abstract: Optical Instrument Transformers (OIT) have been developed as an alternative to traditional instrument transformers (IT). The question "Can optical instrument transformers substitute for the traditional transformers?" is the main motivation of this study. Finding the answer for this question and developing complete models are the contributions of this work. Dedicated test facilities are developed so that the steady state and transient performances of analog outputs of a magnetic current transformer (CT) and a magnetic voltage transformer (VT) are compared with that of an optical current transformer (OCT) and an optical voltage transformer (OVT) respectively. Frequency response characteristics of OIT outputs are obtained. Comparison results show that OITs have a specified accuracy of 0.3% in all cases. They are linear, and DC offset does not saturate the systems. The OIT output signal has a 40~60 μs time delay, but this is typically less than the equivalent phase difference permitted by the IEEE and IEC standards for protection applications. Analog outputs have significantly higher bandwidths (adjustable to 20 to 40 kHz) than the IT. The digital output signal bandwidth (2.4 kHz) of an OCT is significantly lower than the analog signal bandwidth (20 kHz) due to the sampling rates involved. The OIT analog outputs may have significant white noise of 6%, but the white noise does not affect accuracy or protection performance. Temperatures up to 50oC do not adversely affect the performance of the OITs. Three types of models are developed for analog outputs: analog, digital, and complete models. Well-known mathematical methods, such as network synthesis and Jones calculus methods are applied. The developed models are compared with experiment results and are verified with simulation programs. Results show less than 1.5% for OCT and 2% for OVT difference and that the developed models can be used for power system simulations and the method used for the development can be used to develop models for all other brands of optical systems. The communication and data transfer between the all-digital protection systems is investigated by developing a test facility for all digital protection systems. Test results show that different manufacturers' relays and transformers based on the IEC standard can serve the power system successfully. / Dissertation/Thesis / Ph.D. Electrical Engineering 2010

No description available.

Flow control is an area of research of particular interest within automotive and aerospace industries since methods used to affect the fluid flow around vehicles can reduce drag and therefore lower their fuel consumption. One of these methods, which has generated a lot of interest in later years, is called active flow control and uses different types of actuators to impact the surrounding flow. In this thesis a model of a piezoelectric actuator for active flow control has been developed using Lumped Element Modelling and equivalent circuits. This approach, together with the chosen software for implementation, Simulink, provides models which are easy to simulate and evaluate. The actuator model has been validated using a novel methodology with sub-models with the purpose of reducing computational costs. The actuator is therefore divided into two submodels,one for structural and one for fluid dynamics, which are validated separately. This enables the use of simple yet accurate FEM and CFD models instead of time consuming FSI software which the complete model requires. The three implemented models have been validated using cases presented in previous studies and data from CFD-simulations. The results show that the decoupled models can be validated separately and its results can be integrated into the complete model, although further tests with a real actuator is needed. In addition to the modelling, a parameter study of the actuator has been performed in order to prepare for prototype design.

No description available.

How can we evaluate and design integrated photonic circuit performance systematically? Can active photonic circuits be controlled for optimized performance? This work uses control theory to analyze, design, and optimize photonic integrated circuits based on versatile semiconductor optical amplifiers (SOAs). Control theory provides a mathematically robust set of tools for system analysis, design, and control. Although control theory is a rich and well-developed field, its application to the analysis and design of photonic circuits is not widespread. Following control theoretic methods already used for fibreline systems we derive three interrelated state-space models: a core photonic model, a photonic model with gain compression, and a equivalent circuit optoelectronic model. We validate each model and calibrate the gain compression model by pump/probe experiments. We then linearize the state-space models to design and analyze SOA controllers. We apply each linearized model to proof-of-concept SOA control applications such as suppressing interchannel crosstalk and regulating output power. We demonstrate the power of linearized state-space models in controller design and stability analysis. To illustrate the importance of using the complete equivalent circuit model in controller design, we demonstrate an intuitive bias-current controller that fails due to the dynamics of the intervening parasitic circuitry of the SOA. We use the linearized state-space models to map a relationship between feedback delay and controller strength for stable operation, and demonstrate that SOAs pose unusual control difficulties due to their ultrafast dynamics. Finally, we leverage the linearized models to design a novel and successful hybrid controller that uses one SOA to control another via feedback (for reliability) and feedforward (for speed) control. The feedback controller takes full advantage of the equivalent circuit modelling by sampling the voltage of the controlled SOA and using the error to drive the bias current of the controller SOA. Filtering in the feedback path is specified by transfer function analysis. The feedforward design uses a novel application of the linearized models to set the controller bias points correctly. The modelling and design framework we develop is entirely general and opens the way to the robust optoelectronic control of integrated photonic circuits.

How can we evaluate and design integrated photonic circuit performance systematically? Can active photonic circuits be controlled for optimized performance? This work uses control theory to analyze, design, and optimize photonic integrated circuits based on versatile semiconductor optical amplifiers (SOAs). Control theory provides a mathematically robust set of tools for system analysis, design, and control. Although control theory is a rich and well-developed field, its application to the analysis and design of photonic circuits is not widespread. Following control theoretic methods already used for fibreline systems we derive three interrelated state-space models: a core photonic model, a photonic model with gain compression, and a equivalent circuit optoelectronic model. We validate each model and calibrate the gain compression model by pump/probe experiments. We then linearize the state-space models to design and analyze SOA controllers. We apply each linearized model to proof-of-concept SOA control applications such as suppressing interchannel crosstalk and regulating output power. We demonstrate the power of linearized state-space models in controller design and stability analysis. To illustrate the importance of using the complete equivalent circuit model in controller design, we demonstrate an intuitive bias-current controller that fails due to the dynamics of the intervening parasitic circuitry of the SOA. We use the linearized state-space models to map a relationship between feedback delay and controller strength for stable operation, and demonstrate that SOAs pose unusual control difficulties due to their ultrafast dynamics. Finally, we leverage the linearized models to design a novel and successful hybrid controller that uses one SOA to control another via feedback (for reliability) and feedforward (for speed) control. The feedback controller takes full advantage of the equivalent circuit modelling by sampling the voltage of the controlled SOA and using the error to drive the bias current of the controller SOA. Filtering in the feedback path is specified by transfer function analysis. The feedforward design uses a novel application of the linearized models to set the controller bias points correctly. The modelling and design framework we develop is entirely general and opens the way to the robust optoelectronic control of integrated photonic circuits.

Abstract In this dissertation, the operation of planar impulse radio (IR) ultra wideband (UWB) antennas is examined for use in wireless body area networks (WBANs). The objective of the thesis is to consider electromagnetic phenomena due to coupling between an antenna and human body tissues and to analyse the challenges of wideband radiators. The aim is to understand the fundamental behaviour of an antenna in a WBAN, focusing on off-body and on-body communications. The thesis premises follow the international WBAN standard 802.15.6-2012 by the Institute of Electrical and Electronics Engineering (IEEE) and the Federal Communications Commission’s (FCC) UWB regulations (3.1–10.6 GHz). In the examinations, the frequency-dependent modelling of human tissues is considered. The impact of the variation of tissue layer thickness on the performance of an antenna is depicted. The demonstration of the impact of antenna input power is given in terms of generation of heat in tissues and specific absorption rate (SAR). In order to theoretically contemplate the effect of reflections due to tissues on antenna patterns, the opportunities to influence polarization with an artificially anisotropic substrate are derived. With the proposed method, not earlier proposed for WBAN antennas, the smooth patterns without pattern minima can be achieved over the FCC UWB bandwidth. In addition, a theoretical two-path model is applied to the estimation of the antenna pattern shape close to tissues. Various antenna parameters are explored as a function of the use distance to tissue surface to demonstrate the behaviour in the vicinity of a body. The size of the reactive near-field is an important factor for the evaluation of satisfactory on-body performance. The proportions of absorption, mismatch and body losses are analysed close to a body. The connection between the complex input impedance and the dimensions of planar antennas is analysed by using lumped-element equivalent circuits. The impact of the actual width and length of the radiator on the impedance behaviour is presented for the first time. In addition, impedance is analysed in terms of capacitance, inductance and resistance within the reactive near-field for the first time. In order to understand the impact of tissues close to the antenna, the parasitic components for the stages in equivalents are proposed. / Tiivistelmä Tässä väitöskirjassa tarkastellaan laajakaistaisten impulssiradioantennien (IR-UWB) toimintaa langattomissa kehoverkoissa (WBAN). Työn tavoitteena on tarkastella antennin ja ihmiskudoksen kytkeytymisestä johtuvia sähkömagneettisia ilmiöitä ja analysoida laajakaistaisen säteilijän haasteet. Päämääränä on ymmärtää antennin suorituskyky kontekstissa ja kohdeympäristöksi on fokusoitu toiminta kehon pinnalla (on-body) ja keholta poispäin seuraavaan liityntäpisteeseen (off-body). Tutkimustyö pohjautuu IEEE802.15.6-2012-standardiin sekä FCC:n UWB -säännöksiin. Väitöstyössä tarkastellaan taajuusriippuvan ihmiskudoksen mallintamista. Ihmiskudoskerrosten paksuuden vaikutusta antennin suorituskykyyn tutkitaan simuloimalla. Lisäksi tarkastellaan antennin syöttötehon vaikutusta kudoksen lämpiämisen ja tehon absorboitumisen näkökulmasta. Kehon aiheuttamien heijastusten vaikutusta säteilykuvioihin tarkastellaan teoreettisesti ja lisäksi esitetään menetelmä vaikuttaa antennin summapolarisaation kautta säteilykuvion muotoon keinotekoisella epäisotrooppisella substraatilla. Ehdotetulla menetelmällä, mitä ei ole aiemmin kirjallisuudessa esitetty kehoantenneille, voidaan minimoida nollakohtia ja saavuttaa tasainen säteilykuvio FCC UWB -taajuuskaistan yli. Kaksitie-mallia sovelletaan säteilykuvion muodon ennustamiseen kehon läheisyydessä. Useita antenniparametreja havainnollistetaan antennin käyttöetäisyyden funktiona ihmiskudoksesta. Antennin reaktiivisen lähikentän koko on tärkeä tekijä kehoantennille riittävän suorituskyvyn saavuttamiseksi. Absorptio-, epäsovitus- ja kehohäviöiden osuudet edelleen eritellään ja analysoidaan työssä. Työssä tutkitaan kompleksisen syöttöimpedanssin ja antennin fyysisten mittojen yhteyttä hyödyntämällä erilliskomponenteilla muodostettuja vastinpiirejä. Ensimmäistä kertaa antennin käytännön leveyden ja pituuden muutos esitetään suhteessa impedanssikäyttäytymiseen. Impedanssin muutos analysoidaan kapasitanssin, induktanssin ja resistanssin funktiona antennin reaktiivisen lähikentän alueella. Jotta kudoksen vaikutus antennin läheisyydessä voitaan ottaa suunnittelussa huomioon, työssä esitetään tarvittavat parasiittiset komponentit vastinkytkentöjen sarja- ja rinnanasteisiin.

This dissertation presents various systematic design techniques for photovoltaic (PV) source simulators to serve as a convenient tool for the dynamic performance evaluation of solar power conditioning systems and their maximum power point tracking algorithms. A well-designed PV source simulator should accurately emulate the static and the dynamic characteristic of actual PV generator. Four major design features should be adopted in any PV source simulator: (i) high power-stage efficiency, (ii) fast transient response-time, (iii) output impedance matching with actual PV generator, and (iv) precise reference generation technique. Throughout this research, two different PV source simulator systems are designed, modeled, and experimentally verified. The design of the first system focuses mainly on creating new reference generation techniques where the PV equivalent circuit is used to precisely generate the current-voltage reference curves. A novel technique is proposed and implemented with analog components to simplify the reference signal generator and to avoid computation time delays in digital controllers. A two-stage LC output filter is implemented with the switching power-stage to push the resonant frequency higher and thus allowing a higher control-loop bandwidth design while keeping the same switching ripple attenuation as in the conventional one-stage LC output filter. With typical control techniques, the output impedance of the proposed simulator did not  match the closed-loop output impedance of actual PV generator due to the double resonant peaks of the two-stage LC output filter. Design procedures for both control and power-stage circuits are explained. Experimental results verify the steady-state and transient performance of the proposed PV source simulator at around 2.7 kW output. The design concept of the first simulator system is enhanced with a new type of PV source simulator that incorporates the advantages of both analog and digital based simulators. This simulator is characterized with high power-stage efficiency and fast transient response-time. The proposed system includes a novel three-phase ac-dc dual boost rectifier cascaded with a three-phase dc-dc interleaved buck converter. The selected power-stage topology is highly reliable and efficient. Moreover, the multi-phase dc-dc converter helps improve system transient response-time though producing low output ripple, which makes it adequate for PV source simulators. The simulator circuitry emulates precisely the static and the dynamic characteristic of actual PV generator under different environmental conditions including different irradiance and temperature levels. Additionally, the system allows for the creation of the partial shading effect on PV characteristic. This dissertation investigates the dynamic performance of commercial and non-commercial solar power conditioning systems using the proposed simulator in steady-state and transient conditions. Closed-loop output impedance of the proposed simulator is verified at different operating conditions. The impedance profile --magnitude and phase- matches the output impedance of actual PV generator closely. Mathematical modeling and experimental validation of the proposed system is thoroughly presented based on a 2.0 kW hardware prototype. The proposed simulator efficiency including the active-front-end rectifier and the converter stages at the maximum power point is 96.4%. / Ph. D.

Biossensores que empregam dispositivos de efeitos de campo podem ser obtidos em diversas arquiteturas, incluindo dispositivos Eletrólito-Isolante-Semicondutor (EIS), que são capacitores em que o eletrodo metálico é substituído por um filme e uma solução. Medindo-se a capacitância em função do potencial aplicado, é possível detectar variações de pH oriundas de reações ou interações entre o filme e o analito. Nesta dissertação, sensores foram produzidos com a adsorção de filmes automontados de dendrímero (PAMAM) e nanotubos de carbono (SWNT) num chip. Medidas de espectroscopia de impedância foram realizadas para investigar o crescimento de cada bicamada do filme automontado, e os dados foram analisados com circuitos equivalentes que continham uma capacitância de dupla camada, um elemento de fase constante e uma capacitância para a região de depleção. Para o chip, os melhores ajustes foram obtidos na frequência de 2 kHz, em que a concentração de dopantes foi 6,6x1020 m-3 para o chip com isolante de SiO2 e de 1,1x1021 m-3 para o chip com isolante de SiO2/Ta2O5. O potencial de banda plana foi -0,2 V e -0,06V, respectivamente. Para os chips recobertos com os filmes de PAMAM/SWNT, observamos que a região de depleção é causada pelas cargas positivas do PAMAM. Com relação às implicações para biossensores, verificamos que o desempenho ótimo deve ser obtido com 3 bicamadas de PAMAM/SWNT. Isso pode explicar a observação empírica na literatura de que existe uma espessura ideal dos filmes para um desempenho otimizado. / Biosensors based on field effect devices can be produced with several architectures, including Electrolyte-Insulator-Semiconductor (EIS) devices, which are capacitors where conventional metal electrodes are replaced by a sensing layer and an electrolyte solution. By measuring the capacitance as a function of the bias voltage, it is possible to detect pH changes that may originate from reactions or interactions between the film in the sensing unit and the analyte. In this study sensors were obtained by adsorbing layer-by-layer (LbL) films made with dendrimers (PAMAM) and carbon nanotubes (SWNT) on a semiconductor chip. Impedance spectroscopy measurements were performed to monitor the growth of each bilayer in the LbL film, whose data were analyzed with equivalent circuits containing a double-layer capacitance, a constant phase element and a capacitance for the depletion region. The results for the semiconductor chip could be best fitted for a frequency of 2 kHz, where the doping concentration was 6.6 x1020 m-3 for the insulating SiO2 layer and 1.1 x1021 m-3 for the SiO2/Ta2O5 layer. The flat band voltage was -0.2 V and -0.06 V, respectively. In the analysis of the chip coated with different numbers of PAMAM/SWNT bilayers, we found that the depletion region appears as a contribution from the positive charges in the PAMAM layer. With regard to implications for biosensors, we found that optimized performance should be reached with three PAMAM/SWNT bilayers, which may explain the empirical finding in the literature that an ideal thickness exists for enhanced performance.

We present studies on squeeze film effects in dynamic MEMS devices with a special emphasis on the development of compact analytical models. First, the efficacy of lumped parameter modelling of dynamic MEMS devices is illustrated in MATLAB/SIMULINK software environment using a MEMS gyroscope and a MEMS microphone as examples. This is followed by a comparative study of equivalent electrical circuit models for a MEMS microphone wherein the importance of accurate extraction of lumped mass, stiffness and damping is brought into focus. In this context, a need for an in depth study of squeeze film behaviour in MEMS structures is highlighted and a strong motivation is drawn for the development of compact squeeze film models. A 2D analytical model for estimating squeeze film damping and spring force in perforated MEMS structures is presented. The governing equations based on isothermal compressible Reynolds equation are derived by considering an approximate circular pressure cell around a hole which is representative of the spatially invariant pressure pattern over the interior of the flow domain. The advantages and limitations of the solution are discussed with relevance to MEMS structures. Next, a comprehensive analytical model for 3D MEMS structures that includes effects of compressibility, inertia, and rarefaction in the flow between two parallel plates forming the squeeze region as well as the flow through perforations is developed. A modified Reynolds equation that includes the unsteady inertial term is derived from the Navier-Stokes equation to model the flow in the circular cell and the losses through the holes are modelled using Poiseuille flow. Rarefaction effects in the flow through the air-gap as well as the holes are accounted for by considering the slip boundary conditions. The analytical results are compared with extensive numerical simulations carried out using full 3-D Navier-Stokes equation solver in a commercial simulation package (ANSYS-CFX). We show that the analytical solution performs very well in tracking the net force up to the first resonant frequency of the entrapped air.