Multi-split system and control method of enthalpy spraying electronic expansion valve during heating of multi-split system

Abstract

The invention discloses a multi-split system and a control method of an enthalpy spraying electronic expansion valve during heating of the multi-split system. The multi-split system is started up during heating and enters a soft start stage; in the soft start stage, the enthalpy spraying electronic expansion valve is closed, and after the multi-split air conditioning system operates for a duration A, the multi-split air conditioning system enters the normal control stage; in the normal control stage, after the frequency of a compressor reaches B, the multi-split air conditioning system judges whether an enthalpy spraying electronic expansion valve is opened or not and the initial opening degree of the enthalpy spraying electronic expansion valve after the enthalpy spraying electronic expansion valve is opened according to the environment temperature and the load rate of an indoor unit; and if the enthalpy spraying electronic expansion valve is opened and maintained for C duration, the multi-split system determines the target high-pressure saturation temperature according to the current environment temperature, and then the opening degree of the enthalpy spraying electronic expansion valve is adjusted according to the difference value between the target high-pressure saturation temperature and the actual high-pressure saturation temperature. According to the arrangement, the enthalpy spraying electronic expansion valve can be adjusted from multiple aspects, the state of the multi-split system is detected in real time in the enthalpy spraying opening process, and the comfort of customers and the reliability of the system are improved.

Description

Technical Field

[0001] The invention relates to the field of heat pump air conditioners, and in particular to a multi-connected system and a control method for an enthalpy spraying electronic expansion valve during heating. Background Art

[0002] In the air conditioning market, air conditioners can be divided into low-temperature models and normal-temperature models according to different user environments. As we all know, the fluorine system air conditioning system exchanges heat through the temperature difference between the refrigerant and the air. In other words, when the temperature difference between the two is very small, the heat exchange capacity of the air conditioner will be greatly reduced. In winter, the temperature in the north is often below minus 15℃ or even minus 20℃. At this time, the temperature of the refrigerant is also very low, and the heat absorbed from the outer ring is also less, which causes the heating effect of the whole machine to be worse than that of heating at a higher ambient temperature. In response to this problem, many manufacturers have begun to develop enthalpy spray systems.

[0003] There is a type of enthalpy spray system (flash type) that is based on the original first-stage throttling. After the throttling process, the refrigerant in the medium-pressure state is directly supplied to the compressor through the jet port of the flash tank to improve the heating effect. In addition, after the refrigerant is supplied to the compressor, it can also reduce the exhaust temperature of the system and improve the operating reliability of the entire system. Many manufacturers will use solenoid valves or electronic expansion valves to control the flow rate of enthalpy spray, but considering that the opening range of the expansion valve is wider, many manufacturers will use electronic expansion valves for control.

[0004] However, since some manufacturers do not control the opening of the enthalpy spray electronic expansion valve reasonably, it will result in: the expansion valve is opened too large, the compressor returns liquid, the system reliability is reduced, and the compressor service life is affected. Summary of the invention

[0005] In order to solve the problems in the prior art, the purpose of the present invention is to provide a multi-split system and a control method for an enthalpy-spraying electronic expansion valve during heating, which can increase the system high pressure to increase the heating capacity of the multi-split system and avoid the risk of liquid return, thereby improving customer use and the operating reliability of the entire machine and extending the service life of the system.

[0006] In order to achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a control method for an enthalpy spray electronic expansion valve during heating of a multi-split system, in which an enthalpy spray electronic expansion valve is installed at the enthalpy spray port of a compressor in the multi-split system; the multi-split system is turned on for heating and enters a soft start stage; in the soft start stage, the enthalpy spray electronic expansion valve is closed, and after the multi-split system runs for A time, it enters a normal control stage;

[0007] In the normal control stage, when the compressor frequency reaches B, the multi-split system determines whether the heat-spraying electronic expansion valve is opened, and the initial opening degree of the heat-spraying electronic expansion valve after opening, according to the ambient temperature and the indoor unit load rate; if the heat-spraying electronic expansion valve is opened and maintained for C time, the multi-split system determines the target high-pressure saturation temperature according to the current ambient temperature, and then adjusts the opening degree of the heat-spraying electronic expansion valve according to the difference between the target high-pressure saturation temperature and the actual high-pressure saturation temperature.

[0008] Preferably, in the normal control stage, the lower the ambient temperature is, the lower the requirement for the indoor unit load rate is when the enthalpy injection electronic expansion valve is opened, but the initial opening of the enthalpy injection electronic expansion valve is larger.

[0009] Preferably, in the normal control stage, when the ambient temperature is greater than 19° C., the enthalpy spray electronic expansion valve is closed.

[0010] Preferably, the lower the ambient temperature, the higher the target saturation temperature.

[0011] Preferably, in the normal control stage, if the actual high-pressure saturation temperature is lower than the target saturation temperature, the opening of the enthalpy-spraying electronic expansion valve is periodically increased; wherein, the lower the ambient temperature, the larger the opening of the enthalpy-spraying electronic expansion valve needs to be adjusted each time.

[0012] Preferably, in the normal control stage, when the actual high-pressure saturation temperature is higher than the target saturation temperature, the opening of the enthalpy-spraying electronic expansion valve is periodically reduced; wherein, the lower the ambient temperature, the smaller the opening of the enthalpy-spraying electronic expansion valve needs to be adjusted each time.

[0013] Preferably, in the normal control stage, if the actual high-pressure saturation temperature reaches the target saturation temperature and lasts for a period of time D, the opening of the enthalpy injection electronic expansion valve will no longer change.

[0014] Preferably, in the multi-split system, a second gas portion is provided between the enthalpy spray electronic expansion valve and the enthalpy spray port of the compressor, and a ball valve is installed at the inlet of the second gas portion; the multi-split system monitors the return gas superheat in real time, and after the actual return gas superheat is lower than E and lasts for F time, the multi-split system enters the priority control stage; in the priority control stage, the enthalpy spray electronic expansion valve is immediately closed to step G, and the ball valve on the second gas portion is immediately opened until the multi-split system re-enters the normal control stage or shuts down.

[0015] Preferably, in the priority control stage, if the real-time return air superheat is greater than H and lasts for I time, the ball valve is closed and the multi-connected system re-enters the normal control stage; in the priority control stage, if the real-time return air superheat is lower than the corresponding target return air superheat fault value and lasts for 30s, the system is judged to be faulty, the multi-connected system is shut down, and a low return air superheat fault is prompted.

[0016] A multi-split system using the above-mentioned control method of the enthalpy spraying electronic expansion valve when heating the multi-split system.

[0017] The beneficial effects of the technical solution of the present invention are as follows: by limiting the conditions (ambient temperature, load rate, frequency) for opening the enthalpy spray electronic expansion valve when the multi-split system is heating, the influence of low ambient temperature conditions on the heating effect of the multi-split system can be accurately judged; and after the enthalpy spray electronic expansion valve is opened, when the high pressure of the multi-split system changes, the opening of the enthalpy spray electronic expansion valve also changes accordingly; and when there is a risk of liquid return, the enthalpy spray electronic expansion valve is controlled; the above-mentioned control method adjusts the enthalpy spray electronic expansion valve from multiple aspects, and detects the status of the multi-split system in real time during the process of opening the enthalpy spray. When an abnormality occurs in the multi-split system group, timely action is taken to maintain system reliability, so as to extend the service life of the unit and reduce the maintenance risk, thereby comprehensively ensuring that this control method improves customer comfort and system reliability when applied to the multi-split system. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of a multi-connection system.

[0019] Figure numerals: 1. compressor; 2. exhaust temperature sensor; 3. oil separator; 4. four-way valve; 5. second gas separator; 6. ball valve; 7. gas pipe; 8. gas pipe stop valve; 9. first gas separator; 10. spray enthalpy solenoid valve; 11. flash evaporator; 12. liquid pipe stop valve; 13. liquid pipe; 14. indoor unit electronic expansion valve; 15. liquid pipe temperature sensor; 16. indoor unit; 17. gas pipe temperature sensor; 18. outdoor unit; 19. ambient temperature sensor; 20. outdoor unit electronic expansion valve; 21. high pressure sensor; 22. low pressure sensor; 23. return air temperature sensor. DETAILED DESCRIPTION

[0020] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0021] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0022] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "plurality" means two or more, unless otherwise clearly specified.

[0023] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0024] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0025] Example 1

[0026] like Figure 1 A multi-split system is shown, comprising a compressor 1, an oil separator 3, a four-way valve 4, a second gas separator 5, a flash evaporator 11, an outdoor unit 18, a first gas separator 9 and a plurality of indoor units 16;

[0027] A plurality of indoor units 16 are connected in parallel, one port of the indoor unit 16 is connected to the gas pipe 7, the other port of the indoor unit 16 is connected to the liquid pipe 13, and an indoor electronic expansion valve 14 is provided at the connection between any indoor unit 16 and the liquid pipe 13; the outlet of the compressor 1 is connected to one port of the four-way valve 4 through the oil separator 3, the inlet of the compressor 1 is connected to the other port of the four-way valve through the first gas separator 9, the other port of the four-way valve 4 is connected to the gas pipe 7, the other port of the four-way valve 4 is connected to the outdoor unit 18, the outdoor unit 18 is connected to the flash evaporator 11, the flash evaporator 11 is connected to the enthalpy spray port of the compressor 1 through the enthalpy spray solenoid valve 10, and the flash evaporator 11 is connected to the liquid pipe 13; wherein, a second gas separator 5 is installed on the pipeline between the enthalpy spray electronic expansion valve 10 and the compressor 1, and a ball valve 6 is installed at the inlet of the second gas separator 5;

[0028] A gas pipe temperature sensor 17 for monitoring the gas pipe temperature Teoa is provided at the connection between the indoor unit 16 and the gas pipe 7, a liquid pipe temperature sensor 15 for monitoring the liquid pipe temperature Teia is provided between the indoor unit 16 and the indoor electronic expansion valve 14, a middle temperature sensor for monitoring the middle temperature Tzba of the indoor unit 16 is installed on the indoor unit 16; an ambient temperature sensor 19 for detecting the ambient temperature Tao is installed on the outdoor unit 18; an exhaust temperature sensor 2 for monitoring the exhaust temperature Tda is installed at the outlet of the compressor 1; a low-pressure sensor 22 for monitoring the low-pressure saturation temperature PS-t is installed on the pipeline between the first gas separator and the four-way valve, a return air temperature sensor 23 for monitoring the return air temperature ts is installed on the pipeline between the first gas separator 9 and the four-way valve, and a high-pressure sensor 21 for monitoring the high-pressure saturation temperature Pd-t is installed on the pipeline between the oil separator and the four-way valve.

[0029] In this embodiment, a gas pipe stop valve 8 is installed on the gas pipe 7, the second gas divider 5 is arranged between the four-way valve 4 and the gas pipe stop valve 8, and a filter is arranged between the second gas divider 5 and the gas pipe stop valve 8; a liquid pipe stop valve 12 is installed on the liquid pipe 13, and a filter is arranged between the liquid pipe stop valve 12 and the flash evaporator 11; a filter is arranged between the flash evaporator 11 and the enthalpy injection solenoid valve 10, an outdoor unit electronic expansion valve 20 is arranged between the flash evaporator 11 and the outdoor unit 18, and a filter is arranged between the outdoor unit electronic expansion valve 20 and the outdoor unit 18.

[0030] Example 2

[0031] A control method for an enthalpy-spraying electronic expansion valve during heating of a multi-split system, which can be used to control a multi-split system as described in Example 1;

[0032] The specific control method includes: the multi-split system starts heating and enters the soft start stage; in the soft start stage, the enthalpy spray electronic expansion valve is closed, and after the multi-split system runs for A time, it enters the normal control stage; wherein A is 3 minutes;

[0033] In the normal control stage, when the compressor frequency reaches B, the multi-split system determines whether the enthalpy spray electronic expansion valve is opened and the initial opening of the enthalpy spray electronic expansion valve after opening according to the ambient temperature and the load rate of the indoor unit; if the enthalpy spray electronic expansion valve is opened and maintained for C time, the multi-split system determines the target high-pressure saturation temperature according to the current ambient temperature, and then adjusts the opening of the enthalpy spray electronic expansion valve according to the difference between the target high-pressure saturation temperature and the actual high-pressure saturation temperature. Among them, B is 65HZ and C is 1min30s.

[0034] Such setting limits the conditions (ambient temperature, load rate, frequency) for opening the spray enthalpy electronic expansion valve when the multi-split system is heating, so that the influence of low ambient temperature conditions on the heating effect of the multi-split system can be accurately judged; and after the spray enthalpy electronic expansion valve is opened, when the high pressure of the multi-split system changes, the opening of the spray enthalpy electronic expansion valve also changes accordingly; and when there is a risk of liquid return, the spray enthalpy electronic expansion valve is controlled; the above control method adjusts the spray enthalpy electronic expansion valve from multiple aspects, detects the status of the multi-split system in real time during the opening of the spray enthalpy, and when the multi-split system group is abnormal, timely action is taken to maintain system reliability, so as to extend the service life of the unit and reduce the maintenance risk, thereby comprehensively ensuring that this control method improves customer comfort and system reliability when applied to the multi-split system.

[0035] In this embodiment, as shown in Table 1, in the normal control stage, the lower the ambient temperature, the lower the requirement for the load rate of the indoor unit when the enthalpy spray electronic expansion valve is opened, but the initial opening of the enthalpy spray electronic expansion valve is larger; with such a setting, there are many loads in the multi-split system. When the load rate is not very high, the heat of the multi-split system will not be easily dissipated, and the heating effect of the multi-split system will also be guaranteed. Therefore, when the load rate is not high, there is no need to open the enthalpy spray electronic expansion valve to additionally increase the high pressure. Specifically, as shown in Table 1, when the ambient temperature is greater than 15°C, when the compliance rate of the indoor units of the multi-split system is greater than 70%, the enthalpy spray electronic expansion valve is opened, and the opening degree of the enthalpy spray electronic expansion valve is 40 steps; when the ambient temperature is between 7°C and 15°C, when the compliance rate of the indoor units of the multi-split system is greater than 55%, the enthalpy spray electronic expansion valve is opened, and the opening degree of the enthalpy spray electronic expansion valve is 60 steps; when the ambient temperature is less than 7°C, when the compliance rate of the indoor units of the multi-split system is greater than 40%, the enthalpy spray electronic expansion valve is opened, and the opening degree of the enthalpy spray electronic expansion valve is 80 steps;

[0036] Ambient temperature Internal machine load rate Initial opening of the enthalpy spray electronic expansion valve T environment ≥ 15℃ ≥70％ 40 7℃<T environment<15℃ ≥55％ 60 T environment ≤ 7℃ ≥40％ 80

[0037] Table 1. Opening conditions and initial opening of the spray enthalpy electronic expansion valve

[0038] It is worth noting that in the normal control stage, when the ambient temperature is greater than 19°C, it can be determined that the ambient temperature is relatively high at this time, and the pressure of the multi-connected system is very high, which basically meets the heating effect. Therefore, there is no need to increase the high pressure by injecting enthalpy, and the injecting enthalpy electronic expansion valve will not open.

[0039] In this embodiment, the load rate of the indoor unit=the horsepower of the indoor unit / the horsepower of the outdoor unit*100%.

[0040] In this embodiment, as shown in Table 2, the lower the ambient temperature, the higher the target saturation temperature;

[0041] External ambient temperature Target high pressure saturation temperature T environment ≥ 15℃ 49 7℃<T environment<15℃ 50 T environment ≤ 7℃ 51

[0042] Table 2. Target saturation temperature determination table

[0043] In this embodiment, as shown in Table 3, in the normal control stage, if the actual high-pressure saturation temperature is lower than the target saturation temperature, the opening of the enthalpy-spraying electronic expansion valve is periodically increased; wherein, the lower the ambient temperature, the greater the opening of the enthalpy-spraying electronic expansion valve needs to be adjusted each time;

[0044] In the normal control stage, when the actual high-pressure saturation temperature is higher than the target saturation temperature, the opening of the enthalpy spray electronic expansion valve is periodically reduced; wherein, the lower the ambient temperature, the smaller the opening of the enthalpy spray electronic expansion valve needs to be adjusted each time;

[0045] In the normal control stage, if the actual high-pressure saturation temperature reaches the target saturation temperature and lasts for D time, the opening of the enthalpy injection electronic expansion valve will not change; where D is 2 minutes. In this way, the ambient temperature affects the adjustment of the enthalpy injection electronic expansion valve in real time. When the ambient temperature is high, the high pressure of the multi-split system will also be higher. At this time, the heating effect will be better. Although the high pressure has not reached the target, a large opening is no longer required at this time; on the contrary, if the high pressure is higher than the target high pressure, it is necessary to quickly reduce the flow of enthalpy supplementation to ensure the stability of the multi-split system.

[0046]

[0047] Table 3. Control logic table of the enthalpy spray electronic expansion valve in the normal control stage

[0048] In this embodiment, the multi-split system monitors the return air superheat in real time. When the actual return air superheat is lower than E and lasts for F time, it is judged that the system has a risk of liquid return, and it is necessary to close the valve to reduce the refrigerant flow entering the compressor, and give priority to ensuring that the compressor does not return liquid. Then the multi-split system enters the priority control stage; in the priority control stage, the spray enthalpy electronic expansion valve is immediately closed to step G, and the ball valve on the second gas part is immediately opened until the multi-split system re-enters the normal control stage or shuts down. Among them, E is 2°C, F is 1min, and G is 30; among them, return air superheat = return air temperature ts-low pressure saturation temperature PS-t.

[0049] Further preferably, in the priority control stage, if the actual return air superheat is greater than H and lasts for I time, the ball valve is closed and the multi-connected system re-enters the normal control stage; wherein H>G, H is 3°C, and I is 2min;

[0050] Further preferably, in the priority control stage, if the actual return air superheat is lower than the corresponding target return air superheat fault value and lasts for 30 seconds, the training system is judged to be faulty, the multi-connected system is shut down, and a return air superheat fault is prompted. The lower the ambient temperature, the lower the target return air superheat fault.

[0051] Take a multi-split outdoor unit with three indoor units, and all three indoor units are turned on for heating (load rate is 100%) at an outside ambient temperature of 7°C as an example:

[0052] The multi-split system enters the soft start control stage, the opening of the spray enthalpy electronic expansion valve is 0, and after maintaining for 3 minutes, the multi-split system enters the normal control stage. At this time, the compressor frequency is 70HZ. According to Table 1, it is determined that the spray enthalpy electronic expansion valve meets the opening conditions, and then the spray enthalpy electronic expansion valve opens to 80 steps and lasts for 1min30s; then, the high-pressure saturation temperature detected at this time is 50℃, and according to Table 2, the corresponding target high-pressure saturation temperature under 7℃ ambient temperature is 51℃, and then according to Table 3, it is determined that the spray enthalpy electronic expansion valve will open 8 steps per second, and then there will be the following situations: Case 1, after 5s, the spray enthalpy electronic expansion valve opens to 120 steps, at this time the high-pressure saturation temperature is exactly 51℃, and it lasts for 2min10s, then the expansion valve maintains the current number of steps and no longer changes; Case 2, When the enthalpy spray electronic expansion valve opens to 480 steps, the high-pressure saturation temperature is exactly 50.8℃, and the enthalpy spray electronic expansion valve will not continue to open; in case three, after 5s, when the number of steps of the enthalpy spray electronic expansion valve is 120, the high-pressure saturation temperature is exactly 51℃, and the return air superheat is 1.9℃, and it lasts for 1min, the enthalpy spray electronic expansion valve will not be controlled according to Table 3, and it will enter the priority control stage. At this time, the ball valve is opened, and the enthalpy spray expansion valve step is reduced to 30 steps. After running for 5min, the return air superheat is 3.5℃ and it lasts for another 2min. At this time, the ball valve is closed, and the enthalpy spray electronic expansion valve continues to be controlled according to Table 3; in case four, when the return air superheat is -0.4℃ and it lasts for 35s, the multi-connected system will directly shut down for protection, and report the low return air superheat fault at the same time.

[0053] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0054] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and intent of the present invention.

Claims

1. A control method for an enthalpy spray electronic expansion valve in a multi-connected system for heating, characterized in that: In a multi-split system, an electronic expansion valve for enthalpy injection is installed at the enthalpy injection port of the compressor; The multi-split system starts heating and enters the soft start stage; during the soft start stage, the enthalpy spray electronic expansion valve is closed, and after the multi-split system runs for A time, it enters the normal control stage; In the normal control stage, when the compressor frequency reaches B, the multi-split system determines whether the enthalpy spray electronic expansion valve is opened according to the ambient temperature and the load rate of the indoor unit, and the initial opening degree of the enthalpy spray electronic expansion valve after opening; If the enthalpy-spraying electronic expansion valve is opened and maintained for C time, the multi-connected system determines the target high-pressure saturation temperature according to the current ambient temperature, and then adjusts the opening of the enthalpy-spraying electronic expansion valve according to the difference between the target high-pressure saturation temperature and the actual high-pressure saturation temperature.

2. The control method of the enthalpy spraying electronic expansion valve in the heating of a multi-connected system according to claim 1, characterized in that: Normally in the control stage, the lower the ambient temperature is, the lower the requirement for the indoor unit load rate is when the enthalpy injection electronic expansion valve is opened, but the initial opening of the enthalpy injection electronic expansion valve is larger.

3. The control method of the enthalpy spray electronic expansion valve in the heating of a multi-connected system according to claim 1, characterized in that: In the normal control stage, when the ambient temperature is greater than 19°C, the enthalpy spray electronic expansion valve is closed.

4. The control method of the enthalpy spray electronic expansion valve in the heating of a multi-connected system according to claim 1, characterized in that: The lower the ambient temperature, the higher the target saturation temperature.

5. The control method of the enthalpy spray electronic expansion valve in the heating of a multi-connected system according to claim 1, characterized in that: In the normal control stage, if the actual high-pressure saturation temperature is lower than the target saturation temperature, the opening of the enthalpy-spraying electronic expansion valve is periodically increased; wherein, the lower the ambient temperature, the larger the opening of the enthalpy-spraying electronic expansion valve needs to be adjusted each time.

6. The control method of the enthalpy spray electronic expansion valve in the heating of a multi-connected system according to claim 1, characterized in that: In the normal control stage, when the actual high-pressure saturation temperature is higher than the target saturation temperature, the opening of the enthalpy-spraying electronic expansion valve is periodically reduced; wherein, the lower the ambient temperature, the smaller the opening of the enthalpy-spraying electronic expansion valve needs to be adjusted each time.

7. The control method of the enthalpy spray electronic expansion valve in the heating of a multi-connected system according to claim 1, characterized in that: In the normal control stage, if the actual high-pressure saturation temperature reaches the target saturation temperature and lasts for D time, the opening of the enthalpy injection electronic expansion valve will no longer change.

8. The control method of the enthalpy spray electronic expansion valve in the heating of a multi-connected system according to claim 1, characterized in that: In the multi-connected system, a second gas segment is arranged between the enthalpy spray electronic expansion valve and the enthalpy spray port of the compressor, and a ball valve is installed at the inlet of the second gas segment; The multi-split system monitors the return air superheat in real time. When the actual return air superheat is lower than E and lasts for F time, the multi-split system enters the priority control stage; in the priority control stage, the enthalpy injection electronic expansion valve is immediately closed to step G, and the ball valve on the second gas section is immediately opened until the multi-split system re-enters the normal control stage or shuts down.

9. The control method of the enthalpy spray electronic expansion valve in the heating of a multi-connected system according to claim 8, characterized in that: In the priority control stage, if the real-time return air superheat is greater than H and lasts for a period of time I, the ball valve is closed and the multi-connected system re-enters the normal control stage; In the priority control stage, if the real-time return air superheat is lower than the corresponding target return air superheat fault value and lasts for 30 seconds, the training system is judged to be faulty, the multi-connection system is shut down, and a low return air superheat fault is prompted.

10. A multi-split system using the control method of the enthalpy spraying electronic expansion valve during heating of the multi-split system as described in any one of claims 1 to 9.

Images