I am trying to design a controller for the Nrel 5MW Wind Turbine (WT) based on the linearization of the OpenFast V2.5.0 for rotor speed regulation.
Although I stabilized the non-linear WT based on that linearization using simple state feedback controller at the linearized operating point, I am not able to stablize the linear model for the same gains. The linear model of WT required another values of state feedback gains which is greatly different from the ones of nonlinear model. Also, both models gives different response for the same input.
Are there any suggestions in order to get similar response with no big difference between the linear and nonlinear model of WT?
Note that: I simplified the WT model to only one DOF of the genrator (GenDOF). So, I have only two states:
Displacement of variable speed generator DOF (Q_GeAz in rad)
Velocity of variable speed generator DOF (QD_GeAz in rad/s)
The linearization has been made at a pitch angle of 11.5 (deg) with a wind speed of 16 m/s.
The state feedback gains are (K = 10.0981 2.5407 = place(A,B,[-.01 -0.6]))