Environmental Engineering Reference
In-Depth Information
Fig. 11.5 GSPI control structure with pitch system model. Only one pitch system is included in
this diagram. b
i
is the noise-free blade pitch angle (i
¼
1
;
2
;
3), b
i
is the pitch angle
measurement, X
g
is the noise-free generator speed, X
g
is the generator speed measurement.
b
c
¼
3
b
1
þ
b
2
þ
b
ð Þ
is the collective blade pitch angle. T
gen
is the generator torque command,
and b
i
is the blade pitch command, s is Laplace complex variable
As the RWT does not have any model for the pitch system, the pitch system
model block is added between the blade pitch controller and the turbine model.
The measured outputs are the generator speed, generator torque, and the three
blade pitch angles. A Gaussian noise with zero mean and given standard deviation
is added to the deterministic output values in order to emulate measurement noise.
The noise standard deviation depends on sensor type, and the difficulty to get the
measurement. The blade pitch angles are measured for example on the cylinder of
the pitch actuators in the hydraulic pitch systems, while the generator torque is
provided by soft sensors in the converters, and the generator speed is measured
using a speed encoder. The used standard deviations are for the generator speed
noise 0.0158 rad/s, for the generator torque noise 45 Nm, and finally for the pitch
angle measurement noise 0.2 [
15
].
11.2.3.1 Blade Pitch Control
The GSPI control law is given in Eq. (
11.5
) where b
ðÞ
is the collective blade pitch
control command, K
P
is the proportional gain, K
I
is the integral gain, both gains
are functions of the scheduling parameter h, while e(t) is the error signal to be
driven to zero. The error signal is given in Eq. (
11.6
) where X
g
is the measured
generator speed, and X
g
;
rated
is the rated generator speed of the turbine. The
scheduling parameter h is taken to be the previous measured collective blade pitch
angle. As the three pitch angles are measured, the collective pitch angle is obtained
by averaging the measurements of all pitch angles.
b
ð
t
Þ¼
K
P
ðÞ
e
ðÞþ
K
I
ðÞ
Z
t
e
ðÞ
ds
ð
11
:
5
Þ
0
