Wind turbine blade electrothermal composite membrane internal and external synergistic electrothermal de-icing device

Abstract

This invention relates to the field of wind power equipment technology, and more particularly to a wind turbine blade electrothermal composite film synergistic electrothermal de-icing device, comprising a blade body, an inner electrothermal film, an outer electrothermal film, a wind turbine, and an integrated gas-electric de-icing control system. The inner electrothermal film is installed inside the blade cavity near the blade root, while the outer electrothermal film is installed on the outer surface of the blade near the blade tip. The two films do not overlap in the blade's spanwise direction, and a lightning protection safety zone is reserved between the outer electrothermal film and the blade tip. The integrated gas-electric de-icing control system is equipped with a frequency modulation and power regulation unit, capable of independently controlling the heating of either the inner or outer electrothermal film individually, or controlling both films to heat synergistically, and dynamically adjusting the wind turbine speed and heating power according to the environment and icing state. This invention effectively reduces the risk of lightning strikes to the blade, reduces the amount of high-altitude installation work for the outer film, and completely solves the technical problem of difficult-to-remove icing in the blade tip area.

Description

Technical Field

[0001] This invention relates to the field of wind power equipment technology, and in particular to a wind turbine blade electrothermal composite film internal and external synergistic electrothermal de-icing device. Background Technology

[0002] Wind power generation equipment often operates in frigid, high-humidity, high-altitude, or winter environments. Cold air causes ice to form on the surface of wind turbine blades, altering their original aerodynamic shape. This change in shape not only reduces the power generation efficiency of the wind turbine but also significantly increases the structural fatigue load due to uneven mass distribution. To address the blade icing problem, the industry currently mainly employs internal cavity air-thermal de-icing technology and external surface electrothermal de-icing technology.

[0003] Internal air-heated de-icing technology utilizes the circulation of hot air inside the wind turbine blades, transferring heat outward through the blade shell to melt the surface ice layer; however, due to the low thermal conductivity of composite materials, it suffers from slow heat transfer speed and high overall energy consumption. External surface electrothermal de-icing technology lays an electrically heated film on the outside of the blade, offering advantages such as fast heat transfer speed and high local de-icing efficiency. However, in practical engineering applications, conventional full-coverage external surface covering schemes have serious structural and safety defects: First, the risk of lightning strikes is extremely high. Electric heating films are typically made of conductive materials, and the closer the film is to the blade tip (the area with the highest lightning strike rate), the greater the probability of a direct lightning strike. To prevent lightning damage, current construction often terminates the installation several meters from the blade tip, creating a "blind spot" where heat cannot be obtained. During freezing rain, this leads to a large accumulation of ice at the tip, endangering the safe operation of the equipment.

[0004] Secondly, the installation and maintenance costs are high. Applying film to a large area of ​​the outer surface is a high-altitude and high-risk operation, which is difficult to carry out. Moreover, the electric heating film is exposed to the harsh external environment all year round, which makes it very easy to age and peel off.

[0005] Third, thermal stress concentration and rigid control are problems. Existing technologies mostly adopt a single-location centralized heating mode. When dealing with heavy icing, the heating power in that area often needs to be significantly increased to achieve the de-icing effect, resulting in excessive heat concentration on the same cross section. This can easily cause localized overheating and aging of wind turbine blade composite materials (such as fiberglass and carbon fiber). At the same time, existing control strategies mostly rely on simple fixed-frequency and fixed-power start-stop logic or complex virtual calculation algorithms. They lack highly reliable industrial-grade dynamic power regulation (power adjustment) and wind turbine variable frequency regulation (frequency adjustment) strategies. They cannot flexibly allocate energy consumption according to actual meteorological conditions such as "light icing", "heavy icing" or "preset anti-icing", making it difficult to achieve the best engineering balance between de-icing effect and self-consumption.

[0006] Based on the aforementioned pain points in actual engineering, the industry urgently needs to propose a brand-new physical architecture and hardware control logic design approach to solve the technical problems of blade tip icing blind spots, high lightning protection risks, and uneven distribution of heating energy consumption. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a wind turbine blade electrothermal composite membrane internal and external synergistic electrothermal de-icing device.

[0008] To solve the above-mentioned technical problems, the specific contents of the present invention are as follows: The wind turbine blade electrothermal composite film synergistic electrothermal de-icing device provided by the present invention includes: The wind turbine blade body has an internal cavity separated by a blade web. The wind turbine blade body includes a blade root, a blade tip, a blade trailing edge, a suction surface, a pressure surface, and a web. An electric heating film is laid inside and attached to and fixed to the inner wall of the internal cavity; An external electric heating film is laid and fixed to the outer surface of the wind turbine blade body; the internal electric heating film and the external electric heating film do not overlap in the spanwise direction of the wind turbine blade body, and the external electric heating film is far away from the blade tip, so as to retain a lightning protection safety zone of a preset length between the external electric heating film and the blade tip. A fan and a baffle plate are installed in the internal cavity. The fan has an air outlet and an air inlet. The baffle plate separates the internal cavity to define the air outlet channel and the return channel. The integrated gas-electric de-icing control system establishes a power supply and control connection with the inner electric heating film, the outer electric heating film, and the fan; the integrated gas-electric de-icing control system has a variable frequency power regulation control module, which is used to dynamically adjust the heating power of the inner and outer electric heating films, and adjust the operating frequency of the fan.

[0009] Furthermore, the wind turbine blade electrothermal composite film internal and external synergistic electrothermal de-icing device of the present invention has a gas-electric integrated de-icing control system configured with three independently triggered heating operation modes: The inner membrane separate heating mode includes outputting power current to the inner electric heating film and starting the wind turbine, relying on the internal hot airflow to circulate and heat the inner cavity body, outer surface, lightning protection safety area and trailing edge of the wind turbine blade for heating and anti-icing. The outer membrane separate heating mode includes outputting a power supply current to the outer electrothermal film to melt the surface ice in the external area covered by the outer electrothermal film; The combined heating mode of inner and outer membranes includes simultaneously supplying power current to the inner electrothermal film and the outer electrothermal film, and starting the fan.

[0010] Furthermore, in the wind turbine blade electrothermal composite film co-heating de-icing device of the present invention, the variable frequency power control module is connected to a temperature acquisition unit for receiving signals of external ambient temperature and blade surface temperature; when the external ambient temperature is within a preset ambient temperature range and the external surface of the wind turbine blade body is free of ice, the variable frequency power control module triggers the inner film separate heating mode; when the wireless sensor configured on the external surface detects thin ice, the variable frequency power control module triggers the outer film separate heating mode; when the external surface of the wind turbine blade body is locally heavily iced, the variable frequency power control module triggers the combined heating mode of the inner and outer films. The gas-electric integrated de-icing control system has a preset internal and external heating control program. When the variable frequency power control module performs heating, it follows the sequence of first activating the internal heating film and then activating the external heating film. The internal and external heating control program specifically includes: When the external ambient temperature of the unit drops to the first preset ambient temperature threshold, the fan and the internally laid electric heating film are started. When the temperature of the inner heating film reaches the first preset inner film temperature threshold, the heating of the inner heating film is stopped; when the temperature of the inner heating film drops below the second preset inner film temperature threshold, the heating of the inner heating film is restarted, and the fan continues to run during this temperature cycle. In the inner membrane heating cycle, when the wireless sensor detects thin ice, the outer electric heating film automatically starts heating and stops when there is no thin ice, or the outer electric heating film controls the heating according to a preset time length. When the external ambient temperature of the unit rises to the second preset ambient temperature threshold, the frequency conversion power control module controls all the inner and outer electric heating films to automatically stop working.

[0011] Furthermore, in the wind turbine blade electrothermal composite film co-heating de-icing device of the present invention, under the combined heating mode of the inner and outer films, the variable frequency power control module dynamically adjusts the operating frequency of the wind turbine according to the preset temperature rise curve, and dynamically adjusts the output power of the inner electrothermal film and the outer electrothermal film by means of duty cycle or thyristor voltage regulation.

[0012] Furthermore, in the wind turbine blade electrothermal composite film inner and outer synergistic electrothermal de-icing device of the present invention, when the frequency conversion power control module performs power adjustment, it increases the output power of the inner electrothermal film to increase the compensating heat delivered to the inside of the blade tip, while limiting or reducing the output power of the outer electrothermal film to prevent local overheating damage to the wind turbine blade body.

[0013] Furthermore, in the wind turbine blade electrothermal composite film synergistic electrothermal de-icing device of the present invention, the inner electrothermal film is arranged in the internal cavity of the wind turbine blade body, which is biased towards the blade root and close to the air outlet of the wind turbine, and the outer electrothermal film is arranged on the outer surface of the wind turbine blade body. The inner electrothermal film and the outer electrothermal film are distributed in a non-overlapping manner along the span of the wind turbine blade body.

[0014] Furthermore, in the wind turbine blade electrothermal composite film synergistic electrothermal de-icing device of the present invention, the inner electrothermal film is attached to the inner wall of the blade web or the internal cavity, and the insulating material of the wind turbine blade body is used as a shield, so that the inner electrothermal film avoids the risk of direct lightning strike.

[0015] Furthermore, in the wind turbine blade electrothermal composite film co-operated electrothermal de-icing device of the present invention, the surface of the lightning protection safety area is not covered with a composite film to avoid the hidden danger of direct lightning strikes concentrated on the film; the heat generated by the electric heating film laid inside preheats the air in the air outlet channel to form a high-temperature hot airflow, and the high-temperature hot airflow is directionally transported to the blade tip interior corresponding to the lightning protection safety area.

[0016] Furthermore, in the wind turbine blade electrothermal composite film synergistic electrothermal de-icing device of the present invention, one end of the return channel is connected to the inside of the blade tip, and the other end is connected to the air inlet of the wind turbine; after the high-temperature hot airflow reaches the inside of the blade tip and releases heat, it forms a cooling airflow, and the cooling airflow is introduced into the air inlet of the wind turbine along the return channel to establish a closed circulating air passage.

[0017] Furthermore, in the wind turbine blade electrothermal composite film co-operated electrothermal de-icing device of the present invention, the gas-electric integrated de-icing control system is equipped with a hardware protection program. When the external surface temperature signal of the wind turbine blade body obtained by the temperature acquisition unit exceeds the preset temperature safety threshold, the frequency conversion power control module automatically reduces the power of the corresponding inner or outer electrothermal film or performs a circuit disconnection operation.

[0018] Beneficial effects of this invention: This invention innovatively arranges the inner and outer electrothermal films in a staggered manner along the span of the wind turbine blade, avoiding excessive heat concentration on the same cross section. The inner electrothermal film preheats the internal airflow, and when the heat-carrying airflow passes through the area of ​​the outer electrothermal film, the outer film only needs to provide the basic heat required to maintain surface de-icing, forming an efficient stepped thermodynamic complementarity that prevents localized overheating and aging of composite materials such as fiberglass or carbon fiber.

[0019] This invention completely eliminates the need for an electric heating film in the blade tip area, reserving a purely insulated lightning protection zone, significantly reducing the risk of direct lightning strikes to the external heating film. Simultaneously, the fiberglass insulating shell of the blade forms a protective structure, isolating it from direct lightning strikes and preventing damage to the internal heating elements. More importantly, a fan drives the internally heated high-temperature airflow to be directionally delivered to this lightning protection zone, filling the gap of no external heating source at the blade tip and achieving a balance between physical lightning protection and blade tip de-icing.

[0020] This invention's integrated gas-electric de-icing control system directly employs a highly reliable frequency conversion (frequency regulation) and power regulation (power regulation) hardware control strategy. By configuring three modes—inner membrane separate heating, outer membrane separate heating, and combined inner and outer membrane heating—the device can accurately match different meteorological conditions such as "preset anti-icing," "mild localized icing," and "severe icing," dynamically allocating the output power of the inner and outer membranes and the fan flow rate, significantly reducing the fan's self-consumption.

[0021] This invention significantly reduces the total area of ​​the externally laid electric heating film by transferring the large-area heating task to the internal air circulation system. This not only reduces the difficulty and cost of high-altitude and high-risk construction operations, but also reduces the frequency of subsequent maintenance required due to the aging and peeling of the external electric heating film caused by years of exposure to harsh environments. Attached Figure Description

[0022] To more clearly illustrate the technical solution of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the spatial arrangement of the internal and external electric heating composite film on the wind turbine blade according to an embodiment of the present invention; Figure 2 This is a structural diagram of an electric heating film laid in the inner cavity of a blade according to an embodiment of the present invention; Figure 3 This is a structural diagram of the integrated pneumatic and electrical installation on the de-icing blades according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the leading edge state of the blade cavity without an electric heating film in an embodiment of the present invention; Figure 5 This is a schematic diagram of a fan according to an embodiment of the present invention; Figure 6 This is an imaging diagram of the inner membrane heating according to an embodiment of the present invention. Detailed Implementation

[0024] To make the technical solution of the present invention clearer, the present invention will be clearly and completely described below with reference to specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Please see Figures 1 to 6 This embodiment provides a wind turbine blade internal and external electric heating composite film anti-icing and de-icing device, which achieves the directional staggered layout of the internal and external electric heating films and the coordinated control of gas and electricity energy.

[0026] The hardware architecture of this embodiment includes a wind turbine blade body, which has an internal cavity separated by a blade web. The wind turbine blade body includes a blade root, blade tip, blade trailing edge, suction surface, pressure surface, and web. In the initial state before the heating film is laid, the internal cavity is a physical space formed by the support of the blade web.

[0027] The key to this device lies in the special distribution of the heating elements. An inner heating film is laid and fixed to the inner wall of the internal cavity (such as the surface of the web or the inner wall of the shell); an outer heating film is laid and fixed to the outer surface of the wind turbine blade body. The inner and outer heating films do not overlap in the spanwise direction of the wind turbine blade body.

[0028] Specifically, the inner electrothermal film is positioned towards the blade root and near the wind turbine's outlet; while the outer electrothermal film is positioned on the outer surface of the wind turbine blade along the mid-to-rear section of the blade's span. Furthermore, the inner and outer electrothermal films are distributed without overlap along the span of the wind turbine blade. This staggered arrangement avoids excessive heat concentration on the same cross-section, effectively preventing localized overheating and aging of the composite material, and achieving a stepped thermodynamic complementarity.

[0029] Regarding lightning protection, this device employs a "de-metallization" design in the blade tip area, which is most susceptible to lightning strikes. The outer electrothermal film is positioned away from the blade tip, thus maintaining a predetermined length of lightning protection safety zone between the outer electrothermal film and the blade tip. No composite film is laid on the surface of this lightning protection safety zone to avoid the risk of direct lightning strikes concentrating on the film. Meanwhile, the inner electrothermal film adheres to the inner wall of the internal cavity, forming a protective structure with the blade's fiberglass insulating shell, isolating it from external direct lightning strikes and preventing damage to the internal heating elements. This combined internal and external lightning protection design significantly reduces the risk of direct lightning strikes to the entire heating system.

[0030] To maintain heat transfer, a fan and a baffle plate are installed in the internal cavity. The fan has an air outlet and an air inlet. The baffle plate divides the internal cavity, defining an outlet channel and a return channel. The heat generated by the electrically energized electric heating film preheats the air in the outlet channel, forming a high-temperature hot airflow. Under the dynamic pressure generated by the fan, the high-temperature hot airflow is directionally transported to the blade tip corresponding to the lightning protection safety area.

[0031] The control unit in this embodiment is a gas-electric integrated de-icing control system, which has a variable frequency power regulation control module. The system adopts variable frequency regulation (frequency modulation) and power regulation (power regulation) logic. The variable frequency power regulation control module is connected to a temperature acquisition unit to acquire the external ambient temperature and blade surface temperature signals in real time.

[0032] Based on actual meteorological conditions, the gas-electric integrated de-icing control system is equipped with three independently triggered heating operation modes: Inner membrane separate heating mode: When the external ambient temperature is within the preset ambient temperature range and the outer surface of the wind turbine blade is not covered with ice (e.g., during the anti-icing prevention stage), only the inner heating film is supplied with power and the wind turbine is started. After the inner heating film is energized, a large-area uniform heat field is generated in the inner cavity, and the hot air circulation heats the lightning protection safety area at the blade tip.

[0033] Outer membrane separate heating mode: When the temperature acquisition unit detects that the ambient temperature has dropped below 0°C, and the blade surface sensor determines that local icing has occurred on the outer surface of the middle and rear section along the span, while there is no icing in the blade tip lightning protection safety area, the power supply current is output to the outer electrothermal film.

[0034] Combined Inner and Outer Membrane Heating Mode: In extreme cold or heavy icing conditions, both inner and outer heating are activated simultaneously. The variable frequency power control module dynamically adjusts the fan's operating frequency according to a preset temperature rise curve, and dynamically regulates the output power of the inner and outer electric heating films using duty cycle or thyristor voltage regulation. In this mode, the system executes special power adjustment logic: increasing the output power of the inner electric heating film to improve thermal compensation inside the blade tip, while limiting or reducing the output power of the outer electric heating film to prevent simultaneous heating from causing overload on the outer shell.

[0035] To enable those skilled in the art to implement the above-mentioned dynamic adjustment process, a specific control embodiment under the combined heating mode of inner and outer membranes is provided. The "preset temperature rise curve" is set as follows: to avoid thermal stress microcracks in the blade composite material due to rapid heating, the temperature rise rate of the outer surface of the blade is limited to between 2℃ / min and 3℃ / min.

[0036] When the system enters the combined heating mode of the inner and outer membranes, the specific dynamic adjustment steps of the frequency converter power control module are as follows: Phase 1 (De-icing Preheating Period): When the outer surface temperature of the blade is below -5℃, the variable frequency power control module controls the PWM duty cycle (or thyristor conduction angle) of the internally laid electric heating film to output 100% full power, and controls the internal fan to operate at a full-load frequency of 50Hz, rapidly pressing a large amount of heat energy into the blade tip lightning protection safety area; at the same time, in order to prevent the instantaneous superposition of internal and external thermal stress, the duty cycle of the externally laid electric heating film is forcibly limited to no more than 50%.

[0037] The second stage (steady-state de-icing period): When the temperature acquisition unit detects that the temperature of the outer surface of the blade has risen to the range of -5℃ to 0℃, the inner shell of the blade has been fully preheated. At this time, the control module performs reverse power adjustment: the duty cycle of the inner electric heating film is reduced to 60%, and the fan operating frequency is simultaneously reduced to 30Hz to maintain the basic hot airflow circulation; at the same time, the duty cycle of the outer electric heating film is increased to 80% to 100%, so that the high power output of the outer film can quickly break down the interface between the surface ice layer and the blade, causing the ice to fall off over a large area.

[0038] The third stage (heat preservation shutdown period): When the external surface temperature rises to 2°C and the icing signal is released, the inner and outer electric heating films simultaneously reduce their duty cycle to 20% for low-power heat preservation, and then shut down completely after a 5-minute delay. This embodiment achieves smooth control of the "preset temperature rise curve" through a concrete step-like inverse coordination of the duty cycle and the fan frequency, ensuring the absolute safety of the blade material.

[0039] After the high-temperature airflow releases heat at the blade tip, it forms a cooling airflow, which is then introduced into the air inlet of the fan through the return channel, establishing a closed circulating air passage to recover waste heat to the maximum extent.

[0040] In a preferred embodiment, the integrated gas-electric de-icing control system has a pre-set detailed internal and external heating control program. The program's activation conditions follow an "internal-first, external-second" logic, and both internal and external heating are limited by the global maximum threshold of the ambient temperature. The specific operating steps and conditions are as follows: Start-up threshold: When the external ambient temperature of the unit drops to 2℃ (this threshold can be modified by software according to the wind farm's temperature and humidity), the system automatically starts the internal fan and the internally laid electric heating film for anti-icing preheating.

[0041] Inner membrane constant temperature circulation: When the surface temperature of the inner heating film reaches 50℃, the heating of the inner heating film is stopped; when the temperature drops below 40℃, the heating of the inner heating film is restarted. During this constant temperature circulation of the inner membrane, the fan continues to run, continuously delivering hot airflow to the inner cavity.

[0042] On-demand intervention of the outer membrane: During the aforementioned internal thermal circulation process, wireless sensors deployed on the outside of the blades measure in real time. When a thin layer of ice is detected on the outer surface, the outer electrothermal film automatically starts melting the ice; it automatically stops after the absence of ice feedback. In addition, for the control of the outer electrothermal film, besides sensor feedback, a time control mode can also be used, that is, to force start and stop by using a preset heating time.

[0043] Global circuit breaker mechanism: When the ambient temperature of the unit rises to 5°C, it means that the external conditions are no longer suitable for icing. At this time, regardless of the working mode, the frequency converter power control module will trigger all heating (inner and outer membranes) to automatically stop, so as to achieve the best energy saving effect.

[0044] To ensure hardware safety, the integrated gas-electric de-icing control system is equipped with a hardware protection program. When the external surface temperature signal of the wind turbine blade body acquired by the temperature acquisition unit exceeds the preset temperature safety threshold, the variable frequency power control module will automatically execute the load reduction logic, reduce the power of the corresponding electric heating film or disconnect the circuit, thus protecting the structural integrity of the blade from the bottom layer.

[0045] This embodiment, through a stepped layout of built-in membrane for air preheating and external membrane for precise ice melting, not only significantly reduces the risk of lightning strikes at the blade tip, but also significantly reduces the cost of high-altitude construction and maintenance by reducing the area of ​​the outer surface membrane, achieving the best balance between de-icing efficiency and safety.

[0046] In this embodiment of the invention, when wind turbine blades encounter sudden extreme freezing rain and rapidly develop uneven, heavy icing, the integrated gas-electric de-icing control system triggers a combined inner and outer membrane heating mode upon receiving a signal from the temperature acquisition unit indicating a rapid temperature drop and heavy icing. The variable frequency power control module increases the output power of the inner electric heating film near the blade root via thyristor voltage regulation, simultaneously increasing the operating frequency of the internal wind turbine. This directs the high-temperature hot airflow to the lightning protection safety area at the blade tip (where there is no metal covering), achieving internal de-icing at the blade tip. Simultaneously, for the middle and rear sections of the blade, the control module limits and reduces the output power of the outer electric heating film. Since this area already has internal hot airflow, the outer electric heating film only needs to provide supplementary heat to melt and remove the surface ice layer. This dynamic control strategy of internal frequency enhancement and power increase, and external current limitation and power reduction, effectively removes icing from the entire blade and avoids the risk of lightning strikes at the blade tip, while preventing damage to the blade composite material due to thermal stress, thus achieving optimized energy consumption distribution.

Claims

1. A wind turbine blade electrothermal composite film internal and external synergistic electrothermal de-icing device, characterized in that, include: The wind turbine blade body has an internal cavity separated by a blade web. The wind turbine blade body includes a blade root, a blade tip, a blade trailing edge, a suction surface, a pressure surface, and a web. An electric heating film is laid inside and attached to and fixed to the inner wall of the internal cavity; An external electric heating film is laid and fixed to the outer surface of the wind turbine blade body; the internal electric heating film and the external electric heating film do not overlap in the spanwise direction of the wind turbine blade body, and the external electric heating film is far away from the blade tip, so as to retain a lightning protection safety zone of a preset length between the external electric heating film and the blade tip. A fan and a baffle plate are installed in the internal cavity. The fan has an air outlet and an air inlet. The baffle plate separates the internal cavity to define the air outlet channel and the return channel. The integrated gas-electric de-icing control system establishes a power supply and control connection with the inner electric heating film, the outer electric heating film, and the fan; the integrated gas-electric de-icing control system has a variable frequency power regulation control module, which is used to dynamically adjust the heating power of the inner and outer electric heating films, and adjust the operating frequency of the fan.

2. The wind turbine blade electrothermal composite film synergistic electrothermal de-icing device according to claim 1, characterized in that, The gas-electric integrated de-icing control system is equipped with three independently triggered heating operation modes: The inner membrane separate heating mode includes outputting power current to the inner electric heating film and starting the wind turbine, relying on the internal hot airflow to circulate and heat the inner cavity body, outer surface, lightning protection safety area and trailing edge of the wind turbine blade for heating and anti-icing. The outer membrane separate heating mode includes outputting a power supply current to the outer electrothermal film to melt the surface ice in the external area covered by the outer electrothermal film; The combined heating mode of inner and outer membranes includes simultaneously supplying power current to the inner electrothermal film and the outer electrothermal film, and starting the fan.

3. The wind turbine blade electrothermal composite film internal and external synergistic electrothermal de-icing device according to claim 2, characterized in that, The variable frequency power control module is connected to a temperature acquisition unit for receiving signals of external ambient temperature and blade surface temperature. When the external ambient temperature is within a preset range and there is no ice on the outer surface of the wind turbine blade, the variable frequency power control module triggers the inner membrane separate heating mode. When a wireless sensor on the outer surface detects thin ice, the variable frequency power control module triggers the outer membrane separate heating mode. When heavy icing occurs on a localized area of ​​the outer surface of the wind turbine blade, the variable frequency power control module triggers the combined inner and outer membrane heating mode. The gas-electric integrated de-icing control system has a preset internal and external heating control program. When the variable frequency power control module performs heating, it follows the sequence of first activating the internal heating film and then activating the external heating film. The internal and external heating control program specifically includes: When the external ambient temperature of the unit drops to the first preset ambient temperature threshold, the fan and the internally laid electric heating film are started. When the temperature of the inner heating film reaches the first preset inner film temperature threshold, the heating of the inner heating film is stopped; when the temperature of the inner heating film drops below the second preset inner film temperature threshold, the heating of the inner heating film is restarted, and the fan continues to run during this temperature cycle. In the inner membrane heating cycle, when the wireless sensor detects thin ice, the outer electric heating film automatically starts heating and stops when there is no thin ice, or the outer electric heating film controls the heating according to a preset time length. When the external ambient temperature of the unit rises to the second preset ambient temperature threshold, the frequency conversion power control module controls all the inner and outer electric heating films to automatically stop working.

4. The wind turbine blade electrothermal composite film internal and external synergistic electrothermal de-icing device according to claim 3, characterized in that, In the combined heating mode of the inner and outer membranes, the variable frequency power control module dynamically adjusts the operating frequency of the fan according to the preset temperature rise curve, and dynamically adjusts the output power of the inner and outer electric heating films by means of duty cycle or thyristor voltage regulation.

5. The wind turbine blade electrothermal composite film internal and external synergistic electrothermal de-icing device according to claim 4, characterized in that, When performing power regulation, the variable frequency power control module increases the output power of the inner electric heating film to improve the compensation heat delivered to the inside of the blade tip, while limiting or reducing the output power of the outer electric heating film to prevent local overheating damage to the wind turbine blade body.

6. The wind turbine blade electrothermal composite film internal and external synergistic electrothermal de-icing device according to claim 5, characterized in that, The inner heating film is laid in the internal cavity of the wind turbine blade body, which is biased towards the blade root and close to the air outlet of the wind turbine. The outer heating film is laid on the outer surface of the wind turbine blade body. The inner heating film and the outer heating film are distributed in a non-overlapping manner along the span of the wind turbine blade body.

7. The wind turbine blade electrothermal composite film synergistic electrothermal de-icing device according to claim 6, characterized in that, The internally laid electrothermal film is attached to the inner wall of the blade web or the internal cavity, and the insulating material of the wind turbine blade body is used as a shield to prevent the internally laid electrothermal film from being directly struck by lightning.

8. The wind turbine blade electrothermal composite film internal and external synergistic electrothermal de-icing device according to claim 7, characterized in that, The surface of the lightning protection safety zone is not covered with a composite membrane to avoid the hidden danger of direct lightning strikes concentrated on the membrane; the heat generated by the electric heating film laid inside preheats the air in the air outlet channel to form a high-temperature hot airflow, which is then directed to the blade tip corresponding to the lightning protection safety zone.

9. The wind turbine blade electrothermal composite film internal and external synergistic electrothermal de-icing device according to claim 8, characterized in that, One end of the return channel is connected to the inside of the blade tip, and the other end is connected to the air inlet of the fan. After the high-temperature hot airflow reaches the inside of the blade tip and releases heat, it forms a cooling airflow. The cooling airflow is introduced into the air inlet of the fan through the return channel to establish a closed circulating air passage.

10. The wind turbine blade electrothermal composite film internal and external synergistic electrothermal de-icing device according to claim 9, characterized in that, The gas-electric integrated de-icing control system is equipped with a hardware protection program. When the external surface temperature signal of the wind turbine blade body obtained by the temperature acquisition unit exceeds the preset temperature safety threshold, the frequency conversion power control module automatically reduces the power of the corresponding inner or outer electric heating film or performs a circuit disconnection operation.

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