Dynamic behavior of variable speed wind turbines under stochastic wind

It is recognized that the most important advantage of the variable speed wind turbines (VS WTs) over the conventional constant speed (CS) machines are the improved dynamic characteristics, resulting in the reduction of the drive 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 converters, as well as a double output induction generator with a rotor converter cascade. The WT operation is simulated for typical wind speed time series and the examined schemes are comparatively assessed. It is shown that, using suitable converters and controls, a great reduction of the mechanical stresses and output power fluctuations can be achieved, compared to the CS mode of operation of the WT.