Interference source propagation path calculation method based on bus overvoltage condition

Abstract

The invention belongs to the field of electromagnetic field calculation, and discloses a bus overvoltage condition-based interference source propagation path calculation method, which can dynamically evaluate the distance of electromagnetic interference by inputting electromagnetic data of an earth screen conductor into a space interference calculation and analysis model. And the position of the interference source and the influence of the interference source on surrounding equipment are accurately determined. The introduction of the electromagnetic data of the earth screen conductor enables the method to accurately capture the source and propagation characteristics of electromagnetic interference, and solves the problem that the traditional method is difficult to accurately identify an interference source. Compared with static modeling, the method has the advantages that the position and the influence range of the interference source are more accurate, and the method is particularly suitable for coping with complex and dynamically changing electromagnetic environments. According to the method, the earth screen conductor is segmented, and the current flowing through each segment of conductor is collected, so that the induced potential of each segment of conductor is calculated.

Description

Technical Field

[0001] The present invention belongs to the field of electromagnetic field calculation, and particularly relates to a calculation method for the propagation path of interference sources based on the bus overvoltage condition. Background Art

[0002] In modern power systems and electronic devices, electromagnetic compatibility (EMC) issues have gradually become key factors affecting system performance and stability. Especially in the design and application of electrical equipment such as AC filters, electromagnetic interference (EMI) may cause system failures, signal noise, and equipment damage. To effectively evaluate and control these effects, it is necessary to deeply understand the propagation characteristics of electromagnetic interference, electromagnetic coupling between devices, and current and voltage distributions on conductors.

[0003] Around the AC filter, the generation of bus overvoltage often leads to uneven distribution of the electromagnetic field, which in turn affects the electrical performance of surrounding electrical components. The current and voltage relationships between the ground grid conductors and other conductors in the electrical system are complex, and the interaction of their induced electromotive force and current presents different characteristics in different electrical environments. This makes it more difficult to effectively identify electromagnetic interference sources and predict interference effects. The prior art faces technical challenges in the following aspects: In a complex electrical system, especially in the case of multiple electromagnetic sources, how to accurately determine the location and influence range of interference sources has always been a difficult problem. Existing methods often have difficulty in collecting and analyzing interference data in real time and accurately, resulting in large errors in the location and influence assessment of interference sources.

[0004] These technical problems hinder the accurate prediction and control of electromagnetic interference, making it difficult to ensure the stability and performance of electrical equipment in a complex electromagnetic environment. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies of being unable to accurately identify electromagnetic interference sources, current and voltage distributions, and the propagation path of interference sources, and to provide a calculation method for the propagation path of interference sources based on the bus overvoltage condition.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions: The present invention provides a calculation method for the propagation path of interference sources based on the bus overvoltage condition, including the following steps: Construct a spatial interference calculation and analysis model according to historical data, and use Maxwell's equations as the control equations of the spatial interference calculation and analysis model; Obtain the electromagnetic data of the ground grid conductor, and send the interference data into the spatial interference calculation and analysis model to obtain the distance from the interference point to the interference source; According to the distance between the disturbed point and the interference source, the grounded grid conductor affected by interference is segmented into several segments of conductors, the current flowing through each segment of conductor after segmentation is collected, and the induced electromotive force of each segment of conductor is obtained; According to the induced electromotive force of each segment of conductor, calculate the sum of the electromotive forces induced by the currents on all conductor segments on this conductor; Process the segmented grounded grid conductor using Kirchhoff's current law KCL and Kirchhoff's voltage law KVL to obtain the current-voltage relationship of the segmented grounded grid conductor; According to the current-voltage relationship of the segmented grounded grid conductor, establish a nodal admittance equation to obtain the relationship between the potential of the grounded grid conductor and the scattered current; Analyze the relationship between the potential of the grounded grid conductor and the scattered current to obtain the propagation path of the interference source on the secondary equipment.

[0007] A further improvement of the present invention lies in Maxwell's equations:

[0008] Among them, H is the magnetic field strength; B is the magnetic flux density; D is the electric displacement vector; E is the electric field strength; ρ is the space charge density; J s is the conduction current density.

[0009] A further improvement of the present invention lies in obtaining the electromagnetic data of the grounded grid conductor and sending the interference data into the spatial interference calculation and analysis model. The specific method for obtaining the distance between the disturbed point and the interference source is as follows: Based on in Maxwell's equations, introduce the vector magnetic potential A and the scalar potential function φ , so that B =rot A , then:

[0010] In the formula, is the phase constant, μ , ε are the magnetic permeability and the permittivity respectively; According to Maxwell's equations, obtain the d'Alembert equations:

[0011] Among them, is the phase constant, μ is the magnetic permeability, ε is the permittivity; Collect interference data in real time. When the distance from the interference point to the interference source is obtained by sending the interference data into the spatial interference calculation and analysis model, it is calculated by the following method:

[0012] Wherein, is the distance from the interference point to the interference source.

[0013] A further improvement of the present invention is that the ground grid conductor is segmented into several segments of conductors, and the current flowing through each segment of the conductor after segmentation is collected. The specific method for obtaining the induced electromotive force of each segment of the conductor is as follows:

[0014] Wherein, is the induced electromotive force of the i-th segment of the conductor at the k-th segment of the conductor, is the current flowing through the i -th segment of the conductor, is the resistance of the i-th segment of the conductor at the k-th segment of the conductor, μ is the magnetic permeability, ε is the permittivity.

[0015] A further improvement of the present invention is that, according to the induced electromotive force of each segment of the conductor, the specific method for calculating the sum of the electromotive forces induced by the currents on all conductor segments on this conductor is as follows:

[0016] Wherein, is the sum of the electromotive forces induced by the currents on all conductor segments on this conductor, is the number of segments of the segmented ground grid conductor.

[0017] A further improvement of the present invention is that if there are b end points in the segmented ground grid, then due to the shorter length of the segmented ground grid conductor, the potential i on the U i -th segment of the conductor can be taken as the average value of the voltages V j1 and V j2 of the two adjacent end points, that is:

[0018] Written in matrix form as:

[0019] Similarly, the scattered currents I d of each segment of the conductor are evenly divided into two parts and flow into the ground from the two connected nodes, then:

[0020] In the formula, J is the equivalent current of each node for dissipating current.

[0021] A further improvement of the present invention lies in that Kirchhoff's current law (KCL) and Kirchhoff's voltage law (KVL) are applied to the segmented ground grid conductors, and the specific method for obtaining the current and voltage relationship of the segmented ground grid conductors is as follows: Applying Kirchhoff's current law (KCL) and Kirchhoff's voltage law (KVL) to the segmented ground grid conductors, we get:

[0022] Wherein, Y is the branch admittance matrix, including the axial resistance and self-inductive reactance of each conductor segment; A is the incidence matrix; I 1 is the current flowing through each conductor, F is the injection current column vector.

[0023] A further improvement of the present invention lies in that according to the current and voltage relationship of the segmented ground grid conductors, a node admittance equation is established, and the specific method for obtaining the relationship between the conductive potential and the current for dissipating current is as follows: According to the current and voltage relationship of the segmented ground grid conductors, a node admittance equation is established: .

[0024] A further improvement of the present invention lies in that by using the Green's function, the relationship between the potential of the ground grid conductors and the current for dissipating current is obtained:

[0025] Wherein, Z is the mutual impedance matrix between each conductor segment.

[0026] Compared with the prior art, the present invention has the following beneficial effects: By inputting the electromagnetic data of the ground grid conductor into the spatial interference calculation and analysis model, the present invention can dynamically evaluate the distance of electromagnetic interference and accurately determine the location of the interference source and its impact on surrounding devices. The introduction of the electromagnetic data of the ground grid conductor enables this method to accurately capture the source and propagation characteristics of electromagnetic interference, solving the problem that it is difficult for traditional methods to accurately identify the interference source. Compared with static modeling, the present invention makes the location and influence range of the interference source more accurate, especially suitable for dealing with complex and dynamically changing electromagnetic environments. The present invention segments the ground grid conductor and collects the current flowing through each segment of the conductor, thereby calculating the induced electromotive force of each segment. The calculation of these induced electromotive forces is further used to obtain the sum of the electromotive forces of each segment of the current on the conductor. Based on these calculations, the distribution of current and voltage can be accurately obtained, avoiding the limitation of ignoring local current and voltage changes in traditional methods. Segmenting the current and voltage of the conductor can provide more detailed and accurate current and voltage distribution information, providing higher calculation accuracy for the interaction between conductors in complex electrical systems. By using Kirchhoff's current law (KCL) and Kirchhoff's voltage law (KVL) to process the segmented ground grid conductor, the present invention can effectively capture the relationship between current and voltage and establish the relationship between conductive potential and scattered current through the nodal admittance equation. In this way, not only can the current and voltage relationship between conductors be accurately described, but also the influence of the electromagnetic coupling effect can be analyzed. The electromagnetic coupling effect has an important impact on the stability of the electrical system. By accurately calculating the relationship between current and voltage, the electromagnetic coupling effect between conductors can be revealed, helping to optimize the system design and reduce unnecessary interference and energy loss. In summary, the present invention can significantly improve the stability and compatibility of the electrical system in a complex electromagnetic environment by accurately identifying the electromagnetic interference source, accurately calculating the distribution of current and voltage, and analyzing the electromagnetic coupling effect. These beneficial effects not only solve the problems of insufficient current and voltage distribution, interference source location, and electromagnetic coupling effect in traditional calculation methods, but also provide a reliable technical guarantee for the design, optimization, and fault prevention of electrical systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a flowchart of the present invention; Figure 2 is a spectrum diagram of the overvoltage waveform of phase A during bus charging; Figure 3 is a spectrum diagram of the overvoltage waveform of phase A when the small filter is put into operation. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] To further understand the content of the present invention, the following describes the present invention in detail with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments are only for explaining the present invention and not for limiting it.

[0029] SeeFigure 1 , a calculation method for the propagation path of interference sources based on the situation of bus overvoltage, comprising the following steps: S1. Construct a spatial interference calculation and analysis model according to historical data, and use Maxwell's equations as the control equation of the spatial interference calculation and analysis model.

[0030] S2. Obtain the electromagnetic data of the ground grid conductor, and send the interference data into the spatial interference calculation and analysis model to obtain the distance between the interfered point and the interference source.

[0031] S3. According to the distance between the interfered point and the interference source, segment the interfered ground grid conductor into several segments of conductors, collect the current flowing through each segment of the conductor after segmentation, and obtain the induced electromotive force of each segment of the conductor.

[0032] S4. According to the induced electromotive force of each segment of the conductor, calculate the sum of the electromotive forces induced by the currents on all conductor segments on this conductor.

[0033] S5. Process the segmented ground grid conductor by using Kirchhoff's current law KCL and Kirchhoff's voltage law KVL to obtain the current and voltage relationship of the segmented ground grid conductor.

[0034] S6. According to the current and voltage relationship of the segmented ground grid conductor, establish a nodal admittance equation to obtain the relationship between the potential of the ground grid conductor and the scattered current.

[0035] S7. Analyze the relationship between the potential of the ground grid conductor and the scattered current to obtain the propagation path of the interference source on the secondary equipment.

[0036] Example 1: Since the bus of the first large group of AC filters is the closest to the space of the synchronous condenser plant in terms of spatial distance, the electromagnetic field generated by the overvoltage of its bus interferes most strongly with the synchronous condenser plant. Therefore, the position of the excitation source is selected as the position of the bus of the first large group of AC filters. The AC filter bus is enclosed in the GIS structure, and the overvoltage waveform on the A-phase bus is used as the excitation for electromagnetic field calculation. To show the coupling effect between the GIS bus and the shell, the height of the bus from the ground is set to 1 m, and an excitation is applied to it. A long conductor is set 0.5 m below it to simulate the shell of the GIS, and it is set to be connected to the main ground grid every 10 m, and the local model of the AC filter bus is established When the AC filter bus is charged, the excitation is respectively selected as the A-phase overvoltage waveform with the A-phase closing angle of 0° and the bus residual voltage of -1.0 p.u., and the A-phase overvoltage waveform with the A-phase closing angle of 0° and the bus residual voltage of -1.0 p.u. when the small filter is put into operation. Fourier transforms are performed on the two waveforms, and the obtained spectrograms are respectively as Figure 2 and Figure 3As shown in the figure, the 5 data points with the largest frequency amplitude are marked as the frequency and amplitude of the subsequent excitation source.

[0037] Embodiment 2: Step 1, construct an electromagnetic interference analysis model: Construct a spatial interference calculation and analysis model based on historical data, and use Maxwell's equations as the control equations of the spatial interference calculation and analysis model. Among them, the magnetic field strength , electric field strength , electric displacement vector , magnetic flux density and other variables satisfy the following equations:

[0038] Among them, is the conduction current density, is the space charge density, Step 2, obtain the electromagnetic data of the ground grid conductor, and introduce the vector magnetic potential and scalar electric potential: Express the magnetic flux density as the curl of the vector magnetic potential A : =rot A Combined with Maxwell's equations, the electric field strength can be expressed as:

[0039] Among them, is the angular frequency, is the scalar electric potential. Substitute it into Maxwell's equations to obtain the d'Alembert equations:

[0040] Among them, is the phase constant, μ , ε are the magnetic permeability and permittivity respectively.

[0041] Step 3, calculate the influence of the interference source on the affected point: The influence of the electromagnetic interference source on the affected point can be expressed by the following general solution:

[0042] Among them, is the distance between the affected point and the interference source, and V is the volume where the interference source is located.

[0043] Step 4, consider the influence of the ground grid: Assume that the ground grid conductor is divided into ns section, and the current flowing through each section of the conductor is I i , then the i th section of the conductor to the k th section of the conductor's induced electromotive force is:

[0044] The induced electromotive force on the ground grid conductor section is the sum of the electromotive forces induced by the currents on all conductor sections on this conductor:

[0045] Step Five, establish the nodal admittance equation: In the segmented ground grid conductor, assuming there are 𝑏 endpoints, the following equations are obtained through Kirchhoff's Current Law (KCL) and Kirchhoff's Voltage Law (KVL):

[0046] Among them, Y is the branch admittance matrix, which only contains the axial resistance and self-inductive reactance of each conductor section; A is the incidence matrix; I 1 is the current flowing through each conductor, F is the injection current column vector, J is the equivalent spreading current.

[0047] Finally, the nodal admittance equation is:

[0048] Step Six, use the Green's function to represent the relationship between potential and current: According to the Green's function, the relationship between the potential 𝑈 and the spreading current can be obtained:

[0049] Among them, Z is the mutual impedance matrix between each conductor section.

[0050] Step Seven, analyze the relationship between the potential of the ground grid conductor and the spreading current, and obtain the propagation path of the interference source on the secondary equipment.

[0051] Combined with numerical calculation methods, the above equations can be solved. Common numerical methods include: Finite Element Method (FEM): Used to solve the electromagnetic field distribution, especially suitable for electromagnetic problems with irregular geometric shapes.

[0052] Finite Difference Method (FDM): Used to solve the numerical solution of the electromagnetic field equation.

[0053] Matrix solution: Perform matrix operations on the nodal admittance equations to solve for distributions such as current and voltage.

[0054] Through these numerical calculation methods, the potential distribution, current distribution in the grounding grid and their interference effects on secondary equipment can be obtained.

[0055] By modeling and numerically solving the electromagnetic interference source and the grounding grid, the impact of interference on the affected equipment can be predicted. Considering the shielding effect of the soil and the dominant role of inductive coupling, and ignoring the capacitive coupling component, the calculation complexity can be effectively reduced and a more accurate interference analysis result can be obtained.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications or equivalent replacements can still be made to the specific implementation manners of the present invention, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention shall be covered by the protection scope of the claims of the present invention.

Claims

1. A method for calculating the propagation path of interference sources based on bus overvoltage conditions, characterized in that: The following steps are involved: A spatial interference calculation and analysis model is constructed based on historical data, and Maxwell equations are used as the control equations of the spatial interference calculation and analysis model; Obtain the electromagnetic data of the ground grid conductor, send the interference data into the spatial interference calculation and analysis model, and obtain the distance between the interfered point and the interference source; According to the distance between the interfered point and the interference source, the interfered ground grid conductor is segmented into several conductor segments, and the current flowing through each conductor segment after segmentation is collected to obtain the induced potential of each conductor segment; According to the induced potential of each conductor segment, calculate the sum of the potentials induced on the conductor by the current on all conductor segments; The segmented ground grid conductor is processed by Kirchhoff's current law KCL and Kirchhoff's voltage law KVL to obtain the current and voltage relationship of the segmented ground grid conductor. According to the current and voltage relationship of the segmented ground grid conductor, the node admittance equation is established to obtain the relationship between the potential of the ground grid conductor and the scattered current; Analyze the relationship between the potential of the ground grid conductor and the scattered current to obtain the propagation path of the interference source on the secondary equipment.

2. The method for calculating the interference source propagation path based on bus overvoltage conditions according to claim 1 is characterized in that: Maxwell's equations are: in, H is the magnetic field strength; B is the magnetic flux density; D is the electric displacement vector; E is the electric field strength; ρ is the space charge density; J s is the conduction current density.

3. The method for calculating the interference source propagation path based on bus overvoltage conditions according to claim 1, characterized in that: The specific method of obtaining the electromagnetic data of the ground grid conductor and feeding the interference data into the spatial interference calculation and analysis model to obtain the distance between the interfered point and the interference source is as follows: Based on Maxwell's equations , introducing vector magnetic potential A and scalar bit functions φ ,make B =rot A ,but: In the formula, is the phase constant, μ , ε are the magnetic permeability and dielectric constant respectively; According to Maxwell's equations, we get D'Alembert's equations: in, is the phase constant, μ is the magnetic permeability, ε is the dielectric constant; Collect interference data in real time, send the interference data to the spatial interference calculation and analysis model, and calculate the distance between the interfered point and the interference source by the following method: in, is the distance between the interfered point and the interference source.

4. The method for calculating the interference source propagation path based on bus overvoltage conditions according to claim 1, characterized in that: The specific method of dividing the ground grid conductor into several conductor segments, collecting the current flowing through each conductor segment after segmentation, and obtaining the induced potential of each conductor segment is as follows: in, is the induced potential of the i-th conductor at the k-th conductor, For the i The current flows through the conductor segment. is the resistance of the i-th conductor at the k-th conductor, μ is the magnetic permeability, ε is the dielectric constant.

5. The method for calculating the interference source propagation path based on bus overvoltage conditions according to claim 4 is characterized in that: According to the induced potential of each conductor segment, the specific method for calculating the sum of the potentials induced on the conductor by the current on all conductor segments is as follows: in, is the sum of the potentials induced on the conductor by the currents in all conductor segments. The number of segments the ground grid conductor is divided into.

6. The method for calculating the interference source propagation path based on bus overvoltage conditions according to claim 1, characterized in that: If the segmented ground network exists b endpoints, since the ground grid conductor after segmentation is shorter, the first i The potential on the conductor segment U i Take the voltage of the two adjacent points V j1 and V j2 The mean of , that is: Written in matrix form: Similarly, the scattered current of each conductor segment I d It is divided into two parts and flows into the earth from the two nodes connected to it, then: In the formula, J is the equivalent scattered current of each node.

7. The method for calculating the interference source propagation path based on bus overvoltage conditions according to claim 1, characterized in that: The specific method of using Kirchhoff's current law KCL and Kirchhoff's voltage law KVL to process the segmented ground grid conductor to obtain the current and voltage relationship of the segmented ground grid conductor is as follows: Applying Kirchhoff's current law KCL and Kirchhoff's voltage law KVL to the segmented ground grid conductor, we get: in, Y is the branch admittance matrix, including the axial resistance and self-inductance of each conductor segment; A is the correlation matrix; I 1 is the current flowing through each conductor, F is the injected current column vector.

8. The method for calculating the interference source propagation path based on bus overvoltage conditions according to claim 1, characterized in that: According to the current and voltage relationship of the segmented ground grid conductor, the specific method of establishing the node admittance equation is as follows: According to the current and voltage relationship of the segmented ground grid conductor, the node admittance equation is established: 。 9. The method for calculating the interference source propagation path based on bus overvoltage conditions according to claim 8, characterized in that: Using Green's function, the relationship between the potential of the ground grid conductor and the scattered current is obtained: in, Z is the mutual impedance matrix between the conductor segments.

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