Multi-physics field modeling method and system for power electronic equipment in offshore wind power current collection system

Abstract

The invention discloses a multi-physical field modeling method and system for power electronic equipment in an offshore wind power current collection system, and the method comprises the steps: constructing an equipment-level three-dimensional structure model composed of a high-voltage high-power IGBT, a resistor, a capacitor, an inductor and other key devices based on the system-level operation characteristics of the power electronic equipment; and refining to element structures such as a chip, a solder layer, a dielectric layer, a magnetic core and the like in the device layer by layer. The power change caused by wind speed and waves, the marine environment temperature, the cooling condition and other system working conditions are input into the model, and a non-uniform mesh generation strategy is adopted, so that electricity-heat-force multi-physics field coupling solution is achieved. The device can penetrate from an equipment layer to a device layer, the electric heating power distribution of a power electronic device under the complex working condition of offshore wind power is obtained, and then the degradation mechanism of the power electronic device under the complex multi-physical field coupling environment of the offshore wind power is disclosed; and theoretical basis and technical support are provided for equipment state evaluation, early fault identification and operation reliability improvement.

Description

A multiphysics modeling method and system for power electronic equipment in offshore wind power collection systems Technical Field

[0001] This invention belongs to the field of power electronic equipment reliability analysis and multiphysics modeling technology, specifically relating to a multiphysics modeling method and system for power electronic equipment in an offshore wind power collection system. Background Technology

[0002] Offshore wind power equipment, as core energy equipment with high power and long service life, has an internal power electronic converter system that undertakes key functions such as rectification, inversion, regulation, and grid-side control of the wind turbine's output power. This power electronic equipment integrates numerous components, including high-voltage, high-power IGBT power modules, high-power resistors, magnetic inductors, and various types of capacitors. Its performance and health directly determine the energy conversion efficiency of the wind turbine and the availability of the entire offshore wind farm.

[0003] Compared to onshore environments, offshore wind farms operate under far more complex and demanding conditions. Mechanical disturbances and power fluctuations caused by wind speed, tides, and surges keep the converter in a constantly unsteady, highly dynamic state. The current, voltage, and power losses of the devices change continuously with operating conditions, leading to frequent and high-amplitude periodic fluctuations in the junction temperature within the devices. The thermal expansion coefficients of different materials within the device structure vary significantly; for example, silicon chips, solder layers, copper conductors, and magnetic core materials expand at different rates with temperature changes. This mismatch accumulates stress during frequent thermal cycling, inducing solder fatigue, dielectric aging, and demagnetization of magnetic materials, among other encapsulation degradation phenomena. Furthermore, the offshore environment is characterized by high humidity, strong salt spray corrosion, extreme temperature differences, and high wind speeds, posing additional challenges to the device's heat dissipation and structural integrity.

[0004] In existing technologies, multiphysics modeling research mainly focuses on single devices and often employs ideal steady-state conditions or single electrothermal coupling models. It lacks unified modeling for multiple types of devices in converters and fails to penetrate the operational conditions of offshore wind power equipment to the internal structure of the devices. In particular, the electrothermal coupling behavior of typical components such as resistive films, capacitor dielectrics, and magnetic cores under offshore operating conditions still lacks a systematic method for quantitative analysis.

[0005] Therefore, a unified modeling method is needed that covers equipment-level operating condition inputs, device-level multi-physics response calculations, and packaging degradation identification, so that all key components in power electronic equipment can be subjected to electro-thermal-mechanical coupling calculations under a unified framework, thereby truly reflecting the complex stress paths and degradation mechanisms in offshore wind power operation. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a multiphysics modeling method and system for power electronic equipment in offshore wind power collection systems. This method starts from the equipment-level operating conditions, penetrates to the level of high-voltage high-power IGBTs, resistors, capacitors, and inductors, and establishes multiphysics coupling models for each device. This reveals the degradation mechanism of power electronic equipment in the complex multiphysics coupling environment of offshore wind power, providing technical support for the structural design optimization, reliability assessment, and operational status monitoring of power electronic equipment.

[0007] To achieve the above objectives, the present invention provides the following solution: a multiphysics modeling method for power electronic equipment in an offshore wind power collection system, the method comprising: Step 1, constructing a three-dimensional geometric model of various devices of the power electronic equipment in the offshore wind power collection system; Step 2, performing material partitioning and parameter setting for each structure of the three-dimensional geometric model; Step 3, based on the three-dimensional geometric model after material partitioning and parameter setting, setting electro-thermal-mechanical multiphysics boundary conditions under offshore wind power service environment, and constructing an electro-thermal-mechanical multiphysics coupling model; Step 4, using a non-uniform meshing strategy to mesh the electro-thermal-mechanical multiphysics coupling model; Step 5, solving the meshed electro-thermal-mechanical multiphysics coupling model to obtain the electro-thermal distribution of power electronic devices under complex offshore wind power conditions.

[0008] Preferably, the method for constructing three-dimensional geometric models of various devices in the power electronic equipment of the offshore wind power collection system includes: based on the actual structure and size parameters of the power electronic equipment in the offshore wind power collection system, constructing a three-dimensional geometric model in COMSOL that includes high-voltage high-power IGBT modules, resistors, capacitors, and inductors; wherein, for the high-voltage high-power IGBT module, the model includes chip units, DBC copper layers, ceramic insulating layers, solder layers, copper substrates, and terminals; for the resistor, the model includes metal film layers and terminals; for the capacitor, the model includes metal electrodes, electrode plates, and dielectric layers; and for the inductor, the model includes a magnetic core and a magnetic core base.

[0009] Preferably, the method for material classification and parameter setting of each structure in the three-dimensional geometric model includes: assigning conductivity, thermal conductivity, specific heat capacity, elastic modulus, and coefficient of thermal expansion to different material systems of high-voltage high-power IGBTs, resistors, capacitors, and inductors, respectively; setting the conductivity in the high-voltage high-power IGBT chip as a function of temperature; setting the temperature-dependent permeability variation law for the magnetic core material; assigning temperature-dependent dielectric loss characteristics to the capacitor dielectric; and setting all material parameters based on real material properties, while considering performance changes caused by the high humidity and high salt spray long-term service environment of offshore wind power.

[0010] Preferably, based on the three-dimensional geometric model after material division and parameter setting, the method for setting the boundary conditions of the electric-thermal-mechanical multiphysics field under the offshore wind power service environment and constructing the electric-thermal-mechanical multiphysics field coupled model includes: combining the dynamic load in the offshore wind power environment, setting boundary conditions for the electric field, thermal field and force field respectively, and establishing the electric-thermal-mechanical coupling relationship; in the electric field, applying corresponding voltage or current ports to the high-voltage high-power IGBT, resistor, capacitor and inductor according to the actual power load; in the thermal field, applying a convective heat transfer edge that varies with wind speed and seawater temperature to the outer surface; in the force field, applying fixed constraints to the mounting surface; and constructing the electric-thermal-mechanical multiphysics field coupled model under the offshore wind power service conditions based on the electric-thermal-mechanical coupling relationship.

[0011] This invention also provides a multiphysics modeling system for power electronic equipment in an offshore wind power collection system. The system implements the aforementioned method and includes: a first construction module, a partitioning and setting module, a second construction module, a mesh generation module, and a solution module. The first construction module is used to construct three-dimensional geometric models of various devices in the offshore wind power collection system. The partitioning and setting module is used to perform material partitioning and parameter setting for each structure of the three-dimensional geometric model. The second construction module is used to set the electro-thermal-mechanical multiphysics boundary conditions under offshore wind power service conditions based on the three-dimensional geometric model after material partitioning and parameter setting, and construct an electro-thermal-mechanical multiphysics coupling model. The mesh generation module is used to perform mesh generation on the electro-thermal-mechanical multiphysics coupling model using a non-uniform mesh generation strategy. The solution module is used to solve the meshed electro-thermal-mechanical multiphysics coupling model to obtain the electro-thermal distribution of power electronic devices under complex offshore wind power conditions.

[0012] Preferably, the process of constructing a three-dimensional geometric model of various devices in the power electronic equipment of the offshore wind power collection system includes: based on the actual structure and size parameters of the power electronic equipment in the offshore wind power collection system, constructing a three-dimensional geometric model in COMSOL that includes high-voltage high-power IGBT modules, resistors, capacitors, and inductors; wherein, for high-voltage high-power IGBT modules, the model includes chip units, DBC copper layers, ceramic insulating layers, solder layers, copper substrates, and terminals; for resistors, the model includes metal film layers and terminals; for capacitors, the model includes metal electrodes, electrode plates, and dielectric layers; and for inductors, the model includes magnetic cores and magnetic core bases.

[0013] Preferably, the process of material classification and parameter setting for each structure of the three-dimensional geometric model includes: assigning conductivity, thermal conductivity, specific heat capacity, elastic modulus, and coefficient of thermal expansion to different material systems of high-voltage high-power IGBTs, resistors, capacitors, and inductors, and setting the conductivity in the high-voltage high-power IGBT chip as a function of temperature; setting the temperature-dependent permeability variation law for the magnetic core material; assigning temperature-dependent dielectric loss characteristics to the capacitor dielectric; and setting all material parameters based on real material properties, taking into account the performance changes caused by the high humidity and high salt spray long-term service environment of offshore wind power.

[0014] Preferably, based on the three-dimensional geometric model after material division and parameter setting, the process of setting boundary conditions for electric-thermal-mechanical multiphysics fields under offshore wind power service environment and constructing an electric-thermal-mechanical multiphysics coupled model includes: combining the dynamic loads in the offshore wind power environment, setting boundary conditions for the electric field, thermal field and force field respectively, and establishing electric-thermal-mechanical coupling relationship; in the electric field, applying corresponding voltage or current ports to high-voltage high-power IGBTs, resistors, capacitors and inductors according to the actual power load conditions; in the thermal field, applying convective heat transfer edges that change with wind speed and seawater temperature to the outer surface; in the force field, applying fixed constraints to the mounting surface; and constructing an electric-thermal-mechanical multiphysics coupled model under offshore wind power service conditions based on the electric-thermal-mechanical coupling relationship.

[0015] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention establishes a multi-physics coupling model for high-voltage, high-power IGBTs, resistors, capacitors, and inductors in power electronic equipment, obtaining schematic diagrams of the electro-thermal-mechanical distribution of each device. This penetrates from the equipment to the device, revealing the degradation mechanism of power electronic equipment under offshore wind power conditions. The strong fluctuations in offshore wind speed and load cause fluctuations in device power consumption, resulting in changes in internal temperature distribution. Under the influence of mismatched material thermal expansion coefficients, these temperature cycles are transformed into continuously superimposed thermomechanical stresses. For IGBT modules, the solder layer suffers fatigue damage, microcracks, and interface delamination due to repeated thermo-mechanical stresses. For resistors, the alternating stress on the metal film layer and solder joints leads to resistance drift and film rupture. For capacitors, the dielectric layer may develop voids, metallization layer peeling, and insulation degradation under multi-physics coupling. For inductors, stress concentration occurs at the interface between the magnetic core and the core base, leading to cracks and insulation aging. The strong electro-thermal-mechanical coupling effect caused by power fluctuations under complex alternating conditions in offshore wind power is also a key factor. The multiphysics simulation model established by this invention can accurately reveal the degradation mechanism of power electronic equipment in offshore wind power collection systems. Starting from the equipment-level operating conditions, it penetrates to the device level such as high-voltage high-power IGBTs, resistors, capacitors and inductors, providing technical support for the structural design optimization, reliability assessment and operation status monitoring of power electronic equipment. Attached Figure Description

[0016] To more clearly illustrate the technical solution of the present invention, the drawings used in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 is a flowchart of the multiphysics modeling simulation process for power electronic equipment in an offshore wind power collection system according to the present invention; Figure 2 is a three-dimensional geometric model of high-voltage high-power IGBTs, resistors, capacitors, and inductors constructed using COMSOL in the multiphysics modeling method for power electronic equipment in an offshore wind power collection system according to the present invention. Specifically, Figure 2(a) shows the three-dimensional structural model of the disassembled high-voltage high-power IGBT power module, Figure 2(b) shows the three-dimensional geometric model of the high-voltage high-power IGBT power module installed on a water-cooled radiator, Figure 2(c) shows the three-dimensional geometric model of the resistor, Figure 2(d) shows the three-dimensional geometric model of the capacitor, and Figure 2(e) shows the three-dimensional geometric model of the inductor; Figure 3 shows the mesh generation effect of the high-voltage high-power IGBT module, resistors, capacitors, and inductors in the multiphysics modeling method for power electronic equipment in an offshore wind power collection system according to the present invention. Figure 3(a) shows the mesh partitioning effect of the high-voltage high-power IGBT power module after disassembly; Figure 3(b) shows the mesh partitioning effect of the high-voltage high-power IGBT power module installed on a water-cooled heat sink; Figure 3(c) shows the mesh partitioning effect of the resistor; Figure 3(d) shows the mesh partitioning effect of the capacitor; Figure 3(e) shows the mesh partitioning effect of the inductor. Figure 4 is a schematic diagram of the temperature field distribution of the high-voltage high-power IGBT module in the multiphysics field modeling method of power electronic equipment in an offshore wind power collection system according to the present invention. Figure 4(a) shows the temperature field distribution of the high-voltage high-power IGBT module; Figure 4(b) shows the surface temperature distribution of the healthy multi-chip high-voltage high-power IGBT power module. Figure 5 is a schematic diagram of the failure model of the internal solder layer of the high-voltage high-power IGBT module constructed in the multiphysics field modeling method of power electronic equipment in an offshore wind power collection system according to the present invention. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] Example 1: This invention addresses the shortcomings of existing technologies in multiphysics modeling of power electronic equipment by providing a multiphysics modeling method for power electronic equipment in offshore wind power collection systems. By accurately replicating the actual packaging structure of key components such as high-voltage, high-power IGBTs, resistors, inductors, and capacitors within the equipment, as well as the offshore wind power service environment, a coupled electro-thermal-mechanical multiphysics simulation model is constructed. This model achieves accurate simulation of power losses, temperature fields, and thermal stress fields within different components, revealing their degradation and evolution characteristics under multi-field coupling. This provides technical support for the long-term reliability design, condition monitoring, and health management of offshore wind power collection systems. The method includes the following steps: Step 1: Based on the actual structure and dimensional parameters of the power electronic equipment in the offshore wind power collection system, a three-dimensional geometric model containing high-voltage, high-power IGBT modules, resistors, capacitors, and inductors is constructed in COMSOL. For high-voltage, high-power IGBTs, the model includes the chip cell, DBC copper layer, ceramic insulating layer, solder layer, copper substrate, and terminals; for resistors, the model includes the metal film layer and terminals; for capacitors, the model includes the metal electrodes, electrode plates, and dielectric layer; and for inductors, the model includes the magnetic core and core base. All structural dimensions are calibrated through technical documentation and high-precision measurements to ensure consistency between the model and the actual product.

[0021] Step 2: Material partitioning and parameter setting are performed on each structure of the three-dimensional geometric model. Step 3: Based on the dynamic loads caused by high humidity, high salt spray erosion, ambient temperature fluctuations, and wind speed changes in the offshore wind power environment, targeted boundary conditions are set for the electric field, thermal field, and force field to construct an electro-thermal-mechanical multiphysics coupling model. Step 4: A non-uniform meshing strategy is adopted to perform fine meshing on key structures and easily degraded areas, while conventional meshing is performed on the remaining structures, thus balancing computational accuracy and efficiency. Step 5: The multiphysics coupling model is solved to obtain the electrothermal and mechanical distribution of power electronic devices under complex offshore wind power conditions, thereby revealing the degradation mechanism of power electronic equipment in the complex multiphysics coupling environment of offshore wind power.

[0022] The specific implementation process is as follows: For step one, based on the actual structure and size parameters of the power electronic equipment in the offshore wind power collection system, a three-dimensional geometric model including high-voltage high-power IGBT modules, resistors, capacitors, and inductors is constructed in COMSOL. For high-voltage high-power IGBTs, the model includes chip cells, DBC copper layers, ceramic insulating layers, solder layers, copper substrates, and terminals; for resistors, the model includes metal film layers and terminals; for capacitors, it includes dielectric layers, metal electrodes, and termination structures; and for inductors, it includes magnetic cores and core bases. The dimensions of each structure are calibrated through technical documents and high-precision measurements to ensure consistency between the model and the actual components.

[0023] In step two, the materials of each structure in the three-dimensional geometric model are divided and material parameters are set. For different material systems of high-voltage, high-power IGBTs, resistors, capacitors, and inductors, characteristic parameters such as conductivity, thermal conductivity, specific heat capacity, elastic modulus, and coefficient of thermal expansion are assigned. In the high-voltage, high-power IGBT chip, conductivity is set as a function of temperature to reflect its temperature-sensitive characteristics. Temperature-dependent permeability variation laws are set for the magnetic core material; temperature-dependent dielectric loss characteristics are assigned to the capacitor dielectric. All material parameters are set based on actual material properties and consider performance changes caused by the high humidity and high salt spray long-term service environment of offshore wind power.

[0024] For step three, considering the dynamic loads caused by high humidity, high salt spray erosion, ambient temperature fluctuations, and wind speed changes in the offshore wind power environment, boundary conditions are set for the electric field, thermal field, and force field respectively to establish an electro-thermal-mechanical coupling relationship. In the electric field, corresponding voltage or current ports are applied to the high-voltage, high-power IGBTs, resistors, capacitors, and inductors according to the actual power load conditions; in the thermal field, convective heat transfer edges that vary with wind speed and seawater temperature are applied to the outer surface; in the force field, fixed constraints are applied to the mounting surface. Through the above boundary settings, a complete electro-thermal-mechanical multi-field coupling model under the operating conditions of offshore wind power is constructed.

[0025] By defining the aforementioned boundaries, this invention constructs a hierarchical, progressive electro-thermal-mechanical multiphysics coupling model driven by equipment-level operating conditions and responding to device-level structural responses. Structurally, this model consists of an operating condition input layer, a field variable mapping layer, and a device internal coupling solution layer. These layers are nonlinearly coupled through the transfer of physical quantities. Specifically: the operating condition input layer describes power fluctuations, ambient temperature, and cooling condition variations under offshore wind power service conditions; the field variable mapping layer maps these operating conditions to the distribution of electrical and thermal excitations within each device; and the device internal coupling solution layer solves for the co-evolution relationship between the electric field, temperature field, and thermal stress field within a three-dimensional solid structure.

[0026] Electric field structure definition: In the electric field sub-model, each power electronic device is considered as a combination of energy-consuming and exciter structures modulated by operating conditions. The electric field model is not based on the ideal steady-state assumption, but is driven by the equivalent excitation of offshore wind power output power varying with time.

[0027] For any device internal region Its electric field distribution satisfies: in, The potential distribution inside the device; The equivalent conductivity varies with temperature; This represents the equivalent power injection term caused by the actual operating conditions of the device. For gradient.

[0028] Electro-thermal coupling structure: The power loss obtained from the electric field sub-model is not directly applied as a heat source, but is introduced into the thermal field model through a power density mapping function related to the device structure. in, This refers to the non-uniform heat source term inside the device; The operating power function is caused by changes in wind speed and load. This represents the power density mapping relationship related to device structure and materials, where x is a spatial variable. It is a time variable.

[0029] Therefore, the heat conduction equation is established: in, For density, For specific heat capacity, Thermal conductivity, For temperature.

[0030] The heat source is not a constant, but a composite term with spatial location, material temperature-sensitive parameters, and equipment-level power fluctuation function.

[0031] Thermo-mechanical coupling: In the structural mechanics sub-model, the temperature field is not treated as an independent post-processing result, but rather as a thermal strain excitation term that directly participates in the mechanical equilibrium equations.

[0032] For any device structural region Its stress-strain relationship is expressed as: in, To act on the first Each device structural region The internal stress tensor; The total strain tensor of this region represents the geometric deformation of the structure after loading. For the first Each structural region corresponds to the elastic constitutive matrix of the material, the specific form of which is determined by the elastic parameters of the material.

[0033] The thermal strain term is defined as follows: in, Coefficient of thermal expansion of the material; Reference temperature.

[0034] Through the above relationship, the spatiotemporal fluctuations of the temperature field are directly transformed into alternating thermomechanical stresses within the structure, thus constructing a continuous physical channel for the degradation path.

[0035] Unlike existing technologies that establish electro-thermal or thermo-mechanical coupling models for only a single device or a single steady-state operating condition, the electro-thermal-mechanical multi-field coupling model constructed in this invention has the following significant differences: it uses the operating conditions of offshore wind power equipment as the driving source of the model, rather than assuming a fixed electrical excitation; it achieves non-uniform, dynamic heat source modeling through a power density mapping mechanism from the operating conditions to the device's internal structure; it directly couples the temperature field as thermal strain to the mechanical equilibrium equation, forming a continuous degradation evolution channel; and it simultaneously covers multiple types of devices such as IGBTs, resistors, capacitors, and inductors within a unified framework, avoiding the problem of model fragmentation in existing technologies.

[0036] For step four, a non-uniform meshing strategy is adopted. Fine meshing is performed on regions prone to degradation, such as the high-voltage, high-power IGBT solder layer, resistive metal film layer, inductor core, capacitor dielectric-electrode interface, and electrode-electrode plate interface. Conventional meshing is applied to structures such as the DBC copper layer, ceramic layer, copper substrate, and core body, improving solution efficiency while ensuring simulation accuracy. The minimum mesh size in the fine mesh region is no greater than 0.05 mm, and the mesh size in the conventional model region is no greater than 0.5 mm.

[0037] For step five, the constructed multiphysics coupling model is solved to obtain the internal electrothermal distribution of different devices, revealing the degradation and evolution mechanism of power electronic equipment in the complex multiphysics coupling environment of offshore wind power, and providing theoretical basis and technical support for equipment condition assessment, early fault identification and operation reliability improvement.

[0038] For the constructed electro-thermal-mechanical multiphysics coupled model, this invention does not adopt a single steady-state simultaneous solution method, but proposes a staged progressive multiphysics solution method for the dynamic service conditions of offshore wind power. This solution method uses the equipment-level operating condition sequence as the external driver, and through the ordered coupling and feedback update mechanism of electric field, thermal field and force field, it gradually obtains the potential distribution, temperature field distribution and thermal stress distribution inside various power electronic devices under complex operating conditions.

[0039] First, the operating conditions of offshore wind power are represented in time series form: in, The equivalent operating power caused by wind speed and load fluctuations; The ambient temperature; These are the parameters for cooling and heat transfer conditions; This refers to the flow rate or intensity of the cooling medium.

[0040] Discretize the continuous operating condition sequence according to the time step Δt as follows: in, For the first The time nodes corresponding to each discrete working condition; In time The system's operating status at that location.

[0041] In solving the electric field, at the k-th operating step, the electric field sub-model is solved first: in, In the first Under each working condition step, the region The potential distribution function obtained by internal solution; For the first The materials in each area were in the previous working condition step The equivalent conductivity under the influence of temperature field changes with temperature and is dynamically updated between different operating conditions. In order to be with the first The operating power of the system under each working condition step The relevant equivalent electrical excitation source term, the temperature of the previous operating condition step As a basis for updating conductivity; This is the equivalent excitation term related to the power of the k-th operating condition.

[0042] In the thermal field solution, based on the electric field results, a non-uniform heat source is constructed inside the device: in, The heat source mapping function is constructed based on the electric field distribution, conductivity characteristics, and system power. This function is used to convert power loss into a non-uniform heat source distribution within the device's internal space and to solve the heat conduction equation. in, Indicates the first Each device structural region The equivalent thermal conductivity of the corresponding material.

[0043] In the force field solution, when obtaining the temperature field Then, construct the thermal strain field: And substitute it into the structural equilibrium equation: in, This represents the equivalent volumetric force density term acting on this region. This yields the internal stress field of the device. In the solution process, this invention does not adopt a uniform global convergence condition, but defines differentiated physical convergence criteria for different device types: for high-voltage high-power IGBTs: in, For the first The maximum junction temperature of the IGBT chip junction region during each operating condition step; This is the maximum junction temperature corresponding to the previous operating condition step; This is the temperature convergence threshold set for IGBT devices.

[0044] For resistors: in, For the first The equivalent conductivity of the resistive film material under each operating condition step; This represents the conductivity corresponding to the previous operating condition step. This is the conductivity convergence threshold set for the resistive film material.

[0045] For capacitors: in, For the first The characteristic electric field intensity inside the capacitor dielectric layer during each operating step; This represents the characteristic electric field strength corresponding to the previous operating condition step. This is the electric field convergence threshold set for the capacitor dielectric region.

[0046] For inductors: in, For the first Characteristic temperature of the inductor core region under each operating condition step; This is the core temperature corresponding to the previous operating step; This is the temperature convergence threshold set for the magnetic material region.

[0047] After solving for all operating conditions, the following features are extracted as the solution results: the internal potential gradient and distribution path of each device; the peak and average values ​​of the temperature field; the thermal stress concentration area and its evolution trend with the change of operating conditions.

[0048] Unlike existing methods that employ single-step steady-state solutions or simple simultaneous equations to solve multiphysics models, this invention proposes a phased, progressive solution method driven by the dynamic service conditions of offshore wind power. This method achieves precise multiphysics solutions for various types of power electronic devices within a unified framework through condition discretization, ordered coupling of electric, thermal, and force fields, and differentiated convergence criteria for different devices. This solution process accurately reflects the evolution of internal field quantities under complex operating conditions, possessing engineering applicability and physical integrity not found in existing technologies.

[0049] Example 2, as shown in Figure 1, proposes a multiphysics modeling method for power electronic equipment in an offshore wind power collection system. Specifically, it includes the following steps: For step one, in the implementation of this invention, a complete three-dimensional geometric model is constructed in COMSOL based on the actual structure and size parameters of high-voltage high-power IGBTs, resistors, capacitors, and inductors. For the high-voltage high-power IGBT module, its three-dimensional model includes key packaging layers such as chip units, solder layers below the chip, upper and lower copper layers of the DBC, ceramic insulating layer, copper substrate, terminal structure, and water-cooled heat sink. For resistors, the three-dimensional model includes metal film layers and solder joint structures. The capacitor model includes metal electrodes, dielectric layers, outer shell, and termination structures. The inductor model includes the magnetic core and magnetic core base. Figure 2(a) shows a typical three-dimensional model of the unpacked structure of a high-voltage high-power IGBT power module. Subsequently, an overall model of the high-voltage high-power IGBT and water-cooled heat sink is established, as shown in Figure 2(b). The three-dimensional geometric models of resistors, capacitors, and inductors are shown in Figures 2(c), 2(d), and 2(e). They are assembled according to the actual installation method inside the offshore wind power converter. This integrated geometric structure can truly reflect the heat transfer path, current flow direction, and installation stress distribution between the components, providing a reliable basic geometric framework for subsequent electro-thermal-mechanical coupling simulation.

[0050] For step two, based on the geometric model established in step one, corresponding material properties are assigned to each component region. In this invention, the high-voltage, high-power IGBT module uses a silicon-based chip, a Sn-Ag-Cu solder layer, a high thermal conductivity copper layer, an alumina ceramic layer, a copper substrate, and metal terminals; the resistor uses a nickel-chromium metal film layer and copper leads; the inductor uses a ferrite core and epoxy resin encapsulation; and the capacitor uses a ceramic or thin-film dielectric, tin-plated terminals, and a metal casing. Material parameters include constant-pressure heat capacity, density, thermal conductivity, dielectric constant, electrical conductivity, coefficient of thermal expansion, Young's modulus, Poisson's ratio, and relative permeability. It should be noted that, to realistically simulate the dynamic thermal conditions and material response characteristics of offshore wind power, the conductivity of the silicon chip is set as a function of temperature, the permeability of the core material decreases slightly with temperature, and the dielectric loss of the capacitor changes with increasing temperature. These settings can fully describe the changes in the electrothermal and mechanical properties of power electronic equipment during actual operation.

[0051] In high-voltage, high-power IGBT silicon chips, considering the change in conductivity caused by the change in carrier mobility with junction temperature, the equivalent conductivity of the silicon chip is defined as a temperature-dependent function: in, Reference temperature The conductivity of the silicon chip; This refers to the local instantaneous temperature of the chip. The equivalent index parameter is used to characterize the temperature-sensitive properties of silicon chips.

[0052] This model uses an exponential form to characterize the combined effects of increased carrier scattering and decreased mobility caused by rising temperature, avoiding the distortion problem of simple linear models in the high junction temperature range. By introducing an exponential temperature response function, this invention achieves continuously adjustable modeling of the conductivity characteristics of silicon chips over a wide temperature range, enabling a closed-loop feedback relationship between the electric field distribution and junction temperature changes, rather than the fixed conductivity or linear correction methods commonly used in existing technologies.

[0053] To address the phenomenon of magnetic property degradation in inductor core materials under temperature rise conditions, the equivalent permeability of the core is set as a function of temperature: in, Reference temperature The permeability of the magnetic field below; The temperature sensitivity coefficient of the magnetic core material; The temperature represents the local temperature of the magnetic core. As the temperature increases, the order of magnetic domains decreases, and the permeability slowly decays. This function characterizes the change in the equivalent magnetic properties of the magnetic core within its normal service temperature range. Unlike existing models that treat the magnetic core permeability as a constant, this invention introduces a temperature-dependent permeability model, which couples magnetic loss, electromagnetic excitation, and the temperature field, thereby more realistically reflecting the dynamic changes in the inductor's magnetic properties under offshore wind power conditions.

[0054] For the dielectric layer of a capacitor, considering the characteristic of its dielectric loss changing with temperature, the dielectric loss tangent is defined as a temperature-dependent function: in, The dielectric loss tangent at the reference temperature; This is the temperature coefficient of dielectric loss; This refers to the local temperature of the dielectric layer.

[0055] Therefore, the equivalent power density per unit volume inside the capacitor dielectric can be expressed as: in, The electric field angular frequency; The electric field strength inside the dielectric; The relative permittivity of the medium, is the vacuum permittivity.

[0056] By simultaneously relating dielectric loss to temperature and electric field strength, this invention constructs a dielectric heating model that couples electric field, temperature, and loss, avoiding the simplified approach of estimating dielectric loss only under rated operating conditions in existing technologies.

[0057] For step three, considering the high humidity, high salt spray, strong wind, drastic temperature fluctuations, and dynamic load changes of offshore wind power collection systems, corresponding boundary conditions are applied in the electric field, thermal field, and stress field. Regarding the electric field, the rated operating current is applied to the collector of the high-voltage, high-power IGBT chip, and the emitter is set as the ground terminal; a steady-state bias voltage is applied to the resistor and capacitor, and current excitation is applied to the inductor. In this invention, the rated operating current applied to the collector of the high-voltage, high-power IGBT chip is not the device nameplate rating or a single constant current, but rather an equivalent operating current model constructed based on the operating conditions of the offshore wind power collection system.

[0058] The output power of the offshore wind power converter under a certain operating condition is expressed as: The corresponding DC-side equivalent voltage is The equivalent operating current of the IGBT module is defined as follows: When performing steady-state or quasi-steady-state solutions, a time window is used. The average value within the range is used to obtain the rated equivalent operating current: in, Initial time.

[0059] In the three-dimensional multiphysics model, the collector surface of the IGBT chip is defined as the current injection region. And apply current excitation by means of equivalent surface current density: in, This represents the effective conductive area of ​​the chip's collector. It is the unit normal vector pointing to the inside of the chip.

[0060] The launch extreme is defined as the reference potential boundary. .

[0061] For resistors and capacitors, their steady-state bias voltage is determined by the operating voltage of the corresponding node within the converter. Let the equivalent operating voltage of the node containing a certain device be... The steady-state bias voltage is defined as follows: in: To account for the voltage distribution coefficient after parallel and voltage divider structures, This coefficient is determined by the actual connection method of the device in the system.

[0062] Define potential boundaries across the resistor or capacitor respectively: This approach avoids numerical bias caused by single-end application and ensures that the electric field distribution inside the device is approximately symmetrical about the neutral plane.

[0063] Based on the operating conditions of wind power converters, the equivalent operating current of the inductor is defined as: in, This represents the equivalent voltage amplitude on the AC side.

[0064] In steady-state analysis, its root mean square value is taken as the equivalent excitation current: In the inductor winding region Internally, excitation is applied via equivalent volume current density: in, Equivalent number of turns; This refers to the cross-sectional area of ​​the winding. It is the tangential unit vector of the winding current direction.

[0065] Unlike existing technologies that directly apply electrical excitation using device rated parameters or ideal boundary conditions, this invention maps the operating conditions of offshore wind power systems to device-level equivalent current, voltage, and excitation sources, and applies them to the three-dimensional structural model in the form of surface current density, symmetrical potential loading, and volume current density. This makes the electrical excitation consistent with the actual device structure, current distribution, and power loss path, thus providing a more realistic physical basis for subsequent electro-thermal-mechanical multiphysics coupling analysis.

[0066] Simultaneously, the ceramic layer, module shell, and insulating outer surface are set as electrically insulating boundaries to ensure that current is transmitted within the device along the actual path. Regarding the thermal field, to accurately describe the actual thermal behavior of the high-voltage, high-power IGBT power module, an epoxy resin shell filled with silicone is used for insulation and moisture protection. The high-voltage, high-power IGBT model is mounted on a water-cooled heat sink, employing real offshore wind power cooling conditions. The ambient temperature and cooling water inlet temperature are both set to 25 ℃, and the cooling water flow rate is set to 6300 ml / min. Convective heat transfer boundaries are applied to the high-voltage, high-power IGBT model, resistors, capacitors, and inductors' outer packages to accurately simulate heat exchange characteristics under high humidity and high salt spray conditions. In terms of the force field, fixed constraints are set on the bottom mounting surfaces of each module to simulate the actual fastening method inside the converter. Simultaneously, the thermal expansion function is enabled in the structural mechanics module, automatically coupling the temperature field calculation results as thermal load input to accurately reflect the material expansion, contraction, and thermal stress superposition effects caused by temperature changes. By setting the above boundaries, it is possible to realistically simulate the effects of the offshore wind power environment on the internal power loss, temperature fluctuations, thermal gradient changes, and thermomechanical stress cyclic impacts of power electronic equipment.

[0067] In thermal field modeling, this invention does not adopt a uniform and constant convective heat transfer coefficient. Instead, it constructs an equivalent convective heat transfer boundary model that varies with the environment and structural position for offshore wind power in high humidity and high salt spray service environments, and applies it to the outer surface of the packages of high-voltage high-power IGBTs, resistors, capacitors and inductors.

[0068] in, This refers to the surface temperature of the package. The equivalent temperature of the environment; is the location-dependent equivalent convective heat transfer coefficient.

[0069] The equivalent heat transfer coefficient is defined as: in, A reference heat transfer coefficient that takes into account the device's geometric position, orientation, and cooling method; This is an environmental correction factor used to reflect the impact of high humidity and high salt spray on heat transfer characteristics.

[0070] The environmental correction factor is further expressed as: in, The relative humidity of the environment; These are parameters characterizing salt spray concentration; This is an empirical correction factor.

[0071] During model construction, the outer surface of the device package is divided into several heat exchange sub-regions, and different characteristics are assigned to each region based on its contact method with the cooling medium. And dynamically update based on environmental parameters during the solution process. This enables spatial non-uniform loading of convective heat transfer boundary conditions.

[0072] In structural mechanics modeling, this invention does not simply treat the bottom of the device as a rigid fixed body, but adopts an equivalent fixing method that combines surface constraints and directional restrictions to reflect the actual installation and fastening state inside the converter.

[0073] Define the bottom mounting surface of the module as a constraint region. The following displacement constraints are applied in this region: in: This is the normal displacement; This is the tangential displacement.

[0074] This constraint method allows for minute thermal expansion and slippage of the device within the plane while suppressing overall rigid body displacement. In the structural mechanics module, normal displacement constraints are selected for the bottom mounting surfaces of each module, while tangential degrees of freedom are retained to simulate the actual contact state between bolt tightening and the mounting base, thereby avoiding stress overestimation caused by the ideal fully fixed assumption.

[0075] This invention enables a thermal expansion physics interface during the structural mechanics solution process, automatically introducing the temperature field as an internal thermal load source into the mechanical equilibrium equations, rather than as a post-processing parameter.

[0076] For any material region Thermal strain is defined as: in: The coefficient of thermal expansion of the material; For reference temperature; It is a unit tensor.

[0077] Equilibrium equations of mechanics: The stress is given by the following formula: Unlike existing technologies that employ constant heat transfer coefficients, ideal fixed constraints, and post-hoc thermal stress calculations, this invention constructs an environmentally modified convective heat transfer boundary, introduces a directionally selective bottom constraint, and automatically couples the temperature field to the structural mechanics solution process in the form of embedded thermal loads. This enables precise modeling of the thermo-mechanical behavior of power electronic equipment in the complex service environment of offshore wind power. This method can more realistically reveal the stress concentration and degradation risks caused by material thermal expansion mismatch.

[0078] For step four, as shown in Figure 3, a non-uniform meshing strategy is adopted. Fine meshing is performed in key areas prone to degradation, such as the solder layer of high-voltage high-power IGBTs, chip edges, resistor film layers, inductor core stacks, and capacitor electrodes, to improve local calculation accuracy. Conventional meshing is used for areas such as the DBC copper layer, ceramic insulating layer, copper substrate, and core body, thereby taking into account the overall solution efficiency of the model.

[0079] In multiphysics numerical modeling, this invention does not discretize the entire model using a uniform mesh scale. Instead, it constructs a physical gradient-driven partitioned meshing method based on the variation characteristics of electric, temperature, and stress fields within different device regions. This method automatically selects between fine and conventional meshes according to the magnitude of the gradient of physical quantity changes in each region, thereby improving the overall solution efficiency of the model while ensuring the computational accuracy of key areas.

[0080] The model is divided into several sub-regions. For each sub-region, the following physical gradient index is calculated: in, Electric field strength; For temperature field; For stress tensor; Weighting coefficients.

[0081] When the following conditions are met: in, This is the threshold for the physical gradient index.

[0082] This region is then identified as a high-gradient sensitive region. For regions identified as high-gradient sensitive regions, the cell feature size is defined as: in, This serves as the global baseline mesh size for the model. This is the scaling adjustment coefficient.

[0083] When the following conditions are met: The region is then identified as a low-gradient sensitive area and discretized using a conventional grid.

[0084] In a typical grid region, the cell feature size is taken as: Or, within permissible limits, perform a limited scaling up: in, This is the maximum magnification factor.

[0085] Unlike existing methods that rely on human experience or uniform scale for mesh generation, this invention introduces a mesh generation criterion jointly driven by the gradients of electric field, temperature field, and stress field. This allows for adaptive refinement of key regions in a multiphysics model, thereby ensuring computational accuracy in high-gradient regions such as solder layers and chip edges while effectively reducing the computational scale of non-critical regions and improving overall solution efficiency.

[0086] For step five, the electro-thermal-mechanical multiphysics coupling simulation model is numerically solved to obtain schematic diagrams of the temperature field distribution of the high-voltage high-power IGBT module and the surface temperature distribution of the healthy multi-chip high-voltage high-power IGBT power module, as shown in Figure 4(a) and Figure 4(b). Addressing the issue of uneven chip stress caused by initial manufacturing defects, packaging layout differences, and non-uniformity between the cooling system and chip operating conditions in the high-voltage high-power IGBT power module, the focus is on analyzing the solder layer degradation characteristics: the solder layer of the chip bearing the highest stress inside the module (defined as chip a) will degrade first, followed by the adjacent chip (defined as chip b), while the solder layers of the remaining chips remain healthy. Furthermore, solder layer cracks propagate from the four corners to the center. In the simulation, it is assumed that the solder layer of the healthy chip is circular, as shown in Figure 5. The solder layer degradation level (DLi-j) is defined based on normalized thermal resistance, where j is the degradation level of chip a (value 0-5, corresponding to thermal resistance 1.j×R). th ), where i is the degradation level of chip b (i≤j, corresponding to thermal resistance 1.i×R). th Simulations were used to obtain the temperature distribution on the surface of the module chip and the bottom substrate under different degradation levels. The results showed that as the solder layers of chips a and b degraded from the four corners to the center, high temperatures were concentrated in the four corners and edge areas of the chips. The junction temperature increased significantly with the degradation level. When the degradation level reached DL3-5, the junction temperatures of chips a and b rose to over 160℃ and 150℃, respectively, with chip a maintaining the highest junction temperature. Lateral thermal coupling was weak, and the junction temperatures of the other healthy chips were approximately equal and close to the healthy state temperature. The junction temperature difference between chip a and the healthy chips could reach more than 20℃, while the shell temperature difference did not exceed 3℃, revealing the insufficient sensitivity of the traditional thermocouple method for measuring the shell temperature difference. Further key characteristic parameters were extracted, and the high-to-average junction temperature difference ΔT was defined. m-a This parameter represents the difference between the highest and average temperatures of the chips within the module. The highest junction temperature of chip a increases with increasing degradation level. Based on simulation results, failure judgment and monitoring criteria are determined, i.e., when ΔT... m-aAbove 2.5℃, the module can be determined to have experienced initial solder layer failure (corresponding to DL0-1 level). Based on the parallel characteristics of multiple chips, a 50% increase in chip thermal resistance (corresponding to DL0-5 level) is defined as the solder layer failure standard. The degradation level j of chip a can be accurately monitored by the junction temperature difference between chip a and a healthy chip. This step accurately reveals the non-uniform degradation evolution law of the solder layer of high-voltage, high-power IGBT modules in offshore wind power service environments, providing core data support for failure early warning and health management. For resistors, the electric field, temperature field, and stress field distribution of the resistor can be obtained through numerical solution of the electro-thermal-mechanical multiphysics coupling simulation model. Its metal film layer and solder joint area are the main heat-generating bodies. Fluctuations in operating conditions cause the current density to fluctuate with wind speed, resulting in fluctuations in resistor power consumption. Such power consumption changes form a significant thermal effect inside the metal film layer, causing thermal expansion mismatch between the metal film layer and the solder joint. Under long-term temperature cycling, the metal film layer is prone to microcracks and expansion. Stress concentration at the solder joint interface leads to fatigue cracking, ultimately causing resistance drift or even open-circuit failure. For capacitors, the electric field, temperature field, and stress field distribution can be obtained through numerical solution using an electro-thermal-mechanical multiphysics coupling simulation model. A significant potential difference exists between the capacitor's metal electrodes, and a strong electric field region exists within the dielectric layer. As the output ripple of the wind power converter increases, the electric field strength changes regionally, and the dielectric loss increases accordingly. Dielectric loss leads to internal heating, resulting in periodic temperature fluctuations when the wind power output fluctuates, causing repeated thermal expansion and contraction of the dielectric layer. The stress distribution is most concentrated at the dielectric-electrode plate and electrode-electrode plate locations. Due to inconsistent thermal expansion of the materials, periodic temperature changes cause alternating shear stress at the interface. Over long-term accumulation may lead to dielectric layer voids, localized delamination of the metallization layer, or dielectric breakdown. Coupled simulations show that the alternating stress caused by temperature cycling gradually concentrates local stress in the capacitor's internal dielectric layer, exhibiting a trend from elastic response to fatigue damage. For inductors, the electric field, temperature field, and stress field distributions can be obtained through numerical solutions using an electro-thermal-mechanical multiphysics coupling simulation model. Fluctuations in wind power loads cause the potential of the magnetic core laminations to exhibit a periodic, stepped distribution along the winding direction. Electromagnetic losses and copper losses fluctuate synchronously, resulting in localized temperature differences. Due to differences in thermal expansion coefficients, temperature cycling repeatedly applies alternating mechanical stress, leading to stress concentration and localized cracking at the core base interface.

[0087] This invention establishes a multi-physics coupling model for high-voltage, high-power IGBTs, resistors, capacitors, and inductors in power electronic equipment, obtaining schematic diagrams of the electro-thermal-mechanical distribution of each device. Penetrating from the equipment to the device, it reveals the degradation mechanism of power electronic equipment under offshore wind power conditions. The strong fluctuations in wind speed and load at sea cause fluctuating power consumption of devices, resulting in changes in internal temperature distribution. Under the influence of mismatched thermal expansion coefficients of materials, these temperature cycles are transformed into continuously superimposed thermomechanical stresses. For IGBT modules, the solder layer suffers fatigue damage, microcracks, and interface delamination due to repeated thermo-mechanical stresses. For resistors, the alternating stress on the metal film layer and solder joints leads to resistance drift and film rupture. For capacitors, the dielectric layer may develop voids, metallization layer peeling, and insulation degradation under multi-physics coupling. For inductors, stress concentration occurs at the interface between the magnetic core and the core base, leading to cracks and insulation aging. The strong electro-thermal-mechanical coupling effect caused by power fluctuations under the complex alternating conditions of offshore wind power further illustrates this. The multiphysics simulation model established by this invention can accurately reveal the degradation mechanism of power electronic equipment in offshore wind power collection systems. Starting from the equipment-level operating conditions, it penetrates to the device level such as high-voltage high-power IGBTs, resistors, capacitors and inductors, providing technical support for the structural design optimization, reliability assessment and operation status monitoring of power electronic equipment.

[0088] Example 3: This invention provides a multiphysics modeling system for power electronic equipment in an offshore wind power collection system. The system implements the method described in Example 1. The system includes: a first construction module, a partitioning and setting module, a second construction module, a mesh generation module, and a solution module. The first construction module constructs three-dimensional geometric models of various devices in the offshore wind power collection system. The partitioning and setting module performs material partitioning and parameter setting on each structure of the three-dimensional geometric model. The second construction module sets the electro-thermal-mechanical multiphysics boundary conditions under offshore wind power service conditions based on the three-dimensional geometric model after material partitioning and parameter setting, constructing an electro-thermal-mechanical multiphysics coupling model. The mesh generation module uses a non-uniform mesh generation strategy to mesh the electro-thermal-mechanical multiphysics coupling model. The solution module solves the meshed electro-thermal-mechanical multiphysics coupling model to obtain the electro-thermal distribution of power electronic devices under complex offshore wind power conditions.

[0089] In this embodiment, the process of constructing a three-dimensional geometric model of various devices in the power electronic equipment of the offshore wind power collection system includes: based on the actual structure and size parameters of the power electronic equipment in the offshore wind power collection system, constructing a three-dimensional geometric model in COMSOL that includes a high-voltage high-power IGBT module, resistors, capacitors, and inductors; wherein, for the high-voltage high-power IGBT module, the model includes a chip unit, a DBC copper layer, a ceramic insulating layer, a solder layer, a copper substrate, and terminals; for the resistor, the model includes a metal film layer and terminals; for the capacitor, the model includes metal electrodes, electrode plates, and a dielectric layer; and for the inductor, the model includes a magnetic core and a magnetic core base.

[0090] In this embodiment, the process of material classification and parameter setting for each structure of the three-dimensional geometric model includes: assigning conductivity, thermal conductivity, specific heat capacity, elastic modulus, and coefficient of thermal expansion to different material systems of high-voltage high-power IGBTs, resistors, capacitors, and inductors, respectively; setting the conductivity in the high-voltage high-power IGBT chip as a function of temperature; setting the temperature-dependent permeability variation law for the magnetic core material; assigning temperature-dependent dielectric loss characteristics to the capacitor dielectric; and setting all material parameters based on real material properties, while considering the performance changes caused by the high humidity and high salt spray long-term service environment of offshore wind power.

[0091] In this embodiment, based on the three-dimensional geometric model after material division and parameter setting, the process of setting the boundary conditions of the electric-thermal-mechanical multiphysics field under the offshore wind power service environment and constructing the electric-thermal-mechanical multiphysics field coupled model includes: combining the dynamic load in the offshore wind power environment, setting boundary conditions for the electric field, thermal field and force field respectively, and establishing the electric-thermal-mechanical coupling relationship; in the electric field, applying corresponding voltage or current ports to the high-voltage high-power IGBT, resistor, capacitor and inductor according to the actual power load; in the thermal field, applying a convective heat transfer edge that varies with wind speed and seawater temperature to the outer surface; in the force field, applying fixed constraints to the mounting surface; based on the electric-thermal-mechanical coupling relationship, constructing the electric-thermal-mechanical multiphysics field coupled model under the offshore wind power service conditions.

[0092] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A multiphysics modeling method for power electronic equipment in an offshore wind power collection system, characterized in that, The method includes: Step 1, constructing a three-dimensional geometric model of various devices of power electronic equipment in the offshore wind power collection system; Step 2, performing material partitioning and parameter setting for each structure of the three-dimensional geometric model; Step 3, based on the three-dimensional geometric model after material partitioning and parameter setting, setting the boundary conditions of electro-thermal-mechanical multiphysics fields under the offshore wind power service environment, and constructing an electro-thermal-mechanical multiphysics coupling model; Step 4, using a non-uniform meshing strategy to mesh the electro-thermal-mechanical multiphysics coupling model; Step 5, solving the meshed electro-thermal-mechanical multiphysics coupling model to obtain the electro-thermal distribution of power electronic devices under complex offshore wind power conditions.

2. The method according to claim 1, characterized in that, The method for constructing three-dimensional geometric models of various power electronic devices in offshore wind power collection systems includes: based on the actual structure and size parameters of the power electronic devices in the offshore wind power collection system, constructing three-dimensional geometric models in COMSOL that include high-voltage high-power IGBT modules, resistors, capacitors, and inductors; for high-voltage high-power IGBT modules, the model includes chip cells, DBC copper layers, ceramic insulating layers, solder layers, copper substrates, and terminals; for resistors, the model includes metal film layers and terminals; for capacitors, the model includes metal electrodes, electrode plates, and dielectric layers; and for inductors, the model includes magnetic cores and core bases.

3. The method according to claim 2, characterized in that, The method for material classification and parameter setting of each structure in the three-dimensional geometric model includes: assigning conductivity, thermal conductivity, specific heat capacity, elastic modulus, and coefficient of thermal expansion to different material systems of high-voltage high-power IGBTs, resistors, capacitors, and inductors, respectively; setting the conductivity in the high-voltage high-power IGBT chip as a function of temperature; setting the temperature-dependent permeability variation law for the magnetic core material; assigning temperature-dependent dielectric loss characteristics to the capacitor dielectric; and setting all material parameters based on real material properties, while considering the performance changes caused by the high humidity and high salt spray long-term service environment of offshore wind power.

4. The method according to claim 3, characterized in that, Based on the three-dimensional geometric model after material division and parameter setting, the method for constructing an electro-thermal-mechanical multiphysics coupling model under the service environment of offshore wind power includes: setting boundary conditions for the electric field, thermal field, and force field respectively in combination with the dynamic load in the offshore wind power environment, and establishing the electro-thermal-mechanical coupling relationship; in the electric field, applying corresponding voltage or current ports to high-voltage high-power IGBTs, resistors, capacitors, and inductors according to the actual power load; in the thermal field, applying convective heat transfer edges that vary with wind speed and seawater temperature to the outer surface; in the force field, applying fixed constraints to the mounting surface; and constructing an electro-thermal-mechanical multiphysics coupling model under the service conditions of offshore wind power based on the electro-thermal-mechanical coupling relationship.

5. A multiphysics modeling system for power electronic equipment in an offshore wind power collection system, the system being used to implement the method described in any one of claims 1-4, characterized in that, The system includes: a first construction module, a partitioning and setting module, a second construction module, a mesh generation module, and a solution module; the first construction module is used to construct a three-dimensional geometric model of various devices of power electronic equipment in the offshore wind power collection system; the partitioning and setting module is used to perform material partitioning and parameter setting for each structure of the three-dimensional geometric model; the second construction module is used to set the electro-thermal-mechanical multiphysics boundary conditions under the offshore wind power service environment based on the three-dimensional geometric model after material partitioning and parameter setting, and construct an electro-thermal-mechanical multiphysics coupling model; the mesh generation module is used to perform mesh generation on the electro-thermal-mechanical multiphysics coupling model using a non-uniform mesh generation strategy; the solution module is used to solve the meshed electro-thermal-mechanical multiphysics coupling model to obtain the electro-thermal distribution of power electronic devices under complex offshore wind power conditions.

6. The system according to claim 5, characterized in that, The process of constructing three-dimensional geometric models of various power electronic devices in an offshore wind power power collection system includes: based on the actual structure and size parameters of the power electronic equipment in the offshore wind power power collection system, constructing three-dimensional geometric models in COMSOL that include high-voltage high-power IGBT modules, resistors, capacitors, and inductors; for high-voltage high-power IGBT modules, the model includes chip cells, DBC copper layers, ceramic insulating layers, solder layers, copper substrates, and terminals; for resistors, the model includes metal film layers and terminals; for capacitors, the model includes metal electrodes, electrode plates, and dielectric layers; and for inductors, the model includes magnetic cores and core bases.

7. The system according to claim 6, characterized in that, The process of material classification and parameter setting for each structure of the three-dimensional geometric model includes: assigning conductivity, thermal conductivity, specific heat capacity, elastic modulus, and coefficient of thermal expansion to different material systems of high-voltage high-power IGBTs, resistors, capacitors, and inductors, and setting the conductivity in the high-voltage high-power IGBT chip as a function of temperature; setting the temperature-dependent permeability variation law for the magnetic core material; assigning temperature-dependent dielectric loss characteristics to the capacitor dielectric; all material parameters are set based on the actual material properties, and the performance changes caused by the high humidity and high salt spray long-term service environment of offshore wind power are taken into account.

8. The system according to claim 7, characterized in that, Based on the three-dimensional geometric model after material division and parameter setting, the process of setting the boundary conditions of the electric-thermal-mechanical multiphysics field under the offshore wind power service environment and constructing the electric-thermal-mechanical multiphysics field coupled model includes: combining the dynamic load in the offshore wind power environment, setting boundary conditions for the electric field, thermal field and force field respectively, and establishing the electric-thermal-mechanical coupling relationship; in the electric field, applying corresponding voltage or current ports to the high-voltage high-power IGBT, resistor, capacitor and inductor according to the actual power load; in the thermal field, applying a convective heat transfer edge that varies with wind speed and seawater temperature to the outer surface; in the force field, applying fixed constraints to the mounting surface; and constructing the electric-thermal-mechanical multiphysics field coupled model under the offshore wind power service conditions based on the electric-thermal-mechanical coupling relationship.

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