U.S. patent application number 13/361502 was filed with the patent office on 2013-08-01 for wind turbine and vibration damping method thereof.
This patent application is currently assigned to MITSUBISHI HEAVY INDUSTRIES, LTD.. The applicant listed for this patent is Kentaro HAYASHI, Naoyuki NAGAI, Tsuyoshi WAKASA. Invention is credited to Kentaro HAYASHI, Naoyuki NAGAI, Tsuyoshi WAKASA.
Application Number | 20130195653 13/361502 |
Document ID | / |
Family ID | 48870372 |
Filed Date | 2013-08-01 |
United States Patent
Application |
20130195653 |
Kind Code |
A1 |
HAYASHI; Kentaro ; et
al. |
August 1, 2013 |
WIND TURBINE AND VIBRATION DAMPING METHOD THEREOF
Abstract
There are provided a TMD adjusted to damp vibration in a natural
frequency of a wind turbine, an AVC adjusted to damp vibration in a
variable frequency of turbulent wind flowing into the wind turbine
and/or a frequency of a rotation speed of a wind-turbine blade, and
a pitch-angle control portion provided with a correction portion
which adjusts a damping frequency of the AVC. The AVC is configured
to obtain the damping force by changing the pitch angle of the
wind-turbine blade.
Inventors: |
HAYASHI; Kentaro; (Tokyo,
JP) ; NAGAI; Naoyuki; (Tokyo, JP) ; WAKASA;
Tsuyoshi; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HAYASHI; Kentaro
NAGAI; Naoyuki
WAKASA; Tsuyoshi |
Tokyo
Tokyo
Tokyo |
|
JP
JP
JP |
|
|
Assignee: |
MITSUBISHI HEAVY INDUSTRIES,
LTD.
Tokyo
JP
|
Family ID: |
48870372 |
Appl. No.: |
13/361502 |
Filed: |
January 30, 2012 |
Current U.S.
Class: |
416/1 ;
416/36 |
Current CPC
Class: |
F05B 2260/964 20130101;
F03D 80/00 20160501; Y02E 10/72 20130101; F03D 7/0296 20130101 |
Class at
Publication: |
416/1 ;
416/36 |
International
Class: |
F01D 7/00 20060101
F01D007/00 |
Claims
1. A wind turbine comprising: a passive damper adjusted to damp
vibration in a natural vibration frequency of the wind turbine; an
active damper adjusted to damp variation in a variable frequency of
turbulent wind flowing into the wind turbine and/or variation in a
n-th (n is a natural number) frequency of a rotation speed of a
wind-turbine blade; and an active-damper control portion which
adjusts a damping frequency of the active damper.
2. The wind turbine according to claim 1, wherein the active damper
obtains the damping force by changing a pitch angle of the
wind-turbine blade.
3. The wind turbine according to claim 1, further comprising: an
anemometer which detects a flow speed of wind flowing into the wind
turbine, wherein the active-damper control portion controls the
active damper on the basis of the wind speed detected by the
anemometer.
4. The wind turbine according to claim 2, further comprising: an
anemometer which detects a flow speed of wind flowing into the wind
turbine, wherein the active-damper control portion controls the
active damper on the basis of the wind speed detected by the
anemometer.
5. The wind turbine according to claim 1, wherein the passive
damper is a tuned mass damper; and the tuned mass damper uses a
wind-turbine constituent element made relatively movable with
respect to a wind-turbine main body as an added mass.
6. The wind turbine according to claim 2, wherein the passive
damper is a tuned mass damper; and the tuned mass damper uses a
wind-turbine constituent element made relatively movable with
respect to a wind-turbine main body as an added mass.
7. The wind turbine according to claim 3, wherein the passive
damper is a tuned mass damper; and the tuned mass damper uses a
wind-turbine constituent element made relatively movable with
respect to a wind-turbine main body as an added mass.
8. The wind turbine according to claim 4, wherein the passive
damper is a tuned mass damper; and the tuned mass damper uses a
wind-turbine constituent element made relatively movable with
respect to a wind-turbine main body as an added mass.
9. The wind turbine according to claim 1, wherein the passive
damper is a tuned liquid damper; and the tuned liquid damper uses
operating oil or lubricant oil stored in the wind-turbine main body
as an added mass.
10. The wind turbine according to claim 2, wherein the passive
damper is a tuned liquid damper; and the tuned liquid damper uses
operating oil or lubricant oil stored in the wind-turbine main body
as an added mass.
11. The wind turbine according to claim 3, wherein the passive
damper is a tuned liquid damper; and the tuned liquid damper uses
operating oil or lubricant oil stored in the wind-turbine main body
as an added mass.
12. The wind turbine according to claim 4, wherein the passive
damper is a tuned liquid damper; and the tuned liquid damper uses
operating oil or lubricant oil stored in the wind-turbine main body
as an added mass.
13. A vibration damping method of a wind turbine provided with a
passive damper adjusted to damp vibration in a natural frequency of
the wind turbine and an active damper, comprising controlling a
damping frequency of the active damper so as to damp vibration in a
variable frequency of turbulent wind flowing into the wind turbine
and/or variation in a n-th (n is a natural number) frequency of a
rotation speed of a wind-turbine blade.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a wind turbine and a
vibration damping method thereof.
[0003] 2. Description of Related Art
[0004] A wind turbine which converts wind energy to electric power
and generates the electric power has drawn attention as clean
energy. Since a wind turbine has a structure in which heavy
articles such as a wind-turbine blade, a gear box, a power
generator and the like are mounted on an upper part of a tower
having the height of several tens meters in general, vibration
induced by fluctuation in the wind speed flowing into the wind
turbine cannot be ignored. Such vibration increases a fatigue load
of a structural material of the wind turbine and reduces the life
of the wind turbine.
[0005] On the other hand, high-rise structures such as a building
employs AMD (Active Mass Damper) in order to damp vibration caused
by wind. However, the AMD requires an actuator which drives an
added mass in addition to the added mass, whereby cost and weight
are increased. Particularly if it is applied to a wind turbine, the
weight of the upper part of the tower is further increased, which
is not preferable.
[0006] U.S. Pat. No. 5,442,883 discloses the invention in which an
added mass is reduced only by combining a passive damper with the
AMD. However, since an actuator which drives the added mass is
still needed, the increase in weight is not fundamentally
solved.
[0007] PCT International Publication No. WO 2005/083266 discloses
the invention of active vibration damping of a wind turbine
provided with a pitch-angle control mechanism which can control a
pitch angle of a wind-turbine blade without providing a special
actuator for damping vibration. Specifically, a pitch-angle
instruction is outputted to the pitch-angle control mechanism so as
to obtain a thrust power for damping vibration.
[0008] The dominant vibration of a wind turbine is vibration caused
by turbulent wind, vibration caused by a rotor rotation speed (1N,
3N; N is a rotation speed (3N refers to the case of three blades)),
and vibration caused by a natural vibration frequency (1st, 2nd) of
the wind turbine itself as illustrated in FIG. 13. In this case,
the rotor rotation speed component can be reduced by balancing the
wind turbine blades or the like, and the turbulent wind component
and the tower natural vibration frequency component can be reduced
by active vibration damping or a passive damper.
[0009] However, as illustrated in the figures, since a frequency
band which needs to be damped is wide in a wind turbine, the
following problems occur. That is, as illustrated in FIG. 13, since
a peak level with high damping effect is in inverse proportion to
the frequency band in which a damping effect is exerted in general,
if a large damping effect is to be obtained, the frequency band
should be small (see a curve L1), while if a wide frequency band is
to be obtained, the peak level becomes low (see a curve L2).
Therefore, it is difficult to obtain a large damping effect in all
the frequency bands of vibration specific to a wind turbine.
BRIEF SUMMARY OF THE INVENTION
[0010] The present invention was made in view of such circumstances
and has an object to provide a wind turbine which can exert a large
damping effect in a wide frequency band specific to a wind turbine
and a vibration damping method thereof.
[0011] In order to achieve the above object, the wind turbine and
the vibration damping method of the present invention employ the
following means.
[0012] That is, a wind turbine according to a first aspect of the
present invention is provided with a passive damper adjusted so as
to damp vibration in a natural vibration frequency of the wind
turbine, an active damper adjusted so as to damp variation in a
variable frequency of turbulent wind flowing into the wind turbine
and/or variation in an n-th (n is a natural number) frequency of a
rotation speed of a wind-turbine blade, and an active-damper
control portion which controls a damping frequency of the active
damper.
[0013] Since the natural vibration frequency of a wind turbine is
uniquely determined by the shape or constitution of the wind
turbine, the vibration in the natural vibration frequency is damped
by a passive damper which can adjust damping by fixing the
frequency to a specific one.
[0014] On the other hand, the variable frequency of the turbulent
wind flowing into the wind turbine varies by wind conditions such
as weather, season, time and the like. Also, the n-th frequency of
the rotation speed of the wind-turbine blade also varies depending
on the rotation speed of the wind-turbine blade. Therefore, for the
vibration in these frequencies, an active damper (AVC, for example;
Active Vibration Control) which can dynamically change the damping
frequency by the active-damper control portion is used.
[0015] As described above, the active damper and the passive damper
are made to bear the respective corresponding frequencies, and the
damping effects of the respective dampers can be effectively
exerted.
[0016] Moreover, in the wind turbine of the present invention, the
active damper obtains a damping force by changing a pitch angle of
a wind-turbine blade.
[0017] In the wind turbine according to the first aspect of the
present invention, an active damper which exerts a damping action
by using wind energy through change of a pitch angle of a
wind-turbine blade is preferably employed. In this case, limited
wind energy is used as a damping force. In the present invention,
since the active damper is concentrated to a predetermined
frequency for damping, the damping force can be exerted by
effectively using the wind energy.
[0018] Moreover, in the wind turbine according to the first aspect
of the present invention, it is preferable that an anemometer which
detects a flow speed of the wind flowing into the wind turbine and
the active-damper control portion controls the active damper on the
basis of the flow speed detected by the anemometer.
[0019] The active damper is controlled in accordance with
fluctuation of a wind speed detected by the anemometer. Since the
control is made in accordance with fluctuation in speed of the
inflow wind as above, vibration damping can be performed with
better responsiveness than the case of vibration damping after
vibration actually generated in the wind turbine is obtained by an
acceleration sensor or the like.
[0020] Moreover, in the wind turbine according to the first aspect
of the present invention, the passive damper is a tuned mass
damper, and the tuned mass damper preferably uses a wind-turbine
constituent element capable of relative movement with respect to
the wind turbine main body as an added mass.
[0021] As the passive damper, a tuned mass damper (TMD) is
preferable. That is because, by selecting an existing wind-turbine
constituent element provided in order to exert a function of the
wind turbine, not for the purpose of damping, the passive damper
can be constituted without adding a special added component. As a
result, the weight of the wind turbine does not have to be
increased for damping vibration.
[0022] As a wind-turbine constituent element selected as an added
mass, a nacelle cover, a transformer, a ladder (elevating ladder),
a platform of a tower (foothold), a cable suspended downward from
the nacelle, a turning module which turns the nacelle in a yaw
direction and the like capable of relative movement with respect to
the wind turbine main body can be cited, for example.
[0023] Moreover, in the wind turbine according to the first aspect
of the present invention, the passive damper is a tuned liquid
damper, and the tuned liquid damper preferably uses operating oil
or lubricant oil stored in a wind-turbine main body as an added
mass.
[0024] As the passive damper, a tuned liquid damper (TLD) is
preferably used. That is because, by selecting operating oil or
lubricant oil stored in the wind turbine, the passive damper can be
constituted without adding a special added component. As a result,
the weight of the wind turbine does not have to be increased for
damping vibration.
[0025] As the operating oil or machine oil selected as the added
mass, operating oil in a reservoir tank of a hydraulic device,
lubricant oil in a gear box and the like can be cited, for
example.
[0026] Also, a vibration damping method of a wind turbine according
to a second aspect of the present invention is a vibration damping
method of a wind turbine provided with a passive damper adjusted so
as to damp vibration in a natural frequency of a wind turbine and
an active damper and controls a damping frequency of the active
damper so as to damp vibration in a variable frequency of turbulent
wind flowing into the wind turbine and/or variation in a n-th (n is
a natural number) frequency of the rotation speed of a wind-turbine
blade.
[0027] Since the natural vibration frequency of a wind turbine is
uniquely determined by the shape or constitution of the wind
turbine, the vibration in the natural vibration frequency is damped
by a passive damper which can adjust damping by fixing the
frequency to a specific one.
[0028] On the other hand, the variable frequency of the turbulent
wind flowing into the wind turbine varies by wind conditions such
as weather, season, time and the like. Also, the n-th frequency of
the rotation speed of the wind-turbine blade also varies depending
on the rotation speed of the wind-turbine blade. Therefore, for the
vibration in these frequencies, an active damper (AVC, for example;
Active Vibration Control) which can dynamically change the damping
frequency is used.
[0029] As described above, the active damper and the passive damper
are made to bear the respective corresponding frequencies, and the
damping effects of the respective dampers can be effectively
exerted.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0030] FIG. 1 illustrates a basic idea of a vibration damping
method of a wind turbine of the present invention.
[0031] FIG. 2 illustrates a method of changing a damping frequency
in accordance with a turbulent wind component of wind.
[0032] FIG. 3 illustrates a method of changing a damping frequency
in accordance with a change in a rotor rotation speed.
[0033] FIG. 4 is a block diagram illustrating a constitution of an
AVC.
[0034] FIG. 5 is a diagram illustrating a vibration model of a
TMD.
[0035] FIG. 6 is a perspective view illustrating an embodiment in
which an added mass of the TMD is a nacelle cover.
[0036] FIG. 7 illustrates a mounting structure of the nacelle cover
shown in FIG. 6, in which (a) is a side view and (b) is a rear
view.
[0037] FIG. 8 illustrates a fixed portion between the nacelle cover
and a frame, in which (a) illustrates a structure of the present
invention of fixation using an elastic member, and (b) illustrates
a general structure of fixation using a rigid member.
[0038] FIG. 9 is a side view illustrating an embodiment in which
the added mass of the TMD is a ladder.
[0039] FIG. 10 is a side view illustrating an embodiment in which
the added mass of the TMD is a platform.
[0040] FIG. 11 is a side view illustrating an embodiment in which
the added mass of the TMD is a cable.
[0041] FIG. 12 is a side view illustrating an embodiment in which
the added mass of the TMD is a lower module of a nacelle.
[0042] FIG. 13 illustrates vibration generated in the wind turbine
with respect to a frequency.
DETAILED DESCRIPTION OF THE INVENTION
[0043] An embodiment according to the present invention will be
described below by referring to the attached drawings.
[0044] FIG. 1 illustrates a basic idea of vibration damping of the
present invention. The lateral axis of FIG. 1(a) indicates a
frequency [Hz], and the vertical axis indicates a vibration level
[dB] in a nacelle installed on an upper part of a tower of a wind
turbine. As illustrated in FIG. 1(a), vibration caused by a
frequency component of turbulent wind, vibration in a rotor
rotation speed (1N), vibration in a primary component (1st) of a
natural vibration frequency of the wind turbine itself, vibration
in a rotation speed (3N) three times of the rotor rotation speed,
and vibration in a secondary component (2nd) of the natural
vibration frequency of the wind turbine itself appear in the order
from the low-frequency side. The relationship between the frequency
in the rotor rotation speed (1N) and the primary natural vibration
frequency (1st) might be opposite depending on the natural
vibration frequency of the wind turbine itself. Also, the vibration
appearing in the rotation number (3N) three times of the rotor
rotation speed is caused by the fact that the number of
wind-turbine blades is three.
[0045] The lateral axis in FIG. 1(b) indicates a frequency [Hz],
and the vertical axis indicates a damped amount [dB] by a vibration
damping device. As illustrating in this figure, in the present
invention, a passive damper (specifically, a TMD) is made to
function by making adjustment to the primary natural frequency
(1st), and an active vibration damping (AVC; active damper) is made
to function by making adjustment to the turbulent wind frequency
component (and/or the 1N component of the rotor rotation
speed).
[0046] Particularly, with regard to the active damping, as
illustrated in FIG. 2, a frequency band is preferably adjusted in
accordance with fluctuation in the turbulent wind component. Also,
with regard to the active vibration damping, the frequency band is
preferably adjusted in accordance with fluctuation in the rotor
rotation speed (1N) as illustrated in FIG. 3.
[0047] FIG. 4 illustrates a specific configuration for performing
the above-described active vibration damping. The active vibration
damping in this figure uses the same method as Patent Document
2.
[0048] In this figure, a rotation output of a rotor 4 rotated by
wind-turbine blades 3 is led to a gear box 7. The rotation output
whose rotation speed is increased by the gear box 7 is led to a
power generation system 9 and converted to an electric output. The
power output from the power generation system 9 is supplied to a
system, not shown. A pitch-angle control mechanism 11 is provided
on each of the wind-turbine blades 3. By means of this pitch-angle
control mechanism, the pitch angle of the wind-turbine blade 3 is
changed as appropriate from the fine side in which a rotation
output is obtained by receiving wind flowing into the wind-turbine
blades 3 to the feather side in which the wind flows through.
[0049] A pitch-angle instruction value .theta. inputted into the
pitch-angle control mechanism 11 is created in a pitch-angle
control portion 13. The pitch-angle control portion 13 is provided
with a pitch-angle setting portion 15 which sets a pitch angle on
the basis of a power output value P outputted from the power
generation system 9. The pitch angle of the wind-turbine blade 3 is
by this pitch-angle setting portion 15 so as to have a desired
output power value. The pitch angle set by the pitch-angle setting
portion 15 is sent to a correction portion 17.
[0050] In the correction portion 17, the pitch angle is corrected
on the basis of a turbulent wind frequency obtained from turbulent
wind information obtaining means 19 and outputs it as the
pitch-angle instruction value .theta.. As the turbulent wind
information obtaining means 19, an optical-fiber strain meter which
obtains load fluctuation of the wind-turbine blade 3 can be cited,
for example. Alternatively, a laser Doppler anemometer or an
ultrasonic Doppler anemometer may be installed in the wind turbine
so as to measure the wind speed on the upstream side of the wind
turbine for feed-forward control of a pitch angle. A pitch angle is
changed so as to damp vibration in the frequency band of the
turbulent wind component in a concentrated manner by obtaining a
turbulent wind component as above. Specifically, a pitch angle is
controlled so that thrust force to cancel vibration of a tower
caused by the turbulent wind component. In the correction portion
17, even if the frequency band of the turbulent wind component is
changed, the pitch angle is dynamically changed in accordance with
this change.
[0051] Also, into the correction portion 17, an output value from
rotor rotation speed obtaining means 21 which obtains the rotation
speed of the rotor rotated by the wind-turbine blades 3 is
inputted. By obtaining the rotor rotation speed as above, the pitch
angle is changed so as to damp the vibration in the rotor rotation
speed (1N) in a concentrated manner. Specifically, the pitch angle
is controlled so as to generate a thrust force to cancel vibration
of a tower caused by rotation of the rotor. In the correction
portion 17, even if the rotor rotation speed is changed, the pitch
angle is dynamically changed in accordance with this change so as
to perform vibration damping.
[0052] The active vibration damping of the present invention damps
vibration only in accordance with the turbulent wind component or
the rotor rotation speed (1N). However, if these frequency
components are close to each to other or if a peak level of the
damping vibration effect is lowered so as to allow a wider damping
frequency band, vibration damping may be performed in accordance
with the both.
[0053] FIG. 5 illustrates a vibration model of a TMD (Tuned Mass
Damper) adjusted so as to damp the vibration in the primary natural
vibration frequency (1st) of the wind turbine itself.
[0054] In this figure, reference character m1 denotes a mass of the
wind turbine, and reference character m2 denotes an added mass used
for the TMD. Also, reference character y denotes a displacement
direction in vibration.
[0055] The vibration model in FIG. 5 is expressed by an expression
as follows:
My''+Cy'+ky=F
[0056] Here, M, C, k, y, and F are expressed by the following
matrix:
M = ( m 1 0 0 m 2 ) ##EQU00001## C = ( c 1 + c 2 - c 2 - c 2 c 2 )
##EQU00001.2## k = ( k 1 + k 2 - k 2 - k2 k 2 ) ##EQU00001.3## y =
( y 1 y 2 ) ##EQU00001.4## F = ( F 1 0 ) ##EQU00001.5##
[0057] In the present invention, as the added mass m2 expressed by
the above expression, an existing wind-turbine constituent element
provided in order to exert the function of the wind turbine, not
for the purpose of damping, is used. A specific example will be
described below.
[0058] FIGS. 6 to 8 illustrate a case in which the mass of a
nacelle cover is used as the added mass m2. As illustrated in FIG.
6, the nacelle cover 30 is mounted capable of displacement on a
frame 32 fixed to the upper end of a tower 2.
[0059] FIG. 7 illustrates a mounting structure of the nacelle cover
30 to the frame 32. FIG. 7(a) is a side view and FIG. 7(b) is a
rear view of FIG. 7(a). As illustrated in the figures, the frame 32
and the nacelle cover 30 are connected to each other by a linear
guide 34, whereby the nacelle cover 30 can reciprocally move with
respect to the frame 32. Also, a plurality of elastic members
(rubber or the like) 36 which becomes a spring element and damping
element of the TMD are provided between the frame 32 and the
nacelle cover 30. The elastic members 36 are, as illustrated in
FIG. 8, preferably rubber inserted between the frame 32 and the
nacelle cover 30. FIG. 8(b) illustrates a structure as a
comparative example, and a rigid member 38 such as metal or the
like in general is provided.
[0060] FIG. 9 illustrates a case in which the mass of a ladder
(elevation ladder) 40 installed in the tower 2 of the wind turbine
is used as the added mass m2. The upper end of the ladder 40 is
rotatably supported by a pin at a predetermined fixed position 42
on the upper end of the tower 2. In pin supporting, a spring
element and a damping element of the TMD are given by interposing a
predetermined elastic member (rubber or the like). The lower end of
the ladder 40 is not fixed but left as a free end so that the
ladder 40 swings using the upper end as a swing center. A stopper
is preferably provided so that the ladder 40 does not collide
against a wall part of the tower 2 if the ladder 40 swings.
[0061] FIG. 10 illustrates an example in which the mass of a
platform 44 in the tower 2 is used as the added mass m2. The
platform 44 is used as a foothold for workers. As illustrated in
the figure, the platform 44 has a suspended structure using support
members 45. The platform 44 is configured to swing around fixed
positions 46 on the upper end of the support members 45. When the
support members 45 are to be fixed, the spring element and the
damping element of the TMD are given by interposing a predetermined
elastic member (rubber or the like).
[0062] FIG. 11 illustrates a case in which a part of the mass of a
cable 50 extending from the nacelle 5 to the ground is used as the
added mass m2. Specifically, the mass of the cable 50 above a
pulley 52 is used as the added mass m2. In this case, elasticity of
the cable 50 itself is used as the spring element and the damping
element of the TMD.
[0063] FIG. 12 illustrates a case in which the nacelle 5 is divided
vertically into two parts, which are an upper module 5a and a lower
module 5b, and the mass of the lower module 5b is used as the added
mass m2.
[0064] In the upper module 5a, a gear box, a power generator and
the like are arranged. In the lower module 5b, a yaw turning motor
which turns the nacelle 5 and a yaw brake are arranged. The lower
module 5b is capable of relative movement with respect to the upper
module 5a. Also, an elastic member is arranged so that the spring
element and the damping element of the TMD are given, though not
shown, when the upper module 5a and the lower module 5b are
relatively moved.
[0065] Also, though not shown, a transformer in the nacelle is made
relatively movable with respect to the nacelle main body, and the
mass of this transformer may be used as the added mass m2.
Moreover, other than the above, any wind-turbine constituent
element can be used as an added mass of the TMD by installing it
relatively movable with respect to the nacelle or the tower as long
as it has an appropriate weight as the added mass.
[0066] Also, though not shown, a TLD (Tuned Liquid Damper) may be
used instead of the TMD. In this case, operating oil or lubricant
oil stored in the nacelle is preferably used as the added mass.
Specifically, the operating oil in a reservoir tank of a hydraulic
device, the lubricant oil in the gear box and the like can be
cited.
[0067] As described above, according to this embodiment, the
following working effects can be exerted.
[0068] Since the natural vibration frequency of a wind turbine is
uniquely determined by the shape or constitution of the wind
turbine, the vibration in the natural vibration frequency is damped
by a TMD (or a TLD) which can adjust damping by fixing the
frequency to a specific one.
[0069] On the other hand, the variable frequency of the turbulent
wind flowing into the wind turbine varies by wind conditions such
as weather, season, time and the like. Also, the n-th frequency of
the rotation speed of the wind-turbine blade also varies depending
on the rotation speed of the wind-turbine blade. Therefore, for the
vibration in these frequencies, an AVC, which can dynamically
change the damping frequency, is used.
[0070] As described above, TMD and AVC are made to bear the
respective corresponding frequencies, and the damping effects of
the respective dampers can be effectively exerted.
[0071] The AVC which uses wind energy by changing the pitch angle
of the wind-turbine blade 3 so as to exert the damping action is
employed. In this case, though limited wind energy is used as a
damping force, the AVC is concentrated to a predetermined frequency
to perform damping in this embodiment, and thus, the wind energy
can be effectively used and the damping force can be exerted.
[0072] The AVC is controlled in accordance with fluctuation in the
wind speed detected by an anemometer such as an optical-fiber
strain meter, a laser Doppler anemometer and the like. Since
control is made in accordance with fluctuation in the inflow wind
speed as above, vibration damping can be performed with better
responsiveness than the case of vibration damping after vibration
actually generated in the wind turbine is obtained by an
acceleration sensor or the like.
[0073] Also, by selecting the existing wind-turbine constituent
element provided in order to exert the function of the wind
turbine, not for the purpose of vibration damping, as the added
mass, the TMD can be configured without adding a special component.
As a result, the weight of the wind turbine does not have to be
increased for damping vibration.
[0074] Since the existing liquid in the nacelle is used and a
special component is not added in configuring the TLD, the weight
of the wind turbine does not have to be increased for damping
vibration.
* * * * *