Environmental Engineering Reference
In-Depth Information
that includes the structural dynamics. The full nonlinear RWT model is imple-
mented in FAST, and the used barge platform model is as implemented by
Jonkman [
4
]. However, the control part, faults, and simulation are developed and
implemented by the authors in Matlab/Simulink.
11.4.1 Environmental Conditions
Three-dimensional turbulent wind fields according to the design load case DLC2.1
of the international standard IEC61400-3 (power production plus occurrence of
faults) with different mean wind speeds in the full load region are used along with
the corresponding wave conditions. The study is limited to the full load region as
the pitch system is active only in this region (Fig.
11.2
), and only undetected pitch
system faults are included. All ECs are considered to be correlated as shown in
Table
11.2
with wind and wave conditions for the North Sea. The direction of the
wind is assumed to be aligned with the direction of the waves. The number and
length of simulations are chosen according to the offshore wind turbine standards
that suggests for statistical reasons 12 simulations with different wind and wave
profiles with duration of 10 min each to be carried out for power production plus
fault cases [
18
].
The turbulent wind profiles are generated using the TurbSim program [
19
]
based on the Kaimal spectrum for IEC Class C along with a normal turbulence
model (NTM) and wind shear according to the power law with power component
of 0.14 [
18
]. Meanwhile, the simulated wave series are generated using JON-
SWAP spectra for the incident wave kinematics model with significant wave
height H
s
and peak period T
p
. Recorded simulation length is 10 min after intro-
ducing the fault at time step TOF = 100 s. Each simulation is repeated 12 times
with different seeds for the turbulent wind and wave fields.
Table 11.2 Environmental conditions, U
wind
is the mean wind speed, H
s
is the significant wave
height of incident waves, T
p
is peak spectral period of incident waves, TMax is the simulation
time after occurrence of fault
EC
s
H
s
ðÞ
T
p
ðÞ
Turbine model
No. of simulations
TMax
ðÞ
U
wind
EC1
NTM
11.2
3.10
10.10
12
600
EC2
NTM
14.0
3.60
10.30
12
600
EC3
NTM
17.0
4.20
10.50
12
600
EC4
NTM
20.0
4.80
10.80
12
600
EC5
NTM
23.0
5.40
11.00
12
600
