Cascading Kalman Observers of Structural Flexible and Wind States for Wind Turbine Control

We formulate novel observers of the structural flexible states of a wind turbine, as well as of the wind incident on its rotor. Stochastic filtering processes reconstruct on-line optimal estimates of the tower and blade states, by using readings from accelerometers and strain gages placed along the structural members. From these re-constructed states, another filtering process estimates the wind states which, improving on the commonly used mean hub-height wind estimates or the point measurements available from on-board anemometers, also include information on the wind-over-the-rotor distribution. The proposed procedure is able to ap-proximate vertical and horizontal wind shear, yawed flow and a vertical wind component. The instantaneous estimates of the flexible states of tower and blades and of the spatial wind distri-bution can be used for enabling sophisticated individual-blade fatigue and load alleviating control laws. The proposed procedures are demonstrated with the help of numerical experiments conducted using a high-fidelity aero-servo-elastic simulator.