Wind turbine lightning stroke monitoring system control method based on EMTP-RV

Abstract

The invention discloses a wind turbine lightning stroke monitoring system control method based on EMTP-RV, mainly relates to the technical field of wind power plant control, and comprises the following steps: S1, modeling overvoltage and electromagnetic transient characteristics on a wind turbine under a lightning stroke condition; s2, the blades and the tower of the wind turbine are modeled, and modeling analysis is carried out based on the recombination version (EMTP-RV) of an electromagnetic transient program; s3, establishing an EMTP-RV comprehensive computer monitoring system capable of protecting a plurality of mutually connected wind turbines from being influenced by lightning strokes; according to the wind turbine lightning stroke monitoring model based on the EMTP-RV, the model constructs a comprehensive computer monitoring system based on the EMPT-RV under the condition that a plurality of wind turbines are connected with one another, direct lightning stroke of blades is considered or soil near a lightning stroke tower is considered, lightning stroke monitoring under the direct lightning stroke condition and indirect lightning stroke condition is achieved, and the wind turbine lightning stroke monitoring accuracy is improved. And the protection of a plurality of wind turbines under the lightning stroke condition is effectively realized.

Description

Technical Field

[0001] The present invention relates to the field of wind farm control, and in particular to an EMTP-RV-based wind turbine lightning strike monitoring system method. Background Art

[0002] Renewable energy generation is gaining increasing attention worldwide. Wind energy, with its vast reserves, widespread distribution, renewable nature, and pollution-free nature, is gaining global attention as a renewable energy source and a cost-effective method of power generation. Lightning strikes on power systems can generate dangerous overvoltages and damage equipment. Wind turbines are particularly vulnerable to lightning, which can cause significant damage to wind turbine components. Statistics show that 4% to 8% of wind turbines worldwide are damaged by lightning each year. When blades are damaged by lightning, the continued rotation of the damaged blades amplifies the damage. To prevent this secondary damage before it occurs, wind farms in areas of China prone to winter lightning strikes are implementing lightning detection systems. Typically, wind turbines automatically stop upon lightning detection and restart after a visual inspection confirms the integrity of the blades. However, inclement weather often makes it difficult to visually inspect the integrity of the blades, and the resulting delays in the restart process extend downtime and reduce wind turbine availability.

[0003] Lightning protection for wind turbines presents challenges not typically seen with other structures. These challenges are caused by:

[0004] (1) The wind turbine is a tall structure exceeding 150 m in height;

[0005] (ii) Wind turbines are often placed in locations that are very vulnerable to being struck by lightning;

[0006] (iii) The most exposed wind turbine components, such as blades and nacelles, are often made of composite materials. Although most wind turbine systems now have built-in lightning protection systems, lightning currents can still cause serious damage;

[0007] (iv) The blades and nacelle are rotating;

[0008] (v) the lightning current must be conducted through the wind turbine structure to the ground, so a significant portion of the lightning current will pass through or near almost all wind turbine components;

[0009] (6) Wind turbines in a wind farm are electrically interconnected and often placed in locations with poor grounding conditions.

[0010] Modern wind turbines are characterized not only by their greater height but also by an ever-increasing amount of control and processing electronics. Therefore, lightning protection design for modern wind turbines remains a challenging problem.

[0011] The future development of wind power and the construction of more wind farms will require intensified discussions on lightning protection and insulation design for such facilities. However, in China, research on lightning protection for wind turbines using complex numerical codes remains scarce. Therefore, much work remains to be done in this area, and surge propagation during lightning strikes on wind farms located in China is still far from being clearly understood.

[0012] Direct and indirect lightning strikes can cause damage and failure to related electrical and mechanical components. Analyzing the statistics on wind turbine damage caused by lightning and the associated risks has proven that an effective lightning protection system must protect against not only the direct effects of lightning, but also its indirect effects.

[0013] Scale models of electrical systems have been a common tool for predicting transients following different types of disturbances. However, in recent years, scale models have been gradually replaced by sophisticated numerical codes that accurately describe transient behavior, such as EMTP-RV, which specifies the Restructured Version (RV) of the Electromagnetic Transient Program (EMTP). Summary of the Invention

[0014] The purpose of the present invention is to solve the problems existing in the prior art and provide a wind turbine lightning strike monitoring system method based on EMTP-RV. When multiple wind turbines are connected to each other, considering direct lightning strikes on blades or lightning strikes on the soil near the tower, a comprehensive computer monitoring system based on EMPT-RV is constructed to realize lightning strike monitoring for direct and indirect lightning strikes, effectively reducing the protection of multiple wind turbines under lightning strike conditions.

[0015] To achieve the above-mentioned purpose, the present invention is implemented through the following technical solutions:

[0016] A wind turbine lightning strike monitoring system control method based on EMTP-RV includes the following steps:

[0017] S1. Model the overvoltage and electromagnetic transient characteristics of the wind turbine under lightning strike conditions. Based on the above modeling, monitor and distinguish between direct lightning strikes and indirect lightning strikes.

[0018] S2. Modeling of wind turbine blades and towers, using the Electromagnetic Transient Program Revised Version (EMTP-RV) for modeling and analysis.

[0019] S3. Establish an EMTP-RV integrated computer monitoring system that can protect multiple interconnected wind turbines from the effects of lightning strikes.

[0020] In step S1, the conductors of the wind turbine overvoltage and electromagnetic transient characteristics are calculated as shown in the following figure. Figure 1 The existence of grounding is taken into account by image theory, and the superscripts represent the image of each branch relative to the ground plane. Figure 1 As shown in Figure 1, two parallel conductors i and j are perpendicular to the ground, have a length of l, and a radius of a. Their mutual potential coefficient is shown below. The skin effect of the ground is not considered in the calculation, and the resistance of each conductor is assumed to be constant and equal to the DC value.

[0021] 1. Capacitor parameters

[0022] Since the radius of the conductors is much smaller than the distance between them, the charge is considered to be located on the axis of each conductor. According to the average potential method, since the current is in j and j', the average potential on i is expressed as follows:

[0023]

[0024]

[0025] where τ is the charge density on conductor i and ε0 is the dielectric constant of vacuum.

[0026]

[0027]

[0028]

[0029]

[0030]

[0031]

[0032] The mutual potential coefficient between conductors i and j is:

[0033]

[0034] The potential coefficient matrix is ​​expressed as:

[0035]

[0036] And its inverse matrix:

[0037]

[0038] The coupling capacitance matrix is ​​then:

[0039]

[0040] in:

[0041]

[0042]

[0043] 2. Inductance parameters

[0044] According to the Neumann integral formula, the mutual inductance between any two conductors is as follows

[0045]

[0046] where dl1 and dl2 are the two differential elements l and l2 on conductor l, respectively, whose direction vectors are in phase with the reference directions of the two conductors at the differential elements. D represents the distance between the two differential elements, and φ represents the angle formed by the direction vectors of the two differential elements.

[0047] The mutual inductance of conductor i is calculated by subtracting the mutual inductance of conductor j from the mutual inductance of conductor j′, that is:

[0048] When conductors i and j are in the same vertical position, i.e. z 03 =z 01 、z 04 =z 02 , the mutual inductance is calculated as follows:

[0049]

[0050] in:

[0051]

[0052]

[0053] To calculate the self-inductance of each cell, d should be set equal to a. Self-inductance and mutual inductance in other cases can also be calculated using the Neumann integral formula.

[0054] 3. Grounding parameters

[0055] The grounding grid of the 600kW wind turbine system is as follows: Figure 2 Each grounding rod of the grid is represented by its equivalent circuit, which consists of a longitudinal resistor R g , inductance L g , conductivity G g and capacitor C g Relative to the ground.

[0056] The unit length constant parameter for the special case of a horizontal grounding electrode is:

[0057]

[0058] where ρc is the resistivity of the rod, h is the depth of the ground grid, ε is the dielectric constant of the ground, r0 is the radius of the ground rod, and the subscript h represents the parameter of the horizontal rod.

[0059] The electrical parameters per unit length of vertical ground rod are:

[0060]

[0061] where the subscript v represents the parameters of the vertical rod. The mutual parameters between the ground rod segments are neglected because their radii are much smaller than the distance between them.

[0062] 4. Transient response calculation

[0063] According to the parameters calculated in the previous section, the wind turbine tower is represented as an RLC grid. Figure 3 The electrical parameters of the branch are displayed. The power grid is a circuit model of the tower structure, making it easy to simulate using computer software. However, the parameters used in simulations are generally obtained through numerical calculations. For large structures, this is difficult to simulate because the number of nodes and elements exceeds computer memory limitations. Therefore, it is more convenient to use direct numerical methods to calculate lightning characteristics. The algorithm proposed in this patent is a numerical model for calculating lightning transient responses.

[0064] Consider attaching Figure 3 (a) has a coupled branch with a resistance matrix R and an inductance matrix L. When the current vector flowing from node k to m is i 公里 , the voltage between k and m can be described by the following equation:

[0065]

[0066] where u k and u m are the voltage vectors at nodes k and m respectively.

[0067] Applying the trapezoidal integration rule to the above equation, the transient current can then be expressed as:

[0068]

[0069]

[0070] In the attached Figure 3 (b), R e The equivalent resistance matrix of the RL branch and R is S C For the capacitor branch, R C =Δt / 2·3 −1 C is the coupling capacitor matrix; I e(t−Δt) is the vector of the equivalent current source, i.e., I RL系列 (t−Δt) for the RL branch and I C (t−Δt) represents the capacitive branch, where:

[0071]

[0072] Then, the tower is represented by a transient equivalent computational network. The relationship between branch voltage and current can be described in the following matrix form:

[0073]

[0074] Where Y is the branch admittance matrix C that can be obtained from S and R, and I is the current source vector associated with the branch in the circuit. Therefore, by applying Kirchhoff's current law, we have:

[0075]

[0076] The incident matrix A is used to associate branches and nodes. It is a rectangular matrix of order n×b. Substitute the branch voltage vector U into U=A T ·U n ,have:

[0077]

[0078] Among them, A·Y·A T is the so-called node matrix, U n is the node voltage vector and A·I s is the total current source injected into each node in the network, and the transient voltage distribution can then be calculated by solving the node voltage equation:

[0079]

[0080] In step S2, the electrical model of the wind turbine bearings is constructed, taking into account the small vertex angles of both full-scale and reduced-scale bearing rollers. Therefore, they can be approximated as metallic cylindrical elements, simplifying the modeling using a two-dimensional approach. Analysis of the wind turbine main bearings showed that the electrical behavior of these mechanical components within the typical lightning current frequency range can be approximated by a capacitor, as inferred from the implemented scaled-down experimental test setup.

[0081] In order to save computational effort, a basic domain is defined, which contains a roller separated by six surfaces, which represent: 1) the inner and outer bearing rings; 2) the side boundaries representing the equidistant planes between adjacent rollers; 3) the top and bottom surfaces delimiting the space containing the lubricant. Figure 4The 3D basic domain of a full-scale bearing roller is shown. The 2D basic domain is obtained by intersecting the 3D domain with the perpendicular axial plane, which corresponds to its half-height. The so-called "generalized electrostatics" FEMLAB application mode can be used to include both metallic and dielectric domains. In particular, the differential equations used to solve the problem of interest are obtained by approximating the time derivative of the space charge density ρ in the continuity equation.

[0082]

[0083] When J is the current density, it is as follows:

[0084]

[0085] in,

[0086] ρ0 is the space charge density t=0;

[0087] T is a time constant related to the magnitude of σ and ɛ

[0088] σ is the electrical conductivity of the metal element;

[0089] ɛ is the lubricant dielectric constant.

[0090] It can be combined with Gauss's law to obtain the partial differential equation solved by finite element method:

[0091]

[0092] where V is the electric field potential.

[0093] By integrating the electric energy density calculated by finite element method, the capacitance of the entire bearing is finally obtained as follows:

[0094]

[0095] in,

[0096] ΔV is the potential difference between the inner and outer bearing rings;

[0097] S is the surface of the lubricant in the two-dimensional basic domain;

[0098] w e is the electric energy density dS of the elementary domain associated with the surface;

[0099] l is the length of the bearing roller;

[0100] N is the number of rollers.

[0101] The capacitance of the entire bearing can be determined by determining the capacitance matrix, each element of which can be estimated by solving the Poisson equation in the lubricant domain. The boundary conditions are as follows: 1) a non-zero potential on the inner ring surface and zero potential on the outer ring and roller surfaces, which allows the inference of the capacitance values ​​c13 between the inner and outer rings and c12 between the inner ring and rollers; 2) a non-zero potential on the outer ring surface and zero potential on the inner ring and rolling element surfaces, which allows the inference of the capacitance c31 between the outer and inner rings (equal to c13), and the capacitance c32 between the outer ring and the rollers (equal to c23). For both cases, the side boundaries are set to zero normal electric field. The capacitance of the entire bearing can then be calculated as follows:

[0102]

[0103] In step S3, the development of EMTP-RV is based on the concept of a computational core for solving its system of equations. A key aspect of this architecture is the ability to easily incorporate device equations into the main network equation system. A new modified-augmented-nodal analysis system is proposed to eliminate various limitations of classic nodal or modified-nodal analysis:

[0104]

[0105] The above equation can be viewed as a general Ax=b system. For a voltage source connected between two nodes k and m, the source equation is given by:

[0106]

[0107] Insert directly into the main system r by placing 1 and −1 in the k and m columns of V respectively. The source voltage is V bkm The source current condition is explained by the transpose of the submatrix Vc. If the source is disconnected, only its diagonal cells in Vd are set to 1 and Vbkm = 0. A similar approach is used to input the other models. An ideal transformer with secondary nodes k–m, primary nodes i–j, and transformation ratio g is modeled using the following equations:

[0108]

[0109] This equation is then directly incorporated into the submatrix Dr. The equivalent row transpose appears in Dc. The ideal switch is directly included using the submatrix S. When the switch (between nodes k–m) is closed: When the same switch is opened, its current changes from 0d to 1 by setting the corresponding diagonal cell in S. The solved system now has a fixed level and is quickly reformulated every time the switch state changes. Adding a resistor and a fixed voltage drop across the switch (diode effect) with Enter Sr, Sd, and Sb.

[0110] The primary purpose of the steady-state solution in EMTP is to initialize the network state variables to minimize the natural response during startup in the time domain. The formula is the same as before, except that all variables are now complex, and the device must provide a steady-state equivalent value for each frequency in the universal harmonic steady-state solution.

[0111] When initialized from a load flow solution, the steady-state solution provides acceptable operating conditions (power flow). Extending the matrix concept to include the load-flow constraint equations, the nonlinear function to be solved becomes:

[0112]

[0113] Matrix A is the linear network matrix (left matrix), A I is the connectivity matrix L used to calculate the load flow device L LA and Ld provide the load-flow device constraint equations. The unknowns are standard network variables Load device current I and internal voltage E: The above subscripts are: L is load, PQ is PQ control source, and PV is PV control.

[0114] Compared with the prior art, the beneficial effects of the present invention are:

[0115] The present invention proposes a wind turbine lightning strike monitoring system method based on EMTP-RV. When multiple wind turbines are interconnected, a comprehensive computer monitoring system based on EMPT-RV is constructed to consider direct lightning strikes on blades or lightning strikes on the soil near the towers. This system realizes lightning strike monitoring for both direct and indirect lightning strikes, effectively reducing the damage to multiple wind turbines when struck by lightning. BRIEF DESCRIPTION OF THE DRAWINGS

[0116] Figure 1 Schematic diagram of a conductor with overvoltage and electromagnetic transient characteristics;

[0117] Figure 2 This is a schematic diagram of the grounding grid of a 600kW wind turbine system;

[0118] Figure 3 This is a schematic diagram of electrical parameters of the wind turbine tower branch;

[0119] Figure 4 Schematic diagram of the three-dimensional basic domain of a full-scale bearing roller. DETAILED DESCRIPTION

[0120] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the application equally.

[0121] Example: This invention describes a control method for a wind turbine lightning strike monitoring system based on an EMTP-RV. The invention describes a wind farm with two interconnected wind turbines. In this scenario, lightning strikes the ground near one of the wind turbines. For simplicity, the high-voltage cable is represented by an electrical model with distributed parameters.

[0122] Including steps:

[0123] S1. Electrical modeling of wind turbines, including the following steps:

[0124] S11. Establish tower equivalent model:

[0125] To improve modeling accuracy, the tower can be represented as a distributed circuit parameter and divided into several equal parts, consisting of a series inductor with a resistor. In this patent, the number of parts is 10. An attempt was made to complete the model by adding a power line model and make it as close to the real model as possible for simulation. Each part of the tower consists of a series inductor (L tower ) of the total resistance (R tower ) forms impedance (Z), and the following equations are available:

[0126]

[0127]

[0128]

[0129] Where Req is the equivalent radius of the entire tower. In the formula, H is the height of the WT tower, r1 to r3 are the upper, middle and lower radii of the WT tower, h1 and h2 are the upper, middle and lower heights of the wind turbine tower; ρ is the resistivity of the tower material, A is the conductive area of ​​the tower, C is the ratio of the inner and outer radii of the tower; μ0 is the absolute magnetic permeability of vacuum; μ is the absolute magnetic permeability of the tower material,

[0130] S12, control cable model:

[0131] Control cables are typically installed inside the wind turbine tower, 25 cm from the tower. The conductor resistance and the resistance of the control cable's metal shield should be considered based on the cable type. The equivalent inductance of the control cable conductor and the capacitance distribution between the control cable shield and the conductor are calculated using the following formula:

[0132]

[0133]

[0134] Where D12 is the distance between the center conductor and the outer shield, D is the outer insulation radius, d is the conductor radius, and L is the control cable inductance.

[0135] As mentioned previously, lightning is a high-frequency phenomenon, and this characteristic causes induction between the conductor and the control cable shield, and between the shield and the turbine tower. Conductor plate theory can be used to calculate the capacitance between the tower and the shield. The following formula is used to calculate the capacitance between the shield and the wind turbine tower:

[0136]

[0137] Where D23 is the distance between the control line and the tower, r cable : Radius of the control line.

[0138] The distributed equivalent capacitance between the tower and the ground is determined by the capacitance equation between a cylindrical conductor and the ground:

[0139]

[0140] S13. Grounding system model:

[0141] This patent uses a three-phase busbar consisting of an inductor and series capacitors for the control system model. A transformer (566V / 692V, as mentioned in the Nassel model) is used to control the control system's power supply, and a coaxial cable is also connected to this busbar. The coaxial cable is used to transmit control data and plays a significant role in inducing transient voltages during lightning strikes.

[0142] Lightning has been identified as an electrical signal in a wide DC frequency range. Therefore, the tower resistance cannot change with the transient ground potential rise. To obtain the values ​​of the grounding system components, special equations are used:

[0143]

[0144]

[0145]

[0146]

[0147] Where ρ is the soil resistivity, a is the ground electrode radius, l is the vertical ground electrode length, and ε is the dielectric constant.

[0148] S14, Lightning current model:

[0149] The tower grounding system basically consists of a square galvanized steel flange with a depth of 2m, two copper ring wires at different levels and four more copper wires connecting the diamond to the tower. All these parts of the grounding system are connected by aluminothermic welding.

[0150] The grounding system is placed in a homogeneous soil with a relatively high specific resistivity of ρ = 1200 Ω / m, a realistic scenario for a wind farm located off the coast of Croatia. A relative permittivity of ε = 9 is assumed.

[0151] The current along the ground grid configuration is governed by a set of coupled Pocklington integro-differential equations for arbitrarily shaped conductors:

[0152]

[0153] in is the induced current along the wire, is the activation function, represents the lossy medium Green function, and From graph theory. These functions are given by:

[0154]

[0155]

[0156] R0 and R1 are the distances from the source and its image to the observation point, respectively. In addition, k0 and k1 are the propagation constants for air and lossy ground, respectively:

[0157]

[0158]

[0159] where ε, r, and σ are the relative permittivity and conductivity of the ground, respectively, and ω is the operating frequency. This contains the Sommerfeld integral, constructed from the vector components of the horizontal and vertical dipoles:

[0160]

[0161] Unknown current Along the nth line segment, there are finite linearly independent basis functions f ni The sum of the unknown complex coefficients I ni :

[0162]

[0163] Using equivalent parameters yields:

[0164]

[0165] Where n is the number of local nodes on the element. Performing some math, we get the following matrix equation:

[0166]

[0167] Where Nw is the total number of wires, Nm is the number of elements on the mth antenna and Nn is the number of elements on the nth antenna. is the mutual impedance matrix between the jth observation boundary element on the mth antenna and the ith source boundary element on the nth antenna.

[0168] This yields the following mutual impedance matrix expression:

[0169]

[0170] The matrices {f} and {f′} contain the shape functions, while {D} and {D′} contain their directional derivatives.

[0171] S15, input impedance:

[0172] The input impedance is defined by the ratio:

[0173]

[0174] Where Vg and Ig are the voltage and current values ​​at the driving point. After calculating the current distribution, the feed point voltage is obtained by integrating the electric field from infinity (the distant ground where the voltage is zero) to the feed point on the electrode surface:

[0175]

[0176] In all calculations, the integration path is vertical (i.e., on the z-axis), and the frequency-dependent input impedance is multiplied by the current spectrum to obtain the frequency response of the grounding system. Finally, the transient response is calculated using an IFFT.

[0177] S2. Establishing the EMTP-RV model, specifically including the following steps:

[0178] S21. The rising edge I of the current when the nth lightning strike is received during the lightning strike is given by the following formula:

[0179]

[0180] in:

[0181]

[0182]

[0183] The falling edge equation of the current is given by:

[0184]

[0185] To model the blades and tower of a wind turbine, a constant parameter (CP) line is used, which is a frequency-independent transmission line model. The CP line is a distributed parameter model. The basic equation for a single-phase distributed parameter line is:

[0186]

[0187]

[0188] The ground electrode model used in this patent is frequently used for lightning simulation purposes on high-voltage transmission lines and towers. It considers nonlinear resistance using controlled resistance and admittance. The presence of a current source provides the option of creating a piecewise linear resistance function. For any segment k, the function can be expressed using the Norton circuit equivalent:

[0189]

[0190] is the differential at segment k:

[0191]

Claims

1. A wind turbine lightning strike monitoring system control method based on EMTP-RV, characterized in that: The method includes the following steps: S1. Modeling the overvoltage and electromagnetic transient characteristics on the wind turbine under lightning strike conditions, and based on the above modeling, monitoring and distinguishing direct lightning strikes from indirect lightning strikes; S2. Modeling the blades and tower of the wind turbine, and performing modeling analysis based on a restructured version of the electromagnetic transient program (EMTP-RV); S3. Establishing an EMTP-RV integrated computer monitoring system that can protect multiple interconnected wind turbines from the effects of lightning strikes.

2. The wind turbine lightning strike monitoring system control method based on EMTP-RV according to claim 1, characterized in that: Step S1 includes the steps of: S11. Establish tower equivalent model: Represent the tower as a distributed circuit parameter and divide it into several equal parts consisting of a series inductor with a resistor. Each section of the tower consists of a series inductor (L tower ) of the total resistance (R tower ) forms impedance (Z), and the following equations are available: Where Req is the equivalent radius of the entire tower. H is the height of the WT tower, r1 to r3 are the upper, middle, and lower radii of the WT tower, h1 and h2 are the heights of the upper, middle, and lower parts of the wind turbine tower; ρ is the resistivity of the tower material, A is the conductive area of ​​the tower, and C is the ratio of the inner and outer radii of the tower; μ0 is the absolute magnetic permeability of vacuum; and μ is the absolute magnetic permeability of the tower material. S12, control cable model: The equivalent inductance of the control cable conductor and the capacitance distribution between the control cable shield and the conductor are calculated by the following formula: Where D12 is the distance between the center conductor and the outer shield, D is the outer insulation radius, d is the conductor radius, and L is the control cable inductance. Conductor plate theory can be used to calculate the capacitance between the tower and the shield. The following formula is used to calculate the capacitance between the shield and the wind turbine tower: Where D23 is the distance between the control line and the tower, r cable : Radius of the control line. The distributed equivalent capacitance between the tower and the ground is determined by the capacitance equation between a cylindrical conductor and the ground: S13. Grounding system model: The values ​​of the grounding system components are: Where ρ is the soil resistivity, a is the ground electrode radius, l is the vertical ground electrode length, and ε is the dielectric constant. S14, Lightning current model: The current along the ground grid configuration is governed by a set of coupled Pocklington integro-differential equations for arbitrarily shaped conductors: in is the induced current along the wire, is the activation function, represents the lossy medium Green function, and From graph theory. These functions are given by: R0 and R1 are the distances from the source and its image to the observation point, respectively. In addition, k0 and k1 are the propagation constants for air and lossy ground, respectively: ε and rσ are the relative permittivity and conductivity of the ground, respectively, and ω is the operating frequency. This contains the Sommerfeld integral, constructed from the vector components of the horizontal and vertical dipoles: Unknown current Along the nth line segment, there are finite linearly independent basis functions f ni The sum of the unknown complex coefficients I ni : Using equivalent parameters yields: Where n is the number of local nodes on the element. Performing some math, we get the following matrix equation: Where Nw is the total number of wires, Nm is the number of elements on the mth antenna and Nn is the number of elements on the nth antenna. is the mutual impedance matrix between the jth observation boundary element on the mth antenna and the ith source boundary element on the nth antenna. This yields the following mutual impedance matrix expression: The matrices {f} and {f′} contain the shape functions, while {D} and {D′} contain their directional derivatives. S15, input impedance: The input impedance is defined by the ratio: Where Vg and Ig are the voltage and current values ​​at the driving point. After calculating the current distribution, the feed point voltage is obtained by integrating the electric field from infinity (the distant ground where the voltage is zero) to the feed point on the electrode surface: In all calculations, the integration path is vertical (i.e., on the z-axis), and the frequency-dependent input impedance is multiplied by the current spectrum to obtain the frequency response of the grounding system. Finally, the transient response is calculated using an IFFT.

3. The wind turbine lightning strike monitoring system control method based on EMTP-RV according to claim 1, characterized in that: In step S2, an EMTP-RV model is established, specifically including the following steps: S21. The rising edge I of the current when the nth lightning strike is received during the lightning strike is given by the following formula: in: The falling edge equation of the current is given by: To model the blades and tower of a wind turbine, a constant parameter (CP) line is used, which is a frequency-independent transmission line model. The CP line is a distributed parameter model. The basic equation for a single-phase distributed parameter line is: For any segment k, the function can be expressed equivalently using a Norton circuit:

4. The wind turbine lightning strike monitoring system control method based on EMTP-RV according to claim 3, characterized in that: To minimize the natural response during time domain startup: When initialized from a load flow solution, the steady-state solution provides acceptable operating conditions (power flow). Extending the matrix concept to include the load-flow constraint equations, the nonlinear function to be solved becomes: Matrix A is the linear network matrix (left matrix), A I is the connectivity matrix L used to calculate the load flow device L LA and Ld provide the load-flow device constraint equations. The unknowns are standard network variables Load device current I and internal voltage E: The above subscripts are: L is load, PQ is PQ control source, and PV is PV control.

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