LMI approaches for a robust control of a wind turbine with a hydrostatic transmission

In this paper, two alternative Linear Matrix Inequality (LMI) approaches were used to derive a decentralised control for an innovative 5 MW wind turbine with a hydrostatic transmission. With LMIs, given parameter uncertainties can be considered adequately. The proposed control covers the whole range from low to very high wind speeds. An active damping of tower oscillations is achieved by using the pitch angle as control input. Moreover, a robust multi-variable drive train control is designed that allows for tracking of desired trajectories for the angular velocities of both the rotor and the generator. The overall control performance is illustrated by realistic simulation results, which show an improved damping of tower oscillations and an excellent tracking behaviour for the controlled variables despite parameter uncertainties.