Environmental Engineering Reference
In-Depth Information
1.5
2.5
1.5
2
1
1
1.5
1
0.5
0.5
0.5
0
0
0
EC1 EC2 EC3 EC4 EC5
EC1 EC2 EC3 EC4 EC5
EC1 EC2 EC3 EC4 EC5
1.1
1.1
1.1
1
1
1
0.9
0.9
0.9
0.8
0.8
0.8
EC1 EC2 EC3 EC4 EC5
EC1 EC2 EC3 EC4 EC5
EC1 EC2 EC3 EC4 EC5
M1
M2
M3
M4
Fig. 11.11 Fault: blade pitch sensor bias. Normalized RMS (NRMS) of generator power error,
blade pitch rates, and platform motion
Furthermore, the bias fault has minor effect on the power production with the
exception of the first bias magnitude at EC1 and EC2 (see Fig.
11.11
) where the
error shows limited effect for the negative bias, this is due to the pre-switching
between the operating regions. The bias fault also affects the faulty pitch actuator
mostly at EC1, and this effect decreases with the increase of mean wind speed.
Again, the main reason of this high effect is the switching of the GSPI pitch
controller between the operating regions, with negative bias (magnitudes M1 and
M2), the faulty blade starts to move after the healthy blades which means it should
have high pitching rate in order to catch the set-point, the opposite happens to the
positive bias (magnitudes M3 and M4).
The platform pitch and yaw motions show negligible response to the fault,
while the roll motion is affected close to the switching region (EC1 and EC2)
basically due to the usage of the generator torque in response to the increased
power error. The big inertia of the platform minimizes the effects of the rotor
imbalance on the platform motion, at the cost of increasing this effect on the tower
torsional moment and the LSS moments. The faulty blade affects the rotor speed,
and as far as the turbine is operating in the full load region where the constant
output power strategy is engaged and the generator torque is changing according to
rotor speed. With the negative bias in blade pitch angle, the controller is delayed in
switching to the partial load region though the rotor speed is less than rated. This
will increase the generator torque, which will excite the platform roll motion.
The opposite effect happens with positive bias of the blade pitch angle when the
turbine is operating far from the switching region (EC3 till EC5) where this effect