Lightning positioning optimization method and system for correcting the influence of terrain and geological parameters on lightning electromagnetic wave propagation and medium

Abstract

The application is a lightning positioning optimization method and system and a medium for correcting the influence of terrain and geological parameters on lightning electromagnetic wave propagation. The method grids the area around the lightning detection station involved in lightning positioning. Using the ground and ionosphere electromagnetic wave propagation model, the time delay correction value and parameter correction coefficient of lightning electromagnetic wave propagation from the preliminary lightning position to the lightning detection station are calculated without considering terrain and geological parameters and considering terrain and geological parameters. When the closest grid point is found as the lightning point in the time delay correction table and parameter correction coefficient table corresponding to the lightning detection station involved in positioning, the time delay correction value and parameter correction coefficient corresponding to each lightning detection station are used to correct the lightning detection station, and the corrected waveform arrival time and corrected characteristic parameters corresponding to each lightning detection station are obtained. The accurate lightning position and accurate lightning characteristic parameters are calculated.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lightning location, and particularly relates to a lightning location optimization method and system for correcting the influence of terrain and geological parameters on lightning electromagnetic wave propagation and a medium. BACKGROUND

[0002] The lightning location technology currently adopted is to collect lightning electromagnetic waves by constructing a lightning detection network through a VLF / LF frequency band detection device, and to determine the lightning location and inverse the lightning parameters by means of the electromagnetic wave waveform parameters and a multi-station positioning algorithm. Due to the influence of geographical environment, system hardware conditions, station layout and algorithm, etc., the lightning location accuracy and parameter inversion accuracy of lightning location networks in different regions are different. In the process of lightning electromagnetic wave propagation along the ground, the lightning electromagnetic wave is influenced by factors such as irregular terrain with high and low fluctuations, limited soil conductivity, soil anisotropy, etc., so that the waveform peak value and its position, rising edge time and half-peak time, etc. of the electromagnetic wave are changed.

[0003] However, the existing lightning location algorithm basically assumes that the VLF / LF frequency band electromagnetic wave propagates on a standard earth ellipsoid model, without considering the influence of the fluctuating terrain and limited conductivity on electromagnetic wave propagation, especially in complex terrain environment, the lightning electromagnetic wave waveform changes more obviously, which introduces significant errors to the lightning location position and inverted parameters. SUMMARY

[0004] In view of the deficiencies of the prior art, the present application provides a lightning location optimization method and system for correcting the influence of terrain and geological parameters on lightning electromagnetic wave propagation and a medium, which considers the influence of terrain and geological parameters on lightning electromagnetic wave propagation in the lightning location method, proposes a quantitative correction method, and realizes more accurate calculation of lightning location position and lightning parameters.

[0005] To achieve the above purpose, the lightning location optimization method for correcting the influence of terrain and geological parameters on lightning electromagnetic wave propagation designed by the present application has the following steps:

[0006] Step 1, establish an electromagnetic wave propagation model of the ground and the ionosphere, calculate the time delay correction value of lightning electromagnetic wave propagation from the preliminary lightning position to the lightning detection station according to the waveform arrival time under the consideration of terrain and geological parameter factors and the waveform arrival time under the consideration of terrain and geological parameter factors, and calculate the parameter correction coefficient of lightning electromagnetic wave propagation from the preliminary lightning position to the lightning detection station according to the waveform characteristic parameters under the consideration of terrain and geological parameter factors and the waveform characteristic parameters under the consideration of terrain and geological parameter factors;

[0007] Step 2, draw n equidistant circles respectively with each lightning detection station participating in lightning location as the center, draw equi-angle rays with a preset azimuth angle through the corresponding center on each equidistant circle, and the intersection of each equidistant circle and the corresponding equi-angle ray is a grid point in the area of the corresponding lightning detection station; take all grid points in the area of each lightning detection station as the preliminary lightning location, calculate the time delay correction value and the parameter correction coefficient corresponding to each lightning detection station for all grid points in its own area, and make the time delay correction table and the parameter correction coefficient table corresponding to the time delay correction value and the parameter correction coefficient, and take the time delay correction table and the parameter correction coefficient table corresponding to each lightning detection station as the information index of the lightning detection station;

[0008] Step 3, assuming that the earth is a standard ellipsoid model, the preliminary lightning occurrence time and the preliminary lightning location are calculated by using the existing lightning location method through the waveform arrival time of the lightning electromagnetic wave received by each lightning detection station participating in lightning location; and the preliminary characteristic parameters of lightning are calculated through the waveform characteristic parameters extracted from the waveform of the lightning electromagnetic wave received by each lightning detection station participating in lightning location.

[0009] Step 4, according to the preliminary lightning location and the information of the lightning detection stations participating in lightning location, the corresponding nearest grid point closest to the corresponding preliminary lightning location is found on each equidistant circle corresponding to the corresponding lightning detection station; and according to the information index of each lightning detection station, the time delay correction value and the parameter correction coefficient corresponding to each lightning detection station are determined when each nearest grid point is taken as the lightning stroke point.

[0010] Step 5, the time delay correction is performed on each lightning detection station participating in lightning location to obtain the corrected waveform arrival time corresponding to each lightning detection station, and then the accurate lightning occurrence time and the accurate lightning location are calculated by using the lightning location method; the characteristic parameter correction is performed on each lightning detection station participating in lightning location to obtain the corrected characteristic parameter corresponding to each lightning detection station, and then the accurate characteristic parameter of lightning is calculated.

[0011] Further, in step 1, the specific steps for establishing the electromagnetic wave propagation model between the ground and the ionosphere are as follows

[0012] Step 1-1, assuming that the lightning electromagnetic wave propagates in the r-z plane of the cylindrical coordinate system, wherein the r direction is along the ground surface direction, the z direction is the height direction, and the φ direction is the direction satisfying the right-hand rule with the r direction and the z direction, the gradient of the φ direction is always 0, the Maxwell curl equation group of the vertical electric field and the horizontal magnetic field of the VLF / LF lightning electromagnetic wave propagating in the r-z plane between the ground and the ionosphere is derived from the Maxwell original equation group, and the propagation of the lightning electromagnetic wave from the preliminary lightning location to the lightning detection station is solved by using the Maxwell curl equation group.

[0013] Step 1-2, a lightning current excitation source is applied at the initial position of lightning, the lightning current excitation source is a lightning current return stroke channel, which is placed on the symmetry axis of the two-dimensional cylindrical coordinate system, and the base current of the return stroke discharge channel is assumed to be , the lightning current gradually develops upward from the ground, the propagation speed is v, and the amplitude of the lightning current attenuates with height z according to the law f(z), so the current distribution at height z at time t is , the current distribution at height z at time t is The expression is

[0014] ;

[0015] Step 1-3, difference discretization is performed on the Maxwell curl equation set, and the E , H components in the electromagnetic field are discretized by taking an alternating sampling method in space and time, that is, each E and H field component is surrounded by four corresponding H and E field components, and the Maxwell curl equation set containing time variables is converted into a Maxwell discrete equation set, and the space electromagnetic field is solved by frog jump format step-by-step update and promotion in the time domain. The space format distribution in the cylindrical coordinate system adopts Yee cell, and the grid points of the Yee cell are set as (i,j,k), that is, i,j,k represents the grid point in the r direction, i , φ direction, j、 z direction k . The entire calculation domain is composed of many identical Yee cells connected together, and the electric field and the magnetic field also exist in the time step, that is, the update of the electric field and the magnetic field is different by half a time step.

[0016] Step 1-4, the waveform arrival time t a and the characteristic parameter Pr a are extracted from the lightning vertical electric field E z waveform or horizontal magnetic field H φ waveform received by the lightning detection station considering the terrain and geological parameter factors; the waveform arrival time t b and the characteristic parameter Pr b are extracted from the lightning vertical electric field E z waveform or horizontal magnetic field H φ waveform received by the lightning detection station without considering the terrain and geological parameter factors; the formula of the time delay correction value is , and the formula of the parameter correction coefficient is k=Pr a / Pr b .

[0017] Further, in step 1-1, the Maxwell original equations are

[0018] ;

[0019] In the above equations,

[0020] E is the electric field intensity vector in the wave propagation,

[0021] B is the magnetic induction intensity vector in the wave propagation,

[0022] p is the free charge,

[0023] e0 is the permittivity in vacuum,

[0024] j J is the conduction current density vector, ,

[0025] s is the conductivity,

[0026] m0 is the magnetic permeability.

[0027] Further, in step 1-1, the Maxwell curl equations based on the vertical electric field and horizontal magnetic field of the lightning discharge channel are

[0028] ;

[0029] where,

[0030] Eris the component of the electric field intensity E in the r direction,

[0031] Ezis the component of the electric field intensity E in the z direction,

[0032] Bphis the component of the magnetic field intensity B in the f direction.

[0033] Further, in step 1-2, the Heidler double exponential function is used to construct the ground flash return stroke base current The ground flash return stroke base current The expression is

[0034] ;

[0035] where,

[0036] I 01 represents the breakdown current,

[0037] I 02 represents the corona current peak,

[0038] η represents a breakdown current correction factor,

[0039] τ1 represents a waveform rise time of the breakdown current,

[0040] τ2 represents a waveform fall time of the breakdown current,

[0041] τ3 represents a waveform rise time of the corona current,

[0042] τ4 represents a waveform fall time of the corona current.

[0043] Further, in step 1-2, the MTLE engineering model is used as the current return stroke model, and the base current attenuates in an exponential form during the upward development process, so the current distribution at the height z of the channel at time t is The expression is

[0044] ;

[0045] wherein,

[0046] I(z, t) is the current at the height z of the channel at time t,

[0047] z is the height of the return stroke discharge channel,

[0048] e -z / λ is the exponential attenuation of the lightning current amplitude with height z,

[0049] λ is an attenuation factor,

[0050] v is the propagation speed of the lightning current.

[0051] Further, in step 1-3, the Maxwell discrete equation set is

[0052] ;

[0053] wherein,

[0054] Δt represents a time step,

[0055] E r represents the component of the electric field strength E in the r direction,

[0056] E z represents the component of the electric field strength E in the z direction,

[0057] represents the component of the magnetic field strength H in the φ direction,

[0058] μ represents the magnetic permeability,

[0059] ε represents the dielectric constant.

[0060] Further, in step 1-4, the waveform arrival time is extracted based on a waveform peak point, a waveform rising half-peak point or a waveform rising derivative maximum point, and the characteristic parameters include a waveform peak value, a wave head time, a wave tail time, a waveform half-peak width and an electric field amplitude.

[0061] Further, in step 5, the lightning detection stations participating in lightning location respectively receive the waveform arrival time of the lightning electromagnetic wave , and the closest grid point is taken as the lightning stroke point, the lightning detection stations corresponding time delay correction values are , and the lightning detection stations corresponding corrected waveform arrival times are T 21 -Δt1′, T 31 -Δt2′ and T n1 -Δt3′ respectively. n

[0062] Further, in step 5, the lightning detection stations participating in lightning location respectively receive the characteristic parameters of the lightning electromagnetic wave , and the closest grid point is taken as the lightning stroke point, the lightning detection stations corresponding parameter correction coefficients are , and the lightning detection stations corresponding corrected characteristic parameters are .

[0063] Further, in step 4, the method for finding the corresponding closest grid point closest to the corresponding preliminary lightning location is to calculate the distance R and the preset azimuth angle θ of the preliminary lightning location relative to each lightning detection station, and find the grid point closest to the preliminary lightning location in the corresponding equidistant circle of each lightning detection station.

[0064] Further, in step 2, the equidistant circle radii are R1, R2, R3, …, R a , and R1, R2, R3, …, R a are all 6-15 kilometers, wherein a in R a is 20-50; and the preset azimuth angles of the equi-angle rays are θ1, θ2, θ3, …, θ b , and θ1, θ2, θ3, …, θ b are all 1-3°, wherein b in θ b is floor(360 / θ), and floor(·) represents the rounding operation. ​​

[0065] Further, in step 3, the lightning positioning method is to solve the minimum value of the cost function composed of a nonlinear equation set, so as to obtain the preliminary lightning occurrence time t initial , the preliminary lightning position P(x initial , y initial ), (x initial , y initial ) representing the longitude and latitude of the lightning stroke point; the nonlinear equation set includes the observation equation of the arrival time T i of the lightning electromagnetic wave received by the lightning detection station S i and the observation equation of the measured azimuth angle β initial between the preliminary lightning position P(x initial , y i ) and the lightning detection station S i , and the nonlinear equation set is

[0066] ;

[0067] wherein,

[0068] T i is the arrival time of the lightning electromagnetic wave received by a certain participating lightning detection station S i ,

[0069] t is the lightning occurrence time,

[0070] S Pi is the distance from the lightning stroke position P(x, y) to a certain participating lightning detection station S i , S Pi needs to be calculated on the ellipsoid,

[0071] c is the electromagnetic wave propagation speed,

[0072] is the time measurement error,

[0073] β i is the measured azimuth angle of the lightning electromagnetic wave received by a certain participating lightning detection station S i ,

[0074] β Pi is the calculated azimuth angle of the lightning stroke position P(x, y) to a certain participating lightning detection station S i , β Pi needs to be calculated on the ellipsoid,

[0075] is the angle measurement error,

[0076] The coordinates of P(x, y) are known as , wherein i=1, 2, 3…n;

[0077] The nonlinear equation set is recorded in the following simple form

[0078] ;

[0079] Wherein,

[0080] r i is an observation,

[0081] F i (t, x l , y) is an unknown function,

[0082] is a measurement error.

[0083] Further, in step 3, in the simple form of the nonlinear equation set, when , the minimum value of the cost function of the simple form of the nonlinear equation set is That is, the preliminary lightning occurrence time t initial , the preliminary lightning location P (x initial , y initial )

[0084] A computer readable storage medium, the computer readable storage medium stores a computer program, its particularity lies in: the computer program is executed by the processor to realize the steps of the above lightning positioning optimization method.

[0085] The advantages of the present application are:

[0086] 1. In the ground and ionosphere electromagnetic wave propagation model, the lightning electromagnetic wave waveform considering the terrain, geological parameters and not considering the terrain, geological parameters is calculated by electromagnetic wave propagation numerical simulation, the time delay correction value and parameter correction coefficient corresponding to the preliminary lightning location of each lightning detection station are obtained, the real terrain fluctuation and real soil conductivity are considered in the electromagnetic wave propagation numerical simulation, so the lightning positioning optimization effect can be greatly improved, and the lightning positioning accuracy and parameter inversion accuracy are improved.

[0087] 2、The present application carries out target area gridding on the participating lightning detection station, that is, a plurality of equidistant circles are drawn respectively with each lightning detection station as the center, and equi-angle rays with a preset azimuth angle are drawn respectively on each equidistant circle through the corresponding center, the intersection of each equidistant circle and equi-angle ray is a grid point in the target area, and the time delay correction value and parameter correction coefficient of the lightning detection station participating in lightning positioning corresponding to all grid points in its own area are calculated by using the ground and ionosphere electromagnetic wave propagation model, which can greatly reduce the simulation calculation workload, and a equi-angle ray only needs to carry out simulation calculation once to obtain the lightning electromagnetic wave waveform of each grid point along the equi-angle ray;

[0088] 3、The present application makes the time delay correction value and parameter correction coefficient of the lightning detection station participating in lightning positioning corresponding to all grid points in its own area into corresponding time delay correction tables and parameter correction coefficient tables, and takes the time delay correction table and parameter correction coefficient table corresponding to each lightning detection station as the information index of the lightning detection station, that is, the time-consuming numerical simulation is carried out in advance, and in actual business application, only the information index of each lightning detection station needs to be queried, which greatly improves the efficiency of lightning positioning optimization;

[0089] 4、The present application finds the closest grid point closest to the preliminary lightning position on the equidistant circle corresponding to the lightning detection station participating in lightning positioning according to the preliminary lightning position, and determines the time delay correction value and parameter correction coefficient corresponding to each lightning detection station when the closest grid point is taken as the lightning stroke point according to the information index of each lightning detection station participating in lightning positioning, which can improve the retrieval efficiency and is easy to realize in business;

[0090] 5、The present application calculates the corrected waveform arrival time of the lightning electromagnetic wave received by each participating lightning detection station through the time delay correction value corresponding to the closest grid point of each participating lightning detection station, and obtains the accurate lightning occurrence time and accurate lightning position by using the existing lightning positioning method; the corrected characteristic parameter of the lightning electromagnetic wave received by each participating lightning detection station is calculated through the parameter correction coefficient corresponding to the closest grid point of each participating lightning detection station, and the accurate characteristic parameter of lightning is obtained by re-computation;

[0091] The application is a lightning positioning optimization method and system and a medium for correcting the influence of terrain and geological parameters on lightning electromagnetic wave propagation. The method not only establishes a ground and ionosphere electromagnetic wave propagation model, simulates and calculates the time delay correction value and parameter correction coefficient of lightning electromagnetic wave propagation from the preliminary lightning position to the lightning detection station under the condition of considering terrain and geological parameters and not considering terrain and geological parameters, but also grids the target area of the lightning detection station involved in lightning positioning, calculates the time delay correction table and parameter correction coefficient table of all grid points in the corresponding area of the lightning positioning, and recalculates the accurate lightning occurrence time, accurate lightning position and accurate lightning characteristic parameters according to the corresponding lightning preliminary occurrence time, lightning preliminary position and lightning preliminary characteristic parameters of the lightning detection station involved in lightning positioning, and the time delay correction value and parameter correction coefficient of the lightning detection station involved in lightning positioning when the nearest grid point is taken as the lightning point. BRIEF DESCRIPTION OF DRAWINGS

[0092] Figure 1 The flow chart of the lightning positioning optimization method for correcting the influence of terrain and geological parameters on lightning electromagnetic wave propagation of the application;

[0093] Figure 2 The principle schematic diagram of the application;

[0094] Figure 3 The space format distribution diagram under the column coordinate system of the application;

[0095] Figure 4a The overall diagram of the electric field waveform received by a certain lightning detection station under the condition of considering terrain and geological parameters and not considering terrain and geological parameters;

[0096] Figure 4b The local enlarged diagram of the electric field waveform in Figure 4a

[0097] Figure 5 The schematic diagram of the target area gridding of the lightning detection station of the application;

[0098] Figure 6 The method schematic diagram of finding the nearest grid point closest to the preliminary lightning position in the application;

[0099] Figure 7a The altitude distribution diagram within a range of 300 km with a certain lightning detection station in Figures 4a-4b as the center;

[0100] Figure 7b The soil conductivity distribution diagram within a range of 300 km with a certain lightning detection station in Figures 4a-4b as the center;

[0101] Figure 7c The soil conductivity distribution diagram within a range of 300 km with a certain lightning detection station in Figures 4a-4b ​The image shows the distribution of lightning electric field amplitude correction coefficients within a 300km radius of a certain lightning detection station.

[0102] Figure 7d For Figures 4a-4b The image shows the distribution of lightning electric field time delay correction values ​​within a 300km radius of a certain lightning detection station.

[0103] Figure 8 This is a location distribution diagram of a lightning strike point and the seven detection stations involved in the positioning in an embodiment of the present invention;

[0104] Figure 8a for Figure 8 Topographic profile of the area between detection station No. 1 and the lightning strike point;

[0105] Figure 8b for Figure 8 Topographic profile of the area between detection station No. 2 and the lightning strike point;

[0106] Figure 8c for Figure 8 Topographic profile of the area between detection station No. 3 and the lightning strike point;

[0107] Figure 8d for Figure 8 Topographic profile of the area between detection station No. 4 and the lightning strike point;

[0108] Figure 8e for Figure 8 Topographic profile of the area between detection station No. 5 and the lightning strike point;

[0109] Figure 8f for Figure 8 Topographic profile of the area between detection station No. 6 and the lightning strike point;

[0110] Figure 8g for Figure 8 Topographic profile of the area between detection station No. 7 and the lightning strike point;

[0111] Figure 9a for Figure 8a Waveforms of the vertical electric field (Ez) at probe station No. 1 in the diagram, considering and not considering topographic and geological parameters;

[0112] Figure 9b for Figure 8b Waveforms of the vertical electric field (Ez) at probe station No. 2 in the image, considering and not considering topographic and geological parameters;

[0113] Figure 9c for Figure 8c Waveforms of the vertical electric field (Ez) at probe station No. 3 in the image, considering and not considering topographic and geological parameters;

[0114] Figure 9d for Figure 8d Waveforms of the vertical electric field (Ez) at probe station No. 4 in the image, considering and not considering topographic and geological parameters;

[0115] Figure 9e for Figure 8e Waveforms of the vertical electric field (Ez) at probe station No. 5 in the image, considering and not considering topographic and geological parameters;

[0116] Figure 9f for Figure 8f Waveforms of the vertical electric field (Ez) at probe station No. 6 in the image, considering and not considering topographic and geological parameters;

[0117] Figure 9g for Figure 8g Waveforms of the vertical electric field (Ez) at probe station No. 7 in the image, considering and not considering topographic and geological parameters;

[0118] Figure 10 This is a block diagram of the lightning location optimization system of the present invention, which corrects the influence of terrain and geological parameters on the propagation of lightning electromagnetic waves. Detailed Implementation

[0119] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0120] In the description of this invention, it should be understood that the terms "length", "width", "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 the invention.

[0121] like Figure 1 As shown, the lightning location optimization method of the present invention, which corrects the influence of terrain and geological parameters on the propagation of lightning electromagnetic waves, includes the following steps:

[0122] Step 1: Establish a model for the propagation of electromagnetic waves between the ground and the ionosphere to obtain the propagation trajectory of lightning electromagnetic waves from the initial position P(x) of the lightning strike. initial y initial The time delay correction value and parameter correction coefficient propagating to the lightning detection station S.

[0123] In the electromagnetic wave propagation model of the ground and the ionosphere, the ground is regarded as an irregular surface with topographic relief and geological parameter variation, and the ionosphere is regarded as a layer of medium with conductivity σ varying with height. The principle diagram of lightning electromagnetic wave propagation from lightning electromagnetic wave excitation source to the detection station in the cylindrical coordinate system is shown in FIG. 1. Figure 2

[0124] Step 1-1, assuming that the lightning electromagnetic wave propagates in the two-dimensional plane r-z plane in the cylindrical coordinate system, where the r direction is along the ground surface direction, the z direction is the height direction, and the φ direction is the direction satisfying the right-hand rule with the r direction and the z direction, and the gradient of the φ direction is always 0. The Maxwell curl equation of the vertical electric field and the horizontal magnetic field of the VLF / LF lightning electromagnetic wave propagating in the ground and the ionosphere r-z plane is derived from the Maxwell original equation set. The propagation of the lightning electromagnetic wave from the lightning preliminary position P (x initial , y initial ) to the lightning detection station S is solved by the Maxwell curl equation set.

[0125] Specifically, the Maxwell original equation set is

[0126] ;

[0127] In the above formula,

[0128] E is the electric field intensity vector in the electric wave propagation,

[0129] B is the magnetic induction intensity vector in the electric wave propagation,

[0130] ρ is the free charge,

[0131] ε0 is the dielectric constant in the vacuum,

[0132] j is the conduction current density vector, ,

[0133] σ is the conductivity,

[0134] μ0 is the magnetic permeability.

[0135] For a wide-area lightning positioning system, the vertical electric field and the horizontal magnetic field of the lightning discharge channel are mainly detected, and the Maxwell curl equation set based on the vertical electric field and the horizontal magnetic field of the lightning discharge channel is

[0136] ;

[0137] wherein,

[0138] E r represents the component of the electric field intensity E in the r direction,

[0139] ​denotes the component of the electric field strength E in the z direction,

[0140] denotes the component of the magnetic field strength B in the φ direction.

[0141] Step 1-2, a lightning current excitation source is applied at the lightning preliminary position P(x initial , y initial ), the lightning current excitation source is a lightning current return stroke channel, is placed on the symmetry axis of the two-dimensional cylindrical coordinate system, it is assumed that the base current of the return stroke discharge channel at the bottom is, the lightning current gradually develops upward from the ground, the propagation speed is v, the amplitude of the lightning current attenuates according to the law f(z) with the height z, then the current distribution at the channel height z at time t is , wherein the current distribution at the channel height z at time t is The expression is

[0142] ,

[0143] According to the lightning electromagnetic wave propagation equation set in step 1-1, the model of the lightning electromagnetic wave excitation source at the lightning preliminary position P(x initial , y initial ) propagating to the lightning detection station S in the cylindrical coordinate system is obtained.

[0144] Specifically, the Heidler double exponential function is used to construct the base current of the ground flash return stroke , then the base current of the ground flash return stroke The expression is

[0145] ;

[0146] wherein,

[0147] I 01 represents the breakdown current, which is 9.9 kA,

[0148] I 02 represents the peak value of the corona current, which is 7.5 kA,

[0149] η represents the breakdown current correction factor, which is 0.845,

[0150] τ1 represents the waveform rise time of the breakdown current, which is 0.072 μs,

[0151] τ2 represents the waveform fall time of the breakdown current, which is 5 μs,

[0152] τ3 represents the waveform rise time of the corona current, which is 100 μs,

[0153] τ4 represents the waveform fall time of the corona current, which is 6 μs.

[0154] In addition, the MTLE (modified transmission line models with exponential decay of the current with height) engineering model is used as the current return stroke model, and the base current attenuates in an exponential form during upward development, so that the current distribution at the channel height z at time t is The expression is

[0155] ;

[0156] wherein,

[0157] I(z, t) is the current at the channel height z at time t,

[0158] z is the height of the return stroke discharge channel, and the maximum value is 7500 m,

[0159] e -z / λ is an exponential decay of the lightning current amplitude with height z,

[0160] λ is an attenuation factor, and the value is 2000 m,

[0161] v is the propagation speed of the lightning current, and the value is 1.5*10 8 m / s.

[0162] Steps 1-3, the Maxwell curl equation set is discretely separated, and the E , H component in the electromagnetic field is discretely separated by adopting an alternating sampling method in space and time, that is, each E and H field component will be surrounded by four corresponding H and E field components, the Maxwell curl equation set containing time variables is converted into a Maxwell discrete equation set through this discretization method, and the space electromagnetic field is solved by frog jump format step by step in the time domain, the space format distribution in the cylindrical coordinate system adopts the Yee cell, the grid points of the Yee cell are set as (i, j, k), that is, i,j,k ) represents the grid point of r direction, i , φ direction, j、 z direction, k the entire calculation domain is composed of many identical Yee cells connected together, and the electric field and the magnetic field also exist in the time step, that is, the update of the electric field and the magnetic field is different by half a time step.

[0163] The Maxwell discrete equation set is

[0164] ;

[0165] wherein,

[0166] Δt represents a time step,

[0167] E r represents the component of the electric field intensity E in the r direction,

[0168] E z represents the component of the electric field intensity E in the z direction,

[0169] represents the component of the magnetic field intensity H in the φ direction,

[0170] μ represents the magnetic permeability,

[0171] ε represents the dielectric constant.

[0172] In view of the limited computer capacity, the numerical solution of the above Maxwell discrete equation set can only be carried out in a limited area, and in order to simulate the open-field electromagnetic wave propagation process, the absorbing boundary condition must be given at the boundary of the calculation area.

[0173] The magnetic field component of the electromagnetic wave propagating in the medium is split into two sub-components and , and Therefore, the Maxwell curl equation will be rewritten as:

[0174] ;

[0175] wherein σ is the electrical conductivity, and μ is the magnetic permeability; when , the equation degenerates into the Maxwell equation of free space; when the electrical conductivity and the magnetic permeability are not 0, the medium becomes a lossy medium, and the electromagnetic wave will be attenuated in the medium.

[0176] In addition, in the above steps 1-3, the terrain elevation data is obtained through digital elevation model data, and the geological parameter is represented by soil conductivity.

[0177] Step 1-4, from the lightning vertical electric field E z waveform or horizontal magnetic field H φ waveform received by the lightning detection station under the consideration of terrain and geological parameter factors, respectively extract the waveform arrival time t a and the characteristic parameter Pr a ; from the lightning vertical electric field E z waveform or horizontal magnetic field H φ waveform received by the lightning detection station without considering the terrain and geological parameter factors, respectively extract the waveform arrival time t b and the characteristic parameter Prb The formula of the time delay correction value is The formula of the parameter correction coefficient is k = Pr a / Pr b .

[0178] Specifically, the waveform arrival time is extracted based on a waveform peak point, a waveform rising edge half-peak point or a waveform rising edge derivative maximum point, and the characteristic parameters include a waveform peak value, a wave head time, a wave tail time, a waveform half-peak width and an electric field amplitude.

[0179] Specifically, the influence of the terrain and geological parameters is not considered, that is, a flat and lossless ground surface, and the influence of the terrain and geological parameters is considered, that is, a rolling and lossy ground surface.

[0180] In this embodiment, a certain place is taken as a lightning detection station, and the electric field waveforms received by the lightning detection station when the terrain and geological parameters are considered and when the terrain and geological parameters are not considered are as shown in FIG. Figures 4a-4b When a lightning current as represented by the current distribution expression in step 1-2 above occurs 300 km to the west of the lightning detection station, the electric field waveforms obtained in the flat and lossless ground surface and the rolling and lossy ground surface are as shown in FIG. Figure 4a , wherein FIG. Figure 4b is an overall diagram of the electric field waveform, and FIG. Figures 4a-4b is a local enlarged diagram of the electric field waveform.The rolling ground surface model in FIG.

[0181] In the ground and ionosphere electromagnetic wave propagation model, the lightning electromagnetic waveforms with and without considering the terrain and geological parameters are calculated through electromagnetic wave propagation numerical simulation, the time delay correction value and the parameter correction coefficient corresponding to the preliminary lightning location of each lightning detection station are obtained, the real terrain undulation and the real soil conductivity are considered in the electromagnetic wave propagation numerical simulation, and therefore the lightning positioning optimization effect can be greatly improved, and the lightning positioning accuracy and the parameter inversion accuracy are improved.

[0182] Step 2: Taking the lightning detection stations S1, S2, S3, …, SN participating in lightning positioning as the centers, draw equidistant circles with radii R1, R2, R3, …, RN, respectively, and then draw lines with a preset azimuth angle θ1, θ2, θ3, …, θN through the corresponding circle centers on the equidistant circles, respectively. n a b ​The intersection of the equidistant circle and the equi-angle ray is the corresponding lightning detection station S1, S2, S3,..., S n The grid points in the region; the lightning detection stations S1, S2, S3,..., S n The grid points in the region; the lightning detection stations S1, S2, S3,..., S initial , y initial The grid points in the region; the lightning detection stations S1, S2, S3,..., S n The time delay correction value and the parameter correction coefficient corresponding to all the grid points in the region of each lightning detection station, and the time delay correction table and the parameter correction coefficient table corresponding to all the grid points in the region of each lightning detection station are made, and the time delay correction table and the parameter correction coefficient table corresponding to each lightning detection station are taken as the information index of the lightning detection station; steps 1-1~1-4 can be implemented in advance for the target region, and the time delay correction table and the parameter correction coefficient table of the region are obtained in advance.

[0183] Specifically, the schematic diagram of the lightning detection station for target region gridding of the present application is shown in Figure 5 In addition, the radii of the equidistant circles are R1, R2, R3,..., R a , R1, R2, R3,..., R a are all 6~15 kilometers, wherein R a a takes a value of 20~50; the preset azimuth angles of the equi-angle rays are θ1, θ2, θ3,..., θ b , θ1, θ2, θ3,..., θ b are all 1~3°, wherein θ b b takes a value of floor(360 / θ), and floor(·) represents the rounding operation.

[0184] The present application carries out target region gridding for the lightning detection station participating in lightning positioning, that is, the equidistant circles with radii R1, R2, R3,..., R a are drawn with each lightning detection station as the center, the equi-angle rays with preset azimuth angles θ1, θ2, θ3,..., θ b are drawn, the intersection of the circle arc and the ray is the grid point in the target region, and the time delay correction value and the parameter correction coefficient corresponding to all the grid points in the region of the participating lightning detection station are calculated.

[0185] Step 3, assuming that the earth is a standard ellipsoid model, through the participating lightning detection stations S1, S2, S3,..., S nThe arrival times of the received lightning electromagnetic waves, T1, T2, T3, ..., T, are respectively. n The initial occurrence time t of lightning was calculated using existing lightning location methods. initial Preliminary location of lightning P(x) initial y initial ); and then through the participating lightning detection stations S1, S2, S3, ..., S n Each received lightning electromagnetic wave waveform yields waveform feature parameters Pr1, Pr2, Pr3, ..., Pr. n The preliminary characteristic parameter Pr of lightning was calculated. initial .

[0186] Existing lightning location methods assume that the Earth is a standard ellipsoidal model (such as the WGS-84 model), and include time difference methods or grid search methods.

[0187] Specifically, the existing lightning location method obtains the initial lightning occurrence time t by solving for the minimum value of a cost function composed of a system of nonlinear equations. initial Preliminary location of lightning P(x) initial y initial (x) initial y initial () represents the longitude and latitude of the lightning strike point; the nonlinear equation set includes the lightning detection station S i The arrival time T of the received lightning electromagnetic wave i The observation equation and the preliminary location of lightning P(x) initial y initial ) and lightning detection station S i The measured azimuth angle β between i The observation equations, the nonlinear equation set is as follows:

[0188] ;

[0189] in,

[0190] T i For a participating lightning detection station S i The arrival time of the received lightning electromagnetic wave,

[0191] t represents the time of the lightning strike.

[0192] S Pi From the lightning strike location P(x, y) to a participating lightning detection station S i The distance S Pi The calculations need to be performed on an ellipsoid.

[0193] c is the speed of electromagnetic wave propagation.

[0194] For time measurement error,

[0195] β i For a participating lightning detection station S i The measured azimuth angle of the received lightning electromagnetic wave.

[0196] β Pi From the lightning strike location P(x, y) to a participating lightning detection station S i Calculate the azimuth angle, β Pi The calculations need to be performed on an ellipsoid.

[0197] To account for angle measurement error,

[0198] The coordinates are known to be , where i = 1, 2, 3…n.

[0199] The nonlinear equations are denoted in the following simple form.

[0200] ;

[0201] in,

[0202] r i For observation purposes,

[0203] F i (t, x) l (y) is an unknown function.

[0204] This represents measurement error.

[0205] The goal of lightning location calculation is to obtain the optimal estimate of the target's location using observations that contain errors. When the observation errors are small and follow a normal distribution, the distribution of the unknowns also follows a multidimensional normal distribution, in which case the errors are neglected. That is, when When the cost function of the simple form of the nonlinear equation system is minimized. That is, the initial occurrence time t of lightning. initia Preliminary location of lightning P(x) initial y initial ).

[0206] Step 4, based on the initial location of the lightning P(x) initial y initial Information on participating lightning detection stations, including S1, S2, S3, ..., S... n Find the closest initial position P(x) of the lightning on the corresponding equally spaced circles and in the corresponding directions. initial y initial The nearest lattice points A1, A2, A3, ..., A of )n Then, based on the lightning detection stations S1, S2, S3, ..., S... n Each information index determines the nearest grid point A1, A2, A3, ..., A n When acting as a lightning strike point, lightning detection stations S1, S2, S3, ..., S n The corresponding time delay correction values ​​are Δt1′, Δt2′, Δt3…, Δt n And parameter correction coefficients k1′, k2′, k3′…, k n ′.

[0207] This invention creates a time delay correction table and a parameter correction coefficient table for each participating lightning detection station, corresponding to the time delay correction values ​​and parameter correction coefficients of all grid points within its own region. The time delay correction table and parameter correction coefficient table corresponding to each lightning detection station are used as the information index of that lightning detection station. In other words, time-consuming numerical simulations are carried out in advance. In actual business applications, it is only necessary to query the information index of each lightning detection station, which greatly improves the efficiency of lightning location optimization.

[0208] Specifically, find the closest point to the initial location of the lightning, P(x). initial y initial The nearest lattice points A1, A2, A3, ..., A of ) n The method is to calculate the initial location of the lightning P(x) initial y initial Relative to the distance R and preset azimuth angle θ of each lightning detection station, at lightning detection stations S1, S2, S3, ..., S... n The grid point closest to both distance R and the preset azimuth angle θ in the corresponding equally spaced circles is the initial lightning position P(x). initial y initial The nearest lattice points A1, A2, A3, ..., A of ) n .

[0209] This invention finds the closest grid point to the initial lightning location on the equally spaced circles corresponding to the participating lightning detection stations, based on the initial lightning location. Then, based on the information index of each participating lightning detection station, it determines the time delay correction value and parameter correction coefficient corresponding to the participating lightning detection stations when the closest grid point is taken as the lightning strike point. This method can improve retrieval efficiency and is easy to implement in business.

[0210] like Figure 6 The diagram shown illustrates the method for finding the closest grid point to the initial location of a lightning strike in this invention. From... Figure 6 As can be seen from the diagram, when two equally spaced circles are drawn with S1 and S2 as the centers, the initial location of the lightning is at point P(x). initial y initial), the distance R of point P relative to lightning detection station S1 is calculated A1 and preset azimuth angle θ A1 , the distance R of point P relative to lightning detection station S2 is calculated A2 and preset azimuth angle θ A2 . Comparing in the information index of lightning detection station S1, the closest grid point is 1, and comparing in the information index of lightning detection station S2, the closest grid point is 2.

[0211] Step 5, the lightning detection stations S1, S2, S3, …, S n each are corrected, and the corrected waveforms have arrival times of T1-Δt1', T 21 -Δt2', T 31 -Δt3', …, T n1 -Δt n ', and the existing lightning positioning method is used to recalculate the accurate lightning occurrence time t final and the accurate lightning position P' (x final , y final ) ; the corrected waveform characteristic parameters of the lightning detection stations S1, S2, S3, …, S n each receiving the lightning electromagnetic wave are 1 / k1'×Pr1, 1 / k2'×Pr2, 1 / k3'×Pr3, …, 1 / k n '×Pr n , and the accurate lightning waveform characteristic parameter Pr final is calculated.

[0212] Figures 7a-7d Distribution diagrams of the altitude, soil conductivity, and corresponding lightning electric field amplitude correction factor and lightning electric field time delay correction value within a range of 300 km with a certain lightning detection station as the center in the above embodiment are shown. It can be seen from Figures 7a-7d that the lightning current amplitude parameter and the terrain factor have a strong correlation. Taking the lightning detection station as an example, when the altitude of the lightning detection station is similar to that of the surrounding area, the lightning current amplitude ratio fluctuates around 1. The overall area of the lightning detection station has an altitude of more than 4000 m, and the lightning current amplitude ratio in most areas fluctuates around 0.8-1.2. Only in the southern area, the altitude difference is large, and the altitude is about 2000 m. The lightning current amplitude ratio in this area fluctuates greatly in the interval of 0.5-1.5.

[0213] Next, the effect of the lightning positioning optimization method for correcting the influence of terrain and geological parameters on lightning electromagnetic wave propagation will be described in combination with a lightning detected by the power grid lightning positioning system on June 20, 2022.

[0214] At 19:08:28:785 on June 20, 2022, a lightning strike caused a tripping of an ultra-high voltage transmission line. According to the existing power grid lightning location system, the location of the lightning strike at that moment was 907m away from a tower of the ultra-high voltage transmission line, and the lightning current intensity was -15.5kA. The location of the lightning strike coincided with the location of the fault, but the lightning current intensity was too low to cause the ultra-high voltage line to trip.

[0215] Figure 8 The map shows the location distribution of the aforementioned lightning strike point and the seven lightning detection stations involved in the location, as well as topographic maps of the distance from each lightning detection station to the lightning strike point. Figure 8a This is a topographic profile of the area between Detection Station No. 1 and the lightning strike point. Figure 8b This is a topographic profile of the area between Detection Station No. 2 and the lightning strike point. Figure 8c This is a topographic profile of the area between Detection Station No. 3 and the lightning strike point. Figure 8d This is a topographic profile of the area between detection station No. 4 and the lightning strike point. Figure 8e This is a topographic profile of the area between Detection Station No. 5 and the lightning strike point. Figure 8f This is a topographic profile of the area between Detection Station No. 6 and the lightning strike point. Figure 8g This is a topographic profile of the area between Detection Station No. 7 and the lightning strike point.

[0216] from Figures 8a-8g As can be seen, some propagation paths have elevation differences on the order of 1000m, such as at stations 2 and 7. By applying a lightning current excitation source as described in step 2-2 above at the lightning strike point, lightning electric field waveforms are received at each lightning detection station. Figures 9a-9g The vertical electric field (E) of the seven participating lightning detection stations is shown, with and without considering topographic and geological parameters. Z Waveform. From Figures 9a-9g The vertical electric field (E) Z The waveform characteristic parameters (peak amplitude) and waveform arrival time considering terrain and geological parameters are extracted from the waveform, as well as the waveform characteristic parameters (including peak amplitude) and waveform arrival time without considering terrain and geological parameters. The time delay correction value and amplitude correction coefficient shown in Table 1 are calculated, which are the parameters required to correct the location of the lightning strike point.

[0217] Table 1. Time delay correction values ​​and amplitude correction coefficients of participating lightning detection stations

[0218]

[0219] Following step 5 above, based on the arrival times of the lightning electromagnetic waves received by each of the seven lightning detection stations, the simulation-obtained time delay correction value is subtracted. Then, the existing lightning location method from step 1 above is used to recalculate and obtain the precise lightning occurrence time t.final , the precise location P'(x final , y final ) of lightning.

[0220] According to step 5, on the basis of the peak amplitude of the lightning electromagnetic wave received by each of the 7 lightning detection stations, the amplitude correction coefficient obtained by simulation is divided, and then the peak amplitude is extracted from the lightning electromagnetic wave waveform received by each of the 7 lightning detection stations, and the precise peak amplitude Pr final of lightning is calculated. After correction and optimization, the lightning stroke position is 328m away from a certain tower of the ultra-high voltage transmission line, the error is smaller; the current intensity of this lightning stroke is increased to-36.1kA, which exceeds the lightning shielding insulation level of the ultra-high voltage line, and provides data support for fault analysis.

[0221] The lightning positioning optimization method for correcting the influence of terrain and geological parameters on lightning electromagnetic wave propagation not only establishes a ground-ionosphere electromagnetic wave propagation model, simulates and calculates the time delay correction value and parameter correction coefficient of lightning electromagnetic wave propagation from the preliminary lightning position to the lightning detection station under the condition of considering terrain and geological parameters and not considering terrain and geological parameters, but also grids the target area of the lightning detection station participating in lightning positioning, calculates the time delay correction table and parameter correction coefficient table corresponding to all grid points in the own area of the lightning detection station participating in lightning positioning, and recalculates the precise lightning occurrence time, precise lightning position and precise lightning characteristic parameter according to the respective lightning preliminary occurrence time, lightning preliminary position and lightning preliminary characteristic parameter of the lightning detection station participating in lightning positioning, and the time delay correction value and parameter correction coefficient of the nearest grid point as the lightning point.

[0222] As shown in Figure 10 , a lightning positioning optimization system for correcting the influence of terrain and geological parameters on lightning electromagnetic wave propagation comprises a time delay correction value and parameter correction coefficient calculation module, an information index establishment module, a lightning preliminary position and preliminary characteristic parameter calculation module, a nearest grid point time delay correction value and parameter correction coefficient determination module, and a lightning precise position and precise characteristic parameter calculation module.

[0223] The time delay correction value and parameter correction coefficient calculation module is used to establish a ground-ionosphere electromagnetic wave propagation model, calculate the time delay correction value of lightning electromagnetic wave propagation from the preliminary lightning position to the lightning detection station according to the waveform arrival time under the condition of considering terrain and geological parameters and the waveform arrival time under the condition of not considering terrain and geological parameters, and calculate the parameter correction coefficient of lightning electromagnetic wave propagation from the preliminary lightning position to the lightning detection station according to the waveform characteristic parameter under the condition of considering terrain and geological parameters and the waveform characteristic parameter under the condition of not considering terrain and geological parameters.

[0224] The information index establishing module is used for drawing n corresponding equidistant circles respectively with each lightning detection station participating in lightning location as a center, drawing equi-angle rays with a preset azimuth angle through the corresponding circle center on each equidistant circle, and taking the intersection of each equidistant circle and the corresponding equi-angle ray as a grid point in the corresponding lightning detection station area; taking all the grid points in each lightning detection station area as a lightning preliminary position respectively, calculating the time delay correction value and the parameter correction coefficient corresponding to all the grid points in the area of each lightning detection station, and manufacturing the time delay correction table and the parameter correction coefficient table corresponding to the time delay correction value and the parameter correction coefficient, taking the time delay correction table and the parameter correction coefficient table corresponding to each lightning detection station as the information index of the lightning detection station;

[0225] The lightning preliminary position and preliminary characteristic parameter calculating module is used for assuming that the earth is a standard ellipsoid model, calculating the lightning preliminary occurrence time and the lightning preliminary position by using the existing lightning location method according to the waveform arrival time of the lightning electromagnetic wave received by each lightning detection station participating in lightning location, and calculating the lightning preliminary characteristic parameter by using the waveform characteristic parameter extracted from the lightning electromagnetic wave waveform received by each lightning detection station participating in lightning location.

[0226] The most similar grid point time delay correction value and parameter correction coefficient determining module is used for finding the corresponding most similar grid point closest to the corresponding lightning preliminary position on each equidistant circle corresponding to the lightning detection station according to the lightning preliminary position and the information of the lightning detection station participating in lightning location, and determining the time delay correction value and the parameter correction coefficient corresponding to each lightning detection station when taking each most similar grid point as a lightning stroke point according to the information index of each lightning detection station.

[0227] The lightning accurate position and accurate characteristic parameter calculating module is used for performing time delay correction on each lightning detection station participating in lightning location to obtain the corrected waveform arrival time corresponding to each lightning detection station, and calculating the lightning accurate occurrence time and the lightning accurate position by using the lightning location method, performing characteristic parameter correction on each lightning detection station participating in lightning location to obtain the corrected characteristic parameter corresponding to each lightning detection station, and calculating the lightning accurate characteristic parameter.

[0228] The above embodiment is a preferred embodiment of the present application, but the embodiment of the present application is not limited by the above embodiment, and any change, modification, replacement, combination, simplification made without departing from the spirit and principle of the present application should be an equivalent replacement mode, and all should be included in the protection scope of the present application.

Claims

1. A lightning location optimization method for correcting the influence of topographic and geological parameters on lightning electromagnetic wave propagation, characterized in that, Includes the following steps: Step 1: Establish a ground and ionospheric electromagnetic wave propagation model. Based on the waveform arrival time considering topographic and geological parameters and the waveform arrival time without considering topographic and geological parameters, calculate the time delay correction value for the propagation of lightning electromagnetic waves from the initial location of lightning to the lightning detection station. Based on the waveform characteristic parameters considering topographic and geological parameters and the waveform characteristic parameters without considering topographic and geological parameters, calculate the parameter correction coefficient for the propagation of lightning electromagnetic waves from the initial location of lightning to the lightning detection station. Step 2: Taking each lightning detection station participating in lightning location as the center, draw n equally spaced circles. On each equally spaced circle, draw an equal-angle ray passing through the corresponding center and having a preset azimuth angle. The intersection of each equally spaced circle and the corresponding equal-angle ray is the grid point within the corresponding lightning detection station area. Take all grid points within each lightning detection station area as the preliminary lightning location, calculate the time delay correction value and parameter correction coefficient for each lightning detection station corresponding to all grid points within its own area, and make corresponding time delay correction tables and parameter correction coefficient tables. Use the time delay correction table and parameter correction coefficient table corresponding to each lightning detection station as the information index of that lightning detection station. Step 3: Assuming the Earth is a standard ellipsoidal model, the initial occurrence time and initial location of the lightning are calculated using existing lightning location methods based on the arrival time of the lightning electromagnetic waves received by each of the lightning detection stations participating in lightning location. Then, the initial characteristic parameters of the lightning are calculated by extracting the waveform characteristic parameters from the lightning electromagnetic waves received by each of the lightning detection stations participating in lightning location. Step 4: Based on the preliminary location of the lightning strike and the information of the lightning detection stations involved in the lightning location, find the closest grid point to the corresponding preliminary location of the lightning strike on each equally spaced circle corresponding to the corresponding lightning detection station; then, based on the information index of each lightning detection station, determine the time delay correction value and parameter correction coefficient corresponding to each lightning detection station when each closest grid point is taken as the lightning strike point. Step 5: Perform time delay correction on each lightning detection station participating in lightning location to obtain the arrival time of the corrected waveform corresponding to each lightning detection station. Then, use the lightning location method to calculate the precise occurrence time and precise location of the lightning. Perform characteristic parameter correction on each participating lightning detection station to obtain the corrected characteristic parameters corresponding to each lightning detection station. Then, calculate the precise characteristic parameters of the lightning.

2. The lightning location optimization method according to claim 1, which corrects the influence of topographic and geological parameters on lightning electromagnetic wave propagation, is characterized in that: In step 1, the specific steps for establishing the electromagnetic wave propagation model between the ground and the ionosphere are as follows: Step 1-1: Assume that the lightning electromagnetic wave propagates in a two-dimensional plane rz in cylindrical coordinates, where the r direction is along the ground surface, the z direction is the height direction, the φ direction is the direction that satisfies the right-hand rule with the r and z directions, and the gradient of the φ direction is always 0. Derive Maxwell's curl equations for the vertical electric field and horizontal magnetic field of the VLF / LF lightning electromagnetic wave propagating in the rz plane of the ground and ionosphere using Maxwell's original equations. Solve for the propagation of the lightning electromagnetic wave from the initial location of the lightning to the lightning detection station using Maxwell's curl equations. Steps 1-2: Apply a lightning current excitation source at the initial location of the lightning strike. The lightning current excitation source is a lightning current return stroke channel, placed on the axis of symmetry in a two-dimensional cylindrical coordinate system. Assume the base current at the bottom of the return stroke discharge channel is... The lightning current originates from the ground and gradually propagates upwards at a speed of v. The amplitude of the lightning current decreases with height z according to the law f(z). Therefore, the current distribution at height z of the channel at time t is: Where the current distribution at channel height z at time t is The expression is ； Steps 1-3 involve differential discretization of Maxwell's curl equations, and analyzing the electromagnetic field... E , H The components are discretized using alternating sampling in space and time, that is, each E and H There are four corresponding field components around each field component. H and E The field components surround the Maxwell's curl equations with time variables, transforming them into Maxwell's discrete equations through this discretization method. The spatial electromagnetic field is then solved by progressively updating the equations in the time domain using a leapfrog scheme. The spatial scheme distribution in cylindrical coordinates uses Yee cells, with the grid points of these Yee cells set to (i,j,k), i.e. ( i,j,k )express r Direction is i , φ Direction is j、 The z-direction is k The grid points are connected together, and the entire computational domain is composed of many identical Yee cells. The electric field and magnetic field also intersect in time steps, that is, the updates of the electric field and magnetic field are half a time step apart. Steps 1-4: The vertical electric field E of lightning received by the lightning detection station, taking into account topographic and geological parameters. z Waveform or horizontal magnetic field H φ Extract the arrival time t of the waveform from the waveform. a and characteristic parameter Pr a The vertical electric field E of lightning received by a lightning detection station without considering topographic and geological parameters. z Waveform or horizontal magnetic field H φ Extract the arrival time t of the waveform from the waveform. b and characteristic parameter Pr b The formula for the time delay correction value is: The formula for the parameter correction coefficient is k=Pr a / Pr b .

3. The lightning location optimization method according to claim 2, which corrects the influence of topographic and geological parameters on lightning electromagnetic wave propagation, is characterized in that: In step 1-1, the Maxwell's original equations are: ； In the above formula, E is the electric field intensity vector during radio wave propagation. B is the magnetic flux density vector during electromagnetic wave propagation. ρ is the free charge. ε0 is the dielectric constant in vacuum. j The conduction current density vector. , σ is the electrical conductivity. μ0 is the magnetic permeability.

4. The lightning location optimization method according to claim 3, which corrects the influence of topographic and geological parameters on lightning electromagnetic wave propagation, is characterized in that: In step 1-1, the Maxwell's curl equations based on the vertical electric field and horizontal magnetic field of the lightning discharge channel are as follows: ； in, This represents the component of the electric field intensity E in the r direction. This represents the component of the electric field intensity E in the z-direction. This represents the component of the magnetic field strength B in the φ direction.

5. The lightning location optimization method according to claim 4, which corrects the influence of terrain and geological parameters on lightning electromagnetic wave propagation, is characterized in that: In steps 1-2, the Heidler double exponential function is used to construct the base current at the bottom of the ground flashback stroke. Then the ground flashback strikes the bottom base current. The expression is ； in, I 01 Represents the breakdown current. I 02 Represents the peak value of the corona current. 𝜂 represents the breakdown current correction factor. R1 represents the rise time of the breakdown current waveform. R2 represents the fall time of the breakdown current waveform. R3 represents the rise time of the corona current waveform. 4 represents the waveform fall time of the corona current.

6. The lightning location optimization method according to claim 5, which corrects the influence of terrain and geological parameters on lightning electromagnetic wave propagation, is characterized in that: In steps 1-2, the MTLE engineering model is used as the current return stroke model. The base current decays exponentially as it develops upwards. Therefore, the current distribution at channel height z at time t is: The expression is ； in, I(z,t) is the current at height z of the channel at time t. z represents the height of the return discharge channel. e -z / λ The amplitude of the lightning current decreases exponentially with height z. λ is the attenuation factor. v represents the propagation speed of the lightning current.

7. The lightning location optimization method according to claim 6, which corrects the influence of topographic and geological parameters on lightning electromagnetic wave propagation, is characterized in that: In steps 1-3, the Maxwell discrete equations are: ； in, Δt represents a time step. E r This represents the component of the electric field intensity E in the r direction. E z This represents the component of the electric field intensity E in the z-direction. This represents the component of the magnetic field strength H in the φ direction. μ represents magnetic permeability. ε represents the dielectric constant.

8. The lightning location optimization method according to claim 7, which corrects the influence of topographic and geological parameters on lightning electromagnetic wave propagation, is characterized in that: In steps 1-4, the waveform arrival time is extracted based on the waveform peak point, the half-peak point of the waveform rising edge, or the maximum value point of the derivative of the waveform rising edge. The characteristic parameters include waveform peak value, wavehead time, wavetail time, waveform half-peak width, and electric field amplitude.

9. The lightning location optimization method according to claim 2, which corrects the influence of topographic and geological parameters on lightning electromagnetic wave propagation, is characterized in that: In step 5, lightning detection stations participate in lightning location. The arrival times of the received lightning electromagnetic waves are respectively And using the closest grid point When acting as a lightning strike point, the lightning detection station The corresponding time delay correction values ​​are divided into Then lightning detection station The corresponding corrected waveform arrival times are T1-Δt1′ and T, respectively. 21 -Δt2′、T 31 -Δt3′、 T n1 -Δt n ′.

10. The lightning location optimization method according to claim 2, which corrects the influence of topographic and geological parameters on the propagation of lightning electromagnetic waves, is characterized in that: In step 5, lightning detection stations participate in lightning location. The characteristic parameters of the lightning electromagnetic waves received by each are as follows: And using the closest grid point When acting as a lightning strike point, the lightning detection station The corresponding parameter correction coefficients are respectively Then lightning detection station The corresponding corrected feature parameters are as follows: .

11. The lightning location optimization method according to claim 1, which corrects the influence of topographic and geological parameters on lightning electromagnetic wave propagation, is characterized in that: In step 4, the method to find the closest grid point to the initial lightning position is to calculate the distance R and the preset azimuth angle θ of the initial lightning position relative to each lightning detection station, and find the grid point that is closest to both the distance R and the preset azimuth angle θ in the equally spaced circles corresponding to each lightning detection station.

12. The lightning location optimization method according to claim 1 for correcting the influence of topographic and geological parameters on lightning electromagnetic wave propagation, characterized in that: In step 2, the radii of the equally spaced circles are R1, R2, R3, ..., R a R1, R2, R3, ..., R a All are 6-15 kilometers, of which R a The value of 'a' ranges from 20 to 50; the preset azimuth angles for the equal-angle rays are θ1, θ2, θ3, ..., θ b θ1, θ2, θ3, ..., θ b All are 1~3°, where θ b In this case, b takes the value floor(360 / θ), and floor(·) represents the floor operation.

13. The lightning location optimization method according to claim 1 for correcting the influence of topographic and geological parameters on lightning electromagnetic wave propagation, characterized in that: In step 3, the lightning location method obtains the initial occurrence time t of lightning by solving for the minimum value of the cost function composed of a system of nonlinear equations. initial Preliminary location of lightning P(x) initial y initial (x) initial y initial () represents the longitude and latitude of the lightning strike point; the nonlinear equation set includes the lightning detection station S i The arrival time T of the received lightning electromagnetic wave i The observation equation and the preliminary location of lightning P(x) initial y initial ) and lightning detection station S i The measured azimuth angle β between i The observation equations, the nonlinear equation set is as follows: ； in, T i For a participating lightning detection station S i The arrival time of the received lightning electromagnetic wave, t represents the time of the lightning strike. S Pi From the lightning strike location P(x, y) to a participating lightning detection station S i The distance S Pi The calculations need to be performed on an ellipsoid. c is the speed of electromagnetic wave propagation. For time measurement error, β i For a participating lightning detection station S i The measured azimuth angle of the received lightning electromagnetic wave. β Pi From the lightning strike location P(x, y) to a participating lightning detection station S i Calculate the azimuth angle, β Pi The calculations need to be performed on an ellipsoid. To account for angle measurement error, The coordinates are known to be where i = 1, 2, 3…n; The nonlinear equations are denoted in the following simple form. ; in, r i For observation purposes, F i (t, x) l (y) is an unknown function. This is for measurement error.

14. The lightning location optimization method according to claim 13, which corrects the influence of topographic and geological parameters on lightning electromagnetic wave propagation, is characterized in that: In step 3, in the simplified form of the nonlinear equation system, when When the cost function of the simple form of the nonlinear equation system is minimized. That is, the initial occurrence time t of lightning. initial Preliminary location of lightning P(x) initial y initial ).

15. A lightning location optimization system for correcting the influence of terrain and geological parameters on the propagation of lightning electromagnetic waves, characterized in that, It includes a module for calculating time delay correction values ​​and parameter correction coefficients, an information index establishment module, a module for calculating the preliminary location and preliminary characteristic parameters of lightning, a module for determining the time delay correction values ​​and parameter correction coefficients of the closest grid point, and a module for calculating the precise location and precise characteristic parameters of lightning. The time delay correction value and parameter correction coefficient calculation module is used to establish a ground and ionospheric electromagnetic wave propagation model. Based on the waveform arrival time considering terrain and geological parameters and the waveform arrival time without considering terrain and geological parameters, the module calculates the time delay correction value for the propagation of lightning electromagnetic waves from the initial location of lightning to the lightning detection station. Based on the waveform characteristic parameters considering terrain and geological parameters and the waveform characteristic parameters without considering terrain and geological parameters, the module calculates the parameter correction coefficient for the propagation of lightning electromagnetic waves from the initial location of lightning to the lightning detection station. The information index building module is used to draw n equally spaced circles centered on each lightning detection station participating in lightning location, and draw equal-angle rays passing through the corresponding center and having a preset azimuth angle on each equally spaced circle. The intersection of each equally spaced circle and the corresponding equal-angle ray is the grid point in the corresponding lightning detection station area. All grid points in the area of ​​each lightning detection station are used as the initial lightning location, and the time delay correction value and parameter correction coefficient corresponding to all grid points in the area of ​​each lightning detection station are calculated. The time delay correction value and parameter correction coefficient are used to make corresponding time delay correction table and parameter correction coefficient table, and the time delay correction table and parameter correction coefficient table corresponding to each lightning detection station are used as the information index of the lightning detection station. The preliminary lightning location and preliminary characteristic parameter calculation module is used to calculate the preliminary lightning occurrence time and preliminary lightning location by assuming the Earth is a standard ellipsoidal model, based on the arrival time of the lightning electromagnetic waves received by each of the lightning detection stations participating in lightning location, using existing lightning location methods; and then, based on the waveform characteristic parameters extracted from the lightning electromagnetic waves received by each of the lightning detection stations participating in lightning location, the preliminary lightning characteristic parameters are calculated. The module for determining the time delay correction value and parameter correction coefficient of the closest grid point is used to find the closest grid point to the corresponding initial lightning position on each equally spaced circle corresponding to the corresponding lightning detection station, based on the initial lightning position and the information of the lightning detection stations involved in lightning location; and then, based on the information index of each lightning detection station, determine the time delay correction value and parameter correction coefficient corresponding to each lightning detection station when each closest grid point is taken as the lightning strike point. The precise lightning location and precise feature parameter calculation module is used to perform time delay correction on the lightning detection stations participating in lightning location, obtain the arrival time of the corrected waveform corresponding to each lightning detection station, and then use the lightning location method to calculate the precise lightning occurrence time and precise lightning location; and to perform feature parameter correction on the participating lightning detection stations, obtain the corrected feature parameters corresponding to each lightning detection station, and then calculate the precise lightning feature parameters.

16. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by the processor, it implements the lightning location optimization method as described in any one of claims 1 to 14, which corrects the influence of terrain and geological parameters on the propagation of lightning electromagnetic waves.

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