Theme 2 The Turbine Dr Geoff Dutton

SUPERGEN Wind Wind Energy Technology Phase 2 Theme 2 The Turbine Dr Geoff Dutton Supergen Wind Phase 2 General Assembly Meeting 21 March 2012

Normalized spectrum [db] Turbine blade materials The Turbine Drive train dynamics Rotor wind-field interaction Fault detection 0-5 -10-15 -20 373.8 Hz 273.8 Hz MODEL RIG 150 Hz 597.6 Hz 212 Hz 435.7 Hz 535.7 Hz 697.6 Hz -25 Middelgrunden wind farm photo by LM Glasfiber -30-35 -40-45 112 Hz 250 Hz 350 Hz -50 0 100 200 300 400 500 600 700 800 Frequency [Hz] Subsea turbine foundations

Turbine blade materials The Turbine Basic materials 3D fabrics and joints Component testing Blade model

Materials considerations in blade design Labour, Material, Equipment Production rate Bending stiffness Cost Weight Selection of materials and manufacturing process design Maintenance and repair Reliable and cost-effective wind turbine blades Fatigue Resistance Manufacturing processes Environmental effects: UV, radar, Corrosions, Lightening

Novel materials: interlaminar toughness Selective interfacial reinforcement Veils Nano-additives Nano silica particles Through-thickness stitching and tufting Use of 3D fibre formats: braiding & weaving 3D Fabric

3D textile composites 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.

Strain Stitching: Digital Image Correlation Unstitched 400 cycles Unstitched 17,000 cycles Stitched 400 cycles Stitched 17,000 cycles 0.014 0.013 1 Mean strain on stitched line 0.012 0.011 Mean strain between two stitched lines 0.010 1 0.009 2 Mean strain of stitched sample 2 0.008 0.007 Mean strain of unstitched sample 0.006 (a) (b) (c) (d) 2.0 2.5 3.0 3.5 4.0 4.5 5.0 Log (N) Fig. Principal strain for samples. Arrows indicate the stitching lines. Fig. history of strain variations over stitched (line 1) and unstitched (line 2) areas 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. Slide No.7

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

Rotor wind-field interaction The Turbine Vortex lattice wake model Transient rotor load model Integrated wake/rotor model Wind tunnel model testing

Rotor Wind Field Interaction: Unsteady Vortex Lattice Wake Model é ê ê ë ê G 1 G M ù ú ú û ú = é ê ê ë ê C 11 C M 1 C 1N C MN ù ú ú û ú -1 é ê ê ë ê V 1 V N ù ú ú û 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.

Drive train dynamics The Turbine Improving controllers Flexibility of operation Control of model blade devices

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

Normalized spectrum [db] Fault detection 0-5 -10-15 373.8 Hz 273.8 Hz MODEL RIG 150 Hz 597.6 Hz 212 Hz 435.7 Hz 535.7 Hz 697.6 Hz The Turbine -20-25 -30-35 -40-45 112 Hz 250 Hz 350 Hz -50 0 100 200 300 400 500 600 700 800 Frequency [Hz] Application of monitoring techniques Monitoring key sub-assemblies

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 Synchronous wound-rotor generator and gearbox rig at Durham: - Variable speed - SKF WindCon DFIG generator and frequency converter rig at Manchester: - Fixed speed 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

Normalized spectrum [db] Normalized spectrum [db] Generator Fault DFIG induction generator stator winding fault 0-10 -20 150 Hz 273.8 Hz 373.8 Hz 450 Hz 597.6 Hz 697.6 Hz 0-5 -10-15 150 Hz 212 Hz 273.8 Hz 373.8 Hz MODEL RIG 597.6 Hz 435.7 Hz 535.7 Hz 697.6 Hz -20-30 -25-30 -40-35 -50 MODEL 250 Hz 350 Hz RIG -60 0 100 200 300 400 500 600 700 800 Frequency [Hz] -40-45 112 Hz 250 Hz 350 Hz -50 0 100 200 300 400 500 600 700 800 Frequency [Hz] a) Healthy DFIG b) Stator winding fault Line current frequency spectra all frequency components can be identified in healthy and faulted operation using detailed generator model

Acceleration [m/s 2 ] magnitude [normalized] I s [normalized] Induction generator - outer race bearing fault Stator current frequency spectrum, 1600 rpm 10 0 10-1 healthy faulthy 10-2 f o -fs 2f o -f s f o +f s 10-3 10-4 10-5 0 50 100 150 Frequency [Hz] Conventional stator current spectrum difficult to see bearing fault signal! 10 0 f o Vibration frequency spectrum 1600 rpm healthy faulthy 2f o x 10-3 16 Complex envelope frequency spectrum, 1630 rpm I as 10-1 14 12 I bs I cs 10-2 10-3 10-4 80 90 100 110 120 130 140 150 160 170 Frequency [Hz] Vibration signal bearing fault signal clear 10 8 6 4 2 0 81 82 83 84 85 86 Frequency [Hz] Modified current spectrum bearing fault signal now clear! f o Stator current see electrical faults and bearing faults! Vibration signal see bearing fault and electrical faults!

Ongoing work PD test facility: signal comparison for two methods: blue signal from a discharge detector Robinson M5, yellow from a 25-2000 MHz scan antenna 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)

The Turbine Extend hydrodynamic solver to waves Historical data and experiment design Experimental study of wave loading Solver optimisation Numerical experiments Subsea turbine foundations

Wave impact on a vertical cylinder NWT outer dimensions: 8 3.6 0.9 m 3 Water depth : h = 0.45m Diameter of cylinder : d = 0.325m wave gauges 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 Experiments and Theoretical analyses conducted by D.L. Kriebel (1998) and J.R. Chaplin et al. (1997)

Force (N) Force (N) Force (N) Force (N) Time history of horizontal force on cylinder 1 2 3 4 100 50 0-50 -100 0 1 2 3 4 5 6 7 8 9 10 100 t (s) 50 0-50 -100 0 1 2 3 4 5 6 7 8 9 10 t (s) 100 50 0-50 -100 150 100 50 0-50 -100 0 1 2 3 4 5 6 7 8 9 10 t (s) 0 1 2 3 4 5 6 7 8 9 10 t (s)

Wave force time series for combinations of ka and kh (d/a=2.77) F/F 0-2.0-3.14-1.57 0 1.57 3.14 Phase F/F 0 2.0 1.5 1.0 0.5 0.0-0.5-1.0-1.5 2.0 1.5 1.0 0.5 0.0-0.5-1.0-1.5 Case1: ka = 0.271, kh = 0.178 Case3: ka = 0.374, kh = 0.286 Numerical Linear theory Second order Experimental Numerical Linear theory Second order Experimental -2.0-3.14-1.57 0 1.57 3.14 Phase F/F 0 F/F 0-2.0-3.14-1.57 0 1.57 3.14 Phase 2.0 1.5 1.0 0.5 0.0-0.5-1.0-1.5 2.0 1.5 1.0 0.5 0.0-0.5-1.0-1.5 Case2: ka = 0.308, kh = 0.182 Case4: ka = 0.481, kh = 0.438 Numerical Linear theory Second order Experimental Numerical Linear theory Second order Experimetal -2.0-3.14-1.57 0 1.57 3.14 Phase

Typical water surface around cylinder in 2 nd wave period (Case1) (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

Horizontal Force (N) Extreme wave test Input wave energy spectrum 100 80 60 40 20 0-20 -40-60 -80-100 3 4 5 6 7 8 t (s) Time history of horizontal force on cylinder Extreme wave impact on a vertical cylinder

Acknowledgements EPSRC grant nos. EP/D034566/1 & EP/H018662/1 SUPERGEN Wind Energy Technologies Consortium For further information please contact: geoff.dutton@stfc.ac.uk