A stall-regulated wind turbine with fixed-speed operation provides a configuration which is one of the cheapest and simplest forms of wind generation and configurations. This type of turbine, however, is non-optimal at low winds, stresses the component structure and gives rise to significant power peaks during early stall conditions at high wind speeds. These problems can be overcome by having a properly designed generator speed control. Therefore, to track the maximum power locus curve at low winds, suppress the power peaks at medium winds, limit the power at a rated level at high winds and obtain a satisfactory power-wind speed curve performance (that closely resembles the ideal power-wind speed curve) with minimum stress torque simultaneously over the whole range of the wind speed variations, the availability of active control is vital. The main purpose of this study is to develop an internal model control (IMC) design for the squirrel-cage induction generator (SCIG), coupled with a full-rated power converter of a small (25 kW), stall-regulated, variable-speed wind-turbine (SRVSWT) system, which is subject to variations in the generator speed, electromagnetic torque and rotor flux. The study was done using simulations only. The objective of the controller was to optimise the generator speed to maximise the active power generated during the partial load region and maintain or restrict the generator speed to reduce/control the torque stress and the power-peaking between the partial and full load regions, before power was limited at the rated value of 25 kW at the full load region. The considered investigation involved estimating the proportional-integral (PI) and integral-proportional (IP) controllers parameter values used to track the stator-current producing torque, the rotor flux and the angular mechanical generator speed, before being used in the indirect vector control (IVC) and the sensorless indirect vector control (SLIVC) model algorithms of the SCIG system. The design of the PI and IP controllers was based on the fourth-order model of the SCIG, which is directly coupled to the full-rated power converter through the machine stator, whereas the machine rotor is connected to the turbine rotor via a gearbox. Both step and realistic wind speed profiles were considered. The IMC-based PI and IP controllers (IMC-PI-IP) tuning rule was proven to have smoothened the power curve and shown to give better estimation results compared to the IMC-based PI controllers (IMC-PI), Ziegler-Nichols (ZN) and Tyreus-Luyben (ZN) tuning rules. The findings also showed that for the SRVSWT system that employed the IVC model algorithm with the IMC-PI-IP tuning rule, considering the application of a maintained/constant speed (CS) strategy at the intermediate load region is more profitable than utilizing SRVSWT with the modified power tracking (MoPT) strategy. Besides that, the finding also suggested that, for the IMC-PI-IP approach, the IVC does provide better power tracking performance than the SLIVC model algorithm.

This thesis focuses on the optimization of the electric aircraft propeller in order to increaseflight performance. Electric aircraft have limited energy, particularly the electricmotor torque compared to the fuel engine torque. For that, redesign of the propeller forelectric aircraft is important in order to improve the propeller efficiency. The airplanepropeller theory for Glauert is selected as a design method and incorporated with Brattimprovements of the theory. Glauert theory is a combination of the axial momentum andblade element theory. Pipistrel Alpha Electro airplane specifications have been chosen asa model for the design method. Utilization of variable pitch propeller and the influence ofnumber of blades has been investigated. The obtained design results show that the variablepitch propellers at cruise speed and altitude 3000 m reducing the power consumptionby 0.14 kWh and increase the propeller efficiency by 0.4% compared to the fixed pitchpropeller. Variable pitch propeller improvement was pretty good for electric aircraft. Theoptimum blade number for the design specifications is 3 blades. / Denna rapport har som fokus att optimera propellern på ett eldrivet flygplan för att förbättraflygprestationen. Eldrivna flygplan har begränsad energi, i synnerhet motorns vridmomenti jämförelse med bränslemotorns vridmoment. Därav behöver propellern designas om föratt uppnå en större verkningsgrad i propellern. Glauerts teori om flygplanspropellrar haranvänts som metod för designen där vissa modifieringar i teorin har tillämpats enligt Brattför att förbättra teorin. Glauerts teori är en kombination mellan axiell momentum- ochbladelement teori. Specifikationerna för Pipistrel Alpha Electro flygplan har använts sommodell i design metoden. Utnyttjande av propeller med justerbara bladvinklar samt antalblads påverkan har undersökts. De erhållna designresultaten visade att propellern medjusterbara bladvinklar vid planflykt på 3000 m höjd har sparat 0,14 kWh samt ökat propellernsverkningsgrad med 0,4% jämfört med propellern med icke justerbara bladvinklar.Propeller med justerbara stigning var lämplig för elflygplan. Det optimala antalet blad fördesignspecifikationerna är 3 blad.

L'amélioration des performances des chaînes de conversion dédiées à la récupération d'énergie par les hydroliennes est un point particulièrement important pour rendre cette ressource économiquement attractive. La minimisation du coût de l'énergie produite passe nécessairement par une amélioration des performances de la chaîne de conversion électromécanique et une réduction des coûts de maintenance et de production des éléments la constituant. Dans ce contexte particulier, les génératrices à aimants permanents apparaissent particulièrement intéressantes dans la mesure où elles sont bien adaptées à un fonctionnement à basse vitesse et à fort couple. Ceci permet d'éliminer des systèmes mécaniques très complexes, encombrants et exigeants en maintenance, tels que le multiplicateur de vitesse et/ou le système d'orientation des pales. L'objectif de cette thèse est d’explorer un certain nombre de pistes concernant les outils, les concepts et les règles de conception à mettre en oeuvre pour dimensionner une génératrice associée en entraînement direct à une turbine hydrolienne à pas fixe. Les outils mis au point dans ces travaux englobent des modèles multi-physiques intégrés dans une démarche de conception qui se veut la plus globale possible. Cette méthodologie tient compte de la caractéristique de la ressource (courants de marées), de celle de la turbine (hélice), des spécifications de la génératrice à aimants permanents, de la mise en oeuvre d’une stratégie de pilotage associant MPPT et limitation de puissance par défluxage à fort courants de marées, en plus des contraintes liées au convertisseur. L'environnement de conception développé est basé sur un couplage des modèles dans une procédure d'optimisation. Les résultats obtenus mettent en lumière les points clés associés au développement d’une telle génératrice pour un contexte hydrolien. / The improvements of marine current turbines drive train are key features to ensure safe operation and to make tidal energy resource cost-attractive. In this context, eliminating mechanical systems that demand high-level of maintenance can be an interesting way to improve the global behavior of tidal turbines. For that purposes, the presented studies focus on design methodologies and concepts of direct-driven generators associated with fixed-pitch turbines. The proposed designs are based on multiphysics models of the generator that are integrated in an optimization process taking into account the drive train environment. For these reasons, several models have been integrated into a global design strategy in order to find solutions that improve marine current turbines performances. This strategy is based on the use of an optimization process that combines electromagnetic model, thermal model, turbine performances model, and tidal resource velocity profile. This methodology integrates also an efficient control strategy based on a maximum power point tracking (MPPT) approach at low tidal speed and a flux-weakening power limitation control at high tidal speed. This control at high tidal velocities is in this work achieved by considering only the generator electrical control without using blade pitching systems. The obtained results highlight trends that could lead to an improvement of the design and they help designers to set relevant technological choices in order to ensure significant cost reduction and highly improve the reliability of marine current turbines.