A photovoltaic-coupled heat pump system

Abstract

This invention relates to a photovoltaic-coupled heat pump system. Through a specially designed control program, the heat pump system prioritizes and fully utilizes the power generated by the photovoltaic panels, reducing reliance on the power grid. When photovoltaic power generation is sufficient, the heat pump unit and an auxiliary electric heating device are used in conjunction to heat the water in the buffer tank and the main water tank to the maximum heat storage temperature. Excess power is used to charge the energy storage device and supply power to the grid. When power generation is insufficient, the compressor operates at reduced and limited frequencies to match the photovoltaic power generation. The system uses a selective approach, prioritizing the use of the heat pump unit followed by the auxiliary electric heating device, to heat the water in the buffer tank and the main water tank to the maximum operating temperature, maximizing the utilization of photovoltaic power.

Description

Technical Field

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

[0002] Heat pump systems 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. The government is increasing policy guidance on environmental protection and energy conservation; at the same time, with the improvement of living standards in my country, more and more public places and households are choosing heat pump systems to meet their heating needs.

[0003] With the development of new energy sources, heat pump systems are gradually adopting hybrid power supply methods, such as using photovoltaic power generation, energy storage devices, and the power grid to supply power to the compressor. When photovoltaic power generation is coupled to the heat pump via an inverter, simple on / off coupling is often used. This coupling method is prone to the following problems:

[0004] 1) There is a power dispatch problem among photovoltaic power generation, energy storage and the power grid. When the power dispatch is not reasonable, the compressor may give priority to the power grid, resulting in the waste of photovoltaic power generation energy;

[0005] 2) Since photovoltaic power generation is carried out in real time, when the energy storage device is fully charged and there is no corresponding electrical equipment consuming photovoltaic power generation in use, the excess electricity generated by photovoltaic power generation will be lost, resulting in a waste of photovoltaic power generation energy. Summary of the Invention

[0006] Based on this, the purpose of the present invention is to provide a photovoltaic-coupled heat pump system that can match the photovoltaic power generation frequency, prioritize the use of photovoltaic power generation, reduce the supplementary use of the power grid, and improve the utilization efficiency of photovoltaic power generation.

[0007] A photovoltaic-coupled heat pump system includes an inverter, a heat pump unit, an electric auxiliary heating device, a buffer water tank, a water tank, and a controller. The inverter couples the photovoltaic system with the heat pump unit and the electric auxiliary heating device. The heat pump unit and the electric auxiliary heating device heat the medium in the buffer water tank and the water tank. The controller controls the operating power of the heat pump unit and the start / stop of the electric auxiliary heating device in real time based on the photovoltaic power generation through the inverter. The control steps are as follows:

[0008] S10 acquires the photovoltaic power generation, the maximum power of the heat pump unit, and the heating power of the electric auxiliary heating device in real time, and determines whether the power generation is greater than or equal to the sum of the maximum power and the heating power:

[0009] If yes, then execute S20;

[0010] If not, then execute S30;

[0011] S20 obtains the operating mode of the heat pump unit, the buffer water temperature of the buffer tank, the water temperature of the water tank, and the preset maximum operating temperature, maximum heat storage temperature, and minimum buffer water temperature of the heat pump unit.

[0012] If the working mode is heating, the buffer water temperature and the water temperature are compared with the maximum operating temperature and the maximum heat storage temperature, respectively. Based on the comparison results, the operating frequency of the heat pump unit and the start and stop of the electric auxiliary heating device are controlled.

[0013] If the working mode is cooling, the buffer water temperature is compared with the minimum buffer water temperature, and the operating frequency of the heat pump unit and the start and stop of the electric auxiliary heating device are controlled according to the comparison result.

[0014] S30 determines whether the power generation capacity is greater than or equal to the maximum power:

[0015] If yes, then execute S40;

[0016] If not, then execute S60;

[0017] The S40 acquires the heat pump unit's operating mode, buffer water temperature, and current water temperature, as well as the preset maximum operating temperature and minimum buffer water temperature.

[0018] If the working mode is heating, the buffer water temperature and the water temperature are compared with the maximum operating temperature, and the operating frequency of the heat pump unit and the start and stop of the electric auxiliary heating device are controlled according to the comparison result.

[0019] If the working mode is cooling, the buffer water temperature is compared with the minimum buffer water temperature, and the operating frequency of the heat pump unit and the start and stop of the electric auxiliary heating device are controlled according to the comparison result.

[0020] The S60 acquires the operating mode of the heat pump unit, and based on the operating mode, retrieves the maximum allowable operating frequency range for power generation from the heat pump unit's built-in operating frequency band table as the limited operating frequency; it also acquires the buffer water temperature and the used water temperature, as well as the preset maximum operating temperature and minimum buffer water temperature.

[0021] If the working mode is heating, the buffer water temperature and the water temperature are compared with the maximum operating temperature. Based on the comparison result, the heat pump unit is controlled to operate at a limited frequency and the electric auxiliary heating device is turned on and off.

[0022] If the operating mode is cooling, the buffer water temperature will be compared with the minimum buffer water temperature, and the heat pump unit will be controlled to operate within the specified limits based on the comparison result.

[0023] Compared with existing technologies, the present invention enables the heat pump system to prioritize and fully utilize photovoltaic power generation through a set control program. When photovoltaic power generation is sufficient, the heat pump unit and the electric auxiliary heating device are used in combination to heat the water in the buffer tank and the water tank to the highest heat storage temperature. When photovoltaic power generation is insufficient, the compressor is operated at reduced frequency to match the photovoltaic power generation. The heat pump unit is activated first, followed by the electric auxiliary heating device, to heat the water in the buffer tank and the water tank to the highest operating temperature, thus making full use of photovoltaic power.

[0024] Furthermore, in step S60, the operating frequency of the heat pump unit and the on / off control of the electric auxiliary heating device in heating and cooling modes are as follows:

[0025] Heating mode:

[0026] When the buffer water temperature and the water temperature are lower than the maximum operating temperature, the heat pump unit is controlled to run at a limited operating frequency until the indoor temperature reaches the set temperature, then it stops running and the electric auxiliary heating device is turned on.

[0027] When the buffer water temperature and the water temperature are greater than or equal to the maximum operating temperature, the heat pump unit is controlled to operate at a limited operating frequency.

[0028] Cooling mode:

[0029] When the buffer water temperature is lower than the minimum buffer water temperature, the operating water temperature is further obtained and compared with the maximum operating temperature.

[0030] If the water temperature is lower than the maximum operating temperature, the heat pump unit will be controlled to run at a limited operating frequency until the indoor temperature reaches the set temperature, then it will stop running and the electric auxiliary heating device will be turned on.

[0031] If the water temperature is greater than or equal to the maximum operating temperature, the heat pump unit will be controlled to operate at a limited operating frequency.

[0032] When the buffer water temperature is greater than or equal to the minimum buffer water temperature, the heat pump unit is controlled to operate at a limited operating frequency until the buffer water temperature is lower than the minimum buffer water temperature.

[0033] Furthermore, the inverter of the heat pump system is also coupled to the energy storage device and the power grid.

[0034] Furthermore, after controlling the operating frequency of the heat pump unit and the start / stop control of the electric auxiliary heating device in the heating and cooling modes of step S20, the remaining power is first used to charge the energy storage device before being fed back to the power grid.

[0035] Furthermore, step S50 is included before step S60:

[0036] S50 obtains the input energy storage power of the energy storage device and the input grid power of the grid, calculates the total power of the sum of the energy storage power, grid power, and generation power, and determines whether the total power is greater than or equal to the maximum power.

[0037] If so, control the photovoltaic, energy storage devices and grid to supply power to the heat pump unit through the inverter and execute S40;

[0038] If not, then execute S60.

[0039] Compared with existing technologies, by additionally coupling the inverter with the energy storage device and the grid, when the photovoltaic power generation is sufficient, the water in the buffer tank and the water tank is heated to the highest heat storage temperature by using a heat pump unit in conjunction with an electric auxiliary heating device. The excess power generation is used to charge the energy storage device and supply power to the grid, maximizing the utilization of photovoltaic power. When the photovoltaic power generation is insufficient, additional power is supplied to the energy storage device and the grid, and the compressor is operated at reduced frequency and limited frequency, which also maximizes the utilization of photovoltaic power.

[0040] To better understand and implement this invention, the following detailed description is provided in conjunction with the accompanying drawings. Attached Figure Description

[0041] Figure 1 A schematic diagram of a heat pump system coupled with photovoltaics, energy storage devices, and grid power consumption;

[0042] Figure 2 This is a schematic diagram of the water circuit connection of a heat pump system;

[0043] Figure 3 A schematic diagram illustrating a method for controlling the start-up and shutdown of the heat pump unit and electric auxiliary heating in a photovoltaic-coupled heat pump system. Detailed Implementation

[0044] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings of the embodiments of the present invention.

[0045] To address the problem of wasted energy caused by the inability to prioritize and fully utilize photovoltaic power generation when using hybrid power supply in heat pump systems, this invention proposes a photovoltaic-coupled heat pump system. This system can adjust the operating frequency of the heat pump and start / stop the auxiliary heating device according to the power output of the inverter. When the power is sufficient, it can store energy as much as possible, and when the power is insufficient, it can reduce the frequency of the compressor to match the photovoltaic power generation, thereby reducing the need for grid supplementation.

[0046] For specific implementation details, please refer to [link / reference]. Figure 1 and Figure 2 The photovoltaic-coupled heat pump system proposed in this invention includes an inverter 10, a heat pump unit 20, an electric auxiliary heating device 30, a buffer water tank 40, a water tank 50 and a controller (not shown in the figure), and other circuit connectors and water circulation pipelines.

[0047] Inverter 10 includes a DC terminal and an AC terminal. When the heat pump system is coupled only to photovoltaics through the inverter, the photovoltaics convert solar energy into DC power, which is then input to inverter 10 to supply power to the heat pump unit 20 and / or the electric auxiliary heating device. When the heat pump system is coupled to photovoltaics, energy storage devices, and the power grid through the inverter, the DC power output from the photovoltaics and energy storage devices, and the converted DC power output from the power grid, are input through the DC terminal, converted into AC power by inverter 10, and then output through the AC terminal to the heat pump unit 20 and / or the electric auxiliary heating device 30. If there is excess photovoltaic power, the photovoltaics supply power to the energy storage device and the power grid through the inverter.

[0048] The heat pump unit 20 receives electrical energy from photovoltaic and / or energy storage devices and / or the power grid through the inverter 10, performs cooling or heating, and heats the medium water in the buffer water tank 40 and the water tank 50.

[0049] The electric auxiliary heating device 30 receives electrical energy from photovoltaic and / or energy storage devices and / or the power grid through the inverter 10 to heat the medium water in the buffer water tank 40 and the water tank 50.

[0050] The buffer water tank 40 and the water tank 50 are connected to the heat pump unit 20 and the electric auxiliary heating device 30 through water circulation pipelines. Specifically, the city water pipeline delivers cold water to the cold water inlet of the buffer water tank 40 and the water tank 50, and then flows into the inlet of the heat pump unit 20 through the outlet of the buffer water tank 40 and the water tank 50. After being heated by the heat pump unit 20 and the electric auxiliary heating device 30, the water enters the hot water inlet of the buffer water tank 40 and the water tank 50, and is then supplied to users for domestic water or heating through the water supply end.

[0051] The controller is used to control the operating power of the heat pump unit 20 and the start / stop of the electric auxiliary heating device 30 in real time through the inverter 10 according to the photovoltaic power generation, and to supply power to the energy storage device and / or the power grid.

[0052] Specifically, please refer to Figure 3 The controller controls the operation of the heat pump unit 20 and the start / stop of the electric auxiliary heating device 30, and supplies power to the energy storage device and / or the power grid through the following methods.

[0053] S10 acquires photovoltaic power generation in real time. Maximum power of heat pump unit 20 Heating power of electric auxiliary heating device 30 Determine power generation capacity Is it greater than or equal to the maximum power? With heating power sum:

[0054] If yes, then execute S20;

[0055] If not, then execute S30.

[0056] S20 obtains the operating mode of the heat pump unit 20 and the buffer water temperature of the buffer water tank 40. and the water temperature of the water tank 50 and the heat pump unit's preset maximum operating temperature T o-max Maximum thermal storage temperature T hs-max The buffer water tank has a preset minimum buffer water temperature of 50.

[0057] If the operating mode is heating, then the buffer water temperature will be adjusted. and water temperature respectively with the highest operating temperature T o-max Maximum thermal storage temperature T hs-max The comparison is made, and the operating frequency of the heat pump unit 20 and the start and stop of the electric auxiliary heating device 30 are controlled according to the comparison results.

[0058] If the operating mode is cooling, then the buffer water temperature will be adjusted. With minimum buffer water temperature The comparison is made, and the operating frequency of the heat pump unit 20 and the start and stop of the electric auxiliary heating device 30 are controlled according to the comparison results.

[0059] In specific implementation, in heating mode and cooling mode, the controller controls the operating frequency of the heat pump unit 20 and the opening and closing of the electric auxiliary heating device 30 as follows.

[0060] A. Heating Mode:

[0061] Obtain the buffer water temperature and water temperature and buffer water temperature Water temperature With the preset maximum operating temperature T o-max Maximum thermal storage temperature T hs-max Comparison:

[0062] When the buffer water temperature and water temperature Less than the maximum operating temperature T o-max Then control the heat pump unit 20 to operate at the highest frequency F. max The system operates and activates the electric auxiliary heating device 30 to heat the water in the buffer tank 40 and the water tank 50, and prioritizes charging the energy storage device with the remaining power before supplying power to the grid.

[0063] When the buffer water temperature and water temperature Greater than or equal to the highest operating temperature T o-max And less than the highest thermal storage temperature T hs-maxThen control the heat pump unit 20 to operate at the frequency F required to maintain a constant indoor temperature. need The system operates and controls the electric auxiliary heating device 30 to remain on, continuously heating the water in the buffer water tank 40 and the water tank 50, and prioritizing the use of the remaining power to charge the energy storage device before feeding it into the power grid.

[0064] When the buffer water temperature and water temperature Greater than or equal to the highest thermal storage temperature T hs-max Then control the heat pump unit 20 to operate at the frequency F required to maintain a constant indoor temperature. need It operates and shuts down the electric auxiliary heating device 30, and prioritizes charging the energy storage device with the remaining power before transferring it to the power grid.

[0065] B. Cooling Mode

[0066] Obtain the buffer water temperature and buffer water temperature With minimum buffer water temperature Comparison:

[0067] When the buffer water temperature Less than the minimum buffer water temperature The electric auxiliary heating device 30 is turned on to heat the water in the water tank 50; and the water temperature is further obtained. Water temperature With the highest operating temperature T o-max Maximum thermal storage temperature T hs-max Comparison:

[0068] If water temperature Less than the maximum operating temperature T o-max Then control the heat pump unit 20 to operate at the highest frequency F. max It operates and prioritizes charging the energy storage device with the remaining power before feeding it back into the grid;

[0069] If water temperature Greater than or equal to the highest operating temperature T o-max And less than the highest thermal storage temperature T hs-max Then control the heat pump unit 20 to operate at the frequency F required to maintain a constant indoor temperature. need It operates and prioritizes charging the energy storage device with the remaining power before feeding it back into the grid;

[0070] If water temperature Greater than or equal to the highest thermal storage temperature T hs-max Then control the heat pump unit 20 to operate at the frequency F required to maintain a constant indoor temperature. need The system operates and shuts down the electric auxiliary heating device 30, prioritizing the charging of the energy storage device with the remaining power before supplying power to the grid.

[0071] When the buffer water temperature Greater than or equal to the minimum buffer water temperature Then control the heat pump unit 20 at the highest frequency F max Run until the buffer water temperature reaches the specified level. Less than the minimum buffer water temperature

[0072] In specific implementation, the highest operating temperature T o-max The maximum heat storage temperature is 65℃; hs-max The minimum buffer water temperature is 75℃. It is 7℃.

[0073] S30 determines power generation capacity Is it greater than or equal to the maximum power?

[0074] If yes, then execute S40;

[0075] If not, then execute S50.

[0076] It should be noted that if the heat pump system is not coupled to an energy storage device and the power grid, then this step is represented as:

[0077] S`30 determines power generation capacity Is it greater than or equal to the maximum power?

[0078] If yes, then execute S40;

[0079] If not, then execute S60.

[0080] S40 obtains the operating mode and buffer water temperature of heat pump unit 20. and water temperature and the preset maximum operating temperature T o-max Minimum buffer water temperature

[0081] If the operating mode is heating, then the buffer water temperature will be adjusted. and water temperature With the highest operating temperature T o-max The comparison is made, and the operating frequency of the heat pump unit 20 and the start and stop of the electric auxiliary heating device 30 are controlled according to the comparison results.

[0082] If the operating mode is cooling, then the buffer water temperature will be adjusted. With minimum buffer water temperature The comparison is made, and the operating frequency of the heat pump unit 20 and the start and stop of the electric auxiliary heating device 30 are controlled according to the comparison results.

[0083] In heating and cooling modes, the controller controls the operating frequency of the heat pump unit 20 and the on / off state of the electric auxiliary heating device 30 as follows.

[0084] A. Heating Mode

[0085] Obtain the buffer water temperature and water temperature and buffer water temperature and water temperature With the preset maximum operating temperature T o-max Comparison:

[0086] When the buffer water temperature and water temperature Less than the maximum operating temperature T o-max Then control the heat pump unit 20 to operate at the frequency F required to maintain a constant indoor temperature. need Run until the indoor temperature reaches the set temperature, then stop running and turn on the electric auxiliary heating device 30 to heat the water in the buffer water tank 40 and the water tank 50.

[0087] When the buffer water temperature and water temperature Greater than or equal to the highest operating temperature T o-max Then control the heat pump unit 20 to operate at the frequency F required to maintain a constant indoor temperature. need run.

[0088] B. Cooling Mode

[0089] Obtain the buffer water temperature and buffer water temperature With minimum buffer water temperature Comparison:

[0090] When the buffer water temperature Less than the minimum buffer water temperature Then further obtain the water temperature. Will use water temperature With the highest operating temperature T o-max Comparison:

[0091] If water temperature Less than the maximum operating temperature T o-max Then control the heat pump unit 20 to operate at the frequency F required to maintain a constant indoor temperature. need Run until the indoor temperature reaches the set temperature, then stop running and turn on the electric auxiliary heating device 30 to heat the water in the buffer water tank 40 and the water tank 50.

[0092] If water temperature Greater than or equal to the highest operating temperature T o-max Then control the heat pump unit 20 to operate at the frequency F required to maintain a constant indoor temperature.need run;

[0093] When the buffer water temperature Greater than or equal to the minimum buffer water temperature Then control the heat pump unit 20 at the highest frequency F max Run until the buffer water temperature reaches the specified level. Less than the minimum buffer water temperature Then, perform the steps described above.

[0094] S50 obtains the energy storage power that the energy storage device can input. And the grid power that can be input to the grid Calculate energy storage power Grid power and power generation Total power And determine the total power Is it greater than or equal to the maximum power?

[0095] If so, control the photovoltaic, energy storage devices and the power grid to supply power to the heat pump unit 20 through the inverter 10, and execute S40;

[0096] If not, then execute S60.

[0097] S60 obtains the operating mode of the heat pump unit 20, and retrieves the power generation capacity from the built-in operating frequency band table of the heat pump unit 20 according to the operating mode. Maximum allowed operating frequency band F i As a limited operating frequency F R And obtain the buffer water temperature. and water temperature and the preset maximum operating temperature T o-max Minimum buffer water temperature

[0098] If the operating mode is heating, then the buffer water temperature will be adjusted. and water temperature With the highest operating temperature T o-max The comparison is made, and the operation of the heat pump unit 20 and the start and stop of the electric auxiliary heating device 30 are controlled according to the comparison results.

[0099] If the operating mode is cooling, then based on the buffer water temperature Water temperature With the minimum buffer water temperature of the buffer tank 40 The maximum operating temperature of the heat pump unit 20 is T o-max The comparison is made, and the operation of the heat pump unit 20 is controlled based on the comparison results.

[0100] In specific implementation, the operation of the heat pump unit 20 in heating and cooling modes is controlled as follows.

[0101] A. Heating Mode

[0102] Obtain the buffer water temperature and water temperature And with the highest operating temperature T of the heat pump unit 20 o-max Comparison:

[0103] When the buffer water temperature and water temperature The maximum operating temperature T of the heat pump unit is less than 20°C. o-max Then control the heat pump unit 20 to operate at the limited frequency F. R After running until the indoor temperature reaches the set temperature, the heat pump unit 20 stops running and the electric auxiliary heating device 30 is turned on to heat the water in the buffer water tank 40 and the water tank 50.

[0104] When the buffer water temperature and water temperature The maximum operating temperature T of the heat pump unit is greater than or equal to 20. o-max Then control the heat pump unit 20 to operate at the limited frequency F. R run;

[0105] B. Cooling Mode

[0106] Obtain the buffer water temperature and the minimum buffer water temperature of the buffer tank 40. Comparison:

[0107] When the buffer water temperature The minimum buffer water temperature is less than 40°C in the buffer tank. Then further obtain the water temperature.

[0108] If water temperature The maximum operating temperature T of the heat pump unit is less than 20°C. o-max Then control the heat pump unit 20 to operate at the limited frequency F. R After running until the indoor temperature reaches the set temperature, the heat pump unit 20 stops running and the electric auxiliary heating device 30 is turned on to heat the water in the buffer water tank 40 and the water tank 50.

[0109] If water temperature The maximum operating temperature T of the heat pump unit is greater than or equal to 20. o-max Then control the heat pump unit 20 to operate at the limited frequency F. R run;

[0110] When the buffer water temperature T b tuffer The minimum buffer water temperature of the buffer tank is greater than or equal to 40. Then control the heat pump unit 20 to operate at the limited frequency F. R Run until the buffer water temperature reaches the specified level. Less than the minimum buffer water temperature Then, perform the steps described above.

[0111] The following is a frequency band table of compressor operation used in an embodiment. In this embodiment, the heating power and cooling power are divided into 10 frequency bands, and the frequency of each band is determined by EEPROM data, as shown in Table 1.

[0112] Table 1

[0113]

[0114] When a heat pump system uses hybrid power supply, the compressor operates at a low frequency for extended periods, resulting in reduced lubrication effectiveness of the lubricating oil. Therefore, an oil return setting is necessary. This setting ensures that the lubricating oil flows back to the compressor in a timely manner, providing sufficient lubrication and cooling to protect the compressor's normal operation and extend its lifespan.

[0115] The photovoltaic-coupled heat pump system proposed in this invention, through a set control program, enables the heat pump system to prioritize and fully utilize the power generation of the photovoltaic panels, reducing the reliance on the power grid. When photovoltaic power generation is sufficient, the heat pump unit and the electric auxiliary heating device are used in combination to heat the water in the buffer tank and the main water tank to the maximum heat storage temperature, and the excess power generation is used to charge the energy storage device and supply power to the grid. When power generation is insufficient, the compressor operates at a reduced frequency to match the photovoltaic power generation, and the water in the buffer tank and the main water tank is heated to the maximum operating temperature by using the heat pump unit first and then the electric auxiliary heating device, maximizing the utilization of photovoltaic power.

[0116] The above embodiments merely illustrate several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and the present invention also intends to include these modifications and variations.

Claims

1. A photovoltaic-coupled heat pump system, comprising an inverter, a heat pump unit, an electric auxiliary heating device, a buffer water tank, a water tank, and a controller, wherein the inverter is used to couple the photovoltaic system with the heat pump unit and the electric auxiliary heating device, and the heat pump unit and the electric auxiliary heating device are used to heat the medium in the buffer water tank and the water tank, characterized in that, The controller uses the inverter to control the operating power of the heat pump unit and the start / stop of the electric auxiliary heating device in real time based on the photovoltaic power generation. The control steps are as follows: S10 acquires the photovoltaic power generation, the maximum power of the heat pump unit, and the heating power of the electric auxiliary heating device in real time, and determines whether the power generation is greater than or equal to the sum of the maximum power and the heating power: If yes, then execute S20; If not, then execute S30; S20 obtains the operating mode of the heat pump unit, the buffer water temperature of the buffer tank, the water temperature of the water tank, and the preset maximum operating temperature, maximum heat storage temperature, and minimum buffer water temperature of the heat pump unit. If the working mode is heating, the buffer water temperature and the water temperature are compared with the maximum operating temperature and the maximum heat storage temperature, respectively. Based on the comparison results, the operating frequency of the heat pump unit and the start and stop of the electric auxiliary heating device are controlled. If the working mode is cooling, the buffer water temperature is compared with the minimum buffer water temperature, and the operating frequency of the heat pump unit and the start and stop of the electric auxiliary heating device are controlled according to the comparison result. S30 determines whether the power generation capacity is greater than or equal to the maximum power: If yes, then execute S40; If not, then execute S60; The S40 acquires the heat pump unit's operating mode, buffer water temperature, and current water temperature, as well as the preset maximum operating temperature and minimum buffer water temperature. If the working mode is heating, the buffer water temperature and the water temperature are compared with the maximum operating temperature, and the operating frequency of the heat pump unit and the start and stop of the electric auxiliary heating device are controlled according to the comparison result. If the working mode is cooling, the buffer water temperature is compared with the minimum buffer water temperature, and the operating frequency of the heat pump unit and the start and stop of the electric auxiliary heating device are controlled according to the comparison result. The S60 acquires the operating mode of the heat pump unit, and based on the operating mode, retrieves the maximum allowable operating frequency range for power generation from the heat pump unit's built-in operating frequency band table as the limited operating frequency; it also acquires the buffer water temperature and the used water temperature, as well as the preset maximum operating temperature and minimum buffer water temperature. If the working mode is heating, the buffer water temperature and the water temperature are compared with the maximum operating temperature. Based on the comparison result, the heat pump unit is controlled to operate at a limited frequency and the electric auxiliary heating device is turned on and off. If the operating mode is cooling, the buffer water temperature will be compared with the minimum buffer water temperature, and the heat pump unit will be controlled to operate within the specified limits based on the comparison result.

2. The heat pump system according to claim 1, characterized in that, In step S20, the operating frequency of the heat pump unit and the on / off control of the electric auxiliary heating device in heating and cooling modes are as follows: Heating mode: When the buffer water temperature and the water temperature are lower than the maximum operating temperature, the heat pump unit is controlled to operate at the highest frequency and the electric auxiliary heating device is turned on. When the buffer water temperature and the water temperature are greater than or equal to the maximum operating temperature and less than the maximum heat storage temperature, the heat pump unit is controlled to operate at the frequency required to maintain a constant indoor temperature, and the electric auxiliary heating device is controlled to remain on. When the buffer water temperature and the water temperature are greater than or equal to the maximum heat storage temperature, the heat pump unit is controlled to operate at the frequency required to maintain a constant indoor temperature and the electric auxiliary heating device is turned off. Cooling mode: When the buffer water temperature is lower than the minimum buffer water temperature, the electric auxiliary heating device is activated; and the water temperature is acquired and compared with the maximum operating temperature and the maximum heat storage temperature. If the water temperature is lower than the maximum operating temperature, the heat pump unit will be controlled to operate at the highest frequency. If the water temperature is greater than or equal to the maximum operating temperature but less than the maximum heat storage temperature, the heat pump unit will be controlled to operate at the frequency required to maintain a constant indoor temperature. If the water temperature is greater than or equal to the maximum heat storage temperature, the heat pump unit will be controlled to operate at the frequency required to maintain a constant indoor temperature and the electric auxiliary heating device will be turned off. When the buffer water temperature is greater than or equal to the minimum buffer water temperature, the heat pump unit is controlled to operate at the highest frequency until the buffer water temperature is lower than the minimum buffer water temperature.

3. The heat pump system according to claim 1, characterized in that, In step S40, the operating frequency of the heat pump unit and the on / off control of the electric auxiliary heating device in heating and cooling modes are as follows: Heating mode: When the buffer water temperature and the water temperature are lower than the maximum operating temperature, the heat pump unit is controlled to operate at the frequency required to maintain a constant indoor temperature until the indoor temperature reaches the set temperature, then it stops operating and the electric auxiliary heating device is turned on. When the buffer water temperature and the water temperature are greater than or equal to the maximum operating temperature, the heat pump unit is controlled to operate at the frequency required to maintain a constant indoor temperature. Cooling mode: When the buffer water temperature is lower than the minimum buffer water temperature, the operating water temperature is further obtained and compared with the maximum operating temperature. If the water temperature is lower than the maximum operating temperature, the heat pump unit will be controlled to operate at the frequency required to maintain a constant indoor temperature until the indoor temperature reaches the set temperature, then it will stop operating and the electric auxiliary heating device will be turned on. If the water temperature is greater than or equal to the maximum operating temperature, the heat pump unit will be controlled to operate at the frequency required to maintain a constant indoor temperature. When the buffer water temperature is greater than or equal to the minimum buffer water temperature, the heat pump unit is controlled to operate at the highest frequency until the buffer water temperature is lower than the minimum buffer water temperature.

4. The heat pump system according to claim 1, characterized in that, In step S60, the operating frequency of the heat pump unit and the on / off control of the electric auxiliary heating device in heating and cooling modes are as follows: Heating mode: When the buffer water temperature and the water temperature are lower than the maximum operating temperature, the heat pump unit is controlled to run at a limited operating frequency until the indoor temperature reaches the set temperature, then it stops running and the electric auxiliary heating device is turned on. When the buffer water temperature and the water temperature are greater than or equal to the maximum operating temperature, the heat pump unit is controlled to operate at a limited operating frequency. Cooling mode: When the buffer water temperature is lower than the minimum buffer water temperature, the operating water temperature is further obtained and compared with the maximum operating temperature. If the water temperature is lower than the maximum operating temperature, the heat pump unit will be controlled to run at a limited operating frequency until the indoor temperature reaches the set temperature, then it will stop running and the electric auxiliary heating device will be turned on. If the water temperature is greater than or equal to the maximum operating temperature, the heat pump unit will be controlled to operate at a limited operating frequency. When the buffer water temperature is greater than or equal to the minimum buffer water temperature, the heat pump unit is controlled to operate at a limited operating frequency until the buffer water temperature is lower than the minimum buffer water temperature.

5. The heat pump system according to any one of claims 1-4, characterized in that, The inverter of a heat pump system is also coupled to an energy storage device and the power grid.

6. The heat pump system according to claim 5, characterized in that, After controlling the operating frequency of the heat pump unit and the start / stop of the electric auxiliary heating device in the heating and cooling modes of step S20, the remaining power is first used to charge the energy storage device before being fed back to the power grid.

7. The heat pump system according to claim 5, characterized in that, Step S50 is included before step S60: S50 obtains the input energy storage power of the energy storage device and the input grid power of the grid, calculates the total power of the sum of the energy storage power, grid power, and generation power, and determines whether the total power is greater than or equal to the maximum power. If so, control the photovoltaic, energy storage devices and grid to supply power to the heat pump unit through the inverter and execute S40; If not, then execute S60.

8. The heat pump system according to any one of claims 1-4, 6, and 7, characterized in that, The operating frequency band table divides the heating and cooling power into N frequency bands based on the operating characteristics of the heat pump system, and the frequency of each band is determined by EEPROM data.

9. The heat pump system according to claim 8, characterized in that, The maximum operating temperature of the heat pump unit is 65℃, and the maximum heat storage temperature is 75℃.

10. The heat pump system according to claim 9, characterized in that, The minimum buffer water temperature in the buffer tank is 7℃.

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