En esta Tesis ha sido analizado el control de la màquina sincrónica de rotor bobinado actuando en isla. Para esta configuración, la velocidad mecànica determina la frecuencia, y la tensión de rotor se utiliza para fijar la amplitud de la tensión de estator. Debido a que la constante de tiempo eléctrica es mucho más ràpida comparada con la constante de tiempo mecánica, la velocidad mecánica fue considerada constante y externamente regulada y la investigación se enfocó en la regulación de la amplitud de la tensión de estator.Cuatro diferentes controladores basados en técnicas de modos deslizantes fueron diseñados en el marco de referencia dq. Las leyes de control obtenidas regulan la amplitud de la tensión de estator independientemte del valor de la carga. Adicionalmente, sólo las medidas de tensión y posición del rotor (para calcular la transformada dq) son necesarias. La estabilidad de los puntos de equilibrio obtenidos fueron probados al menos utilizando anàlisis de pequeña señal.Se realizó la validación por simulación y experimental de cada controlador en diferentes escenarios. Los resultados obtenidos validan los diseños y muestran las principales ventajas y desventajas de el sistema en lazo cerrado.El capítulo 2 cubre los problemas de modelado de la màquina sincrónica de rotor bobinado. Partiendo de las ecuaciones trifásicas generales, y utilizando la transformada de Park, se encontraron el modelo en dq del generador sincrónico de rotor bobinado (WRSG) en isla, alimentando tanto carga resistiva como inductiva. Los puntos de equilibrio del sistema obtenido fueron analizados y calculados, luego se definió el objetivo de control. Finalmente, se obtuvieron modelos lineales aproximados y sus respectivas funciones de transferencia.Los controladores PI son los más usados en la industria porque ofrecen buen desempeño y son sencillos de implementar. En el capítulo 3, se obtuvieron las reglas de sintonización para el controlador PI, y se analizaron estos resultados con el objetivo de proponer nuevos controladores que mejoraran el desempeño de la clásica aproximación PI.El esquema de control en modos deslizantes para la WRSG conectada a una carga resistiva fue diseñado en el capítulo 4. Éste, también incluye un completo análisis de estabilidad del sistema en lazo cerrado. El capítulo 5 presenta dos diseños basados en modos deslizantes para regular la amplitud de la tensión de estator para el WRSG actuando en isla. Ambos diseños usan la componente d de la tensión de estator en la función de conmutación. El primer caso es un control anidado, donde un lazo externo PI es añadido para proveer la referencia de la componente d de la tensión. En la segunda aproximación un término integral es añadido a la superficie de conmutación.El caso de alimentar una carga inductiva es estudiado en el capítulo 6. El controlador requiere una extensión dinámica debido a que la amplitud de la tensión de estator es una salida de grado relativo cero. Como resultado, un controlador robusto, que no depende de los parámetros de la máquina ni de los valores de carga es obtenido. En el capítulo 7 los resultados de simulación y experimentales para los controladores diseñados para el WRSG actuando en isla son presentados. En primer lugar, una descripción completa del banco es presentada. Esta incluye detalles de la etapa de adquisición de datos y de la DSP utilizada. En segundo lugar, se hace la descripción del procedimiento de simulación. Luego, las simulaciones y experimentos, que contienen diferentes escenarios, con cambios de referencia y variaciones de carga para cada controlador son presentados. / The control of the stand-alone the wound rotor synchronous generator has been analyzed in this dissertation. For this islanded configuration, the mechanical speed determines the frequency, and the rotor voltage is used to set the stator voltage amplitude. Due to the electrical time constant is so fast compared with the mechanical time constants, the mechanical speed was considered constant and externally regulated and the research was focused on the stator voltage amplitude regulation.Four different controllers based on sliding mode control techniques were designed in the dq reference frame. The obtained control laws regulate the stator voltage amplitude irrespectively of the load value. Furthermore, only voltage and rotor position measures (to compute the dq transformation), are required. The stability of the obtained equilibrium points was proved at least using small-signal analysis. Simulation and experimental validation of each controller containing several scenarios were carried out. The obtained results validate the designs and show the main advantages and disadvantages of each closed loop system. Chapter 2 covers the modeling issues of the wound rotor synchronous machine. From the general three-phase dynamical equations, and using the Park transformation, the dq-model of the stand-alone wound rotor synchronous generator feeding both a resistive and an inductive load are obtained. Equilibrium points of the obtained systems are analyzed and, after defining the control objective, the desired equilibrium points are computed.Finally, linear approximated models are obtained and their transfer functions are also presented.PI controllers are the most used in the industry because they offers good performance and are easily implementables. In Chapter 3 we obtain the tuning rule for the PI controller, and we analyze these results in order to propose new controllers which improve the classic PI approach.The sliding mode control scheme for the WRSG connected to a resistive load is designed in Chapter 4. It also includes a complete stability analysis of the closed loop system. Chapter 5 presents two sliding mode designs to regulate the stator voltage amplitude for a stand-alone wound rotor synchronous generator. Both use the stator voltage d-component error in the switching function. The first case is a nested controller, where an outer PI loop is added to provide the proper d-voltage component reference. In the second approach an integral term is added to the switching function. The case of feeding an inductive load is studied in Chapter 6. The controller introduces a dynamic extension because the stator voltage amplitude is a zero relative degree output. As result, a robust controller, which neither depends on the machine parameters nor on the load values, is obtained. In Chapter 7 the simulation and the experimental results of the designed controllers for the stand-alone wound rotor synchronous generator are presented. Firstly, a complete description of the bench is provided. It also includes details of the data acquisition stage and the used DSP card. Secondly, the description of the simulation procedure is commented. Then, the simulation and experiments which contains several scenarios, with reference change and load variations evaluated for each controller are presented.

This thesis is on the space--time variational multiscale (ST-VMS) computation of wind-turbine rotor and tower aerodynamics. The rotor geometry is that of the NREL 5MW offshore baseline wind turbine. We compute with a given wind speed and a specified rotor speed. The computation is challenging because of the large Reynolds numbers and rotating turbulent flows, and computing the correct torque requires an accurate and meticulous numerical approach. The presence of the tower increases the computational challenge because of the fast, rotational relative motion between the rotor and tower. The ST-VMS method is the residual-based VMS version of the Deforming-Spatial-Domain/Stabilized ST (DSD/SST) method, and is also called ``DSD/SST-VMST'' method (i.e., the version with the VMS turbulence model). In calculating the stabilization parameters embedded in the method, we are using a new element length definition for the diffusion-dominated limit. The DSD/SST method, which was introduced as a general-purpose moving-mesh method for computation of flows with moving interfaces, requires a mesh update method. Mesh update typically consists of moving the mesh for as long as possible and remeshing as needed. In the computations reported here, NURBS basis functions are used for the temporal representation of the rotor motion, enabling us to represent the circular paths associated with that motion exactly and specify a constant angular velocity corresponding to the invariant speeds along those paths. In addition, temporal NURBS basis functions are used in representation of the motion and deformation of the volume meshes computed and also in remeshing. We name this ``ST/NURBS Mesh Update Method (STNMUM).'' The STNMUM increases computational efficiency in terms of computer time and storage, and computational flexibility in terms of being able to change the time-step size of the computation. We use layers of thin elements near the blade surfaces, which undergo rigid-body motion with the rotor. We compare the results from computations with and without tower, and we also compare using NURBS and linear finite element basis functions in temporal representation of the mesh motion.

The number of large-scale wind farms integrated to the power system in Sweden is increasing. Two generator concepts that are widely used are Doubly-Fed Induction Generators (DFIG) and Full Power Converters (FPC). The study is of a quantitative character and the aim of the Master thesis is to compare DFIG-models with FPC-models integrated in an area with high concentration of hydropower. Then it is possible to examine how the dynamics in the power system change depending on the selection of technology (DFIG or FPC) when connecting a wind farm. The power system is simulated during a summer night, i.e., a low load is connected. The Master thesis covers stability analysis of the power system by using rotor angle stability that are split into small-signal stability and transient stability (time-domain simulations) and finally voltage stability to see how the hydropower generators react when varying the power production in the wind farm. The Master thesis concludes that independently of wind turbine technique, integration of a wind farm has slight impact on the stability in the power system compared to a power system without a wind farm, even though the load is low. Further, an integration of a wind farms affects the reactive power production in neighbouring hydropower plants. Finally, when increasing the size of the wind farm the neighbouring hydropower station consume less reactive power which can induce problem with the voltage stability.

Despite the high cost of memory and CPU time required to resolve the boundary layer, a viscous unstructured grid solver has many advantages over a structured grid solver such as the convenience in automated grid generation and shock or vortex capturing by solution adaption. Since the geometry and flow phenomenon of a helicopter are very complex, unstructured grid-based methods are well-suited to model properly the rotor-fuselage interaction than the structured grid solver. In present study, an unstructured Cartesian grid solver is developed on the basis of the existing solver, NASCART-GT. Instead of cut-cell approach, immersed boundary approach is applied with ghost cell boundary condition, which increases the accuracy and minimizes unphysical fluctuations of the flow properties. The standard k-epsilon model by Launder and Spalding is employed for the turbulence modeling, and a new wall function approach is devised for the unstructured Cartesian grid solver. It is quite challenging and has never done before to apply wall function approach to immersed Cartesian grid. The difficulty lies in the inability to acquire smooth variation of y+ in the desired range due to the non-body-fitted cells near the solid wall. The wall function boundary condition developed in this work yields stable and reasonable solution within the accuracy of the turbulence model. The grid efficiency is also improved with respect to the conventional method. The turbulence modeling is validated and the efficiency of the developed boundary condition is tested in 2-D flow field around a flat plate, NACA0012 airfoil, axisymmetric hemispheroid, and rotorcraft applications. For rotor modeling, an actuator disk model is chosen, since it is efficient and is widely verified in the study of the rotor-fuselage interaction. This model considers the rotor as an infinitely thin disk, which carries pressure jump across the disk and allows flow to pass through it. The full three dimensional calculations of Euler and RANS equations are performed for the GT rotor model and ROBIN configuration to test implemented actuator disk model along with the developed turbulence modeling. Finally, the characteristics of the rotor-fuselage interaction are investigated by comparing the numerical solutions with the experiments.

Brushless Direct Current (BLDC) motors are one of the motor types rapidly gaining popularity. BLDC motors are being increasingly used in critical high performance industries such as appliances, automotive, aerospace, consumer, medical, industrial automation equipment and instrumentation. Fault detection and condition monitoring of BLDC machines is therefore assuming a new importance. The objective of this research is to advance the field of rotor and load fault diagnosis in BLDC machines operating in a variety of operating conditions ranging from constant speed to continuous transient operation. This objective is addressed as three parts in this research. The first part experimentally characterizes the effects of rotor faults in the stator current and voltage of the BLDC motor. This helps in better understanding the behavior of rotor defects in BLDC motors. The second part develops methods to detect faults in loads coupled to BLDC motors by monitoring the stator current. As most BLDC applications involve non-stationary operating conditions, the diagnosis of rotor faults in non-stationary conditions forms the third and most important part of this research. Several signal processing techniques are reviewed to analyze non-stationary signals. Three new algorithms are proposed that can track and detect rotor faults in non-stationary or transient current signals.

Stator current spectral analysis techniques are usually used to detect rotor faults in induction machines. Magnetic field anomalies in the airgap due to the rotor faults result in characteristic side-band harmonic components in the stator current spectrum, which can be measured as rotor fault signatures. A position-varying load torque oscillation at multiples of the rotational speed, however, has exactly the same effect. Stator current harmonics due to a load torque oscillation often obscure and even overwhelm rotor eccentricity fault detection since the magnitude of load oscillation induced harmonics is usually much larger. Although previous research has suggested some methods to differentiate between these two effects, most of them rely heavily on the accurate estimation of motor parameters. The objective of this research is to develop a far more practical and computationally efficient method to detect rotor faults effectively in the presence of a load torque oscillation. A significant advantage of the proposed scheme is that it does not need any knowledge of motor parameters. The normalized negative sequence information induced by a mixed rotor eccentricity in the stator current or terminal voltage space vector spectra, serves as a reliable rotor fault indicator to eliminate load oscillation effects. Detailed airgap magnetic field analysis for an eccentric motor is performed and all machine inductance matrices as well as their derivatives are reformulated accordingly. Careful observation of these inductance matrices provides a fundamental understanding of motor operation characteristics under a fault condition. Simulation results based on both induction motor dynamic model and Maxwell 2D Finite Element Model demonstrate clearly the existence of the predicted rotor fault indicator. Extensive experimental results also validate the effectiveness and feasibility of the proposed detection scheme.

Lead-lag dampers are present in most rotor systems to provide the desired level of damping for all flight conditions. These dampers are critical components of the rotor system, and the performance of semi-active Coulomb-friction-based lead-lag dampers is examined for the UH-60 aircraft. The concept of adaptive damping, or “damping on demand,” is discussed for both ground resonance and forward flight. The concept of selective damping is also assessed, and shown to face many challenges. In rotorcraft flight dynamics, optimized warping twist change is a potentially enabling technology to improve overall rotorcraft performance. Research efforts in recent years have led to the application of active materials for rotorcraft blade actuation. An innovative concept is proposed wherein the typically closed section blade is cut open to create a torsionally compliant structure that acts as its own amplification device; deformation of the blade is dynamically controlled by out-of-plane warping. Full-blade warping is shown to have the potential for great design flexibility. Recent advances in rotorcraft blade design have also focused on variable-camber airfoils, particularly concepts involving “truss-core” configurations. One promising concept is the use of hexagonal chiral lattice structures in continuously deformable helicopter blades. The static behavior of passive and active chiral networks using piezoelectric actuation strategies is investigated, including under typical aerodynamic load levels. The analysis is then extended to the dynamic response of active chiral networks in unsteady aerodynamic environments.

<p>The design parameters axial gap and stator count of highpressure turbine stages are evaluated numerically towards theirinfluence on the unsteady aerodynamic excitation of rotorblades. Of particular interest is if and how unsteadyaerodynamic considerations in the design could reduce the riskofhigh cycle fatigue (HCF) failures of the turbine rotor.</p><p>A well-documented 2D/Q3D non-linear unsteady code (UNSFLO)is chosen to perform the stage flow analyses. The evaluatedresults are interpreted as aerodynamic excitation mechanisms onstream sheets neglecting 3D effects. Mesh studies andvalidations against measurements and 3D computations provideconfidence in the unsteady results. Three test cases areanalysed. First, a typical aero-engine high pressure turbinestage is studied at subsonic and transonic flow conditions,with four axial gaps (37% - 52% of cax,rotor) and two statorconfigurations (43 and 70 NGV). Operating conditions areaccording to the resonant conditions of the blades used inaccompanied experiments. Second, a subsonic high pressureturbine intended to drive the turbopump of a rocket engine isinvestigated. Four axial gap variations (10% - 29% ofcax,rotor) and three stator geometry variations are analysed toextend and generalise the findings made on the first study.Third, a transonic low pressure turbine rotor, known as theInternational Standard Configuration 11, has been modelled tocompute the unsteady flow due to blade vibration and comparedto available experimental data.</p><p>Excitation mechanisms due to shock, potential waves andwakes are described and related to the work found in the openliterature. The strength of shock excitation leads to increasedpressure excitation levels by a factor 2 to 3 compared tosubsonic cases. Potential excitations are of a typical wavetype in all cases, differences in the propagation direction ofthe waves and the wave reflection pattern in the rotor passagelead to modifications in the time and space resolved unsteadypressures on the blade surface. The significant influence ofoperating conditions, axial gap and stator size on the wavepropagation is discussed on chosen cases. The wake influence onthe rotorblade unsteady pressure is small in the presentevaluations, which is explicitly demonstrated on the turbopumpturbine by a parametric study of wake and potentialexcitations. A reduction in stator size (towards R≈1)reduces the potential excitation part so that wake andpotential excitation approach in their magnitude.</p><p>Potentials to reduce the risk of HCF excitation in transonicflow are the decrease of stator exit Mach number and themodification of temporal relations between shock and potentialexcitation events. A similar temporal tuning of wake excitationto shock excitation appears not efficient because of the smallwake excitation contribution. The increase of axial gap doesnot necessarily decrease the shock excitation strength neitherdoes the decrease of vane size because the shock excitation mayremain strong even behind a smaller stator. The evaluation ofthe aerodynamic excitation towards a HCF risk reduction shouldonly be done with regard to the excited mode shape, asdemonstrated with parametric studies of the mode shapeinfluence on excitability.</p><p><b>Keywords:</b>Aeroelasticity, Aerodynamics, Stator-RotorInteraction, Excitation Mechanism, Unsteady Flow Computation,Forced Response, High Cycle Fatigue, Turbomachinery,Gas-Turbine, High-Pressure Turbine, Turbopump, CFD, Design</p>

In this thesis, a numerical approach based on a potential flow method has been developed in order to simulate unsteady rotor/stator interaction, and to predict the unsteady performance of a propeller and its rudder. The method is first developed and tested in two-dimensions by using a boundary element method in which a front hydrofoil is moving downward, while a back hydrofoil is stationary. The wakes of the two hydrofoils are modeled by continuous dipole sheets and determined in time by applying a force free-condition on each wake surface. The wake/hydrofoil interaction is de-singularized by applying a numerical fence on the surface of the back hydrofoil. The viscous wake/hydrofoil interaction is considered by employing a viscous wake vorticity model on the rotor's wake surface. The present method is validated by comparison with analytical solutions, experimental data and by using the results from a commercial Reynolds Averaged Navier-Stokes (RANS) solver for the same set-up and conditions. The numerical approach is further extended to three-dimensions to predict the mutual interaction between a propeller and rudder. A fully unsteady wake alignment algorithm is implemented into a Vortex Lattice Method to simulate the unsteady propeller flow. The interaction between propeller and rudder is investigated in a fully unsteady manner, where a panel method is used to solve the flow around the rudder, and a vortex lattice method is used to solve the flow around the propeller. The interaction between a propeller and its rudder is considered in an iterative manner by solving the propeller and the rudder problems separately and by including the unsteady effects of one component on the other. The effect of the unsteady propeller-rudder interaction on the mean and on the unsteady propeller/rudder performance, including sheet cavitation on the rudder, is studied. / text

The object of the final work is the magnetic field of the synchronous salient-pole reluctance micro motor and distribution of it in the air gap. The analysis of the magnetic field distribution have been made with three rotor variants: an isosceles rotor, a rotor with an arched slot of, a rotor with a rectangular slot, using a specialized field counting program - “QuickField” 4.2 Beta 1 student version. In the study, the influence of the rotor slot and the constructional air spacing to the distribution of the magnetic flux density in the air gap when the angular position of the rotor alternates from 0 to 900, every 300 was analysed. The distribution and the alternation of the magnetic permeability in the mid-cross section of the rotor vertical to its longitudinal axis was looked at. The results of this analysis could be useful for determination of the rotor magnetic reluctance according to the longitudinal and transversal axis.