A heat pump unit

Abstract

The present application relates to a kind of heat pump unit, including the improved control compressor and the method of bottom heating unit start-stop of it, the method is obtained by comparing the ambient temperature with the preset ring temperature start valve, the water temperature obtained with the preset water temperature start valve, the temperature difference value obtained by the compressor bottom temperature and water temperature with the preset temperature difference threshold value, and according to the comparison result, the start-stop control of compressor and its heating unit.This control method can effectively avoid the refrigerant discharged after the first power-on compressor starts to condense from the compressor cavity and fall into the compressor oil pool, dilute the refrigeration oil, and cause the problem of wear and tear due to lack of oil in the compressor components;It can prolong the service life of compressor.

Description

Technical Field

[0001] This invention relates to the field of heat pumps, and more particularly to a heat pump unit. Background Technology

[0002] Heat pump units are highly efficient and energy-saving devices that can transfer heat from a low-temperature heat source to a high-temperature heat source for utilization. As a result, more and more residential applications are choosing heat pump units to meet the cooling and heating needs of home and work environments.

[0003] Refrigeration oil is an effective medium for protecting the moving parts of the heat pump unit compressor during operation, preventing damage caused by friction between the moving parts. When there is little or no refrigeration oil at the bottom of the compressor, the moving parts of the compressor are very prone to wear.

[0004] For continuously operating heat pump units, the decision to perform oil return operation and protect the compressor from oil shortage is typically based on the compressor's cumulative operating time. This method has limitations. For example, erroneous oil return operations may occur if the cumulative operating time is sufficient but the compressor is not short of oil, leading to repeated frequency increases or decreases in the compressor. Conversely, if the cumulative operating time is insufficient but the compressor is short of oil and oil return cannot be performed in time, it can cause wear and tear on various compressor components.

[0005] For the initial startup of heat pump units that have been shut down for an extended period, especially when the ambient temperature is low and the water temperature fluctuates significantly (particularly when the ambient temperature is below -25°C and the water temperature is above 35°C), and the unit has been shut down for a considerable time, the temperature and viscosity of the refrigerant oil sump at the bottom of the compressor are low. Refrigerant located in the high-temperature condenser will migrate from the condenser to the compressor oil sump. Once the compressor starts, because the temperature at the bottom of the compressor is lower than the condensing temperature, the refrigerant discharged from the compressor will condense and fall back into the compressor oil sump, diluting the oil and causing wear and tear on compressor components due to insufficient oil. Currently, there is no mature and effective control solution to protect the compressor from oil shortage in this situation. Summary of the Invention

[0006] Based on this, the purpose of the present invention is to provide a heat pump unit that, under conditions of extremely low ambient temperature or high water temperature, avoids the problem of wear and tear on the compressor components due to lack of oil by using a pre-defined initial power-on compressor start-up method.

[0007] A heat pump unit includes a compressor, a four-way valve, a condenser, a throttling valve, and an evaporator connected sequentially via a refrigerant circulation pipeline, a plurality of temperature sensors, and a controller electrically and / or communicatively connected to the compressor and the temperature sensors. The compressor includes a heating unit located at its bottom. The controller controls the start-up and shutdown of the compressor upon initial power-on using the following method:

[0008] acquire the current ambient temperature and the current water inlet temperature, and compare the current ambient temperature with a preset ambient temperature starting threshold and the current water inlet temperature with a preset water temperature starting threshold:

[0009] If the current ambient temperature is less than or equal to the ambient temperature starting threshold and the current water inlet temperature is less than or equal to the water temperature starting threshold, the compressor is not started, and the heating unit is controlled to start and run for a period of time and then stop; further, the current compressor bottom temperature and the current water inlet temperature are acquired, the temperature difference between the current compressor bottom temperature and the current water temperature is calculated, and the temperature difference is compared with a preset temperature difference threshold; and according to the comparison result, the compressor starting control or the heating unit starting control is entered;

[0010] If it is the remaining comparison condition, the target frequency of the compressor, a preset first frequency increasing platform frequency and a preset second frequency increasing platform frequency are further acquired, and the target frequency is compared with the first frequency increasing platform frequency and the second frequency increasing platform frequency in sequence, respectively; and according to the comparison result, the compressor is controlled to start and run to the target frequency along different operation paths.

[0011] Compared with the prior art, the heat pump unit of the present application compares the acquired ambient temperature with a preset ambient temperature starting threshold, the acquired water inlet temperature with a preset water temperature starting threshold, and the temperature difference between the acquired compressor bottom temperature and the water inlet temperature with a preset temperature difference threshold, and controls the starting and stopping of the compressor and the heating unit according to the comparison result. The control method can effectively avoid the problem that the refrigerant discharged after the compressor is started for the first time condenses and falls back into the compressor oil pool from the compressor cavity, dilutes the refrigeration oil, and causes the parts of the compressor to be abraded due to lack of oil; and the service life of the compressor can be prolonged.

[0012] Further, the controller controls the starting of the compressor by the following method:

[0013] acquire the current ambient temperature, and compare the current ambient temperature with a preset ambient temperature starting threshold:

[0014] If the current ambient temperature is greater than the ambient temperature starting threshold, the compressor is controlled to start;

[0015] If the current ambient temperature is less than or equal to the ambient temperature starting threshold, the current water inlet temperature is further acquired, and the current water inlet temperature is compared with a preset water inlet temperature starting threshold:

[0016] If the current water inlet temperature is greater than the water inlet temperature starting threshold, the compressor is controlled to start;

[0017] If the current inlet water temperature is less than or equal to the inlet water temperature starting threshold, the compressor is not started and the heating unit is controlled to start.

[0018] Further, the control of the starting of the compressor comprises the following control steps:

[0019] S21 obtains the target frequency of the compressor, a preset first frequency rising platform frequency, and compares the target frequency with the first frequency rising platform frequency:

[0020] If the target frequency is less than the first frequency rising platform frequency, the frequency of the compressor is controlled to rise to the first frequency rising platform frequency at a speed of SP1 and run at the first frequency rising platform frequency for N1 time, and then descend to the target frequency at the speed of SP1;

[0021] If the target frequency is greater than or equal to the first frequency rising platform frequency, step S22 is performed;

[0022] S22 further obtains a preset second frequency rising platform frequency, and compares the target frequency with the second frequency rising platform frequency:

[0023] If the target frequency is less than the second frequency rising platform frequency, the frequency of the compressor is controlled to rise to the first frequency rising platform frequency at the speed of SP1 and run at the first frequency rising platform frequency for N1 time, then rise to the second frequency rising platform frequency at the speed of SP2 and run at the second frequency rising platform frequency for N2 time, and then descend to the target frequency at the speed of SP2;

[0024] If the target frequency is greater than or equal to the second frequency rising platform frequency, the frequency of the compressor is controlled to rise to the first frequency rising platform frequency at the speed of SP1 and run at the first frequency rising platform frequency for N1 time, then rise to the second frequency rising platform frequency at the speed of SP2 and run at the second frequency rising platform frequency for N2 time, and then rise to the target frequency at the speed of SP3.

[0025] Further, for the continuously running heat pump unit, the control of the starting of the heating unit comprises the following control steps:

[0026] S31 controls the starting of the heating unit and continues to run for a period of time, and then controls the stopping of the heating unit;

[0027] S32 obtains the current compressor bottom temperature and the current inlet water temperature, calculates the temperature difference value of the current compressor bottom temperature and the current water temperature, and compares the temperature difference value with a first temperature difference starting threshold:

[0028] If the temperature difference value is greater than or equal to the first temperature difference starting threshold, the compressor is started;

[0029] If the temperature difference value is less than the first temperature difference starting threshold, step S31 is performed.

[0030] Further, for the heat pump unit operating intermittently, the control of the heating unit starting includes the following control steps:

[0031] S`31 controls the heating unit to start and run for a period of time, and then controls the heating unit to stop;

[0032] S`32 obtains the compressor bottom temperature at the current time and the water inlet temperature at the current time, calculates the temperature difference value of the compressor bottom temperature at the current time and the water temperature at the current time, and compares the temperature difference value with the second temperature difference starting threshold value:

[0033] If the temperature difference value is greater than or equal to the second temperature difference starting threshold value, the compressor is controlled to start;

[0034] If the temperature difference value is less than the second temperature difference starting threshold value, step S`31 is executed.

[0035] In order to better understand and implement, the present application will be described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 The structure diagram of the heat pump unit of an embodiment of the present application;

[0037] Figure 2 The flow chart of the heat pump unit of an embodiment of the present application controlling the compressor to start;

[0038] Figure 3 The frequency raising and frequency lowering diagram of the compressor of the heat pump unit of an embodiment of the present application. DETAILED DESCRIPTION

[0039] The technical solutions of the present application will be described in detail below with reference to the accompanying drawings of the embodiments of the present application.

[0040] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the embodiments of the present application. In the embodiments of the present application and the appended claims, the singular forms "a", "an" and "the" are also intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that "a plurality of" means two or more, unless otherwise stated; the term "and / or" used herein means and includes any or all possible combinations of one or more associated listed items.

[0041] The following description refers to the accompanying drawings. Unless otherwise indicated, same or similar elements in different drawings are denoted by the same or similar reference numerals. The embodiments described in the following exemplary embodiments do not represent all the embodiments consistent with the present application. In the description of the present application, it is to be understood that the terms "first", "second", "third", etc. are used only to distinguish one element from another, and are not used to describe a particular order or sequence, nor are they used to indicate or imply relative importance of the elements. The above terms can be understood according to the specific meaning in the present application by those skilled in the art according to the specific circumstances.

[0042] To solve the problem that the heat pump unit stops for a long time in the use scene of low ambient temperature and large water temperature change, the first start of the compressor causes the refrigerant discharged from the compressor to condense back into the compressor oil pool from the compressor cavity, resulting in wear of the compressor components due to lack of oil, the present application proposes a heat pump unit, including an improved method for controlling the start and stop of the compressor and its bottom heating unit, which compares the obtained ambient temperature with the preset ambient temperature start threshold, the obtained water inlet temperature with the preset water temperature start threshold, and the temperature difference between the obtained compressor bottom temperature and the water inlet temperature with the preset temperature difference threshold, and controls the start and stop of the compressor and its heating unit according to the comparison result. The control method can effectively avoid the problem that the refrigerant discharged after the first start of the compressor condenses back into the compressor oil pool from the compressor cavity, dilutes the refrigeration oil, and causes wear of the compressor components due to lack of oil; the service life of the compressor can be prolonged.

[0043] In specific implementation, please refer to Figure 1 The heat pump unit proposed by the present application includes a compressor 10, a four-way valve 20, a condenser 30, a throttling valve 40, an evaporator 50, a temperature acquisition module 60, a controller (not shown in the figure) and other auxiliary pipes. The compressor 10, the four-way valve 20, the condenser 30, the throttling valve 40 and the evaporator 50 are sequentially connected in circulation through refrigerant pipelines; the controller is electrically connected and / or communicatively connected with the compressor 10 and the temperature acquisition module 60.

[0044] The compressor 10 includes a heating unit (not shown in the figure) at the bottom of the compressor, the heating unit is a crankshaft heating belt or a winding coil, and the crankshaft heating belt or the winding coil can heat the refrigerant at the bottom of the compressor after being powered.

[0045] The temperature acquisition module 60 at least includes a first temperature sensor, a second temperature sensor and a third temperature sensor. The first temperature sensor is used for acquiring an ambient temperature signal and transmitting the temperature signal to a controller. The first temperature sensor can be arranged at any position as long as it can transmit the ambient temperature signal to the controller. The second temperature sensor is used for acquiring a water inlet temperature signal of the condenser 30 and transmitting the temperature signal to the controller. The second temperature sensor is arranged at a water inlet port of the condenser 30. The third temperature sensor is used for acquiring a temperature signal of refrigerant at the bottom of the compressor and transmitting the temperature signal to the controller. The third temperature sensor is arranged at the oil level of refrigerant at the bottom of the compressor. The acquisition interval of the temperature signal can be set according to the environment of the heat pump unit. It is recommended to acquire the temperature signal every 10-20 seconds.

[0046] The controller receives the temperature signal transmitted by the temperature acquisition module 60.

[0047] The controller further includes a storage unit and a processing unit. The storage unit is used for storing a ring temperature starting threshold of the compressor in the first start of the heat pump unit a water temperature starting threshold and a temperature difference starting threshold the ambient temperature acquired by the temperature acquisition module 60 at each time acquisition point the water inlet temperature and the temperature at the bottom of the compressor and the program of starting and stopping the compressor 10, starting and stopping the heating unit 11 at the bottom of the compressor 10, and the frequency increasing rule of the compressor 10. The processing unit is used for judging whether the ambient temperature and the water inlet temperature satisfy the starting preliminary condition; the processing unit is also used for calculating the temperature difference between the temperature at the bottom of the compressor and the water inlet temperature and comparing the temperature difference with the compressor starting temperature difference threshold of the heat pump unit to make a judgment. According to the judgment result, a starting and stopping control signal is output to the compressor 10 or the heating unit at the bottom of the compressor 10, so as to control the starting and stopping of the compressor of the heat pump unit.

[0048] Specifically, please refer to Figure 2 The controller controls the starting and stopping of the compressor after the first power-on of the heat pump unit by the following steps, so as to ensure that the compressor components are not short of oil.

[0049] The first power-on of the present application includes the first power-on after installation and the power-on when the unit enters the power-on state from the shutdown state.

[0050] S10 obtains the ambient temperature at the current time and the water inlet temperature at the current time and the current ambient temperature is compared with a preset ambient temperature starting threshold value and the current water inlet temperature is further compared with a preset water temperature starting threshold value and the comparison result is used to control the start and stop of the compressor or the heating unit.

[0051] This step includes the following sub-steps.

[0052] S11 obtains the current ambient temperature and the current ambient temperature is compared with a preset ambient temperature starting threshold value :

[0053] If the current ambient temperature is greater than the ambient temperature starting threshold value , step S20 is executed;

[0054] If the current ambient temperature is less than or equal to the ambient temperature starting threshold value , step S12 is executed.

[0055] The ambient temperature starting threshold value is preferably -5℃ to -3℃, and can be adjusted according to the climate characteristics of the application scene of the heat pump unit. In a colder area, the value of the ambient temperature starting threshold value may be appropriately increased, and in a hotter area, the value of the ambient temperature starting threshold value may be appropriately decreased.

[0056] S12 further obtains the current water inlet temperature and the current water inlet temperature is compared with a preset water temperature starting threshold value :

[0057] If the current water inlet temperature is greater than the water temperature starting threshold value , step S20 is executed;

[0058] If the current water inlet temperature is less than or equal to the water temperature starting threshold value , step S30 is executed.

[0059] The water temperature starting threshold value is preferably 25℃ to 28℃, and can be adjusted according to the climate characteristics of the application scene of the heat pump unit. In a colder area, the value of the water temperature starting threshold value may be appropriately decreased, and in a hotter area, the value of the water temperature starting threshold value may be appropriately increased.

[0060] S20 Obtains the target frequency F of the compressor 10 target The preset first upsampling platform frequency Second upsampling platform frequency and the target frequency F target sequentially with the first upsampling platform frequency Second upsampling platform frequency The comparison is performed, and the compressor is controlled to start and run along different operating paths to the target frequency based on the comparison results.

[0061] This step includes the following sub-steps.

[0062] S21 Obtain the target frequency F of the compressor 10 target The preset first upsampling platform frequency and the target frequency F target Frequency of the first upsampling platform Comparison:

[0063] If the target frequency F target Less than the first upsampling platform frequency Then the compressor frequency is controlled to rise to the first frequency ramp-up plateau at a speed of SP1. and at the first up-frequency platform Run for N1 time, then reduce to the target frequency F at SP1 speed. target run;

[0064] If the target frequency F target Greater than or equal to the first upsampling plateau frequency Then proceed to step S22;

[0065] Specifically, the frequency of the first upsampling platform The frequency is preferably 60Hz. The operating time N1 is preferably 60 to 80 seconds.

[0066] Furthermore, when the compressor 10 restarts after a shutdown, if the discharge temperature and the external coil temperature are relatively high, i.e., the external coil temperature exceeds the external coil temperature protection value, the compressor 10 does not need to operate at the first frequency ramp-up platform. During the N1 operation time, the frequency can be directly increased to the target frequency F. target run.

[0067] Furthermore, after compressor 10 starts, current frequency limiting, voltage frequency limiting, or exhaust frequency limiting occurs, and the frequency limiting frequency is lower than the first frequency ramp-up platform frequency. At this time, compressor 10 no longer needs to operate at the first frequency ramp-up platform. During the N1 operation time, the frequency can be directly increased to the target frequency F. target run.

[0068] S22 further acquires a preset second frequency plateau and compares the target frequency F target with the second frequency plateau

[0069] If the target frequency F target is less than the second frequency plateau , the frequency of the compressor is controlled to rise to the first frequency plateau at a speed of SP1, and run at the first frequency plateau for a time N1, then rise to the second frequency plateau at a speed of SP2, and run at the second frequency plateau for a time N2, and then drop to the target frequency F target at a speed of SP2.

[0070] If the target frequency F target is greater than or equal to the second frequency plateau , the frequency of the compressor is controlled to rise to the first frequency plateau at a speed of SP1, and run at the first frequency plateau for a time N1, then rise to the second frequency plateau at a speed of SP2, and run at the second frequency plateau for a time N2, and then rise to the target frequency F target at a speed of SP3.

[0071] Specifically, the second frequency plateau is preferably 90 Hz. The running time N2 is preferably 60-80 seconds.

[0072] The frequency plateau points, the rising and dropping speeds and the running times of the compressor during the start-up process are shown in the following table. Figure 3

[0073] Further, if the frequency of the compressor 10 running at the second frequency plateau drops due to protection or frequency limiting, etc., the time of running at the second frequency plateau is less than N2, and then rises to the second frequency plateau , the compressor does not need to run at the second frequency plateau again.

[0074] S30 controls the heating unit to start and run for a period of time , then stop, and acquires the current compressor bottom temperature ​​the water temperature at the current time calculating the compressor bottom temperature at the current time the water temperature at the current time the temperature difference value ΔT, and comparing the temperature difference value ΔT with a temperature difference starting threshold value and entering the compressor starting control or the heating unit starting control according to the comparison result.

[0075] For the continuously running heat pump unit, this step includes the following sub-steps.

[0076] S31 controls the heating unit to start and continuously run for a time period , and then controls the heating unit to stop.

[0077] This step preheats the refrigerant at the compressor bottom. The time period is 20-30 minutes, which can be determined according to the climate characteristics of the application scenario of the heat pump unit.

[0078] S32 obtains the compressor bottom temperature at the current time and the water temperature at the current time calculating the compressor bottom temperature at the current time and the water temperature at the current time the temperature difference value ΔT, and comparing the temperature difference value ΔT with a first temperature difference starting threshold value :

[0079] If the temperature difference value ΔT is greater than or equal to the first temperature difference starting threshold value , step S20 is executed.

[0080] If the temperature difference value ΔT is less than the first temperature difference starting threshold value , step S31 is executed.

[0081] The first temperature difference starting threshold value is preferably 5-7°C, which can be adjusted according to the climate characteristics of the application scenario of the heat pump unit.

[0082] For the discontinuously running heat pump unit, this step includes the following sub-steps.

[0083] S`31 controls the heating unit to start and continuously run for a time period , and then controls the heating unit to stop.

[0084] S`32 obtains the compressor bottom temperature at the current time and the water temperature at the current time calculating the compressor bottom temperature at the current time and the water temperature at the current time the temperature difference value ΔT and the second temperature difference starting threshold value are compared:

[0085] If the temperature difference value ΔT is greater than or equal to the second temperature difference starting threshold value Step S20 is performed.

[0086] If the temperature difference value ΔT is less than the second temperature difference starting threshold value Step S31 is performed.

[0087] The second temperature difference starting threshold value is preferably 0-2℃, and can be adjusted according to the climate characteristics of the application scenario of the heat pump unit.

[0088] For a heat pump unit that is intermittently operated, when the ambient temperature is below 0℃, the target frequency of the compressor needs to be set to be above 26Hz, wherein:

[0089] When the target frequency is set to be greater than or equal to 30Hz, the intermittent cycle is set to be greater than or equal to 5 minutes, the compressor startup time is greater than or equal to 2 minutes, and the shutdown time is greater than or equal to 3 minutes.

[0090] When the target frequency is set to be less than 30Hz, the intermittent cycle is set to be greater than or equal to 8 minutes, the compressor startup time is greater than or equal to 5 minutes, and the shutdown time is greater than or equal to 3 minutes.

[0091] For a compressor that is started at low temperature and stationary, the frequency increasing rule is slightly different from the above, and 2-3 frequency increasing platforms need to be set before 0-60Hz, i.e., the first frequency increasing platform frequency It is recommended that the time for maintaining the frequency of each newly added frequency increasing platform be greater than or equal to 3 minutes.

[0092] The heat pump unit of the present application adopts an improved compressor startup control method for the first time, which can effectively avoid the problem that the refrigerant discharged from the compressor condenses and falls back into the compressor oil pool to dilute the refrigeration oil under the condition of low ambient temperature, causing the parts of the compressor to be worn due to lack of oil, and can prolong the service life of the compressor.

[0093] The above-described embodiments only express several embodiments of the present application, and the description is relatively specific and detailed, but it should not be understood as limiting the scope of the patent. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, and the present application also intends to include these modifications and improvements.

Claims

1. A heat pump unit comprising a compressor, a four-way valve, a condenser, a throttle valve, an evaporator, a plurality of temperature sensors and a controller electrically connected and / or communicatively connected to the compressor and the temperature sensors, the compressor comprising a heating unit at the bottom of the compressor, characterized in that, The controller controls the start-stop operation of the compressor at first power-on by the following method: The current ambient temperature and the current water inlet temperature are obtained, and the current ambient temperature is compared with the preset ambient temperature starting threshold, and the current water inlet temperature is compared with the preset water temperature starting threshold: If the current ambient temperature is less than or equal to the ambient temperature starting threshold and the current water inlet temperature is less than or equal to the water temperature starting threshold, the compressor is not started, and the heating unit is controlled to start and run continuously for a period of time and then stop, the current compressor bottom temperature and the current water inlet temperature are further obtained, the temperature difference between the current compressor bottom temperature and the current water temperature is calculated, and the temperature difference is compared with the temperature difference starting threshold, and the compressor starting control or the heating unit starting control is entered according to the comparison result; If it is the remaining comparison condition, the target frequency of the compressor, the preset first frequency increasing platform frequency and the second frequency increasing platform frequency are further obtained, and the target frequency is compared with the first frequency increasing platform frequency and the second frequency increasing platform frequency in turn, and the compressor is controlled to start and run to the target frequency along different operation paths according to the comparison result, specifically: S21 The target frequency of the compressor, the preset first frequency increasing platform frequency are obtained, and the target frequency is compared with the first frequency increasing platform frequency: If the target frequency is less than the first frequency increasing platform frequency, the frequency of the compressor is controlled to increase to the first frequency increasing platform frequency at the speed of SP1 and run at the first frequency increasing platform frequency for N1 time, and then decrease to the target frequency at the speed of SP1; If the target frequency is greater than or equal to the first frequency increasing platform frequency, step S22 is executed; S22 The preset second frequency increasing platform frequency is further obtained, and the target frequency is compared with the second frequency increasing platform frequency: If the target frequency is less than the second frequency increasing platform frequency, the frequency of the compressor is controlled to increase to the first frequency increasing platform frequency at the speed of SP1 and run at the first frequency increasing platform frequency for N1 time, and then increase to the second frequency increasing platform frequency at the speed of SP2 and run at the second frequency increasing platform frequency for N2 time, and then decrease to the target frequency at the speed of SP2; If the target frequency is greater than or equal to the second frequency increasing platform frequency, the frequency of the compressor is controlled to increase to the first frequency increasing platform frequency at the speed of SP1 and run at the first frequency increasing platform frequency for N1 time, and then increase to the second frequency increasing platform frequency at the speed of SP2 and run at the second frequency increasing platform frequency for N2 time, and then increase to the target frequency at the speed of SP3.

2. The heat pump unit of claim 1, wherein, The controller controls the start of the compressor by the following method: The current ambient temperature is obtained, and the current ambient temperature is compared with the preset ambient temperature starting threshold: If the current ambient temperature is greater than the ambient temperature starting threshold, the compressor is controlled to start; If the current ambient temperature is less than or equal to the ambient temperature starting threshold, the current water inlet temperature is further obtained, and the current water inlet temperature is compared with the preset water inlet temperature starting threshold: If the current water inlet temperature is greater than the water inlet temperature starting threshold, the compressor is controlled to start; If the current inlet water temperature is less than or equal to the inlet water temperature starting valve value, the compressor is not started and the heating unit is controlled to start.

3. The heat pump unit of claim 1, wherein, For a continuously operating heat pump unit, the control of the heating unit starting includes the following control steps: S31 controls the heating unit to start and run for a period of time, and then controls the heating unit to stop; S32 obtains the current compressor bottom temperature and the current inlet water temperature, calculates the temperature difference value between the current compressor bottom temperature and the current water temperature, and compares the temperature difference value with the first temperature difference starting threshold value: If the temperature difference value is greater than or equal to the first temperature difference starting threshold value, the compressor is controlled to start; If the temperature difference value is less than the first temperature difference starting threshold value, step S31 is performed.

4. The heat pump unit of claim 3, wherein, The first temperature difference starting threshold value is 5-7℃, which can be adjusted according to the climate characteristics of the application scene of the heat pump unit.

5. The heat pump unit of claim 1, wherein, For a discontinuously operating heat pump unit, the control of the heating unit starting includes the following control steps: S`31 controls the heating unit to start and run for a period of time, and then controls the heating unit to stop; S`32 obtains the current compressor bottom temperature and the current inlet water temperature, calculates the temperature difference value between the current compressor bottom temperature and the current water temperature, and compares the temperature difference value with the second temperature difference starting threshold value: If the temperature difference value is greater than or equal to the second temperature difference starting threshold value, the compressor is controlled to start; If the temperature difference value is less than the second temperature difference starting threshold value, step S`31 is performed.

6. The heat pump unit of claim 5, wherein, The second temperature difference starting threshold value is 0-2℃, which can be adjusted according to the climate characteristics of the application scene of the heat pump unit.

7. - Heat pump package according to claim 5 or 6, characterized in that, When the ambient temperature is lower than 0℃, the target frequency of the compressor needs to be set to be greater than 26Hz, wherein: When the target frequency is set to be greater than or equal to 30Hz, the discontinuous cycle is set to be greater than or equal to 5 minutes, the compressor starting time is greater than or equal to 2 minutes, and the shutdown time is greater than or equal to 3 minutes; When the target frequency is less than 30Hz, the discontinuous cycle is set to be greater than or equal to 8 minutes, the compressor starting time is greater than or equal to 5 minutes, and the shutdown time is greater than or equal to 3 minutes.

8. The heat pump package of any of claims 1-6, wherein, The ring temperature starting threshold value is -5℃--3℃, and the water temperature starting threshold value is 25-28℃, which can be adjusted according to the climate characteristics of the application scene of the heat pump unit.

9. The heat pump unit of claim 8, wherein, The first frequency increasing platform frequency is 60Hz, and the second frequency increasing platform frequency is 90Hz.

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