A multi-mode heat pump system and its control method

Abstract

This invention relates to the field of heat pump technology, specifically to a multi-mode heat pump system and its control method. The multi-mode heat pump system includes a first heat exchanger, a second heat exchanger, a low-temperature stage compressor, a high-temperature stage compressor, a flash tank, a steam compressor, and a water pump. This invention also provides a control method for the multi-mode heat pump system. This multi-mode heat pump system utilizes a high-efficiency heat pump to extract heat from groundwater. Through series and parallel control of the heat pump units and the coupling of the steam compressor, it achieves free control of the steam flow rate and temperature. Using a single thermal system, it meets the heat source needs of different industries such as industrial heating and residential heating, and has profound market application prospects.

Description

Technical Field

[0001] This invention relates to the field of heat pump technology, and specifically to a multi-mode heat pump system and its control method. Background Technology

[0002] By drilling into high-temperature geothermal reservoirs, the steam or hot water from geothermal fluids can be used to drive turbine generators to generate electricity. Water stored in shallow underground layers has a lower but relatively stable temperature, classifying it as a medium-low temperature geothermal resource. Medium-low temperature geothermal resources can be used for heating and cooling through geothermal heat pump systems, directly for heating, cooling, and hot water supply, suitable for factories, schools, hospitals, and residences. However, high- and medium-temperature geothermal resources are relatively limited and geographically dispersed, unable to meet the heat demands of various industries on a large scale.

[0003] Extracting heat from shallow underground water and using high-efficiency heat pumps to generate high-temperature heat for various industries is a practical and feasible scientific technology that plays a significant role in promoting carbon reduction and industrial energy conservation.

[0004] Therefore, there is an urgent need for a new technology to fully utilize medium- and low-temperature geothermal resources. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, this application provides a multi-mode heat pump system and its control method. This multi-mode heat pump system utilizes a high-efficiency heat pump to extract heat from groundwater. Through series and parallel control of the heat pump units and coupling with a steam compressor, it achieves free control of steam flow and temperature. This single thermal system meets the heat source needs of different industries, such as industrial heating and residential heating, and has promising market application prospects.

[0006] To achieve the above objectives, the present invention provides a multi-mode heat pump system.

[0007] The multi-mode heat pump system includes a first heat exchanger, a second heat exchanger, a low-temperature stage compressor, a high-temperature stage compressor, a flash tank, a steam compressor, and a water pump. The first heat exchanger includes a first heat release tube and a first heat absorption tube, and the second heat exchanger includes a second heat release tube and a second heat absorption tube.

[0008] The inlet of the first heat-releasing pipe is connected to the geothermal system, the outlet of the first heat-absorbing pipe is connected to the inlets of the low-temperature compressor and the high-temperature compressor respectively, the outlets of the low-temperature compressor and the high-temperature compressor are connected to the inlets of the second heat-releasing pipe respectively, and the outlet of the low-temperature compressor and the inlet of the high-temperature compressor are connected through a series-parallel switching pipe, and the outlet of the second heat-releasing pipe is connected to the inlet of the first heat-absorbing pipe.

[0009] A first series of parallel switching valves is installed on the pipe connecting the outlet of the first heat absorption tube to the inlet of the high-temperature stage compressor. A second series of parallel switching valves is installed on the series-parallel switching pipe. A third series of parallel switching valves is installed on the pipe connecting the outlet of the low-temperature stage compressor to the inlet of the second heat release tube.

[0010] The outlet of the second heat absorption tube is connected to the inlet of the flash tank, and the inlet of the second heat absorption tube is connected to the outlet of the flash tank, thus forming a hot water circulation loop. The water pump is installed on the hot water circulation loop.

[0011] The outlet of the flash tank is connected to the suction port of the steam compressor.

[0012] Preferably, the multi-mode heat pump system includes an economizer, which comprises a main pipeline and an auxiliary pipeline. The inlet of the main pipeline is connected to the outlet of the second heat-releasing pipe via a main pipeline inlet pipe, and the outlet of the main pipeline is connected to the inlet of the first heat-absorbing pipe via a main pipeline outlet pipe. A first solenoid valve is installed on the main pipeline outlet pipe. The inlet of the auxiliary pipeline is connected to the main pipeline outlet via an auxiliary pipeline inlet pipe, and the outlet of the auxiliary pipeline is connected to the inlet of the high-temperature stage compressor via an auxiliary pipeline outlet pipe. A second solenoid valve is installed on the auxiliary pipeline inlet pipe.

[0013] Preferably, the outlet of the second heat-releasing pipe is connected to the compression chamber of the high-temperature compressor, and a third solenoid valve is provided on the pipe connecting the outlet of the second heat-releasing pipe to the compression chamber of the high-temperature compressor.

[0014] Preferably, the outlet of the flash tank is connected to the outlet of the steam compressor via a bypass pipe. A first shut-off valve is installed on the pipe connecting the outlet of the flash tank to the suction port of the steam compressor, and a second shut-off valve is installed on the bypass pipe.

[0015] Preferably, the multi-mode heat pump system further includes a first pressure gauge, a first temperature gauge and / or a first flow meter, wherein the first pressure gauge and / or the first temperature gauge are disposed on the pipe connecting the outlet of the second heat absorption tube to the inlet of the flash tank, and the first flow meter is disposed on the pipe near the outlet of the water pump.

[0016] Preferably, the outlet of the steam compressor is connected to a high-temperature steam outlet pipe, and a second pressure gauge, a second temperature gauge and / or a second flow meter are installed on the high-temperature steam outlet pipe.

[0017] Preferably, the water pump is a centrifugal pump.

[0018] The present invention also provides a control method for any of the above-mentioned multi-mode heat pump systems.

[0019] Control methods include:

[0020] When the demand for high-temperature steam is low and the required temperature is low, close the first series of parallel switching valves, close the second series of parallel switching valves, and open the third series of parallel switching valves to start the cryogenic compressor. Close the first shut-off valve on the pipe connecting the outlet of the flash tank to the suction port of the steam compressor, and open the second shut-off valve on the bypass pipe connecting the outlet of the flash tank to the outlet of the steam compressor.

[0021] When the demand for high-temperature steam is large and the required temperature is low, open the first series of parallel switching valves, close the second series of parallel switching valves, and open the third series of parallel switching valves, allowing the cryogenic compressor and the high-temperature compressor to operate in parallel. Close the first shut-off valve and open the second shut-off valve.

[0022] When the demand for high-temperature steam is low but the required temperature is high, close the first series of parallel switching valves, open the second series of parallel switching valves, and close the third series of parallel switching valves. The low-temperature stage compressor and the high-temperature stage compressor will then operate in series. Close the first shut-off valve and open the second shut-off valve.

[0023] When the demand for high-temperature steam is large and the required temperature is high, open the first series of parallel switching valves, close the second series of parallel switching valves, and open the third series of parallel switching valves, allowing the low-temperature stage compressor and the high-temperature stage compressor to operate in parallel. Open the first shut-off valve and close the second shut-off valve, and the steam compressor will operate.

[0024] Preferably, when the demand for high-temperature steam flow is small and the temperature requirement is high, the third solenoid valve on the pipe connecting the outlet of the second heat release pipe to the compression chamber of the high-temperature compressor is opened.

[0025] Preferably, the multi-mode heat pump system includes a first pressure gauge, a first temperature gauge, and / or a first flow meter. The first pressure gauge and / or the first temperature gauge are installed on the pipe connecting the outlet of the second heat absorber tube to the inlet of the flash tank, and the first flow meter is installed on the pipe near the outlet of the water pump. When the monitored values ​​of the first pressure gauge, the first temperature gauge, and / or the first flow meter are greater than preset values, the water pump speed is reduced; when the monitored values ​​of the first pressure gauge, the first temperature gauge, and / or the first flow meter are less than preset values, the water pump speed is increased.

[0026] Compared with the prior art, the beneficial effects of this application are as follows:

[0027] First, this invention utilizes a high-efficiency heat pump to extract heat from groundwater. Through series and parallel control of the heat pump units and the technology of coupling with a steam compressor, it achieves free control of steam flow and temperature. A single thermal system meets the heat source needs of different industries such as industrial heating and residential heating, and has a wide range of applications.

[0028] Secondly, the thermal system of this invention has four operating modes to meet the high-temperature steam requirements of different industries. This invention particularly relates to high-temperature steam supply, and this system offers more control modes, wider application scenarios, and greater flexibility than traditional refrigerant heat pumps.

[0029] Furthermore, this invention utilizes a high-efficiency heat pump system to extract heat from groundwater, transfers the heat to hot water through a second heat exchanger, and generates high-temperature steam in a flash tank after the hot water is heated. Based on the user's needs, the steam at the outlet of the flash tank is heated and pressurized before being supplied to the user, which has a significant promoting effect on carbon reduction and industrial energy conservation. Attached Figure Description

[0030] This application can be better understood by describing its embodiments in conjunction with the accompanying drawings, in which:

[0031] Figure 1 This is a schematic diagram of the structure of a multi-mode heat pump system according to this application.

[0032] Explanation of icon numbers:

[0033] 10. First heat exchanger; 11. First heat release tube; 12. First heat absorption tube; 20. Second heat exchanger; 21. Second heat release tube; 22. Second heat absorption tube; 30. Low-temperature stage compressor; 32. High-temperature stage compressor; 34. Flash tank; 36. Steam compressor; 38. Water pump; 40. Economizer; 50. Series-parallel switching pipe; 51. Bypass pipe; 61. First series-parallel switching valve; 62. Second series-parallel switching valve; 63. Third series-parallel switching valve; 64. First solenoid valve; 65. Second solenoid valve; 66. Third solenoid valve; 67. First shut-off valve; 68. Second shut-off valve; 71. First pressure gauge; 72. First temperature gauge; 73. First flow meter; 74. Second pressure gauge; 75. Second temperature gauge; 76. Second flow meter. Detailed Implementation

[0034] Unless otherwise defined, the technical or scientific terms used in this specification and claims shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0035] In the description of this invention, it should be understood that the terms "center", "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0036] Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0037] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] This embodiment relates to a method such as Figure 1 The multi-mode heat pump system shown.

[0040] The multi-mode heat pump system includes a first heat exchanger 10, a second heat exchanger 20, a low-temperature stage compressor 30, a high-temperature stage compressor 32, a flash tank 34, a steam compressor 36, and a water pump 38. Preferably, the water pump 38 is a centrifugal pump.

[0041] The first heat exchanger 10 includes a first heat-dissipating tube 11 and a first heat-absorbing tube 12, and the second heat exchanger 20 includes a second heat-dissipating tube 21 and a second heat-absorbing tube 22.

[0042] The inlet of the first heat-exporting pipe 11 is connected to the geothermal system. The outlet of the first heat-absorbing pipe 12 is connected to the inlets of the low-temperature compressor 30 and the high-temperature compressor 32, respectively. The outlets of the low-temperature compressor 30 and the high-temperature compressor 32 are connected to the inlets of the second heat-exporting pipe 21, respectively. The outlet of the low-temperature compressor 30 and the inlet of the high-temperature compressor 32 are connected through a series-parallel switching pipe 50. The outlet of the second heat-exporting pipe 21 is connected to the inlet of the first heat-absorbing pipe 12.

[0043] A first series-parallel switching valve 61 is installed on the pipe connecting the outlet of the first heat absorption pipe 12 to the inlet of the high-temperature stage compressor 32. A second series-parallel switching valve 62 is installed on the series-parallel switching pipe 50. A third series-parallel switching valve 63 is installed on the pipe connecting the outlet of the low-temperature stage compressor 30 to the inlet of the second heat release pipe 21.

[0044] The outlet of the second heat absorption pipe 22 is connected to the water inlet of the flash tank 34, and the inlet of the second heat absorption pipe 22 is connected to the water outlet of the flash tank 34, thereby forming a hot water circulation loop. The water pump 38 is installed on the hot water circulation loop.

[0045] The outlet of the flash tank 34 is connected to the suction port of the steam compressor 36.

[0046] Preferably, the multi-mode heat pump system includes an economizer 40, which includes a main pipeline and an auxiliary pipeline. The inlet of the main pipeline is connected to the outlet of the second heat-releasing pipe 21 through a main pipeline inlet pipe, and the outlet of the main pipeline is connected to the inlet of the first heat-absorbing pipe 12 through a main pipeline outlet pipe. A first solenoid valve 64 is installed on the main pipeline outlet pipe. The inlet of the auxiliary pipeline is connected to the main pipeline outlet through an auxiliary pipeline inlet pipe, and the outlet of the auxiliary pipeline is connected to the inlet of the high-temperature stage compressor 32 through an auxiliary pipeline outlet pipe. A second solenoid valve 65 is installed on the auxiliary pipeline inlet pipe.

[0047] Preferably, the outlet of the second heat-releasing pipe 21 is connected to the compression chamber of the high-temperature compressor 32, and a third solenoid valve 66 is provided on the pipe connecting the outlet of the second heat-releasing pipe 21 to the compression chamber of the high-temperature compressor 32.

[0048] Preferably, the outlet of the flash tank 34 is connected to the outlet of the steam compressor 36 via a bypass pipe 51. A first shut-off valve 67 is provided on the pipe connecting the outlet of the flash tank 34 to the suction port of the steam compressor 36, and a second shut-off valve 68 is provided on the bypass pipe 51.

[0049] Preferably, the multi-mode heat pump system further includes a first pressure gauge 71, a first temperature gauge 72, and / or a first flow meter 73. The first pressure gauge 71 and / or the first temperature gauge 72 are installed on the pipe connecting the outlet of the second heat absorption pipe 22 to the inlet of the flash tank 34, and the first flow meter 73 is installed on the pipe near the outlet of the water pump 38. The first pressure gauge 71, the first temperature gauge 72, and / or the first flow meter 73 can be set with target values ​​as needed. The first pressure gauge 71 and / or the first temperature gauge 72 can be connected to the first flow meter 73 via a control line, and the first flow meter 73 can be connected to the water pump 38 via a control line.

[0050] Preferably, the outlet of the steam compressor 36 is connected to a high-temperature steam outlet pipe, which is equipped with a second pressure gauge 74, a second temperature gauge 75, and / or a second flow meter 76. The second pressure gauge 74, the second temperature gauge 75, and / or the second flow meter 76 can be set with target values ​​as needed, and are connected to the first parallel switching valve 61, the second parallel switching valve 62, the third parallel switching valve 63, and / or the steam compressor 36 via control lines.

[0051] In such Figure 1 In the illustrated embodiment, the refrigerant in the heat pump system absorbs heat from the first heat exchanger 10, then is heated and pressurized by the low-temperature compressor 30 or the high-temperature compressor 32, and subsequently condenses and releases heat in the second heat exchanger 20. The condensed refrigerant then passes through the economizer 40 and the first solenoid valve 64 for throttling and pressure reduction before entering the first heat exchanger 10. Another path of refrigerant, after passing through the economizer 40, is throttled and cooled by the second solenoid valve 65 before entering the economizer 40 to absorb heat and then flowing into the suction port of the high-temperature compressor 32. Hot water from the outlet of the flash tank 34 is pressurized by the water pump 38 and enters the second heat exchanger 20, where it absorbs heat and heats up before entering the flash tank 34. The high-temperature hot water undergoes flash evaporation in the flash tank 34, and the resulting high-temperature steam exits from the top outlet of the flash tank 34. This steam can then be supplied to the user via the bypass pipe 51, or heated and pressurized by the steam compressor 36 before being supplied to the user.

[0052] This invention also provides a control method for any of the above-mentioned multi-mode heat pump systems. The following is in conjunction with... Figure 1 Explanation is provided. Control methods include:

[0053] When the demand for high-temperature steam is low and the required temperature is low, the first parallel switching valve 61 is closed, the second parallel switching valve 62 is closed, and the third parallel switching valve 63 is opened, allowing the low-temperature compressor 30 to operate. The first shut-off valve 67 on the pipe connecting the outlet of the flash tank 34 to the suction port of the steam compressor 36 is closed, and the second shut-off valve 68 on the bypass pipe 51 connecting the outlet of the flash tank 34 to the outlet of the steam compressor 36 is opened. In this mode, the refrigerant in the heat pump system can absorb heat from the first heat exchanger 10 and then enter the low-temperature compressor 30 for heating and pressurization, subsequently condensing and releasing heat in the second heat exchanger 20. Hot water flowing from the flash tank 34 is pressurized by the water pump 38 and enters the second heat exchanger 20 to absorb heat and increase its temperature, then enters the flash tank 34 for flash evaporation. The high-temperature steam generated by flash evaporation exits from the outlet of the flash tank 34 and is supplied to the user via the bypass pipe 51.

[0054] When the demand for high-temperature steam is large and the required temperature is low, the first parallel switching valve 61 is opened, the second parallel switching valve 62 is closed, and the third parallel switching valve 63 is opened, allowing the low-temperature compressor 30 and the high-temperature compressor 32 to operate in parallel. The first shut-off valve 67 is closed, and the second shut-off valve 68 is opened. In this mode, the refrigerant in the heat pump system absorbs heat from the first heat exchanger 10, with one path leading to the low-temperature compressor 30 and the other path passing through the first parallel switching valve 61 to the high-temperature compressor 32. At this time, the low-temperature compressor 30 and the high-temperature compressor 32 operate in parallel. Subsequently, the refrigerant is heated and pressurized, and then condenses in the second heat exchanger 20, releasing heat. The hot water flowing out of the flash tank 34 is pressurized by the water pump 38 and enters the second heat exchanger 20 to absorb heat and heat up, before entering the flash tank 34 for flash evaporation. The high-temperature steam generated by flash evaporation exits from the outlet of the flash tank 34 and is supplied to the user through the bypass pipe 51.

[0055] When the demand for high-temperature steam is low but the temperature requirement is high, the first parallel switching valve 61 is closed, the second parallel switching valve 62 is opened, and the third parallel switching valve 63 is closed, allowing the low-temperature compressor 30 and the high-temperature compressor 32 to operate in series. The first shut-off valve 67 is closed, and the second shut-off valve 68 is opened. In this mode, the refrigerant in the heat pump system absorbs heat from the first heat exchanger 10 and enters the low-temperature compressor 30. Subsequently, it enters the high-temperature compressor 32 through the second parallel switching valve 62, where it is heated and pressurized, and then condenses in the second heat exchanger 20 to release heat. The hot water flowing out of the flash tank 34 is pressurized by the water pump 38 and enters the second heat exchanger 20 to absorb heat and increase its temperature. It then enters the flash tank 34 for flash evaporation. The high-temperature steam generated by flash evaporation leaves from the outlet of the flash tank 34 and is supplied to the user through the bypass pipe 51. In some embodiments, when the demand for high-temperature steam is low but the temperature requirement is high, the third solenoid valve 66 is opened on the pipe connecting the outlet of the second heat release pipe 21 to the compression chamber of the high-temperature compressor 32. At this time, part of the refrigerant flowing out of the second heat exchanger 20 enters the compression chamber of the high-temperature stage compressor 32, reducing the temperature inside the compression chamber.

[0056] When the demand for high-temperature steam is large and the required temperature is high, the first parallel switching valve 61 is opened, the second parallel switching valve 62 is closed, and the third parallel switching valve 63 is opened, allowing the low-temperature compressor 30 and the high-temperature compressor 32 to operate in parallel. The first shut-off valve 67 is opened, and the second shut-off valve 68 is closed, allowing the steam compressor 36 to operate. In this mode, the refrigerant in the heat pump system absorbs heat from the first heat exchanger 10, entering the low-temperature compressor 30 in one path and the high-temperature compressor 32 after passing through the first parallel switching valve 61 in another. Subsequently, the refrigerant heats up and pressurizes, condensing and releasing heat in the second heat exchanger 20. Hot water flowing from the flash tank 34 is pressurized by the water pump 38 and enters the second heat exchanger 20 to absorb heat and heat up, then enters the flash tank 34 for flash evaporation. The high-temperature steam generated by flash evaporation exits from the outlet of the flash tank 34. At this time, the second shut-off valve 68 is closed, the first shut-off valve 67 is opened, and the high-temperature steam generated by flash evaporation enters the suction port of the steam compressor 36, where it is heated and pressurized before being supplied to the user.

[0057] Preferably, the multi-mode heat pump system includes a first pressure gauge 71, a first temperature gauge 72, and / or a first flow meter 73. The first pressure gauge 71 and / or the first temperature gauge 72 are installed on the pipe connecting the outlet of the second heat absorption pipe 22 to the inlet of the flash tank 34, and the first flow meter 73 is installed on the pipe near the outlet of the water pump 38. When the monitored values ​​of the first pressure gauge 71, the first temperature gauge 72, and / or the first flow meter 73 are greater than preset values, the speed of the water pump 38 is reduced; when the monitored values ​​of the first pressure gauge 71, the first temperature gauge 72, and / or the first flow meter 73 are less than preset values, the speed of the water pump 38 is increased.

[0058] The above specific embodiments further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A control method for a multi-mode heat pump system, characterized in that, The multi-mode heat pump system includes a first heat exchanger, a second heat exchanger, a low-temperature stage compressor, a high-temperature stage compressor, a flash tank, a steam compressor, and a water pump; the first heat exchanger includes a first heat release tube and a first heat absorption tube, and the second heat exchanger includes a second heat release tube and a second heat absorption tube, wherein... The inlet of the first heat-releasing pipe is connected to the geothermal system, the outlet of the first heat-absorbing pipe is connected to the inlet of the low-temperature compressor and the high-temperature compressor respectively, the outlet of the low-temperature compressor and the high-temperature compressor are connected to the inlet of the second heat-releasing pipe respectively, and the outlet of the low-temperature compressor and the inlet of the high-temperature compressor are connected through a series-parallel switching pipe, and the outlet of the second heat-releasing pipe is connected to the inlet of the first heat-absorbing pipe. A first series of parallel switching valves is provided on the pipe connecting the outlet of the first heat absorption tube to the inlet of the high-temperature stage compressor, a second series of parallel switching valves is provided on the series-parallel switching pipe, and a third series of parallel switching valves is provided on the pipe connecting the outlet of the low-temperature stage compressor to the inlet of the second heat release tube. The outlet of the second heat absorption tube is connected to the water inlet of the flash tank, and the inlet of the second heat absorption tube is connected to the water outlet of the flash tank, thereby forming a hot water circulation loop. The water pump is installed on the hot water circulation loop. The outlet of the flash evaporator is connected to the intake port of the steam compressor; The outlet of the second heat-releasing pipe is connected to the compression chamber of the high-temperature stage compressor, and a third solenoid valve is provided on the pipe connecting the outlet of the second heat-releasing pipe to the compression chamber of the high-temperature stage compressor. The outlet of the flash tank is connected to the outlet of the steam compressor via a bypass pipe. A first shut-off valve is installed on the pipe connecting the outlet of the flash tank to the suction port of the steam compressor, and a second shut-off valve is installed on the bypass pipe. The control method includes: When the demand for high-temperature steam is low and the temperature requirement is low, close the first series of parallel switching valves, close the second series of parallel switching valves, open the third series of parallel switching valves, and the low-temperature stage compressor runs; close the first shut-off valve on the pipe connecting the outlet of the flash tank and the suction port of the steam compressor, and open the second shut-off valve on the bypass pipe connecting the outlet of the flash tank and the outlet of the steam compressor. When the demand for high-temperature steam is large and the temperature requirement is low, open the first parallel switching valve, close the second parallel switching valve, and open the third parallel switching valve, so that the low-temperature compressor and the high-temperature compressor can operate in parallel; close the first shut-off valve and open the second shut-off valve. When the demand for high-temperature steam is low and the temperature requirement is high, the first parallel switching valve is closed, the second parallel switching valve is opened, and the third parallel switching valve is closed, so that the low-temperature compressor and the high-temperature compressor operate in series; the first shut-off valve is closed and the second shut-off valve is opened. When the demand for high-temperature steam is large and the temperature requirement is high, the first parallel switching valve is opened, the second parallel switching valve is closed, and the third parallel switching valve is opened, so that the low-temperature stage compressor and the high-temperature stage compressor can operate in parallel; the first shut-off valve is opened and the second shut-off valve is closed, so that the steam compressor can operate.

2. The control method for a multi-mode heat pump system according to claim 1, characterized in that, The multi-mode heat pump system includes an economizer, which comprises a main pipeline and an auxiliary pipeline. The inlet of the main pipeline is connected to the outlet of the second heat-releasing pipe via a main inlet pipe, and the outlet of the main pipeline is connected to the inlet of the first heat-absorbing pipe via a main outlet pipe. A first solenoid valve is installed on the main outlet pipe. The inlet of the auxiliary pipeline is connected to the main outlet pipe via an auxiliary inlet pipe, and the outlet of the auxiliary pipeline is connected to the inlet of the high-temperature compressor via an auxiliary outlet pipe. A second solenoid valve is installed on the auxiliary inlet pipe.

3. The control method for a multi-mode heat pump system according to claim 1, characterized in that, The multi-mode heat pump system further includes a first pressure gauge, a first temperature gauge, and a first flow meter. The first pressure gauge and the first temperature gauge are installed on the pipe connecting the outlet of the second heat absorption tube to the inlet of the flash tank, and the first flow meter is installed on the pipe near the outlet of the water pump.

4. The control method for a multi-mode heat pump system according to claim 1, characterized in that, The outlet of the steam compressor is connected to a high-temperature steam outlet pipe, which is equipped with a second pressure gauge, a second temperature gauge, and a second flow meter.

5. The control method for a multi-mode heat pump system according to claim 1, characterized in that, The water pump is a centrifugal pump.

6. The control method for a multi-mode heat pump system according to claim 1, characterized in that, When the demand for high-temperature steam is low but the temperature requirement is high, open the third solenoid valve on the pipe connecting the outlet of the second heat release pipe to the compression chamber of the high-temperature compressor.

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