Title: Field testing of individual pitch control on the NREL CART2 wind turbine
1Field testing of individual pitch control on the
NREL CART-2 wind turbine E. Bossanyi and A
Wright Garrad Hassan Partners Ltd., NREL
Presented at EWEC 2009, Marseille
2Context
- Work carried out as part of the EU 6th Framework
integrated project UPWIND. - Over many years, simulations have demonstrated
that Individual Pitch Control (IPC) can be an
effective means of reducing wind turbine fatigue
loading. - To date, no publishable field test data is
available to prove that IPC actually lives up to
expectations in reality. - Using the public-domain CART-2 and CART-3
research turbines at NREL, this project provides
a way to achieve the field validation which is
needed to provide the confidence to design new
turbines which rely on the load reductions which
IPC can provide.
3The NREL Turbines
- Two turbines available 42m diameter, 660 kW
- Although not representative of modern multi-MW
designs, turbines are adequate for proof of
principle - Research turbines advantage of being very
accessible with minimum fuss - CART-2 2-bladed aiming for measurements in
spring 2009 - Turbine ready and operational
- Relevant 2-Bladed turbines still a definite
option for large offshore machines - Uses conventional strain gauges, but very robust
well calibrated - Fast pitch actuator should be suitable for IPC
- CART-3 3-bladed aiming for measurements in
spring 2010 - Turbine ready but awaiting completion of the
control system by NREL
4Programme
- July 2008 Principles agreed
- CART-2 testing Spring 2009 (should already be
underway) - CART-3 testing one year later
- October - November 2008 CART-2 algorithm design
completed and tested in simulations. - Delay awaiting final DOE signature of
confidentiality agreement. Once this is in
place - Transfer of algorithm to NREL
- Further NREL proving simulations
- Still hoping to start field tests before end of
current wind season! - Summer 2009 CART-3 algorithm design to start.
- Spring 2010 CART-3 field testing.
5CART-2 turbine
- Teetered rotor, but teeter will be locked with
teeter brake. Principle is to use IPC instead of
teetering to reduce out of plane blade hub
loads. - Bladed model completed.
- CART-2 control algorithm designed by GH
- Optimal power production over nominal speed range
- Speed regulation by interacting torque and
collective pitch control - Drive train damping filter in torque controller
- F/A tower damping by collective pitch control
- 1P individual pitch control to reduce rotating
and non-rotating loads - 2P individual pitch control not required
- Simulation testing completed.
6Simulation at 18 m/sTower F/A damping Tower
base bending moment (My)
- Significant reduction of fore-aft tower vibration
and fatigue loading at 1st tower frequency.
Tower 1st fore-aft mode
7Simulation at 18 m/s IPC Blade root out of
plane bending moment (My)
- 1P out of plane loads virtually eliminated on
rotating components. - Teeter hinge no longer needed!
Rotation frequency (1P)
8Simulation at 18 m/s IPC Rotating hub moment
(My)
- 1P out of plane loads virtually eliminated on
rotating components. - Teeter hinge no longer needed!
Rotation frequency (1P)
9Simulation at 18 m/s IPC Yaw moment (Yaw
bearing Mz) non-rotating frame
- 1P (rotating) becomes 0P and 2P on non-rotating
components. - 0P compensates for wind shear and direction
change reduces peak loads. - Large reduction in 2P fatigue loading.
Blade passing frequency (2P)
Low frequency (0P)
10Simulation at 24 m/s IPC Yaw moment (Yaw
bearing Mz) non-rotating frame
- Reduction at 0P helps to reduce peak yaw nod
moments. - Reduced 3P also helps.
- Reduced 3P means lower fatigue loads.
11Simulation at 18 m/s Pitch activity
- IPC requires extra pitch action
- Additional pitching is concentrated at 1P
Rotation frequency (1P)
12Simulation at 18 m/s Pitch activity
13IPC 2 Blades vs 3 blades
- Control action calculated in non-rotating frame
two axes, just the same for any number of blades. - Number of blades is embodied in the rotational
transformations
- For 2-blades, non-rotating fatigue loads (2P) are
reduced. - For 3 blades, non-rotating fatigue loads are at
3P. Reducing these requires additional (2nd
harmonic) IPC at 2P (rotating), to reduce
non-rotating loads at 1P and 3P. (Higher
harmonics are also possible, but probably
unnecessary.)
142nd Harmonic IPC
- The CART-3 turbine will provide the opportunity
for field testing of both 1P and 2P IPC
- The CART-3 algorithm is not yet designed, but a
similar algorithm has already been designed for
the Upwind 5MW reference turbine.
151st and 2nd Harmonic IPCUpwind 5MW reference
turbine (3 bladed)
- Rotating loads reduced at
- 1P
- 2P
- Non-rotating loads reduced at
- 0P (and 2P)
- 3P (and 1P)
1st harmonic IPC
2nd harmonic IPC
161st and 2nd Harmonic IPCUpwind 5MW reference
turbine (3 bladed)
- Extra pitch action at
- 1P
- 2P
17Conclusions
- IPC can replace teeter hinge on 2-bladed turbine
(reduces 1P loads in rotating components). - IPC on 2-bladed turbine also reduces 2P fatigue
loading on non-rotating components. - On 3-bladed turbine, 2nd harmonic (2P) IPC is
needed to reduce the 3P fatigue loads on
non-rotating components. - CART-2 field measurements to start soon, with 1P
IPC and tower fore-aft damping. - CART-3 field measurements next year, with 1P and
2P IPC and tower fore-aft damping. - 2P IPC proven in simulations for 5MW Upwind
turbine.
18Acknowledgements
- This work has been carried out under the 6th
Framework Integrated Project Upwind. The
support of the European Commission is gratefully
acknowledged.