Simulation verification method and system for multi-physical field electromagnetic compatibility of power electronic device

Abstract

The application discloses a kind of simulation verification methods and systems of power electronic device multi-physical field electromagnetic compatibility, and it is related to power electronic device simulation technical field.The method includes collecting the multi-source basic data set required for designing power electronic device, selectively simplifying the whole machine electromagnetic field model according to electromagnetic leakage sensitivity score, obtaining spatial electromagnetic field result by field-circuit collaborative solution;Combined with field intensity risk index, filter power path, extract busbar and line parasitic parameters, generate structure scheme and carry out device off transient voltage risk evaluation, review heat flow field for the scheme of changing heat source, air duct, after simulation verification, finally generate the structure scheme of power electronic device.Unify electromagnetic, circuit, thermal field simulation in the same modeling and verification process, solve the problem that the simulation verification result of existing power electronic device is greatly deviated from actual working condition, and the evaluation of electromagnetic compatibility is not accurate.

Description

Technical Field

[0001] This invention relates to the field of power electronic device simulation technology, specifically to a simulation verification method and system for the multi-physics electromagnetic compatibility of power electronic devices. Background Technology

[0002] Power electronic devices, such as photovoltaic inverters and energy storage converters, use power semiconductor devices like IGBTs and silicon carbide as their core to achieve power conversion. These devices contain components such as low-frequency high-power transmission, high-frequency pulse-width modulation switches, fast voltage edges, fast current edges, long power connection paths, and sensitive control circuits. Different devices have different operating frequencies, switching voltages, rise times, fall times, and pulse widths, resulting in an electromagnetic environment with multiple frequency bands, multiple paths, and various coupling mechanisms within the device. Therefore, before conducting physical tests on power electronic devices, it is necessary to perform joint simulation verification of electromagnetic compatibility, transient voltage, and thermal performance across multiple physics fields to reduce the number of iterations required for the prototype.

[0003] Existing simulation verification methods typically perform multi-physics simulation verification independently, making it difficult to achieve collaborative modeling and data linkage among the various physics fields. This results in problems such as large deviations between simulation results and actual device operating conditions, and inaccurate assessment of electromagnetic compatibility. Summary of the Invention

[0004] The purpose of this invention is to provide a simulation verification method and system for the electromagnetic compatibility of power electronic devices in multiple physical fields. This method unifies electromagnetic, circuit, and thermal field simulations into a single modeling and verification process, solving the problems of large deviations between existing simulation verification results and actual operating conditions of power electronic devices, and inaccurate assessment of electromagnetic compatibility.

[0005] This invention is achieved through the following technical solution:

[0006] The first aspect of this application provides a multi-physics electromagnetic compatibility simulation and verification method for power electronic devices, including:

[0007] Obtain the multi-source foundational datasets required for designing power electronic devices;

[0008] Based on the sensitivity of each structural unit of the device to electromagnetic leakage, and by combining the geometric structure data and electromagnetic parameter data of the device in a multi-source basic dataset, a whole-machine electromagnetic field model of the device is constructed.

[0009] Multiple lumped ports are configured on the overall electromagnetic field model. Based on the pre-established port mapping record, each pulse excitation source built on the circuit side is connected to the corresponding lumped port to construct a field-circuit cooperative model. The port mapping record contains the mapping relationship between the lumped ports and the pulse excitation sources.

[0010] Each pulse excitation source is triggered to emit a corresponding excitation signal in order to obtain the spatial electromagnetic field distribution results of the field-circuit cooperative model;

[0011] Based on the spatial electromagnetic field distribution results and the power loop topology relationship of the device, the key parasitic parameter extraction objects are determined. Parasitic parameter models are established for the stacked busbar and the power connection paths in the key parasitic parameter extraction objects, and the values ​​of key parasitic parameters are extracted from the parasitic parameter models.

[0012] Based on the extracted key parasitic parameter values, a structural adjustment scheme for the stacked busbar and a layout adjustment scheme for the power connection path are generated. Furthermore, a risk assessment of the turn-off transient voltage of the power semiconductor device is performed based on the equivalent stray inductance of the fast commutation loop. The equivalent stray inductance of the fast commutation loop is the sum of the equivalent stray inductance of the structural adjustment scheme and the equivalent stray inductance of the layout adjustment scheme.

[0013] For candidate schemes that trigger thermal flow field verification in structural adjustment schemes and layout adjustment schemes, thermal flow field verification is performed;

[0014] When the spatial electromagnetic field distribution results, the values ​​of key parasitic parameters, the risk assessment results of the turn-off transient voltage, the thermal flow field verification results, and the structural parameter change trends all meet the corresponding preset verification conditions, the final structural scheme of the output device is determined.

[0015] In one feasible implementation, the sensitivity of the structural unit to electromagnetic leakage is determined by weighted fusion of the normalized structural unit's opening area, the longest side dimension of the opening, the distance from the interference source, the state of crossing the shield boundary, the state of proximity to the sensitive circuit, and the state of participation of the main current path.

[0016] The state of crossing the shielding boundary indicates whether the structural unit crosses the shielding boundary of the device housing or whether it connects two shielding areas.

[0017] In one feasible implementation, based on the sensitivity of each structural unit of the device to electromagnetic leakage, and combining the geometric structure data and electromagnetic parameter data of the device in a multi-source basic dataset, a whole-machine electromagnetic field model of the device is constructed, including:

[0018] The structural unit that determines the electromagnetic propagation path is selected from all structural units;

[0019] The sensitivity of the remaining structural units to electromagnetic leakage is compared with the sensitivity threshold, and the remaining structural units are divided into structural units that exceed the sensitivity threshold and structural units that do not exceed the sensitivity threshold; the remaining structural units are the structural units other than the structural units that determine the electromagnetic propagation path.

[0020] The structural units that determine the electromagnetic propagation path and the structural units that exceed the sensitivity threshold are reserved as objects. A structural model of the reserved objects is constructed, and electromagnetic parameters are assigned to the structural model.

[0021] Structural units that do not exceed the sensitivity threshold are simplified to construct a simplified structural model;

[0022] Based on the structural model of the retained object with assigned electromagnetic parameters and the simplified structural model, a whole-machine electromagnetic field model of the device is formed.

[0023] In one feasible implementation, each pulse excitation source is triggered to emit a corresponding excitation signal to obtain the spatial electromagnetic field distribution results of the field-circuit cooperative model, including:

[0024] The multi-channel pulse excitation source on the drive circuit side outputs corresponding pulse signals to perform transient joint solution on the field-circuit cooperative model. The transient electrical excitation of the lumped port is applied to the whole machine electromagnetic field model to obtain the spatial transient electromagnetic field distribution results of the whole machine.

[0025] In one feasible implementation, the method further includes:

[0026] Based on the spatial electromagnetic field distribution results, the peak values ​​of electric field intensity and magnetic field intensity in each preset monitoring area are extracted respectively;

[0027] If the peak electric field strength and / or the peak magnetic field strength exceed the corresponding threshold, a structural adjustment command for the associated device in the corresponding monitoring area will be output.

[0028] In one feasible implementation, the key parasitic parameter extraction targets are determined based on the spatial electromagnetic field distribution results and the power loop topology relationship of the device, including:

[0029] Based on the power loop topology, the closed power loop is split into multiple independent power connection paths according to the device boundaries;

[0030] The normalized peak magnetic field, peak electric field, rated current, number of bends, distance between round-trip conductors, and distance to high field strength regions are weighted and fused to determine the correlation risk index between each power connection path and the space field.

[0031] Power connection paths whose associated risk indicators exceed preset thresholds are selected as key parasitic parameter extraction targets.

[0032] In one feasible implementation, the heat flow field verification includes:

[0033] The geometric parameters corresponding to the candidate schemes are loaded into the thermal flow field model; the thermal flow field model is constructed by dividing the solid heat conduction domain and the fluid flow domain based on the candidate structure and configuring conjugate heat transfer boundary conditions;

[0034] Simulation calculations are performed based on the material thermophysical parameters and environmental cooling parameters in the multi-source basic dataset to determine the thermal flow field verification parameters; the thermal flow field verification parameters include the device's highest temperature, the temperature of key components, the centroid migration distance in the high-temperature region, and the air duct blockage rate.

[0035] If all the thermal flow field verification parameters meet the corresponding preset conditions, then the thermal performance of the candidate scheme is qualified.

[0036] The second aspect of this application provides a multi-physics electromagnetic compatibility simulation and verification system for power electronic devices, including:

[0037] The data acquisition unit is used to acquire multi-source basic datasets required for the design of power electronic devices.

[0038] The whole-machine electromagnetic modeling unit is used to construct the whole-machine electromagnetic field model of the device by combining the geometric structure data and electromagnetic parameter data of the device with the sensitivity of each structural unit of the device to electromagnetic leakage and the multi-source basic data.

[0039] The field-circuit cooperative solution unit is used to configure multiple lumped ports on the whole-machine electromagnetic field model. Based on the pre-established port mapping record, it connects each pulse excitation source built on the circuit side to the corresponding lumped port to construct the field-circuit cooperative model. The port mapping record contains the mapping relationship between the lumped ports and the pulse excitation sources.

[0040] The spatial electromagnetic field distribution acquisition unit is used to trigger each pulse excitation source to emit corresponding excitation signals in order to obtain the spatial electromagnetic field distribution results of the field-circuit cooperative model.

[0041] The parasitic parameter extraction unit determines the key parasitic parameter extraction objects based on the spatial electromagnetic field distribution results and the power loop topology relationship of the device, establishes parasitic parameter models for the stacked busbar and the power connection paths in the key parasitic parameter extraction objects, and extracts the values ​​of key parasitic parameters from the parasitic parameter models.

[0042] The structural adjustment scheme generation unit generates structural adjustment schemes for the stacked busbars and layout adjustment schemes for the power connection paths based on the extracted values ​​of key parasitic parameters. It also performs a turn-off transient voltage risk assessment for power semiconductor devices based on the equivalent stray inductance of the fast commutation loop. The equivalent stray inductance of the fast commutation loop is the sum of the equivalent stray inductance of the structural adjustment scheme and the equivalent stray inductance of the layout adjustment scheme.

[0043] The thermal flow field verification unit is used to verify the thermal flow field of candidate schemes that trigger thermal flow field verification in structural adjustment schemes and layout adjustment schemes.

[0044] The scheme output unit is used to output the final structural scheme of the device when the spatial electromagnetic field distribution results, the values ​​of key parasitic parameters, the risk assessment results of the turn-off transient voltage, the thermal flow field verification results, and the structural parameter change trends all meet the corresponding preset verification conditions.

[0045] A third aspect of this application provides an electronic device, including: a processor, a memory, and a program or instructions stored in the memory and executable on the processor, wherein the program or instructions, when executed by the processor, implement the steps of the above-described method.

[0046] A fourth aspect of this application provides a storage medium, comprising: storing a program or instructions on the storage medium, wherein the program or instructions, when executed by a processor, implement the steps of the above-described method.

[0047] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0048] This application first constructs a whole-machine electromagnetic field model, and then, combined with port mapping records, connects each pulse excitation source built on the circuit side to the lumped port corresponding to the whole-machine electromagnetic field model to achieve field-circuit coordination. Next, it uses the power loop topology to screen key parasitic parameter extraction objects and extracts key parasitic parameters to generate adjustment schemes. Furthermore, it performs thermal flow field verification on candidate schemes that trigger thermal flow field verification in the adjustment schemes, and finally outputs the final structural scheme of the device through the joint judgment of multi-physics field results and structural parameter change trends. By unifying magnetic field, circuit, and thermal field simulations into a single modeling and verification process, it achieves real-time linkage and mutual verification of various physical field data, closely approximating the actual operating conditions of the device. It also ensures the accuracy of electromagnetic field distribution, parasitic parameters, transient voltage risks, and thermal performance evaluation, and can synchronously iteratively optimize the device structure based on multi-dimensional simulation results, avoiding electromagnetic interference, device overvoltage breakdown, and thermal failure risks, improving the reliability and design efficiency of simulation verification, and reducing the number of iterations and R&D costs of physical prototypes. Attached Figure Description

[0049] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings:

[0050] Figure 1 A flowchart illustrating a multi-physics electromagnetic compatibility simulation and verification method for power electronic devices provided in this application embodiment;

[0051] Figure 2A schematic diagram illustrating the simplified modeling of the whole-machine electromagnetic field in the simulation verification method provided in this application embodiment;

[0052] Figure 3 A schematic diagram of the process for solving the field collaborative problem in the simulation verification method provided in the embodiments of this application;

[0053] Figure 4 A schematic diagram illustrating the parasitic parameter extraction and busbar optimization process in the simulation verification method provided in this application embodiment;

[0054] Figure 5 A schematic flowchart illustrating the process of verifying the thermal flow field of candidate structures in the simulation verification method provided in this application embodiment;

[0055] Figure 6 A schematic diagram of the structure of a multi-physics electromagnetic compatibility simulation and verification system for power electronic devices provided in this application embodiment;

[0056] Figure 7 This is a schematic diagram of the structure of a computing device provided in an embodiment of this application. Detailed Implementation

[0057] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0058] As will be known to those skilled in the art, with the development of technology and the emergence of new scenarios, the technical solutions provided in the embodiments of this application are also applicable to similar technical problems.

[0059] The terms “comprising” and “having”, and any variations thereof, in the specification, claims, and accompanying drawings of this application are intended to cover a non-exclusive inclusion, such that a process, method, system, product, or apparatus that comprises a series of elements is not necessarily limited to those elements, but may include other elements not expressly listed or inherent to such process, method, product, or apparatus.

[0060] Example 1:

[0061] Embodiment 1 of this application provides a multi-physics electromagnetic compatibility simulation verification method for power electronic devices, which solves the problems of large deviation between the existing simulation verification results of power electronic devices and the actual operating conditions of the devices, and inaccurate evaluation of electromagnetic compatibility.

[0062] The subject executing this method can be any computing device capable of implementing the method, such as a server, mobile phone, personal computer, smart wearable device, smart robot, etc.

[0063] Furthermore, the embodiments of this application do not limit the execution order of different steps. When using the method provided in the embodiments of this application, the execution order of different steps can be adjusted according to actual needs.

[0064] For ease of description, the following uses an electromagnetic compatibility simulation and verification device for multi-physics fields of power electronic devices as the execution subject of this method to provide a detailed description of the method provided in this application embodiment.

[0065] like Figure 1 The diagram shown is a flowchart illustrating the specific implementation of a multi-physics electromagnetic compatibility simulation and verification method for power electronic devices according to an embodiment of this application, including the following steps 11 to 18:

[0066] Step 11: Obtain the multi-source basic dataset required for designing power electronic devices.

[0067] The multi-source basic dataset includes the device's geometric structure data, electrical topology data, electromagnetic parameters, material thermal properties parameters, multi-source switch excitation parameters, power loss parameters, and environmental cooling parameters.

[0068] The power electronic device to be designed in this embodiment is a single-phase grid-type static var generator as an example.

[0069] Specifically, the geometric structure data may include the box shape, board shape, device envelope size, heat dissipation hole outline, panel gap outline, cable through hole outline, shielding connection location, critical conductor outline, PCB (Printed Circuit Board) critical conductor layer, stacked busbar conductor layer and insulating layer, power connection path center path, device spatial coordinates, and air inlet and outlet locations.

[0070] The enclosure is a closed metal shell cavity for power electronic devices, used to house all internal components such as internal power devices, stacked busbars, power cables, and control circuit boards, while also serving as a mechanical protection, electromagnetic shielding, air duct constraint, and installation load-bearing function.

[0071] A circuit board is a printed circuit board (PCB) assembly, consisting of a printed circuit board and components such as chips, resistors, capacitors, and connectors soldered onto the board. In power electronic devices, it mainly undertakes functions such as signal acquisition, logic operation, drive control, and communication, and is a carrier of sensitive circuits.

[0072] Device envelope refers to the package shape and physical boundaries of a device, that is, the overall physical outline formed by the device's shell, pins / pads, mounting dimensions, heat dissipation surface, etc.

[0073] A multilayer busbar, also known as a composite busbar, is composed of multiple layers of conductive copper busbars and insulating films that are alternately laminated and bonded together. The positive and negative conductors are arranged closely in parallel. As the power conductor of the DC busbar inside a power electronic device, it is used to connect the DC support capacitor and the power semiconductor module.

[0074] A power connection path is a series of independent paths that divide a closed power loop according to the device boundaries. It is a conductor path used to transmit high-power electrical energy in the power circuit of a power electronic device. It is formed by connecting segmented conductors such as laminated busbars, power copper busbars, power cables, and device terminals, which constitute the various branches of the closed power loop.

[0075] It should be noted that all the geometric structure data mentioned above in this embodiment adopt a unified coordinate system. The origin of the coordinate system is set at the intersection of the bottom surface of the box and the left front reference edge. The length unit is uniformly converted to millimeters during the data import stage. After entering the electromagnetic field solver, a consistency check is performed according to the solver's internal units.

[0076] Electrical topology data includes the connection relationships of the power supply side, DC side, AC side, and drive side within the power electronic device. Each power connection path is assigned a unique path number, and a path record is set for each power connection path. The path record includes the starting device, ending device, conductor type, rated current level, actual current direction, and correspondence with adjacent return paths.

[0077] For the power circuit of a single-phase grid-type static var generator, at least four power connection paths are recorded: DC circuit breaker QF1—current transformer CT2—contactor KM branch terminal, contactor KM branch terminal—reactor L1, reactor L1—current transformer CT1—IGBT power module, and IGBT—QF1. In this embodiment, a path number is assigned to each power connection path to maintain consistency in subsequent whole-machine electromagnetic field analysis, parasitic parameter extraction, and transient risk assessment, ensuring that the geometric data, parasitic parameter data, and risk assessment data of the same power connection path can be correlated.

[0078] Electromagnetic parameter data include conductor conductivity, relative permittivity, and relative permeability.

[0079] The thermal properties of a material include its thermal conductivity, density, and specific heat capacity.

[0080] The excitation parameters of the multi-source switch include the operating frequency, low voltage level, high voltage level, rise time, fall time, high level duration and period, etc., recorded according to the interference source number.

[0081] Power loss parameters include total power loss or volumetric power density recorded according to the heat source number.

[0082] Environmental cooling parameters include ambient temperature, air intake velocity, air intake direction, air intake location, air outlet pressure conditions, and wall conditions.

[0083] The different data in the above multi-source basic dataset are associated with each other through their respective device number, structural unit number, lumped port number, and power connection path number.

[0084] In this embodiment, various types of data operate according to the following process: geometric structure data and electromagnetic parameters are input into the whole machine electromagnetic field model; electrical topology data and multi-source switch excitation parameters are input into the port mapping stage and the field-circuit coordination model; the whole machine electromagnetic field model outputs the spatial electromagnetic field distribution results; the spatial electromagnetic field distribution results, combined with the electrical topology data, are input into the key parasitic parameter extraction object determination process; the selected stacked busbars and power connection paths are used to build the parasitic parameter model and complete the key parasitic parameter extraction; the extracted key parasitic parameters are input into the structural adjustment scheme generation stage and the power semiconductor device turn-off transient voltage risk assessment stage; for candidate structural schemes in the generated structural schemes that will cause changes in the heat source position and internal airflow channels, the material thermal property parameters, power loss parameters, and environmental cooling parameters in the multi-source basic dataset are simultaneously loaded and sent to the thermal flow field model for thermal flow field verification.

[0085] Step 12: Based on the sensitivity of each structural unit of the device to electromagnetic leakage, and combining the geometric structure data and electromagnetic parameter data of the device in the multi-source basic data set, construct the overall electromagnetic field model of the device.

[0086] In this embodiment, the overall structure of the device is selectively simplified to generate a simplified electromagnetic field model of the whole device. Selective simplification does not involve deleting small structures individually according to geometric dimensions, but rather determines whether to retain or simplify them based on the effect of structural units on electromagnetic propagation, electromagnetic leakage, and conductor coupling.

[0087] The structural units are derived from the geometric model of the device by disassembling it based on the characteristics of electromagnetic leakage and interference coupling of different geometric components. Specifically, in this embodiment, the geometric model of the device is divided into box structural units, opening structural units, conductor structural units, shielding connection structural units, PCB structural units, device envelope structural units, and mechanical support structural units.

[0088] like Figure 2 As shown, the simplified whole-machine electromagnetic field model constructed in this embodiment includes the following steps 1201-1204:

[0089] Step 1201: Extract the electromagnetic correlation characteristic parameters of each structural unit.

[0090] Electromagnetic related characteristic parameters include opening area, the longest side dimension of the opening, distance from the interference source, crossing the shield boundary state, proximity to sensitive circuits, and participation of the main current path. Furthermore, each characteristic parameter is normalized, specifically by using the maximum and minimum value normalization method to convert each characteristic parameter to the [0,1] interval.

[0091] For open structural units, the projected opening area and the length of the longest side of the opening are extracted.

[0092] The distance from the interference source refers to the distance from the geometric center of the structural unit to the geometric center of the nearest high-frequency switching interference source. High-frequency switching interference sources refer to power devices and auxiliary switching power supplies that operate on high-frequency PWM (Pulse Width Modulation) pulse switching and generate rapid voltage / current edges (steep rising / falling edges).

[0093] The "crossing the shielding boundary" status indicates whether the structural unit crosses the shielding boundary of the device enclosure, or whether it connects two shielding areas. The enclosure's shielding boundary: The device's metal enclosure (stainless steel / cold-rolled steel enclosure) itself is the electromagnetic shielding shell. The seams, splicing interfaces, opening edges, flange connection surfaces, and the area around cable perforations of the enclosure's metal plates are collectively referred to as the enclosure's shielding boundary. The shielding area is an independent, enclosed space completely surrounded by continuous metal shielding sheet metal and electrically connected to each other.

[0094] The proximity status indicator shows whether the sensitive circuit is within a preset proximity distance range of the sensitive control circuit. The sensitive control circuit is a low-voltage signal circuit in a power electronic device that performs signal sampling, logic operations, device driving, and data communication; it is susceptible to high-frequency electromagnetic field coupling interference from the power circuit and is a circuit within the device that requires special attention to avoid electromagnetic leakage.

[0095] The participation status of the main current path characterizes whether a conductor structural unit belongs to the main current path. The main current path is the power transmission path in power electronic devices that carries high-power power conversion; it typically has the characteristics of large current amplitude and includes PWM high-speed switching current.

[0096] Step 1202: Calculate the electromagnetic leakage sensitivity score.

[0097] The sensitivity to electromagnetic leakage is characterized by an electromagnetic leakage sensitivity score, which is determined by weighted fusion of the normalized structural unit's opening area, the longest side dimension of the opening, the distance from the interference source, the state of crossing the shield boundary, the state of proximity to the sensitive circuit, and the state of participation of the main current path.

[0098] Electromagnetic leakage susceptibility score, specifically, can be expressed as:

[0099] ;

[0100] In the formula, For the first Electromagnetic leakage susceptibility score of each structural unit; For structural unit indexes; Weighted by the opening area; This represents the normalized opening area; The weight of the longest side dimension of the opening; This is the normalized longest side dimension of the opening; Distance weights are used to indicate the distance to the interference source. To normalize the interference source distance, the interference source distance term adopts... Therefore, the closer the distance to the high-frequency switching interference source, the greater the contribution to the electromagnetic leakage susceptibility score; To mask boundary weights; The value is set to 1 when crossing the shielding boundary and 0 when not crossing it. The proximity weights are used for sensitive circuits; This is the proximity status value of the sensitive circuit. It is set to 1 when the circuit is within a preset proximity distance range and to 0 when it is outside the preset proximity distance range. Weights for the main current path; This is the state value for participation in the main current path; it is set to 1 when the current belongs to the main current path and 0 when it does not belong to the main current path.

[0101] Each weight satisfies The values ​​of each weight can be determined through historical rectification records of the device, design experience, and preliminary small-scale sensitivity analysis.

[0102] In a feasible implementation, the values ​​of each weight can be: 0.20 for the opening area, 0.15 for the longest side dimension of the opening, 0.20 for the distance to the interference source, 0.15 for the shielding boundary, 0.15 for the proximity of the sensitive circuit, and 0.15 for the main current path.

[0103] For example, the calculation of electromagnetic leakage susceptibility scores for different structural units:

[0104] For example, in a heat dissipation hole structure unit, the normalized opening area is 0.70, the normalized longest side dimension of the opening is 0.80, the normalized interference source distance is 0.25, the state value for crossing the shield boundary is 1, the state value for proximity to sensitive circuits is 1, and the state value for main current path participation is 0. Substituting these values ​​into the electromagnetic leakage sensitivity scoring formula yields:

[0105] .

[0106] For example, consider a non-conductive mechanical support structure unit located far from a high-frequency switching interference source. Its normalized opening area is 0.05, its normalized longest side dimension is 0.10, and its normalized interference source distance is 0.90. All three state values ​​are 0. The calculated values ​​are... .

[0107] It should be noted that not every structural unit has corresponding characteristic parameters. For example, the conductor itself in the conductor structural unit does not have the openings (holes, gaps, ventilation holes, cable perforations on a continuous metal shielding wall) referred to in electromagnetic shielding theory. Therefore, the opening area parameter of the conductor structural unit is zero.

[0108] Step 1203: Retain key structures such as high-resolution shielding, conductors, and switch holes.

[0109] The key structures include structural units that determine the electromagnetic propagation path, and structural units in the remaining structural units whose electromagnetic leakage sensitivity scores (sensitivity to electromagnetic leakage) exceed a preset sensitivity threshold. The remaining structural units are all structural units other than those that determine the electromagnetic propagation path.

[0110] The sensitivity threshold can be set to 0.55. For example, the heat dissipation hole structure unit in step 1202 has an electromagnetic leakage sensitivity score (0.71) higher than 0.55, so it is determined to be a critical structure; the non-conductive mechanical support structure unit has an electromagnetic leakage sensitivity score (0.045) lower than 0.55, and the structure unit cannot determine the electromagnetic propagation path, so it is determined to be a non-critical structure.

[0111] The structural units that determine the electromagnetic propagation path and the structural units that exceed the sensitivity threshold (critical structures) are selected as reserved objects. A structural model of the reserved objects is constructed, and electromagnetic parameters are assigned to the structural model.

[0112] The sensitivity threshold can be determined by budgeting computational resources and comparing it with previous models. When the full model grid size exceeds the computational resource budget, a simplified model can be built starting from a higher threshold. Then, several boundary scoring structures are selected for restoration calculations, and the changes in peak field strength in key monitoring areas are compared. If the change in peak field strength in key monitoring areas after restoring the boundary structures is lower than the project's allowable error, the current threshold is retained; if the change exceeds the project's allowable error, the threshold is lowered and a new set of retained objects is generated.

[0113] For structural units that determine the electromagnetic propagation path, even if the electromagnetic leakage sensitivity score is below a preset sensitivity threshold, they will still be forcibly retained. This forced retention rule is used to prevent the scoring model from deleting structures that determine the electromagnetic propagation path when the structural data is incomplete.

[0114] The structures that determine the electromagnetic propagation path include heat dissipation holes, enclosure seams, panel gaps, shielding connections, cable perforations, critical power conductors, critical power modules, critical conductor layers on the driver board PCB, and power buses.

[0115] It should be noted that the driver board (which belongs to the PCB structural unit) may not retain all solder mask layers, silkscreen layers, and the outlines of small components that are not related to electromagnetic propagation, but may retain the power input conductor, key drive pulse traces, ground reference conductor, and key conductor layers that connect to the power module.

[0116] For the identified key structures (such as high-resolution shielding, conductors, openings, enclosure shape, heat dissipation holes, and cable penetrations), a structural model is established according to the actual dimensions.

[0117] Different structural units are assigned corresponding electromagnetic parameters.

[0118] For example, the insulating dielectric layer of the laminated busbar adopts a PET material model with a relative permittivity of 3.2, a relative permeability of 1, and a bulk conductivity of 0. The conductor of the laminated busbar adopts a relative permittivity of 1, a relative permeability of 0.999991, and a conductivity of... A model of copper material.

[0119] For a 25-power BVR (copper core PVC insulated flexible wire) connection circuit (conductor structure unit) in physics, the outer diameter of the insulation layer is set to 8 mm, and the outer diameter of the conductor is set to 5.64 mm. The insulation layer adopts a PVC material model with a relative permittivity of 3.5, a relative permeability of 1, and a bulk conductivity of 0. The copper conductor adopts a relative permittivity of 1, a relative permeability of 0.999991, and a conductivity of... The conductor model.

[0120] In one feasible implementation, to accurately simulate the electromagnetic field radiated outward from the enclosure's shielding boundary and the electromagnetic leakage phenomenon from the shielding openings, thus reproducing the actual electromagnetic radiation environment of the device and improving the accuracy of the overall electromagnetic field simulation results, this embodiment also establishes an air domain outside the enclosure.

[0121] Specifically: The enclosure is modeled using stainless steel. An air domain is established outside the enclosure, and the boundary distance of the air domain is determined jointly based on the wavelength corresponding to the lowest non-zero analysis frequency, the maximum external dimensions of the device, and the target solution accuracy. When the low-frequency end contains near-static analysis points, the lowest non-zero frequency within the solution band is used to determine the reference wavelength. An open radiation boundary is adopted for the outer boundary of the air domain to allow outward propagating electromagnetic energy to leave the computational region.

[0122] After the air domain size is determined, a boundary sensitivity check is performed: the peak field strength of the monitoring area outside the enclosure is calculated using the initial air domain, and then the air domain is expanded along the outward normal by a preset ratio and recalculated. When the difference in peak field strength of the monitoring area outside the enclosure before and after expanding the air domain is within the project's allowable error, a smaller air domain is used; when the difference exceeds the project's allowable error, the air domain is further expanded.

[0123] Step 1204: Simplify the small mechanical structures that have no impact on low-resolution analysis and generate a simplified electromagnetic field model of the whole machine.

[0124] Structural units that do not exceed the sensitivity threshold are simplified to construct a simplified structural model. For example, non-critical insulating supports are simplified using an envelope approach, and small chamfers are removed without altering the high-frequency current redirection path.

[0125] This step uses selective simplification driven by electromagnetic action mechanisms to generate a whole-machine electromagnetic field model that retains heat dissipation holes, seams, cable perforations, shielded connections, and key conductor structures. This allows the modeling of irrelevant mechanical details to be reduced while maintaining the main electromagnetic propagation and leakage paths.

[0126] Step 13: Configure multiple lumped ports on the whole machine electromagnetic field model. Based on the pre-established port mapping record, connect each pulse excitation source built on the circuit side to the corresponding lumped port to construct a field-circuit cooperative model.

[0127] For the overall electromagnetic field model, port patches are established between the enclosure, the grounding reference structure, and the critical conductors. Each port patch is equipped with a lumped port. In this embodiment, the port reference impedance of the lumped port can be set to 50Ω, and the port integration line points from the side closer to the grounding reference end to the critical trace end, which is used to unify the port electric field direction and the reference potential relationship.

[0128] For a single-phase grid-type static var generator, this embodiment sets up 12 lumped ports. Based on a pre-established port mapping record, each lumped port establishes a mapping relationship with one of the four types of pulse excitation sources: LHE20 power supply, XDR power supply, driver board fast pulse path, and power bus excitation path. It should be noted that there is a one-to-one correspondence between the lumped ports and the pulse excitation signals. For this embodiment of the single-phase grid-type static var generator, there are a total of 12 pulse excitation signals, belonging to the above four types of excitation sources; therefore, 12 lumped ports are configured.

[0129] The port mapping record mentioned above includes not only the mapping relationship between lumped ports and pulse excitation sources, but also the mapping relationship between lumped ports and reference conductors, integration line direction, pulse high-level voltage, pulse period, pulse rise time, pulse fall time, and pulse high-level duration. Specifically:

[0130] No. The port mapping record of a lumped port is represented as follows:

[0131] ;

[0132] In the formula, For the first Port mapping records for each aggregated port; For port indexing; Number the pulse excitation signal (interference source); Reference conductor number; The direction of the integration line is marked with 1 when the integration line points from the reference conductor to the critical conductor, and -1 when it points from the critical conductor to the reference conductor. It is a pulse high-level voltage; The pulse period; The pulse rise time; The pulse fall time; This represents the duration of the high-level pulse. Port mapping records are used to establish a defined connection between the circuit-side pulse source and the electromagnetic-side port.

[0133] Among them, the reference conductor is the potential reference conductor used for port voltage integration and pulse excitation potential calculation in field-circuit co-simulation. It is a conductive carrier that exists in pairs with the interference source signal conductor.

[0134] For the specific pulse excitation source, the LHE20-20A15A4 power supply, its operating frequency is 65kHz, the period is 15.38μs, the pulse voltage changes from 0V to 310V, the rise time is 50ns, the fall time is 50ns, and the high-level duration is 7.69μs. For the XDR-150E-24 power supply, its operating frequency is 70kHz, the period is 14.28μs, the pulse voltage changes from 0V to 325V, the rise time is 50ns, the fall time is 50ns, and the high-level duration is 7.14μs.

[0135] For the driver board's fast pulse, the operating frequency is 8MHz, the high-level voltage is 3.3V, the rise time is 5ns, the fall time is 5ns, and the high-level duration is 62.5ns. (Period) According to frequency Relationship calculation is .

[0136] For power bus excitation, the operating frequency is 15kHz, the period is 66.67μs, the pulse voltage changes from 0V to 310V, the rise time is 100ns, the fall time is 100ns, and the high level duration is 33.33μs.

[0137] Step 14: Trigger each pulse excitation source to emit the corresponding excitation signal to obtain the spatial electromagnetic field distribution results of the field-circuit cooperative model.

[0138] By outputting corresponding pulse signals from multiple pulse excitation sources on the drive circuit side, transient joint solutions are performed on the field-circuit cooperative model. The transient electrical excitation of the lumped port is applied to the electromagnetic field model of the whole machine to obtain the spatial transient electromagnetic field distribution results of the whole machine.

[0139] The specific implementation of this step is as follows: Figure 3 As shown, it includes the following steps 1401-1404:

[0140] Step 1401: Build a port mapping matrix to bind multi-source switch pulse excitation.

[0141] Multiple pulse excitation sources are established on the circuit side and connected to the corresponding lumped ports of the whole machine electromagnetic field model according to the port mapping record.

[0142] Step 1402: Solve the transient circuit and apply excitation to the electromagnetic field model.

[0143] A voltage monitoring probe is installed on the circuit side. By driving the circuit side to output corresponding pulse signals from multiple pulse excitation sources, transient circuit solutions are performed to obtain data on the changes of lumped port voltage and port current over time. The transient port excitation is transmitted to the whole-machine electromagnetic field model, and a transient joint solution is performed on the field-circuit cooperative model to obtain the spatial transient field response under actual operating excitation conditions.

[0144] Step 1403: Iterate the adaptive mesh until convergence.

[0145] In this embodiment, an electromagnetic field monitoring area is pre-defined. This monitoring area covers the near field of the interference source, the neighborhood of sensitive circuits, the neighborhood of power conductors, the leakage direction outside the enclosure, and the outside of cable holes. Specifically, it includes the following seven types of monitoring areas: the outside of the enclosure, below the driver board, below the LHE20 power supply, below the busbar, inside the driver board, the location near the critical trace path of the XDR power supply, and the location away from the trace path of the XDR power supply.

[0146] Record the geometric center coordinates, area range, associated device number, and associated path number for each monitoring area. The associated device number is used to compare the near-field distribution of the interference source (excitation source), and the associated path number is used for subsequent spatial field-power path correlation analysis.

[0147] To balance computational accuracy and simulation time, this embodiment performs adaptive mesh refinement on the whole-machine electromagnetic field model: the mesh is automatically refined in areas of drastic electromagnetic field changes, while a coarser mesh is maintained in areas of gentle field changes, thus controlling the total number of meshes while ensuring simulation accuracy.

[0148] Scattering parameters describe the energy coupling relationship between incident and outgoing electromagnetic waves at each port in a multi-port network, and quantitatively characterize the strength of signal transmission, reflection and electromagnetic coupling between ports at radio frequency / high frequency.

[0149] In this embodiment, the adaptive solution of the mesh is determined by the change in mesh parameters, specifically:

[0150] The change in scattering parameters between two consecutive rounds of adaptive solving is defined as:

[0151] ;

[0152] In the formula, For the first The maximum change in scattering parameters relative to the previous round is adaptively solved. For grid-adaptive round indexing; , Index of the scattering parameter matrix; These are the corresponding scattering parameters.

[0153] The preset grid convergence threshold is 0.02. When two consecutive rounds meet the condition... At that point, the grid is considered to have met the preset convergence requirements.

[0154] Step 1404: Collect and output electromagnetic field time domain, peak value, and contour map data for the region.

[0155] After grid convergence, a wideband sweep solution is performed to obtain the frequency domain distribution of the electromagnetic field at different frequencies within the monitoring area. Based on the frequency domain electromagnetic field data, an inverse Fourier transform is performed to reconstruct the time domain waveform of the electromagnetic field, and the peak values ​​of the electromagnetic field at each location are further extracted. At the same time, a spatial distribution cloud map of the electromagnetic field at the corresponding frequency point is generated. The sweep range can be extended from the low frequency end to 80MHz, with a frequency interval of 1MHz. For key operating frequencies below 1MHz, additional discrete solution points of 15kHz, 65kHz, and 70kHz are added for encrypted sampling.

[0156] The peak electric field strength, peak magnetic field strength, peak occurrence time, and spatial coordinates of each monitoring area obtained above are recorded in the monitoring results table. The spatial field cloud map is used to locate the shape and extension direction of the high field strength region, and the time curve is used to determine the correspondence between the switching time of different pulse sources and the peak field strength.

[0157] In one feasible implementation, this step also includes:

[0158] Based on the spatial electromagnetic field distribution results, the peak values ​​of electric field strength and magnetic field strength in each preset monitoring area are extracted respectively; if the peak values ​​of electric field strength and / or magnetic field strength exceed the corresponding threshold, the structural adjustment command of the associated device in the corresponding monitoring area is output.

[0159] For example, the peak electric field intensity extracted from the LHE20 power source region is The peak electric field intensity in the XDR power region is The peak electric field intensity in the IGBT driver board region is If the extracted peak electric field intensity exceeds the preset peak electric field intensity threshold, a structural adjustment command for the associated devices within the corresponding monitoring area will be output. The structural adjustment object corresponding to the adjustment command can be at least one of the following: LHE20 key node location, XDR high-coupling trace path, high-density wiring area of ​​the driver board, and local shielding location.

[0160] In this step, the port mapping relationship is established using the excitation parameters of the multi-source switch. The frequency, voltage amplitude, rise time, fall time and pulse width corresponding to different switching power supplies, drive signals and power buses are respectively input into the field-circuit collaborative solution process, so that the spatial electromagnetic field results correspond to the actual multi-source switch environment.

[0161] Step 15: Based on the spatial electromagnetic field distribution results and the power loop topology relationship of the device, determine the key parasitic parameter extraction objects, establish parasitic parameter models for the stacked busbar and the power connection paths in the key parasitic parameter extraction objects, and extract the values ​​of key parasitic parameters from the parasitic parameter models.

[0162] Step 16: Based on the extracted key parasitic parameter values, generate a structural adjustment scheme for the stacked busbar and a layout adjustment scheme for the power connection path, and conduct a turn-off transient voltage risk assessment for power semiconductor devices based on the equivalent stray inductance of the fast commutation loop.

[0163] Combination Figure 4 The specific implementation process of steps 15 and 16 will be introduced. Figure 4 In the process of optimizing the busbar of the parasitic parameter extraction machine, the steps 1-3 are as follows:

[0164] Step 1: Calculate the associated risk indicators of the power connection path based on the field strength distribution, and screen the key parasitic parameter extraction objects.

[0165] The process of determining the key parasitic parameter extraction targets based on the spatial electromagnetic field distribution results and the power loop topology relationship of the device includes the following steps 1501-1503:

[0166] Step 1501: Based on the power loop topology, the closed power loop is split into multiple independent power connection paths according to the device boundaries.

[0167] Step 1502: Weighted fusion of the normalized path neighborhood magnetic field peak, neighborhood electric field peak, rated current, number of bends, distance between round-trip conductors, and distance to high field strength region to determine the correlation risk index between each power connection path and the space field.

[0168] For each power connection path, extract the peak electric field strength and peak magnetic field strength of the path neighborhood, and read the path rated current level, the number of bends in the path, the distance between the outbound and return paths (distance between the conductors), and the distance between the path and the nearest high field strength region.

[0169] The extracted variables were normalized: each continuous variable was transformed to the 0 to 1 interval using the minimum and maximum values ​​in the same batch of candidate power connection paths.

[0170] No. The risk index of the association between a power connection path and the spatial field is defined as follows:

[0171] ;

[0172] In the formula, For the first Risk indicators related to the correlation between power connection paths and the space field; For power connection path index; The weights are for the normalized electric field strength. The peak value of the normalized electric field intensity in the path neighborhood; For normalized magnetic field strength weights; The peak value of the normalized magnetic field strength in the path neighborhood; For normalized path current weights; Normalized path current level; Path bend weight; This represents the normalized path bend count. The weights for the distance between the outbound and return paths; This is the normalized distance between the outbound and return paths; Distance weights are assigned to high field strength regions; This is the normalized distance between the path and the nearest high field strength region. Each weight is set based on the project's level of concern regarding spatial coupling and power loop risks, and the sum of the weights is equal to 1.

[0173] In a specific implementation, the weights in the above formula in this embodiment are 0.20, 0.15, 0.20, 0.15, 0.15, and 0.15, respectively. This associated risk index is used to determine the modeling priority of power connection paths: when there are long-distance, high-current, multi-bend power connection paths with separate outgoing and return routes near high field strength regions, the risk index will increase, and the corresponding power connection paths will be prioritized for establishing three-dimensional parasitic parameter models.

[0174] Step 1503: Power connection paths whose associated risk indicators exceed preset threshold values ​​are selected as key parasitic parameter extraction objects.

[0175] In addition to the power connection paths whose associated risk indicators exceed the threshold mentioned above, the key parasitic parameter extraction targets also include stacked busbars.

[0176] Step 2: Establish a three-dimensional model of the stacked busbar and extract key parasitic parameters such as self-inductance and mutual inductance.

[0177] Parasitic parameter models are established for the stacked busbar and the power connection path in the key parasitic parameter extraction object, respectively, and the values ​​of key parasitic parameters are extracted from the parasitic parameter models.

[0178] The key parasitic parameters include conductor self-inductance, conductor mutual inductance, and path stray inductance.

[0179] For multilayer busbars, a three-dimensional model is established, including at least a forward conductor layer, a reverse conductor layer, and PET (Polyethylene Terephthalate) insulating layers located between and outside the conductor layers. The geometric contours of the conductor layers maintain the shapes of the actual current inlets, connection holes, transition regions, and power module connection terminals.

[0180] The forward and reverse conductor layers each define independent electrical networks, with source and sink terminals set at the conductor ends according to the actual commutation current path. The initial solution frequency is set to 15kHz based on the power switching frequency, and a frequency scan up to 5MHz is performed with a scan interval of 0.5MHz, while retaining the critical operating frequency of 15kHz.

[0181] Extract the self-inductance of the positive conductor from the output inductance matrix. Reverse conductor self-inductance and mutual induction The equivalent inductance of a closed loop is expressed as: In the original structure, the self-inductance of the forward conductor is 84.337 nH, the self-inductance of the reverse conductor is 82.856 nH, and the mutual inductance is 80.173 nH. The equivalent self-inductance of the closed loop is calculated. .

[0182] Step 3: Analyze the contribution of geometric variables to reduce sensitivity and generate an optimized busbar scheme.

[0183] To enable the structural adjustment of the stacked busbar to be driven by parameter results, a set of geometric variables for the stacked busbar is established, including the path length from the capacitor to the power module, bending angle, terminal overlap rate, conductor thickness, insulation layer thickness, conductor spacing, and power module spacing.

[0184] For the Define the normalized contribution of continuous geometric variables to reduce sensitivity:

[0185] ;

[0186] In the formula, Indicates the first Normalized desensitization contribution of a continuous geometric variable; This indicates that only the first one is changed. The change in stray inductance of the stacked busbar circuit when the geometric variables are specified; This indicates the stray inductance of the reference circuit of the multilayer busbar; Indicates the first Dimensional adjustment amount for each geometric variable; Indicates the first The reference dimension for each geometric variable.

[0187] The methodological study of the examples revealed that path length, unnecessary bends, and terminal overlap rate are geometric variables that contribute significantly.

[0188] In a parameterized case, the terminal projection overlap rate of the reference structure is 0.62, and the equivalent stray inductance of the closed loop is 6.847nH. After increasing the terminal projection overlap rate to 1.00, the equivalent stray inductance of the closed loop decreases to 1.911nH, and the calculated contribution is 1.176.

[0189] Prioritizing adjustments to geometric variables such as path length, unnecessary bends, and terminal overlap rate can generate structural adjustment schemes for stacked busbars.

[0190] By ranking the contribution of geometric variables of the stacked busbars, we can distinguish the different effects of material thickness variation, insulation layer variation, path length variation, bending structure variation and terminal overlap relationship variation on parasitic parameters, thus prioritizing the handling of variables directly related to the main current path length and the magnetic field coupling relationship of the outgoing and return paths.

[0191] For power connection paths, the continuous loop is split into multiple power connection paths according to the actual power loop topology. This implementation establishes four path-level models: QF1—CT2—branch terminal, KM branch terminal—L1, L1—CT1—IGBT, and IGBT—QF1.

[0192] An independent electrical network was established for each power connection path, and parasitic parameters were extracted. The obtained AC stray inductance results were 166.62nH, 248.92nH, 978.11nH, and 1703.5nH, respectively. The IGBT-QF1 power connection path was included in the priority structural adjustment set due to its largest stray inductance. During the structural scheme generation process, priority was given to shortening the lines, reducing continuous right-angle bends, and arranging the outbound and return paths close together.

[0193] After the path-level parasitic parameters are extracted, the turn-off transient voltage risk assessment of power semiconductor devices is performed based on the equivalent stray inductance of the fast commutation loop.

[0194] The equivalent stray inductance of the fast commutation loop is the sum of the equivalent stray inductance of the structural adjustment scheme and the equivalent stray inductance of the layout adjustment scheme.

[0195] The turn-off spike voltage component can be defined as follows:

[0196] ;

[0197] in, This represents the equivalent stray inductance of the fast commutation loop; This represents the rate of change of current.

[0198] In a specific verification scenario Taking 1703.5 nH and a current change rate of 350 A / μs, we obtain... If structural adjustments are made... If it drops to 400 nH, then It dropped to 140 V.

[0199] The transient voltage risk ratio is defined as an indicator for evaluating the risk of transient voltage during shutdown. The transient voltage risk ratio can be expressed as:

[0200] ;

[0201] In the formula, , , These represent the DC bus voltage, safety margin voltage, and device rated withstand voltage, respectively.

[0202] Under the conditions of a DC bus voltage of 500V, a safety margin voltage of 100V, and a device rated withstand voltage of 1200V, combined with the shutdown peak charges of 596.225V and 140V mentioned above, the corresponding transient voltage risk ratios are 0.9969 and 0.6167, respectively.

[0203] When the transient voltage risk ratio does not meet (is less than or equal to) the control value (e.g., 0.85), measures such as shortening the commutation path, setting a high-frequency, low-parasitic absorption branch, or adjusting the turn-off drive resistor within the allowable range of the device can be taken. After adjustment, parasitic parameters should be extracted and risk assessment should be carried out again.

[0204] In steps 15 and 16, the spatial electromagnetic field results and the power loop topology are used together to select key parasitic parameter extraction objects, so that the spatial electromagnetic field results are no longer limited to cloud map display, but participate in the determination of path-level modeling objects; the parasitic parameter results continue to be used for the risk assessment of turn-off transient voltage, forming a continuous data transmission relationship.

[0205] Step 17: For candidate schemes that trigger thermal flow field verification in the structural adjustment scheme and layout adjustment scheme, perform thermal flow field verification;

[0206] like Figure 5 As shown, the thermal flow field verification specifically includes the following steps 1701-1703:

[0207] Step 1701: Identify structural schemes that alter device spacing, heat sources, and air ducts, and trigger thermal simulation verification.

[0208] For example, in structural adjustment schemes or / or layout adjustment schemes, shortening the IGBT (Insulated Gate Bipolar Transistor) half-bridge spacing or shortening the distance between the DC support capacitor and the IGBT will change the relative position of the heat source. Therefore, the thermal verification trigger state of the corresponding candidate scheme is set to effective.

[0209] Step 1702: Synchronize the geometric model and load loss and cooling parameters, and calculate temperature and airflow parameters.

[0210] The geometric parameters corresponding to the candidate schemes are loaded into the thermal flow field model. The thermal flow field model is constructed based on the synchronous geometric model of the candidate structure, dividing the solid heat conduction domain and the fluid flow domain, and configuring conjugate heat transfer boundary conditions.

[0211] Simulation calculations are performed based on material thermophysical parameters and environmental cooling parameters from a multi-source basic dataset to determine the thermal flow field verification parameters. The thermal flow field verification parameters include the device's maximum temperature, the temperature of key components, the centroid migration distance in the high-temperature region, and the air duct blockage rate.

[0212] In one specific implementation, reactor L1, charging capacitor C2, and IGBT are used as heat sources, with total power outputs of 30W, 2W, and 50W respectively. The ambient temperature is 40℃, and the air intake velocity is 1m / s. Calculate the maximum temperature. Temperature of key components Duct blockage rate Distance of centroid migration in high-temperature region .

[0213] The high-temperature zone refers to the area where the temperature exceeds a preset threshold (such as 90% of the highest temperature), which can be set according to project requirements.

[0214] Step 1703: Determine whether the thermal compatibility is qualified based on the limitations.

[0215] Thermal compatibility gating mark When all four indicators meet their respective limits, that is, when all the heat flow field verification parameters meet their corresponding preset conditions. A value of 1 indicates that the thermal performance of the candidate solution is qualified; otherwise, a value of 0 indicates that the thermal performance of the corresponding candidate solution is unqualified.

[0216] For example, according to simulation calculations, the highest temperature of candidate structure A is 74.8℃, and the temperature of key components is 72.6℃, which meets the limits of 80℃ and 75℃, and the thermal compatibility gating mark is 1; the highest temperature of candidate structure B is 83.6℃, ​​which exceeds the limit, and the thermal compatibility gating mark is 0, triggering the structural parameter rollback instruction.

[0217] This step verifies the inductance reduction structure scheme through thermal compatibility gating to avoid unacceptable local high temperature concentrations or airflow channel blockages caused by shortening the distance between the capacitor and the power semiconductor device or compressing the power module spacing.

[0218] Step 18: When the spatial electromagnetic field distribution results, the values ​​of key parasitic parameters, the risk assessment results of the turn-off transient voltage, the thermal flow field verification results, and the structural parameter change trends all meet the corresponding preset verification conditions, output the final structural scheme of the device.

[0219] The verification of the spatial magnetic field distribution results is as follows: Based on the spatial electromagnetic field distribution results, the peak values ​​of electric field intensity and magnetic field intensity in each preset monitoring area are extracted respectively; if the peak values ​​of electric field intensity and magnetic field intensity do not exceed the corresponding thresholds, the spatial electromagnetic field distribution results meet the verification conditions.

[0220] Verification of key parasitic parameters: If the equivalent total stray inductance of the commutation loop determined based on the value of the key parasitic parameters is not greater than the preset maximum upper limit threshold, then the key parasitic parameters meet the verification conditions.

[0221] Verification of the risk assessment results of transient voltage shutdown: The transient voltage risk ratio is not greater than the preset safety threshold.

[0222] Verification of the thermal flow field verification results: Each thermal flow field verification parameter does not exceed its respective limit.

[0223] The verification condition corresponding to the trend of structural parameter changes is that the structural parameters converge, specifically by calculating the maximum relative change of parameters in two consecutive rounds of structural optimization iterations. To determine this, the threshold for structural parameter change can be set to 0.03; when the maximum relative change of the parameter in two consecutive rounds of structural optimization iterations is less than 0.03, the structural parameters are considered to have converged.

[0224] The maximum relative change in parameter is calculated using the following formula:

[0225] ;

[0226] In the formula, For the first The maximum relative change in parameters relative to the previous round in the round structure optimization iteration; Index for iterative rounds of structural optimization; For the geometric variable index, the geometric variables include at least the busbar geometric variables, power line layout variables, and device spacing variables; For the first In the iterative optimization of wheel structure, the first Each geometric variable can take values; The values ​​are the corresponding geometric variables from the previous round of structural optimization iterations.

[0227] Joint termination marker ,in, , , , , These represent the spatial electromagnetic field distribution results, the values ​​of key parasitic parameters, the risk assessment results of the turn-off transient voltage, the thermal flow field verification results, and the trend of structural parameter changes, respectively.

[0228] When the spatial electromagnetic field distribution results, the values ​​of key parasitic parameters, the risk assessment results of the turn-off transient voltage, the thermal flow field verification results, and the structural parameter variation trends all meet the corresponding preset verification conditions, Output the final structural scheme; otherwise, write back the corresponding structural parameters according to the mapping relationship of the failed index and enter the next round of simulation.

[0229] If the spatial electromagnetic field distribution results do not meet the corresponding verification conditions, such as the peak magnetic field strength in the monitoring area of ​​the power module port exceeding the preset magnetic field threshold, or the problem of excessive local electromagnetic radiation and magnetic field concentration, then the corresponding structural parameters to be written back are the overlapping area of ​​the positive and negative busbars and the size of the conductor chamfer. By increasing the overlapping area of ​​the conductors, the magnetic field cancellation effect is improved, and the conductor edge structure is optimized to weaken the local magnetic field concentration, so that the peak value of the spatial electromagnetic field falls back to the allowable threshold range.

[0230] If the key parasitic parameters do not meet the corresponding verification conditions, such as the equivalent total stray inductance of the converter loop obtained from simulation being greater than the preset upper limit threshold for inductance, the parasitic parameters of the loop are too large, which can easily cause switching oscillations; then the corresponding structural parameters to be written back are the interlayer insulation spacing of the busbar and the length of the power conductor trace. Combining the contribution of each geometric parameter to inductance reduction, the highly sensitive parameters are optimized first, the converter loop area is compressed, and the overall stray inductance of the loop is reduced so that it meets the limit requirements.

[0231] If the risk assessment result of the turn-off transient voltage does not meet the corresponding verification conditions, such as the calculated transient voltage risk ratio being greater than the preset safety threshold, the IGBT turn-off voltage spike being too high, the device voltage stress exceeding the standard, or the risk of breakdown, then the corresponding structural parameters to be rewritten are the installation spacing between the power module and the supporting capacitor, and the arrangement structure of the commutation circuit, to further shorten the power commutation path, suppress the switching transient voltage spike, and reduce the transient voltage risk ratio to the safe range.

[0232] If the thermal flow field verification results do not meet the corresponding verification conditions, such as the maximum temperature rise or steady-state temperature of the key heat dissipation area of ​​the stacked busbar exceeding the corresponding thermal limit value, or the existence of local hot spot overheating problems that affect the long-term operational reliability of the equipment, then the corresponding structural parameters to be written back are the power conductor thickness and the ventilation gap of the module arrangement. By increasing the conductor cross-sectional area to reduce conduction loss and optimizing the ventilation and heat exchange structure to improve heat dissipation conditions, the thermal field parameters will be controlled within the allowable range.

[0233] If the trend of structural parameter changes does not meet the corresponding verification conditions, specifically if the relative change of the maximum structural parameter obtained from two consecutive iterations is greater than 0.03, and the structural parameter is still in a state of large fluctuation and has not tended to stabilize, then the corresponding structural parameter to be written back is the iteration step size of all geometric variables to be optimized, reducing the parameter adjustment range, refining the parameter iteration interval, and gradually constraining the change range of structural parameters until the convergence threshold condition is met.

[0234] This embodiment establishes an iterative termination determination that involves electromagnetic leakage, stray inductance, turn-off transient voltage, and thermal compatibility conditions. This allows candidate structural schemes to be subject to multiple physical index constraints simultaneously, and to continue adjusting the corresponding structural parameters based on the failed indices.

[0235] Example 2:

[0236] To address the problems of large discrepancies between existing simulation verification results of power electronic devices and actual operating conditions, and inaccurate assessment of electromagnetic compatibility, this application also provides a multi-physics electromagnetic compatibility simulation verification system for power electronic devices, based on the same inventive concept as Embodiment 1.

[0237] The specific structural diagram of the system is as follows: Figure 6 As shown, it includes the following functional units 61-68:

[0238] Data acquisition unit 61 is used to acquire multi-source basic datasets required for designing power electronic devices;

[0239] The whole-machine electromagnetic modeling unit 62 is used to construct the whole-machine electromagnetic field model of the device by combining the geometric structure data and electromagnetic parameter data of the device with the sensitivity of each structural unit of the device to electromagnetic leakage and the multi-source basic data.

[0240] The field-circuit cooperative solution unit 63 is used to configure multiple lumped ports on the whole-machine electromagnetic field model, and connect each pulse excitation source built on the circuit side to the corresponding lumped port based on the pre-established port mapping record to construct the field-circuit cooperative model; the port mapping record contains the mapping relationship between the lumped port and the pulse excitation source;

[0241] The spatial electromagnetic field distribution acquisition unit 64 is used to trigger each pulse excitation source to emit corresponding excitation signals in order to obtain the spatial electromagnetic field distribution results of the field-circuit cooperative model.

[0242] Parasitic parameter extraction unit 65 determines key parasitic parameter extraction objects based on the spatial electromagnetic field distribution results and the power loop topology relationship of the device, establishes parasitic parameter models for the stacked busbar and the power connection paths in the key parasitic parameter extraction objects respectively, and extracts the values ​​of key parasitic parameters from the parasitic parameter models;

[0243] The structural adjustment scheme generation unit 66 generates a structural adjustment scheme for the stacked busbar and a layout adjustment scheme for the power connection path based on the extracted key parasitic parameter values, and performs a turn-off transient voltage risk assessment of the power semiconductor device based on the equivalent stray inductance of the fast commutation loop; the equivalent stray inductance of the fast commutation loop is the sum of the equivalent stray inductance of the structural adjustment scheme and the equivalent stray inductance of the layout adjustment scheme.

[0244] The thermal flow field verification unit 67 is used to perform thermal flow field verification on candidate schemes that trigger thermal flow field verification in structural adjustment schemes and layout adjustment schemes;

[0245] The scheme output unit 68 is used to output the final structural scheme of the device when the spatial electromagnetic field distribution result, the value of key parasitic parameters, the risk assessment result of the turn-off transient voltage, the thermal flow field verification result and the structural parameter change trend all meet the corresponding preset verification conditions.

[0246] The overall electromagnetic modeling unit is specifically used for: calculating the electromagnetic leakage sensitivity of structural elements, specifically including:

[0247] The sensitivity of the structural unit to electromagnetic leakage is determined by weighted fusion of the normalized structural unit's opening area, the longest side dimension of the opening, the distance from the interference source, the state of crossing the shielding boundary, the state of proximity to the sensitive circuit, and the state of participation of the main current path.

[0248] The state of crossing the shielding boundary indicates whether the structural unit crosses the shielding boundary of the device housing or whether it connects two shielding areas.

[0249] The whole-machine electromagnetic modeling unit is also used for:

[0250] Structural units that determine the electromagnetic propagation path are selected from all structural units. The sensitivity of the remaining structural units to electromagnetic leakage is compared with a sensitivity threshold, and the remaining structural units are divided into structural units that exceed the sensitivity threshold and structural units that do not exceed the sensitivity threshold. The remaining structural units are the structural units other than those that determine the electromagnetic propagation path. The structural units that determine the electromagnetic propagation path and the structural units that exceed the sensitivity threshold are retained as objects, and structural models of the retained objects are constructed, and electromagnetic parameters are assigned to the structural models. The structural units that do not exceed the sensitivity threshold are simplified to construct simplified structural models. Based on the structural models of the retained objects with assigned electromagnetic parameters and the simplified structural models, the overall electromagnetic field model of the device is formed.

[0251] The spatial electromagnetic field distribution acquisition unit is specifically used for:

[0252] The multi-channel pulse excitation source on the drive circuit side outputs corresponding pulse signals to perform transient joint solution on the field-circuit cooperative model. The transient electrical excitation of the lumped port is applied to the whole machine electromagnetic field model to obtain the spatial transient electromagnetic field distribution results of the whole machine.

[0253] The space electromagnetic field distribution acquisition unit is also used for:

[0254] Based on the spatial electromagnetic field distribution results, the peak values ​​of electric field strength and magnetic field strength in each preset monitoring area are extracted respectively; if the peak values ​​of electric field strength and / or magnetic field strength exceed the corresponding threshold, the structural adjustment command of the associated device in the corresponding monitoring area is output.

[0255] The parasitic parameter extraction unit is specifically used for:

[0256] Based on the power loop topology, the closed power loop is split into multiple independent power connection paths according to the device boundaries. The normalized path neighborhood magnetic field peak, neighborhood electric field peak, rated current, number of bends, back-and-forth conductor spacing and distance to high field strength region are weighted and fused to determine the correlation risk index between each power connection path and the space field. Power connection paths with correlation risk index exceeding the preset threshold are selected as key parasitic parameter extraction objects.

[0257] The thermal flow field verification unit is specifically used for:

[0258] The geometric parameters corresponding to the candidate schemes are loaded into the thermal flow field model; the thermal flow field model is constructed by dividing the solid thermal conduction domain and the fluid flow domain based on the candidate structure and configuring conjugate heat transfer boundary conditions; simulation calculations are performed based on the material thermophysical parameters and environmental cooling parameters in the multi-source basic dataset to determine the thermal flow field verification parameters; the thermal flow field verification parameters include the highest temperature of the device, the temperature of key components, the centroid migration distance in the high temperature region, and the air duct blockage rate; if the thermal flow field verification parameters all meet the corresponding preset conditions, the thermal performance of the candidate scheme is qualified.

[0259] Based on the same inventive concept as the foregoing embodiments of this application, this application also provides a computing device.

[0260] like Figure 7 As shown, the computing device includes a memory 71 and a processor 72. The memory 71 can be configured to store various other data to support operation on the electronic device. Examples of this data include instructions for any application or method used to operate on the electronic device. The memory 71 can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic storage, flash memory, magnetic disk, or optical disk.

[0261] The processor 72, coupled to the memory 71, is used to execute the computer program stored in the memory 71 to perform the electromagnetic compatibility simulation and verification method for multi-physics fields of a power electronic device as described in the foregoing embodiments.

[0262] When processor 72 executes the computer program to perform an electromagnetic compatibility simulation and verification method for multi-physics fields of a power electronic device, it first constructs a whole-device electromagnetic field model, then connects the pulse excitation sources built on the circuit side to the lumped ports corresponding to the whole-device electromagnetic field model by combining port mapping records, thereby achieving field-circuit coordination; then, it screens key parasitic parameter extraction objects and extracts key parasitic parameters in conjunction with the power loop topology, thereby generating adjustment schemes; and performs thermal flow field verification on candidate schemes that trigger thermal flow field verification in the adjustment schemes, and finally outputs the final structural scheme of the device by jointly judging the multi-physics field results and the trend of structural parameter changes. By unifying magnetic field, circuit, and thermal field simulations into the same modeling and verification process, it realizes real-time linkage and mutual verification of various physical field data, closely reflects the actual operating conditions of the device, and ensures the accuracy of electromagnetic field distribution, parasitic parameters, transient voltage risks, and thermal performance evaluation. It can also synchronously iterate and optimize the device structure based on multi-dimensional simulation results, avoid electromagnetic interference, device overvoltage breakdown, and thermal failure risks, improve the reliability and design efficiency of simulation verification, and reduce the number of iterations and R&D costs of physical prototypes.

[0263] When the processor 72 executes the computer program in the memory 71, in addition to the functions described above, it can also perform other functions, as detailed in the descriptions of the preceding embodiments.

[0264] Furthermore, such as Figure 7 As shown, the computing device also includes other components such as a display 74, a communication component 73, a power supply component 75, and an audio component 76. Figure 7 The diagram only shows some components and does not mean that the computing device includes only these components. Figure 7 The components shown.

[0265] Accordingly, embodiments of this application also provide a computer-readable storage medium storing a computer program, which, when executed by a computer, can implement the methods provided in the above embodiments.

[0266] The system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0267] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in various embodiments or some parts of the embodiments.

[0268] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A multi-physics electromagnetic compatibility simulation and verification method for power electronic devices, characterized in that, include: Obtain the multi-source foundational datasets required for designing power electronic devices; Based on the sensitivity of each structural unit of the device to electromagnetic leakage, and by combining the geometric structure data and electromagnetic parameter data of the device in a multi-source basic dataset, a whole-machine electromagnetic field model of the device is constructed. Multiple lumped ports are configured on the overall electromagnetic field model. Based on the pre-established port mapping record, each pulse excitation source built on the circuit side is connected to the corresponding lumped port to construct a field-circuit cooperative model. The port mapping record contains the mapping relationship between the lumped ports and the pulse excitation sources. Each pulse excitation source is triggered to emit a corresponding excitation signal in order to obtain the spatial electromagnetic field distribution results of the field-circuit cooperative model; Based on the spatial electromagnetic field distribution results and the power loop topology relationship of the device, the key parasitic parameter extraction objects are determined. Parasitic parameter models are established for the stacked busbar and the power connection paths in the key parasitic parameter extraction objects, and the values ​​of key parasitic parameters are extracted from the parasitic parameter models. Based on the extracted key parasitic parameter values, a structural adjustment scheme for the stacked busbar and a layout adjustment scheme for the power connection path are generated. Furthermore, a risk assessment of the turn-off transient voltage of the power semiconductor device is performed based on the equivalent stray inductance of the fast commutation loop. The equivalent stray inductance of the fast commutation loop is the sum of the equivalent stray inductance of the structural adjustment scheme and the equivalent stray inductance of the layout adjustment scheme. For candidate schemes that trigger thermal flow field verification in structural adjustment schemes and layout adjustment schemes, thermal flow field verification is performed; When the spatial electromagnetic field distribution results, the values ​​of key parasitic parameters, the risk assessment results of the turn-off transient voltage, the thermal flow field verification results, and the structural parameter change trends all meet the corresponding preset verification conditions, the final structural scheme of the output device is determined.

2. The method according to claim 1, characterized in that, The sensitivity of the structural unit to electromagnetic leakage is determined by weighted fusion of the normalized structural unit's opening area, the longest side dimension of the opening, the distance from the interference source, the state of crossing the shielding boundary, the state of proximity to the sensitive circuit, and the state of participation of the main current path. The state of crossing the shielding boundary indicates whether the structural unit crosses the shielding boundary of the device housing or whether it connects two shielding areas.

3. The method according to claim 2, characterized in that, Based on the sensitivity of each structural unit of the device to electromagnetic leakage, and combining the geometric structure data and electromagnetic parameter data of the device in a multi-source basic dataset, a whole-machine electromagnetic field model of the device is constructed, including: The structural unit that determines the electromagnetic propagation path is selected from all structural units; The sensitivity of the remaining structural units to electromagnetic leakage is compared with the sensitivity threshold, and the remaining structural units are divided into structural units that exceed the sensitivity threshold and structural units that do not exceed the sensitivity threshold; the remaining structural units are the structural units other than the structural units that determine the electromagnetic propagation path. The structural units that determine the electromagnetic propagation path and the structural units that exceed the sensitivity threshold are reserved as objects. A structural model of the reserved objects is constructed, and electromagnetic parameters are assigned to the structural model. Structural units that do not exceed the sensitivity threshold are simplified to construct a simplified structural model; Based on the structural model of the retained object with assigned electromagnetic parameters and the simplified structural model, a whole-machine electromagnetic field model of the device is formed.

4. The method according to claim 1, characterized in that, Each pulse excitation source is triggered to emit a corresponding excitation signal to obtain the spatial electromagnetic field distribution results of the field-circuit cooperative model, including: The multi-channel pulse excitation source on the drive circuit side outputs corresponding pulse signals to perform transient joint solution on the field-circuit cooperative model. The transient electrical excitation of the lumped port is applied to the whole machine electromagnetic field model to obtain the spatial transient electromagnetic field distribution results of the whole machine.

5. The method according to claim 1, characterized in that, The method further includes: Based on the spatial electromagnetic field distribution results, the peak values ​​of electric field intensity and magnetic field intensity in each preset monitoring area are extracted respectively; If the peak electric field strength and / or the peak magnetic field strength exceed the corresponding threshold, a structural adjustment command for the associated device in the corresponding monitoring area will be output.

6. The method according to claim 1, characterized in that, Based on the spatial electromagnetic field distribution results and the power loop topology of the device, the key parasitic parameter extraction targets are determined, including: Based on the power loop topology, the closed power loop is split into multiple independent power connection paths according to the device boundaries; The normalized peak magnetic field, peak electric field, rated current, number of bends, distance between round-trip conductors, and distance to high field strength regions are weighted and fused to determine the correlation risk index between each power connection path and the space field. Power connection paths whose associated risk indicators exceed preset thresholds are selected as key parasitic parameter extraction targets.

7. The method according to claim 1, characterized in that, The thermal flow field verification includes: The geometric parameters corresponding to the candidate schemes are loaded into the thermal flow field model; the thermal flow field model is constructed by dividing the solid heat conduction domain and the fluid flow domain based on the candidate structure and configuring conjugate heat transfer boundary conditions; Simulation calculations are performed based on the material thermophysical parameters and environmental cooling parameters in the multi-source basic dataset to determine the thermal flow field verification parameters; the thermal flow field verification parameters include the device's highest temperature, the temperature of key components, the centroid migration distance in the high-temperature region, and the air duct blockage rate. If all the thermal flow field verification parameters meet the corresponding preset conditions, then the thermal performance of the candidate scheme is qualified.

8. A multi-physics electromagnetic compatibility simulation and verification system for power electronic devices, characterized in that, include: The data acquisition unit is used to acquire multi-source basic datasets required for the design of power electronic devices. The whole-machine electromagnetic modeling unit is used to construct the whole-machine electromagnetic field model of the device by combining the geometric structure data and electromagnetic parameter data of the device with the sensitivity of each structural unit of the device to electromagnetic leakage and the multi-source basic data. The field-circuit cooperative solution unit is used to configure multiple lumped ports on the whole-machine electromagnetic field model. Based on the pre-established port mapping record, it connects each pulse excitation source built on the circuit side to the corresponding lumped port to construct the field-circuit cooperative model. The port mapping record contains the mapping relationship between the lumped ports and the pulse excitation sources. The spatial electromagnetic field distribution acquisition unit is used to trigger each pulse excitation source to emit corresponding excitation signals in order to obtain the spatial electromagnetic field distribution results of the field-circuit cooperative model. The parasitic parameter extraction unit determines the key parasitic parameter extraction objects based on the spatial electromagnetic field distribution results and the power loop topology relationship of the device, establishes parasitic parameter models for the stacked busbar and the power connection paths in the key parasitic parameter extraction objects, and extracts the values ​​of key parasitic parameters from the parasitic parameter models. The structural adjustment scheme generation unit generates structural adjustment schemes for the stacked busbars and layout adjustment schemes for the power connection paths based on the extracted values ​​of key parasitic parameters. It also performs a turn-off transient voltage risk assessment for power semiconductor devices based on the equivalent stray inductance of the fast commutation loop. The equivalent stray inductance of the fast commutation loop is the sum of the equivalent stray inductance of the structural adjustment scheme and the equivalent stray inductance of the layout adjustment scheme. The thermal flow field verification unit is used to verify the thermal flow field of candidate schemes that trigger thermal flow field verification in structural adjustment schemes and layout adjustment schemes. The scheme output unit is used to output the final structural scheme of the device when the spatial electromagnetic field distribution results, the values ​​of key parasitic parameters, the risk assessment results of the turn-off transient voltage, the thermal flow field verification results, and the structural parameter change trends all meet the corresponding preset verification conditions.

9. An electronic device, characterized in that, include: A processor, a memory, and a program or instructions stored in the memory and executable on the processor, wherein the program or instructions, when executed by the processor, implement the steps of the method as claimed in any one of claims 1-7.

10. A storage medium, characterized in that, include: The storage medium stores a program or instructions that, when executed by a processor, implement the steps of the method as described in any one of claims 1-7.

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