Lightning overvoltage protection method for wind power generation system

Abstract

The invention relates to a lightning overvoltage protection method for a wind power generation system, which relates to the technical field of wind power generation and comprises the following steps: establishing a lightning direct stroke equivalent circuit model of the wind power generation system; on the basis of the equivalent circuit model, back-striking overvoltage and induced overvoltage of the wind power generation system in the lightning stroke state are simulated, and characteristic parameters of the back-striking overvoltage and the induced overvoltage are obtained; comparing the characteristic parameters of the counterattack overvoltage and the induced overvoltage with the overvoltage tolerance strength of the wind power generation system; and adjusting an overvoltage protection system of the wind power generation system according to a comparison result. Therefore, the overvoltage amplitude sensed to the port of the control module of the wind power generation system can be accurately calculated; and a basis is provided for lightning overvoltage protection design of the control module.

Description

Technical Field

[0001] The present disclosure relates to the technical field of wind power generation, and in particular to a method for protecting a wind power generation system from lightning overvoltage. Background Art

[0002] Wind power, known for its green and sustainable nature, is becoming a key alternative to fossil fuels. However, wind turbine blades often face external challenges during operation, such as lightning strikes. Lightning strikes are a frequent cause of wind turbine failures. According to incomplete statistics, lightning strikes account for over 40% of wind farm outages.

[0003] The control system of a wind turbine is installed inside the turbine. When the turbine itself is struck by lightning, the back-strike overvoltage generated in the nacelle and the induced overvoltage generated at the control system ports can easily exceed the insulation withstand capability of the control system, causing damage to the control system. Currently, the lightning failure mechanism of wind turbine blade control systems is not fully understood, and accurate calculation and simulation of the back-strike and induced overvoltages in wind turbine blade control systems is still not possible.

[0004] Therefore, how to accurately calculate and simulate the back-strike and induced lightning overvoltage of the wind turbine blade control system has become a technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0005] In order to solve the above technical problems, the present disclosure provides a wind power generation system lightning overvoltage protection method for accurately calculating and simulating the back-strike and induced lightning overvoltage of the wind turbine blade control system.

[0006] The present disclosure provides a method for protecting a wind power generation system from lightning overvoltage, comprising:

[0007] Establish a lightning direct strike equivalent circuit model for wind power generation systems;

[0008] Based on the equivalent circuit model, simulating the back-strike overvoltage and induced overvoltage of the wind power generation system under a lightning strike state, and obtaining characteristic parameters of the back-strike overvoltage and induced overvoltage;

[0009] comparing the characteristic parameters of the back-strike overvoltage and the induced overvoltage with the overvoltage withstand strength of the wind power generation system;

[0010] An overvoltage protection system for the wind power generation system is designed according to the comparison result.

[0011] Optionally, the wind power generation system includes wind turbine blades, a nacelle and a tower, and the wind turbine blades are connected to the tower through the nacelle;

[0012] The establishing of a lightning direct strike equivalent circuit model for a wind power generation system includes establishing equivalent circuit models of the wind turbine blades, the nacelle, and the tower, respectively.

[0013] Optionally, simulating the back-strike overvoltage and induced overvoltage of the wind power generation system in a lightning strike state based on the equivalent circuit model, and obtaining characteristic parameters of the back-strike overvoltage and induced overvoltage includes:

[0014] A first preset waveform current is used to simulate a lightning current, and the counter-strike overvoltage and induced overvoltage of the equivalent circuit model under the first preset waveform are simulated; the equivalent waveform of the lightning current is as follows:

[0015]

[0016] Wherein, I0 is the lightning current peak value; α is the lightning current wave front time constant; β is the lightning current wave tail time constant; η is the waveform peak correction factor.

[0017] Optionally, the fan blade includes a grounding down conductor;

[0018] Establishing the equivalent circuit model of the fan blade includes:

[0019] A first equivalent circuit model of the ground down conductor is established, wherein the first equivalent circuit model includes multiple sections of first π-type equivalent circuits connected in series, and the length of each section of the first π-type equivalent circuit is less than or equal to 1 m.

[0020] Optionally, the equivalent resistance R of each section of the first π-type equivalent circuit is calculated. b 、Inductor L b , capacitor C b , the calculation formula is as follows:

[0021]

[0022]

[0023] Among them, μ b , σ b are the magnetic permeability and electrical conductivity of the grounding down conductor of the fan blade, respectively, l b is the length of the segmented blade of the fan blade, r b is the grounding down conductor radius of the fan blade.

[0024] Optionally, the nacelle includes a bearing and a carbon brush, and the equivalent circuit model of the nacelle includes the bearing and the brush connected in parallel, wherein the bearing capacitance C h Less than or equal to 0.1μF, the brush resistance R h Less than or equal to 0.1Ω.

[0025] Optionally, the tower comprises multiple segmented tower bodies, and the height h of each segmented tower body is t Less than or equal to 5m;

[0026] Establishing the equivalent circuit model of the tower includes establishing an equivalent circuit model of each segmented tower body.

[0027] Optionally, establishing an equivalent circuit model of each segmented tower body includes:

[0028] Calculate the equivalent resistance R of each segmented tower body t , equivalent inductance L t , Tower body to ground capacitance C t , the calculation formula is as follows:

[0029]

[0030] Where q = 2πf u μ t σ t w 2 , μ t , σ t are the magnetic permeability and electrical conductivity of the segmented tower body respectively; w is the average thickness of the segmented tower body; R t0 is the DC resistance of the segmented tower body; μ0 is the vacuum magnetic permeability; P is the ratio of the inner and outer radii of the segmented tower body; ε0 is the vacuum dielectric constant; and H is the total height of the tower.

[0031] Optionally, the wind power generation system further comprises a control module, the control module is located in the nacelle, the control module is configured to control the rotation of the wind turbine blades, and the control module comprises a control cable;

[0032] The establishment of a lightning direct stroke equivalent circuit model for a wind power generation system includes:

[0033] The mutual inductance M and mutual capacitance C between the control cable and the grounding down conductor are calculated as follows:

[0034]

[0035] Wherein, l is the distance between the control cable and the adjacent grounding down conductor, D is the distance between the center points of two adjacent control cables, r is the radius of the control cable, μ0 is the vacuum permeability; ε is the dielectric constant.

[0036] Optionally, simulating the back-strike overvoltage and induced overvoltage of the wind power generation system in a lightning strike state based on the equivalent circuit model, and obtaining characteristic parameters of the back-strike overvoltage and induced overvoltage includes:

[0037] Apply the simulated lightning current to the wind turbine blades, calculate the back-strike overvoltage of the wind power generation system based on the equivalent circuit model of the wind turbine blades, the nacelle, and the tower, and obtain the amplitude and waveform characteristics of the back-strike overvoltage; calculate the induced overvoltage at the control module port based on the inductance and capacitance coupling between the control cable and the grounding down conductor, and obtain the amplitude and waveform characteristics of the induced overvoltage.

[0038] The technical solution provided by the disclosed embodiments offers the following advantages over existing technologies: Based on transmission line theory, the disclosed embodiments establish a lightning direct strike equivalent circuit model for the grounding down conductor of a wind turbine blade in a wind turbine system; calculate the back-strike overvoltage of the control module based on the wind turbine system structure; and calculate the induced overvoltage of the control cable using an inductor-capacitor coupling method. The calculation method provided by the disclosed embodiments accurately calculates the magnitude of the overvoltage induced to the de-icing system port, providing a basis for the design of a lightning overvoltage protection system for the wind turbine blade control module. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present disclosure and, together with the description, serve to explain the principles of the present disclosure.

[0040] In order to more clearly illustrate the embodiments of the present disclosure or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0041] Figure 1 FIG2 is a flow chart of a method for protecting a wind power generation system from lightning overvoltage provided by an embodiment of the present disclosure;

[0042] Figure 2 The figure shows an equivalent circuit model diagram of a direct lightning strike of a wind power generation system provided by an embodiment of the present disclosure;

[0043] Figure 3 FIG2 is a schematic diagram of a nacelle structure of a wind power generation system provided by an embodiment of the present disclosure;

[0044] Figure 4 Shown Figure 3 Equivalent circuit diagram of

[0045] Figure 5 FIG2 is a schematic diagram of a tower structure of a wind power generation system provided by an embodiment of the present disclosure;

[0046] Figure 6 Shown Figure 5 Equivalent circuit diagram of

[0047] Figure 7 FIG2 is a schematic diagram of the structure of a wind turbine blade of a wind power generation system provided by an embodiment of the present disclosure;

[0048] Figure 8 Shown Figure 7 Equivalent circuit diagram of the neutral ground down conductor;

[0049] Figure 9 Shown is an equivalent circuit diagram of inductive coupling between a control cable and a grounding down conductor provided by an embodiment of the present disclosure. DETAILED DESCRIPTION

[0050] In order to more clearly understand the above-mentioned objectives, features and advantages of the present disclosure, the scheme of the present disclosure will be further described below. It should be noted that the embodiments of the present disclosure and the features therein can be combined with each other in the absence of conflict.

[0051] In the following description, many specific details are set forth to facilitate a full understanding of the present disclosure, but the present disclosure may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present disclosure, rather than all of the embodiments.

[0052] Figure 1 The figure shows a flow chart of a method for protecting a wind power generation system from lightning overvoltage provided by an embodiment of the present disclosure. Figure 1 The present disclosure provides a method for protecting a wind power generation system from lightning overvoltage, comprising:

[0053] Step S1: Establishing a lightning direct stroke equivalent circuit model of a wind power generation system;

[0054] Step S2: Based on the equivalent circuit model, simulate the back-strike overvoltage and induced overvoltage of the wind power generation system under the lightning strike state, and obtain characteristic parameters of the back-strike overvoltage and induced overvoltage;

[0055] Step S3: comparing the characteristic parameters of the counter-attack overvoltage and the induced overvoltage with the overvoltage withstand strength of the wind power generation system;

[0056] Step S4: designing an overvoltage protection system for the wind power generation system according to the comparison result.

[0057] Specifically, in step S1, a lightning direct strike equivalent circuit model for the wind turbine system is established based on transmission line theory. When a wind turbine system is struck by lightning, the lightning current is typically received by the lightning receptors on the turbine blades. The lightning current then enters the ground through the grounding down conductors, bearing brushes, tower, and grounding resistors on the turbine blades. During a lightning strike, the current flowing through the turbine blades generates a reverse overvoltage on the nacelle. Simultaneously, the lightning current flowing through the grounding down conductors of the turbine blades in the wind turbine system may generate an induced overvoltage on the control module. Therefore, the key to establishing a lightning direct strike equivalent circuit model for the wind turbine system is to establish a lightning direct strike equivalent circuit model for the grounding down conductors of the turbine blades. By simulating the lightning direct strike equivalent circuit model for the wind turbine system based on the path of the lightning current in the wind turbine system and the specific structure of the wind turbine system, the overvoltage of the wind turbine generator under lightning strike conditions is determined as accurately as possible, providing a basis for lightning overvoltage protection for the wind turbine system.

[0058] In step S2, the counter-strike overvoltage refers to the phenomenon that when lightning strikes the tower, lightning conductor or nearby objects of the power line or equipment, the lightning current flows into the earth through the tower, lightning conductor or grounding device, generating a high potential on the tower, lightning conductor or grounding device. This high potential generates a potential difference with the conductor (or equipment). When the potential difference exceeds the insulation strength of the conductor (or equipment), a flashover discharge will occur on the conductor (or equipment), thereby generating an overvoltage phenomenon. The present disclosure calculates the counter-strike lightning overvoltage of the wind turbine control system in combination with the structure of the wind power generation system, and the key indicators such as the overvoltage amplitude and waveform of the obtained counter-strike overvoltage are more accurate. Since the lightning current flowing through the grounding down conductor of the wind power generation system may generate an induced overvoltage on the control cable of the control module, the present disclosure calculates the induced overvoltage in the control module based on the method of inductance and capacitance coupling, which can further improve the accuracy of the equivalent circuit model of the direct lightning strike of the wind power generation system, and provide a basis for the lightning overvoltage protection design of the wind power generation system from the two aspects of counter-strike overvoltage and induced overvoltage.

[0059] In step S3, the obtained key indicators such as the overvoltage amplitude and waveform of the counter-strike overvoltage, as well as the overvoltage amplitude and waveform of the induced overvoltage, are compared with the overvoltage tolerance strength of the wind power generation system itself to determine whether the simulated key indicators such as the overvoltage amplitude and waveform of the counter-strike overvoltage and the induced overvoltage exceed the overvoltage tolerance strength of the wind power generation system itself, and obtain a comparison result.

[0060] In step S4, if the overvoltage amplitude, waveform and other key indicators of the simulated counter-attack overvoltage and induced overvoltage exceed the overvoltage tolerance strength of the wind power generation system itself, it is necessary to adjust the overvoltage tolerance strength of the wind power generation system itself according to the key indicators of the simulated counter-attack overvoltage and induced overvoltage. Optionally, by selecting appropriate protective devices, installing lightning arresters, surge protectors, adjusting the grounding network, dividing protection areas, etc., the overvoltage protection scheme and equipment configuration of the wind power generation system are reasonably designed to increase the protection effect of the overvoltage protection system of the wind power generation system. This disclosure does not make specific restrictions on this and can be adjusted according to actual conditions. If the overvoltage amplitude, waveform and other key indicators of the simulated counter-attack overvoltage and induced overvoltage do not exceed the overvoltage tolerance strength of the wind power generation system itself, there is no need to adjust the overvoltage protection system of the wind power generation system itself or reduce the protection level of the control module. This disclosure does not make restrictions on this and is based on actual needs.

[0061] In this way, by establishing a lightning direct strike equivalent circuit model of the grounding down conductor of the wind turbine blade in the wind power generation system based on the transmission line theory; calculating the back-strike overvoltage of the wind power generation system control module according to the structure of the wind power generation system; and calculating the induced overvoltage of the control cable in the control module based on the inductance and capacitance coupling method, the overvoltage amplitude induced to the port of the wind power generation system de-icing system can be accurately calculated, providing a basis for the lightning overvoltage protection design of the wind power generation system control module.

[0062] Figure 2 FIG. 1 is a diagram showing an equivalent circuit model of a lightning strike in a wind power generation system according to an embodiment of the present disclosure. Figure 3 FIG. 1 is a schematic diagram of a nacelle structure of a wind power generation system provided by an embodiment of the present disclosure. Figure 4 Shown Figure 3 The equivalent circuit diagram of Figure 5 FIG. 1 is a schematic diagram of a tower structure of a wind power generation system provided by an embodiment of the present disclosure. Figure 6 Shown Figure 5 The equivalent circuit diagram of Figure 7 FIG. 1 is a schematic diagram of a wind turbine blade structure of a wind power generation system provided by an embodiment of the present disclosure. Figure 8 Shown Figure 7 For the equivalent circuit diagram of the ground down conductor, please refer to Figures 2 to 8 The present disclosure provides a method for protecting a wind power generation system from lightning overvoltage. The wind power generation system includes wind turbine blades, a nacelle, and a tower. The wind turbine blades and the tower are connected through the nacelle. Establishing an equivalent circuit model of a direct lightning strike of the wind power generation system includes: establishing equivalent circuit models of the wind turbine blades, the nacelle, and the tower respectively.

[0063] Specifically, as mentioned above, when a wind power generation system is struck by lightning, the lightning current is usually received by the lightning receptors on the wind turbine blades. The lightning current enters the ground through the grounding down conductors on the wind turbine blades, the bearing brushes in the nacelle, the tower, and the grounding resistor. The disclosed embodiment establishes equivalent circuit models of the wind turbine blades, nacelle, and tower in the wind power generation system. In this way, based on the actual structure of the wind power generation system, the capacitance, inductance, and resistance of each part of the wind power generation system when struck by lightning can be calculated, thereby simulating a relatively accurate back-strike overvoltage of the wind power generation system, providing a design basis for lightning overvoltage protection of the wind power generation system.

[0064] Please continue to refer to Figure 2 The present disclosure provides a method for protecting a wind power generation system from lightning overvoltage. This method simulates the back-strike overvoltage and induced overvoltage of a wind power generation system under a lightning strike based on an equivalent circuit model. Obtaining characteristic parameters of the back-strike overvoltage and induced overvoltage includes: simulating the lightning current using a first preset waveform current, and simulating the back-strike overvoltage and induced overvoltage of the equivalent circuit model under the first preset waveform. In an optional embodiment provided by the present disclosure, the lightning current is simulated using a first preset waveform current with a waveform of 10 / 350μs, and the lightning current channel wave impedance is 300Ω. The equivalent waveform of the lightning current is as follows:

[0065]

[0066] Where, I0 is the peak value of lightning current, I0 is less than or equal to 200kA. α is the time constant of lightning current wave head, and α can be set to 1×10 5 β is the time constant of the lightning current wave tail. Optionally, β is set to 3.43×10 3 η is the waveform peak correction factor, and optionally, η is set to 1.

[0067] Specifically, the lightning current can be simulated using a first preset waveform current with a waveform of 10 / 350μs, or the lightning current can also be simulated using a first preset waveform current of 8 / 20μs, which is not specifically limited in this disclosure. The simulation method includes combining an impulse voltage generator with an artificial impedance network, specifically using an impulse voltage generator to generate a high voltage pulse, and converting the voltage into a lightning current waveform through an artificial impedance network, which can be simulated using a double exponential function. In addition, the lightning current can also be simulated by using a lightning current generator, pulse power technology, computer simulation, etc., which is not specifically limited in this disclosure. In this way, by simulating the lightning current, the back-strike overvoltage and induced overvoltage of the wind power generation system can be obtained in a safe state, reducing damage to the wind power generation system.

[0068] Please continue to refer to Figure 7 and Figure 8The present disclosure provides a method for protecting a wind power generation system from lightning overvoltage, wherein the wind turbine blade includes a grounding down conductor; establishing an equivalent circuit model of the wind turbine blade includes: establishing a first equivalent circuit model of the grounding down conductor, the first equivalent circuit model including multiple sections of a first π-type equivalent circuit connected in series, and the length of each section of the first π-type equivalent circuit is less than or equal to 1m.

[0069] Specifically, the wind turbine blades contain a ground down conductor that attracts lightning for the wind turbine blades and a wind turbine blade signal line. When a wind turbine blade is struck by lightning, the lightning current is usually received by the lightning receptor on the wind turbine blade. The lightning current enters the earth through the ground down conductor on the wind turbine blade, the bearing brush, the tower, and the grounding resistor. Therefore, to establish an equivalent circuit model of direct lightning strikes on a wind power generation system, it is necessary to establish a first equivalent circuit model of the ground down conductor for the wind turbine blade. The ground down conductor impedance of the wind turbine blade can be divided into several sections of first π-type equivalent circuits connected in series, and the length of each section of the first π-type equivalent circuit is less than or equal to 1m. Optionally, the length of the first π-type equivalent circuit can be less than or equal to 0.1m, less than or equal to 0.2m, less than or equal to 0.3m, less than or equal to 0.4m, less than or equal to 0.5m, less than or equal to 0.6m, less than or equal to 0.7m, less than or equal to 0.8m, less than or equal to 0.9m, less than or equal to 1m, etc. The present disclosure does not limit this, and it is only necessary that the length of the first π-type equivalent circuit is within a range of less than or equal to 1m. For example, the length of the first π-type equivalent circuit can be 0.5m, 1m, etc. In this way, by performing segmented calculations on the grounding down conductor impedance of the wind turbine blades, it is helpful to simplify the calculations and reduce the difficulty of the calculations.

[0070] Please continue to refer to Figure 7 and Figure 8 The present disclosure provides a method for protecting a wind power generation system from lightning overvoltage, which calculates the equivalent resistance R of each first π-type equivalent circuit. b 、Inductor L b , capacitor C b , the calculation formula is as follows:

[0071]

[0072] Among them, μ b , σ b are the magnetic permeability and electrical conductivity of the grounding down conductor of the fan blade, l b is the length of the segmented blade of the fan blade, r b is the grounding down conductor radius of the fan blade.

[0073] Specifically, bThe value range of is less than or equal to 2m. Optionally, l b Can be less than or equal to 1.5m, or, l b Can be less than or equal to 1m, or, l b It can be less than or equal to 0.5m... This disclosure does not make any specific restrictions on this, as long as it meets l b It can be within a range of less than or equal to 2m. b The value of is 2m, or 1.5m, or 1m, etc. Calculate the equivalent resistance R of each first π-type equivalent circuit b 、Inductor L b , capacitor C b Then, according to the number of sections of the first π-type equivalent circuit divided by the grounding down conductor of the wind turbine blade, the equivalent resistance R b 、Inductor L b , capacitor C b By accumulating the equivalent impedance of the wind turbine blades, we can obtain the impedance of the grounding down conductor of the wind turbine blades, which provides a basis for calculating the back-strike overvoltage of the wind turbine system under lightning strike conditions.

[0074] Please continue to refer to Figure 3 and Figure 4 The present disclosure provides a method for protecting a wind power generation system from lightning overvoltage. The nacelle includes bearings and carbon brushes. The equivalent circuit model of the nacelle includes the bearings and brushes connected in parallel. The bearing capacitance C h Less than or equal to 0.1μF, the brush resistance R h Less than or equal to 0.1Ω.

[0075] Specifically, the connection between the wind turbine blades and the nacelle is mainly composed of bearings and carbon brushes. The bearings and carbon brushes will conduct lightning current during a lightning strike. To establish an equivalent circuit model of a direct lightning strike of a wind power generation system, it is necessary to further establish an equivalent circuit model of the bearings and carbon brushes in the nacelle. This can improve the accuracy of the simulated back-strike overvoltage. In an optional embodiment provided by the present disclosure, the bearing capacitor C h It can be less than or equal to 0.01μF, less than or equal to 0.02μF, less than or equal to 0.03μF, less than or equal to 0.04μF, less than or equal to 0.05μF, less than or equal to 0.06μF, less than or equal to 0.07μF, less than or equal to 0.08μF, less than or equal to 0.09μF, less than or equal to 0.1μF, etc. This disclosure is not limited to this. It is only necessary to select the bearing capacitance C in the current wind power generation system. hThe actual capacitance value can be used, for example, the bearing capacitance C h The capacitance value can be 0.05μF, or 0.1μF, etc. It can be understood that the brush resistance R h It can be less than or equal to 0.01Ω, less than or equal to 0.02Ω, less than or equal to 0.03Ω, less than or equal to 0.04Ω, less than or equal to 0.05Ω, less than or equal to 0.06Ω, less than or equal to 0.07Ω, less than or equal to 0.08Ω, less than or equal to 0.09Ω, less than or equal to 0.1Ω... and so on. The present disclosure is not limited to this. It is only necessary to select the brush resistance R in the current wind power generation system. h The actual resistance value can be, for example, the brush resistance R h The resistance value can be 0.05Ω, or 0.1Ω, etc. In this way, the bearing capacitance C in the wind power generation system can be h The actual capacitance value and brush resistance R h The actual resistance value is used to simulate the equivalent impedance of the nacelle, providing a calculation basis for simulating the back-strike overvoltage of the wind power generation system under lightning strike.

[0076] Please continue to refer to Figure 5 and Figure 6 The present disclosure provides a method for protecting a wind power generation system from lightning overvoltage. The tower comprises a plurality of segmented tower bodies, each segmented tower body having a height h t Less than or 5m; establishing an equivalent circuit model of the tower includes establishing an equivalent circuit model of each segmented tower body.

[0077] Specifically, the tower of the wind power generation system includes multiple segmented tower bodies, each segmented tower body can be equivalent to a cylindrical shell, and the present disclosure uses a Γ-type RLC equivalent circuit to equate the segmented tower body. Optionally, the height h of each segmented tower body is t It can be less than or equal to 5m, less than or equal to 4m, less than or equal to 3m, less than or equal to 2m, less than or equal to 1m, etc. The present disclosure does not make specific restrictions on this, as long as the height h of each segmented tower body is satisfied. t It can be within the range of less than or equal to 5m. For example, the height h of each segmented tower body is t 5m, 2.5m, 4m, and so on. When a wind turbine blade is struck by lightning, the lightning current is typically received by the lightning receptors on the blades. The lightning current then enters the ground through the grounding down conductors on the blades, the bearing brushes, the tower, and the grounding resistor. Therefore, to establish an equivalent circuit model for a direct lightning strike in a wind turbine system, it is necessary to specifically model the tower. By artificially segmenting the tower, the computational complexity can be reduced.

[0078] Please continue to refer to Figure 5 and Figure 6 The present disclosure provides a method for protecting a wind power generation system from lightning overvoltage, wherein establishing an equivalent circuit model of each segmented tower body includes:

[0079] Calculate the equivalent resistance R of each segmented tower t , equivalent inductance L t , Tower body to ground capacitance C t , the calculation formula is as follows:

[0080]

[0081] Where q = 2πf u μ t σ t w 2 , μ t , σ t are the magnetic permeability and electrical conductivity of the segmented tower body respectively; w is the average thickness of the segmented tower body; R t0 is the DC resistance of the segmented tower body; μ0 is the vacuum magnetic permeability; P is the ratio of the inner and outer radii of the segmented tower body, and P is usually taken as 0.99; ε0 is the vacuum dielectric constant, ε0=8.854×10 -12 F / m; H is the total height of the wind turbine tower.

[0082] Specifically, calculate the equivalent resistance R of each segmented tower body t , equivalent inductance L t , Tower body to ground capacitance C t Then, according to the number of segments of the tower body actually divided, the equivalent resistance R t , equivalent inductance L t , Tower body to ground capacitance C t The tower impedance can be obtained by accumulating the tower impedance, which provides a calculation basis for simulating the back-strike overvoltage of the wind power generation system under the state of lightning strike. t , equivalent inductance L t , Tower body to ground capacitance C t , which can provide a calculation basis for simulating the back-strike overvoltage of wind power generation systems under lightning strike conditions.

[0083] Figure 9 The figure shows an equivalent circuit diagram of inductive coupling between a control cable and a grounding down conductor provided by an embodiment of the present disclosure. Figure 9 The present disclosure provides a method for protecting a wind power generation system from lightning overvoltage. The control module includes a control cable. Establishing an equivalent circuit model of the control module includes calculating the mutual inductance M and mutual capacitance C between the control cable and the grounding down conductor using the following formula:

[0084]

[0085] Where l is the distance between the control cable and the adjacent grounding down conductor, D is the distance between the center points of two adjacent control cables, r is the radius of the control cable, μ0 is the vacuum permeability, and ε is the dielectric constant.

[0086] Specifically, μ0 is usually taken as 4π×10 -7 H / m, ε is about 8.854×10 -12 F / m. The inductance, capacitance, and resistance of the control cable itself can be calculated using the same method used to calculate the inductance, capacitance, and resistance of the wind turbine blade ground down conductor, so this will not be repeated here. During a lightning strike, lightning current flowing through the ground down conductor of a wind turbine system may induce overvoltages on the control cables of the control module. The induced overvoltages between the ground down conductor and the control cable are primarily caused by electromagnetic induction and electrostatic induction. When lightning strikes the ground down conductor or the nearby ground, a large lightning current flows through the ground down conductor, generating a strong transient magnetic field. If the control cable is parallel to or close to the ground down conductor, this magnetic field generates an induced electromotive force in the control cable through electromagnetic induction, resulting in an overvoltage. The closer the control cable is to the ground down conductor, the greater the induced overvoltage. The greater the lightning current, the stronger the magnetic field, and the higher the induced overvoltage. The longer the control cable, the greater the accumulated induced electromotive force. During a lightning discharge, the electric field around the ground down conductor changes dramatically. If the control cable is exposed to this electric field, charges are induced on its metal sheath or conductors, resulting in an overvoltage. The greater the electric field strength, the greater the induced charge and the higher the overvoltage. Furthermore, when the grounding resistance of the grounding down conductor is too large, the lightning current cannot be discharged quickly, causing the grounding down conductor potential to rise, further exacerbating the induced overvoltage on the control cable. This disclosure simulates the induced overvoltage of a wind power generation system using the above formula, thereby graphically and digitizing the induced overvoltage. This allows for a visual comparison of the calculated induced overvoltage with the actual overvoltage tolerance of the control module, facilitating an intuitive assessment of the adequacy of the wind power generation system's lightning protection measures.

[0087] Please continue to refer to Figures 1 to 9 The present disclosure provides a method for protecting a wind power generation system from lightning overvoltage. The method simulates the back-strike overvoltage and induced overvoltage of the wind power generation system under a lightning strike state based on an equivalent circuit model, and obtains characteristic parameters of the back-strike overvoltage and induced overvoltage, including: applying a simulated lightning current to the wind turbine blades, calculating the back-strike overvoltage at the tower control module position, and obtaining the amplitude and waveform characteristics of the back-strike overvoltage; calculating the induced overvoltage at the control module port, and obtaining the amplitude and waveform characteristics of the induced overvoltage.

[0088] Specifically, the tower's grounding resistance R g Less than or equal to 8Ω, optionally, the tower grounding resistance Rg It can be less than or equal to 6Ω, less than or equal to 4Ω, less than or equal to 2Ω, etc., and this disclosure does not make any specific limitations on this. For example, the grounding resistance R of the tower g It can be 8Ω, or 4Ω, etc. The control module outlet resistance R0 is less than or equal to 4MΩ. Optionally, the control module outlet resistance R0 can be less than or equal to 4MΩ, or less than or equal to 3MΩ, or less than or equal to 2MΩ, etc., and this disclosure does not specifically limit this. For example, the control module outlet resistance R0 can be 4MΩ, or 4MΩ, etc. By applying a lightning current to the wind turbine blades and calculating the lightning overvoltage waveform at the location of the wind power system control module, the counter-strike overvoltage can be obtained; calculating the output voltage of the control module port can obtain the control module induced overvoltage when the wind turbine blades are struck by lightning. By obtaining the amplitude, waveform, and other characteristics of the counter-strike overvoltage and the induced overvoltage and comparing them with the overvoltage tolerance of the control system itself, it can be determined whether the lightning protection measures of the wind power system control module are appropriate. If the control module lightning protection measures are inappropriate, the lightning protection measures need to be improved. Optionally, by increasing the cable spacing, ensure that the control cable maintains a sufficient safe distance from the grounding down conductor to reduce electromagnetic and electrostatic induction. Alternatively, use metal-shielded control cables and reliably ground the shielding layer to reduce the impact of induced overvoltages. Alternatively, reduce the grounding resistance of the grounding down conductor to ensure rapid discharge of lightning current and reduce potential rise. Alternatively, install lightning arresters at the input and output ends of the control cables to limit the amplitude of overvoltages. Alternatively, lay the control cables in a crosswise or vertical manner as much as possible to reduce the generation of induced overvoltages. This disclosure does not limit the implementation methods for reducing induced overvoltages, and specific configurations can be made according to actual conditions.

[0089] In summary, the present disclosure provides a method for lightning overvoltage protection in a wind power generation system. This method establishes a lightning direct strike equivalent circuit model for the grounding down conductor of a wind turbine blade in the wind power generation system based on transmission line theory; calculates the back-strike overvoltage of the wind power generation system control module based on the wind power generation system structure; and calculates the induced overvoltage of the control cable in the control module using an inductance-capacitance coupling method. This method accurately calculates the overvoltage amplitude induced to the de-icing system port of the wind power generation system, providing a basis for designing lightning overvoltage protection for the wind power generation system control module. Based on the actual structure of the wind power generation system, the capacitance, inductance, and resistance of each component of the wind power generation system when struck by lightning are calculated, thereby simulating a relatively accurate back-strike overvoltage of the wind power generation system and providing a basis for designing lightning overvoltage protection for the wind power generation system. By simulating lightning current, the back-strike overvoltage and induced overvoltage of the wind power generation system can be obtained in a safe state, reducing damage to the wind power generation system. By performing segmented calculations of the grounding down conductor impedance of the wind turbine blades, the calculations are simplified and reduced in complexity. By performing segmented calculations of the tower, the calculation difficulty is reduced. The induced overvoltage of the wind power generation system is simulated by the above formula, so that the counter-attack overvoltage and the induced overvoltage are graphically and digitized, and the calculated counter-attack overvoltage and induced overvoltage are visually compared with the actual overvoltage tolerance capability of the control module, which is conducive to intuitively judging whether the lightning protection measures of the wind power generation system are appropriate.

[0090] The foregoing description is intended only to provide specific embodiments of the present disclosure, intended to enable those skilled in the art to understand and implement the present disclosure. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present disclosure. Therefore, the present disclosure is not intended to be limited to the embodiments described herein, but rather to be construed in the broadest manner consistent with the principles and novel features disclosed herein.

Claims

1. A method for protecting a wind power generation system from lightning overvoltage, characterized in that: include: Establish a lightning direct strike equivalent circuit model for wind power generation systems; Based on the equivalent circuit model, simulating the back-strike overvoltage and induced overvoltage of the wind power generation system under a lightning strike state, and obtaining characteristic parameters of the back-strike overvoltage and induced overvoltage; comparing the characteristic parameters of the back-strike overvoltage and the induced overvoltage with the overvoltage withstand strength of the wind power generation system; An overvoltage protection system for the wind power generation system is designed according to the comparison result.

2. The method for protecting a wind power generation system from lightning overvoltage according to claim 1, wherein: The wind power generation system includes a wind turbine blade, a nacelle and a tower, wherein the wind turbine blade is connected to the tower through the nacelle; The establishing of a lightning direct strike equivalent circuit model for a wind power generation system includes establishing equivalent circuit models of the wind turbine blades, the nacelle, and the tower, respectively.

3. The method for protecting a wind power generation system from lightning overvoltage according to claim 1, wherein: The simulating, based on the equivalent circuit model, the back-strike overvoltage and the induced overvoltage of the wind power generation system in a lightning strike state, and obtaining characteristic parameters of the back-strike overvoltage and the induced overvoltage includes: A first preset waveform current is used to simulate a lightning current, and the counter-strike overvoltage and induced overvoltage of the equivalent circuit model under the first preset waveform are simulated; the equivalent waveform of the lightning current is as follows: Wherein, I0 is the lightning current peak value; α is the lightning current wave front time constant; β is the lightning current wave tail time constant; η is the waveform peak correction factor.

4. The method for protecting a wind power generation system from lightning overvoltage according to claim 2, wherein: The fan blade includes a grounding down conductor; Establishing the equivalent circuit model of the fan blade includes: A first equivalent circuit model of the ground down conductor is established, wherein the first equivalent circuit model includes multiple sections of first π-type equivalent circuits connected in series, and the length of each section of the first π-type equivalent circuit is less than or equal to 1 m.

5. The method for protecting a wind power generation system from lightning overvoltage according to claim 4, wherein: Calculate the equivalent resistance R of each section of the first π-type equivalent circuit b 、Inductor L b , capacitor C b , the calculation formula is as follows: Among them, μ b , σ b are the magnetic permeability and electrical conductivity of the grounding down conductor of the fan blade, respectively, l b is the length of the segmented blade of the fan blade, r b is the grounding down conductor radius of the fan blade.

6. The method for protecting a wind power generation system from lightning overvoltage according to claim 2, wherein: The nacelle includes a bearing and a carbon brush. The equivalent circuit model of the nacelle includes the bearing and the brush connected in parallel. The bearing capacitance C h Less than or equal to 0.1μF, the brush resistance R h Less than or equal to 0.1Ω.

7. The method for protecting a wind power generation system from lightning overvoltage according to claim 2, wherein: The tower comprises multiple segmented tower bodies, each segmented tower body has a height h t Less than or equal to 5m; Establishing the equivalent circuit model of the tower includes establishing an equivalent circuit model of each segmented tower body.

8. The method for protecting a wind power generation system from lightning overvoltage according to claim 7, wherein: The establishing of an equivalent circuit model of each segmented tower body comprises: Calculate the equivalent resistance R of each segmented tower body t , equivalent inductance L t , Tower body to ground capacitance C t , the calculation formula is as follows: Where q = 2πf u μ t σ t w 2 , μ t , σ t are the magnetic permeability and electrical conductivity of the segmented tower body respectively; w is the average thickness of the segmented tower body; R t0 is the DC resistance of the segmented tower body; μ0 is the vacuum magnetic permeability; P is the ratio of the inner and outer radii of the segmented tower body; ε0 is the vacuum dielectric constant; and H is the total height of the tower.

9. The method for protecting a wind power generation system from lightning overvoltage according to claim 2, wherein: The wind power generation system further includes a control module, the control module is located in the nacelle, the control module is configured to control the rotation of the wind turbine blades, and the control module includes a control cable; The establishment of a lightning direct stroke equivalent circuit model for a wind power generation system includes: The mutual inductance M and mutual capacitance C between the control cable and the grounding down conductor are calculated as follows: Wherein, l is the distance between the control cable and the adjacent grounding down conductor, D is the distance between the center points of two adjacent control cables, r is the radius of the control cable, μ0 is the vacuum permeability; ε is the dielectric constant.

10. The method for protecting a wind power generation system from lightning overvoltage according to claim 2, wherein: The simulating, based on the equivalent circuit model, the back-strike overvoltage and the induced overvoltage of the wind power generation system in a lightning strike state, and obtaining characteristic parameters of the back-strike overvoltage and the induced overvoltage includes: Apply the simulated lightning current to the wind turbine blades, calculate the back-strike overvoltage of the wind power generation system based on the equivalent circuit model of the wind turbine blades, the nacelle, and the tower, and obtain the amplitude and waveform characteristics of the back-strike overvoltage; calculate the induced overvoltage at the control module port based on the inductance and capacitance coupling between the control cable and the grounding down conductor, and obtain the amplitude and waveform characteristics of the induced overvoltage.

Images