Environmental Engineering Reference
In-Depth Information
one gain, with one differentiator, one real zero and a pair of complex poles. In the
designed DTD, K
1
is 641.45 Nms/rad, w
1
is 193 rad/s, w
2
is 10.4 rad/s and n
2
is
0.984.
0
@
1
A
s 1
þ
w
1
s
T
DTD
ðÞ¼
K
1
w
g
ðÞ
ð
5
:
3
Þ
2
s
2
þ
2n
2
1
w
2
w
2
s
þ
1
1
On the other hand, the objective in the transition zone is the regulation of
generator speed varying the generator torque. In the baseline control strategy, it
can be developed by using a proportional-integral (PI) controller (Eq.
5.4
). In the
baseline control strategy, called C1 in this chapter, the PI values in the transition
zone (operating point with wind speed of 11 m/s) used in the Upwind baseline
controller are w
T
and K
T
(Eq.
5.4
), where T(s) is the generator torque control
signal, e
wg
(s) is the generator speed error. In this case, w
T
is 0.5 rad/s and K
T
is
2,685.2 Nm/rad.
1
þ
w
T
s
T
ðÞ¼
K
T
e
wg
ð
s
Þ
ð
5
:
4
Þ
s
The main objective in the above rated zone is the regulation of the generator
speed control at the nominal value of 1,173 rpm varying the collective pitch angle
in the blades and keeping the electric power at the nominal value of 5 MW. The
control structure used in this baseline control strategy in the above rated zone is
shown in Fig.
5.4
. This regulation of the generator speed is based on a Gain-
Scheduled (GS) collective pitch angle PI controller. In this case, the controller input
e
wg
(s) is the generator speed error, and the controller output b
col
(s) is the collective
pitch angle control signal. The linear plants used to tune the gain-scheduled PI
controller are the plants which relate pitch angle and generator speed. These plants
have different gains (see Fig.
5.3
), so gain-scheduling is used to guarantee the
stability of the closed loop system in spite of these differences. Two PI controllers
(Eq.
5.5
), in two operating points with wind speeds of 13 and 21 m/s, are designed
and then a GS is applied to interpolate them. For 13 m/s, K
B13
is 0.00158 and w
B13
is
0.2 rad/s and, for 21 m/s, K
B21
is 0.00092 and w
B21
is 0.2 rad/s.
1
þ
w
B
s
b
col
¼
K
B
e
wg
ð
s
Þ
ð
5
:
5
Þ
s
The gain scheduling interpolation is developed according to an average of the
measured pitch angle in the blades. Nowadays, new sensors that provide infor-
mation about the present wind speed in front of the hub of the wind turbine, like
LIDARs [
25
], are being included in the pitch control systems improving the
