Wind Turbine System Identification and Individual Pitch Control

This paper addresses system identification and control for the wind turbine operating in region 3, where the wind is excessive and blades must pitch to regulate the rotor speed and alleviate the bending moments on the blades. This region is critical for safe operation of the wind turbine. First, this paper develops linear models for controller design of the individual and collective pitch control loop by performing system identification on direct data, instead of relying on the first principles modelling. A Linear Quadratic Gaussian regulator with integral (LQGi) action is designed to control the rotor speed at its rated speed, and another multivariable LQGi individual pitch controller is used to reduce the first harmonic of the bending moment in the blades. Furthermore, an internal model based controller is an add-on to theses existing LQGi controllers to suppress synchronous harmonics directly in the d-q coordinates. Simulation experiments on FAST demonstrates the presented identification and control methods.