This paper compares the dynamic performance of a nonlinear control approach based on flat filtering with respect to a baseline controller on an offshore wind turbine. Feedback linearization and Generalized Proportional Integral (GPI) compesator is used to reduce load and mechanical fatigue in the collective pitch blade, while a PI reset controller is designed to regulate the rotor speed for an uncertain parameter model of the generator torque. In order to validate the control approach a baseline controller is used, which combines an Indirect Speed Controller (ISC) and a collective blade pitch controller (CPC). Simulation results show that the controller based on flatness and reset mechanism is able to greatly reduce rotor speed and power variations in full load conditions and perfect wind preview.