Environmental Engineering Reference
In-Depth Information
1
2
0.5
1.2
1.5
0
1
1
−0.5
0.8
0.5
−1
EC1 EC2 EC3 EC4 EC5
EC1 EC2 EC3 EC4 EC5
EC1 EC2 EC3 EC4 EC5
1.2
1.2
1.2
1
1
1
0.8
0.8
0.8
0.6
0.6
0.6
EC1 EC2 EC3 EC4 EC5
EC1 EC2 EC3 EC4 EC5
EC1 EC2 EC3 EC4 EC5
M1
M2
M3
M4
Fig. 11.17 Fault: actuator stuck. Normalized RMS (NRMS) of generator power, blade pitch
rates, and platform motions
The GSPI pitch controller tries to restore the aerodynamic torque by pitching the
healthy blades to 0 in order to increase the rotor moment, however, with the faulty
blade is pitched to feather (90) the aerodynamic moment is not enough to move the
rotor. If the turbine goes in operation in such condition, the structure of the turbine
will be very affected, especially the tower in addition to the LSS. The tower side-
side (roll) bending moment DEL will be more than 3 times higher at EC4 and EC5,
the tower fore-aft (pitch) moment DEL will be more than 2 times higher at EC2,
while the maximum tower torsional DEL will be about 2.5 times higher at EC1, of
course all compared to the normal operating condition (Fig.
11.18
). The blade root
moments in both directions, flap-wise and edge-wise, show a decrease in DEL for
both faulty and healthy blades as the turbine is shutting down.
On the other side, platform motion is very affected by such fault. The platform
pitching motion increases more than twice over the full load region, while the yaw
motion is highly affected by higher wind speeds (EC4 and EC5) with more than 5
times compared to the normal operating conditions. The roll motion is less
affected, but still above the normal level with up to 47 % more at EC2 and EC4.
The direct dependency of the platform yaw motion excitation with the wind speed
is clear, as this motion is mostly affected by the rotor imbalance with two blades
are pitched to maximum aerodynamic efficiency and one blade is pitched to
feather, this will create a difference between the aerodynamic thrust over the left
and half side of the rotor disk according to the position of the blades, which, in
turn, will build up a moment along the tower axis. As the rotor speed at EC4 and
