System ID Modern Control Algorithms for Active Aerodynamic Load Control and Impact on Gearbox Loading

Prior work on active aerodynamic load control (AALC) of wind turbine blades has demonstrated that appropriate use of this technology has the potential to yield significant reductions in blade loads, leading to a decrease in wind cost of energy. While the general concept of AALC is usually discussed in the context of multiple sensors and active control devices (such as flaps) distributed over the length of the blade, most work to date has been limited to consideration of a single control device per blade with very basic Proportional Derivative controllers, due to limitations in the aeroservoelastic codes used to perform turbine simulations. This work utilizes a new aeroservoelastic code developed at Delft University of Technology to model the NREL/Upwind 5 MW wind turbine to investigate the relative advantage of utilizing multiple-device AALC. System identification techniques are used to identify the frequencies and shapes of turbine vibration modes, and these are used with modern control techniques to develop both Single-Input Single-Output (SISO) and Multiple-Input Multiple-Output (MIMO) LQR flap controllers. Comparison of simulation results with these controllers shows that the MIMO controller does yield some improvement over the SISO controller in fatigue load reduction, but additional improvement is possible with further refinement. In addition, a preliminary investigation shows that AALC has the potential to reduce off-axis gearbox loads, leading to reduced gearbox bearing fatigue damage and improved lifetimes.Aerodynamics & Wind EnergyAerospace Engineerin

Impact of Higher Fidelity Models on Simulation of Active Aerodynamic Load Control For Fatigue Damage Reduction

Active aerodynamic load control of wind turbine blades is being investigated by the wind energy research community and shows great promise, especially for reduction of turbine fatigue damage in blades and nearby components. For much of this work, full system aeroelastic codes have been used to simulate the operation of the actively controlled rotors. Research activities in this area continually push the limits of the models and assumptions within the codes. This paper demonstrates capabilities of a full system aeroelastic code recently developed by researchers at the Delft University Wind Energy Research Institute with the intent to provide a capability to serve the active aerodynamic control research effort, The code, called DU_SWAMP, includes higher fidelity structural models and unsteady aerodynamics effects which represent improvement over capabilities used previously by researchers at Sandia National Laboratories. The work represented by this paper includes model verification comparisons between a standard wind industry code, FAST, and DU_SWAMP. Finally, two different types of active aerodynamic control approaches are implemented in order to demonstrate the fidelity simulation capability of the new code.Aerospace Engineerin