Variable-capacity heat pump system and control method thereof

Abstract

The invention relates to the technical field of heat pump systems, and provides a variable-capacity heat pump system and a control method thereof.The variable-capacity heat pump system comprises a compressor, a first heat exchanger, a second heat exchanger, a variable-capacity gas-liquid separator and a reversing valve used for controlling the refrigerant circulation direction; the variable-capacity gas-liquid separator comprises an inlet pipe, an outlet pipe, a first control valve, an oil return hole, a first liquid storage area and a second liquid storage area, wherein the bottoms of the first liquid storage area and the second liquid storage area are not communicated. The first control valve is arranged at an inlet pipe of the variable-capacity gas-liquid separator and used for controlling refrigerants to flow into the first liquid storage area and / or the second liquid storage area. An outlet pipe of the variable-capacity gas-liquid separator and the oil return hole are arranged in a first liquid storage area, and the oil return hole is connected with an oil return pipe of the compressor; according to the variable-capacity heat pump system, the operation efficiency and the oil return effect of the heat pump system can be both considered.

Description

Technical Field

[0001] The present invention relates to the technical field of heat pump systems, and more particularly to a variable capacity heat pump system and a control method thereof. Background Art

[0002] In order to prevent liquid refrigerant from rushing into the compressor, the existing heat pump system introduces the refrigerant that was originally directly input into the compressor into a gas-liquid separator to ensure that the refrigerant enters the compressor more in the form of gas, avoiding damage to the compressor caused by excessive liquid refrigerant.

[0003] The capacity of the gas-liquid separator in the existing heat pump system is fixed. In order to ensure that the refrigerant has a high efficiency from flowing into the gas-liquid separator to flowing out of the gas separator in the form of gas during the operation of the heat pump system, and that while the oil flowing out of the oil return hole of the gas-liquid separator replenishes the lubricating oil of the compressor, there will not be too much liquid refrigerant flowing into the compressor from the oil return hole of the gas-liquid separator, the capacity of the gas-liquid separator and the aperture size of the oil return hole need to be precisely designed; however, the amount of liquid refrigerant generated by the heat pump system in different operating modes is not fixed. For example, in the defrost mode, when the refrigerant flows through the outdoor unit, its heat is used to melt the frost layer of the outdoor unit, which is more Many places enter the gas-liquid separator in the form of liquid. When designing the capacity of the gas-liquid separator, if in order to maximize the cooling or heating efficiency of the heat pump system in cooling mode and heating mode, the increased amount of liquid refrigerant in the defrost mode is not taken into account, it will often cause a large amount of liquid refrigerant to rush into the compressor, causing damage to the compressor. However, if the capacity of the gas-liquid separator is simply increased to prevent a large amount of refrigerant from rushing into the compressor in the defrost mode, the refrigerant will not be able to flow from the gas-liquid separator to the compressor in time, resulting in reduced cooling and heating efficiency, and there will also be problems with the compressor not returning oil in time or too much liquid refrigerant flowing out of the oil return hole.

[0004] In summary, the existing fixed-capacity gas-liquid separator has the problem of being unable to take into account both the operating efficiency and the oil return effect of the heat pump system. Summary of the invention

[0005] In order to overcome the defect of the fixed capacity gas-liquid separator in the above-mentioned prior art that cannot take into account both the operating efficiency and the oil return effect of the heat pump system, the present invention provides a variable capacity heat pump system and a control method thereof that can take into account both the operating efficiency and the oil return effect of the heat pump system.

[0006] In order to solve the above technical problems, the technical solution of the present invention is as follows:

[0007] A variable capacity heat pump system, the system contains refrigerant, the system includes a compressor, a first heat exchanger, a second heat exchanger, a variable capacity gas-liquid separator and a reversing valve for controlling the circulation direction of the refrigerant;

[0008] When the reversing valve controls the circulation direction of the refrigerant to be the refrigeration circulation direction, the reversing valve introduces the refrigerant flowing out of the compressor into the first heat exchanger, the refrigerant flows through the first heat exchanger, the second heat exchanger and the reversing valve in sequence, the reversing valve introduces the refrigerant into the variable capacity gas-liquid separator, and the refrigerant flows out of the variable capacity gas-liquid separator and then flows into the compressor;

[0009] When the reversing valve controls the circulation direction of the refrigerant to be a heating circulation direction, the reversing valve introduces the refrigerant flowing out of the compressor into the second heat exchanger, the refrigerant flows through the second heat exchanger, the first heat exchanger and the reversing valve in sequence, the reversing valve introduces the refrigerant into the variable capacity gas-liquid separator, and the refrigerant flows out of the variable capacity gas-liquid separator and then flows into the compressor;

[0010] Among them, the variable capacity gas-liquid separator includes an inlet pipe, an outlet pipe, a first control valve, an oil return hole, and a first liquid storage area and a second liquid storage area that are not interconnected at the bottom; the first control valve is arranged at the inlet pipe of the variable capacity gas-liquid separator, and is used to control the flow of refrigerant into the first liquid storage area and / or the second liquid storage area; the outlet pipe of the variable capacity gas-liquid separator and the oil return hole are arranged in the first liquid storage area, and the oil return hole is connected to the oil return pipe of the compressor.

[0011] The present invention also proposes a variable capacity heat pump system control method, using the above variable capacity heat pump system, the method comprises the following steps:

[0012] Continuously detecting whether the variable capacity heat pump system enters a defrosting state, if so, stopping the detection and performing a defrosting protection operation; otherwise, continuously detecting whether the variable capacity heat pump system enters a defrosting state;

[0013] The defrost protection operation comprises the following steps:

[0014] Continuously detecting the refrigerant liquid level in the first liquid storage area of ​​the variable capacity gas-liquid separator, and when the refrigerant liquid level exceeds a preset liquid level threshold, using a first control valve to allow the refrigerant to flow into the first liquid storage area and the second liquid storage area, and using a second control valve to connect the oil return hole with the pipeline between the compressor, and continuously detecting whether the variable capacity heat pump system exits the defrosting state;

[0015] If the defrosting state has not been exited, continuously detecting whether the variable capacity heat pump system has exited the defrosting state;

[0016] If the defrosting state has been exited, the defrosting state detection is stopped, the refrigerant is allowed to flow into the first liquid storage area and not into the second liquid storage area by using the first control valve, and the difference between the exhaust temperature of the first heat exchanger and the refrigerant temperature flowing out of the variable capacity gas-liquid separator is continuously detected to see whether it is greater than a preset difference;

[0017] If the difference is greater than a preset difference, the second control valve is used to disconnect the pipeline between the oil return hole and the compressor; otherwise, the difference is continuously detected to see if it is greater than the preset difference.

[0018] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0019] A variable capacity gas-liquid separator is used. When the heat pump system is operating in a non-defrost mode, the refrigerant is introduced into the first liquid storage area by using a first control valve. When designing the capacity and the oil return hole of the first liquid storage area, the operating efficiency of the heat pump system can be maximized without considering the large amount of liquid refrigerant brought by the defrost mode. When the heat pump system is operating in a defrost mode, the refrigerant is introduced into the first liquid storage area and the second liquid storage area by using the first control valve. While the excess liquid refrigerant brought by the defrost mode is shared by the second liquid storage area, the design of the oil return hole of the first liquid storage area is not affected, thereby being able to take into account both the operating efficiency and the oil return effect of the heat pump system. When used in conjunction with the control method of the heat pump system, it can better take into account both the operating efficiency and the oil return effect of the heat pump system. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A first structural schematic diagram of a variable capacity heat pump system proposed in Example 1;

[0021] Figure 2 A second structural schematic diagram of the variable capacity heat pump system proposed in Example 1;

[0022] Figure 3 This is a schematic diagram of the principle of the four-way valve proposed in Example 1;

[0023] Figure 4 This is a schematic diagram of the defrost protection control logic proposed in Example 2. DETAILED DESCRIPTION

[0024] The accompanying drawings are only used for illustrative purposes and should not be construed as limiting the present embodiment;

[0025] In order to better illustrate the present embodiment, some parts in the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product;

[0026] It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0027] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0028] Example 1

[0029] This embodiment provides a variable capacity heat pump system. Figure 1is a schematic diagram of a first structure of the variable capacity heat pump system of this embodiment;

[0030] like Figure 1 As shown, a variable capacity heat pump system is proposed in this embodiment, the system contains refrigerant, including a compressor, a first heat exchanger, a second heat exchanger, a variable capacity gas-liquid separator and a reversing valve for controlling the circulation direction of the refrigerant;

[0031] When the reversing valve controls the circulation direction of the refrigerant to be the refrigeration circulation direction, the reversing valve introduces the refrigerant flowing out of the compressor into the first heat exchanger, the refrigerant flows through the first heat exchanger, the second heat exchanger and the reversing valve in sequence, the reversing valve introduces the refrigerant into the variable capacity gas-liquid separator, and the refrigerant flows out of the variable capacity gas-liquid separator and then flows into the compressor;

[0032] When the reversing valve controls the circulation direction of the refrigerant to be a heating circulation direction, the reversing valve introduces the refrigerant flowing out of the compressor into the second heat exchanger, the refrigerant flows through the second heat exchanger, the first heat exchanger and the reversing valve in sequence, the reversing valve introduces the refrigerant into the variable capacity gas-liquid separator, and the refrigerant flows out of the variable capacity gas-liquid separator and then flows into the compressor;

[0033] Among them, the variable capacity gas-liquid separator includes an inlet pipe, an outlet pipe, a first control valve, an oil return hole, and a first liquid storage area and a second liquid storage area that are not interconnected at the bottom; the first control valve is arranged at the inlet pipe of the variable capacity gas-liquid separator, and is used to control the flow of refrigerant into the first liquid storage area and / or the second liquid storage area; the outlet pipe of the variable capacity gas-liquid separator and the oil return hole are arranged in the first liquid storage area, and the oil return hole is connected to the oil return pipe of the compressor.

[0034] In the specific implementation process, a variable capacity gas-liquid separator is used. When the heat pump system is operating in a non-defrost mode, the refrigerant is introduced into the first liquid storage area by using the first control valve. When designing the capacity and oil return hole of the first liquid storage area, the operating efficiency of the heat pump system can be maximized without considering the large amount of liquid refrigerant brought by the defrost mode. When the heat pump system is operating in a defrost mode, the refrigerant is introduced into the first liquid storage area and the second liquid storage area by using the first control valve. While the excess liquid refrigerant brought by the defrost mode is shared by the second liquid storage area, the design of the oil return hole of the first liquid storage area is not affected, thereby being able to take into account both the operating efficiency and the oil return effect of the heat pump system. When used in conjunction with the control method of the heat pump system, it can better take into account both the operating efficiency and the oil return effect of the heat pump system.

[0035] As an exemplary illustration, the reversing valve may be replaced by other devices capable of controlling the circulation direction of the refrigerant.

[0036] As an exemplary explanation, the refrigerant circulation direction of the refrigeration mode and the defrost mode are both refrigeration circulation directions. The difference between the refrigeration mode and the defrost mode is that, in the refrigeration mode, the first heat exchanger is mainly used to evaporate the liquid refrigerant in the first heat exchanger into gaseous refrigerant, so that most of the refrigerant entering the gas-liquid separator is gaseous refrigerant; in the defrost mode, the first heat exchanger is mainly used to remove the frost layer in the first heat exchanger, and the temperature fails to evaporate most of the liquid refrigerant into gaseous refrigerant. Therefore, in the defrost mode, the amount of liquid refrigerant entering the gas-liquid separator is greater than the amount of liquid refrigerant in the refrigeration mode.

[0037] As an example, Figure 1 The position and connection relationship of the electronic expansion valve are common designs of heat pump systems and will not be described here.

[0038] In an optional embodiment, the variable capacity gas-liquid separator further includes a second control valve, and the second control valve is used to control whether the pipeline between the oil return hole and the compressor is connected or not connected.

[0039] As an exemplary illustration, the first control valve includes a first solenoid valve, and the second control valve includes a second solenoid valve.

[0040] In an optional embodiment, the inlet pipe of the variable capacity gas-liquid separator is divided into a first inlet branch and a second inlet branch, wherein the first inlet branch is connected to the first liquid storage area, and the first solenoid valve is arranged on the second inlet branch, and the first solenoid valve is used to control whether the second inlet branch is connected to the second liquid storage area or not.

[0041] In an optional embodiment, the variable capacity gas-liquid separator further includes a liquid level detector, and the liquid level detector is disposed in the first liquid storage area.

[0042] In an optional embodiment, a first temperature detector is provided on the outlet pipe of the variable capacity gas-liquid separator; and a second temperature detector is provided on the first heat exchanger.

[0043] In an optional embodiment, the first heat exchanger includes a fin heat exchanger.

[0044] In an optional embodiment, the second heat exchanger comprises a double-tube heat exchanger.

[0045] In an optional embodiment, the reversing valve comprises a four-way reversing valve.

[0046] As an example, Figure 2 This is a second structural schematic diagram of the variable capacity heat pump system proposed in this embodiment. Figure 2The figure shows the connection status of each device of the heat pump system when using a four-way reversing valve, wherein solenoid valve 1 represents the first control valve and solenoid valve 2 represents the second control valve; the electronic expansion valve and its position design are common designs of the heat pump system and are not described here.

[0047] As an example, Figure 2 As shown, the first end of the four-way valve is connected to the outlet pipe of the compressor, the second end of the four-way valve is connected to the second heat exchanger, the third end of the four-way valve is connected to the inlet pipe of the variable capacity gas-liquid separator, the outlet pipe of the variable capacity gas-liquid separator is connected to the inlet pipe of the compressor, the fourth end of the four-way valve is connected to the first heat exchanger, and the first heat exchanger is connected to the second heat exchanger;

[0048] As an example, Figure 3 This is a schematic diagram of the principle of the four-way valve proposed in this embodiment; Figure 3 It is shown that the four-way valve controls the circulation direction of the refrigerant to be the refrigerant flow direction of the refrigeration cycle, Figure 3 The outdoor unit is equivalent to the first heat exchanger, Figure 3 The indoor unit is equivalent to the second heat exchanger, Figure 3 The location of the variable volume gas-liquid separator is not shown, and Figure 3 A, B, C and D represent the first end, the second end, the third end and the fourth end of the four-way valve respectively; when the heat pump system is in the cooling state, the four-way valve is not energized, and the four-way valve is in the state where AD is connected and BC is connected. The refrigerant is compressed by the compressor and converted into a high-temperature and high-pressure gas, passes through the A port of the four-way valve, is discharged from the D port, and enters the outdoor heat exchanger (the first heat exchanger, used as a condenser). After absorbing cold and releasing heat in the condenser, it becomes a medium-temperature and high-pressure liquid. After passing through the expansion valve, it becomes a low-temperature and low-pressure liquid. After passing through the indoor heat exchanger (the second heat exchanger, used as an evaporator) and absorbing heat and releasing cold, it becomes a low-temperature and low-pressure gas. , passes through the B port of the four-way valve, returns to the compressor from the C port, and then continues the cycle; when the heat pump system is in the heating state, the four-way valve is energized, the piston moves to the right, AB is connected, CD is connected, the refrigerant is compressed by the compressor and converted into a high-temperature and high-pressure gas, passes through the A port of the four-way valve, is discharged from the B port, enters the indoor heat exchanger (condenser), and becomes a medium-temperature and high-pressure liquid after absorbing cold and releasing heat in the condenser, and becomes a low-temperature and low-pressure liquid after passing through the expansion valve, and becomes a low-temperature and low-pressure gas after passing through the outdoor heat exchanger (evaporator) absorbing heat and releasing cold, passes through the D port of the four-way valve, returns to the compressor from the C port, and then continues the cycle.

[0049] Example 2

[0050] This embodiment is based on the variable capacity heat pump system proposed in Embodiment 1, and proposes the following specific implementation examples:

[0051] When a traditional heat pump air-conditioning unit without an economizer is defrosted, there is often an influx of refrigerant, which causes the compressor oil film to become thinner or even worn away, resulting in overheating or overcurrent in the compressor. Figure 4 This is a schematic diagram of the defrost protection control logic proposed in this embodiment, as shown in FIG. Figure 4 As shown, this embodiment introduces two solenoid valves. After evaporation, the refrigerant is controlled by one solenoid valve to enter the variable volume gas part, and the other solenoid valve is used for defrosting and controlling oil return. The main board monitors the unit status. When the unit enters defrosting, the liquid refrigerant level will be determined. If the refrigerant exceeds the liquid level detection device, the first logic will be triggered, and the solenoid valve 1 (the first control valve) will be opened to store excess refrigerant to prevent excessive influx into the compressor. At this time, the solenoid valve 2 will be opened at the same time to return the oil. Because of the difference in density between the compressor and the refrigerant, the oil will be on the top of the refrigerant. At this time, a small amount of refrigerant will enter the compressor with the oil for oil return. When the unit exits defrosting, the solenoid valve 2 (the second control valve) is closed. At this time, the exhaust temperature T and the saturated condensing temperature T1 are detected every 30 seconds. If the difference between the two is greater than 30°C, the solenoid valve 1 is closed until the next judgment that the unit is defrosting and opening. After the solenoid valve 1 is closed, the stored refrigerant will also be gradually evaporated during the cycle.

[0052] This embodiment relates to a problem in which excessive refrigerant flows into the compressor during the defrosting process of a traditional heat pump air conditioner, causing an overcurrent in the compressor. The traditional heat pump air conditioner can avoid overcurrent, use less and store more, and improve the safety factor of the unit.

[0053] When traditional heat pump air conditioner units without economizers use R32 (a refrigerant), they will face exhaust problems. The amount of refrigerant is often 10% more than that of ordinary units. The problems associated with the large amount of refrigerant will also increase. At present, most compressors use rotary compressors, and the compressors have high-pressure chambers, that is, the high-speed movement area of ​​the compressor; during the defrosting process of the unit, the frequency will decrease. At this time, the oil cannot be replenished to the compressor in time. Instead, a large amount of refrigerant cannot evaporate and flows into the compressor in liquid form because the fan is turned off. Too much or too little gas will cause liquid refrigerant to flow into the compressor, especially When the gas separation is small, a large amount of liquid refrigerant will directly go to the high-pressure chamber. At this time, the refrigerant will continuously flush the oil film of the compressor bearing. After repeated flushing, the oil film in the compressor gap will directly rupture and disappear. At this time, it is equivalent to the direct friction between the bearings of the compressor, which will directly lead to compressor overheating, overcurrent and other phenomena. The unit will frequently report faults, affecting the normal use of the unit. To address this phenomenon, this application can also prevent a large amount of refrigerant from pouring in during defrosting through the density of the compressor oil and the refrigerant, while also replenishing lubricating oil to the compressor.

[0054] Example 3

[0055] This embodiment proposes a variable capacity heat pump system, which is used to implement the variable capacity heat pump system proposed in Embodiment 1.

[0056] The variable capacity heat pump system control method comprises the following steps:

[0057] Continuously detecting whether the variable capacity heat pump system enters a defrosting state, if so, stopping the detection and performing a defrosting protection operation; otherwise, continuously detecting whether the variable capacity heat pump system enters a defrosting state;

[0058] The defrost protection operation comprises the following steps:

[0059] Continuously detecting the refrigerant liquid level in the first liquid storage area of ​​the variable capacity gas-liquid separator, and when the refrigerant liquid level exceeds a preset liquid level threshold, using a first control valve to allow the refrigerant to flow into the first liquid storage area and the second liquid storage area, and using a second control valve to connect the oil return hole with the pipeline between the compressor, and continuously detecting whether the variable capacity heat pump system exits the defrosting state;

[0060] If the defrosting state has not been exited, continuously detecting whether the variable capacity heat pump system has exited the defrosting state;

[0061] If the defrosting state has been exited, the defrosting state detection is stopped, the refrigerant is allowed to flow into the first liquid storage area and not into the second liquid storage area by using the first control valve, and the difference between the exhaust temperature of the first heat exchanger and the refrigerant temperature flowing out of the variable capacity gas-liquid separator is continuously detected to see whether it is greater than a preset difference;

[0062] If the difference is greater than a preset difference, the second control valve is used to disconnect the pipeline between the oil return hole and the compressor; otherwise, the difference is continuously detected to see if it is greater than the preset difference.

[0063] As an exemplary illustration, the preset difference is designed according to actual conditions. As an exemplary illustration, the preset difference can be set to 30 degrees Celsius.

[0064] As an exemplary explanation, the heat pump system monitors whether the unit enters the defrost state by detecting the main board; the heat pump system detects the refrigerant liquid level through the liquid level detector in the first liquid storage area, and when the refrigerant liquid level in the first liquid storage area touches the liquid level detector, the refrigerant liquid level is deemed to exceed a preset liquid level threshold; the heat pump system detects the exhaust temperature of the first heat exchanger through the second temperature detector of the first heat exchanger; the heat pump system detects the refrigerant temperature flowing out of the variable capacity gas-liquid separator through the first temperature detector on the outlet pipe of the variable capacity gas-liquid separator.

[0065] In an optional embodiment, when continuously detecting whether the variable capacity heat pump system enters the defrosting state, the detection is performed once at intervals of a first preset time length;

[0066] When continuously detecting whether the variable capacity heat pump system has exited the defrosting state, the detection is performed once at intervals of a second preset time length;

[0067] When continuously detecting whether the difference between the exhaust temperature of the first heat exchanger and the temperature of the refrigerant flowing out of the variable capacity gas-liquid separator is greater than a preset difference, the detection is performed once every third preset time interval.

[0068] As an exemplary illustration, the first, second and third preset time lengths are designed according to actual needs. As an exemplary illustration, the first preset time length can be set to 1 minute, the second preset time length can be set to 1 minute, and the third preset time length can be set to 30 seconds.

[0069] It can be understood that the variable capacity heat pump system control method of this embodiment applies the system of embodiment 1, and the options in the above embodiment 1 are also applicable to this embodiment, so they will not be described repeatedly here.

[0070] The same or similar reference numerals correspond to the same or similar components;

[0071] The terms used to describe the positional relationship in the drawings are only used for illustrative purposes and should not be construed as limiting the present embodiment;

[0072] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A variable capacity heat pump system, the system containing a refrigerant, characterized in that: It includes a compressor, a first heat exchanger, a second heat exchanger, a variable capacity gas-liquid separator and a reversing valve for controlling the circulation direction of the refrigerant; When the reversing valve controls the circulation direction of the refrigerant to be the refrigeration circulation direction, the reversing valve introduces the refrigerant flowing out of the compressor into the first heat exchanger, the refrigerant flows through the first heat exchanger, the second heat exchanger and the reversing valve in sequence, the reversing valve introduces the refrigerant into the variable capacity gas-liquid separator, and the refrigerant flows out of the variable capacity gas-liquid separator and then flows into the compressor; When the reversing valve controls the circulation direction of the refrigerant to be a heating circulation direction, the reversing valve introduces the refrigerant flowing out of the compressor into the second heat exchanger, the refrigerant flows through the second heat exchanger, the first heat exchanger and the reversing valve in sequence, the reversing valve introduces the refrigerant into the variable capacity gas-liquid separator, and the refrigerant flows out of the variable capacity gas-liquid separator and then flows into the compressor; Among them, the variable capacity gas-liquid separator includes an inlet pipe, an outlet pipe, a first control valve, an oil return hole, and a first liquid storage area and a second liquid storage area that are not interconnected at the bottom; the first control valve is arranged at the inlet pipe of the variable capacity gas-liquid separator, and is used to control the flow of refrigerant into the first liquid storage area and / or the second liquid storage area; the outlet pipe of the variable capacity gas-liquid separator and the oil return hole are arranged in the first liquid storage area, and the oil return hole is connected to the oil return pipe of the compressor.

2. The variable capacity heat pump system according to claim 1, characterized in that: The variable capacity gas-liquid separator further comprises a second control valve, and the second control valve is used to control whether the pipeline between the oil return hole and the compressor is connected or not connected.

3. The variable capacity heat pump system according to claim 1, characterized in that: The inlet pipe of the variable capacity gas-liquid separator is divided into a first inlet branch and a second inlet branch, wherein the first inlet branch is connected to the first liquid storage area, and the first control valve is arranged on the second inlet branch, and the first control valve is used to control whether the second inlet branch is connected to the second liquid storage area or not.

4. The variable capacity heat pump system according to claim 1, characterized in that: The variable capacity gas-liquid separator further includes a liquid level detector, which is disposed in the first liquid storage area.

5. The variable capacity heat pump system according to claim 1, characterized in that: The outlet pipe of the variable capacity gas-liquid separator is provided with a first temperature detector; the first heat exchanger is provided with a second temperature detector.

6. The variable capacity heat pump system according to claim 1, characterized in that: The first heat exchanger includes a fin heat exchanger.

7. The variable capacity heat pump system according to claim 1, characterized in that: The second heat exchanger comprises a double-tube heat exchanger.

8. The variable capacity heat pump system according to any one of claims 1 to 7, characterized in that: The reversing valve comprises a four-way reversing valve.

9. A control method for a variable capacity heat pump system, using the variable capacity heat pump system according to any one of claims 2 to 8, characterized in that: The following steps are involved: Continuously detecting whether the variable capacity heat pump system enters a defrosting state, if so, stopping the detection and performing a defrosting protection operation; otherwise, continuously detecting whether the variable capacity heat pump system enters a defrosting state; The defrost protection operation comprises the following steps: Continuously detecting the refrigerant liquid level in the first liquid storage area of ​​the variable capacity gas-liquid separator, and when the refrigerant liquid level exceeds a preset liquid level threshold, using a first control valve to allow the refrigerant to flow into the first liquid storage area and the second liquid storage area, and using a second control valve to connect the oil return hole with the pipeline between the compressor, and continuously detecting whether the variable capacity heat pump system exits the defrosting state; If the defrosting state has not been exited, continuously detecting whether the variable capacity heat pump system has exited the defrosting state; If the defrosting state has been exited, the defrosting state detection is stopped, the refrigerant is allowed to flow into the first liquid storage area and not into the second liquid storage area by using the first control valve, and the difference between the exhaust temperature of the first heat exchanger and the refrigerant temperature flowing out of the variable capacity gas-liquid separator is continuously detected to see whether it is greater than a preset difference; If the difference is greater than a preset difference, the second control valve is used to disconnect the pipeline between the oil return hole and the compressor; otherwise, the difference is continuously detected to see if it is greater than the preset difference.

10. The variable capacity heat pump system control method according to claim 9, characterized in that: When continuously detecting whether the variable capacity heat pump system enters a defrosting state, the detection is performed once at intervals of a first preset time length; When continuously detecting whether the variable capacity heat pump system has exited the defrosting state, the detection is performed once at intervals of a second preset time length; When continuously detecting whether the difference between the exhaust temperature of the first heat exchanger and the temperature of the refrigerant flowing out of the variable capacity gas-liquid separator is greater than a preset difference, the detection is performed once every third preset time interval.

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