Power equipment port voltage full waveform reconstruction method and system based on transient radiation electric field signal

Abstract

This invention discloses a method and system for reconstructing the full waveform of port voltage of power equipment based on transient radiated electric field signals. This method reconstructs the average voltage across the equipment based on the transient radiated near-electric field generated when the high-voltage direct current (HVDC) power equipment operates, obtaining a fitted full waveform of the port voltage. This can be used for non-contact online monitoring, fault diagnosis, and situational awareness of HVDC power equipment. This invention effectively overcomes the shortcomings of traditional methods for calculating electromagnetic radiation interference in converter stations, such as high computational resource consumption and low simulation efficiency. The monitoring method based on electric field sensors overcomes the disadvantages of traditional voltage measurement devices, such as large size, high cost, and high maintenance difficulty. This invention enriches the means of online monitoring of power equipment in HVDC converter valve halls and improves the maintenance efficiency of DC systems.

Description

Technical Field

[0001] This invention belongs to the field of fault diagnosis technology for key power equipment in the valve hall of a high-voltage DC converter station, specifically involving a method and system for full waveform reconstruction of power equipment port voltage based on transient radiated electric field signals. Background Technology

[0002] DC transmission technology and DC grid engineering are widely used technologies for solving the problems of new energy power generation, consumption, and grid connection. Therefore, high-voltage direct current (HVDC) transmission systems based on modular multilevel converters (MMCs) have developed rapidly in the past decade. However, flexible DC transmission networks also face severe challenges, such as short-circuit faults causing system currents to rise to the kA level within milliseconds, which can subject some critical power electronic equipment in converter stations to destructive electrical stress. Therefore, condition monitoring of critical power equipment in converter stations is an important means to ensure the safety of flexible DC systems.

[0003] Existing research indicates that the transient electromagnetic field (TEMF) generated during the operation of power equipment can accurately determine the timing and health status of the equipment. However, research on the spatial electromagnetic fields generated by various devices within valve halls generally focuses on electromagnetic compatibility, and there are no reports of theoretical research and experimental verification specifically targeting non-contact situational awareness technology for power equipment regarding spatial electromagnetic fields. Furthermore, voltage testing of equipment and lines is unavoidable during power grid operation. Traditional measurement systems for steady-state and transient high-voltage signals often require large voltage dividers, but their dynamic characteristics are poor, and the sampling frequency of traditional measurement systems is low (generally below 10kHz), making it difficult to respond in real time to transient voltage changes in power equipment and potentially missing high-frequency components carrying important fault information. While numerous scholars have conducted research on non-contact voltage measurement using transmission lines as the research object, achieving certain results in theoretical research, detection methods and devices, and voltage reconstruction algorithm optimization, there are currently no reports on theoretical and computational research on non-contact voltage reconstruction for high-voltage DC power equipment. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, the present invention aims to provide a method and system for full waveform reconstruction of port voltage of power equipment based on transient radiated electric field signal, so as to overcome the defects of traditional voltage measurement methods of power equipment, such as large measurement equipment size, poor dynamic characteristics and low monitoring flexibility.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] This invention discloses a method for reconstructing the full waveform of port voltage of power equipment based on transient radiated electric field signals, comprising the following steps:

[0007] 1) Based on electromagnetic field theory, obtain analytical expressions for the near-electric field of a finite-length ideal current-carrying straight conductor radiating in the Cartesian coordinate system, specifically the x, y, and z coordinate axis components.

[0008] 2) Based on the actual three-dimensional geometric dimensions and actual current-carrying loops of the key power equipment in the valve hall of the high-voltage DC converter station, the key power equipment in the valve hall of the high-voltage DC converter station is simplified into a simplified model of the near-electric field of radiation composed of several segments of ideal current-carrying straight conductors of finite length, and a local Cartesian coordinate system is established for each segment of ideal current-carrying straight conductor of finite length.

[0009] 3) Deploy several transient electric field detection devices at any spatial location within the valve hall where key power equipment is located in the high-voltage DC converter station valve hall;

[0010] 4) Based on the finite-length ideal current-carrying straight conductor model established for key power equipment in step 2), obtain the coordinate values ​​of several transient electric field detection devices in each local coordinate system in step 3);

[0011] 5) Substitute the coordinate values ​​obtained in step 4) into the analytical expression obtained in step 1) to re-establish a system of linear equations with multiple variables between the radiated near-electric field of the key power equipment and its port, solve the system of equations, and obtain the analytical solution of the power equipment port voltage.

[0012] Preferably, in step 1), the finite-length ideal current-carrying straight conductor is an ideal conductor, and the wave process during the current-carrying process of the entire straight conductor is ignored, and the surface potential at any point is equal.

[0013] Preferably, in step 1), the analytical expressions for the three coordinate axis components x, y, and z are as follows:

[0014]

[0015] in, and V represents the three coordinate axis components of the near-electric field radiated by the straight conductor in the Cartesian coordinate system; sLet be the surface potential of a finite-length ideal current-carrying straight conductor; r be the diameter of the finite-length ideal current-carrying straight conductor; C be the equivalent capacitance per unit length of conductor to ground; ε0 be the vacuum permittivity; the geometric angular quantity φ is the angle between the line connecting the projection point of the field point on the xoy plane and the origin of the Cartesian system and the positive x-axis, i.e., the azimuth of the field point; the geometric angular quantity α1 represents the angle between the line connecting the field point and the lower vertex of the straight conductor and the positive z-axis, i.e., the pitch angle of the field point relative to the lower vertex of the straight conductor; the geometric angular quantity α2 represents the angle between the line connecting the field point and the upper vertex of the straight conductor and the positive z-axis, i.e., the pitch angle of the field point relative to the upper vertex of the straight conductor.

[0016] Preferably, in step 2), the three-dimensional geometry of the actual current-carrying circuit of the key power equipment is taken into account, while the polarized electric field generated by the metal shielding device and various insulation devices on the outside of the key power equipment body is ignored.

[0017] Preferably, in step 2), the vertical axis of the local coordinate system established by each finite-length ideal current-carrying straight conductor in the simplified model of the near-field radiation should be consistent with the reference direction of the current flowing through the finite-length ideal current-carrying straight conductor.

[0018] Preferably, in step 3), the number of transient electric field detection devices deployed at any spatial location within the valve hall where each key power equipment is located is at least two.

[0019] Preferably, in step 3), if there are multiple critical power devices in the valve hall at the same time, when performing voltage reconstruction for one of the critical power devices, the transient electric field detection device is set close to the critical power device, and there are no obstructions between the receiving antenna of the transient electric field detection device and the critical power device to be tested.

[0020] More preferably, the transient electric field detection device adopts a nanosecond-level transient electric field fiber optic measurement device based on a rod-shaped electric small antenna.

[0021] Preferably, the transient electric field detection device has a measurement bandwidth of 200Hz to 680MHz and a measurement electric field amplitude range of -50kV / m to 50kV / m.

[0022] Preferably, in step 5), the system of linear equations is as follows:

[0023]

[0024] Among them, E z-1 E is the measured electric field along the z-axis at point 1. z-2 It is the measured electric field in the z-axis direction at point 2; V p-av It is the average voltage at the positive terminal of the circuit breaker, V n-av It is the average voltage at the negative terminal of the circuit breaker; K a-b-c-d(a can be p or n, representing the polarity of the circuit breaker where the equivalent conductor is located; b is z, representing the z-axis direction; c takes values ​​from 1 to 10, representing the number of the equivalent conductor; d can be 1 or 2, representing the number of the electric field measurement point) are the coordinate parameters of the field point in the local coordinate system of each segment of the equivalent conductor; A ef (e can be 1 or 2; f can be 1 or 2) represents ten wire segments K. a-b-c-d The set coefficients of the parameters.

[0025] This invention also discloses a system based on the above-described method for full waveform reconstruction of power equipment port voltage based on transient radiated electric field signals, comprising:

[0026] The module for simplifying the near-electric field of critical power equipment is used to simplify the critical power equipment into a simplified model of the near-electric field of radiation composed of several segments of ideal current-carrying straight conductors of finite length, and to establish a local Cartesian coordinate system for each segment of ideal current-carrying straight conductor of finite length.

[0027] The transient radiation near-electric field measurement module is used to monitor and record the transient electric field of key power equipment in the valve hall of the high-voltage DC converter station, and to provide the field point coordinate information of the electric field measurement point in the local Cartesian coordinate system of each finite-length ideal current-carrying straight conductor.

[0028] The power equipment port average voltage reconstruction calculation module is used to establish the relationship between the radiated near electric field of the key power equipment and the average voltage at both ends of the key power equipment using a set of multiple linear equations. Based on the monitoring data and coordinate information obtained by the transient radiated near electric field measurement module, the module solves the set of multiple linear equations to complete the reconstruction of the average voltage at both ends of the key power equipment.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] This invention discloses a method for reconstructing the full waveform of port voltage of power equipment based on transient radiated electric field signals. It reconstructs the average voltage across the equipment based on the transient radiated near-electric field generated during the operation of high-voltage direct current (HVDC) power equipment, obtaining a fitted full waveform of the port voltage. This method can be used for non-contact online monitoring, fault diagnosis, and situational awareness of HVDC power equipment. The innovation of this method lies in proposing an analytical calculation model of the radiated near-electric field of a finite-length ideal current-carrying straight conductor, establishing the coupling relationship between the radiated near-electric field within the equipment's valve hall and the equivalent circuit of key power equipment. The invention has been experimentally verified using a hybrid HVDC circuit breaker as a typical application. The inverted voltage signal obtained by this voltage reconstruction calculation method shows high agreement with the experimentally measured voltage signal in both the time and frequency domains, and the calculation errors are all within acceptable engineering ranges. This method can fully overcome the shortcomings of traditional methods for calculating electromagnetic radiation interference in converter stations, such as large computational resources and low simulation efficiency. The monitoring method based on electric field sensors overcomes the shortcomings of traditional voltage measurement devices, such as large size, high cost and high maintenance difficulty. This invention can enrich the means of online monitoring of the status of power equipment in the high voltage DC converter valve hall and improve the maintenance efficiency of DC system. Attached Figure Description

[0031] Figure 1 This is a schematic diagram illustrating the calculation of the near-electric field radiated by an ideal current-carrying straight conductor of finite length according to the present invention.

[0032] Figure 2 This is a spatial topology diagram of the current-carrying conductors inside the DC circuit breaker of the present invention (containing only the positive circuit breaker);

[0033] Figure 3 This is a simplified schematic diagram of the DC circuit breaker of the present invention as 10 segments of ideal current-carrying straight conductors of finite length (only the positive circuit breaker is included);

[0034] Figure 4 The diagram shows the complete circuit topology and voltage and electric field measurement point layout for the artificial short-circuit test at the Zhouding converter station of this invention (solid circles represent the voltage measurement point layout positions, and dashed circles represent the electric field measurement point layout positions).

[0035] Figure 5 This is a simplified calculation diagram of the near-electric field radiated inside the valve hall of the circuit breaker in the Zhouding converter station of the present invention (only including the positive circuit breaker);

[0036] Figure 6 This invention is based on the time-frequency domain reconstruction of the average voltage across the positive circuit breaker by the transient radiated near-electric field in the valve hall during a bipolar short-circuit test.

[0037] Figure 7 This invention is based on the time-frequency domain reconstruction of the average voltage across the negative circuit breaker by the transient radiated near-electric field in the valve hall during a bipolar short-circuit test. Detailed Implementation

[0038] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0039] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0040] The present invention will now be described in further detail with reference to the accompanying drawings:

[0041] This invention discloses a method for reconstructing the full waveform of port voltage of power equipment based on transient radiated electric field signals, comprising the following steps:

[0042] 1) Based on electromagnetic field theory, obtain analytical expressions for the near-electric field of a finite-length ideal current-carrying straight conductor radiating in the Cartesian coordinate system, specifically the x, y, and z coordinate axis components.

[0043] 2) Based on the actual three-dimensional geometric dimensions and actual current-carrying loops of the key power equipment in the valve hall of the high-voltage DC converter station, the key power equipment in the valve hall of the high-voltage DC converter station is simplified into a simplified model of the near-electric field of radiation composed of several segments of ideal current-carrying straight conductors of finite length, and a local Cartesian coordinate system is established for each segment of ideal current-carrying straight conductor of finite length.

[0044] 3) Deploy several transient electric field detection devices at any spatial location within the valve hall where key power equipment is located in the high-voltage DC converter station valve hall;

[0045] 4) Based on the finite-length ideal current-carrying straight conductor model established for key power equipment in step 2), obtain the coordinate values ​​of several transient electric field detection devices in each local coordinate system in step 3);

[0046] 5) Substitute the coordinate values ​​obtained in step 4) into the analytical expression obtained in step 1) to re-establish a system of multiple linear equations between the radiated near-electric field of the key power equipment and its port (as shown in formula (9) in the following embodiment), solve the system of equations, and obtain the analytical solution of the power equipment port voltage.

[0047] The present invention discloses a method for reconstructing the average voltage across the two ends of a high-voltage direct current (HVDC) power equipment based on the transient radiated near-electric field generated during the operation of the equipment. As can be seen from the foregoing, the present invention must establish a calculation model based on the three-dimensional spatial geometry of a specific power equipment. Therefore, the present invention will be described in detail using a hybrid HVDC circuit breaker as the research object.

[0048] as follows Figure 1 As shown, assuming a time-harmonic current signal flows through the finite-length straight conductor, the near-field expression for the radiation produced by the finite-length straight conductor shown in the figure should be calculated according to the following formula, based on the formula for calculating the near-field of line charge radiation:

[0049]

[0050] Where, ρ l is the linear charge density, L is the total length of the conductor, and r is the radial vector of any field point.

[0051] Depend on Figure 1 The geometric relationships shown indicate that:

[0052]

[0053] Substituting the above relationship into formula (1), we get:

[0054]

[0055] The above equation represents the calculation result in cylindrical coordinates. Based on the transformation matrix between cylindrical and rectangular coordinates, the components of the electric field calculation result shown in the above equation in rectangular coordinates are:

[0056]

[0057] The capacitance per unit length formed by a single conductor and its mirror image can be calculated using the following formula:

[0058]

[0059] In the above formula, r0 is the radius of the conductor, and h is the height of the conductor. Let the surface potential of an ideal current-carrying conductor be V. s Then the linear charge density ρ of the current-carrying conductor l Surface potential V sThe relationship between the conductor's equivalent capacitance to ground per unit length, and the equivalent capacitance C can be expressed as follows:

[0060] ρ l =V s C (6)

[0061] Therefore, the expressions for the rectangular coordinate components of the electric field can be further written as follows:

[0062]

[0063] As can be seen from the above formula, if the surface potential of a certain finite-length ideal current-carrying straight conductor is known, this formula can be used to quantitatively calculate the near-electric field value of the radiation generated by the conductor.

[0064] Based on the geometry of the current-carrying conductors within the circuit breaker valve hall, the entire equipment within the hall is simplified into several segments of finite-length ideal current-carrying straight conductors. Since the current-carrying circuit changes during the interruption of fault current by the circuit breaker, that is, in the following... Figure 2 In this circuit, the current-carrying loop undergoes a transfer from ① to ③ (where ① is the main branch of the hybrid high-voltage DC circuit breaker, ② is the transfer branch, and ③ is the energy-dissipating branch). This transfer process can now be approximated as a process where the current-carrying loop remains unchanged. The equivalent current-carrying loop is geometrically located at the central axis of the entire circuit breaker (i.e.,...). Figure 2 (The thick black solid line inside the circuit breaker shown); Based on the above simplification, we can obtain the following... Figure 3 The diagram shown is a simplified calculation of the near-electric field radiated from the circuit breaker valve hall (this diagram uses 10 equivalent conductor segments as an example, and the gray plane in the diagram represents the ground):

[0065] As can be seen from the aforementioned formula (7), this result is in Figure 1 The results derived in the coordinate system shown are intended to be applied directly in practical engineering for the convenience of this invention. Figure 3 A so-called "local coordinate system" is established on each segment of the conductor shown. The orientation of this coordinate system follows the following rules: the vertical axis is aligned with the reference direction of the current flowing through it, and the horizontal and vertical axes form a right-handed screw relationship with the vertical axis. The aforementioned formulas (6) and (7) both use mirrored conductors to represent the effect of the earth in their derivation. Therefore... Figure 3 Each conductor shown has a corresponding mirror conductor (the mirror conductor is not shown in the figure), and the local coordinate system orientation rules for the mirror conductor are the same as described above.

[0066] The following conventions are made for the surface potential of each conductor segment during the electric field calculation: Figure 3The surface potentials of conductors 1 to 4 shown are equal and are all the surface potentials of conductor 1; the surface potentials of conductors 6 to 10 are equal and are all the surface potentials of conductor 10; conductor 5 is the "equivalent current-carrying loop" inside the aforementioned circuit breaker, and its surface potential is assumed to be the average of the surface potentials of conductors 1 and 10.

[0067] The physical meaning of the above "agreement" is explained below: Considering that there must be internal resistance in all connection parts and inside the actual electrical equipment, therefore Figure 3 There must be a voltage drop between each conductor segment shown. This convention is a simplified calculation rule proposed to eliminate (or reduce) the calculation error caused by the internal resistance of the power equipment itself in actual use.

[0068] In summary, to obtain the near-field value of the radiated electric field at a specific point within the circuit breaker valve hall, it is only necessary to calculate it based on the coordinates of that point relative to several local coordinate systems and in conjunction with equation (7). That is, the near-field value of the radiated electric field at any point within the valve hall can be expressed as follows:

[0069]

[0070] In the above formula, a series of parameters K a-b-c It depends only on the coordinates of the field point, where parameter a can take the values ​​p and q, representing the polarity of the circuit breaker; parameter b can take the values ​​x, y, and z, representing a specific rectangular coordinate component of the electric field; parameter c can take positive integers 1, 2, ..., 10, representing the conductor number; V p-1 With V p-10 V represents the surface potential of conductors 1 and 10 of the positive circuit breaker, respectively. n-1 With V n-10 The surface potentials of conductors 1 and 10 of the negative circuit breaker are represented respectively.

[0071] Equations (7) and (8) above both reflect the proportional relationship between the radiated near-electric field in the circuit breaker valve hall and the voltage across the circuit breaker. Below, we will propose a method for reconstructing the average voltage across the radiated near-electric field of a hybrid high-voltage DC circuit breaker, based on equation (8). In the following text, the average voltage (V) across the positive circuit breaker will be... p-1 +V p-10 ) / 2 is denoted as V p-av The average voltage (V) across the negative circuit breaker n-1 +V n-10 ) / 2 is denoted as V n-av .

[0072] The mathematical essence of inverting the average voltage across the positive and negative terminals of a circuit breaker using electric field data is solving a system of two linear equations in two variables, where V... p-avWith V n-av This is a quantity to be determined. During the inversion calculation, it is assumed that the surface potential of the 10 equivalent conductors of the positive circuit breaker within the circuit breaker valve hall is V. p-av The surface potential of the 10 equivalent conductors of the negative circuit breaker is V. n-av Mathematically speaking, V can be calculated simply by detecting the electric field at any two points within the circuit breaker valve hall. p-av With V n-av .

[0073] Electric field sensors typically detect electric fields only in a fixed polarization direction. Let's assume two electric field sensors (denoted as field point 1 and field point 2) are arbitrarily placed in the circuit breaker valve hall. Each sensor measures the electric field only in the direction perpendicular to the ground plane (i.e., relative to the direction of the ground plane). Figure 3 In the local coordinate system of the Earth's surface shown, the sensor only detects the electric field component in the z-direction. Based on the electric field signals from the two measuring points, the following formula can be used to calculate V. p-av With V n-av Perform the calculation.

[0074]

[0075] In equation (9) above, the last subscript of the variable E and parameter K is the field point number, and the physical meanings of the other subscripts are the same as before. z-1 E is the measured electric field along the z-axis at point 1. z-2 It is the measured electric field in the z-axis direction at point 2; V p-av It is the average voltage at the positive terminal of the circuit breaker, V n-av It is the average voltage at the negative terminal of the circuit breaker; K a-b-c-d (a can be p or n, representing the polarity of the circuit breaker where the equivalent conductor is located; b is z, representing the z-axis direction; c takes values ​​from 1 to 10, representing the number of the equivalent conductor; d can be 1 or 2, representing the number of the electric field measurement point) are the coordinate parameters of the field point in the local coordinate system of each segment of the equivalent conductor; A ef (e can be 1 or 2; f can be 1 or 2) represents ten wire segments K. a-b-c-d The set coefficients of the parameters.

[0076] As shown in (9), V can be obtained through the matrix operation shown in the following formula. p-av With V n-av :

[0077]

[0078] The following analysis, using application examples, illustrates the feasibility of the method for reconstructing the average voltage across the two ends of a device based on the transient radiated near-electric field generated during the operation of a high-voltage direct current power device.

[0079] See Figure 4 This figure shows the complete circuit topology and the actual layout of voltage and electric field measurement points during an artificial short-circuit test at a converter station. Solid circles indicate the locations of voltage measurement points, and dashed circles represent the locations of electric field measurement points. During the test, a resistive-capacitive voltage divider was used to measure the transient voltage signal across the circuit breaker in the circuit breaker valve hall. A nanosecond-level transient electric field fiber optic measurement system based on a rod-shaped electric small antenna was used to measure the transient radiated near-electric field. The bandwidth of this transient electric field measurement device is 200Hz to 680MHz.

[0080] See Figure 5 Electric field measuring point 1 was placed at the midpoint of the line connecting the centers of the two circuit breakers. Measuring point 2 was placed on the shielding fence near the energy-dissipating branch of the positive circuit breaker. Measuring points 3 and 4 were placed on the shielding fences near the main branches of the positive and negative circuit breakers, respectively. The electric field sensors at measuring points 2, 3, and 4 were all placed 1.8m above the ground, while the electric field sensor at measuring point 1 was placed 0.5m above the ground. All measuring points detected the electric field perpendicular to the ground plane. During the three short-circuit tests, the spatial positions of the four voltage measuring points and four electric field measuring points within the circuit breaker valve hall remained unchanged.

[0081] The positive and negative hybrid high-voltage DC circuit breaker in the Zhouding converter station is still simplified to 10 finite-length ideal current-carrying conductors, that is, with Figure 3 Correspondingly, based on relevant engineering parameters, we can obtain the following: Figure 5 The diagram shows a simplified calculation of the near-electric field of radiation. To keep the diagram simple, only the simplified result of the positive circuit breaker is shown; the negative circuit breaker and the mirror equivalent conductors of the two circuit breakers are not shown. Since the two circuit breakers are symmetrically arranged in the valve hall, the simplified geometry of the negative circuit breaker is symmetrically distributed with that of the positive circuit breaker.

[0082] Figure 5 In the diagram, the radius r0 of each equivalent conductor segment is 1 cm; the three black solid dots represent... Figure 4 The diagram shows electric field measuring points 1, 2, and 3. The spatial geometric location of measuring point 4 is omitted from the diagram. In fact, measuring point 4 and measuring point 3 are arranged symmetrically about measuring point 1. The geometric information of the coordinates of measuring point 4 can be found in... Figure 5 It is also easy to see that the length of each equivalent traverse segment and its local coordinate system orientation are clearly marked on the map. Figure 5 middle.

[0083] Based on the above explanation and in combination Figure 5The geometric information marked in the figure can be used to obtain the coordinates of the electric field measuring points in various local coordinate systems. Substituting the coordinate information of the field points into equations (7), (9), and (10), the average voltage (i.e., V) across the positive and negative pole circuit breakers can be calculated using the electric field data inversion. p-av and V n-av ).

[0084] It should also be noted that the bandwidth of the transient electric field measurement system used in the experiment is 200Hz-680 MHz. Therefore, the average voltage obtained by inverting the electric field data detected in this experiment using Equation (10) is not the calculation result of the entire frequency band. Theoretically, it can only reflect the information within the specific frequency band of 200Hz-680 MHz. In order to more clearly compare the inversion calculation result with the actual voltage measurement result, the measured voltage data in this paper are all processed by 200Hz high-pass filtering.

[0085] See Figure 6 and Figure 7 The time and frequency domain results are obtained by inverting the average voltage across the circuit breaker when breaking a bipolar short-circuit fault using the calculation formula (10). In the time domain waveform, the inverted calculation results are in good agreement with the actual measurement results, and can clearly reflect the timing of the operation of key power electronic equipment such as MMC and circuit breaker in the converter station. In the two figures, t0 is 0ms, which is the moment when the artificial bipolar short-circuit fault occurs, t1 is 1.99ms, which is the moment when the MMC valve is locked, and t2 is 3.93ms, which is the moment when the transfer branch of the hybrid high-voltage DC circuit breaker is locked. In the frequency domain waveform, Figure 6 and Figure 7 The characteristic frequency points of the calculation results shown are in good agreement with the characteristic frequency points of the measured results, and the calculation error of the characteristic frequency points is within the acceptable range for engineering.

[0086] The voltage reconstruction calculation results from the examples show that when conducting simulation analysis, calculation, and non-contact situational awareness mechanism analysis on the near-electric field radiated by power equipment, the complex shielding structure of the equipment can be ignored and only its charged structure can be considered. From the perspective of electromagnetic waves, the shielding structure itself is to suppress the interference of VHF electromagnetic radiation on secondary equipment, and its impact on the near-electric field is not severe.

[0087] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for full waveform reconstruction of power device port voltages based on transient radiated electric field signals, characterized by, The method comprises the following steps: 1) According to the electromagnetic field theory, the analytical expressions of the three coordinate axis components of the near electric field radiated by a finite length ideal current-carrying straight wire are obtained x , y , z ​ wherein x , y , z Analytical expressions for the three coordinate axis components are given by the following equations: in, , and These represent the three coordinate axis components of the near-electric field radiated by the straight conductor in the Cartesian coordinate system; The surface potential of an ideal current-carrying straight conductor of finite length; The diameter of a finite-length ideal current-carrying straight conductor; The equivalent capacitance per unit length of conductor to ground; The vacuum permittivity; geometric angular quantity For the venue xoy The line connecting the projection point on the plane to the origin of the Cartesian coordinate system and... x The angle between the positive axes, i.e., the azimuth of the field point; a geometric angular quantity. The line connecting the field point and the vertex of the straight conductor is... z The angle between the positive axes, i.e., the pitch angle of the field point relative to the vertex of the straight conductor; a geometric angular quantity. The line connecting the field point and the vertex on the straight conductor is... z The angle between the positive directions of the axes, that is, the pitch angle of the field point relative to the vertex on the straight conductor; 2) According to the actual three-dimensional geometric size and the actual through-flow loop of the key power equipment in the valve hall of the high-voltage direct-current converter station, the key power equipment in the valve hall of the high-voltage direct-current converter station is simplified into a radiation near electric field simplified model composed of a plurality of finite-length ideal current-carrying straight conductors, and a local Cartesian coordinate system is established for each finite-length ideal current-carrying straight conductor; 3) A plurality of transient electric field detection devices are arranged at any spatial position in the valve hall where the key power equipment is located; 4) Based on the plurality of finite-length ideal current-carrying straight conductor models established for the key power equipment in step 2), the coordinate values of the plurality of transient electric field detection devices in the local coordinate systems are obtained in step 3); 5) The coordinate values obtained in step 4) are substituted into the analytical expression obtained in step 1), and a multivariate linear equation set between the radiation near electric field of the key power equipment and the port thereof is re-established, the equation set is solved, and the analytical solution of the port voltage of the power equipment is obtained.

2. The method of full waveform reconstruction of the voltage at the port of a power device based on a transient radiated electric field signal according to claim 1, characterized in that, In step 1), the finite-length ideal current-carrying straight conductor is an ideal conductor, and the wave process in the current-carrying process of the whole straight conductor is ignored, and the surface potential of any point is equal.

3. The method of claim 1, wherein, In step 2), the three-dimensional geometric structure of the actual through-flow loop of the key power equipment is considered, and the polarization electric field generated by the metal shielding device and various insulation equipment outside the key power equipment body is ignored.

4. The method of claim 1, wherein, In step 2), the vertical coordinate axis of the local coordinate system established in connection with each finite-length ideal current-carrying straight conductor in the radiation near electric field simplified model should be consistent with the reference direction of the through-flow current in the finite-length ideal current-carrying straight conductor.

5. The method of claim 1, wherein, In step 3), the number of transient electric field detection devices arranged at any spatial position in the valve hall where each key power equipment is located is at least two.

6. The method of claim 1, wherein, In step 3), when there are a plurality of key power equipments in the valve hall, when the voltage reconstruction is performed on a certain key power equipment, the transient electric field detection devices are close to the port position of the key power equipment, and there is no shielding object between the receiving antenna of the transient electric field detection device and the key power equipment to be measured. The transient electric field detection device adopts a nanosecond-level transient electric field optical fiber measurement device based on a rod-shaped electric small antenna.

7. The method of claim 1, wherein, The measurement bandwidth of the transient electric field detection device is 200Hz to 680MHz, and the measurement electric field amplitude range is-50kV / m to 50kV / m.

8. The method of claim 1, wherein, In step 5), the multivariate linear equation set is as follows: ； in, It is at point 1 z The electric field measured along the axial direction, It is at point 2. z The measured electric field along the axial direction; It is the average voltage at the positive terminal of the circuit breaker. It is the average voltage at the negative terminal of the circuit breaker. These are the coordinate parameters of the field points in the local coordinate system of each equivalent traverse segment, where... a Pick p or n , representing the polarity of the circuit breaker where the equivalent conductor is located; b Pick z ,represent z Axial direction; c Iterate through the natural numbers 1 to 10, which represent the numbers of the equivalent conductors; d Choose 1 or 2 to represent the number of the electric field measurement point; A ef It is ten wire segments The set of coefficients of the parameters, where, e Choose 1, 2; f Choose 1 and 2.

9. A system for full waveform reconstruction of the voltage at the port of an electrical power device based on the transient radiation electric field signal according to any one of claims 1 to 8, characterized in that, It comprises: a key power equipment radiation near electric field simplified calculation module, which is used for simplifying the key power equipment into a radiation near electric field simplified model composed of a plurality of finite-length ideal current-carrying straight conductors, and establishing a local Cartesian coordinate system for each finite-length ideal current-carrying straight conductor; a transient radiation near electric field measurement module, which is used for monitoring and recording the transient electric field of the key power equipment in the valve hall of the high-voltage direct-current converter station, and providing field point coordinate information of the electric field measurement points in the local Cartesian coordinate system of each finite-length ideal current-carrying straight conductor; The power equipment port average voltage reconstruction calculation module is used to establish a multiple first-order equation set relationship between the critical power equipment radiation near electric field and the average voltage across the critical power equipment, solve the multiple first-order equation set based on the monitoring data and coordinate information obtained by the transient radiation near electric field measurement module, and complete the operation of reconstructing the average voltage across the critical power equipment.

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