Environmental Engineering Reference
In-Depth Information
According to wind turbine reliability analysis (Fig.
11.3
), the most common
faults occur in the pitch system, power electronics and generator assembly and in
turbine sensors. Faults in the pitch system and sensors result in structural loading
of the turbine due to rotor imbalance and might affect the stability of the floating
platform. These faults are originated by either electrical or mechanical anomalies,
and they can result in different fault scenarios in sensors and pitch system. Fur-
thermore, the optimal operation of wind turbines depends highly on the right rotor
adjustment and balance, and the blade angles have a strong impact not only on the
performance, but also on the emerging loads.
In order to model the faults, the pitch system/sensor equations are to be
updated. The incipient faults are introduced gradually through their magnitude and
rate of change. On the other side, the abrupt faults are modeled by rewriting the
system and measurement equations such that the new equations correspond to the
enforced changes by the introduced fault.
11.3.1 Sensor Faults
Sensor faults are more frequent compared to the turbine structure lifetime. As
turbine monitoring and control uses the sensor data for decision, it is important that
the data acquired are accurate and reliable. Generally, the fault-free sensor is
modeled as
S
m
ðÞ¼
S
r
ðÞþ
v
ðÞ
ð
11
:
12
Þ
where S
m
ðÞ
is the fault-free sensor measurement (e.g., pitch angle or generator
speed), S
r
ðÞ
is the noise-free value, and v(t) is the measurement noise. The
dynamics of the sensor is ignored as it is too fast compared to the system
dynamics. Sensors might produce different types of faults including—but not
limited to—the following.
11.3.1.1 Bias
The bias could be represented with a constant value that is introduced to the final
measurement such as
S
f
ðÞ¼
S
r
ðÞþ
B
þ
v
ðÞ
ð
11
:
13
Þ
where B is the bias value (constant), and S
f
ðÞ
is the faulty sensor measurement.
