Wind Power Application – State of the Art

Hugh NguyenSupervisor Engineering – Resource Integration

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Outline1. About PSE2. PSE Wind Assets3. Wind Integration and Benefits4. Pacific Northwest Transmission Requirements

Transmission and wind characteristics5. Wind Power Application -- State of the Art:

TurbineForecastingTechnical challenges (i.e., modeling, VAR support, stability, etc.)

6. Wind Bright Future

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PSE - a Washington CompanyState’s oldest and largest utility

6,000 sq. miles

11 counties

1 million+ electric customers735,000 natural gas customersPublic Service Company with an obligation to serve

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PSE Wind Assets• 429 MW of capacity and counting

• Makes up 5% of PSE’s annual average load

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Relative Size of Wind Turbines

Vestas V80-1.8MW

Statue of Liberty

2-Story House2-Story House

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Wind Turbine Facts

Rotor Dia = 80 metersSwept Area = 5,026 m2

Rotation = 15.5 RPMGen Voltage = 690 VoltsCapacity = 1,800 kW

Nacelle Weight = 77 tonsRotor Weight = 41 tonsTower Weight = 105 tonsTotal Weight = 223 tons

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Inside a Wind Turbine

1. Hub controller 2. Pitch cylinder 3. Main shaft 4. Oil cooler 5. Gearbox 6. VMP-Top controller with converter 7. Mechanical disc brake 8. Service crane 9. Transformer 10. Blade hub 11. Blade bearing 12. Blade 13. Rotor lock system 14. Hydraulic system 15. Hydraulic clamp ring 16. Turntable 17. Machine foundation 18. Yaw gears 19. OptiSpeed™ generator 20. Air cooler for generator

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PSE Wind Integration

Wild HorseIntegrated in PSE’s balancing authority

Hopkins RidgeIntegrated in BPA’s balancing authority

Klondike IIIIntegrated in BPA’s balancing authority

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Managing Wind Variability

Utilize Mid-Columbia hydro generationRely on wind forecast for flexibilityUse load following flexibility at PSE hydro

Purchase needed reserves from other BA’sCall on combustion turbines to meet unexpected wind generation gapsRamp internal resourcesCurtail wind if truly necessary, as a last resource

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Wind BenefitsClean emission-free wind energy that reduces the impact on climate changeA federal wind power credit could be passed through to Puget Sound Energy customers.

The credit is a federal income tax benefit from PSE's ownership of wind power generating plants. If approved by the Washington Utilities and Transportation Commission, the wind credit will rise 28¢ and bring the total monthly credit to $1.68 for homes using 1,000 kwh/month.

Renewable Energy Credit (REC). PSE is monetizing these until 2011, and seeing market rates ~ $5/MwhJobs created and local economies benefit

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Power Type Legend

Hydro

Thermal

Gas Storage

Wind

PSE Existing Resources

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Hopkins Ridge Wind Project

Developed by Renewable Energy SystemsAll-in cost of $200 million in 2005150 MW38% capacity factor – YTD 2008Vestas Turbines

1.8 MW Capacity220 feet tall at hub320 feet to tip of blade

Project Site

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Wild Horse Wind ProjectDeveloped by Horizon Wind≈11 miles east of Ellensburg in Kittitas County, WashingtonShrub steppe habitat - primarily grazing land≈8-mile 230kV transmission line to PSE IP Line at new Wind Ridge Substation 230 MWCapacity factor 37% - YTD 2008

Private land owned by PSE≈5,400 acres (≈87 WTGs)≈1,280 acres (site access)

State land leased by PSEDNR ≈2,560 acres (≈31 WTGs)WDFW ≈640 acres (≈9 WTGs)

Five (5) transmission leasesAll-in cost of $380 million in 2006Commercial Operation Dec 22, 2006

Project Area

KittitasCounty

Project Site

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Wind Characteristics

Regulation and Load FollowingVariation will dictate the use of system reserves

Relying on wind during peak conditions is less than idealAccurate forecast into the hour is premiumUsually rich in remote locations therefore requiring more transmission to transfer to load center

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Wind Variability

Wind speed varies every hourForecast uncertaintySystem level plan for daily or weekly forecastSchedule for upcoming O&M activities

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Wind Variability

One Hour Period

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Voltage Control

Hopkins Ridge6 Hour Trace

August 10, 2006Varying Output

5 to 65 MWCollection Voltage

34.9 to 35.3 kVStable VARsSystem Voltage

123.9 to 126.3 kV

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Renewable Resource Strategy

Identify links between needs and available resourcesWashington Renewable Portfolio Standard requirements influence renewable acquisition Optimize development and deployment of resources based on their benefits to:

Electricity systemEnvironmentLocal economies

Develop/ Acquire smart planning tools that help integrate resource characteristics effectively

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Objectives

Determine performance characteristics for renewable technologyInvestigate how renewable distributed electricity generation can help address transmission constraints and serve loadsIdentify locations where renewable generation can effectively be integrated:

First, Look for weak elements in the system by simulating impacts from lost transmission or capacityThen, identify locations in system where new generation can provide grid reliability benefits

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Normal System Operation100 MW

50 MW

280 MW 187 MW

110 MW 40 Mvar

80 MW 30 Mvar

130 MW 40 Mvar

40 MW 20 Mvar

1.0

1.01 pu

1.04 pu1.04 pu

1.04 pu

0.9930 pu1.05 pu

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA A

MVA

A

MVA

A

MVA

67 MW

67 MW

33 MW 32 MW

57 MW 58 MW

21 MW

21 MW

66 MW 65 MW

11 MW

11 MW

23 MW

42 MW

43 MW 28 MW 29 MW

23 MW

23 MW

1

200 MW 0 Mvar

200 MW 0 Mvar

A

MVA

29 MW 28 MW

OneThree

Fo

Two

Five

Six Seven

23 MW

87%

A

MVA

82%

A

MVA

System does not have operation violations

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Abnormal Condition – A line is out100 MW

50 MW

280 MW 188 MW

110 MW 40 Mvar

80 MW 30 Mvar

130 MW 40 Mvar

40 MW 20 Mvar

1.00 pu

1.01 pu

1.04 pu1.04 pu

1.04 pu

0.9675 pu1.05 pu

A

MVA

A

MVA

A

MVA

A

MVAA

MVA

A

MVA 45 MW

45 MW

55 MW 53 MW

0 MW 0 MW

58 MW

56 MW

52 MW 51 MW

26 MW

25 MW

43 MW

36 MW

37 MW 24 MW 25 MW

30 MW

30 MW

150 MW

200 MW 0 Mvar

200 MW 0 Mvar

A

MVA

25 MW 24 MW

OneThree

Four

Two

Five

Six Seven

44 MW

83%A

MVA

83%A

MVA

95%A

MVA

156%A

MVA

Then this line getsoverloaded

(is a weak element)This is a serious problem for the

system

Planning Solutions:New line to bus 3

OR New generation

at bus 3

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Wind Resource Locations

Generally not heavily populated and far away from load centersOriginal plan for the area probably not intended for generation integrationAnd “transmission” in the area is usually weak

i.e., small conductors, limited capacity, and the system was designed to serve small native loads

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Getting Wind Resources Home

May require costly transmission upgradesComplex and usually involve lengthy negotiations with neighbor utilitiesPacific Northwest grid:

CongestedBPA manages for most part

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Transmission ConstraintsWind desperately needs transmission in the PNW

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GoldendaleGoldendale

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NW Paths & Seasonal Power Flow Directions

Summer Transfers

Winter Transfers

Constrained Transmission

Path

27 OLINDA

OLYMPIA

FAIRMONT

RAVER

MONROE

INGLEDOW

PAUL

OSTRANDER

MARION

MALIN

GRIZZLY

JOHN DAY

HANFORD

BELL

COULEE

NICOLA LANGDON

GARRISON

MIDPOINT

MICA

REVELSTOKE

SELKIRK

ASHE

TAFT

BIG EDDY MCNARY

MERIDIAN

KELLY LAKE

DUNSMUIR

BORAH

CHEEKYE

CRANBROOK

SUMMER LAKE

ROUND BUTTE

EDMONTON

ALLSTON DWORSHAK

ROUND MOUNTAIN

SCHULTZ

ALVEY

WILLISTON

VASEUX LK

TOWNSEND

P-1

P-2

P-8

P-11

P-9 P-7

P-6

P-4

P-3

P-5

P-10

Path Name & Rating:

P-1 -- Northwest-Canada: 3150 MW N-S; 2000 MW S-NP-2 -- West Cascades North: 10200 MW E-WP-3 -- Monroe-Echo Lake: 1200 MW N-SP-4 -- Raver-Paul: 2010 MW N-SP-5 -- North of Hanford: 3700 MW N-S P-6 -- Paul-Allston: 2500 MW N-SP-7 -- North of John Day: 8400 MWP-8 -- West Cascades South: 7000 MW E-WP-9 -- South of Allston: 2640 MW N-SP-10 -- West of McNary: 2980 MW E-WP-11 – West of Hatwai: 4300 MW E-W

Major Transmission Paths around Washington

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Proposed NW Transmission Projects

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Power System Basics

Three major power system componentsGeneration creates electric powerLoad consumes electric powerTransmission transmits electric power from generation to load centerDistribution distributes power to load

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Transmission and Distribution

Typical high voltage transmission voltages500, 345, 230, 161, 138 and 69 kV

Transmission tends to be a grid systemEach bus is typically supplied from two or more directions

Lower voltage lines are used for distributionTypical voltage of 12 kVtend to be radial

Transformers are used to change the voltage

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Ideal Vs. Real Power System Operation

Ideal Generators supply energy and loads remove energyHas no transmission constraints

RealDifferent operating control centers impose different supply and demand constraintsTransmission system imposes constraints.

Line outage dictates the flowability of power

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Power System Analysis

Major ChallengesTurbine designPlant designShort project lead timesModeling complexity

Harmonics Capacitor Switching TransientsFrequency responsePhenomena dealing with machine interactions and stabilityOthers not yet known

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Turbine Design

Fixed Speed DesignEarly adoption by industryInduction generatorSimple, Robust, ProvenMax efficiency at one wind speedFluctuating voltage and power to the gridUncontrollable reactive powerHigh structural stresses in turbine and tower

Variable Speed DesignDominant design todayInduction generatorHigh efficiency over broad range of wind speedGenerator torque fairly constantImproved power qualityReduced mechanical stressComplex power electronics

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Induction Generator

Asynchronous generator allows slip to keep rotor speed close to synchronous speedPitch system used to control or limit speedMinimizes gust loads on turbine structureRequires variable rotor current, or double-feed, to capture power from speed variation

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Standard Generator Control

Type A: Simple Induction GeneratorType B: Induction Generator with Variable Rotor ResistanceType C: Doubly Fed RotorType D: Full Converter

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Grid Interconnection Issues

Wind VariabilityDaily or WeeklyHourly

Voltage ControlLow Voltage Ride-ThroughReactive PowerPower quality

System HarmonicsTransients

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Power Quality Distortion Frequencies

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Harmonics

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Switching Transients

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Low Voltage Ride Through

Older wind turbines without external devices would disconnect from grid on low-voltage event

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Low Voltage Ride Through

Contemporary units can tolerate low-voltage, or even zero voltage with external devices (D-VAR), and stay online through event

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Simplified 1-Line Diagram*

230 kV stepped down to 34.5 kVAnd further stepped down to 690 V at the turbines

* Taken from RAI’s Harmonics Measurements Reports

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Example of Harmonic AnalysisHarmonic resonances due to combination of

Substation capacitor banksReactance from system equivalent impedanceTransmission line and transformersSystem collector cables.

Measurements revealedSome issues were found upon reviewing a broad spectrum of harmonic currents Harmonic currents existed and confirmed based on data recorded at turbines terminals.

Effective filtering suppressed harmonic currents well below limits

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Simulations – Existing System230 kV system

normally open 34.5 k Tie line

HV Reactor

HV

OH

Lin

e

CAP21 CAP23CAP22CAP13CAP12CAP11

Sub Trans 1Substation HV cap bank Sub Trans 2

Bar 2

Wild Horse

Wind Ridge

Bar 1Trans Delta 1 Trans Delta 2

DIg

SILE

NT

3.00 5.00 7.00 9.00 11.0 13.0 15.0 17.0 19.0 21.0 23.0 [-]

16.00

12.00

8.00

4.00

0.00

Bar 1: Harmonic Distortion A in %Bar 1: Harmonic Distortion B in %Bar 1: Harmonic Distortion C in %

Distortion Bar1

Date: 4/11/2007

Annex: /2

DIg

SILE

NT

Harmonic currents out of

bandwidth

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230 kV system

normally open 34.5 k Tie line

HV Reactor

HV

OH

Lin

e

CAP21 CAP23CAP22CAP13CAP12CAP11

Sub Trans 1Substation HV cap bank Sub Trans 2

Bar 2

Wild Horse

Wind Ridge

Bar 1Trans Delta 1 Trans Delta 2

DIg

SILE

NT

Simulations – Effective Filtering

34.5 kV Cap Banks used as Filters

Harmonic currents within

bandwidth

3.00 5.00 7.00 9.00 11.0 13.0 15.0 17.0 19.0 21.0 23.0 [-]

16.00

12.00

8.00

4.00

0.00

Bar 1: Harmonic Distortion A in %Bar 1: Harmonic Distortion B in %Bar 1: Harmonic Distortion C in %

Distortion Bar1

Date: 4/11/2007

Annex: /2

DIg

SILE

NT

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Wind Bright FutureMarket Share

Wind is a mature reliable technologyPTCs and RPS standards will drive additional wind development throughout the U.S.Units are getting bigger and more complex

Grid Interconnection Increased use of wind turbines and external devices for voltage stability and VAR compensationImproved LVRT capability with D-VARCan operate with leading and lagging power factors

Hurdles need to go overTransmission limitationsAdditional dispatchable generationSystem reliability