In this study, an innovative solution is examined for transmission problems and frequency control for wind Turbines. Power electronics and the gear boxes are the parts which are responsible of a significant amount of failures and they are increasing the operation and maintenance cost of wind turbines. Continuously transmission (CVT) systems are investigated as an alternative for conventional gear box technologies for wind turbines in terms of frequency control and power production efficiency. Even though, it has being used in the car industry and is proven to be efficient, there are very limited amount of studies on the CVT implementation on wind turbines. Therefore, this study has also an assertion on being a useful mechanical analyse on that topic. After observing several different types of possibly suitable CVT systems for wind turbines; a blade element momentum code is written in order to calculate the torque, rotational speed and power production values of a wind turbine by using aerodynamic blade properties. Following to this, a dynamic model is created by using the values founded by the help of the blade element momentum theory code, for the wind turbine drive train both including and excluding the CVT system. Comparison of these two dynamic models is done, and possible advantages and disadvantages of using CVT systems for wind turbines are highlighted. The wind speed values, which are simulated according to measured wind speed data, are used in order to create the dynamic models, and Matlab is chosen as the software environment for modelling and calculation processes. Promising results are taken out of the simulations for both in terms of energy efficiency and frequency control. The wind turbine model, which is using the CVT system, is observed to have slightly higher energy production and more importantly, no need for power electronics for frequency control. As an outcome of this study, it is possible to say that the CVT system is a candidate of being a research topic for future developments of the wind turbine technology.

Electro-hydrostatic compact drives are an emerging technology within a range of industrially available translational drive solutions, combining the specific advantages of hydraulic and electromechanical screw drives. Compared to electromechanical screw drives, hydrostatic drives can vary their transmission ratio with comparably little effort, giving them the key advantage of downsizing the electric drive components for a given load cycle. This paper provides a guideline on how to calculate the downsizing potential of electric motors and inverters arising from variable transmission ratio based on the load regime of a given application. Furthermore, a comprehensive systematisation of the actual switching process is described for systems that are switched by means of switching valves. The presented set of methodology is applied to demonstrators in order to validate the general findings.

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Hydrostatische Zylinderantriebe mit drehzahlvariablem Pumpenantrieb stellen modulare translatorische Antriebssysteme dar, die die Vorteile der elektrome-chanischen und hydraulischen Domänen verbinden. Zusätzlich bieten diese sog. elektrohydrostatischen Kompaktantriebe den Vorteil einer einfach umsetzbaren, diskret variablen Übersetzung. Diese erlaubt es, bei Arbeitsspielen mit dedizierten Eil- und Kraftphasen den elektrischen Antriebsmotor kleiner auszulegen als bei einer Referenz mit fester Übersetzung. Dadurch kann Downsizing-Potential in Bezug auf Größe und Masse des elektrischen Antriebsmotors und der Leistungselektronik erschlossen werden. In der vorliegenden Arbeit werden zunächst die möglichen Ersparnisse durch diese Technologie beleuchtet und die prinzipiellen Möglichkeiten einer schaltbaren Übersetzung dargestellt. Es wird eine Methodik erarbeitet, die es erlaubt, den gesamten Lösungsraum diskret umschaltbarer elektrohydrostatischer Kompaktantriebe systematisch zu erfassen und zu bewerten. Schließlich werden anhand von zwei Demonstratoren die Grenzen und Potentiale der Technologie experimentell untersucht und unterschiedliche, im Rahmen der Arbeit erarbeitete Strategien für den Umschaltvorgang zwischen zwei Übersetzungsstufen validiert. / Hydrostatic cylinder drives with variable speed pumps pose a modern form of modular translational drive systems, which merge the benefits of both electro-mechanic and hydraulic domains. Beyond that, these so called electrohydrostatic compact drives feature a possibility of implementing a discrete variable trans-ission ratio in a cost-effective manner. In the case of work cycles with dedicated rapid and force strokes, this allows the electric drive motor to be designed smaller than in the case of a reference with a fixed transmission ratio. In this way, downsizing potential can be exploited in terms of the size and mass of the electric drive motor and power electronics. In this thesis, the possible gains through this technology are first examined and the fundamental possibilities of a variable transmission are presented. A methodology is developed that allows the entire solution space of discretely switchable electrohydrostatic compact drives to be systematically mapped and evaluated. Finally, the limits and potentials of the technology are investigated experimentally by means of two demonstrators, and different strategies for the switching process between two transmission stages developed in the course of the thesis are validated.

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