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SUPERGEN Wind Wind Energy Technology Phase 2 Theme 2 – The Turbine Dr Geoff Dutton Supergen Wind Phase 2 – General Assembly Meeting 21 March 2012
SUPERGEN Wind Wind Energy Technology Phase 2
Theme 2 – The Turbine Dr Geoff Dutton
Supergen Wind Phase 2 – General Assembly Meeting
21 March 2012
Rotor wind-field
interaction
Turbine blade
materials Drive train
dynamics
Fault detection
0 100 200 300 400 500 600 700 800-50
-45
-40
-35
-30
-25
-20
-15
-10
-5
0
Frequency [Hz]
No
rma
lize
d s
pe
ctru
m [d
B]
MODEL
RIG
112 Hz
212 Hz
150 Hz
373.8 Hz
435.7 Hz
273.8 Hz
535.7 Hz
597.6 Hz
697.6 Hz
250 Hz 350 Hz
Subsea turbine foundations
The
Turbine
Middelgrunden wind farm – photo by LM
Glasfiber
The
Turbine
• Basic materials
• 3D fabrics and joints
• Component testing
• Blade model
Turbine blade
materials
Reliable and cost-effective
wind turbine blades
Selection of
materials and
manufacturing
process design
Weight Bending
stiffness
Cost
Fatigue
Resistance Manufacturing
processes
Labour,
Material,
Equipment
Production rate
Maintenance
and repair
Environmental effects:
UV, radar,
Corrosions,
Lightening
Materials considerations in blade design
• Selective interfacial reinforcement
• Veils
• Nano-additives
• Through-thickness stitching and tufting
• Use of 3D fibre formats: braiding & weaving
3D Fabric
Novel materials: interlaminar toughness
Nano silica particles
• Why 3D Textiles?
Current UD prepreg technology is excellent for thin flat structures
But……
• It is slow to lay up, difficult to work with complex 3D shapes, and struggles to allow load transfer in connections and across right angle shapes.
3D textile composites
Slide
No.7
1
2
0.006
0.007
0.008
0.009
0.010
0.011
0.012
0.013
0.014
2.0 2.5 3.0 3.5 4.0 4.5 5.0
Log (N)S
tra
in
Mean strain on
stitched line
Mean strain
between two
stitched lines
Mean strain of
stitched sample
Mean strain of
unstitched
sample
1
2
(a) (b) (c) (d)
Fig. Principal strain for samples. Arrows indicate the
stitching lines.
Fig. history of strain variations over stitched (line 1) and
unstitched (line 2) areas
Unstitched
400 cycles
Unstitched
17,000 cycles
Stitched
400 cycles
Stitched
17,000 cycles
• Stitching generates high strain concentration areas along the sample.
• The strains on stitching line are much higher than unstitched area.
• The strains on stitching line are increasing gradually while the fatigue test is ongoing.
However, the average strains of the stitched sample exhibit almost same values as that
of the unstitched sample during the fatigue test.
Stitching: Digital Image Correlation
Structural blade model Materials
Parametric blade model: – 3D coupled shell/solid
element model
– Geometry sweeps
– Realistic quasi-static aerodynamic/gravity load
– Static failure criteria
– Cohesive failure model for shear web bonding line
– “First look” fatigue strength analysis
– Lay-up optimisation (under development)
Structural blade model Fully distributed aerodynamic loading
The
Turbine
• Vortex lattice wake model
• Transient rotor load model
• Integrated wake/rotor model
• Wind tunnel model testing
Rotor wind-field
interaction
Rotor Wind Field Interaction: Unsteady Vortex Lattice Wake Model
G1
GM
é
ë
ê ê ê
ù
û
ú ú ú
=
C11 C1N
CM 1 CMN
é
ë
ê ê ê
ù
û
ú ú ú
-1V1
VN
é
ë
ê ê ê
ù
û
ú ú ú
Rotor Wind Field Interaction: Wind Tunnel Model Testing
Rotor Wind Field Interaction: Transient Rotor Load Model
Rotor Wind Field Interaction: Transient Rotor Load Model
Rotor Wind Field Interaction:
Use model to simulate the flow conditions surrounding a turbine in an array
Study the effects of upstream rotor wake interaction on downstream turbines.
Investigate the effects of wind shear and incident turbulence on the rotor loads.
Develop semi-empirical models for use with industry standard BEM codes to predict the impact on rotor induction factors and loading of these unsteady flow conditions.
The
Turbine
• Improving controllers
• Flexibility of operation
• Control of model blade devices
Drive train
dynamics
Improving controllers Bode Plot before Gain Scheduling
tower blade
edge
increasing
size
Non-linearities due
to blade pitching
Improving controllers Bode Plot after Gain Scheduling
Flexibility of operation
Flexibility of operation General layout of the controller
“Outer” controller (independent of the wind turbine’s inner controller)
Applicable to any wind turbine, regardless of the specific design of the inner controller and without any effect under normal conditions General layout of the
additional power controller
The
Turbine
• Application of monitoring techniques
• Monitoring key sub-assemblies
Fault detection
0 100 200 300 400 500 600 700 800-50
-45
-40
-35
-30
-25
-20
-15
-10
-5
0
Frequency [Hz]
No
rma
lize
d s
pe
ctru
m [d
B]
MODEL
RIG
112 Hz
212 Hz
150 Hz
373.8 Hz
435.7 Hz
273.8 Hz
535.7 Hz
597.6 Hz
697.6 Hz
250 Hz 350 Hz
Why is fault detection needed?
• Generator and gearbox failures contribute significantly to wind turbine downtime
• Generators and gearboxes have v. high replacement costs
• Spectral analysis of vibration signals commonly used in commercial condition monitoring systems for fault detection
• Spectral analysis of line current common in other fields for detection of motor/generator faults
Aims of fault detection
• Fundamental understanding of potential failure mechanisms and resulting fault signals in generators, drive train and frequency converters
• Develop practical methods of tracking fault signals under normal operating conditions
• Extend to all generator types and associated supply converters
• Mixed signal sources: current, power, vibration, temperature etc
Drive Train Test Rigs
DFIG generator and frequency converter rig at Manchester:
- Fixed speed Synchronous wound-rotor generator and gearbox rig at Durham: - Variable speed - SKF WindCon
Screened test chamber for PD testing at Manchester
Generator Fault
• Wound rotor induction generator rotor electrical asymmetry
– eg slip-ring/brush gear fault/unbalance
Raw data of generator speed, current and instantaneous power
Example of fault frequency tracking the power under wind conditions – 2sf component tracked : onset of rotor asymmetries clearly evident
0 100 200 300 400 500 600 700 800-60
-50
-40
-30
-20
-10
0
Frequency [Hz]
No
rma
lize
d s
pe
ctru
m [d
B]
MODEL
RIG
273.8 Hz
373.8 Hz597.6 Hz
697.6 Hz150 Hz
250 Hz 350 Hz
450 Hz
0 100 200 300 400 500 600 700 800-50
-45
-40
-35
-30
-25
-20
-15
-10
-5
0
Frequency [Hz]
No
rma
lize
d s
pe
ctru
m [d
B]
MODEL
RIG
112 Hz
212 Hz
150 Hz
373.8 Hz
435.7 Hz
273.8 Hz
535.7 Hz
597.6 Hz
697.6 Hz
250 Hz 350 Hz
a) Healthy DFIG b) Stator winding fault
• DFIG induction generator stator winding fault
• Line current frequency spectra – all frequency components can be identified in healthy and faulted operation using detailed generator model
Generator Fault
0 50 100 15010
-5
10-4
10-3
10-2
10-1
100
Stator current frequency spectrum, 1600 rpm
Frequency [Hz]
I s [nor
maliz
ed]
healthy
faulthy
fo-fs
2fo-f
sfo+f
s
Conventional stator current spectrum – difficult to see bearing fault signal!
80 90 100 110 120 130 140 150 160 170
10-4
10-3
10-2
10-1
100
Frequency [Hz]
Acce
lera
tio
n [
m/s
2]
Vibration frequency spectrum 1600 rpm
healthy
faulthy
2fo
fo
Vibration signal – bearing fault signal clear
81 82 83 84 85 860
2
4
6
8
10
12
14
16
x 10-3 Complex envelope frequency spectrum, 1630 rpm
Frequency [Hz]
ma
gn
itu
de
[n
orm
aliz
ed
]
Ias
Ibs
Ics
fo
Modified current spectrum –
bearing fault signal now clear!
• Stator current – see electrical
faults and bearing faults!
• Vibration signal – see bearing
fault and electrical faults!
Induction generator - outer race bearing fault
Ongoing work
• Bearing faults in DFIG’s • Detection of converter faults • Develop link from condition
monitoring to maintenance • Electrical fault models for
other generator types (eg direct-drive/hybrid pm generators)
• PD test facility: signal comparison for two methods: blue signal from a discharge detector Robinson M5, yellow from a 25-2000 MHz scan antenna
Subsea turbine foundations
The
Turbine • Extend hydrodynamic
solver to waves
• Historical data and experiment design
• Experimental study of wave loading
• Solver optimisation
• Numerical experiments
Experiments and Theoretical analyses conducted by D.L. Kriebel (1998) and J.R. Chaplin et al. (1997)
NWT outer dimensions: 8 × 3.6 × 0.9 m3
Water depth : h = 0.45m Diameter of cylinder : d = 0.325m
Case1 Case2 Case3 Case4
Wave amplitude (m) 0.0535 0.048 0.0621 0.074
Wave period (s) 1.95 1.75 1.50 1.25
Scattering parameter ka 0.271 0.308 0.374 0.481
wave gauges
Wave impact on a vertical cylinder
-100
-50
0
50
100
0 1 2 3 4 5 6 7 8 9 10
Forc
e (N
)
t (s)
-100
-50
0
50
100
150
0 1 2 3 4 5 6 7 8 9 10
Forc
e (N
)
t (s)
-100
-50
0
50
100
0 1 2 3 4 5 6 7 8 9 10
Forc
e (N
)
t (s)
Time history of horizontal force on cylinder
-100
-50
0
50
100
0 1 2 3 4 5 6 7 8 9 10
Forc
e (N
)
t (s)
1
2
3
4
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
-3.14 -1.57 0 1.57 3.14
F/F
0
Phase
Numerical Linear theory Second order Experimetal
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
-3.14 -1.57 0 1.57 3.14
F/F
0
Phase
Numerical
Linear theory
Second order
Experimental
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
-3.14 -1.57 0 1.57 3.14
F/F
0
Phase
Numerical
Linear theory
Second order
Experimental
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
-3.14 -1.57 0 1.57 3.14
F/F
0
Phase
Numerical
Linear theory
Second order
Experimental
Wave force time series for combinations of ka and kH (d/a=2.77)
Case2:
ka = 0.308, kH = 0.182
Case1:
ka = 0.271, kH = 0.178
Case4:
ka = 0.481, kH = 0.438
Case3:
ka = 0.374, kH = 0.286
(1) t = 0/8 T (2) t = 1/8 T (3) t = 2/8 T
(4) t = 3/8 T (5) t = 4/8 T (6) t = 5/8 T
(7) t = 6/8 T (8) t = 7/8 T (9) t = 8/8 T
Typical water surface around cylinder in 2nd wave period (Case1)
Extreme wave impact on a vertical cylinder
-100 -80 -60 -40 -20
0 20 40 60 80
100
3 4 5 6 7 8
Hori
zon
tal
Forc
e (N
)
t (s)
Extreme wave test
Input wave energy spectrum Time history of horizontal force on cylinder
Acknowledgements
For further information please contact:
EPSRC grant nos.
EP/D034566/1 & EP/H018662/1
SUPERGEN Wind Energy Technologies Consortium
