High-frequency transformer three-dimensional thermal network modeling method considering heat transfer mechanism

Abstract

The invention discloses a high-frequency transformer three-dimensional thermal network modeling method considering a heat transfer mechanism, and belongs to the technical field of high-frequency transformers, and the method comprises the following steps: S1, constructing a high-frequency transformer finite element model, and carrying out magnetothermal coupling simulation; s2, node area division is carried out on an iron core and a winding of the high-frequency transformer; s3, for different node areas, calculating thermal resistance of the 3D geometric model of the high-frequency transformer; s4, according to a simulation result of S1, constructing heat conduction resistance, convective heat transfer resistance and radiation heat transfer resistance; and S5, based on the heat flow source, the heat conduction heat resistance, the convective heat transfer heat resistance, the radiation heat resistance, the heat capacity and the environment node temperature, establishing a complete high-frequency transformer 3D heat network model. According to the method, by introducing a convection and radiation heat transfer mechanism and combining refined heat source division and thermal resistance calculation, the high-frequency transformer temperature rise prediction precision can be improved while high calculation efficiency is kept.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-frequency transformers, in particular to a high-frequency transformer three-dimensional thermal network modeling method considering heat transfer mechanisms. BACKGROUND

[0002] High-frequency transformers are crucial components in modern power electronic devices, widely used in power conversion, power transformation equipment and other fields. With the continuous expansion of high-frequency transformers in high-frequency power transmission applications, their high efficiency and precise control requirements are increasingly increasing. Transformer temperature rise prediction is one of the key technologies to ensure its safe and stable operation. However, existing high-frequency transformer thermal network models often have some shortcomings, especially in the accurate prediction of temperature distribution.

[0003] Traditional high-frequency transformer thermal network modeling methods focus on thermal conduction models, ignoring the effects of convection and radiation heat transfer, resulting in low prediction accuracy of temperature rise under complex operating conditions. Especially on the surface of high-frequency transformers, as the operating temperature of the device increases, the contribution of radiation and convection heat transfer mechanisms to heat dissipation gradually increases, so ignoring these factors will affect the accuracy of thermal prediction. In addition, existing models usually use a simplified heat source division method, which makes the prediction results of loss distribution and temperature rise under complex spatial layouts unable to truly reflect the actual situation.

[0004] Currently, although some methods attempt to combine finite element analysis for thermal field simulation and optimization, these methods usually require long computation time and high computational cost. Due to the complexity of finite element models, many methods are not easy to implement in actual engineering, especially in situations requiring real-time prediction and optimization, computational efficiency becomes a limiting factor. Therefore, how to accurately predict the temperature rise of high-frequency transformers under complex operating conditions while ensuring computational efficiency has become a difficulty in current research. SUMMARY

[0005] The purpose of the present application is to provide a high-frequency transformer three-dimensional thermal network modeling method considering heat transfer mechanisms, aiming to solve the problem of existing high-frequency transformer thermal network models ignoring the coupling effect of convection and radiation in the temperature rise prediction process, resulting in insufficient calculation accuracy of temperature distribution. By introducing real convection and radiation heat transfer coefficients and combining refined node division and thermal resistance calculation, high-precision and high-efficiency steady-state temperature rise prediction is achieved.

[0006] To achieve the above purpose, the present application provides a high-frequency transformer three-dimensional thermal network modeling method considering heat transfer mechanisms, comprising the following steps: S1, constructing a high-frequency transformer finite element model and performing magnetic-thermal coupling simulation; S2, dividing the node regions of the core and winding of the high-frequency transformer; S3, calculate the thermal resistance of the high-frequency transformer 3D geometric model for different node areas; S4, construct the thermal conduction thermal resistance, convective heat transfer thermal resistance and radiation heat transfer thermal resistance according to the simulation results of S1; S5, based on the heat flow source, thermal conduction thermal resistance, convective heat transfer thermal resistance, radiation thermal resistance, heat capacity and environmental node temperature, establish a complete high-frequency transformer 3D thermal network model.

[0007] Preferably, step S1 is specifically: based on the topological structure and electrical design parameters of the actual high-frequency transformer, a finite element model of the high-frequency transformer is established, and a physical field simulation of magnetic-thermal coupling is performed on the high-frequency transformer to extract the loss distribution and surface temperature of the high-frequency transformer; through magnetic-thermal coupling, bidirectional iterative solution of loss and temperature field is performed, considering the nonlinear magnetic hysteresis characteristic of the core and the skin and proximity effect loss of the wire, to ensure the physical accuracy of the initial loss distribution, and the loss distribution and surface temperature are extracted to provide data for thermal network modeling.

[0008] Preferably, step S2 is specifically: according to the spatial position and loss distribution of the core and winding, the core is divided into 7 regions along the geometric structure, and the primary winding and secondary winding are divided into 8 regions along the radial direction, a total of 15 heat source nodes are constructed; the heat generation power of each heat source node is taken from the copper loss or iron loss of the corresponding region in the simulation results in step S1, and is converted into a quantitative heat source input into the thermal network; based on simulation analysis, the loss values of each region of the core and winding are extracted.

[0009] Preferably, step S3 is specifically: for different geometric shapes of the region, the equivalent method of cuboid element and arc element is used to calculate the thermal conduction thermal resistance in three-dimensional direction, and the equivalent thermal resistance network of the core, winding and epoxy resin in X, Y and Z directions is obtained; the corner part of the core is an arc element, the yoke part of the core is a cuboid element, and the winding is considered as a cuboid element.

[0010] Preferably, in step S3, for the cuboid element, the thermal resistance in three directions is calculated by the following equation: ; ; ; wherein, , and respectively represent the thermal resistance of the cuboid element in three directions, , and are the lengths of the cuboid element in , y and z directions, , and Respectively, the rectangular unit material is x 、 y and z Thermal conductivity in the direction.

[0011] Preferably, in step S3, for the arc-shaped unit, the thermal resistance in two radial directions is expressed as: ; ; in, and The thermal resistance of the arc unit in two radial directions, represents the angle of the arc unit, Represents an arc unit x Thermal conductivity in the direction, represents the inner radius of the arc element, represents the outer radius of the arc element; For arc-shaped units, the thermal resistance in the circumferential direction R X 、 R Y Expressed as: ; in, Represents an arc unit y Thermal conductivity in the direction; For arc-shaped units, the axial thermal resistance R Z Expressed as: ; in, Represents an arc unit y Thermal conductivity in the direction.

[0012] Preferably, in step S4, the heat conduction between the internal components of the high-frequency transformer is calculated by the following heat equation: ; in, It is the heat conducted between the internal components of the high-frequency transformer. is the thermal conductivity of the material, A s is the cross-sectional area perpendicular to the direction of heat transfer, Δ T is the temperature difference between objects, represents the path length in the heat transfer direction; Thermal resistance R t It can be expressed by the following expression: ; wherein, is the path length in the direction of heat transfer.

[0013] Preferably, in step S4, the convective heat transfer between the epoxy surface and the air at the surface of the high frequency transformer is expressed by the following equation: ; wherein, is the convective heat transfer heat between the epoxy surface and the air, h c is the convective heat transfer coefficient at the surface of the high frequency transformer, T s is the surface temperature of the high frequency transformer, represents the ambient temperature; the convective heat transfer thermal resistance R c is expressed by the following expression: ; The convective heat transfer coefficient at the surface of the high frequency transformer is calculated by extracting the convective heat flux density at the epoxy surface and the temperature difference between the surface and the environment from the temperature field of the finite element model: ; wherein, q c represents the convective heat flux density at the epoxy surface, Δ T represents the temperature difference between the epoxy surface and the environment.

[0014] Preferably, in step S4, the radiative heat transfer between the epoxy surface of the high frequency transformer and the ambient air is calculated by the following heat equation: ; wherein, Q r is the radiative heat transfer heat between the epoxy surface of the high frequency transformer and the ambient air, h r is the radiative heat transfer coefficient between the epoxy surface of the high frequency transformer and the ambient air, T s is the temperature of the epoxy surface of the high frequency transformer; the radiative heat transfer thermal resistance R r is expressed by the following expression: ; The temperature of the epoxy surface in the temperature field extracted based on the finite element analysis T s , the radiative heat transfer coefficient at the surface of the high frequency transformer is calculated: ; wherein, σ is the Boltzmann constant, σ =5.67x10 -8 W / (m 2 2K 4 4), ε is the radiation coefficient, ε =0.8.

[0015] Therefore, the application adopts the above-mentioned high-frequency transformer three-dimensional thermal network modeling method considering heat transfer mechanism, and has the following beneficial effects: (1) Not only the three heat transfer modes of heat conduction, convection and radiation are considered, but also the spatial distribution of core and winding loss is reflected through refined heat source division, further improving the accuracy and applicability of the thermal model.

[0016] (2) Through the thermal resistance equivalent calculation of cuboid and arc elements, the rapid generation of the three-dimensional heat conduction model is realized, solving the problem of traditional finite element mesh refinement difficulty, in addition, the adopted modular modeling method effectively improves the calculation efficiency and reduces the development cycle, which can better meet the dual demands of temperature rise prediction accuracy and calculation efficiency in engineering application.

[0017] (3) The heat transfer mechanisms of heat conduction, convection and radiation are comprehensively considered, and the prediction accuracy of internal temperature rise of high-frequency transformer is significantly improved by introducing real convection and radiation heat transfer coefficients; the node temperature rise error of the optimized thermal network model is controlled within ±5%, which greatly improves the accuracy and reliability of the prediction results, and is especially suitable for temperature simulation under complex working conditions.

[0018] (4) Through 15-node refined heat source division, the spatial distribution of core and winding loss is accurately reflected, avoiding the error caused by excessive simplification in traditional thermal network model, ensuring higher accuracy of heat source distribution, and the prediction of heat flow is more accurate under variable working environment, further improving the application range and accuracy of the model.

[0019] (5) The thermal resistance equivalent method of cuboid and arc elements is proposed, which can quickly generate thermal resistance parameters without repeated refinement of finite element mesh for analysis, greatly improving the calculation efficiency, making the establishment and iteration of thermal network model more convenient and efficient, greatly shortening the development cycle, and being especially suitable for engineering applications requiring rapid response.

[0020] The technical solutions of the application will be further described in detail below with the help of drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a flow chart of the high-frequency transformer three-dimensional thermal network modeling method considering heat transfer mechanism according to an embodiment of the application; Figure 2 is a node distribution diagram of a high-frequency transformer 3D thermal network model according to an embodiment of the present application; Figure 3 is an equivalent thermal network structure diagram of a cuboid and an arc-shaped element according to an embodiment of the present application; Figure 4 is a distribution diagram of convective and radiative heat transfer coefficients of an inner and outer surface of an epoxy resin according to an embodiment of the present application; Figure 5 is a complete high-frequency transformer 3D thermal network model structure diagram according to an embodiment of the present application. DETAILED DESCRIPTION

[0022] In order to make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. The components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work are within the scope of protection of the present application.

[0023] It should be noted that: similar reference numerals and letters represent similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0024] Embodiment: As shown in Figure 1 , the present application provides a high-frequency transformer three-dimensional thermal network modeling method considering heat transfer mechanisms, comprising the following steps: S1, constructing a high-frequency transformer finite element model and performing magnetic-thermal coupling simulation.

[0025] Based on the topological structure and electrical design parameters of an actual high-frequency transformer, a finite element model of the high-frequency transformer is established. The high-frequency transformer in this embodiment also adopts an epoxy resin casting technology to achieve uniform heat dissipation and improve electrical insulation and thermal conductivity performance. Table 1 shows the electrical design parameters of the high-frequency transformer in this embodiment.

[0026] Table 1 Electrical design parameters of high-frequency transformer ;

[0027] Ansys software was used to perform a bidirectional magnetothermal coupling physical field simulation of the high-frequency transformer to extract the transformer's loss distribution and surface temperature. This bidirectional iterative solution of the loss and temperature fields was performed through magnetothermal coupling, taking into account the nonlinear hysteresis characteristics of the core and the skin and proximity effect losses of the conductors to ensure the physical accuracy of the initial loss distribution. The loss distribution and surface temperature were then extracted to provide data for thermal network modeling.

[0028] S2. Divide the core and winding of the high-frequency transformer into node areas.

[0029] In order to construct an accurate 3D thermal network model, the core is divided into 7 regions along the geometric structure according to the spatial position and loss distribution of the core and winding. The primary and secondary windings are divided into 8 regions along the four radial directions. A total of 15 heat source nodes are constructed to capture the spatial distribution characteristics of loss and temperature. Figure 2 The heating power of each heat source node is taken from the copper loss or iron loss of the corresponding area in the simulation results of S1 and converted into a quantitative heat flow source input into the thermal network. Based on the simulation analysis, the loss values ​​of each area of ​​the core and winding are extracted. The specific results are shown in Table 2.

[0030] Table 2 Loss distribution of each sub-area of ​​the high-frequency transformer core and winding ;

[0031] S3. Calculate the thermal resistance of the 3D geometric model of the high-frequency transformer for different node areas. Specifically, for areas with different geometric shapes, use the equivalent method of rectangular and arc units to calculate the thermal resistance of heat conduction in the three-dimensional direction, and obtain the equivalent thermal resistance network of the core, winding and epoxy resin in the X, Y and Z directions.

[0032] Based on the 3D geometric model of the high-frequency transformer cast in epoxy resin, the basic model of the thermal network model can be divided into two types: rectangular unit and arc unit. S 2. S 6) is an arc-shaped unit, the yoke of the core ( S 1. S 3. S 4. S 5. S 7) is a rectangular unit, and the winding is also approximately considered as a rectangular unit, refer to Figure 3 The equivalent method of rectangular parallelepiped and arc-shaped units is used to calculate the thermal resistance of heat conduction in three-dimensional directions, and the equivalent thermal resistance network of the core, winding and epoxy resin in the X, Y and Z directions is obtained; For a rectangular element, the thermal resistance in three directions can be calculated using the following equations: ; ; ; where, , and are the thermal resistances in the three directions of the cuboid element, respectively. , and are the lengths of the cuboid element in the , y and z directions, respectively. , and are the thermal conductivities of the cuboid element material in the , y and z directions, respectively.

[0033] Since the areas of the heat dissipation surfaces in the two radial directions of the arc element are different, the thermal resistances in the two radial directions of the arc element R O , R I are also different. Therefore, R O , R I should be calculated using the following formulas, respectively: ; ; where, is the angle of the arc element, is the thermal conductivity of the arc element in the direction, is the inner radius of the arc element, is the outer radius of the arc element.

[0034] For the thermal resistance in the circumferential direction R X , R Y , the heat flow length is the average arc length of the arc element, so R X , R Y can be calculated using the following formula: ; where, is the thermal conductivity of the arc element in the y direction.

[0035] For the thermal resistance in the axial direction R Z , it is calculated using the following formula: ; wherein, represents an arc unit y thermal conductivity in the direction of heat transfer.

[0036] S4, according to the simulation results of S1, construct the thermal resistance of heat conduction, the thermal resistance of convective heat transfer and the thermal resistance of radiation heat transfer.

[0037] The heat exchange of high-frequency transformer is mainly realized through three ways of heat conduction, convective heat transfer and radiation heat transfer. Inside the high-frequency transformer, heat is transferred through the heat conduction of the core, winding and epoxy resin; on the surface of the high-frequency transformer, heat is dissipated to the surrounding air through convective heat transfer and radiation heat transfer.

[0038] The heat conduction between the internal components of the high-frequency transformer can be calculated by the following heat equation: ; wherein, is the conduction heat between the internal components of the high-frequency transformer, is the thermal conductivity of the material, A s is the cross-sectional area perpendicular to the direction of heat transfer, Δ T is the temperature difference between objects, represents the path length in the direction of heat transfer.

[0039] Thermal resistance of heat conduction R t which can be expressed by the following expression: ; wherein, is the path length in the direction of heat transfer.

[0040] On the surface of the high-frequency transformer, there is convective heat transfer between the epoxy resin surface and the air. The heat equation can be represented by the following equation: ; wherein, is the convective heat transfer heat between the epoxy resin surface and the air, h c is the convective heat transfer coefficient of the surface of the high-frequency transformer, T s is the surface temperature of the high-frequency transformer, represents the ambient temperature.

[0041] Thermal resistance of convective heat transfer R c which can be expressed by the following expression: ; The core of the calculation of the convective heat transfer thermal resistance is to determine the convective heat transfer coefficient hc . The present embodiment calculates the convective heat transfer coefficient of the surface of the high-frequency transformer by extracting the convective heat flux density of the surface of the epoxy resin in the temperature field of the finite element model q c and the temperature difference between the surface and the environment Δ T The calculation formula is: ; When the epoxy resin cast high-frequency transformer is in stable operation, the surface heat dissipation reaches a steady state, and the surface temperature exceeds 80°C. Due to the large temperature difference between the surface and the environment, the contribution of radiation heat transfer to the total heat dissipation cannot be ignored. The radiation heat transfer between the epoxy resin surface of the high-frequency transformer and the ambient air can be described by the following heat equation: ; wherein is the radiation heat transfer heat between the epoxy resin surface of the high-frequency transformer and the ambient air, h r is the radiation heat transfer coefficient between the epoxy resin surface of the high-frequency transformer and the ambient air, T s is the temperature of the epoxy resin surface of the high-frequency transformer.

[0042] The radiation heat transfer thermal resistance R r can be expressed by the following expression: ; Based on the temperature of the epoxy resin surface in the temperature field extracted by the finite element analysis T s , the radiation heat transfer coefficient of the surface of the high-frequency transformer can be calculated, and the calculation formula is: ; wherein σ is the Boltzmann constant, σ =5.67×10 -8 W / (m 2 ×K 4 ), ε is the radiation coefficient, ε =0.8.

[0043] Figure 4 Among them, h c_is and h c_os are the convective heat transfer coefficients of the inner surface and the outer surface, h r_is and h r_os are the radiation heat transfer coefficients of the inner surface and the outer surface.

[0044] S5, based on the heat flow source, thermal conduction thermal resistance, convective heat transfer thermal resistance, radiation thermal resistance, heat capacity and environmental node temperature, a complete high-frequency transformer 3D thermal network model is established.

[0045] The 3D thermal network (TN) model of the epoxy resin cast high-frequency transformer is composed of the following five parts: heat flow source, thermal conduction thermal resistance, convective heat transfer thermal resistance, radiation thermal resistance, heat capacity and environmental node temperature T 0. These components together build an equivalent thermal network for accurate prediction of the steady-state temperature distribution of the transformer. The core and winding losses are injected into the corresponding nodes of the 3D TN model through the heat flow source module in Simulink, and the value of the heat flow source is taken from the loss values of each region in Table 2 of step two. There are 8 nodes in the primary and secondary windings, and the total winding loss is evenly distributed based on the volume ratio of each node to reflect the spatial distribution characteristics of winding loss.

[0046] The core thermal network model is divided into two types of geometric elements: cuboid elements for the yoke part and arc elements for the corners to accurately capture the spatial characteristics of the loss distribution. The thermal resistance of the cuboid element and the thermal resistance of the arc element are calculated by the formula in step three.

[0047] Due to the small cross-sectional area of the winding in the axial (Y direction), the axial heat conduction has limited contribution to the overall temperature distribution, and the winding is approximated as a cuboid element to simplify the construction of the thermal network model. The thermal resistance of the winding cuboid element is calculated by the formula in step three, fully considering the radial heat flow characteristics.

[0048] The epoxy resin adopts a cuboid-like structure and completely wraps the high-frequency transformer to form an external packaging layer for heat transfer. The thermal network module of the epoxy resin of the high-frequency transformer is composed of thermal conduction thermal resistance, convective heat transfer thermal resistance and radiation thermal resistance, which is used to accurately describe the heat transfer characteristics of the transformer. The thermal conduction thermal resistance is based on the geometric characteristics of the cuboid element and is calculated by the formula in step three. The convective heat transfer thermal resistance and the radiation thermal resistance are calculated by the formula in step four, respectively, considering the convective and radiation heat dissipation mechanisms of the surface and the environment.

[0049] According to the establishment of the 3D thermal network model of each component of the epoxy resin cast high-frequency transformer, the completed high-frequency transformer 3D thermal network model can be established. Figure 5 , P n ( n =1-12) is the node loss, R icn_X ( n =1-7), R icn_Y ( n =1-7), Ricn_Z n =1-7) are the conduction thermal resistances of the core in X, Y and Z directions, respectively, R icn_O n =2,6) and R icn_I n =2,6) are the conduction thermal resistances of the core circular element in the outer diameter and inner diameter directions, respectively, R con_X n =8-11) are the conduction thermal resistances of the winding in X direction, R con_Z n =12-15) are the conduction thermal resistances of the winding in Z direction, R ern_X n =3,4,5,9,11), R ern_Y n =1,7), R ern_Z n =1-7,13,15) are the conduction thermal resistances of the epoxy in X, Y, Z directions, respectively, R chn_X n =3,5,9,11), R chn_Y n =1,7), R chn_Z n =1-3,5-7,13,15) are the convection thermal resistances of the epoxy surface in X, Y, Z directions, respectively, R rhn_X n =3,5,9,11), R rhn_Y n =1,7), R rhn_Z n =1-3,5-7,13,15) are the radiation thermal resistances of the epoxy surface in X, Y, Z directions, respectively, T 0 is the ambient temperature, C th_ir , C th_co are the thermal capacities of the core and winding, respectively.

[0050] The temperature rise prediction results of the high-frequency transformer 3D thermal network model nodes are shown in Table 3: Table 3 Temperature rise prediction results of high-frequency transformer nodes ; ​​​​​​​​​​​​​​

[0051] The method of the present application extracts the loss distribution and surface temperature by constructing a high-frequency transformer finite element model, coupling the magnetic field and the temperature field. The core and winding are divided into 15 heat source nodes, and the three-dimensional heat conduction thermal resistance is calculated based on the equivalent method of cuboid and arc element. Combined with the finite element analysis results, the surface convective heat transfer coefficient and the radiation heat transfer coefficient are calculated to construct the convection and radiation resistance. A 3D thermal network model is built on the Simulink platform, and the steady-state temperature rise of each node is output, with an error less than 5%, meeting the engineering precision requirements. The present application significantly improves the temperature rise prediction accuracy and calculation efficiency by comprehensively considering the heat conduction, convection and radiation heat transfer mechanism, and is suitable for thermal analysis of high-frequency transformers under complex working conditions.

[0052] Therefore, the present application adopts the above-mentioned three-dimensional thermal network modeling method of high-frequency transformer considering heat transfer mechanism, which can accurately reflect the temperature distribution of high-frequency transformer in three-dimensional space by establishing a 3D thermal network model of high-frequency transformer. This three-dimensional thermal network model can accurately predict the temperature rise change inside the transformer, especially under complex working conditions, providing more intuitive and accurate temperature prediction, thereby effectively avoiding the blind spot of the traditional two-dimensional model which cannot be fully predicted.

[0053] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application and not to limit them, although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that: it can still modify or equivalently replace the technical solutions of the present application, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present application.

Claims

1. A method of modeling a three-dimensional thermal network of a high-frequency transformer taking into account heat transfer mechanisms, characterized in that, The method comprises the following steps: S1, constructing a high-frequency transformer finite element model and performing magnetic-thermal coupling simulation; S2, dividing the nodes and regions of the core and winding of the high-frequency transformer; S3, calculating the thermal resistance of the 3D geometric model of the high-frequency transformer for different node regions; S4, constructing the thermal conduction thermal resistance, convective heat transfer thermal resistance and radiation heat transfer thermal resistance according to the simulation results of S1; S5, based on the heat flow source, thermal conduction thermal resistance, convective heat transfer thermal resistance, radiation thermal resistance, heat capacity and environmental node temperature, establishing a complete 3D thermal network model of the high-frequency transformer.

2. The method of claim 1, wherein the method is characterized by, Step S1 is specifically: based on the topological structure and electrical design parameters of the actual high-frequency transformer, a finite element model of the high-frequency transformer is established, and a physical field simulation of magnetic-thermal two-way coupling of the high-frequency transformer is performed to extract the loss distribution and surface temperature of the high-frequency transformer; the two-way iterative solution of the loss and temperature field is performed through magnetic-thermal coupling, the nonlinear magnetic hysteresis characteristic of the core and the skin and proximity effect loss of the wire are considered to ensure the physical accuracy of the initial loss distribution, and the loss distribution and surface temperature are extracted to provide data for thermal network modeling.

3. The method of claim 1, wherein the method is characterized by, Step S2 is specifically: according to the spatial position and loss distribution of the core and winding, the core is divided into 7 regions along the geometric structure, and the primary winding and secondary winding are divided into 8 regions along the four radial directions, a total of 15 heat source nodes are constructed; the heat generation power of each heat source node is taken from the copper loss or iron loss of the corresponding region in the simulation results in step S1, and is converted into a quantitative heat source input into the thermal network; based on simulation analysis, the loss values of each region of the core and winding are extracted.

4. The method of claim 1, wherein the method is characterized by, Step S3 is specifically: for different geometric shapes of the region, the equivalent method of cuboid element and arc element is adopted to calculate the thermal conduction thermal resistance in three-dimensional direction, and the equivalent thermal resistance network of the core, winding and epoxy resin in X, Y and Z directions is obtained; the corner part of the core is an arc element, the yoke part of the core is a cuboid element, and the winding is considered as a cuboid element.

5. The method of claim 4, wherein the method further comprises: In step S3, for the cuboid element, the thermal resistance in three directions is calculated by the following equation: ； ； ； wherein, , and denote the thermal resistance of the cuboid cell in three directions, , and are the length of the cuboid cell in , y and z directions, , and are the thermal conductivity of the cuboid cell material in , y and z directions.

6. The method of claim 5, wherein the method further comprises: In step S3, for the arc element, the thermal resistance in two radial directions is expressed as: ； ； wherein and Rth, Rth represent the thermal resistance in the radial direction of the arcuate element, Rth, Rth represent the thermal conductivity in the radial direction of the arcuate element, Rth, Rth represent the thermal conductivity in the radial direction of the arcuate element Rth, Rth represent the thermal conductivity in the radial direction of the arcuate element, Rth, Rth represent the thermal conductivity in the radial direction of the arcuate element, Rth, Rth represent the thermal conductivity in the radial direction of the arcuate element, For the arcuate cells, the thermal resistance in the circumferential direction R X , R Y is represented as: ； wherein represents an arcuate element y thermal conductivity in the direction For the arcuate cells, the axial thermal resistance R Z is represented as: ； wherein represents an arcuate element y thermal conductivity in the direction.

7. The method of claim 6, wherein the method further comprises: In step S4, the heat conduction between the internal components of the high-frequency transformer is calculated by the following heat equation: ； wherein, is the conductive heat between the internal components of the high frequency transformer, is the thermal conductivity of the material, A s is the cross-sectional area perpendicular to the heat transfer direction, Δ T is the temperature difference between the objects, denotes the path length in the direction of heat transfer; Thermal conduction thermal resistance R t This can be expressed by the following equation: ； wherein is the path length in the heat transfer direction.

8. The method of claim 7, wherein the method further comprises: In step S4, on the surface of the high-frequency transformer, the convective heat transfer between the surface of the epoxy resin and the air is represented by the following equation: ； wherein, is the convective heat transfer heat between the epoxy surface and the air, h c is the convective heat transfer coefficient of the surface of the high frequency transformer, T s is the surface temperature of the high frequency transformer, denotes the ambient temperature; Convection heat transfer thermal resistance R c is expressed by the following expression: ； By extracting the convective heat flux density of the epoxy resin surface in the temperature field of the finite element model and the temperature difference between the surface and the environment, the convective heat transfer coefficient of the surface of the high-frequency transformer is calculated: ； wherein, represents the convective heat flux density of the surface of the epoxy resin, Δ T represents the temperature difference between the surface of the epoxy resin and the environment.

9. The method of claim 8, wherein the method further comprises: In step S4, the radiation heat transfer between the surface of the epoxy resin of the high-frequency transformer and the environmental air is calculated by the following heat equation: ； wherein, is the radiative heat transfer between the high frequency transformer epoxy surface and the ambient air, h r is the radiative heat transfer coefficient between the high frequency transformer epoxy surface and the ambient air, T s is the temperature of the high frequency transformer epoxy surface; Radiation heat transfer thermal resistance R r is expressed by the following expression: ； the temperature of the surface of the epoxy resin in the temperature field extracted based on finite element analysis T s calculating the radiation heat transfer coefficient of the surface of the high-frequency transformer: ； wherein σ is the Boltzmann constant, σ = 5.67 x 10 -8 W / (m 2 2K 4 )4, ε is the emissivity, ε = 0.8.

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