Environmental Engineering Reference
In-Depth Information
0
-20
-40
-60
p=-6
p=0
p=6
-80
-100
10
-3
10
-2
10
-1
10
0
10
1
10
2
Frequency (Hz)
Fig. 5.11 Bode diagram of the gain scheduled collective pitch H
?
controller in different
operating points
Coleman transformation. The IPC to align the rotor frame has been field tested not
only in the CART2 wind turbine [
39
], but it has also recently tested in the CART3
turbine with very promising results [
40
]. The load mitigation in the tower can be
also considered as a control objective in the design of the Individual Pitch Con-
troller. The tower side-to-side damping is commonly carried out with a generator
torque contribution from measured side-to-side nacelle acceleration. This torque
contribution affects to the quality of the generated electric power. In [
41
-
43
],
different control strategies based on IPC are proposed to make the tower side-to-
side damping with IPC signals. The interaction between the supervisory control
and the IPC of the wind turbine is very important to reduce the loads in some
components for shutdown and load sensor failure cases [
10
].
The IPC presented in this section, called H
?
IPC, is composed of one MIMO
controller based on the H
?
norm reduction to generate individual pitch set-point
signals for each blade with a multi-objective point of view (to align the rotor plane
and to reduce the wind effect in the tower side-to-side first mode).
The first step when designing the H
?
IPC is to create the nominal plant which
will be included in the mixed sensitivity problem to make the H
?
controller
synthesis. To create this plant, firstly, the flapwise and edgewise moments
extracted from strain gauges in the blade roots are transformed [
44
] to the out-of-
plane moment M
oop
using the transformation T (Eq.
5.14
), where h
T
and b are the
twist and pitch angles at the blade root section. The M
tilt
and M
yaw
rotor tilt and
yaw moments are obtained using the transformation (Eq.
5.15
) where w is the
azimuth angle in each blade and M
oop1
, M
oop2
and M
oop3
the out-of-plane moments
in each blade. The tilt and yaw moments show how the blade loads developed in a
rotating reference frame are transferred to a fixed reference frame. In this case, the
Coleman transformation [
45
] C is used, and it is a transformation from a rotating to
