A composite linear state-space controller was developed for a multi-objective problem in the variable-speed operation of wind turbines. Disturbance Tracking Control theory was applied to the design of a torque controller to optimize energy capture under the influence of persistent wind disturbances. A limitation in the theory for common multi-state models is described; this led to the design of a complementary pitch controller. The goal of the independent blade pitch design was to minimize blade root fatigue loads. A SymDyn model of a two-bladed, 600-kW machine was used for the simulation studies. Results indicate a 24% reduction in blade fatigue damage using the proposed controllers, compared to a conventional torque-only design. However, energy capture was not improved as much as expected, partly due to nonlinearity effects degrading the performance of the state-space estimator design. Tower base fatigue damage was shown to decrease significantly using active pitch.

Issue Section:
Technical Papers
Keywords:
variable speed gear, wind turbines, state-space methods, torque control, machine control, fatigue, control system synthesis
Topics:
Blades, Control equipment, Design, Fatigue, Stress, Torque, Tracking control, Wind turbines, Rotors, Machinery, Fatigue damage, Torque control, Turbines
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