Environmental Engineering Reference
In-Depth Information
Fig. 6.1 Total installed wind
power capacity from 2001 to
2011 in [MW]
there is a control system causing the turbine to behave in a suitable manner. Over
the years, there have been presented many ways to model the wind turbine, for
instance, single mass models [
1
], multiple mass models [
19
], and complex flexible
multibody models. The latter seems to have gained a lot of interest in recent years,
much because these methods are incorporated into special wind turbine simulation
software, such as HAWC2 [
16
], Cp-Lambda [
8
] and FAST [
13
]. Recently, a robust
data-driven fault detection approach is proposed with application to a wind turbine
benchmark [
24
]. More recently, modeling and optimization of a passive structural
control design for a spar-type floating wind turbine is addressed in [
22
]. Besides,
an application of adaptive output-feedback control design to wind turbine col-
lective pitch control and load mitigation is proposed in [
18
]. In this work, the main
objective is the design of an output-feedback controller without wind speed esti-
mation, ensuring that the generator speed tracks the reference trajectory with
robustness to uncertain parameters and time-varying disturbances.
The region of operation for a typical wind turbine is often divided into four
regions, shown in Fig.
6.2
. In region I
ð
t\t
cut
in
Þ
the wind speed is lower than the
cut-in wind speed and no power can be produced. In region II
ð
t
cut
in
\t\t
rated
Þ
the blade pitch is usually kept constant, while the generator torque is the con-
trolling variable. In region III
ð
t
rated
\t\t
cut
out
Þ
the main concern is to keep the
rated power and generator speed by pitching the blades. In region IV
ð
t [ t
cut
out
Þ
the wind speed is too high, and the turbine is shut down. This chapter is focused on
the above-rated wind speed scenario, i.e., region III.
It is tempting to just put a well-designed onshore controller and install it on an
offshore turbine. In principle, one can do this, but there is no guarantee that the
closed-loop system will be stable. The major difference between the onshore and
the offshore turbine is the natural frequencies. The natural frequencies will
decrease significantly once the turbine is mounted on a floating foundation. First,
lets say the turbine is located onshore. Then, the lowest tower frequency is typi-
cally 0.5 Hz, which is the tower fore-aft bending mode. Once this turbine is put
