A charge accumulation prevention wind power generation blade grounding device based on nonlinear resistance material and application method thereof

Abstract

The application discloses a wind power generation blade grounding device based on a nonlinear resistance material and an application method thereof. The grounding device comprises a conductive layer arranged in the interior of a blade body, a grounding down lead and a grounding component arranged at the root of the blade. A nonlinear conductive unit composed of a nonlinear resistance material is arranged in series in the grounding down lead. The unit is in a high resistance state under low voltage and in a low resistance state under high voltage. When space charges generated by the operation of the blade are in a normal level and the ground potential of the conductive layer is lower than a first threshold value, the nonlinear conductive unit maintains the high resistance state and limits the static discharge current to a microampere level. When the space charges continuously accumulate at the tip or edge of the blade, the ground potential of the conductive layer exceeds a second threshold value and the local field intensity approaches the upper limit of the insulation allowance, the resistivity of the nonlinear conductive unit significantly decreases with the enhancement of the electric field, thereby forming a controlled low-impedance discharge channel, rapidly releasing part of the charges and reducing the local field intensity.

Description

Technical Field

[0001] This invention belongs to the field of electrostatic control and safe operation technology of wind power generation equipment, specifically relating to a grounding device for wind power generation blades based on nonlinear resistive materials to prevent charge accumulation and its application method. Background Technology

[0002] Wind turbine blades are made of insulating composite materials such as fiberglass and carbon fiber. Especially at the leading or trailing edge of the blade, where the relative velocity with the air is highest and friction is most intense, it is the region where static charge accumulates most significantly. During long-term rotation, this region continuously generates microampere-level static charge, causing the local electric field strength at the tip and blade edge to continuously increase.

[0003] The aforementioned static electricity buildup typically exhibits the following characteristics:

[0004] (1) High voltage range, reaching thousands to tens of thousands of volts;

[0005] (2) The current is extremely low, and the duration is in the microampere range;

[0006] (3) It is mainly distributed along the edge of the leaf and gradually migrates to the tip, thus forming a higher field strength at the leaf tip.

[0007] Traditional technologies often use a single metal conductor as the grounding down conductor, continuously dissipating the static charge generated at the blade edges. Although the static current is extremely small, the continuous operation of the wind turbine throughout the year leads to considerable energy loss over a long period, resulting in a consistently low potential at the blade edge and failing to inhibit the continued migration and accumulation of static charge towards the blade tip. Existing technologies generally lack the ability to differentiate between different voltage levels; that is, they exhibit a fixed conductive state under both electrostatic (low voltage, low energy, continuous) and lightning strike (high voltage, high energy, transient) conditions. This leads to long-term energy loss during the electrostatic phase and may also cause damage to the material due to excessive thermal stress during lightning strikes. Therefore, a new grounding structure is needed that can automatically adjust its resistance according to the different voltage conditions generated by the blade's operating state, maintaining high resistance to reduce energy loss under electrostatic conditions and switching to low resistance for safe current discharge under lightning strike conditions.

[0008] In view of the above factors, a grounding device for wind turbine blades based on nonlinear resistive materials to prevent charge accumulation is provided and its application method is also provided. Under normal electrostatic conditions, it forms a high impedance limit for static charge, reducing energy loss caused by continuous discharge. When space charge accumulates excessively in a local area, causing the potential of the conductive layer to ground and the local field strength to approach the preset safety limit, it automatically switches to a low resistance state, quickly releases part of the charge, and reduces the local field strength. This improves power generation efficiency while suppressing the long-term adverse effects of space charge on the blade insulation and structure. Summary of the Invention

[0009] The purpose of this invention is to provide a grounding device for wind turbine blades that prevents charge accumulation based on nonlinear resistive materials and its application method, so as to solve the problems mentioned in the background art.

[0010] The objective of this invention is achieved through the following technical solution: a grounding device for wind turbine blades based on nonlinear resistive materials to prevent charge accumulation, comprising a blade body, a conductive layer disposed inside the blade body, a grounding lead wire connected to the conductive layer, and a grounding component disposed at the root of the blade body.

[0011] A nonlinear conductive unit made of voltage-sensitive nonlinear resistive material is connected in series in the grounding down conductor. The nonlinear conductive unit is connected in series in the grounding down conductor between the conductive layer and the grounding component.

[0012] The conductive layer, nonlinear conductive unit, and grounding component constitute an adaptive electrostatic control path from the blade body surface to the wind turbine's main grounding network. Under electrostatic conditions, the nonlinear conductive unit limits the discharge current from the conductive layer to the grounding component to the range of 10–50 μA. Under strong field conditions where the local field strength exceeds the second threshold or under impulse voltage test conditions, the nonlinear conductive unit switches from a high-resistance state to a low-resistance state within nanoseconds, exhibiting sufficient transient current carrying capacity and stability to ensure that the conductive layer potential can be pulled back to a safe range in a short time, thereby achieving limited discharge and rapid discharge under strong field conditions.

[0013] in:

[0014] 1) When the voltage across the nonlinear conductive unit is lower than the first threshold U1, it is in a high-resistance state, which is used to limit the electrostatic discharge current;

[0015] 2) When the voltage across the nonlinear conductive unit is higher than the second threshold U2 (U2 > U1), it is in a low-resistance state, which is used to provide a low-impedance discharge channel for excessively accumulated space charge.

[0016] Furthermore, the blade body is made of glass fiber composite material, and a conductive layer is pre-embedded or laid in the blade body, which is a metal mesh or conductive foil.

[0017] The conductive layer is connected to a grounding component located at the root of the blade body via a grounding lead. The grounding component is a grounding carbon brush, which is connected to the grounded hub and then connected to the main grounding grid of the wind turbine.

[0018] Furthermore, the main body of the nonlinear conductive unit includes a core made of a nonlinear resistive material and a glass fiber reinforced epoxy resin tubular shell covering the core.

[0019] The nonlinear conductive unit is installed inside a tubular shell made of glass fiber reinforced epoxy resin. The tubular shell has tapered transition sections at both ends to reduce electric field distortion and improve mechanical fatigue performance.

[0020] Furthermore, the grounding lead includes: a first section made of a metal conductor, and a second section made of the nonlinear resistive material and connected in series, the second section constituting the nonlinear conductive unit.

[0021] Furthermore, the second section is a modular structure, and each end of it is provided with a metal cylindrical transition joint; the inner cavity of the transition joint has an annular barb structure for crimping conductor strands, and the connection resistance is not greater than 100 μΩ; the transition joint is covered with an insulating and waterproof sheath and filled with cured insulating adhesive.

[0022] The two ends of the second section are respectively connected to metal cylindrical transition joints. The transition joints are integrally formed by conductive metal material and are in the shape of a hollow cylinder. The inner cavity is used to accommodate the conductor strands of the first section. The inner cavity wall is provided with several annular barbs arranged in the circumferential direction.

[0023] Further, the voltage-sensitive nonlinear resistor material is one or a combination of the following: (1) ZnO-based varistor ceramic material, whose commercial models include TDK SIOV series (such as S14K460, S20K550) and CR HV series (such as HV-20D471K).

[0024] A silicon carbide / silicone rubber-based nonlinear composite material comprising 50%–80% SiC conductive particles, 18%–45% silicone rubber matrix, and 0.5%–5% additives.

[0025] Furthermore, the volume resistivity of the nonlinear conductive unit under the low voltage condition corresponding to U1 is 10. 6 ~10 9 The volume resistivity under the high voltage conditions corresponding to U2 is 1 to 10 Ω·m.

[0026] The ratio L1 / L of the length L1 of the nonlinear conductive unit to the total length L of the grounding lead is 0.05 to 0.5, preferably 0.1 to 0.3.

[0027] A wind turbine generator set includes at least one wind turbine blade body, the blade body being equipped with the aforementioned anti-charge accumulation grounding device.

[0028] A method for suppressing charge accumulation on wind turbine blades and achieving controlled electrostatic discharge, applied to the grounding device, includes the following steps:

[0029] (1) Nonlinear conductive units are connected in series inside the blade body and placed in the grounding lead between the conductive layer and the grounding component;

[0030] (2) Based on the operating data of the wind turbine in the target wind farm, determine the maximum electrostatic voltage of the conductive layer relative to ground under the electrostatic condition of the blade. The minimum target overvoltage of the conductive layer relative to ground under extreme space charge accumulation or applied impulse voltage test conditions. Set the first threshold voltage to U1, so that... ≤ U1 ≤ 2· And when U = U1, the equivalent resistance of the nonlinear conductive unit is not less than 10. 7 Ω;

[0031] (3) Set the second threshold voltage to U2, so that 0.3· ≤ U2 ≤ 0.6· And when U = U2, the equivalent resistance of the nonlinear conductive unit is no greater than 10 Ω;

[0032] (4) During the operation of the unit, when the voltage across the nonlinear conductive unit is lower than U1, the nonlinear conductive unit is in a high-resistivity state, which limits the electrostatic discharge current; when the voltage across its terminals is higher than U2, the nonlinear conductive unit switches to a low-resistivity state, providing a low-resistivity release channel for locally excessively accumulated charge, and rapidly reducing the potential of the conductive layer and the local electric field strength.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] Under normal electrostatic conditions, this invention forms a high impedance limit for static charge, reducing energy loss caused by continuous discharge. When space charge accumulates excessively in a local area, causing the conductive layer's potential to ground and the local field strength to approach the preset safety limit, it automatically switches to a low-resistance state, rapidly releasing some of the charge and reducing the local field strength. This improves power generation efficiency while suppressing the long-term adverse effects of space charge on blade insulation and structure.

[0035] This invention improves power generation efficiency and economic benefits: by suppressing the static charge discharge current from the milliampere level to the microampere level, it fundamentally eliminates the energy loss caused by the continuous discharge of static charge in traditional metal down conductors. It is estimated that it can increase the net output power of a single wind turbine by about 0.1%-0.5%, which has significant economic benefits.

[0036] This invention achieves intelligent adjustment that adapts to different operating conditions: by utilizing the intrinsic properties of nonlinear materials, it realizes automatic identification and response to space charge conditions at different voltage levels ("low field, high resistance limits electrostatic discharge, high field, low resistance rapidly releases excessively accumulated charge"), without the need for external power supply or control circuit, and has high reliability and simple structure.

[0037] This invention extends system lifespan: the high-impedance state cuts off the continuous microcurrent path that leads to electrochemical corrosion of the grounding terminal, significantly reducing the corrosion rate of the grounding system and extending the maintenance cycle and service life of the blades and the grounding system.

[0038] This invention is easy to implement and modify: the core of the solution can be connected in series with the existing grounding down conductor as a modular component, without the need for large-scale modifications to the main structure of the blades. It is especially suitable for the technical transformation of the grounding system of existing wind farms and has low promotion costs. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the wind turbine blade structure of the present invention;

[0040] In the figure: 1-blade body, 2-conductive layer, 3-grounding lead, 31-nonlinear conductive unit, 4-grounding component.

[0041] Figure 2 Table of current-voltage characteristic curves of the nonlinear conductivity material of this invention

[0042] Figure 3 This is an overall schematic diagram of the modular structure of the nonlinear conductive unit of the present invention;

[0043] In the figure: 31-Nonlinear conductive unit, 311-Metal cylindrical transition joint, 312-Core, 313-Tube-shaped outer shell.

[0044] Figure 4 This is a cross-sectional view of the metal cylindrical transition joint of the present invention.

[0045] In the diagram: 311-metal cylindrical transition joint, 3111-inner cavity, 3112-annular barb structure. Detailed Implementation

[0046] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and 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.

[0047] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0048] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0049] like Figure 1-4 As shown, a grounding device for wind turbine blades based on nonlinear resistive materials to prevent charge accumulation is characterized by comprising a blade body 1, a conductive layer disposed inside the blade body 1, a grounding lead wire connected to the conductive layer, and a grounding component disposed at the root of the blade body 1.

[0050] A nonlinear conductive path 31, made of voltage-sensitive nonlinear resistive material, is connected in series in the grounding down conductor. The nonlinear conductive path 31 is connected in series in the grounding down conductor 3 between the conductive layer 2 and the grounding component 4.

[0051] The conductive layer, nonlinear conductive unit, and grounding component constitute an adaptive electrostatic control path from the surface of the blade body 1 to the main grounding network of the wind turbine. Under electrostatic conditions, the nonlinear conductive unit limits the discharge current from the conductive layer 2 to the grounding component 4 to the range of 10 to 50 μA. Under strong field conditions where the local field strength exceeds the second threshold or under impulse voltage test conditions, the nonlinear conductive unit switches from a high-resistance state to a low-resistance state within nanoseconds, exhibiting sufficient transient current carrying capacity and stability to ensure that the potential of the conductive layer can be pulled back to a safe range in a short time, thereby achieving limited discharge and rapid discharge under strong field conditions.

[0052] in:

[0053] 1) When the voltage across the nonlinear conductive unit is lower than the first threshold U1, it is in a high-resistance state, which is used to limit the electrostatic discharge current;

[0054] 2) When the voltage across the nonlinear conductive unit is higher than the second threshold U2 (U2 > U1), it is in a low-resistance state, which is used to provide a low-impedance discharge channel for excessively accumulated space charge.

[0055] The blade body 1 is made of glass fiber composite material, and a conductive layer is pre-embedded or laid in the blade body 1. The conductive layer is a metal mesh or conductive foil.

[0056] The conductive layer is connected to the grounding component located at the root of the blade body 1 via a grounding lead wire. The grounding component is a grounding carbon brush, which is connected to the grounded hub and connected to the main grounding grid of the wind turbine.

[0057] The main body of the nonlinear conductive unit includes a core made of nonlinear resistive material and a glass fiber reinforced epoxy resin tubular shell covering the core.

[0058] The nonlinear conductive unit is installed inside a tubular shell made of glass fiber reinforced epoxy resin. The tubular shell has tapered transition sections at both ends to reduce electric field distortion and improve mechanical fatigue performance.

[0059] The grounding lead includes: a first section made of a metal conductor, and a second section made of the nonlinear resistive material and connected in series, the second section constituting the nonlinear conductive unit.

[0060] The second section is a modular structure, and each end of it is provided with a metal cylindrical transition joint; the inner cavity of the transition joint has an annular barb structure for crimping conductor strands, with a connection resistance of no more than 100 μΩ; the transition joint is covered with an insulating and waterproof sheath and filled with cured insulating adhesive.

[0061] The two ends of the second section are respectively connected to metal cylindrical transition joints. The transition joints are integrally formed by conductive metal material and are in the shape of a hollow cylinder. The inner cavity is used to accommodate the conductor strands of the first section. The inner cavity wall is provided with several annular barbs arranged in the circumferential direction.

[0062] The voltage-sensitive nonlinear resistor material is one of the following or a combination thereof: (1) ZnO-based varistor ceramic material, whose commercial models include TDK SIOV series (such as S14K460, S20K550) and CR HV series (such as HV-20D471K).

[0063] A silicon carbide / silicone rubber-based nonlinear composite material comprising 50%–80% SiC conductive particles, 18%–45% silicone rubber matrix, and 0.5%–5% additives.

[0064] The volume resistivity of the nonlinear conductive unit under the low voltage condition corresponding to U1 is 10. 6 ~10 9The volume resistivity under the high voltage conditions corresponding to U2 is 1 to 10 Ω·m.

[0065] The ratio L1 / L of the length L1 of the nonlinear conductive unit to the total length L of the grounding lead is 0.05 to 0.5, preferably 0.1 to 0.3. Specific Implementation Example 1:

[0067] like Figure 1 As shown, the wind turbine blade body 1 is typically made of fiberglass composite material. A conductive layer 2, which can be a metal mesh or conductive foil, is pre-embedded or laid later within it. The conductive layer 2 is connected to a grounding component 4 (usually a grounding carbon brush) located at the blade root via a grounding down conductor 3. The carbon brush is connected to the grounded hub and ultimately to the wind turbine's main grounding grid. The grounding down conductor located inside the leading or trailing edge of the blade is improved by arranging nonlinear conductive units in series in this area. Since the blade edge is the region with the strongest electrostatic friction, deploying nonlinear materials in this area can effectively block the migration of static charge along the edge towards the blade tip and significantly reduce electrostatic discharge energy consumption. The modular nonlinear units are arranged within the internal structural cavity of the blade, not on the outer surface, and do not alter the blade's aerodynamic shape.

[0068] As shown in Figure 3, the nonlinear conductive unit 31 in this embodiment serves as the second segment of the grounding lead and is constructed as a modular structure that can be independently replaced. The main body of the nonlinear conductive unit 31 includes a core 312 made of nonlinear resistive material and a glass fiber reinforced epoxy resin tubular outer shell 313 covering the core, providing necessary mechanical protection and electric field homogenization functions. Figure 3 , Figure 4 As shown, the two ends of the modular unit are respectively connected to metal transition connectors 311. The metal transition connector 311 is integrally machined from conductive metal material and is in the shape of a hollow cylinder. It has an inner cavity 314 to accommodate the stranded conductor wire of the first section. In order to improve the connection reliability and reduce the contact resistance, the inner cavity 314 has a number of annular barbs arranged in the circumferential direction on its wall surface.

[0069] The core material of the nonlinear conductive unit is a silicon carbide / silicone rubber composite material optimized for wind power environments. Its specific mass composition and preparation process are as follows: Composition: Silicon carbide (SiC) conductive particles: 65 parts. A bimodal particle size distribution is used to optimize the conductive network: 60% (39 parts) of coarse particles (50-70 μm) are used to construct the main conductive pathways; 40% (26 parts) of fine particles (1-5 μm) are used to fill voids, reduce the threshold voltage, and improve material density. Methyl vinyl silicone rubber raw rubber: 32 parts. Provides a flexible matrix, ensuring the material can withstand blade bending and vibration. Additives: 3 parts. Includes a crosslinking agent (dicumyl peroxide, 1.5 parts) to form a three-dimensional network, a structure control agent (hydroxyl silicone oil, 1 part) to improve filler dispersion, and a heat-resistant agent (ferric oxide, 0.5 parts) to enhance long-term thermal stability. Preparation process: The above components are mixed evenly on a two-roll mill at room temperature, then placed in a mold and molded and vulcanized at 170°C and 10MPa for 15 minutes to form a core with stable nonlinear current-voltage characteristics.

[0070] The nonlinear conductive unit is constructed as a robust and sealed module, specifically comprising: a core: a silicon carbide / silicone rubber composite column prepared by the aforementioned process; a tubular outer shell: made of glass fiber reinforced epoxy resin through a pultrusion process, providing excellent mechanical protection; tapered stress cones at both ends of the outer shell to uniformly distribute the electric field and prevent corona discharge; a metal transition joint: machined from T2 copper, with an annular barbed structure machined into its inner cavity; during installation, the copper stranded wire of the grounding lead is inserted and crimped using a special hydraulic crimping tool; the annular barbs embed into the stranded wire, ensuring a contact resistance of less than 80 μΩ and withstanding more than 1000 bending fatigue tests; and a sealing system: flexible silicone gel is injected between the core and the outer shell for cushioning and internal moisture protection. After crimping, the entire transition joint area is injection molded with a polyolefin heat-shrinkable sheath to form a final airtight and watertight seal.

[0071] The ratio L1 / L of the length L1 of the nonlinear conductive unit 31 to the total length L of the grounding lead 3 is preferably 0.1 to 0.3. This range is the optimal range derived from electromagnetic transient simulation and experiments: a ratio that is too small (<0.1) may result in a high residual voltage across the nonlinear unit under conditions of rapid release of local space charge or impulse voltage test; a ratio that is too large (>0.3) will increase manufacturing costs and may introduce unnecessary distributed capacitance under electrostatic conditions, affecting the current limiting effect. In this embodiment, L1 / L = 0.2 is taken. To fully illustrate the beneficial effects of the present invention, the following embodiments are provided and compared with conventional solutions.

[0072] The grounding device of the present invention is prepared according to the above, wherein the length ratio of the nonlinear conductive unit is L1 / L=0.2.

[0073] Comparative Example 1: The traditional method is adopted, that is, the entire grounding down conductor is a tin-plated copper cable with the same cross-sectional area.

[0074] Comparative Example 2: A compromise solution is adopted, in which a fixed linear resistor of power type 1MΩ is connected in series in the copper cable.

[0075] Electrostatic discharge current 3.5 ± 0.5 mA 95 ± 10 μA 38 ± 5 μA Apply DC 15 kV Inrush current voltage drop 0.75 kV Breakdown damage 10.5 kV 8 / 20μs, 50kA Response time not applicable not applicable < 200 ns A leap from 15kV to 50kV Annual loss estimate ~ 400 kWh ~ 15 kWh < 3 kWh Calculations are based on the measured electrostatic discharge current value and the operating time. Salt spray test The connection points were severely corroded. Resistive film layer degradation It functions perfectly and its appearance remains unchanged. 1000h Current capacity excellent Difference Excellent (performance degradation <5% after 20 impacts) 8 / 20μs, 20kA, 2 times / 60s interval

[0076] Test conclusions: (1) Significant energy saving effect: Compared with traditional metal grounding down conductors, this invention can effectively suppress electrostatic discharge at the blade edge under electrostatic conditions, reducing long-term electrostatic energy loss by more than 90%; at the same time, it avoids the accumulation of static electricity towards the blade tip, fundamentally reducing the tip potential. When lightning transient high voltage occurs, the nonlinear unit automatically enters a low-resistance state, providing a low-resistance discharge path for the lightning current located inside the blade, without relying on the external conductive mesh or high-resistance coating structure.

[0077] (2) Reliable strong field release capability: Under simulated extreme space charge release or impulse voltage conditions, the nonlinear unit of this invention can provide an effective low impedance path. Its residual voltage (10.5kV) is much lower than the tolerance level of typical blade insulation (>100kV). Moreover, after multiple impulse tests, the current carrying capacity and performance remain stable, far exceeding Comparative Example 2.

[0078] (3) Adaptive intelligence: The nanosecond-level fast response and automatic switching capability of high / low resistance state unique to this invention are completely absent in comparatives 1 and 2, which solves the fundamental contradiction that traditional technology cannot distinguish between static electricity and lightning. Specific Implementation Example 2:

[0080] A wind turbine generator set, characterized in that: the wind turbine generator includes at least one wind turbine blade body, the blade body being equipped with the aforementioned anti-charge accumulation grounding device. Specific Implementation Example 3:

[0082] A method for suppressing charge accumulation on wind turbine blades and achieving controlled electrostatic discharge, applied to the grounding device, is characterized by comprising the following steps:

[0083] Inside the blade body, a nonlinear conductive unit is connected in series in the grounding lead between the conductive layer and the grounding component;

[0084] Based on the operating data of the wind turbine at the target wind farm, the maximum electrostatic voltage of the conductive layer relative to ground under electrostatic conditions of the blades was determined. The minimum target overvoltage of the conductive layer relative to ground under extreme space charge accumulation or applied impulse voltage test conditions. Set the first threshold voltage to U1, so that... ≤ U1 ≤ 2· And when U = U1, the equivalent resistance of the nonlinear conductive unit is not less than 10. 7 Ω;

[0085] Set the second threshold voltage to U2, so that 0.3... ≤ U2 ≤ 0.6· And when U = U2, the equivalent resistance of the nonlinear conductive unit is no greater than 10 Ω;

[0086] During unit operation, when the voltage across the nonlinear conductive unit is lower than U1, the nonlinear conductive unit is in a high-resistivity state, limiting the electrostatic discharge current; when the voltage across it is higher than U2, the nonlinear conductive unit switches to a low-resistivity state, providing a low-impedance release channel for locally excessive charge accumulation, and rapidly reducing the potential of the conductive layer and the local electric field strength.

[0087] The core step in the above embodiments lies in the targeted design and configuration of the nonlinear conductive unit:

[0088] 1. Parameter Acquisition

[0089] The maximum electrostatic voltage of the target wind farm blades under typical operating conditions is obtained through the site monitoring system. The voltage is 12 kV, and the minimum overvoltage during a lightning strike is determined according to IEC standards. It is 120 kV.

[0090] 2. Threshold setting

[0091] ① Set the first threshold voltage U1 = 15 kV (satisfying) ≤ U1 ≤ 2· At this voltage, the unit's equivalent resistance is > 10. 8 Ω.

[0092] ② Set the second threshold voltage U2 = 50 kV (satisfying 0.3 kV). ≤ U2 ≤ 0.6·ULmin), at this voltage, the unit's equivalent resistance is < 5 Ω.

[0093] 3. Operation and Results

[0094] During unit operation, when the static voltage is below 15kV, the unit is in a high-resistivity state, and the discharge current is limited to about 40 μA. When local space charge accumulates on the blades, causing the potential of the conductive layer relative to ground to exceed 50 kV, the nonlinear unit switches from a high-resistivity state to a low-resistivity state within a timescale of approximately 200 ns, rapidly releasing some charge and reducing the local field strength and potential to a safe range. Long-term operational data comparison confirms that units using this method significantly reduce electrostatic discharge energy consumption and increase net power generation by approximately 0.3%. This invention mainly targets the electrostatic accumulation condition generated during blade rotation, using internally arranged nonlinear units for adaptive voltage regulation. This technical approach differs from existing technologies that utilize external conductive meshes and high-resistivity material coatings to equalize the electric field distribution before lightning strikes, and there are fundamental differences in applicable operating conditions, working mechanisms, and structural positions.

[0095] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0096] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A grounding device for wind turbine blades based on nonlinear resistive materials to prevent charge accumulation, characterized in that: It includes a blade body (1), a conductive layer disposed inside the blade body (1), a grounding lead connected to the conductive layer, and a grounding component disposed at the root of the blade body (1). A nonlinear conductive path (31) made of voltage-sensitive nonlinear resistive material is connected in series in the grounding down conductor. The nonlinear conductive path (31) is connected in series in the grounding down conductor (3) between the conductive layer (2) and the grounding component (4). The conductive layer, nonlinear conductive unit, and grounding component constitute an adaptive electrostatic control path from the surface of the blade body (1) to the main grounding network of the wind turbine. Under electrostatic conditions, the nonlinear conductive unit limits the discharge current from the conductive layer (2) to the grounding component (4) to the range of 10 to 50 μA. Under strong field conditions where the local field strength exceeds the second threshold or under impulse voltage test conditions, the nonlinear conductive unit switches from a high resistance state to a low resistance state within a nanosecond time, exhibiting sufficient transient current carrying capacity and stability to ensure that the potential of the conductive layer can be pulled back to a safe range in a short time, thereby achieving limited discharge and rapid discharge under strong field conditions. in: 1) When the voltage across the nonlinear conductive unit is lower than the first threshold U1, it is in a high-resistance state, which is used to limit the electrostatic discharge current; 2) When the voltage across the nonlinear conductive unit is higher than the second threshold U2 (U2> U1), it is in a low-resistance state, which is used to provide a low-impedance discharge channel for excessively accumulated space charge.

2. The anti-charge accumulation wind turbine blade grounding device based on nonlinear resistive material according to claim 1, characterized in that: The blade body (1) is made of glass fiber composite material, and a conductive layer is pre-embedded or laid in the blade body (1) later. The conductive layer is a metal mesh or conductive foil. The conductive layer is connected to the grounding component located at the root of the blade body (1) via a grounding lead wire. The grounding component is a grounding carbon brush, which is connected to the grounded hub and connected to the main grounding grid of the wind turbine.

3. The anti-charge accumulation wind turbine blade grounding device based on nonlinear resistive material according to claim 2, characterized in that: The main body of the nonlinear conductive unit includes a core made of nonlinear resistive material and a glass fiber reinforced epoxy resin tubular shell covering the core. The nonlinear conductive unit is installed inside a tubular shell made of glass fiber reinforced epoxy resin. The tubular shell has tapered transition sections at both ends to reduce electric field distortion and improve mechanical fatigue performance.

4. The anti-charge accumulation wind turbine blade grounding device based on nonlinear resistive material according to claim 3, characterized in that: The grounding lead includes: a first section made of a metal conductor, and a second section made of the nonlinear resistive material and connected in series, the second section constituting the nonlinear conductive unit.

5. The anti-charge accumulation wind turbine blade grounding device based on nonlinear resistive material according to claim 4, characterized in that: The second section is a modular structure, and each end of it is provided with a metal cylindrical transition joint; the inner cavity of the transition joint has an annular barb structure for crimping conductor strands, with a connection resistance of no more than 100 μΩ; the transition joint is covered with an insulating and waterproof sheath and filled with cured insulating adhesive. The two ends of the second section are respectively connected to metal cylindrical transition joints. The transition joints are integrally formed by conductive metal material and are in the shape of a hollow cylinder. The inner cavity is used to accommodate the conductor strands of the first section. The inner cavity wall is provided with several annular barbs arranged in the circumferential direction.

6. The anti-charge accumulation wind turbine blade grounding device based on nonlinear resistive material according to claim 5, characterized in that: The voltage-sensitive nonlinear resistor material is one of the following or a combination thereof: (1) ZnO-based varistor ceramic material, whose commercial models include TDK SIOV series and CR HV series; A silicon carbide / silicone rubber-based nonlinear composite material comprising 50%–80% SiC conductive particles, 18%–45% silicone rubber matrix, and 0.5%–5% additives.

7. The anti-charge accumulation wind turbine blade grounding device based on nonlinear resistive material according to claim 6, characterized in that: The volume resistivity of the nonlinear conductive unit under the low voltage condition corresponding to U1 is 10. 6 ~10 9 The volume resistivity under the high voltage conditions corresponding to U2 is 1 to 10 Ω·m. The ratio L1 / L of the length L1 of the nonlinear conductive unit to the total length L of the grounding lead is 0.05 to 0.5, preferably 0.1 to 0.

3.

8. A wind turbine generator set, characterized in that: The wind turbine includes at least one wind turbine blade body, the blade body being equipped with an anti-charge accumulation grounding device as described in any one of claims 1 to 8.

9. A method for suppressing charge accumulation on wind turbine blades and achieving controlled electrostatic discharge, applied to the grounding device as described in any one of claims 1 to 8, characterized in that, Includes the following steps: (1) Nonlinear conductive units are connected in series inside the blade body and placed in the grounding lead between the conductive layer and the grounding component; (2) Based on the operating data of the wind turbine in the target wind farm, determine the maximum electrostatic voltage of the conductive layer relative to ground under the electrostatic condition of the blade. The minimum target overvoltage of the conductive layer relative to ground under extreme space charge accumulation or applied impulse voltage test conditions. Set the first threshold voltage to U1, so that... ≤ U1 ≤ 2· And when U = U1, the equivalent resistance of the nonlinear conductive unit is not less than 10. 7 Ω; (3) Set the second threshold voltage to U2, so that 0.3· ≤ U2≤ 0.6· And when U = U2, the equivalent resistance of the nonlinear conductive unit is no greater than 10 Ω; (4) During the operation of the unit, when the voltage across the nonlinear conductive unit is lower than U1, the nonlinear conductive unit is in a high-resistivity state, which limits the electrostatic discharge current; when the voltage across its terminals is higher than U2, the nonlinear conductive unit switches to a low-resistivity state, providing a low-resistivity release channel for locally excessively accumulated charge, and rapidly reducing the potential of the conductive layer and the local electric field strength.

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