Variable-working-condition self-adaptive cold and heat combined supply environment-friendly heat pump system and control method thereof

Abstract

The invention discloses a variable-working-condition self-adaptive cold and heat combined supply environment-friendly heat pump system and a control method thereof, and belongs to the technical field of heat pump cold and heat combined supply. Through multi-mode circulation switching and combined with the enhanced vapor injection module, the system adapts to wide-range environment temperature and load changes, the cross-working-condition circulation stability is remarkably improved, and the problem that an existing system is poor in variable-working-condition circulation adaptation is solved; through collaborative design of the grading air supply module and the heat regenerator, low-pressure side air supply optimizes interstage pressure matching, high-pressure side air supply improves the compression efficiency, supercooling and superheating energy collaborative optimization is achieved through the heat regenerator, the refrigerating energy efficiency and the heating energy efficiency are remarkably improved, and the comprehensive energy efficiency performance is excellent. Rapid function switching between modules is achieved through valves, automatic control and response of a unit are facilitated, and energy consumption of the unit is reduced; an energy closed loop combining waste heat recovery and power consumption recovery is constructed, and the energy utilization rate of the system is increased; the system is suitable for residences, commercial buildings, industrial factory buildings and other scenes with large cold and heat demand fluctuation and wide environment temperature span.

Description

Technical Field

[0001] This invention relates to the field of heat pump combined cooling and heating technology, specifically to an environmentally friendly heat pump system with adaptive cooling and heating under varying operating conditions and its control method. Background Technology

[0002] Current state of technology: (1) Application trend of environmentally friendly working fluid: CO2, as an environmentally friendly working fluid with a global warming potential (GWP) of 1 and an ozone depletion potential (ODP) of 0, is increasingly widely used in the field of heat pumps. Its transcritical cycle characteristics are suitable for high water temperature heating and wide temperature range operation.

[0003] (2) Existing structural foundation: Heat pump structures such as two-stage compression with intermediate gas injection, main and auxiliary circuit combination, and modular units have emerged, and load regulation is achieved through multi-compressor coordination and valve switching.

[0004] (3) Development of control technology: Some systems use thermostatic expansion valves and bypass valves to regulate superheat, or use variable frequency compressors and PID algorithms to adjust parameters and optimize operation under subcritical, supercritical and other conditions.

[0005] The shortcomings of existing technology: (1) Limitations of operating condition adaptation: Existing systems are mostly designed for a single operating condition, and the start / stop program is set according to the compressor pressure to realize the algorithm operation. They lack accurate adaptation to all operating conditions with a large temperature difference range, and the energy efficiency fluctuates greatly when switching between operating conditions.

[0006] (2) Single superheat control: Relying solely on single superheat regulation can easily lead to compressor overheating under high return water / ambient temperature and insufficient heat exchange efficiency under low temperature.

[0007] (3) Low-load operation is inefficient: Due to the minimum speed limit of the compressor, it starts and stops frequently at low load, resulting in high energy consumption and shortened equipment life.

[0008] (4) Insufficient coordinated control: The gas supply parameters, compressor operation and heat exchange area adjustment lack coupling logic, the response to changing operating conditions is lagging, and the matching is unbalanced when switching between cold and hot demand. Summary of the Invention

[0009] To address the problems existing in the prior art, this invention proposes an environmentally friendly heat pump system with adaptive cooling and heating under varying operating conditions and its control method. It is suitable for scenarios with large fluctuations in cooling and heating demand and a wide range of ambient temperatures (-30℃~35℃), such as residential buildings, commercial buildings, and industrial plants. It can achieve separate or simultaneous supply of cooling and heating, and is especially suitable for scenarios with dynamic load changes (10%~100%).

[0010] One objective of this invention is to propose an environmentally friendly combined cooling and heating heat pump system that adapts to varying operating conditions.

[0011] The variable operating condition adaptive combined cooling and heating environmentally friendly heat pump system of the present invention includes: a gas-liquid separator, first to third heat exchangers, a medium-pressure compressor, a high-pressure compressor, a regenerator, first to third three-way valves, an ejector, an expansion valve, a four-way reversing valve, and a controller; wherein, the liquid outlet of the gas-liquid separator is connected to the first heat exchanger via the first three-way valve and to the second heat exchanger via the expansion valve; the first heat exchanger is connected to the four-way reversing valve; the second heat exchanger is connected to the four-way reversing valve via the second three-way valve and to the four-way reversing valve via the medium-pressure compressor; the four-way reversing valve is connected to the ejector, forming a staged gas replenishment module; The ejector is connected to the inlet of the gas-liquid separator; the gas outlet of the gas-liquid separator is connected in sequence to the heat recovery side of the regenerator, the high-pressure compressor, the third heat exchanger, the waste heat release side of the regenerator and the ejector, and the regenerator and ejector constitute the jet enthalpy enhancement module. The third heat exchanger is also connected to the waste heat release side of the regenerator via a third three-way valve; The first to third three-way valves and the expansion valve are connected to the controller.

[0012] The liquid outlet at the bottom of the gas-liquid separator is connected to the first port of the first three-way valve. The second port of the first three-way valve is connected to the working fluid inlet of the first heat exchanger. The working fluid outlet of the first heat exchanger is connected to the first port of the four-way reversing valve. The second port of the four-way reversing valve is connected to the secondary flow inlet of the ejector. The third port of the first three-way valve is connected to the working fluid inlet of the second heat exchanger via an expansion valve. The working fluid outlet of the second heat exchanger is connected to the first port of the second three-way valve. The second port is connected to the fourth port of the four-way reversing valve. The third port of the second three-way valve is connected to the low-pressure side of the medium-pressure compressor. The high-pressure side of the medium-pressure compressor is connected to the third port of the four-way reversing valve.

[0013] The gas outlet at the top of the gas-liquid separator is connected to the heat recovery inlet of the regenerator, and the heat recovery outlet of the regenerator is connected to the low-pressure side of the high-pressure compressor. The high-pressure side of the high-pressure compressor is connected to the working fluid inlet of the third heat exchanger, and the working fluid outlet of the third heat exchanger is connected to the first port of the third three-way valve. The second port of the third three-way valve is connected to the waste heat release inlet of the regenerator, and the waste heat release outlet of the regenerator is connected to the primary flow inlet of the ejector. The third end of the third three-way valve is connected to the working fluid inlet of the second heat exchanger, and the working fluid outlet of the second heat exchanger is also connected to the waste heat release inlet of the regenerator. The nozzle of the ejector is connected to the inlet of the gas-liquid separator.

[0014] The other pair of inlets and outlets of the first heat exchanger serves as water inlets and outlets, connecting to an external water source; the other pair of inlets and outlets of the second heat exchanger serves as air inlets and outlets, connecting to external air; the other pair of inlets and outlets of the third heat exchanger serves as water inlets and outlets, connecting to an external water source. The working fluid is CO2.

[0015] Another objective of this invention is to propose a control method for an environmentally friendly combined cooling and heating heat pump system that adapts to varying operating conditions.

[0016] The control method of the variable operating condition adaptive combined cooling and heating environmentally friendly heat pump system of the present invention has three different circulation modes according to the ambient temperature: 1) Refrigeration cycle (ambient temperature 26℃~35℃): The first port of the first three-way valve is open, the second port is open, and the third port is closed; the second three-way valve is closed, and the expansion valve is closed. The liquid CO2 from the gas-liquid separator enters the first heat exchanger through the first three-way valve, absorbs heat from the external water source, evaporates and changes into gaseous CO2, and the external water source is cooled down. The cooled water is used to supply the terminal refrigeration. The gaseous CO2 after phase change passes through the four-way reversing valve and is injected into the gas-liquid separator by the ejector for medium-pressure side circulation. When producing domestic hot water: The first port of the third three-way valve is open, the second port is open, and the third port is closed; The gaseous CO2 from the gas-liquid separator absorbs heat in the regenerator and enters the high-pressure compressor to become high-temperature and high-pressure gaseous CO2. It then enters the third heat exchanger to release heat and heat the water from the tap to produce hot water (around 50°C) for users. Afterward, it enters the regenerator through the third three-way valve. After recovering heat through the regenerator, it enters the ejector. After the gas and liquid mix and increase enthalpy, it returns to the gas-liquid separator for high-pressure side circulation. When hot water is not needed for domestic use: The first port of the third three-way valve is open, the second port is closed, and the third port is open; The gaseous CO2 from the gas-liquid separator absorbs heat through the regenerator and enters the high-pressure compressor to become high-temperature and high-pressure gaseous CO2. It then passes through the third heat exchanger and enters the second heat exchanger through the third three-way valve to release heat to the outside air. After that, it enters the waste heat release inlet of the regenerator, recovers heat through the regenerator, and enters the ejector. After the gas and liquid mix and increase enthalpy, it returns to the gas-liquid separator. 2) Single-stage heating cycle (-10℃ < ambient temperature < 16℃): The first three-way valve has its first port open, the second port closed, and the third port open; the second three-way valve has its first port open, the second port open, and the third port closed; the third three-way valve has its first port open, the second port open, and the third port closed. The liquid CO2 from the gas-liquid separator enters the second heat exchanger through the first three-way valve and the expansion valve to exchange heat with the outside air and undergo phase change evaporation. The air is discharged into the atmosphere. The gaseous CO2 after phase change is injected into the gas-liquid separator by the ejector through the second three-way valve and the four-way reversing valve. The gaseous CO2 from the gas-liquid separator absorbs heat through the regenerator, enters the high-pressure compressor and becomes high-temperature, high-pressure gaseous CO2, enters the third heat exchanger to release heat to the heating water, and replaces it with high-temperature heating water (>65℃). The condensed two-phase CO2 passes through the third three-way valve, recovers heat through the regenerator and enters the ejector. After the gas and liquid mix and increase enthalpy, it returns to the gas-liquid separator for high-pressure side circulation. 3) Two-stage heating circulation (-30℃ < ambient temperature < 16℃): The first three-way valve has its first to third ports open; the second three-way valve has its first to third ports open; the third three-way valve has its first port open, its second port open, and its third port closed. In dual-stage operation, the first and second heat exchangers act as evaporators. Liquid CO2 from the gas-liquid separator enters the first and second heat exchangers respectively through the first three-way valve to undergo evaporation and phase change. Critical-state CO2 exits from the first heat exchanger and enters the ejector through the four-way reversing valve. Critical-state CO2 exits from the second heat exchanger and enters the medium-pressure compressor through the second three-way valve. After pressurization, gaseous CO2 enters the ejector through the four-way reversing valve and is injected into the gas-liquid separator. The system's energy efficiency is controlled by adjusting the flow rates of the first and second heat exchangers. The gaseous CO2 from the gas-liquid separator absorbs heat through the regenerator and enters the high-pressure compressor to become high-temperature, high-pressure gaseous CO2. It then enters the third heat exchanger to release heat to the heating water, replacing it with high-temperature heating water (>70℃). The condensed two-phase CO2 passes through the third three-way valve and the regenerator to recover heat before entering the gas-liquid separator through the ejector. After the gas and liquid mix and increase enthalpy, the CO2 returns to the gas-liquid separator for high-pressure side circulation.

[0017] Advantages of this invention: (1) Significantly improved adaptability to variable operating conditions: This invention, through multi-mode cycle switching and combined with the jet enthalpy enhancement module, can adapt to a wide range of ambient temperature and load changes, significantly improving cross-operating condition cycle stability and solving the problem of poor adaptability to variable operating conditions in existing systems. (2) The cycle energy efficiency is greatly improved: Through the coordinated design of the staged gas injection module and the regenerator, the gas injection on the medium-pressure side optimizes the interstage pressure matching, the gas injection on the high-pressure side improves the compression efficiency, and the regenerator realizes the energy synergistic optimization of subcooling and superheating. The cooling and heating energy efficiency are significantly improved, and the overall energy efficiency is excellent. (3) The rapid switching of functions between modules is facilitated by valves, which is beneficial to the automatic control and response of the unit. At the same time, the unit's energy consumption is saved by utilizing the thermal inertia of the terminal, rather than relying solely on intelligent software control. (4) Comprehensive improvement in energy utilization: Constructing a closed-loop energy system that integrates waste heat recovery and power consumption recovery, maximizing the recovery of recycled energy, realizing the cascade utilization of energy, and significantly improving the system's energy utilization rate; (5) It combines environmental protection and practicality: it adopts natural and environmentally friendly working fluid, has no risk of ozone layer depletion, and meets environmental protection requirements; the system has a modular design, clear circulation path, supports seamless switching between cooling and heating modes, is suitable for various application scenarios, and is easy to operate and maintain. Attached Figure Description

[0018] Figure 1 This is a connection block diagram of an embodiment of the variable operating condition adaptive combined cooling and heating environmentally friendly heat pump system of the present invention. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0020] like Figure 1 As shown, the variable operating condition adaptive combined cooling and heating environmentally friendly heat pump system of this embodiment includes: a gas-liquid separator, first to third heat exchangers, a medium-pressure compressor, a high-pressure compressor, a regenerator, first to third three-way valves, an ejector, an expansion valve, a four-way reversing valve, and a controller; wherein, the liquid outlet located at the bottom of the gas-liquid separator is connected to the first port of the first three-way valve, and the second port of the first three-way valve is connected to the working fluid inlet of the first heat exchanger; the working fluid outlet of the first heat exchanger is connected to the first port of the four-way reversing valve, and the second port of the four-way reversing valve is connected to the secondary flow inlet of the ejector; the third port of the first three-way valve is connected to the working fluid inlet of the second heat exchanger via the expansion valve, the working fluid outlet of the second heat exchanger is connected to the first port of the second three-way valve, and the second port is connected to the fourth port of the four-way reversing valve; the third port of the second three-way valve is connected to the low-pressure side of the medium-pressure compressor, and the high-pressure side of the medium-pressure compressor is connected to the third port of the four-way reversing valve, forming a staged gas replenishment module; The gas outlet at the top of the gas-liquid separator is connected to the heat recovery inlet of the regenerator, and the heat recovery outlet of the regenerator is connected to the low-pressure side of the high-pressure compressor. The high-pressure side of the high-pressure compressor is connected to the working fluid inlet of the third heat exchanger, and the working fluid outlet of the third heat exchanger is connected to the first port of the third three-way valve. The second port of the third three-way valve is connected to the waste heat release inlet of the regenerator, and the waste heat release outlet of the regenerator is connected to the primary flow inlet of the ejector. The third end of the third three-way valve is connected to the working fluid inlet of the second heat exchanger, and the working fluid outlet of the second heat exchanger is also connected to the waste heat release inlet of the regenerator. The nozzle of the ejector is connected to the inlet of the gas-liquid separator. The regenerator and the ejector constitute a jet enthalpy-enhancing module, which forms a high-pressure side circulation, and the working fluid is CO2. The first to third three-way valves and the expansion valve are connected to the controller.

[0021] The other pair of inlets and outlets of the first heat exchanger serves as the water source inlet and outlet, connected to the water source via water pipes. Whether for cooling or heating, the first heat exchanger acts as the evaporator, transferring heat from the external water source to the working fluid. The external water source is cooled, and the cooled water flows to the end user. In a cooling cycle, it provides cooling to the end user; in a single-stage heating cycle, it does not operate; in a two-stage heating cycle, the cooled water returns to the storage tank. The other pair of inlets and outlets of the second heat exchanger serves as the air inlet and outlet, connected to the external air. In a cooling cycle, when domestic hot water is not needed, the working fluid exiting the third heat exchanger is too hot and passes through the second heat exchanger to continue releasing heat to the external air. The heated air is directly discharged into the atmosphere. In a single-stage heating cycle, the working fluid in the second heat exchanger absorbs heat from the air, and the cooled air is directly discharged into the atmosphere. In a two-stage heating cycle, both the first and second heat exchangers operate simultaneously. The working fluid in the second heat exchanger absorbs heat from the air, and the cooled air is discharged into the atmosphere. The other pair of inlets and outlets of the third heat exchanger are connected to the water source inlet and outlet, connecting to external water. After exchanging energy and heating in the third heat exchanger, the water is supplied to the end users as hot water. Users switch between different water sources at the end based on the ambient temperature. In the cooling cycle, the end is connected to the tap water pipe, and the working fluid in the third heat exchanger exchanges heat with the water to produce hot water for domestic use. In the single-stage heating cycle, it is connected to the circulating heating water, and the working fluid in the third heat exchanger heats the 40-50℃ water to a temperature above 65℃, which is then supplied to the users for heating. In the two-stage heating cycle, it is connected to the circulating heating water, and the working fluid in the third heat exchanger heats the heating water to a temperature above 70℃, which is then supplied to the users for heating.

[0022] The control method of the variable operating condition adaptive combined cooling and heating environmentally friendly heat pump system in this embodiment involves the controller automatically switching between three different circulation modes based on the ambient temperature: 1) Refrigeration cycle (ambient temperature 26℃~35℃) includes both domestic hot water production and non-domestic hot water production: The first port of the first three-way valve is open, the second port is open, and the third port is closed; the second three-way valve is closed, and the expansion valve is closed. Liquid CO2 from the gas-liquid separator enters the first heat exchanger through the first three-way valve, where it absorbs heat from the external water source and evaporates into gaseous CO2. The external water source is cooled down, and the cooled water is supplied to the terminal refrigeration unit. The gaseous CO2 after phase change goes to the four-way reversing valve, where the pressure difference guides the fluid to the second port. The low-pressure CO2 enters the ejector as a secondary flow, and the CO2 circulates on the medium-pressure side. When producing domestic hot water: The first port of the third three-way valve is open, the second port is open, and the third port is closed; The gaseous CO2 from the gas-liquid separator absorbs heat in the regenerator and enters the high-pressure compressor to become high-temperature and high-pressure gaseous CO2. It then enters the third heat exchanger to release heat and heat the water from the tap to produce hot water (around 50°C) for users. Subsequently, it enters the regenerator through the third three-way valve, where it recovers heat. The high-pressure CO2 enters the ejector as a primary stream. After the gas and liquid mix and increase in enthalpy, it is injected by the ejector into the gas-liquid separator, where the CO2 undergoes high-pressure side circulation. When hot water is not needed for domestic use: The first port of the third three-way valve is open, the second port is closed, and the third port is open; The gaseous CO2 from the gas-liquid separator absorbs heat through the regenerator and enters the high-pressure compressor to become high-temperature and high-pressure gaseous CO2. It then passes directly through the third heat exchanger without exchanging heat with an external energy source. After passing through the third three-way valve, it enters the second heat exchanger to release heat to the outdoor air. Subsequently, it enters the waste heat release inlet of the regenerator, recovers heat through the regenerator, and then enters the ejector. After the gas and liquid mix and increase enthalpy, it returns to the gas-liquid separator. 2) Single-stage heating cycle (-10℃ < ambient temperature < 16℃): The first three-way valve has its first port open, the second port closed, and the third port open; the second three-way valve has its first port open, the second port open, and the third port closed; the third three-way valve has its first port open, the second port open, and the third port closed. The liquid CO2 from the gas-liquid separator enters the second heat exchanger through the first three-way valve and the expansion valve to exchange heat with the outside air and undergo phase change evaporation. The air is discharged into the atmosphere. The gaseous CO2 after phase change is injected into the gas-liquid separator by the ejector through the second three-way valve and the four-way reversing valve. The gaseous CO2 from the gas-liquid separator absorbs heat through the regenerator and enters the high-pressure compressor to become high-temperature and high-pressure gaseous CO2. It then enters the third heat exchanger to release heat to the 40-50°C heating water and exchange it for high-temperature heating water above 65°C. The condensed two-phase CO2 passes through the third three-way valve and the regenerator to recover heat before entering the ejector. After the gas and liquid mix and increase enthalpy, it returns to the gas-liquid separator, and the CO2 undergoes high-pressure side circulation. 3) Two-stage heating circulation (-30℃ < ambient temperature < 16℃): The first three-way valve has its first to third ports open; the second three-way valve has its first to third ports open; the third three-way valve has its first port open, its second port open, and its third port closed. The system operates in a dual-stage configuration. In this mode, the first and second heat exchangers function as evaporators, with the evaporation temperature determined by the ambient temperature. Liquid CO2 from the gas-liquid separator enters the first and second heat exchangers respectively through the first three-way valve. In the first heat exchanger, the evaporation temperature is >2°C, and the external water source is cooled, returning to the storage tank. In the second heat exchanger, the cooled air is released to the atmosphere. Critical-state CO2 exits the first heat exchanger and enters the ejector through the four-way reversing valve, and exits the second heat exchanger and enters the medium-pressure compressor through the second three-way valve. After pressurization, gaseous CO2 enters the ejector through the four-way reversing valve and is injected into the gas-liquid separator. The flow rates of the first and second heat exchangers are controlled by adjusting the opening amounts of the second and third ports of the first three-way valve, thus controlling the system's energy efficiency. The gaseous CO2 from the gas-liquid separator absorbs heat through the regenerator and enters the high-pressure compressor to become high-temperature, high-pressure gaseous CO2. It then enters the third heat exchanger to release heat to the 40-50°C heating water and exchange it for high-temperature heating water above 70°C. The condensed two-phase CO2 passes through the third three-way valve and recovers heat through the regenerator before entering the gas-liquid separator through the ejector. After the gas and liquid mix and increase in enthalpy, the CO2 returns to the gas-liquid separator, and the CO2 undergoes high-pressure side circulation.

[0023] Finally, it should be noted that the purpose of disclosing the embodiments is to help further understand the present invention. However, those skilled in the art will understand that various substitutions and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the present invention should not be limited to the content disclosed in the embodiments, and the scope of protection of the present invention is defined by the claims.

Claims

1. A variable-condition adaptive combined cooling and heating environmentally friendly heat pump system, characterized in that, The combined cooling and heating environmentally friendly heat pump system includes: a gas-liquid separator, first to third heat exchangers, a medium-pressure compressor, a high-pressure compressor, a regenerator, first to third three-way valves, an ejector, an expansion valve, a four-way directional valve, and a controller; wherein, the liquid outlet of the gas-liquid separator is connected to the first heat exchanger via the first three-way valve and to the second heat exchanger via the expansion valve; the first heat exchanger is connected to the four-way directional valve; the second heat exchanger is connected to the four-way directional valve via the second three-way valve and to the four-way directional valve via the medium-pressure compressor; the four-way directional valve is connected to the ejector, forming a staged gas replenishment module; The ejector is connected to the inlet of the gas-liquid separator; the gas outlet of the gas-liquid separator is connected in sequence to the heat recovery side of the regenerator, the high-pressure compressor, the third heat exchanger, the waste heat release side of the regenerator and the ejector, and the regenerator and ejector constitute the jet enthalpy enhancement module. The third heat exchanger is also connected to the waste heat release side of the regenerator via a third three-way valve; The first to third three-way valves and the expansion valve are connected to the controller.

2. The combined cooling and heating environmentally friendly heat pump system according to claim 1, characterized in that, The liquid outlet at the bottom of the gas-liquid separator is connected to the first port of the first three-way valve. The second port of the first three-way valve is connected to the working fluid inlet of the first heat exchanger. The working fluid outlet of the first heat exchanger is connected to the first port of the four-way reversing valve. The second port of the four-way reversing valve is connected to the secondary flow inlet of the ejector. The third port of the first three-way valve is connected to the working fluid inlet of the second heat exchanger via an expansion valve. The working fluid outlet of the second heat exchanger is connected to the first port of the second three-way valve. The second port is connected to the fourth port of the four-way reversing valve. The third port of the second three-way valve is connected to the low-pressure side of the medium-pressure compressor. The high-pressure side of the medium-pressure compressor is connected to the third port of the four-way reversing valve.

3. The combined cooling and heating environmentally friendly heat pump system according to claim 2, characterized in that, The gas outlet at the top of the gas-liquid separator is connected to the heat recovery inlet of the regenerator, and the heat recovery outlet of the regenerator is connected to the low-pressure side of the high-pressure compressor. The high-pressure side of the high-pressure compressor is connected to the working fluid inlet of the third heat exchanger, and the working fluid outlet of the third heat exchanger is connected to the first port of the third three-way valve. The second port of the third three-way valve is connected to the waste heat release inlet of the regenerator, and the waste heat release outlet of the regenerator is connected to the primary flow inlet of the ejector. The third end of the third three-way valve is connected to the working fluid inlet of the second heat exchanger, and the working fluid outlet of the second heat exchanger is also connected to the waste heat release inlet of the regenerator. The nozzle of the ejector is connected to the inlet of the gas-liquid separator.

4. The combined cooling and heating environmentally friendly heat pump system according to claim 1, characterized in that, The other pair of inlets and outlets of the first heat exchanger serve as water inlets and outlets, connecting to an external water source; the other pair of inlets and outlets of the second heat exchanger serve as air inlets and outlets, connecting to external air; and the other pair of inlets and outlets of the third heat exchanger serve as water inlets and outlets, connecting to an external water source.

5. A control method for a variable operating condition adaptive combined cooling and heating environmentally friendly heat pump system according to claim 1, characterized in that, The control method includes three cyclic modes: 1) Refrigeration cycle: Liquid CO2 from the gas-liquid separator is sequentially injected back into the gas-liquid separator through the first three-way valve, the first heat exchanger, the four-way reversing valve, and the ejector for medium-pressure side circulation; the first heat exchanger provides cooling to the terminal. When producing domestic hot water: The gaseous CO2 from the gas-liquid separator passes sequentially through the regenerator, high-pressure compressor, third heat exchanger, third three-way valve, regenerator, and ejector before being injected back into the gas-liquid separator for high-pressure side circulation; the third heat exchanger provides domestic hot water. When hot water is not needed for domestic use: Gaseous CO2 passes through the regenerator and high-pressure compressor, then through the third heat exchanger, and through the third three-way valve into the second heat exchanger to release heat to the outside air. It then enters the waste heat release inlet of the regenerator, and through the regenerator enters the ejector to be injected into the gas-liquid separator. 2) Single-stage heating cycle: Liquid CO2 enters the second heat exchanger through the first three-way valve and the expansion valve to exchange heat with the outside air and undergo phase change evaporation. The air is discharged into the atmosphere. The gaseous CO2 after phase change passes through the second three-way valve and the four-way reversing valve and is injected into the gas-liquid separator by the ejector. Gaseous CO2 is circulated on the high-pressure side, and the third heat exchanger provides heating water; 3) Two-stage heating cycle: Liquid CO2 enters the first heat exchanger and the second heat exchanger through the first three-way valve and undergoes evaporation and phase change. Critical CO2 exits from the first heat exchanger and enters the ejector through the four-way reversing valve. Critical CO2 exits from the second heat exchanger and enters the medium-pressure compressor through the second three-way valve. After being pressurized, gaseous CO2 enters the ejector through the four-way reversing valve and is injected into the gas-liquid separator by the ejector. Gaseous CO2 is circulated on the high-pressure side, and the third heat exchanger provides heating water.

6. The control method according to claim 5, characterized in that, The high-pressure side circulation includes: gaseous CO2 from the gas-liquid separator absorbs heat through the regenerator and enters the high-pressure compressor to become high-temperature and high-pressure gaseous CO2; it enters the third heat exchanger to release heat and heat water to produce hot water, which then enters the regenerator through the third three-way valve. After recovering heat through the regenerator, it enters the ejector, and after the gas and liquid mix and increase enthalpy, it returns to the gas-liquid separator.

7. The control method according to claim 5, characterized in that, The medium-pressure side circulation includes: liquid CO2 from the gas-liquid separator enters the first heat exchanger through the first three-way valve, absorbs heat from the external water source and evaporates into gaseous CO2, the external water source is cooled down, and the cooled water is provided to the terminal refrigeration; the gaseous CO2 after phase change passes through the four-way reversing valve and is injected into the gas-liquid separator by the ejector.

8. The control method according to claim 5, characterized in that, The ambient temperature for the refrigeration cycle is 26℃~35℃. During the refrigeration cycle, the first port of the first three-way valve is open, the second port is open, and the third port is closed; the second three-way valve is closed, and the expansion valve is closed. When producing domestic hot water, the first port of the third three-way valve is open, the second port is open, and the third port is closed. When domestic hot water is not required, the first port of the third three-way valve is open, the second port is closed, and the third port is open.

9. The control method according to claim 5, characterized in that, The ambient temperature for a single-stage heating cycle is -10℃ to 16℃. Under a single-stage heating cycle, the first port of the first three-way valve is open, the second port is closed, and the third port is open; the first port of the second three-way valve is open, the second port is open, and the third port is closed; the first port of the third three-way valve is open, the second port is open, and the third port is closed.

10. The control method according to claim 5, characterized in that, The ambient temperature for the two-stage heating cycle is -30℃ to 16℃. Under the two-stage heating cycle, the first to third ports of the first three-way valve are open; the first to third ports of the second three-way valve are open; the first port of the third three-way valve is open, the second port is open, and the third port is closed.

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