The main objective for physics based modeling of the power converter components is to design the whole converter with respect to physical and operational constraints. Therefore, all the elements and components of the energy conversion system are modeled numerically and combined together to achieve the whole system behavioral model. Previously proposed high frequency (HF) models of power converters are based on circuit models that are only related to the parasitic inner parameters of the power devices and the connections between the components. This dissertation aims to obtain appropriate physics-based models for power conversion systems, which not only can represent the steady state behavior of the components, but also can predict their high frequency characteristics. The developed physics-based model would represent the physical device with a high level of accuracy in predicting its operating condition. The proposed physics-based model enables us to accurately develop components such as; effective EMI filters, switching algorithms and circuit topologies [7]. One of the applications of the developed modeling technique is design of new sets of topologies for high-frequency, high efficiency converters for variable speed drives. The main advantage of the modeling method, presented in this dissertation, is the practical design of an inverter for high power applications with the ability to overcome the blocking voltage limitations of available power semiconductor devices. Another advantage is selection of the best matching topology with inherent reduction of switching losses which can be utilized to improve the overall efficiency. The physics-based modeling approach, in this dissertation, makes it possible to design any power electronic conversion system to meet electromagnetic standards and design constraints. This includes physical characteristics such as; decreasing the size and weight of the package, optimized interactions with the neighboring components and higher power density. In addition, the electromagnetic behaviors and signatures can be evaluated including the study of conducted and radiated EMI interactions in addition to the design of attenuation measures and enclosures.

This diploma thesis deals with the issue of EMC of tram vehicles and traction system. The first chapter defines the issues that are then dealt with in the thesis. The next chapter lists the objectives of the work. Subsequent chapters analyze the issues described in chapter 2. In the last chapter, a flow chart is proposed, which should serve as a tool to estimate the hazards of the traction drive due to induced bearing currents.

<div>The high-frequency switching of transistors in power electronic (PE) converters is known to cause unintended common-mode (CM) current that flows through parasitically-coupled ground paths. One way to model these currents is to utilize time-domain simulations that capture switching dynamics and the corresponding parasitic response. Although potentially useful, the small time steps required can create a computational burden and limit the usefulness of the approach. In addition, access to internal hardware needed to characterize parasitic parameters is often limited.</div><div><br></div><div>In this thesis, frequency-domain Thevenin equivalent circuits (TECs) are derived to model the CM behavior of PE converters. To do so, periodic linear time-varying (PLTV) analysis is used to develop Thevenin-like models that account for switching behavior of PE circuits. Subsequently, it is shown that in many applications these PLTV TECs can be reduced to traditional linear time-invariant (LTI) forms. Methods to experimentally characterize LTI TEC parameters and couple multiple TECs together for system-level analysis are then established. Finally, the TEC approach is extended to model converters in which common- and differential-mode (CM/DM) behavior are strongly coupled. Simulation and experimental results are used to validate the proposed TEC techniques.</div>

No / The probability density and exceedance probability functions of the induced currents in a screened cable connecting two enclosures, resulting from the close. presence of single and multiple mobile phones working at 900 MHz, are investigated. The analysis of the problem is undertaken using the Method of Moments, but due to weak coupling, the impedance matrix was modified to reduce the memory and time requirements for the problem, to enable it to be executed multiple times. The empirical probability distribution functions (PDFs) and exceedance probabilities for the induced currents are presented. The form of the PDFs is seen to be quite well approximated by a log-normal distribution for a single source and by a Weibull distribution for multiple sources

The emergence of silicon-carbide (SiC) devices has been a 'game changer' in the field of power electronics. With desirable material properties such as low-loss characteristics, high blocking voltage, and high junction temperature operation, they are expected to drastically increase the power density of power electronics systems. Recent state-of-the-art designs show the power density over 17 ; however, certain factors limit the power density to increase beyond this limit. In this dissertation, three key factors are selected to increase the power density of SiC-based grid-connected three-phase converters. Throughout this dissertation, the techniques and strategies to increase the power density of SiC three-phase converters were investigated. Firstly, a magnetic integration method was introduced for the coupled inductors in the interleaved three-phase converters. Due to limited current-capacity compared to the silicon insulated-gate bipolar transistors (Si-IGBTs), discrete SiC devices or SiC modules, operate in parallel to handle a large current. When three-phase inverters are paralleled, interleaving can be used, and coupled inductors are employed to limit the circulating current. In Chapter 2, the conventional integration method was extended to integrate three coupled inductors into two; one for differential-mode circulating current and the other for common-mode circulating current. By comparing with prior research work, a 20% reduction in size and weight is demonstrated. From Chapter 3 to Chapter 5, a full-SiC uninterruptible power supply (UPS) was investigated. With the high switching frequency and fast switching dynamics of SiC devices, strategies on electromagnetic inference become more important, compared to Si-IGBT based inverters. Chapter 3 focuses on a common-mode equivalent circuit model for a topology and pulse width modulation (PWM) scheme selection, to set a noise mitigation strategy in the design phase. A three terminal common-mode electromagnetic interference (EMI) model is proposed, which predicts the impact of the dc-dc stage and a large battery-rack on the output CM noise. Based on the model, severe deterioration of noise by the dc-dc stage and battery-rack can be predicted. Special attention was paid on the selection of the dc-dc stage's topology and the PWM scheme to minimize the impact. With the mitigation strategy, a maximum 16 dB reduction on CM EMI can be achieved for a wide frequency range. In Chapter 4, an active PWM scheme for a full-SiC three-level back-to-back converter was proposed. The PWM scheme targets the size reduction of two key components: dc-link capacitors and a common-mode EMI filter. The increase in switching frequency calls for a large common-mode EMI filter, and dc-link capacitors in the three-level topology may take a considerable portion in the total volume. To reduce the common-mode noise emission, different combinations of the voltage vectors are investigated to generate center-aligned single pulse common-mode voltage. By such an alignment of common-mode voltage with different vector combinations, noise cancellation between the rectifier and the inverter can be maximally utilized, while the balancing of neutral point voltage can be achieved by the transition between the combinations. Also, to reduce the size of the dc-link capacitor for the three-level back-to-back converter, a compensation algorithm for neutral point voltage unbalance was developed for both differential-mode voltage and the common-mode voltage of the ac-ac stage. The experimental results show a 4 dB reduction on CM EMI, which leads to a 30% reduction on the required CM inductance value. When a 10% variation of neutral point voltage can be handled, the dc-link capacitance can be reduced by 56%. In Chapter 5, a 20 kW full-SiC UPS prototype was built to demonstrate a possible size-reduction with the proposed PWM scheme, as well as a selection of topologies and PWM schemes based on the model. The power density and efficiency are compared with the state-of-the-art Si-IGBT based UPSs. Chapter 6 seeks to improve power density by a change in a modulation method. Triangular conduction mode (TCM) operation of the three-level full-SiC inverter was investigated. The switching loss of SiC devices is reported to be concentrated on the turn-on instant. With zero-voltage turn-on of all switches, the switching frequency of a three-level three-phase SiC inverter can be drastically increased, compared to the hard-switching operation. This contributes to the size-reduction of the filter inductors and EMI filters. Based on the design to achieve a 99% peak efficiency, a comparison was made with a full-SiC three-level inverter, operating in continuous conduction mode (CCM), to verify the benefit of the soft switching scheme on the power density. A design procedure for an LCL filter of paralleled TCM inverters was developed. With 3.5 times high switching frequency, the total weight of the filter stage of the TCM inverter can be reduced by 15%, compared to that of the CCM inverter. Throughout this dissertation, techniques for size reduction of key components are introduced, including coupled inductors in parallel inverters, an EMI filter, dc-link capacitors, and the main boost inductor. From Chapter 2 to 5, the physical size or required value of these key components could be reduced by 20% to 56% by different schemes such as magnetic integration, EMI mitigation strategy through modeling, and an active PWM scheme. An optimization result for a full-SiC UPS showed a 40% decrease in the total volume, compared to the state-of-the-art Si-IGBT solution. Soft-switching modulation for SiC-based three-phase inverters can bring a significant increase in the switching frequency and has the potential to enhance power-density notably. A three-level three-phase full-SiC 40 kW PV inverter with TCM operation contributed to a 15% reduction on the filter weight. / Doctor of Philosophy / The power density of a power electronics system is regarded as an indicator of technological advances. The higher the power density of the power supply, the more power it can generate with the given volume and weight. The size requirement on power electronics has been driven towards tighter limits, as the dependency on electric energy increases with the electrification of transportation and the emergence of grid-connected renewable energy sources. However, the efficiency of a power electronics system is an essential factor and is regarded as a trade-off with the power density. The size of power electronics systems is largely impacted by its magnetic components for filtering, as well as its cooling system, such as a heatsink. Once the switching frequency of power semiconductors is increased to lower the burden on filtering, more loss is generated from filters and semiconductors, thus enlarging the size of the cooling system. Therefore, considering the efficiency has to be maintained at a reasonable value, the power density of Si-based converters appears to be saturated. With the emergence of wide-bandgap devices such as silicon carbide (SiC) or gallium nitride (GaN), the switching frequency of power devices can be significantly increased. This is a result of superior material properties, compared to Si-based power semiconductors. For grid-connected applications, SiC devices are adopted, due to the limitations of voltage ratings in GaN devices. Before commercial SiC devices were available, the power density of SiC- based three-phase inverters was expected to go over 20 𝑘𝑊 𝑑𝑚3 ⁄ . However, the state-of-the art designs shows the power density around 3 ~ 4 𝑘𝑊 𝑑𝑚3 ⁄ , and at most 17 𝑘𝑊 𝑑𝑚3 ⁄ . The SiC devices could increase the power density, but they have not reached the level expected. The adoption of SiC devices with faster switching was not a panacea for power density improvement. This dissertation starts with an analysis of the factors that prevent power density improvement of SiC-based, grid-connected, three-phase inverters. Three factors were identified: a limited increase in the switching frequency, large high-frequency noise generation to be filtered, and smaller but still significant magnetic components. Using a generic design procedure for three-phase inverters, each chapter seeks to frame a strategy and develop techniques to enhance the power density. For smaller magnetic components, a magnetic integration scheme is proposed for paralleled ac-dc converters. To reduce the size of the noise filter, an accurate modeling approach was taken to predict the noise phenomena during the design phase. Also, a modulation scheme to minimize the noise generation of the ac-ac stage is proposed. The validity of the proposed technique was verified by a full-SiC three-phase uninterruptible power supply with optimized hardware design. Lastly, the benefit of soft-switching modulation, which leads to a significant increase in switching frequency, was analyzed. The hardware optimization procedure was developed and compared to hard-switched three-phase inverters.

In recent years, increased use of electronic devices and wireless operations resulted in unavoidable electromagnetic (EM) pollution which has a significant impact on civil and military sectors. Considering the foremost requirement, huge efforts were invested in the development of electromagnetic interference (EMI) shielding materials. In this context, metals are usually preferred but design complexities like high density and susceptibility towards corrosion are limiting factors; additionally, the reflection of microwaves from the surface fails to serve as EM absorbers. The concern here is to minimize the reflection of the high frequency electromagnetic wave from the surface and to enhance the microwave absorption in GHz frequencies. In this thesis, we have made an attempt to design EMI shielding materials with exceptional absorption ability derived from Polycarbonate (PC)/ Poly styrene-co-acrylonitrile (SAN) based polymer blends. Herein, unique co-continuous micro-phase separated blend structures with selective localization of microwave active nanoparticles in one of the phases were realized to be most effective for microwave attenuation over just dispersing it in one polymer matrix (i.e. PC and SAN composites). The synergistic attenuation of electric and magnetic field associated with EM radiation was achieved through incorporation of various magnetic nanoparticles, however, dispersion of magnetic nanoparticles was a challenging task. Therefore, in order to localize magnetic nanoparticles in PC phase of the blends and to enhance the dispersion state, various modification strategies have been designed. In summary, we have developed a library of engineered nanoparticles to achieve synergistic attenuation of EM radiation mostly through absorption. For instance, the PC/SAN blends containing MWNTs and rGO-Fe3O4 nanoparticles manifested in exceptional EMI shielding, well above required shielding effectiveness value for most of the commercial applications, essentially through absorption. Taken together, the finding suggests that immiscible blends containing MWNTs and the decoration of magnetic nanoparticles (rGO-Fe3O4) on the surface of reduced graphene oxide sheets can be utilized to engineer high-performance EMI shielding materials with exceptional absorption ability.

ITC/USA 2011 Conference Proceedings / The Forty-Seventh Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2011 / Bally's Las Vegas, Las Vegas, Nevada / This paper concentrates on aircraft specific issues and impacts of utilizing a "C" band telemetry system on a new or existing instrumentation system.

Abstract Carbon nanotubes (CNTs) are known for their excellent mechanical, electrical and thermal properties, that have fostered a vast number of applications during the last two decades, from composites, electrodes and nanoelectonics components, to sensors and biological scaffolds. Direct integration of CNTs into devices is not straightforward, as high growth temperatures (above 600 °C) challenge the chemical and thermal stability of substrates, catalysts and other nearby materials or components. However, by decreasing growth temperature and/or working out protocols that take into account the thermal stability of the materials involved, it is possible to create several new types of architectures and devices with functionalities not shown before. In this work, we show that, with selection of the appropriate substrate, diffusion barrier and catalyst materials, direct growth of functional CNT films and their micropatterns may be achieved, not only on Si chips, but also on other atypical surfaces, using chemical vapor deposition. This thesis explores low-temperature CNT synthesis over bi- and trimetallic catalysts, and investigates the effect of diffusion barrier layers on the electrical properties of substrate-to-CNT contacts. On one hand, the lowest achieved CNT synthesis temperature (400 °C) is compatible with most silicon technologies, thus enabling direct integration of CNTs with materials and devices with low thermal budgets. On the other hand, the results of diffusion barrier studies helped us in designing and demonstrating on-chip micropatterned CNT structures for super and pseudocapacitor electrodes. In addition, we also show a method for maskless growth of CNT micropatterns using laser-treated steel and superalloy surfaces, whose surface diffusion properties change as a result of barrier-type metal oxide formation. Furthermore, we present CNT growth on carbon materials and demonstrate entirely carbon-based hierarchical composites for electromagnetic interference shielding applications, exhibiting outstanding absorption-based shielding performance. The results presented in this thesis are expected to contribute to a further expansion of CNT-based technologies, in particular with potential for future advances in high-frequency devices (arrays, amplifiers and shielding materials), energy materials (electrodes and scaffolds), as well as in nanoelectromechanical systems (sensors and actuators). / Tiivistelmä Hiilinanoputket tunnetaan niiden erinomaisista mekaanisista, sähköisistä ja termisistä ominaisuuksista, joita on hyödynnetty lukuisissa sovelluksissa viimeisen kahden vuosikymmenen aikana alkaen komposiiteista, elektrodeista, nanoelektroniikkakomponenteista ja sensoreista aina biologisiin tukirakenteisiin. Nanoputkien synteesi suoraan laitteessa ei ole suoraviivaista, sillä korkeat, yli 600 °C synteesilämpötilat asettavat haasteita substraatin, katalyytin sekä muiden lähellä olevien materiaalien ja komponenttien kemialliselle ja termiselle vakaudelle. Alentamalla synteesilämpötilaa ja/tai kehittämällä termisen vakauden huomioivia menetelmiä on mahdollista luoda uudenlaisia arkkitehtuureja ja sovelluksia ennennäkemättömillä ominaisuuksilla. Tässä työssä osoitetaan, että sopivan substraatin, diffuusiosuojan ja katalyyttimateriaalin valitsemalla funktionaalisten hiilinanoputkien synteesi on mahdollista piin lisäksi myös muille, epätavallisille pinnoille käyttäen kemiallista kaasufaasipinnoitusta. Väitöstyössä käsitellään hiilinanoputkien matalan lämpötilan synteesiä hyödyntäen kaksi- ja kolmimetallisia katalyyttejä sekä tutkitaan diffuusiosuojakerroksen sähköistä vaikutusta substraatin ja hiilinanoputkien väliseen kontaktiin. Alin saavutettu synteesilämpötila (400 °C) on yhteensopiva useimpien piiteknologioiden kanssa, mikä mahdollistaa nanoputkien suoran integroinnin matalaa lämpötilaa edellyttäville materiaaleille. Työssä tutkitun diffuusiosuojakerroksen kehitys mahdollisti myös piisirun päälle toteutettujen hiilinanoputkipohjaisten super- ja pseudokondensaattorielektrodien demonstroinnin. Lisäksi työssä esitetään menetelmä, jossa laserkäsittelemällä teräs- ja supermetalliseospinta, jonka avulla mikrokuvioitu hiilinanoputkien kasvu ilman litografiaprosessia on mahdollista. Viimeisenä työssä esitetään hiilinanoputkien synteesi suoraan toiselle hiilimateriaalille ja demonstroidaan täysin hiilipohjainen, hierarkkinen komposiittimateriaali erinomaisella absorptioon perustuvalla suojauskyvyllä sähkömagneettisiin häiriösuojaussovelluksiin. Väitöstyössä esitettyjen tulosten odotetaan osaltaan edistävän hiilinanoputkipohjaisten teknologioiden kehitystä erityisesti korkean taajuuden laitteissa, energiamateriaaleissa sekä nanosähkömekaanisissa järjestelmissä.

<p>As the interest in intentional electromagnetic interference (IEMI) increases, so does the need of a suitable antenna which endures those demanding conditions. The ultrawideband (UWB) technology provides an elegant way of generating high-voltage UWB pulses which can be used for IEMI. One UWB antenna, invented solely for the purpose of radiating pulses, is the impulse radiating antenna (IRA). In the course of this master thesis work, a suitable geometry of the IRA is suggested, and modelled, for the high-voltage application of 90 kV.</p>

The fields of health care and environment control have an increasing demand for sensors able to detect low concentrations of specific molecules in gaseous or liquid samples. The recent introduction of microfabricated devices in these fields gave rise to sensors with attractive properties. A cutting edge technology is based on guided acoustic waves, which are perturbed by events occurring at the nanometer scale. A first part of the thesis investigates the Love mode waveguide, a versatile structure in which a thin film is guiding the acoustic wave generated in a piezoelectric substrate. A systematic analysis of its sensitivity was obtained using a transmission line model generalized to discriminate the rigid or viscous nature of the probed layers. We developed a novel integrated combination of the Love mode device with a Surface Plasmon Resonance optical sensor to quantify the thickness and the composition of soft layers. The electromagnetic interferences in the recorded signal were modeled to determine the phase velocity in the sensing area and to provide new mechanisms for an enhanced sensitivity. The experimental aspects of this work deal with the fabrication, the important issue of the packaging and the sensitivity calibration of the Love mode biosensor. A second part of the thesis investigates nanocrystalline diamond under the form of a thin film membrane suspended to a rigid silicon frame. The high mechanical and chemical resistance of nanocrystalline diamond, close to single-crystal diamond, open ways to membrane based acoustic sensors such as Flexural Plate Wave and thin Film Bulk Acoustic Resonators (FBAR). A novel dynamic characterization of the thin film is reported and the properties of composite FBAR devices including a diamond thin film membrane and a piezoelectric aluminum nitride layer are assessed using the perturbation theory. This study is applied to evaluate the high sensing potential of the first prototype of an actual diamond-based composite FBAR.