Type-2 fuzzy logic pitch controller for wind turbine rotor blades

Wind energy contribution as a new source of green energy in electric utility systems around the world is on fast increase. One of the major challenges is its natural intermittency; unpredictability, and uncertainty. In this paper, two and three dimensional profiles are presented for the torque coefficient and turbine output torque surface response. Interval Type-2 Fuzzy Controllers (IT2FCs) are proposed to control the nonlinear pitch angle system of the rotor blades in variable speed wind turbine. The IT2FCs proposed in this paper were designed to deal with uncertainty and noisy inputs. In addition, the nonlinear pitch angle system is piecewise linearized based on two linear time invariant (LTI) models. The LTIs were controlled using a regional switched controller schemes that allow the controllers to cover the state space of the pitching system.