Advanced digital control for the harmonization of wind-based energy in the electric power supply

As wind turbines continue to grow in size and flexibility and are deployed in more hostile environments, the need to develop advanced control schemes will be elemental to deliver the lowest possible energy costs. This paper explores controller design based on modeling the wind speed as a stochastic process, and the wind generating system (WGS) as a multi-mass system with a soft shaft linking the turbine with the asynchronous generator. The control objectives are to enhance reduction in stresses on the drive-train and to ensure operation geared toward optimal power conversion. A sophisticated control strategy incorporating a multi-objective, full-state feedback with state estimation linear quadratic Gaussian (LQG) for generator torque control is proposed. This study focuses on above rated wind speeds, and the LQG's main purpose is to add damping to the drive-train, thereby minimizing cyclic fatigue, while a pitch mechanism prevents rotor overspeed thus ensuring the maximum power constraint is respected. Simulations show the efficacy of the proposed paradigm in meeting the control objectives.