Control method of heat pump water heater system and heat pump water heater system

Abstract

The present application relates to the technical field of heat pump system, and particularly provides a control method of heat pump water machine system and the heat pump water machine system, aiming at solving the problem that the outdoor fan speed and system load are not matched during the lag period from the change of water inlet temperature to the change of coil temperature of the heat pump water machine system, and the system energy efficiency ratio is low. For this purpose, the control method of the heat pump water machine system comprises the following steps: calculating the target coil temperature according to the operation mode, compressor frequency, water inlet temperature and coil temperature of the heat pump water machine system; adjusting the speed of the outdoor fan according to the operation mode and the target coil temperature. The present application takes the water inlet temperature as the parameter for calculating the target coil temperature, adjusts the speed of the outdoor fan according to the target coil temperature, can predict the load trend of the system before the load demand of the system changes but the coil temperature does not change obviously, and adjusts the speed of the outdoor fan in advance, so that the speed and the load are matched, and the energy efficiency ratio of the heat pump water machine system is improved.

Description

Technical Field

[0001] This invention relates to the field of heat pump system technology, and specifically provides a control method for a heat pump water heater system and a heat pump water heater system. Background Technology

[0002] Heat pump water chiller systems, as highly efficient and energy-saving heating and cooling devices, have a wide range of applications. A heat pump water chiller system includes a compressor, a four-way valve, an air-side heat exchanger, an outdoor fan, a throttling device, a water-side heat exchanger, a water pump, and terminal equipment. The compressor, four-way valve, air-side heat exchanger, throttling device, and water-side heat exchanger are connected via a refrigerant circulation loop. The outdoor fan is used to dissipate heat by allowing air to flow through the air-side heat exchanger. The water-side heat exchanger is connected to inlet and outlet pipes, which are connected to the terminal equipment. After exchanging heat with the refrigerant in the water-side heat exchanger, the water flows into the terminal equipment, driven by the water pump. The terminal equipment includes fan coil units, underfloor heating coils, or radiators. The fan speed of the outdoor fan is a crucial factor affecting the heat exchange efficiency of the air-side heat exchanger, which in turn affects the energy efficiency ratio (EER) of the heat pump water chiller system.

[0003] In existing technologies, the control method for heat pump water chiller systems typically calculates the target coil temperature based on the outdoor ambient temperature, compressor frequency, and the coil temperature of the water-side heat exchanger. The fan speed is then adjusted in real-time based on the difference between the target and actual coil temperatures to improve the heat exchange efficiency of the air-side heat exchanger. During the operation of the heat pump water chiller system, changes in the load demand of the terminal equipment cause a change in the inlet water temperature of the water-side heat exchanger, which in turn alters the heat exchange temperature difference of the water-side heat exchanger and the system load. This load change is transmitted through the refrigerant circulation, ultimately causing a change in the coil temperature of the air-side heat exchanger.

[0004] However, heat pump water heater systems have significant thermal inertia. There is a considerable time lag between changes in inlet water temperature and changes in coil temperature. During this lag, the outdoor fan speed does not match the system load, resulting in relatively low energy efficiency of the heat pump water heater system.

[0005] Accordingly, there is a need in the field for a new control method for a heat pump water heater system and a new heat pump water heater system to solve the above problems. Summary of the Invention

[0006] The present invention aims to solve the above-mentioned technical problems, namely, to solve the problem that the heat pump water heater system has a large thermal inertia, and there is a significant time lag between the change of inlet water temperature and the change of coil temperature. During the lag period, the wind speed of the outdoor fan does not match the system load, resulting in the low energy efficiency of the heat pump water heater system.

[0007] In a first aspect, the present invention provides a control method for a heat pump water heater system; the heat pump water heater system includes a compressor, a water-side heat exchanger, an air-side heat exchanger, and an outdoor fan, wherein the outdoor fan is used to allow air to flow through the air-side heat exchanger; The control method for the heat pump water system includes the following steps: The target coil temperature is calculated based on the operating mode of the heat pump water system, the compressor frequency, the inlet water temperature of the water-side heat exchanger, and the coil temperature of the air-side heat exchanger. The speed of the outdoor fan is adjusted according to the operating mode and the target coil temperature.

[0008] In the preferred technical solution of the control method for the above-mentioned heat pump water heater system, "calculating the target coil temperature based on the operating mode of the heat pump water heater system, the compressor frequency, the inlet water temperature of the water-side heat exchanger, and the coil temperature of the air-side heat exchanger" specifically includes: When the heat pump water heater system is in cooling mode, the target coil temperature is calculated using the following formula: T m = (T s +k1·P y )·(1+k2·(T) j -a℃)); Among them, T m It is the target coil temperature, T s This is the actual coil temperature, k1 is the compressor coefficient in cooling mode, and P... y It is the compressor frequency, k2 is the water temperature correction factor in cooling mode, and T j 'a' is the inlet water temperature, and 'a' is a constant.

[0009] In the preferred embodiment of the control method for the aforementioned heat pump water heater system, "adjusting the speed of the outdoor fan according to the operating mode and the target coil temperature" specifically includes: When the heat pump water heater system is in cooling mode, the speed of the outdoor fan is adjusted according to the target coil temperature, the first preset temperature, and the second preset temperature. Preferably, "adjusting the speed of the outdoor fan according to the target coil temperature, the first preset temperature, and the second preset temperature" specifically includes: If the target coil temperature is not greater than the first preset temperature, reduce the speed of the outdoor fan; and / or If the target coil temperature is greater than the first preset temperature but not greater than the second preset temperature, the outdoor fan speed remains unchanged, wherein the first preset temperature is less than the second preset temperature; and / or If the target coil temperature is greater than the second preset temperature, increase the speed of the outdoor fan.

[0010] In the preferred embodiment of the control method for the above-mentioned heat pump water system, the rotation speed of the outdoor fan is divided into multiple gears; "If the target coil temperature is not greater than the first preset temperature, reduce the speed of the outdoor fan" specifically includes: If the target coil temperature is not greater than the first preset temperature, reduce the speed of the outdoor fan by one level; and / or "If the target coil temperature is greater than the second preset temperature, increase the speed of the outdoor fan" specifically includes: If the target coil temperature is greater than the second preset temperature, the speed of the outdoor fan will be increased by one level.

[0011] In the preferred embodiment of the control method for the aforementioned heat pump water heater system, "calculating the target coil temperature based on the operating mode of the heat pump water heater system, the compressor frequency, the inlet water temperature of the water-side heat exchanger, and the coil temperature of the air-side heat exchanger" further includes: When the heat pump water heater system is in heating mode, the target coil temperature is calculated using the following formula: T m = (T s -k3·P y )·(1+k4·(T) j -b℃)); Among them, T m It is the target coil temperature, T s This is the actual coil temperature, k3 is the compressor coefficient in heating mode, and P... y This is the compressor frequency, k4 is the water temperature correction factor in heating mode, and T... j is the inlet water temperature, and b is a constant.

[0012] In the preferred embodiment of the control method for the aforementioned heat pump water heater system, "adjusting the speed of the outdoor fan according to the operating mode and the target coil temperature" specifically includes: When the heat pump water heater system is in heating mode, the speed of the outdoor fan is adjusted according to the target coil temperature, the third preset temperature, and the fourth preset temperature. Preferably, "adjusting the speed of the outdoor fan according to the target coil temperature, the third preset temperature, and the fourth preset temperature" specifically includes: If the target coil temperature is not greater than the third preset temperature, increase the speed of the outdoor fan; and / or If the target coil temperature is greater than the third preset temperature but not greater than the fourth preset temperature, the outdoor fan speed remains unchanged, wherein the third preset temperature is less than the fourth preset temperature; and / or If the target coil temperature is greater than the fourth preset temperature, reduce the speed of the outdoor fan.

[0013] In the preferred embodiment of the control method for the above-mentioned heat pump water system, the rotation speed of the outdoor fan is divided into multiple gears; "If the target coil temperature is not greater than the third preset temperature, increase the speed of the outdoor fan" specifically includes: If the target coil temperature is not greater than the third preset temperature, increase the speed of the outdoor fan by one level; and / or "If the target coil temperature is greater than the fourth preset temperature, reduce the speed of the outdoor fan" specifically includes: If the target coil temperature is greater than the fourth preset temperature, the outdoor fan speed will be reduced by one level.

[0014] In the preferred embodiment of the control method for the above-mentioned heat pump water heater system, before the step of "calculating the target coil temperature based on the operating mode of the heat pump water heater system, the compressor frequency, the inlet water temperature of the water-side heat exchanger, and the coil temperature of the air-side heat exchanger", the control method further includes: The initial speed of the outdoor fan is determined based on the compressor frequency and the outdoor ambient temperature. The outdoor fan operates at its initial speed for a first preset duration.

[0015] In a second aspect, the present invention also provides a heat pump water heater system; the heat pump water heater system includes a control module configured to perform the control method described above.

[0016] In the preferred embodiment of the above-mentioned heat pump water system, the heat pump water system further includes a water pump and terminal equipment. The water-side heat exchanger is connected to the terminal equipment by an inlet pipe and an outlet pipe. The water in the water-side heat exchanger exchanges heat with the refrigerant. The water pump can supply the water after heat exchange to the terminal equipment through the outlet pipe and supply the water after heat exchange with the terminal equipment to the water-side heat exchanger through the inlet pipe.

[0017] When adopting the above technical solution, the heat pump water heater system of the present invention calculates the target coil temperature based on the operating mode, compressor frequency, inlet water temperature of the water-side heat exchanger, and coil temperature of the air-side heat exchanger; and adjusts the speed of the outdoor fan according to the operating mode and the target coil temperature. By using the operating mode and inlet water temperature as parameters for calculating the target coil temperature, and then adjusting the speed of the outdoor fan according to the target coil temperature, the load trend of the heat pump water heater system can be predicted based on the inlet water temperature and operating mode before the coil temperature changes, and the speed of the outdoor fan can be adjusted in advance to match the speed of the outdoor fan with the load of the heat pump water heater system, thereby improving the energy efficiency ratio of the heat pump water heater system.

[0018] The formula for calculating the target coil temperature differs between the cooling and heating modes of a heat pump water heater system. This ensures that the outdoor fan speed matches the system load in different operating modes, reducing compressor power consumption and improving the system's energy efficiency ratio. Attached Figure Description

[0019] The preferred embodiments of the present invention are described below with reference to the accompanying drawings, in which: Figure 1 This is a flowchart of the main steps of the control method for the heat pump water system of the present invention; Figure 2 This is a flowchart illustrating the specific steps of the control method for the heat pump water heater system of the present invention; Figure 3 yes Figure 2 Flowchart of the specific steps in step S61; Figure 4 yes Figure 2 The flowchart of the specific steps in step S62. Detailed Implementation

[0020] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the invention and are not intended to limit the scope of protection of the invention. Those skilled in the art can make adjustments as needed to adapt to specific applications.

[0021] It should be noted that in the description of this invention, terms such as "upper," "lower," "left," and "right," indicating directional or positional relationships, are based on the directional or positional relationships shown in the accompanying drawings. These are merely for ease of description and do not indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on this invention. Furthermore, the terms "first," "second," "third," and "fourth" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0022] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "connected" should be interpreted broadly. For example, they can refer to a fixed connection or a detachable connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0023] To address the significant thermal inertia of heat pump water heater systems, where there is a substantial time lag between changes in inlet water temperature and changes in coil temperature, and the mismatch between outdoor fan speed and system load during this lag period, resulting in relatively low energy efficiency of the heat pump water heater system.

[0024] like Figures 1 to 4 As shown, this embodiment discloses a control method for a heat pump water heater system. The heat pump water heater system includes a compressor, a four-way valve, an air-side heat exchanger, an outdoor fan, a throttling device, a water-side heat exchanger, a water pump, and terminal equipment. The refrigerant pipelines of the compressor, four-way valve, air-side heat exchanger, throttling device, and water-side heat exchanger are connected through a refrigerant circulation loop. The outdoor fan is located on one side of the air-side heat exchanger to promote airflow through the air-side heat exchanger for heat exchange, thereby improving the heat exchange effect of the air-side heat exchanger. The outdoor fan has multiple speed settings; the higher the setting, the faster the speed, and the better the heat exchange effect on the air-side heat exchanger. A coil temperature sensor is installed on the coil of the air-side heat exchanger to detect the coil temperature.

[0025] The water inlet of the water-side heat exchanger is connected to an inlet pipe, and the water outlet is connected to an outlet pipe. The inlets of all terminal devices are connected to the inlet pipe, and the outlets of all terminal devices are connected to the outlet pipe. A water pump is installed on either the inlet or outlet pipe. An inlet water temperature sensor is installed on the inlet pipe to detect the temperature of the water entering the water-side heat exchanger, i.e., the inlet water temperature.

[0026] Water exchanges heat with the refrigerant in the refrigerant piping within the water-side heat exchanger. After heat exchange, the water flows into the terminal equipment driven by a water pump. After heat exchange within the terminal equipment, it flows back into the water-side heat exchanger through the inlet pipe. Terminal equipment includes fan coil units, underfloor heating coils, or radiators, etc. Terminal equipment can include one type of equipment or multiple types of equipment. There can be one or more terminal equipment. The inlets of multiple terminal equipment are all connected to the outlet pipes, and the outlets of multiple terminal equipment are all connected to the inlet pipes.

[0027] The heat pump water heater system also includes a control module, which is electrically connected to the compressor, outdoor fan, inlet water temperature sensor and coil temperature sensor. The control module is configured to perform the control method of the heat pump water heater system as described below.

[0028] like Figure 1 As shown, the main steps of the control method for a heat pump water system include: S1. Calculate the target coil temperature based on the operating mode of the heat pump water heater system, the compressor frequency, the inlet water temperature of the water-side heat exchanger, and the coil temperature of the air-side heat exchanger.

[0029] S2. Adjust the speed of the outdoor fan according to the operating mode and target coil temperature.

[0030] By using the operating mode and inlet water temperature as parameters for calculating the target coil temperature, and then adjusting the outdoor fan speed according to the target coil temperature, the load trend of the heat pump water heater system can be predicted based on the inlet water temperature and operating mode before the coil temperature changes significantly. This allows for advance adjustment of the outdoor fan speed to match the load of the heat pump water heater system, thereby improving the energy efficiency ratio of the heat pump water heater system.

[0031] like Figure 2 As shown, the specific steps of the control method for a heat pump water system include: S1. After the heat pump water system is turned on, obtain the compressor frequency and outdoor ambient temperature.

[0032] S2. Determine the initial operating level of the outdoor fan based on the compressor frequency and outdoor ambient temperature. Alternatively, the initial speed of the outdoor fan can also be determined based on the compressor frequency and outdoor ambient temperature. When the heat pump water system receives the start-up command, the control module determines the initial operating level of the outdoor fan based on the current outdoor ambient temperature and compressor frequency using an internally stored initialization mapping table. The initialization mapping table records the mapping relationship between outdoor ambient temperature, compressor frequency, and initial operating level.

[0033] S3. The outdoor fan operates at its initial setting for a first preset time, preferably 60 seconds. During this first preset time after the heat pump water system is turned on, the refrigerant completes initial circulation and distribution, and the system pressure and temperature tend to stabilize, providing a smooth starting point for subsequent adjustments to the outdoor fan setting based on the operating mode, compressor frequency, inlet water temperature, and coil temperature.

[0034] S4. Obtain the operating mode, compressor frequency, inlet water temperature, and coil temperature of the heat pump water heater system. The operating modes include heating mode and cooling mode. In heating mode, the water-side heat exchanger heats the water, and conversely, in cooling mode, the water-side heat exchanger cools the water.

[0035] S5. Determine if the heat pump water heater system is operating in cooling mode. If it is, execute S61 to calculate the target coil temperature based on the compressor frequency, inlet water temperature, and coil temperature, and adjust the outdoor fan speed accordingly. If it is not operating in cooling mode, execute S62 to calculate the target coil temperature based on the compressor frequency, inlet water temperature, and coil temperature, and adjust the outdoor fan speed accordingly. Based on the inlet water temperature and operating mode, predict the load trend of the heat pump water heater system and adjust the outdoor fan speed in advance to match the system load, thereby improving the system's energy efficiency ratio.

[0036] S7. The outdoor fan runs at the current speed for a second preset time, preferably 60 seconds. Then return to step S4 to reacquire the operating mode, compressor frequency, inlet water temperature, and coil temperature of the heat pump water heater system. This cycle repeats. When the load of the heat pump water heater system changes, the speed of the outdoor fan can be adjusted in time to better match the system load and improve the system energy efficiency ratio.

[0037] like Figure 3 As shown, Figure 2 The specific steps of step S61 include: S611, Calculate T m = (T s +k1·P y )·(1+k2·(T) j -a℃)); Among them, T m It is the target coil temperature, T s This is the actual coil temperature, k1 is the compressor coefficient in cooling mode, and P... y It is the compressor frequency, k2 is the water temperature correction factor in cooling mode, and T j Here, is the inlet water temperature, and 'a' is a constant. Preferably, the value of 'a' is in the range of 18-23. In this embodiment, the value of 'a' is 20 as an example.

[0038] S612. Determine if the target coil temperature is ≤ the first preset temperature. Preferably, the first preset temperature is 24℃. If it is not greater than the first preset temperature, execute S614 to reduce the outdoor fan speed by one level. If the target coil temperature is ≤ the first preset temperature, it indicates that the current system load is low and the air-side heat exchange demand is low. Excessive airflow may waste energy or cause the condensing temperature to be too low. In this case, reduce the outdoor fan speed by one level. If it is already at the lowest level, maintain the lowest level operation. If it is greater than the first preset temperature, execute S613.

[0039] S613. Determine if the target coil temperature is greater than the second preset temperature. The first preset temperature is less than the second preset temperature. Preferably, the second preset temperature is 36℃. If it is greater than the second preset temperature, execute S615 to increase the outdoor fan speed by one level. A target coil temperature greater than the second preset temperature indicates a high system load, and the existing airflow is insufficient to maintain the condensing temperature within the preset range. If heat dissipation is not timely, it will lead to increased condensing pressure and increased compressor power consumption. In this case, increase the outdoor fan speed by one level. If it is already at the highest speed, maintain that speed. If it is not greater than the second preset temperature (i.e., the target coil temperature is greater than the first preset temperature but not greater than the second preset temperature), execute S616. The outdoor fan speed remains unchanged, thus matching the system load.

[0040] like Figure 4 As shown, Figure 2 The specific steps of step S62 include: S621, Calculate T m = (T s -k3·P y )·(1+k4·(T) j -45℃) Among them, T m It is the target coil temperature, T s This is the actual coil temperature, k3 is the compressor coefficient in heating mode, and P... y This is the compressor frequency, k4 is the water temperature correction factor in heating mode, and T... j Here, is the inlet water temperature, and 'b' is a constant. Preferably, the value of 'b' is in the range of 42-48. In this embodiment, a value of 45 is used as an example for explanation.

[0041] S622. Determine if the target coil temperature is ≤ the third preset temperature. Preferably, the third preset temperature is 0℃. If it is not greater than the third preset temperature, execute S624 to increase the outdoor fan speed by one level. If the target coil temperature is ≤ the third preset temperature, it indicates that the evaporation temperature is too low, the heat exchange capacity is insufficient, and there may be a risk of frosting or a decrease in heating capacity. Increase the outdoor fan speed by one level to enhance the evaporator's heat absorption from the air. If it is already at the highest setting, maintain the highest setting operation.

[0042] S623. Determine if the target coil temperature is greater than the fourth preset temperature. The third preset temperature is less than the fourth preset temperature. Preferably, the fourth preset temperature is 8℃. If it is greater than the fourth preset temperature, execute S625 to reduce the outdoor fan speed by one level. A target coil temperature greater than the fourth preset temperature indicates a high evaporation temperature and a low system load. Excessive airflow may cause unnecessary power consumption. Reduce the outdoor fan speed by one level; if it is already at the lowest setting, maintain that setting. If it is not greater than the fourth preset temperature (i.e., the target coil temperature is greater than the third preset temperature but not greater than the fourth preset temperature), execute S626. The outdoor fan speed remains unchanged, thus matching the system load.

[0043] The formula for calculating the target coil temperature differs between the cooling and heating modes of a heat pump water heater system. This ensures that the outdoor fan speed matches the system load in different operating modes, reducing compressor power consumption and improving the system's energy efficiency ratio.

[0044] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A control method for a heat pump water system, characterized in that, The heat pump water system includes a compressor, a water-side heat exchanger, an air-side heat exchanger, and an outdoor fan, wherein the outdoor fan is used to allow air to flow through the air-side heat exchanger. The control method for the heat pump water system includes the following steps: The target coil temperature is calculated based on the operating mode of the heat pump water system, the compressor frequency, the inlet water temperature of the water-side heat exchanger, and the coil temperature of the air-side heat exchanger. The speed of the outdoor fan is adjusted according to the operating mode and the target coil temperature.

2. The control method according to claim 1, characterized in that, "Calculating the target coil temperature based on the operating mode of the heat pump water heater system, the compressor frequency, the inlet water temperature of the water-side heat exchanger, and the coil temperature of the air-side heat exchanger" specifically includes: When the heat pump water heater system is in cooling mode, the target coil temperature is calculated using the following formula: T m =(T s +k1·P y )·(1+k2·(T j -a℃)); Among them, T m It is the target coil temperature, T s This is the actual coil temperature, k1 is the compressor coefficient in cooling mode, and P... y It is the compressor frequency, k2 is the water temperature correction factor in cooling mode, and T j 'a' is the inlet water temperature, and 'a' is a constant.

3. The control method according to claim 1, characterized in that, "Adjusting the speed of the outdoor fan according to the operating mode and the target coil temperature" specifically includes: When the heat pump water heater system is in cooling mode, the speed of the outdoor fan is adjusted according to the target coil temperature, the first preset temperature, and the second preset temperature. Preferably, "adjusting the speed of the outdoor fan according to the target coil temperature, the first preset temperature, and the second preset temperature" specifically includes: If the target coil temperature is not greater than the first preset temperature, reduce the speed of the outdoor fan; and / or If the target coil temperature is greater than the first preset temperature but not greater than the second preset temperature, the outdoor fan speed remains unchanged, wherein the first preset temperature is less than the second preset temperature; and / or If the target coil temperature is greater than the second preset temperature, increase the speed of the outdoor fan.

4. The control method according to claim 3, characterized in that, The outdoor fan speed is divided into multiple gears; "If the target coil temperature is not greater than the first preset temperature, reduce the speed of the outdoor fan" specifically includes: If the target coil temperature is not greater than the first preset temperature, reduce the speed of the outdoor fan by one level; and / or "If the target coil temperature is greater than the second preset temperature, increase the speed of the outdoor fan" specifically includes: If the target coil temperature is greater than the second preset temperature, the speed of the outdoor fan will be increased by one level.

5. The control method according to claim 1, characterized in that, "Calculating the target coil temperature based on the operating mode of the heat pump water heater system, the compressor frequency, the inlet water temperature of the water-side heat exchanger, and the coil temperature of the air-side heat exchanger" also includes: When the heat pump water heater system is in heating mode, the target coil temperature is calculated using the following formula: T m =(T s -k3·P y )·(1+k4·(T j -b℃)); Among them, T m It is the target coil temperature, T s This is the actual coil temperature, k3 is the compressor coefficient in heating mode, and P... y This is the compressor frequency, k4 is the water temperature correction factor in heating mode, and T... j is the inlet water temperature, and b is a constant.

6. The control method according to claim 1, characterized in that, "Adjusting the speed of the outdoor fan according to the operating mode and the target coil temperature" specifically includes: When the heat pump water heater system is in heating mode, the speed of the outdoor fan is adjusted according to the target coil temperature, the third preset temperature, and the fourth preset temperature. Preferably, "adjusting the speed of the outdoor fan according to the target coil temperature, the third preset temperature, and the fourth preset temperature" specifically includes: If the target coil temperature is not greater than the third preset temperature, increase the speed of the outdoor fan; and / or If the target coil temperature is greater than the third preset temperature but not greater than the fourth preset temperature, the outdoor fan speed remains unchanged, wherein the third preset temperature is less than the fourth preset temperature; and / or If the target coil temperature is greater than the fourth preset temperature, reduce the speed of the outdoor fan.

7. The control method according to claim 6, characterized in that, The outdoor fan speed is divided into multiple gears; "If the target coil temperature is not greater than the third preset temperature, increase the speed of the outdoor fan" specifically includes: If the target coil temperature is not greater than the third preset temperature, increase the speed of the outdoor fan by one level; and / or "If the target coil temperature is greater than the fourth preset temperature, reduce the speed of the outdoor fan" specifically includes: If the target coil temperature is greater than the fourth preset temperature, the outdoor fan speed will be reduced by one level.

8. The control method according to claim 1, characterized in that, Before the step of "calculating the target coil temperature based on the operating mode of the heat pump water heater system, the compressor frequency, the inlet water temperature of the water-side heat exchanger, and the coil temperature of the air-side heat exchanger", the control method further includes: The initial speed of the outdoor fan is determined based on the compressor frequency and the outdoor ambient temperature. The outdoor fan operates at its initial speed for a first preset duration.

9. A heat pump water system, characterized in that, The heat pump water system includes a control module configured to perform the control method as described in any one of claims 1-8.

10. The heat pump water system according to claim 9, characterized in that, The heat pump water system also includes a water pump and terminal equipment. The water-side heat exchanger is connected to the terminal equipment by an inlet pipe and an outlet pipe. The water in the water-side heat exchanger exchanges heat with the refrigerant. The water pump can supply the water after heat exchange to the terminal equipment through the outlet pipe and supply the water after heat exchange with the terminal equipment to the water-side heat exchanger through the inlet pipe.

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