Environmental Engineering Reference
In-Depth Information
Table 12.3
Relevant system
System property
Parameter
parameters
of
the
reference
Rating/configuration
5 MW/3 Blades
wind turbine
Control
Variable speed, collective
pitch
Cut-in, rated and cut-out wind
speed
3, 11.4, 25 m/s
Cut-in and rated rotor speed
6.9, 12.1 rpm
Hub height
90 m
Rotor diameter
126 m
12.4.1 System Properties of the Reference Wind Turbine
The turbine specifications are described by the U.S. Department of Energy's
National Renewable Energy Laboratory (NREL). The relevant system properties
are summarized in Table
12.3
. Further specifications relating to the reference wind
turbine can be found in the technical report by NREL [
21
].
The dynamic parameters of the turbine tower modes in fore-aft direction are
listed in Table
12.4
. In Fig.
12.10
, the tower fundamental frequency and the
number of rotor revolutions per minute are shown. As shown by this diagram, the
first fore-aft tower frequency is placed between one- and three-per-revolution
frequencies to avoid the occurrence of a resonant condition. However, the tower
frequency is still quite near the three-per-revolution frequency. Therefore, espe-
cially by low wind speeds resonant tower vibrations are to be expected.
12.4.2 General Simulation Parameters
The simulation of the reference wind turbine with TMD is carried out by the
aeroelastic dynamic horizontal axis wind turbine simulator FAST [
22
] with FAST-
SC [
23
]. FAST is developed by NREL. FAST can simulate two fore-aft and two
side-to-side bending modes of turbine tower. FAST-SC is an expanded code of
FAST, which can simulate wind turbines with TMD and is developed by the
University of Massachusetts. The wind turbine is simulated with a TMD connected
in the nacelle to the tower top. TMD controls hereby vibrations in fore-aft
direction. Seismic calculations are carried out combining FAST-Seismic [
27
] with
FAST-SC and main program FAST.
Table 12.4 Natural frequen-
cies, modal masses, and the
structural
1. Mode
2. Mode
Natural frequency
f
1
= 0.324 Hz
f
2
= 2.900 Hz
damping
ratio
of
tower fore-aft modes
Modal mass
m
1
= 403.969 t
m
2
= 480.606 t
Damping ratio
D
1
= 1%
D
2
= 1%
