Heat pump system and control method thereof

Abstract

The application relates to a heat pump system and a control method thereof. The heat pump system comprises a first heat pump group, a second heat pump group, a circulating water pipeline mechanism, a valve reversing assembly and a controller. The first heat pump group comprises at least two heat pump units, and the second heat pump group comprises at least two heat pump units. The first heat pump group and the second heat pump group are connected with the circulating water pipeline mechanism respectively, and the valve reversing assembly is arranged in the circulating water pipeline mechanism. A temperature sensor is arranged at the water outlet end of the circulating water pipeline mechanism. The controller is configured to judge a heat load level according to a temperature value measured by the temperature sensor, and control the valve reversing assembly to switch the water flow direction in the circulating water pipeline mechanism according to the heat load level. The heat pump system introduces a series connection mode at each level, so that the upstream heat pump unit in the series connection relationship does not have the same water inlet temperature or water outlet temperature as the downstream unit.

Description

Technical Field

[0001] This application relates to the field of heat pump systems, and more particularly to a heat pump system and its control method. Background Technology

[0002] Air source heat pump systems have been widely used in building air conditioning and heating due to their advantages such as energy saving, environmental protection, and convenient installation. Traditional air source heat pump systems typically adopt a structure in which multiple units operate in fixed parallel. They roughly adapt to changes in cooling and heating loads by starting and stopping the number of units. The inlet and outlet water temperatures of each unit in the system are kept consistent. Under the same operating conditions, the energy efficiency levels of each unit are similar, and the overall energy efficiency of the system is significantly lower than that of a series system. Summary of the Invention

[0003] This application provides a heat pump system and its control method to solve the technical problems mentioned in the background art.

[0004] In a first aspect, this application provides a heat pump system, including a first heat pump group, a second heat pump group, a circulating water pipeline mechanism, a valve reversing assembly, and a controller; the first heat pump group includes at least two heat pump units, and the second heat pump group includes at least two heat pump units. The first heat pump unit and the second heat pump unit are respectively connected to the circulating water pipeline mechanism, and the valve reversing assembly is located inside the circulating water pipeline mechanism; A temperature sensor is installed at the outlet of the circulating water pipeline mechanism; The controller is configured to determine the heat load level based on the temperature value measured by the temperature sensor, and control the valve reversing assembly to switch the water flow direction in the circulating water pipeline mechanism according to the heat load level; When the heat load level is at the first level, the heat pump units of the first heat pump group are connected in series, and the second heat pump group is disconnected from the circulating water pipeline mechanism. When the heat load level is at the second level, the heat pump units of the first heat pump group are connected in series, the heat pump units of the second heat pump group are connected in series, and the first heat pump group and the second heat pump group are connected in parallel. When the heat load level is at level three, the heat pump units of the first heat pump group are connected in series, the heat pump units of the second heat pump group are connected in parallel, and the first heat pump group and the second heat pump group are connected in parallel. When the heat load level is at level four, the heat pump units of the first heat pump group are connected in parallel, the heat pump units of the second heat pump group are connected in parallel, and the first heat pump group and the second heat pump group are connected in series. The heat load levels of level four, level three, level two, and level one gradually decrease.

[0005] According to one embodiment of this application, the first heat pump unit includes a first heat pump unit and a second heat pump unit, and the second heat pump unit includes a third heat pump unit and a fourth heat pump unit; The first heat pump unit, the second heat pump unit, the third heat pump unit, and the fourth heat pump unit are each provided with a heat pump inlet pipe and a heat pump outlet pipe at their inlet and outlet, respectively. The valve reversing assembly includes a first three-way valve and a second three-way valve; The inlet of the first three-way valve is connected to the outlet of the heat pump outlet pipe of the second heat pump unit. The first outlet of the first three-way valve is connected to a manifold. The second outlet of the first three-way valve is connected to the opening on the side wall of the heat pump inlet pipe of the first heat pump unit through a connecting pipe. The heat pump outlet pipe of the fourth heat pump unit is connected to the inlet of the second three-way valve. The first outlet of the second three-way valve is connected to a manifold. The second outlet of the second three-way valve is connected to the opening on the side wall of the heat pump inlet pipe of the third heat pump unit through a connecting pipe.

[0006] According to one embodiment of this application, the circulating water pipeline system includes a main inlet pipe, a confluence inlet pipe, a connecting pipe, a confluence outlet pipe, a branch pipe, and a return main pipe; The valve reversing assembly also includes a third three-way valve, a first electric valve, a second electric valve, and a third electric valve; The heat pump inlet pipes of the first heat pump unit and the second heat pump unit are respectively connected to the main inlet pipe. The heat pump outlet pipe of the first heat pump unit is connected to the manifold inlet pipe. The end of the manifold pipe of the second heat pump unit away from the first three-way valve is connected to the opening on the side wall of the manifold inlet pipe. The first electric valve is installed on the main inlet pipe and is located between the heat pump inlet pipes of the first heat pump unit and the second heat pump unit. One end of the water distribution pipe is connected to an opening on the side wall of the main water inlet pipe. The third electric valve is installed at the end of the water distribution pipe near the main water inlet pipe. The heat pump inlet pipes of the third heat pump unit and the fourth heat pump unit are respectively connected to the water distribution pipe. The heat pump outlet pipe of the third heat pump unit is connected to the main return water pipe. The end of the manifold of the fourth heat pump unit away from the second three-way valve is connected to an opening on the side wall of the main return water pipe. One end of the manifold inlet pipe is connected to the inlet of the third three-way valve. The first outlet of the third three-way valve is connected to the opening on the side wall of the return main pipe through the manifold outlet pipe. The second outlet of the third three-way valve is connected to the opening on the side wall of the branch pipe through the connecting pipe. The second electric valve is installed on the water distribution pipe and is located between the heat pump inlet pipes of the third heat pump unit and the fourth heat pump unit.

[0007] According to one embodiment of this application, when the heat load level is at the first level, the inlet of the first three-way valve is connected to the second outlet, the inlet of the third three-way valve is connected to the first outlet, and the first electric valve and the third electric valve are closed. When the heat load level is at the second level, the inlet of the first three-way valve is connected to the second outlet, the inlet of the second three-way valve is connected to the second outlet, the inlet of the third three-way valve is connected to the first outlet, the first electric valve and the second electric valve are both closed, and the third electric valve is open. When the heat load level is at the third level, the inlet of the first three-way valve is connected to the second outlet, the inlet of the second three-way valve is connected to the first outlet, and the inlet of the third three-way valve is connected to the first outlet. The first electric valve is closed, and the second and third electric valves are open; When the heat load level is at the fourth level, the inlet of the first three-way valve is connected to the first outlet, the inlet of the second three-way valve is connected to the first outlet, and the inlet of the third three-way valve is connected to the second outlet. The first electric valve, the second electric valve, and the third electric valve are all open.

[0008] According to one embodiment of this application, it further includes a first circulating water pump and a second circulating water pump connected in parallel on the main water inlet pipe; The first circulating water pump is installed on the main water inlet pipe, and a parallel pipeline is connected to the main water inlet pipe. The second circulating water pump is installed in the parallel pipeline.

[0009] Secondly, this application provides a control method for a heat pump system, applied to the aforementioned heat pump system, the method comprising the following steps: Obtain the actual water supply temperature detected by the temperature sensor; The current heat load level is determined based on the actual water supply temperature and the target water supply temperature threshold. Based on the current heat load level, controlling the valve reversing assembly to switch the water flow direction within the circulating water pipeline mechanism to switch the heat pump system to the corresponding series-parallel mode includes: When the heat load level is at level one, the heat pump system is switched to mode one to control the heat pump units of the first heat pump group to be connected in series, and the second heat pump group to be disconnected from the circulating water pipeline mechanism; when the heat load level is at level two, the heat pump system is switched to mode two to control the heat pump units of the first heat pump group to be connected in series, the heat pump units of the second heat pump group to be connected in series, and the first and second heat pump groups to be connected in parallel; when the heat load level is at level three, the heat pump system is switched to mode three to control the heat pump units of the first heat pump group to be connected in series, the heat pump units of the second heat pump group to be connected in parallel, and the first and second heat pump groups to be connected in parallel; when the heat load level is at level four, the heat pump system is switched to mode four to control the heat pump units of the first heat pump group to be connected in parallel, the heat pump units of the second heat pump group to be connected in parallel, and the first and second heat pump groups to be connected in series. The heat load levels of the fourth, third, second, and first levels gradually decrease.

[0010] According to one embodiment of this application, when the heat pump system switches to any mode, the current water supply temperature is obtained; Determine whether the deviation between the current water supply temperature and the target water supply temperature meets the conditions for frequency increase or decrease; If the frequency increase conditions are met, the compressors of each heat pump unit are controlled to increase their frequency synchronously. If the frequency reduction condition is met, the compressors of each heat pump unit will be controlled to reduce their frequency synchronously.

[0011] According to one embodiment of this application, after controlling the compressors of each heat pump unit to synchronously increase their frequency, the method further includes: Obtain the current water supply temperature and determine whether the current water supply temperature still meets the frequency increase condition; If the frequency increase condition is still met, the valve reversing component is controlled to switch the current mode of the heat pump system to the next mode with a higher heat load level. If the frequency increase conditions are not met, the current mode remains unchanged.

[0012] According to one embodiment of this application, after controlling the compressors of each heat pump unit to synchronously reduce their frequency, the method further includes: Obtain the current water supply temperature and determine whether the current water supply temperature still meets the frequency reduction condition; If the frequency reduction condition is still met, the valve reversing component is controlled to switch the current mode of the heat pump system to the next mode with a lower heat load level. If the frequency reduction condition is not met, the current series-parallel connection mode remains unchanged.

[0013] According to one embodiment of this application, The frequency increase conditions include cooling frequency increase conditions and heating frequency increase conditions, and the frequency decrease conditions include cooling frequency decrease conditions and heating frequency decrease conditions. The cooling frequency increase condition is: the current water supply temperature is greater than the sum of the target water supply temperature and the first water temperature allowable deviation threshold; The cooling frequency reduction condition is: the current water supply temperature is less than the difference between the target water supply temperature and the second water temperature allowable deviation threshold; The heating frequency increase condition is: the current water supply temperature is less than the difference between the target water supply temperature and the third water temperature allowable deviation threshold; The heating frequency reduction condition is: the current water supply temperature is greater than the sum of the target water supply temperature and the fourth water temperature allowable deviation threshold.

[0014] The technical solutions provided in this application have the following advantages compared with the prior art: The heat pump system provided in the first aspect of this application detects the actual supply water temperature at the outlet of the circulating water pipeline mechanism using a temperature sensor, enabling the controller to determine the current heat load level and then control the valve reversing assembly to switch the water flow direction within the circulating water pipeline mechanism according to different heat load levels. When the heat load level is at the first level, the heat pump units of the first heat pump group are connected in series, and the second heat pump group is disconnected from the circulating water pipeline mechanism. When the heat load level is at the second level, the heat pump units of the first heat pump group are connected in series, the heat pump units of the second heat pump group are connected in series, and the first and second heat pump groups are connected in parallel. When the heat load level is at the third level, the heat pump units of the first heat pump group are connected in series, the heat pump units of the second heat pump group are connected in parallel, and the first and second heat pump groups are connected in parallel. When the heat load level is at the fourth level, the heat pump units of the first heat pump group are connected in parallel, the heat pump units of the second heat pump group are connected in parallel, and the first and second heat pump groups are connected in series.

[0015] In this way, the heat pump system is no longer limited to a fixed parallel architecture, but can adjust the connection relationship between each heat pump unit according to the actual load. Especially at various heat load levels, the heat pump system introduces a series connection, so that the upstream heat pump unit in the series connection no longer has the same inlet or outlet water temperature as the downstream unit. Instead, the upstream heat pump unit preheats or precools the water flow before supplying it to the downstream unit for further heat exchange. This results in a higher evaporation temperature for the upstream unit in cooling mode compared to the traditional parallel architecture, and a lower condensation temperature for the upstream unit in heating mode compared to the traditional parallel architecture. This solves the problem of low energy efficiency caused by the uniform inlet and outlet water temperatures of all units in a traditional fixed parallel architecture.

[0016] The control method for the heat pump system provided in the second aspect of this application realizes automatic switching between four series and parallel modes according to the heat load level, so that the system can operate in the optimal series and parallel mode under different load conditions, which not only ensures sufficient cooling or heating capacity, but also maximizes the system energy efficiency and achieves the technical effect of energy saving and consumption reduction. Attached Figure Description

[0017] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] One or more embodiments are illustrated by way of example with reference numerals in the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Elements with the same reference numerals in the drawings are denoted as similar elements. Unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0020] Figure 1 This is a schematic diagram of the structure of a heat pump system provided in an embodiment of this application; Figure 2 A schematic diagram of a heat pump system in a first mode provided in an embodiment of this application; Figure 3 A schematic diagram of a heat pump system in a second mode as provided in an embodiment of this application; Figure 4 A schematic diagram of a heat pump system in a third mode provided in an embodiment of this application; Figure 5 A schematic diagram of a heat pump system in a fourth mode provided in an embodiment of this application; Figure 6 This is a schematic diagram of a control method for a heat pump system provided in an embodiment of this application.

[0021] Explanation of reference numerals in the attached figures: 1. First heat pump unit; 2. Second heat pump unit; 3. Third heat pump unit; 4. Fourth heat pump unit; 5. First circulating water pump; 6. Second circulating water pump; 7. First three-way valve; 8. Second three-way valve; 9. First electric valve; 10. Second electric valve; 11. Third three-way valve; 12. Third electric valve; 13. Main inlet pipe; 14. Main return pipe; 15. First temperature sensor; 16. Second temperature sensor; 17. Check valve; 18. Heat pump inlet pipe; 19. Heat pump outlet pipe; 20. Connecting pipe; 21. Branch pipe; 22. Combination inlet pipe; 23. Connecting pipe; 24. Combination outlet pipe; 25. Parallel pipeline; 26. Collecting pipe. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0023] The following disclosure provides numerous different embodiments or examples for implementing various structures of the invention. To simplify the disclosure, specific examples of heat pump systems and their control methods and arrangements are described below. These are merely examples and are not intended to limit the invention. Furthermore, reference numerals and / or letters may be repeated in different examples. Such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed.

[0024] For ease of description, spatial relative terms may be used in the text to describe the relative position or movement of one element or feature relative to another element or feature, as shown in the figure. These relative terms include, for example, "inside," "outside," "middle," "outer," "below," "below," "above," "front," "back," etc. Such spatial relative terms are intended to include different orientations of the device in use or operation, other than those depicted in the figure. For example, if the device in the figure undergoes a positional flip, orientation change, or change of motion, these directional indications will change accordingly. For instance, an element described as "below other elements or features" or "below other elements or features" will subsequently be oriented "above other elements or features" or "above other elements or features." Therefore, the example term "below" can include both upper and lower orientations. The device may be otherwise oriented (rotated 90 degrees or in other directions), and the spatial relative descriptors used in the text will be interpreted accordingly.

[0025] The first aspect of this application provides a heat pump system, including a first heat pump group, a second heat pump group, a circulating water pipeline mechanism, a valve reversing assembly, and a controller; the first heat pump group includes at least two heat pump units, and the second heat pump group includes at least two heat pump units. The first heat pump unit and the second heat pump unit are respectively connected to the circulating water pipeline mechanism, and the valve reversing assembly is located inside the circulating water pipeline mechanism. A temperature sensor is installed at the outlet end of the circulating water pipeline system; The controller is configured to determine the heat load level based on the temperature value measured by the temperature sensor, and control the valve reversing assembly to switch the water flow direction in the circulating water pipeline mechanism according to the heat load level; When the heat load level is at the first level, the heat pump units controlling the first heat pump group are connected in series, and the second heat pump group is disconnected from the circulating water pipeline mechanism. When the heat load level is at the second level, the heat pump units controlling the first heat pump group are connected in series, the heat pump units controlling the second heat pump group are connected in series, and the first heat pump group and the second heat pump group are connected in parallel. When the heat load level is at level 3, the heat pump units controlling the first heat pump group are connected in series, the heat pump units controlling the second heat pump group are connected in parallel, and the first heat pump group and the second heat pump group are connected in parallel. When the heat load level is at level four, the heat pump units of the first heat pump group are connected in parallel, the heat pump units of the second heat pump group are connected in parallel, and the first and second heat pump groups are connected in series; the heat load levels of the fourth, third, second, and first levels gradually decrease.

[0026] In this embodiment, the actual water supply temperature at the outlet of the circulating water pipeline mechanism is detected by a temperature sensor, enabling the controller to determine the current heat load level. Based on this, the controller controls the valve reversing assembly to switch the water flow direction within the circulating water pipeline mechanism according to different heat load levels. When the heat load level is at level one, the heat pump units of the first heat pump group are connected in series, and the second heat pump group is disconnected from the circulating water pipeline mechanism. When the heat load level is at level two, the heat pump units of the first heat pump group are connected in series, the heat pump units of the second heat pump group are connected in series, and the first and second heat pump groups are connected in parallel. When the heat load level is at level three, the heat pump units of the first heat pump group are connected in series, the heat pump units of the second heat pump group are connected in parallel, and the first and second heat pump groups are connected in parallel. When the heat load level is at level four, the heat pump units of the first heat pump group are connected in parallel, the heat pump units of the second heat pump group are connected in parallel, and the first and second heat pump groups are connected in series.

[0027] In this way, the heat pump system is no longer limited to a fixed parallel architecture, but can adjust the connection relationship between each heat pump unit according to the actual load. In particular, a series connection method is introduced in all modes, so that the upstream heat pump unit in the series connection no longer has the same inlet or outlet water temperature as the downstream unit. Instead, the upstream heat pump unit preheats or precools the water flow before supplying it to the downstream unit for further heat exchange. As a result, in cooling mode, the evaporation temperature of the upstream unit is higher than that in the traditional parallel architecture, and in heating mode, the condensation temperature of the upstream unit is lower than that in the traditional parallel architecture. This solves the problem of low energy efficiency caused by the uniform inlet and outlet water temperatures of all units in the traditional fixed parallel architecture.

[0028] In this embodiment, as Figure 1 As shown, the first heat pump unit includes a first heat pump unit 1 and a second heat pump unit 2, and the second heat pump unit includes a third heat pump unit 3 and a fourth heat pump unit 4. The first heat pump unit 1, the second heat pump unit 2, the third heat pump unit 3 and the fourth heat pump unit 4 are each provided with a heat pump inlet pipe 18 and a heat pump outlet pipe 19; the valve reversing assembly includes a first three-way valve 7 and a second three-way valve 8. The inlet of the first three-way valve 7 is connected to the outlet of the heat pump outlet pipe 19 of the second heat pump unit 2. The first outlet of the first three-way valve 7 is connected to the manifold 26. The second outlet of the first three-way valve 7 is connected to the opening on the side wall of the heat pump inlet pipe 18 of the first heat pump unit 1 through the connecting pipe 20. The heat pump outlet pipe 19 of the fourth heat pump unit 4 is connected to the inlet of the second three-way valve 8. The first outlet of the second three-way valve 8 is connected to a manifold 26. The second outlet of the second three-way valve 8 is connected to the opening on the side wall of the heat pump inlet pipe 18 of the third heat pump unit 3 through a connecting pipe 20.

[0029] In this embodiment, the circulating water pipeline mechanism includes a main inlet pipe 13, a confluence inlet pipe 22, a connecting pipe 23, a confluence outlet pipe 24, a branch pipe 21, and a return main pipe 14; the valve reversing assembly also includes a third three-way valve 11, a first electric valve 9, a second electric valve 10, and a third electric valve 12.

[0030] The outlet of the main inlet pipe 13 is connected to the inlet of the heat pump inlet pipe 18 of the first heat pump unit 1, and the heat pump inlet pipe 18 of the second heat pump unit 2 is connected to the opening on the side wall of the main inlet pipe 13. The outlet of the heat pump outlet pipe 19 of the first heat pump unit 1 is connected to the inlet of the manifold inlet pipe 22, and the end of the manifold 26 of the second heat pump unit 2 away from the first three-way valve 7 is connected to the opening on the side wall of the manifold inlet pipe 22. The first electric valve 9 is installed on the main inlet pipe 13 and is located between the heat pump inlet pipes 18 of the first heat pump unit 1 and the second heat pump unit 2.

[0031] One end of the water distribution pipe 21 is connected to the opening on the side wall of the main water inlet pipe 13. The third electric valve 12 is installed at the end of the water distribution pipe 21 near the main water inlet pipe 13. The outlet of the water distribution pipe 21 is connected to the outlet of the heat pump inlet pipe 18 of the third heat pump unit 3. The heat pump inlet pipe 18 of the fourth heat pump unit 4 is connected to the opening on the side wall of the water distribution pipe 21. The outlet of the heat pump outlet pipe 19 of the third heat pump unit 3 is connected to the inlet of the return water main pipe 14. The end of the manifold 26 of the fourth heat pump unit 4 away from the second three-way valve 8 is connected to the opening on the side wall of the return water main pipe 14.

[0032] The outlet of the manifold inlet pipe 22 is connected to the inlet of the third three-way valve 11. The first outlet of the third three-way valve 11 is connected to the opening on the side wall of the return water main pipe 14 through the manifold outlet pipe 24. The second outlet of the third three-way valve 11 is connected to the opening on the side wall of the distribution pipe 21 through the connecting pipe 23. The second electric valve 10 is installed on the distribution pipe 21 and is located between the heat pump inlet pipes 18 of the third heat pump unit 3 and the fourth heat pump unit 4.

[0033] In this embodiment, the heat pump system also includes a first circulating water pump 5 and a second circulating water pump 6 connected in parallel on the main inlet pipe 13. The first circulating water pump 5 is located on the main inlet pipe 13, and a parallel pipeline 25 is connected in parallel to the main inlet pipe 13. The second circulating water pump 6 is located within the parallel pipeline 25. Both the first circulating water pump 5 and the second circulating water pump 6 are variable frequency circulating water pumps, and their operating frequency can be controlled by a controller. The first circulating water pump 5 and the second circulating water pump 6 are connected in parallel, and both can be turned on individually or simultaneously. When the system load is low, only one circulating water pump can be turned on to meet the water flow demand, reducing pump energy consumption; when the system load is high, both circulating water pumps can be turned on simultaneously to ensure sufficient water flow.

[0034] In some embodiments, each heat pump unit may be a variable frequency air source heat pump unit, and each unit is equipped with a variable frequency compressor. The operating frequency of the compressor can be controlled independently or synchronously by the controller.

[0035] It should be noted that the inlet end of the main inlet pipe 13 is connected to the user's return water end. The user's return water flows into the heat pump system through the main inlet pipe 13. The outlet end of the return water pipe 14 is connected to the user's supply water end. The user's water enters the heat pump system from the inlet end of the main inlet pipe 13, flows through each heat pump unit for heat exchange treatment, and then flows back to the user side from the outlet end of the return water pipe 14, forming a complete circulating water circuit.

[0036] In this embodiment, a first temperature sensor 15 is installed at the inlet end of the main inlet pipe 13, and a second temperature sensor 16 is installed at the outlet end of the return water main pipe 14. It should be noted that the second temperature sensor 16 measures the supply water temperature flowing out of the heat pump system, which is the actual supply water temperature output by the heat pump system.

[0037] Optionally, both the first temperature sensor 15 and the second temperature sensor 16 can be thermocouple-type temperature sensors or thermistor-type temperature sensors, with a detection accuracy of not less than ±0.5℃. The first temperature sensor 15 and the second temperature sensor 16 are electrically connected to the controller, transmitting the detected temperature signals to the controller in real time.

[0038] In some implementations, the controller can be a programmable logic controller (PLC) or a microcontroller, which stores the control program internally. The controller is electrically connected to the first three-way valve 7, the second three-way valve 8, the third three-way valve 11, the first electric valve 9, the second electric valve 10, the third electric valve 12, the first circulating water pump 5, the second circulating water pump 6, the first temperature sensor 15, and the second temperature sensor 16. The controller is configured to determine the current heat load level based on the actual supply water temperature detected by the first temperature sensor 15 and the return water temperature detected by the second temperature sensor 16, and control the valve reversing assembly to switch the water flow direction within the circulating water pipeline mechanism according to the heat load level.

[0039] In some embodiments, a check valve 17 is installed on the return water main 14. The check valve 17 is located between the inlet of the return water main 14 and the manifold outlet 24. The check valve 17 is configured to allow water to flow unidirectionally from the inlet to the outlet of the return water main 14, while preventing water from flowing back in the opposite direction.

[0040] The specific operating modes of the heat pump system in this embodiment under different heat load levels are described in detail below.

[0041] When the heat load level is at level one, the heat pump system is in mode one. At this time, if... Figure 2As shown, the controller connects the inlet of the first three-way valve 7 to the second outlet, and the inlet of the third three-way valve 11 to the first outlet, while the first electric valve 9 and the third electric valve 12 are closed. Because the inlet of the first three-way valve 7 is connected to the second outlet, water flowing from the heat pump outlet pipe 19 of the second heat pump unit 2 flows through the inlet of the first three-way valve 7, the second outlet, and the connecting pipe 20 into the heat pump inlet pipe 18 of the first heat pump unit 1, thus achieving a series connection between the first heat pump unit 1 and the second heat pump unit 2.

[0042] In this mode, only the first circulating water pump 5 is activated, while the second circulating water pump 6 remains shut down. No medium flows within the parallel pipeline 25, thus reducing pump power consumption. The complete medium flow process is as follows: the medium first flows into the main inlet pipe 13, then through the first circulating water pump 5, and is then sent to the heat pump inlet pipe 18 of the second heat pump unit 2, where heat exchange is completed. After heat exchange, the medium flows out from the heat pump outlet pipe 19 of the second heat pump unit 2 and is sent to the connecting pipe 20 via the second outlet of the first three-way valve 7. The medium flows along the connecting pipe 20 into the heat pump inlet pipe 18 of the first heat pump unit 1, and then enters the first heat pump unit 1 through the heat pump inlet pipe 18, where heat exchange is completed. After heat exchange, the medium flows from the heat pump outlet pipe 19 of the first heat pump unit 1 into the manifold inlet pipe 22, and continues to flow through the third three-way valve 11. The first outlet enters the confluence outlet pipe 24, and finally the water is delivered to the user side through the return water main pipe 14.

[0043] In this mode, since only the first heat pump unit operates and is connected in series, the system operates with minimal energy consumption, making it suitable for low-load conditions. Simultaneously, since only the first circulating water pump 5 needs to be turned on to meet the water flow requirements, the second circulating water pump 6 remains off, further reducing pump energy consumption.

[0044] When the heat load level is at level two, the heat pump system is in mode two. At this time, such as... Figure 3 As shown, the first circulating water pump 5 and the second circulating water pump 6 start up synchronously to increase the overall flow rate of the medium in the system. At the same time, the controller controls the inlet of the first three-way valve 7 to be connected to the second outlet, the inlet of the second three-way valve 8 to be connected to the second outlet, and the inlet of the third three-way valve 11 to be connected to the first outlet. The first electric valve 9 is closed, the second electric valve 10 is closed, and the third electric valve 12 is opened.

[0045] In the second mode, the medium first enters the main inlet pipe 13, is jointly transported by two parallel water pumps, and then flows into the heat pump inlet pipe 18 of the second heat pump unit 2. The medium then flows into the second heat pump unit 2 through the heat pump inlet pipe 18, where it completes heat exchange. After heat exchange, the medium flows out from the heat pump outlet pipe 19 of the second heat pump unit 2 to the first three-way valve 7, and then through the second outlet of the first three-way valve 7 into the connecting pipe 20. The medium flows along the connecting pipe 20 into the heat pump inlet pipe 18 of the first heat pump unit 1, and then enters the first heat pump unit 1 through the heat pump inlet pipe 18, where it completes heat exchange. After heat exchange, the medium flows from the heat pump outlet pipe 19 of the first heat pump unit 1 into the manifold inlet pipe 22, and then continues to flow through the first outlet of the third three-way valve 11 into the manifold outlet pipe 24.

[0046] Simultaneously, the medium in the main inlet pipe 13 flows into the branch pipe 21 via the third electric valve 12. The medium in the branch pipe 21 flows into the heat pump inlet pipe 18 of the fourth heat pump unit 4, thus entering the fourth heat pump unit 4. After heat exchange within the fourth heat pump unit 4, the medium flows into the second three-way valve 8, then into the connecting pipe 20 via the second outlet of the second three-way valve 8, and then into the heat pump inlet pipe 18 of the third heat pump unit 3. It then enters the third heat pump unit 3 to complete heat exchange. The medium, after heat exchange, flows directly from the heat pump outlet pipe 19 of the third heat pump unit 3 into the return water main pipe 14. Thus, the medium flowing out from the first and second heat pump units ultimately converges into the return water main pipe 14 and is uniformly transported to the user side.

[0047] As can be seen, in the second mode, the second heat pump unit 2 in the first heat pump group acts as the upstream unit to preheat or precool the water flow, while the first heat pump unit 1 acts as the downstream unit to further heat or cool the water flow, achieving two-stage heat exchange. Similarly, the fourth heat pump unit 4 in the second heat pump group acts as the upstream unit to preheat or precool the water flow, while the third heat pump unit 3 acts as the downstream unit to further heat or cool the water flow, also achieving two-stage heat exchange. Compared to the first mode, the second mode adds the participation of the second heat pump group, improving the system's cooling or heating capacity. It is suitable for medium- and low-load conditions. The series connection within each heat pump group allows the upstream units (second heat pump unit 2 and fourth heat pump unit 4) to operate under more optimal thermal conditions, with higher evaporation temperatures during cooling and lower condensation temperatures during heating, thereby improving unit energy efficiency.

[0048] When the heat load level is level three, the heat pump system is in mode three. At this time, if... Figure 4As shown, the controller controls the inlet of the first three-way valve 7 to remain connected to the second outlet, thereby maintaining the two heat pump units of the first heat pump group in a series flow structure; it controls the inlet of the second three-way valve 8 to remain connected to the first outlet, so that the two heat pump units of the second heat pump group form a parallel flow structure; it controls the inlet of the third three-way valve 11 to remain connected to the first outlet, so that the two media of the first heat pump group and the second heat pump group can be independently connected to the return water main pipe 14, realizing the parallel arrangement of the two groups of units outside the group; in addition, the controller controls the first electric valve 9 to be closed, the second electric valve 10 to remain open, and the third electric valve 12 to remain open.

[0049] In this mode, the first circulating water pump 5 and the second circulating water pump 6 start synchronously and continuously. The medium first enters the main inlet pipe 13, is jointly transported by the two parallel water pumps, and then flows into the heat pump inlet pipe 18 of the second heat pump unit 2, thus entering the interior of the second heat pump unit 2 to complete the heat exchange operation. After heat exchange, the medium flows out from the heat pump outlet pipe 19 of the second heat pump unit 2 to the first three-way valve 7, and is sent into the connecting pipe 20 through the second outlet of the first three-way valve 7. The medium flows along the connecting pipe 20 into the heat pump inlet pipe 18 of the first heat pump unit 1, thus entering the interior of the first heat pump unit 1 to complete the heat exchange. After heat exchange, the medium flows from the heat pump outlet pipe 19 of the first heat pump unit 1 into the manifold inlet pipe 22, and the medium continues to flow through the first outlet of the third three-way valve 11 into the manifold outlet pipe 24, and is finally sent into the return water main pipe 14.

[0050] Meanwhile, the medium inside the main inlet pipe 13 flows into the branch pipe 21 through the third electric valve 12. The medium in the branch pipe 21 is simultaneously diverted to the heat pump inlet pipe 18 of the third heat pump unit 3 and the heat pump inlet pipe 18 of the fourth heat pump unit 4. The medium enters the third heat pump unit 3 and the fourth heat pump unit 4 respectively to complete heat exchange independently. The medium after heat exchange in the fourth heat pump unit 4 flows out from its own heat pump outlet pipe 19 to the second three-way valve 8, flows into the manifold 26 through the first outlet of the second three-way valve 8, and finally merges into the return water main pipe 14. The medium after heat exchange in the third heat pump unit 3 directly merges into the return water main pipe 14 from its own heat pump outlet pipe 19. In this way, all the medium flowing out from the first heat pump unit and the second heat pump unit is collected in the return water main pipe 14 and finally transported to the user side through the return water main pipe 14.

[0051] As can be seen, in the third mode, the first heat pump unit operates in series internally, the second heat pump unit operates in parallel internally, and the first and second heat pump units operate in parallel with each other. Compared to the second mode, the third heat pump unit 3 and the fourth heat pump unit 4 within the second heat pump unit switch from series to parallel operation, increasing the system water flow and further enhancing the cooling or heating capacity, making it suitable for medium- to high-load conditions. The series connection within the first heat pump unit allows the second heat pump unit 2 to operate under more optimal thermal conditions, while the parallel connection within the second heat pump unit ensures sufficient water flow and heat exchange capacity. In this mode, the system balances the needs of improved energy efficiency and enhanced heat exchange capacity, representing a transitional optimized operating mode.

[0052] When the heat load level is level four, the heat pump system is in mode four. At this time, such as Figure 5 As shown, the controller keeps the inlet of the first three-way valve 7 connected to the first outlet, switching the internal flow structure of the first heat pump unit to parallel flow. It also keeps the inlet of the second three-way valve 8 connected to the first outlet, switching the internal flow structure of the second heat pump unit to parallel flow. The controller keeps the inlet of the third three-way valve 11 connected to the second outlet, ensuring that all the medium produced by the first heat pump unit is delivered to the distribution pipe 21, forming an external series connection between the two units. The controller keeps the first electric valve 9, the second electric valve 10, and the third electric valve 12 all open.

[0053] In this mode, the first circulating water pump 5 and the second circulating water pump 6 start. The medium first enters the main inlet pipe 13 and is transported by the two parallel pumps. The medium in the main inlet pipe 13 is simultaneously diverted to the heat pump inlet pipe 18 of the first heat pump unit 1 and the heat pump inlet pipe 18 of the second heat pump unit 2. The medium enters the first heat pump unit 1 and the second heat pump unit 2 respectively to complete heat exchange independently. The medium after heat exchange in the second heat pump unit 2 flows out from its own heat pump outlet pipe 19 to the first three-way valve 7, and then flows into the manifold 26 through the first outlet of the first three-way valve 7, and then merges into the manifold inlet pipe 22. The medium after heat exchange in the first heat pump unit 1 directly merges into the manifold inlet pipe 22 from its own heat pump outlet pipe 19. All the medium collected in the manifold inlet pipe 22 flows into the third three-way valve 11, and is sent into the connecting pipe 23 through the second outlet of the third three-way valve 11. The medium flows along the connecting pipe 23. The medium flows into the distribution pipe 21; the medium inside the distribution pipe 21 is simultaneously diverted to the heat pump inlet pipe 18 of the third heat pump unit 3 and the heat pump inlet pipe 18 of the fourth heat pump unit 4. The medium enters the third heat pump unit 3 and the fourth heat pump unit 4 respectively to complete heat exchange independently. The medium after heat exchange in the fourth heat pump unit 4 flows out from its own heat pump outlet pipe 19 to the second three-way valve 8, and is led out through the first outlet of the second three-way valve 8 to the manifold 26 and flow into the return water main pipe 14. The medium after heat exchange in the third heat pump unit 3 flows directly from its own heat pump outlet pipe 19 into the return water main pipe 14. The medium after all heat exchange is completed is collected in the return water main pipe 14 and finally delivered to the user side.

[0054] In the fourth mode, the first heat pump unit operates in parallel internally, the second heat pump unit operates in parallel internally, and the first and second heat pump units operate in series. The first heat pump unit acts as the upstream unit, and the second heat pump unit acts as the downstream unit. Water first flows through the first heat pump unit for initial heating or cooling, and then flows through the second heat pump unit for further heating or cooling. In this mode, the system's cooling or heating capacity is maximized, suitable for peak load conditions. Simultaneously, as the upstream unit, the first heat pump unit has a more optimal evaporation temperature (during cooling) or condensation temperature (during heating), improving the unit's operating efficiency. Because the first heat pump unit is internally connected in parallel, the inlet water temperature of each unit is consistent, ensuring that the first heat pump unit can fully utilize its cooling or heating capacity under peak load conditions. The second heat pump unit is also internally connected in parallel, ensuring sufficient water flow through it, allowing the second heat pump unit to receive the water processed by the first heat pump unit and further exchange heat, meeting the cooling or heating demands of peak load.

[0055] In the heat pump system of this embodiment, the controller is also configured to control the compressors of each heat pump unit to synchronously increase or decrease frequency based on the deviation between the actual water supply temperature T detected by the second temperature sensor 16 and the target water supply temperature after the system switches to any mode, and further determine whether it is necessary to switch to a series-parallel mode with a higher or lower heat load level.

[0056] Specifically, when the heat pump system switches to any mode, the controller acquires the actual water supply temperature T detected by the second temperature sensor 16. The second temperature sensor 16 is installed at the outlet of the return water main 14 and is used to detect the water supply temperature flowing out of the system after heat exchange treatment by each heat pump unit. This water supply temperature is the actual water supply temperature output by the system to the user.

[0057] In cooling mode, the controller determines whether the deviation between the actual supply water temperature T and the target supply water temperature T1 meets the cooling frequency increase or decrease condition. The cooling frequency increase condition is: the actual supply water temperature T is greater than the sum of the target supply water temperature T1 and the first control accuracy δ1, i.e., T > T1 + δ1. The cooling frequency decrease condition is: the actual supply water temperature T is less than the difference between the target supply water temperature T1 and the second control accuracy δ2, i.e., T < T1 - δ2. Here, δ1 and δ2 are preset temperature control accuracy values, which can be set according to actual conditions, for example, δ1 = 1℃ and δ2 = 1℃.

[0058] If the cooling frequency increase condition is met, it indicates that the current supply water temperature is higher than the target temperature and exceeds the upper limit of the allowable deviation, indicating insufficient system cooling capacity. The compressor frequency needs to be increased to enhance the cooling effect. At this time, the controller controls the compressors of each operating heat pump unit to synchronously increase their operating frequency by the same amount of frequency change. After the compressors of each heat pump unit synchronously increase their frequency, the controller waits for a first preset time, such as 30 to 60 seconds, to allow the system to reach a stable state. After the system stabilizes, the controller again acquires the actual supply water temperature T' detected by the second temperature sensor 16 and determines whether the actual supply water temperature T' still meets the cooling frequency increase condition, i.e., T' > T1 + δ1. If it still meets the condition, it indicates that the system cooling capacity is still insufficient after the compressor frequency increase, and further increases in system cooling capacity are needed. At this time, the controller controls the valve reversing component to switch the system to the next mode with a higher heat load level, for example, switching from the first mode to the second mode. If the condition is not met, it indicates that the compressor frequency increase has caused the supply water temperature to fall back to within the allowable deviation range of the target temperature, and the current series-parallel mode remains unchanged.

[0059] If the cooling frequency reduction condition is met, it indicates that the current water supply temperature is lower than the target temperature and exceeds the lower limit of the allowable deviation, suggesting that the system's cooling capacity is excessive and the compressor frequency needs to be reduced to decrease the cooling effect. At this time, the controller controls the compressors of each operating heat pump unit to synchronously reduce their operating frequency by the same amount of frequency change. During the synchronous frequency reduction process, the controller determines whether the current operating frequency of each compressor has reached the preset minimum operating frequency. The minimum operating frequency is the lower limit frequency for safe compressor operation; below this frequency may lead to poor compressor lubrication or increased vibration, affecting the compressor's reliability and service life. Once the current operating frequency of each compressor has reached the minimum operating frequency, the controller waits for a second preset time, such as 30 to 60 seconds, to allow the system to reach a stable state. After the system stabilizes, the controller again acquires the actual water supply temperature T'' detected by the second temperature sensor 16 and determines whether the actual water supply temperature T'' still meets the cooling frequency reduction condition, i.e., T'' < T1 - δ2. If the condition is still met, it means that the system's cooling capacity is still excessive after the compressor frequency is reduced to the lowest frequency. In this case, the controller controls the valve reversing component to switch the system to the previous mode with a lower heat load level, such as switching from mode 3 to mode 2. If the condition is not met, it means that the compressor frequency reduction has brought the water supply temperature back up to the allowable deviation range of the target temperature, and the current series-parallel mode remains unchanged.

[0060] In heating mode, the controller determines whether the deviation between the actual supply water temperature T and the target supply water temperature T2 meets the heating frequency increase or decrease condition. The heating frequency increase condition is: the actual supply water temperature T is less than the difference between the target supply water temperature T2 and the third control precision δ3, i.e., T < T2 - δ3. The heating frequency decrease condition is: the actual supply water temperature T is greater than the sum of the target supply water temperature T2 and the fourth control precision δ4, i.e., T > T2 + δ4. Here, δ3 and δ4 are preset temperature control precision values, which can be set according to actual conditions, for example, δ3 = 1℃ and δ4 = 1℃.

[0061] If the heating frequency increase condition is met, it indicates that the current supply water temperature is lower than the target temperature and exceeds the lower limit of the allowable deviation, indicating insufficient heating capacity of the system. The compressor frequency needs to be increased to enhance the heating effect. At this time, the controller controls the compressors of each operating heat pump unit to synchronously increase their operating frequency by the same amount of frequency change. After the compressors of each heat pump unit synchronously increase their frequency, the controller waits for a first preset time to allow the system to reach a stable state. After the system stabilizes, the controller again obtains the actual supply water temperature T' detected by the second temperature sensor 16 and determines whether the actual supply water temperature T' still meets the heating frequency increase condition, i.e., T' < T2 - δ3. If it still meets the condition, it indicates that the system heating capacity is still insufficient after the compressor frequency increase, and further increases in system heating capacity are needed. At this time, the controller controls the valve reversing component to switch the system to the next mode with a higher heat load level. If the condition is not met, it indicates that the compressor frequency increase has brought the supply water temperature back to within the allowable deviation range of the target temperature, and the current series-parallel mode remains unchanged.

[0062] If the heating frequency reduction condition is met, it indicates that the current supply water temperature is higher than the target temperature and exceeds the upper limit of the allowable deviation, indicating that the system's heating capacity is excessive and the compressor frequency needs to be reduced to decrease the heating effect. At this time, the controller controls the compressors of each heat pump unit in operation to synchronously reduce their operating frequency by the same frequency change. During the synchronous frequency reduction process, the controller determines whether the current operating frequency of each compressor has reached the preset minimum operating frequency. When the current operating frequency of each compressor has reached the minimum operating frequency, the controller waits for a second preset time to allow the system to reach a stable state. After the system stabilizes, the controller again obtains the actual supply water temperature T'' detected by the second temperature sensor 16 and determines whether the actual supply water temperature T'' still meets the heating frequency reduction condition, i.e., T'' > T2 + δ4. If it still meets the condition, it indicates that the system's heating capacity is still excessive after the compressor frequency is reduced to the minimum frequency. At this time, the controller controls the valve reversing component to switch the system to the previous mode with a lower heat load level. If it does not meet the condition, it indicates that the compressor frequency reduction has reduced the supply water temperature to within the allowable deviation range of the target temperature, and the current series-parallel mode remains unchanged.

[0063] In this embodiment, the four modes of the heat pump system are arranged in order of increasing heat load level as follows: mode 1, mode 2, mode 3, and mode 4.

[0064] When it is necessary to switch to a mode with a higher heat load level, the specific switching path is as follows: If the current mode is the first mode, the controller controls the valve reversing component to switch the system to the second mode; if the current mode is the second mode, the controller controls the valve reversing component to switch the system to the third mode; if the current mode is the third mode, the controller controls the valve reversing component to switch the system to the fourth mode; if the current mode is the fourth mode, it means that the system is already in the highest heat load level mode, and the current mode remains unchanged.

[0065] When it is necessary to switch to a series-parallel mode with a lower heat load level, the specific switching path is as follows: If the current mode is the second mode, the controller controls the valve reversing component to switch the system to the first mode; if the current mode is the third mode, the controller controls the valve reversing component to switch the system to the second mode; if the current mode is the fourth mode, the controller controls the valve reversing component to switch the system to the third mode; if the current mode is the first mode, it means that the system is already in the lowest heat load level mode, and the current mode remains unchanged.

[0066] Furthermore, in this embodiment, the controller is also configured to control the operating status of the first circulating water pump 5 and the second circulating water pump 6 according to the current mode. When the heat pump system is in the first mode, the controller controls the first circulating water pump 5 to turn on and the second circulating water pump 6 to turn off. The first mode is the minimum load mode, in which only the first heat pump unit 1 and the second heat pump unit 2 in the first heat pump group participate in operation. The system water flow demand is small, and at this time, only the first circulating water pump 5 needs to operate to meet the water flow demand. Turning off the second circulating water pump 6 can effectively reduce water pump energy consumption. When the heat pump system is in the second, third, or fourth mode, the controller controls the first circulating water pump 5 and the second circulating water pump 6 to turn on simultaneously. Because the water flow demand is large, both circulating water pumps need to work simultaneously to ensure sufficient water flow and heat exchange effect, avoiding poor heat exchange of the units or triggering low flow protection due to insufficient water flow. Through the above water pump control strategy, the water pumps are operated on demand, and the water pump energy consumption is reduced to the maximum extent while ensuring the normal operation of the system, further improving the overall energy efficiency of the system.

[0067] The heat pump system in this embodiment achieves automatic switching between four series-parallel operation modes based on the heat load level through the above-described technical solution. At low loads, the system operates in the first mode, with only the first heat pump unit operating in series, resulting in the lowest energy consumption. As the load increases, the system sequentially switches to the second, third, and fourth modes, gradually increasing the number of participating heat pump units and adjusting the series-parallel connection method to meet the ever-increasing cooling or heating demands. Throughout the entire load variation range, the system always operates in the optimal series-parallel connection mode, ensuring sufficient cooling or heating capacity while maximizing the operation of upstream units under optimal thermodynamic conditions (higher evaporation temperature during cooling and lower condensation temperature during heating), thereby improving the overall energy efficiency of the system.

[0068] A second aspect of this application provides a control method for a heat pump system, applied to the heat pump system of the above embodiments, the method comprising the following steps: S100: Obtain the actual water supply temperature T detected by the second temperature sensor 16; S200: Determine the current heat load level based on the deviation between the actual water supply temperature T and the target water supply temperature threshold; S300: Based on the current heat load level, control the valve reversing component to switch the water flow direction in the circulating water pipeline mechanism to switch the heat pump system to the corresponding series-parallel mode.

[0069] In some embodiments, it should be noted that in step S200, the target water supply temperature threshold includes a cooling target water supply temperature T1 and a heating target water supply temperature T2. When the heat pump system is operating in cooling mode, the target water supply temperature threshold is the cooling target water supply temperature T1; when the heat pump system is operating in heating mode, the target water supply temperature threshold is the heating target water supply temperature T2.

[0070] In step S200, determining the current heat load level based on the deviation between the actual water supply temperature T and the target water supply temperature threshold specifically includes: the controller calculates the difference between the actual water supply temperature T and the target water supply temperature threshold, and determines the corresponding heat load level based on the preset range in which the difference is located.

[0071] For example, in cooling mode, the difference ΔT = T - T1. When ΔT is in the first preset range, the heat load level is determined to be Level 1; when ΔT is in the second preset range, the heat load level is determined to be Level 2; when ΔT is in the third preset range, the heat load level is determined to be Level 3; and when ΔT is in the fourth preset range, the heat load level is determined to be Level 4. The first, second, third, and fourth preset ranges correspond to progressively increasing heat load levels. The specific numerical range of each preset range can be set according to actual conditions. For example, the first preset range can be set to ΔT < 2℃, the second preset range to 2℃ ≤ ΔT < 4℃, the third preset range to 4℃ ≤ ΔT < 6℃, and the fourth preset range to ΔT ≥ 6℃.

[0072] In heating mode, the difference ΔT = T2 - T. When ΔT is in the first preset range, the heat load level is determined to be Level 1; when ΔT is in the second preset range, the heat load level is determined to be Level 2; when ΔT is in the third preset range, the heat load level is determined to be Level 3; and when ΔT is in the fourth preset range, the heat load level is determined to be Level 4. The specific numerical range of each preset range can also be flexibly set according to the actual situation.

[0073] In some embodiments, step S300, according to the current heat load level, controlling the valve reversing assembly to switch the water flow direction in the circulating water pipeline mechanism to switch the heat pump system to the corresponding series-parallel mode includes the following steps: When the heat load level is at Level 1, the controller switches the heat pump system to Mode 1. In Mode 1, the first heat pump unit 1 and the second heat pump unit 2 of the first heat pump group are connected in series, while the second heat pump group is disconnected from the circulating water pipeline. The specific valve control method to achieve Mode 1 is as follows: the controller controls the inlet of the first three-way valve 7 to connect with the second outlet, controls the inlet of the third three-way valve 11 to connect with the first outlet, and controls the first electric valve 9 and the third electric valve 12 to close. At this time, only the first heat pump unit 1 and the second heat pump unit 2 within the first heat pump group participate in operation, and the first heat pump unit 1 and the second heat pump unit 2 are connected in series, with the heat pump system operating at minimum energy consumption.

[0074] When the heat load level is at level two, the controller switches the heat pump system to mode two. In mode two, the first heat pump unit 1 and the second heat pump unit 2 of the first heat pump group are connected in series, the third heat pump unit 3 and the fourth heat pump unit 4 of the second heat pump group are connected in series, and the first and second heat pump groups are connected in parallel. The specific valve control method to achieve mode two is as follows: the controller controls the inlet of the first three-way valve 7 to connect with the second outlet, controls the inlet of the second three-way valve 8 to connect with the second outlet, controls the inlet of the third three-way valve 11 to connect with the first outlet, controls the first electric valve 9 and the second electric valve 10 to close, and controls the third electric valve 12 to open. At this time, both the first and second heat pump groups are operating, each group is internally connected in series, and the two groups are connected in parallel.

[0075] When the heat load level is at level three, the controller switches the heat pump system to the third mode. In the third mode, the first heat pump unit 1 and the second heat pump unit 2 of the first heat pump group are connected in series, the third heat pump unit 3 and the fourth heat pump unit 4 of the second heat pump group are connected in parallel, and the first heat pump group and the second heat pump group are connected in parallel. The specific valve control method to achieve the third mode is as follows: the controller controls the inlet of the first three-way valve 7 to connect with the second outlet, controls the inlet of the second three-way valve 8 to connect with the first outlet, controls the inlet of the third three-way valve 11 to connect with the first outlet, controls the first electric valve 9 to close, and controls the second electric valve 10 and the third electric valve 12 to open. At this time, the first heat pump group operates in series internally, the second heat pump group operates in parallel internally, and the two groups operate in parallel externally.

[0076] When the heat load level is at level four, the controller switches the heat pump system to mode four. In mode four, the first heat pump unit 1 and the second heat pump unit 2 of the first heat pump group are connected in parallel, the third heat pump unit 3 and the fourth heat pump unit 4 of the second heat pump group are connected in parallel, and the first and second heat pump groups are connected in series. The specific valve control method to achieve mode four is as follows: the controller controls the inlet of the first three-way valve 7 to connect with the first outlet, controls the inlet of the second three-way valve 8 to connect with the first outlet, controls the inlet of the third three-way valve 11 to connect with the second outlet, and controls the first electric valve 9, the second electric valve 10, and the third electric valve 12 to all open. At this time, the first heat pump group operates in parallel internally, the second heat pump group operates in parallel internally, and the two groups operate in series, maximizing the system's cooling or heating capacity.

[0077] In some embodiments, the method further includes step S400, whereby the controller continues to execute the following sub-steps after the heat pump system switches to any mode.

[0078] Step S410: The controller acquires the actual water supply temperature T detected by the second temperature sensor 16; Step S420: The controller determines whether the deviation between the actual water supply temperature T and the target water supply temperature meets the frequency increase or decrease conditions. In step S430, if the frequency increase conditions are met, the controller controls the compressors of each heat pump unit to synchronously increase their frequency; if the frequency increase conditions are not met, the current mode remains unchanged. In step S440, if the frequency reduction condition is met, the controller controls the compressors of each heat pump unit to synchronously reduce their frequency; if the frequency reduction condition is not met, the current mode remains unchanged.

[0079] In this embodiment, in step 420, the frequency increase conditions include cooling frequency increase conditions and heating frequency increase conditions, and the frequency decrease conditions include cooling frequency decrease conditions and heating frequency decrease conditions. The cooling frequency increase condition is that the actual water supply temperature T is greater than the sum of the cooling target water supply temperature T1 and the first control precision δ1, i.e., T > T1 + δ1. The cooling frequency decrease condition is that the actual water supply temperature T is less than the difference between the cooling target water supply temperature T1 and the second control precision δ2, i.e., T < T1 - δ2. The heating frequency increase condition is that the actual water supply temperature T is less than the difference between the heating target water supply temperature T2 and the third control precision δ3, i.e., T < T2 - δ3. The heating frequency decrease condition is that the actual water supply temperature T is greater than the sum of the heating target water supply temperature T2 and the fourth control precision δ4, i.e., T > T2 + δ4. Here, δ1, δ2, δ3, and δ4 are all preset temperature control precision values, and their specific values ​​can be set according to actual conditions, typically ranging from 0.5℃ to 2℃.

[0080] In this embodiment, step S430 further includes the following sub-steps: S4301: Obtain the current water supply temperature and determine whether the current water supply temperature still meets the frequency increase condition; S4302: If the frequency increase conditions are still met, the control valve reversing component will be activated to switch the current mode of the heat pump system to the next mode with a higher heat load level. If the conditions for frequency increase are not met, the current mode will remain unchanged.

[0081] In this embodiment, step S4301, obtaining the current water supply temperature and determining whether the current water supply temperature still meets the frequency increase condition, includes: After the compressors of each heat pump unit synchronously increase their frequency, the controller waits for a first preset time, such as 30 to 60 seconds, to allow the system to reach a stable state. After the system stabilizes, the controller again acquires the actual water supply temperature T' detected by the second temperature sensor 16 and determines whether the actual water supply temperature T' still meets the frequency increase condition, i.e., T' > T1 + δ1 in cooling mode or T' < T2 - δ3 in heating mode.

[0082] In this embodiment, step S4302 specifically includes: if the frequency increase condition is met, the controller determines that it needs to switch to a series-parallel mode with a higher heat load level, and controls the valve reversing component to switch the system to the next mode with a higher heat load level (for example, switching from the second mode to the third mode); if the frequency increase condition is not met, that is, the current water supply temperature has fallen back to the target temperature allowable deviation range, the controller keeps the current series-parallel mode unchanged and continues to operate in the current mode.

[0083] In this embodiment, step S440 further includes the following sub-steps: S4401: Obtain the current water supply temperature and determine whether the current water supply temperature still meets the frequency reduction condition; S4402: If the frequency reduction condition is still met, the control valve reversing component will be activated to switch the current mode of the heat pump system to the next mode with a lower heat load level. If the frequency reduction condition is not met, the current series-parallel connection mode will remain unchanged.

[0084] In this embodiment, step S4401, obtaining the current water supply temperature and determining whether the current water supply temperature still meets the frequency reduction condition, specifically includes: after the current operating frequency of each compressor reaches the minimum operating frequency, the controller waits for a second preset time, such as 30 to 60 seconds, to allow the system to reach a stable state. After the system stabilizes, the controller again obtains the actual water supply temperature T'' detected by the second temperature sensor 16 and determines whether the actual water supply temperature T'' still meets the frequency reduction condition, i.e., T'' < T1-δ2 in cooling mode or T'' > T2+δ4 in heating mode.

[0085] Furthermore, step S4402 specifically includes: if the frequency reduction condition is still met, the controller determines that it needs to switch to a series-parallel mode with a lower heat load level, and controls the valve reversing component to switch the system to the next mode with a lower heat load level (e.g., switching from the third mode to the second mode). If the frequency reduction condition is not met, that is, the current water supply temperature has risen back to within the allowable deviation range of the target temperature, the controller maintains the current series-parallel mode and continues to operate in the current mode.

[0086] It should be noted that during frequency increase, the compressors of each operating heat pump unit synchronously increase their operating frequency by the same amount of frequency change, for example, each compressor simultaneously increases by 5Hz or 10Hz. Synchronized frequency increase ensures that the water flow and heat exchange of each unit increase simultaneously, avoiding hydraulic imbalance and energy efficiency reduction caused by inconsistent unit frequencies. Conversely, during frequency decrease, the compressors of each operating heat pump unit synchronously decrease their operating frequency by the same amount of frequency change, for example, each compressor simultaneously decreases by 5Hz or 10Hz.

[0087] In this embodiment, in step S4302, when switching to the next mode with a higher heat load level, the switching is performed step by step in the order of first mode to second mode, second mode to third mode, and third mode to fourth mode.

[0088] In this embodiment, in step S4402, when switching the current mode of the heat pump system to the next mode with a lower heat load level, the switching is performed step by step in the order of fourth mode to third mode, third mode to second mode, and second mode to first mode. By switching step by step rather than jumping, hydraulic shock and system instability caused by excessive mode jumps can be avoided, ensuring the smooth operation of the system during the mode switching process.

[0089] As can be seen, the control method of this embodiment, by switching between four series and parallel modes according to the heat load level, and by synchronously adjusting the compressor frequency and further switching modes according to the deviation between the supply water temperature and the target temperature in each mode, achieves the following technical effects: First, under low load conditions, the system operates in the first mode, with only the first heat pump unit operating in series. This avoids the mixing phenomenon and high energy consumption of the water pump in traditional parallel systems under low load, thus reducing the system's operating energy consumption.

[0090] Secondly, under low to medium load conditions, the system operates in the second mode, with both heat pump units connected in series internally and in parallel between units. The series connection within each unit ensures that the evaporation temperature (during cooling) of the upstream unit is higher than that of the traditional parallel system, or the condensation temperature (during heating) is lower than that of the traditional parallel system, thereby improving the energy efficiency of the upstream unit.

[0091] Third, under medium-to-high load conditions, the system operates in a third mode, with the first heat pump unit connected in series internally, the second heat pump unit connected in parallel internally, and the two units connected in parallel with each other. This mode ensures sufficient cooling or heating capacity while retaining the energy efficiency advantage of the first heat pump unit connected in series internally.

[0092] Fourth, under the highest load condition, the system operates in the fourth mode, with both groups internally connected in parallel and inter-group connected in series. The first heat pump unit, as the upstream unit, can operate under more favorable thermal conditions, thus improving the system's peak capacity.

[0093] Fifth, through a closed-loop control strategy of progressively increasing and decreasing frequency and progressively switching modes, the system achieves efficient and stable operation across the full load range, avoiding frequent mode switching and frequent compressor start-stop, thus improving the system's reliability and service life.

[0094] Sixth: It realizes automatic switching between four series and parallel modes according to the heat load level, so that the system can operate in the optimal series and parallel mode under different load conditions, which not only ensures sufficient cooling or heating capacity, but also maximizes the system energy efficiency, achieving the technical effect of energy saving and consumption reduction.

[0095] It should be understood that the terminology used herein is for the purpose of describing particular exemplary embodiments only and is not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “described” as used herein may also mean including the plural forms. The terms “comprising,” “including,” “containing,” and “having” are inclusive and therefore indicate the presence of the stated features, steps, operations, elements, and / or heat pump systems and their control methods, but do not exclude the presence or addition of one or more other features, steps, operations, elements, heat pump systems and their control methods, and / or combinations thereof. The method steps, processes, and operations described herein are not construed as requiring them to be performed in a specific order as described or illustrated, unless the order of performance is explicitly indicated. It should also be understood that additional or alternative steps may be used.

[0096] Although terms such as first, second, third, etc., may be used in this document to describe multiple components, heat pump systems and their control methods, areas, layers, and / or sections, these components, heat pump systems and their control methods, areas, layers, and / or sections should not be limited by these terms. These terms may be used only to distinguish one component, heat pump system and its control method, area, layer, or section from another area, layer, or section. Unless the context clearly indicates otherwise, terms such as "first," "second," and other numerical terms used herein do not imply order or sequence. Therefore, the first component, heat pump system and its control method, area, layer, or section discussed below may be referred to as the second component, heat pump system and its control method, area, layer, or section without departing from the teachings of the exemplary embodiments.

[0097] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A heat pump system, characterized in that, It includes a first heat pump unit, a second heat pump unit, a circulating water pipeline system, a valve reversing assembly, and a controller; the first heat pump unit includes at least two heat pump units, and the second heat pump unit includes at least two heat pump units. The first heat pump unit and the second heat pump unit are respectively connected to the circulating water pipeline mechanism, and the valve reversing assembly is located inside the circulating water pipeline mechanism; A temperature sensor is installed at the outlet of the circulating water pipeline mechanism; The controller is configured to determine the heat load level based on the temperature value measured by the temperature sensor, and control the valve reversing assembly to switch the water flow direction in the circulating water pipeline mechanism according to the heat load level; When the heat load level is at the first level, the heat pump units of the first heat pump group are connected in series, and the second heat pump group is disconnected from the circulating water pipeline mechanism. When the heat load level is at the second level, the heat pump units of the first heat pump group are connected in series, the heat pump units of the second heat pump group are connected in series, and the first heat pump group and the second heat pump group are connected in parallel. When the heat load level is at level three, the heat pump units of the first heat pump group are connected in series, the heat pump units of the second heat pump group are connected in parallel, and the first heat pump group and the second heat pump group are connected in parallel. When the heat load level is at level four, the heat pump units of the first heat pump group are connected in parallel, the heat pump units of the second heat pump group are connected in parallel, and the first heat pump group and the second heat pump group are connected in series; the heat load levels of level four, level three, level two, and level one gradually decrease.

2. The heat pump system according to claim 1, characterized in that, The first heat pump unit includes a first heat pump unit (1) and a second heat pump unit (2), and the second heat pump unit includes a third heat pump unit (3) and a fourth heat pump unit (4). The first heat pump unit (1), the second heat pump unit (2), the third heat pump unit (3) and the fourth heat pump unit (4) are respectively provided with a heat pump inlet pipe (18) and a heat pump outlet pipe (19). The valve reversing assembly includes a first three-way valve (7) and a second three-way valve (8); The inlet of the first three-way valve (7) is connected to the outlet of the heat pump outlet pipe (19) of the second heat pump unit (2). The first outlet of the first three-way valve (7) is connected to a manifold (26). The second outlet of the first three-way valve (7) is connected to the opening on the side wall of the heat pump inlet pipe (18) of the first heat pump unit (1) through a connecting pipe (20). The heat pump outlet pipe (19) of the fourth heat pump unit (4) is connected to the inlet of the second three-way valve (8). The first outlet of the second three-way valve (8) is connected to a manifold (26). The second outlet of the second three-way valve (8) is connected to the opening on the side wall of the heat pump inlet pipe (18) of the third heat pump unit (3) through a connecting pipe (20).

3. The heat pump system according to claim 2, characterized in that, The circulating water pipeline system includes a main inlet pipe (13), a confluence inlet pipe (22), a connecting pipe (23), a confluence outlet pipe (24), a branch pipe (21), and a return main pipe (14). The valve reversing assembly also includes a third three-way valve (11), a first electric valve (9), a second electric valve (10), and a third electric valve (12). The heat pump inlet pipes (18) of the first heat pump unit (1) and the second heat pump unit (2) are respectively connected to the main inlet pipe (13). The heat pump outlet pipe (19) of the first heat pump unit (1) is connected to the manifold inlet pipe (22). The end of the manifold pipe (26) of the second heat pump unit (2) away from the first three-way valve (7) is connected to the opening on the side wall of the manifold inlet pipe (22). The first electric valve (9) is installed on the main inlet pipe (13) and is located between the heat pump inlet pipes (18) of the first heat pump unit (1) and the second heat pump unit (2). One end of the water distribution pipe (21) is connected to the opening on the side wall of the main water inlet pipe (13). The third electric valve (12) is installed at the end of the water distribution pipe (21) near the main water inlet pipe (13). The heat pump inlet pipes (18) of the third heat pump unit (3) and the fourth heat pump unit (4) are respectively connected to the water distribution pipe (21). The heat pump outlet pipe (19) of the third heat pump unit (3) is connected to the main return water pipe (14). The end of the manifold (26) of the fourth heat pump unit (4) away from the second three-way valve (8) is connected to the opening on the side wall of the main return water pipe (14). One end of the manifold inlet pipe (22) is connected to the inlet of the third three-way valve (11), the first outlet of the third three-way valve (11) is connected to the opening on the side wall of the return main pipe (14) through the manifold outlet pipe (24), and the second outlet of the third three-way valve (11) is connected to the opening on the side wall of the branch pipe (21) through the connecting pipe (23). The second electric valve (10) is installed on the water distribution pipe (21) and is located between the heat pump inlet pipe (18) of the third heat pump unit (3) and the fourth heat pump unit (4).

4. The heat pump system according to claim 3, characterized in that, When the heat load level is at the first level, the inlet of the first three-way valve (7) is connected to the second outlet, the inlet of the third three-way valve (11) is connected to the first outlet, and the first electric valve (9) and the third electric valve (12) are closed. When the heat load level is at the second level, the inlet of the first three-way valve (7) is connected to the second outlet, the inlet of the second three-way valve (8) is connected to the second outlet, the inlet of the third three-way valve (11) is connected to the first outlet, the first electric valve (9) and the second electric valve (10) are both closed, and the third electric valve (12) is open. When the heat load level is at the third level, the inlet of the first three-way valve (7) is connected to the second outlet, the inlet of the second three-way valve (8) is connected to the first outlet, and the inlet of the third three-way valve (11) is connected to the first outlet. The first electric valve (9) is closed, and the second electric valve (10) and the third electric valve (12) are open; When the heat load level is at the fourth level, the inlet of the first three-way valve (7) is connected to the first outlet, the inlet of the second three-way valve (8) is connected to the first outlet, and the inlet of the third three-way valve (11) is connected to the second outlet. The first electric valve (9), the second electric valve (10), and the third electric valve (12) are all open.

5. The heat pump system and its control method according to claim 1, characterized in that, It also includes a first circulating water pump (5) and a second circulating water pump (6) connected in parallel on the main water inlet pipe (13); The first circulating water pump (5) is installed on the main water inlet pipe (13), and a parallel pipeline (25) is connected in parallel on the main water inlet pipe (13). The second circulating water pump (6) is installed in the parallel pipeline (25).

6. A control method for a heat pump system, applied to the heat pump system as described in any one of claims 1 to 5, characterized in that, The method includes the following steps: Obtain the actual water supply temperature detected by the temperature sensor; The current heat load level is determined based on the actual water supply temperature and the target water supply temperature threshold. Based on the current heat load level, controlling the valve reversing assembly to switch the water flow direction within the circulating water pipeline mechanism to switch the heat pump system to the corresponding series-parallel mode includes: When the heat load level is at level one, the heat pump system is switched to mode one to control the heat pump units of the first heat pump group to be connected in series, and the second heat pump group to be disconnected from the circulating water pipeline mechanism; when the heat load level is at level two, the heat pump system is switched to mode two to control the heat pump units of the first heat pump group to be connected in series, the heat pump units of the second heat pump group to be connected in series, and the first and second heat pump groups to be connected in parallel; when the heat load level is at level three, the heat pump system is switched to mode three to control the heat pump units of the first heat pump group to be connected in series, the heat pump units of the second heat pump group to be connected in parallel, and the first and second heat pump groups to be connected in parallel; when the heat load level is at level four, the heat pump system is switched to mode four to control the heat pump units of the first heat pump group to be connected in parallel, the heat pump units of the second heat pump group to be connected in parallel, and the first and second heat pump groups to be connected in series. The heat load levels of the fourth, third, second, and first levels gradually decrease.

7. The control method for a heat pump system according to claim 6, characterized in that, When the heat pump system switches to any mode, the current water supply temperature is obtained; Determine whether the deviation between the current water supply temperature and the target water supply temperature meets the conditions for frequency increase or decrease; If the frequency increase conditions are met, the compressors of each heat pump unit are controlled to increase their frequency synchronously. If the frequency reduction condition is met, the compressors of each heat pump unit will be controlled to reduce their frequency synchronously.

8. The control method for a heat pump system according to claim 7, characterized in that, After controlling the compressors of each heat pump unit to synchronously increase their frequency, the method also includes: Obtain the current water supply temperature and determine whether the current water supply temperature still meets the frequency increase condition; If the frequency increase condition is still met, the valve reversing component is controlled to switch the current mode of the heat pump system to the next mode with a higher heat load level. If the frequency increase conditions are not met, the current mode remains unchanged.

9. The control method for a heat pump system according to claim 7, characterized in that, After controlling the compressors of each heat pump unit to synchronously reduce their frequency, the method also includes: Obtain the current water supply temperature and determine whether the current water supply temperature still meets the frequency reduction condition; If the frequency reduction condition is still met, the valve reversing component is controlled to switch the current mode of the heat pump system to the next mode with a lower heat load level. If the frequency reduction condition is not met, the current series-parallel connection mode remains unchanged.

10. The control method for a heat pump system according to claim 7, characterized in that, The frequency increase conditions include cooling frequency increase conditions and heating frequency increase conditions, and the frequency decrease conditions include cooling frequency decrease conditions and heating frequency decrease conditions. The cooling frequency increase condition is: the current water supply temperature is greater than the sum of the target water supply temperature and the first water temperature allowable deviation threshold; The cooling frequency reduction condition is: the current water supply temperature is less than the difference between the target water supply temperature and the second water temperature allowable deviation threshold; The heating frequency increase condition is: the current water supply temperature is less than the difference between the target water supply temperature and the third water temperature allowable deviation threshold; The heating frequency reduction condition is: the current water supply temperature is greater than the sum of the target water supply temperature and the fourth water temperature allowable deviation threshold.

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