Applications throughout the World - Hybrid Anisotropic Materials for Wind Power Turbine Blades - page 7

Yawdrive :.Upwind.turbines.face.into.the.wind;.the.yaw.drive.is.used.
to.keep.the.rotor.facing.into.the.wind.as.the.wind.direction.changes..
Downwind.turbines.don't.require.a.yaw.drive,.the.wind.blows.the.
rotor.downwind.
Yawmotor :.Powers.the.yaw.drive.

1.3.4 Contradictory Goals

Paul. Dvorak,. a. wind. power. engineer,. mentioned. that. various. control. sys-
tems. with. competing. goals. must. interact. with. each. other,. and. this. creates.
a. dificult. design. challenge. 1 . For. example,. the. turbine. monitoring. system.
must.ensure.it.generates.electricity.upon.demand..At.the.same.time,.it.must.
protect.individual.parts.from.unnecessary.wear.and.tear..The.supervisory.
control.system.must.observe.both.of.these.contradictory.goals.
Normally,. the. generator. is. only. switched. on. when. the. wind. reaches. a.
speed.of.2.to.4 m/s..Lower.wind.speeds.fail.to.generate.enough.power.and.
unnecessarily. wear. turbine. parts.. In. high. winds,. controls. shut. down. the.
generator.and.set.the.rotor.spin.slowly.(or.not.at.all).so.as.to.reduce.load.on.
the.drive.train..The.system.that.controls.the.blades.attempts.to.keep.the.gen-
erator's.speed.in.a.relatively.narrow.range.so.it.can.generate.the.maximum.
amount.of.power..Additionally,.it.also.must.react.to.imminent.power.failures.
to.control.or.actuate.systems.within.the.turbine.to.prevent.the.turbine.from.
becoming.unstable.and.destroying.itself.
Proper.yaw.control.keeps.the.turbine.facing.the.wind.during.normal.opera-
tion..The.yaw.controller.also.must.ensure.that.the.nacelle.doesn't.turn.in.the.
same.direction.all.the.time.so.that.the.cables.in.the.tower.do.not.twist.beyond.
their.limit..Again,.it.is.up.to.the.supervisory.controller.to.reconcile.these.poten-
tially.conlicting.goals..Adding.to.the.challenge.is.the.fact.that.the.system.is.non-
linear,.including.backlash.in.the.gearbox.and.friction.in.its.large.ball.bearings.

1.3.5 Smooth and Continuous Development

All.subsystems.in.a.turbine.can.be.simulated.and.tested.as.part.of.an.inte-
grated.system.at.an.early.development.stage.by.using.a.model-based.design..
Controller.hardware.can.be.tested.before building.prototypes.of.the.full.sys-
tem..Systems.that.must.eventually.work.together,.such.as.the.pitch.and.yaw.
actuators,.can.be.simulated.together.and.matched.for.best.performance.
Wind. turbine. developers. who. use. this. design. philosophy. proit. from.
a. smooth. and continuous. development. process.. The. models. and. simula-
tions. exist. in. a. single. environment. and. are. linked. directly. to. the. require-
ments.and.speciications..In.addition,.embedded.software.can.be.generated.
directly.from.the.model..Doing.so.simpliies.communication.between.var-
ious. teams. and. enables. integration. issues. to. be. discovered. earlier. in. the.
design.process. 1