Simulation analysis method and system for transformer vibration noise under direct current magnetic bias

Abstract

The invention discloses a simulation analysis method and system for transformer vibration noise under direct current magnetic bias, and the method comprises the steps: building a transformer geometric model, and carrying out the mesh generation of the transformer geometric model; external excitation of the transformer is set in the field-circuit coupling model of the transformer under the direct-current magnetic bias condition, and magnetic density distribution of the transformer under different magnetic bias currents is obtained through simulation; in the transformer electromagnetic structure coupling model, calculating to obtain vibration acceleration of the transformer under different bias currents; the vibration acceleration of the transformer serves as excitation, and sound pressure levels around the transformer under different bias currents are calculated; and analyzing the influence rule of different bias currents on the vibration noise of the transformer through the characteristic quantity of the frequency spectrum signal. According to the invention, the vibration noise characteristics of the transformer under different magnetic bias currents can be accurately simulated, and technical support is provided for judging whether the transformer has a direct current magnetic bias phenomenon or not. The method can improve the evaluation efficiency and simulation accuracy, and improve the noise pollution and overall performance of the transformer.

Description

Technical Field

[0001] The present invention belongs to the technical field of digital analysis of electric power equipment, and in particular relates to a simulation analysis method and system for transformer vibration noise under direct current bias. Background Art

[0002] As a common and important equipment in the current power system, the safe and stable operation of the transformer is crucial to the stable operation of the power system. With the rapid development of the power system and the large-scale construction of urban rail transit, the DC bias problem of transformers has not only caused serious interference in long-distance high-voltage transmission systems, but also affected the normal operation of transformers in urban power systems. DC bias in transformers not only leads to iron core saturation, but also causes abnormal vibration and noise in the transformer, affecting the stable operation of the power grid and even endangering the surrounding environment and human health. In addition, the vibration and noise generated by the transformer during operation are directly related to its operating status and internal defects. By analyzing the transformer's soundprint information, the transformer's operating status can be determined. However, at present, due to the difficulty in reproducing transformer tests under DC bias, the existing simulation methods of transformer vibration and noise characteristics have insufficient stability and accuracy of the simulation model, and cannot provide an effective reference for subsequent judgment of whether the transformer has a DC bias fault. Summary of the Invention

[0003] The present invention provides a simulation analysis method and system for transformer vibration noise under DC bias, aiming to solve the problem that the simulation method of the vibration noise characteristics of the transformer in the existing technology has insufficient stability and accuracy of the simulation model and cannot provide an effective reference for subsequent judgment whether the transformer has a DC bias fault.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions: A simulation analysis method for transformer vibration noise under DC bias magnetic conditions includes the following steps: S1. Based on the structural parameters of the transformer, establish a transformer geometric model; set the material parameters of the transformer, and mesh the transformer geometric model; S2. In the field-circuit coupling model of the transformer under DC bias conditions, set the external excitation of the transformer and simulate the magnetic flux density distribution of the transformer under different bias currents, where: The field-circuit coupling model of the transformer under DC bias conditions is constructed based on the transformer geometry model after meshing. S3. Using the magnetic flux density distribution as the excitation of the transformer electromagnetic structure coupling model, in the transformer electromagnetic structure coupling model, the vibration acceleration of the transformer under different bias currents is calculated; S4. Based on the acoustic-structure coupling model, the vibration acceleration of the transformer is used as the excitation to calculate the sound pressure level around the transformer under different bias currents. S5: Obtain characteristic quantities of the spectrum signal based on the sound pressure level around the transformer, and analyze the influence of different bias currents on the transformer vibration noise through the characteristic quantities of the spectrum signal.

[0005] In some embodiments, in S2, the field-circuit coupling model of the transformer under DC bias conditions includes a magnetic field model and a circuit model.

[0006] Furthermore, in S2, the field-circuit coupling of the field-circuit coupling model of the transformer specifically includes: if the initial voltage or initial current of the winding is known, the dynamic inductance of the winding is calculated using the magnetic field model, the dynamic inductance value is substituted into the circuit model, the instantaneous current is calculated, and then the current value is substituted into the magnetic field model as the excitation in the next calculation step to calculate the dynamic inductance until all calculation steps are completed.

[0007] In some embodiments, in S2, the magnetic field equation in the magnetic field model is as follows (1): (1); in, σ is the conductivity, A is the vector magnetic potential, μ 0 is the vacuum permeability, μ r is the relative magnetic permeability, J e is the winding current density. If the winding current density is known, the appropriate magnetic potential of the grid node can be calculated by this formula. A , thus obtaining the magnetic field distribution.

[0008] In some embodiments, in S3, in the solid mechanics physics field, all domains are selected in the linear elastic material, the core and winding are selected in the domain selection, and the load type is set to the force per unit volume Lorentz force contribution to simulate the electromagnetic force on each unit of the core and winding, and the magnetostrictive force of the core is calculated using the elastic mechanics model.

[0009] In some embodiments, in S3, calculating the magnetostrictive force of the core using an elastic mechanics model specifically includes: Assume that the stress of the core material is simulated as: (2); Where, S is the stress of the core material, C H is the elasticity tensor, is the initial strain, me (M) is the magnetostrictive strain,M is the magnetization field, and the magnetically induced secondary contraction model of the core material is set to nonlinear isotropic, with the following relationship: (3); Where, λ S is the core saturation magnetostriction coefficient, M S is the saturation magnetization, where M Vector tensor product: (4); At the same time, the nonlinear magnetization relationship of the core material is considered: (5); Where, M S is the saturation magnetization, L is the Langevin function, H eff is the effective magnetic field of the core material, and the relationship is as follows: (6); Where, χ m is the initial magnetic susceptibility of the core material, and the effective magnetic field of the core material can be obtained by the following formula: (7); Where, S ed is the elastic stress deviator, and H is the magnetic field strength of the core material.

[0010] In some embodiments, S4 specifically includes: assuming that the medium surrounding the transformer is a lightweight fluid, setting the acoustic-structural coupling model to single-phase coupling, adding time domain to frequency domain FFT and frequency domain respectively in the study; solving structural mechanics in the time domain, solving acoustics in the frequency domain, and using the FFT solver to convert the vibration acceleration from the time domain to the frequency domain.

[0011] In some implementations, in S4, in the frequency domain interface, the equation for solving the acoustic field is as follows: (8); In the formula p is the sound pressure, c is the speed of sound in air, w is the angular frequency, ρ is the air density.

[0012] In some embodiments, in S4, the characteristic quantities of the spectrum signal include the frequency domain amplitude average, the center frequency, and the odd-even harmonic ratio; the frequency domain amplitude average reflects the magnitude of the energy, the center frequency reflects the position of the main frequency band in the spectrum signal, and the odd-even harmonic ratio reflects the proportion of odd and even harmonics in the spectrum signal; if the noise spectrum signal at a point around the transformer is known, the expression for calculating the frequency domain amplitude average is: (9); Where, S a is the average value of the frequency domain amplitude, N is the number of frequency points, For the k The amplitude of each frequency point; The expression for calculating the center of gravity frequency is: (10); Where, f c is the center of gravity frequency, f k For the k The frequency value of each frequency point; The expression for calculating the odd-even harmonic ratio is: (11); Where, S o / e is the odd-even harmonic ratio, T is the number of odd and even harmonic frequencies, 、 They are the amplitudes of odd and even multiple harmonics of the fundamental frequency 50Hz respectively.

[0013] The present invention also provides a simulation system for transformer vibration noise under DC bias magnetic conditions, the system comprising a model construction module, a field-circuit coupling simulation module, an electromagnetic-structural coupling analysis module, an acoustic-structural coupling analysis module, and a spectrum signal analysis module, wherein: The model building module is used to establish a transformer geometric model based on the structural parameters of the transformer; The field-circuit coupling simulation module is used to construct a field-circuit coupling model of the transformer based on the meshed transformer geometry model under DC bias conditions, set external excitation for the transformer, and simulate the magnetic flux density distribution of the transformer under different bias currents. The electromagnetic structure coupling analysis module is used to input the magnetic flux density distribution as excitation into the transformer electromagnetic structure coupling model to calculate the vibration acceleration of the transformer under different bias currents; The acoustic-structure coupling analysis module is used to calculate the sound pressure level around the transformer under different bias currents based on the acoustic-structure coupling model and using the transformer's vibration acceleration as excitation. The spectrum signal analysis module is used to obtain the characteristic quantity of the spectrum signal based on the sound pressure level around the transformer, and evaluate the influence of different bias currents on the transformer vibration noise by analyzing the characteristic quantity of the spectrum signal.

[0014] Compared with the prior art, the simulation analysis method and system of transformer vibration noise under DC bias in the present invention have the following beneficial effects: The present invention provides a simulation analysis method for transformer vibration noise under direct current bias, comprising the following steps: S1, establishing a transformer geometric model based on structural parameters of the transformer; setting material parameters of the transformer, and meshing the transformer geometric model; S2, setting external excitation of the transformer in a field-circuit coupling model of the transformer under direct current bias conditions, and simulating to obtain magnetic flux distribution of the transformer under different bias currents, wherein the field-circuit coupling model of the transformer under direct current bias conditions is constructed based on the meshed transformer geometric model; S3, using the magnetic flux distribution as excitation of a transformer electromagnetic structure coupling model, and calculating the vibration acceleration of the transformer under different bias currents in the transformer electromagnetic structure coupling model; S4, based on the acoustic-structural coupling model, using the vibration acceleration of the transformer as excitation, and calculating the sound pressure levels around the transformer under different bias currents; S5: obtaining characteristic quantities of a spectrum signal based on the sound pressure levels around the transformer, and analyzing the influence of different bias currents on the vibration noise of the transformer through the characteristic quantities of the spectrum signal. Based on the above, the simulation analysis method of the present invention establishes an electromagnetic vibration model of the transformer under DC bias conditions, calculates the vibration acceleration of the transformer, establishes a transformer acoustic structure model, calculates the sound pressure level distribution around the transformer under DC bias, and uses the spectrum signal characteristics to analyze the vibration noise characteristics of the transformer under different bias currents. Finally, the change law of the transformer noise spectrum with the bias current is obtained, which can relatively accurately simulate the vibration noise characteristics of the transformer under different bias currents, and provide technical support for the subsequent judgment of whether the transformer has DC bias phenomenon.

[0015] The present invention can fully simulate the actual working state of the transformer under DC bias conditions, thereby accurately predicting the vibration noise characteristics of the transformer. This helps to evaluate the noise level of the transformer and avoid modifications and cost increases caused by noise problems in the later stage. In addition, the present invention not only focuses on the vibration noise results of the transformer, but also deeply analyzes the influence of different bias currents on vibration noise through the spectrum signal analysis module. This helps to more deeply understand the generation mechanism of transformer vibration noise and provide a theoretical basis for subsequent noise control and optimization. Through the simulation analysis of the present invention, the influence of different design parameters on transformer vibration noise can be quickly evaluated, which is expected to improve the overall performance of the transformer. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings in the specification are used to provide further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0017] Figure 1 A schematic diagram of a simulation analysis method for transformer vibration noise under DC bias and a flow chart of the method in the system according to the present invention; Figure 2 A schematic diagram of a geometric model of a transformer provided in an embodiment of a simulation analysis method and system for transformer vibration noise under DC bias magnetic field of the present invention.

[0018] Figure 3 The invention provides an external equivalent circuit of a transformer under DC bias magnetic field in a simulation analysis method and system for transformer vibration noise under DC bias magnetic field.

[0019] Figure 4 The present invention provides a simulation analysis method for transformer vibration noise under DC bias and a system for calculating the transformer core magnetic flux distribution according to an embodiment of the present invention.

[0020] Figure 5 The present invention provides a simulation analysis method for transformer vibration noise under DC bias and a system for calculating the transformer oil tank vibration acceleration distribution according to an embodiment of the present invention.

[0021] Figure 6 The xz plane sound pressure level distribution of the transformer is calculated in an embodiment of a simulation analysis method and system for transformer vibration noise under DC bias magnetic field of the present invention.

[0022] Figure 7 The yz plane sound pressure level distribution of the transformer is calculated in an embodiment of a simulation analysis method and system for transformer vibration noise under DC bias magnetic field of the present invention.

[0023] Figure 8 It is the frequency domain amplitude average value of the sound pressure spectrum signal 1m away from the transformer under different bias currents calculated in the embodiment of the simulation analysis method and system of the transformer vibration noise under DC bias of the present invention.

[0024] Figure 9 The centroid frequency of the sound pressure spectrum signal 1 meter away from the transformer under different bias currents calculated in an embodiment of a simulation analysis method and system for transformer vibration noise under DC bias of the present invention.

[0025] Figure 10 The odd-even subharmonic ratio of the sound pressure spectrum signal 1 meter away from the transformer under different bias currents is calculated in an embodiment of a simulation analysis method and system for transformer vibration noise under DC bias of the present invention. DETAILED DESCRIPTION

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0027] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0028] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0029] In the description of the embodiments of the present invention, it should be noted that if the terms "upper," "lower," "horizontal," "inner," etc. appear, the orientation or positional relationship indicated is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the inventive product is typically placed when in use. These terms are merely for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first," "second," etc. are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0030] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0031] In the description of the embodiments of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0032] like Figure 1As shown, the present invention provides a simulation analysis method for transformer vibration noise under DC bias, comprising the following steps: S1. Based on the structural parameters of the transformer, establish a transformer geometric model; set the material parameters of the transformer, and mesh the transformer geometric model; S2. In the field-circuit coupling model of the transformer under DC bias conditions, set the external excitation of the transformer and simulate the magnetic flux density distribution of the transformer under different bias currents, where: The field-circuit coupling model of the transformer under DC bias conditions is constructed based on the transformer geometry model after meshing. S3. Using the magnetic flux density distribution as the excitation of the transformer electromagnetic structure coupling model, in the transformer electromagnetic structure coupling model, the vibration acceleration of the transformer under different bias currents is calculated; S4. Based on the acoustic-structure coupling model, the vibration acceleration of the transformer is used as the excitation to calculate the sound pressure level around the transformer under different bias currents. S5: Obtain characteristic quantities of the spectrum signal based on the sound pressure level around the transformer, and analyze the influence of different bias currents on the transformer vibration noise through the characteristic quantities of the spectrum signal. The present invention provides a simulation analysis method for transformer vibration noise under DC bias. By establishing an electromagnetic vibration model of the transformer under DC bias conditions, the vibration acceleration of the transformer is calculated, and a transformer acoustic structure model is established. The sound pressure level distribution around the transformer under DC bias is calculated. Finally, based on the sound pressure level distribution, characteristic quantities of the spectrum signal such as the frequency domain amplitude average, center of gravity frequency, and odd-even subharmonic ratio are calculated. This method can comprehensively analyze the spectrum characteristics of the transformer vibration noise, provide more detailed data support for transformer noise control and optimization, and lay a foundation for subsequent transformer maintenance or early transformer design. The method has certain practical significance.

[0033] The simulation analysis presented in this paper takes into account the nonlinearity of the core's magnetostrictive force through an elastic mechanics model, making the simulation results more realistic. Furthermore, the present invention uses a spectrum signal analysis module to deeply analyze the effects of different bias currents on vibration noise. This helps engineers gain a deeper understanding of the mechanisms that generate transformer vibration noise, ultimately improving the accuracy and effectiveness of the simulation.

[0034] The present invention also provides a simulation system for transformer vibration noise under DC bias, the system comprising: A model building module is used to establish a transformer geometric model based on the structural parameters of the transformer, set the material parameters of the transformer, and perform meshing on the transformer geometric model; The field-circuit coupling simulation module is used to construct a field-circuit coupling model of the transformer under DC bias conditions based on the meshed transformer geometric model. It sets external excitation for the transformer and simulates the magnetic flux density distribution of the transformer under different bias currents. The field-circuit coupling model includes a magnetic field model and a circuit model, and implements iterative coupling calculations of the magnetic field and circuit. The electromagnetic structure coupling analysis module uses the magnetic flux density distribution as an excitation input into the transformer electromagnetic structure coupling model to calculate the transformer's vibration acceleration under different bias currents. This module also considers the calculation of the electromagnetic force acting on the core and windings, as well as the magnetostrictive force of the core. The acoustic-structure coupling analysis module is used to calculate the sound pressure level around the transformer under different bias currents based on the acoustic-structure coupling model, using the transformer's vibration acceleration as excitation. This module supports time-domain to frequency-domain conversion and frequency-domain acoustic field analysis. The spectrum signal analysis module is used to obtain the characteristic quantities of the spectrum signal based on the sound pressure level around the transformer, and evaluate the influence of different bias currents on the vibration noise of the transformer by analyzing the characteristic quantities of the spectrum signal; wherein the characteristic quantities of the spectrum signal include but are not limited to the frequency domain amplitude average, center of gravity frequency and odd-even harmonic ratio.

[0035] The simulation analysis method and system for transformer vibration noise under DC bias of the present invention are further described in detail below through specific embodiments.

[0036] In this embodiment, taking a three-phase transformer as an example, the simulation analysis method of transformer vibration noise under DC bias magnetic condition specifically includes the following steps: Step 1: Based on the transformer structural parameters, establish the transformer geometric model, set the material parameters, and mesh the transformer geometric model; like Figure 2 As shown, the sizes of different transformers are different, and this application does not limit them. This embodiment is based on the geometric drawings of the transformer provided by the target transformer manufacturer, and establishes a geometric model of the transformer core, windings, structural parts and oil tank in the multi-physics field simulation software. The diameter of the transformer core column is 640mm, the center distance of the main column core is 1180mm, the core window height is 1040mm, the iron yoke height is 630mm, the high and low voltage winding inner radius is 450mm and 338mm, the high and low voltage winding radial width is 75mm and 81.5mm respectively, the distance from the high and low voltage winding to the upper and lower iron yokes are 115mm and 45mm respectively, and the length, width and height of the transformer oil tank are 4420mm, 1380mm and 2445mm respectively. Establish a simulation model as follows Figure 2 Based on the material properties of each transformer component, the corresponding material parameters are set in the finite element calculation. The material properties of each transformer component are shown in Table 1.

[0037] Table 1 Material properties of transformer components

[0038] Step 2: Build a field-circuit coupling model of the transformer under DC bias conditions, set external excitation for the transformer, and simulate to obtain the transformer magnetic flux distribution under different bias currents; like Figure 3 and Figure 4 As shown in the figure, in the "Magnetic Field" physics field, set the coil excitation form to "Circuit (Current)". Under the "Circuit" physics field, add circuit interfaces such as voltage source, resistor, external I vs. U, and ground node, and follow the Figure 3 The circuit diagram shown sets up the connection nodes. Figure 3 middle E A 、 E B 、 E C Represent the three-phase AC voltage of the transformer, I d Indicates the intrusion bias current, R p is the high voltage side equivalent resistance, R s is the load resistor on the low-voltage side of the transformer. After completing the circuit model, add the "Coil Geometry Analysis" and "Transient" solution steps in Study 1, set the solution step size to 0.0005s, and the total solution time to 0.6s. By modifying the bias current, the magnetic flux density distribution of the transformer core under different bias currents is calculated. When the transformer has no bias current, the core magnetic flux density distribution is as follows: Figure 4 shown.

[0039] Step 3: Establish an electromagnetic-structural coupling model for the transformer and calculate the vibration acceleration of the transformer under different bias currents using the nonlinear magnetostrictive coupling interface and body load. like Figure 5 As shown, in the "Solid Mechanics" physical field, add fixed constraints, body loads, and boundary load interfaces, set the bottom of the transformer tank as a fixed constraint, set the contact surface between the core and the structural member as a boundary load, calculate the winding acceleration through the Lorentz force contribution in the body load, and calculate the core acceleration through the nonlinear magnetostriction in the multi-physics interface. After completing the setting of the solid mechanics physical field, add the "transient" solution step, set the solution step size to 0.0005s, and the total solution time to 0.6s. By modifying the bias current, the overall vibration acceleration of the transformer under different bias currents is calculated. When the transformer has no bias current, the distribution of the transformer tank vibration acceleration is as follows Figure 5 shown.

[0040] Step 4: Establish an acoustic-structure coupling model, use the vibration acceleration of the transformer tank surface as the excitation, and calculate the sound pressure level around the transformer under different bias currents; like Figure 6 and Figure 7 As shown, in the "Pressure Acoustics, Frequency Domain" physical field, add the spherical wave radiation and external field calculation interfaces, set the outer boundary of the air domain to spherical wave radiation, use the acoustic-structure boundary in the multi-physics interface to use the vibration acceleration of the transformer tank surface as the excitation for the pressure acoustics physical field calculation, and calculate the far-field sound pressure through the external field calculation interface. Complete the settings in the pressure acoustics physical field, add the "time domain to frequency domain FFT" and "frequency domain" calculation steps, set the frequency domain step to 10Hz, and the total solution frequency domain range to 0~1000Hz. By modifying the bias current, calculate the sound pressure level distribution around the transformer under different bias currents. Select a point 1m away from the surface of the transformer tank, and use the COMSOL post-processing function to extract the sound pressure level spectrum data of this point, as shown below. Figure 6 and Figure 7 shown.

[0041] Step 5: Result analysis: Based on the characteristic quantities of the spectrum signal, analyze the influence of different bias currents on the transformer vibration noise.

[0042] like Figure 8 、 Figure 9 and Figure 10 As shown in the figure, the frequency domain amplitude average value, center frequency and odd-even harmonic ratio of the sound pressure spectrum signal at a distance of 1m from the transformer under different bias currents are calculated. Figure 8 、 Figure 9 and Figure 10 It can be seen from the figure that with the increase of bias current, the frequency domain amplitude average value of the sound pressure spectrum signal increases accordingly, the center of gravity frequency gradually shifts, and the odd-even harmonic ratio also increases accordingly. However, when the bias current increases to a certain value, the frequency domain amplitude average value, center of gravity frequency and odd-even harmonic ratio all show saturation.

[0043] In summary, the present invention provides a simulation and analysis method and system for transformer vibration noise under DC bias. By constructing a multidimensional coupling model, it accurately predicts the vibration noise characteristics of the transformer under DC bias conditions, comprehensively analyzes the spectral signal characteristics, and provides detailed data support for noise optimization. This method improves prediction accuracy, enables operators to effectively assess noise levels, provides a theoretical basis for optimized design and noise control, improves evaluation efficiency, enhances simulation accuracy, and helps improve transformer noise pollution and enhances the overall performance and stability of the transformer.

[0044] Finally, it should be noted that the above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any ordinary technician in this industry can smoothly implement the present invention as shown in the specification and described above. However, any equivalent changes, modifications and evolutions made by technicians familiar with this profession without departing from the scope of the technical solution of the present invention using the technical content disclosed above are all equivalent embodiments of the present invention. At the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the scope of protection of the technical solution of the present invention.

Claims

1. A simulation analysis method for transformer vibration noise under DC bias, characterized in that: The steps include: S1. Based on the structural parameters of the transformer, establish a transformer geometric model; set the material parameters of the transformer, and mesh the transformer geometric model; S2. In the field-circuit coupling model of the transformer under DC bias conditions, set the external excitation of the transformer and simulate the magnetic flux density distribution of the transformer under different bias currents, where: The field-circuit coupling model of the transformer under DC bias conditions is constructed based on the transformer geometry model after meshing. S3. Using the magnetic flux density distribution as the excitation of the transformer electromagnetic structure coupling model, in the transformer electromagnetic structure coupling model, the vibration acceleration of the transformer under different bias currents is calculated; S4. Based on the acoustic-structure coupling model, the vibration acceleration of the transformer is used as the excitation to calculate the sound pressure level around the transformer under different bias currents. S5: Obtain characteristic quantities of the spectrum signal based on the sound pressure level around the transformer, and analyze the influence of different bias currents on the transformer vibration noise through the characteristic quantities of the spectrum signal.

2. The simulation analysis method for transformer vibration noise under DC bias according to claim 1, characterized in that: In S2, the field-circuit coupling model of the transformer under DC bias conditions includes a magnetic field model and a circuit model.

3. The simulation analysis method for transformer vibration noise under DC bias according to claim 2, characterized in that: In S2, the field-circuit coupling of the field-circuit coupling model of the transformer specifically includes: if the initial voltage or initial current of the winding is known, the dynamic inductance of the winding is calculated using the magnetic field model, the dynamic inductance value is substituted into the circuit model, the instantaneous current is calculated, and then the current value is substituted into the magnetic field model as the excitation in the next calculation step to calculate the dynamic inductance until all calculation steps are completed.

4. The simulation analysis method for transformer vibration noise under DC bias according to claim 2, characterized in that: In the S2, the magnetic field equation in the magnetic field model is as follows (1): （1）； in, σ is the conductivity, A is the vector magnetic potential, μ 0 is the vacuum permeability, μ r is the relative magnetic permeability, J e is the winding current density. If the winding current density is known, the appropriate magnetic potential of the grid node can be calculated by this formula. A , thus obtaining the magnetic field distribution.

5. The simulation analysis method for transformer vibration noise under DC bias according to claim 1, characterized in that: In S3, in the solid mechanics physics field, all domains are selected in the linear elastic material, the core and winding are selected in the domain selection, and the load type is set to the Lorentz force contribution per unit volume to simulate the electromagnetic force on each unit of the core and winding. The magnetostrictive force of the core is calculated using the elastic mechanics model.

6. The simulation analysis method for transformer vibration noise under DC bias according to claim 5, characterized in that: In said S3, the magnetostrictive force of the core is calculated by using the elastic mechanics model and specifically includes: Assume that the stress of the core material is simulated as: （2）； Where, S is the stress of the core material, C H is the elasticity tensor, is the initial strain, me (M) is the magnetostrictive strain, M is the magnetization field, and the magnetically induced secondary contraction model of the core material is set to nonlinear isotropic, with the following relationship: （3）； Where, λ S is the core saturation magnetostriction coefficient, where M Vector tensor product: （4）； At the same time, the nonlinear magnetization relationship of the core material is considered: （5）； Where, M S is the saturation magnetization, L is the Langevin function, H eff is the effective magnetic field of the core material, and the relationship is as follows: （6）； Where, χ m is the initial magnetic susceptibility of the core material, and the effective magnetic field of the core material can be obtained by the following formula: （7）； Where, S ed is the elastic stress deviator of the core material, and H is the magnetic field strength of the core material.

7. The simulation analysis method for transformer vibration noise under DC bias according to claim 1, characterized in that: The S4 specifically includes: assuming that the medium surrounding the transformer is a lightweight fluid, setting the acoustic-structural coupling model to single-phase coupling, adding time domain to frequency domain FFT and frequency domain respectively in the study; solving structural mechanics in the time domain, solving acoustics in the frequency domain, and using the FFT solver to convert vibration acceleration from the time domain to the frequency domain.

8. The simulation analysis method for transformer vibration noise under DC bias according to claim 7, characterized in that: In the frequency domain interface in S4, the equation for solving the acoustic field is as follows: （8）； In the formula p is the sound pressure, c is the speed of sound in air, w is the angular frequency, ρ is the air density.

9. The simulation analysis method for transformer vibration noise under DC bias according to claim 7, characterized in that: In S4, the characteristic quantities of the spectrum signal include the frequency domain amplitude average, the center frequency, and the odd-even harmonic ratio; the frequency domain amplitude average reflects the magnitude of the energy, the center frequency reflects the position of the main frequency band in the spectrum signal, and the odd-even harmonic ratio reflects the proportion of odd and even harmonics in the spectrum signal; if the noise spectrum signal at a point around the transformer is known, the expression for calculating the frequency domain amplitude average is: （9）； Where, S a is the average value of the frequency domain amplitude, N is the number of frequency points, For the k The amplitude of each frequency point; The expression for calculating the center of gravity frequency is: （10）； Where, f c is the center of gravity frequency, f k For the k The frequency value of each frequency point; The expression for calculating the odd-even harmonic ratio is: （11）； Where, S o / e is the odd-even harmonic ratio, T is the number of odd and even harmonic frequencies, 、 They are the amplitudes of odd and even multiple harmonics of the fundamental frequency 50Hz respectively.

10. A system for simulating and analyzing transformer vibration noise under DC bias according to any one of claims 1 to 9, characterized in that: The system includes a model building module, a field-circuit coupling simulation module, an electromagnetic-structural coupling analysis module, an acoustic-structural coupling analysis module, and a spectrum signal analysis module, wherein: The model building module is used to establish a transformer geometric model based on the structural parameters of the transformer; The field-circuit coupling simulation module is used to construct a field-circuit coupling model of the transformer based on the meshed transformer geometry model under DC bias conditions, set external excitation for the transformer, and simulate the magnetic flux density distribution of the transformer under different bias currents. The electromagnetic structure coupling analysis module is used to input the magnetic flux density distribution as excitation into the transformer electromagnetic structure coupling model to calculate the vibration acceleration of the transformer under different bias currents; The acoustic-structure coupling analysis module is used to calculate the sound pressure level around the transformer under different bias currents based on the acoustic-structure coupling model and using the transformer's vibration acceleration as excitation. The spectrum signal analysis module is used to obtain the characteristic quantity of the spectrum signal based on the sound pressure level around the transformer, and evaluate the influence of different bias currents on the transformer vibration noise by analyzing the characteristic quantity of the spectrum signal.

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