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ETK seminars -- Seminar series at Electromagnetic Engineering

Seminars 2010 - spring:

• 2010-05-07 : Magnus Höijer: Title to be announced -- 14:00- Teknikringen 33, The seminar room.

• 2010-04-30 : Anders Ellgardt: Title to be announced -- 14:00- Teknikringen 33, The seminar room.

• 2010-04-23 : Murari Saha from ABB: Power System Protection -- 14:00- Teknikringen 33, The seminar room.

• 2010-04-16 :Dirk Van Hertem: Coordination in the international power system with power flow controllers -- 14:00- Teknikringen 33
  Abstract: The European power system has changed considerably in the last 15 years. The liberalisation and unbundling of the electricity market has led to increased international power flows and reduced influence of the system operators. Meanwhile, renewable and other small-scale uncontrolled and variable energy sources are being installed in the system. The system operators experience more variable power flows through their system while they have less control over them. **This lecture will focus the coordination in the international power system. As power flow controlling devices are increasingly present in the international system, there use is covered in detail. The coordination of power flow controllers is especially important because of their possible negative effects on neighbouring systems.

• 2010-04-08 : Rajeev Thottappillil: Title to be announced -- 14:00- Teknikringen 33, The seminar room.

• 2010-03-19 : Nathaniel Taylor: `Electric power systems': a broad introduction. -- 14:00- Teknikringen 33, The seminar room. Abstract: This seminar is a `tutorial overview' to the physical systems and the academic subject both known as `power systems'. We shall lightly cover the following: the major power-system components and their parameters, from generators to loads; some common methods used in static and dynamic analyses of the systems; instability mechanisms; ongoing changes in technology and operation, and major topics of current research interest. It is hoped that this will make the audience better able to understand the context of later seminars in which specific areas of power systems will be presented in more detail by people actually working with them(!). It is also hoped that this wider perspective will be interesting to those of us who normally work at the component-level, and that there will be a few (small) surprises to people familiar with circuit analysis on small circuits.

• 2010-03-11 : Mats Gustafsson from EIT at Lunds University: Physical bounds and sum rules in antenna and electromagnetic theory -- 14:00- Teknikringen 33, The seminar room.
  Abstract: In this seminar, recently developed identities and physical bounds in antenna theory are discussed. The physical bounds relate the performance of an antenna to the electric- and magnetic polarizability dyadics of a circumscribing geometry. This generalizes the classical bounds by Chu to geometries of arbitrary shape. The approach can also be used to estimate the performance of small antennas if the polarizability of the antenna is used instead of the circumscribing geometry. Moreover, related sum rules and physical bounds for the antenna input impedance, periodic structures, and metamaterials are reviewed.

• 2010-03-05 : Göran Engdahl: Ultra Fast Electrical Commutation Switches -- 14:00- Teknikringen 33, The seminar room.
  Abstract: The seminar will present history, principal function, and challenges regarding ultra fast electrical commutation switches that are of interest in the development of new components for so-called smart grids. There also will be a presentation of what activities are on-going and planned at the department regarding research in the field.

• 2010-02-26 : Hans Peter Nee from Electrical Machines and Power Electronics: "What is power electronics?" 14:00- Teknikringen 33, The seminar room.
  Abstract: The seminar aims to explain what power electronics actually is. One description is "high-efficiency high-performance electric power conversion using switch-mode semiconductor devices". Converters with efficiencies higher than 99% are in operation, and in the future the efficiency can be increased even more. Hundreds of megawatts can be controlled in milliseconds. The concepts of switching, power semiconductor devices, pulse width modulation, and EMI problems are described briefly. Various application areas are also presented, and finally an overview of the research activities of the power electronics group is given.

• 2010-02-19 : Roland Eriksson: "Electric power transmission" -- 14:00- Teknikringen 33, The seminar room.
  Abstract: The seminar will contain a short tutorial part followed by a little on history, technical development, today’s challenges and some future perspectives.

• 2010-02-12 : Rajeev Thottappillil: The Lightning Flash -- 14:00- Teknikringen 33, The seminar room.
  Abstract: A popular scientific presentation on the phenomena of lightning flash will be given. Generation of lightning, different types of lightning, basic parameters of lightning, methods of research employed to study lightning, safety from lightning, and principles of lightning protection will be covered.

• 2010-02-05 : Daniel Månsson: "Response of Surge Protection Components to UWB pulses and EFT." -- 14:00- Teknikringen 33, The seminar room.
  Abstract: As the characteristics of the disturbances associated with IEMI1 often have very high frequency content, the existing mitigation measures and protection components may not be adequate and it has been seen that for UWB2 transients and EFT3 surge protection components may not work as intended. 1) Intentional Electromagnetic Interference 2) Ultra wideband 3) Electrically fast transients

• 2010-01-29 : Peter Fuks: What are x-parameters? Should I care? -- 14:00- Teknikringen 33, The seminar room.
  Abstract: In 2008 Agilent Technologies launched a new device, Nonlinear Vector Network Analyzer together with a superset of the familiar s-parameters and a simulation tool which enable the characterization of nonlinear components in mismatched environments.
  I will give a short presentation of different ways of describing multiport circuits using traditional parameters and introduce the large signal model which can be useful for many practical applications.

• 2010-01-20 : Xiao Fei: Several microstrip filter designs -- 14:00 in the seminar room at Teknikringen 33
  Abstract: Microstrip filters have found wide applications in various RF/microwave circuits and systems. Especially, microstrip filters with a generalized Chebyshev response attract considerable attention for its light weight, compact size and ability to generate finite transmission zeros to improve selectivity. In my presentation, several microstrip filter designs will be discussed in detail.

• 2010-01-13 : Martin Norgren: About using the mode-matching method for propagation and scattering problems. -- 14:00 Teknikringen 33, The big conference room at Teknikringen 33.
  Abstract: The modematching (MM) method for solving scattering problems for guided waves will be discussed. It is a quasi-analytical method where in different parts of a system the fields are expanded into eigenmodes of the specific parts and then connected via the boundary conditions. First, MM will be discussed in the framework of connecting voltage and current waves at joints between multiconductor transmission lines. Secondly, the full wave implementation of MM is discussed for waves in classical waveguides. Also some combinations of MM with other methods (MM) will be discussed. Generic results for waveguides and in-door wave propagation will be presented. Finally, the use of MM for 3D scattering is discussed briefly.

Seminars 2009 - autumn:

• 2009-12-17 : Patrik Hilber, "Power system reliability analysis" 13:30-14:30 in the seminar room at Teknikringen 33
  Abstract: We dive into the topic of power system reliability analysis. The presentation begins at basic reliability theory and ends with an discussion of the problems that we approach when we are modeling power systems.
  Example of questions:
  -Why not use differential equations?
  -Why is optimization difficult in this context?

• 2009-12-09 : Gökhan Cinar from Växjö University: "Dyadic Green's Function Analysis of a Coaxial Line with Coated Walls" 9:30, in the small seminar room, Teknikringen 33.
  Abstract: The dyadic Green's function analysis has been done for the coaxial lines with material coatings on the inner and outer walls. The Leontovich impedance boundary conditions are assumed at the walls and the related dyadic functions are determined in terms of vector wave functions satisfying these boundary conditions.

• 2009-12-07 : Jun Yuan, from National Key Lab of Antenna and Microwave Tech, Xidian University. "On Multilevel Fast Multipole Algorithm" 13:00-14:00 in the seminar room at Teknikringen 33
  Abstract: The speaker will describe the principle of Multilevel Fast Multipole Algorithm for calculating the scattering from electrically very large objects, and his team's work in this area.

• 2009-12-04 : Nils Brenning, "Faster-than-Bohm cross-B electron transport in strongly pulsed plasmas" 11:00 -- 12:00 in the seminar room at Teknikringen 33
  Abstract: In a collaboration between the Space and Plasma Physics group at KTH, an applied plasma physics group in Linköping, and a plasma experimental group in USA, we have found a new feature in plasma physics: an exceptionally high cross-magnetic electron transport rate in magnetized plasmas, in which transverse currents are driven with abruptly applied high power. Potential applications range from technical sputtering magnetron devices, through the roots of the Earth's auroras, to interstellar supernova shock fronts. The transport processes we have studied have been driven by magnetic pressure, electric fields, internal pressure gradients, or ion flow kinetic energy. By choise of a suitable normalization parameter we have found a remarkable consistency between all these different cases.

• 2009-11-27 : Hans Edin, High Voltage Insulation Systems and Material Requirements 14:00 -- 15:00 in the seminar room at Teknikringen 33
  Abstract: Electric power apparatuses are generally designed to be used at high voltage stress. The design put high demands on the properties of the electrical insulation. This lecture gives an overview of important material aspects that influence the design of a high voltage insulation system.

• 2009-11-11 : Pu Zhang: "Transformation Optics and Invisibility Device Design by Metamaterials." -- 14:00 Teknikringen 33, The seminar room.
  Abstract: This presentation will give a brief introduction to the recently proposed method of transformation optics and invisibility device design using metamaterials.

• 2009-11-23 : Gunnar Larsson: "Att mäta är att veta" -- 14:00-15:00 Teknikringen 33, The seminar room.
  Abstract: En diskussion över matematisk modell bildning.

• 2009-08-06: David Wall of Biomathematics Research Centre, Department of Mathematics & Statistics, University of Canterbury, Christchurch, New Zealand: "The mathematics of Imaging in magnetic resonance elastography" 14:00 in the seminar room
  Abstract: Early and accurate detection of tumours in the female breast is of clinical importance. Use of a combination of low frequency acoustic waves excitation and magnetic resonance imaging (MRI) of the displacement field within the tissue is thought to result in better image reconstruction of the tumour than from standard scattering measurements. Breast cancer tumours are about ten times stiffer than normal tissue.
  This elastography imaging problem is an inverse problem. The nature of an inverse problem is that it is ill-conditioned. We consider properties of the mathematical map which describes how the elastic properties of the tissue being reconstructed vary with the field measured by MRI. This map is a nonlinear mapping and our interest is in proving certain conditioning and regularity results for this operator which occurs naturally in this problem of imaging in elastography. In this treatment we consider the tissue to be linearly elastic, anisotropic and spatially heterogeneous. The emphasize on anisotropy in this problem should provide better contrast of the tumour to the background tissue.

Seminars 2009 - spring:

• 2009-06-08: Johan Setreus "How to prevent future blackouts in the electric power transmission system?", The seminar room 15:15.
  Abstract: In the operation, planning and design of the transmission system it is of greatest concern to quantify the reliability security margin to unwanted conditions. The deterministic N-1 criterion has traditionally provided this security margin to reduce the consequences of severe conditions such as widespread blackouts. However, a deterministic criterion does not include the likelihood of different outage events.
  Moreover, experience from blackouts shows, e.g. in Sweden-Denmark September 2003, that the outages were not captured by the N-1 criterion. The question addressed in this presentation is how this system security margin can be quantified with probabilistic methods. A quantitative measure provides one valuable input to the decision-making process of selecting e.g. system expansions alternatives and maintenance actions in the planning and design phases. It is also beneficial for the operators in the control room to assess the associated security margin of existing and future network conditions.
  -----
  Definition N-1 criterion for transmission system: The N-1 criterion is a rule according to which elements remaining in operation after failure of a single network element (such as transmission line / transformer or generating unit, or in certain instances a busbar) must be capable of accommodating the change of flows in the network caused by that single failure.

• 2009-06-01: Kelin Jia: (no title), 15:15 in the seminar room. Abstract: The development of electrified railways has been remarkable since the beginning of 20th century. Pulse-width-modulated (PWM) control strategy is extremely significant in the railway propulsion system. Between the different conversion stages, harmonics are generated and propagate inside the train as well as back to the contact wires through the transformer. These Electromagnetic (EM) noise can lead to damaging effects on auxiliary circuits, signaling systems and even nearby environment. Therefore, it is worthwhile to investigate harmonics produced by the electrified railway propulsion system as a first step in assessing the electromagnetic compatibility (EMC).This presentation depicts a way to simulate electrified railway propulsion drive rectifiers in PSpice for assessing EMC. A PWM controlled rectifier is implemented in PSpice. The detailed description of the process to construct the model is given. Based on the modulation in PSpice, the harmonics generated by PWM control rectifiers with different loads are simulated and compared.

• 2009-05-25: Robert Farkas "Helical flow: theory, conservation laws and invariant solutions using Lie symmetries", 14:00 in the seminar room

• 2009-0-18: Alireza Motevasselian "Jaumann Absorber and Frequency Selective Surfaces" at 15:15 in the seminar room Abstract: Jaumann absorber and frequency selective surfaces (FSS) are two widely used concepts in microwave and optics. In this lecture the fundamentals and applications of these concepts will be presented. The characteristics of different shape Jaumann screen and some typical FSS unit cell geometries will be shown. The effects of element size and permittivity of the substrate in Gang buster FSS will be presented. Finally the combination of Jaumann absorber and FSS for designing a low radar cross section Radome in aircraft front end will be given. The advantages and disadvantages of the design will be discussed.

• 2009-05-08: Dr. M P Chandrasekharan "Block-diagonalization of sparse binary matrices", 15:15 in the seminar room
  Abstract: Sparse zero-one matrices are of great interest to many different fields of engineering. The present work emerges from the design of Cellular Manufacturing, although the resulting algorithm is now being used for a variety of problems including pattern recognition.
  The approach adopted for solution is ‘cluster analysis’. In conventional classification the number of groups is decided ‘a priori’ and the members are assigned to each group according to a predetermined criterion. The approach followed here is double blind in the sense that the number and identity of clusters are not known. The algorithm tries to elicit the “natural cluster structure” from the data using a technique called “natural seeding”

• 2009-05-04: Francois Besnard "Maintenance optimization: Problems, basics and challenges." 15:15 in the seminar room
  Abstract: The presentation will give an introduction to maintenance optimization. Common optimization problem will be discussed in relation with the work performed within the RCAM group. A failure classification will be presented as a first step toward maintenance modeling and optimization. Maintenance optimization will be illustrated with a simple model. Finally some challenges in maintenance optimization will be discussed.

• 2009-04-25: Peter Fuks "KTH ionosonde", 15:15 in the seminar room,
  Abstract: Division of Electromagnetic Engineering in cooperation with Space and Plasma division designed and built a ionosonde, e.g. a system for analyzing the reflection of radio waves from the ionosphere during 2008 . Many such systems exist but they are very expensive and require very large lots to erect the antennas. Our ionosonde is a low cost system operating at low power and with very compact antennas. Simulations show however that good results can be expected. The parts of the system were tested and an unsuccessful attempt was made to test the whole system.
  I will describe the system, the encountered problems and discuss possible ways to make it operational.

• 2009-04-20: Rajeev Thottappillil 15:15 in the seminar room ,
  Abstract: It is argued that the ideal and exact field solution for a vertical wire antenna of infinite length and vanishing radius (radius approaching zero) above a ground plane excited by a point time-varying source at the bottom, all conductors being perfect (infinite conductivity), is spherical TEM. The energy lost due to radiation from such an antenna appears to originate from the source at the bottom. The electric and magnetic fields at any point in space from such a radiating system is directly proportional to the time-varying current at the source. At any point in space, both near as well as far, the wave-impedance is the same as the impedance of the medium assumed to be linear, isotropic and homogeneous.
  Challenge 1: Disprove all or parts of above statements.
  Challenge 2: For wire of finite radius (increasing from zero), but perfectly conducting, what would be the departure of the field from the ideal solution above?
  Challenge 3: What would be the departure of the field from the ideal solution if the conductors are made of copper (finite, but highly conducting)?
  Challenge 4: What would be the field structure if the wire is inclined to the ground plane in the original problem?

• 2009-04-06: Helin Zhou "A New Approach to Estimation of Effective Height of Towers on Mountain Tops for Lightning Incidence Studies: Sensitivity Analysis" at 1515 in the seminar room, Teknikringen 33.
  Abstract: It is observed that the total number of lightning strikes to the tower and also the percentage of lightning discharges initiated by the tower, called upward flashes, both increase with tower height. It is thought that upward flashes can occur only when the tower height is exceeding100 m. Similar increases in the total number of lightning strikes to the tower and in percentage of upward flashes are observed if the tower, even with height less than 100 m, is located on mountaintop. To account for these observations, towers on mountaintops are said to have an effective height that is considerably larger than the physical height of the tower.
  In this presentation, we review and evaluate the definitions and methods that could be used to estimate the effective height of a given tower on mountaintop based on the statistical observations and on engineering models of lighting attachment. We examine variations in the effective height as a function of model parameters, including the final quasi-stationary leader gradient, minimum positive streamer gradient, upward connecting positive leader speed, and mountain base radius. The information presented here could be used in designing lightning protection of communication/transmission line towers and masts on mountain tops.

• 2009-03-30: Julia Nilsson "An opportunistic maintenance optimization model for shaft seals in feed-water pump systems in nuclear power plants" at 1515 in the seminar room at Teknikringen 33
  Abstract: The feed-water pump system in the nuclear power plant is critical for the availability of the entire plant. The system is necessary for maintaining a stable level of water in the reactor. Mechanical failures that dominate in feed-water pumps are failures of shaft seals. Each pump has two shaft seals and it is investigated if it is beneficial to replace both of them when one is broken, that is to use opportunistic replacements. A general mathematical optimization model, applied for example to the replacement of components in aircraft engines, is used to gain a replacement schedule for shaft seals.

• 2009-03-23: David Ribbenfjärd "Modeling of excess eddy losses in magnetic materials" at 1515 in the seminar room
  Abstract: The excess losses (aka anomalous losses) appear when a magnetic material is exposed to an alternating magnetic field. The material is divided into magnetic domains with different magnetization and with so called domain walls in between them. When the field changes the domains are forced into the field direction and some domains grow and other diminish. In this processes the domain walls move and create microscopic eddy currents which opposes the movement and thereby also the cange in magnetization. Thereby the area of the hysteresis loop increases and the losses increase.
  In this seminar I will present:
  - Different models for the total dynamic hysteresis losses including the excess losses
  - Compare the model we are using with a more widespread model
  - Measurement results regarding excess loss parameters

• 2009-03-16: Nathaniel Taylor "Pulse propagation in stator windings." at 15:15 in the seminary room
  Abstract: The term `high voltage rotating machines' describes a wide range of generators and motors, responsible for generating practically all of our electric power and consuming some tens of percent of it. The stator winding of such machines is a complex construction with several distinct regions, in which the propagation of high-frequency signals is not a trivial matter to comprehend!
  In several situations one may be interested in the nature of this propagation: my interest is the case when measurements are made of the small, rapid electrical discharges that occur in insulation defects. It would be good to know how large a pulse was at its source. The measurement, however, is often just at the terminals, and the complex system of loops, iron core, adjacent conductors, resistive coating, etc. gives the potential for resonances and frequency-dependent attenuation.
  In this presentation an overview will be given of the purpose of these pulse measurements and the construction of stator windings, to make the subject accessible to people from a range of electromagnetics backgrounds. Then some conclusions from a literature review will be given, and the audience will be welcomed to provide suggestions that help me to understand good ways of modelling and measuring the frequency response of such windings.

• 2009-03-09: Martin Norgren "The potential of a thin metallic plate in a transversal plane inside a cylindrical cavity" at 15:15 in 'stora konferansrummet'
  Abstract: We consider the generic problem of determining the electrostatic potential inside a cylindrical cavity within which there is a thin metallic plate in a transversal plane. At the cylindrical part of the cavity wall, the boundary conditions are chosen so as to admit a complete system of eigenfunctions to the transverse Laplace operator. In the longitudinal direction, the cavity can be closed, semi-open or open. The potential is expanded into the eigenfunctions, and the solution is determined from a mixed boundary value problem in the plane containing the plate, where the shape of the plate can be quite arbitrary. The method has applications in for example the calculation of the capacitances of shielded capacitors or in polarisability analysis of thin metallic objects. Especially, with periodic boundary conditions on the cavity, the method can be used for homogenization, in the long wavelength limit, of artificial dielectrics realized as arrays of metallic plates. Numerical results, illustrating the convergence of the method, are presented.

• 2009-02-16: Surajit Midya "DC component from pantograph arcing and its consequences on AC fed traction system." at 15:15 in the seminar room.
  Abstract: Pantograph arcing is a polarity dependent phenomenon and as a result there is a net DC component in the AC fed traction system. Both the pantograph arcing and the DC component become significant in winter, especially when there is a layer of ice on the overhead contact wire. This DC component saturates the transformers present in the traction power system (Both the Auto transformers, Booster Transformers and the Vehicle transformers). New and modern transformers used by many railways are more vulnerable to this DC component because of the improved BH curves to have lower magnetic losses. We have an idea about the levels of the DC current and different influencing parameters. The question is how to simulate the impact on different transformers of different traction feeding configuration!

• 2009-01-26: Hans Edin: "Understanding nanodielectrics as high voltage insulation" at 15:15 in the seminar room
  Abstract Nanodielectrics is a composite material where inorganic particles (particles with one dimension at least is below 100 nm) are used as a fillers in a polymer matrix. These materials have a potential usefulness as high voltage insulation if they could show superior properties compared to existing materials. This short discussion is around the observed features and the attempts made to understand them.
  Nadja: en liten "surprise" kanske - men vi får se vad jag kokar ihop.....

• 2009-01-19: Xin Hu "Metamaterials Based on Transmission Lines" at 15:15 in the seminar room
  Abstract: 1) Basic introduction to metamaterial and how to realize such material in a transmission line approach
  2) Research work about Split ring resonator and Complementary Split ring resonator 3) My recent work
  -Equivalent circuit model for microstrip line loaded with Split ring resonator
  -Dual band Split ring resonator
  4) Existing problems and future work

• Electromagetic Engineering