Wind energy has widely grown through the last two decades. Due to the significant increase of the number of wind turbines connected to the grid, new technologies aimed to assure power system quality and stability have become an important area for research and development. In particular, the design of advanced control techniques has recently emerged as a crucial issue for wind energy to penetrate into the electrical market. On the other hand, the need of more reliable control systems has become even more crucial with the increasing size of the machines and the related shift of their natural frequencies. As wind turbines become larger and more flexible, the design of innovative control strategies with load reduction as an explicit objective turns out to be more critical.