Wind Turbine Electrical Systems

7/23/2019 Wind Turbine Electrical Systems

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An introduction to windAn introduction to wind--turbineturbine

electrical systemselectrical systems

Lee Jay FingershLee Jay Fingersh

Given at CU BoulderGiven at CU Boulder

April 18, 2008April 18, 2008


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What does a windWhat does a wind--turbineturbineelectrical system do?electrical system do?

Produces our productProduces our product Controls the rotorControls the rotor

Interacts with the power gridInteracts with the power grid Protects itself from harmProtects itself from harm

Protects the turbine from harmProtects the turbine from harm


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Wind turbine operationWind turbine operation


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Classical wind turbine designClassical wind turbine design


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Alternative train designsAlternative train designs


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Rotating Magnetic FieldsRotating Magnetic Fields

RotatingField.html


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Induction generator torqueInduction generator torque--speedspeedcharacteristiccharacteristic

-25000

-20000

-15000

-10000

-5000

0

5000

10000

15000

20000

25000

0 300 600 900 1200 1500 1800 2100 2400 2700 3000 3300 3600

HSS speed, RPM

GeneratorTorque,Nm


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Synchronous machinesSynchronous machines

Very stiffVery stifflittle dampinglittle damping Can produce rather thanCan produce rather than

absorb reactive powerabsorb reactive power

Hard to get onlineHard to get online Requires aRequires a cushioncushion

between it an the rotorbetween it an the rotor

Fluid couplings can beFluid couplings can bedangerousdangerous


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Fluid coupling failureFluid coupling failure


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Torque responseTorque response constant speedconstant speed


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Torque responseTorque response variable speedvariable speed


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Torque speed vector for VSTorque speed vector for VS


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What is a power converter?What is a power converter?

ConvertsConverts

variablevariable--frequencyfrequency

variablevariable--voltagevoltageintointo

constantconstant--frequencyfrequency

constantconstant--voltagevoltage


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Passive rectificationPassive rectification


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1212--pulsepulse


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FullFull--processingprocessing


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Current linkCurrent link


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DoublyDoubly--fedfed


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WeibullWeibull Probability functionProbability functionWind, Energy

0 5 10 15 20 25 30 35 40

Windspeed (m/s)

Weibull Probability Weibull Betz


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Gearbox efficiencyGearbox efficiency

0%

15%

30%

45%

60%

75%

90%

810

1215

1665

2115

25650%

10%20%30%40%50%60%

70%80%90%

100%

Efficiency

% of Rated Power

RPM

Variable Speed Gearbox Efficiency Surface


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Generator efficiencyGenerator efficiency

0%

25%

50%

75%

100%

125%

150%

0%5

%10%1

5%2

0%

25%

30%

35%

40%

45%

50%

55%

60%

65%

70%

75%

80%

85%

90%

95%

100%

70%

75%

80%

85%

90%

95%

100%

Efficiency

% of rated RPM

% of rated power

Permanent-magnet generator efficiency surface


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Power converter efficiencyPower converter efficiencyVariable Speed Converter Efficiency

0%

20%

40%

60%

80%

100%

120%

0% 20% 40% 60% 80% 100% 120%

Percent of Rated Load

Efficienc

y

Standard Converter

90% Converter

94% Converter


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Interaction with the gridInteraction with the grid

Requirements areRequirements aregetting toughergetting tougher

Must provide VARMust provide VAR

compensationcompensation

Must rideMust ride--through faultsthrough faults

Must provide faultMust provide faultcurrentcurrent

Still no dispatchabilityStill no dispatchability


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The dispatchability issueThe dispatchability issueLoad versus wind

0

5000

10000

15000

2000025000

30000

35000

40000

45000

0 6 12 18 24

Hour of the day

Megaw

atts

LoadWind


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What to do about itWhat to do about it Ignore itIgnore it

Wind produces 10%Wind produces 10%--20% of20% of

our electricityour electricity

Geographical distributionGeographical distribution

Add dispatchable loadAdd dispatchable load

Add storageAdd storage CAESCAES

BatteriesBatteries

HydrogenHydrogen

V2GV2G

The problem is cost!!!The problem is cost!!!

CAESCAES Current technologyCurrent technology

Combined with naturalCombined with naturalgas electrical plantsgas electrical plants

50% to 70% efficiency50% to 70% efficiency

BatteriesBatteries

Currently expensiveCurrently expensive Efficient (85% to 95%)Efficient (85% to 95%)

HydrogenHydrogen MassiveMassive

Inefficient (25% to 35%)Inefficient (25% to 35%)

V2GV2G EmergingEmerging


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ApproachApproach Simulation of power grid energySimulation of power grid energy--flowflow

Analysis of timeAnalysis of time

--series data for 2002series data for 2002

California ISO hourly load dataCalifornia ISO hourly load data

Lake Benton wind farm hourly power dataLake Benton wind farm hourly power data

ComponentsComponents WindWindCurrent costs ($1,000 / kW)Current costs ($1,000 / kW) BatteryBatteryProjected costsProjected costs

ElectrolyzerElectrolyzerProjected costsProjected costs

Fuel CellFuel CellProjected costsProjected costs

Dispatchable load/curtailmentDispatchable load/curtailment

Traditional generationTraditional generation


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Interesting resultInteresting result An optimizer (Excel solver) is used to minimizeAn optimizer (Excel solver) is used to minimize

cost by optimizing the sizes of the componentscost by optimizing the sizes of the components ElectrolyzerElectrolyzer

Fuel cellFuel cell

Control parametersControl parameters

Hydrogen system is optimized to zero size!Hydrogen system is optimized to zero size!Cause is the low efficiency of the hydrogen systemCause is the low efficiency of the hydrogen system

compared to the batterycompared to the battery

Hydrogen systemHydrogen system

37.5% (75% electrolyzer, 50% fuel cell)37.5% (75% electrolyzer, 50% fuel cell)

BatteryBattery 85.5% (95% charge, 90% discharge)85.5% (95% charge, 90% discharge)

True even when costs of hydrogen componentsTrue even when costs of hydrogen components(electrolyzer and fuel cell) are set to zero!(electrolyzer and fuel cell) are set to zero!


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Optimized windOptimized wind

--battery systembattery system

$0.024

$0.026

$0.028

$0.030

$0.032

$0.034

$0.036

$0.038

$0.040

0% 10% 20% 30% 40% 50% 60% 70%

Capacity Reduction

CostofEnergy

EnergyPenetration

2%

EnergyPenetration

20%


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What about making hydrogen?What about making hydrogen?

Fix the electrolyzer size so the optimizerFix the electrolyzer size so the optimizer

doesndoesnt optimize it awayt optimize it away DonDont use the hydrogen to regeneratet use the hydrogen to regenerate

electricity onelectricity on--sitesite

Sell the hydrogen created as a fuelSell the hydrogen created as a fuel Assume no hydrogen storage neededAssume no hydrogen storage needed

Result: Hydrogen production is lessResult: Hydrogen production is lessexpensive when electrolyzers areexpensive when electrolyzers arecombined with windcombined with wind ANDANDbatteriesbatteries


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Hydrogen production resultsHydrogen production results

$1.50

$1.75

$2.00

$2.25

$2.50

$2.75

$3.00

$3.25

$3.50

$0 $200 $400 $600 $800 $1,000 $1,200

Electrolyzer cost ($/kW)

HydrogenCost($/kg

)

PTC$0.02

PTC$0.00


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ConclusionsConclusions

Hydrogen is not economical as an energyHydrogen is not economical as an energystorage medium for grid electricitystorage medium for grid electricity

Batteries are economically competitive forBatteries are economically competitive for

onon--grid electricity storagegrid electricity storageHydrogen can be produced from wind forHydrogen can be produced from wind for

$1.50 to $3.00 per kg in a hybrid system$1.50 to $3.00 per kg in a hybrid system

(wind(wind--batterybattery--electrolyzerelectrolyzer--grid)grid)


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Wind turbine controlsWind turbine controls


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The controlsThe controls--design processdesign process

DesignDesign

SimulateSimulate

Field TestField Test

AnalyzeAnalyzeModifyModify


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Controls on wind turbinesControls on wind turbines

To test controls onTo test controls onwind turbines, wewind turbines, we

needed a controlsneeded a controls

test bed turbinetest bed turbine

Two WestinghouseTwo Westinghouse

600kW 43.28 meter600kW 43.28 meter

twotwo--bladed windbladed wind

turbines wereturbines were

acquired fromacquired from

Kahuku point, OahuKahuku point, Oahu


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Turbine shipment/installationTurbine shipment/installation

The turbines wereThe turbines werebrought to thebrought to the

NWTC, refurbishedNWTC, refurbished

and installedand installed

Instrumentation andInstrumentation and

data acquisitiondata acquisition

equipment wereequipment were

addedadded


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Turbine operationTurbine operation

Both turbines wereBoth turbines wereplaced intoplaced intooperationoperation

ART (left)ART (left)19991999 ConstantConstant--speedspeed

LIST experimentLIST experiment

CART (right)CART (right)20012001

Constant or variableConstant or variable--speedspeed

Controls testingControls testing


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CART CapabilitiesCART Capabilities

Turbine heavilyTurbine heavilymodified for controlsmodified for controlstestingtesting HighHigh--speed independentspeed independent

pitch controlpitch control

ConstantConstant--speed modespeed mode Full variableFull variable--speedspeed

Flexible controller (PCFlexible controller (PC--based)based)

Fast data acquisitionFast data acquisition(100 Hz, 90 channels)(100 Hz, 90 channels)

InstrumentationInstrumentation

PerformancePerformance

HSS, LSS torqueHSS, LSS torque

Power, current, voltagePower, current, voltage

LoadsLoads Blade root loadsBlade root loads

Tower bendingTower bending

AccelerationsAccelerations

RateRate--gyrosgyros

MeteorologicalMeteorological

UpUp--wind vertical arraywind vertical array

Sonic anemometerSonic anemometer


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Turbine characterizationTurbine characterization

0.00

0.10

0.20

0.30

0.40

0.50

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0 5 10 15 20

TSR

Cp

Constant Speed - LSS Predicted


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Adaptive controllerAdaptive controller

0 50 100 150 200 250 300 3500.5

1.0

1.5

2.0

NormalizedM(M/M+)

0 50 100 150 200 250 300 350

0.3

0.4

0.5

Fractiona

lAveragePower

Time (hours)5 10 15 20

0

100

200

300

400

500

600

GridPower(kW)

Mean Equivalent Wind Speed (m/s)

Standard ControlAdaptive Control

Region 3Region 2


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StateState--spacespace controlcontrol

StateState--space control allows the designer great flexibilityspace control allows the designer great flexibility

Multiple inputs (RPM, blade bending, nacelle acceleration, etc.)Multiple inputs (RPM, blade bending, nacelle acceleration, etc.)

Multiple outputs (shaft torque, individual blade pitch)Multiple outputs (shaft torque, individual blade pitch)

Ability toAbility to dramaticallydramatically reduce turbine vibrationsreduce turbine vibrations

Measured Shaft Torque

60

80

100

120

140

160

180

200

0 5 10 15 20 25 30

Time (sec)

Low-SpeedSha

ft

Torque

PI Control

State-space (FAST) controller

Wh do e need to red ceWhy do we need to reduce


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Why do we need to reduceWhy do we need to reduce

vibrations?vibrations? Turbines are gettingTurbines are getting muchmuch

larger in response to the needlarger in response to the needto meet LWST goalsto meet LWST goals Increased economies of scaleIncreased economies of scale

Stretched rotors for moreStretched rotors for moreenergy captureenergy capture

Physics dictates that a largerPhysics dictates that a largermachine made out of the samemachine made out of the samematerials will be more flexiblematerials will be more flexible

More flexibility =More flexibility =More vibrations =More vibrations =More loads =More loads =More costMore cost

Controls may be the mostControls may be the mostimportant solution to reducingimportant solution to reducingcostcost

Boeing 747-200


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PreliminaryPreliminary StateState--space resultsspace results

306306

((--21%)21%)385385

BladeBlade--root flap fatigueroot flap fatigueDEL [DEL [kNmkNm]]

2525

((--40%)40%)4242

LowLow--speed shaft torquespeed shaft torquefatigue DEL [fatigue DEL [kNmkNm]]

15861586

((--30%)30%)22662266

Tower foreTower fore--aft fatigueaft fatigueDEL [DEL [kNmkNm]]

RMS pitch current [A]RMS pitch current [A]

15.515.514.914.9Max. pitch rate [deg/s]Max. pitch rate [deg/s]

.380.380.389.389RMS speed error [RPM]RMS speed error [RPM]

SymDynSymDyn StateState--SpaceSpaceControllerController

((SimulationSimulation))

Baseline PIBaseline PIControllerController

((SimulationSimulation))

Performance MeasurePerformance Measure

8686

((--32%)32%)126126

7.77.7

((--51%)51%)15.815.8

272272

((--53%)53%)578578

16.016.0

((--44%)44%)

28.828.8

9.49.413.713.7

.213.213.233.233

SymDynSymDyn StateState--SpaceSpaceControllerController

((Field TestField Test))

Baseline PIBaseline PIControllerController

((Field TestField Test))


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Questions and commentsQuestions and comments

Documents

Wind Turbine Electrical Systems