Beitrag zur Entwicklung leistungselektronischen Komponenten für Windkraftanlagen

Development of Power Electronics converter topologies and control concepts for Wind turbines173 pages, 163 figures, 72 reference literatures Technical University Ilmenau, Faculty of Electrical Engineering and Information Technology, Dissertation, 2008This thesis deals over certain selective problems occurring in the wind turbine, more specific to electrical energy conversion using generator and converter.The fixed speed stall controlled wind turbines generally inject more current over and above the rated current during the starting phase under strong wind conditions. A developed patented concept illustrates the use of parallel load resistors under such conditions, to reduce the total current delivered to grid and to bring its magnitude within the rated current range. By switching from a faster to a slower speed steps, the pole changeable generators can deal with electrical oscillations through control of anti parallel thyristor bridge.The basic working concept of variable speed stall controlled wind turbine is illustrated in this work. The choice of the operating point on the power curve of the wind turbine determines the generator speed range and therefore, this necessitates the over dimensioning of converter or alternative loads, to consume extra power and energy of the wind rotor.Furthermore, the several converter topologies (PWM based voltage and current converter, boost and buck converter and diode bridge) for the doubly fed induction generator (DFIG) are compared with each other. For the case of rotor side diode bridge with boost converter, a simulation based result shows that the torque can be regulated at a constant value by the boost converter. In doing so, however the induction generator draws harmonics currents, which is needed to be compensated by the grid side converter.For the sine triangle modulation, various offset functions were chosen and there corresponding pulse frequency spectrum was analyzed. During this analysis, one newer insight comes to light, that on selective phase shifting of the ...