Modeling wind generators with full-scale frequency converters: Stability and passivity properties

State-space models of wind generators connected to the grid through full-scale converters that are suitable for advanced variable speed applications and stability/passivity analysis, are obtained. Two different concepts, namely the induction generator and the PM synchronous generator concept, are addressed. The dynamic models obtained are of 8
^th
-and 6
^th
-order respectively and contain as variables in their state vector the ones that advanced control methods, such as vector control techniques, require. Applying on these models a Lyapunov-storage-function based analysis, it is proved that the fundamental property of passivity holds true independently from the selection of the converter control. Thus, one can effectively exploit this fact in the control design in order to achieve further improvements in the wind system performance.