Converter transformer vibration noise control method and system, terminal and medium

Abstract

The invention belongs to the technical field of converter transformers, and particularly discloses a converter transformer vibration noise control method and system, a terminal and a medium, and the method comprises the steps: constructing a converter transformer structure geometric model, setting material attributes, and carrying out the grid division; based on the geometric model, establishing an electromagnetic field simulation model, applying excitation conditions, obtaining electromagnetic field distribution, establishing an iron core magnetostriction mathematical model, calculating vibration acceleration caused by magnetostriction and transient electromagnetic force of an iron core and a winding, and solving and extracting a displacement field and stress-strain response; establishing an acoustic coupling model on the basis of a structure vibration result, and calculating sound pressure level distribution under different frequencies by setting a structure-air coupling boundary and a matching layer; according to an acoustic simulation result, an iron core positioning structure and an oil tank reinforcing rib arrangement mode are optimized, vibration noise prediction and control of the converter transformer in a multi-harmonic excitation environment are realized, and equipment structure stability, operation reliability and environment adaptability are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of converter transformers, and particularly relates to a vibration and noise control method, system, terminal and medium for a converter transformer. Background Art

[0002] A converter transformer is a core device in a high-voltage direct current (HVDC) transmission system, playing a key role in AC-DC high-voltage conversion and electrical isolation. It is crucial for long-distance power transmission, new energy grid connection, and grid interconnection across regions, directly affecting the efficiency and safety of the entire power system.

[0003] With the increase in voltage levels and electrical loads, the operating converter transformer brings some negative impacts. In particular, the mechanical vibrations and noises caused by high-order harmonics brought about by the characteristics of the converter valve itself not only affect the service life of the converter transformer but also cause serious environmental pollution problems. Moreover, to improve the fire resistance performance of the equipment, the new converter transformer abandons the traditional "BOX-IN" technology, that is, abandons the isolation baffle, which leads to more serious noise problems. Currently, the vibrations of the converter transformer are mainly transmitted to the tank wall through liquid media such as transformer oil, resulting in amplified vibrations and increased noises.

[0004] Most of the existing studies mainly focus on the magnetostrictive effect of the iron core and the vibration and noise mechanisms of traditional power transformers. Their results are mainly applied to fault diagnosis technologies based on transformer vibration and noise signals, under power frequency excitation and idealized load conditions, lacking the modeling and response analysis of the actual working state of the converter transformer in a multi-harmonic environment in the HVDC system. Especially under the action of non-sinusoidal harmonic currents, factors such as the local magnetostrictive intensity of the iron core, uneven distribution of winding electromagnetic forces, and coupled vibration of the tank structure are coupled with each other. Traditional analysis methods are difficult to accurately reveal the transfer relationship between excitation and response, restricting the development of effective structure optimization and noise control means. Summary of the Invention

[0005] In view of the problems in the existing technology, the present invention provides a vibration and noise control method, system, terminal and medium for a converter transformer, solving the problem that under the action of non-sinusoidal harmonic currents in the existing technology, factors such as the local magnetostrictive intensity of the iron core, uneven distribution of winding electromagnetic forces, and coupled vibration of the tank structure are coupled with each other, and traditional analysis methods are difficult to accurately reveal the transfer relationship between excitation and response, restricting the development of effective structure optimization and noise control means.

[0006] The technical solution adopted by the present invention is as follows: In a first aspect, the present application provides a vibration and noise control method for a converter transformer, the method comprising the following steps: Step S1, construct a structural geometric model of the converter transformer, set the material properties of the converter transformer, and perform mesh division on the model; Step S2: Establish an electromagnetic field simulation model based on the geometric model. Define the magnetic flux density and the relationship between the magnetic field and current in the electromagnetic field simulation model, and apply electromagnetic excitation conditions in the electromagnetic field simulation model to obtain the electromagnetic field distribution in the iron core and winding. The electromagnetic field distribution includes the magnetic induction intensity distribution and the current density distribution. Step S3: Based on the electromagnetic field distribution, establish a magnetostriction mathematical model of the iron core, calculate the vibration acceleration caused by the magnetostriction of the iron core, and calculate the electromagnetic forces on the iron core and winding. Step S4: Establish a finite element model, set mechanical vibration boundary conditions in the finite element model. The mechanical vibration boundary conditions include fixed constraints on both end faces of the iron core and elastic constraints on the connection surface with the oil tank. Apply the vibration acceleration of the iron core and the electromagnetic force on the winding obtained in Step S3 as external excitations to the finite element model, conduct transient structural mechanics simulation analysis, and solve and extract the displacement field distribution and stress-strain response of the iron core and winding. Step S5: Construct a coupled sound field model, set a matching layer at the structure-air coupling boundary, calculate the sound pressure level based on the mechanical vibration boundary displacement results, and obtain the sound pressure response of the converter transformer body at different frequencies. Step S6: Based on the analysis results of the sound pressure response, optimize the iron core positioning structure and the arrangement method of the oil tank stiffeners of the converter transformer.

[0007] Further, in Step S2, in the electromagnetic field simulation model, the magnetic flux density is defined as:

[0008] When current passes through the winding, the relationship between the magnetic field and current is as follows:

[0009] where, is the magnetic permeability, with the unit of H / m; is the vector magnetic potential; is the current density, is the conductivity, is the differential operator.

[0010] Further, in Step S3, the vibration acceleration caused by the magnetostriction of the converter transformer iron core is expressed as:

[0011] where, a is the vibration acceleration; L is the length of the iron core; is the length change; is the number of turns; is the cross-sectional area of the iron core; is the saturation magnetic induction intensity; is the angular frequency of the excitation current; is the peak value of the excitation voltage; is the magnetostrictive coefficient; The magnetostriction mathematical model of the iron core is expressed as:

[0012]

[0013] where, is the magnetostrictive acceleration coefficient; is the elastic modulus of the iron core; is the Poisson's ratio of the iron core; is the thickness direction of the iron core; is the magnetostrictive coefficient of the iron core in the Z direction; is the length of the iron core in the Z direction; is the change in the length of the iron core in the Z direction, and t is the time variable, is the strain of the iron core in the Z direction; The expression for the electromagnetic force on the winding is:

[0014] In the formula, is the electromagnetic force exerted by the current element on the winding; is the magnetic flux at the location of the current element, that is, the magnetic induction intensity of the leakage magnetic field; is the current in the winding; is the effective length of the winding.

[0015] Furthermore, in the sound pressure level calculation of step S5, a wave equation describing the propagation of transformer vibration in air is established, and its mathematical expression is:

[0016] where, is the speed of sound, is the effective sound pressure of the measured sound pressure, represents the differential operator, where .

[0017] Furthermore, the expression for the effective sound pressure of the measured sound pressure is:

[0018] where, is the measured sound pressure; is the measurement time window; Calculate the sound pressure level:

[0019] where, represents the minimum audible threshold that can be perceived by the human ear at a frequency of 1 kHz. In air, take 2×10-5 Pa.

[0020] Further, in step S5, a matching layer is set at the structure-air coupling boundary, and the Galerkin method is used to discretize the structural-acoustic coupling control equation. Integration is performed at the connection between the air domain and the transformer structure to obtain the finite element discretization equation for the coupling of air and the core winding of the converter transformer:

[0021] Wherein, is the mass matrix of the converter transformer structure domain, , is the acoustic-solid coupling mass matrix, is the coupling matrix, is the air density, , is the acoustic-solid coupling stiffness matrix, is the nodal sound pressure value, nodal sound pressure acceleration vector, is the nodal sound pressure velocity vector, is the damping matrix of the structure domain, is the acoustic damping matrix of the air domain, is the mass matrix of the coupling connection surface between air and the transformer, is the stiffness matrix of the structure domain, is the stiffness matrix of the air domain sound field, is the mass matrix of air, is the acceleration vector of the transformer structure nodes, is the velocity vector of the transformer structure nodes, is the displacement vector of the structure domain nodes, is the external excitation force vector acting on the structure nodes.

[0022] Further, in step S6, the core positioning structure of the converter transformer adopts a cast-in positioning pin structure.

[0023] Second, the present application provides a vibration and noise control system for a converter transformer. The system includes: A modeling module for constructing a geometric model of the converter transformer structure, setting the material properties of the converter transformer, and performing mesh division on the geometric model; An electromagnetic simulation module for establishing an electromagnetic field simulation model based on the geometric model, defining the magnetic flux density and the relationship between magnetic field and current in the electromagnetic field simulation model, applying electromagnetic excitation conditions, and obtaining the electromagnetic field distribution in the core and winding. The electromagnetic field distribution includes the magnetic induction intensity distribution and the current density distribution; The electromagnetic force calculation module is used to establish a mathematical model of magnetostriction of the iron core according to the electromagnetic field distribution, calculate the vibration acceleration caused by the magnetostriction of the iron core, and calculate the electromagnetic forces on the iron core and windings; The structural simulation module is used to establish a finite element model and set mechanical vibration boundary conditions. The boundary conditions include fixed constraints on both end faces of the iron core and elastic constraints on the connection surface with the oil tank. The vibration acceleration and electromagnetic forces are used as external excitations and loaded onto the finite element model to perform transient structural mechanics simulation analysis to obtain the displacement field and stress-strain distribution of the iron core and windings; The sound field simulation module is used to construct a structure-air coupled sound field model, set a matching layer at the coupled boundary, and calculate the sound pressure level based on the mechanical vibration boundary displacement results to obtain the sound pressure response of the converter transformer body at different frequencies; The structural optimization module is used to output an optimized adjustment plan for the iron core positioning structure and the arrangement method of the oil tank stiffeners based on the analysis results of the sound pressure response.

[0024] In a third aspect, the present application provides a terminal, including: A memory for storing a converter transformer vibration and noise control program; A processor for implementing the steps of the converter transformer vibration and noise control method as described in the first aspect when executing the converter transformer vibration and noise control system.

[0025] In a fourth aspect, the present application provides a computer-readable storage medium. The storage medium stores computer instructions. When a computer reads the computer instructions in the storage medium, the computer executes the converter transformer vibration and noise control method as described in the first aspect.

[0026] It can be seen from the above technical solutions that the advantages of the present invention are: (1) This method system integrates the structural geometric modeling of the converter transformer, the solution of electromagnetic field excitation, the calculation of magnetostriction vibration acceleration and winding electromagnetic forces, the transient response analysis of finite element structural mechanics, and the acoustic sound pressure coupling simulation, realizing the coupled calculation process of multiple physical fields. It can accurately predict the impact of transformer structure design on vibration and noise in a digital simulation environment, improve the design optimization efficiency and product reliability, and reduce the investment in physical tests.

[0027] (2) An electromagnetic field model based on parameters such as magnetic permeability, vector magnetic potential, and current density is adopted to accurately reflect the magnetic flux density distribution generated by the winding excitation current, realizing the physical consistency of electromagnetic force calculation. Combining the magnetostriction mathematical model of the iron core with the winding electromagnetic force expression, the key excitation sources are quantitatively described, providing a theoretical basis for the input of structural vibration excitation and improving the accuracy and scientific nature of vibration response analysis.

[0028] (3) Through finite element transient mechanics simulation, taking the core vibration acceleration and winding electromagnetic force as external excitations, solve the displacement field and stress-strain response of the structure. Combine the structure-air coupled acoustic model and the acoustic wave propagation wave equation to comprehensively simulate the sound field distribution and sound pressure response caused by structural vibration, and scientifically evaluate the noise characteristics in the transformer operating environment.

[0029] (4) Introduce the Galerkin method to perform finite element discretization on the continuous medium acoustic wave equation, accurately handle the structure-air coupling boundary conditions, improve the numerical stability and accuracy of acoustic simulation, enhance the applicability of the model under complex boundary and heterogeneous medium conditions, and meet the high-precision sound field simulation requirements in engineering practice.

[0030] (5) Based on the effective sound pressure calculation and sound pressure level conversion of the measured sound pressure, combined with the human ear auditory threshold standard, quantify the simulation acoustic results into objective sound pressure level indicators, provide a scientific basis for noise performance evaluation of different structural schemes, and support the structural optimization decision-making based on acoustic indicators.

[0031] (6) Optimize the core positioning structure of the converter transformer based on the sound pressure response results. Adopt the cast-in-place positioning pins combined with the arrangement of the tank stiffeners to effectively suppress the structural vibration and noise generation, improve the stability and vibration resistance of the transformer structure, extend the service life of the equipment, and improve the operation safety and reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions of the present invention, the drawings required for description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0033] Figure 1 It is a schematic flow chart of the vibration and noise control method for the converter transformer; Figure 2 It is a schematic structural diagram of the physical model of the converter transformer; Figure 3 It is a schematic diagram of the finite element mesh division of the converter transformer; Figure 4 It is a sound field model diagram of the converter transformer; Figure 5 It is a magnetic flux distribution diagram of the core and winding before and after filtering; Figure 5 In (a), it is the magnetic flux distribution diagram of the core before filtering; Figure 5 In (b), it is the magnetic flux distribution diagram of the core after filtering; Figure 5 In (c), it is the magnetic flux distribution diagram of the winding before filtering; Figure 5 In (d) is the distribution diagram of the filtered winding magnetic flux; Figure 6 Are the distribution diagrams of the iron core force and displacement before and after filtering; Figure 6 In (a) is the distribution diagram of the iron core force before filtering; Figure 6 In (b) is the distribution diagram of the iron core force after filtering; Figure 6 In (c) is the distribution diagram of the iron core displacement before filtering; Figure 6 In (d) is the distribution diagram of the iron core displacement after filtering; Figure 7 Are the distribution diagrams of the winding force and displacement before and after filtering; Figure 7 In (a) is the distribution diagram of the winding force before filtering; Figure 7 In (b) is the distribution diagram of the winding force after filtering; Figure 7 In (c) is the distribution diagram of the winding displacement before filtering; Figure 7 In (d) is the distribution diagram of the winding displacement after filtering; Figure 8 Is the time-frequency curve diagram of the converter transformer sound pressure; Figure 8 In (a) is the time domain diagram of the converter transformer sound pressure on the side; Figure 8 In (b) is the frequency domain diagram of the converter transformer sound pressure on the side; Figure 8 In (c) is the time domain diagram of the converter transformer sound pressure directly in front; Figure 8 In (d) is the frequency domain diagram of the converter transformer sound pressure directly in front; Figure 8 In (e) is the time domain diagram of the converter transformer sound pressure directly above; Figure 8 In (f) is the frequency domain diagram of the converter transformer sound pressure directly above; Figure 9 Are the no-load and load vibration waveform diagrams of three positioning methods; Figure 9 In (a) is the no-load time domain waveform diagram of three positioning methods; Figure 9 In (b) is the no-load frequency domain waveform diagram of three positioning methods; Figure 9 In (c) is the load time domain waveform diagram of three positioning methods; Figure 9 In (d) is the load frequency domain waveform diagram of three positioning methods; Figure 10Vibration waveform diagram of no-load under harmonic influence; Figure 10 In (a) is the no-load harmonic vibration waveform diagram under harmonic influence; Figure 10 In (b) is the load harmonic vibration waveform diagram under harmonic influence; Figure 11 Vibration waveform diagram of no-load for two kinds of fuel tank structures; Figure 11 In (a) is the no-load time-domain waveform diagram of two kinds of fuel tank structures; Figure 11 In (b) is the no-load frequency-domain waveform diagram of two kinds of fuel tank structures; Figure 11 In (c) is the load time-domain waveform diagram of two kinds of fuel tank structures; Figure 11 In (d) is the load frequency-domain waveform diagram of two kinds of fuel tank structures. Specific implementation manner

[0034] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0035] Please refer to Figure 1 As shown, the present invention provides a method for controlling the vibration and noise of a converter transformer, including the following steps: Step S1: Construct a geometric model of the converter transformer structure, set the material properties of the converter transformer, and perform mesh division on the model; Step S2: Based on the geometric model, establish an electromagnetic field simulation model, define the magnetic flux density and the relationship between the magnetic field and current in the electromagnetic field simulation model, and apply electromagnetic excitation conditions in the electromagnetic field simulation model to obtain the electromagnetic field distribution in the iron core and winding. The electromagnetic field distribution includes the magnetic induction intensity distribution and the current density distribution; Step S3: According to the electromagnetic field distribution, establish a magnetostriction mathematical model of the iron core, calculate the vibration acceleration caused by the magnetostriction of the iron core, and calculate the electromagnetic forces on the iron core and winding; Step S4: Establish a finite element model, set mechanical vibration boundary conditions in the finite element model. The mechanical vibration boundary conditions include fixed constraints on both end faces of the iron core and elastic constraints on the fuel tank connection surface. Apply the vibration acceleration of the iron core and the electromagnetic force of the winding obtained in step S3 as external excitations to the finite element model, perform transient structural mechanics simulation analysis, and solve and extract the displacement field distribution and stress-strain response of the iron core and winding; Step S5: Build a coupled sound field model, set a matching layer at the structure-air coupling boundary, calculate the sound pressure level based on the mechanical vibration boundary displacement results, and obtain the sound pressure response of the converter transformer body at different frequencies; Step S6: Optimize the core positioning structure and the arrangement of the tank stiffeners based on the analysis results of the sound pressure response.

[0036] In some embodiments, in Step S2, the magnetic flux density is defined as:

[0037] When current passes through the winding, the relationship between the magnetic field and the current is as follows:

[0038] Where, is the magnetic permeability, with the unit of H / m; is the vector magnetic potential; is the current density, with the unit of A / mm 2 ; is the conductivity, with the unit of S / m; is the differential operator.

[0039] In some embodiments, in Step S3, the vibration of the converter transformer is mainly divided into two categories: the vibration of the main body and the vibration of the cooling system. Among them, the vibration of the main body is directly generated by the electromagnetic force and the magnetostrictive force, and can be specifically divided into the vibration of the core and the vibration of the winding.

[0040] The generation of the vibration noise of the converter transformer core is the result of the coupling of the electromagnetic-mechanical multi-physical fields, and its main reasons are the magnetostrictive effect, the leakage magnetic field and the electromagnetic force.

[0041] The transformer core is laminated with silicon steel sheets with high magnetic permeability and low conductivity. This material can significantly suppress the eddy current loss and optimize the electromagnetic performance. However, in an alternating magnetic field, the silicon steel sheets will undergo microscopic deformation due to the magnetostrictive effect - when the magnetic field strength changes, its lattice structure will produce periodic expansion and contraction (usually in the ppm order). This microscopic strain accumulates on the macroscopic scale of the core, forming a mechanical vibration synchronized with the magnetic field, thus triggering the periodic vibration of the core, which becomes one of the main sources of the vibration of the transformer body. The magnitude of the magnetostrictive deformation has a non-linear relationship with the magnetic field strength, especially significant when approaching the magnetic saturation region.

[0042] The vibration acceleration caused by the magnetostriction of the converter transformer core is expressed as:

[0043] Where, a is the vibration acceleration; L is the core length; is the length change; is the number of turns; is the core cross-sectional area; is the saturation magnetic induction intensity; is the angular frequency of the excitation current; is the peak value of the excitation voltage; is the magnetostriction; The mathematical model of the iron core considering magnetostriction is expressed as:

[0044]

[0045] in, is the magnetostrictive acceleration coefficient; is the elastic modulus of the core; is the Poisson's ratio of the core; is the thickness direction of the core; is the magnetostriction of the core in the Z direction; is the length of the core in the Z direction; is the length change of the core in the Z direction, t is the time variable, is the strain of the core in the Z direction; Under the excitation of an alternating magnetic field, silicon steel sheets undergo a periodic magnetization process, resulting in a pulsating electromagnetic attraction at 100 Hz (twice the power frequency) between adjacent laminations. If the core clamping structure has insufficient preload or mechanical looseness, this electromagnetic force can disrupt the frictional balance between the silicon steel sheets, causing periodic relative displacement of the laminations. This forced vibration, with a fundamental frequency of 100 Hz, is amplified by structural resonance, ultimately manifesting as significant core vibration and characteristic electromagnetic noise.

[0046] During converter transformer operation, the excitation current generates magnetic flux in the core, known as the main magnetic flux. When the transformer is connected to a load, the load current flows through the coils, generating a corresponding magnetic flux. In practice, due to factors such as the winding process, this magnetic flux cannot completely pass through the core. Some flux forms a magnetic linkage outside the core with the windings, a portion known as leakage flux. The transformer windings are exposed to a leakage magnetic field, and when current flows through them, they vibrate due to electromagnetic forces.

[0047] The expression of the electromagnetic force on the winding is:

[0048] In the formula, is the electromagnetic force exerted by the current element on the winding; is the magnetic flux at the location of the current element, that is, the magnetic induction intensity of the leakage magnetic field; is the current in the winding; is the effective length of the winding.

[0049] The alternating leakage magnetic flux generates a periodically varying electromagnetic force on the winding. When the winding becomes loose between turns due to manufacturing processes or long-term operation, these alternating electromagnetic forces force adjacent wires to undergo mechanical collisions and friction, thereby triggering high-frequency vibration noise. This effect of converting electromagnetic excitation into mechanical collision is one of the important causes of transformer winding noise.

[0050] In some embodiments, in step S5, for the vibration of the converter transformer to form a propagable sound wave, two basic elements must be present simultaneously: one is the mechanical vibration of the transformer body, and the other is the presence of a surrounding elastic medium (such as air). The sound wave propagating in air is essentially a longitudinal wave, and its propagation mechanism is manifested as follows: the vibration of the sound source causes the air molecules to undergo periodic density changes along the wave propagation direction, and this density fluctuation is essentially a process of compression and expansion of the medium under the action of sound pressure. When the sound wave passes through, the air molecules are subjected to alternating tensile and compressive forces, and the elastic restoring force of the medium itself pushes this perturbation to continue propagating forward. According to Stokes' hydrodynamic theory, a wave equation describing the propagation of transformer vibration in air is established, and its mathematical expression is:

[0051] where, is the speed of sound, is the sound pressure, represents the differential operator, where .

[0052] In some embodiments, noise measurement usually uses sound pressure (unit: Pa) and its logarithmic form - sound pressure level as quantization indicators. When a fluid medium (such as air) is perturbed by a sound wave, its static pressure will generate a dynamic fluctuation, and this instantaneous pressure change is defined as sound pressure. In actual measurement, to accurately characterize the energy characteristics of the sound wave, the effective sound pressure (i.e., the root mean square of the sound pressure instantaneous value, RMS) is used as the standard measure, and its mathematical expression is:

[0053] where, is the effective sound pressure of the measured sound pressure; is the instantaneous sound pressure; is the measurement time window; The actual sound pressure values span a very large range (from 20 micro-Pa at the human ear's hearing threshold to hundreds of Pa for a jet engine), and it is extremely inconvenient to express them using a linear scale. To solve the problem of the too large dynamic range in sound pressure measurement and to match the sound intensity with the human auditory perception characteristics, scholars introduced the concept of sound pressure level, which not only compresses the data range but also conforms to the non-linear perception characteristics of the human ear for sound intensity.

[0054] Calculate the sound pressure level:

[0055] Among them, represents the minimum audible threshold perceptible by the human ear at a frequency of 1 kHz, taking 2×10 -5 Pa in air.

[0056] In some embodiments, in step S5, a matching layer is set at the structure-air coupling boundary, and the Galerkin method is used to discretize the structural-acoustic coupling control equation, and integration is performed at the connection between the air domain and the transformer structure to obtain the finite element discretization equation for the coupling of air and the core winding of the converter transformer:

[0057] Among them, is the mass matrix of the converter transformer structure domain, , is the sound-solid coupling mass matrix, is the coupling matrix, is the air density, , is the sound-solid coupling stiffness matrix, is the nodal sound pressure value, nodal sound pressure acceleration vector, is the nodal sound pressure velocity vector, is the damping matrix of the structure domain, is the acoustic damping matrix of the air domain, is the mass matrix of the coupling connection surface between air and the transformer, is the stiffness matrix of the structure domain, is the stiffness matrix of the air domain sound field, is the mass matrix of air, is the acceleration vector of the transformer structure node, is the velocity vector of the transformer structure node, is the displacement vector of the structure domain node, is the external excitation force vector acting on the structure node.

[0058] In some embodiments, in step S6, the core positioning structure of the converter transformer adopts a cast-in-place positioning pin structure.

[0059] When studying the acoustic field characteristics around a converter transformer, it is necessary to comprehensively consider the coupling effect of multiple noise sources and the influence of the equipment structure complexity on the acoustic field distribution. The traditional simplified model, which equivalent the transformer to a spherical sound source, has certain limitations and cannot accurately reflect its true sound radiation characteristics. Therefore, this application adopts a high-precision modeling method and uses three-dimensional solid modeling technology to accurately restore the transformer body structure (including key components such as iron core, winding, and clamping parts), retaining the true geometric characteristics of the equipment and avoiding the acoustic field distortion error caused by spherical simplification. When establishing the fluid-structure interaction vibration transfer model, it is assumed that the vibration energy propagates without dissipation in the iron core-winding-air domain, the air-body interface satisfies the vibration displacement continuity condition, and the air medium damping effect is ignored (based on the analysis of acoustic wave propagation characteristics).

[0060] This application uses the operating and structural parameters of a ±800 kV converter transformer for modeling, and uses finite element analysis software to establish a physical model of the converter transformer. As Figure 2 shown, it can effectively solve the internal electric field, magnetic field, vibration, and sound pressure data of the converter transformer, obtain the distribution characteristics of displacement, magnetic field, force, and acoustic field, and study the mapping relationship between vibration, sound pressure, and other parameters on this basis.

[0061] To study the influence of multiple harmonic currents on the vibration and noise of the converter transformer, this application uses the method of multi-field coupling of electricity-magnetism-structure-acoustic field to establish a finite element simulation model of the transformer. Considering factors such as computational complexity, this application simplifies the finite element model to a certain extent on the premise of ensuring the model accuracy. The transformer spacers, end insulation, clamping parts, etc. are replaced by air domains, the iron core and winding adopt standard geometric structures, and the material properties of each module of the converter transformer finite element model are shown in Table 1. Due to the symmetry of the transformer structure and acoustic field properties, this application uses a 1 / 2 model for calculation, and the finally meshed finite element simulation model is as Figure 3 shown.

[0062] Table 1 Model material property table

[0063] In multi-physics field coupling simulation, usually two methods of direct coupling and indirect coupling are adopted. Direct coupling realizes high-precision simulation by simultaneously solving the control equations of different physical fields, but the computational amount is huge and the solution is complex; while indirect coupling adopts a sequential solution strategy, taking the calculation results of the previous physical field as the boundary conditions of the subsequent field, which significantly improves the computational efficiency while ensuring the calculation accuracy. For the electromagnetic-structure-acoustic coupling problem of the converter transformer, this application adopts an engineering practical indirect coupling method. The hemispherical air domain around the converter transformer with a radius of 4 m is set as the acoustic boundary, and a spherical shell with a thickness of 0.5 m is set as the perfectly matched layer. The acoustic field model of the converter transformer is as Figure 4 shown.

[0064] To study the influence of harmonic current on transformer vibration, in this application, the currents before and after filtering are respectively introduced into the transformer coil, and the vibration conditions of the internal components of the transformer are simulated and compared under different conditions. Figure 5 are the magnetic flux distribution conditions of the iron core and winding before and after filtering. From Figure 5 (a) in Figure 5 and (b) in it can be seen that the magnetic force lines generate a relatively high magnetic flux density at the inner corner of the iron core. This phenomenon indicates that the magnetostrictive effect at this place is more obvious than that at other positions. By comparing the magnetic flux distribution of the iron core before and after filtering, it can be found that the distribution of the magnetic flux density modulus of the iron core before filtering is uneven. The reason is that the input current of the transformer before filtering contains a large harmonic component, and this unstable current signal exacerbates the uneven distribution of the magnetic flux in the iron core. From Figure 5 (c) in Figure 5 and (d) in it can be seen that the current signal is relatively stable after filtering, has little influence on the magnetic field of the winding, and therefore the leakage magnetic flux is relatively small.

[0065] Figure 6 are the electromagnetic force and displacement distribution conditions of the iron core before and after filtering. For the convenience of observation, the force deformation factor is appropriately enlarged in this application. From Figure 6 (a) in, Figure 6 (b) in, Figure 6 (c) in, Figure 6 (d) in it can be seen that the maximum amplitude of the force on the iron core before and after filtering decreases from 8.6×10 7 N / m 2 to 5.6×10 7 N / m 2 , and the main force area is the side column of the iron core; the maximum displacement of the iron core decreases from 25.0×10 -4 m to 14.3×10 -4 m, and the displacement direction of the transformer is mainly perpendicular to the surface direction. After the current is filtered, the vibration displacement of the transformer decreases significantly, and this method can improve the operation stability of the converter transformer.

[0066] Figure 7 are the force and displacement conditions of the primary winding before and after filtering. From Figure 7 (a) in, Figure 7 (b) in, Figure 7 (c) in, Figure 7 (d) in it can be seen that the force amplitude of the winding before and after filtering decreases from 5.6×10 6 N / m 2 to 1.5×10 6 N / m 2 , and the main force area is the top edge area of the winding; due to the edge force, the surface of the winding is subjected to an inward squeezing force, resulting in deformation vibration. The displacement of the winding before and after filtering decreases from 10.8×10 -5 m to 3.8×10-5 For m, the improvement effect of current filtering on the stress and displacement of the transformer winding is more obvious. By current filtering, the high-frequency signal components in the winding can be reduced, the extremely rapid change and jump process of the signal can be alleviated, thereby reducing the force and displacement of the winding, improving the operating environment of the winding, and reducing the risk of winding failure.

[0067] To deeply explore the propagation mechanism of transformer noise, three measuring points are set around the transformer. Among them, measuring point 1 is located 1 m to the side of the transformer, measuring point 2 is located 1 m directly in front of the transformer, and measuring point 3 is located 1 m directly above the transformer. The time-domain waveforms of the transformer noise are collected at the three measuring points, and a fast Fourier transform is performed to obtain the relationship between the noise frequency and amplitude at the measuring points. The sound pressure distribution of the transformer in the time domain and frequency domain is as Figure 8 shown. The main concentration of the noise at each frequency is within 1 kHz. Among them, at 100 Hz and its multiples, the noise amplitude is relatively prominent.

[0068] The noise measurement parameter is the instantaneous sound pressure , with the unit of Pa, which means the air pressure minus the atmospheric pressure. The magnitude of its peak value can intuitively reflect the strength of the noise. From Figure 8 in (a), Figure 8 in (b), Figure 8 in (c), Figure 8 in (d), Figure 8 in (e), Figure 8 in (f), it can be seen that the sound pressure amplitude of the noise directly in front of the transformer is the largest, the average value of the sound pressure amplitude of the noise directly above the transformer is about 1 / 2 of the sound pressure amplitude of the noise directly in front of the transformer, and the sound pressure amplitude of the noise on the side is the smallest. The main reasons are related to the magnetostriction of the iron core and the vibration of the winding. Since the noise at the measuring point is affected by multiple vibration sources, the magnetostriction of the iron core has non-linear characteristics, the cross-sections of the corresponding levels of the multi-stage iron core center column and yoke are different, and the magnetic path lengths along the inner and outer frames of the iron core are different. The measuring point directly in front is more affected by the superimposed noise generated by each vibration source, and the noise amplitude is higher. From the frequency-domain distribution, it can be seen that the noise amplitude generated by the noise spectrum within 500 Hz in the spectra of the three measuring points is relatively large. Among them, the spectrum amplitude at 200 Hz in the side area is the largest, the spectrum amplitude at 300 Hz in the directly above area is the largest, and the directly in front area contains relatively high noise amplitudes at 300 Hz and 400 Hz.

[0069] This study designed the following three iron core positioning schemes for comparative analysis: Eccentric circular positioning nail structure. This structure realizes the upper positioning and fixation by fixing the positioning nail and the positioning part made of hot-pressed polyester laminate with bolts. This structure can well solve the problem of upper positioning error.

[0070] Cast-in-place positioning pin structure. This structure forms a matching positioning structure through the steel positioning pins on the box cover side, the positioning bowls on the iron core side, and the quick-setting epoxy resin casting layer, realizing the rigid connection between the iron core and the box cover.

[0071] Pressing pin positioning structure. The upper pressing pin positioning forms a pressing pin structure by arranging nuts and bolts on the box cover. The pressing pin is fixed to the upper beam of the iron core with upper positioning through a rubber plate. The positioning is firm and reliable, and it is commonly used in AC products.

[0072] Under power frequency conditions, no-load and load tests are respectively carried out on the converter transformers under the above three positioning methods, and the results are as Figure 9 shown. From Figure 9 the vibration acceleration results shown in (a) and Figure 9 (c), it can be seen that the vibration amplitude of the converter transformer under the cast-in-place positioning pin structure is the smallest, followed by the pressing pin positioning structure, and the anti-vibration effect of the eccentric circular positioning pin structure is the worst. From Figure 9 (b) and Figure 9 (d), it can be seen that the vibration frequency spectra of the iron core under the three positioning methods are concentrated in the range of 0 - 1 kHz, and the characteristic frequencies of the amplitudes are integer multiples of 100 Hz. The main vibration frequencies are distributed between 100 Hz and 400 Hz. Through comprehensive analysis of the time-domain and frequency-domain waveforms of the converter transformer, it can be known that among the three positioning methods, the cast-in-place positioning has the smallest vibration acceleration and the best anti-vibration effect, while the eccentric circular positioning pin structure has the worst effect.

[0073] No-load and load tests are respectively carried out on the converter transformers under the above three positioning methods, and the injected current contains harmonic components. From Figure 10 (a), it can be seen that compared with the no-load power frequency domain, the no-load harmonic frequency domain has a wider distribution, and the vibration frequency spectrum is distributed between 0 - 2 kHz. The main vibration frequency value increases, mainly the multiple frequency components of 100 Hz, and the reason is the influence of high-order harmonics such as the 7th harmonic in the current harmonics. Under no-load conditions, by analyzing the time-domain and frequency-domain waveforms, it can be known that the converter transformer under the positioning method of adding positioning pins to the upper beam has the smallest vibration acceleration and the best anti-vibration effect, while the positioning pin positioning method has the worst effect. From Figure 10 (b), it can be seen that compared with the load power frequency domain, the load harmonic frequency domain has a wider distribution, and the vibration frequency spectrum is distributed between 0 - 1 kHz. Affected by the high-order harmonics in the current harmonics, the main vibration frequencies are mainly between 500 Hz and 1 kHz, mainly the multiple frequency components of 100 Hz. According to the time-domain and frequency-domain waveforms, it can be known that under this condition, the vibration acceleration values of the cast-in-place positioning method and the positioning method of adding positioning pins to the upper beam are basically the same, and the anti-vibration effect is the best.

[0074] Adding stiffeners to the structure of the converter transformer tank can enhance the structural tightness of the tank and strengthen its physical structure strength. At the same time, adopting a better welding process can reduce the deformation of the welding points on the tank wall, increase the damping amount to reduce the change in vibration frequency during the vibration of the tank, thereby reducing resonance. Research and analysis are carried out on the improvement of the stiffener structure of the box body, and the effectiveness of the structural improvement is verified through the test of the scaled-down prototype.

[0075] No-load and load tests were carried out on two types of tank structures, and the results are as Figure 11 shown in (a), Figure 11 shown in (b), Figure 11 shown in (c), Figure 11 shown in (d). By comparing the time-domain and frequency-domain waveforms of the converter transformer tank before and after adding stiffeners, the following conclusions can be drawn: After adding stiffeners, the vibration amplitude of the converter transformer under no-load conditions decreases significantly. The stiffeners can enhance the stiffness of the converter transformer tank and reduce the influence of resonance. Due to the fixing effect of the stiffeners, the original vibration spectrum changes, with an increase in high-frequency components and a decrease in low-frequency components. Even when harmonic current is increased, the vibration amplitude of the converter transformer decreases and the harmonic frequency response weakens.

[0076] After adding stiffeners, the vibration amplitude of the converter transformer under load conditions decreases, which helps to improve the stability and anti-vibration ability of the transformer. The converter transformer shows a smoother characteristic in the frequency spectrum, which can reduce or eliminate resonance at certain frequencies. In summary, adding stiffeners to the converter transformer tank can change the vibration characteristics of the transformer, affect the vibration amplitude and frequency spectrum distribution under different working conditions to a certain extent, improve its stability, and reduce resonance conditions.

[0077] In some embodiments, the present application provides a vibration and noise control system for a converter transformer, which includes: A modeling module for constructing a three-dimensional structural geometric model of the converter transformer, setting the material properties of the iron core and windings, and completing mesh division; An electromagnetic simulation module for applying electromagnetic excitation conditions containing high-order harmonics in the model and calculating the magnetic flux density and electromagnetic force distribution in the iron core and windings based on the vector magnetic potential equation; A structural simulation module for setting mechanical boundary conditions and performing structural finite element analysis with the electromagnetic excitation as the input to obtain the stress and displacement distribution of the iron core and windings; An acoustic field analysis module for establishing a structure-air coupled acoustic field model, setting the matching layer boundary, performing sound pressure level calculation, and obtaining the acoustic response spectrum; A structural optimization module for outputting an optimization plan for the iron core positioning structure and the layout of the tank stiffeners based on the analysis results of the sound pressure response.

[0078] In some embodiments, the present application provides a terminal, including: A memory for storing a commutation transformer vibration and noise control program; A processor for implementing the steps of the commutation transformer vibration and noise control method when executing the commutation transformer vibration and noise control system.

[0079] In some embodiments, the present application provides a computer-readable storage medium, and the storage medium stores computer instructions. When a computer reads the computer instructions in the storage medium, the computer executes the commutation transformer vibration and noise control method.

[0080] The above content is only an example and illustration of the concept of the present invention. Those skilled in the art of the present technology can make various modifications or supplements to the described specific embodiments or use similar methods for substitution, as long as they do not deviate from the concept of the invention or exceed the scope defined by the present invention, they should fall within the protection scope of the present invention.

Claims

1. A vibration and noise control method for a converter transformer, characterized in that It includes the following steps: Step S1: Construct a geometric model of the converter transformer structure, set the material properties of the converter transformer, and perform mesh division on the model; Step S2: Establish an electromagnetic field simulation model based on the geometric model, define the magnetic flux density and the relationship between the magnetic field and current in the electromagnetic field simulation model, apply electromagnetic excitation conditions in the electromagnetic field simulation model, and obtain the electromagnetic field distribution in the iron core and windings. The electromagnetic field distribution includes the magnetic induction intensity distribution and the current density distribution; Step S3: According to the electromagnetic field distribution, establish a magnetostrictive mathematical model of the iron core, calculate the vibration acceleration caused by the magnetostriction of the iron core, and calculate the electromagnetic forces on the iron core and windings; Step S4: Establish a finite element model, set mechanical vibration boundary conditions in the finite element model. The mechanical vibration boundary conditions include fixed constraints on both end faces of the iron core and elastic constraints on the connection surface with the oil tank. Apply the vibration acceleration of the iron core and the electromagnetic force on the windings obtained in Step S3 as external excitations to the finite element model, perform transient structural mechanics simulation analysis, and solve and extract the displacement field distribution and stress-strain response of the iron core and windings; Step S5: Construct a coupled sound field model, set a matching layer at the structure-air coupling boundary, calculate the sound pressure level based on the mechanical vibration boundary displacement results, and obtain the sound pressure response of the converter transformer body at different frequencies; Step S6: Optimize the iron core positioning structure and the arrangement method of the oil tank stiffeners based on the analysis results of the sound pressure response; 2. The vibration and noise control method of the commutation transformer according to claim 1, characterized in that, In Step S2, in the electromagnetic field simulation model, the magnetic flux density is defined as: When current passes through the windings, the relationship between the magnetic field and current is as follows: wherein, is the magnetic permeability, with the unit of H / m; is the vector magnetic potential; is the current density, is the conductivity, is the differential operator.

3. The converter transformer vibration noise control method according to claim 2, characterized in that: In Step S3, the vibration acceleration caused by the magnetostriction of the converter transformer iron core is expressed as: Among them, a is the vibration acceleration; L is the core length; is the length change; is the number of turns; is the core cross-sectional area; is the saturation magnetic induction intensity; is the angular frequency of the exciting current; is the peak value of the exciting voltage; is the magnetostriction coefficient; The magnetostrictive mathematical model of the iron core is expressed as: Among them, is the magnetostrictive acceleration coefficient; is the elastic modulus of the iron core; is the Poisson's ratio of the iron core; is the thickness direction of the iron core; is the magnetostriction rate of the iron core in the Z direction; is the length of the iron core in the Z direction; is the change in the length of the iron core in the Z direction, where t is the time variable, is the strain of the iron core in the Z direction; The expression for the electromagnetic force on the windings is: Where, is the electromagnetic force exerted by the current element on the winding; is the magnetic flux at the location of the current element, that is, the magnetic induction intensity of the leakage magnetic field; is the current in the winding; is the effective length of the winding.

4. The vibration and noise control method of the commutation transformer according to claim 1, characterized in that In the sound pressure level calculation of Step S5, establish a wave equation describing the propagation of transformer vibration in the air, and its mathematical expression is: Among them, is the sound speed, is the effective sound pressure of the measured sound pressure, represents the differential operator, where .

5. The vibration and noise control method of the commutation transformer according to claim 4, wherein The effective sound pressure expression of the measured sound pressure is: Among them, is the measured sound pressure; is the measurement time window; Calculate the sound pressure level: in, It represents the minimum audible threshold that the human ear can perceive at a frequency of 1kHz, and 2×10 -5 Pa.

6. The converter transformer vibration noise control method according to claim 5, characterized in that: In Step S5, set a matching layer at the structure-air coupling boundary, and use the Galerkin method to discretize the structural-acoustic coupling control equation, and perform integration at the connection between the air domain and the transformer structure to obtain the finite element discretization equation for the coupling of air and the converter transformer iron core windings; Among them, is the mass matrix of the converter transformer structure domain, , is the acoustic-solid coupling mass matrix, is the coupling matrix, is the air density, , is the acoustic-solid coupling stiffness matrix, is the node acoustic pressure value, Node acoustic pressure acceleration vector, is the node acoustic pressure velocity vector, is the damping matrix of the structure domain, is the acoustic damping matrix of the air domain, is the mass matrix of the coupling connection surface between air and transformer, is the stiffness matrix of the structure domain, is the stiffness matrix of the air domain sound field, is the mass matrix of air, is the acceleration vector of the transformer structure node, is the velocity vector of the transformer structure node, is the displacement vector of the structure domain node, is the external excitation force vector acting on the structure node.

7. The vibration and noise control method of the commutation transformer according to claim 1, characterized in that In Step S6, the iron core positioning structure of the converter transformer adopts a cast-in-place positioning pin structure; 8. A converter transformer vibration noise control system, characterized in that: The system includes: A modeling module for constructing a geometric model of the converter transformer structure, setting the material properties of the converter transformer, and performing mesh division on the geometric model; An electromagnetic simulation module for establishing an electromagnetic field simulation model based on the geometric model, defining the magnetic flux density and the relationship between the magnetic field and current in the electromagnetic field simulation model, and applying electromagnetic excitation conditions to obtain the electromagnetic field distribution in the iron core and windings. The electromagnetic field distribution includes the magnetic induction intensity distribution and the current density distribution; An electromagnetic force calculation module for establishing a magnetostrictive mathematical model of the iron core according to the electromagnetic field distribution, calculating the vibration acceleration caused by the magnetostriction of the iron core, and calculating the electromagnetic forces on the iron core and windings; A structural simulation module, which is used to establish a finite element model, set mechanical vibration boundary conditions, where the boundary conditions include fixed constraints on both end faces of the iron core and elastic constraints on the connection surface of the oil tank, load vibration acceleration and electromagnetic force as external excitations to the finite element model, and perform transient structural mechanics simulation analysis to obtain the displacement field and stress-strain distribution of the iron core and windings; An acoustic field simulation module, which is used to construct a structure-air coupled acoustic field model, set a matching layer at the coupled boundary, and calculate the sound pressure level based on the boundary displacement results of mechanical vibration to obtain the sound pressure response of the converter transformer body at different frequencies; A structural optimization module, which is used to output an optimized adjustment plan for the iron core positioning structure and the arrangement method of the oil tank stiffeners based on the analysis results of the sound pressure response.

9. A terminal, characterized in that, Comprising: A memory, which is used to store the vibration and noise control program of the converter transformer; A processor, which is used to implement the steps of the converter transformer vibration and noise control method as described in claim 1 when executing the converter transformer vibration and noise control system.

10. A computer-readable storage medium, characterized in that, The storage medium stores computer instructions, and when the computer reads the computer instructions in the storage medium, the computer executes the converter transformer vibration and noise control method as described in claim 1.

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