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High Voltage (HV) rotating machines are widely used in power generation and heavy industry companies. Silicon Carbide (SiC) material is used in the stress grading structure of HV electric machines because of its non-linear characteristic. In this thesis, the resistance characteristics of SiC-based stress grading tape in time domain and the dielectric parameters in frequency domain were measured. The measurement results of samples with axial current-direction in time domain and frequency domain are about ten times that of the samples with radial current-direction, which might be a feature of the tape construction although it also can depend on the measurement method. The finite element method (FEM) simulation of the coil insulation system was carried out by using the experimental parameters, and the results were compared with the actual measurement results. The calculation results show that the non-linearity of SiC-based material does not have much effect on the real part of frequency response of the whole coil. The relative difference of the real part of complex capacitance is less than 5%. However, the influence on the imaginary part is relatively large, the relative difference is about 4% - 60%. / Högspänningsmaskiner används ofta i kraftproduktion och tunga industriella anläggningar. Kiselkarbidmaterial (SiC) används i sådana maskiners potential-styrningssstruktur på grund av dess icke-linjära egenskaper. I denna avhandling mättes ledningsförmågan hos SiC-baserade fältstyrningstejp i tidsdomänen och de dielektriska parametrarna i frekvensdomänen. Resultaten med axiell strömriktning vid tiddomän och frekvensdomänmetoder tyder på omkring tio gånger så stor konduktivitet jämfört med den radiella ström-riktningen, vilken kan bero på tejpkonstruktionen fast även eventuellt på mätmetoden. Simuleringen av en statorhärvas isoleringssystem utfördes med finita element metoden (FEM) med parametrar från materialproven, och resultaten jämfördes med mätresultat från en sådan härva. Beräkningsresultaten visar att det SiC-baserade materialets ickelinjäritet inte har någon större effekt på hela spolens verkliga frekvensrespons. Den relativa skillnaden mellan den verkliga delen av komplex kapacitans är mindre än 5%. Påverkan på den imaginära delen är dock relativt stor, med en relativ skillnad på ca 4% - 60%.

Tesis por compendio / [ES] Con esta tesis se pretende dar solución a algunos de los problemas más habituales que aparecen en los Sistemas de control basados en red (NCS) como son los retardos variables en el tiempo, las pérdidas y el desorden de paquetes, y la restricción de ancho de banda y de recursos computacionales y energéticos de los dispositivos que forman parte del sistema de control. Para ello se ha planteado la integración de técnicas de control multifrecuencial, de control basado en paquetes, de control basado en predictor y de control basado en eventos. Los diseños de control realizados se han simulado utilizando Matlab-Simulink y Truetime, se ha analizado su estabilidad mediante LMIs y QFT, y se han validado experimentalmente en un péndulo invertido, un robot cartesiano 3D y en robots móviles de bajo coste. El artículo 1 aborda el control basado en eventos, el cual minimiza el ancho de banda consumido en el NCS mediante un control basado en eventos periódicos y presenta un método para obtener sus parámetros óptimos para el sistema específico en que se utilice. Los artículos 2, 4 y 6 añaden el control basado en paquetes, así como el control multifrecuencia, que aborda problemas de falta de datos por bajo uso del sensor y los retardos, pérdidas y desórdenes de paquetes en la red. También afrontan, mediante tecnicas de predicción basadas en un filtro de Kalman multifrecuencia variable en el tiempo, los problemas de ruido y perturbaciones, así como la observación de los estados completos del sistema. El artículo 7 hace frente a un modelo no lineal que utiliza las anteriores soluciones junto con un filtro de Kalman extendido para presentar otro tipo de estructura para un vehículo autónomo que, gracias a la información futura obtenida mediante estas técnicas, puede realizar de forma remota tareas de alto nivel como es la toma de decisiones y la monitorización de variables. Los artículos 3 y 5, presentan una forma de obtener y analizar la respuesta en frecuencia de sistemas SISO multifrecuencia y estudian su comportamiento ante ciertas incertidumbres o problemas en la red haciendo uso de procedimientos QFT. / [CA] Amb aquesta tesi es pretén donar solució a alguns dels problemes més habituals que apareixen als Sistemes de Control Basats en xarxa (NCS) com son els retards d'accés i transferència variables en el temps, les pèrdues y desordenament de paquets, i la restricció d'ampli de banda així com de recursos computacionals i energètics dels dispositius que foment part del sistema de control. Per tal de resoldre'ls s'ha plantejat la integració de tècniques de control multifreqüencial, de control basat en paquets, de control basat en predictor i de control basat en events. Els dissenys de control realitzats s'han simulat fent ús de Matlab-Simulink i de TrueTime, s'ha analitzat la seua estabilitat mitjançant LMIs i QFT, i s'han validat experimentalment en un pèndul invertit, un robot cartesià 3D i en robots mòbils de baix cost. L'article 1 aborda el control basat en events, el qual minimitza l'ampli de banda consumit a l'NCS mitjançant un control basat en events periòdics i presenta un mètode per a obtindré els seus paràmetres òptims per al sistema específic en el qual s'utilitza. Els articles 2, 4 i 6 afegeixen el control basat en paquets, així com el control multifreqüència, que aborda problemes de falta de dades per el baix us del sensor i els retards, pèrdues i desordre de paquets en la xarxa. També afronten, mitjançant tècniques de predicció basades en un filtre de Kalman multifreqüència variable en el temps. Els problemes de soroll i pertorbacions, així com la observació dels estats complets del sistema. L'article 7 fa referència a un model no lineal que utilitza les anteriors solucions junt a un filtre de Kalman estès per a presentar altre tipus d'estructura per a un vehicle autònom que, gracies a la informació futura obtinguda mitjançant aquestes tècniques, pot realitzar de manera remota tasques d'alt nivell com son la presa de decisions i la monitorització de variables. Els articles 3 y 5 presenten la manera d'obtindre i analitzar la resposta en frequencia de sistemes SISO multifreqüència i estudien el seu comportament front a certes incerteses o problemes en la xarxa fent us de procediments QFT. / [EN] This thesis attempts to solve some of the most frequent issues that appear in Networked Control Systems (NCS), such as time-varying delays, packet losses and packet disorders and the bandwidth limitation. Other frequent problems are scarce computational and energy resources of the local system devices. Thus, it is proposed to integrate multirate control, packet-based control, predictor-based control and event-based control techniques. The control designs have been simulated using Matlab-Simulink and Truetime, the stability has been analysed by LMIs and QFT, and the experimental validation has been done on an inverted pendulum, a 3D cartesian robot and in low-cost mobile robots. Paper 1 addresses event-based control, which minimizes the bandwidth consumed in NCS through a periodic event-triggered control and presents a method to obtain the optimal parameters for the specific system used. Papers 2, 4 and 6 include packet-based control and multirate control, addressing problems such as network delays, packet dropouts and packet disorders, and the scarce data due to low sensor usage in order to save battery in sensing tasks and transmissions of the sensed data. Also addressed, is how despite the existence of measurement noise and disturbances, time-varying dual-rate Kalman filter based prediction techniques observe the complete state of the system. Paper 7 tackles a non-linear model that uses all the previous solutions together with an extended Kalman filter to present another type of structure for an autonomous vehicle that, due to future information obtained through these techniques, can remotely carry out high level tasks, such as decision making and monitoring of variables. Papers 3 and 5, present a method for obtaining and analyzing the SISO dual-rate frequency response and using QFT procedures to study its behavior when faced with specific uncertainties or network problems. / This work was supported by the Spanish Ministerio de Economía y Competitividad under Grant referenced TEC2012-31506. / Alcaina Acosta, JJ. (2020). Design and implementation of event-based multi-rate controllers for networked control systems [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/159884 / Compendio

Optical current sensors (OCSs) are initially developed to measure relatively large current over a wide range of frequency band. They are also used as protective devices in the event a fault occurs due to a short circuit, in the power generation and distribution industries. The basic principal used in OCS is the Faraday effect. When a light guiding faraday medium is placed in a magnetic field which is produced by the current flowing in the conductor around the magnetic core, the plane of polarization of the linearly polarized light is rotated. The angle of rotation is proportional to the magnetic field strength, proportionality constant and the interaction length. The proportionality constant is the Verdet constant V (λ, T), which is dependent on both temperature and wavelength of the light. Opto electrical methods are used to measure the angle of rotation of the polarization plane. By measuring the angle the current flowing in the current carrying conductor can be calculated. But the accuracy of the OCS is lost of the angle of rotation of the polarization plane is dependent on the Verdet constant, apart from the magnetic field strength. As temperature increases the Verdet constant decreases, so the angle of rotation decreases. To compensate the effect of temperature on the OCS, a new method has been proposed. The current and temperature are measured with the help of a duel frequency method. To detect the line current in the conductor or coil, a small signal from the line current is fed to the reference of the lock in. To detect the temperature, the coil is excited with an electrical signal of a frequency different from the line frequency, and a small sample of this frequency signal is applied to the reference of the lock in. The temperature and current readings obtained are look up at the database value to give the actual output. Controlled environment is maintained to record the values in the database that maps the current and temperature magnitude values at the DSP lock in amplifier, to the actual temperature and current. By this method we can achieve better compensation to the temperature changes, with a large dynamic range and better sensitivity and accuracy.

Dans cette thèse, on étudie les écoulements oscillatoires en milieux poreux (non saturés ou partiellement saturés) dus à des oscillations tidales des niveaux d'eau dans des milieux ouverts adjacents aux milieux poreux. L'étude est centrée sur le cas des plages de sable en hydrodynamique côtière, mais les applications concernent, potentiellement et plus généralement, les problèmes d'oscillation et de variation temporelle des niveaux d'eau dans des systèmes couplés, lorsque ceux-ci mettent en jeu des interactions entre les écoulements de sub-surface (milieux poreux) et les eaux de surface (milieux ouverts) : plages naturelles et artificielles; digues portuaires; barrages en terre; berges de fleuves; estuaires. Le forçage tidal des écoulements souterrains est représenté et modélisé ici, tant expérimentalement que numériquement, par une oscillation quasi-statique du niveau d'eau dans un réservoir externe ouvert, connecté au domaine poreux. On s'intéresse plus particulièrement aux écoulements verticaux forcés par une pression oscillatoire imposée au bas d'une colonne de sol. Sur le plan expérimental, ce type de forçage est obtenu par une machine à marée équipée d'un arbre rotatif. Au total, on utilise dans ce travail trois types d'approches (expérimentale, numérique, analytique), l'objectif étant d'étudier le mouvement vertical de la surface "libre" et l'écoulement non saturé sus-jacent, de façon à prendre en compte aussi bien les pertes de charge dans la zone saturée que les gradients de pression capillaire dans la zone non saturée. […] / In this thesis, we study hydrodynamic oscillations in porous bodies (unsaturated or partially saturated), due to tidal oscillations of water levels in adjacent open water bodies. The focus is on beach hydrodynamics, but potential applications concern, more generally, time varying and oscillating water levels in coupled systems involving subsurface / open water interactions (natural and artificial beaches, harbor dykes, earth dams, river banks, estuaries). The tidal forcing of groundwater is represented and modeled (both experimentally and numerically) by quasi-static oscillations of water levels in an open water reservoir connected to the porous medium. Specifically, we focus on vertical water movements forced by an oscillating pressure imposed at the bottom of a soil column. Experimentally, a rotating tide machine is used to achieve this forcing. Overall, we use three types of methods (experimental, numerical, analytical) to study the vertical motion of the groundwater table and the unsaturated flow above it, taking into account the vertical head drop in the saturated zone as well as capillary pressure gradients in the unsaturated zone. Laboratory experiments are conducted on vertical sand columns, with a tide machine to force water table oscillations, and with porous cup tensiometers to measure both positive pressures and suctions along the column (among other measurement methods). Numerical simulations of oscillatory water flow are implemented with the BIGFLOW 3D code (implicit finite volumes, with conjugate gradients for the matrix solver and modified Picard iterations for the nonlinear problem). In addition, an automatic calibration based on a genetic optimization algorithm is implemented for a given tidal frequency, to obtain the hydrodynamic parameters of the experimental soil. Calibrated simulations are then compared to experimental results for other non calibrated frequencies. Finally, a family of quasi-analytical multi-front solutions is developed for the tidal oscillation problem, as an extension of the Green-Ampt piston flow approximation, leading to nonlinear, non-autonomous systems of Ordinary Differential Equations with initial conditions (dynamical systems). The multi-front solutions are tested by comparing them with a refined finite volume solution of the Richards equation. Multi-front solutions are at least 100 times faster, and the match is quite good even for a loamy soil with strong capillary effects (the number of fronts required is small, no more than N≈ to 20 at most). A large set of multi-front simulations is then produced in order to analyze water table and flux fluctuations for a broad range of forcing frequencies. The results, analyzed in terms of means and amplitudes of hydrodynamic variables, indicate the existence, for each soil, of a characteristic frequency separating low frequency / high frequency flow regimes in the porous system.

Orientador: Sérgio Kurokawa / Resumo: Este trabalho apresenta uma proposta de representação de sistemas de aterramento elétrico diretamente no domínio do tempo, tendo como vantagem os benefícios da modelagem realizada no domínio da frequência, com os resultados fornecidos diretamente no domínio do tempo, sem passar por transformadas inversas (Laplace ou Fourier). Os modelos no domínio do tempo são facilmente inseridos nos softwares convencionais de análise transitória, onde as tensões e correntes são melhor compreendidas. A maior contribuição deste trabalho está no desenvolvimento de uma técnica capaz de representar o aterramento com elementos discretos e positivos de circuitos (resistores-R, capacitores-C e indutores-L). Assim, o circuito equivalente representativo do aterramento será sempre um circuito possível de ser implementado fisicamente. Nesta proposta o aterramento é inicialmente modelado no domínio da frequência, sua impedância harmônica é obtida e representada por meio de elementos discretos de circuitos (RLC) associados em série e/ou paralelo. Aterramentos constituídos por um eletrodo horizontal ou uma haste vertical foram representados por meio de aproximação usando o método dos mínimos quadrados (vector fitting), que permite obter a função racional equivalente à admitância do aterramento, a partir da qual são extraídos os ramos de circuitos e consequentemente o circuito equivalente. Apesar de ser possível representar uma infinidade de aterramentos, dependendo do comprimento e diâmetro do eletrodo/ha... (Resumo completo, clicar acesso eletrônico abaixo) / Doutor

After decades of routine operation, the hydropower industry faces new challenges. Large-scale integration of other renewable sources of generation in the power system accentuates the role of hydropower as a regulating resource. At the same time, an extensive reinvestment programme has commenced where many old components and apparatus are being refurbished or replaced. Introduction of new technical solutions in existing power plants requires good systems knowledge and careful consideration. Important tools for research, development and analysis are suitable mathematical models, numerical simulation methods and laboratory equipment. This doctoral thesis is devoted to studies of the electromechanical interaction between hydropower units and the power system. The work encompasses development of mathematical models, empirical methods for system identification, as well as numerical and experimental studies of hydropower generator and power system interaction. Two generator modelling approaches are explored: one based on electromagnetic field theory and the finite element method, and one based on equivalent electric circuits. The finite element model is adapted for single-machine infinite-bus simulations by the addition of a network equivalent, a mechanical equation and a voltage regulator. Transient simulations using both finite element and equivalent circuit models indicate that the finite element model typically overestimates the synchronising and damping properties of the machine. Identification of model parameters is performed both numerically and experimentally. A complete set of equivalent circuit parameters is identified through finite element simulation of standard empirical test methods. Another machine model is identified experimentally through frequency response analysis. An extension to the well-known standstill frequency response (SSFR) test is explored, which involves measurement and analysis of damper winding quantities. The test is found to produce models that are suitable for transient power system analysis. Both experimental and numerical studies show that low resistance of the damper winding interpole connections are vital to achieve high attenuation of rotor angle oscillations. Hydropower generator and power system interaction is also studied experimentally during a full-scale startup test of the Nordic power system, where multiple synchronised data acquisition devices are used for measurement of both electrical and mechanical quantities. Observation of a subsynchronous power oscillation leads to an investigation of the torsional stability of hydropower units. In accordance with previous studies, hydropower units are found to be mechanically resilient to subsynchronous power oscillations. However, like any other generating unit, they are dependent on sufficient electrical and mechanical damping. Two experimentally obtained hydraulic damping coefficients for a large Francis turbine runner are presented in the thesis.

Submitted by CLAUDINER MENDES DE SEIXAS null (claudiner2010@gmail.com) on 2017-10-21T02:06:24Z No. of bitstreams: 1 Tese_Claudiner_seixas_ac_dr_ilha.pdf: 3441885 bytes, checksum: 9e1f3e2ff82a0a8220457c535d4cea55 (MD5) / Approved for entry into archive by Luiz Galeffi (luizgaleffi@gmail.com) on 2017-10-26T14:27:13Z (GMT) No. of bitstreams: 1 seixas_cm_dr_ilha.pdf: 3441885 bytes, checksum: 9e1f3e2ff82a0a8220457c535d4cea55 (MD5) / Made available in DSpace on 2017-10-26T14:27:13Z (GMT). No. of bitstreams: 1 seixas_cm_dr_ilha.pdf: 3441885 bytes, checksum: 9e1f3e2ff82a0a8220457c535d4cea55 (MD5) Previous issue date: 2017-08-25 / Este trabalho apresenta uma proposta de representação de sistemas de aterramento elétrico diretamente no domínio do tempo, tendo como vantagem os benefícios da modelagem realizada no domínio da frequência, com os resultados fornecidos diretamente no domínio do tempo, sem passar por transformadas inversas (Laplace ou Fourier). Os modelos no domínio do tempo são facilmente inseridos nos softwares convencionais de análise transitória, onde as tensões e correntes são melhor compreendidas. A maior contribuição deste trabalho está no desenvolvimento de uma técnica capaz de representar o aterramento com elementos discretos e positivos de circuitos (resistores-R, capacitores-C e indutores-L). Assim, o circuito equivalente representativo do aterramento será sempre um circuito possível de ser implementado fisicamente. Nesta proposta o aterramento é inicialmente modelado no domínio da frequência, sua impedância harmônica é obtida e representada por meio de elementos discretos de circuitos (RLC) associados em série e/ou paralelo. Aterramentos constituídos por um eletrodo horizontal ou uma haste vertical foram representados por meio de aproximação usando o método dos mínimos quadrados (vector fitting), que permite obter a função racional equivalente à admitância do aterramento, a partir da qual são extraídos os ramos de circuitos e consequentemente o circuito equivalente. Apesar de ser possível representar uma infinidade de aterramentos, dependendo do comprimento e diâmetro do eletrodo/haste combinado com determinadas resistividade e permissividade elétricas do solo, esse método pode não garantir que todos os elementos RLC sejam positivos. Por isso foi desenvolvido uma nova técnica e testada em aplicações com configurações de aterramento mais complexas (malhas). Essa técnica fornece resultados precisos e garante que todos os elementos RLC serão positivos. Sua validação foi realizada comparando os resultados propostos com os resultados obtidos pelo modelo de linha de transmissão (no caso de eletrodo/haste) e pelo modelo eletromagnético híbrido HEM (no caso das malhas). Essa técnica permite o uso de qualquer modelo capaz de fornecer a impedância harmônica, podendo ser aplicada a configurações genéricas de aterramento, o que a torna muito versátil e atrativa. / This work presents a proposal to represent of electrical grounding systems directly in time domain, taking into account the benefits in frequency domain modelling, without employing inverse Laplace or Fourier transforms. The time domain models are easily inserted in conventional electromagnetic transient software, where voltages and currents are better understood. The main contribution of this work is the development of a technique that can represent grounding by discrete and positive circuits elements (R-resistors, C-capacitors and L-inductors). The representation of the grounding is an electric circuit, possible to be implemented physically. Grounding systems is initially modelled in the frequency domain, where its harmonic impedance is obtained and then represented by elements of circuit (RLC) made in series and/or parallel association. Grounding systems constituted by a horizontal electrode or a vertical rod were represented by means of an approximation using the method of the least squares (vector fitting). It reproduces the rational function equivalent to the admittance of the grounding, which branches of circuits are extracted, forming an equivalent circuit. Although it is possible to represent an infinity of groundings, depending on the length and diameter of the electrode / rod combined with certain electrical resistivity and permittivity of the soil, this technique may not guarantee that all RLC elements are positive. However, a new technique was developed and tested in more complex grounding systems (grids). This technique provides accurate results and ensures that all RLC elements will be positive. Its validation was performed comparing the proposed results with the results obtained by the TLM (Transmission Line Model) employed for the horizontal electrodes and vertical rods and by the HEM (Hybrid Electromagnetic Model) employed for grounding grids. This technique allows the use of any model capable of providing harmonic impedance, and can be applied to generic ground configurations, making it very attractive to electromagnetics transient analyses.

Master’s thesis deals with the issue of electronic filtering circuits with arbitrary frequency characteristics. First part of the thesis describes theoretical basis. Second part explores the possibilities of design procedures for filters with arbitrary frequency characteristics. Design procedures are demonstrated on examples accordingly to the presented methods, including their circuit implementation and computer simulation to verify the correctness of theoretical assumptions. Thesis also explores the possibilities of tuning circuit structures and electronic setting for characteristics using controllable active elements.

The aim of this master’s thesis is to create a multiband stop derived from Lynn filters for suppressing mains hum and baseline variation (drift). The first part of the thesis is focused on brief theoretical introduction to the distortion types affecting ECG signal and twelve lead connection. The following practical part describes free realizations of ECG filter and ECG signal filtration. The filter has been tested both on distorted and on non-distorted signal. Finally filters’ error rate was computed from CSE database signals.