Orientador: Carlos Alberto Favarin Murari / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-22T04:03:37Z (GMT). No. of bitstreams: 1 Duque_MarinaBorges_M.pdf: 1960535 bytes, checksum: 1d0e3bb5b148b1377f1e8e33d3ab25ac (MD5) Previous issue date: 2013 / Resumo: Para garantir o bom desempenho das redes de distribuição de energia elétrica, bem como aumentar a qualidade dos serviços prestados aos consumidores, faz-se necessário o desenvolvimento e a implementação de metodologias que permitam avaliar tanto os custos como os benefícios que trazem as diferentes alternativas de projeto propostas e os seus impactos no sistema como um todo, mantendo sempre aceitáveis os índices de qualidade e confiabilidade do fornecimento aos diferentes consumidores: residencial, comercial e industrial. Nesse contexto, um programa computacional que realize o cálculo dos fluxos de potência é uma ferramenta imprescindível na análise dos sistemas elétricos de potência tendo-se como principais grandezas de interesse, as tensões nas diferentes barras e os fluxos de potência ativa e reativa em todos os componentes da rede elétrica (linhas, transformadores, etc.). E como a maior parte das redes de distribuição de energia elétrica é trifásica, é de fundamental importância adotar uma formulação trifásica que represente de forma adequada os desequilíbrios, e, portanto nesta dissertação é apresentada uma versão de fluxo de carga trifásico baseada no Método Iterativo de Correção de Tensão com possibilidade de inserção de cargas não lineares para contemplar as frequências harmônicas e assim obter o estado da rede (magnitude e ângulo das tensões nodais) e também de outras grandezas elétricas contemplando os efeitos causados por cargas não lineares, com ênfase para o motor de indução trifásico / Abstract: To ensure a good performance of power distribution networks as well as to increase the quality of services provided for the consumers, it is necessary the development and implementation of methodologies to assess the costs and the benefits of the different operating alternatives and their impacts on the system as a whole, while maintaining acceptable levels of quality and the reliability of electricity supply to the various consumers: residential, commercial and industrial. In this context, a computer program that performs the calculation of power flows is an essential tool in the analysis of electrical power systems having as main quantities of interest - nodal voltages and active and reactive power flows - at all electrical network components (lines, transformers, etc.). Once the electrical distribution networks are three-phase, it is crucial to adopt a three-phase formulation that adequately represents the load unbalance. We propose a version of a three-phase load flow based on the Voltage Correction Iterative Method with the possibility of including non-linear loads - with emphasis for three-phase induction motor - to simulating harmonic frequencies and getting the corresponding node voltages and other electrical quantities / Mestrado / Energia Eletrica / Mestra em Engenharia Elétrica

Submitted by Renata Lopes (renatasil82@gmail.com) on 2015-12-16T11:21:48Z No. of bitstreams: 1 igordelgadodemelo.pdf: 4931795 bytes, checksum: cf03c45f0f2492c6cf9186af1b3866a2 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2015-12-16T11:57:23Z (GMT) No. of bitstreams: 1 igordelgadodemelo.pdf: 4931795 bytes, checksum: cf03c45f0f2492c6cf9186af1b3866a2 (MD5) / Made available in DSpace on 2015-12-16T11:57:23Z (GMT). No. of bitstreams: 1 igordelgadodemelo.pdf: 4931795 bytes, checksum: cf03c45f0f2492c6cf9186af1b3866a2 (MD5) Previous issue date: 2015-09-18 / Este trabalho objetiva apresentar uma metodologia capaz de estimar os componentes harmônicos em sistemas de distribuição com topologia radial utilizando PMUs (Phasor Measurement Units). Os estados a serem estimados serão as correntes passantes em todas as linhas do sistema em coordenadas retangulares. Uma vez que essas correntes são obtidas, torna-se possível o cálculo de outras grandezas elétricas através das equações de fluxo de potência e leis de Kirchhoff. A metodologia considera poucas unidades de medição fasorial (as PMUs) instaladas efetuando a leitura dos sinais de tensões nodais e correntes nas linhas com distorção harmônica. A fim de restaurar a observabilidade do sistema por completo, são considerados dados históricos de demanda de potência ativa/reativa, os quais serão tratados como restrições de desigualdades excursionando entre um valor mínimo e máximo considerados em um problema de otimização não linear que visa diminuir a diferença entre os valores monitorados pelas PMUs e os calculados pela metodologia. As mencionadas restrições permitem ao estimador o acompanhamento das variações sofridas ao longo do tempo na curva de carga para a frequência fundamental e também para as demais frequências. A abordagem proposta neste trabalho considera a modelagem trifásica de equipamentos e linhas de distribuição, portanto, são modelados os efeitos de acoplamento mútuo entre fases e a operação não linear de equipamentos de eletrônica de potência tiristorizados. O método demonstra eficiência não apenas em estimar os componentes harmônicos de um certo espectro considerado no estudo, como também se mostra uma ferramenta prática de detecção e identificação de fontes harmônicas no sistema elétrico de potência, além de explicitar um exemplo prático do uso de PMUs no que tange ao monitoramento de redes de distribuição, carentes de acompanhamento em tempo real. A metodologia ainda se mostra capaz de ser aliada a grandes estudos contextualizados em qualidade de energia, uma vez que permite a estimação de índices de distorção harmônica. / This work aims to present a methodology which is capable of estimating harmonic components for distribution systems with radial topology, using PMUs (Phasor Measurement Units). The estimated states will be all branch currents of the system expressed in rectangular coordinates. Once these currents are obtained, it is possible to calculate other electrical quantities using power flow equations and also Kirchhoff’s law. The methodology considers the installation of a few number of phasor measurement units which will measure voltage and branch currents signals distorted by harmonic sources. In order to make the whole system observable, historical data of active/reactive power demand will be treated as inequality constraints varying between minimum and maximum limits described in a non linear optimization problem, which aims to minimize the difference between the values monitored by PMUs and the ones calculated by the methodology. The already mentioned constraints allows the accompaniment of the variations occured in a typical load curve during a period of time for the fundamental frequency and also for their multiples, allowing the accompaniment of the harmonic load curve, normally unknown. The proposed approach considers a three-phase modelling of equipments and distribution lines, subject to their mutual coupling effects caused by mutual impedances between the lines. It will also be considered electronic-based devices using thyristors located along the distribution feeder, injecting harmonic currents in the system. The method demonstrates efficiency in estimating the harmonic states of the net and also in detecting and identifying harmonic sources in an eletric power system, besides showing a practical use of PMUs for the monitoring of distribution systems, lacking in information and real-time accompaniment. The method also enables the estimation of power quality indicators such as total harmonic distortion.

La synthèse d’images réalistes repose sur des modèles physiques décrivant les interactions entre la lumière et les matériaux attachés aux objets dans une scène tridimensionnelle. Ces modèles mathématiques sont complexes et, dans le cas général, n’admettent pas de solution analytique. Pour cette raison, l’utilisation de méthodes numériques robustes et efficaces est nécessaire. Les méthodes de Monte Carlo ou techniques alternatives comme l’utilisation de développement par fonction de base sont appropriées pour résoudre ce type de problème. Dans cette thèse par articles, nous présentons deux nouvelles techniques permettant l’in- tégration numérique efficace de matériaux complexes. En premier lieu, nous introduisons une nouvelle méthode permettant d’intégrer simultanément plusieurs dimensions définies dans le domaine angulaire et spatiale. Avoir une technique efficace est essentiel pour intégrer des matériaux avec des normales variant rapidement sous différentes conditions d’éclairage. Notre technique utilise une nouvelle formulation basée sur un histogramme sphérique définie de façon directionnelle et spatial. Ce dernier nous permet d’utiliser des harmoniques sphé- riques pour intégrer les différentes dimensions rapidement, réduisant le temps de calcul d’un facteur approximatif de 30× par rapport aux méthodes de l’état de l’art. Dans notre second travail, nous introduisons une nouvelle stratégie d’échantillonnage pour estimer le transport de lumière à l’intérieur de matériaux multicouches. En identifiant les meilleures stratégies d’échantillonnage, nous proposons une technique efficace et non biaisée pour construire des chemins de lumière à l’intérieur de ce type de matériau. Notre nouvelle approche permet d’obtenir un estimateur de Monte Carlo efficace et de faible variance dans des matériaux contenant un nombre arbitraire de couches. / Realistic computer generated images and simulations require physically-based models to properly capture and reproduce light-material interactions. The underlying mathematical formulations are complex and mandate the use of efficient numerical methods, since analytic solutions are not available. Monte Carlo integration is one such commonly used numerical method, although, alternative approaches leveraging, e.g., basis expansions, may be suitable to solve these challenging problems. In this thesis by articles, we present two works where we efficiently devise numerical integration strategies for the rendering of complex materials. First, we propose a method to compute a spatial-angular multi-dimensional integration problem present when rendering materials with high-frequency normal variation under large, angularly varying illumination. By computing and manipulating a novel spherical histogram data representation, we are able to use spherical harmonics to efficiently solve the integral, outperforming the state-of-the-art by a factor of roughly 30×. Our second work describes a high-performance Monte Carlo integration strategy for rendering layered materials. By identifying the best path sampling strategies in the micro-scale light transport context, we are able to tailor an unbiased and efficient path construction method to evaluate high throughput, low variance paths through an arbitrary number of layers.

L'analyse des propriétés statistiques de la distribution de la matière dans le cosmos (Grandes Structures, LSS or Large Scale Structure) est l'une des principales sondes cosmologiques qui permettent l'étude du modèle standard cosmologique, en particulier les paramètres caractérisant la matière noire et l'énergie noire. Les Oscillations Acoustiques Baryoniques (BAO's) sont l'une des mesures qui peuvent être extraites de l'étude de la distribution de matière à grande échelle (LSS).L'observation de la distribution cosmique de la matière à partir de l'émission à 21 cm de l'hydrogène atomique neutre (HI) est une nouvelle méthode, complémentaire des relevés optiques pour cartographier la distribution de la matière dans le cosmos. La méthode de cartographie d'intensité (Intensity Mapping) a été proposée depuis moins d'une dizaine d'années comme une méthode efficace pour cartographier en trois dimensions l'émission radio à 21 cm. Elle n'implique en particulier pas la détection des objets individuels (galaxies), et peut donc être effectué avec des instruments plus modestes en taille que ceux comme SKA ou FAST qui sont conçus pour détecter les galaxies à 21 cm à des distances cosmologiques. Des interféromètres radio utilisant un ensemble de réflecteurs cylindriques ou paraboliques fixes, observant le ciel en mode transit sont adaptés à la cartographie d'intensité. Le mode d'observation spécifique de ce type de radio télescope en cartographie d'intensité est étudié dans le cadre de ce travail de thèse. On montre en particulier qu'une méthode spécifique de reconstruction des cartes du ciel à partir des visibilités peut être appliquée aux observations de ces interféromètres fonctionnant en mode transit. Cette méthode correspond à la décomposition en modes m des harmoniques sphériques et est très performante pour la reconstruction de grandes zones du ciel observées en mode transit. Un code de reconstruction fondé sur ce principe a été développé, ainsi que différents critères de comparaison des performances instrumentales, comme le lobe d'antenne synthétisé, le spectre de bruit sur les cartes reconstruites et la réponse globale de l'instrument dans le plan (l,m) des harmoniques sphériques. La méthode a été appliquée à différentes configurations des interféromètres composés de réflecteurs paraboliques ou cylindriques dans le cadre des projets PAON-4 et Tianlai. Outre l'optimisation des configurations des interféromètres Tianlai et PAON-4, le travail présenté inclut une première application de la méthode aux données PAON-4. / The analysis of the statistical properties of the distribution of matter in the cosmos (LSS or Large Scale Structure) is one of the main cosmological probes that allow the study of the cosmological standard model, in particular the parameters characterizing dark matter and dark energy. Baryonic Acoustic Oscillations (BAO's) are one of the measurements that can be extracted from the study of matter distribution in large-scale structure (LSS).The observation of the cosmic distribution of the matter from neutral atomic hydrogen (HI) 21 cm emission is a new method, complementary to the optical observation to map the distribution of matter in the cosmos. In the last decade, the Intensity Mapping method has been proposed as an effective method for mapping the 21cm radio emission in three dimensions. In particular, it does not require the detection of individual objects (galaxies), and can therefore be performed with instruments smaller in size than those such as SKA or FAST, which are designed to detect 21 cm galaxies at cosmological distances. A radio interferometer using a set of fixed cylindrical or parabolic reflectors observing the sky in transit mode are suitable instruments for intensity mapping surveys. The specific observational mode from this type of radio telescope by intensity mapping is studied in the context of this thesis. We show in particular that a specific sky maps reconstruction method from the visibilities can be applied to the observations of these interferometers operating in transit mode. This method corresponds to the m-modes decomposition of the spherical harmonics and is very efficient for the reconstruction of large sky areas observed in transit mode. A reconstruction code based on this principle has been developed, as well as different criteria for the comparison of instrumental performances, such as the synthesized antenna lobe, the noise spectrum of the reconstructed maps and the overall instrument response in the spherical harmonics (l,m) plane. The method has then been applied to different configurations of interferometers composed of parabolic or cylindrical reflectors in the PAON-4 and Tianlai projects. In addition to optimizing the Tianlai and PAON-4 interferometer configurations, the work presented here includes a first application of the method to the PAON-4 data.

The aim of master thesis is to describe different calculation of global illumination methods including Light Propagation Volumes. All three steps of LPV calculation are widely described: injection, propagation and rendering. It is also proposed several custom extensions improving graphics quality of this method. Two parts of design and implementation are focused on scene description, rendering system, shadow rendering, implementation of LPV method and proposed extensions. As conclusion, measurement and several images of application are presented, followed by comparison in environment with diffenent parameters, thesis summary with evaluation of achieved results and suggestions of further improvements.

An AC system’s voltage unbalance by a fundamental frequency negative sequence system is usually the main cause for the emission of non-characteristic harmonics by current source converters as used in conventional HVDC systems. This emission takes place on both sides of each 12-pulse converter. On the DC side mainly a 2nd harmonic voltage appears driving a 2nd harmonic current. The magnitude of this harmonic current can exceed the magnitudes of the characteristic harmonics even if no low order resonance exists. Further non-characteristic harmonics generated by the converter under such unbalanced supply voltage conditions have frequencies with a frequency distance to the characteristic harmonics of 2 times the fundamental frequency. The main technical drawbacks are the unintended coupling between both AC systems and the risk of thyristor over-stresses by DC current discontinuities at low power transfer levels. On both AC sides the largest 2 non-characteristic current harmonics generated by a 12-pulse HVDC converter under unbalanced supply voltage conditions are a negative sequence system of the fundamental harmonic and a positive sequence system of the 3rd harmonic. Also on the AC sides further harmonics are emitted by the converter with a order number distance of 2 to the orders of the characteristic harmonics. However, in practical AC system operation special attention has to be paid to the 3rd harmonic distortion level, in particular when low order resonance appears between the system impedance and the impedance of the converter station AC filters. In order to avoid the above mentioned problems, large smoothing reactors and sometimes large blocking filters are installed on the DC side and the voltage distortion on the AC sides is reduced by AC filters. However, these filters require an expensive high component rating if they are tuned to the 2nd or 3rd harmonic respectively. The work shows that a modification of the valve firing can reduce the levels of the 2nd and 3rd harmonic without investment into additional primary equipment. Furthermore, this offers the chance to reduce the minimum power transfer level since also the risk of an intermittent DC current can be reduced. A corresponding algorithm and a control strategy are proposed. However, the calculation of an appropriate firing pattern requires a detailed modelling of the processes within the converters, especially the formation of the harmonics and the harmonic transfer between AC and DC sides. The work proposes a component vector model for the calculation of the harmonics. This model assumes that each harmonic consists of a first component representing the ideal conversion process, a 2nd component representing the impact of different commutation angles and in the case of the modified firing a 3rd component considering the impact of the intended non-equidistant firing. The work shows, that the harmonic component vectors resulting from voltage unbalance and from firing modulation can be treated separately and superimposed linearly. The calculation of the harmonic component vectors is performed applying the method of switching functions. For the consideration of the commutation and firing angle differences the modelling of switching functions based on differential impulses is proposed. However, especially an accurate representation of the above mentioned 2nd component vector requires a correct calculation of the commutation angles and their valve-specific differences. The investigations of this work have revealed that the conventional method of calculating the commutation angles – assuming an ideal smoothed DC current - may not produce results of sufficient accuracy. This is especially true in the case of a high ripple of the DC current, e.g. smoothed with a small smoothing reactor. A small smoothing reactor is typical for HVDC back-to-back applications. Therefore a new analytical method for the calculation of the commutation angles has been developed which in particular considers the typical pulse form of the DC current and additionally the impacts of the voltage unbalance and of the proposed modification of the firing on the ripple shape of the DC current. Moreover, as this analytical method requires the instantaneous values of the DC current at the instants of valve firing, a further analytical method for the calculation of these discrete current values has been developed. The equations are valid under the same conditions as the new ones for calculation of the commutation angles, i.e. resistive-inductive AC system fundamental frequency impedances, any degree of DC current smoothing between ideal smoothing and a ripple at the limit for current discontinuities. Symmetrical conditions, supply voltage unbalances and non-equidistant firing as proposed are applied. It is shown that, using this method, also the discrete values of the DC current at the end of the commutation intervals can be determined. In practice one of these discrete current values indicates the minimum value during one period of the fundamental frequency. This offers the chance for a more exact analytical determination of the limit for the appearance of DC current discontinuities. For typical parameters of a back-to-back installation the new methods and the new analytical equations have been compared with simulation results showing excellent correlation for typical voltage unbalances of not more than 1...2% and firing angle differences of not more than 2.5°. This verification is performed for the harmonics, the commutation angles and the discrete values of the DC current at the firing instants as well.:1 Einleitung und Ziel der Arbeit 1.1 Einführung in die Problematik 1.2 HGÜ-Systeme als Quelle von Strom- und Spannungsharmonischen 1.3 Netzspannungsunsymmetrien 1.4 Abgrenzung der betrachteten technischen Systeme 1.5 Beweggründe für die Betrachtung 1.6 Zielstellungen 2 Erkenntnisstand und Analyse der Aufgabenstellung 2.1 Harmonische 2.2 Aktive Kompensation von Harmonischen 2.3 Diskrete Werte des Zwischenkreisstromes am Beginn und Ende der Kommutierungsintervalle 2.4 Kommutierungswinkel 3 Grundlagen 3.1 Methodischer Ansatz 3.2 Allgemeine Voraussetzungen, Annahmen und Festlegungen 3.3 Maßgebliche Impedanzen für die Stromaufteilung 3.4 Maßgebliche Impedanz für die gleichstromseitigen Stromharmonischen 3.5 Leerlauf-Klemmenspannung des Stromrichters 3.6 Kommutierungsspannung 3.7 Nummerierungssystem der Ventile 3.8 Überlappungsformen der Kommutierungsintervalle 3.9 Komplexer Spannungsunsymmetriefaktor 3.10 Anwendung und Modifikation von Schaltfunktionen 3.11 Verifikation der Ergebnisse 4 Harmonische auf der Gleichstromseite 4.1 Bildungsgesetz 4.2 Charakteristische Harmonische 4.3 Nichtcharakteristische Harmonische infolge unsymmetrischer Netzspannungen 4.4 Nichtcharakteristische Harmonische infolge Ansteuermodifikation 5 Diskreter Wert des Zwischenkreisstromes im Zündzeitpunkt 5.1 Vorgehensweise 5.2 Lösungsansatz 5.3 Konstante Gegenspannung 5.4 Reale Gegenspannung des HGÜ-Stromrichters 5.5 Berücksichtigung von Resistanzen 5.6 Unsymmetrische Netzspannungen 5.7 Ansteuermodifikation 5.8 Unsymmetrische Netzspannungen und gleichzeitige Ansteuermodifikation 5.9 Ergebnisse 6 Kommutierungswinkel 6.1 Vorgehensweise 6.2 Konstante Gegenspannung 6.3 Reale Gegenspannung des HGÜ-Stromrichters 6.4 Berücksichtigung von Resistanzen 6.5 Unsymmetrische Netzspannungen 6.6 Ansteuermodifikation 6.7 Unsymmetrische Netzspannungen und gleichzeitige Ansteuermodifikation 6.8 Ergebnisse 7 Vertiefende Betrachtung der nichtcharakteristischen Harmonischen auf der Gleichstromseite 7.1 Vorbemerkungen 7.2 Unsymmetrische Netzspannungen 7.3 Ansteuermodifikation 7.4 Spannungsunsymmetrie und gleichzeitige Ansteuermodifikation 7.5 Ergebnisse 8 Harmonische auf der Netzseite 8.1 Bildungsgesetz 8.2 Charakteristische Harmonische 8.3 Nichtcharakteristische Harmonische 9 Betrachtungen zur aktiven Kompensation 9.1 Vorbemerkungen 9.2 Betrachtungsumfang 9.3 Grundlagen 9.4 Konzeptioneller Vorschlag für die Kompensation der 2. Stromharmonischen 9.5 Betrachtung der Drehstromseite 9.6 Vorschlag zur Weiterentwicklung des Konzeptes 9.7 Berechnungsbeispiel zur Kompensation der 2. Harmonischen im Zwischenkreis 9.8 Ergebnisse und Schlussfolgerungen 10 Zusammenfassung 11 Literatur 12 Formelzeichen und Abkürzungen 13 Anlagenverzeichnis

I denna rapport analyseras för- och nackdelar med eldistributionssystem av typ TN-C (fyrledarsystem) respektive TN-S (femledarsystem) system. Det finns olika uppfattningar om vilket system som är lämpligast att bygga ut i distributionsnätet (lågspänningsnätet) och i fastigheternas huvudledning. Med hjälp av litteraturstudier och kontakt med olika elföretag och elbolag har olika ståndpunkter diskuterats och därefter har en sammanställning av resultatet tagits fram. Enligt analysen är TN-C det lämpligaste alternativet att använda i distributionsnätet och TN-S bör användas i fastighetens huvudledning. Detta för att kunna uppnå en god och stabil elmiljö. Detta examensarbete skall underlätta val av teknik och förhoppningsvis öka kunskapen angående ämnet. / In this report analysis the advantages and disadvantages of the TN-C (four conductor system) and TN-S (five conductor system) system. There are different opinion about which system is most appropriate to use in the distribution network and the building main lines. With the help of literature studies and contacts with various power companies and electric companies different opinion have been discussed . TN-C is the most appropriate option in the distribution network and TN-S should be used in the building main lines. This for achieving high and stable electrical environment. This thesis will facilitate the choice of technology and hopefully increase the knowledge about the subject.

The installation of wind power plant has significantly increased since several years due to the recent necessity of creating renewable and clean energy sources. Before the accomplishment of a wind power project many pre-studies are required in order to verify the possibility of integrating a wind power plant in the electrical network. The creation of models in different software and their simulation can bring the insurance of a secure operation that meets the numerous requirements imposed by the electrical system. Hence, this Master thesis work consists in the creation of a wind turbine model. This model represents the turbines installed at Lillgrund wind farm, the biggest wind power plant in Sweden. The objectives of this project are to first develop an accurate model of the wind turbines installed at Lillgrund wind farm and further to use it in different kinds of simulations. Those simulations test the wind turbine operating according to different control modes. Also, a power quality analysis is carried out studying in particular two power quality phenomena, namely, the response to voltage sags and the harmonic distortion. The model is created in the software PSCAD that enables the dynamic and static simulations of electromagnetic and electromechanical systems. The model of the wind turbine contains the electrical machine, the power electronics (converters), and the controls of the wind turbine. Especially, three different control modes, e.g., voltage control, reactive power control and power factor control, are implemented, tested and compared. The model is tested according to different cases of voltage sag and the study verifies the fault-ride through capability of the turbine. Moreover, a harmonics analysis is done. Eventually the work concludes about two power quality parameters.

This thesis presents two transient models for a prototype integrated charger for use in a plug-in hybrid-electrical vehicle application. The models can be useful in order to develop control algorithms for the system or to recommend improvements to the machine design. A flux map based method, obtaining input data from simulations using the finite element method (FEM) is used to model the grid synchronization process. The grid side voltage can then be predicted by incorporating spatial flux linkage harmonics. The model is implemented in Matlab/Simulink and compared to stand alone FEM simulations with good agreement. The charging process is modeled using an inductance based model also requiring FEM simulations as input data. Since the flux linkages in the grid and inverter side windings are dependent on each other, the presented transient model is linearized around a specific operating point. This model is also implemented in a Matlab/Simulink environment. Sensorless control of a PMSynRel drive is also studied in this thesis. Focus is put on operating limits due to magnetic saturation when operating at low speeds. The rotating and pulsating voltage vector injection methods for sensorless control are studied in detail. A technique to map the feasible sensorless control region is proposed which utilizes the resulting position error signal rather than data of differential inductances. This technique is implemented experimentally and compared to corresponding FEM simulations with good agreement. The impact of spatial inductance harmonics on the quality of the position estimates is also studied. A method to predict the maximum position estimation error due to the inductance harmonics is proposed based on simplified analytical models. A technique is presented and experimentally verified which can compensate for this effect by injecting a modified rotating voltage carrier. Lastly, the impact of saturation in the rotor structure on the initial magnet polarity detection is investigated. The experimental results, in good agreement with the corresponding FEM simulations, indicate that the impact of saturation in the magnet bridges of rotor is the dominant phenomenon at lower peak current magnitudes. / QC 20110928

Le transport de la lumière permet de simuler physiquement le movement de photons dans un environnement virtuel. En rendu d’images, la lumière se propage une dernière fois vers un capteur virtuel la transformant en une image, affichée pour un observateur. Durant ce voyage la lumière peut être analysée fréquentiellement pour comprendre ses variations spatiales et angulaires afin d’accélerer le rendu. La génération d’images réalistes a subit de grandes avancées au cours des dernières années, réduisant l’écart entre simulation et réalité. Cependant les contraintes en terme de performance et de mémoire empêchent toujours aux applications interactives et en temps-réel de bénéficier des effets de rendu les plus complexes. Pour cela, les moteurs de rendu professionels modernes dépendent toujours de méthodes de pré-calculation de données et de procédures asynchrones de traitement. Cette thèse par article présente deux projets traitant du transport de la lumière à travers une perspective fréquentielle dans le contexte d’applications interactives et en temps-réel. Nous proposons premièrement une méthode pour réutiliser efficacement le calcul préalable de chemins de lumière par méthode Monte Carlo pour des séquences animées. Nous prenons avantage de l’analyse fréquentielle du transport de la lumière réalisée dans des travaux antérieurs, étendue ici à l’échantillonement et reconstruction spatial, angulaire et temporel. Notre seconde méthode pré-calcule le transport de la lumière à travers les volumes participatifs jusqu’aux surfaces, que nous encodons comme réponse impulsive. Cet opérateur compacte et efficace nous permet d’accélerer le transport à travers des volumes jusqu’aux surfaces dans le contexte de diffusion multiple dans des conditions arbitraires de média participatifs. / Light transport is the method of physically simulating the movement of photons in an environment. Applied to rendering, light travels one last time to a virtual sensor that captures it as an image displayed to an observer. As it travels, light is analysable frequentially to understand how it varies spatially and angularly to accelerate rendering. Recent advances in physically-based realistic rendering have been closing the gap between reality and simulation but the memory and performance costs still preclude the inclusion of the more computationally expensive effects in interactive and real-time applications. Because of this, modern production renderers rely on the ahead-of-time precomputation of data for efficient reuse in the form of offline computational processes and asynchronously distributed procedures. This thesis by publication investigates with two papers the simulation of light transport from a frequency-based perspective for interactive and precomputed real-time applications. We first propose a method for efficiently reusing light path computations over time in interactive Monte Carlo path-traced animation sequences. We leverage to this end the frequency analysis of light transport introduced in previous works, extended to spatial, angular and temporal sampling and reconstruction. Our second method investigates the precomputation of participating volume-to-surface light transport as impulse responses, a compact and efficient frequency-based transport operator. In turn, these operators accelerate by orders of magnitude the computation of multi-scattered volume-to-surface transport in arbitrary, potentially heterogeneous media conditions.