• Giuseppe Battista Abbate
4. term, Control and Automation, Master (Master Programme)
The increasing demand for renewable energy all the world led to a development in
wind power technologies. Thus, wind turbines are increasing in dimension and power
production. So far they are mounted on land or in shallow waters with basement. The
main disadvantage is that wind turbines have a visual impact that sometimes cannot
be accepted. Also, because of the aerodynamic interaction between the wind and the
blades, they cause ambient noise near the structure. Hence, the objective during the
last years is to install these structures in deeper water, where there’s no visual impact
and the ambient noise is not relevant. There’s also another advantage for going further
offshore into deeper waters: wind is less turbulent due to the fact that there are no
mountains, buildings or something else that can deviate the wind flow.
The unique economically favourable way to move in deeper water is using floating
platform. Fortunately, floating platforms were deeply studied by the oil and gas
companies for their oil plants, and these studies have also been used for the wind
turbines. However, using a floating wind platform introduces additional motions that
must be taken into account in the design stage. Therefore, the control system becomes
an important component in controlling these motions. It has been shown that using the
onshore baseline controller (PI blade pitch controller plus variable speed generator
torque controller) can cause the problem of negative damping in the offshore wind
The first part of the report aims to describe briefly the tuning procedure of the
baseline controller and the development of a simplified control-oriented model of
offshore floating wind turbine for a ballast stabilized platform. The analysis focuses
on the dynamics of a wind turbine, the development of a model starting from the
forces that act on the system, the identification of the parameters and finally the
validation of the model using the detailed wind turbine simulator FAST, freely
available online and accessible in the literature (1).
The second part of the report describes three types of control techniques for the wind
turbines, based on both classic and advanced control theory. It has been used a
baseline PI controller and an three LQ controller with different objectives. The
purpose is to apply and to analyze a control law that aims to reduce the fatigue in the
tower. The main idea was to minimize the variance of the tower deflection or the
variance of the tower deflection velocity. The results showed that with the LQ
controllers, reducing the tower deflection velocity, it is possible to reduce the fatigue
in the tower base.
The last part of the report consists in a comparison between the three LQ controller
described before and the baseline PI, based on the Damage Equivalent Loads and on a
statistic analysis. Each controller will be used in simulation with FAST in order to
understand if the control law actually minimizes the fatigue and legitimates the use of
an advanced controller.
Publication date7 Jan 2013
Number of pages34
ID: 174601387