Control Of Offshore Windmills

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1 Control of offshore windmills Rambabu Kandepu
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Transcript of Control Of Offshore Windmills

  • 1. 1 Control of offshore windmills Rambabu Kandepu

2. 2Contents Introduction Physics Classification of wind turbines Offshore wind turbines Control of wind turbines 3. 3 Introduction Source of wind energy The sun is source of all renewable energy (except tidal and geothermal power) The earth receives 1.74 1014 kWH energy per hour from sun 1-2% of this energy converted to wind energy Wind energy > 50 to 100 times biomass energy 4. 4 Introduction Advantages of wind energy Clean energy Widely distributed Generation at local level Low risk Energy diversity 5. 5Introduction History Wind power to Mechanical power (Persia, Tibet and China, 1000 AD) Wind power to Electrical power (Dane Poul LaCour, 1891) 6. 6 Introduction Wind energy conversion systems Aerodynamic drag Aerodynamic lift Vertical axis (VAWT) (ex., Darrieus trubine) Horizontal axis (HAWT) 7. 7Introduction - components Rotor blades The hub Gearbox Generator Nacelle. Tower. 8. 8 Introduction Wind turbines Downwind The wind passes the tower first before the rotor free-yaw wind turbine Upwind the wind impinges upon the rotor first yaw-driven machine 9. 9Introduction Power Wind force to torque Wind energy transferred density, wind velocity rotor area 10. 10 Introduction power curve The Physics1 Power in wind = AV 3 (watts),2 where = air density (kg m -3 )V = wind speed (m s -1 )A = the intercepting area (m 2 ) Maximum power extraction is 59% (Betz) 11. 11 Introduction power curve Cut-in wind speed Rated wind speed (12-16 m/s) Cut-out wind speed (20-25 m/s) Depends on air pressure, aerodynamic shape of rotor,placing of turbine 12. 12 Introduction power curve Power produced 1P = ACPV 3 2 Tip speed ratio R= V 13. 13 Wind turbine topologiesFixed speedVariable speedMax. efficiency at one Max. efficiency over a wideparticular wind speedrange of wind speeds Simple, robust, reliable and Increased energy capture,well provenimproved power quality, reduced mechanical stress Mechanical stress, limited Losses in power electronics,power quality controlmore components, increased cost 14. 14Types of power control Stall control (passive control) The blades are bolted to the hub at a fixedangle Design of rotor aerodynamics causes therotor to stall Simplest, robust and cheapest Lower efficiency at low wind speeds, noassisted start up 15. 15Types of power control Pitch control (active control) Blades can be turned out or into the wind Extra complexity and higher fluctuations athigh wind speeds Good power control, assisted startup andemergency stop Requires fast response control loop additional costs and fatigue loading increases 16. 16Types of power control Active stall control The stall of the blade is actively controlledby pitching the blades Smoother power control without highpower fluctuations Easier to carry out emergency stops andto start up 17. 17Offshore wind turbines More faster and uniformwindThe most critical aspectis the substructures. Over 11 GW of newoffshore wind projects areplanned before the year Technology progression of offshore wind turbines 2010 18. 18 Offshore wind turbinesTypical cost breakdown of an offshore wind plant in shallow water 19. 19Offshore substructuresCost of Offshore Wind Turbine Substructures with Water Depth 20. 20 Shallow water foundations 5-18m deep Monoplies 160 MW wind farmat Horns Rev (Denmark) Simple and minimal design Depth limited due inherentflexibility Gravity based 160 MW Nystedproject (Denmark) Overcome flexibility Increase of cost with waterdepth Suction bucket foundations Not yet used 21. 21Transitional technology1) tripod tower, 2) guyed monopole, 3) full-height jacket(truss), 4) submerged jacket with transition to tube tower,5) enhanced suction bucket or gravity base. 22. 22 Transitional technology Two wind turbine generatorsnear the Beatrice Oil Field,North sea. 22km offshore Water depth off approximately45 meters 87 meters above sea level 5 MW for each turbine 23. 23 Floating technology The Spar-buoy concept, stability by ballast The Tension Leg Platform (TLP), stability by mooring line tension The barge concept, stability through its waterplane area 24. 24 Floating technology challenges Turbulent winds Irregular waves Gravity / inertia Aerodynamics Hydrodynamics Elasticity Mooring dynamics Control system Fully coupled 25. 25Floating technology Hywind Power > 5MWHydro currently has a license to Height above sea 80m place a demonstration turbine Rotor diameter 120moffshore near Karmy Water depth 200-700m 26. 26Control of wind turbine Wind turbines are relatively simple compared withcomplex electrical power plants The stochastic nature of the wind introducescomplexity Control system objectives Improve energy capture Keep the power output and rotor speed with in design limits Reduce structural dynamic loading Offshore wind turbine More dynamics Vertical stability in case of floating turbines 27. 27 Control of wind turbine Classical control PI controllers Multiple control loops, dynamics unknown Modern control Pole placement Linear Quadratic Control H control Adaptive control Disturbance Accommodating Control (DAC) Model Predictive Control 28. 28 Control of offshore wind turbine P CP = 1 Av3 2 is the tip-speed ratio 29. 29 Wind model Wind field varies both in space and time A slowly varying component with a mean wind speed A slowly varying wind shear component A rapidly varying turbulent wind component 30. 30 Aerodynamics of blade section 1 FL = AW 2 CL 2 1 FD = AW 2 CD 2 CL , CD - lift and drag coeff. depend on (AoA) 31. 31Control of offshore wind turbine Variable speed turbine with pitch control Four independent control inputs Three blade pitch inputs Generator torque command Regulated variables Power captured Mechanical loads on turbine structure 32. 32Control of offshore wind turbine State-of-the-art in control Control below rated speed Control above rated speed Drive train damping 33. 33Control of offshore wind turbine Control below rated speed Objective is maximize power capture Torque control Pitch angle is maintained constant 34. 34Control of offshore wind turbine Control above rated wind speed Objective is keep power output and loadson turbine structure within design limits Collective pitch control Keep generator torque constant 35. 35Control of offshore wind turbine Drive train damping Serious impact on gear box J (t ) + K (t ) = Taero Tgen - angular displacement Taero - aerodynamic torque Tgen - generator torqueJ - lumped inertiaK - lumped stiffness 36. 36Control of offshore wind turbine Decentralized control Below rated speed torque control Above rated speed pitch control Advantage in absence of reliable windspeed information Easy to implement and tune the controlalgorithms Simple to design for SISO case 37. 37 Control of offshore wind turbine Dynamics using 5 DOFmodel Blade flap Blade edge Tower fore-aft Tower side-to-side Drive train torsion Coupled dynamics 38. 38Control of offshore wind turbine Advanced control design is necessary The neglected coupled dynamics cause problems Present research State space control design Pole placement, LQR, H control, adaptive control,Disturbance Accommodating Control (DAC), MPC State estimator 39. 39 Control of offshore wind turbine DAC control Augment states with disturbancesH Control Include uncertinitoes MPC Include constraints (generator power, shaft speed, limits on DOFs) Adaptive control Updating model parameters Controller complexities Vs implementation 40. 40Control of offshore wind turbine Use of nonlinear models Present research focuses on linearizedmodels Vertical stability in case of floatingturbines Tension in mooring lines 41. 41Conclusions Classical control Decentralized control Present research State feed back control Linearized models Challenges Complex dynamics Unknown disturbances Design issues 42. 42Thank youfor your attention 43. 43 References Keld Hammerum, A Fatigue Approach to Wind Turbine Control, Master Thesis, TechnicalUniversity of Denmark Alexandra Bech Gjrv, Hywind - Floating wind power production, Hydro Beatrice Wind Farm Demonstrator, Project Scoping Report, Talisman Energy Shashikanth Suryanarayanan and Amit Dixit, Control of Large Wind Turbines: Review andSuggested Approach to Multivariable Design W. E. Leitheat and B. Connor, Control of variable speed wind turbines: design task, Int. J.Control, 2000, VOL. 73, NO. 13, 1189-1212 William E. Leithead and Sergio Dominguez, Coordinated Control Design for Wind TurbineControl Systems E.N. Wayman, P.D. Sclavounos, S. Butterfield, J. Jonkman, and W. Musial, CoupledDynamic Modeling of Floating Wind Turbine Systems, Offshore Technology ConferenceHouston, Texas May 14, 2006 Alan D. Wright, Mark J. Balas, Design of State-Space-Based Control Algorithms for WindTurbine Speed Regulation, Transactions of the ASME, Vol. 125, November, 2003 W. Musial, S. Butterfield and B. Ram, Energy from Offshore Wind, Offshore TechnologyConference, Houston, Texas, May 14, 2006 S. Butterfield, W. Musial, J. Jonkman and P. Sclavounos, Engineering Challenges forFloating Offshore Wind Turbines, Offshore Wind Conference, Copenhagen, Denmark,October 2628, 2005 Alan D. Wright, Modern Control Design for Flexible Wind Turbines, Technical report, July2004. Danish wind industry association, ( Lars Christian Henriksen, Model Predictive Control of a Wind Turbine, Master's thesis,Informatics and Mathematical Modelling, Technical University of Denmark, DTU