Intelligent anti-icing composite insulator system and deicing method thereof
By integrating a nano-triboelectric generator and a heating resistance wire onto the insulator, and combining impedance analysis and power management, self-powered operation and refined heating control were achieved, solving the problem of insulator icing and improving operational reliability and safety.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-03-31
- Publication Date
- 2026-05-12
Smart Images
Figure CN122025316A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the technical field of high-voltage power transmission equipment, specifically relating to an intelligent anti-icing composite insulator system and its de-icing method. Background Technology
[0002] The statements herein provide only background information in relation to this invention and do not necessarily constitute prior art.
[0003] Insulators, as critical equipment in power transmission systems, are highly susceptible to icing in cold and humid environments. This not only significantly reduces their insulation performance but also greatly increases mechanical load, potentially leading to flashover accidents and posing a major threat to the safe and stable operation of the power grid. Traditional insulator anti-icing and de-icing methods mainly include coating anti-icing, mechanical de-icing, and thermal de-icing. In practice, coating anti-icing often involves applying hydrophobic / anti-icing materials (such as RTV, PRTV, and superhydrophobic coatings) to the insulator surface to reduce ice adhesion and make it easier for the ice to detach naturally. However, the coating is prone to aging and requires regular maintenance; its anti-icing effect is limited in extreme icy and snowy weather, and ice can still form. Mechanical de-icing often requires a large number of workers to work at heights, and this method is not only affected by weather conditions but is also time-consuming, labor-intensive, and poses considerable safety hazards.
[0004] Currently, thermal de-icing technology, as a common de-icing method, often relies on a continuous external energy supply during anti-icing and de-icing operations. However, the stability of this external energy supply (such as the power grid) affects de-icing efficiency under extreme environmental conditions. Systems relying on external energy supply require regular maintenance to ensure long-term stable operation. In harsh weather conditions or in remote areas far from the power grid or unattended locations, system maintenance becomes difficult, hindering stable operation. Furthermore, the operating costs of a continuous external energy supply are high. In addition, most existing thermal de-icing systems lack precise feedback control, often employing constant power heating, leading to overheating and energy waste, high operating costs, and difficulty in achieving intelligent operation and maintenance. Summary of the Invention
[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide an intelligent anti-icing composite insulator system and its de-icing method, which organically integrates energy harvesting, icing state sensing and precise control of heating power to form an intelligent anti-icing composite insulator system that can self-power and adaptively adjust heating power.
[0006] To achieve the above objectives, the present invention is implemented through the following technical solution: In a first aspect, the present invention provides an intelligent anti-icing composite insulator system, comprising: a power generation mechanism, an anti-icing mechanism, and a power management mechanism; the power generation mechanism includes an energy collection module, which is used to convert vibrations caused by the external environment into electrical energy; the anti-icing mechanism includes a heating mechanism and an icing monitoring feedback mechanism; the power management mechanism is connected to the power generation mechanism and the anti-icing mechanism respectively, and is used to receive and store electrical energy from the power generation mechanism, and control the power supply to the heating mechanism according to the feedback signal transmitted by the icing monitoring feedback mechanism; The icing monitoring and feedback mechanism includes an impedance analysis module, which is used to apply excitation to the composite insulator and collect response signals, and convert them into complex impedance parameters characterizing the icing state of the insulator through calculation. The power management mechanism includes a power adjustment module, which is communicatively connected to the impedance analysis module, and is used to adjust the heating power to at least one of a first power mode, a second power mode, and a third power mode based on the comparison result of the complex impedance parameters with a preset threshold range.
[0007] In at least one embodiment, the energy harvesting module is specifically a nano-triboelectric generator; the nano-triboelectric generator is connected to the composite insulator through a waterproof encapsulation shell.
[0008] In at least one embodiment, an arc-shaped buffer pad is provided between the waterproof encapsulation shell and the composite insulator.
[0009] In at least one embodiment, the impedance analysis module includes at least two voltage sensors, at least one current sensor, and a complex impedance calculation module; wherein, the voltage sensors are installed at both ends of the composite insulator core rod, the current sensors are arranged around the composite insulator core rod, and the complex impedance calculation module is connected to the voltage sensors and the current sensors to convert the synchronously acquired voltage and current signals into complex impedance parameters.
[0010] In at least one embodiment, the heating mechanism employs a heating resistance wire; the heating resistance wire is embedded in the skirt of the composite insulator in a circumferential manner to convert electrical energy into heat energy and distribute it evenly on the surface of the composite insulator.
[0011] In at least one embodiment, the power management mechanism further includes a rectifier and filter module, an energy storage battery module, and an inductive switch; the rectifier and filter module is connected to the output terminal of the power generation mechanism and is used to convert AC power into DC power; the energy storage battery module is connected to the rectifier and filter module and is used to store electrical energy; the inductive switch is connected between the energy storage battery module and the heating mechanism and is used to control the power supply on and off according to the feedback signal.
[0012] In at least one embodiment, the first power mode corresponds to low duty cycle heating for heat preservation and anti-icing conditions. The second power mode corresponds to medium duty cycle heating, which is used for medium icing conditions. The third power mode corresponds to high duty cycle heating and is used in severe icing conditions.
[0013] In at least one embodiment, the power management mechanism adopts a sealed box structure and is integrated into the insulator core rod; the box is made of weather-resistant material.
[0014] Secondly, the technical solution of the present invention also provides a method for de-icing an intelligent anti-icing composite insulator system, comprising: The mechanical energy generated by the composite insulator due to environmental vibration is collected by the power generation mechanism and converted into electrical energy for storage. The complex impedance parameters of the composite insulator are monitored in real time by the impedance analysis module, and the complex impedance parameters are compared with multiple preset threshold ranges to determine the degree of icing. Based on the degree of icing, the power management mechanism selects the appropriate power mode to supply power to the heating unit through the power regulation module inside, so as to perform de-icing or anti-icing operations that match the degree of icing.
[0015] In at least one embodiment, selecting an appropriate power mode to supply power to the heating mechanism based on the degree of icing is specifically included: When the complex impedance parameter falls into the first threshold range, it is determined that there is no icing or the risk of slight icing is extremely low. The induction switch is kept off and the system is in standby monitoring state. When the complex impedance parameter falls into the second threshold range, it is determined to be a state of mild icing or needing heat preservation and anti-icing, and the first power mode is activated to heat with a low duty cycle. When the complex impedance parameter falls into the third threshold range, it is determined to be a moderate icing state, and the second power mode is activated to heat with a medium duty cycle. When the complex impedance parameter exceeds the third threshold range, it is determined to be a severe icing state, and the third power mode is activated to heat with a high duty cycle.
[0016] The beneficial effects of the above-described technical solution of the present invention are as follows: 1) By real-time monitoring of the complex impedance parameters of the insulator and combining the intelligent adjustment function of the power adjustment module, the present invention can adjust the power generation and heating power according to the feedback of the complex impedance parameters of the insulator, thereby avoiding the problems of overheating and energy waste in the traditional heating process and effectively improving energy utilization efficiency.
[0017] 2) By integrating a nano-triboelectric generator and a heating module, this invention can effectively convert vibrations caused by the external environment into electrical energy and store it in a power management mechanism, reducing dependence on external energy and achieving self-sufficient energy supply. This energy collection and storage method can effectively reduce energy consumption in traditional de-icing methods and promote technological progress in energy collection, storage and self-regulation of power transmission systems.
[0018] 3) This invention, through its integrated intelligent anti-icing composite insulator system, can complete de-icing tasks without external power support. It can also ensure stable operation in remote or unattended areas through self-powered operation, avoiding frequent maintenance issues caused by power outages or equipment failures. This advantage improves equipment reliability and reduces operating and maintenance costs. Attached Figure Description
[0019] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.
[0020] Figure 1 This is a schematic diagram of an intelligent anti-icing composite insulator structure based on the integration of a nano-triboelectric generator and a heating module, provided in Embodiment 1 of the present invention. Figure 2 This is a schematic diagram of the internal structure of an intelligent anti-icing composite insulator based on the integration of a nano-triboelectric generator and a heating module, provided in Embodiment 1 of the present invention. Figure 3 This is a structural diagram of the energy harvesting module provided in Embodiment 1 of the present invention; Figure 4 This is a structural diagram of the impedance analysis module provided in Embodiment 1 of the present invention; Figure 5 This is a schematic diagram of the power management mechanism structure provided in Embodiment 1 of the present invention; Figure 6 This is a structural diagram of the buck-boost circuit provided in Embodiment 1 of the present invention; Figure 7 This is a block diagram of the control principle of the inductive switch provided in Embodiment 1 of the present invention; Figure 8 This is a block diagram illustrating the principle of power adjustment provided in Embodiment 1 of the present invention.
[0021] In the diagram: 1. Power management mechanism; 2. Voltage sensor; 3. Energy harvesting module; 4. Heating resistance wire; 5. Buck-boost module; 6. Rectifier and filter module; 7. Inductive switch; 8. Power regulation module; 9. PTFE friction layer; 10. PET support layer; 11. Spring steel electrode layer; 12. Control unit; 13. Arc-shaped buffer pad; 14. Waterproof encapsulation shell; 15. Composite insulator core rod; 16. Logic unit; 17. Impedance analysis module; 18. Energy storage battery module; 19. Connector; 20. Complex impedance calculation module; 21. Synchronous sampling ADC module; 22. Current sensor; 23. Voltage sensor receiver; 24. DDS excitation and gain amplifier; 25. Current sensor receiver. Detailed Implementation
[0022] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.
[0023] As described in the background section, the purpose of this invention is to overcome the shortcomings of the prior art and provide an intelligent anti-icing composite insulator system and its de-icing method, which organically integrates energy harvesting, icing state sensing and precise control of heating power to form an intelligent anti-icing composite insulator system that is self-powered and adaptively adjusts heating power.
[0024] Example 1 In a typical embodiment of the present invention, such as Figures 1 to 8 As shown, this embodiment discloses an intelligent anti-icing composite insulator system, including: a power generation mechanism, a de-icing mechanism, and a power management mechanism 1. The power generation mechanism provides electrical energy to the system and includes an energy harvesting module 3, which converts vibrations caused by the external environment into electrical energy. The de-icing mechanism includes an icing monitoring feedback mechanism and a heating mechanism, used to perform icing monitoring and heating de-icing. The power management mechanism 1 is connected to both the power generation mechanism and the de-icing mechanism, receiving and storing electrical energy from the power generation mechanism, and controlling the power supply to the heating mechanism based on feedback signals transmitted from the icing monitoring feedback mechanism, thus achieving energy management and intelligent control.
[0025] Specifically, such as Figure 1 and Figure 2As shown, the power generation mechanism includes an energy harvesting module 3, a waterproof enclosure 14, and an arc-shaped buffer pad 13. In this embodiment, the energy harvesting module 3 is a nano-triboelectric generator, which is disposed inside the waterproof enclosure 14 and fixed to the composite insulator core rod 15 by the waterproof enclosure 14. The arc-shaped buffer pad 13 is disposed between the waterproof enclosure 14 and the composite insulator core rod 15 to reduce the impact of external environmental vibrations on the nano-triboelectric generator.
[0026] As a further implementation method, such as Figure 3 As shown, the nano-triboelectric generator adopts a contact-separation mode, specifically including a PTFE friction layer 9 (i.e., a polytetrafluoroethylene friction layer), a PET support layer 10 (i.e., a polyethylene terephthalate support layer), and a spring steel electrode layer 11. The PTFE friction layer 9 and the PET support layer 10 are arranged parallel to each other, with the spring steel electrode layer 11 inserted in between. One end of the spring steel electrode layer 11 is connected to the PET support layer 10, and the other end is fixed to the inner wall of the waterproof encapsulation shell 14. The spring steel electrode layer 11 serves as both a support layer and an electrode. When the composite insulator is subjected to environmental vibrations that cause elastic deformation of the spring steel electrode layer 11, the PTFE friction layer 9 and the opposing friction layer undergo periodic contact-separation, generating alternating current based on triboelectric charging and electrostatic induction. Two output wires are led out from the spring steel electrode layer 11 of the nano-triboelectric generator, pass through the sealed interface of the waterproof encapsulation shell 14, and connect to the power management mechanism 1. As a further embodiment, the opposing friction layer can be a friction layer on another electrode layer, or an independent friction layer can be used.
[0027] The de-icing mechanism includes an icing monitoring and feedback mechanism and a heating mechanism. In this embodiment, the heating mechanism uses a heating resistance wire 4, which is made of a material with good thermal conductivity and high temperature resistance. The heating resistance wire 4 is embedded in the insulator skirt in a circular pattern using a silicone rubber insulator skirt manufacturing process, enabling the conversion of electrical energy into heat energy and ensuring that the heat is evenly transferred to the surface of the composite insulator. The electrode leads of the heating resistance wire 4 are connected to the output terminal of the power management mechanism 1, receiving the regulated electrical energy and converting it into heat energy.
[0028] like Figure 4As shown, the impedance analysis module 17 for real-time monitoring of the icing state of composite insulators includes a DDS excitation and gain amplifier 24, multiple voltage sensors 2, multiple current sensors 22, and a complex impedance calculation module 20. The voltage sensors 2 are uniformly mounted on the connectors 19 at both ends of the composite insulator core rod 15, and the current sensors 22 are uniformly surrounding the composite insulator core rod 15, monitoring the complex impedance changes caused by icing in the composite insulator in real time. The DDS excitation and gain amplifier 24 provides a specific frequency excitation to both ends of the composite insulator, providing voltage and current signals with insulator impedance characteristics to the voltage sensors 2 and current sensors 22. The voltage and current sensors 22 transmit the synchronously acquired voltage and current signals to the synchronous sampling ADC module 21 for analog-to-digital conversion via voltage sensor receiver 23 and current sensor receiver 25. The complex impedance calculation module 20 then calculates the complex impedance parameters that sensitively reflect the dielectric characteristic changes caused by icing on the insulator surface, and transmits them to the control unit 12 and logic unit 16 for analysis and judgment.
[0029] like Figure 2 and Figure 5 As shown, the power management mechanism 1 includes a rectifier and filter module 6, an energy storage battery module 18, an inductive switch 7, a buck-boost module 5, a control unit 12, and a logic unit 16. The rectifier and filter module 6 uses a full-bridge rectifier circuit and is connected to the output wires of the nano-triboelectric generator. It converts the AC power output from the nano-triboelectric generator into DC power, which is then filtered by an RC circuit and stored in the energy storage battery module 18. The inductive switch 7 is connected between the energy storage battery module 18 and the heating mechanism and is controlled by the control unit 12. It determines whether to connect the heating circuit based on the risk of icing. When there is no risk of icing, the inductive switch 7 is disconnected to avoid standby power consumption.
[0030] like Figure 6 As shown, the buck-boost module 5 includes a Buck-Boost circuit and a power regulation module 8. The input of the Buck-Boost circuit is connected to the energy storage battery module 18 via an inductive switch 7, and the output is connected to the heating resistance wire 4 of the heating mechanism. The power regulation module 8 is communicatively connected to the control unit 12. The control unit 12 receives complex impedance parameter signals fed back from the impedance analysis module 17. The logic unit 16 determines the degree of icing based on the complex impedance parameters and a preset threshold range. The control unit 12 sends an adjustment command to the power regulation module 8 based on the degree of icing. The power regulation module 8 adjusts the output voltage and power of the buck-boost module 5 by changing the duty cycle of the switching transistor of the inductive switch 7, thereby controlling the heating intensity of the heating resistance wire 4.
[0031] Specifically, the impedance analysis module 17 applies excitation to the composite insulator at fixed time intervals (e.g., once per minute), collects voltage and current signals, and calculates real-time complex impedance parameters through the complex impedance calculation module 20. Logic unit 16 will display the real-time complex impedance parameters. Values and impedance based on icing-free reference Compare multiple preset consecutive threshold intervals: like Falling into the first threshold interval, for example If the system is determined to have no icing or a very low risk of light icing, the control unit 12 keeps the sensor switch 7 off, and the system is in standby monitoring mode. like Falling into the second threshold range, for example If the condition is determined to be mild icing, the induction switch 7 is triggered to close, the control unit 12 starts the first power mode, the power adjustment module 8 adjusts the switching tube of the induction switch 7 to a low duty cycle (e.g., the duty cycle is adjusted to 20%), and the heating resistance wire 4 performs gentle heating to prevent icing. like Falling into the third threshold interval, for example If the ice accumulation is determined to be moderate, the control unit 12 starts the second power mode, and the power adjustment module 8 adjusts the switching tube of the induction switch 7 to a medium duty cycle (such as adjusting the duty cycle to 50%) to carry out stable ice melting. like Exceeding the third threshold interval, for example If the system is determined to be severely iced, the control unit 12 will activate the third power mode, and the power adjustment module 8 will adjust the switching transistor of the induction switch 7 to a high duty cycle (e.g., adjust the duty cycle to 80%) to quickly melt the ice.
[0032] As a further implementation, during the heating process, the impedance analysis module 17 continuously monitors the complex impedance parameters, and once the real-time complex impedance parameters are... When the value falls back to the first threshold range (e.g., less than Z0+5%), the control unit 12 determines that the icing has been eliminated, immediately controls the induction switch 7 to open, the heating resistance wire 4 to stop heating, and the system returns to standby mode.
[0033] This embodiment presets multiple threshold ranges based on the impedance characteristics of the insulator under icing conditions. The degree of icing of the composite insulator is determined by comparing the complex impedance parameters fed back by the impedance analysis module 17 with the preset threshold ranges. Based on the determination results, the heating power is adjusted to no heating, first power mode, second power mode, or third power mode, realizing intelligent control of heating power and thus achieving on-demand heating. This ensures the de-icing effect, saves stored electrical energy to the maximum extent, and extends the self-sustaining operation time.
[0034] As a further implementation, the power management mechanism 1 adopts a sealed box structure and is integrated into the composite insulator core rod 15. The box is made of weather-resistant materials (such as engineering plastics or a metal shell with a sealing ring), which has waterproof, dustproof and anti-aging properties, ensuring that the internal components can work stably for a long time in harsh outdoor environments. The intelligent anti-icing composite insulator system of this embodiment, by setting up a power generation mechanism, a de-icing mechanism, and a power management mechanism 1, can convert and store external environmental vibrations into electrical energy. Combined with feedback of complex impedance parameters, it can adjust the heating power in real time, thereby realizing intelligent anti-icing and de-icing of composite insulators, reducing dependence on external energy, and realizing intelligent control of heating power. This solves the problems of overheating, energy waste, poor energy supply stability, and maintenance difficulties in harsh environments in existing thermal de-icing technologies, and improves the operational safety and stability of transmission line insulators.
[0035] Example 2 In a typical embodiment of the present invention, this embodiment discloses a de-icing method for an intelligent anti-icing composite insulator system, comprising: The mechanical energy generated by the composite insulator due to environmental vibration is collected by the power generation mechanism and converted into electrical energy for storage. The complex impedance parameters of the composite insulator are monitored in real time by the impedance analysis module 17, and the complex impedance parameters are compared with multiple preset threshold ranges to determine the degree of icing. Based on the degree of icing, the power adjustment module 8 inside the power management mechanism 1 selects the appropriate power mode to supply power to the heating mechanism in order to perform de-icing or anti-icing operations that match the degree of icing.
[0036] As a further implementation, the appropriate power mode is selected to supply power to the heating mechanism according to the degree of icing, specifically including: When the complex impedance parameter falls into the first threshold range, it is determined that there is no icing or the risk of light icing is extremely low. The induction switch 7 is kept open and the system is in standby monitoring state. When the complex impedance parameter falls into the second threshold range, it is determined to be a state of mild icing or needing heat preservation and anti-icing, and the first power mode is activated to heat with a low duty cycle. When the complex impedance parameter falls into the third threshold range, it is determined to be a moderate icing state, and the second power mode is activated to heat with a medium duty cycle. When the complex impedance parameter exceeds the third threshold range, it is determined to be a severe icing state, and the third power mode is activated to heat with a high duty cycle.
[0037] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. An intelligent anti-icing composite insulator system, characterized in that, include: The system comprises a power generation mechanism, a de-icing mechanism, and a power management mechanism. The power generation mechanism includes an energy harvesting module for converting vibrations caused by the external environment into electrical energy. The de-icing mechanism includes a heating mechanism and an icing monitoring and feedback mechanism. The power management mechanism is connected to both the power generation mechanism and the de-icing mechanism, and is used to receive and store electrical energy from the power generation mechanism, and to control the power supply to the heating mechanism based on the feedback signal transmitted by the icing monitoring and feedback mechanism. The icing monitoring and feedback mechanism includes an impedance analysis module, which is used to apply excitation to the composite insulator and collect response signals, and convert them into complex impedance parameters characterizing the icing state of the insulator through calculation. The power management mechanism includes a power adjustment module, which is communicatively connected to the impedance analysis module, and is used to adjust the heating power to at least one of a first power mode, a second power mode, and a third power mode based on the comparison result of the complex impedance parameters with a preset threshold range.
2. The intelligent anti-icing composite insulator system as described in claim 1, characterized in that, The energy harvesting module is specifically a nano-triboelectric generator; the nano-triboelectric generator is connected to the composite insulator through a waterproof encapsulation shell.
3. The intelligent anti-icing composite insulator system as described in claim 2, characterized in that, An arc-shaped buffer pad is provided between the waterproof encapsulation shell and the composite insulator.
4. The intelligent anti-icing composite insulator system as described in claim 1, characterized in that, The impedance analysis module includes at least two voltage sensors, at least one current sensor, and a complex impedance calculation module. The voltage sensors are installed at both ends of the composite insulator core rod, the current sensors are arranged around the composite insulator core rod, and the complex impedance calculation module is connected to the voltage and current sensors to convert the synchronously acquired voltage and current signals into complex impedance parameters.
5. The intelligent anti-icing composite insulator system as described in claim 1, characterized in that, The heating mechanism uses a heating resistance wire; the heating resistance wire is embedded in the skirt of the composite insulator in a loop form to convert electrical energy into heat energy and distribute it evenly on the surface of the composite insulator.
6. The intelligent anti-icing composite insulator system as described in claim 1, characterized in that, The power management mechanism also includes a rectifier and filter module, an energy storage battery module, and an inductive switch; the rectifier and filter module is connected to the output of the power generation mechanism to convert AC power into DC power; the energy storage battery module is connected to the rectifier and filter module to store electrical energy; and the inductive switch is connected between the energy storage battery module and the heating mechanism to control the power supply on and off according to the feedback signal.
7. The intelligent anti-icing composite insulator system as described in claim 1, characterized in that, The first power mode corresponds to low duty cycle heating, used for heat preservation and anti-icing conditions. The second power mode corresponds to medium duty cycle heating, which is used for medium icing conditions. The third power mode corresponds to high duty cycle heating and is used in severe icing conditions.
8. The intelligent anti-icing composite insulator system as described in claim 1, characterized in that, The power management mechanism adopts a sealed box structure and is integrated into the insulator core rod; the box is made of weather-resistant material.
9. A method for de-icing an intelligent anti-icing composite insulator system, characterized in that, include: The mechanical energy generated by the composite insulator due to environmental vibration is collected by the power generation mechanism and converted into electrical energy for storage. The complex impedance parameters of the composite insulator are monitored in real time by the impedance analysis module, and the complex impedance parameters are compared with multiple preset threshold ranges to determine the degree of icing. Based on the degree of icing, the power management mechanism selects the appropriate power mode to supply power to the heating unit through the power regulation module inside, so as to perform de-icing or anti-icing operations that match the degree of icing.
10. The de-icing method for an intelligent anti-icing composite insulator system as described in claim 9, characterized in that, The appropriate power mode is selected to supply power to the heating mechanism based on the degree of icing, specifically including: When the complex impedance parameter falls into the first threshold range, it is determined that there is no icing or the risk of slight icing is extremely low. The induction switch is kept off and the system is in standby monitoring state. When the complex impedance parameter falls into the second threshold range, it is determined to be a state of mild icing or needing heat preservation and anti-icing, and the first power mode is activated to heat with a low duty cycle. When the complex impedance parameter falls into the third threshold range, it is determined to be a moderate icing state, and the second power mode is activated to heat with a medium duty cycle. When the complex impedance parameter exceeds the third threshold range, it is determined to be a severe icing state, and the third power mode is activated to heat with a high duty cycle.