Auto cascade heat pump system and control method thereof

Abstract

The present application relates to heat pump system technical field, disclose a self cascade heat pump system and its control method, wherein the self cascade heat pump system, including compressor, condenser, rectifier, primary regenerator, evaporator and gas-liquid separator, the outlet of compressor is connected with condenser, rectifier is equipped with from bottom to top sequentially communicating liquid storage cavity, primary separation cavity, first filling layer, secondary separation cavity and second filling layer, primary separation cavity is connected with feed pipe, liquid storage cavity is connected with liquid outlet pipe, the top of rectifier is equipped with gas outlet pipe, primary separation cavity is communicated with secondary separation cavity through bypass pipeline, bypass pipeline is equipped with switch valve, the outlet of condenser is connected with feed pipe.The rectifier of self cascade heat pump system of the present application is communicated or closes bypass pipeline through switch valve, can keep liquid storage cavity always in liquid seal state, gas-liquid separation is more thorough, to improve the energy efficiency of self cascade heat pump system.

Description

Technical Field

[0001] The present invention relates to the technical field of heat pump systems, and in particular to a self-cascade heat pump system and a control method thereof. Background Art

[0002] The main function of the rectifier in the heat pump system is to separate the gas-liquid two-phase working fluid in the operation of the heat pump system to prevent the compressor of the heat pump system from liquid hammer and excessive working fluid from diluting the compressor oil.

[0003] Existing rectifiers are unable to effectively control the liquid level in the liquid storage chamber. Once the liquid level drops to a certain level, the liquid seal in the liquid storage chamber deteriorates, allowing the gaseous working fluid to easily escape from the liquid outlet pipe. Consequently, the gas-liquid separation effect is poor, leading to lower energy efficiency in the heat pump system. Summary of the Invention

[0004] The first technical problem solved by the present invention is to provide a self-cascade heat pump system, which effectively solves the problem of poor liquid sealing effect of the liquid storage cavity of the rectifier in the heat pump system, resulting in poor gas-liquid separation effect and low energy efficiency of the heat pump system.

[0005] The second technical problem solved by the present invention is to provide a control method for a self-cascade heat pump system, which effectively solves the problem that the liquid sealing effect of the liquid storage chamber of the distillation device in the heat pump system is poor, resulting in poor gas-liquid separation effect and low energy efficiency of the heat pump system.

[0006] The first technical problem mentioned above is solved by the following technical solution:

[0007] A self-cascade heat pump system comprises a compressor, a condenser, a rectifier, a primary regenerator, an evaporator and a gas-liquid separator, the outlet of the compressor being connected to the condenser, the rectifier being provided with a liquid storage chamber, a primary separation chamber, a first filling layer, a secondary separation chamber and a second filling layer being sequentially connected from bottom to top, the primary separation chamber being connected with a feed pipe, the liquid storage chamber being connected with a liquid outlet pipe, an air outlet pipe being provided on the top of the rectifier, the primary separation chamber being connected with the secondary separation chamber via a bypass pipe, a switch valve being provided on the bypass pipe, the outlet of the condenser being connected to the feed pipe, the liquid outlet pipe being sequentially connected with a first throttle valve, the primary regenerator and the gas-liquid separator, the air outlet pipe being sequentially connected with the primary regenerator, the second throttle valve, the evaporator and the gas-liquid separator, and the gas-liquid separator being connected to the inlet of the compressor.

[0008] Compared with the background art, the self-recovery heat pump system has the beneficial effects that: when the self-recovery heat pump system is running, the two non-azeotropic working substances are compressed by the compressor and then enter the condenser to release heat, and are input from the outlet of the condenser to the feed pipe of the rectifier, and then enter the first separation cavity through the feed pipe. The bypass pipeline is arranged between the first separation cavity and the second separation cavity, and the switch valve is arranged on the bypass pipeline. When the liquid sealing effect of the liquid storage cavity is not good, the switch valve is opened. After the gas-liquid two-phase body enters the first separation cavity, part of the gas-liquid two-phase body directly enters the second separation cavity through the bypass pipeline. The part of the gas-liquid two-phase body only needs to flow through the second filling layer, thereby improving the exhaust efficiency, reducing the gas pressure of the liquid storage cavity, and reducing the liquid discharge speed of the liquid storage cavity, thereby increasing the liquid storage amount in the liquid storage cavity and raising the liquid level. When the liquid level of the liquid storage cavity is too high, the amount of refrigerant participating in the heat pump system heating cycle will be reduced, thereby affecting the heating efficiency of the heat pump. Therefore, when the liquid level of the liquid storage cavity is too high, the switch valve can be closed, so that all the gas-liquid two-phase bodies need to pass through the first filling layer and the second filling layer for twice separation, thereby reducing the exhaust efficiency, increasing the gas pressure of the liquid storage cavity, and thereby increasing the liquid discharge speed of the liquid storage cavity to reduce the liquid level. Through repeated circulation, the liquid level in the liquid storage cavity can be maintained within a certain range, that is, the liquid storage cavity is always in a liquid sealing state, thereby effectively preventing the gas working substance from flowing out of the liquid outlet pipe and improving the gas-liquid separation effect. At the same time, it can also ensure that there is enough refrigerant participating in the heat pump system heating cycle to ensure the heating efficiency of the heat pump system.

[0009] Moreover, after the liquid working substance is discharged from the liquid outlet pipe, it is throttled by the first throttle valve, and the throttled liquid working substance and the gas working substance discharged from the gas outlet pipe are evaporated to absorb heat and become gas-liquid two-phase state, and then are mixed with the gas working substance and enter the gas-liquid separator for gas-liquid separation to form mixed gas working substance. The gas working substance enters the first regenerator from the gas outlet pipe and is condensed, and then is throttled by the second throttle valve, evaporated to absorb heat by the evaporator, and finally enters the gas-liquid separator. The mixed gas working substance is input from the outlet of the gas-liquid separator to the inlet of the compressor to form a self-recovery heating cycle, which can effectively recover the heat of the self-recovery heat pump system itself, reduce the temperature of the low-boiling-point working substance before throttling, and enable the low-boiling-point working substance to absorb more heat, thereby improving the energy efficiency. After the first throttle valve and the switch valve are closed, a single-stage heating cycle can also be formed. The single-stage heating cycle and the self-recovery heating cycle can be applied in different environmental conditions to ensure the running efficiency of the self-recovery heat pump system.

[0010] In one embodiment, the first-stage heat exchanger is provided with a first heat exchange pipeline and a second heat exchange pipeline, the air outlet pipe is connected to one end of the first heat exchange pipeline through the first pipeline, the other end of the first heat exchange pipeline is connected to the gas-liquid separator through the second pipeline, the second throttle valve is provided on the second pipeline, the liquid outlet pipe is connected to one end of the second heat exchange pipeline through the third pipeline, the first throttle valve is provided on the third pipeline, and the other end of the second heat exchange pipeline is connected to the gas-liquid separator through the fourth pipeline.

[0011] In one embodiment, a secondary heat exchanger is further included, and the secondary heat exchanger is provided with a third heat exchange pipeline and a fourth heat exchange pipeline. The second pipeline includes a first branch, a second branch, a third branch and a fourth branch. One end of the third heat exchange pipeline is connected to the first heat exchange pipeline through the first branch, and the other end of the third heat exchange pipeline is connected to the second branch, the evaporator, the third branch, the fourth heat exchange pipeline, the fourth branch and the gas-liquid separator in sequence.

[0012] In one embodiment, a liquid reservoir is further included. The liquid reservoir and the second throttle valve are arranged on the second branch, and the liquid reservoir is located between the second throttle valve and the third heat exchange pipeline.

[0013] In one embodiment, it also includes a controller and a liquid level sensor. The liquid level sensor is arranged in the liquid storage chamber and is used to detect the liquid level height in the liquid storage chamber. The controller is electrically connected to the switch valve and the liquid level sensor respectively. The controller is used to control the switch valve to open or close according to the liquid level height detected by the liquid level sensor.

[0014] The second technical problem mentioned above is solved by the following technical solution:

[0015] A control method for an auto-cascade heat pump system, using the above-mentioned auto-cascade heat pump system, comprises:

[0016] detecting an ambient temperature, and controlling the first throttle valve to open or close according to a difference between the ambient temperature and a preset temperature value;

[0017] detecting a compression ratio of the compressor based on the opening of the first throttle valve;

[0018] According to the difference between the compression ratio of the compressor and the preset compression ratio, the liquid level in the liquid storage chamber is detected, and the switch valve is controlled to be opened or closed according to the liquid level in the liquid storage chamber.

[0019] Compared with the background technology, the control method of the self-cascade heat pump system described in the present invention has the following beneficial effects: the opening and closing of the first throttle valve is controlled by the ambient temperature, that is, the single-stage heating cycle and the self-cascade heating cycle are switched, and the compression ratio of the compressor is further detected under the self-cascade heating cycle to determine whether to detect the liquid level height in the liquid storage chamber. It can automatically switch to a more efficient heating mode according to different environmental conditions, thereby improving the energy efficiency of the self-cascade heat pump system. Under the self-cascade heating cycle, by detecting the liquid level height in the liquid storage chamber, when the liquid sealing effect of the liquid storage chamber is not good, the switch valve is opened, and after the gas-liquid two-phase body output by the feed pipe enters the first separation chamber, part of the gas-liquid two-phase body directly enters the second separation chamber from the bypass pipe, thereby increasing the liquid storage capacity in the liquid storage chamber and raising the liquid level. When the liquid level in the liquid storage chamber is too high, the on-off valve is closed, and the gas-liquid two-phase body needs to be separated twice. The drainage speed of the liquid storage chamber is increased to reduce the liquid level, thereby maintaining the liquid level in the liquid storage chamber within a certain range, ensuring that the liquid storage chamber is always in a liquid-sealed state, thereby effectively preventing the gas working medium from flowing out of the liquid outlet pipe, improving the gas-liquid separation effect. At the same time, it can ensure that there is enough refrigerant to participate in the heating cycle of the heat pump system, thereby ensuring the heating efficiency of the heat pump system.

[0020] In one embodiment, the detecting of the ambient temperature and controlling the first throttle valve to open or close according to the difference between the ambient temperature and a preset temperature value further includes:

[0021] When the ambient temperature is less than or equal to a preset temperature value, controlling the first throttle valve to open;

[0022] When the ambient temperature is greater than a preset temperature value, the first throttle valve is controlled to close.

[0023] In one embodiment, the method further comprises detecting the liquid level in the liquid storage chamber according to the difference between the compression ratio of the compressor and a preset compression ratio, and controlling the switch valve to open or close according to the liquid level in the liquid storage chamber.

[0024] When the compression ratio of the compressor is less than or equal to a preset compression ratio, the liquid level in the liquid storage chamber is detected.

[0025] In one embodiment, the method further comprises detecting the liquid level in the liquid storage chamber according to the difference between the compression ratio of the compressor and a preset compression ratio, and controlling the switch valve to open or close according to the liquid level in the liquid storage chamber.

[0026] When the liquid level in the liquid storage chamber drops to a preset low liquid level, the switch valve is controlled to open, and part of the gas-liquid two-phase body in the primary separation chamber enters the secondary separation chamber through the bypass pipe;

[0027] When the liquid level in the liquid storage chamber rises to a preset high liquid level, the switch valve is controlled to close, and the gas-liquid two-phase body in the primary separation chamber enters the secondary separation chamber after preliminary separation by the first filling layer.

[0028] In one embodiment, after the step of controlling the first throttle valve to open when the ambient temperature is less than or equal to a preset temperature value, the method further includes: adjusting the opening of the first throttle valve according to the heat exchange temperature difference;

[0029] And / or, before the step of detecting the ambient temperature and controlling the opening or closing of the first throttle valve according to the difference between the ambient temperature and a preset temperature value, the method further includes: adjusting the opening of the second throttle valve according to the return air superheat. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0031] Figure 1 Schematic diagram of the structure of a self-cascade heat pump system according to an embodiment of the present invention;

[0032] Figure 2 This is a schematic structural diagram of a rectifier of a self-cascade heat pump system according to an embodiment of the present invention;

[0033] Figure 3 A cross-sectional view of a rectifier of a self-cascade heat pump system according to an embodiment of the present invention;

[0034] Figure 4 This is a schematic structural diagram of a filling body of a rectifier of a self-cascade heat pump system according to an embodiment of the present invention;

[0035] Figure 5 for Figure 4 The main view;

[0036] Figure 6 for Figure 4 A top view of

[0037] Figure 7 A schematic diagram of the partial structure of a rectifier of a self-cascade heat pump system according to an embodiment of the present invention;

[0038] Figure 8 Schematic diagram of a flow chart of a control method for a cascade heat pump system according to an embodiment of the present invention.

[0039] Description of reference numerals:

[0040] 1. Compressor; 2. Condenser; 3. Rectifier; 301. Liquid storage chamber; 3011. Liquid storage space; 3012. Third filling layer; 302. Primary separation chamber; 303. First filling layer; 304. Secondary separation chamber; 305. Second filling layer; 306. Feed pipe; 307. Liquid outlet pipe; 308. Gas outlet pipe; 309. Bypass pipe; 310. On-off valve; 311. Liquid level sensor; 312. Gas storage chamber; 313. First baffle; 314. First through hole; 315. Second baffle; 316. Second through hole Hole; 4. Primary regenerator; 401. First heat exchange pipeline; 402. Second heat exchange pipeline; 5. Evaporator; 6. Gas-liquid separator; 7. First throttle valve; 8. Second throttle valve; 9. First pipeline; 10. Second pipeline; 1001. First branch; 1002. Second branch; 1003. Third branch; 1004. Fourth branch; 11. Third pipeline; 12. Fourth pipeline; 13. Secondary regenerator; 1301. Third heat exchange pipeline; 1302. Fourth heat exchange pipeline; 14. Liquid reservoir; 15. Filling body. DETAILED DESCRIPTION

[0041] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0042] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application.

[0043] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature specified as "first" or "second" may explicitly or implicitly include one or more of such features. Throughout this application, unless otherwise specified, "plurality" means two or more.

[0044] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0045] The following combination Figures 1 to 8 , describing embodiments of the present invention.

[0046] According to an embodiment of the present invention, on the one hand, Figure 1 As shown, a self-cascade heat pump system is provided, which mainly includes a compressor 1, a condenser 2, a rectifier 3, a primary regenerator 4, an evaporator 5 and a gas-liquid separator 6.

[0047] Furthermore, the outlet of the compressor 1 is connected to the condenser 2, and the gas-liquid two-phase body enters the condenser 2 after being compressed by the compressor 1. Figure 2 As shown, the rectifier 3 is provided with a liquid storage chamber 301, a primary separation chamber 302, a first filling layer 303, a secondary separation chamber 304, and a second filling layer 305, which are connected in sequence from bottom to top. The primary separation chamber 302 is connected to a feed pipe 306, and the liquid storage chamber 301 is connected to a liquid outlet pipe 307. The top of the rectifier 3 is provided with an air outlet pipe 308. The primary separation chamber 302 is connected to the secondary separation chamber 304 via a bypass pipe 309, and the bypass pipe 309 is provided with an on-off valve 310. The opening or closing of the on-off valve 310 is controlled in real time according to the liquid level in the liquid storage chamber 301.

[0048] The outlet of condenser 2 is connected to feed pipe 306, and the gas-liquid two-phase body enters the primary separation chamber 302 from feed pipe 306. The gaseous working medium in the gas-liquid two-phase body, as well as some of the liquid working medium in the bubbling liquid state, flows upward. The gaseous working medium passes upward through the first packing layer 303 and the second packing layer 305, and is finally discharged through the gas outlet pipe 308. The liquid working medium in the bubbling liquid state is blocked at the first packing layer 303 and the second packing layer 305 and converges into the liquid working medium, which flows downward to the liquid storage chamber 301. The liquid working medium is then discharged through the liquid outlet pipe 307.

[0049] The liquid outlet pipe 307 is connected to the first throttle valve 7, the first-stage heat regenerator 4 and the gas-liquid separator 6 in sequence, and the gas outlet pipe 308 is connected to the first-stage heat regenerator 4, the second throttle valve 8, the evaporator 5 and the gas-liquid separator 6 in sequence. The gas-liquid separator 6 is also connected to the inlet of the compressor 1.

[0050] It can be seen that in the self-cascade heat pump system provided by the embodiment of the present invention, when the self-cascade heat pump system is in operation, the two working fluids are compressed by the compressor 1 and then enter the condenser 2 to release heat. The high-boiling-point working fluid is cooled into liquid, and the low-boiling-point working fluid is still gas, thereby forming a gas-liquid two-phase body, which is then input from the outlet of the condenser 2 into the feed pipe 306 of the distillation device 3 and enters the first-level separation chamber 302 through the feed pipe 306. By setting a bypass pipe 309 between the primary separation chamber 302 and the secondary separation chamber 304, and providing an on-off valve 310 on the bypass pipe 309, when the liquid sealing effect of the liquid storage chamber 301 is poor, the on-off valve 310 is opened, and after the gas-liquid two-phase body enters the primary separation chamber 302, part of the gas-liquid two-phase body directly enters the secondary separation chamber 304 from the bypass pipe 309. This part of the gas-liquid two-phase body only needs to flow through the second filling layer 305, thereby improving the exhaust efficiency, reducing the air pressure in the liquid storage chamber 301, thereby reducing the drainage speed of the liquid storage chamber 301, thereby increasing the liquid storage capacity in the liquid storage chamber 301 and raising the liquid level. When the liquid level in the liquid storage chamber 301 is too high, the amount of refrigerant participating in the heating cycle of the heat pump system will decrease, thereby affecting the heating efficiency of the heat pump. Therefore, when the liquid level in the liquid storage chamber 301 is too high, the on-off valve 310 can be closed so that all gas-liquid two-phase bodies need to pass through the first filling layer 303 and the second filling layer 305 for separation twice, thereby reducing the exhaust efficiency, increasing the air pressure in the liquid storage chamber 301, and thus increasing the drainage speed of the liquid storage chamber 301 to reduce the liquid level. This repeated cycle can maintain the liquid level in the liquid storage chamber 301 within a certain range, that is, the liquid storage chamber 301 is always in a liquid-sealed state, thereby effectively preventing the gas working medium from flowing out of the liquid outlet pipe 307 and improving the gas-liquid separation effect. At the same time, it can ensure that there is enough refrigerant participating in the heating cycle of the heat pump system to ensure the heating efficiency of the heat pump system.

[0051] Furthermore, after the liquid working medium is discharged from the liquid outlet pipe 307, it enters the first throttle valve 7 for throttling. The throttled liquid working medium and the gas working medium discharged from the gas outlet pipe 308 evaporate and absorb heat, becoming a gas-liquid two-phase state. The liquid working medium then mixes with the gas working medium and enters the gas-liquid separator 6 for gas-liquid separation, forming a mixed gas working medium. The gas working medium enters the primary regenerator 4 from the gas outlet pipe 308 for condensation, then passes through the second throttle valve 8 for throttling. After throttling, it evaporates and absorbs heat in the evaporator 5, and finally enters the gas-liquid separator 6. The mixed gas working medium is input from the outlet of the gas-liquid separator 6 to the inlet of the compressor 1, forming an auto-cascade heating cycle. This effectively recovers the heat of the auto-cascade heat pump system itself, reduces the temperature of the low-boiling-point working medium before throttling, and allows the low-boiling-point working medium to absorb more air energy, thereby improving energy efficiency. After closing the first throttle valve 7 and the switch valve 310, a single-stage heating cycle can be formed. The single-stage heating cycle and the auto-cascade heating cycle can be applied respectively under different environmental conditions to ensure the operating efficiency of the auto-cascade heat pump system.

[0052] Specifically, a single-stage heating cycle is suitable for scenarios with high ambient temperatures. In scenarios with low ambient temperatures, the single-stage heating cycle cannot meet heating requirements, and the first throttle valve 7 needs to be opened to implement a self-cascade heating cycle. Furthermore, the switching between the single-stage heating cycle and the self-cascade heating cycle in the embodiment of the present invention is also related to the compression ratio of the compressor 1.

[0053] For example, when the ambient temperature is greater than 10°C, the first throttle valve 7 and the on-off valve 310 are closed, and a single-stage heating cycle is performed. When the ambient temperature is less than or equal to 10°C, the first throttle valve 7 is opened, and the compression ratio of the compressor 1 is detected. When the compression ratio of the compressor 1 is less than or equal to a preset compression ratio, the on-off valve 310 is controlled to open or close according to the liquid level in the liquid storage chamber 301, and a self-cascade heating cycle is performed. When the compression ratio of the compressor 1 is greater than the preset value, the first throttle valve 7 and the on-off valve 310 are closed, and a single-stage heating cycle is performed.

[0054] In one embodiment, Figure 1 As shown, the primary regenerator 4 is provided with a first heat exchange pipeline 401 and a second heat exchange pipeline 402. The gas outlet pipe 308 is connected to one end of the first heat exchange pipeline 401 via a first pipeline 9. The other end of the first heat exchange pipeline 401 is connected to the gas-liquid separator 6 via a second pipeline 10. The second throttle valve 8 is provided on the second pipeline 10. The liquid outlet pipe 307 is connected to one end of the second heat exchange pipeline 402 via a third pipeline 11. The first throttle valve 7 is provided on the third pipeline 11. The other end of the second heat exchange pipeline 402 is connected to the gas-liquid separator 6 via a fourth pipeline 12.

[0055] Furthermore, in one embodiment, Figure 1 As shown, the auto-cascade heat pump system also includes a secondary regenerator 13. The secondary regenerator 13 is provided with a third heat exchange pipeline 1301 and a fourth heat exchange pipeline 1302. The second pipeline 10 includes a first branch 1001, a second branch 1002, a third branch 1003, and a fourth branch 1004. One end of the third heat exchange pipeline 1301 is connected to the first heat exchange pipeline 401 via the first branch 1001. The other end of the third heat exchange pipeline 1301 is sequentially connected to the second branch 1002, the evaporator 5, the third branch 1003, the fourth heat exchange pipeline 1302, the fourth branch 1004, and the gas-liquid separator 6.

[0056] By providing the secondary regenerator 13 , the temperature of the low-boiling-point working medium before throttling can be further reduced, so that the low-boiling-point working medium can absorb more heat when flowing through the evaporator 5 , thereby increasing the heating capacity.

[0057] Furthermore, in one embodiment, Figure 1As shown, the self cascade heat pump system further comprises a liquid accumulator 14, the liquid accumulator 14 and the second throttling valve 8 are arranged on the second branch 1002, and the liquid accumulator 14 is located between the second throttling valve 8 and the third heat exchange pipeline 1301. The liquid accumulator 14 is used for collecting liquid, so as to ensure that the refrigerant passing through the evaporator 5 is in a liquid state, thereby improving the heat absorption amount.

[0058] In one embodiment, as shown in Figure 2 and Figure 3 As shown, the self cascade heat pump system further comprises a controller and a liquid level sensor 311 arranged in the liquid storage cavity 301 for detecting the liquid level height in the liquid storage cavity 301, the controller is electrically connected with the on-off valve 310 and the liquid level sensor 311 respectively, and the controller is used for controlling the on-off valve 310 to open or close according to the liquid level height detected by the liquid level sensor 311. Through the controller, automatic control of the on-off valve 310 can be realized, so as to automatically maintain the liquid storage cavity 301 in a liquid sealing state at all times, thereby further improving the gas-liquid separation effect.

[0059] Specifically, the controller sets a preset low liquid level and a preset high liquid level of the liquid storage cavity 301 according to actual needs. In the case that the liquid level sensor 311 detects that the liquid level height in the liquid storage cavity 301 drops to the preset low liquid level, the controller controls the on-off valve 310 to open, thereby increasing the liquid level height. In the case that the liquid level sensor 311 detects that the liquid level height in the liquid storage cavity 301 rises to the preset high liquid level, the controller controls the on-off valve 310 to close, thereby reducing the liquid level height.

[0060] It should be noted that the controller can select any existing controller according to needs. For example, the controller can select a micro control unit (MCU), a central processing unit, an electronic control unit (ECU) or other existing controllers. Of course, other conventional controllers can also be selected according to needs. The embodiments of the present application do not limit this.

[0061] In addition, the embodiments of the present application also do not limit the liquid level sensor 311 and the on-off valve 310. For example, the liquid level sensor 311 can select a differential pressure liquid level gauge, a float liquid level gauge or other conventional structures. The on-off valve 310 can adopt an electromagnetic valve.

[0062] In one embodiment, as shown in Figure 2 and Figure 3 As shown, the rectifier 3 further comprises a gas storage cavity 312 for collecting the separated gas working medium. The second filling layer 305 is arranged between the secondary separation cavity 304 and the gas storage cavity 312, and the gas outlet pipe 308 is in communication with the gas storage cavity 312.

[0063] The gaseous working medium and a very small amount of liquid working medium in the bubble liquid state that enter the secondary separation chamber 304 continue to flow upward into the second filling layer 305. The gaseous working medium can directly pass through the second filling layer 305 and continue to move upward into the gas storage chamber 312 for storage, and be discharged through the air outlet pipe 308. The liquid working medium in the bubble liquid state cannot continue to move upward due to the resistance of the second filling layer 305 during the upward process, and gradually forms a liquid film in the second filling layer 305. The liquid film is affected by the tension and gathers to form liquid working medium. After the liquid working medium gathers to a certain amount, it can overcome the upward air pressure and, under the influence of gravity, pass downward through the secondary separation chamber 304 and flow to the first filling layer 303. After passing through the first filling layer 303, it enters the primary separation chamber 302 and finally merges with the liquid working medium in the gas-liquid two-phase body output by the feed pipe 306.

[0064] In one embodiment, Figure 2 and Figure 3 As shown, the liquid storage chamber 301 comprises a liquid storage space 3011 and a third filling layer 3012 located above the liquid storage space 3011. A first baffle 313 is disposed between the third filling layer 3012 and the primary separation chamber 302. The first baffle 313 defines a plurality of first through-holes 314. The plurality of first through-holes 314 are spaced apart along the edge of the first baffle 313. Furthermore, a fourth baffle is disposed between the liquid storage space 3011 and the third filling layer 3012, and the fourth baffle defines a plurality of fourth through-holes.

[0065] When the switch valve 310 is closed, after the gas-liquid two-phase body enters the first separation chamber 302, the gas working medium and a portion of the liquid working medium in the bubble liquid state move upward into the first filling layer 303. The gas working medium and a very small portion of the liquid working medium in the bubble liquid state can directly pass through the first filling layer 303 and continue to move upward into the secondary separation chamber 304. During the upward process, the liquid working medium in the bubble liquid state is affected by the resistance of the first filling layer 303 and cannot continue to move upward. A liquid film gradually forms in the first filling layer 303, and the liquid film gathers under the influence of tension to form a liquid working medium. After the liquid working medium gathers to a certain amount, it can overcome the upward gas pressure and flow downward to the first separation chamber 302 under the influence of gravity, and finally merge with the liquid working medium in the gas-liquid two-phase body output by the feed pipe 306.

[0066] The liquid working medium in the gas-liquid two-phase solution output by feed pipe 306, as well as the liquid working medium formed after distillation in first and second packing layers 303 and 305, flows downward under the influence of gravity to first baffle 313, passes through first through-hole 314, and enters third packing layer 3012 for further gas-liquid separation. The separated liquid working medium continues to flow downward, passes through the fourth through-hole in the fourth baffle, and enters liquid storage chamber 301 for collection, finally flowing out through liquid outlet pipe 307.

[0067] Furthermore, in one embodiment, Figure 3As shown, a second baffle 315 is disposed between the primary separation chamber 302 and the first packing layer 303. The second baffle 315 is provided with a plurality of second through-holes 316. The density of the plurality of first through-holes 314 is less than the density of the plurality of second through-holes 316. In other words, the upper and lower baffles of the primary separation chamber 302 form a pattern of dense openings at the top and sparse openings at the bottom, making it easier for the gaseous working medium to flow upward and less likely to flow downward, thereby facilitating and more thorough gas-liquid separation.

[0068] In addition, a fifth baffle is provided between the secondary separation chamber 304 and the first filling layer 303, and a plurality of fifth through-holes are defined on the fifth baffle. A sixth baffle is provided between the secondary separation chamber 304 and the second filling layer 305, and a plurality of sixth through-holes are defined on the sixth baffle. A third baffle is provided between the second filling layer 305 and the gas storage chamber 312, and a plurality of third through-holes are defined on the third baffle. Each of these baffles and through-holes enables better storage of the mixed or separated gas / liquid working medium within the rectifier 3. The through-holes may have conventional structures such as circular holes or strip holes.

[0069] Furthermore, if Figure 3 As shown, the density of the first through hole 314 and the fourth through hole is smaller than the density of the second through hole 316 , the fifth through hole, the sixth through hole and the third through hole, so as to further improve the gas-liquid separation effect.

[0070] It should be noted that the embodiment of the present invention does not limit the structures of the first filling layer 303 , the second filling layer 305 and the third filling layer 3012 , and any existing structure can be adopted as needed.

[0071] In one embodiment, the first filling layer 303, the second filling layer 305, and the third filling layer 3012 are all filled with regularly and / or irregularly shaped filling bodies 15. The regularly shaped filling bodies 15 include at least one of a triangular spiral, a spherical, and a toroidal shape. During the upward movement, the liquid working medium in the bubble liquid state is affected by the resistance of the filling body 15 and cannot continue to move upward. A liquid film gradually forms on the surface of the filling body 15. The liquid working medium, formed by the tension of the liquid film, aggregates and flows downward.

[0072] For example, Figures 4 to 7 As shown, the filling body 15 is a triangular spiral stainless steel. The first filling layer 303, the second filling layer 305 and the third filling layer 3012 are all irregularly filled with the filling body 15, and are tightly filled to ensure the effect of gas-liquid separation. Taking the first filling layer 303 as an example, the filling form of the triangular spiral filling body 15 is as follows Figure 7 shown.

[0073] The working principle of the auto-cascade heating cycle of the auto-cascade heat pump system of the embodiment of the present invention is as follows:

[0074] The two non-azeotropic working fluids are compressed by the compressor 1 and enter the condenser 2 to release heat. They are then discharged from the outlet of the condenser 2 into the feed pipe 306 of the rectifier 3 and enter the primary separation chamber 302 through the feed pipe 306 .

[0075] When the liquid level sensor 311 detects that the liquid level in the liquid storage chamber 301 has risen to a preset high liquid level, the controller controls the on-off valve 310 to close. The feed pipe 306 inputs the gas-liquid two-phase body into the primary separation chamber 302, where the low-boiling-point gas working medium and some high-boiling-point liquid working medium in the bubble liquid state flow upward into the first filling layer 303. Most of the high-boiling-point liquid working medium in the bubble liquid state is affected by the resistance of the first filling layer 303 during the upward movement and cannot continue to move upward. A liquid film gradually forms in the first filling layer 303, and the liquid film is affected by the tension and gathers to form high-boiling-point liquid working medium. After the high-boiling-point liquid working medium accumulates to a certain amount, it can overcome the upward gas pressure and flow downward to the primary separation chamber 302 under the influence of gravity, merging with the high-boiling-point liquid working medium in the gas-liquid two-phase body output by the feed pipe 306.

[0076] The low-boiling-point gas working medium and a very small amount of high-boiling-point liquid working medium in the form of bubble liquid can directly pass through the first filling layer 303 and continue upward to enter the secondary separation chamber 304, and then enter the second filling layer 305. The low-boiling-point gas working medium can directly pass through the second filling layer 305 and continue upward to enter the gas storage chamber 312 for storage, and then be discharged through the outlet pipe 308. After that, it enters the first heat exchange pipeline 401 of the primary regenerator 4 for condensation, and then enters the third heat exchange pipeline 1301 of the secondary regenerator 13 for secondary condensation and heat release to form a low-boiling-point liquid working medium. The low-boiling-point liquid working medium enters the liquid reservoir 14 for collection and storage, and then enters the second throttle valve 8 for throttling. After throttling, the low-boiling-point liquid working medium enters the evaporator 5 for evaporation and heat absorption. Then it enters the fourth heat exchange pipeline 1302 of the secondary regenerator 13 for evaporation and heat absorption again, and then enters the gas-liquid separator 6 for gas-liquid separation.

[0077] During its upward movement, the liquid working medium in the bubble liquid state is affected by the resistance of the second filling layer 305 and cannot continue to move upward. A liquid film gradually forms in the second filling layer 305. The liquid film, under the influence of tension, aggregates to form the liquid working medium. Once the liquid working medium accumulates to a certain amount, it overcomes the upward pressure and flows downward under the influence of gravity to the first filling layer 303. After passing through the first filling layer 303, it enters the primary separation chamber 302.

[0078] The liquid working medium in the gas-liquid two-phase body input by the feed pipe 306 and the liquid working medium that enters the primary separation chamber 302 after distillation by the first filling layer 303 and the second filling layer 305, flow downward to the first baffle 313 under the influence of gravity. After passing through the first through hole 314 of the first baffle 313, it enters the third filling layer 3012 for further gas-liquid separation. The separated liquid working medium continues to flow downward, and after passing through the fourth through hole on the fourth baffle, it enters the liquid storage chamber 301 for collection, and finally flows out through the liquid outlet pipe 307. Since the intake pressure of the gas-liquid two-phase body input by the feed pipe 306 remains unchanged. The gas-liquid separation needs to pass through three layers of filling layers, the exhaust efficiency is reduced, which increases the air pressure in the liquid storage chamber 301, thereby increasing the discharge speed of the liquid storage chamber 301 to reduce the liquid level.

[0079] The high-boiling-point liquid flowing out of liquid outlet pipe 307 enters first throttle valve 7 for throttling, then enters second heat exchange pipeline 402 of primary regenerator 4 to evaporate and absorb heat with the low-boiling-point gaseous working medium. After absorbing heat, the high-boiling-point liquid working medium becomes a gas-liquid two-phase state, merges with the low-boiling-point gaseous working medium flowing out of fourth heat exchange pipeline 1302, and enters gas-liquid separator 6 for gas-liquid separation. The mixed gas working medium is then input into the inlet of compressor 1, that is, into the low-pressure chamber of compressor 1, and compressed before entering the next cycle.

[0080] When the liquid level sensor 311 detects that the liquid level in the liquid storage chamber 301 has dropped to a preset low liquid level, the controller switch valve 310 opens. Part of the gas-liquid two-phase body in the first separation chamber 302 directly enters the secondary separation chamber 304 through the bypass pipe 309, and the gas working medium can be discharged quickly, thereby improving the exhaust efficiency, reducing the gas pressure in the liquid storage chamber 301, thereby reducing the liquid discharge speed of the liquid storage chamber 301, thereby increasing the liquid storage capacity in the liquid storage chamber 301 and raising the liquid level. The working process after the gas-liquid two-phase body enters the secondary separation chamber 304 is consistent with the process in the first separation state. For the sake of brevity, the embodiments of the present invention will not be repeated. The flow direction of the gas working medium is as follows: Figure 2 As shown by the solid arrow in the figure, the flow direction of the liquid working medium is as follows: Figure 2 Indicated by the hollow arrows in .

[0081] The working principle of the single-stage heating cycle of the auto-cascade heat pump system according to the embodiment of the present invention is as follows:

[0082] The controller controls the first throttle valve 7 and the on-off valve 310 to close. The non-azeotropic gas-liquid two-phase liquid is compressed by the compressor 1 and enters the condenser 2 to release heat. It is then discharged from the outlet of the condenser 2 into the feed pipe 306 of the rectifier 3 and enters the primary separation chamber 302 through the feed pipe 306.

[0083] The low-boiling-point gaseous refrigerant passes upward through the first packing layer 303, the secondary separation chamber 304, and the second packing layer 305, before entering the gas storage chamber 312 for storage. It then enters the first heat exchange line 401 of the primary regenerator 4 through the gas outlet pipe 308 for condensation. It then enters the third heat exchange line 1301 of the secondary regenerator 13 for secondary condensation, releasing heat and forming a low-boiling-point liquid refrigerant. The low-boiling-point liquid refrigerant enters the liquid reservoir 14 for storage, then enters the second throttle valve 8 for throttling. After throttling, the low-boiling-point liquid refrigerant enters the evaporator 5 for evaporation and heat absorption. It then enters the fourth heat exchange line 1302 of the secondary regenerator 13 for further evaporation and heat absorption, before entering the gas-liquid separator 6. The gas-liquid separator 6 separates the partially vaporized mixed refrigerant into gas and liquid. The resulting mixed gaseous refrigerant is then fed into the inlet of the compressor 1, i.e., into the low-pressure chamber of the compressor 1, for compression and the next cycle.

[0084] According to an embodiment of the present invention, on the other hand, Figure 8 As shown, a control method for a cascade heat pump system is also provided, which adopts the above-mentioned cascade heat pump system and includes:

[0085] S100, detecting the ambient temperature, and controlling the first throttle valve 7 to open or close according to the difference between the ambient temperature and the preset temperature value. The ambient temperature can be detected and obtained by a temperature sensor.

[0086] S200 : Based on the opening of the first throttle valve 7 , the compression ratio of the compressor 1 is detected.

[0087] S300 , detecting the liquid level in the liquid storage chamber 301 according to the difference between the compression ratio of the compressor 1 and the preset compression ratio, and controlling the switch valve 310 to open or close according to the liquid level in the liquid storage chamber 301 .

[0088] The self-cascade heat pump system provided in an embodiment of the present invention controls the opening and closing of the first throttle valve 7 by the ambient temperature, that is, switches between a single-stage heating cycle and a self-cascade heating cycle. In the self-cascade heating cycle, the compression ratio of the compressor 1 is further detected to determine whether to detect the liquid level height in the liquid storage chamber 301. It can automatically switch to a more efficient heating mode according to different environmental conditions, thereby improving the energy efficiency of the self-cascade heat pump system. In the self-cascade heating cycle, by detecting the liquid level height in the liquid storage chamber 301, when the liquid sealing effect of the liquid storage chamber 301 is not good, the switch valve 310 is opened, and after the gas-liquid two-phase body output by the feed pipe 306 enters the first separation chamber 302, part of the gas-liquid two-phase body directly enters the second separation chamber 304 from the bypass pipe 309, thereby increasing the liquid storage capacity in the liquid storage chamber 301 and raising the liquid level. When the liquid level in liquid storage chamber 301 is too high, the on-off valve 310 is closed, requiring the gas-liquid two-phase separation to proceed twice. The liquid discharge rate of liquid storage chamber 301 is increased to lower the liquid level, thereby maintaining the liquid level within liquid storage chamber 301 within a certain range and ensuring that liquid storage chamber 301 is always in a liquid-sealed state. This effectively prevents the gaseous working medium from escaping from liquid outlet pipe 307, improving the gas-liquid separation effect and achieving higher energy efficiency. At the same time, this ensures that sufficient refrigerant is available for the heat pump system's heating cycle, thereby ensuring the heat pump system's heating efficiency.

[0089] In one embodiment, S100, detecting the ambient temperature, and controlling the first throttle valve 7 to open or close according to the difference between the ambient temperature and a preset temperature value, further includes:

[0090] S110: When the ambient temperature is less than or equal to the preset temperature value, the first throttle valve 7 is controlled to open. This activates the auto-cascade heating cycle, effectively recovering the auto-cascade heat pump system's own heat, raising the evaporation temperature, and thereby increasing the refrigerant flow rate of the auto-cascade heat pump system, increasing the heating capacity, reducing the heat exchange time of the evaporator 5, and lowering the suction superheat temperature, thereby reducing the exhaust gas temperature. This ensures high-efficiency and reliable operation under both high and low pressure differential conditions.

[0091] S120: When the ambient temperature is greater than the preset temperature value, the first throttle valve 7 is controlled to close. This activates a single-stage heating cycle to improve energy efficiency. At this point, the liquid level of the liquid storage chamber 301 is not adjusted, that is, the liquid level sensor 311 and the switch valve 310 are controlled to close.

[0092] In one embodiment, Figure 8 As shown, S300, based on the difference between the compression ratio of the compressor 1 and the preset compression ratio, the liquid level in the liquid storage chamber 301 is detected, and the switch valve 310 is controlled to be opened or closed according to the liquid level in the liquid storage chamber 301, further comprising:

[0093] S310 , when the compression ratio of the compressor 1 is less than or equal to the preset compression ratio, the liquid level in the liquid storage chamber 301 is detected.

[0094] Specifically, when the ratio of the outlet pressure P1 to the inlet pressure P2 of the compressor 1 is less than or equal to the preset compression ratio P M In this case, the liquid level sensor 311 is turned on and the liquid level height in the liquid storage chamber 301 is detected by the liquid level sensor 311.

[0095] When the ratio of the outlet pressure P1 to the inlet pressure P2 of the compressor 1 is greater than the preset compression ratio P M In this case, the first throttle valve 7, the liquid level sensor 311 and the switch valve 310 are closed to enter a single-stage heating cycle.

[0096] Furthermore, in one embodiment, S300, based on the difference between the compression ratio of the compressor 1 and the preset compression ratio, detecting the liquid level in the liquid storage chamber 301, and controlling the switch valve 310 to open or close according to the liquid level in the liquid storage chamber 301, further includes:

[0097] S320 , based on the liquid level in the liquid storage chamber 301 dropping to a preset low liquid level, the switch valve 310 is controlled to open, and part of the gas-liquid two-phase body in the primary separation chamber 302 enters the secondary separation chamber 304 through the bypass pipe 309 .

[0098] S330 , based on the liquid level in the liquid storage chamber 301 rising to the preset high liquid level, the switch valve 310 is controlled to close, and the gas-liquid two-phase body in the primary separation chamber 302 is initially separated by the first filling layer 303 and then enters the secondary separation chamber 304 .

[0099] Specifically, the liquid level in the liquid storage chamber 301 is detected and obtained by the liquid level sensor 311. The preset low liquid level and the preset high liquid level can be set according to actual needs. For example, the preset low liquid level is as follows: Figure 2 As shown in the liquid level A, the preset high liquid level is as follows Figure 2 The liquid level B is shown in FIG.

[0100] In one embodiment, after the step of controlling the first throttle valve 7 to open when the ambient temperature is less than or equal to a preset temperature value in S110, the process further includes:

[0101] S400: Adjust the opening of the first throttle valve 7 according to the heat exchange temperature difference.

[0102] In one embodiment, before the step of S100, detecting the ambient temperature and controlling the first throttle valve 7 to open or close according to the difference between the ambient temperature and a preset temperature value, the process further includes:

[0103] S500: Adjust the opening of the second throttle valve 8 according to the return air superheat.

[0104] Specifically, the return air superheat T se=T1-T2, where T1 is the temperature corresponding to the inlet pressure P2 of the compressor 1, and T2 is the outlet temperature of the secondary regenerator 13. The maximum return air superheat and the minimum return air superheat are preset in advance. If the return air superheat T se Between the maximum return air superheat and the minimum return air superheat, the opening of the second throttle valve 8 remains unchanged. If the return air superheat T se If the return air superheat is greater than the maximum return air superheat, the second throttle valve 8 is closed in steps of -5. se If the return air superheat is less than the minimum, the second throttle valve 8 is opened in +5 steps. When the detection difference deviation is greater than 10°C, the second throttle valve 8 is opened or closed with 10 steps as the adjustment value.

[0105] In addition, the heat transfer temperature difference T ck = T3 - T4, where T3 is the inlet temperature of the primary regenerator 4, and T4 is the outlet temperature of the primary regenerator 4. The opening adjustment of the first throttle valve 7 is similar to that of the second throttle valve 8, and will not be repeated here.

[0106] In the specific contents of the above-mentioned specific implementation methods, the various technical features can be combined in any non-contradictory manner. In order to make the description concise, not all possible combinations of the above-mentioned technical features are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0107] The specific contents of the above-mentioned specific embodiments merely represent several embodiments of the present invention. While the description is relatively specific and detailed, it should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art may make various modifications and improvements without departing from the scope of the present invention, and these modifications and improvements fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be based on the appended claims.

Claims

1. A self-cascade heat pump system, characterized in that: The invention comprises a compressor (1), a condenser (2), a rectifier (3), a first-stage regenerator (4), an evaporator (5) and a gas-liquid separator (6), wherein the outlet of the compressor (1) is connected to the condenser (2), the rectifier (3) is provided with a liquid storage chamber (301), a first-stage separation chamber (302), a first filling layer (303), a second-stage separation chamber (304) and a second filling layer (305) which are sequentially connected from bottom to top, the first-stage separation chamber (302) is connected to a feed pipe (306), the liquid storage chamber (301) is connected to a liquid outlet pipe (307), and the top of the rectifier (3) is provided with an air outlet pipe (308). The primary separation chamber (302) is connected to the secondary separation chamber (304) via a bypass pipe (309), and a switch valve (310) is provided on the bypass pipe (309). The outlet of the condenser (2) is connected to the feed pipe (306), and the liquid outlet pipe (307) is sequentially connected to the first throttle valve (7), the primary regenerator (4) and the gas-liquid separator (6). The gas outlet pipe (308) is sequentially connected to the primary regenerator (4), the second throttle valve (8), the evaporator (5) and the gas-liquid separator (6), and the gas-liquid separator (6) is connected to the inlet of the compressor (1).

2. The auto-cascade heat pump system according to claim 1, characterized in that: The first-stage regenerator (4) is provided with a first heat exchange pipeline (401) and a second heat exchange pipeline (402); the gas outlet pipe (308) is connected to one end of the first heat exchange pipeline (401) through a first pipeline (9); the other end of the first heat exchange pipeline (401) is connected to the gas-liquid separator (6) through a second pipeline (10); the second throttle valve (8) is provided on the second pipeline (10); the liquid outlet pipe (307) is connected to one end of the second heat exchange pipeline (402) through a third pipeline (11); the first throttle valve (7) is provided on the third pipeline (11); the other end of the second heat exchange pipeline (402) is connected to the gas-liquid separator (6) through a fourth pipeline (12).

3. The auto-cascade heat pump system according to claim 2, characterized in that: The invention also includes a secondary heat exchanger (13), wherein the secondary heat exchanger (13) is provided with a third heat exchange pipeline (1301) and a fourth heat exchange pipeline (1302); the second pipeline (10) includes a first branch (1001), a second branch (1002), a third branch (1003) and a fourth branch (1004); one end of the third heat exchange pipeline (1301) is connected to the first heat exchange pipeline (401) through the first branch (1001); the other end of the third heat exchange pipeline (1301) is connected to the second branch (1002), the evaporator (5), the third branch (1003), the fourth heat exchange pipeline (1302), the fourth branch (1004) and the gas-liquid separator (6) in sequence.

4. The auto-cascade heat pump system according to claim 3, characterized in that: It also includes a liquid reservoir (14), wherein the liquid reservoir (14) and the second throttle valve (8) are arranged on the second branch (1002), and the liquid reservoir (14) is located between the second throttle valve (8) and the third heat exchange pipeline (1301).

5. The auto-cascade heat pump system according to any one of claims 1 to 4, characterized in that: The invention also includes a controller and a liquid level sensor (311). The liquid level sensor (311) is arranged in the liquid storage chamber (301) and is used to detect the liquid level height in the liquid storage chamber (301). The controller is electrically connected to the switch valve (310) and the liquid level sensor (311) respectively. The controller is used to control the switch valve (310) to open or close according to the liquid level height detected by the liquid level sensor (311).

6. A control method for a cascade heat pump system, characterized in that: The self-cascade heat pump system according to any one of claims 1 to 5 comprises: detecting the ambient temperature and controlling the first throttle valve (7) to open or close according to the difference between the ambient temperature and a preset temperature value; detecting a compression ratio of the compressor (1) based on the opening of the first throttle valve (7); According to the size of the compression ratio of the compressor (1) and a preset compression ratio, the liquid level in the liquid storage chamber (301) is detected, and the switch valve (310) is controlled to be opened or closed according to the liquid level in the liquid storage chamber (301).

7. The control method of the auto-cascade heat pump system according to claim 6, characterized in that: The detecting of the ambient temperature and controlling the first throttle valve (7) to open or close according to the difference between the ambient temperature and a preset temperature value further include: When the ambient temperature is less than or equal to a preset temperature value, controlling the first throttle valve (7) to open; When the ambient temperature is greater than a preset temperature value, the first throttle valve (7) is controlled to close.

8. The control method of the auto-cascade heat pump system according to claim 7, characterized in that: The method further comprises detecting the liquid level in the liquid storage chamber (301) based on the difference between the compression ratio of the compressor (1) and a preset compression ratio, and controlling the switch valve (310) to open or close based on the liquid level in the liquid storage chamber (301), and further comprising: When the compression ratio of the compressor (1) is less than or equal to a preset compression ratio, the liquid level in the liquid storage chamber (301) is detected.

9. The control method of the auto-cascade heat pump system according to claim 8, characterized in that: The method further comprises detecting the liquid level in the liquid storage chamber (301) based on the difference between the compression ratio of the compressor (1) and a preset compression ratio, and controlling the switch valve (310) to open or close based on the liquid level in the liquid storage chamber (301), and further comprising: Based on the liquid level in the liquid storage chamber (301) dropping to a preset low liquid level, the switch valve (310) is controlled to open, and part of the gas-liquid two-phase body in the primary separation chamber (302) enters the secondary separation chamber (304) through the bypass pipe (309); When the liquid level in the liquid storage chamber (301) rises to a preset high liquid level, the switch valve (310) is controlled to close, and the gas-liquid two-phase body in the primary separation chamber (302) enters the secondary separation chamber (304) after preliminary separation through the first filling layer (303).

10. The control method of the auto-cascade heat pump system according to claim 7, characterized in that: After the step of controlling the first throttle valve (7) to open when the ambient temperature is less than or equal to a preset temperature value, the method further comprises: adjusting the opening of the first throttle valve (7) according to the heat exchange temperature difference; And / or, before the step of detecting the ambient temperature and controlling the opening or closing of the first throttle valve (7) according to the difference between the ambient temperature and a preset temperature value, the step further includes: adjusting the opening of the second throttle valve (8) according to the return air superheat.

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