calculated opening degree of the expansion valve corresponding to the air handling unit until the set oil return valve adjustment cycle ends, or until the expansion valve opening degree has been adjusted to the set minimum opening degree, wherein the liquid pipe temperature is the temperature of the liquid pipe upstream of the expansion valve corresponding to the air handling unit in the on state; when the set oil return valve adjustment cycle ends and the expansion valve opening degree is not the set minimum opening degree, the control unit performs valve adjustment control in the oil return stage again until the difference between the liquid pipe temperature and the saturation temperature obtained according to the valve front pressure of the expansion valve no longer meets the set valve adjustment condition in the oil return stage, and the valve adjustment control in the oil return stage ends, and the oil return control is maintained until the set time point is reached, and the first stable operation stage is restored.

7. The air conditioning system according to claim 6, characterized in that When the number of air handling units in the powered-on state is multiple, the control unit performs oil return stage valve adjustment control when the difference between the maximum liquid pipe temperature and the saturation temperature obtained based on the pressure in front of the expansion valve satisfies the set oil return stage valve adjustment condition; the maximum liquid pipe temperature is the highest temperature of the liquid pipe upstream of the expansion valve corresponding to the air handling unit in the powered-on state.

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