Non-linear control design for optimized power regulations in spar wind turbines under wind and wave loads
Abstract
Controlling motions for spar wind turbines (SWT) is necessary for reliable power production. In this paper, a control design is developed and its efficacy is demonstrated through the application to wind turbines installed on spar. SWT is expected to generate rated power under stochastic wind and wave loads. The controller design is derived from the quadratic regulator algorithm, which involves changing the dynamics of the system matrices (which are state dependent) of wind turbine. Three turbulent wind velocities are chosen at which the controller algorithm is working for turbines operational region. The ensemble average is used to eliminate statistical uncertainty, since the loads are stochastic. Illustrations through the generated power, torque and rotor speed show that the proposed controller (i.e., nonlinear quadratic one) works better than the existing baseline algorithm. More specifically, the achieved generated power through the proposed method is 29% higher than conventional one for 21 m/s stochastic wind field scenario. Along with controlling the desired variables, this algorithm also maintains the motions of platforms and forces at base of tower. Also, the ensemble means and the maxima of responses are closer to reference values with considerably lower standard-deviation.