Dissertations / Theses on the topic 'HARMONIC COMPONENT'

Os métodos de amortecimento exponencial, apesar de originalmente proposto nos anos 60, continuam em pleno uso nos dias de hoje. Neste trabalho apresentamos um método novo para previsão de séries temporais com ou sem sazonalidade utilizando as teorias de amortecimento exponencial e análise harmônica. Assume-se que a série seja composta por uma tendência secular (constante, linear ou quadrática) e seus parâmetros são atualizados seqüencialmente pelo procedimento de amortecimento direto. Já a parte sazonal é tratada separadamente através da técnica de análise harmônica, conforme sugerida por Harrison, 1964. Dessa forma, o método proposto se apresenta como uma alternativa ao método de Souza & Epprecht, (1983) ; tendo como principal vantagem a rotina de estimação inicial dos parâmetros que no método de Souza & Epprecht produz estimadores tendenciosos em alguns casos.
The method of exponential smoothing, although originally propesed during the 60´s, still continues in use up to today. In this thesis we present a new forecasting method for time series / with and/or without seasonality, applying the theory of exponential smoothing and harmonic analysis. It is assume that the series is composed of secular trend (constant, linear or quadratic) and a seasonal part. The trend parameters are sequentially using direct smoothing procedure. The seasonal part of the process is treated / separately through the technic of harmonica analysis according to Harrison´s suggestion, (1964). In this way, the proposed method can be viewed as an alternative to that of Souza & Epprecht, (1983), which has, as the most important advantage, the routine of initial estimation of the parameters, which in Souza & Epprecht method produces, in some cases, biased estimators.

Although the overall levels of harmonics in modern power supply systems are in most of the practical cases still below the prescribed tolerance limits and thresholds (e.g. these stipulated in [IEC 61000-3-2 and 61000-3-12]), the sources of harmonics are constantly increasing in numbers and are expected to increase even more in the future. Some of the examples of modern non-linear power electronic (PE) devices that are expected to be employed on a much wider scale in LV networks in the future include: light-emitting diode (LED) lamps, switched-mode power supplies (SMPS'), electric vehicle battery chargers (EVBCs) and photovoltaic inverters (PVIs), which are all analysed in this thesis. The thesis first reviews the conventional harmonic analysis methods, investigating their applicability to modern PE devices. After that, the two most widely used forms of harmonic models, i.e. component-based models (CBMs) and frequency-domain models (FDMs), are applied for modelling of the four abovementioned types of modern PE devices and their models are fully validated by measurements. The thesis next investigates the impact of supply voltage conditions and operating modes (e.g. low vs high operating powers) on the device characteristics and performance, using both measurements and developed CBMs and FDMs. The obtained results confirm that both supply conditions and operating modes have an impact on the characteristics of most of the considered PE devices, which is taken into account in the developed models and demonstrated on a number of case studies. As the next contribution, the thesis proposes new indices for the evaluation of current waveform distortions, allowing for a separate analysis of contributions of low and high frequency harmonics and interharmonics to the total waveform distortion of PE devices. As the modern PE devices are normally based on high-frequency switching converters or inverters, the impact of circuit topologies and control algorithms on their harmonic emission characteristics and performance is also investigated. Special attention is given to the operation of PE devices at low powers, when there is a significant increase of current waveform distortion, a substantial decrease of efficiency and power factors and when input ac current might lose its periodicity with the supply voltage frequency. This is analysed in detail for SMPS', resulting in the proposal of a new methodology ("operating cycle based method") for evaluating overall performance of PE devices across the entire range of operating powers. Finally, a novel and simple hybrid harmonic modelling technique, allowing for the use of both time-domain and frequency-domain models in the same simulation environment, is proposed and illustrated on the selected case studies. This is accompanied with a frequency-domain aggregation approach, which is applied in the thesis to investigate the impact of increasing numbers of different types of modern PE devices on the LV network. The implementation of the developed hybrid harmonic modelling approach and frequency-domain aggregation technique is demonstrated on the example of a typical (UK) urban generic LV distribution network and used for the analysis of different deployment levels of EVs and PVIs. The presented harmonic modelling framework for individual PE devices and, particularly, for their aggregate models, fills the gap in the existing literature on harmonic modelling and characterisation of modern PE devices, which is important for the correct evaluation of their harmonic interactions and analysis of the impact of their large-scale deployment on the overall network performance.

Three-phase voltage source converters(VSCs) have become the converter of choice in many ac medium and high power applications due to their many advantages, including low harmonics, high power factor, and high efficiency. Modular VSCs have also been a popular choice as building blocks to achieve even higher power, primarily through converter paralleling. In addition to high power ratings, paralleling converters can also provide system redundancy through the so-called (N+1) configuration for improved availability, as well as allow easy implementation of converter power management. Interleaving can further improve the benefit of paralleling VSCs by reducing system harmonic currents, which potentially can increase system power density. There are many challenges to implement interleaving in paralleled VSCs system due to the complicated relationships in a three-phase power converter system. In addition, to maximize the benefit of interleaving, current knowledge of symmetric interleaving is not enough. More insightful understanding of this PWM technology is necessary before implement interleaving in a real paralleled VSCs system. In this dissertation, a systematic methodology to analyze and design a paralleled three-phase voltage source converters with interleaving is developed. All the analysis and proposed control methods are investigated with the goal of maximizing the benefit of interleaving based on system requirement. The dissertation is divided into five sections. Firstly, a complete analysis studying the impact of interleaving on harmonic currents in ac and dc side passive components for paralleled VSCs is presented. The analysis performed considers the effects of modulation index, pulse-width-modulation (PWM) schemes, interleaving angle and displacement angle. Based on the analysis the method to optimize interleaving angle is proposed. Secondly, the control methods for the common mode (CM) circulating current of paralleled three-phase VSCs with discontinuous space-vector modulation (DPWM) and interleaving are proposed. With the control methods, DPWM and interleaving, which is a desirable combination, but not considered possible, can be implemented together. In addition, the total flux of integrated inter-phase inductor to limit circulating current can be minimized. Thirdly, a 15 kW three phase ac-dc rectifier is built with SiC devices. With the technologies presented in this dissertation, the specific power density can be pushed more than 2kW/lb. Fourthly, the converter system with low switching frequency is studied. Special issues such as beat phenomenon and system unbalance due to non-triplen carrier ratio is explained and solved by control methods. Other than that, an improved asymmetric space vector modulation is proposed, which can significantly reduce output current total harmonic distortion (THD) for single and interleaved VSCs system. Finally, the method to protect a system with paralleled VSCs under the occurrence of internal faults is studied. After the internal fault is detected and isolated, the paralleled VSCs system can continue work. So system reliability can be increased.
Ph. D.

Este trabalho consiste em apresentar um método alternativo para a identificação de fontes de correntes harmônicas comumente encontradas em sistemas elétricos residenciais. Desta identificação, soluções viáveis poderão ser aplicadas com o intuito de mitigar os níveis de emissão das correntes harmônicas geradas, principalmente, por cargas com características não lineares. Para a identificação empregou-se redes neurais artificiais (RNAs), sendo esta técnica inteligente, apresentada como uma alternativa aos métodos convencionais. Os resultados reportados neste contexto procuram validar a proposta apresentada com dados experimentais obtidos em ensaios laboratoriais.
This work presents an alternative method for the identification of current harmonic sources commonly encountered in residential electrical systems. For this purpose, feasible solutions can be applied to minimize the levels of harmonic currents emission caused by nonlinear loads. Artificial neural networks are employed as alternative to conventional methods. The experimental results will be reported in order to validate the proposal presented with the experimental data obtained in laboratory.

This diploma thesis deals with design of positioning unit for laser spectroscopy and its realization to shape of prototype. The design of positioning unit is based on the analysis of the current state of knowledge in the field of remote laser spectroscopy systems. Precise harmonic drive and worm drive with stepper motors are used to drive. The main parts of positioning unit are designed primarily from duraluminium. The positioning unit will be used for experimental measurements at the Institute of Physical Engineering Faculty of Mechanical Engineering Brno University of Technology. 3D digital prototype and technical drawings were created in Autodesk Inventor 2010.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
A Análise Modal envolvendo apenas as respostas da estrutura é ainda um desafio que requer o uso de técnicas de identificação especiais. Este trabalho discute a identificação baseada apenas na resposta utilizando um método de identificação no tempo, mais especificamente, o método Identificação Estocástica de Subespaço. É mostrado que uma estrutura vibrando excitada por forças não conhecidas, pode ser modelada como um modelo de espaço de estado estocástico. A partir da aplicação de técnicas numéricas robustas como fatorização QR e Decomposição em Valores Singulares para a matriz bloco de Hankel semi-infinita, contendo os dados de resposta, é obtida a estimativa dos estados do modelo. Uma vez que os estados são conhecidos, o sistema de matrizes é encontrado através da solução de um problema de mínimos quadrados. Encontrado o modelo matemático da estrutura, os parâmetros modais são estimados diretamente através da decomposição em autovalores. O trabalho apresenta ainda uma metodologia que utiliza a função densidade de probabilidade para identificar possíveis componentes harmônicos contidos nos sinais de respostas. Os sinais são filtrados em uma faixa de freqüência contendo um provável modo e é verificado se este corresponde a um modo natural ou operacional. A metodologia é avaliada com dados simulados e experimentais e os resultados obtidos mostraram-se promissores para identificação dos parâmetros modais de sistemas estocásticos lineares e invariantes no tempo, utilizando apenas as respostas.
Modal analysis using output-only measurements is still a challenge in the experimental modal analysis community. It requires the use of special modal identification techniques. This work discusses the concepts involved in the output-only modal analysis and the implementation of the Stochastic Subspace Identification time domain method. It is shown that a vibrating structure excited by an unknown force can be modelled as a stochastic state space model. In this approach, the SSI method estimates the state sequences directly from the response data and the modal parameters are estimated by using the eigenvalues decomposition of the state matrix. The steps of the procedure are implemented using the well-known numerical linear algebra algorithms, Singular Value Decomposition and the QR decomposition. It also includes a methodology based on the Probability Density Function to identify harmonic components of the response signals. The signals are filtering in a range of frequency containing a mode, to verify if it is a natural or operational mode. The approach is evaluated with simulated and experimental data and the results have shown to be promising to identify the modal parameters of stochastic linear time-invariant systems, based only on the output data.

Esta tese consiste em apresentar um método para localização e identificação de consumidores com alta contribuição para a distorção harmônica de tensão medida em subestações de sistemas de distribuição de energia elétrica. Cabe comentar que a etapa de localização visa obter uma lista das possíveis posições onde possa estar alocado o consumidor que possua cargas não lineares com grande consumo de potências harmônicas. Partindo-se desta lista, realiza-se a etapa de identificação, em que são estimadas as amplitudes de cada harmônica na posição selecionada. Por fim, um algoritmo para ajuste/sintonia do método de localização é empregado com o intuito de se realizar uma possível correção com relação à posição do consumidor. Desta forma, por meio de estudos de caso (simulados), os resultados obtidos procuram validar a metodologia proposta.
This thesis provides a method for location and identification of consumers with larger contribution to harmonic distortion of voltage in power distribution substations. It is worth to mention that the stage of consumers location must furnish a list of possible positions where there may be consumers, who have nonlinear loads with high consumption of harmonic power. From this list, the identification stage is performed in order to estimate the amplitude of each harmonic from the location selected. Finally, a method for improve the location algorithm is employed in order to refine the consumer position. Therefore, by means of simulated case studies, the results obtained for these stages seek to validate the methodology proposed.

This research presents a pulse-by-pulse analysis of Oscillometric blood pressure waveform at systolic, diastolic and mean arterial pressure points. Using a mathematical optimization technique, pulses are characterized into component harmonic by minimizing the least square error. The results at the important pressure points are analyzed and compared for different subject using different waveform extraction techniques. Blood pressure is estimated using the harmonic parameters. The approach studies changes in the parameters as oscillometric blood pressure recording is done. 8 harmonic parameters are obtained from the pulse characterization and are used to estimate Systolic arterial Blood Pressure, Mean arterial Blood Pressure, and Diastolic arterial Blood Pressure. The estimates are compared with our reference value to determine which has the best agreement. The proposed method is further compared with Maximum Amplitude Algorithm and Pulse Morphology Algorithm. The effect of oscillometric waveform extraction methods on the proposed method is observed. The experiment established the fact that the extraction technique can alter the shape of oscillometric pulses. The methods were compared and it was observed that the used extraction methods did not make any significant difference on the accuracy, using this technique.

Includes bibliographical references.
Harmonic distortion of three phase power systems is caused by large amounts of electric power consumers using power electronic installations (e.g. drives and rectifiers). It has a number of undesirable consequences and has become an increasingly important problem with the rapid growth and ready availability of the power electronic devices and installations. A famous mathematical technique called "symmetrical components" was used to model the fundamental components of three phase systems. This method was extended to various harmonics. The aim of this thesis is to measure both the magnitude and phase angles of various harmonics which exist in three phase power systems, and to express them in symmetrical components. A digital electronics and microprocessor-based instrument was designed and constructed using the novel signal modulation technique called "+1 and -1" which was developed by the author of this thesis. This instrument was employed to achieve the above objectives.

This work deals with an origin of the harmonic currents, their classification into symmetrical components and their influence on neutral conductor in distribution systems. It analyses the heat strain increase in distribution cables and distortion of supply tension in consequence of harmonic zero component flows in distribution system and it provides possibilities of neutral conductor overload and break-in protection.

L'augmentation considérable ces dernières années du nombre de convertisseur sur le réseau d'alimentation se traduit par la nécessite de s'intéresser a la compatibilité entre les convertisseurs et le réseau. Le redresseur à mli est un convertisseur dont les caractéristiques lui permettent d'absorber des courants réseaux sinusoïdaux, et d'échanger de la puissance active et réactive avec le réseau. Le présent travail concerne l'étude de la modélisation et la commande de ce convertisseur ainsi que l'extension au cas d'un réseau déséquilibre. Le redresseur est contrôlé par une régulation cascade: des boucles internes régulent les courants réseaux, une boucle externe régule la tension de capacité. Les conséquences de l'apparition d'une perturbation de type creux de tension (distorsion harmonique sur les courants réseaux, oscillation a l'harmonique 2 des composantes continues) sont analysées puis simulées et vérifiées expérimentalement. Deux solutions sont étudiées: - une compensation s'appuyant sur une étude théorique du système. - la construction d'un régulateur robuste appliquant le principe du modèle interne de Wohnam et la méthode de placement de pôles par -stabilité. Les avantages obtenus permettent d'envisager une meilleure continuité de fonctionnement face aux creux de tension, un dimensionnement réduit du convertisseur, et la conservation des performances. Les domaines d'application concernes sont varies. Dans le domaine industriel, il s'agit des alimentations à bon facteur de puissance ou des procédés nécessitant le réglage du réactif

This thesis describes the flexible voltage control of a multi-level-voltage-reinjection voltage source converter. The main purposes are to achieve reactive power generation flexibility when applied for HVdc transmission systems, reduce dynamic voltage balancing for direct series connected switches and an improvement of high power converter efficiency and reliability. Waveform shapes and the impact on ac harmonics caused by the modulation process are studied in detail. A configuration is proposed embracing concepts of multi level, soft-switching and harmonic cancellation. For the configuration, the firing sequence, waveform analysis, steady-state and dynamic performances and close-loop control strategies are presented. In order not to severely compromise the original advantages of the converter, the modulated waveforms are proposed based on the restrictions imposed mathematically by the harmonic cancellation concept and practically by the synthesis circuit complexity and high switching losses. The harmonic impact on the ac power system prompted by the modulation process is studied from idealistic and practical aspects. The circuit topology being proposed in this thesis is developed from a 12-pulse bridge and a converter used classically for inverting power from separated dc sources. Switching functions are deduced and current paths through the converter are analysed. Safe and steady-state operating regions of the converter are studied in phasor diagrams to facilitate the design of simple controllers for active power transfer and reactive power generations. An investigation into the application of this topology to the back-to-back VSC HVdc interconnection is preformed via EMTDC simulations.

La thèse étudie tout d’abord la relation entre les harmoniques à fentes du rotor (RSHs) et la vitesse du rotor instantanée. Pour suivre directement l'RSH, les exigences du système sont pleinement prises en compte.Dans un deuxième temps, les travaux de thèse ont permis de développer un système sans capteur en fonction de boucle à verrouillage de phase (PLL): La largeur de bande centrale est réglée en ligne sur la base des valeurs de référence, des fréquences d'alimentation et de glissement prévues au convertisseur PWM, la PLL est réglée pour suivre le rotor de la machine à RSH sans la nécessité de toute injection de signal à haute fréquence, ni en rotation, ni de pulsation. Ce système d'estimation de vitesse, qui est approprié pour le contrôleur scalaire, avait été intégré avec le lecteur scalaire, conduisant à un simple calcul peu exigeant, à faible coût de l’entraînement de la machine à induction sans capteur à faible coût. Les résultats expérimentaux montrent que le système est en mesure de suivre la vitesse de la machine dans une plage de vitesse très étendue.Enfin, un système sans capteur amélioré basé sur l'analyse de composant mineur (MCA) neurones est décrit. Selon la théorie de Pisarenko, il a été vérifié que le MC qui se trouve dans le sous-espace de bruit est orthogonale au sous-espace de signal, par conséquent, les fré-quences de signal contenues dans l'entrée peuvent être calculées à partir d'un polynôme formé par la MC. Classiquement, ce qui nécessitera la décomposition propre encombrants, néan-moins, la méthode de neurones proposée dans cette thèse peut récupérer le MC de façon ré-cursive avec moins de calculs et des performances améliorées d'erreur (la solution est sur un total de moins sens carré). En outre, l'estimateur de vitesse est appliquée à l'entraînement scalaire avec vérification expérimentale, l'ensemble du système se comporte bien, et la méthode MCA renforcée par réseaux neuronaux a fourni un bon potentiel dans l'application des harmoniques récupérer
The thesis first studies the relation between the rotor slot harmonics (RSHs) and the instan-taneous rotor speed. To directly track the RSH, the requirements of the system are fully ad-dressed.Second, the thesis presents a sensorless scheme based on phase-locked loop (PLL): The centre bandwidth is tuned on-line on the basis of the reference values of the supply and slip frequencies provided to the PWM converter, the PLL is tuned to track the machine rotor slot-ting harmonic without the need of any high frequency signal injection, neither rotating nor pulsating. This speed estimation scheme, which is suitable for the scalar controller, had been integrated with the scalar drive, leading to a simple, computationally not demanding, low cost sensorless IM drives. The experiment results show that the system is able to track the machine speed in a very wide speed range.Finally, an improved sensorless scheme based on minor component analysis (MCA) neu-rons is described. According to the Pisarenko’s theory, it has been verified that the MC which lies in the noise subspace is orthogonal to the signal subspace, thus, the signal frequencies contained in the input can be computed from a polynomial formed by the MC. Conventional-ly, this will require the bulky eigen-decomposition, nevertheless, the neural method proposed in this thesis can retrieve the MC recursively with less computation and improved error per-formance (the solution is of total least square meaning). Moreover, the speed estimator is ap-plied to the scalar drive with experimental verification, the overall system is well behaved, and the MCA method enhanced by neural networks has provided a good potential in the ap-plication of harmonics retrieve

In 1997 the Federal Communications Commission (FCC) released 300 MHz of spectrum between 5-6 GHz designated the unlicensed national information infrastructure (U-NII) band. The intention of the FCC was to provide an unlicensed band of frequencies that would enable high-speed wireless local area networks (WLANs) and facilitate wireless access to the national information infrastructure with a minimum interference to other devices. Currently, there is a lack of cost-effective technologies for developing U-NII band components. With the commercial market placing emphasis on low cost, low power, and highly integrated implementations of RF circuitry, alternatives to the large and expensive distributed element components historically used at these frequencies are needed. Silicon Germanium (SiGe) BiCMOS technology represents one possible solution to this problem. The SiGe BiCMOS process has the potential for low cost since it leverages mature Si process technologies and can use existing Si fabrication infrastructure. In addition, SiGe BiCMOS processes offer excellent high frequency performance through the use of SiGe heterojunction bipolar transistors (HBTs), while coexisting Si CMOS offers compatibility with digital circuitry for high level 'system-on-a-chip' integration. The work presented in this thesis focuses on the development of a SiGe RFIC front-end for operation in the U-NII bands. Specifically, three variants of a packaged low noise amplifier (LNA) and a packaged active x2 sub-harmonic mixer (SHM) have been designed, simulated and measured. The fabrication of the Rifts was through the IBM SiGe foundry; the packaging was performed by RF Micro devices. The mixer and LNA designs were fabricated on separate die, packaged individually, and on-chip matched to a 50 ohm system so they could be fully characterized. Measurements were facilitated in a coaxial system using standard FR4 printed circuit boards. The LNA designs use a single stage, cascoded topology. The input ports are impedance matched using inductive emitter degeneration through bondwires to ground. One version of the LNA uses an shunt inductor/series capacitor output match while the other two variation use a series inductor output match. Gain, isolation, match, linearity and noise figure (NF) were used to characterize the performance of the LNAs in the 5 - 6 GHz frequency band. The best LNA design has a maximum gain of 9 dB, an input VSWR between 1.6:1 and 2:1, an output match between 1.7:1 and 3.6:1, a NF better than 3.9 dB and an input intercept point (IIP3) greater than 5.4 dBm. The LNA operates from a 3.3 V supply voltage and consumes 4 mA of current. The SHM is an active, double-balance mixer that achieves x2 sub-harmonic mixing through two quadrature (I/Q) driven, stacked Gilbert-cell switching stages. Single-ended-to-differential conversion, buffering and I/Q phase separation of the LO signal are integrated on-chip. Measurements were performed to find the optimal operating range for the mixer, and the mixer was characterized under these sets of conditions. It was found that the optimal performance of the mixer occurs at an IF of 250-450 MHz and an LO power of -5 dBm. Under these conditions, the mixer has a measured conversion gain of 9.3 dB, a P_1-dB of -15.7 dBm and an 2LO/RF isolation greater than 35 dB at 5.25 GHz. At 5.775 GHz, the conversion gain is 7.7 dB, the P_1-dB is -15.0 dBm, and the isolation is greater than 35 dB. The mixer core consumes 9.5 mA from a 5.0 V supply voltage. This work is sponsored by RF Microdevices (RFMD)through the CWT a liate program.The author was supported under a Bradley Foundation fellowship.
Master of Science

Orientador: João Antônio Pereira
Banca: Luiz de Paula do Nascimento
Banca: Domingos Alves Rade
Resumo: A Análise Modal envolvendo apenas as respostas da estrutura é ainda um desafio que requer o uso de técnicas de identificação especiais. Este trabalho discute a identificação baseada apenas na resposta utilizando um método de identificação no tempo, mais especificamente, o método Identificação Estocástica de Subespaço. É mostrado que uma estrutura vibrando excitada por forças não conhecidas, pode ser modelada como um modelo de espaço de estado estocástico. A partir da aplicação de técnicas numéricas robustas como fatorização QR e Decomposição em Valores Singulares para a matriz bloco de Hankel semi-infinita, contendo os dados de resposta, é obtida a estimativa dos estados do modelo. Uma vez que os estados são conhecidos, o sistema de matrizes é encontrado através da solução de um problema de mínimos quadrados. Encontrado o modelo matemático da estrutura, os parâmetros modais são estimados diretamente através da decomposição em autovalores. O trabalho apresenta ainda uma metodologia que utiliza a função densidade de probabilidade para identificar possíveis componentes harmônicos contidos nos sinais de respostas. Os sinais são filtrados em uma faixa de freqüência contendo um provável modo e é verificado se este corresponde a um modo natural ou operacional. A metodologia é avaliada com dados simulados e experimentais e os resultados obtidos mostraram-se promissores para identificação dos parâmetros modais de sistemas estocásticos lineares e invariantes no tempo, utilizando apenas as respostas.
Abstract: Modal analysis using output-only measurements is still a challenge in the experimental modal analysis community. It requires the use of special modal identification techniques. This work discusses the concepts involved in the output-only modal analysis and the implementation of the Stochastic Subspace Identification time domain method. It is shown that a vibrating structure excited by an unknown force can be modelled as a stochastic state space model. In this approach, the SSI method estimates the state sequences directly from the response data and the modal parameters are estimated by using the eigenvalues decomposition of the state matrix. The steps of the procedure are implemented using the well-known numerical linear algebra algorithms, Singular Value Decomposition and the QR decomposition. It also includes a methodology based on the Probability Density Function to identify harmonic components of the response signals. The signals are filtering in a range of frequency containing a mode, to verify if it is a natural or operational mode. The approach is evaluated with simulated and experimental data and the results have shown to be promising to identify the modal parameters of stochastic linear time-invariant systems, based only on the output data.
Mestre

Les mémoires magnétiques actuelles commencent à atteindre leurs limites physiques en terme de stabilité, vitesse et consommation énergétique, alors que la course à la miniaturisation s'intensifie. Le champ émergeant de la spintronique étudie le comportement collectif des spins dans la matière ainsi que leurs interactions aux interfaces, afin de trouver une solution en termes de matériaux, architectures et sources excitatrices. En particulier, les matériaux antiferromagnétiques sont particulièrement prometteurs. Ces matériaux ordonnées sont abondants, naturellement stables, robustes, ultra rapides et compatibles avec l'électronique des isolants. En effet, la plupart des oxydes à base de métaux de transition sont des isolants antiferromagnétiques ayant leur fréquence de résonance dans le terahertz et un champ de flop de quelques dizaines de teslas. Ils peuvent aussi être semi-métalliques, métalliques, semiconducteurs, supraconducteurs ou multiferroïques. Cette thèse s'intéresse aux deux antiferromagnétiques: oxyde de nickel (NiO) et ferrite de bismuth (BiFeO₃). NiO est un antiferromagnétique type à température ambiante, avec une structure cristalline simple. Une étude basée sur des simulations dynamiques atomiques montre que des courants de spin atteignables peuvent réaliser une mémoire à trois états avec ce composé, avec un temps de réponse de l'ordre de la picoseconde. La simulation explique aussi la formation de structures chirales dans BiFeO₃, un antiferromagnétique également ferroélectrique, présentant un couplage magnétoélectrique entre ses deux ordres. Dans une deuxième partie, les domaines antiferromagnétiques dans BiFeO₃ sont observés expérimentalement par génération de seconde harmonique optique, avec une résolution spatiale de un micron. Les domaines antiferromagnétiques de BiFeO₃ sont ensuite excités par une impulsion laser intense, et la dynamique des deux ordres couplés (antiferromagnétisme et ferroélectricité) est étudiée dans le régime picoseconde. Enfin, l'injection d'impulsions de spins dans dans un antiferromagnétique, tel que BiFeO₃ ou NiO est envisagée en utilisant la génération de courant de spin induite par la désaimantation ultrarapide de couches adjacentes magnétiques par des impulsions laser
Current magnetic memory devices are reaching their physical limits in terms of stability, speed and power consumption as the race to miniaturization intensifies. The emergent research field of spintronics studies the collective behavior of spins in matter and their interplay at interfaces, to find new avenues in terms of materials, architectures and stimulation sources. A particularly promising group of materials are the antiferromagnets. These abundant magnetically ordered materials are naturally stable, robust, ultra-fast and compatible with insulator electronics. Indeed, most transition metal oxide compounds are antiferromagnetic insulators, have resonance in the terahertz range and flop fields of tens of teslas. They can also be semi-metals, metals, semiconductors, superconductors or multiferroics. This thesis focuses on two antiferromagnets: nickel oxide (NiO) and bismuth ferrite (BiFeO₃). NiO is the archetypical antiferromagnet at ambient temperature with a simple crystalline structure. Using dynamical atomistic simulations, I show that this compound can be the elemental brick of a three state memory device controlled by currently available pulses of spin currents, with a picosecond response time. The simulations also explain the formation of chiral structures in BiFeO₃, a ferroelectric antiferromagnet with magnetoelectric coupling between the two orders. In a second part, antiferromagnetic domains in BiFeO₃ are experimentally observed using second harmonic generation of light, with a sub-micron spatial resolution. Antiferromagnetic domains of BiFeO₃ are then excited by an intense femtosecond laser pulse, and the dynamics of the two coupled orders (antiferromagnetism and ferroelectricity) is studied with a sub-picosecond time resolution. Finally, the injection of spin current in an antiferromagnet such as BiFeO₃ or NiO is envisioned by characterizing the spin bursts generated by ultrafast laser-induced demagnetization of adjacent ferromagnetic layers

It is known from the literature that conventional voltage and current transformers measure inaccurate values for voltage and current harmonics which are parts of power quality. Maximum bandwidth of conventional current transformers, which are used in electricity transmission and distribution systems, is 1.5-2 kHz and it is lower for conventional voltage transformers. Also, it is known that
voltages in some frequency spectrum are measured higher and voltages in another frequency spectrum are measured lower by the conventional voltage transformers. Furthermore, because of the phase shift of fundamental component caused by the conventional current and voltage transformers, losses and efficiency can not be calculated accurately. In this work, through the simultaneous measurements taken at the same feeder by both conventional transformers and new technology measurement transformers
amplitude and phase shift errors which are caused by conventional transformers depending on frequency and so harmonics, are examined and evaluated. Amplitude coefficients and phase shifts are determined for different types of conventional transformers to be able to calibrate measurement deviation. Through this work, measured data by conventional transformers will be accurate and realistic in terms of harmonic components. This matter is important to determine whether the accurate limits which will be set in the future possibly concerning with harmonics and interharmonics, are surpassed or not
also for punitive sanction.

Orientador: Luís Carlos Origa de Oliveira
Banca: Júlio Borges de Souza
Banca: Olivio Carlos Nascimento Souto
Resumo: O acelerado desenvolvimento da eletrônica de potência vem desencadeando uma série de transformações no sistema elétrico, sendo possível destacar a constante alteração da natureza das cargas consumidoras, a proliferação da co-geração e o peso crescente de questões ambientais relacionadas à questão da geração. Grande parte das cargas atuais é composta por dispositivos não-lineares que, por muitas vezes, são a causa de problemas relacionados à qualidade da energia elétrica. Considerando a variedade da distribuição sequencial das harmônicas de corrente na utilização dos filtros passivos, destacam-se os filtros e bloqueadores eletromagnéticos, os quais têm merecido especial atenção devido à sua robustez e baixo custo de implantação. Este trabalho está particularmente direcionado à investigações relacionadas ao uso desses dispositivos que possibilitam uma atenuação do fluxo das principais componentes harmônicas que compõe as distorções harmônicas de sequência zero. Neste contexto, esta dissertação apresenta contribuições inéditas relacionadas com o desenvolvimento de modelos matemáticos no domínio da frequência para bloqueadores eletromagnéticos, e um estudo de modelos matemáticos para filtros eletromagnéticos, compondo então, o aqui denominado supressor eletromagnético de componentes de sequência zero. Apresenta-se ainda, a utilização de metodologias para análise de desempenho baseado no comportamento das componentes harmônicas sequenciais. É estabelecida uma base comparativa de natureza experimental que possibilita a avaliação do desempenho e da aderência do modelo proposto. São utilizados protótipos de baixa potência de um filtro e um bloqueador, ambos eletromagnéticos, construídos a partir de análises teóricas. Os modelos desenvolvidos são utilizados na composição de um aplicativo computacional para análise... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The accelerated development of power electronics has promoted a series of changes in the electrical system, so it is possible to highlight the constant changing of consumer loads, the proliferation of co-generation and the growing importance of environmental issues related to generation. Much of the current loads are composed of non-linear devices which, in many cases are the cause of problems related to power quality. Considering the sequential distribution variety of harmonic currents in the use of passive filters, highlight the electromagnetic filters and blockers, which have received special attention due to its robustness and low cost of deployment. This work is particularly directed to investigations related to the use of these devices which enable an attenuation of the flow of the principal harmonic components that compound the zero-sequence harmonic distortion. In this context, this work presents unedited contributions related to the development of mathematical models in the frequency domain for electromagnetic blocking, and a study of mathematical models of electromagnetic filters, making then, the here called electromagnetic zero-sequence components suppressor. It presents also, the use of methodologies for performance analysis based on the sequential behavior of harmonic components. It is established a comparison basis of experimental nature that enables the performance and adherence analysis of the model. Are used a low-power prototypes of a filter and a blocker, both electromagnetic, constructed from theoretical analysis. These models are used in the composition of a software for performance analysis and optimal project of harmonic filtering systems. This tool allows an individualized and systematic investigation of the electrical system behavior for distinct harmonic sequence components. Thus, through a detailed investigation it is possible to identify appropriated actions... (Complete abstract click electronic access below)
Mestre

Orientador: Sérgio Kurokawa
Resumo: Esta dissertação apresenta um estudo realizado sobre o método de recapacitação de linhas de transmissão por injeção de tensão de terceira harmônica (TTH). O método foi publicado em 2017 por Alaei e Khajehoddin como uma proposta mais economicamente viável de elevar a tensão de transmissão sem a necessidade de alterações nas estruturas das linhas de transmissão. A injeção de TTH em linhas convencionais tem como objetivo provocar um achatamento na forma de onda das tensões de fase, causando uma redução em seu valor de pico. O método se mostra vantajoso pelo fato de que a largura das faixas de servidão e as distâncias entre cabos condutores e solo são especificadas com base no valor de pico das tensões de fase. Logo, a redução da tensão de pico não somente permitiria às estruturas existentes transmitirem maior potência como também possibilitaria a construção de novas torres de transmissão com tamanho reduzido e faixas de servidão mais estreitas, tornando uma proposta economicamente atrativa para as companhias de transmissão de energia elétrica. No artigo em que o método de recapacitação em questão foi proposto, os autores realizam análises de tensões e correntes apenas nos terminais das LTs. A contribuição deste trabalho para os estudos do método de recapacitação por injeção de TTH, consiste nas análises feitas através de um modelo de linha de transmissão a parâmetros distribuídos, que permitiu o monitoramento das tensões de fase ao longo da extensão de linhas com diferentes comp... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: This work presents a study concerning the transmission line uprating method by injection of third harmonic voltage (THV). The method was published in 2017 by Alaei and Khajehoddin as a more economically feasible proposal to raise the transmission voltage level without the requirement for changes in the structural elements of overhead lines. The THV injection in conventional overhead lines aims to flatten the waveform of the phase voltages, resulting in a reduction in its peak values. This represents a significant advantage, since the specification of right-of-way (ROW) width and ground clearance bases on the peak value of the phase voltages. Therefore, a reduction in the peak voltage would not only allow the existing structures to transmit electricity at higher voltages but also the construction of new transmission towers with reduced size and narrower ROW, making it an economically attractive proposal for electric power transmission companies. In the article in which the referred uprating method was proposed, the authors perform voltage and current analyzes only at the TL ends. The contribution of this work to the studies of the uprating method by THV injection consists in the analyzes made through a distributed parameter transmission line model, which allowed the monitoring of the phase voltages along the extension of lines with different lengths, both at steady-state and during the system switching. The results showed that THV injection causes overvoltage along the extent ... (Complete abstract click electronic access below)
Mestre

Mestrado em Ciências do Mar e da Atmosfera
Ria de Aveiro is a shallow lagoon, located in the Northwest of Portugal, separated from the sea by a barrier island, with which is connected through an artificial channel fixed by breakwaters. This work aims to study the tidal changes induce by geomorphologic modifications occurred in Ria de Aveiro between 1987/88 and 2017, analysing the variations on the tidal amplitude and phase of tidal constituents: 𝑀2, 𝑆2, 𝑀4, 𝑀6 and 𝑀𝑆𝑓. This work also aims to determine the frequency of storm surge phenomena occurrence, between 2012 and 2017, determining which factors influence the generation of the storm - variation in atmospheric pressure, intensity and direction of the wind and precipitation - and verify the increase of the water level in Ria de Aveiro caused by these meteorological events. Data were collected on tidal gauges in the main channels of the lagoon. Annual amplitude and phase variation graphics of tidal constituents: 𝑀2, 𝑆2, 𝑀4, 𝑀6 and 𝑀𝑆𝑓 (which were computed using the T-Tide Matlab package), were drawn for the different years. This allowed to observe the annual tidal evolution and to verify if there had been any relevant changes during the time interval in which the data collection took place. Annual series of the residual meteorological tide were determined for each year between 2012 and 2017, by subtracting the astronomical predicted tides from the measured tidal signal, and to identify the distribution of the positive and negative anomalies in each station studied, and find the relationship between meteorological variables and the generation of tidal elevations. For this purpose, were drawn graphs of the atmospheric pressure, wind intensity and direction, precipitation and water level and residual graphs. From the results obtained, in general and for each station, the annual amplitude values are increasing while the phase is decreasing. Between 1987/88 and 2002/03 there was an increase in amplitude in the studied stations. This change is a consequence of the increase in the depth of the navigation channels due to dredging operations in 1998. From 2012 to 2017 and after the North breakwater extension there are no significant variations in tidal amplitude or phase. Thus, the extension of the North breakwater did not produce appreciable changes in the tidal dynamics in Ria de Aveiro. By the analysis of the meteorological tide was verified that positive anomalies are more frequent than negative. From the different events occurring between 2012 and 2017, only two positive storm surges influenced the entire lagoon, having been generated by adverse meteorological conditions verified at national level. The remaining were manifested only locally. The events with negative anomalies occurred in a smaller number. From the analysis of all the studied events, it was verified that the higher values of the level of the sea water did not result from the existence of meteorological tides, but from the spring tides. Therefore, the joining of a positive storm event at high tide of spring tides will constitute a high risk for the marginal areas of the lagoon, which may be flooded.
A Ria de Aveiro é um sistema lagunar pouco profundo situado na costa noroeste portuguesa, separado do mar por uma ilha barreira e está ligado ao mar por um canal fixado pelos molhes Norte e Sul. Neste trabalho pretende-se estudar as alterações das marés induzidas por modificações geomorfológicas entre 1987/88 a 2017, verificando as alterações na amplitude e fase dos constituintes de maré: 𝑀2, 𝑆2, 𝑀4, 𝑀6 e 𝑀𝑆𝑓, durante esse intervalo de tempo. Este trabalho também visa a determinação da frequência das sobre-elevações da maré de origem meteorológica na Ria de Aveiro, entre 2012 e 2017, determinando quais os fatores que mais as influenciam - variação na pressão atmosférica, intensidade e direção do vento e precipitação. Os dados utilizados neste trabalho foram recolhidos por marégrafos localizados nos principais canais da laguna. Foram elaborados gráficos de variação anual da amplitude e da fase dos constituintes de maré: 𝑀2, 𝑆2, 𝑀4, 𝑀6 e 𝑀𝑆𝑓 (determinados por análise harmónica usando a aplicação T-Tide do Matlab), para estudar a sua evolução entre 1987/88 e 2017, permitindo assim, verificar a existência de alterações relevantes ao longo do tempo. Séries anuais da maré meteorológica foram determinadas para cada ano entre o período de 2012 a 2017, subtraindo ao nível da água medido nos marégrafos a previsão da maré astronómica, para se fazer o estudo da distribuição das anomalias positivas e negativas em cada estação estudada, e compreendendo a relação entre as variáveis meteorológicas e a formação da sobre-elevação das marés. Com esta finalidade, foram elaborados gráficos da pressão atmosférica, intensidade e direção do vento, precipitação, o nível da água medido e com as residuais. A partir dos resultados obtidos, verifica-se que, para cada estação, de uma forma geral, os valores anuais de amplitude dos constituintes estudados, estão a aumentar enquanto a fase está a diminuir. Entre 1987/88 e 2002/03 houve um aumento de amplitude nas estações estudadas, sendo esta mudança uma consequência do aumento da profundidade dos canais de navegação devido às operações de dragagem realizadas em 1998. De 2012 a 2017, e após o aumento do molhe Norte, os valores anuais permitem concluir que não há variações significativas na amplitude ou fase. Assim, o aumento do molhe Norte não produziu mudanças significativas na dinâmica da maré na Ria de Aveiro. Através da análise da maré meteorológica, verificou-se que as anomalias positivas são mais frequentes do que anomalias negativas. Dos diferentes eventos ocorridos entre 2012 e 2017, apenas dois influenciaram toda a laguna, tendo sido determinados pelas condições meteorológicas adversas verificadas a nível nacional. Os restantes apenas ocorreram localmente. Os eventos de anomalias negativas ocorreram em menor número. Verificou-se ainda, que os valores mais altos do nível da água do mar registados não resultaram da existência de marés meteorológicas, mas foram devidos às marés vivas. Portanto, a ocorrência conjunta de marés vivas e condições meteorológicas extremas será um risco para as zonas envolventes à laguna, já que poderão ficar sujeitas a inundações.

The advent of high-fT silicon CMOS/BiCMOS technologies has led to a dramatic upsurge in the research and development of radio and microwave frequency integrated circuits (ICs) in silicon. The integration of silicon-germanium heterojunction bipolar transistors (SiGe HBTs) into established "digital" CMOS processes has provided analog performance in silicon that is not only competitive with III-V compound-semiconductor technologies, but is also potentially lower in cost. Combined with improvements in silicon on-chip passives, such as high-Q metal-insulator-metal (MIM) capacitors and monolithic spiral inductors, these advanced RF CMOS and SiGe BiCMOS technologies have enabled complete silicon-based RF integrated circuit (RFIC) solutions for emerging wireless communication standards; indeed, both the analog and digital functionalities of an entire wireless system can now be combined in a single IC, also known as a wireless "system-on-a-chip" (SoC). This approach offers a number of potential benefits over multi-chip solutions, such as reductions of parasitics, size, power consumption, and bill-of-materials; however, a number of critical challenges must be considered in the integration of such SoC solutions. The focus of this research is the application of SiGe BiCMOS technology to on-going challenges in the development of receiver components for high speed wireless data networks. The research seeks to drive SoC integration by investigating circuit topologies that eliminate the need for off-chip components and are amenable to complete on-chip integration. The first part of this dissertation presents the design, fabrication, and measurement of a 5--6GHz sub-harmonic direct-conversion-receiver (DCR) front-end, implemented in the IBM 0.5um 5HP SiGe BiCMOS process. The design consists of a fully-differential low-noise amplifier (LNA), a set of quadrature (I and Q)x~2 sub-harmonic mixers, and an LO conditioning chain. The front-end design provides a means to address performance limitations of the DCR architecture (such as DC-offsets, second-order distortion, and quadrature phase and amplitude imbalances) while enabling the investigation of high-frequency IC design complications, such as package parasitics and limited on-chip isolation. The receiver front-end has a measured conversion gain of ~18dB, an input second-order intercept point of +17.5dBm, and a noise figure of 7.2dB. The quadrature phase balance at the sub-harmonic mixer IF outputs was measured in the presence of digital switching noise; 90 balance was achieved, over a specific range of LO power levels, with a square wave noise signal injected onto the mixer DC supply rails. The susceptibility of receiver I/Q balance to mixed-signal effects in a SoC environment motivates the second part of this dissertation --- the design of a phase and amplitude tunable, quadrature voltage-controlled oscillator (QVCO) for the on-chip synthesis of quadrature signals. The QVCO design, implemented in the Freescale (formerly Motorola) 0.18um SiGe:C RFBiCMOS process, uses two identical, differential LC-tank VCOs connected such that the two oscillator outputs lock in quadrature to the same frequency. The QVCO designs proposed in this work provide the additional feature of phase-tunability, i.e. the relative phase balance between the quadrature outputs can be adjusted dynamically, offering a simulated tuning range of ~90+/-10â ¹degree> in addition, a variable-gain buffer/amplifier circuit that provides amplitude tunability is introduced. One potential application of the QVCO is in a self-correcting RF receiver architecture, which, using the phase and amplitude tunability of the QVCO, could dynamically adjust the IF output quadrature phase and amplitude balance, in near real-time, in the analog-domain. The need for high-quality inductors in both the DCR and QVCO designs motivates the third aspect of this dissertation --- the characterization and modeling of on-chip spiral inductors with patterned ground shields, which are placed between the inductor coil and the underlying substrate in order to improve the inductor quality factor (Q). The shield prevents the coupling of energy away from the inductor spiral to the typically lossy Si substrate, while the patterning disrupts the flow of induced image currents within the shield. The experimental effort includes the fabrication and testing of a range of inductors with different values, and different types of patterned ground shields in different materials. Two-port measurements show a ~50% improvement in peak-Q and a ~20% degradation in self-resonant frequency for inductors with shields. From the measured results, a scalable lumped element model is developed for the rapid simulation of spiral inductors with and without patterned ground shields. The knowledge gained from this work can be combined and applied to a range of future RF/wireless SoC applications. The designs developed in this dissertation can be ported to other technologies (e.g. RF CMOS) and scaled to other frequency ranges (e.g. 24GHz ISM band) to provide solutions for emerging applications that require low-cost, low-power RF/microwave circuit implementations.
Ph. D.

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O acelerado desenvolvimento da eletrônica de potência vem desencadeando uma série de transformações no sistema elétrico, sendo possível destacar a constante alteração da natureza das cargas consumidoras, a proliferação da co-geração e o peso crescente de questões ambientais relacionadas à questão da geração. Grande parte das cargas atuais é composta por dispositivos não-lineares que, por muitas vezes, são a causa de problemas relacionados à qualidade da energia elétrica. Considerando a variedade da distribuição sequencial das harmônicas de corrente na utilização dos filtros passivos, destacam-se os filtros e bloqueadores eletromagnéticos, os quais têm merecido especial atenção devido à sua robustez e baixo custo de implantação. Este trabalho está particularmente direcionado à investigações relacionadas ao uso desses dispositivos que possibilitam uma atenuação do fluxo das principais componentes harmônicas que compõe as distorções harmônicas de sequência zero. Neste contexto, esta dissertação apresenta contribuições inéditas relacionadas com o desenvolvimento de modelos matemáticos no domínio da frequência para bloqueadores eletromagnéticos, e um estudo de modelos matemáticos para filtros eletromagnéticos, compondo então, o aqui denominado supressor eletromagnético de componentes de sequência zero. Apresenta-se ainda, a utilização de metodologias para análise de desempenho baseado no comportamento das componentes harmônicas sequenciais. É estabelecida uma base comparativa de natureza experimental que possibilita a avaliação do desempenho e da aderência do modelo proposto. São utilizados protótipos de baixa potência de um filtro e um bloqueador, ambos eletromagnéticos, construídos a partir de análises teóricas. Os modelos desenvolvidos são utilizados na composição de um aplicativo computacional para análise...
The accelerated development of power electronics has promoted a series of changes in the electrical system, so it is possible to highlight the constant changing of consumer loads, the proliferation of co-generation and the growing importance of environmental issues related to generation. Much of the current loads are composed of non-linear devices which, in many cases are the cause of problems related to power quality. Considering the sequential distribution variety of harmonic currents in the use of passive filters, highlight the electromagnetic filters and blockers, which have received special attention due to its robustness and low cost of deployment. This work is particularly directed to investigations related to the use of these devices which enable an attenuation of the flow of the principal harmonic components that compound the zero-sequence harmonic distortion. In this context, this work presents unedited contributions related to the development of mathematical models in the frequency domain for electromagnetic blocking, and a study of mathematical models of electromagnetic filters, making then, the here called electromagnetic zero-sequence components suppressor. It presents also, the use of methodologies for performance analysis based on the sequential behavior of harmonic components. It is established a comparison basis of experimental nature that enables the performance and adherence analysis of the model. Are used a low-power prototypes of a filter and a blocker, both electromagnetic, constructed from theoretical analysis. These models are used in the composition of a software for performance analysis and optimal project of harmonic filtering systems. This tool allows an individualized and systematic investigation of the electrical system behavior for distinct harmonic sequence components. Thus, through a detailed investigation it is possible to identify appropriated actions... (Complete abstract click electronic access below)

This thesis presents a new DC/AC inverter circuit which is based on a switched-capacitor circuit topology with reduced components (power switch and capacitor) count for low power applications. The proposed circuit has distinct features of both voltage boost-up and near sinusoidal (multi-level/staircase) AC output voltage. The main idea is to utilise a simple circuit technique called resonant-based Double Switch Single Capacitor Switched-Capacitor (DSSC SCC) with variable duty cycle Pulse Width Modulation (PWM) control technique in such a way that multi-level voltage can be realised across a capacitor. In order to show the superiority of the applied technique, comparisons with other techniques/circuits configurations are presented. The circuit technique can significantly reduce the number of multiple stages of switched-capacitor circuit cells of the recent switched-capacitor multi-level inverter topology. The proposed inverter (with integrated DSSC SCC technique) can generate a line-frequency with 13-levels near sinusoidal AC output voltage with low total harmonics distortion. The output voltage can be achieved with the least number of components use and only a single DC source is used as an input. The proposed inverter topology is also reviewed against other inverter-based switched-capacitor circuit topology and the well-known multi-level inverter topology. The proposed inverter has shown a tremendous reduction in the total harmonics distortion and circuit component count in comparison with the recent Switched-Capacitor Boost multi-level inverter and the classical Cascaded H-Bridge multi-level inverter. Mathematical analysis shows the design of the proposed inverter and PSPICE simulation result to verify the design is also presented. The practical experiment implementation of the proposed system is presented and proves the correct operation of the proposed inverter topology by showing consistency between simulation results and practical results.

Orientador: Antonio Padilha Feltrin
Resumo: As redes elétricas de distribuição em sua maioria apresentam cargas elétricas desequilibradas. Por isso é necessário estudar as potências envolvidas em sistemas trifásicos desequilibrados e a compensação das mesmas. O desequilíbrio aumenta as perdas elétricas e diminui o fator de potência da rede elétrica. Esse trabalho propõe a compensação da potência reativa e do desequilíbrio na rede com a finalidade da diminuição das perdas elétricas e a compensação das componentes de sequência desequilibradas da corrente. A utilização da teoria da potência efetiva em sistemas desequilibrados permite calcular as potências reativas e de desequilíbrio, sendo estas as potências compensadas no método proposto. A teoria da potência efetiva mede a eficiência dos métodos testados. Os objetivos da compensação do desequilíbrio são reduzir as perdas elétricas no neutro e o fator de desequilíbrio da tensão, além da potência de desequilíbrio na rede, potência exclusiva do desequilíbrio e que não realiza trabalho. O método proposto para compensação do desequilíbrio e dos reativos na rede de distribuição a quatro fios consiste na alocação de capacitores em delta ou estrela nas barras trifásicas. O método proposto é comparado com dois métodos existentes na literatura. A comparação entre os métodos permite constatar que o método proposto é mais eficiente na redução do desequilíbrio conjuntamente com a compensação das perdas elétricas. Quanto maior é o desequilíbrio da rede elétrica maior é a vantagem da ... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Distribution electrical networks mostly have unbalanced electrical loads. Therefore it is necessary to study the powers involved in unbalanced three-phase systems and their compensation. The unbalance increases the power losses and decreases the power factor of the electrical network. This work proposes the compensation of the reactive power and the unbalance in the network with the purpose of reducing the power losses and the compensation of the unbalanced sequence components of the current. The use of the effective power theory in unbalanced systems allows to calculate the reactive and unbalanced power, these being the powers compensated in the proposed method. Effective power theory measures the efficiency of the methods tested. The objectives of the unbalance compensation are to reduce the power losses in the neutral and the unbalance factor of the voltage, besides the unbalanced power in the network, exclusive power of the unbalance and that do not realize work. The proposed method for unbalance and reactive compensation in the four-wire distribution network consists of the allocation of delta or wye-connected capacitors to the three-phase bus. The proposed method is compared with two methods in the literature. The comparison between the methods allows to verify that the proposed method is more efficient in reducing the unbalance together with the compensation of the power losses. The greater the unbalance in power network, the greater the advantage of the compensation b... (Complete abstract click electronic access below)
Doutor

Oberschwingungen als ein Merkmal der Elektroenergiequalität gewinnen durch die starke Netzintegration leistungselektronisch geregelter Anlagen wie Windenergieanlagen und nichtlineare Lasten zunehmend an Bedeutung. Bestehende Normen entsprechen nicht den zukünftigen Erfordernissen des Elektroenergiesystems und bedürfen diesbezüglich einer Überarbeitung. In der Arbeit werden wesentliche Einflussfaktoren auf das Oberschwingungsverhalten von Windparks identifiziert, beschrieben und modelliert. Dabei wird der stochastische Charakter der Oberschwingungen mithilfe von probabilistischen Ansätzen erfasst. Des Weiteren wird ein neuer Ansatz zur Untersuchung der Wechselwirkung zwischen dem Windpark und dem vorgelagerten Netz entwickelt. Der Ansatz ermöglicht, die vom Windpark verursachte Änderung der Oberschwingungsspannung am Netzanschlusspunkt zu ermitteln. Diese Arbeit liefert einen Beitrag zur Verbesserung bestehender Normen für die Anbindung von Windparks
Harmonics, as one of the power quality criteria, are increasingly gaining attention due to the progressive contribution of renewable energy resources and the application of the nonlinear load in the power system. Current standards do not conform to the future requirements of the power system, thus requiring a revision. In this work, main influence factors on the harmonic behavior of wind farms are identified, explained, and modelled. Thereby, the stochastic nature of harmonics is taken into account using probabilistic approaches. Moreover, a novel approach is developed to investigate the interaction between the wind farm and the upstream grid. With the aid of this approach, it is possible to determine the voltage change caused by the wind farm at the point of connection. This work contributes to improve the existing standards for the connection of wind farms

PMMA is a widely used biomaterial especially in the fields of orthopedia, orthodontia and ophthalmology. When biocompatibility is considered, modification of the biomaterials&
#8217
surface may be needed to optimize interactions of the biomaterial with the biological environment. After the surface modifications one of the most important changes that occur is the change in the surface free energy (SFE). SFE is an important but an obscure property of the material and evaluation methods with different assumptions exist in the literature. In this study, SFE of pristine and oxygen plasma modified PMMA films were calculated by means of numerous theoretical approaches (Zisman, Saito, Fowkes, Berthelot, Geometric and Harmonic Mean and Acid-Base) using numerous liquids and the results were compared to each other to elucidate the differences of methods. Dispersive, polar, acidic and basic components of the SFE were calculated by the use of different liquid couples and triplets with the application of Geometric and Harmonic mean methods and Acid-Base approach. The effect of SFE and the components of SFE on the cell attachment efficiencies were examined by using fibroblast cells. It was observed that with the treatment of oxygen plasma, cell attachment capability and hydrophilicity of PMMA surfaces were altered depending on the applied power and duration of the plasma.

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This study objective was to analyze the space distribution of components of the reference evapotranspiration (ETo) in Brazil and afterwards the weather variability by applying the technique of harmonic analysis, given for this was initially an analysis of variance, phase and amplitude for the present time (1980-2000), subsequently made a projection of future time (2080-2100), based on scenario A2 of intergovernmental panel to Climatic changes. The equation used was Penman-Monteith sampled by Food and Agriculture and Organization of the United Nations (FAO) 1998. The simulations were conducted with the clime regional model (MM5), attached to a model of potential vegetation (MVP). The results show that under the actual conditions the model presented good performance of the annual cycle when compared to the ERA-40 and CRU data. The aero dynamical and radioactive terms presented an annual cycle that is dominant in the Amazonian and Brazil's south regions, while in the southeast region the semester cycle has a higher notability. The biggest variations at ETo amplitude were identified in northeastern semiarid and in the Brazil's extreme south. The changes in ETo due to the global warmness were maximum at the Brazil's central region and in the Amazonian region. In future conditions, the annual cycle showed itself dominant in Brazil's greatest part, presenting dry and rainy well defined weathers. Still was observed that under global warmness conditions the variations of aerodynamic term become more important than the variations of the irradiative terms to the total ETo.
O objetivo do presente estudo foi analisar a distribuição espacial dos componentes da evapotranspiração de referência (ETo) no Brasil e posteriormente a variabilidade temporal por meio da técnica da análise harmônica, sendo para isso foi feito inicialmente uma análise de variância, fase e amplitude para o tempo presente (1980-2000) e, posteriormente, feita uma projeção com o tempo futuro (2080-2100), com base no cenário A2 do Painel Intergovernamental para as Mudanças Climáticas. A equação utilizada foi a de Penman-Monteith padronizada pela Food and Agriculture and Organization of the United Nations (FAO) 1998. As simulações foram conduzidas com o modelo regional de clima (MM5), acoplado a um modelo de vegetação potencial (MVP). Os resultados mostram que sob condições atuais o modelo apresentou bom desempenho do ciclo anual quando comparado aos dados do ERA-40 e CRU. Os termos aerodinâmico e radiativo apresentaram um ciclo anual que é dominante na região Amazônica e sul do Brasil, enquanto na região sudeste o ciclo semestral tem maior destaque. As maiores variações na amplitude da ETo foram identificadas no semi-árido nordestino e no extremo sul do Brasil. As mudanças na ETo devido ao aquecimento global foram máximas na região central do Brasil e Amazônica. Em condições futuras, o ciclo anual apresentou-se dominante na maior parte do Brasil, indicando estações secas e chuvosas de forma bem definida. Ainda foi observado que sob condições de aquecimento global as variações do termo aerodinâmico tornam-se mais importantes que as variações do termo radiativo para a ETo total.

Les produits de contraste ultrasonore constituent un véritable apport pour l'imagerie échographique et sont aujourd'hui utilisés en clinique pour l'évaluation de la perfusion cardiaque ou encore la détection de tumeurs. Depuis quelques années, les transducteurs capacitifs micro-usinés (cMUTs) se présentent comme une alternative intéressante aux transducteurs piézoélectriques classiques et offrent certains avantages comme une large bande passante. Nous proposons dans cette thèse d'évaluer le potentiel de cette technologie pour l'imagerie de contraste. Dans un premier temps, notre étude s'est orientée vers l'adaptation des cMUTs à l'imagerie non linéaire. Ensuite, de nouvelles méthodes de détection de contraste, basées sur le comportement spécifique des microbulles, ont été développées pour exploiter les avantages de la technologie cMUT. Comparés aux méthodes conventionnelles, les résultats obtenus montrent une meilleure visualisation des agents de contraste par rapport aux tissus environnants. L'utilisation de cMUTs améliore l'efficacité de ces méthodes démontrant, ainsi, leur intérêt pour l'imagerie de contraste.

Дисертація на здобуття наукового ступеню кандидата технічних наук (доктора філософії) за спеціальністю 05.22.09 – "Електротранспорт" 141 – електроенергетика, електротехніка та електромеханіка) – Національний технічний університет "Харківський політехнічний інститут" МОН України. Харків, 2020. Дисертація присвячена створенню наукових основ вибору оптимальних параметрів та режимів роботи системи компенсації реактивної потужності на електровозах змінного струму та адаптації роботи системи компенсації до параметрів тягового електропостачання. Для виконання досліджень розроблені математичні та програмно-орієнтовані моделі роботи тягового та допоміжного приводу електровозу змінного струму (на прикладі електровозу ВЛ-80К). Відмінними особливостями цих моделей є можливість врахування взаємного впливу роботи тягового приводу і допоміжних агрегатів та режимів роботи електровозу. Виконано експериментальне підтвердження адекватності розроблених імітаційних моделей з реальним тяговим та допоміжним приводом для рухомого складу. На основі розроблених моделей досліджено електромагнітні процеси в тяговому та допоміжному приводах, що дозволило якісно та кількісно їх оцінити. Розроблено силову схему гібридного КРП та схему керування його активної частини. Основою системи керування є метод визначення спектрального складу тягового струму на основі алгоритму Левінсона-Дарбіна, що дозволить адаптувати роботу компенсатора до параметрів системи електропостачання. Запропоновано в системі допоміжного приводу застосувати статичний перетворювач замість фазорозчіплювача. Розрахунок втрат повної потужності до та після модернізації підтвердив економічну доцільність впровадження компенсатора реактивної потужності та застосування статичного перетворювача в системі допоміжних машин замість фазорозчіплювача. Розроблені наукові положення є ефективним інструментом модернізації існуючого парку вантажних електровозів змінного струму серій ВЛ-80Т та ВЛ-80К і створення нового електрорухомого складу залізниць. Результати дисертаційної роботи впроваджені у "Науково-дослідному та конструкторсько-технологічному інституті залізничного транспорту" АТ "Укрзалізниця" (м. Київ), ДП "Український науково-дослідницький інститут вагонобудування" (м. Кременчук) та у навчальному процесі Державного університету інфраструктури та технологій (м. Київ).
Thesis for a Candidate Degree in Engineering (Doctor of Philosophy) in specialty 05.22.09 - "Electrotransport" 141 - Electric Power Engineering, Electrical Engineering and Electromechanics) - National Technical University "Kharkiv Polytechnic Institute", MES of Ukraine. Kharkiv, 2020. The dissertation is devoted to creation of scientific bases of choice of optimum parameters and modes of operation of the system of reactive power compensation on electric locomotives operating on alternating current. The factors that have the greatest impact on the quality of traction power supply from the side of the electric rolling stock of alternating current are analyzed. Factors that cause the greatest distortion of the voltage form of the catenary include higher harmonic components, which are introduced into the traction power supply system by electric rolling stock. It is shown that such factors as poor current collection, passage of electric rolling stock of the feeder zone, the presence of several units of electric rolling stock in one feeder zone, modes of operation of electric rolling stock lead to the fact that the process of voltage change in the catenary is nondeterministic for the analysis of the spectral composition of the traction current of an electric locomotive, the application of classical Fourier transform methods is incorrect. Analysis of circuit solutions for compensation of reactive power consumed by electric rolling stock of alternating current showed that to date the most optimal solution is the use of hybrid compensators. In such compensators, the passive part reduces the phase shift between the voltage of the secondary winding of the traction transformer and the traction current, and the active part removes the higher harmonic components of the traction current. The active part of the hybrid compensator is a stand-alone current inverter and an inverter control system. The control system performs spectral analysis of the traction current, forms an algorithm for the generation of autonomous inverter higher harmonics, the same amplitude but antiphase to the higher harmonics of the traction current. Existing control systems use Fourier transform methods to determine the spectral components of the traction current, but in real operating conditions of the electric rolling stock they are incorrect. It is proposed to apply the methods of correlation spectral analysis to determine the spectral components of the traction current. Mathematical and program-oriented models of work of traction and auxiliary drive of an electric locomotive of an alternating current (on the example of the locomotive VL-80k) have been created. The unique features of these models are the ability to take into account the mutual influence of the traction and auxiliary drives and the operating modes of electric locomotives. The technique of calculating the parameters of asynchronous motors for asymmetrical stator windings has been improved. The relationship between such parameters as the scattering inductance and the mutual inductance with the geometric parameters of the windings is shown. This technique was used to create a mathematical model for the drive of auxiliary machines, in particular for the simulation of the phase splitter. It is proposed to investigate electrodynamic processes in auxiliary machine actuators in steady state operation, to replace the phase splitter with an asymmetrical voltage system that feeds the motors of fans. The mutual influence of traction actuator and auxiliary motors operation was investigated. The results of the study made it possible to clarify the spectral composition of the current in the traction and auxiliary drive circuits. The use of a hybrid reactive power compensator in traction drive circuits is substantiated. The elements of the passive and active part of the compensator are calculated. A control system for the active part of the reactive power compensator has been developed, which is based on the block of determination of harmonic components of traction current and suppression in the current spectrum of zero and higher harmonic components. A new scientific approach to the determination of the spectral components of the traction current is proposed. It is based on the application of the linear prediction method of Levinson-Darbin. This approach allows to take into account the random nature of the voltage and, as a consequence, the traction current, and to adapt the work of the compensator to the voltage of the contact network. The application of this approach also allows taking into account such factors as the nature of the mode of operation of the electric locomotive, the passage of the boundaries of the sections of the contact network, etc. Adjusted mathematical model of traction actuator when using of reactive power compensator, calculated and constructed amplitude-frequency and phase-frequency spectral characteristics of voltage and current on the traction winding of the transformer. The power factor of the upgraded traction actuator is calculated. The justified is use of a static converter instead of a phase splitter in the auxiliary drive power supply system. The system of mathematical modeling of the auxiliary drive of the electric locomotive is executed; the amplitude-frequency and phasefrequency spectral characteristics of the voltage on the winding of the transformer and the current flowing through the winding of its own needs are calculated and constructed. The power factor of the upgraded auxiliary actuator is calculated. The losses of active and full power in the traction and auxiliary drives of the locomotive were calculated before and after the modernization. The dependences of the efficiency and the power factor of the drives before and after the modernization were calculated. The results obtained indicate that the efficiency of the traction drive after the use of the compensator decreased by 0,6% a factor and the power factor increased by 3,2%. Auxiliary drive efficiency after upgrading increased by 1,5%, and power factor increased by 26,4%. The developed scientific provisions are an effective tool for modernization of the existing fleet of electric locomotives of the VL-80t and VL-80k series and the creation of a new electric rolling stock of railways. The results of the dissertation were implemented at the Scientific Research Design and Engineering Institute of Railway Transport of OJSC "Ukrzaliznytsya" (Kyiv), SE "Ukrainian Research Institute of Carriage" (Kremenchuk) and in the educational process of the State University of Infrastructure and Technology (Kyiv).

Дисертація на здобуття наукового ступеню кандидата технічних наук (доктора філософії) за спеціальністю 05.22.09 – "Електротранспорт" 141 – електроенергетика, електротехніка та електромеханіка) – Національний технічний університет "Харківський політехнічний інститут" МОН України. Харків, 2020. Дисертація присвячена створенню наукових основ вибору оптимальних параметрів та режимів роботи системи компенсації реактивної потужності на електровозах змінного струму. Проаналізовані фактори, що мають найбільший вплив на якість тягового електропостачання збоку електрорухомого складу змінного струму. До факторів, що вносять найбільше спотворення форми напруги контактної мережі слід віднести вищі гармонійні складові, які вносяться в систему тягового електропостачання електрорухомим складом. Показано, що такі чинники, як неякісне струмознімання, проходження електрорухомим складом фідерної зони, наявність декількох одиниць електрорухомого складу на одній фідерній зоні, режими робот електрорухомого складу призводять до того, що процес зміни напруги в контактній мережі є недетермінованим, неергодичним негаусовим процесом, при якому для аналізу спектральних складових тягового стуму електровозу застосування класичних методів перетворення Фур‘є є некоректним. Аналіз схемотехнічних рішень щодо компенсації реактивної потужності, яка споживається електрорухомим складом змінного струму, показав, що на сьогоднішній день найбільш оптимальним рішенням є застосування гібридних компенсаторів реактивної потужності (ГКРП). В таких компенсаторах пасивна частина зменшує фазовий зсув між напругою вторинної обмотки тягового трансформатора та тяговим струмом, активна частина – видаляє вищі гармонійні складові тягового струму. Пасивною частиною ГКРП є LC-фільтр, а активною - автономний інвертор струму і система керування інвертором. Система керування виконує спектральний аналіз тягового струму, формує алгоритм для генерації автономним інвертором вищих гармонік, однакових по амплітуді але протифазними до вищих гармонік тягового струму. В існуючих системах керування для визначення спектральних складових тягового струму використовуються методи перетворення Фур‘є, які в реальних умовах експлуатації електрорухомого складу дають некоректні результати. Запропоновано для визначення спектральних складових тягового струму застосувати методи кореляційного спектрального аналізу. Створено математичні та програмно-орієнтовані моделі роботи тягового та допоміжного приводу електровозу змінного струму (на прикладі електровозу ВЛ-80к). Відмінними особливостями цих моделей є можливість врахування взаємного впливу роботи тягового та допоміжного приводів, а також режимів роботи електровозу. Доопрацьовано методику розрахунку параметрів асинхронних двигунів при несиметричних обмотках статора. Показано взаємозв‘язок таких параметрів, як індуктивність розсіювання та взаємна індуктивність із геометричними параметрами обмоток. Ця методика використовувалась при створенні математичної моделі приводу допоміжних машин, зокрема для моделювання роботи розчіплювача фаз. Запропоновано для дослідження електродинамічних процесів в приводах допоміжних машин у сталому режимі роботи замінити розчіплювач фаз несиметричною системою напруги, яка живить мотор-вентилятори. Досліджено взаємний вплив роботи тягового приводу і приводу допоміжних машин. Результати дослідження дозволили уточнити спектральний склад струму в ланцюгах тягового та допоміжного приводів. Розраховано елементи пасивної та активної частин ГКРП. Розроблено систему керування активною частиною ГКРП, основою якого є блок визначення гармонійних складових тягового струму та видалення із спектру струму нульової та вищих гармонійних складових. Запропоновано новий підхід до визначення спектральних складових тягового струму, в основі якого лежить застосування методу лінійного прогнозування Левінсона-Дарбіна. Такий підхід дозволяє враховувати випадковий характер зміни напруги на струмоприймачі електровозу і, як наслідок, тягового струму, та адаптувати роботу компенсатора до параметрів напруги контактної мережі. Застосування зазначеного підходу дозволяє також враховувати такі фактори, як характер режиму роботи електровозу, прохід меж ділянок контактної мережі, тощо. Скорегована математична модель тягового приводу при застосуванні ГКРП, розраховано та побудовано амплітудно-частотні та фазо-частотні спектральні характеристики напруги та струму тягової обмотки трансформатора. Розраховано коефіцієнт потужності модернізованого тягового приводу. Обґрунтовано застосування в системі живлення допоміжних машин статичного перетворювача замість фазорозчіплювача. Виконано математичне моделювання системи допоміжного приводу електровозу, розраховано та побудовано амплітудно-частотні та фазочастотні спектральні характеристики напруги на обмотці власних потреб трансформатора та струму, що протікає по обмотці власних потреб. Розраховано коефіцієнт потужності модернізованого допоміжного приводу. Розраховано втрати активної та повної потужності в тяговому та допоміжному приводах електровозу до та після модернізації. Розраховано залежності ККД і коефіцієнту потужності приводів до та після модернізації. Отримані результати свідчать про те, що ККД тягового приводу після застосування компенсатора знизився на 0,6%, а коефіцієнт потужності збільшився на 3,2%. ККД допоміжного приводу після модернізації збільшився на 1,5%, а коефіцієнт потужності – на 26,4%. Розроблені наукові положення є ефективним інструментом модернізації існуючого парку вантажних електровозів змінного струму серій ВЛ-80т та ВЛ-80к і створення нового електрорухомого складу залізниць. Результати дисертаційної роботи впроваджені у "Науково-дослідному та конструкторсько-технологічному інституті залізничного транспорту" АТ "Укрзалізниця" (м. Київ), ДП "Український науково-дослідницький інститут вагонобудування" (м. Кременчук) та у навчальному процесі Державного університету інфраструктури та технологій (м. Київ).
Thesis for a Candidate Degree in Engineering (Doctor of Philosophy) in specialty 05.22.09 - "Electrotransport" 141 - Electric Power Engineering, Electrical Engineering and Electromechanics) - National Technical University "Kharkiv Polytechnic Institute", MES of Ukraine. Kharkiv, 2020. The dissertation is devoted to creation of scientific bases of a choice of optimum parameters and operating modes of system of compensation of reactive power on electric locomotives of alternating current. The factors that have the greatest impact on the quality of traction power supply from the side of the electric rolling stock of alternating current are analyzed. The factors that cause the greatest distortion of the voltage form of the catenary include the higher harmonic components, which are introduced into the traction power supply system by electric rolling stock. It is shown that such factors as poor current collection, passage of electric rolling stock of the feeder zone, the presence of several units of electric rolling stock in one feeder zone, modes of operation of electric rolling stock lead to the fact that the process of voltage change in the catenary is nondeterministic for the analysis of the spectral composition of the traction current of an electric locomotive, the application of classical Fourier transform methods is incorrect. The analysis of circuit solutions for the compensation of reactive power consumed by the electric rolling stock of alternating current showed that to date the most optimal solution is the use of hybrid reactive power compensators (НRPС). In such compensators, the passive part reduces the phase shift between the voltage of the secondary winding of the traction transformer and the traction current, the active part - removes the higher harmonic components of the traction current. The passive part of the НRPС is LC-filter, and the active stand-alone current inverter and control system of inverter. The control system of inverter performs spectral analysis of the traction current, forms an algorithm for the generation of autonomous inverter higher harmonics, the same amplitude but antiphase to the higher harmonics of the traction current. Existing control systems use Fourier transform methods to determine the spectral components of the traction current, but in real operating conditions of the electric rolling stock they are incorrect. It is proposed to apply the methods of correlation spectral analysis to determine the spectral components of the traction current. Mathematical and program-oriented models of operation of the traction and auxiliary drive of the AC electric locomotive (on the example of the VL-80k electric locomotive) were created. Distinctive features of these models are the ability to take into account the mutual influence of traction and auxiliary drives, as well as modes of operation of the electric locomotive. The method of calculating the parameters of induction motors with asymmetric stator windings has been improved. The relationship between parameters such as scattering inductance and mutual inductance with the geometric parameters of the windings is shown. This technique was used in the creation of a mathematical model of the drive of auxiliary machines, in particular for modeling the operation of the phase release. It is proposed to replace the phase release with an asymmetric voltage system that feeds the motor-fans to study the electrodynamic processes in the drives of auxiliary machines in steady-state operation. The mutual influence of the work of the traction drive and the drive of auxiliary machines is investigated. The results of the study allowed clarifying the spectral composition of the current in the circuits of traction and auxiliary drives. The elements of the passive and active parts of НRPС are calculated. A control system for the active part of the НRPС has been developed, the basis of which is a unit for determining the harmonic components of the traction current and removing zero and higher harmonic components from the current spectrum. A new approach to determining the spectral components of traction current is proposed. This approach is based on the application of the Levinson-Darbin linear prediction method. This approach allows to take into account the random nature of the voltage change at the current collector of the electric locomotive and, as a consequence, the traction current, and to adapt the operation of the compensator to the voltage parameters of the catenary. The application of this approach also allows taking into account such factors as the nature of the mode of operation of the electric locomotive, the passage of the boundaries of the catenary, and so on. The mathematical model of the traction drive when using НRPС is corrected, the amplitude-frequency and phase-frequency spectral characteristics of the voltage and current of the traction winding of the transformer are calculated and constructed. The power factor of the modernized traction drive is calculated. The use of a static converter instead of a phase breaker in the power supply system of auxiliary machines is substantiated. Mathematical modeling system of auxiliary drive of the electric locomotive is performed, amplitude-frequency and phase-frequency spectral characteristics of the voltage of the winding of the transformer's own winding and the current flowing in the winding of the own needs are calculated and constructed. The power factor of the modernized auxiliary drive is calculated. The losses of active and full power in the traction and auxiliary drives of the electric locomotive before and after the modernization are calculated. The dependences of factor efficiency and factor power of drives before and after modernization are calculated. The obtained results show that the factor efficiency of the traction drive after the application of the compensator decreased by 0,6%, and the power factor increased by 3,2%. The factor efficiency of the auxiliary drive after modernization increased by 1,5%, and the power factor - by 26,4%. The developed scientific provisions are an effective tool for modernization of the existing fleet of electric locomotives of the VL-80t and VL-80k series and the creation of a new electric rolling stock of railways. The results of the dissertation were implemented at the Scientific Research Design and Engineering Institute of Railway Transport of OJSC "Ukrzaliznytsya" (Kyiv), SE "Ukrainian Research Institute of Carriage" (Kremenchuk) and in the educational process of the State University of Infrastructure and Technology (Kyiv).

The ability of a piezoelectric transducer in energy conversion is rapidly expanding in several applications. Some of the industrial applications for which a high power ultrasound transducer can be used are surface cleaning, water treatment, plastic welding and food sterilization. Also, a high power ultrasound transducer plays a great role in biomedical applications such as diagnostic and therapeutic applications. An ultrasound transducer is usually applied to convert electrical energy to mechanical energy and vice versa. In some high power ultrasound system, ultrasound transducers are applied as a transmitter, as a receiver or both. As a transmitter, it converts electrical energy to mechanical energy while a receiver converts mechanical energy to electrical energy as a sensor for control system. Once a piezoelectric transducer is excited by electrical signal, piezoelectric material starts to vibrate and generates ultrasound waves. A portion of the ultrasound waves which passes through the medium will be sensed by the receiver and converted to electrical energy. To drive an ultrasound transducer, an excitation signal should be properly designed otherwise undesired signal (low quality) can deteriorate the performance of the transducer (energy conversion) and increase power consumption in the system. For instance, some portion of generated power may be delivered in unwanted frequency which is not acceptable for some applications especially for biomedical applications. To achieve better performance of the transducer, along with the quality of the excitation signal, the characteristics of the high power ultrasound transducer should be taken into consideration as well. In this regard, several simulation and experimental tests are carried out in this research to model high power ultrasound transducers and systems. During these experiments, high power ultrasound transducers are excited by several excitation signals with different amplitudes and frequencies, using a network analyser, a signal generator, a high power amplifier and a multilevel converter. Also, to analyse the behaviour of the ultrasound system, the voltage ratio of the system is measured in different tests. The voltage across transmitter is measured as an input voltage then divided by the output voltage which is measured across receiver. The results of the transducer characteristics and the ultrasound system behaviour are discussed in chapter 4 and 5 of this thesis. Each piezoelectric transducer has several resonance frequencies in which its impedance has lower magnitude as compared to non-resonance frequencies. Among these resonance frequencies, just at one of those frequencies, the magnitude of the impedance is minimum. This resonance frequency is known as the main resonance frequency of the transducer. To attain higher efficiency and deliver more power to the ultrasound system, the transducer is usually excited at the main resonance frequency. Therefore, it is important to find out this frequency and other resonance frequencies. Hereof, a frequency detection method is proposed in this research which is discussed in chapter 2. An extended electrical model of the ultrasound transducer with multiple resonance frequencies consists of several RLC legs in parallel with a capacitor. Each RLC leg represents one of the resonance frequencies of the ultrasound transducer. At resonance frequency the inductor reactance and capacitor reactance cancel out each other and the resistor of this leg represents power conversion of the system at that frequency. This concept is shown in simulation and test results presented in chapter 4. To excite a high power ultrasound transducer, a high power signal is required. Multilevel converters are usually applied to generate a high power signal but the drawback of this signal is low quality in comparison with a sinusoidal signal. In some applications like ultrasound, it is extensively important to generate a high quality signal. Several control and modulation techniques are introduced in different papers to control the output voltage of the multilevel converters. One of those techniques is harmonic elimination technique. In this technique, switching angles are chosen in such way to reduce harmonic contents in the output side. It is undeniable that increasing the number of the switching angles results in more harmonic reduction. But to have more switching angles, more output voltage levels are required which increase the number of components and cost of the converter. To improve the quality of the output voltage signal with no more components, a new harmonic elimination technique is proposed in this research. Based on this new technique, more variables (DC voltage levels and switching angles) are chosen to eliminate more low order harmonics compared to conventional harmonic elimination techniques. In conventional harmonic elimination method, DC voltage levels are same and only switching angles are calculated to eliminate harmonics. Therefore, the number of eliminated harmonic is limited by the number of switching cycles. In the proposed modulation technique, the switching angles and the DC voltage levels are calculated off-line to eliminate more harmonics. Therefore, the DC voltage levels are not equal and should be regulated. To achieve this aim, a DC/DC converter is applied to adjust the DC link voltages with several capacitors. The effect of the new harmonic elimination technique on the output quality of several single phase multilevel converters is explained in chapter 3 and 6 of this thesis. According to the electrical model of high power ultrasound transducer, this device can be modelled as parallel combinations of RLC legs with a main capacitor. The impedance diagram of the transducer in frequency domain shows it has capacitive characteristics in almost all frequencies. Therefore, using a voltage source converter to drive a high power ultrasound transducer can create significant leakage current through the transducer. It happens due to significant voltage stress (dv/dt) across the transducer. To remedy this problem, LC filters are applied in some applications. For some applications such as ultrasound, using a LC filter can deteriorate the performance of the transducer by changing its characteristics and displacing the resonance frequency of the transducer. For such a case a current source converter could be a suitable choice to overcome this problem. In this regard, a current source converter is implemented and applied to excite the high power ultrasound transducer. To control the output current and voltage, a hysteresis control and unipolar modulation are used respectively. The results of this test are explained in chapter 7.

In modern power systems, there is a great demand to control the power flow actively. Power flow controlling devices (PFCDs) are required for such purpose, because the power flow over the lines is depends on the nature of the impedance of the each line. Due to the control capabilities of different types (of PFCDs, the trend is that mechanical PFCDs are gradually being replaced by Power Electronics (PE) PFCDs. Among all Power Electronic PFCDs, the Unified Power Flow Controller (UPFC) is the most versatile device. However, the UPFC is not widely applied in utility grids, because the cost of such device is much higher than the rest of PFCDs and the reliability is relatively low due to its complexity. The objective of this project is to present a new PFCD that offers the same control capability as the UPFC, at a reduced cost and with an increased reliability. The new device, so-called Distributed Power Flow Controller (DPFC), is introduced and presented in this project. The DPFC is a further development of the UPFC. The DPFC provides comparable performance as the combined FACTS device - the UPFC, acceptable cost to electric utilities and reliability for power systems. The DPFC eliminates the common DC link within the UPFC, to enable the independent operation of the shunt and the series converter. The DFACTS concept is employed in the design of the series converter. Multiple low-rating singlephase converters replace the high-rating three-phase series converter, which greatly reduces the cost and increases the reliability. The active power that used to exchange through the common DC link in the UPFC, is now transferred through the transmission line at the 3rd harmonic frequency. This project starts with the review the state-of-art of current PFCDs, followed by the research at the DPFC device level, including the operation principle, the modeling and control, and experimental demonstrations and the feasibility of the DPFC for real networks. The DPFC has been modeled in a rotating dq-frame. Based on this model, the basic control of the DPFC is developed. The basic control stabilizes the level of the capacitor DC voltage of each converter and ensures that the converters inject the voltages into the network according to the command from the central control. The shunt converter injects a constant current at the 3rd harmonic frequency, while its DC voltage is stabilized by the fundamental frequency component. For the series converter, the reference of the output voltage at the fundamental frequency is obtained from the central controller and the DC voltage level is maintained by the 3rd harmonic component.

The main purpose of spectral analysis in time series is to determine what patterns exist in a particular set of data. To accomplish this, one often calculates the Fourier periodogram of the data and inspects it for peaks. However, since the periodogram is not a consistent estimate of the true spectral density, peaks can be obscured. Therefore, it is necessary to test for significance of the peaks. One of the most widely used tests for significance of periodicities in the periodogram is Fisher's test. The test statistic for Fisher's test is the quotient of the maximum periodogram ordinate and the sum of all the ordinates. If the test statistic is too large, we reject the null hypothesis that the data are white noise. In this thesis, I develop a test for categorical time series which is an analog of Fisher's test for continuous parameter time series. The test involves finding the Walsh-Fourier periodogram of the data and then calculating the test statistic for Fisher's test. I explain the theory behind Walsh-Fourier analysis and compare the theory to that of Fourier analysis. Asymptotic results for the distribution of Fisher's test for Walsh-Fourier spectra are presented and compared with a simulated distribution. I also perform power studies in order to assess the detection capability of the test. In the presence of multiple peaks, this test tends to loose power. Therefore, I also explore several alternatives to Fisher's test for Walsh-Fourier spectra and apply all of the alternative methods to several real data sets.

碩士
中國醫藥大學
中西醫結合研究所碩士班
96
Wang, W.K. and his group had built up a physical model to simulate circulatory system. Then he developed “Organs resonance” theory, which the frequency spectrum analysis of radial artery can be response to internal conditions. Serial studies demonstrate that the pulse frequency spectrum analysis and resonance theory can support traditional Chinese medicine (TCM ) for basic physiologic theory. As we know, major alternations in maternal anatomy and physiology are required for a successful pregnancy. This study is the first time to read the women’s pulse spectra completely since first trimester to postpartum during their pregnancy. The pulse-reading system used in this study is PDS-2000 produced by Skylark Device & System Co. The measured pulse spectra were calculated through fast Fourier transform program to generate frequency spectra. Eighteen subjects were who are patient of the gynecology department of the Chinese Medicine University Hospital involved in this investigation. We measured the patients’ bilateral radial arteries pulse spectra in different stages of their pregnancy and within one month after delivery to compare the variation during the study period. The statistics results of original data revealed the intensity of primary(C0, as heart system), 1st(C1, as liver system), 2nd(C2, as kidney system) and 3rd(C3, as spleen system) harmonics are increasing significantly before delivery. They also have linear relationship within the time. But the statistics results based on spectra percentage shown that bilateral 1st(C1) and left 10th(C10, as intestinal system) harmonics were increased significantly and 4th(C4, as lung system), 5th(C5, as stomach system), 6th(C6, as gallbladder system), 7th(C7, bladder system) and 9th(C9, san-jiao system) decreased significantly. This study results indicated that pulse harmonic spectra analysis can reflect internal change objectively on harmonics variation during pregnancy. If we can conduct a further study for collecting more comprehensive pulse data, it would be helpful perform pulse diagnosis with computer.

Defence date: 26 May 2014
Examining Board: Professor Hanspeter Kriesi, EUI (Supervisor) Professor Stefano Bartolini, EUI Professor Roger Eatwell, Bath Professor Piero Ignazi, Bologna.
The protection of nature constitutes a core component of the ideology of contemporary far right political parties in Western Europe. Through a cross-national comparative study utilizing mixed methods, this research finds that the far right promotes policies aimed at protecting nature based on the connection of organic nationalism and political ecology, challenging perceptions in academia and society that the protection of nature is a leftwing issue or the domain of left-wing parties, and that far right positions regarding ecological issues are incompatible, oppositional, hostile, indifferent, and/or incoherent. Organic nationalist connections with the protection of nature, present at least from Romanticism to National Socialism, provide a theoretical framework to explain the position of contemporary far right parties, including the integration of elements of a critique of Judeo-Christian and Enlightenment ideas and subsequent modern developments perceived as breaking the cherished harmony between man and nature. Influenced by elements of this ecological worldview of organic nationalists of anti-anthropocentrism, organicism, and the sanctity and supremacy of nature, contemporary far right parties promote many ecological goals. A quantitative analysis of manifesto, media, and expert survey data and qualitative analysis of party documents indicate that nature protection for the far right is salient, fundamental, and comprehensive, particularly permeating a number of policy areas, including agriculture, animals, conservation, economics, energy, fish, immigration, individualism, international relations, science and technology, spatial planning, traditional culture, transportation, and waste management, and many associated sub-issues. Furthermore, a case study on Austria reveals that nature protection also remains an important priority for far right activity in a legislature. Overall, far right parties located further right on the political spectrum, or more organic nationalist, are more supportive of the protection of nature and adhere to a more ecological perspective.

In this thesis we investigate the experimental guided spherical harmonics based Head-Related Transfer Function (HRTF) modeling where HRTFs are parameterized as frequency and source location. We focus on efficiently representing the HRTF variations in sufficient detail by mathematical modeling and the experimental measurements. The goal of this work is towards an optimal functional HRTF modeling taking into account the demands of decreasing the computational cost and alleviating the HRTF interpolation and/or extrapolation in the headphone based binaural systems. To represent HRTF by models, we firstly consider the high variability of HRTFs among individuals caused by the differentiation of the scattering effects of the individual bodies on the sound waves. We conduct a series of statistical analyses on an experimental HRTF database of human subjects to reveal the correlation between the physical features of human beings, especially pinna, head, and torso, and the corresponding HRTFs. The strategy enables us to identify a minimal set of physical features which strongly influence the HRTFs in a direct physical way. We next consider the continuity of the HRTF representation in both spatial and frequency domain. We define a functional HRTF model class in which the HRTF spatial representation has been justified to be well approximated by a finite number of spherical harmonics while HRTF frequency representation remains the focus of this thesis. In order to seek an efficient representation for HRTF frequency portion, we derive a metric that is able to numerically evaluate the efficiency of different complete orthonormal bases. We show that the complex exponentials form the most efficient basis. Given the identified basis, we then provide a solution to determine the dimensionality of the representation. To represent HRTF by measurements, we firstly consider the required angular resolution and the most suitable sampling scheme taking into account the two dimensional angular direction and the wide audio frequency range. We review the spherical harmonic analysis of the HRTF from which the least required number of spatial samples for HRTF measurement is derived. Considering how the HRTF data should be sampled on the sphere, we propose a list of requirements for the determination of the HRTF measurement grid. In addition to explaining how to measure the HRTF over sphere according to the identified scheme, we propose a fast spherical harmonic transform algorithm. We next consider the feasible experimental setup for a non-anechoic situation, that is, the measurements can be made when there is some reverberation. We emphasize on the design of the test signal and the post-processing to extract HRTFs.

The subject of this diploma thesis is the harmony of the visual and verbal component in childrens' books. In the theoretical part, fundamental definitions of the underlying terms (visual component, ilustrator, verbal component in its written context, writer) with respect to scientific literature are given. Further, carefully selected opinions of experts on childrens' literature are delved into and supplmeneted with author's comments. The popularization of books for children is to be credited not only to experts from the specified field, but also to individuals who promote them to the general public by recognition awards. A detailed overview of authors of the past 70 years, i.e. from the turn of the first and second half of the 20th century up until today, is presented. The harmony of both, the visual and verbal component present in their works is further enquired. Selected books are introduced and classified in terms of the connection of their text and artistic components. The practical part of this thesis introduces the aggregate of conclusions drawn from teaching four lessons on the subject of literary education and an additional lesson on art education. The book used in class was Frantisek Skala's "Jak Cilek Lidu nasel". This work presents the preparation materials, descriptions of the lessons...

Programa doutoral em Engenharia Electrónica e de Computadores
Railway systems have progressively been developed since James Watt presented a technique of converting steam power into a circular movement back in 1763. With the novelty of steam engines at that time and the increasing of railway networks, railway industry quickly became an economic catalyst throughout the world due to the advantages of passenger and freight transport. In 1879, Siemens & Halske company introduced the world’s first electric train in the city of Berlin, consisting of a locomotive and three wagons, and supplied via an insulated third rail with 150 V direct current (DC). From that time, the world has begun to recognize the important transition from steam power to electric power, and the potential of the electrified railway as a mode of mass transport. Due to the plenty of fuel in the last century, Diesel trains were not only common, but they also dominated the railway sector for a few decades. Consequently, the development in the infrastructures of electric trains decelerated, and the path to having fully electrified trains was long enough. In this context, electric trains have introduced progressively, in which Diesel and electric power have been combined to create hybrid locomotives. However, and with the increased demand for transportation and the higher fuel prices in the last decades, electric trains can substantially offer lower operating costs and lower emissions compared with the Diesel-powered trains. Nowadays, most of the high-speed electric trains use alternating current (AC) power supply for their traction power systems, which provide better performance under long-distance power transmission than DC power supply. However, as the need for railway transportation increases due to more passengers and higher mobility requirements, more flexible and efficient traction systems are always needed. In Europe, AC traction power systems are mainly classified according to the voltage and frequency parameters (15 kV, 16.7 Hz) or (1×25 kV or 2×25 kV, 50 Hz). In all cases, railway operators have an absolute interest to run the electrified trains with the lowest possible operation and maintenance costs. In this context, power quality improvement at the three-phase power grid, associated with the AC electrified railway has drawn more attention in the last decades, especially after the evolution in the Power Electronics field. Subsequently, various solutions based on Power Electronics converters have been proposed to improve power quality in the electrified railway, e.g., the flexible AC transmission systems (FACTS). The rail power conditioner (RPC) is one of the FACTS devices that can be used to improve power quality by compensating harmonic contents, reactive power and negative sequence components of currents generated by the railway system. Among the other possible multilevel power converters, the modular multilevel converter (MMC) is an attractive solution for medium-voltage applications due to harmonics reduction, lower switching losses, and higher flexibility, scalability and reliability. Therefore, the MMC has been enhanced to be combined with the FACTS family. Taking into consideration the existing opportunities in the railway industry, not only in the development of the electric train itself, but also on the power quality improvement in the electrified railway, there is a strong investment in technological development for electrified railway systems. Therefore, this work presents a new topology of Power Electronics converter (RPC based on MMC) that compensates power quality problems associated with traction power systems, thus, reducing the operating costs of the electrified trains and increasing the power capacity of the electric traction grid. The main innovations of the RPC based on MMC are the integration of the MMC topology to operate as a railway power quality conditioner, benefiting from the advantages of the MMC in the traction power supply system. In this context, the research work proposed and developed in this Ph.D. thesis aimed to design, develop and validate a reduced-scale laboratory prototype of the RPC based on MMC, including all the necessary control algorithms and simulation models that are important to support the correct operation of the proposed system. Under simulation conditions, this work developed control algorithms for different RPC topologies, (full-bridge, half-bridge, three-wire, etc.) for demonstrating the general capabilities of the RPC system, and also for two different transformers connections (V/V and Scott). The most favorable RPC based on MMC topology (based on half-bridge MMC) was deeply and extensively simulated, namely employing predictive control approach. The experimental results obtained from a developed reduced-scale prototype confirm the validity of the presented control theory, as well as the power quality improvement capability of the proposed solution.
Os sistemas ferrovias foram progressivamente desenvolvidos desde que James Watt apresentou uma técnica de conversão da energia a vapor para um movimento circular em 1763. Com a novidade dos motores a vapor e a sua implementação nas redes ferroviárias, a indústria ferroviária rapidamente se tornou um catalisador econômico em todo o mundo devido às vantagens no transporte de passageiros e mercadorias. Em 1879, a empresa Siemens & Halske introduziu o primeiro comboio elétrico do mundo na cidade de Berlim, consistindo numa locomotiva com três vagões, alimentado por um terceiro trilho isolado alimentado com corrente contínua em 150 V (CC). A partir desse momento, o mundo começou a reconhecer a importante transição da energia a vapor para a energia elétrica e o potencial na ferrovia eletrificada como um meio de transporte de massa. Devido à abundância de combustível fóssil no século passado, os comboios a Diesel não eram apenas comuns, mas também dominaram o setor ferroviário. Consequentemente, o desenvolvimento das infraestruturas dos comboios elétricos desacelerou, e o caminho para haver comboios totalmente eletrificados tornou-se bastante longo. Nesse contexto, os comboios elétricos começaram a impor-se progressivamente, inicialmente pela combinação do motor Diesel e do motor elétrico, resultando numa locomotiva híbrida. No entanto, com o aumento da demanda pelo transporte, e com o aumento do preço dos combustíveis nas últimas décadas, os comboios elétricos afirmaram-se por poderem oferecer custos operacionais mais baixos, assim como melhor desempenho ambiental. Atualmente, a maioria dos comboios elétricos de alta velocidade utilizam sistema de tração em corrente alternada (CA), que oferece melhor desempenho na transmissão de energia a longa distância do que sistema de tração em corrente contínua CC. No entanto, o aumento do transporte ferroviário requer a melhoria da eficiência energética devido a haver mais passageiros e maiores requisitos de mobilidade. Na Europa, os sistemas de tração elétrica são classificados principalmente de acordo com os parâmetros de tensão e frequência (15 kV, 16,7 Hz) ou (1×25 kV ou 2×25 kV, 50 Hz). Em ambos os casos, os operadores ferroviários têm interesse absoluto em otimizar os custos. Nesse contexto, a melhoria da qualidade de energia elétrica na ferrovia suscitou mais atenção nas últimas décadas, principalmente pela introdução da eletrônica de potência. Posteriormente, várias soluções baseadas em conversores de eletrônica de potência foram propostas para melhorar a qualidade de energia elétrica na ferrovia, como por exemplo, os sistemas flexíveis de transmissão CA (FACTS – Flexible AC Transmission Systems). O condicionador ativo de potência ferroviário (RPC – Rail Power Conditioner) é um dos dispositivos FACTS que pode ser usado para melhorar a qualidade da energia elétrica, compensando o conteúdo harmônico, a potência reativa e os componentes de sequência negativa das correntes. Por outro lado, o conversor multinível modular (MMC – Modular Multilevel Converter) é uma solução atraente para aplicações de média tensão, devido à redução dos harmónicos e das perdas de comutação, e ao aumento da flexibilidade, confiabilidade e escalabilidade. Deste modo, o MMC foi aprimorado para ser integrado na família FACTS. Levando em consideração as oportunidades existentes no setor ferroviário, não apenas no desenvolvimento do próprio comboio elétrico, mas também na melhoria da qualidade de energia elétrica na ferrovia, existe um forte investimento no desenvolvimento tecnológico para os sistemas ferroviários eletrificados. Assim sendo, este trabalho apresenta uma nova topologia de conversor de eletrônica de potência (RPC baseado em MMC) que compensa os problemas de qualidade de energia elétrica associados aos sistemas de tração, reduzindo os custos operacionais dos comboios elétricos e otimizando a qualidade de energia da rede elétrica. As inovações principais do RPC baseado em MMC são a integração da topologia do MMC para operar como condicionador de qualidade de energia elétrica na ferrovia, beneficiando das vantagens do MMC. Neste contexto, o trabalho de investigação proposto e desenvolvido nesta tese apontou como objetivo projetar, desenvolver e validar um protótipo laboratorial em escala reduzida do RPC baseado em MMC, incluindo todos os algoritmos de controlo necessários e os modelos de simulação que são importantes para suportar a operação correta do sistema. Sob condições de simulação, este trabalho desenvolveu algoritmos de controlo para diferentes topologias do RPC (ponte completa, meia ponte, três fios, etc.), para demonstrar as capacidades gerais do sistema do RPC, e também para dois transformadores diferentes (V/V e Scott). O RPC mais favorável baseado na topologia do MMC (baseado no MMC de meia ponte) foi profunda e extensivamente simulado, nomeadamente utilizando uma abordagem de controlo preditivo. As simulações e os resultados experimentais confirmam a validade da teoria de controlo apresentada, bem como a capacidade de melhoria da qualidade de energia elétrica na solução proposta.
Fundação para a Ciência e a Tecnologia – FCT), which allowed me to continue my studies with the PD/BD/127815/2016 Ph.D. scholarship under the Innovation in Railway Systems and Technologies Doctoral Program – iRail.

This Master of Applied Science thesis proposes a new design of low power, power factor corrected (PFC), power supplies. By lifting the hold up time restriction for devices that have a battery built in, the energy storage elements of the converter can be reduced, permitting a small and inexpensive power converter to be built. In addition, a new control technique for controlling cascaded converters is presented, named duty mode control (DMC). Its advantages are shown through simulations. The system was proven using a prototype developed in the laboratory designed for a universal ac input voltage (85 - 265VRMS at 50 - 60Hz) and a 40W output at 12V. It consisted of two interleaved phases sensed and digitally controlled on the isolated side of the converter. The prototype was able to achieve a power factor of greater than 0.98 for all operating conditions, and input harmonic current distortion well below any set of standards.