Environmental Engineering Reference
In-Depth Information
Fig. 12.5 Comparison of
vibration mitigation methods
and tower vibration
characteristics
Table 12.2
Stiffness and damping coefficients for the modeling of the foundation-soil system [
14
]
Stiffness coefficients
Damping coefficients
K
x
¼
K
y
¼
8G
S
r
F
2
t
S
C
x
¼
C
y
¼
4
:
6r
F
2
t
S
p
G
S
q
S
Horizontal translation
p
Vertical translation
K
z
¼
4G
S
r
F
1
t
S
C
z
¼
3
:
4r
F
1
t
S
G
S
q
S
p
Rocking
8G
S
r
F
3
ð
1
t
S
Þ
0
:
8r
F
ð
1
t
S
Þð
1
þ
B
u
Þ
G
S
q
S
K
u
¼
C
u
¼
B
u
¼
3
ð
1
t
S
Þ
8
h
u
r
F
q
S
p
Torsion
K
uz
¼
16G
S
r
F
3
2
:
3r
F
1
þ
2B
uz
B
uz
G
S
q
S
C
uz
¼
B
uz
¼
h
uz
r
F
q
S
In case of embedded foundations, a modification of the above reported coef-
ficients is necessary. An investigation of the soil-structure interaction effects on
the wind turbine dynamics is presented in Sect.
12.4.3.4
.
12.3 Vibration Mitigation Methods
In order to mitigate wind turbine tower vibrations several systems are invented and
applied. The most common methods can be classified as blade pitch control,
auxiliary dampers, and tuned mass dampers (TMD). Figure
12.5
shows some of
these methods and categorizes them according to the vibration characteristics by
means of a soft tower. As discussed in Sect.
12.2.1
, the dynamic tower response
depends mainly on the wind speed and contains both transient and periodic
components.
The
efficiency
of
a
mitigation
method
relies
on
the
response
