Wind turbine generator set heat pump hybrid cooling system and control method thereof

Abstract

The application discloses a heat pump participating type hybrid cooling system for a wind turbine generator unit and a control method thereof, which comprises a nacelle cooling water circulating unit, a radiator cooling water circulating unit, a heat pump unit, a first cooling liquid reversing valve and a second cooling liquid reversing valve. The nacelle cooling water circulating unit is connected with the radiator cooling water circulating unit through the heat pump unit, and the forward and reverse operation of refrigerant is switched through the heat pump unit. The two ends of the nacelle cooling water circulating unit are connected with the two ends of the radiator cooling water circulating unit through the first cooling liquid reversing valve and the second cooling liquid reversing valve respectively, and the flow direction of the cooling liquid is controlled through the opening of the first cooling liquid reversing valve and the second cooling liquid reversing valve. The application can effectively compensate the heat dissipation performance of a natural wind cooling radiator under the condition of medium and low wind speed, improve the economy of the wind turbine generator unit, and realize effective preheating of the wind turbine generator unit through the characteristics that the heat pump can switch the forward and reverse operation.

Description

Technical Field

[0001] This invention relates to the technical field of cooling systems for wind turbine generator sets, and in particular to a heat pump-assisted hybrid cooling system for wind turbine generator sets and its control method. Background Technology

[0002] In recent years, the power generation capacity of wind turbine generators has been continuously increasing, and the cooling gearboxes and generator heat dissipation devices required for them have become increasingly demanding in terms of heat dissipation power. To meet the high-power heat dissipation requirements of offshore wind turbine generators, wind turbine cooling systems typically use one or two sets of pumps with large flow rates to push cooling water through the gearbox or generator to absorb heat, and then flow through the radiator. After being cooled, the cooling water returns to the pump for the next cycle.

[0003] The resulting increase in radiator size, power, and system flow rate poses significant challenges to the structural design and self-consumption requirements of wind turbines. To address the issues of self-consumption and cooling fan noise in wind turbines, manufacturers have developed natural air-cooled radiators. These radiators utilize the natural airflow following the impeller to remove heat generated by components such as the gearbox and generator during power generation through cooling channels.

[0004] Naturally cooled radiators require the air inlet of the radiator fins to face the wind direction and a large frontal area to ensure sufficient airflow. However, naturally cooled radiators suffer from poor air permeability, insufficient ventilation, and inadequate heat dissipation in low to medium wind speed ranges. This necessitates increasing the radiator area to compensate for the reduced heat dissipation power. The increased weight and structural stress from this increased radiator area pose significant challenges to the structural strength, transportation, and installation of the wind turbine generator set. Furthermore, wind turbine generator sets require preheating of the nacelle equipment during cold starts. Currently available electric heating equipment suffers from high power consumption, low efficiency, and long preheating times. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a heat pump-participated hybrid cooling system for wind turbine generators, which can effectively compensate for the heat dissipation performance of natural air-cooled radiators under low and medium wind speeds, thereby improving the economy of wind turbine generators; at the same time, it can take advantage of the heat pump's ability to switch between forward and reverse operation to achieve effective preheating of wind turbine generators.

[0006] Another objective of this invention is to provide a control method for a heat pump-participated hybrid cooling system for wind turbine generator sets.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A heat pump-assisted hybrid cooling system for wind turbine generator sets includes a nacelle cooling water circulation unit, a radiator cooling water circulation unit, a heat pump unit, a first coolant reversing valve, and a second coolant reversing valve. The nacelle cooling water circulation unit is connected to the radiator cooling water circulation unit via the heat pump unit, which switches the refrigerant flow in both directions. The two ends of the nacelle cooling water circulation unit are connected to the two ends of the radiator cooling water circulation unit via the first and second coolant reversing valves, respectively, and the flow direction of the coolant is controlled by opening the first and second coolant reversing valves.

[0009] Furthermore, the nacelle cooling water circulation unit includes a nacelle pump station and a nacelle heat exchanger. The two ends of the nacelle pump station are respectively connected to the nacelle heat exchanger and the heat-generating devices of the wind turbine generator through pipelines. The nacelle pump station provides circulation power for the coolant circulation in the nacelle. The nacelle heat exchanger and the heat pump unit are connected through pipelines. The pipeline between the nacelle pump station and the nacelle heat exchanger is connected to one end of the radiator cooling water circulation unit through a first coolant reversing valve. The pipeline between the nacelle heat exchanger and the heat-generating devices is connected to the other end of the radiator cooling water circulation unit through a second coolant reversing valve.

[0010] Furthermore, the cabin heat exchanger is a shell-and-tube heat exchanger, and the cabin cooling water circulation unit uses antifreeze coolant.

[0011] Furthermore, the radiator cooling water circulation unit includes a radiator heat exchanger, a radiator pump station, and a natural air-cooled radiator. The two ends of the radiator pump station are connected to the radiator heat exchanger and the natural air-cooled radiator respectively through pipelines. The radiator pump station provides circulation power for the radiator coolant circulation. The radiator heat exchanger is connected to the heat pump unit through pipelines. The pipeline between the radiator pump station and the natural air-cooled radiator is connected to one end of the engine room cooling water circulation unit through a first coolant reversing valve. The pipeline between the natural air-cooled radiator and the radiator heat exchanger is connected to the other end of the engine room cooling water circulation unit through a second coolant reversing valve.

[0012] Furthermore, the natural air-cooled radiator uses a plate radiator or a tube-fin radiator to achieve heat exchange between the coolant and the air, the radiator heat exchanger uses a pressure-resistant shell-and-tube heat exchanger to achieve heat exchange between the refrigerant and the coolant, and the radiator cooling water circulation unit uses antifreeze coolant.

[0013] Furthermore, the heat pump unit includes a compressor, an expansion valve, and a four-way reversing valve, which is connected to the compressor, the expansion valve, the cabin heat exchanger of the cabin cooling water circulation unit, and the radiator heat exchanger of the radiator cooling water circulation unit, respectively.

[0014] Furthermore, the heat pump unit is internally controlled by a PLC control unit, and the PLC control unit exchanges data and instructions with the main control system of the fan.

[0015] Furthermore, the heat pump unit, the cabin cooling water circulation unit's cabin heat exchanger, and the radiator cooling water circulation unit's radiator heat exchanger are integrated into one unit and installed in the cabin.

[0016] Another objective of this invention is achieved through the following technical solution:

[0017] A control method for a heat pump-assisted hybrid cooling system for wind turbine generator sets, comprising:

[0018] When the wind turbine is ready to start, the hybrid cooling system switches to heating mode. At this time, the first and second coolant reversing valves are closed, the radiator cooling water circulation unit and the nacelle cooling water circulation unit operate independently, the heat pump unit receives a command to control and operates in reverse, the four-way reversing valve of the heat pump unit switches, and the compressor of the heat pump unit runs. At this time, the radiator heat exchanger of the radiator cooling water circulation unit is an evaporator, where the refrigerant absorbs heat, and the nacelle heat exchanger of the nacelle cooling water circulation unit is a condenser, where the refrigerant releases heat. At this time, the radiator cooling water circulation unit is in low-temperature circulation, the natural air-cooled radiator of the radiator cooling water circulation unit absorbs heat from the external space, and the heat pump unit transfers the heat from the natural air-cooled radiator to the heat-generating components of the wind turbine. The nacelle cooling water circulation unit is in high-temperature circulation, preheating the heat-generating components and preparing for start-up.

[0019] During the low to medium wind speed range of wind turbine startup, the hybrid cooling system switches to cooling mode. The first and second coolant reversing valves are closed, the radiator cooling water circulation unit and the nacelle cooling water circulation unit operate independently, the heat pump unit is controlled to start with variable power, the four-way reversing valve of the heat pump unit does not switch, the compressor runs, the radiator heat exchanger is a condenser where the refrigerant releases heat, the nacelle heat exchanger is an evaporator where the refrigerant absorbs heat, and the heat pump unit transfers heat from the self-heating device to the naturally air-cooled radiator.

[0020] During the start-up and operation of the wind turbine generator set in the medium to high wind speed range, the hybrid cooling system switches to direct heat dissipation mode. The first and second coolant reversing valves open, and the radiator cooling water circulation unit and the nacelle cooling water circulation unit are integrated into the same system. At this time, the heat pump unit receives a command to shut down, the compressor shuts down, and the radiator pump station of the radiator cooling water circulation unit shuts down. Only the nacelle pump station of the nacelle cooling water circulation unit pumps the coolant that has passed through the heat-generating components directly to the natural air-cooled radiator for heat dissipation.

[0021] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0022] 1. This invention can effectively improve the heat dissipation efficiency of natural air-cooled radiators at low and medium wind speeds, while taking into account the advantages of high heat dissipation and low power consumption of natural air-cooled radiators in medium and high wind speed ranges. It achieves a relatively balanced heat dissipation efficiency in various wind speed ranges, reduces the additional design margin of natural air-cooled radiators, and reduces the windward area of ​​heat dissipation plates. Therefore, it reduces the windward load of natural air-cooled radiators, making it more friendly to the structural design of wind turbine generator sets.

[0023] 2. The compressor in the heat pump unit of this invention is a variable power operating device, which can dynamically adjust the cooling power according to the changes in the system's heating power. Its cooling COP (coefficient of performance) is between 3 and 4, which is highly efficient. At the same time, because the system uses a phase change refrigerant, the temperature at the evaporator end and the condenser end is stable, which is beneficial to equipment temperature control and effective thermal management of heating devices.

[0024] 3. Wind turbine generator sets typically incorporate gear oil and IGBT preheating steps before startup to ensure normal turbine operation. Therefore, traditional cooling systems require additional electric heating equipment, resulting in high power consumption and significant time and space constraints. This invention, however, only requires controlling the heat pump valve group to switch between cooling and heating modes, eliminating the need for additional electric heating equipment. The heat pump unit's heating COP (coefficient of performance) is between 2 and 3, offering higher efficiency compared to electric heating equipment, and eliminating the risk of overheating and dry burning.

[0025] 4. In this invention, because the refrigerant temperature at the evaporator end of the heat pump is relatively low and the temperature at the condenser end is relatively high, the heat exchange efficiency is high. This allows for a reduction in the heat exchange area of ​​the heat exchangers within the radiator cooling water circulation and nacelle cooling water circulation, thus reducing the volume and weight of the heat exchange equipment. This is beneficial for the structural design of the internal components of the wind turbine generator set and for overall weight reduction of the wind turbine generator set. Simultaneously, the high heat exchange efficiency allows for a reduction in system cooling water flow, reducing pipeline losses and pump power, achieving overall optimized design. Attached Figure Description

[0026] Figure 1 This is a system schematic diagram of the hybrid cooling system of the present invention.

[0027] Figure 2 This is a control structure diagram of the hybrid cooling system of the present invention.

[0028] Figure 3 This is a system operation diagram of the hybrid cooling system of the present invention in heating mode.

[0029] Figure 4 This is a system operation diagram of the hybrid cooling system of the present invention in refrigeration mode.

[0030] Figure 5 This is a system operation diagram of the hybrid cooling system of the present invention under direct heat dissipation conditions.

[0031] Figure 6 This is a control principle diagram of the hybrid cooling system of the present invention. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0033] Example 1:

[0034] like Figure 1 , Figure 2 As shown, this embodiment provides a heat pump-assisted hybrid cooling system for wind turbine generator sets, including a nacelle cooling water circulation unit, a radiator cooling water circulation unit, a heat pump unit, a first coolant reversing valve 10, and a second coolant reversing valve 9. The nacelle cooling water circulation unit is connected to the radiator cooling water circulation unit through the heat pump unit, which switches the refrigerant flow in both directions. The two ends of the nacelle cooling water circulation unit are connected to the two ends of the radiator cooling water circulation unit through the first coolant reversing valve 10 and the second coolant reversing valve 9, respectively. The opening of the first coolant reversing valve 10 and the second coolant reversing valve 9 controls the flow direction of the coolant. The nacelle cooling water circulation unit, the radiator cooling water circulation unit, the heat pump unit, and the two coolant reversing valves are electrically connected to the wind turbine main control system, which controls the switching of the hybrid cooling system's operating mode.

[0035] Specifically, the nacelle cooling water circulation unit includes a nacelle pump station 1 and a nacelle heat exchanger 2. The two ends of the nacelle pump station 1 are connected to the nacelle heat exchanger 2 and the heat-generating device 11 of the wind turbine generator set through pipelines, respectively. The nacelle pump station 1 provides circulation power for the coolant circulation in the nacelle. The nacelle heat exchanger 2 exchanges the heat generated by the heat-generating device 11 from the coolant to the refrigerant. The nacelle heat exchanger 2 and the four-way reversing valve 8 are connected through pipelines. The pipeline between the nacelle pump station 1 and the nacelle heat exchanger 2 is connected to one end of the radiator cooling water circulation unit through a first coolant reversing valve 10. The pipeline between the nacelle heat exchanger 2 and the heat-generating device 11 is connected to the other end of the radiator cooling water circulation unit through a second coolant reversing valve 9.

[0036] Furthermore, the nacelle heat exchanger 2 is a shell-and-tube heat exchanger, and the nacelle cooling water circulation unit uses antifreeze coolant, the grade of which is determined by the unit's installation environment.

[0037] Specifically, the radiator cooling water circulation unit includes a radiator heat exchanger 3, a radiator pump station 4, and a natural air-cooled radiator 5. The two ends of the radiator pump station 4 are connected to the radiator heat exchanger 3 and the natural air-cooled radiator 5 respectively through pipelines. The radiator pump station 4 provides circulation power for the radiator coolant circulation. The radiator heat exchanger 3 exchanges heat from the refrigerant to the radiator coolant, and the natural air-cooled radiator 5 dissipates heat into the air. The radiator heat exchanger 3 and the four-way reversing valve 8 are connected through pipelines. The pipeline between the radiator pump station 4 and the natural air-cooled radiator 5 is connected to one end of the cabin cooling water circulation unit through a first coolant reversing valve 10. The pipeline between the natural air-cooled radiator 5 and the radiator heat exchanger 3 is connected to the other end of the cabin cooling water circulation unit through a second coolant reversing valve 9.

[0038] Furthermore, the natural air-cooled radiator 5 uses a plate radiator or a tube-fin radiator to achieve heat exchange between the coolant and the air, and the radiator heat exchanger 3 uses a pressure-resistant shell-and-tube heat exchanger to achieve heat exchange between the refrigerant and the coolant. The radiator cooling water circulation unit uses antifreeze coolant, the grade of which is determined by the unit installation environment.

[0039] Specifically, the heat pump unit includes a compressor 6, an expansion valve 7, and a four-way reversing valve 8. The four-way reversing valve 8 is connected to the compressor 6, the expansion valve 7, the nacelle heat exchanger 2, and the radiator heat exchanger 3, respectively. The heat pump unit transfers the heat exchanged with the refrigerant in the nacelle heat exchanger 2 to the radiator heat exchanger 3. The heat pump unit uses a separate PLC control unit to control internal refrigerant pressure, expansion valve 7 opening, compressor 6 starting mode, and other parameters, as well as to automatically regulate the energy of the heat pump unit. The PLC control unit exchanges data and commands with the main fan control system. An environmentally friendly refrigerant is used, and the refrigerant grade is determined by the unit's installation environment.

[0040] In this embodiment, a screw compressor is used, which is a variable power operating device. It can dynamically adjust its cooling power according to the changes in the heating power of the hybrid cooling system. Its cooling COP (coefficient of performance) ranges from 3 to 4, exhibiting high efficiency. Simultaneously, the system uses a phase change refrigerant, resulting in stable temperatures at both the evaporator and condenser ends, which is beneficial for equipment temperature control and effective thermal management of the heating components. The compressor's thermal COP ranges from 2 to 3, eliminating the need for additional electric heating equipment. Switching between cooling and heating modes of the heat pump can be achieved simply by controlling the heat pump valve group.

[0041] In the entire system, to reduce the risk of refrigerant leakage, the heat pump unit and the heat exchanger connected to it are placed as an independent integrated component in the nacelle, while the other components such as the pump station, reversing valve, and radiator are distributed according to requirements.

[0042] In this embodiment, the pump station can be replaced by any method of driving coolant flow, and the heat pump unit can be replaced by any phase change refrigeration system that uses a compressor as the driving force.

[0043] This embodiment uses a heat pump-participated hybrid cooling system with switchable operating modes to compensate for the heat dissipation performance of natural air-cooled radiators under low wind speed conditions, thereby improving the economy of wind turbine generator sets. At the same time, it can take advantage of the heat pump's ability to switch between forward and reverse operation to achieve effective preheating of wind turbine generator sets.

[0044] Example 2:

[0045] like Figures 3 to 6 As shown in the figure, this embodiment provides a control method for a heat pump-assisted hybrid cooling system for wind turbine generators. The hybrid cooling system mainly has three operating modes: heating mode, cooling mode, and direct heat dissipation mode. The control methods for the three modes are as follows.

[0046] When the wind turbine generator is ready to start, the hybrid cooling system switches to heating mode. At this time, the first and second coolant reversing valves are closed, the radiator cooling water circulation unit and the nacelle cooling water circulation unit operate independently, and the heat pump unit is controlled by the wind turbine main control system to run in reverse. The four-way reversing valve is reversed, and the compressor runs. At this time, the radiator heat exchanger is an evaporator where the refrigerant absorbs heat, and the nacelle heat exchanger is a condenser where the refrigerant releases heat. At this time, the radiator cooling water circulation unit is in low-temperature circulation, the natural air-cooled radiator absorbs heat from the external space, and the heat pump unit transfers the heat from the natural air-cooled radiator to the heat-generating components. The nacelle cooling water circulation unit is in high-temperature circulation to preheat the heat-generating components and prepare for start-up.

[0047] During the low to medium wind speed range of wind turbine startup, the wind turbine's heat output is relatively low, and the natural air-cooled radiator has poor ventilation, making it unable to efficiently dissipate heat from the turbine. At this time, the hybrid cooling system switches to cooling mode. The first and second coolant reversing valves close, and the radiator cooling water circulation unit and the nacelle cooling water circulation unit operate independently. The heat pump unit is controlled by the wind turbine's main control system for variable power startup. The four-way reversing valve does not switch, and the compressor runs. In this mode, the radiator heat exchanger acts as a condenser, where the refrigerant releases heat, while the nacelle heat exchanger acts as an evaporator, where the refrigerant absorbs heat. The heat pump unit transfers heat from its self-heating components to the natural air-cooled radiator. Because the refrigerant condensation temperature of the heat pump unit is high and the evaporation temperature is low, the radiator cooling water circulation is at a high temperature, while the nacelle cooling water circulation is at a low temperature. The internal circulating water temperature of the radiator is high, significantly increasing its heat exchange capacity with the environment, which is beneficial for the natural air-cooled radiator to dissipate heat at low wind speeds.

[0048] During the start-up operation of wind turbine generators in the medium to high wind speed range, the generators generate a high amount of heat, but the natural air-cooled radiators also have high ventilation capacity, significantly increasing their heat dissipation capacity. At this time, the hybrid cooling system switches to direct cooling mode. The first and second coolant reversing valves open, and the radiator cooling water circulation unit and the nacelle cooling water circulation unit are integrated into a single system. The heat pump unit receives commands from the wind turbine's main control system to shut down, the compressor stops, and the radiator pump station shuts down. Only the nacelle pump station pumps the coolant directly to the natural air-cooled radiators for heat dissipation.

[0049] The above three operating conditions cover the heat exchange requirements of wind turbine generator sets at each stage from start-up preparation to power increase to rated power.

[0050] In the above scheme, the first operating mode solves the problem that the existing electric heating equipment has high power consumption, low efficiency and long preheating time when the wind turbine generator needs to be preheated during cold start.

[0051] The second operating mode solves the problems of poor air permeability, insufficient ventilation flow, and insufficient heat dissipation performance in the low to medium wind speed range of natural air-cooled radiators.

[0052] The third operating mode can take advantage of the low self-power consumption of natural air-cooled radiators and improve the economic efficiency of wind turbine generators.

[0053] In summary, this invention utilizes the wind turbine's main control system to switch operating modes. Through the coordinated operation of the heat pump system and the water-cooling system, it can compensate for the heat dissipation performance of wind turbine generators under low to medium wind speeds, reduce the windward area of ​​naturally cooled radiators, lower the structural design requirements of wind turbine generators, improve the heat exchange efficiency of the cooling system, and enhance the economic efficiency of wind turbine generators. Simultaneously, leveraging the heat pump's ability to switch between forward and reverse operation, it efficiently preheats the wind turbine generator during startup, enabling rapid cold starts.

[0054] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope disclosed in the present invention, based on the technical solution and inventive concept of the present invention, shall fall within the scope of protection of the present invention.

Claims

1. A heat pump-assisted hybrid cooling system for wind turbine generator sets, characterized in that: The system includes a nacelle cooling water circulation unit, a radiator cooling water circulation unit, a heat pump unit, a first coolant reversing valve, and a second coolant reversing valve. The nacelle cooling water circulation unit is connected to the radiator cooling water circulation unit via the heat pump unit, which switches the refrigerant flow in both directions. The two ends of the nacelle cooling water circulation unit are connected to the two ends of the radiator cooling water circulation unit via the first and second coolant reversing valves, respectively, controlling the coolant flow direction by opening and closing these valves. The nacelle cooling water circulation unit includes a nacelle pump station and a nacelle heat exchanger. The radiator cooling water circulation unit includes a radiator heat exchanger, a radiator pump station, and a naturally cooled radiator. The heat pump unit includes a compressor, an expansion valve, and a four-way reversing valve. The two ends of the nacelle pump station are connected to the nacelle heat exchanger and the heat-generating components of the wind turbine generator via pipelines. The engine room provides circulating power for the coolant circulation within the engine room via a nacelle pump station. The engine room heat exchanger and heat pump unit are connected by pipelines. The pipeline between the engine room pump station and the engine room heat exchanger is connected to the pipeline between the radiator pump station and the naturally cooled radiator of the radiator cooling water circulation unit via a first coolant reversing valve. The pipeline between the engine room heat exchanger and the heat-generating device is connected to the pipeline between the radiator heat exchanger and the naturally cooled radiator of the radiator cooling water circulation unit via a second coolant reversing valve. Both ends of the radiator pump station are connected to the radiator heat exchanger and the naturally cooled radiator via pipelines, respectively. The radiator pump station provides circulating power for the radiator coolant circulation. The radiator heat exchanger is connected to the heat pump unit via pipelines. The four-way reversing valve is connected to the compressor, expansion valve, engine room heat exchanger of the engine room cooling water circulation unit, and radiator heat exchanger of the radiator cooling water circulation unit, respectively.

2. The heat pump-assisted hybrid cooling system for wind turbine generator sets according to claim 1, characterized in that: The engine room heat exchanger is a shell-and-tube type, and the engine room cooling water circulation unit uses antifreeze coolant.

3. The heat pump-assisted hybrid cooling system for wind turbine generator sets according to claim 1, characterized in that: The natural air-cooled radiator uses a plate radiator or a tube-fin radiator to achieve heat exchange between the coolant and the air. The radiator heat exchanger uses a pressure-resistant shell-and-tube heat exchanger to achieve heat exchange between the refrigerant and the coolant. The radiator cooling water circulation unit uses antifreeze coolant.

4. The heat pump-assisted hybrid cooling system for wind turbine generator sets according to claim 1, characterized in that: The heat pump unit is internally controlled by a PLC control unit, which exchanges data and instructions with the main control system of the fan.

5. The heat pump-assisted hybrid cooling system for wind turbine generator sets according to claim 1, characterized in that: The heat pump unit, the cabin cooling water circulation unit's cabin heat exchanger, and the radiator cooling water circulation unit's radiator heat exchanger are integrated into one unit and installed in the cabin.

6. The control method for a heat pump-assisted hybrid cooling system for wind turbine generator sets according to any one of claims 1 to 5, characterized in that, include, When the wind turbine is ready to start, the hybrid cooling system switches to heating mode. At this time, the first and second coolant reversing valves are closed, the radiator cooling water circulation unit and the nacelle cooling water circulation unit operate independently, the heat pump unit receives a command to control and operates in reverse, the four-way reversing valve of the heat pump unit switches, and the compressor of the heat pump unit runs. At this time, the radiator heat exchanger of the radiator cooling water circulation unit is an evaporator, where the refrigerant absorbs heat, and the nacelle heat exchanger of the nacelle cooling water circulation unit is a condenser, where the refrigerant releases heat. At this time, the radiator cooling water circulation unit is in low-temperature circulation, the natural air-cooled radiator of the radiator cooling water circulation unit absorbs heat from the external space, and the heat pump unit transfers the heat from the natural air-cooled radiator to the heat-generating components of the wind turbine. The nacelle cooling water circulation unit is in high-temperature circulation, preheating the heat-generating components and preparing for start-up. During the low to medium wind speed range of wind turbine startup, the hybrid cooling system switches to cooling mode. The first and second coolant reversing valves are closed, the radiator cooling water circulation unit and the nacelle cooling water circulation unit operate independently, the heat pump unit is controlled to start with variable power, the four-way reversing valve of the heat pump unit does not switch, the compressor runs, the radiator heat exchanger is a condenser where the refrigerant releases heat, the nacelle heat exchanger is an evaporator where the refrigerant absorbs heat, and the heat pump unit transfers heat from the self-heating device to the naturally air-cooled radiator. During the start-up and operation of the wind turbine generator set in the medium to high wind speed range, the hybrid cooling system switches to direct heat dissipation mode. The first and second coolant reversing valves open, and the radiator cooling water circulation unit and the nacelle cooling water circulation unit are integrated into the same system. At this time, the heat pump unit receives a command to shut down, the compressor shuts down, and the radiator pump station of the radiator cooling water circulation unit shuts down. Only the nacelle pump station of the nacelle cooling water circulation unit pumps the coolant that has passed through the heat-generating components directly to the natural air-cooled radiator for heat dissipation.

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