Controller design for blade load reduction using synthetic jets

As the size of modern wind turbines increase, the blades become longer and more flexible. Consequently, fatigue loads due to the structural vibration become more important and turn to be a constraint on enlarging the size of the new turbines. Thus, it becomes more necessary to use nontraditional actuators to damp structural vibration. This paper, presents the design of a control system that acts on blade synthetic jets to reduce and damp the vibration of the desired blade modes. The design of model-based estimators is addressed. These estimators use the measurements of several accelerometers and strain gauges along the blade and the tower to estimate the contribution of each blade modal state to the vibration of the tower and the blades. The synthetic jet actuators are then controlled, such that the desired vibration modes are damped effectively. Designed estimator and controller are implemented on a FEM-based wind turbine simulation code. The results show significant damping of blade vibration.