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Abstract: The objectives of this work have been to design and analyze a discrete Linear Quadratic Gaussian (LQG) controller which contributes to the primary frequency control of the grid and to the reduction of the drive-train fatigue loads of a Wind Turbine (WT). The WT rotational speed and electrical power are controlled using the generator torque and the pitch angle as control variables. The rotational speed and electrical power references are generated in a higher control level depending on the wind speed and a frequency droop. The controller has been designed in Matlab® and has been simulated in Simulink®, in some linear simulation models corresponding to different operating points. These linear models have been obtained from a 5 MW WT model implemented in the commercial wind turbine simulation tool Bladed. The results validate the efficiency of the designed controller, in comparison with another discrete LQG controller which has not been designed to reduce drive-train fatigue loads. [Copyright &y& Elsevier]

Abstract: Wind energy technology has experienced important improvements this last decade. The transition from fixed speed to variable speed wind turbines has been a significant element of these improvements. It has allowed adapting the turbine rotational speed to the wind speed variations with the aim of optimizing the aerodynamic efficiency. A classic controller that has slow dynamics relative to the mechanical dynamics of the drive train is implemented in commercial wind turbines. The objective of the work related in this paper has been to evaluate the implementation, on a test bench, of a controller whose dynamics can be adjusted to be faster and to compare in particular its aerodynamic efficiency with the conventional controller. In theory, the higher dynamics of the non-classic controller has to lead to a better efficiency. A 180kW wind turbine whose simulation model has been validated with field data is emulated on an 18kW test bench. The emulator has also been validated. Test bench trials are a very useful step between numerical simulation and trials on the real system because they allow analyzing some phenomena that may not appear in simulations without endangering the real system. The trials on the test bench show that the non-conventional controller leads to a higher aerodynamic efficiency and that this is offset by higher mechanical torque and electric power fluctuations. Nevertheless, the amplitudes of these fluctuations are relatively low compared to their rated values. [Copyright &y& Elsevier]