PostDoc projekt utfört vid Univ. of L'Aquila finansierat av Vetenskapsrådet.
To help products comply with international Electromagnetic Compatibility (EMC)regulations or as a help in a design process numerical simulation of electromagnetic (EM) characteristics are a valuable tool. With the development of high-speed computers the complexity of EM simulation programs and the systems they can simulate has increased considerable. But still, problems must be partitioned due to computer resource and/or EM simulation technique limitations. In this thesis, four different EM simulation techniques are described and the nature of these are discussed. The focus is on the partial element equivalent circuit (PEEC) method for which the following improvements and investigations have been proposed in the enclosed papers. First, a recent proposed formulation for the direct simulation of the radiated electric field from a device is compared against traditional post-processing equations and measurements. The results show that the proposed direct method, the electric field sensor, is unreliable for arbitrarily implementations since the length of the sensor strongly affects the results. Second, a technique to obtain simplified PEEC models are presented. The first step is to use a discretisation procedure where partial elements with small effect on the complete PEEC model are excluded. Then, instead of using numerical integration, closed-form equations are used to calculate the partial elements. The obtained simplified PEEC models are shown to comply well against measurements. Third, an introductory paper to the PEEC method is presented. The international interest for the method has been gaining rapidly for the past years resulting in considerable progress for the technique. But, in the Nordic countries the research effort has been low. The paper presents the technique using simple antenna examples, both printed and free space, and illustrations. For verification, simulations have been compared against analytical solutions and measurements.
It is well known that time domain integral equation techniques may suffer from stability problems and frequency domain models may provide non-passive results. A main source of these issues is the delay of the coupled elements. In the classical Partial Element Equivalent Circuit (PEEC) method, a single delay was used for each couple of partial element which results in a delay differential equation with reduced stability and accuracy. In this paper, we consider multiple delay coefficients which can be used for both the time and frequency domain. Also, filters are introduced which remove unwanted eigenvalues or resonances in the partial element couplings. This can substantially improve the response of the frequency domain and the time domain models. Stability improvements also means passivity improvements.
This paper characterizes the different artifacts observed within time- and frequency- domain partial element equivalent circuit based electromagnetic modeling. The main focus is on frequency domain artifacts since time domain instabilities have been treated extensively in the literature. Guidelines and examples are given on how to suppress this type of artifact by showing correlation to PEEC model geometrical meshing and PEEC model complexity reduction.
As a tool for prediction of electromagnetic field phenomena in electric and electronics design, the Partial Element Equivalent Circuit (PEEC) method has received a great interest over the last years. Besides being a powerful full-wave 3-d numerical method which competes with other popular techniques (FDTD, FEM,MoM) it is especially suited for mixed electromagnetic circuit problems, in both the time and frequency domains. The recent literature is confirming that the PEEC method is becoming more and more popular in EMC-EMI-Signal Integrity areas especially for its capability to combine electromagnetic fields and lumped elements in the same numerical framework [1]–[3]. Furthermore its recent extension to magnetic materials and the development of fast solvers have made it powerful and well tailored for a comprehensive treatment of EMC problems.The aim of the tutorial is to present the basic theory of the method up to the most recent advancements of the technique. Furthermore, in order to make it easier for the audience, a step-by-step implementation of the method clarifying the key points to make it fast and efficient will be presented. The tutorial will be subdivided into three sections, dealing with:1) History of PEEC. Inductance calculations from Rosa through Grover to Ruehli;2) Most recent progress of the method (acceleration techniques, dispersive dielectrics, and magnetic materials);3) Circuit and electromagnetic co-simulation for active, non-linear circuit systems.
The partial element equivalent circuit (PEEC) method has shown to be useful in mixed circuit and electromagnetic analysis. In PEECs, the extensions from two to three dimensional modeling are mainly in the calculation of the partial self and mutual capacitive couplings. The considerable increase in problem size for 3D PEEC models results in a larger number of partial elements that has to be calculated. This results in excessive calculation times if the capacitive calculation routines are poorly constructed. In this paper it is shown that by using local reduction matrices for the capacitive calculations, the calculation time for PEEC model capacitance matrices can be decreased while keeping the accuracy.
This paper proposes a technique to re- duce the calculation time for the complex partial el- ements used in a retarded partial element equivalent circuit (rPEEC) frequency domain solver. The tech- nique utilizes a thresholding scheme where strongly coupled PEEC cells are calculated with higher accu- racy than the weakly coupled. Guidelines for limiting the order of integration used in the evaluation of the complex partial elements are presented. The trade-o® between accuracy and computation time of the par- tial elements and the resulting PEEC system solution is investigated and displayed.
This paper details the impact of partial element accuracy on quasi-static partial element equivalent circuit (PEEC) model stability in the time domain. The potential sources of inaccurate partial element values are found to be poor geometrical meshing and the use of unsuitable partial element calculation routines. The impact on PEEC model stability of erroneous partial element values, and the coefficients of potential and partial inductances, are shown as theoretical constraints and practical results. Projection meshing, which is a discretization strategy suitable for the PEEC method, is shown to improve calculated partial element values for the same number of unknowns, thus improving model stability.
We examine the passivity and stability of quasi-static partial element equivalent circuit (PEEC) models. The impact of inaccuracies in the computed partial element values is considered as a possible source of time domain instabilities. Our analysis shows how existing partial element calculation routines, analytical and numerical, and the use of poor mesh generators can introduce large errors in partial element values. We also show how this affects the passivity and stability of the PEEC model. Theoretical constraints for passivity are derived which depend on accuracy of partial element values. The conditions are verified by performing practical PEEC model analysis.
The Graduate School of Space Technology
This paper presents a parallel implementation of a partial element equivalent circuit (PEEC) based electromagnetic modeling code. The parallelization is based on the GMM++ and ScaLAPACK packages. The parallel PEEC solver was successfully implemented and tested on several high performance computer systems. Large structures containing over 50 000 unknown current and voltage basis functions were successfully analyzed and memory, performance, and speedup results are presented. The numerical examples are both of orthogonal and nonorthogonal type with analysis in the time- and frequencydomain.
Vid dödnätstart av produktionsanläggningar och drift av svaga nät eller ö-drift är frekvensomriktare som driver pumpar och fläktar kritiska komponenter. Om frekvensomriktare påverkas av störningar i nätet kan elproduktion kopplas bort och det svaga nätet eller ö-driften kollapsa. Projektet ska studera frekvensomriktare ur ett antal aspekter såsom uppbyggnad, styrning och implementering i syfte att utveckla mer robusta frekvensomriktare och implementering av dessa för att säkerställa drift av svaga nät och ö-drift och minimera ytterligare driftstörningar vid svåra påfrestningar på elnätet.
The project has the following main objectives.(i) Detail an systematic approach for the generation of equivalent circuit descriptionsfor power components in the high frequency range. Demonstration include time-and frequency- domain analysis of free space coils.(ii) Introduce, evaluate, and develop the PEEC method for combined electric andelectromagnetic (EM) modeling of power components.(iii) Transfer of knowledge from microelectronics- to power engineering- modeling and simulation.
Utveckla metodik och verktyg för att simulera och undersöka sambandet mellan mjukvarudesign och elektromagnetiska fält inom inbyggda system. Mjukvaran skall skrivas i språket Timber och elektromagnetiska fält skall simuleras i PEEC. Lämpliga verktyg för att simulera hårdvara skall undersökas och tillämpas, så att ett komplett simuleringsflöde med feedback kan åstadkommas. Utveckla en designparadigm för mjukvara så att oönskade elektromagnetiska effekter och inkompatibiliteter kan undvikas.
The LKAB SAR project is implemented to measure the subsidence and terrain deformation around the Kiruna iron ore mine and in the Kiruna city area. The LKAB SAR project has two components. One is the monitoring component in which MDA (main contractor) provides the SAR deformation maps to LKAB and the second is the technology transfer component in where MDA provides theoretical and practical knowledge to LKAB so that LKAB can produce deformation maps by their own. And Cranfield University and Luleå University of technology will carryout the LKAB SAR research. During the SAR project it is expected to use “DInSAR” and “CTM” techniques to measure the deformations. By using DInSAR and CTM techniques, LKAB can achieve the required accuracy levels during the summer season but it is likely that the quality and quantity of the measurements will largely differ during winter season (due to the thick snow cover). Similarly, areas which have thick forest cover will prevent radar waves reaching the ground and because of that it is likely the quality and quantity of the measurements will decrease in such areas during the mid summer period. Therefore LKAB is planning to carry out a research program to improve the SAR measurements.
This report summarizes the work to compare 12 conductive thermoplastics using three measurement methods. The 12 thermoplastic materials were chosen to observe the influence of variation of base polymer, variation of additives, different mechanical properties and processing and mouldability properties. Test samples were manufactured to be useful in fixtures for far field insertion loss measurements, and to load a coaxial transmission line. Boxes were made to make an enclosure for an electric field source, this arrangement was used for simple application-like near field insertion loss measurements. With all three methods data was obtained in the frequency range from 100 MHz to 1000 MHz for- far field shielding effectiveness- near field shielding effectiveness- complex permeability- complex permittivityResults were obtained showing that variations in the manufacturing process where extra heated thermoplastics or yeast additive was tested, did not improve the shielding efficiency for the particular compounds that was used. The mesurements indicates that a higher amount of additive improves both the near field SE and the far field SE. Measured far field SE is in good agreement with the numerical simulations based on the measured material data.
Syftet med doktorandprojektet är att utveckla en programvara som kan lösa kretsekvationer för passiva och aktiva komponenter samtidigt som elektromagnetiska problem beskrivna mha ekvivalenta kretsar (Eng. PEEC) löses. Projektet bygger vidare på programvara som tagits fram på EISLAB under de senaste 10 åren och som nu används i flertalet projekt med regionala, nationella och internationella parter. I feb. 2011 har doktoranden en första implementation av en fungerande PEEC-lösare som stödjer aktiva komponenter i form av transistorer (BJTs) och dioder. Nästa steg är att utöka stödet för olika transistormodeller, förna implementationen och inkorporera den i den existerande MultiPEEC-programvaran som utvecklas i ett parallellt projekt.
The transport of iron ore from the Swedish mining areas to the harbors is carried out by electric trains. In 2003, there was a dramatic increase in the number of bearings discarded due to electric current corrosion. No evident reason to this increase could be found and a project was initiated measuring electrical currents in engines and couplings as well as position and velocity of the train in an attempt to find countermeasures to the excess currents in the bearings. The RMS-magnitudes of the currents have been recorded and compared for different positions on the train, for different train configurations, and at different driving conditions. The results showed substantial electrical currents going through the couplings and much higher currents in modern trains with 30 tons axle load compared to old trains with 25 tons axle load.
Faced with the challenges of increasing operational frequencies and switching rates of modern power electronics devices used in power systems, there is need for high frequency models (up to a few megahertz) for power components like reactors, capacitors banks and transformers. This paper presents the application of PEEC theory forthe creation of high frequency, electromagnetic models for air-core reactors. The electromagnetic field couplings are separated in mutual partial inductances and mutual coefficients of potential giving a correct solution from DC to a maximum frequency determined by the meshing. The PEEC models are validated by comparing simulation results, for both time and frequency domain analysis, against measurements and other established modeling methods, and show good agreement. The model created by PEEC theory, could be helpful in the design and diagnostics of air-core reactors and other power system components.
This paper presents recent advancements in creating high frequency model for air-core reactors using partial element equivalent circuit (PEEC) theory. By meshing each turn into rectangular bars, PEEC theory can be applied and the reactors can be studied in detail. Measurements results are compared to PEEC model results for the frequency domain while time domain results are presented solely for the models. It is shown that the time complexity for modeling a realistic reactor is acceptable on a regular workstation.
This paper presents a partial element equivalent circuit (PEEC) model for air-core reactors modeling skin and proximity effects at higher frequencies using the volume filament approach. Modeling results are compared to measurements in both time domain and frequency domain, and show good agreement.
The distortionless propagation of signals in a medium offers a way to preserve the signal integrity. There exists a condition for distortionless propagation on a transmission line known as the Heaviside condition. This paper proposes the use of the Heaviside condition to characterize and design magnetodielectric materials that provide distortionless propagation in a specified finite frequency band. Plane wave propagation in a magneto-dielectric material is modeled by a transmission line model, thereby assuming TEM mode propagation. Then, the Heaviside condition is employed to derive the frequency-dependent permittivity and permeability functions of the material in rational form, so they satisfy the condition in a specified frequency interval. A procedure to design such materials is described. A numerical example of the design process is provided and an illustration of the effectiveness of modeled material in fulfilling the Heaviside condition in a specified frequency interval both in the time and frequency domains is given, indicating the validity of the approximation. The design procedure areas such a suitable preliminary design guide for deriving a realizable description of a magneto-dielectric, exhibiting the distortionless property in the desired frequency interval, with certain specified requirements put on the loss, or the permeability and permittivity values satisfied. The obtained results may initiate further investigations into the bandwidth restrictions of the approximation, on closed-form design solutions, and the practical realization of such materials.
With rising frequencies involved in electronics, losses and dispersion exhibited by dielectrics become important to consider in electromagnetic modeling. The Partial Element Equivalent Circuit (PEEC) method is suitable for a mixed electromagnetic and circuit setting, forming equivalent circuits that can be interconnected with circuit elements. In this paper, a descriptor form representation of PEEC models incorporatingdispersive and lossy dielectrics is developed. By representing the electrical permittivity with a Debye-Lorentz model equivalent circuits can be synthesized. The synthesized circuits for the permittivity are included in the PEEC equations by formulating the circuit equations for the additional circuit unknowns. This yields an input/output formulation that can handle an arbitrary number of finite dielectrics and be integrated by any kind of integration scheme. Furthermore, it offers a straightforward way to incorporate lossy and dispersive dielectrics into a PEEC solver compared to using recursive convolution. The proposed descriptor form representation is tested for a setup consisting of three microstrips over a ground plane, separated by a dielectric substrate. Both the ideal and the lossy and dispersive case are tested and compared. Furthermore, the proposed formulation is verified against an existing implementation in the frequency domain. Good agreement between the proposed formulation andthe existing frequency-domain PEEC formulation is obtained.
In wireless condition monitoring systems the antenna serves as a critical part of the data transmission link. A condition monitoring application usually pose a challenging environment for an antenna system, as they are often found in harsh machine environments. As conventional antennas usually are designed for free-space operation and for some design temperature range, the presence of additional materials and their temperature variation are commonly not accounted for. In this paper an attempt to highlight the impact of materials' temperature-dependence, in their electrical properties, on printed antenna characteristics is presented. Partial element equivalent circuit models of a common printed antenna design are developed. By incorporating temperature-dependent permittivity models of pure water, and a mixture of an industrial lubricant and water, the impact on the antenna's resonant behavior is demonstrated. The numerical examples highlight that the temperature variation in the permittivity of materials surrounding the printed antenna may impact the antenna characteristics enough to be considered in the design, if a degradation in performance is not an option.
During recent years anisotropic materials have received an increasing interest and found important applications in the field of shielding and antennas. The anisotropy may be due to intrinsic properties, or as a consequence of mixing. Intentionally or not, the anisotropy impacts the electromagnetic (EM) behavior of a system. Therefore, it is desirable to be able to incorporate the anisotropic effects in an EM model, to allow design tasks and analysis. In this paper, the partial element equivalent circuit (PEEC) formulation is extended to handle nondispersive linear anisotropic dielectrics. The anisotropic dielectric PEEC cell is derived and the resulting PEEC equations are developed into a descriptor system form, which is well suited for implementation in SPICE-like solvers, and for reduction by model-order reduction techniques. A verification of the model is given by a numerical example of a patch antenna situated on an anisotropic substrate and the results are in good agreement with a finite-difference time-domain implementation. The proposed PEEC model is of interest for further work, i.e., in the modeling of setups involving mixtures of materials, with an orientational alignment, and engineered materials, encountered in different EM compatibility applications.
Broadband electromagnetic (EM) modeling increases in importance for virtual prototyping of advanced power electronics systems (PES), enabling a more accurate prediction of fast switching converter operation and its impact on energy conversion efficiency and EM interference. With the aim to predict and reduce an adverse impact of parasitics on the dynamic performance of fast switching power semiconductor devices, the circuit-oriented EM modeling based on the extraction of equivalent lumped R-L-C-G circuits is frequently selected over the Finite Element Method (FEM)-based EM modeling, mainly due to its lower computational complexity. With requirements for more accurate virtual prototyping of fast-switching PES, the modeling accuracy of the equivalent-RLCG-circuit-based EM modeling has to be re-evaluated. In the literature, the equivalent-RLCG-circuit-based EM techniques are frequently misinterpreted as the quasi-static (QS) 3-D Partial Element Equivalent Circuit (PEEC) method, and the observed inaccuracies of modeling HF effects are attributed to the QS field assumption. This paper presents a comprehensive analysis on the differences between the QS 3-D PEEC-based and the equivalent-RLCG-circuit-based EM modeling for simulating the dynamics of fast switching power devices. Using two modeling examples of fast switching power MOSFETs, a 3-D PEEC solver developed in-house and the well-known equivalent-RLCG-circuit-based EM modeling tool, ANSYS Q3D, are compared to the full-wave 3-D FEM-based EM tool, ANSYS HFSS. It is shown that the QS 3-D PEEC method can model the fast switching transients more accurately than Q3D. Accordingly, the accuracy of equivalent-RLCG-circuit-based modeling approaches in the HF range is rather related to the approximations made on modeling electric-field induced effects than to the QS field assumption.
A major requirement for further development of wide-band gap (WBG) power devices and their applications is the optimization of packages and PCB layouts to enable fast-switching capabilities. Electromagnetic modelling allows the prediction of parasitic inductances, capacitances, and resistances of the current paths within power modules, which cannot be easily approached in measurements. As a result, electromagnetic-circuit-coupled modeling enables the optimization of package layouts and interconnections before manufacturing actual power modules. The accuracy and limitations of present numerical techniques for three-dimensional (3D) electromagnetic modeling of power modules is still neither well understood nor verified. This paper presents the extraction of parasitics of power semiconductor packages using two electromagnetic modelling approaches. The first approach is based on a well-established 3D electromagnetic quasi-static solver, ANSYS Q3D Extractor. For the second approach, a numerical solver based on the Partial Element Equivalent Circuit (PEEC) method is developed and assessed in terms of modelling accuracy required by fast switching WBG-based power converters. The PEEC method is presented as a promising numerical technique, which can potentially be used to overcome the limitations of the EM modeling based on the ANSYS Q3D Extractor.
High frequency power electronics utilizing wide-band gap semiconductor devices imposes more stringent requirements for highly accurate extraction of parasitics of power electronics systems in a wide frequency range. This paper presents the state-of-the-art modeling approaches used to predict the electromagnetic behavior of power electronic systems and components in terms of accuracy and computational cost. The potential of the Partial Element Equivalent Circuit (PEEC) technique for virtual prototyping of power electronic systems is assessed. The main advantage of this numerical technique is its capability for direct coupling between the circuit and electromagnetic domains provided by the PEEC meshing of three-dimensional geometries in partial elements. The aim of this paper is to provide a more comprehensive understanding of PEEC-based modeling for power electronics packaging.
The Partial Element Equivalent Circuit (PEEC) method is promising numerical technique for three-dimension electromagnetic modeling across various application fields. In the framework of the PEEC method, the partial elements modeling the magnetic and electric field coupling between elementary volumes and surfaces are computed by double-folded volume and surface integrals. Assuming the quasi-static hypothesis and an orthogonal mesh, the integrals have been computed by the analytical formulas derived in literature, which significantly reduces the computational time in comparison to the numerical integration. However, the existing analytical formulas are affected by significant numerical errors for certain PEEC structural mesh necessary to model the skin and proximity effects with a higher accuracy. To utilize the full potential of the PEEC method, the calculation of partial elements has to be carefully addressed, which has not been investigated in a comprehensive way so far. Accordingly, this paper presents a systematic accuracy analysis of the existing closed-form analytical formulas and methods for calculating the self and mutual inductances between two rectangular conductors. Additionally, a new strategy to select a proper analytical formula depending on the dimensions and positions of two conductors is proposed, which allows the mutual inductance extraction with a relative error of less than 0.1 % . The new method is systematically validated on examples of 3-D dense PEEC systems using the quadruple precision arithmetic as reference.
Systems based on radio frequency identification (RFID) techniques are finding new markets and uses. For maximal readability, RFID-systems have to be tailored to its specific environment. In this paper, the partial element equivalent circuit (PEEC) method is used to analyze an RFID-system with reader, tag, and additional electronic circuitry. The results show how the method can be used to match antennas with discrete, external components and study the backscattered energy from the tag. The simulations are very fast which allows for studying multiple locations of the tag in order to tailor the RFID-system.
Precipitation in the form of snow could severely degrade the performance of the planned EISCAT_3D radar antenna array. In this paper the performance of the antenna elements, crossed yagi antennas, is studied using both simulations and measurements. The results shows that during snowfall the performance of the antenna is degraded, and under severe conditions the antenna becomes non-operational. To guarantee operability of the system, the effect of snow cover should be taken into account when designing the final antenna.
Precipitation in the form of snow or rain could severely degrade the performance of large antenna arrays, in particular if knowledge about the beam shape and pointing direction in absolute numbers is necessary. In this paper, a method of estimating the far-field of each individual antenna element using the equivalent electric current approach is presented. Both a least squares estimator and a Kalman filter was used to solve the resulting system of equation and their performance was compared. Simulation results shows that the estimated far-field for one antenna element is very accurate if there is no noise on the signal. During noisier conditions the Kalman filter gives less noisy results while the systematic errors are slightly larger compared to the least squares estimator.
When designing an radio frequency identification system it is important to take both the position and the movement of the transponders into account. In this study, a simulation method that enables the description of a complete RFID system including moving and rotating transponders as well as a complex, industrial environment is presented. By using the partial element equivalent circuit method to calculate the magnetic field generated by the reader antenna and describing the transponders using a magnetic dipole, it is possible to use the Monte Carlo method to describe the dynamic behaviour of the complete system. The method is used in this study to describe the difference in performance between two different reader antennas and these results are also compared to measurements of similar systems operating in an industrial environment. The difference in performance between the two systems is similar in both the simulations and the measurements. A small discrepancy was seen between the results from the simulations and the measurements which is for the most part because of the limited read rate of the RFID systems used in the measurements.
In this paper, we investigate the distortionless conditions for multiconductor transmission lines (MTLs) with frequency-independent per-unit-length (p.u.l.) parameters. In fact, the well-known distortionless Heaviside condition is valid only for single-conductor transmission lines. The MTL is modeled using the delayed Green's-function-based method recently proposed by the authors. In this method, the impedance matrix is described in terms of a rational part, which accounts for the low-frequency behavior, and a hyperbolic part, which determines the high-frequency response of the MTL. We find that the hyperbolic part is already distortionless at high frequency and that this property can be used to identify the p.u.l. parameters of the distortionless lossy MTL associated with the original line. To serve this purpose, the line is decoupled using a frequency-independent modal decomposition. The Heaviside condition can be enforced in the modal domain on each of the single-conductor decoupled lines. The features of the distortionless lines in the modal domain are preserved in the physical domain as a consequence of the real-valued similarity transform. The numerical results demonstrate that the new line completely characterizes the distortionless propagation of a generic MTL with frequency-independent p.u.l. parameters. The proposed formulation could be used in the optimization design process by enforcing the distortionless condition along with other design constraints.
Ten different commercially available conductive thermoplastic materials have been tested for near- and far-field shielding effectiveness (SE). Far-field SE was tested using a modified standard measurement technique to provide results comparable with the company-provided data. Further, housings of different thermoplastic materials were constructed and equipped with an electromagnetic interference (EMI) source to model a realistic near-field SE situation. The SE data up to 1 GHz is presented. Conductive thermoplastic materials with fillings of stainless steel fibers and nickel-coated carbon fibers were the two materials that offer the best far-field shielding performance. For the near-field shielding, two materials with filling of stainless steel fibers were the best performing ones. A thermoplastic with polycarbonate (PC) base and stainless steel content of 1.5 vol% showed the best combined far- and near-field shielding results.
The partial element equivalent circuit (PEEC) method is a electromagnetic simulation technique suitable for mixed circuit and field problems. The technique is numerically equivalent to a method of moments solution using Galerkin solution. In this paper, the PEEC method is illustrated and applied to printed antenna structures where measurements are compared to simulations and analytical solutions. The possibility to use simplified PEEC models to decrease computation time is discussed with illustrative examples.