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Control of Wind Turbines: Past, Present and Future American Control Conference St. Louis, MO 11 June 2009 OUTLINE • HAWT TURBINE OVERVIEW • BASIC TURBINE CONTROL – – – – – – TORQUE AND PITCH CONTROL LOOPS BASIC TURBINE MODEL PITCH ORIENTATION POWER COEFFICIENT REGIONS OF OPERATION BASIC TORQUE/ PITCH CONTROLLER SIMULATION • DESIGN TOOLS • ADVANCED CONTROL American Control Conference St. Louis, MO 11 June 2009 TURBINE OVERVIEW Upwind HAWT Horizontal Axis Turbine Types Fixed Speed FIXED PITCH VARIABLE PITCH Variable Speed Low Power Utility Scale Turbines ½ MW and Larger CART3 [figure courtesy of US Dept. of Energy] Laks , Pao & Wright 3 American Control Conference, 11 June 2009 BASIC TURBINE CONTROL w Wind w wd Pitch Motor we Pitch Controller Ka Pitch Angle b 1 t aero t b t c J ta tb Kb Load Torque Torque Controller tc Power Converter Speed Sensor Laks , Pao & Wright Rotor Speed 4 American Control Conference, 11 June 2009 BASIC TURBINE CONTROL Wind Ka w wd we Pitch Angle Pitch Controller b ta tb Kb Load Torque Torque Controller tc Rotor Speed OPERATIONAL CONTROLLER Laks , Pao & Wright 5 American Control Conference, 11 June 2009 BASIC TURBINE CONTROL Pitch Angle b Blade Direction Tower Nacelle Rotor Wind Direction Blade Laks , Pao & Wright 6 American Control Conference, 11 June 2009 BASIC TURBINE CONTROL Blade Velocity: Blade b Relative Velocity Direction Wind Direction Wind Velocity: w Laks , Pao & Wright 7 American Control Conference, 11 June 2009 BASIC TURBINE CONTROL Blade “Thrust” (torque) b Lift Wind Direction Tip Speed Ratio: Relative Velocity Laks , Pao & Wright Direction 8 American Control Conference, 11 June 2009 BASIC TURBINE CONTROL • Available Wind Power CART3 Cp Level Curves 10 0.3 Normalized Torque Versus Tip Speed Ratio 0.1 9 0.25 0.09 • Power Harvested 8 0.08 0.2 7 TPS, Normalized Torque 0.07 60.06 0.15 50.05 0.1 0.04 4 0.05 0.03 3 0.02 0 2 • Region 2: 0.01 1 0 1 -4 2 -2 3 0 4 25 Pitch [deg] Laks , Pao & Wright 9 64 7 6 8 8 9 10 American Control Conference, 11 June 2009 BASIC TURBINE CONTROL • Region 2: torque control at optimal (tc=ta*) • Region 3: regulate speed/power • Region 4: shut down (“cut out”) (Rated Power) w Laks , Pao & Wright 10 American Control Conference, 11 June 2009 BASIC TURBINE CONTROL • Regions 1 & 2: Generator speed < 1800 rpm – Pitch Held constant at b* – Torque adjusted according to sqare law once generator speed is > 200 rpm • Region 3: Generator speed > 1800 rpm – Torque is held constant at rated (~3500 KN-m) – wPitch is adjusted based on speed error using a PID controller . • Cut-Out: Once wind speed > 28m/sec – Pitch is ramped up to near perpendicular – Torque is held constant until generator speed is < 200 rpm and then regulated with a 2nd PID (no brake!) Laks , Pao & Wright 11 American Control Conference, 11 June 2009 BASIC TURBINE CONTROL • PID Pitch Loop Response Laks , Pao & Wright (HSSV = gen. speed) 12 American Control Conference, 11 June 2009 BASIC TURBINE CONTROL Laks , Pao & Wright 13 American Control Conference, 11 June 2009 DESIGN TOOLS Wind Modeling FAST Structural and aeroelastic simulation of two and three bladed wind turbines Dynamically linked with simulink System Simulation TURBSIM Generation of model-based wind fields for input to simulation WindSet TIMEsim PITCHff FFsim Clock To Workspace FeedForward GENTQsim LSSV Tq Tg Transport Delay Torque Controller 667e3 Electrical Power Out1 Gen. Torque (Nm ) and Power (W) OutData OutData f(u) Yaw Position (rad) and Rate (rad/s) q_out w WINDsim extract w Yaw Controller PitchSet*pi/180 actmod PITCH _op (rad) Blade Pitch Angles (rad) Pitch Limits CTRLsim qdot_out PitchActuator PITCHlimit FAST Nonlinear Wind Turbine PitchControl PITCHsim LSSVsim HSSVEsim HSSVE measurements LSSV Simulink SelectShaftMeasures MathWorks integration engine Scope Scope 2 Scope 1 Laks , Pao & Wright 14 American Control Conference, 11 June 2009 ADVANCED TURBINE CONTROL Drive Train Torsional Compliance Blade-1 Flap Blade Flexible Modes (Flap & Edge) Blade-2 Lag Generator Rotation Rotor Rotation Drive-train Torsion Rotor Teeter Blade-1 Lag Tower Side-Side Tower Fore-Aft Blade-2 Flap Tower Flexible Modes (Fore-Aft, Side-Side) (a) Sideview (b) Frontview Laks , Pao & Wright 15 American Control Conference, 11 June 2009 ADVANCED TURBINE CONTROL Laks , Pao & Wright Numerically Linearized Model 16 American Control Conference, 11 June 2009 ADVANCED TURBINE CONTROL Torque Command Generator Speed TORQUE CONTROL TORQUE MIMO CONTROL TORQUE CONTROL TURBINE Individual Pitch Blade Measurements Tower Measurements • • • ADD FEEDBACK FROM INDIVIDUAL BLADES INSTRUMENT TOWER TO DETECT SWAY USE MIMO DESIGN TECHNIQUES – INDIVIDUAL BLADE PITCH – INCORPORATE WIND DISTURBANCE MODELS Laks , Pao & Wright 17 American Control Conference, 11 June 2009 ADVANCED TURBINE CONTROL • LIDAR BASED FEEDFORWARD – MEASURE WIND UPSTREAM DELAY FROM TURBINE – REAL TIME WIND SPEED S TURBINE – PRE-VIEW OF WIND SPEED CHANGES DIST Laks , Pao & Wright 18 American Control Conference, 11 June 2009 ADVANCED TURBINE CONTROL Low Speed Shaft Response 46 PID Speed [rpm] 45 FB FBFFprev 44 42.5 42 43 41.5 38 42 Rm [kN-m] 41 30 40 50 400 100 300 0 200 -100 38 100 39 39 40 41 42 43 60 44 70 45 80 Blade Flap Bending Moment Response 40 41 42 43 44 90 100 90 100 45 0 -100 -200 -300 30 Laks , Pao & Wright 40 50 60 Time [sec] 70 80 19 American Control Conference, 11 June 2009 SUMMARY • Operational controllers can be constructed using basic parallel torque and collective pitch controllers. • There are public domain tools and modelling codes available so that you can get started relatively quickly. • MIMO Control approaches can improve load mitigation with additional instrumentation on the turbine. • Advanced wind measurement technologies hold the promise of great improvements in performance. 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