The synchronous machine is one of the critical components of electric power systems. Modeling of synchronous machines is essential for power systems analyses. Electric machines are often interfaced with power electronic components. This work presents an advanced synchronous machine modeling, which emphasis on the modeling and simulation of systems that contain a mixture of synchronous machines and power electronic components. Such systems can be found in electric drive systems, dc power systems, renewable energy, and conventional synchronous machine excitation. Numerous models and formulations have been used to study synchronous machines in different applications. Herein, a unified derivation of the various model formulations, which support direct interface to external circuitry in a variety of scenarios, is presented. Selection of the formulation with the most suitable interface for the simulation scenario has better accuracy, fewer time steps, and less run time. Brushless excitation systems are widely used for synchronous machines. As a critical part of the system, rotating rectifiers have a significant impact on the system behavior. This work presents a numerical average-value model (AVM) for rotating rectifiers in brushless excitation systems, where the essential numerical functions are extracted from the detailed simulations and vary depending on the loading conditions. The proposed AVM can provide accurate simulations in both transient and steady states with fewer time steps and less run time compared with detailed models of such systems and that the proposed AVM can be combined with AVM models of other rectifiers in the system to reduce the overall computational cost. Furthermore, this work proposes an alternative formulation of numerical AVMs of machine-rectifier systems, which makes direct use of the natural dynamic impedance of the rectifier without introducing low-frequency approximations or algebraic loops. By using this formulation, a direct interface of the AVM is achieved with inductive circuitry on both the ac and dc sides allowing traditional voltage-in, current-out formulations of the circuitry on these sides to be used with the proposed formulation directly. This numerical AVM formulation is validated against an experimentally validated detailed model and compared with previous AVM formulations. It is demonstrated that the proposed AVM formulation accurately predicts the system's low-frequency behavior during both steady and transient states, including in cases where previous AVM formulations cannot predict accurate results. Both run times and numbers of time steps needed by the proposed AVM formulation are comparable to those of existing AVM formulations and significantly decreased compared with the detailed model.

Sustainable energy solutions are aimed to reduce the consumption of fossil fuels by using renewable energy sources and energy efficiency techniques. This thesis presents two new sustainable energy applications in the field of electrical machines.Polyphase induction motors dominate the energy usage spectrum for industrial and commercial applications. The conventional winding structure used in both synchronous and induction machines has a basic unit of the winding with a 60 degree phase belt and a three phase connection either in star or delta. A new winding structure using an innovative Star-Delta Series Connection (SDSC) which has a high winding coefficient and low harmonic content is presented in this thesis. The principle of the SDSC winding is described. The Electro-Magnetic Belt and Electro-Magnetic Space diagram are two important means to be used for optimization of the new winding. Experimental results from two prototypes confirm the theoretical analysis. The efficiency of the new machine at rated load increased by about 3.8% as compared to the standard machine with a conventional winding structure.Wind energy is one of the most attractive renewable energy options. Wind turbines are designed to couple either synchronous or asynchronous generators with various forms of direct or indirect connection with grid or diesel generators. Permanent magnet (PM) generators using high energy Neodymium- Iron-Boron magnets offer advantages such as direct coupling without gear box, absence of excitation winding and slip rings, light weight and smaller size. This thesis presents the design and development of an outer-rotor PM generator suitable for wind energy conversion. The initial electromagnetic design followed by a Finite Element Analysis is presented in detail. A 20 kW prototype machine was built and extensively tested. It was found that the machine could maintain an ++ / efficiency of about 85% for a wide operating range. Equivalent circuit models were developed. The results of the Finite Element analysis matches closely with the experimental and the designed values.

This thesis analyzes the power losses in induction machines and how the losses depend on the harmonic content of the applied voltages. Two cases are compared, one case where a machine is fed with a sinusoidial voltage and one case with a modular multilevel converter (M2C). The sine is representing an ideal grid while the M2C represents a case with harmonic content. The usage of converters for electrical drive systems is increasing due to advantages when the rotor speed could be variable by changing the frequency of the voltage. This is usually increasing the efficiency of the overall system, but is also adding harmonics fed to the machine and switching losses in the converter. Low switching losses in the inverter usually create higher harmonic content that instead increases the losses of the machine. The M2C is then proposed as a converter topology that can keep the harmonic content low while keeping the switching losses relatively low. This study focuses on the iron losses, the part of the total losses that is most hard to predict or measure. Today’s methods used to calculate the iron losses are often rough approximations that do not take the impact of the harmonic content of voltage into consideration, even though the iron losses are dependent on the harmonics. Experimental results in the study show that the losses of a M2C-fed case do not differ much from a sine-fed case. The difference could be explained by low increase of iron losses caused by the small harmonic content from the M2C. The increase of iron losses was linked to the harmonic content of the voltage. / Detta examensarbete analyserar effektförluster i induktionsmaskiner och hur förlusterna beror på övertonsinnehållet i den matande spänningen. Två fall kommer att jämföras, ett fall där en maskin är matad från en sinus spänning och ett fall med en modulär multinivå omvandlare (M2C). Sinusen representerar ett idealt nät medan M2C representerar ett fall med övertonsinnehåll. Användning av omvandlare för elekriska drivsystem ökar på grund av fördelarna när rotorhastighet kan varieras genom att ändra frekvensen från den matande växelriktaren. Detta ökar vanligtvis verkningsgraden på det sammanlagda systemet, men detta bidrar även med övertonsinnehåll matat till maskinen och switchförluster i omvandlaren. Låga switchförluster i omvandlaren medför oftast ett högt övertonsinnehåll som istället ökar förlusterna i maskinen. M2C är därför föreslaget som en teknik som håller övertonsinnehållet lågt medan switchförlusterna är relativt låga. Denna studie fokuserar på järnförluster, den del av de totala förlusterna som är som svårast att förutse eller mäta. De metoder som finns för att beräkna järnförlusterna är vanligtvis grova skattningar som inte tar hänsyn till inverkan från spänningens övertoninnehåll, även om järnförluster beror på övertonerna i stor utsträckning. Experimentella resultat i studien visar att förlusterna i ett M2C-matat fall inte avviker i stor utsträkning jämte ett sinusmatat fall. Skillnanen kan förklaras utifrån den lilla ökningen av järnförluster från det låga övertonsinnehållet från M2C:n. Järnförlusterna ses vara kopplade till övertonsinnehållet i spänningen.

Les stratégies de commande avancée des machines électriques nécessitent une connaissance précise de la position et/ou de la vitesse du rotor. Ces grandeurs mécaniques sont traditionnellement mesurées par des capteurs, ce qui augmente le coût et diminue la fiabilité et la robustesse du système. D’où l’importance de la commande sans capteurs mécaniques, dite commande sensorless : elle consiste à remplacer les capteurs physiques par un observateur d’état, qui estime les grandeurs mécaniques en se basant sur un modèle de la machine et à partir de ses entrées (tensions) et ses sorties (courants mesurés). Toutefois, avant d’entamer la synthèse d’un observateur, il faut examiner l’observabilité du système, c.à.d. vérifier si les grandeurs à estimer peuvent être reconstruites à partir des mesures et des entrées du système.Ce travail de thèse concerne la modélisation et l’étude d’observabilité des machines électriques en vue de la commande sensorless. Dans un premier temps, les modèles des machines électriques sont établis, et il est montré qu’une modélisation unifiée des machines à courant alternatif est possible. Ensuite, en se basant sur ces modèles, l’observabilité des machines électriques est étudiée en vue de la commande sensorless. La théorie d’observabilité instantanée locale est appliquée, ce qui permet de formuler des conditions analytiques, faciles à interpréter et à vérifier en temps-réel, et qui font le lien avec les phénomènes physiques dans les machines. La validité des conditions d’observabilité est confirmée par des simulations et sur des données expérimentales, en appliquant un observateur de type Kalman étendu.Cette thèse contribue à une nouvelle vision des machines à courant alternatif commandées sans capteurs mécaniques, et à une compréhension plus profonde de leurs propriétés. Elle contribue ainsi à la synthèse de stratégies d’observation plus performantes dans les régimes de fonctionnement critiques (à vitesse nulle et/ou à fréquence d’entrée nulle).Les nouveaux concepts proposés dans cette thèse, tels que le flux équivalent et le vecteur d’observabilité, avec les résultats obtenus, ouvrent de nouveaux horizons dans un domaine qui paraît devenir assez mature. / High-performance control of electric drives requires an accurate knowledge of the rotor position and/or speed. These mechanical variables are traditionally measured using sensors, which increases the cost and reduces both the robustness and the reliability of the system. This emphasizes the importance of electric drives control without shaft sensors, often referred to as sensorless control : it consists of replacing sensors with a state observer algorithm, that estimates the desired mechanical variables from currents and voltages sensing and based on the system’s model. Nevertheless, before designing a state observer, the observability ofthe system should be examined, that is, it should be checked whether the states to be estimated can be reconstructed, unambiguously, from the input/output signalsof the system.This work addresses the modeling and the observability analysis of electric drives in the view of mechanical sensors removal. Firstly, electrical machines models areelaborated, and it is shown that a unified modeling of alternating current machines is feasible, for the purpose of designing unified control and estimation strategies.The observability of the machines’ models is next studied in the view of sensorless control. The local instantaneous observability theory is applied, which enables us to formulate physically insightful analytic conditions that can be easily interpreted and tested in real time. The validity of the observability conditions is confirmed by numerical simulations and experimental data, using an extended Kalman observer.This work contributes to novel outlooks on the sensorless alternating current drives and to a deeper understanding of its properties, in order to develop higher performance estimation techniques in the critical operating conditions (mainly at standstill and/or zero-stator-frequency).The concepts introduced throughout this thesis, such as the equivalent flux and the observability vector, with the obtained results, open new horizons in a domainthat seems to become mature enough.

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As the major electricity consumer, electrical machines play a key role for global energy savings. Machine manufacturers put considerable efforts into the development of more efficient electrical machines for loss reduction and higher power density achievements. A consolidated knowledge of the occurring losses in electrical machines is a basic requirement for efficiency improvements. This thesis deals with iron losses in electrical machines. The major focus is on the influences of the stator core magnetic material due to the machine manufacturing process, temperature influences, and the impact of inverter operation. The first part of the thesis gives an overview of typical losses in electrical machines, with focus put on iron losses. Typical models for predicting iron losses in magnetic materials are presented in a comprehensive literature study. A broad comparison of magnetic materials and the introduction of a new material selection tool conclude this part. Next to the typically used silicon-iron lamination alloys for electrical machines, this thesis investigates also cobalt-iron and nickel-iron lamination sheets. These materials have superior magnetic properties in terms of saturation magnetization and hysteresis losses compared to silicon-iron alloys. The second and major part of the thesis introduces the developed measurement system of this project and presents experimental iron loss investigations. Influences due to machine manufacturing changes are studied, including punching, stacking and welding effects. Furthermore, the effect of pulse-width modulation schemes on the iron losses and machine performance is examined experimentally and with finite-element method simulations. For nickel-iron lamination sheets, a special focus is put on the temperature dependency, since the magnetic characteristics and iron losses change considerably with increasing temperature. Furthermore, thermal stress-relief processes (annealing) are examined for cobalt-iron and nickel-iron alloys by magnetic measurements and microscopic analysis. A thermal method for local iron loss measurements is presented in the last part of the thesis, together with experimental validation on an outer-rotor permanent magnet synchronous machine. / <p>QC 20140516</p>