Environmental Engineering Reference
In-Depth Information
unsymmetrical than if all three blades were pitching. This will introduce additional
fluctuations in the yaw moment, as seen from the histogram. Although, the mean
value is almost 40 % lower than the baseline value, see Fig.
6.14
.
A table describing the most critical natural frequencies are shown in Table
6.4
.
These are found by calculating the Fast Fourier Transform (FFT) from the closed-
loop time-series. From the discussion about critical frequencies in the introduction,
it is seen from the table that the natural frequencies are where they should be.
6.5 Conclusions
This chapter studied modeling, analysis, and control design for offshore floating
wind turbine systems. To this aim, an individual pitch static output-feedback
controller is designed for the system under consideration with constrained infor-
mation. The constrained information can be utilized in the case of sensor failures
and from mathematical point of view means that a special zero-nonzero structure
is imposed on the output-feedback gain matrix. In the considered system, there are
three inputs and three outputs. If one sensor fails, only one blade pitch actuator
will be influenced. The model under consideration is obtained from the software
FAST. The model is fully nonlinear and in addition to the added pitch actuators the
model consists of 27 DOFs. A linear model is obtained in order to perform the
controller design, and simulations are carried out to verify the design. Simulation
results performed both on the linear model and on the fully nonlinear system are
presented in order to show the effectiveness of the controller design methodology.
6.6 Future Work
It is noted that the extensions of the proposed method to the observer-based
controller design for wind turbine control systems deserve further investigation.
Also, considering the delay in actuators and its effect in the performance of the
closed-loop system will be part of our future works. Besides, application of the
developed method for wind farm control systems can be addressed as an inter-
esting further work.
A.1 6.7
Appendix
A dynamic model is constructed for each of the three linear pitch actuators:
