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The WinDrive –
An Innovative Drive Train Concept for Wind Turbines
Power quality as delivered by traditional power plants
Power generated by wind energy is gaining importance around the
world. This is due to decreasing fossil fuel reserves and the need to
cut global CO2 emissions. The technological challenge facing on and
offshore wind farms is finding reliable and efficient wind turbines that
satisfy all the requirements of feed-in power quality with exacting
power station standards.
Offshore wind farms
With the WinDrive, Voith Turbo has developed a
drive train concept that controls speed and can
be used in wind turbines ranging from two to ten
megawatts. The WinDrive is a highly dynamic
mechatronic drive component that, for the first
time, enables proven power plant technologies to
be employed in wind turbines. Thanks to this
component, wind farms can gen­erate power of a
quality that satis­fies stringent power station and
grid standards.
WinDrive
Large-scale plants with an output of up to ten
megawatts are subjected to extreme loads, with
operators expecting a high level of efficiency. The
wind turbines are equipped with variable-speed
wind rotors, the speed of which is optimally ad­
justed to match the variable wind speed. Con­ven­
tional drives require a frequency converter to be
installed between the generator and power grid.
These converters generate an alternating current
of 50 Hz or 60 Hz to be used by the power grid.
However, frequency converter technology does
not meet all of today‘s power feed-in quality re­
quirements when it comes to supplying the power
grid. The ne­cessary components, fre­quency con­
verters and step-up transformers all increase the
com­plexity of wind turbines and reduce their
avail­ability.
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Unique benefits
For wind farm operators, one thing is paramount: using multi-mega­
watt wind turbines that provide outstanding revenue and availability.
This means that wind turbines must be of a durable and servicefriendly design, with minimal complexity while applying power station
components. WinDrive technology fulfills all of these requirements.
WinDrive technology enables energy to be created as if
from a traditional power plant
Increased availability thanks to the omission of power electronics
without WinDrive
Power electronics with
frequency converter
with WinDrive
Drive train
with WinDrive
technology
Availability
Availability
Drive train
High power feed-in quality
High reliability
WinDrive technology enables synchronous gen­
erators to be used to generate power, thereby
guaranteeing control of reactive power and grid
stabilization in the event of a short circuit.
The omission of the frequency converter and
step-up transformers minimizes the wind turbine‘s
complexity. The occurrence of malfunctions and
downtimes are reduced, while the availability en­
joys a considerable boost.
Optimum efficiency
Minimal maintenance requirement
The speed of the wind rotor varies with differing
wind speeds. Because the WinDrive is designed
for variable-speed operation, the wind rotor is
operated at different speeds with variable wind
speeds, always maintaining the aerodynamic
optimum for the rotor. The synchronous gener­
ators work at medium voltage level, which re­
duces losses due to transformers and cables.
These factors considerably improve a wind tur­
bine‘s overall efficiency.
Synchronous generators without slip rings reduce
the complexity of wind turbines, and the servicing
these require. The WinDrive has response times
in the millisecond range, thereby producing a
considerable load reduction in the drive train
during dynamic load conditions in the drive. The
service life of assemblies that conduct power are
increased.
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No matter where –
WinDrive stands for reliability
The WinDrive technology can be installed and operated at a var­iety of
locations. On and offshore plants, connecting to weak energy grids or
installing in rough conditions pose no problems for the WinDrive.
Cuxhaven, Germany
Offshore
Weak grids
The technology offered by the variable-speed
gearbox with its robust design allows wind tur­
bines to be used in the most varied of locations.
Using components that offer out­standing reli­abil­
ity ensures that the wind turbines can be used on
and offshore.
WinDrive technology enables synchronous gen­
erators to be used; these deliver high-quality
power (low proportion of harmonics and flickers),
even in weak power grids. The strengths of
WinDrive technology lie in being able to generate
reactive power and support the grid in the event
of severe voltage drops (up to three times the
nominal reactive power and nominal current).
The high reliability provided by the WinDrive
basic technology has proven itself on offshore
platforms over and over again, with typical MTBF
(mean time between failures) values of more than
40 years. Additional units are not required for use
in offshore plants. The high level of availability
results in less time needing to be spent on main­
tenance.
4
Sweetwater, USA
Veladero, Argentina
BARD, offshore plant (Project 7 MVA)
Rough conditions
The robust mechanical design and the omission
of sensitive electronics (i.e. frequency converters)
ensure that the WinDrive is resistant to extreme
operating conditions.
Temperatures dropping to below -40 °C, heatwaves and low air density at 4200 m do not
prevent the WinDrive from working to a high
degree of reliability.
Installations
Location
Country
Commissioning
Drive train
availability 1
1. Installation
Cuxhaven
Germany
2006
100 %
Near Offshore
2. Installation
Veladero
Argentina
2007
100 %
World‘s highest installation (4200 m)
3. Installation
Sweetwater
U.S.A.
2008
100 %
Weak grid connection
4. Installation
Minnesota
U.S.A.
2009
100 %
Operating temperatures up to -30 °C
5. – 6. Installation
Willmar
U.S.A.
2009
100 %
Weak grid connection
7. – 16. Installation
Little Pringle
U.S.A.
2010
100 %
Wind farm
Operating conditions
1
Reference table
As of September 2010
5
Compact design – reliable operation
The WinDrive works the same way as a variable automatic transmission
by converting the wind rotor‘s variable speed into a constant output
speed suitable for the generator. The design of the WinDrive is based on
a hydrodynamic torque converter combined with a planetary gear.
Located in the wind turbine drive train, the
WinDrive controls the wind rotor‘s speed to be at
constant output speed. This process means that
the wind rotor is always operating at the working
point with the greatest efficiency, according to the
wind speed. In the full load operating range, the
WinDrive limits the maximum torque by con­
trolling the speed.
1
3
This control is achieved by a hydrodynamic
torque converter coupled to a “superimposing”
planetary gear set. This design allows a variety
of conversion ratios to be set between the input
speed and output speed.
2
Longitudinal section of the WinDrive:
1 Planetary gear (superimposed gear)
2 Stationary gear
3 Hydrodynamic torque converter
Wind
rotor
Variable speed
6
Drive train design
Main
gear box
Variable speed
WinDrive
WinDrive: speed
control system
Synchronous
generator
Constant speed
Power grid
Constant frequency
(alternating current)
2009 Hermes Award at the Hanover Fair
The WinDrive during testing
The superimposed gear adds two variable
speeds to achieve a constant output speed: The
first speed is the variable one produced by the
wind rotor; the second is a correction speed produced by the hydrodynamic torque converter. A
double-fed asynchronous machine with frequency
converter works along the same principle.
In the partial load operating range, the WinDrive
immediately responds to changes in wind speed
– without the wind turbine control system needing to intervene. The reason for this behavior is,
as a fluid machine, the hydrodynamic torque converter has a similar power characteristic to the
wind rotor and is therefore ideally suited to being
coupled to this rotor without any need of control.
Rotor
characteristic curve
In the nominal load operating range, the response times for the WinDrive are 20 ms. At the
same time, the power transmission in the hydrodynamic torque converter dampens the vibrations
and torque peaks in the drive train. The WinDrive
therefore protects the main gear and generator in
an effective manner.
Awards
Voith Turbo Wind with our WinDrive technology
has received a number of awards. One of the
most significant awards was the 2009 Hermes
Award, the Hanover Fair International Technology
Prize. An independent panel awarded the
WinDrive technology the „Oscar for engineers“.
WinDrive
characteristic curve
Blade angle
Position of the WinDrive actuator
Generator speed
WinDrive input speed
Power
Power
Generator power
Wind speed
Speed
Time
Two fluid machines in perfect harmony: the WinDrive follows the wind rotor‘s natural characteristic.
Speed
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cr355en, 09.2010, S&F-SDL / WA , 1000. Dimensions and illustrations without obligation. Subject to modifications.
Voith Turbo Wind GmbH & Co. KG
Voithstr. 1
74564 Crailsheim, Germany
Tel. +49 7951 32-1867
Fax +49 7321 37-138149
[email protected]
www.voithturbo.com/wind-technology