Waterway anti-freezing control method of heat pump system

Abstract

According to the waterway anti-freezing control method of the heat pump system, the heat pump system comprises a heat pump unit, a buffer water tank and a heating tail end, a water inlet and a water outlet of the heat pump unit are connected with the buffer water tank through a first circulating pipeline, and the buffer water tank is connected with the heating tail end through a second circulating pipeline. The heat pump unit heats first circulating water and then exchanges heat with second circulating water in the buffer water tank through a circulating water pump, and a secondary water pump conveys the second circulating water to the heating tail end. The heat pump unit is provided with a first temperature sensor used for detecting the current environment temperature value Ta, a second temperature sensor used for detecting the current water inlet temperature value Tb of a water inlet of the heat pump unit, and a third temperature sensor used for detecting the current water outlet temperature value Tc of a water outlet of the heat pump unit. And an auxiliary electric heater is arranged on a compressor of the heat pump unit. The method has the characteristics of safety and reliability.

Description

Technical Field

[0001] The present invention relates to a heat pump, in particular to a water channel antifreeze control method for a heat pump system. Background Art

[0002] With the promotion of energy conservation and emission reduction policies, clean heating technologies have garnered widespread attention, with heat pump heating systems being particularly prominent. A complete heat pump heating system consists of two components: a heat pump unit and a heating terminal. During operation, the heat pump unit heats circulating water to an appropriate temperature. The circulating water pump then exchanges heat with water in a buffer tank. A secondary water pump then delivers the hot water to the heating terminal, which dissipates heat and transfers it to the room, maintaining a comfortable temperature.

[0003] During the heating season, the ambient temperature in northern China is often below 0°C. Users who are away from home for short periods of time generally choose to shut down their heat pump units because they don't need heating. Even if the water system is properly insulated, the low ambient temperature can easily cause the water system to freeze if the heat pump unit doesn't enter antifreeze protection in time, resulting in unnecessary losses. Therefore, it's particularly important for heat pump heating units used in cold northern regions to have a comprehensive antifreeze protection mechanism for the water system.

[0004] How to protect the water circuit of the heat pump heating system from freezing? The current main technical solution is to selectively start the circulating water pump and compressor under different ambient temperatures and water temperatures. However, this technical solution will cause the water circuit system to be at risk of freezing, so it needs to be improved. Summary of the Invention

[0005] The object of the present invention is to provide a safe and reliable water channel antifreeze control method for a heat pump system, so as to overcome the deficiencies in the prior art.

[0006] A water circuit antifreeze control method for a heat pump system designed for this purpose is characterized in that the heat pump system includes a heat pump unit, a buffer water tank and a heating terminal, the water inlet and water outlet of the heat pump unit are connected to the buffer water tank through a first circulation pipe, the buffer water tank is connected to the heating terminal through a second circulation pipe, the heat pump unit heats the first circulating water and then exchanges heat with the second circulating water in the buffer water tank through a circulating water pump, and the secondary water pump then transports the second circulating water to the heating terminal, the heat pump unit is provided with a first temperature sensor for detecting the current ambient temperature value Ta, a second temperature sensor for detecting the current water inlet temperature value Tb of the water inlet of the heat pump unit and a third temperature sensor for detecting the current water outlet temperature value Tc of the water outlet of the heat pump unit, the compressor of the heat pump unit is provided with an auxiliary electric heater, the heat pump unit is electrically connected to the circulating water pump, the secondary water pump, the auxiliary electric heater, the first temperature sensor, the second temperature sensor and the third temperature sensor respectively, and the operation includes the following steps:

[0007] Step 1: Power on the heat pump unit and proceed to step 2;

[0008] Step 2: The central controller of the heat pump unit determines whether the current operating mode is the heating mode. If yes, it proceeds to step 3; otherwise, it proceeds to step 11.

[0009] Step 3: The central controller controls the circulating water pump and the heat pump unit to start simultaneously, and then proceeds to step 4;

[0010] Step 4: The central controller obtains the current inlet water temperature value Tb obtained through detection and proceeds to step 5;

[0011] Step 5: The central controller determines whether Tb>M1 is established. If it is established, it proceeds to step 6; otherwise, it proceeds to step 7, where M1 is a first preset temperature value, and the value range of M1 is 15-28°C;

[0012] Step 6: The central controller controls the secondary water pump to start, and then goes to step 2;

[0013] Step 7: The central controller obtains the current ambient temperature value Ta obtained through detection and proceeds to step 8;

[0014] Step 8: The central controller determines whether Ta≤M2 is established. If it is established, it proceeds to step 9; otherwise, it proceeds to step 10, where M2 is a second preset temperature value, and the value range of M2 is -10°C to 20°C.

[0015] Step 9: The central controller controls the secondary water pump to start, and then goes to step 2;

[0016] Step 10: The central controller controls the secondary water pump not to start, and goes to step 2;

[0017] Step 11: The central controller determines whether the current operating mode is the standby mode. If yes, it proceeds to step 12; otherwise, it proceeds to step 16.

[0018] Step 12: The central controller obtains the current ambient temperature value Ta obtained through detection and proceeds to step 13;

[0019] Step 13: The central controller determines whether Ta≤M2 is established. If it is established, it proceeds to step 14; otherwise, it proceeds to step 15;

[0020] Step 14: The central controller controls the circulating water pump and the secondary water pump to start simultaneously, run for 2 minutes and stop for 8 minutes, and then enter step 2;

[0021] Step 15: The central controller controls the heat pump unit to not operate, and enters step 2;

[0022] Step 16: The central controller determines whether the current operating mode is the shutdown mode. If yes, it proceeds to step 17; otherwise, it proceeds to step 2.

[0023] Step 17: The central controller obtains the current ambient temperature value Ta obtained through detection and proceeds to step 18;

[0024] Step 18: The central controller determines whether Ta>M2 is established. If it is established, it proceeds to step 19; otherwise, it proceeds to step 20;

[0025] Step 19: The central controller controls the heat pump unit to not operate, and enters step 2;

[0026] Step 20: The central controller determines whether M3≤Ta≤M2 is established. If so, the process proceeds to step 21; otherwise, the process proceeds to step 23, wherein M2>M3, M3 is a third preset temperature value, and the value range of M3 is -10°C to 20°C.

[0027] Step 21: The central controller obtains the detected stop time Tf of the circulating water pump and proceeds to step 22;

[0028] In step 22, the central controller determines whether Tf>K minutes is established. If it is established, the process proceeds to step 23; otherwise, the process proceeds to step 28, where K is a first preset time value and the value range of K is 3 to 50 minutes.

[0029] Step 23: Enter antifreeze protection and go to step 24;

[0030] Step 24: The central controller controls the circulating water pump and the secondary water pump to start simultaneously, and then proceeds to step 25;

[0031] Step 25: The central controller determines the antifreeze temperature value Te. The central controller defines the smaller temperature value between the current water inlet temperature value Tb and the current water outlet temperature value Tc of the heat pump unit as the antifreeze temperature value Te, and then proceeds to step 26.

[0032] In step 26, the central controller determines whether Te>M4 is established. If so, the process proceeds to step 27; otherwise, the process proceeds to step 29, where M4 is a fourth preset temperature value, and the value range of M4 is -10°C to 20°C.

[0033] Step 27: The central controller controls the circulating water pump and the secondary water pump to continue running for 1 minute and then stop, and then proceeds to step 36;

[0034] Step 28: The central controller controls the heat pump unit to not operate, and enters step 2;

[0035] In step 29, the central controller determines whether M5<Te≤M4 is established. If so, the process proceeds to step 30; otherwise, the process proceeds to step 32, wherein M5 is a fifth preset temperature value, M4>M5, and the value range of M5 is -10℃~20℃;

[0036] Step 30: The central controller controls the circulating water pump and the secondary water pump to continue running, and then proceeds to step 31;

[0037] In step 31, the central controller determines whether Te≥M6 or Ta≥M5 is true. If so, the process proceeds to step 36; otherwise, the process proceeds to step 25, where M6 is a sixth preset temperature value, the value range of M6 is -10°C to 20°C, and M6>M5.

[0038] Step 32: The central controller determines whether M2≤Ta≤M5 is established. If so, the process proceeds to step 33; otherwise, the process proceeds to step 37, wherein M5>M2;

[0039] Step 33: The central controller controls the circulating water pump and the secondary water pump to continue running, and then proceeds to step 34;

[0040] In step 34, the central controller controls the auxiliary electric heating of the compressor to start, and then proceeds to step 35;

[0041] In step 35, the central controller determines whether any one of Te≥M7 or Ta≥M8 is established. If it is established, the process proceeds to step 36; otherwise, the process proceeds to step 25, where M7 is the seventh preset temperature value, and the value range of M7 is -10°C to 20°C. M8 is the eighth preset temperature value, and the value range of M8 is -10°C to 20°C.

[0042] Step 36: Exit antifreeze protection and enter step 2;

[0043] Step 37: The central controller controls the circulating water pump and the secondary water pump to continue running, and then proceeds to step 38;

[0044] Step 38: The central controller determines whether the compressor is currently in protection or fault state. If so, the process proceeds to step 39; otherwise, the process proceeds to step 41.

[0045] Step 39: The central controller controls the auxiliary electric heating of the compressor to start and continue to operate, and then proceeds to step 40;

[0046] In step 40, the central controller determines whether Te≥M9 or Ta≥M4 is established. If so, the process proceeds to step 36; otherwise, the process proceeds to step 25, where M9 is a ninth preset temperature value, and the value range of M9 is -10°C to 20°C.

[0047] In step 41, the central controller controls the compressor to start heating operation, and then proceeds to step 40.

[0048] After adopting the above technical solution, the present invention divides antifreeze protection into three levels according to the current ambient temperature value Ta and the antifreeze temperature value Te: the first level is water pump antifreeze protection, at which time the circulating water pump and the secondary water pump continue to run; the second level is electric heating antifreeze protection, at which time the auxiliary electric heating of the heat pump unit is put into operation; the third level is compressor antifreeze protection, at which time the compressor starts heating operation. If the compressor cannot start, the auxiliary electric heating is turned on and continues to run.

[0049] The present invention optimizes the startup control of the circulating water pump and the secondary water pump. In heating mode, when the current inlet water temperature value Tb of the heat pump unit is higher than the secondary water pump's startup inlet water temperature, the secondary water pump starts. When the current inlet water temperature value Tb of the heat pump unit is not higher than the secondary water pump's startup inlet water temperature, and if the current ambient temperature value Ta of the heat pump unit is lower than the secondary water pump's startup ambient temperature, the secondary water pump starts. In standby mode, when the current ambient temperature value Ta of the heat pump unit is lower than the startup temperature of the circulating water pump, the circulating water pump and the secondary water pump will start and operate intermittently. In shutdown mode, the secondary water pump starts and operates following the circulating water pump, responding to antifreeze protection.

[0050] After adopting the above technical solution, the present invention can ensure timely and effective anti-freezing protection for the circulating water circuit and secondary water circuit of the heat pump heating system under low ambient temperature, making the operation of the heat pump unit more intelligent and improving the reliability and stability of the heat pump heating system to a certain extent.

[0051] The present invention completely solves the problem of waterway freezing caused by failure of the compressor, circulating water pump and secondary water pump in the existing heat pump heating system antifreeze control technology by improving the antifreeze protection logic and optimizing the startup control of the circulating water pump and the secondary water pump.

[0052] The present invention uses the current ambient temperature Ta, the current water inlet temperature Tb, and the current water outlet temperature Tc as the basis for determining whether to initiate antifreeze protection. Antifreeze protection is also categorized into water pump antifreeze protection, electric heating antifreeze protection, and compressor antifreeze protection. In the event of compressor failure, auxiliary electric heating is activated, making the antifreeze protection function more precise, timely, and effective. Furthermore, the startup control of the circulating water pump and secondary water pump is optimized to prevent freezing of the water system due to the failure of the circulating water pump or secondary water pump to start in a timely manner at low ambient temperatures, thus ensuring the reliability and stability of the heat pump heating system operating at relatively low ambient temperatures.

[0053] In summary, the present invention has the characteristics of safety and reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 It is a structural diagram of an embodiment of the present invention.

[0055] Figure 2 This is one of the operational flow charts of the present invention.

[0056] Figure 3 This is the second operational flow chart of the present invention.

[0057] In the figure: 1 is the heat pump unit, 2 is the buffer water tank, 3 is the secondary water pump, 4 is the heating terminal, and 5 is the circulating water pump. DETAILED DESCRIPTION

[0058] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0059] See also Figure 1-Figure 3 A water antifreeze control method for a heat pump system is characterized in that the heat pump system includes a heat pump unit 1, a buffer water tank 2 and a heating terminal 4. The water inlet and outlet of the heat pump unit 1 are connected to the buffer water tank 2 through a first circulation pipe, and the buffer water tank 2 is connected to the heating terminal 4 through a second circulation pipe. The heat pump unit 1 heats the first circulating water and then exchanges heat with the second circulating water in the buffer water tank 2 through a circulating water pump 5. The secondary water pump 3 then transports the second circulating water to the heating terminal 4. The heat pump unit 1 A first temperature sensor for detecting the current ambient temperature value Ta, a second temperature sensor for detecting the current water inlet temperature Tb of the water inlet of the heat pump unit 1, and a third temperature sensor for detecting the current water outlet temperature Tc of the water outlet of the heat pump unit 1 are provided. The compressor of the heat pump unit 1 is provided with an auxiliary electric heater. The heat pump unit 1 is electrically connected to the circulating water pump 5, the secondary water pump 3, the auxiliary electric heater, the first temperature sensor, the second temperature sensor and the third temperature sensor respectively.

[0060] The main control objects of the present invention are: ambient temperature Ta, water inlet temperature Tb, water outlet temperature Tc, antifreeze temperature Te, circulating water pump, secondary water pump, auxiliary electric heating and compressor.

[0061] The specific implementation plan is as follows:

[0062] 1. Antifreeze protection logic

[0063] (1) When the heat pump unit is in shutdown mode, the central controller continuously obtains the current ambient temperature value Ta obtained through detection:

[0064] When Ta>2℃, the heat pump unit does not operate;

[0065] When 0℃≤Ta≤2℃, and the stop time Tf of the circulating water pump reaches 20 minutes, it enters antifreeze protection;

[0066] When Ta is less than 0℃, it enters antifreeze protection.

[0067] (2) After entering the antifreeze protection mode, the circulating water pump and the secondary water pump are started and run for 2 minutes at the same time. The central controller continuously obtains the current inlet water temperature value Tb and the current outlet water temperature value Tc obtained through detection. The central controller selects the lower temperature value of the two as the antifreeze temperature Te:

[0068] When Te>6℃, the circulating water pump and the secondary water pump will continue to run for 1 minute and then stop, exiting the antifreeze protection;

[0069] When 4℃<Te≤6℃, the heat pump unit enters antifreeze protection, and the circulating water pump and secondary water pump continue to run at the same time. When Te≥8℃ or Ta≥4℃, the antifreeze protection is exited;

[0070] When 2℃<Te≤4℃, the heat pump unit enters the electric heating antifreeze protection, the circulating water pump and the secondary water pump continue to run at the same time, and the auxiliary electric heating is turned on and continues to run. When Te≥10℃ or Ta≥5℃, the antifreeze protection is exited;

[0071] When Te≤2℃, the heat pump unit enters the compressor antifreeze protection, the circulating water pump and the secondary water pump continue to run at the same time, and the compressor starts heating operation;

[0072] If the compressor cannot start due to preheating protection or fault, the auxiliary electric heating will be turned on and run continuously. When Te≥14℃ or Ta≥6℃, the anti-freeze protection will be exited.

[0073] 2. Start-up control of water pump

[0074] (1) In heating mode, the circulating water pump and the heat pump unit are started together, and then the central controller continuously obtains the current inlet water temperature Tb obtained through detection:

[0075] When Tb>22℃, the secondary water pump starts;

[0076] When Tb≤22℃, the central controller continuously obtains the current ambient temperature Ta obtained through detection. When Ta≤2℃, the secondary water pump starts.

[0077] (2) In standby mode, when Ta≤2℃, the circulating water pump and the secondary water pump start running for 2 minutes and stop for 8 minutes.

[0078] (3) In shutdown mode, the circulating water pump and the secondary water pump respond to antifreeze protection at the same time and are controlled by the antifreeze protection logic.

[0079] The specific operation includes the following steps:

[0080] Step 1: Power on the heat pump unit and proceed to step 2;

[0081] Step 2: The central controller of the heat pump unit determines whether the current operating mode is the heating mode. If yes, it proceeds to step 3; otherwise, it proceeds to step 11.

[0082] Step 3: The central controller controls the circulating water pump 5 and the heat pump unit 1 to start simultaneously, and then proceeds to step 4;

[0083] Step 4: The central controller obtains the current inlet water temperature value Tb obtained through detection and proceeds to step 5;

[0084] In step 5, the central controller determines whether Tb>M1 is established. If so, it proceeds to step 6, otherwise it proceeds to step 7, wherein M1 is a first preset temperature value, and the value range of M1 is 15-28°C.

[0085] In this embodiment, M1 can be selected as 22°C.

[0086] Step 6: The central controller controls the secondary water pump 3 to start, and then goes to step 2;

[0087] Step 7: The central controller obtains the current ambient temperature value Ta obtained through detection and proceeds to step 8;

[0088] In step eight, the central controller determines whether Ta≤M2 is established. If it is established, it proceeds to step nine, otherwise it proceeds to step ten, wherein M2 is a second preset temperature value, and the value range of M2 is -10°C to 20°C.

[0089] In this embodiment, M2 can be selected as 2°C.

[0090] Step 9: The central controller controls the secondary water pump 3 to start, and then proceeds to step 2;

[0091] Step 10: The central controller controls the secondary water pump 3 not to start, and enters step 2;

[0092] Step 11: The central controller determines whether the current operating mode is the standby mode. If yes, it proceeds to step 12; otherwise, it proceeds to step 16.

[0093] In this embodiment, the heat pump unit currently has three operating modes, including heating mode, standby mode and shutdown mode.

[0094] Step 12: The central controller obtains the current ambient temperature value Ta obtained through detection and proceeds to step 13;

[0095] Step 13: The central controller determines whether Ta≤M2 is established. If it is established, it proceeds to step 14; otherwise, it proceeds to step 15;

[0096] Step 14: The central controller controls the circulating water pump 5 and the secondary water pump 3 to start simultaneously, run for 2 minutes and stop for 8 minutes, and then enter step 2;

[0097] Step 15: The central controller controls the heat pump unit to not operate, and enters step 2;

[0098] Step 16: The central controller determines whether the current operating mode is the shutdown mode. If yes, it proceeds to step 17; otherwise, it proceeds to step 2.

[0099] Step 17: The central controller obtains the current ambient temperature value Ta obtained through detection and proceeds to step 18;

[0100] Step 18: The central controller determines whether Ta>M2 is established. If it is established, it proceeds to step 19; otherwise, it proceeds to step 20;

[0101] Step 19: The central controller controls the heat pump unit to not operate, and enters step 2;

[0102] In step 20, the central controller determines whether M3≤Ta≤M2 is established. If so, it proceeds to step 21, otherwise it proceeds to step 23, wherein M2>M3, M3 is the third preset temperature value, and the value range of M3 is -10℃~20℃.

[0103] In this embodiment, M3 can be selected as 0°C.

[0104] In step 21, the central controller obtains the detected stop time Tf of the circulating water pump 5 and proceeds to step 22;

[0105] In step 22, the central controller determines whether Tf>K minutes is established. If it is established, it proceeds to step 23, otherwise it proceeds to step 28, wherein K is a first preset time value, and the value range of K is 3 to 50 minutes.

[0106] In this embodiment, K can be selected as 20 minutes.

[0107] Step 23: Enter antifreeze protection and go to step 24;

[0108] Step 24: The central controller controls the circulating water pump 5 and the secondary water pump 3 to start simultaneously, and then proceeds to step 25;

[0109] Step 25: The central controller determines the antifreeze temperature value Te. The central controller defines the smaller temperature value between the current water inlet temperature value Tb and the current water outlet temperature value Tc of the heat pump unit as the antifreeze temperature value Te, and then proceeds to step 26.

[0110] In step 26, the central controller determines whether Te>M4 is established. If so, the process proceeds to step 27; otherwise, the process proceeds to step 29, wherein M4 is a fourth preset temperature value, and the value range of M4 is -10°C to 20°C.

[0111] In this embodiment, M4 can be selected as 6°C.

[0112] In step 27, the central controller controls the circulating water pump 5 and the secondary water pump 3 to continue running for 1 minute and then stop, and then proceeds to step 36;

[0113] Step 28: The central controller controls the heat pump unit to not operate, and enters step 2;

[0114] In step 29, the central controller determines whether M5<Te≤M4 is established. If so, it proceeds to step 30, otherwise it proceeds to step 32, wherein M5 is the fifth preset temperature value, M4>M5, and the value range of M5 is -10℃~20℃.

[0115] In this embodiment, M5 can be selected as 4°C.

[0116] Step 30: The central controller controls the circulating water pump 5 and the secondary water pump 3 to continue running, and then proceeds to step 31;

[0117] In step 31, the central controller determines whether any one of Te≥M6 or Ta≥M5 is established. If it is established, it proceeds to step 36, otherwise it proceeds to step 25, where M6 is the sixth preset temperature value, the value range of M6 is -10℃~20℃, and M6>M5.

[0118] In this embodiment, M6 can be selected as 8°C.

[0119] Step 32: The central controller determines whether M2≤Ta≤M5 is established. If so, the process proceeds to step 33; otherwise, the process proceeds to step 37, wherein M5>M2;

[0120] Step 33: The central controller controls the circulating water pump 5 and the secondary water pump 3 to continue running, and then proceeds to step 34;

[0121] In step 34, the central controller controls the auxiliary electric heating of the compressor to start, and then proceeds to step 35;

[0122] In step 35, the central controller determines whether any one of Te≥M7 or Ta≥M8 is established. When it is established, it enters step 36, otherwise it enters step 25, where M7 is the seventh preset temperature value, and the value range of M7 is -10℃~20℃; M8 is the eighth preset temperature value, and the value range of M8 is -10℃~20℃.

[0123] In this embodiment, M7 can be selected as 10°C, and M8 can be selected as 5°C.

[0124] Step 36: Exit antifreeze protection and enter step 2;

[0125] Step 37: The central controller controls the circulating water pump 5 and the secondary water pump 3 to continue running, and then proceeds to step 38;

[0126] Step 38: The central controller determines whether the compressor is currently in protection or fault state. If so, the process proceeds to step 39; otherwise, the process proceeds to step 41.

[0127] Step 39: The central controller controls the auxiliary electric heating of the compressor to start and continue to operate, and then proceeds to step 40;

[0128] In step 40, the central controller determines whether any one of Te≥M9 or Ta≥M4 is established. If it is established, it proceeds to step 36, otherwise it proceeds to step 25, where M9 is the ninth preset temperature value, and the value range of M9 is -10℃~20℃.

[0129] In this embodiment, M9 can be selected as 14°C.

[0130] In step 41, the central controller controls the compressor to start heating operation, and then proceeds to step 40.

[0131] In the description of the present invention, it should be understood that the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features.

[0132] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A water channel antifreeze control method for a heat pump system, characterized by The heat pump system comprises a heat pump unit (1), a buffer water tank (2) and a heating terminal (4). The water inlet and the water outlet of the heat pump unit (1) are connected to the buffer water tank (2) through a first circulation pipe, and the buffer water tank (2) is connected to the heating terminal (4) through a second circulation pipe. The heat pump unit (1) heats the first circulation water and then exchanges heat with the second circulation water in the buffer water tank (2) through a circulation water pump (5). The secondary water pump (3) then transports the second circulation water to the heating terminal (4). The heat pump unit (1) is provided with a device for detecting the current A first temperature sensor for detecting a previous ambient temperature value Ta, a second temperature sensor for detecting a current water inlet temperature value Tb of the water inlet of the heat pump unit (1), and a third temperature sensor for detecting a current water outlet temperature value Tc of the water outlet of the heat pump unit (1), the compressor of the heat pump unit (1) is provided with an auxiliary electric heater, the heat pump unit (1) is electrically connected to the circulating water pump (5), the secondary water pump (3), the auxiliary electric heater, the first temperature sensor, the second temperature sensor, and the third temperature sensor, respectively, and the operation includes the following steps: Step 1: Power on the heat pump unit and proceed to step 2; Step 2: The central controller of the heat pump unit determines whether the current operating mode is the heating mode. If yes, it proceeds to step 3; otherwise, it proceeds to step 11. Step 3: The central controller controls the circulating water pump (5) and the heat pump unit (1) to start simultaneously, and then proceeds to step 4; Step 4: The central controller obtains the current inlet water temperature value Tb obtained through detection and proceeds to step 5; Step 5: The central controller determines whether Tb>M1 is established. If so, it proceeds to step 6; otherwise, it proceeds to step 7, where M1 is a first preset temperature value, and the value range of M1 is 15-28°C. Step 6: The central controller controls the secondary water pump (3) to start, and then enters step 2; Step 7: The central controller obtains the current ambient temperature value Ta obtained through detection and proceeds to step 8; Step 8: The central controller determines whether Ta≤M2 is established. If it is established, it proceeds to step 9; otherwise, it proceeds to step 10, where M2 is a second preset temperature value, and the value range of M2 is -10°C to 20°C. Step 9: The central controller controls the secondary water pump (3) to start, and then enters step 2; Step 10: The central controller controls the secondary water pump (3) not to start, and enters step 2; Step 11: The central controller determines whether the current operating mode is the standby mode. If yes, it proceeds to step 12; otherwise, it proceeds to step 16. Step 12: The central controller obtains the current ambient temperature value Ta obtained through detection and proceeds to step 13; Step 13: The central controller determines whether Ta≤M2 is established. If it is established, it proceeds to step 14; otherwise, it proceeds to step 15; Step 14: The central controller controls the circulating water pump (5) and the secondary water pump (3) to start simultaneously, run for 2 minutes and stop for 8 minutes, and then enter step 2; Step 15: The central controller controls the heat pump unit to not operate, and enters step 2; Step 16: The central controller determines whether the current operating mode is the shutdown mode. If yes, it proceeds to step 17; otherwise, it proceeds to step 2. Step 17: The central controller obtains the current ambient temperature value Ta obtained through detection and proceeds to step 18; Step 18: The central controller determines whether Ta>M2 is established. If it is established, it proceeds to step 19; otherwise, it proceeds to step 20; Step 19: The central controller controls the heat pump unit to not operate, and enters step 2; Step 20: The central controller determines whether M3≤Ta≤M2 is established. If so, the process proceeds to step 21; otherwise, the process proceeds to step 23, wherein M2>M3, M3 is a third preset temperature value, and the value range of M3 is -10°C to 20°C. In step 21, the central controller obtains the detected stop time Tf of the circulating water pump (5) and proceeds to step 22; In step 22, the central controller determines whether Tf>K minutes is established. If it is established, the process proceeds to step 23; otherwise, the process proceeds to step 28, where K is a first preset time value and the value range of K is 3 to 50 minutes. Step 23: Enter antifreeze protection and go to step 24; Step 24: The central controller controls the circulating water pump (5) and the secondary water pump (3) to start simultaneously, and then proceeds to step 25; Step 25: The central controller determines the antifreeze temperature value Te. The central controller defines the smaller temperature value between the current water inlet temperature value Tb and the current water outlet temperature value Tc of the heat pump unit as the antifreeze temperature value Te, and then proceeds to step 26. In step 26, the central controller determines whether Te>M4 is established. If so, the process proceeds to step 27; otherwise, the process proceeds to step 29, where M4 is a fourth preset temperature value, and the value range of M4 is -10°C to 20°C. In step 27, the central controller controls the circulating water pump (5) and the secondary water pump (3) to continue running for 1 minute and then stop, and then proceeds to step 36; Step 28: The central controller controls the heat pump unit to not operate, and enters step 2; In step 29, the central controller determines whether M5<Te≤M4 is established. If so, the process proceeds to step 30; otherwise, the process proceeds to step 32, wherein M5 is a fifth preset temperature value, M4>M5, and the value range of M5 is -10℃~20℃; Step 30: The central controller controls the circulating water pump (5) and the secondary water pump (3) to continue running, and then proceeds to step 31; In step 31, the central controller determines whether Te≥M6 or Ta≥M5 is true. If so, the process proceeds to step 36; otherwise, the process proceeds to step 25, where M6 is a sixth preset temperature value, the value range of M6 is -10°C to 20°C, and M6>M5. Step 32: The central controller determines whether M2≤Ta≤M5 is established. If so, the process proceeds to step 33; otherwise, the process proceeds to step 37, wherein M5>M2; Step 33: The central controller controls the circulating water pump (5) and the secondary water pump (3) to continue running, and then proceeds to step 34; In step 34, the central controller controls the auxiliary electric heating of the compressor to start, and then proceeds to step 35; In step 35, the central controller determines whether any one of Te≥M7 or Ta≥M8 is established. If it is established, the process proceeds to step 36; otherwise, the process proceeds to step 25, where M7 is the seventh preset temperature value, and the value range of M7 is -10°C to 20°C. M8 is the eighth preset temperature value, and the value range of M8 is -10°C to 20°C. Step 36: Exit antifreeze protection and enter step 2; In step 37, the central controller controls the circulating water pump (5) and the secondary water pump (3) to continue running, and then proceeds to step 38; Step 38: The central controller determines whether the compressor is currently in protection or fault state. If so, the process proceeds to step 39; otherwise, the process proceeds to step 41. Step 39: The central controller controls the auxiliary electric heating of the compressor to start and continue to operate, and then proceeds to step 40; In step 40, the central controller determines whether Te≥M9 or Ta≥M4 is established. If so, the process proceeds to step 36; otherwise, the process proceeds to step 25, where M9 is a ninth preset temperature value, and the value range of M9 is -10°C to 20°C. In step 41, the central controller controls the compressor to start heating operation, and then proceeds to step 40.

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