Cascade high-temperature hot water system

Abstract

The utility model provides a cascade type high-temperature hot water system which comprises a low-temperature-stage system and a high-temperature-stage system, and the low-temperature-stage system comprises a first loop, a second loop, a third loop, a first four-way valve, a second four-way valve and a controller; the high-temperature stage system comprises a high-temperature stage loop; the controller is used for controlling the power-on state of the first four-way valve and the second four-way valve so that any one of the first loop, the second loop and the third loop can be switched on. When the first loop is conducted, the cascade high-temperature hot water system is used for outputting medium-temperature hot water; when the second loop is conducted, the cascade high-temperature hot water system is used for achieving the defrosting function; and when the third loop and the high-temperature loop are conducted at the same time, the cascade high-temperature hot water system is used for outputting high-temperature hot water. Mode switching of the cascade type high-temperature hot water system is achieved through the four-way valve, the invalid flow path can be completely sealed when the four-way valve is used for mode switching, residual refrigerants in the invalid flow path can be pumped out through pressure difference, and the refrigerant utilization rate of the system is increased.

Description

Technical Field

[0001] The present application relates to the technical field of heat pump water heaters, and in particular to a cascade high-temperature hot water system. Background Art

[0002] In a cascade high-temperature hot water unit, it is usually composed of two independent systems using different refrigerants: a low-temperature stage and a high-temperature stage. Usually, the exhaust gas of the low-temperature stage compressor is divided into two paths, and the throttle valves on the two pipelines control the exhaust flow path of the low-stage compressor to reach the low-stage condenser or the intermediate heat exchanger, thereby realizing the switching between high and low-stage modes.

[0003] However, in existing technologies, when switching between modes in a cascade high-temperature hot water unit, if the throttle valve is fully closed, refrigerant will migrate to the intermediate heat exchanger when the low-temperature, low-stage system is operating independently, causing refrigerant to be lost from the low-stage system and reducing refrigerant utilization. If the throttle valve is not fully closed, a certain amount of bypass will occur, resulting in energy waste. Utility Model Content

[0004] In view of this, the present application provides a cascade high-temperature hot water system to solve the problem of low refrigerant utilization and energy waste in the prior art.

[0005] To achieve the above objectives, this application provides the following technical solutions:

[0006] In a first aspect, the present application discloses a cascade high-temperature hot water system, comprising a low-temperature stage system and a high-temperature stage system, wherein the low-temperature stage system comprises a first circuit, a second circuit, a third circuit, a first four-way valve, a second four-way valve, and a controller; the high-temperature stage system comprises a high-temperature stage circuit;

[0007] The controller is used to control the power supply state of the first four-way valve and the second four-way valve to make any one of the first circuit, the second circuit, and the third circuit conductive;

[0008] When the first circuit is turned on, the cascade high-temperature hot water system is used to output low- and medium-temperature hot water;

[0009] When the second circuit is turned on, the cascade high-temperature hot water system is used to achieve a defrosting function;

[0010] When the third circuit and the high-temperature circuit are turned on at the same time, the cascade high-temperature hot water system is used to output high-temperature hot water.

[0011] Optionally, in the above-mentioned cascade high-temperature hot water system, the low-temperature stage system includes:

[0012] Low temperature stage compressor, low temperature stage heat exchanger, first throttle valve, air heat exchanger and low temperature stage gas-liquid separator;

[0013] When the first four-way valve is powered off and the second four-way valve is powered on, the first four-way valve, the second four-way valve, the low-temperature compressor, the low-temperature heat exchanger, the first throttle valve, the air heat exchanger and the low-temperature gas-liquid separator constitute the first circuit;

[0014] The output end of the low-temperature compressor is connected to the D port of the first four-way valve, and the input end of the low-temperature compressor is connected to the output end of the low-temperature gas-liquid separator;

[0015] The S port of the first four-way valve is connected to the input end of the low-temperature gas-liquid separator, and the C port of the first four-way valve is connected to the D port of the second four-way valve;

[0016] The E port of the second four-way valve is connected to the first end of the low-temperature heat exchanger, the S port of the second four-way valve is connected to the connection point between the S port of the first four-way valve and the low-temperature gas-liquid separator, and the C port of the second four-way valve is connected to one end of the air heat exchanger;

[0017] The other end of the air heat exchanger is connected to one end of the first throttle valve, and the other end of the first throttle valve is connected to the second end of the low-temperature stage heat exchanger.

[0018] Optionally, in the above-mentioned cascade high-temperature hot water system, when the first four-way valve and the second four-way valve are powered off, the first four-way valve, the second four-way valve, the low-temperature compressor, the low-temperature heat exchanger, the first throttle valve, the air heat exchanger and the low-temperature gas-liquid separator constitute the second circuit.

[0019] Optionally, in the above-mentioned cascade high-temperature hot water system, the low-temperature stage system includes a control valve, and the high-temperature stage system includes an intermediate heat exchanger, a high-temperature stage compressor, a high-temperature stage heat exchanger, a second throttle valve, and a high-temperature stage gas-liquid separator;

[0020] When the first four-way valve and the second four-way valve are both energized, the low-temperature compressor, the first throttle valve, the air heat exchanger, the low-temperature gas-liquid separator, the first four-way valve, the second four-way valve, the control valve, and the intermediate heat exchanger form the third circuit;

[0021] The high-temperature stage compressor, the high-temperature stage heat exchanger, the second throttle valve, the intermediate heat exchanger and the high-temperature stage gas-liquid separator constitute the high-temperature stage circuit;

[0022] The control valve is arranged between the low-temperature stage heat exchanger and the first throttle valve;

[0023] The first end of the intermediate heat exchanger is connected to the E port of the first four-way valve, the second end of the intermediate heat exchanger is connected between the control valve and the first throttle valve, the third end of the intermediate heat exchanger is connected to the input end of the high-temperature stage gas-liquid separator, and the fourth end of the intermediate heat exchanger is connected to one end of the second throttle valve;

[0024] The input end of the high-temperature stage compressor is connected to the output end of the high-temperature stage gas-liquid separator, and the output end of the high-temperature stage compressor is connected to the first end of the high-temperature stage heat exchanger;

[0025] The second end of the high-temperature stage heat exchanger is connected to the other end of the second throttle valve, and the third end of the high-temperature stage heat exchanger is connected to the third end of the low-temperature stage heat exchanger.

[0026] Optionally, the above-mentioned cascade high-temperature hot water system further includes a first one-way valve and a second one-way valve;

[0027] The input port of the first one-way valve is connected to the S port of the first four-way valve, and the output port of the first one-way valve is connected to the connection point between the input end of the low-temperature gas-liquid separator and the S port of the second four-way valve;

[0028] An input port of the second one-way valve is connected to the second end of the intermediate heat exchanger, and an output port of the second one-way valve is connected between the control valve and the first throttle valve.

[0029] Optionally, in the above-mentioned cascade high-temperature hot water system, the first throttle valve and the second throttle valve are both electronic expansion valves.

[0030] Optionally, in the above-mentioned cascade high-temperature hot water system, the control valve is a solenoid valve.

[0031] As can be seen from the above technical solution, the present application provides a cascade high-temperature hot water system, including a low-temperature stage system and a high-temperature stage system, the low-temperature stage system including a first circuit, a second circuit, a third circuit, a first four-way valve, a second four-way valve, and a controller; the high-temperature stage system includes a high-temperature stage circuit; the controller is used to control the power supply state of the first four-way valve and the second four-way valve so that any one of the first circuit, the second circuit, and the third circuit in the low-temperature stage system is conductive; when the first circuit is conductive, the cascade high-temperature hot water system is used to output medium-temperature hot water; when the second circuit is conductive, the cascade high-temperature hot water system is used to achieve a defrost function; when the third circuit and the high-temperature stage circuit are simultaneously conductive, the cascade high-temperature hot water system is used to output high-temperature hot water. The present application uses two four-way valves to achieve mode switching of the cascade high-temperature hot water system, and the conversion between different circuits is achieved by coordinating and controlling the two four-way valves in sequence. When the four-way valves are used for mode switching, the invalid flow path can be completely blocked, eliminating bypass volume, thereby improving system capacity, and the refrigerant remaining in the invalid flow path can be extracted through the pressure difference, thereby improving the refrigerant utilization rate in the system and reducing the refrigerant charge. The invention aims to solve the problem of low refrigerant utilization rate and energy waste in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without any creative work.

[0033] Figure 1 Schematic diagram of the system architecture of the cascade high-temperature hot water system provided in an embodiment of the present application. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0035] In this application, the terms "comprises," "comprising," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not preclude the presence of additional identical elements in the process, method, article, or apparatus that includes the element.

[0036] Furthermore, in this document, relational terms such as first and second, etc. are used merely to distinguish one entity or operation from another entity or operation, but do not necessarily require or imply any actual relationship or order between these entities or operations.

[0037] As can be seen from the background, in existing cascade high-temperature hot water units, if the throttle valve is fully closed during mode switching, refrigerant will migrate to the intermediate heat exchanger when the low-temperature, low-stage system is operating independently, resulting in loss of refrigerant circulating in the low-stage system and low refrigerant utilization. If the throttle valve is not fully closed, a certain amount of bypass will occur, resulting in energy waste.

[0038] In view of this, the present application provides a cascade high-temperature hot water system to solve the problem of low refrigerant utilization and energy waste in the prior art.

[0039] The present application embodiment provides a cascade high temperature hot water system, the overall structure of which can be seen in Figure 1 , where the components and their corresponding numbers are: low-temperature compressor 1, first four-way valve 2, low-temperature heat exchanger 3, second four-way valve 4, air heat exchanger 5, control valve 6, first check valve 14, first throttle valve 8, high-temperature gas-liquid separator 9, second throttle valve 10, high-temperature heat exchanger 11, high-temperature compressor 12, low-temperature gas-liquid separator 13, second check valve 7, intermediate heat exchanger 15. The power-on status of the first four-way valve 2 and the second four-way valve 4 is controlled by a controller. When the four-way valve is powered off, the DC port and the ES port are connected; when the four-way valve is powered on, the DE port and the SC port are connected.

[0040] The cascade high-temperature hot water system can be divided into two parts: the low-temperature stage system and the high-temperature stage system. The low-temperature stage system includes the low-temperature stage compressor 1, the first four-way valve 2, the second four-way valve 4, the low-temperature stage heat exchanger 3, the control valve 6, the first throttle valve 8, the air heat exchanger 5, and the low-temperature stage gas-liquid separator 13. The high-temperature stage system includes the high-temperature stage compressor 12, the high-temperature stage heat exchanger 11, the second throttle valve 10, the intermediate heat exchanger 15, and the high-temperature stage gas-liquid separator 9. The low-temperature stage system transfers heat to the high-temperature stage system through the intermediate heat exchanger 15, forming a complete heat exchange operation system.

[0041] The output end of the low-temperature compressor 1 is connected to the D port of the first four-way valve 2, and the input end of the low-temperature compressor 1 is connected to the output end of the low-temperature gas-liquid separator 13;

[0042] The S port of the first four-way valve 2 is connected to the input end of the low-temperature gas-liquid separator 13, and the C port of the first four-way valve 2 is connected to the D port of the second four-way valve 4;

[0043] The E port of the second four-way valve 4 is connected to the first end of the low-temperature heat exchanger 3, the S port of the second four-way valve 4 is connected to the connection point between the S port of the first four-way valve 2 and the low-temperature gas-liquid separator 13, and the C port of the second four-way valve 4 is connected to one end of the air heat exchanger 5;

[0044] The other end of the air heat exchanger 5 is connected to one end of the first throttle valve 8, and the other end of the first throttle valve 8 is connected to the second end of the low-temperature stage heat exchanger 3;

[0045] The control valve 6 is provided between the low temperature stage heat exchanger 3 and the first throttle valve 8;

[0046] A first end of the intermediate heat exchanger 15 is connected to port E of the first four-way valve 2, a second end of the intermediate heat exchanger 15 is connected between the control valve 6 and the first throttle valve 8, a third end of the intermediate heat exchanger 15 is connected to the input end of the high-temperature gas-liquid separator 9, and a fourth end of the intermediate heat exchanger 15 is connected to one end of the second throttle valve 10;

[0047] The input end of the high-temperature stage compressor 12 is connected to the output end of the high-temperature stage gas-liquid separator 9, and the output end of the high-temperature stage compressor 12 is connected to the first end of the high-temperature stage heat exchanger 11;

[0048] The second end of the high-temperature heat exchanger 11 is connected to the other end of the second throttle valve 10, and the third end of the high-temperature heat exchanger 11 is connected to the third end of the low-temperature heat exchanger 3;

[0049] The input port of the first one-way valve 14 is connected to the S port of the first four-way valve 2, and the output port of the first one-way valve 14 is connected to the connection point between the input end of the low-temperature gas-liquid separator 13 and the S port of the second four-way valve 4;

[0050] An input port of the second one-way valve 7 is connected to the second end of the intermediate heat exchanger 15 , and an output port of the second one-way valve 7 is connected between the control valve 6 and the first throttle valve 8 .

[0051] It should be noted that when the cascade high-temperature hot water system needs to deliver low-temperature water, the controller de-energizes the first four-way valve 2, energizes the second four-way valve 4, and fully opens the control valve 6. The first four-way valve 2, the second four-way valve 4, the low-temperature compressor 1, the low-temperature heat exchanger 3, the first throttle valve 8, the air heat exchanger 5, and the low-temperature gas-liquid separator 13 form the first circuit. During this operation, the low-temperature stage operates alone, delivering low-temperature water at a temperature of approximately 20°C to 50°C. The low-temperature compressor 1 compresses the refrigerant into medium-temperature, medium-pressure gas before discharging it. The gaseous refrigerant enters the second four-way valve 4 directly from port C of the first four-way valve 2, then enters the low-temperature heat exchanger 3 through port E, where it is condensed into a low-temperature, medium-pressure liquid. The liquid refrigerant passes through the fully-open control valve 6, is throttled by the throttle valve 8, and is reduced to a low-temperature, low-pressure gas-liquid two-phase state before entering the air heat exchanger 5, where it evaporates into a room-temperature, low-pressure gas. The gaseous refrigerant returns to the low-temperature gas-liquid separator 13 through the connection between the C port and the S port of the second four-way valve 4 for gas-liquid separation and then returns to the low-temperature compressor 1 for intake, thus completing the complete low-temperature cycle.

[0052] It should also be noted that in relatively cold areas, where the average temperature is below zero degrees Celsius, the temperature of the air heat exchanger during operation of the water heater will be lower than the ambient temperature, causing frost to form. As the operating conditions deteriorate, if defrosting is not performed, the frost layer will accumulate thicker and the heating effect will deteriorate, so defrosting operation is required. When the cascade high-temperature hot water system needs to implement the refrigeration and defrosting function, the controller controls the first four-way valve 2 to be in the power-off state, the second four-way valve 4 to be in the power-off state, and the control valve 6 to be in the fully open state. The first four-way valve 2, the second four-way valve 4, the low-temperature compressor 1, the low-temperature heat exchanger 3, the first throttle valve 8, the air heat exchanger 5, and the low-temperature gas-liquid separator 13 constitute the second circuit. At this time, the low-temperature stage is also operated alone. The exhaust of the low-temperature stage compressor 1 directly enters the second four-way valve 4 from the C port of the first four-way valve 2, and then enters the air heat exchanger 5 from the C port for condensation heat exchange. After throttling through the first throttle valve 8, it passes through the fully opened control valve 6 and enters the low-temperature stage heat exchanger 3 for evaporation heat exchange. The E port and the S port of the second four-way valve 4 are connected to return to the low-temperature stage gas-liquid separator 13 for gas-liquid separation and then return to the low-temperature stage compressor 1 for intake.

[0053] It should also be noted that when the cascade high-temperature hot water system needs to output high-temperature hot water, the low- and high-temperature stages operate simultaneously, i.e., in cascade operation, forming a cascade system. The controller energizes the first four-way valve 2, the second four-way valve 4, and fully closes the solenoid valve 6. The low-temperature stage compressor 1, the first throttle valve 8, the air heat exchanger 5, the low-temperature stage gas-liquid separator 13, the first four-way valve 2, the second four-way valve 4, the control valve 6, and the intermediate heat exchanger 15 constitute the third circuit. The high-temperature stage compressor 12, the high-temperature stage heat exchanger 11, the second throttle valve 10, and the high-temperature stage gas-liquid separator 9 constitute the high-temperature stage circuit. This circuit is used to output high-temperature hot water at a temperature of approximately 50°C to 80°C. Both the high- and low-temperature stages are activated simultaneously. The flow path of the high-temperature stage is as follows: the high-temperature stage compressor 12 compresses the refrigerant into a high-temperature, high-pressure gas, which is then discharged into the high-temperature stage heat exchanger 11, where it is condensed into a high-pressure, medium-temperature liquid. The liquid refrigerant is throttled to a medium-pressure and medium-temperature gas-liquid two-phase state through the second throttle valve 10 and then enters the intermediate heat exchanger 15 where the high-temperature stage evaporates and absorbs the heat released by the low-temperature stage condensation. After the refrigerant evaporates to a medium-pressure gas, it goes to the high-temperature stage gas-liquid separator 9 and returns to the high-temperature stage compressor 12 for intake.

[0054] The flow path of the low-temperature stage is as follows: the low-temperature stage compressor 1 compresses the refrigerant into a medium-temperature and medium-pressure gas and discharges it. The gaseous refrigerant enters the low-temperature stage from the E port of the first four-way valve 2, is condensed into a liquid phase through the intermediate heat exchanger 15, and releases heat to the high-temperature stage. After the medium-pressure liquid refrigerant passes through the one-way valve 7, it enters the first throttle valve 8 and is throttled into a low-temperature and low-pressure gas-liquid two-phase refrigerant. The low-temperature and low-pressure gas-liquid two-phase refrigerant is evaporated into a normal-temperature and low-pressure gas through the air heat exchanger 5. The gaseous refrigerant returns to the low-temperature stage gas-liquid separator 13 through the connection between the C port and the S port of the second four-way valve 4 for gas-liquid separation, and then returns to the low-temperature stage compressor 1 for intake. The first one-way valve 14 and the second one-way valve 7 can prevent the migration of the refrigerant and prevent invalid flow paths from participating in the main circuit refrigerant circulation under different modes.

[0055] During the process of switching from single low-temperature stage operation to cascade operation, the switching of the first four-way valve 2 causes some high-temperature and high-pressure refrigerant from the previous operating state to remain in the pipeline between port C of the first four-way valve 2 and port E of the second four-way valve 4, and between the low-temperature stage heat exchanger 3 and the control valve 6. At this time, port C of the first four-way valve 2 is connected to port S, and port S is connected to the second one-way valve 7 and returns to the low-temperature stage gas-liquid separator 13. Port S is on the low-pressure side, and the high-temperature and high-pressure gaseous refrigerant at port C can be continuously pumped back to the low-temperature stage gas-liquid separator 13 through the pressure difference, participating in the current system circulation.

[0056] During the process of switching from cascade operation to single low-temperature stage operation, the switching of the first four-way valve 2 causes some high-temperature and high-pressure refrigerant from the previous operating state to remain in the pipeline between port E of the first four-way valve 2, the intermediate heat exchanger 15, and the second one-way valve 7. At this time, port E of the first four-way valve 2 is connected to port S, and port S is connected to the first one-way valve 14 and returns to the low-temperature stage gas-liquid separator 13. Port S is on the low-pressure side, and the high-temperature and high-pressure gaseous refrigerant at port C can be continuously pumped back to the low-temperature stage gas-liquid separator 13 through the pressure difference, participating in the current system circulation.

[0057] During the process of switching from cascade operation to refrigeration defrost, the switching of the first four-way valve 2 causes some high-temperature and high-pressure refrigerant in the previous operating state to remain in the pipeline between the E port of the first four-way valve 2, the intermediate heat exchanger 15, and the second one-way valve 7. At this time, the E port of the first four-way valve 2 is connected to the S port, and the S port is connected to the first one-way valve 14 and returns to the low-temperature gas-liquid separator 13. The S port is on the low-pressure side, and the high-temperature and high-pressure gaseous refrigerant at the C port can be continuously pumped back to the low-temperature gas-liquid separator 13 through the pressure difference, participating in the current system circulation.

[0058] The process of switching from the low-temperature stage to refrigeration and defrosting is performed independently, i.e., the exchange of the two devices of the low-temperature stage, and no invalid flow path is involved.

[0059] It can be seen from this that in the cascade high-temperature hot water system provided in the embodiment of the present application, when switching between different circuits to achieve different functions, the invalid flow path can be completely blocked, there is no bypass volume, and the system capacity is effectively improved. At the same time, the high-temperature and high-pressure gaseous refrigerant retained in the invalid flow path is extracted through the high and low pressure differences, thereby improving the refrigerant utilization rate in the system and reducing the refrigerant filling amount.

[0060] Optionally, in another embodiment of the present application, the first throttle valve 8 and the second throttle valve 10 are both electronic expansion valves.

[0061] Optionally, in another embodiment of the present application, the control valve 6 may be a solenoid valve.

[0062] The present application provides a cascade high-temperature hot water system, comprising a low-temperature stage system and a high-temperature stage system, wherein the low-temperature stage system comprises a first circuit, a second circuit, a third circuit, a first four-way valve, a second four-way valve, and a controller; the high-temperature stage system comprises a high-temperature stage circuit; the controller is configured to control the power-on state of the first four-way valve and the second four-way valve so as to connect any one of the first circuit, the second circuit, and the third circuit in the low-temperature stage system; when the first circuit is connected, the cascade high-temperature hot water system is configured to output medium-temperature hot water; when the second circuit is connected, the cascade high-temperature hot water system is configured to implement a defrosting function; and when the third circuit and the high-temperature stage circuit are simultaneously connected, the cascade high-temperature hot water system is configured to output high-temperature hot water. The present application implements mode switching of the cascade high-temperature hot water system through two four-way valves, and achieves conversion between different circuits by coordinating and controlling the two four-way valves in succession. When the four-way valves are used for mode switching, the ineffective flow path can be completely blocked, eliminating bypass volume, thereby improving system capacity, and the refrigerant remaining in the ineffective flow path can be extracted through a pressure difference, thereby improving refrigerant utilization in the system and reducing refrigerant charge volume. The invention aims to solve the problem of low refrigerant utilization rate and energy waste in the prior art.

[0063] Each embodiment in this specification is described in a progressive manner. The same or similar parts between the embodiments can be referred to each other. Each embodiment focuses on the differences from other embodiments. In particular, for system or system embodiments, since they are basically similar to method embodiments, the description is relatively simple. For relevant parts, refer to the partial description of the method embodiment. The system and system embodiments described above are merely schematic, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment. A person of ordinary skill in the art can understand and implement it without expending creative work.

[0064] Professionals may further appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the above description has generally described the components and steps of each example according to their functions. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians may use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0065] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one 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 present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to encompass the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A cascade high-temperature hot water system, characterized in that: It includes a low-temperature system and a high-temperature system, wherein the low-temperature system includes a first circuit, a second circuit, a third circuit, a first four-way valve, a second four-way valve and a controller; the high-temperature system includes a high-temperature circuit; The controller is used to control the power supply state of the first four-way valve and the second four-way valve to make any one of the first circuit, the second circuit, and the third circuit conductive; When the first circuit is turned on, the cascade high-temperature hot water system is used to output medium-temperature hot water; When the second circuit is turned on, the cascade high-temperature hot water system is used to achieve a defrosting function; When the third circuit and the high-temperature circuit are turned on at the same time, the cascade high-temperature hot water system is used to output high-temperature hot water.

2. The cascade high-temperature hot water system according to claim 1, characterized in that: The low temperature system comprises: Low temperature stage compressor, low temperature stage heat exchanger, first throttle valve, air heat exchanger and low temperature stage gas-liquid separator; When the first four-way valve is powered off and the second four-way valve is powered on, the first four-way valve, the second four-way valve, the low-temperature compressor, the low-temperature heat exchanger, the first throttle valve, the air heat exchanger and the low-temperature gas-liquid separator constitute the first circuit; The output end of the low-temperature compressor is connected to the D port of the first four-way valve, and the input end of the low-temperature compressor is connected to the output end of the low-temperature gas-liquid separator; The S port of the first four-way valve is connected to the input end of the low-temperature gas-liquid separator, and the C port of the first four-way valve is connected to the D port of the second four-way valve; The E port of the second four-way valve is connected to the first end of the low-temperature heat exchanger, the S port of the second four-way valve is connected to the connection point between the S port of the first four-way valve and the low-temperature gas-liquid separator, and the C port of the second four-way valve is connected to one end of the air heat exchanger; The other end of the air heat exchanger is connected to one end of the first throttle valve, and the other end of the first throttle valve is connected to the second end of the low-temperature stage heat exchanger.

3. The cascade high-temperature hot water system according to claim 2, characterized in that: When the first four-way valve and the second four-way valve are powered off, the first four-way valve, the second four-way valve, the low-temperature compressor, the low-temperature heat exchanger, the first throttle valve, the air heat exchanger and the low-temperature gas-liquid separator constitute the second circuit.

4. The cascade high-temperature hot water system according to claim 2, characterized in that: The low-temperature stage system includes a control valve, and the high-temperature stage system includes an intermediate heat exchanger, a high-temperature stage compressor, a high-temperature stage heat exchanger, a second throttle valve, and a high-temperature stage gas-liquid separator; When the first four-way valve and the second four-way valve are both energized, the low-temperature compressor, the first throttle valve, the air heat exchanger, the low-temperature gas-liquid separator, the first four-way valve, the second four-way valve, the control valve, and the intermediate heat exchanger form the third circuit; The high-temperature stage compressor, the high-temperature stage heat exchanger, the second throttle valve, the intermediate heat exchanger and the high-temperature stage gas-liquid separator constitute the high-temperature stage circuit; The control valve is arranged between the low-temperature stage heat exchanger and the first throttle valve; The first end of the intermediate heat exchanger is connected to the E port of the first four-way valve, the second end of the intermediate heat exchanger is connected between the control valve and the first throttle valve, the third end of the intermediate heat exchanger is connected to the input end of the high-temperature stage gas-liquid separator, and the fourth end of the intermediate heat exchanger is connected to one end of the second throttle valve; The input end of the high-temperature stage compressor is connected to the output end of the high-temperature stage gas-liquid separator, and the output end of the high-temperature stage compressor is connected to the first end of the high-temperature stage heat exchanger; The second end of the high-temperature stage heat exchanger is connected to the other end of the second throttle valve, and the third end of the high-temperature stage heat exchanger is connected to the third end of the low-temperature stage heat exchanger.

5. The cascade high-temperature hot water system according to claim 4, characterized in that: Also included are a first one-way valve and a second one-way valve; The input port of the first one-way valve is connected to the S port of the first four-way valve, and the output port of the first one-way valve is connected to the connection point between the input end of the low-temperature gas-liquid separator and the S port of the second four-way valve; An input port of the second one-way valve is connected to the second end of the intermediate heat exchanger, and an output port of the second one-way valve is connected between the control valve and the first throttle valve.

6. The cascade high-temperature hot water system according to claim 4, characterized in that: The first throttle valve and the second throttle valve are both electronic expansion valves.

7. The cascade high-temperature hot water system according to claim 4, characterized in that: The control valve is a solenoid valve.

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