Heat pump air conditioning system control method and system

Abstract

The present application relates to rail transit (subway) vehicle air conditioning design and manufacturing technical field, especially relates to a kind of heat pump air conditioning system control method and system thereof.The heat pump air conditioning system control method includes: judging the mode that heat pump air conditioning system currently is;If heat pump air conditioning system is in heating mode, the first pressure value P i At the suction port of compressor is obtained, compared with the first preset pressure threshold P de1 , if P i P de , then control heat pump air conditioning system switches to defrost mode;If heat pump air conditioning system is in defrost mode, the second pressure value P d At the exhaust port of compressor is obtained, compared with the second preset pressure threshold P de2 , if P d P de2 , then control heat pump air conditioning system exits defrost mode.The present application also provides a kind of heat pump air conditioning system, and the above-mentioned heat pump air conditioning system control method is applied to heat pump air conditioning system.Compared with prior art, the advantages of the present application are: it is convenient to carry out real-time defrosting control to heat pump air conditioning system 100, and setting value can also be changed in real time by program.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of rail transit vehicle air conditioning design and manufacturing, in particular to a heat pump air conditioning system control method and system. BACKGROUND

[0002] The existing heat pump air conditioning system performs heating in winter, and when the ambient temperature is low and the humidity is high, the outdoor heat exchanger will freeze, and the heat pump air conditioning system almost all has a defrosting process. The commonly used defrosting control uses indoor and outdoor coil temperature sensors and high and low pressure switches in cooperation, and the pressure switch cannot be detected in real time. With the promotion of air conditioning intelligence and digitization, the high and low pressure switch will be replaced.

[0003] In the rail transit refrigeration system, the pressure and temperature of the refrigerant are detected by the cooperation between the high and low pressure switch and the outdoor coil temperature sensor to determine whether the system should be defrosted, and the high and low pressure switch is factory-set with a set value and connected to the air conditioning pipeline. When the system detects that the set value is reached, defrosting is performed, and the pressure value cannot be transmitted in real time, and the set value cannot be changed by the program. SUMMARY

[0004] Therefore, in view of the above technical problems, the present application provides a heat pump air conditioning system control method in an embodiment.

[0005] In order to solve the above technical problems, the present application provides the following technical scheme: a heat pump air conditioning system control method applied to a heat pump air conditioning system, the heat pump air conditioning system control method comprising: judging the current mode of the heat pump air conditioning system; if the heat pump air conditioning system is in a heating mode, acquiring a first pressure value P i at the suction port of the compressor and comparing it with a first preset pressure threshold P de1 , if P i <P de , controlling the heat pump air conditioning system to switch to a defrosting mode; if the heat pump air conditioning system is in a defrosting mode, acquiring a second pressure value P d at the discharge port of the compressor and comparing it with a second preset pressure threshold P de2 , if P d >P de2 , controlling the heat pump air conditioning system to exit the defrosting mode.

[0006] It can be understood that the present application adopts the heat pump air conditioning system control method, so as to facilitate real-time defrosting control of the heat pump air conditioning system by the controller, and the set value can be changed in real time by the program, which simplifies the control process of defrosting of the heat pump air conditioning system, avoids the freezing of the outdoor heat exchanger of the heat pump air conditioning system and affects the normal operation of the heat pump air conditioning system.

[0007] In one embodiment, the heat pump air conditioning system control method further comprises: obtaining an ambient temperature value T; within a preset time Xmin, if the ambient temperature value T > t1 °C, and the first pressure value P i < P1, then controlling the heat pump air conditioning system to switch to a defrosting mode, wherein, when the ambient temperature value T > t1 °C, the first preset pressure threshold P de1 is P1.

[0008] In one embodiment, the heat pump air conditioning system control method further comprises: obtaining an ambient temperature value T; within a preset time Xmin, if the ambient temperature value t1 °C ≥ T > t2 °C, and the first pressure value P i < P2, then controlling the heat pump air conditioning system to switch to a defrosting mode, wherein, when the ambient temperature value t1 °C ≥ T > t2 °C, the first preset pressure threshold P de1 is P2.

[0009] In one embodiment, the heat pump air conditioning system control method further comprises: obtaining an ambient temperature value T; within a preset time Xmin, if the ambient temperature value t2 °C ≥ T > t3 °C, and the first pressure value P i < P3, then controlling the heat pump air conditioning system to switch to a defrosting mode, wherein, when the ambient temperature value t2 °C ≥ T > t3 °C, the first preset pressure threshold P de1 is P3.

[0010] In one embodiment, the heat pump air conditioning system control method further comprises: obtaining an ambient temperature value T; within a preset time Xmin, if the ambient temperature value T ≤ t3 °C, and the first pressure value P i < P4, then controlling the heat pump air conditioning system to switch to a defrosting mode, wherein, when the ambient temperature value T ≤ t3 °C, the first preset pressure threshold P de1 is P4.

[0011] In one embodiment, the heat pump air conditioning system control method further comprises: obtaining an ambient temperature value T; within a preset time Yh, if the ambient temperature value T ≤ t3 °C, then controlling the heat pump air conditioning system to switch to a defrosting mode.

[0012] In one embodiment, the heat pump air conditioning system control method further comprises: obtaining a second pressure value P d of the compressor exhaust port, and comparing it with a second preset pressure threshold P de2 ; within a preset time Ns, if P d > P de2 , then controlling the heat pump air conditioning system to exit the defrosting mode.

[0013] In one embodiment, the heat pump air conditioning system control method further includes: within a preset time N de If the heat pump air conditioning system is in defrost mode within s, then control the heat pump air conditioning system to exit defrost mode.

[0014] In one embodiment, the heat pump air conditioning system control method further includes: obtaining a second pressure value P at the compressor exhaust port. d and the third preset pressure threshold P de3 Compare; if P d >P de3 Then, the heat pump air conditioning system will be controlled to exit the defrost mode.

[0015] One embodiment of the present invention also provides the following technical solution:

[0016] A heat pump air conditioning system, wherein the heat pump air conditioning system is controlled by a heat pump air conditioning system control method.

[0017] Compared with the prior art, the heat pump air conditioning system control method provided in one embodiment of the present invention facilitates real-time defrosting control of the heat pump air conditioning system through the controller, and the set value can also be changed in real time through the program, simplifying the control process for defrosting the heat pump air conditioning system and avoiding the outdoor heat exchanger of the heat pump air conditioning system from freezing and affecting the normal operation of the heat pump air conditioning system. Attached Figure Description

[0018] Figure 1 A schematic diagram of the control logic principle of the heat pump air conditioning system control method provided by the present invention;

[0019] Figure 2 A schematic diagram of the heat pump air conditioning system provided by the present invention.

[0020] The symbols in the diagram represent the following meanings:

[0021] 100. Heat pump air conditioning system; 10. First system; 11. First outdoor heat exchanger; 12. Second outdoor heat exchanger; 13. First indoor heat exchanger; 14. First compressor; 141. First pressure sensor; 142. Second pressure sensor; 20. Second system; 21. Third outdoor heat exchanger; 22. Fourth outdoor heat exchanger; 23. Second indoor heat exchanger; 24. Second compressor; 241. Third pressure sensor; 242. Fourth pressure sensor. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the scope of protection of this invention.

[0023] It should be noted that when a component is described as "mounted on" another component, it can be directly on the other component or there may be an intermediate component. When a component is described as "set on" another component, it can be directly set on the other component or there may be an intermediate component. When a component is described as "fixed to" another component, it can be directly fixed to the other component or there may be an intermediate component. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "or / and" as used herein includes any and all combinations of one or more of the associated listed items.

[0025] Please see Figure 1 and Figure 2 In one embodiment of the present invention, a heat pump air conditioning system control method is applied to a heat pump air conditioning system 100, which is used to monitor and control the heat pump air conditioning system 100 to enter / exit the defrost mode in real time through a controller.

[0026] Existing heat pump air conditioning systems operate in winter, where the outdoor heat exchanger freezes when the ambient temperature is low and humidity is high. Almost all heat pump air conditioning systems require a defrosting process. Common defrosting control uses indoor and outdoor coil temperature sensors in conjunction with high and low pressure switches, but the pressure switch cannot be detected in real time. With the advancement of intelligent and digital air conditioning systems, the high and low pressure switches will inevitably be replaced.

[0027] In rail transit refrigeration systems, the pressure and temperature of the refrigerant are detected by a combination of high and low pressure switches and outdoor coil temperature sensors to determine whether the system should defrost. Moreover, the high and low pressure switches are factory-set with preset values ​​and are connected to the air conditioning pipes. When the system detects that the set value has been reached, it will defrost. The detected pressure value cannot be transmitted in real time, and the set value cannot be changed by the program.

[0028] like Figure 1As shown, to solve the existing problems of heat pump air conditioning system, the application provides a heat pump air conditioning system 100 control method in an embodiment, which comprises the following steps:

[0029] Judging the mode of the heat pump air conditioning system 100;

[0030] If the heat pump air conditioning system 100 is in the heating mode, the first pressure value P i at the suction port of the compressor is obtained and compared with the first preset pressure threshold P de1 , if P i <P de1 , the heat pump air conditioning system 100 is switched to the defrosting mode;

[0031] If the heat pump air conditioning system 100 is in the defrosting mode, the second pressure value P d at the exhaust port of the compressor is obtained and compared with the second preset pressure threshold P de2 , if P d >P de2 , the heat pump air conditioning system 100 exits the defrosting mode.

[0032] The application adopts the heat pump air conditioning system 100 control method, so that the heat pump air conditioning system is controlled in real time by the controller, and the set value can be changed in real time through the program, which simplifies the defrosting control process of the heat pump air conditioning system 100 and avoids the icing of the outdoor heat exchanger of the heat pump air conditioning system 100, thereby affecting the normal operation of the heat pump air conditioning system 100.

[0033] As Figure 2As shown, the application also provides a heat pump air conditioning system 100, a heat pump air conditioning system 100 control method is applied to the heat pump air conditioning system 100, the heat pump air conditioning system 100 includes a first system 10 and a second system 20 which are independently operated, the first system 10 includes a first outdoor heat exchanger 11, a second outdoor heat exchanger 12 and a first indoor heat exchanger 13, the first outdoor heat exchanger 11 and the second outdoor heat exchanger 12 are connected in parallel, and are respectively connected in series with the first indoor heat exchanger 13; the second system 20 includes a third outdoor heat exchanger 21, a fourth outdoor heat exchanger 22 and a second indoor heat exchanger 23, the third outdoor heat exchanger 21 and the fourth outdoor heat exchanger 22 are connected in parallel, and are respectively connected in series with the second indoor heat exchanger 23; the first system 10 further includes a first compressor 14, the exhaust port of the first compressor 14 is respectively connected with the first outdoor heat exchanger 11 and the second outdoor heat exchanger 12, and the suction port of the first compressor 14 is respectively connected with the first indoor heat exchanger 13 and the second indoor heat exchanger 23; the second system 20 further includes a second compressor 24, the exhaust port of the second compressor 24 is respectively connected with the third outdoor heat exchanger 21 and the fourth outdoor heat exchanger 22, and the suction port of the second compressor 24 is respectively connected with the first indoor heat exchanger 13 and the second indoor heat exchanger 23; the suction port of the first compressor 14 is provided with a first pressure sensor 141, the exhaust port of the first compressor 14 is provided with a second pressure sensor 142, the suction port of the second compressor 24 is provided with a third pressure sensor 241, and the exhaust port of the second compressor 24 is provided with a fourth pressure sensor 242.

[0034] Among them, the first pressure sensor 141 and the third pressure sensor 241 are used to obtain the first pressure value P i of the suction port of the first compressor 14 and the second compressor 24, and the second pressure sensor 142 and the fourth pressure sensor 242 are used to obtain the second pressure value P d of the exhaust port of the first compressor 14 and the second compressor 24. The first pressure sensor 141, the second pressure sensor 142, the third pressure sensor 241 and the fourth pressure sensor 242 can detect the refrigerant pressure value and transmit the detected pressure value to the controller in real time, and the set value in the first pressure sensor 141, the second pressure sensor 142, the third pressure sensor 241 and the fourth pressure sensor 242 can also be changed in real time through the program.

[0035] It should be noted that the pressure is generally related to the state of the refrigerant, which is related to the external environment due to heat exchange between the refrigerant and the external environment. When the heat pump air conditioning system 100 is in a heating state, the first outdoor heat exchanger 11, the second outdoor heat exchanger 12, and the third outdoor heat exchanger 21, the fourth outdoor heat exchanger 22 are connected with the suction port of the first compressor 14 and the suction port of the second compressor 24 respectively. At this time, if the first outdoor heat exchanger 11, the second outdoor heat exchanger 12, and the third outdoor heat exchanger 21, the fourth outdoor heat exchanger 22 are frosted, the frost layer attached to the fins will affect the heat exchange efficiency of the heat exchange tubes of the first outdoor heat exchanger 11, the second outdoor heat exchanger 12, and the third outdoor heat exchanger 21, the fourth outdoor heat exchanger 22, which will cause the first outdoor heat exchanger 11, the second outdoor heat exchanger 12, and the third outdoor heat exchanger 21, the fourth outdoor heat exchanger 22 to have difficulty in absorbing heat. Then the temperature of the refrigerant flowing to the suction port of the first compressor 14 and the suction port of the second compressor 24 will be reduced, thereby reducing the pressure of the refrigerant flowing to the suction port of the first compressor 14 and the suction port of the second compressor 24. At this time, the first pressure sensor 141 and the third pressure sensor 241 detect the first pressure value P i of the refrigerant at the suction port of the first compressor 14 and the suction port of the second compressor 24, and compare it with the first preset pressure threshold P de1 , to determine whether the heat pump air conditioning system 100 should be defrosted; conversely, when the heat pump air conditioning system 100 enters the defrosting mode, the first outdoor heat exchanger 11, the second outdoor heat exchanger 12, and the third outdoor heat exchanger 21, the fourth outdoor heat exchanger 22 are connected with the exhaust port of the first compressor 14 and the exhaust port of the second compressor 24 respectively. The heat pump air conditioning system 100 sets the pressure value of the exhaust port of the first compressor 14 and the exhaust port of the second compressor 24 to the second preset pressure threshold P de2 by the controller. When the outdoor heat exchanger is fully defrosted, the second pressure sensor 142 and the fourth pressure sensor 242 obtain the second pressure value P d of the exhaust port of the first compressor 14 and the exhaust port of the second compressor 24 reaches the second preset pressure threshold P de2 , the controller controls the heat pump air conditioning system 100 to automatically exit the defrosting mode.

[0036] Since the state of the refrigerant is related to the external environment due to heat exchange between the refrigerant and the external environment, in order to further accurately control whether the heat pump air conditioning system 100 enters the defrosting mode, the first preset pressure threshold P de1 needs to be set differently according to different environmental temperatures.

[0037] That is, when the ambient temperature is relatively high, the first outdoor heat exchanger 11, the second outdoor heat exchanger 12 and the third outdoor heat exchanger 21 and the fourth outdoor heat exchanger 22 can generally defrost by the ambient temperature, and when the ambient temperature is relatively low, defrosting is needed by switching the heat pump air conditioning system 100 to the defrosting mode. Therefore, when the ambient temperature is relatively high, the first preset pressure threshold P de1 may be relatively high, and when the ambient temperature is relatively low, the first preset pressure threshold P de1 may be relatively low.

[0038] The ambient temperature is divided into different regions, and an outdoor ring temperature sensor (not shown in the figure) for detecting the ambient temperature is arranged in the heat pump air conditioning system 100. In one case, the ambient temperature value T is obtained by the outdoor ring temperature sensor within a preset time Xmin, and if the outdoor ring temperature sensor detects that the ambient temperature value T>t1℃, and the first pressure value P i <P1, the controller controls the heat pump air conditioning system 100 to switch to the defrosting mode; wherein, when the ambient temperature value T>t1℃, the controller automatically sets the first preset pressure threshold P de1 to P1.

[0039] It should be noted that, in the case of the ambient temperature value T>t1℃, the controller controls the heat pump air conditioning system 100 to switch to the defrosting mode needs to meet two conditions, one is the condition that the first pressure value P i <P1, and the other is the condition that the first pressure value P i is less than P1 for Xmin, and both conditions are indispensable.

[0040] In one case, the ambient temperature value T is obtained by the outdoor ring temperature sensor within a preset time Xmin, and if the outdoor ring temperature sensor detects that the ambient temperature value t1℃≥T>t2℃, and the first pressure value P i <P2, the controller controls the heat pump air conditioning system 100 to switch to the defrosting mode; wherein, when the ambient temperature value t1℃≥T>t2℃, the controller automatically sets the first preset pressure threshold P de1 to P2.

[0041] It should be noted that, in the case of the ambient temperature value t1℃≥T>t2℃, the controller controls the heat pump air conditioning system 100 to switch to the defrosting mode needs to meet two conditions, one is the condition that the first pressure value P i <P2, and the other is the condition that the first pressure value P i is less than P2 for Xmin, and both conditions are indispensable.

[0042] In one case, within a preset time Xmin, the ambient temperature value T is obtained by the outdoor ring temperature sensor, if the outdoor ring temperature sensor detects the ambient temperature value t1℃≥T>t2℃, and the first pressure value is P i When the ambient temperature value t2℃≥T>t3℃, the controller automatically sets the first preset pressure threshold P de1 to P3.

[0043] It should be noted that in the case of the ambient temperature value t1℃≥T>t2℃, the controller controls the heat pump air conditioning system 100 to switch to the defrosting mode to meet two conditions, one is the first pressure value P i <P3, the second is the first pressure value P i <P3 for Xmin, both of which are indispensable.

[0044] In one case, within a preset time Xmin, the ambient temperature value T is obtained by the outdoor ring temperature sensor, if the outdoor ring temperature sensor detects the ambient temperature value T≤t3℃, and the first pressure value is P i When the ambient temperature value T≤t3℃, the controller automatically sets the first preset pressure threshold P de1 to P4.

[0045] It should be noted that in the case of the ambient temperature value T≤t3℃, the controller controls the heat pump air conditioning system 100 to switch to the defrosting mode to meet two conditions, one is the first pressure value P i <P4, the second is the first pressure value P i <P4 for Xmin, both of which are indispensable.

[0046] In one case, within a preset time Yh, the ambient temperature value T is obtained by the outdoor ring temperature sensor, if the ambient temperature value T≤t3℃, the controller controls the heat pump air conditioning system 100 to switch to the defrosting mode.

[0047] It should be noted that in the case of the ambient temperature value T≤t3℃, the controller controls the heat pump air conditioning system 100 to switch to the defrosting mode to meet one condition, that is, the ambient temperature value T≤t3℃ for Yh.

[0048] It is worth noting that the size relationship between the above temperature values is t1℃>t2℃>t3℃, and the size of the above pressure values is P1>P2>P3>P4. When the ambient temperature value is still between t1℃≥T>t3℃, that is, the ambient temperature is not low enough at this time, the first pressure value P i corresponding to the ambient temperature value is set by the controller. When the first pressure sensor 141 and the second pressure sensor 142 detect that the first pressure value P i at the suction port of the first compressor 14 and the second compressor 24 is lower than the corresponding first preset pressure threshold P de1 , it indicates that the first outdoor heat exchanger 11, the second outdoor heat exchanger 12, and the third outdoor heat exchanger 21, the fourth outdoor heat exchanger 22 have been frosted to a certain extent, and the heat pump air conditioning system 100 needs to enter the defrosting mode. The controller controls the heat pump air conditioning system 100 to switch to the defrosting mode. When the ambient temperature value T≤t3℃ continues for Yh, that is, the heat pump air conditioning system 100 has been in a situation where the ambient temperature is low enough for a long time, at this time, it is not necessary to determine whether the heat pump air conditioning system 100 needs to enter the defrosting mode by the pressure value, and the controller directly controls the heat pump air conditioning system 100 to switch to the defrosting mode.

[0049] When the heat pump air conditioning system 100 enters the defrosting mode, the heat pump air conditioning system 100 is in a refrigeration state, and the first outdoor heat exchanger 11, the second outdoor heat exchanger 12, and the third outdoor heat exchanger 21, the fourth outdoor heat exchanger 22 are defrosted. When the defrosting is completed, the heat pump air conditioning system 100 needs to exit the defrosting mode and continue to enter the heating mode. At this time, the second pressure sensor 142 and the fourth pressure sensor 242 arranged at the exhaust port of the first compressor 14 and the second compressor 24 are needed to detect the second pressure value P d at the exhaust port of the first compressor 14 and the second compressor 24. The second preset pressure threshold P de2 is set in the controller. When the second pressure value P d is greater than the second preset pressure threshold P de2 within a preset time Ns, the controller controls the heat pump air conditioning system 100 to exit the defrosting mode.

[0050] Of course, the heat pump air conditioning system 100 cannot be in the defrosting mode for a long time. In addition to determining whether to exit the defrosting mode by the pressure value at the exhaust port of the compressor, the running time of the defrosting mode can also be used for determination. If the heat pump air conditioning system 100 is in the defrosting mode within a preset time N de s, the controller controls the heat pump air conditioning system 100 to exit the defrosting mode.

[0051] There is also a case that when the heat pump air conditioning system 100 is in the defrosting mode, the second pressure sensor 142 and the fourth pressure sensor 242 obtain the second pressure value P d of the first compressor 14 and the second compressor 24 exhaust port de3 , and compare with the third preset pressure threshold P d ; if P de3 >P de3 , the controller controls the heat pump air conditioning system 100 to exit the defrosting mode.

[0052] It is worth noting that the third preset pressure threshold P de3 is much larger than the second preset pressure threshold P de2 , when the second pressure value P d is greater than P de3 , it means that the heat pump air conditioning system 100 has failed to produce high pressure protection, at this time, the second pressure sensor 142 and the fourth pressure sensor 242 detect the second pressure value P d of the first compressor 14 and the second compressor 24 exhaust port rises straight, so at this time, the heat pump air conditioning system 100 also needs to be controlled to directly exit the defrosting mode.

[0053] In addition, the heat pump air conditioning system 100 is also provided with a brake switch, if it is necessary to make the heat pump air conditioning system 100 exit the defrosting mode, the brake switch can also be manually controlled at any time to control the start and stop of the defrosting mode.

[0054] The heat pump air conditioning system 100 control method provided by the application, by adopting the heat pump air conditioning system control method, so as to facilitate the real-time defrosting control of the heat pump air conditioning system 100 by the controller, and the set value can also be changed in real time through the program, simplify the control process of the heat pump air conditioning system 100 defrosting, avoid the outdoor heat exchanger of the heat pump air conditioning system 100 icing and affect the normal operation of the heat pump air conditioning system 100.

[0055] The technical features of the above-mentioned embodiments can be combined arbitrarily, in order to make the description simple, not all possible combinations of the technical features in the above-mentioned embodiments are described, however, as long as the combination of these technical features does not exist contradictory, it should be considered as the scope of the description.

[0056] The above-mentioned embodiments only express several embodiments of the application, the description is more specific and detailed, but it cannot be understood as the limitation of the patent scope of the application. It should be pointed out that for ordinary skilled in the art, without departing from the concept of the application, a number of variations and improvements can be made, which belong to the protection scope of the application. Therefore, the protection scope of the patent of the application should be subject to the appended claims.

Claims

1. A heat pump air conditioning system control method applied to a heat pump air conditioning system, characterized in that, The heat pump air conditioning system control method comprises: judging the mode in which the heat pump air conditioning system is currently located; If the heat pump air conditioning system is in heating mode, the first pressure value P at the compressor suction port is obtained in real time. i and the first preset pressure threshold P de1 Comparison, if P i <P de1 Then, the heat pump air conditioning system is switched to defrost mode. If the heat pump air conditioning system is in a defrosting mode, a second pressure value P at a compressor exhaust port is acquired in real time d , and compared with a second preset pressure threshold P de2 , if P d >P de2 , the heat pump air conditioning system is controlled to exit the defrosting mode; The heat pump air conditioning system control method further comprises: obtaining an ambient temperature value T; If the ambient temperature value T > t1 °C and the first pressure value continues P < P1 within a preset time Xmin, the heat pump air conditioning system is switched to the defrosting mode. i <P1, the heat pump air conditioning system is switched to the defrosting mode. If the ambient temperature value t1℃≥T>t2℃ and the first pressure value continues P i <P2, the heat pump air conditioning system is switched to defrost mode. Wherein, the first preset pressure threshold P is set differently according to different ambient temperature values; when the ambient temperature value T>t1℃, the first preset pressure threshold P is P1; when the ambient temperature value t1℃≥T>t2℃, the first preset pressure threshold P is P2. de1 de1 de1 ​​​ 2. The heat pump air conditioning system control method according to claim 1, characterized by, The heat pump air conditioning system control method further comprises: obtaining an ambient temperature value T; If the ambient temperature value t2℃≥T>t3℃ and the first pressure value continues P i <P3, the heat pump air conditioning system is switched to the defrosting mode, wherein the first preset pressure threshold P de1 is P3 when the ambient temperature value t2℃≥T>t3℃.

3. The heat pump air conditioning system control method according to claim 1, characterized by, The heat pump air conditioning system control method further comprises: obtaining an ambient temperature value T; If the ambient temperature value T≤t3℃ and the first pressure value continues P i <P4 for a preset time Xmin, the heat pump air conditioning system is switched to the defrosting mode, wherein the first preset pressure threshold P de1 is P4 when the ambient temperature value T≤t3℃.

4. The heat pump air conditioning system control method according to claim 1, characterized by, The heat pump air conditioning system control method further comprises: obtaining an ambient temperature value T; If the ambient temperature value continuously satisfies T≤t3℃ within a preset time Yh, the heat pump air conditioning system is controlled to switch to a defrosting mode.

5. The heat pump air conditioning system control method according to claim 1, wherein The heat pump air conditioning system control method further comprises: If P d >P de3 Then, the heat pump air conditioning system is controlled to exit the defrost mode, where Pde3 is the third preset pressure threshold, and the third preset pressure threshold P... de3 Much greater than the second preset pressure threshold P de2 .

6. A heat pump air conditioning system characterised in that, being controlled by the heat pump air conditioning system control method according to any one of claims 1-5.

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