<p>Тема докторске дисертације је развој и верификација новог динамичког<br />модела трофазне кавезне асинхроне машине, који је заснован на<br />методи коначних елемената. Применом линеарних магнетостатичких<br />симулација и time-harmonic нелинеарних симулација се реконструишу<br />индуктивности динамичког модела машине заснованог на вишеструко<br />спрегнутим електричним колима. Модел се затим користи у<br />истраживању феномена везаних за појаву жљебних хармоника,<br />сатурацијом индукованих хармоника, као и у развоју нове методе<br />детекције сломљних шипки у роторском кавезу.</p> / <p>Tema doktorske disertacije je razvoj i verifikacija novog dinamičkog<br />modela trofazne kavezne asinhrone mašine, koji je zasnovan na<br />metodi konačnih elemenata. Primenom linearnih magnetostatičkih<br />simulacija i time-harmonic nelinearnih simulacija se rekonstruišu<br />induktivnosti dinamičkog modela mašine zasnovanog na višestruko<br />spregnutim električnim kolima. Model se zatim koristi u<br />istraživanju fenomena vezanih za pojavu žljebnih harmonika,<br />saturacijom indukovanih harmonika, kao i u razvoju nove metode<br />detekcije slomljnih šipki u rotorskom kavezu.</p> / <p>Topic of this thesis is development and verification of the novel dynamical<br />model of the three phase squirrel-cage induction machine, which is based on<br />the finite elements method. Linear magnetostatic simulations and nonlinear<br />time-harmonic simulations are used for calculation of the inductances of the<br />dynamic model of the machine based on the moultiple coupled circuit<br />approach. Model is then used for investigation of the rotor slot harmonics,<br />saturation induced harmonics and in the development of the novel method<br />for broken rotor bars detection.</p>

Orientador: Prof. Dr. Alfeu Joãozinho Sguarezi Filho / Coorientador: Prof. Dr. Joel David Melo Trujillo / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Engenharia Elétrica, Santo André, 2018. / Neste trabalho é proposto um algoritmo de rastreamento de máxima potência com a utilização da equação de Monod. O algoritmo aplica-se em sistemas fotovoltaicos conectados à rede elétrica. Os resultados e as comparações mostram que o algoritmo proposto apresenta algumas vantagens em comparação ao algoritmo de perturbação e observação para diversas condições de operação, em especial quando os painéis são submetidos a sombreamento parcial. / In this work we propose an algorithm of maximum power point tracking with using the Monod Equation. The algorithm applies to photovoltaic systems connected to the grid. The results and the comparition show that the algoritmo proposal has some advantages compared to algoritm Perturb and Observe in many situation of operation, in special when the fotovoltaics painels have parcial shading.

Les actionneurs électromécaniques supplantent les solutions d’actionnement hydrauliques concurrentes dans un nombre croissant d’applications industrielles, particulièrement en aéronautique. Ils le doivent à leurs rendements élevés et à une relative simplicité de commande. Fort de ces avantages, cette technologie a été mise en place dans le cadre du projet ELEXC, en vue de remplacer les vérins hydrauliques sur une mini-excavatrice tout-électrique et s’attaquant pour la première fois au secteur du bâtiment et des travaux publics. Cependant, cette intégration s’accompagne de doutes sur la performance et la durabilité de ces actionneurs dans ce cas précis d’utilisation. Pour répondre à ces interrogations, ce manuscrit se focalisera dans un premier volet sur la caractérisation des performances d’une structure spécifique, permise par la mise en place d’un banc de test multi-énergies instrumenté. Cette étude aboutira à la mise en place d’un modèle par lois physiques dont les paramètres auront été identifiés expérimentalement.Deux solutions innovantes vont ensuite être proposées, visant respectivement à réduire les répercussions, notamment énergétiques, de la caractéristique discrète du convertisseur à découpage, et à parer au manque de compliance de l’actionneur tout en conservant ses capacités de creusage. Elles seront toutes deux associées au concept de commande prédictive, mais offriront chacune une spécificité par rapport à l’implémentation standard de ce type de commande tout en conservant ses avantages. La première prendra la forme d’un modulateur fondé sur le principe d’une modulation de largeur d’impulsion vectorielle, dont la séquence sera sélectionnée par un contrôleur prédictif en rapport avec une fonction de coût alliant les ondulations de courant, les pertes par commutation et la tension de mode commun spécifiques aux séquences. La seconde consistera en un contrôleur d’impédance à boucle de position interne, dont les paramètres d’impédance seront variables et définis par un contrôleur prédictif afin de permettre une bonne pénétration dans l’environnement tout en limitant la dynamique et la valeur maximale de l’effort de compression sur la transmission. / Nowadays, the electro-mechanical actuators (EMA) are seen as an alternative to the conventional hydraulic cylinders in a growing number of industrial applications, including the aeronautic sector, thanks to their high efficiency and relatively simple commandability. According to this features, this actuator technology was selected to replace the hydraulic cylinders of the actuation system of a full-electric compact excavator in the ELEXC project. However, some concerns arose from the lack of existing examples with EMA functioning in relatively severe working conditions implying collisions of the actuators with stiff environments. Therefore, this manuscript will first focus on the characterization of the electro-mechanical actuator and of its performances in this specific case of application, enabled by the development of a multi-energy test-rig. Beside the validation of the EMA capacities, a physic law model will be developed, and its parameters tuned according to the experimental results. In a second part of this manuscript, two novel control laws will be proposed, aiming respectively to reduce the negative repercussions of the discrete characteristic of the electrical converter, and to counterpart the lack of natural compliance of the mechanical actuator. They will be both based on the concept of predictive control, but will differ from the conventional implementation of this type of controller. The first proposed topology is a modulator based on a vector Pulse Width Modulation, in which the PWM sequence to be used is defined online by a predictive controller according to a cost function that takes into account the current ripples, the switching losses and the common mode voltages specific to the sequences. Next, a position-based impedance controller, whose impedance parameters are defined online by a predictive controller, is introduced, in order to enable the EMA to penetrate a stiff environment with a relatively low dynamic increase of compression force on the mechanical transmission.

In this work, a proposal for BLDC motor control, which will be used as a drive linear actuator. Control with microcontroller focuses mainly aspects such as motor mode, regenerative mode, measuring rotor position sensors and measuring the motor current, which corresponds to the moment. The result of the work is focused on upgrading the existing Honeywell actuator, where the processor-controlled BLDC motor to replace the existing system and take over the actuator working function and emergency function.

This work is focused on innovative construction of the industrial radial sealless pump and mainly on construction of the three phase DC/AC converter based on new semiconductor technology SiC. These new semiconductor devices allow move switching frequency up to 100 kHz. For such high switching frequency new non-conventional topology of the output filter was designed. This high frequency is currently unusual in three-phase application with output voltage 400V. High switching frequency reduces size of wound components of the output filter and its presence is accepted in terms of total weight and price of the whole system. Clear sinus waveform of the output converter voltage reduces torque ripple, EMC and extend the lifetime and reliability of mechanical parts and the whole pump drive. Three phase synchronous motor is directly placed into the pump body and is designed as slotless motor. In the inlet area is the classical bearing replaced by active magnetic bearing. It is used due to possibility to pump aggressive liquids or substances where high level of cleanness has to be guaranteed.

Master thesis deals with design and construction of the most widely used engines currently. Overall, it is divided into five chapters, the first chapter deals with constructional features of various three-phase asynchronous motors, the second chapter briefly paid attention to single-phase motors. The next chapter focuses on the specific engine types, which differ from standard induction motors in its design implementation. This is an engine with full rotor, hysteresis, linear and with shaded field. Although asynchronous motors are considered the most reliable machines work in imperfect conditions, it leads to frequent breakdowns. This is covered in chapter four. Based on the findings from previous chapters the fifth chapter includes a preliminary draft of the asynchronous motor with a full rotor. The last chapter is devoted to the measurement on functional models.

This Master thesis is based on problems of force effects of the magnetic field of short-circuit current. Firstly, I analysed the force action of the three phase busbars during the three-pole short circuit. The analysis was performed in the Ansys Maxwell program and I verified the correctness of the analysis by numerical calculation. The second practical part was executed for ABB company. The main task was to analyse the force effects of the short-circuit current in the HV switchgear with focusing on the arms and contact system of the circuit breaker. The simulations of the following configurations were performed in more details: three configurations of the simplified VD4 circuit breaker, two types of VD4 circuit-breaker contact systems and a linear circuit breaker configuration model. The objective was to calculate the forces acting on the current path of the arms and contact system of the VD4 circuit breaker during the three-phase short-circuit and to simulate the effects of forces on these current parts. For modelling of individual assemblies, calculations and simulations I used: SolidWorks 2014, Ansys Maxwell 16.0 and Ansys Workbench 14.5 programs. With SolidWorks 2014 3D CAD software were modelled simplified assemblies of circuit breakers and contact systems. These systems were imported into the Ansys Maxwell software, where the force effects of the magnetic field of the short-circuit current were calculated. In Ansys Workbench programme was simulated the effect of forces on the current circuit breakers. Moreover, the final deformations of the materials (with respect to the mechanical properties of the structure) were plotted. The analysis of force effects of the magnetic field was performed for the specified static short - circuit current value.

In der Niederspannungstechnik werden die Anlagen zum Übertragen und Verteilen von Elektroenergie als Niederspannungs-Schaltgerätekombinationen bezeichnet. Die Anlagen sollen ihre Aufgaben möglichst wartungsfrei über einen Zeitraum von mehreren Jahrzehnten erfüllen. Damit ein langzeitstabiler Betrieb der Niederspannungs-Schaltgerätekombinationen möglich ist, müssen die Anlagen mindestens normgerecht thermisch dimensioniert sein. Um die Erwärmung von Niederspannungs-Schaltgerätekombinationen zuverlässig und effizient zu berechnen, wird in dieser Arbeit die Wärmenetzmethode genutzt. In der Wärmenetzmethode werden die Vorgänge der Erwärmung mit Hilfe von Wärmestromquellen, Temperaturquellen, Wärmewiderständen und Wärmekapazitäten nachgebildet. Einen wesentlichen Einfluss auf die Erwärmung einer Schaltgerätekombination haben die in den Wärmequellen der Anlage erzeugten Verlustleistungen. Die dominanten Wärmequellen (Hauptwärmequellen) innerhalb von Niederspannungs-Schaltgerätekombinationen werden in dieser Arbeit untersucht und die Ergebnisse in die Wärmenetzmethode integriert. Mit den Ergebnissen werdenmit Hilfe der Wärmenetzmethode die Erwärmungen verschiedener Betriebsmittel einer Niederspannungs-Schaltgerätekombination berechnet und anhand von Experimenten verifiziert. Die Wärmenetze der einzelnen Betriebsmittel werden zum Gesamt-Wärmenetz einer Niederspannungs-Schaltgerätekombination zusammengeschaltet. Die mit diesem Wärmenetz berechneten Temperaturen werden dann durch Experimente an der Versuchsanlage einer Niederspannungs-Schaltgerätekombination verifiziert. Eine der Hauptwärmequellen in Niederspannungs-Schaltgerätekombinationen sind die ohmschen Leitungsverluste in den Strombahnen der Hauptsammel- und Feldverteilerschienen. Bei Drehstrombelastung werden die hier in den einzelnen Teilleitern erzeugten Verlustleistungen durch die Stromverdrängung aufgrund des Skin- und den überlagerten Proximity-Effekts maßgeblich beeinflusst. Gegenüber einer Gleichstrombelastung unterscheiden sich die Verlustleistungen jedes einzelnen Teilleiters um den Leistungsfaktor k3~. Für Drehstromschienensysteme mit mehreren Teilleitern existieren bisher nur unzureichende Angaben zum Leistungsfaktor k3~ durch den Skin- und den Proximity-Effekt. In dieser Arbeit wurden FEM-Modelle aufgebaut, die Leistungsfaktoren k3~ für unterschiedliche Schienenanordnungen berechnet und anhand experimenteller Untersuchungen verifiziert. Weitere Hauptwärmequellen in Niederspannungs-Schaltgerätekombinationen sind die in den Anlagen eingebauten Betriebsmittel zum Schalten, Trennen und Schützen (z. B. Leistungsschalter, Trennschalter, Trenneinrichtungen, Sicherungen). Neben den Schaltkontakten selbst gehören die thermischen Schutzauslöser und Sicherungen zu den Hauptwärmequellen in den Strombahnen der Schaltgeräte. Um die Erwärmung der Geräte genau zu berechnen, müssen der Aufbau der Strombahnen und die Verteilung der Widerstände bekannt sein. Diese Widerstände können im Allgemeinen nur gemessen werden. Dabei hat sich zum einen gezeigt, dass die gemessenen Widerstände der Schaltkontakte von Kompaktleistungsschaltern auch im selben Gerät stark variieren können. Zum anderen sind die Widerstände der Schaltkontakte so dominant, dass in ihnen bis zu 47 % der gesamten Verlustleistungen eines Kompaktleistungsschalters entstehen können. Bedingt durch die zunehmende kompakte Bauweise der Anlagen erzeugen die Drehstromfelder der Sammelschienen hohe magnetische Feldstärken in umgebenden Metallteilen. In den Gehäusen, Einbauplatten, Wänden, Umhüllungen und Verkleidungen in Niederspannungs-Schaltgerätekombinationen können daher hohe Verlustleistungen entstehen, die maßgeblich die Erwärmung der Anlagen beeinflussen. Rechnerische und experimentelle Untersuchungen haben gezeigt, dass bei typischen Anordnungen von Schienen und Umhüllungen Verlustleistungen entstehen, die bis zu 32,7% der gesamten in der Versuchsanordnung gemessenen Verlustleistungen betragen. Sind die Ergebnisse der untersuchten Wärmequellen in die Wärmenetze der verschiedenen Betriebsmittel von Niederspannungs-Schaltgerätekombinationen integriert, ermöglichen die aufgebauten Wärmenetze die Berechnung von Temperaturen mit geringen Abweichungen (+4,4 K, -3,5 K) verglichen mit gemessenen Temperaturen. Mit den verifizierten und modularisierten Wärmenetzen der Betriebsmittel ist eine Möglichkeit geschaffen, Wärmenetze von Niederspannungs-Schaltgerätekombinationen effizient und wirtschaftlich aufzubauen.:1 Einleitung 1 2 Problemstellung 2 2.1 Stand der Technik / Ausgangssituation 2 2.2 Normen zur Erwärmung 3 2.3 Aufgabenstellung 5 2.4 Aufbau der Versuchsanlage 7 3 Grundlagen der Erwärmungsberechnung 11 3.1 Erzeugte Wärmeleistungen 11 3.2 Wärmeübertragung 17 3.3 Erwärmungsberechnung mit Wärmenetzen 39 4 Grundlagen zur Stromverdrängung 43 4.1 Stromdichteverteilung im Vollzylinder 43 4.2 Stromverdrängung und der Leistungsfaktor k 48 5 Untersuchungen zu den Wärmequellen 54 5.1 Stromwärmeverluste in den elektrischen Leiter von Sammel- und Feldverteilerschienen 57 5.2 Stromwärmeverluste in Schaltgeräten und zugehörigen Betriebsmitteln 90 5.3 Wirbelstrom- und Hystereseverluste in Metallteilen 105 6 Wärmenetze für die Betriebsmittel einer Niederspannungs- Schaltgerätekombination 126 7 Wärmenetz einer Niederspannungs-Schaltgerätekombination 148 8 Zusammenfassung und Ausblick 155 9 Literaturverzeichnis 158 10 Anhang 163 / In low-voltage engineering the systems for transmission and distribution of electric energy are named as low-voltage switchgear and controlgear assemblies. The systems have to perform their functions maintenance free as much as possible for a period of some decades. To achieve a long-time stable operation, the systems have to be designed thermally at least according to standards. In this thesis the thermal network method is used to calculate the heating of low-voltage switchgear and controlgear assemblies reliably and efficiently. The thermal network method simulates the processes of heating by heat sources, temperature sources thermal resistors and thermal capacities. The thermal power losses which are produced in the heat sources of the systems have significant influence on the heating of switchgear and controlgear assemblies. The dominant heat sources (main heat sources) within low-voltage switchgear and controlgear assemblies are researched at this thesis and the results are integrated to the thermal network method. The results are used to calculate the heating of various electrical components of a low-voltage switchgear and controlgear assembly using the thermal network method and verified by means of experiments. The thermal networks of the individual components are interconnected to form the overall thermal network of a low-voltage switchgear and controlgear assembly. The temperatures computed with this thermal network are then verified by experiments at the test setup of a low-voltage switchgear and controlgear assembly. In low-voltage switchgear and controlgear assemblies one of the main heat sources are the ohmic losses in the current paths of the main busbars and the distribution busbars. If the busbars are loaded with a three-phase current, the generated power losses of every individual subconductors are significantly influenced by the current displacement due to the skin effect and the superposed proximity effect. The power losses of each individual subconductor differ by the power factor k3~ compared to a DC load. For three-phase busbar systems with several subconductors there is only insufficient information on the power factor k3~ which takes into account the current displacement by the skin effect and the proximity effect. In this thesis, FEM models were developed to calculate the power factor k3~ for different busbar systems. The results were verified by experimental investigations. The installed electrical devices for switching, isolating and protection (e. g. circuit breakers, disconnectors, devices for disconnecting and fuses) are further main heat sources in low-voltage switchgear and controlgear assemblies. In addition to the main switching contacts themselves, thermal protection trips and the fuses are the main heat sources in the current paths of the switching devices. In order to calculate the heating of the electrical devices properly, the structure of the current paths and the distribution of the electrical resistances have to be known. In general these resistances can only determine by measuring. On one hand, it was found that the measured resistances vary widely even inside the same device. On the other hand, the resistances of the switching contacts are dominating, that up to 47 % of the entire power losses of a molded case circuit breaker can be generated there. Conditioned by the more and more compact design of the switchgears, the three-phase fields of the main busbars causes high magnetic fields at the surrounding metallic components. High power losses can therefore occur in housings, panels, walls, casings and enclosures in low-voltage switchgear and controlgear assemblies, which have a significant influence on the heating of the systems. Computational and experimental investigations have shown that typical arrangements of busbars and enclosures result in power losses of up to 32.7% of the total power losses measured in the test setup. If the results of the investigated heat sources are integrated into the networks of the various equipment of low-voltage switchgear and controlgear assemblies, the thermal networks set up enable the calculation of temperatures with small deviations (+4.4 K, -3.5 K) compared with measured temperatures. The verified and modularised thermal networks of the equipment provide an efficient and economical way of setting up heating networks of low-voltage switchgear and controlgear assemblies.:1 Einleitung 1 2 Problemstellung 2 2.1 Stand der Technik / Ausgangssituation 2 2.2 Normen zur Erwärmung 3 2.3 Aufgabenstellung 5 2.4 Aufbau der Versuchsanlage 7 3 Grundlagen der Erwärmungsberechnung 11 3.1 Erzeugte Wärmeleistungen 11 3.2 Wärmeübertragung 17 3.3 Erwärmungsberechnung mit Wärmenetzen 39 4 Grundlagen zur Stromverdrängung 43 4.1 Stromdichteverteilung im Vollzylinder 43 4.2 Stromverdrängung und der Leistungsfaktor k 48 5 Untersuchungen zu den Wärmequellen 54 5.1 Stromwärmeverluste in den elektrischen Leiter von Sammel- und Feldverteilerschienen 57 5.2 Stromwärmeverluste in Schaltgeräten und zugehörigen Betriebsmitteln 90 5.3 Wirbelstrom- und Hystereseverluste in Metallteilen 105 6 Wärmenetze für die Betriebsmittel einer Niederspannungs- Schaltgerätekombination 126 7 Wärmenetz einer Niederspannungs-Schaltgerätekombination 148 8 Zusammenfassung und Ausblick 155 9 Literaturverzeichnis 158 10 Anhang 163

1. Unterschiedliche Definitionen der Gesundheit mit verschiedenen Betrachtungsweisen (WHO: Der Mensch eine biopsychosoziale Einheit. Schulmedizin: ohne klinischen und paraklinischen Befund mit Orientierung an kritikbedürftigen Referenzmittelwerten) führt bei Fachleuten, Behörden und Laien zu Verwirrungen, wenn es um die Beurteilung gesundheitlicher Schäden geht. 2. Es wurde die Aufgabe gestellt zu prüfen, welche der beiden Definitionen der Realität näher kommt. 3. Mittels der chronopsychobiologischen Regulationsdiagnostik, des Dreiphasenentspannungstests (Hecht und Balzer 2001), wurden unter dem Aspekt der beiden Gesundheitsdefinitionen drei Gruppen untersucht (je 40 Probanden). - klinisch Gesunde (klinisch Gesunde nach Schulmedizin ) - Gesunde nach Definition der WHO - Probanden mit nichtorganische Insomnie (ohne pathologische klinische und paraklinische Befunde) 4. Die mit den verwendeten Methoden gewonnenen Daten wiesen aus, dass zwischen den klinisch Gesunden und den Probanden mit nichtorganischer Insomnie weitgehend größere Ähnlichkeiten bestehen. Beide Gruppen zeigten aber zu der Gruppe der Gesunden nach WHO-Definition, welche die biopsychosoziale Einheit des Menschen berücksichtigt, noch hochsignifikante Unterschiede. Die Gruppe der klinisch Gesunden kann daher auf Grund unserer Ergebnisse nicht den Anspruch erheben, real gesund zu sein. 5. Mit der Bezugnahme auf die Internationale Klassifikation der Krankheiten (ICD 10F) haben die von uns untersuchten klinisch Gesunden und die nichtorganischen Insomniker eine mehr oder weniger stark ausgeprägte Symptomatik von psychischen Störungen. Dies müsste bei der Beurteilung von Schadstoff-, Lärm-, und EMF-Wirkungen auf den Menschen, wie auch bei den klinisch-pharmakoloischen Untersuchungen beachtet werden. Die in der Arbeit erzielten Ergebnisse bedürfen durch weitere Untersuchungen eine Fundierung. Sie signalisieren aber sowohl unter praktischen als auch unter theoretischen Aspekten einen dringenden Forschungsbedarf. / 1. Differing definitions of health using different criterea (WHO: The human being as a bio- psycho-social unit versus classical medicine: without clinical and paraclinical results based on suspect reference values) bring confusion to experts, authorities and laymen when assessing health damages. 2. The given task was to check which of the two definitions is closer to reality. 3. Using the chrono-psycho-biological diagnostic of regulation, the three-phase-relaxation test (Hecht and Balzer 2001), three groups were examined considering the aspects of the two health definitions (40 test subjects in the study group). - clinically healthy (clinically healthy per classical medicine definition) - healthy per definition of the WHO - test persons with non organic insomnia (i.e. no pathological or paraclinical findings) 4. The data gained from the employed methods revealed bigger similarities between clinically healthy persons and those with non organic insomnia. Both groups still showed highly significant differences to the group which fulfils the definition of the WHO regarding a human as a bio-psycho-social unit. As a result of this study, persons, though classified as "clinically healthy" might nevertheless not absolutely be healthy in reality. 5. In reference to the international classification of illnesses (ICD 10 F) the groups examined, both of clinically healthy and those with non organic insomnia, have more or less severe psychological symptoms. This should be taken into account when assessing the effects of pollution, noise, and EMF as well as clinical pharmacological studies. These present findings still need broader confirmation by further investigations. However, they clearly indicate, for practical and theoretical considerations, an urgent need for further research.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Neste trabalho é apresentado um novo método acurado com passo de tempo fracionário, baseado em uma técnica de decomposição de operadores, para a solução numérica de um sistema governante de equações diferenciais parciais que modela escoamento trifásico água-gás-óleo imiscível em reservatórios de petróleo heterogêneos no qual os efeitos de compressibilidade do gás não foram levados em conta. A técnica de decomposição de operadores em dois níveis permite o uso de passos de tempo distintos para os três problemas definidos pelo procedimento de decomposição: convecção, difusão e pressão-velocidade. Um sistema hiperbólico de leis de conservação que modela o transporte convectivo das fases fluidas é aproximado por um esquema central de diferenças finitas explícito, conservativo, não oscilatório e de segunda ordem. Este esquema é combinado com elementos finitos mistos, localmente conservativos, para a aproximação numérica dos sistemas de equações parabólico e elíptico associados aos problemas de transporte difusivo e de pressão-velocidade, respectivamente. O operador temporal associado ao sistema parabólico é resolvido fazendo-se uso de uma estratégia implícita de solução (Backward Euler). O modelo matemático para escoamento trifásico considerado neste trabalho leva em conta as forças de capilaridade e expressões gerais para as funções de permeabilidade relativa, campos variáveis de porosidade e de permeabilidade e os efeitos da gravidade. A escolha de expressões gerais para as funções de permeabilidade relativa pode levar à perda de hiperbolicidade escrita e, desta maneira, à existência de uma região elíptica ou de pontos umbílicos para o sistema não linear de leis de conservação hiperbólicas que descreve o transporte convectivo das fases fluidas. Como consequência, a perda de hiperbolicidade pode levar à existência de choques não clássicos (também chamados de choques transicionais ou choques subcompressivos) nas soluções de escoamentos trifásicos. O novo procedimento numérico foi usado para investigar a existência e a estabilidade de choques não clássicos, com respeito ao fenômeno de fingering viscoso, em problemas de escoamentos trifásicos bidimensionais em reservatórios heterogêneos, estendendo deste modo resultados disponíveis na literatura para problemas de escoamentos trifásicos unidimensionais. Experimentos numéricos, incluindo o estudo de estratégias de injeção alternada de água e gás (Water-Alternating-Gas (WAG)), indicam que o novo procedimento numérico proposto conduz com eficiência computacional a resultados numéricos com precisão. Perspectivas para trabalhos de pesquisa futuros são também discutidas, tomando como base os desenvolvimentos reportados nesta tese. / We present a new, accurate fractional time-step method based on an operator splitting technique for the numerical solution of a system of partial differential equations modeling three-phase immiscible water-gas-oil flow problems in heterogeneous petroleum reservoirs in which the compressibility effects of the gas was not take into account. A two-level operator splitting technique allows for the use of distinct time steps for the three problems defined by the splitting procedure: convection, diffusion and pressure-velocity. A system of hyperbolic conservation laws modelling the convective transport of the fluid phases is approximated by a high resolution, nonoscillatory, second-order, conservative central difference scheme in the convection step. This scheme is combined with locally conservative mixed finite elements for the numerical solution of the parabolic and elliptic problems associated with the diffusive transport of fluid phases and the pressure-velocity problem, respectively. The time discretization of the parabolic problem is performed by means of the implicit backward Euler method. The mathematical model for the three-phase flow considered in this work takes into account capillary forces and general expressions for the relative permeability functions, variable porosity and permeability fields, and the effect of gravity. The choice of general expressions for the relative permeability functions may lead to the loss of strict hyperbolicity and, therefore, to the existence of an elliptic region of umbilic points for the systems of nonlinear hyperbolic conservation laws describing the convective transport of the fluid phases. As a consequence, the loss of hyperbolicity may lead to the existence of nonclassical shocks (also called transitional shocks or undercompressive shocks) in three-phase flow solutions. The numerical procedure was used in an investigation of the existence and stability of nonclassical shocks with respect to viscous fingering in heterogeneous two-dimensional flows, thereby extending previous results for one-dimensional three-phase flow available in the literature. Numerical experiments, including the study of Water-Alternating-Gas (WAG) injection strategies, indicate that the proposed new numerical procedure leads to computational efficiency and accurate numerical results. Directions for further research are also discussed, based on the developments reported in this thesis.