Design of State-Space-Based Control Algorithms for Wind Turbine Speed Regulation

Control can improve the performance of wind turbines by enhancing energy capture and reducing dynamic loads. At the National Renewable Energy Laboratory, we are beginning to design control algorithms for regulation of turbine speed and power using state-space control designs. In this paper, we describe the design of such a control algorithm for regulation of rotor speed in full-load operation (Region 3) for a two-bladed wind turbine. We base our control design on simple linear models of a turbine, which contain rotor and generator rotation, drive train torsion, rotor flap (first mode only), and tower fore-aft degrees of freedom (DOFs). Wind-speed fluctuations are accounted for using Disturbance Accommodating Control (DAC). We show the capability of these control schemes to stabilize the modeled turbine modes via pole placement, while using state estimation to reduce the number of turbine measurements that are needed for these algorithms. These controllers are incorporated into a simulation code and simulated for various conditions. Finally, conclusions to this work and future studies are outlined.