Heat pump system and control method therefor

Abstract

A heat pump system, which comprises at least one heat pump indoor unit. The heat pump indoor unit comprises a cascade heat exchanger (11) and a terminal heat exchanger assembly (16). The cascade heat exchanger (11) comprises a first heat exchange portion (12) and a second heat exchange portion (14), wherein the first heat exchange portion (12) is connected to a low-temperature-stage circulation pipeline (13), and there is a first refrigerant in the low-temperature-stage circulation pipeline (13); and the second heat exchange portion (14) is connected to a high-temperature-stage circulation pipeline (15), there is a second refrigerant in the high-temperature-stage circulation pipeline (15), and the second heat exchange portion (14) is configured to exchange heat with the first heat exchange portion (12). The terminal heat exchanger assembly (16) comprises a third heat exchange portion (18), a fourth heat exchange portion (19) and a terminal heat exchange portion (17), wherein the third heat exchange portion (18) is connected to the low-temperature-stage circulation pipeline (13); the fourth heat exchange portion (19) is connected to the high-temperature-stage circulation pipeline (15); and the terminal heat exchange portion (17) is connected to an indoor end apparatus, and is configured to exchange heat with the third heat exchange portion (18), or exchange heat with the fourth heat exchange portion (19), or exchange heat with the third heat exchange portion (18) and the fourth heat exchange portion (19).

Description

[0001] This application claims priorities to Chinese Patent Application No. 202110639064.6, filed on June 8, 2021; Chinese Patent Application No. 202110709626.X, filed on June 25, 2021; Chinese Patent Application No. 202123050748.7, filed on December 7, 2021; and Chinese Patent Application No. 202210374161.1, filed on April 11, 2022, which are incorporated herein by reference in their entireties.TECHNICAL FIELD

[0002] The present disclosure relates to the field of heat pump technologies, and in particular, to a heat pump system and a control method of a heat pump system.BACKGROUND

[0003] Heat pump systems uses electric energy as a driving power and uses outdoor ambient air as a heat source to provide heat to the adjusted object. Compared with electric water heaters and gas water heaters, the heat pump systems have characteristics of high energy efficiency and low energy consumption, so that the heat pump systems have received widespread attention in the industry.SUMMARY

[0004] In an aspect, some embodiments of the present disclosure provide a heat pump system. The heat pump system includes at least one heat pump indoor unit. The heat pump indoor unit includes a cascade heat exchanger and a terminal heat exchanger assembly. The cascade heat exchanger includes: a first heat exchange portion and a second heat exchange portion. The first heat exchange portion is connected to a low-temperature-stage circulation pipeline, and there is a first refrigerant in the low-temperature-stage circulation pipeline. The second heat exchange portion is connected to a high-temperature-stage circulation pipeline, and there is a second refrigerant in the high-temperature-stage circulation pipeline, and the second heat exchange portion is configured to perform heat exchange with the first heat exchange portion. The terminal heat exchanger assembly includes: a third heat exchange portion, a fourth heat exchange portion, and a terminal heat exchange portion. The third heat exchange portion is connected to the low-temperature-stage circulation pipeline. The fourth heat exchange portion is connected to the high-temperature-stage circulation pipeline. The terminal heat exchange portion is connected to an indoor end apparatus, and the terminal heat exchange portion is configured to perform heat exchange with the third heat exchange portion, or the fourth heat exchange portion, or the third heat exchange portion and the fourth heat exchange portion.

[0005] In another aspect, some embodiments of the present disclosure further provide a control method of the above heat pump system. The heat pump system is any heat pump system described above. The control method of the heat pump system includes: determining whether the heat pump system satisfies a preset condition, and the preset condition including a low-temperature heating condition, a defrosting condition, a high-temperature heating condition or a rapid heating condition; controlling the terminal heat exchange portion to exchange heat with the third heat exchange portion if the heat pump system satisfies the low-temperature heating condition or the defrosting condition; controlling the terminal heat exchange portion to exchange heat with the fourth heat exchange portion if the heat pump system satisfies the high-temperature heating condition; controlling the terminal heat exchange portion to exchange heat with the third heat exchange portion and the fourth heat exchange portion if the heat pump system satisfies the rapid heating condition.BRIEF DESCRIPTION OF THE DRAWINGS

[0006] In order to describe the technical solutions in the present disclosure more clearly, accompanying drawings to be used in some embodiments of the present disclosure will be introduced briefly below. However, the accompanying drawings to be described below are merely accompanying drawings of some embodiments of the present disclosure, and a person of ordinary skill in the art may obtain other drawings according to these drawings. In addition, the accompanying drawings to be described below may be regarded as schematic diagrams but are not limitations on an actual size of a product, an actual process of a method, and an actual timing of a signal involved in the embodiments of the present disclosure. FIG. 1 is a diagram showing a structure of a heat pump system, in accordance with some embodiments; FIG. 2 is a diagram showing a structure of another heat pump system, in accordance with some embodiments; FIG. 3 is a schematic diagram showing a cycle of a refrigerant in a case where a heat pump system operates in a low-temperature heating mode, in accordance with some embodiments; FIG. 4 is a schematic diagram showing a cycle of a refrigerant in a case where a heat pump system operates in a defrosting mode, in accordance with some embodiments; FIG. 5A is a schematic diagram showing a cycle of a refrigerant in a case where a heat pump system operates in a high-temperature heating mode, in accordance with some embodiments; FIG. 5B is a schematic diagram showing a cycle of a refrigerant in a case where a heat pump system operates in a rapid heating mode, in accordance with some embodiments; FIG. 6A is a diagram showing a structure of yet another heat pump system, in accordance with some embodiments; FIG. 6B is a schematic diagram showing a cycle of a refrigerant in a case where a heat pump system operates in a high-temperature heating mode, in accordance with some embodiments; FIG. 7 is a diagram showing a structure of yet another heat pump system, in accordance with some embodiments; FIG. 8 is a diagram showing a structure of yet another heat pump system, in accordance with some embodiments; FIG. 9 is a diagram showing a structure of yet another heat pump system, in accordance with some embodiments; FIG. 10 is a diagram showing an operating principle of a heat pump system for producing medium-temperature water, in accordance with some embodiments; FIG. 11 is a diagram showing an operating principle of a heat pump system for producing high-temperature water, in accordance with some embodiments; FIG. 12 is a diagram showing an operating principle of a heat pump system for defrosting, in accordance with some embodiments; FIG. 13 is a diagram showing a structure of yet another heat pump system, in accordance with some embodiments; FIG. 14 is a diagram showing a structure of a heat pump system with a one-to-one online mode, in accordance with some embodiments; FIG. 15 is a diagram showing a structure of a heat pump system with a one-to-multi online mode, in accordance with some embodiments; FIG. 16 is a diagram showing a structure of another heat pump system with a one-to-multi online mode, in accordance with some embodiments; FIG. 17 is a diagram showing a structure of yet another heat pump system with a one-to-multi online mode, in accordance with some embodiments; FIG. 18 is a diagram showing a structure of yet another heat pump system, in accordance with some embodiments; FIG. 19 is a diagram showing an operating principle of a relay reversing device, in accordance with some embodiments; FIG. 20 is a diagram showing an operating principle of another relay reversing device, in accordance with some embodiments; FIG. 21 is a diagram showing a structure of yet another heat pump system, in accordance with some embodiments; FIG. 22 is a flow chart of emptying control of a water pump before a heat pump system performs a water pump characteristic test, in accordance with some embodiments; FIG. 23 is a flow chart of a water pump characteristic test performed by a heat pump system, in accordance with some embodiments; FIG. 24 is a curve diagram of a water pump characteristic test of a heat pump system, in accordance with some embodiments; FIG. 25 is a flow chart of emptying control of a water pump before a heat pump system performs a pipeline characteristic test, in accordance with some embodiments; FIG. 26 is a flow chart of a pipeline characteristic test performed by a heat pump system, in accordance with some embodiments; FIG. 27 is a curve diagram of a pipeline characteristic test of a heat pump system, in accordance with some embodiments; FIG. 28 is a flow chart of a constant rotational speed control of a heat pump system, in accordance with some embodiments; FIG. 29 is a curve diagram of a water pump and pipeline characteristic test of a heat pump system, in accordance with some embodiments; FIG. 30 is a flow chart of a constant flow rate control of a heat pump system, in accordance with some embodiments; FIG. 31 is a flow chart of a constant temperature difference control of a heat pump system, in accordance with some embodiments; and FIG. 32 is a flow chart of a control method of a heat pump system, in accordance with some embodiments. DETAILED DESCRIPTION

[0007] The technical solutions in some embodiments of the present disclosure will be clearly and completely described below with reference to the accompanying drawings. However, the described embodiments are merely some but not all embodiments of the present disclosure. All other embodiments obtained by a person of ordinary skill in the art based on embodiments of the present disclosure shall be included in the protection scope of the present disclosure.

[0008] A heat pump system may use outdoor ambient air or other media as a heat source, and uses a compressor, a condenser, a throttling device, and an evaporator to perform a refrigerant cycle, so as to provide heat to an indoor end apparatus. The present disclosure does not limit a type of the heat pump system, and the following embodiments are described by considering an example in which the heat pump system is an air source heat pump.

[0009] Generally, during the use of the air source heat pump, the air source heat pump cannot produce hot water from 55 °C to 60 °C or above due to limitation of a pressure ratio of the compressor and physical properties of the refrigerant. Moreover, in a case where an outdoor temperature decreases, the temperature of the water produced by the air source heat pump will also have a significant attenuation. For example, a maximum heating temperature of the air source heat pump reaches only 60 °C. Although the maximum heating temperature of the air source heat pump may meet most requirements of domestic hot water and winter heating, usage scenes such as hospitals, food, and hotels widely using high temperature water are still unable to directly produce high-temperature hot water at a temperature of 80 °C to 90 °C through traditional air source heat pump products. In order to produce high-temperature hot water, a cascade heat pump system may be used.

[0010] The cascade heat pump system includes a low-temperature-stage circulation system and a high-temperature-stage circulation system. The low-temperature-stage circulation system and the high-temperature-stage circulation system operate simultaneously to produce high-temperature hot water. However, the flexibility of the cascade heat pump system is poor. In a case where a set water temperature is low, the cascade heat pump system must also start the low-temperature-stage circulation system and the high-temperature-stage circulation system simultaneously, which will cause the high-temperature-stage circulation system to fail to generate sufficient pressure difference. As a result, the pressure ratio deviates from the normal operating range, which is not conducive to the reliable operation of the high-temperature-stage circulation system. Moreover, in the case where the set water temperature is low, starting the high-temperature-stage circulation system will cause high energy consumption of the cascade heat pump system.

[0011] Therefore, some embodiments of the present disclosure provide a heat pump system. As shown in FIG. 1, the heat pump system includes a heat pump indoor unit 10. The heat pump indoor unit 10 includes a cascade heat exchanger 11 and a terminal heat exchanger assembly 16.

[0012] In some embodiments, as shown in FIG. 1, the cascade heat exchanger 11 includes a first heat exchange portion 12 and a second heat exchange portion 14. The first heat exchange portion 12 is connected to a low-temperature-stage circulation pipeline 13, and there is a first refrigerant in the low-temperature-stage circulation pipeline 13. The second heat exchange portion 14 is connected to a high-temperature-stage circulation pipeline 15. There is a second refrigerant in the high-temperature-stage circulation pipeline 15, and the second heat exchange portion 14 is configured to exchange heat with the first heat exchange portion 12.

[0013] In some embodiments, the cascade heat exchanger 11 may also be referred to as an evaporative condenser. For example, according to differences in a cooling mode or a heating mode of the heat pump system, the first heat exchange portion 12 and the second heat exchange portion 14 in the cascade heat exchanger 11 have different functions. In a case where the heat pump system is heating, the first refrigerant in the first heat exchange portion 12 condenses and releases heat, and the second refrigerant in the second heat exchange portion 14 absorbs the heat released by the first refrigerant in the first heat exchange portion 12; in a case where the heat pump system is cooling, the first refrigerant in the first heat exchange portion 12 evaporates and absorbs heat, and the second refrigerant in the second heat exchange portion 14 exchanges heat with the first refrigerant in the first heat exchange portion 12.

[0014] For example, the first refrigerant and the second refrigerant may be same or different. For example, the first refrigerant and the second refrigerant each may be any one of refrigerants such as R410A, R134a, R12, R22, R32, R290, or R744. The following embodiments are described by considering an example in which the first refrigerant is R41 0A and the second refrigerant is R134a.

[0015] In some embodiments, as shown in FIG. 1, the terminal heat exchanger assembly 16 includes a terminal heat exchange portion 17, a third heat exchange portion 18, and a fourth heat exchange portion 19. The third heat exchange portion 18 is connected to the low-temperature-stage circulation pipeline 13, the fourth heat exchange portion 19 is connected to the high-temperature-stage circulation pipeline 15, and the terminal heat exchange portion 17 is connected to the indoor end apparatus. The terminal heat exchange portion 17 includes a medium to be heated, and the medium to be heated is mainly water. The indoor end apparatus may be a water terminal, such as a floor heating, a radiator or a water heater.

[0016] The terminal heat exchange portion 17 is configured to perform heat exchange with the third heat exchange portion 18, or perform heat exchange with the fourth heat exchange portion 19, or perform heat exchange with the third heat exchange portion 18 and the fourth heat exchange portion 19.

[0017] In some embodiments, operating modes of the heat pump system include but are not limited to the heating mode and the cooling mode. The heating mode includes but is not limited to a low-temperature heating mode, a high-temperature heating mode and a rapid heating mode. The cooling mode includes but is not limited to a defrosting mode. In a case where the heat pump system satisfies a low-temperature heating condition, the heat pump system operates in the low-temperature heating mode. The low-temperature heating condition includes but is not limited to that a set temperature (e.g., a water temperature required by a user) is lower than a first preset temperature, and the low-temperature heating mode may produce medium-temperature water. In a case where the heat pump system satisfies a high-temperature heating condition, the heat pump system operates in the high-temperature heating mode; the high-temperature heating condition includes but is not limited to that a set temperature is higher than a third preset temperature, and the high-temperature heating mode may produce high-temperature water. In a case where the heat pump system satisfies a defrosting condition, the heat pump system operates in the defrosting mode; the defrosting condition includes but is not limited to that a temperature of the terminal heat exchange portion 17 is higher than a second preset temperature. In a case where the heat pump system satisfies a rapid heating condition, the heat pump system operates in the rapid heating mode, and the rapid heating mode may also produce high-temperature water.

[0018] For example, the rapid heating mode means that the heat pump system needs to be heated up to a fourth preset temperature in short time. For example, in a case where the indoor end apparatus is a water heater, when the user uses the water heater, the heat pump system needs to complete heating in short time, so that the heat pump system enters the rapid heating mode.

[0019] In some embodiments, the operating modes of the heat pump system are related to instructions sent by the user, and parameters such as a water inlet temperature of the terminal heat exchange portion 17. For example, if an instruction for entering the rapid heating mode sent by the user is received and a water inlet temperature of a water circulation flow path is low, the heat pump system enters the rapid heating mode. For another example, if an instruction for defrosting sent by the user is received, the heat pump system enters the defrosting mode.

[0020] In the embodiments of the present disclosure, the term "lower" includes less than or equal to, and the term "higher" includes greater than or equal to.

[0021] In the embodiments of the present disclosure, the first preset temperature may be less than or equal to the third preset temperature. The embodiments of the present disclosure do not limit values of the first preset temperature, the second preset temperature, the third preset temperature, and the fourth preset temperature.

[0022] In a case where the heat pump system operates in the low-temperature heating mode, the low-temperature-stage circulation system operates, and the terminal heat exchange portion 17 exchanges heat with the third heat exchange portion 18. In a case where the heat pump system operates in the high-temperature heating mode, the high-temperature-stage circulation system operates, and the terminal heat exchange portion 17 exchanges heat with the fourth heat exchange portion 19. In a case where the heat pump system operates in the rapid heating mode, the low-temperature-stage circulation system and the high-temperature-stage circulation system operates simultaneously, and the terminal heat exchange portion 17 performs heat exchange with the third heat exchange portion 18 and the fourth heat exchange portion 19 simultaneously, so as to reach a temperature set by the user in short time. In a case where the heat pump system operates in the defrosting mode, the low-temperature-stage circulation system operates, and the terminal heat exchange portion 17 exchanges heat with the third heat exchange portion 18. The difference between the operation of the heat pump system in the defrosting mode and the operation of the heat pump system in the low-temperature heating mode is that a flow direction of the first refrigerant in the defrosting mode is opposite to that in the low-temperature heating mode.

[0023] There is no need for the heat pump system provided by the embodiments of the present disclosure to turn on the high-temperature-stage circulation system in the scene where the set water temperature is low, so as to avoid the problem that the high-temperature-stage circulation system cannot generate sufficient pressure difference, causing low reliability of system operation, thereby ensuring reliable operation of the heat pump system. Moreover, since the terminal heat exchange portion 17 may also perform heat exchange with the third heat exchange portion 18 connected to the low-temperature-stage circulation pipeline and the fourth heat exchange portion 19 connected to the high-temperature-stage circulation pipeline, the usage scene where the set water temperature is high may also be satisfied. Therefore, the heat pump system provided in the embodiments of the present disclosure has high flexibility and low energy consumption.

[0024] Some embodiments of the present disclosure further provide a heat pump system. As shown in FIG. 2, the heat pump system further includes a heat pump outdoor unit 1, and the heat pump outdoor unit 1 and the heat pump indoor unit 10 together form the high-temperature-stage circulation system and the low-temperature-stage circulation system. The heat pump outdoor unit 1 includes an outdoor heat exchanger 32, a second compressor 30 and a four-way valve 31. The outdoor heat exchanger 32, the second compressor 30 and the four-way valve 31 are connected with each other through the low-temperature-stage circulation pipeline 13. The outdoor heat exchanger 32 includes a finned heat exchanger. The second compressor 30 may also be referred to as a low-temperature-stage compressor. The second compressor 30 and a first compressor 33 may be same or different.

[0025] For example, the low-temperature-stage circulation system includes a low-temperature-stage circulation pipeline 13, and the low-temperature-stage circulation pipeline 13 has the first refrigerant R410A. The high-temperature-stage circulation system includes the high-temperature-stage circulation pipeline 15, and the high-temperature-stage circulation pipeline 15 has the second refrigerant R134a.

[0026] In some embodiments, the heat pump indoor unit 10 may further include a first valve element 22, a second valve element 23, and a third valve element 24. By controlling opening and closing of the first valve element 22, the second valve element 23, and the third valve element 24, it is possible for the heat pump system to control whether the high-temperature-stage circulation system operates according to actual usage requirements.

[0027] As shown in FIG. 2, the first valve element 22 is disposed between the first heat exchange portion 12 and the low-temperature-stage circulation pipeline 13, and the first valve element 22 is configured to adjust a flow rate of the first refrigerant entering the first heat exchange portion 12. The second valve element 23 is disposed between the second heat exchange portion 14 and the fourth heat exchange portion 19, and the second valve element 23 is configured to adjust a flow rate of the second refrigerant entering the second heat exchange portion 14 and the fourth heat exchange portion 19. The third valve element 24 is disposed between the third heat exchange portion 18 and the low-temperature-stage circulation pipeline 13, and the third valve element 24 is configured to adjust a flow rate of the first refrigerant entering the third heat exchange portion 18.

[0028] For example, the valve elements (e.g., the first valve element 22, the second valve element 23, and the third valve element 24) provided in the embodiments of the present disclosure are electronic expansion valves that may adjust an opening degree between a fully open position and a fully closed position. Operating states of the first valve element 22, the second valve element 23, and the third valve element 24 may include, for example, an opening state, a closed state, and a throttling state.

[0029] In some embodiments, the heat pump indoor unit 10 further includes a first compressor 33, and the first compressor 33 is connected to the high-temperature-stage circulation pipeline 15. The first compressor 33 may also be referred to as a high-temperature-stage compressor.

[0030] Operating principles of the heat pump system in different operating modes, and operating states of the first valve element 22, the second valve element 23, the third valve element 24, and the first compressor 33, will be described below considering an example in which the heat pump system operates in the low-temperature heating mode, the defrosting mode, the high-temperature heating mode and the rapid heating mode with reference to FIG. 2.

[0031] As shown in FIG. 3, in a case where the heat pump system operates in the low-temperature heating mode, the first compressor 33 stops (i.e., stops operating). The first valve element 22 is configured to operate in the closed state, so as to close a passage between the first heat exchange portion 12 and the low-temperature-stage circulation pipeline 13. The third valve element 24 is configured to operate in the open state, so as to open a passage between the third heat exchange portion 18 and the low-temperature-stage circulation pipeline 13. The first refrigerant in the outdoor heat exchanger 32 absorbs heat from the outdoor environment or other external media and evaporates, and then enters the second compressor 30 for compression, so as to obtain a high-temperature and high-pressure gaseous first refrigerant. The first refrigerant enters the low-temperature-stage circulation pipeline 13 of the heat pump system. Since the first valve element 22 closes the refrigerant passage between the first heat exchange portion 12 and the low-temperature-stage circulation pipeline 13, the first refrigerant cannot circulate through the first heat exchange portion 12, but enters the third heat exchange portion 18, and exchanges heat with the medium (e.g., water) in the terminal heat exchange portion 17. The first refrigerant releases heat in the third heat exchange portion 18, and heats water in the terminal heat exchange portion 17 to a set temperature, so as to achieve low-temperature-stage heating of the heat pump system. After the first refrigerant completes heating the medium in the terminal heat exchange portion 17, the first refrigerant flows out from the third heat exchange portion 18, and then returns to the heat pump outdoor unit 1 through the third valve element 24 in the open state. Then, the first refrigerant is throttled back to a low-temperature and low-pressure state by a throttling device 29 disposed in the heat pump outdoor unit 1. In a case where the heat pump system operates in the low-temperature heating mode, a flow path of the first refrigerant is shown as F1 in FIG. 3.

[0032] In a case where the heat pump system operates in the heating mode, the outdoor heat exchanger 32 is used as an evaporator. In a case where the outdoor temperature is low, frosting may occur on the outdoor heat exchanger 32. In order to improve the heating effect of the heat pump system, the medium in the terminal heat exchange portion 17 may transfer heat to the third heat exchange portion 18, so as to increase the temperature of the first refrigerant and improve a defrosting speed of the outdoor heat exchanger 32, thereby improving the heating effect of the heat pump system.

[0033] In some embodiments, in a case where the temperature of the terminal heat exchange portion 17 is higher than the second preset temperature, the heat pump system may operate in the defrosting mode. For example, in a case where the temperature of the terminal heat exchange portion 17 is greater than or equal to 8 °C, the heat pump system operates in the defrosting mode. The temperature of the terminal heat exchange portion 17 includes a temperature of water or other medium in the terminal heat exchange portion 17.

[0034] For example, the heat pump system may operate periodically in the defrosting mode. For example, if the temperature of the terminal heat exchange portion 17 is greater than or equal to 8 °C every 48 hours, the heat pump system enters the defrosting mode.

[0035] As shown in FIG. 4, in a case where the heat pump system operates in the defrosting mode, the first compressor 33 stops operating. The first valve element 22 is configured to operate in the closed state, so as to close the passage between the first heat exchange portion 12 and the low-temperature-stage circulation pipeline 13. The third valve element 24 is configured to operate in the throttling state. The four-way valve 31 in the low-temperature-stage circulation system changes a flow direction. The first refrigerant in the third heat exchange portion 18 exchanges heat with water in the terminal heat exchange portion 17, and evaporates after absorbing heat. Since the first valve element 22 closes the passage between the first heat exchange portion 12 and the low-temperature-stage circulation pipeline 13, the first refrigerant after absorbing heat is unable to enter the low-temperature-stage circulation pipeline 13 through the cascade heat exchanger 11, but flows into the outdoor heat exchanger 32 after being compressed in the second compressor 30, and releases heat in the outdoor heat exchanger 32 to complete defrosting. Then, the first refrigerant passes through the third valve element 24 in the throttling state and returns to the terminal heat exchange portion 17. In a case where the heat pump system operates in the defrosting mode, a flow path of the first refrigerant is shown as F3 in FIG. 4. It may be seen from FIGS. 3 and 4 that, the flow direction F3 of the first refrigerant in a case where the heat pump system operates in the defrosting mode is opposite to the flow direction F1 of the first refrigerant in a case where the heat pump system operates in the low-temperature heating mode. Therefore, the defrosting mode may also be referred to as a reverse cycle defrosting mode.

[0036] As shown in FIG. 5A, in a case where the heat pump system operates in the high-temperature heating mode, the first compressor 33 operates. The first valve element 22 is configured to operate in the open state, so as to open the passage between the first heat exchange portion 12 and the low-temperature-stage circulation pipeline 13. The second valve element 23 is configured to operate in the throttling state, so as to open the passage between the second heat exchange portion 14 and the fourth heat exchange portion 19. The third valve element 24 is configured to operate in the closed state, so as to close the passage between the third heat exchange portion 18 and the low-temperature-stage circulation pipeline 13. The first refrigerant in the outdoor heat exchanger 32 absorbs heat from the outdoor environment or other external media and evaporates, and then enters the second compressor 30 for compression. The obtained high-temperature and high-pressure gaseous first refrigerant enters the first heat exchange portion 12 in the cascade heat exchanger 11. In this case, the first heat exchange portion 12 operates in a condensation state, and the second heat exchange portion 14 operates in an evaporation state. After the second refrigerant in the second heat exchange portion 14 absorbs the heat released by the first refrigerant in the first heat exchange portion 12, the second refrigerant evaporates and enters the first compressor 33 for compression. The obtained high-temperature and high-pressure gaseous second refrigeration enters the fourth heat exchange portion 19, and exchanges heat with the water in the terminal heat exchange portion 17, so as to heat the water in the terminal heat exchange portion 17 to the set temperature, thereby achieving high-temperature heating of the heat pump system. In a case where the heat pump system operates in the high-temperature heating mode, a flow path of the first refrigerant is shown as F1 in FIG. 5A, and a flow path of the second refrigerant is shown as F2 in FIG. 5A.

[0037] As shown in FIG. 5B, in a case where the heat pump system operates in the rapid heating mode, the first valve element 22 is configured to operate in the open state, so as to open the passage between the first heat exchange portion 12 and the low-temperature-stage circulation pipeline 13. The second valve element 23 is configured to operate in the throttling state, so as to open the passage between the second heat exchange portion 14 and the fourth heat exchange portion 19. The third valve element 24 is configured to operate in the open state, so as to open the passage between the third heat exchange portion 18 and the low-temperature-stage circulation pipeline 13.

[0038] Therefore, the difference between the operation of the heat pump system in the rapid heating mode and the operation of the heat pump system in the high-temperature heating mode is that, the third valve element 24 is configured to operate in the open state in a case where the heat pump system operates in the rapid heating mode. As a result, the high-temperature and high-pressure gaseous first refrigerant compressed by the second compressor 30 may enter the first heat exchange portion 12 of the cascade heat exchanger 11, and also enter the third heat exchange portion 18 for heat exchange with the terminal heat exchange portion 17. The operating principle of the high-temperature and high-pressure gaseous first refrigerant entering the first heat exchange portion 12 of the cascade heat exchanger 11 for heat exchange is the same as that of the heat pump system operating in the high-temperature heating mode, and details will not be repeated herein. In the rapid heating mode, the high-temperature-stage circulation system and the low-temperature-stage circulation system may be used to heat the water in the terminal heat exchange portion 17 simultaneously, so as to achieve the purpose of rapid heating. In a case where the heat pump system operates in the rapid heating mode, a flow path of the first refrigerant is shown as F1 in FIG. 5B, and a flow path of the second refrigerant is shown as F2 in FIG. 5B.

[0039] In some embodiments, corresponding stop valves (27, 28) and valves (25, 26) may also be arranged at connecting pipelines between the heat pump indoor unit 10 and the heat pump outdoor unit 1. The terminal heat exchange portion 17 may also be correspondingly provided with valves (20, 21) or valves (not shown in FIG. 2) for controlling connection of waterways.

[0040] In some embodiments, the terminal heat exchange portion 17 may further include a first terminal heat exchange sub-portion 36 and a second terminal heat exchange sub-portion 37. The first terminal heat exchange sub-portion 36 communicates with the second terminal heat exchange sub-portion 37 in series.

[0041] As shown in FIG. 6A, the terminal heat exchanger assembly 16 may include a first terminal heat exchanger 34 and a second terminal heat exchanger 35. The first terminal heat exchanger 34 and the second terminal heat exchanger 35 may be, for example, a water fluorine heat exchanger. The first terminal heat exchanger 34 includes the first terminal heat exchange sub-portion 36 and the third heat exchange portion 18, water in the first terminal heat exchange sub-portion 36 exchanges heat with the first refrigerant in the third heat exchange portion 18; the second terminal heat exchanger 35 includes the second terminal heat exchange sub-portion 37 and the fourth heat exchange portion 19, water in the second terminal heat exchange sub-portion 37 exchanges heat with the second refrigeration in the fourth heat exchange portion 19.

[0042] As shown in FIG. 6B, the heat pump system may be used to produce high-temperature water, such as water higher than 60 °C. In a case where the heat pump system produces high-temperature water, the operating mode of the heat pump system is the high-temperature heating mode. In this case, the first compressor 33 is operating. The first valve element 22 is configured to operate in the open state, so as to open the passage between the first heat exchange portion 12 and the low-temperature-stage circulation pipeline 13. The second valve element 23 is configured to operate in the throttling state, so as to open the passage between the second heat exchange portion 14 and the fourth heat exchange portion 19. The third valve element 24 is configured to operate in the closed state, so as to close the passage between the third heat exchange portion 18 and the low-temperature-stage circulation pipeline 13. The first refrigerant in the outdoor heat exchanger 32 absorbs heat from the outdoor environment or other external media and evaporates, and then enters the second compressor 30 for compression, so as to form the high-temperature and high-pressure gaseous first refrigerant. The high-temperature and high-pressure gaseous first refrigerant enters the first heat exchange portion 12. In the cascade heat exchanger 11, the first heat exchange portion 12 operates in the condensation state, and the second heat exchange portion 14 operates in the evaporation state. The second refrigerant in the second heat exchange portion 14 exchanges heat with the first refrigerant in the first heat exchange portion 12, the second refrigerant absorbs heat and evaporates, and enters the first compressor 33 for compression after evaporating. The formed high-temperature and high-pressure gaseous second refrigerant enters the fourth heat exchange portion 19 in the second terminal heat exchanger 36, and exchanges heat with the water in the second terminal heat exchange sub-portion 37, so as to heat the water to a temperature above 60 °C. In a case where the heat pump system produces high-temperature water, a flow path of the first refrigerant is shown as F4 in FIG. 6B, and a flow path of the second refrigerant is shown as F5 in FIG. 6B.

[0043] Therefore, the heat pump system shown in FIG. 6A may also operate in the low-temperature heating mode, the defrosting mode and the rapid heating mode. For the operating principles of the heat pump system in a case where the heat pump system operates in the low-temperature heating mode, the defrosting mode and the rapid heating mode, reference may be made to the relevant descriptions in the FIGS. 3, 4 and 5B, and details will not be repeated herein.

[0044] In some embodiments, the difference between the heat pump systems shown in FIGS. 6A and 6B is that there are other connection manners between the first terminal heat exchanger 34 and the second terminal heat exchanger 35. As shown in FIGS. 7, 8, and 9, the second valve element 23 may also be connected to a first port of the fourth heat exchange portion 19 and a first port of the second heat exchange portion 14. An end of the first compressor 33 is connected to a second port of the fourth heat exchange portion 19, and another end of the first compressor 33 is connected to a second port of the second heat exchange portion 14. The second valve element 23, the fourth heat exchange portion 19, the first compressor 33 and the second heat exchange portion 14 constitute the high-temperature-stage circulation system.

[0045] In some embodiments, the heat pump outdoor unit 1 further includes a fourth valve element 104. As shown in FIGS. 7 and 9, two ends of the fourth valve element 104 are connected to a first port of the third heat exchange portion 18 and a first port of the outdoor heat exchanger 32 respectively. A first end and a second end of the four-way valve 31 are connected to a second port of the first heat exchange portion 12 and a second port of the outdoor heat exchanger 32 respectively. A third end and a fourth end of the four-way valve 31 are connected to two ends of the second compressor 30 respectively. A second port of the third heat exchange portion 18 is connected to the second port of the first heat exchange portion 12. The fourth valve element 104, the third heat exchange portion 18, the first heat exchange portion 12, the four-way valve 31, the second compressor 30 and the outdoor heat exchanger 32 constitute the low-temperature-stage circulation system.

[0046] In some embodiments, as shown in FIG. 8, the two ends of the fourth valve element 104 are connected to the second port of the first heat exchange portion 12 and the first port of the outdoor heat exchanger 32 respectively. The first end and the second end of the four-way valve 31 are connected to the second port of the third heat exchange portion 18 and the second port of the outdoor heat exchanger 32 respectively. The third end and the fourth end of the four-way valve 31 are connected to the two ends of the second compressor 30 respectively. The first port of the third heat exchange portion 18 is connected to the first port of the first heat exchange portion 12.

[0047] In order to further improve the reliability of the heat pump system, in some embodiments, the heat pump indoor unit 10 may further include a water inlet pipe, a water pump 402, a first electric three-way valve 401 and a water outlet pipe.

[0048] In some embodiments, as shown in FIG. 7, an inlet of the water pump 402 is connected to the water inlet pipe, and an outlet of the water pump 402 is connected to an inlet of the first electric three-way valve 401. A first outlet of the first electric three-way valve 401 is connected to a first port of the first terminal heat exchange sub-portion 36, and a second outlet of the first electric three-way valve 401 is connected to a first port of the second terminal heat exchange sub-portion 37. A second port of the first terminal heat exchange sub-portion 36 and a second port of the second terminal heat exchange sub-portion 37 are connected to the water outlet pipe.

[0049] In some embodiments, as shown in FIGS. 8 and 9, the inlet of the water pump 402 is connected to the water inlet pipe, and the outlet of the water pump 402 is connected to the first port of the first terminal heat exchange sub-portion 36. The second port of the first terminal heat exchange sub-portion 36 is connected to the inlet of the first electric three-way valve 401, and the first outlet of the first electric three-way valve 401 is connected to the first port of the second terminal heat exchange sub-portion 37. The second port of the second terminal heat exchange sub-portion 37 and the second outlet of the first electric three-way valve 401 are connected to the water outlet pipe.

[0050] In some embodiments, the heat pump system shown in FIG. 7 may also produce medium-temperature water and high-temperature water. For example, the temperature of the low-temperature water may be any value within a range of 40 °C to 60 °C, and the temperature of the high-temperature water may be any value within a range of 60 °C to 80 °C.

[0051] As shown in FIG. 10, in a case where the heat pump system shown in FIG. 7 produces medium-temperature water, the second compressor 30 operates, the first compressor 33 stops operating, the high-temperature-stage circulation system does not operate, and the low-temperature-stage circulation system operates. The inlet of the first electric three-way valve 401 communicates with the first outlet of the first electric three-way valve 401. That is to say, the first electric three-way valve 401 is in a straight-through state. The water in the water inlet pipe flows into the first terminal heat exchange sub-portion 36 through the water pump 402. In this case, the high-temperature and high-pressure gaseous first refrigerant compressed by the second compressor 30 passes through the first heat exchange portion 12. Since the high-temperature-stage circulation system does not operate, the first refrigerant does not perform heat exchange in the cascade heat exchanger 11. In a case where the first refrigerant enters the third heat exchange portion 18 from the first heat exchange portion 12, the first refrigerant in the first terminal heat exchanger 34 exchanges heat with the water in the first terminal heat exchange sub-portion 36, so as to produce hot water at a temperature of 40 °C to 60 °C. Arrows in FIG. 10 may represent a direction of heat transfer during the production of medium-temperature water.

[0052] As shown in FIG. 11, in a case where the heat pump system shown in FIG. 7 produces high-temperature water, the first compressor 33 and the second compressor 30 operate, and the low-temperature-stage circulation system and the high-temperature-stage circulation system operate. The inlet of the first electric three-way valve 401 communicates with the second outlet of the first electric three-way valve 401. That is to say, the first electric three-way valve 401 is in a bend-through state. The water in the water inlet pipe flows into the second terminal heat exchange sub-portion 37 through the water pump 402. In this case, in the low-temperature-stage circulation system, the high-temperature and high-pressure gaseous first refrigerant compressed by the second compressor 30 enters the first heat exchange portion 12, and releases heat in the first heat exchange portion 12. In the high-temperature-stage circulation system, after the second refrigerant in the second heat exchange portion 14 absorbs the heat released by the first heat exchange portion 12, the second refrigerant enters the fourth heat exchange portion 19. The second refrigerant in the first terminal heat exchanger 35 exchanges heat with water in the second terminal heat exchange sub-portion 37, so as to produce hot water at a temperature of 60 °C to 80 °C. For example, the temperature of high-temperature water is related to the second refrigerant used in the high-temperature-stage circulation system. For example, in a case where the second refrigerant is R134a, the temperature of high-temperature water may reach 80 °C. Arrows in FIG. 11 may represent a direction of heat transfer during the production of high-temperature water.

[0053] FIG. 12 is a diagram showing an operating principle of the heat pump system shown in FIG. 7 in a case where the heat pump system operates in the defrosting mode. It may be seen from FIGS. 7 and 12 that, the operating principle of the heat pump system shown in FIG. 7 in a case where the heat pump system operates in the defrosting mode is similar to that in a case where the heat pump system operates in the low-temperature heating mode. The difference is that, the flow direction of the first refrigerant in a case where the heat pump system shown in FIG. 7 operates in the defrosting mode is opposite to that in a case where the heat pump system operates in the low-temperature heating mode. Arrows in FIG. 12 may represent a direction of heat transfer in the defrosting mode.

[0054] The heat pump system shown in FIGS. 8 and 9 may also operate in the low-temperature heating mode, the defrosting mode, the high-temperature heating mode, and the rapid heating mode. For the operating principles of the heat pump system shown in FIGS. 7 to 9 operating in different modes, reference may be made to the relevant descriptions in FIGS. 3 to 5B and FIGS. 10 to 12, and details are not repeated herein.

[0055] In some embodiments, in order to further improve the reliability of the heat pump system, the heat pump indoor unit may further include a temperature sensing assembly. The temperature sensing assembly is configured to detect a temperature of the medium in the terminal heat exchange portion 17. The heat pump system is configured to operate in the low-temperature heating mode, the defrosting mode, the high-temperature heating mode, or the rapid heating mode in response to the temperature of the medium in the terminal heat exchange portion 17 detected by the temperature sensing assembly.

[0056] As shown in FIG. 7, the temperature sensing assembly may include a first temperature sensor 301, a second temperature sensor 302, a third temperature sensor 303, a fourth temperature sensor 304, a fifth temperature sensor 305, a sixth temperature sensor 403, a seventh temperature sensor 404.

[0057] The first temperature sensor 301 is disposed between the four-way valve 31 and the first heat exchange portion 12. The second temperature sensor 302 is disposed between the first heat exchange portion 12 and the third heat exchange portion 18. The third temperature sensor 303 is disposed between the third heat exchange portion 18 and the fourth valve element 104. The fourth temperature sensor 304 is disposed at an outlet of the first compressor 33. The fifth temperature sensor 305 is disposed between the fourth heat exchange portion 19 and the second valve element 23. The sixth temperature sensor 403 is disposed between the water pump 402 and the first electric three-way valve 401. The seventh temperature sensor 404 is disposed in the water outlet pipe.

[0058] In some embodiments, as shown in FIG. 13, the fourth valve element 104 may include an indoor valve element 1041 and an outdoor valve element 1042. The second compressor 30, the four-way valve 31, the outdoor heat exchanger 32 and the outdoor valve element 1042 may be disposed in the heat pump outdoor unit 1. The water pump 402, the first electric three-way valve 401, the cascade heat exchange portion 11, the terminal heat exchanger assembly 16, the second valve element 23, the first compressor 33, and the indoor valve element 1041 may be disposed on the heat pump indoor unit 10.

[0059] In some embodiments, the heat pump system may include one heat pump indoor unit 10 or a plurality of heat pump indoor units 10. As shown in FIG. 14, in a case where the heat pump system includes a heat pump indoor unit 10, the heat pump indoor unit 10 and the heat pump outdoor unit 1 form a heat pump system with a one-to-one online mode. As shown in FIG. 15, in a case where the heat pump system includes a plurality of heat pump indoor units 10, the plurality of heat pump indoor units 10 and the heat pump outdoor unit 1 form a heat pump system with a one-to-multi online mode.

[0060] In some embodiments, as shown in FIG. 16, the heat pump indoor unit 10 may also be connected to a same heat pump outdoor unit 1 together with other indoor units (e.g., the indoor unit for ambient temperature adjustment), so as to form a multi-split heat pump system with a one-to-multi online mode. For example, as shown in FIG. 17, other indoor units may be at least one air-cooling indoor unit 2, and the at least one air-cooling indoor unit 2 is connected to the heat pump outdoor unit 1 together with the heat pump indoor unit 10.

[0061] In a case where a plurality of indoor end apparatuses with different types connected to the terminal heat exchange portion 17 have operating requirements for cooling and heating simultaneously, a large amount of water in a buffer water tank may change from cold water to hot water or from hot water to cold water. In order to reduce the load of the buffer water tank, in some embodiments, as shown in FIG. 18, the heat pump indoor unit 10 further includes a relay reversing device 201, a buffer water tank 202 and indoor end apparatuses 205, 206, 207. The indoor end apparatuses 205, 206, 207 include a domestic hot water tank and at least one of space heating or cooling devices, and at least two of the indoor end apparatuses 205, 206, 207 switch with each other for operation.

[0062] As shown in FIG. 18, the buffer water tank 202 includes a first water inlet A', a first water outlet B, a first return water inlet C and a second water outlet D. The relay reversing device 201 has a second water inlet A' communicating with a water outlet of the terminal heat exchange portion 17, a third water outlet B' communicating with a return water inlet of the terminal heat exchange portion 17, and a second return water inlet C' and a fourth water outlet D' that communicate with main pipes of the indoor end apparatuses 205, 206, 207.

[0063] The relay reversing device 201 further includes a first straight-through path, a first bypass path, a second straight-through path and a second bypass path.

[0064] The first straight-through path directly communicates with the second water inlet A' and the fourth water outlet D'. The first bypass path includes a first bypass sub-path and a second bypass sub-path. The first bypass sub-path communicates with the second water inlet A' and the first water inlet A, and the second bypass sub-path communicates with the first water outlet B and the fourth water outlet D'. The first straight-through path communicates with the first bypass path in a switching manner, so as to achieve a communication pipeline from the terminal heat exchange portion 17 to the indoor end apparatuses 205, 206, 207.

[0065] As shown by the solid line arrows in FIG. 19, in a case where the first straight-through path is opened, the first bypass path is closed. In this case, the water flowing out from the water outlet of the terminal heat exchange portion 17 does not exchange heat through the buffer water tank 202. As shown by the solid line arrows in FIG. 20, in a case where the first bypass path is opened, the first straight-through path is closed. In this case, the water flowing out from the water outlet of the terminal heat exchange portion 17 exchanges heat through the buffer water tank 202.

[0066] The second straight-through path directly communicates with the second return water inlet C' and the third water outlet B'. The second bypass path includes a third bypass sub-path and a fourth bypass sub-path. The third bypass sub-path communicates with the second return water inlet C' and the first return water inlet C, and the fourth bypass sub-path communicates with the second water outlet D and the third water outlet B'. The second straight-through path communicates with the second bypass path in a switching manner, so as to achieve a communication pipeline from the indoor end apparatuses 205, 206, 207 to the terminal heat exchange portion 17.

[0067] As shown by the dotted line arrows in FIG. 19, in a case where the second straight-through path is opened, the second bypass path is closed. In this case, the water flowing from the indoor end apparatuses 205, 206, 207 back to the terminal heat exchange portion 17 does not exchange heat through the buffer water tank 202. As shown by the dotted line arrows in FIG. 20, in a case where the second bypass path is opened, the second straight-through path is closed. In this case, the water flowing from the indoor end apparatuses 205, 206, 207 back to the terminal heat exchange portion 17 exchanges heat through the buffer water tank 202.

[0068] In some embodiments, the relay reversing device 201 may switch between the straight-through path and the bypass path through the plurality of electric three-way valves or the plurality of check valves.

[0069] As shown in FIGS. 18 to 20, the relay reversing device 201 includes a second electric three-way valve 2011, a third electric three-way valve 2012, a fourth electric three-way valve 2013 and a fifth electric three-way valve 2014.

[0070] A first end of the second electric three-way valve 2011 communicates with the second water inlet A', a second end of the second electric three-way valve 2011 communicates with a first end of the third electric three-way valve 2012. A second end of the third electric three-way valve 2012 communicates with the fourth water outlet D', a third end of the second electric three-way valve 2011 communicates with the first water inlet A, and a third end of the third electric three-way valve 2012 communicates with the first water outlet B.

[0071] As shown in the solid line arrows in FIG. 19, in a case where the first end of the second electric three-way valve 2011 communicates with the second end of the second electric three-way valve 2011, and the first end of the third electric three-way valve 2012 communicates with the second end of the third electric three-way valve 2012, the first straight-through path is formed. In this case, the water flowing out from the water outlet of the terminal heat exchange portion 17 flows to sides of the indoor end apparatuses 205, 206, 207 through the first straight-through path.

[0072] As shown in the solid line arrows in FIG. 20, in a case where the first end of the second electric three-way valve 2011 communicates with the third end of the second electric three-way valve 2011, the first bypass sub-path is formed. In a case where the second end of the third electric three-way valve 2012 communicates with the third end of the third electric three-way valve 2012, the second bypass sub-path is formed. In this case, the water flowing out from the water outlet of the terminal heat exchange portion 17 flows to the indoor end apparatuses 205, 206, 207 through the first bypass sub-path, the buffer water tank 202 and the second bypass sub-path.

[0073] Similarly, a first end of the fourth electric three-way valve 2013 communicates with the third water outlet B', and a second end of the fourth electric three-way valve 2013 communicates with a first end of the fifth electric three-way valve 2014. A second end of the fifth electric three-way valve 2014 communicates with the second return water inlet C', a third end of the fourth electric three-way valve 2013 communicates with the second water outlet D, and a third end of the fifth electric three-way valve 2014 communicates with the first return water inlet C.

[0074] As shown in the dotted arrows in FIG. 19, in a case where the first end of the fourth electric three-way valve 2013 communicates with the second end of the fourth electric three-way valve 2013, and the first end of the fifth electric three-way valve 2014 communicates with the second end of the fifth electric three-way valve 2014, the second straight-through path is formed. In this case, the return water on the sides of the indoor end apparatuses 205, 206, 207 flows back to the return water inlet of the terminal heat exchange portion 17 through the second straight-through path.

[0075] As shown in the dotted arrows in FIG. 20, in a case where the first end of the fourth electric three-way valve 2013 communicates with the third end of the fourth electric three-way valve 2013, the third bypass sub-path is formed. In a case where the second end of the fifth electric three-way valve 2014 communicates with the third end of the fifth electric three-way valve 2014, the fourth bypass sub-path is formed. In this case, the return water on the sides of the indoor end apparatuses 205, 206, 207 flows back to the return water inlet of the terminal heat exchange portion 17 through the fourth bypass sub-path, the buffer water tank 202 and the third bypass sub-path.

[0076] In some embodiments, in a case of controlling the first straight-through path to open, it is also necessary to control the second straight-through path to open; in a case of controlling the first bypass path to open, it is necessary to control the second bypass path to open correspondingly.

[0077] In some embodiments, the relay reversing device 201 may also achieve the switching between the straight-through path and the bypass path through the plurality of check valves. For example, the relay reversing device 201 may include a first check valve, a second check valve, and a third check valve.

[0078] A first end of the first check valve is connected to the second water inlet A' and an end of the second check valve, and another end of the first check valve is connected to the fourth water outlet D' and an end of the third check valve. Another end of the second check valve is connected to the first water inlet A, and another end of the third check valve is connected to the first water outlet B.

[0079] In a case where the first check valve is closed, the first straight-through path is opened. In a case where the second check valve is closed, the first bypass sub-path is closed. In a case where the third check valve is closed, the second bypass sub-path is closed.

[0080] Similarly, the plurality of check valves may also be used to form the second straight-through path, the third bypass sub-path and the fourth bypass sub-path, and the details will not be repeated herein.

[0081] In order to further improve the flow capacity of water in the relay reversing device 201, in some embodiments, as shown in FIG. 18, the relay reversing device further includes a first force lift pump 2015 and a second force lift pump 2016. The first force lift pump 2015 is disposed on the pipeline between the second water inlet A' and the second electric three-way valve 2011, so as to increase a pressure of the water in the pipeline. The second force lift pump 2016 is disposed on the pipeline between the third electric three-way valve 2012 and the fourth water outlet D', so as to increase a pressure of the water in the pipeline.

[0082] In some embodiments, the domestic hot water tank 206 and the space heating or cooling devices 205 and 207 may belong to the indoor end apparatuses with different types. For example, the domestic hot water tank 206 is in the heating mode when operating, but the space heating or cooling devices 205 and 207 may be in the heating mode or in the cooling mode when operating.

[0083] In some embodiments, the electric three-way valve may be used to achieve the switching among the indoor end apparatuses 205, 206, 207. As shown in FIG. 18, an electric three-way valve 203 and an electric three-way valve 204 may be used to achieve the switching among the domestic hot water tank 206 and the space heating or cooling devices 205 and 207. A first end of the electric three-way valve 203 communicates with the fourth water outlet D', a second end of the electric three-way valve 203 communicates with a water inlet side of a fan coil 205, and a third end of the electric three-way valve 203 communicates with a first end of the electric three-way valve 204. A second end of electric three-way valve 204 communicates with a water inlet side of the domestic hot water tank 206, and a third end of the electric three-way valve 204 communicates with a water inlet side of a floor heating 207. In a case where another space heating or cooling device is added, another electric three-way valve may be added correspondingly, and adjacent ports of the electric three-way valves are communicates with each other. In some other embodiments, the plurality of check valves may also be used to form the switching operation among the indoor end apparatuses 205, 206, 207, and the details will not be repeated herein.

[0084] The operating principle of the relay reversing device 201 will be introduced below in a case where the domestic hot water tank 206 performs heating and the space heating or cooling devices 205, 207 perform cooling or heating switching, or the space heating or cooling devices 205, 207 switch between the cooling mode and the heating mode.

[0085] In some embodiments, the buffer water tank 202 may be used as a heat storage device or a cold storage device.

[0086] (1) The buffer water tank 202 is used as the heat storage device.

[0087] (1-1) In winter, in a case where the space heating or cooling devices 205, 207 perform heating and the domestic hot water tank 206 also performs heating, the following is given.

[0088] The relay reversing device 201 is controlled by collecting a water temperature and a target temperature of the indoor end apparatuses 205, 206, 207, so that the water flowing out from the water outlet of the terminal heat exchange portion 17 may exchange heat through or without the buffer water tank 202.

[0089] In some embodiments, the relay reversing device 201 may be controlled by the heat pump indoor unit 10, or may be controlled by an independent controller. The control of the independent controller may prevent the buffer water tank 202 from communicating with the auxiliary heat source in a case where the heat pump indoor unit 10 has malfunctioned, so as to provide heat source for the indoor end apparatuses 205, 206, 207. The auxiliary heat source may be, for example, a gas wall mounted furnace, a solar water heater, or a gas water heater.

[0090] a. In a case where a temperature difference between the water temperature and the target temperature of the indoor end apparatuses 205, 206, 207 is within a preset temperature range (e.g., a range of -5 °C to 5 °C), the relay reversing device 201 is controlled, so as to make the first bypass path communicate with the buffer water tank 202 (the first straight-through path is closed). At this time, the heat of the water in the buffer water tank 202 is used to provide heat sources for the indoor end apparatuses 205, 206, 207. In a case where the heating is performed and the water temperature fluctuates little, the heat in the buffer water tank 202 is used to ensure the stable temperature during the space is heated, so as to improve user comfort.

[0091] b. In a case where the difference between the water temperature and the target temperature of the indoor end apparatuses 205, 206, 207 is outside the preset temperature range, and the domestic hot water tank 206 is heating, the relay reversing device 201 is controlled, so as to make the first straight-through path open. The water flowing out from the water outlet of the terminal heat exchange portion does not pass through the buffer water tank 202, so that the heating capacity of the heat pump system is used to provide the heat source for the indoor end apparatuses 205, 206, 207, and the pressure of the buffer water tank 202 is reduced.

[0092] c. In a case where the difference between the water temperature and the target temperature of the indoor end apparatuses 205, 206, 207 is outside the preset temperature range, and the space heating or cooling devices 205, 207 perform heating, the relay reversing device 201 is controlled, so as to make the first bypass path communicate with the buffer water tank 202. The water flowing out from the water outlet of the terminal heat exchange portion passes through the buffer water tank 202, so as to make full use of the heat in the buffer water tank 202, so that the stable temperature during the space is heated may be ensured, and user comfort may be improved.

[0093] (1-2) During transition seasons, such as spring or autumn, in a case where the space heating or cooling devices 205, 207 automatically switch with each other for operation (called an automatic operation mode), and the domestic hot water tank 206 is still required to perform heating, the following is given.

[0094] By collecting an outdoor ambient temperature, it is determined whether the space heating or cooling devices 205, 207 are required to perform cooling or heating. a. In a case where the space heating or cooling devices 205, 207 are required to perform heating, the relay reversing device 201 is controlled, so as to make the first bypass path communicate with the buffer water tank 202. The water flowing out from the water outlet of the terminal heat exchange portion 17 passes through the buffer water tank 202, so as to make full use of the heat in the buffer water tank 202, so that the stable temperature during the space is heated may be ensured, and user comfort may be improved. In a case where the space heating or cooling devices 205, 207 are required to perform cooling, the relay reversing device 201 is controlled, so as to make the first straight-through path open. The water flowing out from the water outlet of the terminal heat exchange portion 17 does not pass through the buffer water tank 202, and the cooling capacity of the heat pump system is used to achieve the cooling of the space heating or cooling devices 205, 207, so that the pressure of the buffer water tank 202 may be reduced. b. In the automatic operation mode, in a case where the heating of the space heating or cooling devices 205, 207 and the heating of the domestic hot water tank 206 switch with each other for operation, processes of the heating of the space heating or cooling devices 205, 207 and the heating of the domestic hot water tank 206 are as described in (1-1), and the details will not be repeated herein. c. In the automatic operation mode, in a case where the cooling of the space heating or cooling devices 205, 207 and the heating of the domestic hot water tank 206 switch with each other for operation, the relay reversing device 201 is controlled, so as to make the first straight-through path open. The water flowing out from the water outlet of the terminal heat exchange portion 17 does not pass through the buffer water tank 202, so as to avoid that the water in the buffer water tank 202 changes from cold water to hot water or from hot water to cold water, thereby reducing the load of the buffer water tank 202 and avoiding the energy waste.

[0095] (1-3) The heat pump system may further include an auxiliary heat source 102, and the auxiliary heat source 102 is used to provide heat for the buffer water tank 202. For example, the auxiliary heat source 102 and the heat pump system jointly provide heat for the water in the buffer water tank 202.

[0096] In some embodiments, the auxiliary heat source 102 communicates with the buffer tank 202 through a connecting pipeline. In a case where the buffer water tank 202 is used as the heat storage device, the auxiliary heat source 102 operates, and the start and stop of the auxiliary heat source 102 may be controlled by the heat pump system.

[0097] In a case where the heating of the space heating or cooling devices 205, 207 and the heating of the domestic hot water tank 206 switch with each other for operation, the target temperature of the buffer water tank 202 for heating may be changed according to the different indoor end apparatuses 205, 206, 207. In this case, the auxiliary heat source 102 and the heat pump indoor unit 10 may jointly provide heat for the water in the buffer water tank 202.

[0098] In a case where the cooling of the space heating or cooling devices 205, 207 and the heating of the domestic hot water tank 206 switch with each other for operation, the following is given. In a case where the space heating or cooling devices 205, 207 perform cooling, the relay reversing device 201 is controlled, so as to make the first straight-through path open. The water flowing out from the water outlet of the terminal heat exchange portion 17 does not pass through the buffer water tank 202, so as to prevent the water for cooling from flowing into the buffer water tank 202. In a case where the domestic hot water tank 206 performs heating, the relay reversing device 201 is controlled, so as to make the first bypass path communicate with the buffer water tank 202. The water flowing out from the water outlet of the terminal heat exchange portion 17 passes through the buffer water tank 202, so as to use the heat provided by the auxiliary heat source 102.

[0099] For example, in a case where the auxiliary heat source 102 is the solar water heater, the water in the buffer water tank 202 may be heated in a case where a temperature condition that may be heated by solar energy is satisfied, so as to effectively use the energy.

[0100] In some embodiments, the heat pump system may further include an alarm device. In a case where the heat pump system malfunctions (e.g., the compressor malfunctions), the alarm device may give an alarm to remind the user in time.

[0101] For the heat pump system with the auxiliary heat source 102, in a case where the heat pump indoor unit 10 malfunctions, the cooling mode may not be performed, but the heating mode may enter an emergency operation mode, so that the auxiliary heat source 102 may be used to heat the water in the buffer water tank 202, thereby meeting the heating demands of the indoor end apparatuses 205, 206, 207.

[0102] (2) The buffer water tank 202 is used as the cold storage device.

[0103] In summer or transition seasons, in a case where the cooling of the space heating or cooling devices 205, 207 and the heating of the domestic hot water tank 206 switch with each other for operation, the following is given.

[0104] In a case where the space heating or cooling devices 205, 207 perform cooling, the relay reversing device 201 is controlled, so as to make the first bypass path communicate with the buffer water tank 202. The water flowing out from the water outlet of the terminal heat exchange portion 17 passes through the buffer water tank 202, so as to use the cold storage capacity of the buffer water tank 202, so that the water temperature may remain low for a long time and user comfort may be improved.

[0105] In a case where the domestic hot water tank 206 performs heating, the relay reversing device 201 is controlled, so as to make the first straight-through path open. The water flowing out from the water outlet of the terminal heat exchange portion 17 does not pass through the buffer water tank 202, so as to avoid changing the water in the buffer water tank 202 from cold water to hot water, thereby reducing the load of the buffer water tank 202 and avoiding energy waste.

[0106] In a case where the domestic hot water tank 206 and three or more space heating or cooling devices switch with each other for operation, the operating process of the switching among the domestic hot water tank 206 and three or more space heating or cooling devices is similar to the above.

[0107] In some embodiments, in a case where the indoor end apparatuses include at least two space heating or cooling devices, the space heating or cooling devices switch with each other for operation. As shown in FIG. 18, in a case where the space heating or cooling device 205 (e.g., the fan coil) and the space heating or cooling device 207 (e.g., the floor heating) switch with each other for operation, the following is given. If the buffer water tank 202 is used as the heat storage device, for example, in winter, the heating switching process of the floor heating 207 and the fan coil 205 is as described in (1-1), and the details will not be repeated herein. If the buffer water tank is used as the cold storage device, for example, in summer or transition seasons, one of the fan coil 205 and the floor heating 207 is selected for cooling. In this case, the relay reversing device 201 is controlled, so as to make the first bypass path communicate with the buffer water tank 202. The water flowing out from the water outlet of the terminal heat exchange portion passes through the buffer water tank 202, so as to make full use of the cold storage capacity of the buffer water tank 202, so that the water temperature of the system may remain low for a long time and user comfort may be improved. In a case of the plurality of space heating or cooling devices, the operating process of the switching among the plurality of space heating or cooling devices is similar to the above, and the details will not be repeated herein.

[0108] In some embodiments provided by the present disclosure, by providing the relay reversing device 201 and the buffer water tank 202, it is possible to effectively reduce the pressure of the buffer water tank 202 while the different requirements of the indoor end apparatuses 205, 206, 207 are satisfied, thereby reducing energy loss and effectively improving user experience.

[0109] In order to achieve an automatic adjustment of a rotational speed of a water pump without manual repeated debugging, in some embodiments of the present disclosure, the heat pump indoor unit 10 may also include a pressure detecting device, a flow rate detecting device, a temperature detecting device, a water pump self-circulation pipeline, a water system full-circulation pipeline and a controller.

[0110] As shown in FIG. 21, the pressure detecting device is used to detect an upstream pressure and a downstream pressure of the water pump 402. The pressure detecting device includes a water pressure sensor 8-2 for detecting the upstream pressure of the water pump 402 and a water pressure sensor 8-1 for detecting the downstream pressure of the water pump 402.

[0111] The flow rate detecting device includes a water flow meter 9 for detecting a flow rate of the water pump 402.

[0112] The water pump self-circulation pipeline includes the water pump 402 and an electric regulating valve 5. The water system full-circulation pipeline includes the water pump 402, a terminal heat exchanger 32 and the indoor end apparatus. That is to say, the water pump self-circulation pipeline and the water system full-circulation pipeline share a same water pump 402. The water pump 402 may be a variable-speed pump.

[0113] The controller is coupled to the pressure detecting device and the flow rate detecting device, and is configured to perform a water pump characteristic test through the water pump self-circulation pipeline and a pipeline characteristic test through the water system full-circulation pipeline based on at least one of the upstream pressure of the water pump, the downstream pressure of the water pump, or the flow rate of the water pump.

[0114] In some embodiments, the switching between the water pump self-circulation pipeline and the water system full-circulation pipeline may be achieved through a sixth electric three-way valve. As shown in FIG. 21, the sixth electric three-way valve may include an electric three-way valve 3-1 and an electric three-way valve 3-2.

[0115] In some embodiments, the heat pump indoor unit 10 further includes the temperature detecting device, and the temperature detecting device is used to detect an outlet water temperature and a return water temperature of the terminal heat exchange portion 17. As shown in FIG. 21, the temperature detecting device may include, for example, an outlet water temperature sensor 501 and a return water temperature sensor 502.

[0116] In some embodiments, the heat pump indoor unit 10 also includes an automatic exhaust valve 6-1 and a safety valve 7-1 located in the water system full-circulation pipeline, and an automatic exhaust valve 6-2 and a safety valve 7-2 located in the water pump self-circulation pipeline.

[0117] As shown in FIG. 21, the water system full-circulation pipeline includes the water pump 402, the water pressure sensor 8-1, the electric three-way valve 3-1, the terminal heat exchanger 32, the automatic exhaust valve 6-1, the safety valve 7-1, the outlet water temperature sensor 501, the indoor end apparatus, the return water temperature sensor 502, the electric three-way valve 3-2, the water flow meter 9, and the water pressure sensor 8-2 that are connected in sequence by means of a pipeline. The water pump self-circulation pipeline includes the water pump 402, the water pressure sensor 8-1, the electric three-way valve 3-1, the automatic exhaust valve 6-2, the safety valve 7-2, the electric regulating valve 5, the electric three-way valve 3-2, the water flow meter 9, and the water pressure sensor 8-2 that are connected in sequence by means of a pipeline.

[0118] For example, the water pump 402 may achieve the automatic adjustment of different rotational speeds according to a control input parameter. The electric three-way valve 3-1 and the electric three-way valve 3-2 may switch between different pipelines according to a control signal, so as to achieve the conversion of waterways. The electric regulating valve 5 may have function of adjusting a plurality of opening degrees. The automatic exhaust valve 6-1 and the automatic exhaust valve 6-2 may release excess air in the pipeline. The safety valve 7-1 and the safety valve 7-2 release the pressure in a case where the pressure of the pipeline exceeds a limit value, so as to play a protective role. The water pressure sensor 8-1 and the water pressure sensor 8-2 may collect the downstream water pressure and the upstream water pressure of the water pump 402 for resistance measurement, respectively. The water flow meter 9 may detect a flow rate of the water flowing into and out from the water pump 402. The outlet water temperature sensor 501 and the return water temperature sensor 502 are used to detect the outlet water temperature and the return water temperature of the terminal heat exchange portion 17 respectively, so as to participate in the adjustment of the rotational speed of the water pump during the constant temperature difference control.

[0119] In some embodiments, the water pump self-circulation pipeline and the water system full-circulation pipeline include a first water supply port and a second water supply port, respectively. As shown in FIG. 21, the first water supply port includes a water supply port 1, and the second water supply port includes a water supply port 2. The water supply port 1 is located between the water pump 402 and the electric three-way valve 3-2, and the water supply port 2 is located between the indoor end apparatus 205 and the electric three-way valve 3-2.

[0120] In order to improve the accuracy of the water pump characteristic test and the pipeline characteristic test, in some embodiments, the controller is configured to perform emptying control of the water pump before performing the water pump characteristic test and the pipeline characteristic test.

[0121] The heat pump indoor unit 10 may achieve automatic emptying of the water pump self-circulation pipeline and the automatic water pump characteristic test through the water pump self-circulation, and automatic emptying of the entire water system full-circulation pipeline and the automatic pipeline characteristic test through the water system full-circulation.

[0122] Operating principles of the heat pump system shown in FIG. 21 in a case where the heat pump system operates in the heating mode, the cooling mode, the water pump self-circulation mode and the water system full-circulation mode each are introduced below.1. Heating mode

[0123] As shown in FIG. 21, the heat pump outdoor unit 1 obtains heat from outdoor air or other media. After the refrigerant is compressed by the compressor, the refrigerant enters the terminal heat exchanger assembly 16 of the heat pump indoor unit 10, and exchanges heat with the terminal heat exchange portion 17, so as to heat the water in the terminal heat exchange portion 17. An internal valve core of the electric three-way valve 3-1 is controlled to make a pipeline (6) communicate with a pipeline (7). An internal valve core of the electric three-way valve 3-2 is controlled to make a pipeline (4) communicate with a pipeline (5). The electric regulating valve 5 is fully closed, and the water pump 402 operates. An electronic expansion valve 2 is controlled and adjusted according to a control rule of the heat pump system.

[0124] In a case where the heat pump system is in the heating operating mode, as shown in FIG. 21, the refrigerant flows through a refrigerant gas pipe, a pipeline (1), a pipeline (2) and a pipeline (3) of the heat pump outdoor unit 1, and reaches a refrigerant liquid pipe of the heat pump outdoor unit 1, so that a refrigerant cycle loop is formed. Water flows through the pipeline (4), the pipeline (5), the pipeline (6), the pipeline (7), the pipeline (8), and the pipeline (4), so that a water system circulation flow path is formed.2. Cooling mode

[0125] As shown in FIG. 21, the heat of the heat pump indoor unit 10 is transferred to the liquid refrigerant through the water system. The liquid refrigerant passes through the refrigerant pipeline, and after the pressure of the liquid refrigerant is increased by the compressor, the liquid refrigerant releases the heat to the outdoor air. The internal valve core of the electric three-way valve 3-1 is controlled to make the pipeline (6) communicate with the pipeline (7). The internal valve core of the electric three-way valve 3-2 is controlled to make the pipeline (4) communicate with the pipeline (5). The electric regulating valve 5 is fully closed, and the water pump 402 operates. The electronic expansion valve 2 is controlled and adjusted according to a control rule of the heat pump system.

[0126] In a case where the heat pump system is in the cooling operating mode, as shown in FIG. 21, the refrigerant flows through the refrigerant liquid pipe, the pipeline (3), the pipeline (2), the pipeline (1), and the refrigerant air pipe of the heat pump outdoor unit 1, so that the refrigerant cycle loop is formed. Water flows through the pipeline (4), the pipeline (5), the pipeline (6), the pipeline (7), the pipeline (8), and the pipeline (4), so that the water system circulation flow path is formed.3. Water pump self-circulation mode

[0127] Such mode is suitable for the water resistance calibration during installation and debugging of a heat pump unit. The heat pump system may start such mode only if the cooling mode or the heating mode is closed.

[0128] As shown in FIG. 21, the internal valve core of the electric three-way valve 3-1 is controlled to make the pipeline (6) communicate with a pipeline (9). The internal valve core of the electric three-way valve 3-2 is controlled to make a pipeline (10) communicate with the pipeline (5). The electric regulating valve 5 is adjusted according to a set opening degree. The water pump 402 operates. The electronic expansion valve 2 is fully closed.

[0129] In a case where the heat pump system operates in the water pump self-circulation mode, the refrigerant cycle loop is closed. Water in a portion of the system pipelines in the heat pump system flows through the pipeline (5), the pipeline (6), the pipeline (9), the pipeline (10), and the pipeline (5), so that the water system circulation flow path is formed.

[0130] In a case where the heat pump system operates in the water pump self-circulation mode, it is necessary to perform automatic emptying control and then perform the automatic water pump characteristic test.

[0131] The controller is used to replenish water through the water supply port 1 in a case where the downstream pressure P1 of the water pump is lower than a lower limit value M of a water system pressure after the water pump self-circulation mode starts; in a case where the downstream pressure P1 of the water pump is higher than the lower limit value M of the water system pressure, control the water pump 402 to operate intermittently until the downstream pressure P1 of the water pump 402 is between the lower limit value M and an upper limit value N of the water system pressure, and an absolute value of a difference between the downstream pressure of the water pump 402 at a first moment and the downstream pressure of the water pump 402 at a second moment is lower than a water pressure fluctuation limit value K within a third preset duration.

[0132] For example, the first moment and the second moment may be any moment. For example, in a case where the first moment is the n-th moment, the second moment may be a moment before the first moment, such as the (n-1)-th moment. The third preset duration may be any duration, for example, the third preset duration may be time t5.

[0133] In the automatic emptying control of the water pump self-circulation mode, the water supply port 1 may not be closed until the automatic emptying ends. In a case where the controller controls the water pump 402 to operate intermittently, the rotational speeds of the water pump 402 at two adjacent times are different.

[0134] In some embodiments, the water pump 402 may operate at a maximum rotational speed, or at any rotational speed lower than the maximum rotational speed. For example, the water pump 402 may operate at A of the maximum rotational speed, where A is a value greater than 0 and less than 1.

[0135] As shown in FIG. 22, a water pump emptying control method of the heat pump unit before the water pump characteristic test includes step 1 to step 11.

[0136] In step 1, the water pump self-circulation starts.

[0137] In step 2, it is determined whether P1 is greater than M (P1 > M); if so, step 4 is performed; if not, step 3 is performed.

[0138] In step 3, water is replenished through the water supply port 1, and step 2 is performed.

[0139] In step 4, the water pump 402 operates at the maximum rotational speed. Time t1 elapses.

[0140] In step 5, the water pump 402 stops operating. Time t2 elapses.

[0141] In step 6, the water pump 402 operates at A of the maximum rotational speed. Time t3 elapses.

[0142] In step 7, the water pump 402 stops operating. Time t4 elapses.

[0143] In step 8, the water pump 402 operates at the maximum rotational speed.

[0144] In step 9, it is determined whether P1 is greater than M and less than N (M < P1 < N); if so, step 10 is performed; if not, step 4 is performed.

[0145] In step 10, it is determined whether an absolute value of a difference between P1(n) and P1(n-1) is less than K (|(P1(n)-P1(n-1)|<K) and time when the absolute value of the difference between P1(n) and P1(n-1) is less than K lasts a set time t5; if so, step 11 is performed; if not, step 4 is performed.

[0146] In step 11, the emptying control is completed. P1 is a pressure detected by the water pressure sensor 8-1, and the unit is megapascal (MPa); P2 is a pressure detected by the water pressure sensor 8-2, and the unit is MPa; M is the lower limit value of the water system pressure, and the unit is MPa; N is the upper limit value of the water system pressure, and the unit is MPa; P1(n) is the water pressure at the n-th moment, and the unit is MPa; P1(n-1) is the water pressure at the (n-1)-th moment, and the unit is MPa; K is the water pressure fluctuation limit value, and the unit is MPa; A is a rotational speed ratio, the unit is %; Time t1 to Time t5 each are a duration, the unit is second (s).

[0147] After the water pump has completed emptying, the water pump characteristic test may be performed.

[0148] The controller performs the water pump characteristic test through the water pump self-circulation pipeline, and the method includes: first, controlling the water pump self-circulation pipeline to open, controlling the water pump to operate at a first rotational speed, and controlling the electric regulating valve 5 at a first opening degree corresponding to the first rotational speed within a first preset duration; then, calculating an average of differences between the downstream pressures and the upstream pressures detected by the pressure detecting device within the first preset duration, so as to obtain first operating parameters, the first operating parameters corresponding to a lift of the water pump, and the first operating parameters including the first rotational speed and the first opening degree; next, calculating an average of the flow rates detected by the flow rate detecting device within the first preset duration, so as to obtain an average of the flow rates of the water pump corresponding to the first operating parameters; finally, obtaining a test result of the water pump characteristic test according to the lifts of the water pump corresponding to the plurality of operating parameters and the averages of the flow rates of the water pump corresponding to the plurality of operating parameters, the plurality of operating parameters including the first operating parameters, and the test result of the water pump characteristic test including a water pump characteristic curve.

[0149] The water pump 402 may include a plurality of first rotational speeds. Each rotational speed may correspond to a plurality of opening degrees of the electric regulating valve 5, and it is required that the water pump 402 operates for a set duration at the opening degrees corresponding to each rotational speed. The average ΔP of differences between the downstream pressures and upstream pressures detected by the pressure detecting device within the set duration is calculated, and ΔP is the lift of the water pump; meanwhile, the average Q of the flow rates detected by the flow rate detecting device in each rotational speed within the set duration is calculated. The first preset duration may be any duration. For example, the first preset duration may be time t11.

[0150] The method for the water pump characteristic test of the heat pump unit is described below with reference to FIG. 23.

[0151] In step 1, the emptying control is completed.

[0152] In step 2, the water pump 402 operates at the maximum rotational speed.

[0153] In step 3, a program 1 that the electric regulating valve 5 is fully closed and then is opened (at 20% opening degree) is performed. After time t11 elapses, ΔP and Q are calculated, and the ΔP and Q correspond to a coordinate point of the electric regulating valve 5 at the 20% opening degree shown in FIG. 24.

[0154] In step 4, a program 2 that the electric regulating valve 5 is opened (at 50% opening degree) is performed. After time t11 elapses, ΔP and Q are calculated, and the ΔP and Q correspond to a coordinate point of the electric regulating valve 5 at the 50% opening degree shown in FIG. 24.

[0155] In step 5, a program 3 that the electric regulating valve 5 is opened (at 70% opening degree) is performed. After time t11 elapses, ΔP and Q are calculated, and the ΔP and Q correspond to a coordinate point of the electric regulating valve 5 at the 70% opening degree shown in FIG. 24.

[0156] In step 6, a program 4 that the electric regulating valve 5 is opened (at 100% opening degree) is performed. After time t11 elapses, ΔP and Q are calculated, and the ΔP and Q correspond to a coordinate point of the electric regulating valve 5 at the 100% opening degree shown in FIG. 24.

[0157] The water pump characteristic curve corresponding to the maximum rotational speed of the water pump 402 may be obtained according to the coordinate point of the electric regulating valve 5 at the 20% opening degree shown in FIG. 24, the coordinate point of the electric regulating valve 5 at the 50% opening degree shown in FIG. 24, the coordinate point of the electric regulating valve 5 at the 70% opening degree shown in FIG. 24, and the coordinate point of the electric regulating valve 5 at the 100% opening degree shown in FIG. 24 in a case where the water pump 402 operates at the maximum rotational speed.

[0158] In step 7, the water pump 402 operates at 75% of the maximum rotational speed.

[0159] In step 8, step 3 to step 7 are repeated.

[0160] In a case where the water pump 402 operates at 75% of the maximum rotational speed of the water pump 402, step 3 to step 7 are repeated, so as to obtain a water pump characteristic curve corresponding to 75% of the maximum rotational speed of the water pump 402.

[0161] In step 9, the water pump 402 operates at 50% of the maximum rotational speed. If the rotational speed of the water pump reaches a set lower limit rotational speed of the water pump, the test ends after the operation is completed.

[0162] In step 10, step 3 to step 7 are repeated.

[0163] In a case where the water pump 402 operates at 50% of the maximum rotational speed of the water pump 402, step 3 to step 7 are repeated, so as to obtain a water pump characteristic curve corresponding to 50% of the maximum rotational speed of the water pump 402.

[0164] In step 11, the water pump 402 operates at 25% of the maximum rotational speed, the curve corresponding to 25% of the maximum rotational speed of the water pump 402 is as shown in FIG. 24. If the rotational speed of the water pump reaches the set lower limit rotational speed of the water pump, the test ends after the operation is completed.

[0165] In step 12, step 3 to step 7 are repeated.

[0166] In a case where the water pump 402 operates at 25% of the maximum rotational speed, step 3 to step 7 are repeated, so as to obtain a water pump characteristic curve corresponding to 25% of the maximum rotational speed of the water pump 402.

[0167] In step 13, the water pump 402 operates at the lower limit rotational speed, the curve corresponding to the lower limit rotational speed of the water pump 402 is as shown in FIG. 24.

[0168] In step 14, step 3 to step 7 are repeated.

[0169] In a case where the water pump 402 operates at 50% of the maximum rotational speed of the water pump 402, step 3 to step 7 are repeated, so as to obtain a water pump characteristic curve corresponding to the lower limit rotational speed of the water pump 402.

[0170] In step 15, the automatic water pump characteristic test ends. P is the lift of the water pump, and ΔP is an average of differences (P1-P2) between P1 and P2 of the water pump within time t11, the unit is MPa; P1 is the pressure detected by the water pressure sensor 8-1, and the unit is MPa; P2 is the pressure detected by the water pressure sensor 8-2, and the unit is MPa; Q is an average of the data detected by the water flow meter 9 within the time t11, and the unit is m 3< / h; Time t11 is a duration when the electric regulating valve 5 lasts at a fixed opening degree, the unit is second.

[0171] In some embodiments, the heat pump system automatically draws the water pump characteristic curves according to the data of the automatic water pump characteristic test. The curves are embedded in an internal program of the heat pump system, or may also be displayed on an interface of a user-side controller, which is convenient for installation and maintenance people to check the waterway.4. Water system full-circulation mode

[0172] Such mode is suitable for the water resistance calibration during installation and debugging of the heat pump unit. The heat pump system may perform such mode only in a case where the cooling mode or the heating mode is closed.

[0173] As shown in FIG. 21, the internal valve core of the electric three-way valve 3-1 is controlled to make the pipeline (6) communicate with the pipeline (7). The internal valve core of the electric three-way valve 3-2 is controlled to make the pipeline (4) communicate with the pipeline (5). The electric regulating valve 5 is fully closed. The water pump 402 operates. The electronic expansion valve 2 is fully closed. In a case where the heat pump system operates in the water system full-circulation mode, the refrigerant cycle loop is closed. Water in a portion of the system pipelines in the heat pump system flows through the pipeline (5), the pipeline (6), the pipeline (7), the pipeline (8), the pipeline (4), and the pipeline (5), so that the water system circulation flow path is formed.

[0174] In a case where the heat pump system operates in the water system full-circulation mode, it is necessary to perform automatic emptying control and then perform the automatic pipeline characteristic test.

[0175] The controller is used to replenish water through the water supply port 2 in a case where the downstream pressure P1 of the water pump is lower than the lower limit value M of the water system pressure after the water system full-circulation mode starts; in a case where the downstream pressure P1 of the water pump is higher than the lower limit value M of the water system pressure, control the water pump 402 to operate intermittently until the downstream pressure P1 of the water pump 402 is between the lower limit value M and the upper limit value N of the water system pressure, and the absolute value of the differences between the downstream pressures of the water pump 402 at the first moment and the downstream pressures of the water pump 402 at the second moment is lower than the water pressure fluctuation limit value K within the third preset duration. The first moment and the second moment may be any moment. For example, in a case where the first moment is the n-th moment, the second moment may be a moment before the first moment, such as the (n-1)-th moment. The third preset duration may be any duration, for example, the third preset duration may be the time t5.

[0176] In the automatic emptying control of the water system full-circulation mode, the water supply port 2 may not be closed until the automatic emptying ends. In a case where the controller controls the water pump 402 to operate intermittently, the rotational speeds of the water pump 402 at two adjacent times are different.

[0177] In some embodiments, the water pump 402 may operate at the maximum rotational speed, or at any rotational speed lower than the maximum rotational speed. For example, the water pump 402 may operate at A of the maximum rotational speed, where A is a value greater than 0 and less than 1.

[0178] As shown in FIG. 25, the water pump emptying control method of the heat pump unit before the pipeline characteristic test is as following.

[0179] In step 1, the water system full-circulation starts.

[0180] In step 2, it is determined whether P1 is greater than M (P1 > M); if so, step 4 is performed; if not, step 3 is performed.

[0181] In step 3, water is replenished through the water supply port 2, and step 2 is performed.

[0182] In step 4, the water pump 402 operates at the maximum rotational speed. Time t6 elapses.

[0183] In step 5, the water pump 402 stops operating. Time t7 elapses.

[0184] In step 6, the water pump 402 operates at A of the maximum rotational speed. Time t8 elapses.

[0185] In step 7, the water pump 402 stops operating. Time t9 elapses.

[0186] In step 8, the water pump 402 operates at the maximum rotational speed.

[0187] In step 9, it is determined whether P1 is greater than M and less than N (M < P1 < N); if so, step 10 is performed; if not, step 4 is performed.

[0188] In step 10, it is determined whether an absolute value of a difference between P1(n) and P1(n-1) is less than K (|(P1(n)-P1(n-1)|<K) and time when the absolute value of the difference between P1(n) and P1(n-1) is less than K lasts a set time t5; if so, step 11 is performed; if not, step 4 is performed.

[0189] In step 11, the emptying control is completed. P1 is the pressure detected by the water pressure sensor 8-1, and the unit is MPa; P2 is the pressure detected by the water pressure sensor 8-2, and the unit is MPa; M is the lower limit value of the water system pressure, and the unit is MPa; N is the upper limit value of the water system pressure, and the unit is MPa; P1(n) is the water pressure at the n-th moment, and the unit is MPa; P1(n-1) is the water pressure at the (n-1)-th moment, and the unit is MPa; K is the water pressure fluctuation limit value, and the unit is MPa; A is a rotational speed ratio, the unit is %; Time t6 to time t10 each are a duration, the unit is second.

[0190] After the water pump has completed emptying, the pipeline characteristic test may be performed.

[0191] The controller performs the pipeline characteristic test through the water system full-circulation pipeline, and the method includes: first, controlling the water system full-circulation pipeline to open, controlling the water pump to operate at a second rotational speed for a second preset duration; then, calculating an average of differences between the downstream pressures and the upstream pressures detected by the pressure detecting device within the second preset duration, so as to obtain a pipeline resistance corresponding to the second rotational speed; next, calculating an average of the flow rates detected by the flow rate detecting device within the second preset duration, so as to obtain an average of the flow rates corresponding to the second rotational speed; finally, obtaining a test result of the pipeline characteristic test according to the pipeline resistances corresponding to the plurality of rotational speeds and the averages of the flow rates corresponding to the plurality of rotational speeds, and the test result of the pipeline characteristic test including a pipeline characteristic curve.

[0192] The water pump 402 may include a plurality of second rotational speeds, and it is required that the water pump 402 operates for a set duration at each rotational speed. The average ΔP' of differences between the downstream pressures and the upstream pressures detected by the pressure detecting device within the set duration is calculated, and ΔP' is the pipeline resistance; meanwhile, the average Q' of the flow rates detected by the flow rate detecting device within the set duration is calculated. The second preset duration may be any duration. For example, the second preset duration may be time t12. The method for the pipeline characteristic test is described below with reference to FIG. 26.

[0193] In step 1, the emptying control is completed.

[0194] In step 2, the water pump 402 operates at the maximum rotational speed. After time t12 elapses, ΔP' and Q' are calculated, and the ΔP' and Q' correspond to a coordinate point of the maximum rotational speed of the water pump 402 shown in FIG. 27.

[0195] In step 3, the water pump 402 operates at 75% of the maximum rotational speed. After time t12 elapses, ΔP' and Q' are calculated, and the ΔP' and Q' correspond to a coordinate point of 75% of the maximum rotational speed of the water pump 402 shown in FIG. 27.

[0196] In step 4, the water pump 402 operates at 50% of the maximum rotational speed. After time t12 elapses, ΔP' and Q' are calculated, and the ΔP' and Q' correspond to a coordinate point of 50% of the maximum rotational speed of the water pump 402 shown in FIG. 27.

[0197] In step 5, the water pump 402 operates at 25% of the maximum rotational speed. After time t12 elapses, ΔP' and Q' are calculated, and the ΔP' and Q' correspond to a coordinate point of 25% of the maximum rotational speed of the water pump 402 shown in FIG. 27.

[0198] The pipeline characteristic curve may be obtained according to the coordinate point of the maximum rotational speed of the water pump 402 shown in FIG. 24, the coordinate point of 75% of the maximum rotational speed of the water pump 402, the coordinate point of 50% of the maximum rotational speed of the water pump 402, and the coordinate point of 50% of the maximum rotational speed of the water pump 402.

[0199] In step 6, the automatic water pump characteristic test ends. ΔP' is the pipeline resistance, ΔP' is an average of differences (P1 - P2) between P1 and P2 of the water pump 402 within time t12, the unit is MPa; P1 is the pressure detected by the water pressure sensor 8-1, and the unit is MPa; P2 is the pressure detected by the water pressure sensor 8-2, and the unit is MPa; Q' is an average of the data detected by the water flow meter 9 within the time t12, and the unit is m 3< / h; Time t12 is a duration when the water pump 402 lasts at a fixed rotational speed, the unit is second.

[0200] In some embodiments, the heat pump system automatically draws the pipeline characteristic curve according to the data of the automatic pipeline characteristic test. The curves are embedded in the internal program of the heat pump system, or may also be displayed on the interface of the user-side controller, which is convenient for installation and maintenance people to check the waterway.

[0201] In order to satisfy the different requirements of the user for water temperature control, the heat pump system may define three different water pump control functions such as constant rotational speed, constant water volume and constant water temperature difference in the heating mode and the cooling mode.

[0202] In the constant rotational speed function, the water pump 402 operates according to a set rotational speed. In the constant water volume function, the rotational speed of water pump 402 is adjusted through frequency conversion, so as to keep the water flow rate in the circulation of the heat pump system at a set value. In the constant water temperature difference function, the rotational speed of water pump 402 is adjusted through frequency conversion, so as to keep the water temperature difference (in the cooling mode, the water temperature difference is equal to a difference between a return water temperature and an outlet water temperature; in the heating mode, the water temperature difference is equal to a difference between the outlet water temperature and the return water temperature) of the heat pump system at a set value. The user may set different maximum rotational speed and lower limit rotational speed of the water pump according to requirements.1. Constant rotational speed function

[0203] Such function is suitable for a case where the heat pump system normally operates in the cooling mode or the heating mode. The heat pump system may perform such function only in a case where the cooling mode or the heating mode starts. In such function, the water pump 402 operates at a set rotational speed.

[0204] The internal valve core of the electric three-way valve 3-1 is controlled, so as to make the pipeline (6) communicate with the pipeline (7). The internal valve core of the electric three-way valve 3-2 is controlled, so as to make the pipeline (4) communicate with the pipeline (5). The electric regulating valve 5 is fully closed. The water pump 402 operates at the set rotational speed. The electronic expansion valve 2 is controlled and adjusted according to a control rule of the heat pump system.

[0205] As shown in FIG. 28, the constant rotational speed control method is as following.

[0206] In step 1, a user sets a rotational speed on an operating interface. The operating rotational speed of the water pump 402 defaults to the maximum rotational speed. If the user does not actively set a rotational speed, the water pump 402 operates at the maximum rotational speed.

[0207] In step 2, the cooling mode or the heating mode starts.

[0208] In step 3, the water pump 402 operates at the set rotational speed.

[0209] In step 4, the cooling mode or the heating mode is closed. Time t13 elapses, and time t13 is a duration when the water pump delays in stopping, the unit is second.

[0210] In step 5, the water pump 402 stops operating.2. Constant water flow rate function

[0211] Such function is suitable for a case where the heat pump system normally operates in the cooling mode or the heating mode. Such function is performed only in a case where the cooling mode or the heating mode starts.

[0212] The internal valve core of the electric three-way valve 3-1 is controlled, so as to make the pipeline (6) communicate with the pipeline (7). The internal valve core of the electric three-way valve 3-2 is controlled, so as to make the pipeline (4) communicate with the pipeline (5). The electric regulating valve 5 is fully closed. The water pump 402 operates. An electronic expansion valve 2 is controlled and adjusted according to a control rule of the heat pump system.

[0213] In such function, the unit installation or maintenance people may set the water flow rate required for the operation of the heat pump system according to requirements. The heat pump system draws a water pump and pipeline characteristic curve according to the water pump characteristic curve measured in the water pump self-circulation mode (FIG. 24) and the pipeline characteristic curve measured in the water system full-circulation mode (FIG. 27), and the water pump and pipeline characteristic curve is as shown in FIG. 29.

[0214] The controller is further configured to: firstly, obtain a target water flow rate; then obtain a rotational speed corresponding to the target water flow rate according to the target water flow rate and the pipeline characteristic curve; finally, control the water pump to operate at the rotational speed corresponding to the target water flow rate.

[0215] The target water flow rate is the required water flow rate. For example, the target water flow rate is the required water flow rate set by the user. A corresponding operating point on the pipeline characteristic curve is obtained according to the required water flow rate, and a rotational speed of the water pump corresponding to the water pump characteristic curve passing through the operating point is selected as a target rotational speed of the water pump, which is used to control the operation of the water pump.

[0216] For example, in a case where the user sets the water flow rate to 0.6 m 3< / h, as shown in FIG. 29, the heat pump system first obtains a corresponding operating point (e.g., the operating point 1) on the pipeline characteristic curve through the water flow rate, and selects the water pump characteristic curve (25% of the maximum rotational speed of water pump 4) passing through the operating point, and the rotational speed of the water pump corresponding to the curve (25% of the maximum rotational speed of water pump 4) may be used as the determined rotational speed of the water pump.

[0217] In some embodiments, in a case where the operating point is not on the measured water pump characteristic curves, the controller may also perform linear interpolation on adjacent water pump characteristic curves, so as to obtain the target rotational speed of the water pump.

[0218] For example, the user sets the water flow rate to 0.5 m 3< / h, as shown in FIG. 29, the heat pump system first obtains a corresponding operating point (e.g., the operating point 2) on the pipeline characteristic curve through the water flow rate. If the operating point is not on the measured water pump characteristic curves, the heat pump system performs linear interpolation on adjacent water pump characteristic curves (the curve of 25% of the maximum rotational speed of the water pump 4 and the curve of lower limit rotational speed of the water pump 4), so as to finally obtain the appropriate rotational speed of the water pump.

[0219] During the operation of the water pump, the rotational speed of the water pump is dynamically adjusted according to the real-time data detected by the water flow meter 9, and the process is as shown in FIG. 30.

[0220] In step 1, the water pump 402 operates at a rotational speed corresponding to a constant water flow rate. Time t14 elapses.

[0221] In step 2, ΔR1(n) = η1 × {ΔQ(n) - AQ(n-1)} + η2 × ΔQ(n). ΔR2(n) = η3 × Q(n-1).

[0222] In step 3, ΔR(n) = ΔR1(n) + ΔR2(n).

[0223] In step 4, R(n) = R(n-1) + ΔR(n). Step 1 is performed. R(n) is a water pump rotational speed ratio at the n moment (i.e., a ratio of a rotational speed of the water pump at the n moment to the maximum rotational speed, the unit being %); R(n-1) is a water pump rotational speed ratio at the (n-1) moment (i.e., a ratio of a rotational speed of the water pump at the (n-1) moment to the maximum rotational speed, the unit being %); R(n) is a water pump rotational speed change ratio at the n moment (the constant water flow rate control), and the unit is %; R1(n) is a water pump rotational speed change ratio in PID control at the n moment (the constant water flow rate control), and the unit is %; R2(n) is a water pump rotational speed change ratio in the over modulation control and the under modulation control at the n moment (the constant water flow rate control), and the unit is %; η1 and η2 are PID control constants in the constant water flow rate control (being less than 0); η3 is a control constant in the over modulation and the under modulation of the constant water flow rate control; Q(n) is a difference between the water flow rate detected by the water flow meter 9 and the set water flow rate at the n moment, ΔQ(n) = Q(n) - Qs(n); Q(n) is the water flow rate at the n moment, the unit is m 3< / h; Qs(n) is the set water flow rate at the n moment, the unit is m 3< / h; Time t14 is an operating time of the water pump at a rotational speed corresponding to a constant water volume, the unit is second. 3. Constant water temperature difference function

[0224] Such function is suitable for a case where the heat pump system normally operates in the cooling mode or the heating mode. The heat pump system may perform such mode only in a case where the cooling mode or the heating mode starts.

[0225] The internal valve core of the electric three-way valve 3-1 is controlled, so as to make the pipeline (6) communicate with the pipeline (7). The internal valve core of the electric three-way valve 3-2 is controlled, so as to make the pipeline (4) communicate with the pipeline (5). The electric regulating valve 5 is fully closed. The water pump 402 operates. The electronic expansion valve 2 is controlled and adjusted according to a control rule of the air source heat pump.

[0226] The controller is further configured to: firstly, obtain a water temperature difference required by the user; then, obtain a current water temperature difference according to a current outlet water temperature and a current return water temperature of the terminal heat exchange portion; next, calculate a target water flow rate according to the current water temperature difference, a current water flow rate detected by the flow rate detecting device, and the water temperature difference required by the user; finally, control the water pump to operate at a preset maximum rotational speed, and after the water pump operates stably, control the water pump to operate at a target rotational speed corresponding to the target water flow rate.

[0227] The target water flow includes a required water flow rate, which is determined by the current water temperature difference and the current water flow rate. The operation of the water pump 402 is controlled by obtaining the target rotational speed of the water pump according to the required water flow rate.

[0228] For example, the unit installation or maintenance people may set the water temperature difference required for the operation of the heat pump system (in the cooling mode, the water temperature difference is equal to the difference between the return water temperature and the outlet water temperature; in the heating mode, the water temperature difference is equal to the difference between the outlet water temperature and the return water temperature) according to requirements. In an initial stage of the operation of the heat pump system, the water pump 402 operates at a set maximum rotational speed. When the initial stage is over (i.e., after the operating parameters of the heat pump system are stable), the heat pump system collects the return water temperature, the outlet water temperature and the water flow rate in real time, calculates the corresponding water flow rate satisfying the set water temperature difference according to a relationship (e.g., Q1 × ΔT1 = Q2 × ΔT2) between the water temperature difference and the water flow rate. The water flow rate Q2 corresponding to the set water temperature difference is equal to a quotient of a product of the current water flow rate Q1 and the current water temperature difference ΔT1 and the set water temperature difference ΔT2 (e.g., Q2 = Q1 × ΔT1 / ΔT2). Then, a rotational speed of the water pump corresponding to initial constant temperature difference is obtained through the same control method as the constant water flow rate function. During operation of the water pump, the rotational speed of the water pump is dynamically adjusted according to the temperature values detected by the outlet water temperature sensor 501 and the return water temperature sensor 502, and the process is as shown in FIG. 31.

[0229] In step 1, the water pump 402 operates at a rotational speed corresponding to a constant water temperature difference. Time t15 elapses.

[0230] In step 2, ΔR3(n) = η4 × {Δtr(n) - Δtr(n-1)} + η5 × Δtr(n). ΔR4(n) = η6 × Δtr(n).

[0231] In step 3, ΔR'(n) = ΔR3(n) + ΔR4(n).

[0232] In step 4, R(n) = R(n-1) + ΔR'(n). Step 1 is performed. R(n) is a water pump rotational speed ratio at the n moment (i.e., a ratio of a rotational speed of the water pump at the n moment to the maximum rotational speed, the unit being %); R(n-1) is a water pump rotational speed ratio at the (n-1) moment (i.e., a ratio of a rotational speed of the water pump at the (n-1) moment to the maximum rotational speed, the unit being %); R'(n) is a water pump rotational speed change ratio at the n moment (the constant water temperature difference control), and the unit is %; R3(n) is a water pump rotational speed change ratio in PID control at the n moment (the constant water temperature difference control), and the unit is %; R4(n) is a water pump rotational speed change ratio in the over modulation control and the under modulation control at the n moment (the constant water temperature difference control), and the unit is %; η4 and η5 are PID control constants in the constant water temperature difference control (being less than 0); η6 is a control constant in the over modulation and the under modulation of the constant temperature difference control; tr(n) is a difference between the detected water temperature difference and the set water temperature difference at the n moment, Δtr(n) = Δt(n) - Δts(n); t(n) is the detected water temperature difference at the n moment, and the unit is °C; ts(n) is the set water temperature difference at the n moment, and the unit is °C; Time t15 is a duration when the water pump operates at a rotational speed corresponding to a constant water temperature difference, the unit is second.

[0233] The present disclosure may achieve the water pump characteristic test and the pipeline characteristic test through the heat pump system as shown in FIG. 21, and achieve the automatic adjustment of the rotational speed of the water pump according to the test results without repeated debugging. Moreover, constant rotational speed control, constant water flow rate control, and constant water temperature difference control of the heat pump system may also be achieved according to requirements of the user.

[0234] Some embodiments of the present disclosure provide a control method of a heat pump system, and the heat pump system may be the heat pump system described in any of the above embodiments. As shown in FIG. 32, the control method of the heat pump system includes step 321 to step 324.

[0235] In step 321, it is determined whether the heat pump system satisfies a preset condition; the preset condition includes a low-temperature heating condition, a defrosting condition, a high-temperature heating condition or a rapid heating condition.

[0236] In step 322, the terminal heat exchange portion is controlled to exchange heat with the third heat exchange portion if the heat pump system satisfies the low-temperature heating condition or the defrosting condition.

[0237] The low-temperature heating condition includes but is not limited to a set temperature being lower than a first preset temperature; the defrosting condition includes but is not limited to a temperature of the terminal heat exchange portion 17 being higher than a second preset temperature, and the second preset temperature may be, for example, 8 °C.

[0238] In some embodiments, in a case where the heat pump system satisfies the low-temperature heating condition or the defrosting condition, the first compressor 33 is controlled to stop; or, the first compressor 33 is controlled to stop while the first valve element 22 and the second valve element 23 are controlled to be closed, and the third valve element 24 is controlled to open.

[0239] In step 323, the terminal heat exchange portion is controlled to exchange heat with the fourth heat exchange portion if the heat pump system satisfies the high-temperature heating condition.

[0240] The high-temperature heating condition includes that the set temperature is higher than a third preset temperature.

[0241] In a case where the heat pump system satisfies the high-temperature heating condition, the first compressor 33 is controlled to operate; or the first compressor 33 is controlled to operate while the first valve element 22 and the second valve element 23 are controlled to communicate with each other and the third valve element 24 is controlled to be closed.

[0242] In step 324, the terminal heat exchange portion is controlled to exchange heat with the third heat exchange portion and the fourth heat exchange portion if the heat pump system satisfies the rapid heating condition.

[0243] The rapid heating condition includes that the heat pump system is required to be heated to a fourth preset temperature within a short time. For example, in a case where the water heater is turned on and the set temperature is 40 °C, the heat pump system is required to be heated to 40 °C within a short time.

[0244] In a case where the heat pump system satisfies the rapid heating condition, the first compressor 33 is controlled to operate; or, the first compressor 33 is controlled to operate while the first valve element 22, the second valve element 23 and the third valve element 24 are controlled to communicate with each other.

[0245] In the control method of the heat pump system provided by the embodiments of the present disclosure, in a case where the heat pump system satisfies the low-temperature heating condition, the terminal heat exchange portion is controlled to perform heat exchange with the third heat exchange portion. In this case, the low-temperature-stage circulation system operates and the high-temperature-stage circulation system stops. Compared with that the low-temperature-stage circulation system and the high-temperature-stage circulation system must be started simultaneously in the low-temperature heating condition, the control method of the heat pump system provided by the embodiments of the present disclosure may avoid a problem of low reliability of system operation caused by insufficient pressure difference in the high-temperature-stage circulation system by controlling the high-temperature-stage circulation system to stop operating, so as to ensure the reliable operation of the heat pump system. That is to say, the control method of the heat pump system provided by the embodiments of the present disclosure may independently control whether the low-temperature-stage circulation system and the high-temperature-stage circulation system operate, so as to achieve high flexibility and low energy consumption.

[0246] The foregoing descriptions are merely specific implementations of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any person skilled in the art could conceive of changes or replacements within the technical scope of the present disclosure, which shall be included in the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure shall be subject to the protection scope of the claims.

Claims

1. A heat pump system, comprising: a heat pump indoor unit, the heat pump indoor unit including: a cascade heat exchanger, the cascade heat exchanger including: a first heat exchange portion connected to a low-temperature-stage circulation pipeline, there being a first refrigerant in the low-temperature-stage circulation pipeline; a second heat exchange portion connected to a high-temperature-stage circulation pipeline, there being a second refrigerant in the high-temperature-stage circulation pipeline, and the second heat exchange portion being configured to perform heat exchange with the first heat exchange portion; a terminal heat exchanger assembly, the terminal heat exchanger assembly including: a third heat exchange portion connected to the low-temperature-stage circulation pipeline; a fourth heat exchange portion connected to the high-temperature-stage circulation pipeline; and a terminal heat exchange portion connected to an indoor end apparatus, the terminal heat exchange portion being configured to perform heat exchange with the third heat exchange portion, or the fourth heat exchange portion, or the third heat exchange portion and the fourth heat exchange portion.

2. The heat pump system according to claim 1, wherein the heat pump indoor unit further includes: a first valve element disposed between the first heat exchange portion and the low-temperature-stage circulation pipeline, the first valve element being configured to adjust a flow rate of the first refrigerant in the first heat exchange portion; a second valve element disposed between the second heat exchange portion and the fourth heat exchange portion, the second valve element being configured to adjust a flow rate of the second refrigerant in the second heat exchange portion and the fourth heat exchange portion; and a third valve element disposed between the third heat exchange portion and the low-temperature-stage circulation pipeline, the third valve element being configured to adjust a flow rate of the first refrigerant in the third heat exchange portion.

3. The heat pump system according to claim 2, wherein the heat pump indoor unit further includes a first compressor; in a case where the heat pump system satisfies a low-temperature heating condition or a defrosting condition, the first compressor stops, the first valve element and the second valve element are configured to operate in a closed state, and the third valve element is configured to operate in an opening state, and a medium in the terminal heat exchange portion performs heat exchange with the first refrigerant in the third heat exchange portion; in a case where the heat pump system satisfies a high-temperature heating condition, the first compressor operates, the first valve element and the second valve element are configured to operate in the opening state, and the third valve element is configured to operate in the closed state, the medium in the terminal heat exchange portion performs heat exchange with the second refrigerant in the fourth heat exchange portion; in a case where the heat pump system satisfies a rapid heating condition, the first compressor operates, the first valve element, the second valve element, and the third valve element are configured to operate in the opening state, and the medium in the terminal heat exchange portion performs heat exchange with the first refrigerant in the third heat exchange portion and the second refrigerant in the fourth heat exchange portion.

4. The heat pump system according to any one of claims 1 to 3, wherein the terminal heat exchange portion includes: a first terminal heat exchange sub-portion, a medium in the first terminal heat exchange sub-portion performing heat exchange with the first refrigerant in the third heat exchange portion; and a second terminal heat exchange sub-portion, a medium in the second terminal heat exchange sub-portion performing heat exchange with the second refrigerant in the fourth heat exchange portion.

5. The heat pump system according to claim 4, wherein the heat pump indoor unit further includes a first compressor and a second valve element; wherein the second valve element is connected to a first port of the fourth heat exchange portion and a first port of the second heat exchange portion, an end of the first compressor is connected to a second port of the fourth heat exchange portion, and another end of the first compressor is connected to a second port of the second heat exchange portion.

6. The heat pump system according to claim 5, further comprising a heat pump outdoor unit, the heat pump outdoor unit including an outdoor heat exchanger, a second compressor, a four-way valve, and a fourth valve element; wherein two ends of the fourth valve element are connected to a first port of the third heat exchange portion and a first port of the outdoor heat exchanger respectively, two ends of the four-way valve are connected to a first port of the first heat exchange portion and a second port of the outdoor heat exchanger respectively, another two ends of the four-way valve are connected to two ends of the second compressor respectively, and a second port of the third heat exchange portion is connected to a second port of the first heat exchange portion; or the two ends of the fourth valve element are connected to the second port of the first heat exchange portion and the first port of the outdoor heat exchanger respectively, the two ends of the four-way valve are connected to the second port of the third heat exchange portion and the second port of the outdoor heat exchanger respectively, the another two ends of the four-way valve are connected to the two ends of the second compressor respectively, and the first port of the third heat exchange portion is connected to the first port of the first heat exchange portion.

7. The heat pump system according to claim 6, wherein the heat pump indoor unit further includes a water inlet pipe, a water pump, a first electric three-way valve, and a water outlet pipe; an inlet of the water pump is connected to the water inlet pipe, an outlet of the water pump is connected to an inlet of the first electric three-way valve, and a first outlet of the first electric three-way valve is connected to a first port of the first terminal heat exchange sub-portion, a second outlet of the first electric three-way valve is connected to a first port of the second terminal heat exchange sub-portion, and a second port of the first terminal heat exchange sub-portion and a second port of the second terminal heat exchange sub-portion each are connected to the water outlet pipe; or the inlet of the water pump is connected to the water inlet pipe, the outlet of the water pump is connected to the first port of the first terminal heat exchange sub-portion, and the second port of the first terminal heat exchange sub-portion is connected to the inlet of the first electric three-way valve, the first outlet of the first electric three-way valve is connected to the first port of the second terminal heat exchange sub-portion, the second port of the second terminal heat exchange sub-portion and the second outlet of the first electric three-way valve each are connected to the water outlet pipe.

8. The heat pump system according to any one of claims 1 to 7, wherein the heat pump indoor unit further includes: a buffer water tank having a first water inlet, a first water outlet, a first return water inlet and a second water outlet; the indoor end apparatus including a domestic hot water tank and at least one space heating or cooling device, at least two of the domestic hot water tank or the at least one space heating or cooling device switching with each other for operation; a relay reversing device having a second water inlet communicating with a water outlet of the terminal heat exchange portion, a third water outlet communicating with a return water inlet of the terminal heat exchange portion, and a second return water inlet and a fourth water outlet that communicate with main pipes of the indoor end apparatus, and the relay reversing device further including: a first straight-through path communicating with the second water inlet and the fourth water outlet; a first bypass path, the first bypass path including: a first bypass sub-path communicating with the first water inlet and the second water inlet; a second bypass sub-path communicating with the first water outlet and the fourth water outlet; the first straight-through path communicating with the first bypass path in a switching manner; a second straight-through path communicating with the second return water inlet and the third water outlet; a second bypass path, the second bypass path including: a third bypass sub-path communicating with the first return water inlet and the second return water inlet; a fourth bypass sub-path communicating with the second water outlet and the third water outlet; the second straight-through path communicating with the second bypass path in a switching manner.

9. The heat pump system according to claim 8, wherein the relay reversing device includes: a second electric three-way valve, a third electric three-way valve, a fourth electric three-way valve and a fifth electric three-way valve; wherein a first end of the second electric three-way valve communicates with the second water inlet, a second end of the second electric three-way valve communicates with a first end of the third electric three-way valve, and a second end of the third electric three-way valve communicates with the fourth water outlet, a third end of the second electric three-way valve communicates with the first water inlet, and a third end of the third electric three-way valve communicates with the first water outlet; a first end of the fourth electric three-way valve communicates with the third water outlet, the second end of the second electric three-way valve communicates with a first end of the fifth electric three-way valve, and a second end of the fifth electric three-way valve communicates with the second return water inlet, a third end of the fourth electric three-way valve communicates with the second water outlet, and a third end of the fifth electric three-way valve communicates with the first return water inlet.

10. The heat pump system according to claim 9, wherein the relay reversing device further includes: a first force lift pump disposed on a pipeline between the second water inlet and the first end of the second electric three-way valve, so as to increase a pressure of water in the pipeline; a second force lift pump disposed on a pipeline between the second end of the third electric three-way valve and the fourth water outlet, so as to increase a pressure of water in the pipeline.

11. The heat pump system according to claim 9, wherein the heat pump indoor unit further includes: an auxiliary heat source communicating with the buffer water tank through a connecting pipeline, the auxiliary heat source including a gas wall mounted furnace, a solar water heater, or a gas water heater; the space heating or cooling device including at least one of a fan coil or a floor heating.

12. The heat pump system according to any one of claims 1 to 7, wherein the heat pump indoor unit further includes: a pressure detecting device configured to detect an upstream pressure and a downstream pressure of a water pump; a flow rate detecting device configured to detect a flow rate of the water pump; a water pump self-circulation pipeline provided with the water pump and an electric regulating valve; a water system full-circulation pipeline provided with the water pump, the terminal heat exchange portion and the indoor end apparatus; and a controller coupled to the pressure detecting device and the flow rate detecting device, the controller being configured to perform a water pump characteristic test through the water pump self-circulation pipeline and perform a pipeline characteristic test through the water system full-circulation pipeline based on at least one of the upstream pressure of the water pump, the downstream pressure of the water pump, or the flow rate of the water pump.

13. The heat pump system according to claim 12, wherein the controller is configured to: control the water pump to operate at a first rotational speed and control the electric regulating valve to maintain a first opening degree corresponding to the first rotational speed within a first preset duration; calculate an average of differences between the downstream pressures and the upstream pressures detected by the pressure detecting device within the first preset duration, so as to obtain a first operating parameter, the first operating parameter corresponding to a lift of the water pump, and the first operating parameter including the first rotational speed and the first opening degree; calculate an average of the flow rates detected by the flow rate detecting device within the first preset duration, so as to obtain an average of the flow rates of the water pump corresponding to the first operating parameter; obtain a test result of the water pump characteristic test according to the lifts of the water pump corresponding to a plurality of operating parameters and the averages of the flow rates of the water pump corresponding to the plurality of operating parameters, the plurality of operating parameters including the first operating parameter, and the test result of the water pump characteristic test including a water pump characteristic curve.

14. The heat pump system according to claim 12, wherein the controller is configured to: control the water pump to operate at a second rotational speed for a second preset duration; calculate an average of differences between the downstream pressures and the upstream pressures detected by the pressure detecting device within the second preset duration, so as to obtain a resistance in the pipeline corresponding to the second rotational speed; calculate an average of the flow rates detected by the flow rate detecting device within the second preset duration, so as to obtain an average of the flow rates corresponding to the second rotational speed; obtain a test result of the pipeline characteristic test according to the resistances in the pipeline corresponding to a plurality of rotational speeds and the averages of the flow rates corresponding to the plurality of rotational speeds, and the test result of the pipeline characteristic test including a pipeline characteristic curve.

15. The heat pump system according to claim 12, the water pump self-circulation pipeline includes a first water supply port, and the water system full-circulation pipeline includes a second water supply port; the controller is further configured to: replenish water through the first water supply port or the second water supply port, before the water pump characteristic test or the pipeline characteristic test is performed, and after a water pump self-circulation or a water system full-circulation starts, in a case where the downstream pressure of the water pump is lower than a lower limit value of a water system pressure; control the water pump to operate intermittently until the water pump has completed emptying, in a case where the downstream pressure of the water pump is higher than the lower limit value of the water system pressure; wherein in a case where the water pump has completed emptying, the downstream pressure of the water pump is between the lower limit value and an upper limit value of the water system pressure, and an absolute of a difference between the downstream pressure of the water pump at a first moment and the downstream pressure of the water pump at a second moment is lower than a water pressure fluctuation limit value within a third preset duration.

16. The heat pump system according to claim 14, wherein the controller is further configured to: obtain a first water flow rate; obtain a rotational speed corresponding to the first water flow rate according to the first water flow rate and the pipeline characteristic curve; control the water pump to operate at the rotational speed corresponding to the first water flow rate.

17. The heat pump system according to claim 12, wherein the heat pump indoor unit further includes a temperature detecting device for detecting an outlet water temperature and a return water temperature of the terminal heat exchange portion; the controller is further configured to: obtain a water temperature difference required by a user; obtain a current water temperature difference according to a current outlet water temperature and a current return water temperature of the terminal heat exchange portion; calculate a target water flow rate according to the current water temperature difference, a current water flow rate detected by the flow rate detecting device, and the water temperature difference required by the user; control the water pump to operate at a preset maximum rotational speed, and control the water pump to operate at a target rotational speed corresponding to the target water flow rate after the water pump operates stably.

18. A control method of a heat pump system, the heat pump system being the heat pump system according to any one of claims 1 to 17, the method comprising: determining whether the heat pump system satisfies a preset condition, and the preset condition including a low-temperature heating condition, a defrosting condition, a high-temperature heating condition or a rapid heating condition; controlling the terminal heat exchange portion to perform heat exchange with the third heat exchange portion, if the heat pump system satisfies the low-temperature heating condition or the defrosting condition; controlling the terminal heat exchange portion to perform heat exchange with the fourth heat exchange portion, if the heat pump system satisfies the high-temperature heating condition; controlling the terminal heat exchange portion to perform heat exchange with the third heat exchange portion and the fourth heat exchange portion, if a set temperature satisfies the rapid heating condition.

19. The method according to claim 18, wherein the heat pump indoor unit further includes a first compressor, an end of the first compressor is connected to the second port of the fourth heat exchange portion, and another end of the first compressor is connected to the second port of the second heat exchange portion; the method further comprises: controlling the first compressor to stop in a case where the heat pump system satisfies the low-temperature heating condition or the defrosting condition; controlling the first compressor to operate in a case where the heat pump system satisfies the high-temperature heating condition or the rapid heating condition.

20. The method according to claim 19, wherein the heat pump indoor unit further includes the first valve element, the second valve element and the third valve element, wherein the first valve element is disposed between the first heat exchange portion and the low-temperature-stage circulation pipeline, the second valve element is disposed between the second heat exchange portion and the fourth heat exchange portion, and the third valve element is disposed between the third heat exchange portion and the low-temperature-stage circulation pipeline; that controlling the first compressor to stop in the case where the heat pump system satisfies the low-temperature heating condition or the defrosting condition, includes controlling the first compressor to stop, the first valve element and the second valve element to be closed, and the third valve element to open, in a case where the heat pump system satisfies the low-temperature heating condition or the defrosting condition; that controlling the first compressor to operate in the case where the heat pump system satisfies the high-temperature heating condition or the rapid heating condition, includes controlling the first compressor to operate, the first valve element and the second valve element to communicate with each other, and the third valve element to be closed, in a case where the heat pump system satisfies the high-temperature heating condition; and controlling the first compressor to operate, the first valve element, the second valve element and the third valve element to communicate with each other, in a case where the heat pump system satisfies the rapid heating condition.

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