implementation

Implementationofwindturbinecontrollers

AD

Threeoftheimportantgenericimplementationissuencounteredwhendevelop-

ingcontrollersforpitch-regulatedconstant-speedwindturbinesareconsidered;

namely,accommodationofthestronglynonlinearrotoraerodynamics,automatic

controllerstart-up±shut-downandaccommodationofvelocityandacceleration

rectlinearizationandfeedbacklinearization

methodsforaccommodatingthenonlinearaerodynamicsareinvestigatedandcom-

yemployedtechniqueforaccommodatingthenonlinearaerody-

namics,originallydevelopedonthebasisofphysicalinsight,isrigorously

derivedandextendedtocaterforallwindturbinecon®ous

stabilityanalysisofcontrollerstart-upisprentedforthersttime,andnovel

designguidelinesarepropodwhichcansigni®cantlyreducethepowertransients

ationtoanti-wind-upisnotedandveralaspectsof

anexistingwind-turbinecontrollerstart-upstrategyareobrvedtobenovelinthe

ctiveposition,velocityandaccelerationconstraints

mayallbeprentinwindturbinesandthedynamicbehaviouroftheactuator

,andquitegeneral,anti-wind-upmethod,badonthe

start-upstrategy,arate

strategiesforresolvingtheimplementationissuesarecombinedtoachieveanele-

gantcontrollerrealizationwhichaccommodatesalltheimplementationissuesinan

ortanceofadoptinganappropriatecontrollerrealiza-

lementa-

tionissuencounteredinthispaperare,ofcour,notcon®nedtowindturbines

butareofwiderconcern.

uction

Windturbinetechnologyhasundergonerapiddevelopmentinrecentyearsin

respontowidespreaddemandsfortheincreaduofrenewablesourcesof

ndardcommercialdesignofwindturbineisahorizontal-axisgrid-

connectedup-windmachinewitharatingofapproximately300±500kW(medium

scale).Itisanticipatedthatthenextgenerationofwindturbines,whichareatprent

beingdeveloped,

rotorusuallyhastwoorthreeblades,andinpitch-regulatedmachinesthepitchangle

ofeitherthefullspanoftheblades,orjusttheoutertips,trol

designtaskforconstant-speedpitch-regulatedmachinesistoexploitthiscapability

inordertoregulatethepoweroutputwhilstminimizingtheloadtransientsand

ectivesanddesignofthesingle-input

single-output(SISO)controlsystemhavebeendiscusdfullybyLeitheadetal.

(1991a,b,1992a).

0020-7179/97$12.001997Taylor&FrancisLtd.

L,1997,VOL.66,NO.3,349±380

Received29April1996.

DepartmentofElectronicandElectricalEngineering,UniversityofStrathclyde,

GlasgowG11QE,UK.

Inthispaper,threeoftheimportantimplementationissuencounteredwhen

developingcontrollersforpitch-regulatedconstant-speedwindturbinesareinvesti-

gated;namely

(1)compensationofthestronglynonlinearrotoraerodynamics;

(2)automaticcontrollerstart-up±shut-down;

(3)accommodationofvelocityandaccelerationconstraintswithintheactuator.

Theissuesare,ofcour,notcon®nedtowindturbinesbutareofwider

concern.

Therstimplementationissuerelatestotheaerodynamicbehaviourofthe

alinearizedplantreprentationistypicallyemployedduring

thesynthesisofthecontrollertransferfunction,awindturbineisanonlinearsystem;

inparticular,heroleofthe

turbinerotorinconvertingwindenergyintomechanicalenergyisacentralone,the

nonlinearbehaviouroftherotorexertsasubstantialin¯uenceonthecharacteristics

ofthewholewindturbineandcannotbeneglected(e,forexample,Leitheadetal.

(1991b,1992a)).

Thecondimplementationissuerelatestothewindturbineoperationalrequire-

certain`ratedwindspeed’,thepowergeneratedislessthanthe

r,whenthewindspeed

risaboverated,thepoweroutputisregulatedattheratedvalueoftheturbine,

`ratedpower’,,itis

necessarytostartupandtoshutdownthecontrollerautomaticallyasthewindspeed

¯uctuates.(Inverylowwindspeeds,thereisinsu