Dual-system cascade explosion-proof heat pump and control method

Abstract

The invention relates to a dual-system cascade explosion-proof heat pump and a control method. The dual-system cascade explosion-proof heat pump comprises a frame, and a plurality of heating units are arranged in the frame; the heating unit comprises a plate heat exchanger fixedly installed on the inner bottom wall of the frame, a gas-liquid separator is fixedly installed on the inner bottom wall of the frame, and liquid storage tanks are fixedly installed on the inner bottom wall of the frame and located on the two sides of the plate heat exchanger. The system has the beneficial effects that the high-temperature side unit is provided with two heat sources, when the environment temperature is high, the low-temperature side unit is stopped, the high-temperature side evaporator channel is switched, and the two high-temperature side units are used for directly supplying heat, and when the environment temperature is low, the high-temperature side plate heat exchanger channel is switched, the low-temperature side unit is used for absorbing heat in air and transferring the heat to the plate heat exchanger; and then the heat in the plate heat exchanger is absorbed by the high-temperature side unit, high heat is prepared and transmitted to the built-in condenser, and the system can keep high operation efficiency under different working conditions through the flexible adjusting mechanism.

Description

Technical Field

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

[0002] In the production of oil and gas, the produced liquid of the oil field has high wax content, low freezing point, poor fluidity, and is easy to clog the pipeline, which is directly reflected in the increase of wellhead back pressure, affecting the production of a single well and the stable production operation of the entire block. Therefore, cascade heat pump units are commonly used at wellheads and metering stations to heat the pipeline.

[0003] Since some oil fields are located in the northwest region, which is hot in summer and extremely cold in winter, the heat pump unit needs to heat the water temperature to above 70°C. The inverter of the low-temperature side variable frequency compressor of the ordinary cascade heat pump generates a lot of heat in summer, so it is necessary to stop the low-temperature side variable frequency compressor when the room temperature is above 20°C, and only the high-temperature side fixed frequency compressor will work, which will lead to reduced system efficiency or unstable heat pump performance, easily affecting the overall heating effect of the system. Summary of the invention

[0004] The object of the present invention is to provide a dual-system cascade explosion-proof heat pump and a control method to solve the above-mentioned problems existing in the prior art.

[0005] The technical solution of the present invention to solve the above technical problems is as follows:

[0006] A dual-system cascade explosion-proof heat pump comprises a frame, wherein a plurality of heating units are arranged inside the frame;

[0007] The heating unit comprises a plate heat exchanger fixedly mounted on the inner bottom wall of the frame, a gas-liquid separator fixedly mounted on the inner bottom wall of the frame, a liquid storage tank fixedly mounted on the inner bottom wall of the frame and on both sides of the plate heat exchanger, the plate heat exchanger is connected to the liquid storage tank via a pipeline, a plurality of evaporators are fixedly mounted on the inner top wall of the frame and above the plate heat exchanger, and a high-temperature side unit and a low-temperature side unit are arranged inside the frame;

[0008] The heating unit also includes a fixing frame fixedly mounted on the inner bottom wall of the frame and located on both sides of the plate heat exchanger; the high-temperature side unit includes a high-temperature compressor fixedly mounted on the inner bottom wall of the frame, the return air port of the high-temperature compressor is connected to the gas-liquid separator through a pipeline, a high-temperature four-way reversing valve is fixedly mounted on the surface of the fixing frame on one side, the exhaust port of the high-temperature compressor is connected to one port of the high-temperature four-way reversing valve through a pipeline, an oil separator is fixedly mounted on the inner bottom wall of the frame, and the other three ports of the high-temperature four-way reversing valve are respectively connected to the oil separator, the evaporator and the plate heat exchanger through pipelines;

[0009] The low-temperature side unit includes a low-temperature compressor fixedly mounted on the inner bottom wall of the frame, the return air port of the low-temperature compressor is connected to the gas-liquid separator through a pipeline, a low-temperature four-way reversing valve is fixedly mounted on the surface of the fixed frame on the other side, four ports of the low-temperature four-way reversing valve are respectively connected to the evaporator, the exhaust port of the low-temperature compressor, the low-temperature four-way reversing valve and the plate heat exchanger through pipelines, an economizer is fixedly mounted on the inner bottom wall of the frame and on one side of the gas-liquid separator, and both ends of the economizer are respectively connected to the evaporator and the liquid storage tank through pipelines.

[0010] The beneficial effects of the present invention are as follows: the evaporator adopts a microchannel structure with two layers, the inner layer is connected to the high temperature side unit, and the high temperature side unit directly absorbs heat, and the outer layer is connected to the low temperature side unit, and the low temperature side unit absorbs heat. The plate heat exchanger is used as the low temperature side to supply heat to the high temperature side. The high temperature side unit has two heat sources. When the ambient temperature is high, the low temperature side unit is stopped, and the high temperature side evaporator channel is switched to directly heat the two units on the high temperature side. When the ambient temperature is low, the high temperature plate heat exchanger channel is switched to absorb heat in the air with the low temperature side unit and transfer it to Plate heat exchanger, and then the high temperature side unit absorbs the heat in the plate heat exchanger, produces high heat and transfers it to the built-in condenser. When the heating load demand is large, two groups of heat pump units are used to work simultaneously, in which the high temperature and low temperature sides are coupled into one group through a plate heat exchanger. When the heating load demand is small, only one of the coupled units of the high temperature side unit and the low temperature side unit is started separately. The ambient temperature only cuts off the low temperature compressor heating mode, and uses the high temperature side to directly absorb heat from the air. This flexible adjustment mechanism enables the system to maintain a high operating efficiency under different working conditions.

[0011] Based on the above technical solution, the present invention can also be improved as follows.

[0012] Furthermore, a plurality of fans are fixedly mounted on the upper surface of the frame.

[0013] Furthermore, wind and sand protection covers are provided on the four side surfaces of the frame.

[0014] Furthermore, the wind and sand protection cover comprises a protective cover which is fixedly mounted on the surface of the frame and has a triangular side surface and a front surface inclined outward, and a sand protection net is fixedly mounted on the bottom of the protective cover.

[0015] Furthermore, sealing plates are detachably mounted on the four side surfaces of the frame and below the protective cover.

[0016] Furthermore, a plurality of strip-shaped supporting legs are fixedly mounted on the bottom of the frame.

[0017] The present application also provides a control method for a dual-system cascade explosion-proof heat pump, comprising the following steps:

[0018] Step 1, the heat pump is started and defrosts;

[0019] Step 2: After the heat pump performs the defrosting operation, it enters the normal heating state. The heating state includes the following steps:

[0020] Step 2.1, the heat pump detects the temperature inside the water tank to determine whether the water temperature is greater than a set value. If it is greater than the set value, the heating unit stops running and enters a standby state; otherwise, the heating unit enters a running state;

[0021] Step 2.2, the heating unit determines whether the ambient temperature is greater than the high and low temperature switching value. If it is greater than the switching value, the high temperature compressor is turned on, and the high temperature side unit is directly used for heating to directly produce hot water; otherwise, the low temperature compressor is turned on, and when the coupling pressure is reached, the high temperature compressor 251 is turned on, and the low temperature side unit absorbs the heat in the air and transfers it to the plate heat exchanger, and then the high temperature side unit absorbs the heat in the plate heat exchanger to produce high heat and transfer it to the built-in condenser, thereby producing hot water;

[0022] Step 2.3: After the hot water is produced, re-execute step 2 to determine again whether the water temperature is greater than the set value.

[0023] Further, the defrosting operation in step 1 includes the following steps:

[0024] Step 1.1, when the fin temperature is lower than the set value, the defrosting time interval exceeds the set value, the compressor running time exceeds the set value, the ambient temperature is lower than the ambient temperature set value required for defrosting, and it remains for a period of time, and the number of heating unit units in the defrosting state at the same time does not exceed two; the heat pump performs a defrosting operation and executes step 2; otherwise, the heat pump directly performs a normal heating state;

[0025] Step 1.2, the fan stops running, and the low-temperature four-way reversing valve and the high-temperature four-way reversing valve are switched to cooling mode;

[0026] Step 1.3, delay detection of the low-temperature compressor, the high-temperature compressor and the compressor oil pressure difference protection, and perform protection detection on the low-temperature compressor and the high-temperature compressor at the same time. When the detection results are normal, perform the defrosting operation and execute step 4; when the detection results are abnormal, it means that the heat pump has a fault and is immediately shut down for maintenance;

[0027] Step 1.4, when the heat pump performs defrosting operation, when the fin temperature is greater than the set value, the defrosting time is greater than the set value, or the number of fan starts and stops reaches the set value, the defrosting operation ends and step 5 is executed; otherwise, the process returns to step 3;

[0028] Step 1.5, perform fault detection and start defrost termination countdown. If the fault detection is abnormal, immediately shut down for maintenance; otherwise, proceed to step 6;

[0029] Step 1.6, the low-temperature four-way reversing valve and the high-temperature four-way reversing valve lose power, the fan starts, the running time of the low-temperature compressor and the high-temperature compressor is reset, the defrosting ends, and the heat pump enters the normal heating state.

[0030] Furthermore, the high and low temperature switching value in step 2.1 can be set to 20°C. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The internal structure of the present invention is shown in FIG. Figure 1 ;

[0032] Figure 2 The internal structure of the present invention is shown in FIG. Figure 2 ;

[0033] Figure 3 The internal structure of the present invention is shown in FIG. Figure 3 ;

[0034] Figure 4 It is a schematic diagram of the overall structure of the present invention;

[0035] Figure 5 For the present invention Figure 2 Enlarged view of point A in the middle;

[0036] Figure 6 For the present invention Figure 2 Enlarged view of point B in the middle;

[0037] Figure 7 is a flow chart of the method of the present invention;

[0038] Figure 8 This is a flow chart of the defrosting operation in the present invention.

[0039] In the accompanying drawings, the components represented by the reference numerals are listed as follows:

[0040] 1. Frame; 2. Heating unit; 21. Plate heat exchanger; 22. Gas-liquid separator; 23. Liquid storage tank; 24. Evaporator; 25. High-temperature side unit; 251. High-temperature compressor; 252. High-temperature four-way reversing valve; 253. Oil separator; 26. Low-temperature side unit; 261. Low-temperature compressor; 262. Low-temperature four-way reversing valve; 263. Economizer; 27. Fixed frame; 3. Fan; 4. Wind and sand cover; 41. Protective cover; 42. Anti-sand net; 5. Support legs; 6. Sealing plate. DETAILED DESCRIPTION

[0041] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0042] like Figures 1 to 6 As shown, Embodiment 1 of the present invention is a dual-system cascade explosion-proof heat pump, comprising a frame 1, wherein a plurality of heating units 2 are arranged inside the frame 1;

[0043] The heating unit 2 includes a plate heat exchanger 21 fixedly mounted on the inner bottom wall of the frame 1, a gas-liquid separator 22 fixedly mounted on the inner bottom wall of the frame 1, a liquid storage tank 23 fixedly mounted on the inner bottom wall of the frame 1 and on both sides of the plate heat exchanger 21, the plate heat exchanger 21 is connected to the liquid storage tank 23 through a pipeline, a plurality of evaporators 24 fixedly mounted on the inner top wall of the frame 1 and above the plate heat exchanger 21, and a high-temperature side unit 25 and a low-temperature side unit 26 are arranged inside the frame 1;

[0044] The heating unit 2 also includes a fixing frame 27 fixedly mounted on the inner bottom wall of the frame 1 and located on both sides of the plate heat exchanger 21; the high-temperature side unit 25 includes a high-temperature compressor 251 fixedly mounted on the inner bottom wall of the frame 1, the return air port of the high-temperature compressor 251 is connected to the gas-liquid separator 22 through a pipeline, a high-temperature four-way reversing valve 252 is fixedly mounted on the surface of one side of the fixing frame 27, the exhaust port of the high-temperature compressor 251 is connected to one port of the high-temperature four-way reversing valve 252 through a pipeline, an oil separator 253 is fixedly mounted on the inner bottom wall of the frame 1, and the other three ports of the high-temperature four-way reversing valve 252 are respectively connected to the oil separator 253, the evaporator 24 and the plate heat exchanger 21 through pipelines;

[0045] The low-temperature side unit 26 includes a low-temperature compressor 261 fixedly mounted on the inner bottom wall of the frame 1, and the return air port of the low-temperature compressor 261 is connected to the gas-liquid separator 22 through a pipeline. A low-temperature four-way reversing valve 262 is fixedly mounted on the surface of the fixed frame 27 on the other side. The four ports of the low-temperature four-way reversing valve 262 are respectively connected to the evaporator 24, the exhaust port of the low-temperature compressor 261, the low-temperature four-way reversing valve 262 and the plate heat exchanger 21 through pipelines. An economizer 263 is fixedly mounted on the inner bottom wall of the frame 1 and on one side of the gas-liquid separator 22. The two ends of the economizer 263 are respectively connected to the evaporator 24 and the liquid storage tank 23 through pipelines.

[0046] The evaporator 24 adopts a microchannel structure with two layers. The inner layer is connected to the high temperature side unit 25 to directly absorb heat for the high temperature side unit 25, and the outer layer is connected to the low temperature side unit 26 to absorb heat for the low temperature side unit 26. The plate heat exchanger 21 is used as the low temperature side to supply heat to the high temperature side. The high temperature side unit 25 has two heat sources. When the ambient temperature is high, the low temperature side unit 26 is stopped, and the high temperature side evaporator 24 channel is switched to directly heat the two units on the high temperature side. When the ambient temperature is low, the high temperature plate heat exchanger 21 channel is switched to absorb heat in the air with the low temperature side unit 26 and transfer it to the plate heat exchanger 21. Heat exchanger 21, and then the high-temperature side unit 25 absorbs the heat in the plate heat exchanger 21, and produces high heat to transfer to the built-in condenser. When the heating load demand is large, two groups of heat pump units are used to work simultaneously, in which the high-temperature and low-temperature sides are coupled as a group through the plate heat exchanger 21. When the heating load demand is small, only one of the coupled units of the high-temperature side unit 25 and the low-temperature side unit 26 is started separately. The ambient temperature only cuts off the heating mode of the low-temperature compressor 261, and uses the high-temperature side to directly absorb heat from the air. This flexible adjustment mechanism enables the system to maintain a high operating efficiency under different working conditions.

[0047] In a specific implementation, a pressure sensor is provided inside the frame 1, and long capillary copper tubes are provided at both ends of the pressure sensor. The other ends of the two long capillary copper tubes are respectively connected to the pipes near the compressor intake and exhaust and the pipes on the plate heat exchanger 21. By providing the pressure sensor and the long capillary copper tubes, the refrigerant flowing in the pipe can be cooled down to reduce the damage to various components caused by high temperature. At the same time, when the plate heat exchanger 21 performs heat exchange coupling, the temperature is no longer sensed by the temperature sensor probe, but the pressure sensor is used to detect the pressure of the low-temperature side unit 26, and the evaporation temperature is calculated by the pressure, which is more accurate.

[0048] Embodiment 2 of the present invention is a dual-system cascade explosion-proof heat pump. Based on Embodiment 1, a plurality of fans 3 are fixedly mounted on the upper surface of the frame 1.

[0049] The presence of the fan 3 can speed up the flow of air around the evaporator 24, so that when the air flows through the evaporator 24, the evaporation process can more effectively absorb the heat in the air and reduce the temperature.

[0050] Embodiment 3 of the present invention is a dual-system cascade explosion-proof heat pump. Based on Embodiment 1 or 2, wind and sand protection covers 4 are provided on the four side surfaces of the frame 1.

[0051] The sand-proof cover 4 is provided to block the sand in the air, thereby preventing the sand in the air from entering the interior of the frame 1 .

[0052] Embodiment 4 of the present invention is a dual-system cascade explosion-proof heat pump. Based on embodiment 3, the wind and sand protection cover 4 includes a protective cover 41 which is fixedly mounted on the surface of the frame 1 and has a triangular side surface and a front face inclined outward, and a sand protection net 42 is fixedly mounted on the bottom of the protective cover 41.

[0053] The external protective cover 41 directly fixes the air inlet downward, which can prevent wind and sand, and can use gravity to make sand fall to avoid sand accumulation. It can also better gather the air volume, so that the evaporator 24 absorbs heat evenly and avoid regional frost affecting the heating amount. At the same time, by setting a sand-proof net 42, small particles of sand in the air are prevented from entering the interior of the frame 1.

[0054] Embodiment 5 of the present invention is a dual-system cascade explosion-proof heat pump. Based on Embodiment 4, sealing plates 6 are detachably installed on the four side surfaces of the frame 1 and below the protective cover 41 .

[0055] In a specific implementation, the sealing plate 6 is fixed to the frame 1 by means of bolts.

[0056] By installing the sealing plate 6 in a detachable manner, the staff can inspect and repair the components inside the frame 1 at any time.

[0057] Embodiment 6 of the present invention is a dual-system cascade explosion-proof heat pump. Based on any one of embodiments 1 to 5, a plurality of strip-shaped supporting legs 5 are fixedly installed on the bottom of the frame 1.

[0058] The frame 1 is supported by the supporting legs 5 so that the bottom of the frame 1 is suspended. The suspended design allows air to flow freely under the frame 1, which helps to dissipate heat and prevent moisture.

[0059] like Figures 7 and 8 As shown, a control method of a dual-system cascade explosion-proof heat pump according to embodiment 7 of the present invention adopts the dual-system cascade explosion-proof heat pump, comprising the following steps:

[0060] Step 1: Start the heat pump and perform defrosting operation;

[0061] Step 2: After the heat pump performs the defrosting operation, it enters the normal heating state. The heating state includes the following steps:

[0062] Step 2.1, the heat pump detects the temperature inside the water tank to determine whether the water temperature is greater than the set value. If it is greater than the set value, the heating unit 2 stops running and enters the standby state; otherwise, the heating unit 2 enters the running state;

[0063] Step 2.4, the heating unit 2 determines whether the ambient temperature is greater than the high and low temperature switching value. If it is greater than the switching value, the high temperature compressor 251 is turned on, and the high temperature side unit 25 is directly used for heating to directly produce hot water; otherwise, the low temperature compressor 261 is turned on, and when the coupling pressure is reached, the high temperature compressor 251 is turned on, and the low temperature side unit 26 absorbs the heat in the air and transfers it to the plate heat exchanger 21, and then the high temperature side unit 25 absorbs the heat in the plate heat exchanger 21 to produce high heat and transfer it to the built-in condenser, thereby producing hot water;

[0064] Step 2.3: After the hot water is produced, re-execute step 2 to determine again whether the water temperature is greater than the set value.

[0065] Embodiment 8 of the present invention is a dual-system cascade explosion-proof heat pump. Based on Embodiment 7, the defrosting operation in step 1 includes the following steps:

[0066] Step 1.1, when the fin temperature is lower than the set value, the defrosting time interval exceeds the set value, the compressor running time exceeds the set value, the ambient temperature is lower than the ambient temperature set value required for defrosting, and it remains for a period of time, and the number of heating units 2 in the defrosting state at the same time does not exceed two; the heat pump performs the defrosting operation and executes step 2; otherwise, the heat pump directly enters the normal heating state;

[0067] Step 1.2, the fan 3 stops running, and the low-temperature four-way reversing valve 262 and the high-temperature four-way reversing valve 252 are switched to the cooling mode;

[0068] Step 1.3, delay detection of the low-temperature compressor 261, the high-temperature compressor 251 and the compressor oil pressure difference protection, and at the same time, perform protection detection on the low-temperature compressor 261 and the high-temperature compressor 251. When the detection results are normal, perform defrosting operation and execute step 4; when the detection results are abnormal, it means that the heat pump is faulty and it is immediately shut down for maintenance;

[0069] Step 1.4: When the heat pump is defrosting, if the fin temperature is greater than the set value, the defrosting time is greater than the set value, or the number of fan starts and stops reaches the set value, the defrosting operation ends and step 5 is executed; otherwise, the process returns to step 3;

[0070] Step 1.5, perform fault detection and start defrost termination countdown. If the fault detection is abnormal, immediately shut down for maintenance; otherwise, proceed to step 6;

[0071] Step 1.6, the low-temperature four-way reversing valve 262 and the high-temperature four-way reversing valve 252 lose power, the fan 3 starts, the running time of the low-temperature compressor 261 and the high-temperature compressor 251 is reset, the defrosting ends, and the heat pump enters the normal heating state.

[0072] Embodiment 9 of the present invention is a dual-system cascade explosion-proof heat pump. Based on Embodiment 7, the high and low temperature switching value in step 2.1 can be set to 20°C.

[0073] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A dual-system cascade explosion-proof heat pump, characterized in that: It comprises a frame (1), wherein a plurality of heating units (2) are arranged inside the frame (1); The heating unit (2) comprises a plate heat exchanger (21) fixedly mounted on the inner bottom wall of the frame (1); a gas-liquid separator (22) is fixedly mounted on the inner bottom wall of the frame (1); liquid storage tanks (23) are fixedly mounted on the inner bottom wall of the frame (1) and located on both sides of the plate heat exchanger (21); the plate heat exchanger (21) is connected to the liquid storage tank (23) via a pipeline; a plurality of evaporators (24) are fixedly mounted on the inner top wall of the frame (1) and located above the plate heat exchanger (21); and a high-temperature side unit (25) and a low-temperature side unit (26) are arranged inside the frame (1); The heating unit (2) further comprises a fixing frame (27) fixedly mounted on the inner bottom wall of the frame (1) and located on both sides of the plate heat exchanger (21); the high-temperature side unit (25) comprises a high-temperature compressor (251) fixedly mounted on the inner bottom wall of the frame (1); the return air port of the high-temperature compressor (251) is connected to the gas-liquid separator (22) via a pipeline; a high-temperature four-way reversing valve (252) is fixedly mounted on the surface of one side of the fixing frame (27); the exhaust port of the high-temperature compressor (251) is connected to one port of the high-temperature four-way reversing valve (252) via a pipeline; an oil separator (253) is fixedly mounted on the inner bottom wall of the frame (1); the other three ports of the high-temperature four-way reversing valve (252) are respectively connected to the oil separator (253), the evaporator (24) and the plate heat exchanger (21) via pipelines; The low-temperature side unit (26) comprises a low-temperature compressor (261) fixedly mounted on the inner bottom wall of the frame (1); the return air port of the low-temperature compressor (261) is connected to the gas-liquid separator (22) through a pipeline; a low-temperature four-way reversing valve (262) is fixedly mounted on the surface of the fixed frame (27) on the other side; four ports of the low-temperature four-way reversing valve (262) are respectively connected to the evaporator (24), the exhaust port of the low-temperature compressor (261), the low-temperature four-way reversing valve (262) and the plate heat exchanger (21) through pipelines; an economizer (263) is fixedly mounted on the inner bottom wall of the frame (1) and located on one side of the gas-liquid separator (22); two ends of the economizer (263) are respectively connected to the evaporator (24) and the liquid storage tank (23) through pipelines.

2. A dual-system cascade explosion-proof heat pump according to claim 1, characterized in that: A plurality of fans (3) are fixedly mounted on the upper surface of the frame (1).

3. A dual-system cascade explosion-proof heat pump according to claim 1, characterized in that: The four side surfaces of the frame (1) are provided with wind and sand protection covers (4).

4. A dual-system cascade explosion-proof heat pump according to claim 3, characterized in that: The wind and sand protection cover (4) comprises a protection cover (41) which is fixedly mounted on the surface of the frame (1) and has a triangular side surface and a front face inclined outward, and a sand protection net (42) is fixedly mounted on the bottom of the protection cover (41).

5. A dual-system cascade explosion-proof heat pump according to claim 4, characterized in that: Sealing plates (6) are detachably mounted on the four side surfaces of the frame (1) and below the protective cover (41).

6. A dual-system cascade explosion-proof heat pump according to claim 1, characterized in that: A plurality of strip-shaped supporting legs (5) are fixedly mounted on the bottom of the frame (1).

7. A control method for a dual-system cascade explosion-proof heat pump, characterized in that: The dual-system cascade explosion-proof heat pump according to any one of claims 1 to 6 is used, comprising the following steps: Step 1, the heat pump is started and defrosts; Step 2: After the heat pump performs the defrosting operation, it enters the normal heating state. The heating state includes the following steps: Step 2.1, the heat pump detects the temperature inside the water tank to determine whether the water temperature is greater than a set value. If the water temperature is greater than the set value, the heating unit (2) stops running and enters a standby state; otherwise, the heating unit (2) enters an operating state; Step 2.2, the heating unit (2) determines whether the ambient temperature is greater than the high and low temperature switching value. If the ambient temperature is greater than the switching value, the high temperature compressor (251) is turned on, and the high temperature side unit (25) is directly used to supply heat, thereby directly producing hot water. Otherwise, the low temperature compressor (261) is turned on, and when the coupling pressure is reached, the high temperature compressor (251) is turned on, and the low temperature side unit (26) absorbs heat from the air and transfers it to the plate heat exchanger (21). The high temperature side unit (25) then absorbs heat from the plate heat exchanger (21), produces high heat, and transfers it to the built-in condenser, thereby producing hot water. Step 2.3: After the hot water is produced, re-execute step 2 to determine again whether the water temperature is greater than the set value.

8. A control method for a dual-system cascade explosion-proof heat pump according to claim 7, characterized in that: The defrosting operation in step 1 comprises the following steps: Step 1.1, when the fin temperature is lower than the set value, the defrosting time interval exceeds the set value, the compressor operation time exceeds the set value, the ambient temperature is lower than the ambient temperature set value required for defrosting, and remains for a period of time, and the number of heating units (2) in the defrosting state at the same time does not exceed two; the heat pump performs a defrosting operation and executes step 2; otherwise, the heat pump directly enters a normal heating state; Step 1.2, the fan (3) stops running, and the low-temperature four-way reversing valve (262) and the high-temperature four-way reversing valve (252) are switched to the cooling mode; Step 1.3, delay detection of the low-temperature compressor (261), the high-temperature compressor (251) and the compressor oil pressure difference protection, and at the same time, perform protection detection on the low-temperature compressor (261) and the high-temperature compressor (251). When the detection results are normal, perform defrosting operation and execute step 4; when the detection results are abnormal, it means that the heat pump has a fault and is immediately shut down for maintenance; Step 1.4, when the heat pump performs defrosting operation, when the fin temperature is greater than the set value, the defrosting time is greater than the set value, or the number of fan starts and stops reaches the set value, the defrosting operation ends and step 5 is executed; otherwise, the process returns to step 3; Step 1.5, perform fault detection and start defrost termination countdown. If the fault detection is abnormal, immediately shut down for maintenance; otherwise, proceed to step 6; Step 1.6, the low-temperature four-way reversing valve (262) and the high-temperature four-way reversing valve (252) lose power, the fan (3) starts, the running time of the low-temperature compressor (261) and the high-temperature compressor (251) is reset, the defrosting ends, and the heat pump enters a normal heating state.

9. A control method for a dual-system cascade explosion-proof heat pump according to claim 7, characterized in that: The high and low temperature switching value in step 2.1 can be set to 20°C.

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