Dynamic behavior of variable speed wind turbines under stochastic wind

It is recognized that the most important advantage of the variable speed wi nd turbines (VS WTs) over the conventional constant speed (CS) machines are the improved dynamic characteristics, resulting in the reduction of the dr ive train mechanical stresses and output power fluctuations. In this paper alternative configurations of the electrical part of a VS WT are considered , using a squirrel cage induction generator and voltage or current source c onverters, as well as a double output induction generator with a rotor conv erter cascade. The WT operation is simulated for typical wind speed time se ries and the examined schemes are comparatively assessed. It is shown that, using suitable converters and controls, a great reduction of the mechanica l stresses and output power fluctuations can be achieved, compared to the C S mode of operation of the WT.