I Description
Title of Invention: WIND TURBINE GENERATOR SYSTEM AND
OPERATION CONTROL METHOD THEREOF
[OOO 11
Technical Field
The present invention relates to a wind turbine generator which transmits rotation of
a rotor to a generator via a hydraulic transmission including a hydraulic pump and a
hydraulic motor, and an operation control method thereof.
Background Art 1
In recent years, from a ierspective of preserving the environment, it is becoming
popular to use a wind turdine generator utilizing wind power which is one fo~mof
renewable energy.
The wind turbine generator converts motion energy of the wind to the rotation energy
of the rotor and further converts the rotation energy of the rotor to electric power by
the generator. In a common wind turbine generator, the rotation speed of the rotor is
about a few rotations per minute to tens of rotations per minute. Meanwhile, a rated
speed of the generator is normally 1500rpm or 1800rpm and thus a mechanical
gearbox is provided between the rotor and the generator. Specifically, the rotation
speed of the rotor is increased to the rated speed of the generator by the gearbox and
then inputted to the generator.
In recent years, the gearbox tends to become heavier and more expensive as the wind
turbine generators are getting larger to improve power generation efficiency. Thus, a
wind turbine generator equipped with a hydraulic transmission adopting a combination
of a hydraulic pump and a hydraulic motor of a variable capacity type is getting much
attention.
For instance, Patent Document 1 discloses a wind turbine generator using a hydraulic
transmission including a hydraulic pump rotated by a rotor and a hydraulic motor
connected to a generator. In the hydraulic transmission of this wind turbine generator,
the hydraulic pump and the hydraulic motor are connected via a high pressure reservoir
and a low pressure reservoir. By this, the rotation energy of the rotor is transmitted to
the generator via the hydraulic transmission. Further, the hydraulic pump is constituted
of a plurality of sets of pistons and cylinders, and cams which periodically reciprocate
the pistons in the cylinders. --
Further, Patent Document 2 describes a wind turbine generator adopting a hydraulic
transmission constituted of a hydraulic pump rotated by a rotor, a hydraulic motor
connected to a generator, and an operating oil path arranged between the hydraulic
pump and the hydraulic motor. In the hydraulic transmission of this wind turbine
generator, the hydraulic pump is cqnstituted of a plurality of sets of pistons and
cylinders, cams which periodically reciprocate the pistons in the cylinders, and high
pressure valves and low pressure valves which opens and closes with the reciprocation
of the pistons. By latching the piston near a top dead center, a working chamber
,
surrounded by the cylinder and the piston is disabled, and then the displacement of the
,
hydraulic pump is changed.
[0007] Although the hydraulic pump and the hydraulic motor are not variable displacement
type, Patent Document 3 discloses a wind turbine generator having a hydraulic pump
and a hydraulic motor. n;e wind turbine generator of Patent Document 3 maintains the
1,
rotation speed of the genekator constant by adjusting the pressure of operating oil to be
1 supplied from a hydraulic pump to a hydraulic motor. In this wind turbine generator, a
discharge side of the hyd aulic pump is connected to an intake side of ? the hydraulic motor via an inner space pf the tower functioning as a high pressure tank, and an intake
side of the hydraulic is connected to a discharge side of the hydraulic motor vi a
low pressure tank arranged below the tower. Further, a proportional valve is provided
between the high pressure tank and the hydraulic motor. The pressure of the operating
oil to be supplied to the hydraulic motor is adjusted by the proportional valve.
Citation List
Patent Literature
[0008] PTL 1: US 201010032959
PTL 2: US 201010040470
PTL 3: US 7436086
Summary of Invention
Technical Problem .
[0009] In the conventional wind turbine generator, it is necessary to appropriately perform
efficient and stable operation thereof in response to the change of the wind conditions
such as the low wind speed or the occurrence of a gust. Further, to synchronized the
wind turbine generator with the grid, the wind turbine generator must be equipped with
a Ride Through function at Grid low voltage condition according to a grid code set by
every country. The Ride ,Through function at Grid low voltage condition enables an
uninterrupted operation without being disconnected from the grid even when the
voltage of the grid decliried momentarily.
[0010] However, none of the wind turbine generators disclosed in Patent Documents 1 to 3
takes measures against the situation when the wind speed is low and when there arises
a gust. Therefore, the wind turbine generators of Patent Documents 1 to 3 do not
necessary achieve an operation efficiency or stability when the wind speed is low and
when there arises a gust.
Further, none of Patent D~cuments1 to 3 discloses a structure to realize the Ride
Through function at Grid low voltage condition and there was an issue on how to
realize the Ride Through function at Grid low voltage condition in the wind turbine
[OO 1 11
[OO 121
[00 131
[00 141
generator using a hydraulic transmission.
In view of the problems-above, an object of the present invention is to provide a wind
I
turbine generator system and an operation control method thereof, which has a superior
operation efficiency and stability at a low wind speed and during the occurrence of a
gust and is equipped with Ride Through function at Grid low voltage condition.
Solution to Problem
A wind turbine generatcr system in relation to the present invention, comprises: a
hub; a main shaft which iR coupled to the hub; a generator which is synchronized with
a grid; a hydraulic pump df variable displacement type which is driven by the main
shaft; a hydraulic motor ck variable displacement type which is connected to the
t
generator; a high pressure oil line which is arranged between a discharge side of the
hydraulic pump and an intake side of the hydraulic motor; a low pressure oil line
which is arranged between an intake side of the hydraulic pump and a discharge side of
the hydraulic motor; an accumulator which is connected to the high pressure oil line
via an accumulator valve; and a control unit which controls the hydraulic pump, the
hydraulic motor and the accumulator valve; wherein the control unit controls opening
and closing of the accumulator valve based on at least one of wind speed and a state of
the grid.
In this wind turbine genpator system, the opening and closing of the accumulator
valve is controlled based bn at least of wind speed and the state of the grid. When the
accumulator valve is opelied, the accumulator is in communication with the high
pressure oil line, and the pressure in the high pressure oil line is absorbed in the accumulator
or the pressure; in accumulator is released to the high pressure oil line
depending on which one of the pressure in the accumulator and the pressure in the high
pressure oil line is higher. Meanwhile, when the accumulator valve is closed, the communication
between the accumulator and the high pressure oil line is disconnected and
thus the pressure in the accumulator is maintained on its own without depending on the
pressure in the high presspre oil line.
Therefore, the opening 8nd closing of the accumulator valve is controlled base on at
least one of the wind spe$d and the state of the grid, so as to improve the operation ef- --
ficiency and stability whbn the wind speed is low and when there arises a gust, and to
41 realize the Ride Throughfinction at Grid low voltage condition.
The wind turbine generator system preferably further comprises a grid state determination
unit, wherein the state of the grid is determined by the grid state determination
unit. I
I
[0015] The wind turbine generitor system may further comprise a bypass oil line which is
arranged between the higd pressure oil line and the low pressure oil line to bypass the
hydraulic motor; and a re)ef valve which is arranged in the bypass oil line to maintain
the hydraulic pressure in ihe high pressure oil line not more than a set pressure.
[0016] In this manner, by the ielief valve in the bypass line, the pressure in the
high pressure oil line rise$ to the prescribed pressure of the relief valve by the high
t
pressure oil supplied from the hydraulic pump rAises the pressure, and then the relief
valve automatically opens to discharge excessive high pressure oil to the low pressure
oil line via the bypass line.
[0017] In the wind turbine generator system, when the wind speed is below a cut-in wind
speed, the control unit m control a displacement of the hydraulic motor ap- * proximately to zero, and keep the accumulator valve open so as to store in the acell
cumulator a pressure of operating oil discharged from the hydraulic pump which
pressure can be reached t6 a set value of a relief valve.
Alternatively, in the wind turbine generator system, when the wind speed is below a
cut-in wind speed, the coetrol unit controls a displacement of the hydraulic motor approximately
to zero, and opens the accumulator valve so as to store in the accumulator
a pressure of operating oil discharged from the hydraulic pump and closes the accumulator
valve when the pressure in the accumulator detected by the first pressure
sensor reaches a threshold value which is decided in advance.
[0018] In the conventional wind turbine generator system, there is not power generation
when the wind speed is below the cut-in wind speed and thus, the wind energy at the
low wind speed is wasteq. Thus, the accumulator valve is opened when the wind speed
is below the cut-in wind $peed so as to store pressure in the accumulator. As a result,
the wind energy previousty wasted at the low wind speed is utilized,. resulting in
improved operation efficiency.
The wind turbine generator system may further comprise a first pressure sensor
which detects a pressure in the accumulator and a second pressure sensor which detects
a pressure in the high pressure oil line, and the control unit may preferably control a
displacement of the hydraulic motor approximately to zero leaving some displacement,
opens the accumulator vqlve so as to store in the accumulator a pressure of operating
oil discharged from the h' draulic pump in such a case that the pressure in P the ac- cumulator detected by thy first pressure sensor is lower than the pressure in the high
id pressure oil line detected,by the second pressure sensor, and closes the accumulator
valve when the pressure i'h the accumulator detected by the first pressure sensor
reaches a threshold value,
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[0019] In such a case, the wind turbine generator system may further comprises: a first
pressure sensor which detects the pressure in the accumulator; a bypass oil li,n e which
is arranged between the high pressure oil line and the low pressure oil line to bypass
the hydraulic motor; and a relief valve which is arranged in the bypass oil line to
maintain the hydraulic prqssure in the high pressure oil line not more than a set
pressure, wherein, when t$e pressure in the accumulator detected by the first pressure
i
sensor reaches the set pressure of the relief valve, the control unit closes the accumulator
valve. r
In this manner, by the relief valve in the bypass line, the pressure in the
high pressure oil line rise; to the prescribed pressure of the relief valve by the high
pressure oil supplied from the hydraulic pump raises the pressure, and then the relief
valve automatically opens to discharge excessive high pressure oil to the low pressure
oil line via the bypass line. Further, when the pressure in the accumulator reaches the
prescribed pressure of the;relief valve, the wind energy at the low wind speed can be
stored maximally as a in the accumulator.
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Further, when the wind tpeed is not less than the cut-in wind speed, the control unit
keeps the accumulator vahe open so as to assist rotation of the hydraulic motor with
use of pressure of operatibg oil in the accumulator.
Alternatively, when the wind speed is not less than the cut-in wind speed, the control
unit opens the accumulator valve so as to assist rotation of the hydraulic motor with
use of pressure of operating oil in the accumulator in such a case that the pressure in
the accumulator detected by the first pressure sensor is higher than the pressure in the .
high pressure oil line detected by the second pressure sensor.
By this, with use of the pressure of the fluid in the accumulator stored at the low
wind speed, more electri? power can be generated, resulting in improving the operation
i efficiency. 1
The above wind turbine generator system may further comprises: a pitch driving
r mechanism which adjusts a pitch angle of a blade mounted on the hub, wherein, when
the grid state determinati4n unit determines that a voltage of the grid has decreased to a
prescribed voltage or lowgr and the condition based on Gid Code rule continues, the
control unit may controls'the pitch driving mechanism to change the pitch angle of the
blade toward a feathering position, changes the displacements of the hydraulic pump to
meet the load of the rotor and reduces the hydraulic motor to an amount required for
keeping the generator synchronized with the grid, and keeps the accumulator valve
open so as to store in-the $ccumulator a pressure of the operating oil discharged from
the hydraulic pump. i,
Alternatively, the windkurbine generator system may further a pitch driving
mechanism which adjust# a pitch angle of a blade mounted on the hub, wherein, when
the grid state determinatipn unit determines that a voltage of the grid has decreased to a
prescribed voltage or lower and the condition based on Gid Code rule continues, the
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control unit controls the pitch driving mechanism to change the pitch angle of the blade
to a feathering position, changes the displacements of the hydraulic pump to meet the
load of the rotor and reduqes the hydraulic motor to an amount required for keeping the
generator synchronized ~ ~ tthteh g rid, and opens the accumulator valve so as to store in
, ).
the accumulator a pressurp of the fluid discharged from the hydraulic pump in such a
case that the pressure in d e accumulator detected by the fist pressure sensor is lower
than the pressure in the high pressure oil line detected by the second pressure sensor.
[0024] As described above, whpn the voltage of the grid is decreased, the pitch angle is
changed to the feathering position and, the displacements of the hydraulic pump are
changed to meet the load of the rotor and the hydraulic motor is reduced to an amount
required for keeping the generator synchronized with the grid, so as to continue the
operation of the system without being disconnected from the grid. That is, the Ride
Through function at Grid .low voltage condition is realized.
Herein, after the voltagd of the grid has decreased to the prescribed voltage or lower,
if the displacement of the-$hydraulic pump is suddenly reduced, the adjusting of the
pitch angle does not catch up with the reduced displacement and thus the force acting
f
from the wind acting on the rotor with respect to the torque required for driving the
hydraulic pump becomes too strong and the rotation of the rotor increases dramatically.
Meanwhile, after the voltage of the grid has declined, the load of the
generator declines dramatically and thus, the rotation of the hydraulic motor gets too
fast unless the displacement of the hydraulic motor is reduced instantly. Therefore,
after the voltage of the grid has decreased, the displacement of the hydraulic motor
needs to be reduced promptly in comparison to the hydraulic pump. Unless the displacement
of the hydrauljc motor is reduced promptly, the discharge amount from the
hydraulic pump momentply exceeds the discharge amount from the hydraulic motor
1
and thus the pressure in the high pressure oil line rises, which can result in dysfunction
of the hydraulic transmisiion. By providing a relief valve for releasing the excessive
pressure from the high pressure oil line to the low pressure oil line, the pressure in the
high pressure oil line does not exceed the prescribed pressure. However, the friction
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heat cause when passing through the relief valve rises the temperature of the fluid, and
it is difficult to promptly return to the normal operation once the voltage of the grid is
restored.
Therefore, when the voltage of the grid has decreased to the prescribed voltage or
below, the accumulator valve is opened in such a case that the pressure in the accumulator
is lower than @e pressure in the high pressure oil line, thereby preventing
the pressure in the high $essure oil line from being too high or the temperature of the
fluid from rising by the aktuation of the relief valve.
I
Furthermore, the wind turbine generator system may further comprise an uninterruptible
power supply which supplies electrical power to the pitch driving mechanism
when the voltage of the grid becomes zero.
Further, the wind turbine generator system may further comprise an uninten-uptible
power supply which supplies electrical power to the hydraulic pump and the hydraulic
motor when the voltage of the grid becomes zero. I
By this, even when the toltage of the grid becomes zero, the pitch driving
mechanism and/or the hy@aulic pump and the hydraulic motor can be operated to put
the wind turbine generato; system into a Ride Through operation state at Grid low
voltage condition or a shdtoff state.
It is preferable that, wh& the grid state determination unit determines that voltage of
the grid starts to be restored, the control unit changes the pitch angle of the blade to a
fine position, and sets the displacements ofthe hydraulic pump so that ipower coefficient
becomes at a maximum thereof, and increases the displacement of the
hydraulic motor so that the power generated by the generator into the grid increases.
In this manner, when th6 voltage of the grid starts to be is restored, the pitch angle is
C
changed to the fine positim and the displacements of the hydraulic pump is set so that
a power coefficient beco~iesa t a maximum thereof, and the displacement of the
hydraulic motor is increased so that the power generated by the generator into the grid
increases. As a result, the'operation of the system can promptly returns to the efficient
operation.
Moreover, in this situation, the accumulator valve may be opened so as to assist
rotation of the hydraulic motor with use of pressure of fluid in the accumulator in such
a case that the pressure in, the accumulator is higher than the pressure in the high
pressure oil line.
The wind turbine generator system may also comprise: a oil tank which stores fluid
and is connected to the lob pressure oil line; an accumulator pressure relief line
provided between the acc$mulator valve and the accumulator and connected to one of
the low pressure oil line apd the oil tank; and a pressure relief valve provided in the ac-
1
cumulator pressure relief line, wherein, when the grid state determination unit determines
that voltage of the grid is restored, the control unit opens the pressure relief
valve to allow the pressure in the accumulator to escape to the one of the low pressure
oil line and the oil tank.
As described above, when the voltage of the grid is restored, the pressure relief valve
is opened to allow the pressure in the accumulator to escape to the low pressure oil line
or the oil tank. As a result, the pressure in the accumulator can be reduced to take
measure against the reoccllrrence of the voltage decline of the grid.
I i In the above wind turbil?e generator system, when there arises a gust having a wind
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speed greater than a prescribed threshold value, the control unit may keep the accumulator
valve open so as to store in the accumulator a of operating oil
discharged from the hydraulic pump, and when the wind speed of the gust becomes not
greater than the prescribe4 threshold value, the control unit keeps the accumulator
valve open so as to assist rotation of the hydraulic motor with use of the pressure of the
operating oil in the accuiulator.
Alternatively, a first pressure sensor which detects a pressure in the accumulator and a
second pressure sensor wkch detects a pressure in the high pressure oil line may also
be provided and when thwe arises a gust having a wind speed greater than a prescribed
threshold value, the contrtl unit opens the accumulator valve so as to store in the accumulator
a pressure of flbid discharged from the hydraulic pump in such a case that
the pressure in the accumplator detected by the first pressure sensor is lower than the
pressure in the high pressure oil line detected by the second pressure sensor; and when
the wind speed of the gust becomes not greater than the prescribed threshold value, the
control unit keeps the accumulator valve open until the pressure in the accumulator
detected by the first pressure sensor becomes the same as the pressure in the high
pressure oil line detected by the second pressure sensor.
[0032] When there arises a gud, the rotation of the rotor rises and the discharge amount
from the hydraulic pump increases, thereby rising the pressure in the high pressure oil
line. Therefore, when the5e arises a gust, the accumulator valve is opened in such a
case that pressure in the aixumulator is lower than the pressure in the high pressure oil
line so as to absorb the excessive pressure of the high pressure oil line in the accumulator.
And once the wind speed of the gust becomes equal to or lower than the
threshold value, the accumulator valve is kept open so as to release the pr4essure in the
accumulator. In this manner, the effect of the gust on the wind turbine generator
system can be minimized,
100331 Further, the prescribed hreshold value may be 60mlsec which is obtained as an
I
average wind speed for a period of three seconds or longer.
1
[0034] Further, the wind turbi generator system further comprises: an oil f tank which
stores operating oil and iq connected to the low pressure oil line; an accumulator
pressure relief line between the accumulator valve and the accumulator and
connected to one of the 1 ~ pwre ssure oil line and the oil tank; and a pressure relief
valve provided in the accpmulator pressure relief line, wherein, when the grid state deteimination
unit determines that voltage of the grid is restored,the control unit opens
the pressure relief valve to allow the pressure in the accumulator to escape to the one
of the low pressure oil line and the oil tank.
100351 As described above, when the wind speed of the gust becomes not greater than the
threshold value, the pressure relief valve is opened so as to allow the pressure in the
F
I' accumulator to escape to the low pressure oil line or fhe oil tank via the accumulator
1,
pressure relief line. As a result, the pressure in the accumulator is reduced and thus, it
is possible to take measure against the recurrence of the gust.
[0036] The wind turbine generator system may further comprise: a oil tank which stores
fluid; and a boost pump which replenishes the low pressure oil line with the fluid from
I ,
the oil tank.
[0037] By this, even if the fluid leaks in the hydraulic transmission, the boost pump replenishes
the low pressurd oil line with the fluid from the oil tank so as to keep the
amount of the fluid circulating in the hydraulic transmission.
$1
[0038] In this situation, the winb turbine generator system may also comprise: a return line
which returns the fluid in ihe low pressure oil line to the oil tank; and a low pressure
relief valve which is arr4ged in the return line to maintain the hydraulic pressure in
the low pressure oil line &proximately at a set pressure.
[0039] By this, although the bdost pump replenishes the low pressure oil line with the fluid,
the low pressure relief valve automatically opens once the pressure in the low pressure
oil line reaches the prescribed pressure of the low pressure relief valve. Thus, the fluid
is returned to the oil tank via the return line and the amount of the fluid circulating in
the hydraulic transmission is appropriately maintained.
[0040] The present invention avo proposes an operation control method of a wind turbine
generator system which cgmprises a hub, a main shaft coupled to the hub, a generator
which is synchronized with a grid, a hydraulic pump of variable displacement type
which is driven by the mdjn shaft, a hydraulic motor of variable displacement type
which is connected to the generator, a high pressure oil line which is arranged between
a discharge side of the hydraulic pump and an intake side of the hydraulic motor, a low
pressure oil line which is arranged between an intake side of the hydraulic pump and a
discharge side of the hydraulic motor, an accumulator which is connected to the high
pressure oil line via an acbumulator valve, and a grid state determination unit which
determines a state of the grid, the method comprising the step of controlling opening
and closing of the accumulator valve based on: at least one of wind speed and the state
of the grid determined by b e grid state determination unit.
%q [0041] According to the operation control method of the wind turbine generator system, the
opening and closing of thi accumulator valve is controlled based on at least one of
wind speed and the state 'f the grid determined by the grid state determination. As a
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result, the operation efficigncy and stability at the low wind speed or when there arises
a gust, can be improved abd the Ride Through function at Grid low voltage condition
can be achieved as well.
Advantageous Effects of Invention
r:
3
According to the present invention, the accumulator is connected to the high pressure
J
oil line via the accumulatQr valve and the opening and closing of the accumulator valve
is controlled based on at l&ast one of wind speed and the state of the grid determined
by the grid state determination unit and both of the pressure in the accumulator
detected by the first pressure sensor and the pressure in the high pressure oil line
L
detected by the second pressure sensor. As a result, the operation efficiency and
stability at the low wind speed or when there arises a gust, can be improved and the
Ride Through function at Grid low voltage condition can be achieved as well.
Brief Description of Drawings
[fig. l]Fig. 1 is a general structure of a wind turbine generator system.
4
[fig.2]Fig. 2 is a diagram Showing a structure of a pitch driving mechanism.
[fig.3]Fig. 3 is a diagram khowing a sUvcture of a hydraulic transmission.
[fig.4]Fig. 4 is a diagram ihowing a system structure of the wind turbine generator
system. 1
I
[fig.S]Fig. 5 is a flow chai-t showing an operation control of an accumulator at a low
wind speed.
[fig.6]Fig. 6 is a flow chart showing an operation control of releasing pressure in the
accumulator.
[fig.7]Fig. 7 is a flow chart showing an operation control when a voltage of a grid has
decreased. u:
[fig.B]Fig. 8 is a flow chqt showing an operation control when there arises a gust.
Description of Embodiments
3 A preferred embodiment of the present invention will now be described in detail with
reference to the accompaiying drawings. It is intended, however, that unless particularly
specified, dimensions, materials, shape, its relative positions and the like shall
be interpreted as illustrative only and not lirnitative of the scope of the present.
A general structure of the wind turbine generator system in relation to a preferred
embodiment is described.: Fig. 1 illustrates a general structure of a wind turbine
generator system.
As an example of the wind turbine generator, a three-bladed wind turbine is used.
However, the preferred ekbodiment is not limited to this example and can be applied
$1
to various types of wind t'hrbine generator systems.
As illustrated in Fig. 1, $ wind turbine generator system 1 comprises a rotor 2 rotated
by the wind, a hydraulic @ansmission 10 for increasing rotation speed of the rotor 2, a
generator 20 for generatidg electric power, a nacelle 22, a tower 24 system for
4'
supporting the nacelle 22Jand a control unit 30 for controlling each controller of the
wind turbine generator system 1.
The rotor 2 is construct+ such that a main shaft 8 is connected to a hub 6 having
blades 4. Specifically, thrfe blades 4 extend radially from the hub 6 and each of the
blades 4 is mounted on th& hub 6 connected to the main shaft 8. By this, the power of
the wind acting on the blailes 4 rotates the entire rotor 2, the rotation of the rotor 2 is
inputted to the hydraulic transmission 10 via the main shaft 8.
The hydraulic transmission 10 includes a hydraulic' pump 12 of a variable displacement
type which is rotated by the main shaft 8, a hydraulic motor 14 of a variable
displacement type which is connected to the generator 20, and a high pressure oil line
16 and a low pressure oil line 1 8 which are arranged between the hydraulic pump 12
and the hydraulic motor 14. The detailed structure of the hydraulic transmission 10 is
described later.
f
The generator 20 is con$iected to the hydraulic motor 14 of the hydraulic
transmission 10. An existing asynchronous generator or synchronous generator can be
1
used as the generator 20. The torque having the rotation speed that is almost constant is
inputted from the hydraulic motor 14 to the generator 20 and then the generator 20
generates alternating clurint having a frequency that is almost constant. Further, the
generator 20 is synchroniked with a grid 50 which will be described later, and the
current generated by the generator 20 is transmitted to the grid 50.
The nacelle 22 supports the hub of the rotor 2 rotatably and houses a variety of
devices such as the hydraulic transmission 10 and the generator 20. The nacelle 22 is
further supported on the tower 24 rotatably and may be turned in accordance with the
wind direction by a yaw &otor which is not shown.
The tower 24 is formedf11 into a column shape extending upward from a base 26. For
instance, the tower 22 cad be constituted of one column member or a plurality of units
that are connected in a v h c a l direction to form a column shape. If the tower 24 is
constituted of the plurality of units, the nacelle 22 is mounted on the top-most unit.
The control unit 30 comprises a pump controller 32 for adjusting the displacement of
the hydraulic pump 12, a motor controller for adjusting the displacement of the
hydraulic motor 14, a pitch controller for adjusting the pitch angle of the blade 4, and
an ACC valve controller 38 for controlling the opening and closing of an accumulator
valve described later. i
Further, a pitch driving )mechanism 40 for changing the pitch angle of the blade 4 is
t
housed in the hub 6. Fig. is a diagram showing a structure of the pitch driving
mechanism 40. The figure illustrates the pitch driving mechanism 40 comprising a
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hydra~~lciycl inder 42, a servo valve 44, a hydraulic pressure source 46 and an accumulator
48. The servo balve 44 adjusts the supply of the high pressure oil generated
by the hydraulic pressur& source 46 and the high pressure oil stored in the accumulator
48 to the hydraulic cylinder 42 so as to achieve a desired pitch angle of the blade 4
under the control of the pitch controller 36.
[0054] The pitch controller 36 $omally receives the electric power from the grid 50.
However, when the voltaje of the grid becomes zero, the electric power is supplied
from an uninterruptible ptwer supply 52. Further, a state of the grid 50 is monitored by
a grid state deterrninati0n:unit 54. The grid state determination unit 42 preferably
includes a voltage sensor for measuring a voltage of the grid 50. However, the voltage
sensor can be replaced with a power-factor meter or a reactive volt-ampere meter to indirectly
determine the state of the grid 50.
100551 Next, a detailed structur~o f the hydraulic transmission 10 is explained. Fig. 3 is a
diagram showing a struchre of the hydraulic transmission 10.
[0056] As described above, the hydraulic transmission comprises the hydraulic pump 12, the
hydraulic motor 14, the high pressure oil line 16 and the low pressure oil line 18. The
discharge side of the hydrpulic pump 12 is connected to the intake side of the hydraulic
5
motor 14 and the intake side of the hydraulic pump 12 is connected to the discharge
side of the hydraulic mot& 14.
Fig. 3 illustrates the hy+aulic transmission 10 including only one hydraulic motor
14. However, the hydrauljc transmission 10 may comprise a plurality of hydraulic
motors 14 and the hydraulic motors 14 may be connected to the hydraulic pump 12 via
the high pressure oil lines 16 and the low pressure oil lines 18 respectively. In this
case, the high pressure oil line 16 having one end thereof connected to the discharge
side of the hydraulic pump 12, splits midway and each of the split lines of the high
pressure oil line 16 is connected to the intake side of each of the hydraulic motors 14
while a plurality of lines 6f the low pressure oil line 18 having one end thereof
connected to the dischargk side of each of the hydraulic motors 14 flow into one and
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then connected to the discharge side of the hydraulic pump 12.
[0057] Accumulators 60 (60A7;60B) are connected to the high pressure oil line 16 via accumulator
valves 62 (62A, 62B). The accumulator 60 may be, for instance, a bladdertype
in which air and the operating oil are separated by a deformable bag, e.g. a
bladder or a piston. In the accumulator 60, the operating oil of high pressure is introduced
during an accumulating process so as to deform the bladder or the piston and
compress the air. In contiast, during a pressure-releasing process, the compressed air
expands or the high pressure air from outside pushes the bladder or piston and then the
operating oil is pushed out of the accumulator 60.
Further, at least one set;of the accumulator 60 and the accumulator valve 62 is
I
needed. However, if a plurality of sets of the accumulators 60 (60A, 60B) and the accumulator
valves 62 (62ii., 62B) are arranged as shown in Fig. 3, the plurality of accumulators
60 can be adequately used depending on intended purposes.
'i
Furthermore, at least oge of the accumulators 60 may have an air part whose displacement
is greater than that of an operating oil part at the time of initially sealing the
air, and the pressure of the initially-sealed air of each accumulator 60 may be different
from one another. Moreo*r, it is possible that the operating oil is introduced into the
accumulator 60 via the aciumulator valve 62 instantaneously and the pressure in the
accumulator 60 changes tb follow the pressure change in the high pressure oil line 16
without delay in terms of 'ilm e, and the p;essure in the accumulatbr 60 may be equal to
the pressure in the high p:essure oil line 16 in such state that the accumulator valve 62
is open.
Between the accumulatdr valve 62 (62A, 62B) and the accumulator 60 (60A, 60B),
provided is a first pressure sensor PI. In the high pressure oil line 16, provided is a
second pressure sensor pi. The first pressure sensor P1 measures the pressure of the
operating oil in the accumulator 60 (60A, 60B). Meanwhile, the second pressure sensor
P2 measure the pressure df the operating oil in the high pressure oil Line 16.
Measurement results of h e first pressure sensor P1 and the second pressure sensor P2
are sent to the ACC valve. i controller 38 to be used for controlling the opening and
closing of the accumulate$ valves 62 (62A, 62B). The ACC valve controller 38
controls the opening and closing of the accumulator valves 62 based on the wind speed
and determination results .of the grid state determination unit 54 in addition to the
results of the first pressurk sensor P1 and the second pressure sensor P2. Specifically,
the ACC valve controller 38 controls the opening and closing of the accumulator
valves 62 based on at least one of the wind speed and the state of the grid 50 determined
by the grid state determination unit 54 and the pressure in the high pressure
oil line 16 measured by the second pressure sensor P2.
Further, separately of tk& accumulator 60, an anti-pulsation accumulator 64 is
provided in the high pres 4o re oil line 16 and the low pressure oil line 18. These
suppress the pressure cha$ge (pulsation) in the high pressure oil line 16 and the low
pressure oil line 18. In thk! l ow pressure oil line 18, provided are an oil filter 66 for
removing impurities fro$ the operating oil and an oil cooler for cooling the operating
oil.
Between the high pressure oil line 16 and the low pressure oil line 18, provided is a
bypass line 70 for bypassing the hydraulic motor 14. And, a relief valve 72 is provided
in the bypass line 70 to &intain the pressure of the operating oil in the high pressure
oil line 16 the same as a prescribed pressure or below. In this manner, when the
pressure in the high presspre oil line 16 rises to the prescribed pressure of the relief
valve 72, the relief valve i72 automatically opens so as to release the high pressure oil
r
to the low pressure oil lirk 18 via the bypass line 70.
Furthermore, in the hy&aulic transmission 10, provided are an oil tank 80, a supplementary
line 82, a boipt pump 84, an oil filter 86, a return line 88 and a low
pressure relief valve 89.
[0063] The oil tank stores supplementary operating oil. The supplementary line connects the
oil tank 80 to the low pressure oil line 18. The boost pump 84 is arranged in the sup-
I
plementary line 82 so low pressure oil line 18 with the supplementary
operating oil the oil tank 80. In such a case, the oil filter 86 arranged
b in the supplementary impurities from the operating oil to be supplied
to the low pressure oil l i 4 18.
9 Even when the operating oil leaks in the hydraulic transmission 10, the boost pump
84 replenishes the low pressure oil line with the operating oil from the oil tank 80 and
thus, the amount of the oeerating oil circulating in the hydraulic transmission can be
maintained.
[0064] The return line 88 is installed between the oil tank 80 and the low pressure oil line
18. The low pressure relief valve 89 is arranged in the return line 88 and the pressure in
the low pressure oil line 48 is maintained near the prescribed pressure.
By this, even though thti boost pump 84 supplies the operating oil to the low pressure
I
oil line 18, once the presspre in the low pressure oil line 18 reaches the prescribed
pressure of the low pressure relief valve 89, the low pressure relief valve 89 auto-
1
matically opens so as to release the operating oil to the oil tank 80 via the return line
88. Thus, the amount of the operating oil circulating in the hydraulic transmission 10
can be adequately maint&ned.
[0065] Further, an accumulator pressure relief line 61 is arranged between the accumulator
valve 62 (62A, 62B) and the accumulator 60 (60A, 60B). The accumulator pressure
relief line 61 is equipped with a pressure relief valve 63 and connected to the oil tank
80. When the pressure relief valve 63 is opened under the control of the control unit
i
30, the accumulator 60 becomes in communication with the oil tank 80 and the
pressure in the accurnula4r 60 is released to a side of the oil tank 80.
Fig. 3 illustrates the ca+ in which the accumulator pressure relief line 61 is
connected to the oil tank 80. However, the accumulator pressure relief line 60 may be
connected to the low pre{iure oil line 18.
[0066] Furthermore, the hydraulic pump 12 and the hydraulic motor 14 are variable displacement
type, the displacement of which can be adjusted. Thus, actuating the same
requires electric power. Therefore, in the wind turbine generator system 1, the electric
power is normally supplied from the grid 50 to the hydraulic pump controller 3212 and
* -
the hydraulic motor controller 34. In such a case that a solenoid valve is used to control
the displacements of the hydraulic pump 12 and the hydraulic motor 14, the electric
power is supplied to the solenoid valve as well. When the voltage of the grid 50
becomes zero, the uninteyuptible power supply 52 supplies electric power to the
hydraulic pump controller 32 and the hydraulic motor controller 34 and may further be
supplied to the solenoid valve for adjusting the displacements of the hydraulic pump
12 and the hydraulic motor 14.
[0067] In the hydraulic transmission 10, when the hydraulic pump 12 is driven by the
rotation of the main shaft 8, a pressure difference occurs between the high pressure oil
line 16 and the low pressdre oil line 18. This pressure difference drives the hydraulic
motor 14. In such a case, h e hisplacement of the hydraulic pump 12 is adjusted by the
pump controller 32 so thd a power coefficient becomes at a maximum thereof.
6
Meanwhile, the displacement of the hydraulic motor 14 is adjusted by the motor
controller 34 depending oXI the rotation speed of the main shaft 8 and the displacement
of the hydraulic pump 127~0th at a rotation speed of the hydraulic motor 14 becomes
constant. ,
[0068] The wind turbine generator system 1 has the above structure and each controller
thereof is controlled by the control unit 30. Fig. 4 is a diagram showing a system
structure of the wind turbine generator system 1. As shown in the drawing, the
following items are sent tb the control unit 30, which are the wind speed V obtained in
a wind speed obtaining unit 56, a grid state S of the grid 50 determined by the grid
state determination unit 54, a pressure PAcc in the accumulator 60 measqred by the fust
pressure sensor P1 and a pressure PH in the high pressure oil line 16 measured by the
second pressure sensor P2. And each controller (32, 34,36,38) of the control unit 30
controls the hydraulic pump 12, the hydraulic motor 14, the pitch driving mechanism
40 (i.e. servo valve 44) and the accumulator valve 62 based on the wind speed V, the
grid state S, the pressure PAC,, the pressure PH and so on.
Moreover, the wind speed obtaining unit 56 is not limited as long as being capable of
measuring or estimating the wind speed V. For instance, the wind speed obtaining unit
56 may be a wind speed meter mounted on the nacelle, or a combination of a rotation
meter for measuring the rptation speed of the main shaft 8 and a calculator for estimating
the wind speed $! from measuring results of the rotation meter.
I
[0069] Next, an operation cont#ol of the wind turbine generator system 1 by the control unit
30 is explained. Hereinaf1 e r, three types of the operation control are explained in the order of a low wind spee4 control wherein the wind speed V is below a cut-in wind speed, a low voltage control wherein the voltage of the grid 50 decreases and a gust
control wherein there arises a gust. Then, the operation method for efficiently
operating the three types of the operation control is explained.
. -
[0070] (Low wind speed contrgl)
Fig. 5 is a flow chart showing an operation control of the accumulator 60 to accumulate
pressure thereifi at a low wind speed. Fig. 6 is a flow chart showing an
operation control of relea;ing the pressure of the accumulator 60.
[0071] Fig. 5 illustrates the following process. First, the wind speed obtaining unit 56
obtains the wind speed V in a step S2, and the wind speed V and the cut-in wind speed
1
Vc are compared in a step S4. Then, in the step S4, if it is determined that the wind
speed V is smaller than the cut-in speed Vc, the process advances to a step S6. In the
step S6, the motor controller 34 controls the displacement of the hydraulic motor 14
approximately to zero and the power generation by the generator 20 is stopped. In
contrast, if it is determined that the wind speed V is not less than the cut-in speed VC,
the process returns to the atep S2 to obtain the wind speed V again.
The cut-in wind speed VcJis defined as a wind speed to start the power generation by
the generator 20. 1
i
After the step S6 in which the displacement of the hydraulic motor 14 is controlled
approximately to zero, th; pressure PACc in the accumulator 60 is measured by the first
pressure sensor P1 and the pressure PH in the high pressure oil line 16 is measured by
the second pressure sensor P2 in a step S8. Then, the process advances to a step S 10 in
which the pressure PAcc in the accumulator 60 and the pressure P, in the high pressure
oil line 16 are compared.
In the step S 10, if it is determined that the pressure PACC in the accumulator 60 is
lower than the pressure PA in the high pressure oil line 16, the process advances to a
step S12 in which the ACC valve controller 38 closes the accumulator valve 62. In
contrast, if it is determined in the step S 10 that the pressure PACCin the accumulator 60
is not lower than the pressure PH in the high pressure oil line 16, the process returns to
the step S2 so that the wind speed obtaining unit 56 obtains the wind speed V again.
Once the accumulator 62 is opened in the step S12, the pressure PAcc in the accumulator
60 is measure4 by the first pressure sensor P1 in a step S13. Then, it is determined
in a step S14 if the pressure PAcc has reached a threshold value. If it is determined
in the step S 14 that the pressure PAcc in the accumulator 60 has reached or
exceeds the threshold value, the process advances to a step S 16 in which the ACC
valve controller 38 closes( the accumulator valve 62. In contrast, if it is determined in
the step S 14 that the preshure PAC, in the accumulator 60 is less than the threshold
value, the process retumsito the step S 12 to keep the accumulator valve 62 open.
As the threshold value, kith which the pressure PAcc is compared with in the step
11 S 14, a small amount, e.g.;5bar, less than the prescribed pressure of the relief valve 72
arranged in the bypass link 70 may be used.
In this manner, the accumulator valve 62 is opened at the low wind speed when the
wind speed V is below the cut-in wind speed Vc to charge the accumulator, and then
when the wind speed becomes the same as the cut-in wind speed Vc or above again,
the pressure in the accumblator 60 is released so as to assist the rotation of the
hydraulic motor 14.
As Fig. 6 illustrates, fir8t the wind speed obtaining unit 56 obtains the wind speed V
i
in a step S 17, and in a step S 18 it is determined if the wind speed V is again the same
r,
as or above the cut-in w i d speed Vc. If it is determined that the wind speed V is again
the same as or above the Cut-in wind speed Vc, the displacement of the hydraulic
motor 14 is increased by the motor controller 34 and the power generation by the
generator 20 starts again. In contrast, if it is determined that the wind speed V remains
less than the cut-i; wind speed Vc, the process returns to the step S17 to obtain the
wind speed V again.
[0077] After the step S20 in wk'ich the displacement of the hydraulic motor 14 d is increased, the pressure sensor P1 an$ the pressure sensor P2 measure the pressure PAC, in the accumulator
60 and the pre$sure PH in the high pressure oil line 16 respectively in a step
S22, and then the measur$d pressure PAcc ahd the measured pressure PH are compared
in a step S24. And if it is betermined that the pressure PAcc in the accumulator 60 is
greater than the pressure I!+, in the high pressure oil line 16 in the step S24, the process
advances to a step S26 in'which the ACC valve controller 38 opens the accumulator
valve 62. In contrast, if it is determined in the step S24 that the pressure PAcc in the accumulator
60 is not greatkr than the pressure PH in the high pressure oil line 16, the
process returns to the step S17 to obtain the wind speed V again.
100781 In this manner, the accumulator valve 62 is opened when the wind speed V becomes
the same as or above the cut-in wind speed Vc. As a result, it is possible to utilize the
pressure stored in the accumulator when the wind speed is small and thus, more
electric power can be generated and the operation efficiency is improved.
[0079] Explained so far is the case wherein, the pressure of the fluid is stored at the low
wind speed operation when the wind speed V is below the cut-in wind speed Vc and
once the wind speed V becomes again the same as or above the cut-in wind speed Vc,
the rotation of the hydra&c motor 14 is assisted with use of pressure of fluid in the accumulator.
However, the pressure accumulated in the accumulator at the low wind
speed may be used in different situations. For instance, the rotation of the hydraulic
motor 14 may be assisted with the use of the accumulator 60 having the pressure
reserved in advance at th low wind speed to resume the operation of the wind turbine
generator system 1 after i e maintenance.
'I Further, the case was a@o explained in reference to Fig. 5 and Fig. 6, in which the accumulator
60 reserves thh pressure when the wind speed V is less than the cut-in wind
L
speed Vc and once the wind speed V becomes again not less than the cut-in wind speed
Vc, the rotation of the hydraulic motor 14 is assisted with the use of the accumulator
60. However, there is a case sometimes wherein the pressure PACCis already high
enough when the wind speed V becomes less than the cut-in wind speed Vc. In such a
case, instead of reserving the pressure in the accumulator 60 as shown in Fig. 5, it is
also possible to wait for ;he wind speed V to return to the same as or above the cut-in
wind speed Vc and then release the pressure of the accumulator 60 in the process
shown in Fig. 6 so as to Gsist the rotation of the hydraulic motor 14.
[0080] Moreover, Fig. 5 illustrites the case wherein, when the pressure PAcc in the accumulator
60 is lower thin the pressure PH in the high pressure oil line 16 (YES in the
step SlO), the accumulatok valve 62 opens so as to save the fluid in the accumulator 60.
However, it is also possible to control the opening and closing of the a'ccumulator 62
based on the result of comparing the pressure PACc in the accumulator 60 and a
pressure threshold value Pth in the accumulator. The pressure threshold value Pth may
be the same value as the irescribed pressure of the operating oil in the high pressure oil
line 16, or lower than thesrescribed pressure of the operating oil in the high pressure
oil line 16. C
It is also possible to ski* the steps S8 through S10 of Fig. 5 so that, after the displacement
of the hydraulgi motor 14 is reduced in the step S6 (reduced approximately
to zero but leaving some displacement), the accumulator valve 62 is opened to save the
fluid in the accumulator 60. If the accumulator valve 62 is already open, the step S12
may be skipped as well the steps S8 through S 10.
[0081] Further, Fig. 5 illustrates the case in which the accumulator valve 62 opens when the
pressure PACC in the accumulator 60 is lower than the pressure PH in the high pressure
oil line 16 (YES in the step S lo), but the accumulator valve 62 may be kept open consistently.
More specifically, when the wind speed V is below the cut-in wind speed Vc,
the control unit may contxol the displacement of the hydraulic motor 14 approximately
to zero, and keeps the accumulator valve 62 open so as to store in the accumulator 60 a
I pressure of operating oil discharged from the hydraulic pump 12.
Further, Fig. 6 illustrat+ the case in which the accumulator valve 62 opens when the
pressure PACC in the accuinulator 60 is higher than the pressure PH in the high pressure
oil line 16 (YES in the stlp S24), but the accumulator valve 62 may be kept open consistently.
More specifically, when the wind speed V is not less than the cut-in wind
speed Vc, the control unit may keep the accumulator valve 62 open so as to assist
rotation of the hydraulic motor 14 with use of the pressure of the operating oil in the
accumulator 60. 1
[0082] Fig. 7 is a flow chart s$wing an operation control when a voltage of a grid has
,I
decreased. As described &I the drawing, it is determined by the grid state determination
unit 54 in a step S30 if voltage of the grid 50 has decreased to the prescribed
voltage or lower. If it is determined in the step S30 that the voltage of the grid 50 has
decreased to the prescribkd voltage or lower, the process advances to a step S32 in
which the pitch controller 36 controls the pitch driving mechanism 40, i.e. a servo
valve 44 so as to control the supply of the high pressure oil to the hydraulic cylinder 42
and change the pitch angie of the blade 4 to a feathering position. In contrast, if it is determined
in the step S30 that the voltage of the grid 50 is greater than the prescribed +
voltage, which means tha? the grid 50 is in a normal state, the process returns to the
steps S30 to continue mohitoring the state of the grid 50 by the grid state determination
unit 54. F
The prescribed voltage h$rein refers to a low voltage set defined in the grid code and
may iiclude the case whekein the voltage is practically zero temporarily. And the
changing of the pitch angle to the feathering position means that the pitch angle of the
blade 4 is changed to such a position that the wind acting on the blades 4 provides no
net torque to the rotor shaft 8.
[0083] After the pitch angle of !the blade 4 is changed to the feathering position in the step
S32, the process advanced) to a step S34. In the step 34, the displacements of the
hydraulic pump 12 and tl& hydraulic motor 14 are reduced to an amount required for
keeping the generator 20 bynchronized with the grid 50.
The displacement hereii refers to a geometric volume that a capacitive pump or a capacitive
motor pushes ped one rotation according to JIS B0142, Japanese Industrial
Standard. Specifically, the displacement of the hydraulic pump 12 means the volume
of the operating oil being discharged from the hydraulic pump 12 to the high pressure
oil line 16 while the main shaft 8 makes one rotation, and the displacement of the
hydraulic motor 14 means the volume of the operating oil discharged from the
hydraulic motor 14 to the low pressure oil h e 18 while the output shaft of the
hydraulic motor 14 makes one rotation.
[0084] Next in a step S36, the first pressure sensor P1 measures the pressure PACCin the accumulator
60 and the secbnd pressure sensor P2 measures the pressure PH in the high
pressure oil line 16. Thed the process advances to a step S38 in which the pressure PACC
in the accumulator 60 and the pressure PH in the high pressure oil line 16 are compared.
If it is determined in the step S38 that the pressure PAcc in the accumulator 60 is lower
I
than the pressure PH in the high pressure oil line 16, the process advances to a step S40
to open the accumulator valve 62 by the ACC valve controller 38. In contrast, it is determined
in the step S38 that the pressure PAC, in the accumulator 60 is not lower than
the pressure PH in the high pressure oil line 16, the process skips the step 40 and
advances to a step S42 which is described later.
In this manner, after it .& determined in the step S30 that the voltage of the grid 50
has decreased, the accunplator valve is opened in a step S40 in such a case that the
pressure PAcc in the accukulator 60 is lower than the pressure PH in the high pressure
fi oil line 16. Thus, the pressure in the high pressure oil line 16 is absorbed in the accumulator
60, thereby prdventing the pressure in the high pressure oil line 16 from
being too high or the temperature of the operating oil from rising due to the actuation
of the relief valve 72.
COO851 After the accumulator vilve 62 is opened in the step S40, it is determined in a step
S42 by the grid state dete6nation unit 54 if the voltage of the grid 50 starts restoring
to be greater than the prekribed voltage again. Specifically, in the step 42, it is determined
whether the voltbge of the grid 50 has started to be restored.
In the similar manner, ii it is determined in the step S38 that the pressure Pm in the
accumulator 60 is not loeer than the pressure P, in the high pressure oil line 16, it is
judged if the voltage of t$e grid 50 has started to be restored in the step S42.
[0086] If it is determined in the step S42 that the grid 50 has started to be restored, a
restoration operation to the normal operation mode is performed as described below in
the steps S44 to S52.
[0087] First, in a step S44, the pitch controller 36 controls the pitch driving mechanism 40
(specifically, the servo va ve 44 to adjust the supply of the high pressure oil 1 ) to the
hydraulic cylinder 42 and~hangetsh e pitch angle of the blade 4 to the fine position.
The changing of the pitcd*a. ngle to the fine position means that the pitch angle is
changed so that the blade? receives the wind and applies torque to the rotor 8.
Next in a step S46, the bump controller 32 and the motor controller 34 set the displacements
of the hydraulic pump 12 so that the power coefficient becomes at a
maximum thereof and increases the displacements of the hydraulic motor 14 so that the
power generated by the generator 20 into the grid increases.
In a step S48, the pressure sensor P1 measures the pressure PAcc in the accumulator
and the second pressure sensor P2 measures the pressure P" in the high pressure oil
line 16. The process advances to a step S50 in which the pressure PAcc in the accumulator
60 and the preqsure PH in the high pressure oil line 16 are compared. If it is
determined in the step ~ 5th6at the pressure PACi=n the accumulator 60 is greater than
the pressure PH in the higp pressure oil line 16, the process advances to a step S52 to
open the accumulator valve 62 by the ACC valve controller 38. In contrast, if it is determined
in the step S50 &at the pressure PAcc in the accumulator 60 is not greater than
the pressure PH in the high pressure oil line 16, a step S52 is not performed.
In this manner, after it is determined in the step S42 that the voltage of the grid 50 is
restored, the accumulator valve 62 is opened in a step S52 in such a case that the
pressure PAcc in the accumulator 60 is greater than the pressure PH in the high pressure
oil line 16, so as to assist,the rotation of the hydraulic motor 14 with use of the
pressure of the operating Pi l in the accumulator 60.
[a881 Although not shown in:F ig. 7, after opening the accumulator valve 62 in the step t
S52, it is possible to talcelmeasure against the recurrence of the voltage decline of the
'.
grid 50 by reducing the *sure in the accumulator 60.
For example, the pressure relief valve 63 is opened while the accumulator valve 62 is
closed so that the pressure in the accumulator 60 is allowed to escape to the oil tank via
the accumulator pressure relief line 6 1 (if the accumulator pressure relief line 6 1 is
connected to the low presSure oil line 18, the pressure is released to the low pressure
oil line 18) to reduce the dressure in the accumulator 60. Alternatively, it is possible to
t
reduce the pressure of thefair in the bladder-type or the piston-type accumulator 60
while the accumulator vakve 62 is closed so as to reduce the pressure of the operating
I I oil in the accumulator 60..
[0089] In contrast, if it is deterhned in the step S42 that the grid 50 is not restored and the
voltage of the grid 50 rerriains the same as or below the prescribed voltage, the process
advances to a step S54. In the step S54, it is determined if a condition in which the
voltage of the grid 50 is decreased continues for a set period of time. And if it determined
that the condition continues for a set period of time, the process moves to a
shutoff mode (steps S56 to S62) as described below. In contrast, if it is determined in
the step S54 that the condition does not continue for a set period of time, the process
returns to the step S42 infvhich it is determined again by the grid state determination
unit 54 if the gird 50 is reftored.
The set period of time &re refers to the time defined in the grid code.
[0090] The transition to the shdtoff mode is performed in the steps S56 to S62. First, in the
step S56 the pump controller 32 and the motor controller 34 reduce the displacements
of the hydraulic pump 12 and the hydraulic motor 14. (approximately to zero).
Next, in the step S58 the first pressure sensor P1 measures the pressure PAcc in the
accumulator 60 and the second pressure sensor P2 measures the pressure PH in the high
pressure oil line 16. After the step S58, the process advances to the step S60 in which
the pressure PAcc in the aqcumulator 60 and the pressure PH in the high pressure oil line
16 are compared. If it is determined in the step S60 that the pressure PAcc in the ac-
I
curnulator 60 is lower th$ the pressure PH in the high pressure oil line 16, the process
advances to the step S62 in which the ACC valve controller 38 opens the accumulator
f
valve 62. In contrast, if it is determined in the step S60 that the pressure PAcc in the accumulator
60 is not lowet than the pressure PH in the high pressure oil line 16, the
process returns to the stei S42 and it is determined again if the voltage of the grid 50
return to the prescribed voltage or higher.
In this manner, after it is determined in the step S54 that the condition in which the
voltage of the grid 50 is decreased continues for a set period of time, the accumulator
valve 62 is opened in the step S62 in such a case that the pressure PACCin the accumulator
60 is lower than the pressure PH in the high pressure oil line 16. As a result,
the pressure in the high bessure oil line 16 is absorbed in the accumulator 60, thereby
!
preventing the pressure i$ the high pressure oil line 16 from being too high or the temperature
of the operatingoil from rising due to the actuation of the relief valve 72.
And after opening the $,ccumulator valve 62 in the step S62, the process returns to the
step S42 so that the grid state determination unit 54 determines again if the grid 50 is
restored. Subsequently, if the grid 50 is restored, the restoration operation to the
normal operation mode i~'~erformeind t he step S44 to S51. If the grid 50 is not
restored, the wind turbinebgenerator system 1 stands by in a shutoff state in the steps
$56 to S62. .i
[0091] In this manner, when th: voltage of the grid id decreased, the pitch angle of the blade
4 is changed to the feathefing position and the displacements of the hydraulic pump 12
and the hydraulic motor la are reduced to the amount required for keeping the grid 50
v
synchronized with the gelrerator 20. As a result, the operation of the wind turbine
generator system can coniinue without being disconnected from the grid 50. In other
words, it is possible to achieve the Ride Through function at Grid low voltage
condition.
Further, when the voltage of the grid 50 is decreased, the accumulator valve 62 is
opened in such a case that the pressure PAcc in the accumulator 60 is lower than the
pressure PH in the high plhssure oil line 16, thereby preventing the pressure in the high
pressure oil line 16 from $eing too high or the temperature of the operating oil from
rising due to the actuatio4 of the relief valve 72.
E
[0092] Furthermore, when the condition in which the voltage of the grid 50 is decreased
continues for a set period of tie, the displacements of the hydraulic pump 12 and the
hydraulic motor 14 are controlled approximately to zero and the operation of the wind
turbine generator system 1 is shutoff. However, during this process, if the pressure P
ACC in the accumulator 60 is lower than the pressure PH in the high pressure oil line 16,
the accumulator valve 62 is opened, thereby preventing the pressure in the high
pressure oil line 16 from being too high or the temperature of the operating oil from
rising due to the actuatioi of the relief valve 72.
[0093] Moreover, when the grijd 50 is restored, the pitch angle of the blade 4 is changed to
the fine position and the displacements of the hydraulic pump 12 and the hydraulic
motor 14 are set so that the power coefficient becomes at a maximum thereof and a
rotation speed of the generator 20 becomes constant. As a result, it is possible to
promptly restore the efficient operation thereof. In this process, the accumulator valve
62 is opened in such a case that the pressure PAC, in the accumulator 60 is greater than
the pressure PH in the high pressure oil line 16 so as to assist the rotation of the
hydraulic motor 14 with ase of the pressure of the operating oil in the accumulator 60.
[0094] Further, Fig. 7 illustrates the case in which the accumulator valve 62 opens in step
S40 when the pressure PACicn the accumulator 60 is lower than the pressure PHi n the
high pressure oil line 164YES in the step S38), but the accumulator valve 62 may be
kept open regardless of qhich one of the pressure PAcco r the pressure PHi s lower.
More specifically, when :t is determined that the voltage of the grid 50 has decreased
i '
to a prescribed voltage oryower and the condition based on Gid Code rule continues,
the control unit may condols the pitch driving mechanism 40 tochange the pitch angle
of the blade 4 toward the heathering position, changes the displacements of the
hydraulic pump 12 to me6t the load of the rotor 2 and reduces displacements of the
hydraulic motor 14 to an amount required for keeping the generator 20 synchronized
with the grid 50, and keeps the accumulator valve 62 open so as to store in the accumulator
60 a pressure of the operating oil discharged from the hydraulic pump 12.
[0095] (Gust control)
Fig. 8 is a flow chart showing an operation control when there arises a gust. As
shown in the drawing, first, the wind speed obtaining unit 56 obtains the wind speed V
in a step 570. And in a stdp S72, it is determined if the wind speed V is greater than the
threshold value Vth, i.e. i$ there is a gust. If it is determined in the step S72 that the
wind speed V is greater t$an the threshold value Vth, the process advances to a step
S74 in which the first prersi' sure sensor P1 measures the pressure PAcci n the accumulator
60 and the second pressure sensor P2 measures the pressure PH in the high
pressure oil line 16. In contrast, if it is determined in the step S72 that the wind speed
V is not greater than the threshold value Vth, the process returns to the step S70 to
obtain the wind speed V again.
Herein, the threshold value Vth may be, for example, 60mIsec which is obtained as
an average wind speed for a period of three seconds or longer.
[0096] After measuring the pressure PACcin the accumulator 60 and the pressure PH in the
pressure oil line 16 in theistep S74, the process advances to a step S76 in which the pressure PAcca nd the pre 1s ure PHa re compared. If it is determined in the step S76 that
the pressure PACc in the aicumulator 60 is lower than the pressure PH in the high
pressure line 16, the prockss advances to a step S78 to open the accumulator valve 62
by the ACC valve controiler 38.
In this manner, when there arises a gust (the wind speed V > the threshold value
Vth), the accumulator valve 62 is opened in such a case that the pressure PACC in the
accumulator 60 is lower than the pressure PH in the high pressure line 16 so as to
absorb the pressure from 'the high pressure line in the accumulator 601
Meanwhile, if it is detefmined in the step S76 that the pressure PAcc in the accumulator
60 is not lowe4 than the pressure PH in the high pressure line 16, the process
returns to the step S70 tobbtain the wind speed V again by the wind speed obtaining
unit 56. I
I ! [0097] After opening the accudnulator valve 62 in the step S78, the wind speed obtaining
unit 56 obtains the wind kpeed V in a step S80. In a step S82, it is determined if the
wind speed V has decreased to the threshold value Vth or below. If it is determined in
the step S82 that the wind speed V has decreased to the threshold value Vth or below,
the process advances to a step S84 to keep the accumulator valve 62 open. In contrast,
if the wind speed V still remains greater than the threshold value Vth, the process
returns to the step S80 to bbtain the wind speed V again.
[0098] After keeping the accuqulator valve 62 open in the step S84, the first pressure sensor
PI measures the pressure PACCin the accumulator 60 and the second pressure sensor P2
I
measures the pressure PH in the high pressure oil line 16 in a step S86. Then, in a step
S88, it is determined if th! pressure PAcc in the accumulator 60 becomes the same as
the pressure PH in the high pressure oil line 16.
[0099] If it is determined in the step S88 that the pressure PAcc in the accumulator 60
becomes the same as the pressure PH in the high pressure oil line 16, the process
advances to a step S90 to lclose the accumulator valve 62 by the ACC valve controller
38. In contrast, if it is deti rmined in the step S88 that the pressure PAcc in the ac- cumulator 60 is not the saqne as the pressure PH in the high pressure oil line 16, the
process returns to the step! S 84 to keep the accumulator valve 62 open.
[0100] In this manner, when &re arises a gust (the wind speed V > the threshold value
i
Vth), the accumulator valbe 62 is opened in such a case that the pressure PACCin the
accumulator 60 is lower than the pressure PH in the high pressure line 16 so as to
absorb the pressure of the high pressure line 16 in the accumulator 60. When the wind
speed V of the gust is decreased to the threshold value Vth or below, the accumulator
valve 62 is kept open until the pressure PAcc in the accumulator 60 becomes the same
as the pressure PH in the high pressure oil line 16 so as to release the pressure in the accumulator
60. In this manner, it is possible to minimize the impact of the gust on the
wind turbine generator syftem 1.
[0101] As described above, Fid. 8 illustrates the case wherein once the wind speed V
becomes as slow as equali to or lower than the threshold value Vth, the accumulator
valve 62 is kept open until the pressure PAcc in the accumulator 60 becomes the same
t
as the pressure PH in the high pressure oil line 16 so as to release the pressure PACC in
the accumulator (S84 through S88). If the operating oil flows instantaneously into the
4
accumulator 60 via the adcumulator valve 62 and the pressure PAcc in the accumulator
60 changes following the change of the pressure PH in the high pressure oil line 16
without delay, the steps S84 through S88 may be skipped as well.
[0102] Further, Fig. 8 illustrates the case in which the accumulator valve 62 opens when the
1
pressure PAcci n the accu F ulator 60 is lower than the pressure PHi n the high pressure oil line 16 (YES in the stqp S76), but the accumulator valve 62 may be kept open re-
41 gardless of which one of be pressure PAcc or the pressure PH is lower. More
specifically, when there &ises a gust having the wind speed V greater than the
prescribed threshold value Vth, the control unit keeps the accumulator valve 62 open
so as to store in the accumulator 60 the pressure of the operating oil discharged from
the hydraulic pump 12, and when the wind speed V of the gust becomes not greater
than the prescribed threshold value Vth, the control unit keeps the accumulator valve
62 open so as to assist rotation of the hydraulic motor 14 with use of the pressure of the
operating oil in the accunfulator 60.
[0103] (Operation control method to efficiently perform three types of the operation control)
Next, the operation conk01 method for performing the above three types of the
operation control efficienby. According to the operation control method, two accumulators
60A and 60B (ref. Fig. 3) are used for different control purposes and the
pressures of the accumul~tors6 0A and 60B are adjusted in advance as a preparation
for performing each control efficiently. Explained herein is the example in which the
accumulator 60A is used for the control when the wind speed is low, and the accumulator
60B is used for the control when the grid voltage is decreased and when
1 there arises a gust.
r,
The accumulator 60A ubed for the control when the wind speed is small is referred to
as a first accumulator 604 and the accumulator 60B used for the control when the grid
voltage is decreased and $e control when there is a gust is referred to as a second accumulator
60B. Further, h e accumulator valve 62a provided for the accumulator 60A
is referred to as a first accumulator valve 62A and the accumulator valve provided for
the accumulator 60B is referred to as a second accumulator valve 62B.
[0104] First, the pressure sensors P1 and P2 measure the pressure PAccl in the first accumulator
60A and the pressure PAcc2 in the second accumulator 60B, and the pressure
PH in the high pressure oil line 16.
[0105] And, in such a case that the pressure PAccl in the first accumulator 60A is lower than
the pressure PAcc2 in the second accumulator 60B, the first accumulator valve 62A is
1
opened so as to store the pressure in the fust accumulator 60A. The storing of the
pressure in the first accumulator 60A is preferably performed at a low wind speed not
greater than the cut-in wibd speed in which there is no power generation by the
generator 20, or in the rafpd operation to control the output constant by adjusting the
pitch angle so as to preve~th e impact on the power generation efficiency of the wind
turbine generator system 1.
In this manner, the pressure PAccl in the first accumulator 60A is always kept comparatively
high.
[0106] In contrast, in such a case that the pressure PAccl in the first accumulator 60A is
higher than the pressure fiAcc2 in the second accumulator 60B, the second accumulator
valve 62B is opened to rdease the pressure of the second accumulator 60B.
'I In this manner, the p r e s F PAcc2 in the second accumulator 60B is always kept
comparatively low. r:
[O 1071 In this manner, by keeping the pressure PAcc 1 of the first accumulator 60A comparatively
high to be used for the control when the wind speed is low, the rotation of
the hydraulic motor 14 cah be efficiently assisted with the use of the first accumulator
60A when the wind speed V becomes not less than the cut-in wind speed Vc again
I
after being below the cut-,in wind speed Vc.
Further, by always keepidg the pressure PAcc2 comparatively low to be used for the
' *
control when the grid voltage is decreased and when there arises a gust, the pressure in
the high pressure oil line 'l6 can be efficiently absorbed with the use of the second accumulator
60B when the Soltage of the grid 50 is decreased or when the wind speed V
exceeds the threshold valge Vth.
[0108] Above explained is the base wherein the use of the first accumulator 60A and the use
of the second accumulator 60B are decided in a d a c e (the first accumulator 60A for
the control at the low wind speed, and the second accumulator 60B for the control at
the low grid voltage or at the occurrence of the gust). However, the uses of the first accumulator
60A and the sekond accumulator 60B may be adequately changed
depending on a situation.4
For instance, the pressuie PAc,l in the first accumulator 60 and the pressure PAcc2 in
the second accumulator $OB are regularly measured and the accumulator with higher
measured pressure is used for the control when the wind speed is low and the accumulator
with lower measured pressure is used for the control when the voltage of the
gird is decreased or when there arises a gust.
[0109] As described above, in the preferred embodiment, the ACC valve controller 38 of the
control unit 30 controls the opening and closing of the accumulator valve 62 based on
at least one of the wind speed and the state of the grid 50 determined by the grid state
determination unit 54, and the pressure in the accumulator 60 measured by the first
pressure sensor P1 and t& pressure in the high pressure oil line 16 measured by the
second pressure sensor Pz.
<
Therefore, not only the operation efficiency and the safety at the low wind speed and
at the occurrence of a gudt can be improved but also the Ride Through function at Grid
low voltage condition can be achieved.
[0110] While the present inverttion has been described with reference to exemplary embodiments,
it is to be understood that the invention is not limited to the disclosed
exemplary embodiments and that modifications and variations are possible within the
scope of the appended claims.
[Ol 1 11 For instance, in the above preferred embodiment, the example of controlling the
opening and closing of &e accumulator valve 62 by the ACC valve controller 38 was
explained. However, the bpening of the accumulator valve 62 may be adjusted in accordance
with the pressug difference between the pressure PAcc in the accumulator 60
and the pressure PH in the high pressure oil line 16. For example, when the pressure
I
between the pressure PACcin the accumulator 60 and the pressure PH in the high
pressure oil line 16 is large, the accumulator valve 62 is gradually opened (the opening
amount of the accumulator valve 62 is gradually made large) so as to suppress the
pressure fluctuation of the high8jun pressure oil line caused by the opening of the accumulator
valve 62. Meanwhile, when the pressure between the pressure PACcin the
accumulator 60 and the pqessure P, in the high pressure oil line 16 is small, the ac-
I
cumulator valve 62 is prohptly opened (the opening amount of the accumulator valve
62 is promptly made largi) so as to respond promptly to the change of the situation.
Reference Signs List
[O 1 121 1 wind turbine generator
? 2 rotor
4 blade
6 hub
8 main shaft
10 hydraulic transmission
12 hydraulic pump
14 hydraulic motor ,:
16 high pressure oil linq
18 low pressure oil lind'
20 generator
22 nacelle
24 tower
26 base
30 control unit
32 pump controller
34 motor controller
36 pitch controller
I
38 ACC valve controll6r
40 pitch driving mechanism
42 hydraulic cylinder
44 servo valve
46 oil pressure source ,
48 accumulator
50 grid system
52 unintermptible power supply
54 grid status judging unit
60A first accumulator 4
4
60B second accumulator
6 1 Accumulator pressure relief line
62A first acci&ulator valve
62B second accumulator valve
63 Accumulator pressure relief line
>
64 anti-pulsation accumulator
66 oil filter
68 oil cooler 1
t
70 bypass line
72 relief valve
80 oil tank
82 supplementary line '
84 boost pump
86 oil filter
88 return line
89 low pressure relief valve

9
[Claim 11
[Claim 21
[Claim 31
[Claim 41
.-
[Claim 51
1
1 Claims
A wind tutbine generator system comprising:
a hub; l
a main shaft which is coupled to the hub;
a generatok which is synchronized with a grid; .
a hydraulik pump of variable displacement type which is driven by the
main shaftj;
a hydraulic motor of variable displacement type which is connected to
the generdor;
a high pressure oil line which is arranged between a discharge side of
the hydrailic pump and an intake side of the hydraulic motor;
a low oil line which is arranged between an intake side of the
hydraulic bump and a discharge side of the hydraulic motor;
an accumdlator which is connected to the high pressure oil line via an
accumulator valve; and
a control unit which controls the hydraulic pump, the hydraulic motor
and the accumulator valve;
wherein the control unit controls opening and closing of the accumulator
valve based on at least one of wind speed and a state of the
grid.
The wind turbine generator system according to claim 1, further
comprising a grid state determination unit,
wherein the state of the grid is determined by the grid state determination
unit.
The wind turbine generator system according to claim 2, further
comprising:
a bypass oil line which is arranged between the high pressure oil line
and the low pressure oil line to bypass the hydraulic motor; and
a relief valve which is arranged in the bypass oil line to maintain the
hydraulic pressure in the high pressure oil line not more than a set
pressure. .
The wind turbine generator system according to claim 2, further
comprising:
a first pressure sensor which detects a pressure in the accumulator; and
a second pressure sensor which detects a pressure in the high pressure
oil line.
The wind turbine generator system according to claim 3,
8 [Claim 61
[Claim 71
[Claim 81
[Claim 91
4
LI
i
wherein, when the wind speed is below a cut-in wind speed, the control
unit contrdls a displacement of the hydraulic motor approximately to
zero, and !eeps the accumulator valve open so as to store in the accumulator
'a pressure of operating oil discharged from the hydraulic
pump.
The wind turbine generator system according to claim 5,
wherein, $hen the wind speed is not less than the cut-in wind speed,
the control unit keeps the accumulator valve open so as to assist
rotation of the hydraulic motor with use of pressure of operating oil in
the accum$lator.
The wind lurbine generator system according to claim 4,
wherein, $hen the wind speed is below a cut-in wind speed, the control
unit contrqls a displacement of the hydraulic motor approximately to
zero, and dpens the accumulator valve so as to store in the accumulator
a pressure'of operating oil discharged from the hydraulic pump, and
closes the accumulator valve when the pressure in the accumulator
detected by the first pressure sensor reaches a threshold value which is
decided in advance.
The wind turbine generator system according to claim 7,
wherein, when the wind speed is not less than the cut-in wind speed,
the contro; unit opens the accumulator valve so as to assist rotation of
the hydraulic motor with use of pressure of operating oil in the accumu1ator"
in such a case that the pressure in the accumulator detected
7
by the first pressure sensor is higher than the pressure in the high
pressure oil line detected by the second pressure sensor.
The wind turbine generator system according to claim 3, further
comprising:
a pitch dribing mechanism which adjusts a pitch angle of a blade
mounted on the hub,
wherein, when the grid state determination unit determines that a
1
voltage oqthe grid has decreased to a prescribed voltage or lower and
the condition based on Gid Code rule continues, the control unit may
controls tqe pitch driving mechanism to change the pitch angle of the
blade toward a feathering changes the displacements of the
9 hydraulic pump to meet the load of the rotor and reduces the displacement%
of the hydraulic motor to an amount required for keeping
1
the generz'tor synchronized with the grid, and keeps the accumulator
valve open so as to store in the accumulator a pressure of the operating
[Claim 101
[Claim 1 I]
[Claim 121
[Claim 131
[Claim 141
4 oil dischmsed from the hydraulic pump.
The wind turbine generatorbsystem according to claim 9,
wherein, $hen the grid state determination unit determines that voltage
9
of the gri4 starts to be restored, the control unit changes the pitch angle
of the blade toward a fine position, and sets the displacement of the
hydraulic pump so that a power coeffibent becomes at a maximum
thereof, and increases the displacement of the hydraulic motor so that
the powerlgenerated by the generator into the grid increases.
The wind turbine generator system according to claim , 4, further
comprising:
a pitch driying mechanism which adjusts a pitch angle of a blade
d
mounted $I the hub,
wherein, yhen the grid state determination unit determines that a
voltage oflthe grid has decreased to a prescribed voltage or lower and
the condidon based on Gid Code rule continues, the control unit may
control thi pitch driving mechanism to change the pitch angle of the
blade towhd a feathering position, change the displacements of the
hydraulic pump to meet the load of the rotor and reduce the displacements
of the hydraulic motor to an amount required for keeping
the generator synchronized with the grid, and open the accumulator
valve so as to store in the accumulator a pressure of the operating oil
discharged from the hydraulic pump in such a case that the pressure in
the accumblator detected by the first pressure sensor is lower than the
pressure i i the high pressure oil line detected by the second pressure
sensor. I
The wind turbine generator system according to claim 7,
wherein, when the grid state determination unit determines that voltage
of the grid start to be restored, the control unit changes the pitch angle
of the blade to a fine position, and sets the displacement of the
hydraulic pump so that a power coefficient becomes at a maximum
thereof, aid increases the displacement of the hydraulic motor so that
the powerlgenerated by the generator into the grid increases.
I
The wind furbine generator system according to claim 9 or 11, further
comprisinF : an uninterfuptible power supply which supplies electrical power to the
pitch drivhg mechanism when the voltage of the grid becomes zero.
The wind iurbine generator system according to claim 9 or 11, further
comprising:
[Claim 151
,
[Claim 161
[Claim 171
[Claim 181
an uninterfuptible power supply which supplies electrical power to the
I
hydraulic bump and the hydraulic motor when the voltage of the grid
becomes $ro.
The wind rurbine generator system according to claim 11 or 12, further
11
comprisinI :
an oil tank! which stores operating oil and is connected to the low
pressure oil line;
an accumulator pressure relief line provided between the accumulator
valve and the accumulator and connected to one of the low pressure oil
6
line or thefoil tank; and
a pressure:relief valve provided in the accumulator pressure relief line,
wherein, when the grid state determination unit determines that voltage
of the grid is restored, the control unit opens the pressure relief valve to
4 allow the pressure in the accumulator to escape to the one of the low
pressure oil line or the oil tank.
The wind brbine generator system according to claim 3, further
1
comprisinl:
Wherein, when there arises a gust having a wind speed greater than a
prescribed threshold value, the control unit keeps the accumulator valve
open so as to store in the accumulator a pressure of operating oil
discharged from the hydraulic pump,
and when The wind speed of the gust becomes not greater than the
prescribed threshold value, the control unit keeps the accumulator valve
open so a4 to assist rotation of the hydraulic motor with use of pressure
of operatibg oil in the accumulator.
li
The wind ilurbine generator system according to claim 16,
i
wherein the prescribed threshold value is 60m/sec which is obtained as
an average wind speed for a period of three seconds or longer.
The wind "turbine generator system according to claim 4,
Wherein, when there arises a gust having a wind speed greater than a
prescribed threshold value, the control unit opens the accumulator
valve so as to store in the accumulator a pressure of operating oil
dischargeh from the hydraulic pump in such a case that the pressure in
the accuqhlator detected by the fist pressure sensor is lower than the
pressure : i Y the high pressure oil line detected by the second pressure
sensor; a&
when the wind speed of the gust becomes not greater than the
Y
prescribed threshold value, the control unit keeps the accumulator valve
[Claim 191
[Claim 201
[Claim 211
[Claim 221
[Claim 231
open until the pressure in the accumulator detected by the first pressure
sensor becomes the same as the pressure in the high pressure oil line
detected b,ij the second pressure sensor.
The wind urbine generator system according to 1 claim 18,
wherein tee prescribed threshold value is 60mIsec which is obtained as
an average wind speed for k period of three seconds or longer.
The wind iurbine generator system according to claim 18, further
comprising:
an oil tank which stores operating oil and is connected to the low
pressure oil line;
an accumdlator pressure relief line provided between the accumulator
valve and ;the accumulator and connected to one of the low pressure oil
line and d e oil tank; and
a pressureirelief valve provided in the accumulator pressure relief line,
wherein, &hen there arises a gust having a wind speed greater than a
prescribed threshold value, the control unit opens the pressure relief
valve to allow the pressure in the accumulator to escape to one of the
low presscre oil line and the oil tank.
The wind kurbine generator system according to claim 1, further
comprising:
a oil tank which stores operating oil; and
a boost pump which replenishes the low pressure oil line with the
operating pi1 from the oil tank.
The wind i urbine generator system according to claim 21, further
comprisirrb4 :
a return line which returns the operating oil in the low pressure oil line
to the oil dank; and
!
a low pre$ure relief valve which is arranged in the return line to
maintain the hydraulic pressure in the low pressure oil line approximately
at a set pressure.
An operation control method of a wind turbine generator system which
comprise$ a hub, a main shaft coupled to the hub, a generator which is
synchroniged with a grid, a hydraulic pump of variable displacement
type which is driven by the main shaft, a hydraulic motor of variable
displaceqent type which is connected to the generator, a high pressure
oil line wiich is arranged between a discharge side of the hydraulic
pump an4 an intake side of the hydraulic motor, a low pressure oil line
which is Fanged between an intake side of the hydraulic pump and a
discharge side of the hydraulic motor, and an accumulator which is
t
connected to the high pressure oil line via an accumulator valve, the
method comprising
the step of controlling opening and closing of the accumulator valve
based on s4t least one of wind speed and the state of the grid determined
9
by the gri4 state determination unit.