Environmental Engineering Reference
In-Depth Information
b
k
¼
K
p
ð
h
Þð
x
g
x
ng
Þþ
K
i
ð
h
Þ
Z
t
0
ð
x
g
x
ng
Þ
dt
;
K
p
[ 0
;
K
i
[ 0
;
k
¼
1
;
2
;
3
;
where x
g
is the generator speed, x
ng
is the nominal generator speed (at which the
rated electrical power of the wind turbine is obtained) and the scheduling
parameter h is taken to be the previous measured collective blade pitch angle. As
the three pitch angles are measured, b
k
, the collective pitch angle is obtained by
averaging the measurements of all pitch angles. The scheduled gains are calculated
following [
9
]. Finally, a pitch limit saturation to a maximum of 45 and a pitch rate
saturation of 8/s is implemented, see [
9
].
Recall that when using the baseline torque controller the filtered generator
speed measurement is used for both the torque and pitch controllers. However,
when using the chattering controller no filters are needed neither in the torque
control nor in the pitch control.
Note that the pitch control is not simulated as HIL. Only the torque control is
implemented in the Arduino hardware.
15.6 HIL Results
For the proposed controller in Eq. (
15.5
), the values a = 1 and K
a
¼
1
:
5
10
5
have been used in the simulations. This controller depends on x
g
, thus we com-
puted a first order approximation of x
g
in the Arduino board.
15.6.1 Healthy
The simulation results for the healthy case show that for both controllers:
• The electrical power follows the reference independently of the wind fluctua-
tions, as shown in Fig.
15.4
(left).
• The torque action achieves reasonable values, as shown in Fig.
15.4
(right).
• The blade pitch angle is always within the authorized variation domain, as
shown in Fig.
15.5
(left).
• The generator speed is near its nominal value of (1173.7 rpm) due to the pitch
control action, as shown in Fig.
15.5
(right).
15.6.2 Faulty
Blade pitch system faults have the highest failure rate in WT. In this chapter a fault
related to the third pitch actuator has been studied. In the studied fault the gain
scheduled PI collective pitch control is performed by using the average of the
