Environmental Engineering Reference
In-Depth Information
Bode Diagram
90
W
11
(s)
W
12
(s)
W
13
(s)
W
21
(s)
W
22
(s)
80
70
60
50
40
30
20
10
0
10
-3
10
-2
10
-1
10
0
10
1
10
2
Frequency (Hz)
Fig. 5.12
Weight functions in the design of the individual pitch H
?
control
D
u1
¼
0
:
001; D
u2
¼
0
:
001;
D
d1
¼
0
:
1; D
d2
¼
1e6; D
d3
¼
1e6;
D
e1
¼
0
:
1; D
e2
¼
0
:
5e6; D
e3
¼
0
:
5e6;
ð
5
:
17
Þ
After finishing the controller synthesis, the obtained controller has to be
re-scaled to adapt the inputs and the outputs to the real non-scaled plant. The
designed H
?
IPC controller has three inputs (tower top side-to-side acceleration
a
Tss
in m/s
2
, tilt moment in the rotor M
tilt
in Nm and yaw moment in the rotor M
yaw
in Nm) and two outputs (pitch angle in the rotor reference frame b
tilt
in rad and
yaw pitch angle b
yaw
in the rotor reference frame in rad). This designed controller
is state space represented and its order is 54. The reduction of the order of mul-
tivariable controllers is difficult due to coupling between the channels, so this
controller is not reduced. The last step is the controller discretization with a sample
time of 0.01 s. The Bode diagram of the discretized state space represented con-
troller (Eq.
5.18
) is shown in Fig.
5.13
. Finally, the Coleman and its inverse have
to be included in the control strategy to calculate the individual pitch angle con-
tribution for each blade b
rot1
, b
rot2
and b
rot3
. Figure
5.14
shows the complete
control scheme of the IPC strategy from the signals from the loads in the blade
roots to the individual pitch angle contributions. These pitch contributions for each
blade are added to the collective pitch angle set-point obtained in the previously
designed collective pitch angle controllers.
