Control of Wind Turbines Past Present and Future

Control of Wind Turbines: Past, Present and Future Jason Laks, Lucy Pao American Control Conference St. Louis, MO Alan Wright 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 CART 3 [figure courtesy of US Dept. of Energy] Laks , Pao & Wright 3 American Control Conference, 11 June 2009

BASIC TURBINE CONTROL Wind w wd Pitch Motor we Pitch Controller Ka Pitch Angle b Kb ta tb Load 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 tb Load Torque Controller tc Rotor Speed OPERATIONAL CONTROLLER Laks , Pao & Wright Kb ta 5 American Control Conference, 11 June 2009

BASIC TURBINE CONTROL Pitch Angle Blade b 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 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 Normalized Torque Versus Tip Speed Ratio 0. 1 0. 09 Normalized Torque • Power Harvested 0. 08 0. 07 0. 06 0. 05 0. 04 0. 03 0. 02 • Region 2: 0. 01 0 1 2 3 4 5 6 7 8 9 10 l Laks , Pao & Wright 9 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) – w. Pitch is adjusted based on speed error using a PID controller. • Cut-Out: Once wind speed > 28 m/sec – Pitch is ramped up to near perpendicular – Torque is held constant until generator speed is < 200 rpm and then regulated with a 2 nd 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 v System Simulation FAST § Structural and aeroelastic simulation of two and three bladed wind turbines § Dynamically linked with simulink v TURBSIM § Generation of model-based wind fields for input to simulation v Simulink § Math. Works integration engine FAST/SIMULINK SIMULATION Laks , Pao & Wright 14 American Control Conference, 11 June 2009

ADVANCED TURBINE CONTROL Drive Train Torsional Compliance Blade Flexible Modes (Flap & Edge) Tower Flexible Modes (Fore-Aft, Side-Side) Laks , Pao & Wright 15 American Control Conference, 11 June 2009

ADVANCED TURBINE CONTROL v Laks , Pao & Wright Numerically Linearized Model 16 American Control Conference, 11 June 2009

ADVANCED TURBINE CONTROL TORQUE CONTROL MIMO TORQUE CONTROL Torque Command Generator Speed 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 S – REAL TIME WIND SPEED 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 Speed [rpm] PID 45 FB FBFFprev 44 42. 5 43 42 42 41. 5 38 41 30 40 39 50 40 41 60 42 43 44 70 45 80 90 100 Rm [k. N-m] Blade Flap Bending Moment Response 400 100 300 0 200 -100 38 100 39 40 41 42 43 44 45 0 -100 -200 -300 30 40 50 60 70 80 90 100 Time [sec] Laks , Pao & Wright 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. Laks , Pao & Wright 20 American Control Conference, 11 June 2009

Control of Wind Turbines: Past, Present and Future Jason Laks, Lucy Pao Alan Wright THANK YOU American Control Conference St. Louis, MO 11 June 2009