lessons learned from wind integration studies

8/19/2019 LESSONS LEARNED FROM WIND INTEGRATION STUDIES

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Tomas AckermannRena Kuwaha a

AEMO WIND IN EGRA ION WP4(A)

LESSONS LEARNED FROM INTERNATIONALWIND INTEGRATION STUDIES

Energynau ics GmbH, GermanyCommissioned by Aus ralian Energy Marke Opera or


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16 November 2011

Energynau ics GmbHMühls rasse 5163225 Langen, Germany

Phone: +49 (0)151 226 619 55

.ackermann@energynau ics.comh p://www.energynau ics.com

Aus ralian Energy Marke Opera orLevel 22, 530 Collins S , Melbourne, Vic oria 3000, Aus raliahtp://www.aemo.com.au/

© [2011] - All righ s reserved.

Cover Design: © energynau ics

http://www.aemo.com.au/http://www.aemo.com.au/


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htp://www.energy nautics .com 3

EXECU IVE SUMMARY

EXECU IVE SUMMARY

Te Aus ralian Energy Marke Opera or (AEMO) is expec ing a signican increase in windpower genera ion in he Aus ralian Na ional Elec rici y Marke (NEM). o accura ely iden i y

issues ha migh affec he NEM and adequa ely deal wi h he in egra ion o wind power,AEMO solici ed assis ance rom a number o in erna ional exper s o research and repor onin erna ional experiences and work being done on wind power in egra ion. Te work wasdivided in o hree work packages, o summarise and pu in o he con ex o he NEM:

1) experiences in wind in egra ion across he world (WP1);2) he implica ions on grid codes (WP2); and3) he approaches used o assess he impac o increasing wind power genera ion on

power sys em opera ions (WP4(A)).

energynau ics was selec ed o carry ou he hird ask (Work Package 4(A)), o review experiencesrepor ed in various wind in egra ion s udies, wi h a specic ocus on echnical power sys em issues.

Issues ha are considered major challenges or high pene ra ion o wind power in a power sys emvary rom region o region. Some o hem may affec he securi y o he en ire sys em while someo hem may only affec local opera ion. In his con ex , he objec ives o Work Package 4(A) are o:

• assess he key issues rea ed in wind in egra ion s udies worldwide;• summarise he me hodologies and general resul s o wind in egra ion s udies; and• repor on key lessons learned.

Tis work package is also o de ermine in conjunc ion wi h AEMO which o he key resul sand lessons are relevan o he NEM or considera ion in u ure wind in egra ion s udies.

A. echnical issues ypically considered

A broad review o wind in egra ion s udies around he world iden ied he issues commonlyinves iga ed, as lis ed in Figure 1 below.

System adequacy System security System operation

Capaci y credicon ribu iono genera ionadequacy

Grid planning

Sys em s abili ycharac eris ics

Iner ia andrequency

response

Balancingme hodologyand reserve

requiremen s

Vol age con rol,real- ime

moni oringand ne workmanagemen

Faul currencon ribu ion

Figure 1: Overview o echnical issues considered by wind in egra ion s udies. Source: energynau ics


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Capaci y credio wind power

ransmission planningor renewables

in egra ion

EXECU IVE SUMMARY

Sys em adequacy: As wind power is added o a genera ion mix i may in roduce an ex ralevel o uncer ain y in he abili y o he power supply o mee load. Tis is par icularly re-levan or power sys ems where he peak load is expec ed o increase a he same ime asconven ional power plan s o be replaced by in ermi en renewable power genera ion. I

is impor an ha a reasonable es ima ion o he capaci y credi o wind power is made soha adequa e genera ion capaci y can be secured o mee he u ure load. Fur hermore,because wind power plan s are ofen buil in remo e areas, grid ex ension and/or rein orce-men s are also ofen required. Since he lead ime or cons ruc ion o wind power plan s ismuch shor er han ha o ransmission lines and conven ional power plan s, i becomes cri i-cal ha grid augmen a ions are planned wi h signican oresigh in o poli ical and indus ryin en ions or he developmen o renewable energy based genera ion.

Sys em securi y:Like all new genera ion, he addi ion o wind power may affec sys ems abili y and requency response charac eris ics. Te impac depends on he loca ion, size,connec ion vol age level, and echnical per ormance o he wind power plan . Mos wind

urbines use conver ers which decouple hem rom he grid, so direc impac on ro or angles abili y is negligible. However, i he urbines displace signican propor ions o synchro-nous genera ion hey may have an indirec impac . Te mos signican impac s are seen

ollowing a vol age dip, which can cause wind power plan s o disconnec i hey do no havelow vol age aul ride- hrough (FR ) capabili y (which is nowadays manda ed by many GridCodes around he world). When wind power genera ion is high and conven ional powergenera ion is displaced, he predominan oscilla ory mode may be changed, or minimumsys em iner ia migh be required o con rol requency excursions and main ain ro or angle

s abili y. o ensure good securi y, he con ribu ion ha wind power plan s make o aulcurren s mus be assessed o ensure ha he aul levels are adequa e or he proper unc-

ioning o pro ec ion equipmen and HVDC devices. Depending on he nding, his mayrequire redesigning he pro ec ion scheme.

Sys em opera ion: Wind power ou pu depends on he wind speed (and wea her) which is con-s an ly changing. Wind orecas ing helps o reduce he uncer ain y inheren in na ure and give acer ain level o predic abili y or shor - erm planning and he genera ion dispa ch process. Fore-cas ing sys ems have improved signican ly over he pas years, however, orecas errors s ill exis ,

and may impac balancing and he requiremen s or reserves. While mos sys ems are designedo handle some degree o uncer ain y, i is pruden o assess he reserve requiremen s wi h wind

power added o he sys em and make sure ha he balancing procedures in place can manage headdi ional level o uncer ain y. Many s udies on wind in egra ion ound ha high pene ra ion ra esare likely o increase bo h secondary and er iary reserve requiremen s1, even i orecas errorsare minimised. Te impac on secondary reserve is less compared o he la er, due o he ac ha

orecas errors ge smaller he closer o dispa ch. In some cases, especially in shor er ime rames,price vola ili y in he power marke may also cause severe impac s on reserve requiremen s.

1 Te erminology or reserves varies be ween coun ries. In his repor , secondary reserve corresponds oregula ion reserve, dened as reserves made available in 5-15 minu es. er iary reserve corresponds o dis-pa ch or load ollowing reserve, available in 15-30 minu es and shor - erm capaci y reserve, available in 30minu es o some hours (and up o a day).

Faul ride- hroughand vol age supporcapabili y

Wind power plancon ribu ion o

aul levels

Sys em iner ia and

requency con rol

Reserve requiremen s

Vol age con rol


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EXECU IVE SUMMARY

B. Measures ha suppor wind in egra ion

Several solu ions are sugges ed o deal wi h he echnical issues inves iga ed. Some o hecommon measures are lis ed below:

• Aggrega ing wind power plan s over a larger area o reduce he variabili y o windpower ou pu and improve he capaci y credi . Tis also improves he accuracy o windpower ou pu orecas ing, here ore reducing he requiremen s on balancing reserves.

• Augmen ing he grido increase access o wind power resources and share balancingresources over a wider area. Tis includes ransmission rein orcemen s o relieveconges ion, s reng hening o ie-lines o acili a e power exchange be ween regionsand ex ending he ne work o provide access o areas wi h excellen wind resources.Since i akes ime o build ransmission asse s however, op imising he use o exis ingin ras ruc ure using dynamic line ra ing, Flexible Al erna ing Curren ransmission Sys em(FAC S) devices and phase shifing rans ormers are sugges ed as a possible in ermedia emeasure.

• Implemen ing opera ion cons rain s o secure minimum con ingency and balancingreserves, sys em iner ia, vol age suppor , aul curren level and dynamic s abili y, so hasynchronous genera ors can adequa ely provide hese services. However, modern windpower plan s can also provide many o hese services and hey should be included in heGrid Code i no already he case.

• Real- ime ne work managemen based on wind power ou pu can acili a e heransi ion rom he curren sys em o he u ure one. A good example is he con rol cen reor renewable energies (CECRE) in Spain and Por ugal, where aggrega ed con rol o wind

power plan s and o her renewable energy genera ion such as solar power are used ocalcula e dynamic opera ing cons rain s.

Some s udies evalua e he effec iveness o hese measures, hrough marke simula ions insimple nancial and environmen al erms, such as he likely impac on marke per ormance

(cos s and price vola ili y), and he resul ing CO2 emissions. In some s udies opera ion effici-ency is measured by ne work losses, he amoun o unused (or cur ailed) wind energy, and

he cos impac s ha high wind power genera ion has on he per ormance requiremen s oconven ional power plan s.

C. Relevance o NEM

Given he charac eris ics o he NEM and he expec ed wind power developmen in heNEM area, i was iden ied ha some echnical issues are likely o be more impor an hano hers. Figure 2 summarises he echnical issues ha have highes signicance or u ure windin egra ion s udies in he NEM.


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EXECU IVE SUMMARY

op priori y issues

Fundamen al issues ha need ur her analysis

Developmen ocomprehensive

renewable energyscenarios

Use a sys em-wideapproach

Review o gridplanning approach

Power balanceluc ua ions &

requencyregula ion

Modelling WPPsuppor ovol age and

requencydynamic issues

Frequencys abili y

ransiens abili y

Developmen o comprehensive renewable energy scenarios

In par icular, discussions wi h various ransmission sys ems opera ors indica ed ha solar PVgrow h should also be considered in renewable in egra ion s udies. For example, in Germanyand I aly, he grow h o solar PV has been so rapid ha some giga-wa s are connec ed in he

dis ribu ion ne works, and considerable challenges have been observed affec ing vol ages abili y and balancing issues similar o hose o wind.

Te Aus ralian NEM only has a ew hundred megawa s o solar PV power ins alled o da e,however, policy suppor and developmen o larger scale solar PV plan s in he planningpipeline could mean as expansion in a shor ime rame. Tis could raise challenges in dis-

ribu ion and possibly ransmission levels and i is recommended ha solar PV is included inany u ure renewable energy in egra ion s udies or he NEM area.

Use a sys em-wide approach

I is recommended ha genera ion adequacy, balancing and dynamic s abili y impac s owind power are evalua ed across he NEM ra her han or individual s a es. Even houghin erconnec ions be ween s a es are curren ly limi ed, here are bene s ha sys em-wides udies can bring in cer ain si ua ions. For example, in he case o a s orm ron hi ing hecoas line o Sou h Aus ralia, here migh be he risk ha a large amoun o wind power plan sin he s a e are shu down consecu ively wi hin a ew hours due o ex remely high windspeeds exceeding he sa e opera ing limi s o he wind urbines. In his si ua ion i may bemore benecial o allow impor o reserve genera ion rom ano her s a e ra her han osecure i locally.

Figure 2: Overview o opics ha should be considered by he NEM. Source: energynau ics

Include solar PVin u ure s udies

Inves iga e hebene s o asys em-wideapproach


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Renewables in egra ionas primary objec ive

EXECU IVE SUMMARY

Review o grid planning approach

Te grid planning approach in he NEM is also impor an in in egra ing wind energy. Wi hhe curren approach, much o he wind power resources ha are available a remo e areas

will no be able o access he grid because hey are likely o require grid ex ensions whichare deemed more expensive han building conven ional genera ion closer o he demandcen re. However, in o her coun ries and regions grid augmen a ions are considered in abroader policy con ex , wi h long- erm securi y o supply and renewables in egra ion as heprimary objec ive. Unless he way he NEM plans grid augmen a ion is revised, long- ermsecuri y o supply may be compromised.

Modelling wind power plan suppor capabili ies

I is impor an ha he abili y o he wind power plan o suppor vol age and requency aremodelled appropria ely when assessing requency response and ransien s abili y aspec s.Some s udies per ormed in he NEM assume he “wors case” scenario, ha wind powergenera ion is expanded using old urbine echnology wi hou vol age suppor capabili ies.Tis is an unrealis ic assump ion, as he echnology is developing owards providing moreand more grid suppor capabili y op ions. Many urbines can now offer no only FR capa-bili ies bu requency con rol and vir ual iner ia capabili ies. Tere ore, i is recommended

ha a sys em-wide s udy is per ormed wi h a varie y o urbine echnology capabili ies, ando es i he curren Grid Code is sufficien or mixed urbines scenarios.

Balancing and requency regula ion

Compared o many o her power sys ems which se le genera ion bidding in a day-aheadmarke and manage he balancing wi h ancillary services, balancing issues in he NEM will beeasier o deal wi h since i has a 5-minu e dispa ch marke . However, his also indica es ha

he marke prices will be subjec o higher vola ili y wi h low prices resul ing rom high windpower genera ion and high prices rom momen s o low wind power genera ion. Tere ore,i is impor an o inves iga e he impac on long- erm price in marke s or high pene ra iono wind power.

O her issues

O her issues ha may be inves iga ed i he par icular circums ances require i , are small-signal s abili y ( or example, o es power sys em s abiliser capabili y o wind power plan s),sub-synchronous in erac ion (i series-compensa ed lines are in roduced o connec remo ewind power plan s) and he impac o wind power plan con ribu ion o shor -circui aulcurren , especially or weakly connec ed par s o he ne work and o ensure correc opera-

ion o HVDC devices.

Wind urbineechnology or

grid suppor

Marke pricevola ili y


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CON EN S

CON EN S

EXECU IVE SUMMARY .........................................................................................................3

ABBREVIA ED ERMS ...........................................................................................................9

GLOSSARY............................................................................................................................10

1. IN RODUC ION ............................................................................................................15

2. S UDY APPROACH ........................................................................................................17

3. KEY ECHNICAL ISSUES ................................................................................................283.1. Genera ion adequacy .........................................................................................................................283.2. Grid planning ........................................................................................................................................353.3. S eady-s a e analysis ...........................................................................................................................373.4. Power sys em securi y ........................................................................................................................413.5. Balancing ( requency regula ion, dispa ch, and shor - erm capaci y reserve) .................53

4. KEY ECHNICAL SOLU IONS: MEASURES HA SUPPOR WIND IN EGRA ION ...654.1. Wind urbine echnical requiremen s ...........................................................................................654.2. Use o exibili y mechanisms o suppor wind power in egra ion ......................................67

5. EVALUA ION OF ECHNICAL IMPAC S WI H SYS EM PERFORMANCE .............715.1. Wind energy cur ailmen ..................................................................................................................715.2. CO2 emission .........................................................................................................................................735.3. Change in power ow charac eris ics on sys em losses ...........................................................73

6. CONCLUSIONS ................................................................................................................75

7. BIBLIOGRAPHY ...............................................................................................................84

8. APPENDICES ....................................................................................................................968.1. Appendix 1: Summary o selec ed wind in egra ion s udies reviewed (non-NEM s udies) ....968.2. Appendix 2: Summary o selec ed wind in egra ion s udies in he NEM .................................. 106


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ABBREVIA ED ERMS

AEMO Aus ralian Energy Marke Opera or

CECRE Con rol Cen re o Renewable EnergiesCREZ Compe i ive Renewable Energy ZoneDFIG Doubly Fed Induc ion Genera orDSM Demand-side ManagemenDSO Dis ribu ion Sys em Opera orEN SO-E European Ne work o ransmission Sys em Opera ors or Elec rici yERCO Elec rici y Reliabili y Council o exasFAC S Flexible Al erna ing Curren ransmission Sys emFCAS Frequency Con rol Ancillary ServicesFR Faul ride- hroughFSFC Full Scale Frequency Conver ersHVAC High Vol age Al erna ing CurrenHVDC High Vol age Direc CurrenIMO Independen Marke Opera orISO Independen Sys em Opera orLVR Low vol age ride- hroughNEM Na ional Elec rici y MarkeN NDP Na ional ransmission Ne work Developmen PlanNYISO New York Independen Sys em Opera or

NYSERDA New York S a e Energy Research and Developmen Au hori yOPF Op imal Power FlowPSS Power Sys em S abiliserPUC Public U ili y Commission o exasRES-E Elec rici y rom Renewable Energy SourceSCIG Squirrel Cage Induc ion Genera orSSCI Sub Synchronous Con rol In erac ionSSI Sub Synchronous In erac ionSSR Sub Synchronous Resonance

SS I Sub Synchronous orsional In erac ionSVC S a ic VAR Compensa or

SO ransmission Sys em Opera orYNDP en Year Ne work Developmen Plan

UPS Unin errup ible Power SupplyVAR Vol age‐ampere Reac iveWPP Wind Power PlanW G Wind urbine Genera or

ABBREVIA ED ERMS


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ASYNCHRONOUS

GENERA OR

An asynchronous or induc ion genera or is a ype o AC elec-

rical genera or ha uses he principles o induc ion mo ors oproduce power.

CAPACI Y CREDI See CAPACI Y VALUE

CAPACI Y VALUE Also deno ed as CAPACI Y CREDI . Te amoun o conven i-onal genera ion ha can be replaced by wind power capaci ywhile main aining exis ing level o supply securi y.

DEL A CON ROL Fas secondary reserve made available by rs down regula inghe wind urbine by a cer ain del a applying pi ch con rol, which

can hen be used o very as up-regula e he wind urbine ineeded.

DYNAMIC VOL AGECON ROL

Con inuous vol age con rol by differen genera ion resources.

FIRM GENERA ION/SUPPLY

Firm genera ion is he percen age o a genera or’s maximumcapaci y ha is coun ed oward calcula ion o he reserve margin.

GENERA IONRESERVE

Reserves o mi iga e a con ingency, which is dened as heunexpec ed ailure or ou age o a sys em componen such asa genera or, ransmission line, circui breaker, swi ch, or o herelec rical elemen .

HARMONICDIS OR ION

Harmonic dis or ion is ound in bo h he vol age and he currenwave orm. Mos curren dis or ion is genera ed by elec ronicloads, also called non-linear loads. As he curren dis or ion is

conduc ed hrough he normal sys em wiring, i crea es vol agedis or ion according o Ohm's Law.

INS AN ANEOUSMAXIMUM PENE-

RA ION RA E

Te ins an aneous maximum pene ra ion ra e o wind power iscalcula ed as he ins alled wind capaci y divided by he off-peakdemand.

IN ERCONNEC ORS In erconnec ors are ransmission links (e.g. ie-line or rans ormer)which connec wo con rol areas.

GLOSSARY

GLOSSARY


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MAXIMUM FAUL Larges possible single loss o genera ing capaci y resul ing romei her orced ou age o genera ion or ransmission equipmen .

MINIMUM SYS EM

INER IA

Te minimum sys em iner ial cons rain is analogous o imposing

a cons rain whereby a minimum number o synchronous gene-ra ors mus be online a all imes (“mus run uni s”).

N1- SI UA ION Te N-1 cri erion is a rule according o which elemen s remai-ning in opera ion afer ailure o a single ne work elemen (suchas ransmission line/ rans ormer or genera ing uni , or in cer ainins ances a bus bar) mus be capable o accommoda ing hechange o ows in he ne work caused by ha single ailure.

POWER FLOWSIMULA IONS

Power ow simula ions involve numerical analysis applied o apower sys em. I usually uses simplied no a ion such as a one-line diagram and per-uni sys em, and ocuses on various ormso AC power (ie: vol ages, vol age angles, real power and reac-

ive power). A number o sofware power ow simula ion oolsexis such as DIgSILEN PowerFac ory and Siemens PSS/E.

POWER VOL AGE/REAC IVE POWERVOL AGE

S eady-s a e analysis o vol age s abili y limi s is done by calcu-la ing he ac ive power versus vol age (PV) curves and reac ivepower versus vol age (QV) curves or dispa ches wi h zero

exchange over in erconnec or.

PRIMARY,SECONDARYAND ER IARYRESERVES

Primary reserve is o mi iga e a con ingency, which is dened ashe unexpec ed ailure or ou age o a sys em componen such

as a genera or, ransmission line, circui breaker, swi ch, or o herelec rical elemen .

Secondary reserve is an amoun o reserve ha is sufficien oallow or normal regula ing margins. Regula ing reserves, which

are responsive o AGC, are he primary ool or main aining herequency.

er iary reserve: Capabili y above rm sys em demand requi-red or regula ion, load orecas ing error, orced and scheduledequipmen ou ages, and local area pro ec ion. Tis ype oreserve consis s o bo h genera ion synchronized o he gridand genera ion ha can be synchronized and made capable oserving load wi hin a specied period o ime.

GLOSSARY


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SYNCHRONOUSGENERA OR

Synchronous genera ors are capable o conver ing mechanicalenergy in o elec rici y when opera ed as a genera or and powermechanics when opera ed as a mo or. Synchronous genera orsare used in he majori y o hydroelec ric and hermoelec ric

plan s.

AP CHANGERS A rans ormer ap is a connec ion poin along a rans ormer win-ding ha allows a cer ain number o urns o be selec ed. Tismeans ha a rans ormer wi h variable urns ra io is produced,enabling vol age regula ion o he ou pu . Te ap selec ion ismade via a ap changer mechanism.

RANSIENOVERVOL AGE

ransien overvol ages are brie , high- requency increases invol age on AC mains.

RANSIENS ABILI Y

Te abili y o an elec ric sys em o main ain synchronism be -ween i s par s when subjec ed o a dis urbance o speciedseveri y and o regain a s a e o equilibrium ollowing hadis urbance.

UNI Y POWERFAC ORS

Te power ac or o an AC elec ric power sys em is dened ashe ra io o he real power owing o he load over he apparen

power in he circui , and is a dimensionless number be ween 0

and 1 ( requen ly expressed as a percen age, e.g. 0.5 p = 50% p ).

GLOSSARY


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IN RODUC ION

1 1


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IN RODUC ION

1. IN RODUC ION

Te use o wind power or elec rici y genera ion is growing in many places around he world.Coun ries such as Denmark, Germany and Spain deal wi h a high pene ra ion o wind power

already oday and are leading in heir in egra ion o he grid. O her coun ries which areshowing s rong grow h and signican research ac ivi ies are Ireland, UK, Scandinavia, Sou hAus ralia and he USA. Al hough he curren ra e o pene ra ion may be low, wind power isgrowing rapidly in China and India, and should be kep in mind.

Based on planning s udies conduc ed by AEMO, wind power produc ion is predic ed ogrow ur her in Aus ralia. Tis is due o a combina ion o ac ors, namely he governmen ‘sgoal o achieve 20% o elec ric energy supply rom renewables by 2020, he in roduc iono carbon ax, necessi y o build more supply o ca er or rising demand, and alling cos s obuilding wind power plan s which is making he inves men more a rac ive.

According o he la es Na ional ransmission Ne work Developmen Plan (N NDP) pub-lished by AEMO in December 2010, he NEM could see up o 5,480 MW o wind power by2020, wi h 2,177 MW in Sou h Aus ralia and 1,298 MW in asmania (1).

Like mos power sys ems, he NEM is designed o deliver elec rici y rom large-scale powerplan s wi h con rollable ou pu s o large load cen res loca ed around he coun ry. Whenin ermi en power sources such as wind power are in roduced in large quan i ies, his mayimpac cer ain exis ing regula ory, echnical and marke aspec s.

o gain a be er unders anding o he possible impac s o increasing wind pene ra ion in heNEM, AEMO con rac ed energynau ics o inves iga e how o her sys em opera ors around

he world approach he uncer ain y o possible wind in egra ion, in par icular, regardingechnical issues rela ed o power sys em opera ion.

echnical issues are ypically inves iga ed using power sys em s udies based on simula ionmodels o he power sys em in ques ion, considering he expec ed u ure developmen , orins ance u ure wind power ins alla ions. Te de ails o he simula ion model as well as he

scenarios vary depending on he echnical issues o be inves iga ed.

o iden i y he relevan echnical issues and possible me hods o inves iga e hem, as wellheir relevance o he NEM con ex , energynau ics has reviewed selec ed power sys em s u-

dies per ormed by differen ransmission Sys em Opera ors ( SOs) and similar organisa-ions around he world. Based on he review ndings, his repor develops key sugges ionsor possible similar s udies o be conduc ed by AEMO in he near u ure.

Tis repor (corresponding o work package 4(A)) orms par o heAEMO Wind In egra-ion S udy: In erna ional Experience, oge her wi h work packages 1 and 2, which cover

general experience and grid codes or wind in egra ion around he world respec ively. o-ge her hese s udies can be used o ormula e u ure wind in egra ion s udies or he NEM.

1


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S UDY APPROACH

2 2


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S UDY APPROACH

2. S UDY APPROACH

A. Overview o NEM

In Aus ralia, he Na ional Elec rici y Marke (NEM) is expec ing signican grow h in windpower genera ion. According o he la es gures rom he N NDP2, up o 5,480 MW owind is expec ed by 2020 predominan ly in sou hern regions covering he s a es o asma-nia ( AS), Vic oria (VIC) and Sou h Aus ralia (SA).

Since he geographic loca ions where wind power developmen is expec ed are remo erom major demand cen res (Figure 3), i is expec ed ha much o he energy will have o

ow hrough he high vol age ransmission ne work. Te ransmission sys em o he NEMcovers a very large dis ance and has rela ively weak in erconnec ion be ween s a es.

2 N NDP is he Na ional ransmission Ne work Developmen Plan published on a yearly base by AEMO. Tela es version is available on:h p://www.aemo.com.au/planning/n ndp.h ml

QLD

TAS

NSW

VIC

SA

Max. Demand: 10,012 MW

Total Generation: 13,855 MW





Max. Demand: 1,694 M

Total Generation: 2,883 M



672 MW

1,298 MW

3,200 MW

478 MW

594 MW

580 MW

680 MW* 1,900 MW

max. interconnector transfer capacitytheoretical max. interconnector transfer capacity

areas with high wind potential

NEM

major demand centres

*

Figure 3: Map o in erconnec ed regions o he NEM, wi h highligh ed regionso expec ed wind developmen and demand cen res. Modied rom (1)

2

http://www.aemo.com.au/planning/ntndp.htmlhttp://www.aemo.com.au/planning/ntndp.html


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In he s a es where large wind power developmen is expec ed (SA and VIC), he high vol ageransmission sys em will be subjec o ex remely high pene ra ion ra es. In ac , he ins an a-

neous maximum pene ra ion ra e3 in Sou h Aus ralia is already oday one o he highes inhe world or weakly in erconnec ed ne work areas, wi h over 80% ins an pene ra ion level

(wi hou considering in erconnec or ow) observed. Tis can be seen in able 1, where heins an aneous maximum pene ra ion wi h and wi hou in erconnec ors are compared orhe s a es wi hin he NEM and a number o selec ed power sys ems which are known o be

almos island sys ems wi h high pene ra ion o wind power genera ion. As i s ands in 2011,he ins an aneous maximum pene ra ion o wind power in Sou h Aus ralia is comparable oha experienced in he in erconnec ed power sys em o Ireland and Nor hern Ireland.

Year Sys em4Ins alled

windcapaci y

(MW)

O -peakdemand

(MW)

heore icalins an aneous

maximumpene ra ion

wi houin erconnec or5

heore icalins an aneousmaximum

pene ra ion wi hmaximum expor6

2 0 1 1

SA 1,019 859 119%(observed: >80%)71%

(observed: 54%)

AS 223 776 29%(observed: 17%)16%

(observed: 10%)

VIC 531 3,718 14%

(observed: 8%)

7%

(observed: 6%)

NSW 186 5,739 3% 2%

QLD 12 4,371 0% 0%

2 0 2 0

SA 2,177 1,247 175% 105%

AS 1,298 948 137% 84%

VIC 1,390 5,062 27% 14%

NSW 536 6,935 8% 5%

QLD 79 6,918 1% 1%

3 Te ins an aneous maximum pene ra ion ra e o wind power is calcula ed as he ins alled wind capaci ydivided by he off-peak demand.

4 In orma ion corresponding o he NEM was aken rom (122) or hrough correspondence wi h AEMO.

5 Calcula ed values: Ins alled wind capaci y / Off-peak demand6 Calcula ed values: Ins alled wind capaci y / (Off-peak demand + Maximum expor capaci y)

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Year Sys em4Ins alled

windcapaci y

(MW)

O -peakdemand

(MW)


maximumpene ra ion

wi houin erconnec or5


maximumpene ra ion wi h

maximum expor6

2 0 1 1

All Island7 1,8898 1,6649 114% 108%

IberianPeninsula 24,378

10 19,20511 127% 118%

ERCO 12 9,50013 22,42614 42% 41%

Québec 67515 19,14316 4% 2%

2 0 2 0

All Island 5,96217 1,678 355% 264%

IberianPeninsula 38,000

1819,205 198% 184%

ERCO 19,50019 22,426 87% 69%

Québec 4,000 19,143 21% 14%

Wi hou any subs an ial plans or increasing he in erconnec or capaci y, he heore icalmaximum pene ra ion ra es in asmania and Sou h Aus ralia will reach levels comparable o

hose o he Iberian Peninsula20 by 2020, where concre e plans already exis or increasinghe in erconnec or rans er capabili y. While here are some en a ive plans in he NEM o

enhance he in erconnec ion be ween s a es ( able 2), wind power pene ra ion levels inselec ed s a es will be some o he highes in he world.

7 All Island re ers o he in erconnec ed power sys em o Ireland and Nor hern Island.8 Source: h p://www.iwea.com/index.c m/page/barchar(Accessed 26/9/2011)9 Source: h p://www.eirgrid.com/media/ ransmission%20Forecas %20S a emen %202011-2017-web%20version2.pd

10 Figures a end o 2010 according o GWEC:h p://www.gwec.ne /index.php?id=9 (Accessed 26/9/2011)11 Corresponding o 24/4/2011, RED ELEC RICA:h p://www.ree.es/ingles/operacion/curvas_demanda.asp and

REN:h p://www.cen rodein ormacao.ren.p /EN/In ormacaoExploracao/Pages/DiagramadeCargadaRN .aspx12 ERCO (Elec rici y Reliabili y Council o exas) re ers o he in erconnec ed sys em o exas, USA.13 Source: h p://www.erco .com/con en /news/presen a ions/2011/ERCO %20Quick%20Fac s%20-%20March%202011.pd 14 According o he Ancillary Services Requiremen Repor by GE Energy (70) Page 3-28.15 Source: h p://www.hydroquebec.com/genera ion/index.h ml16 Peak: 38,286 MW according o Annual Repor 2010 (h p://www.hydroquebec.com/publica ions/en/annual_

repor /pd /rappor -annuel-2010.pd ), (110) es ima es minimum load o be hal o maximum, here ore38,286/2 = 19,143 MW.

17 4350 MW in Ireland + 1012 MW onshore + 600 MW offshore wind in Nor hern Ireland.Source:h p://www.eirgrid.com/media/GCS%202011-2020%20as%20published%2022%20Dec.pd

18 Source: h p://www.gwec.ne /index.php?id=131 (Accessed 26/9/2011)

19 Source: h p://www.seco.cpa.s a e. x.us/re_rps-portolio.h m (Accessed 26/9/2011)20 Iberian Peninsula re ers o he in erconnec ed region o Spain and Por ugal.

able 1: Ins alled wind power capaci y and pene ra ion wi h and wi hou in ercon-nec ors or he NEM and some selec ed sys ems. Source: Various, see oo no es.

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2

http://www.iwea.com/index.cfm/page/barcharthttp://www.eirgrid.com/media/Transmission%20Forecast%20Statement%202011-2017-web%20version2.pdfhttp://www.gwec.net/index.php?id=9http://www.ree.es/ingles/operacion/curvas_demanda.asphttp://www.centrodeinformacao.ren.pt/EN/InformacaoExploracao/Pages/DiagramadeCargadaRNT.aspxhttp://www.ercot.com/content/news/presentations/2011/ERCOT%20Quick%20Facts%20-%20March%202011.pdfhttp://www.hydroquebec.com/generation/index.htmlhttp://www.hydroquebec.com/publications/en/annual_report/pdf/rapport-annuel-2010.pdfhttp://www.hydroquebec.com/publications/en/annual_report/pdf/rapport-annuel-2010.pdfhttp://www.eirgrid.com/media/GCS%202011-2020%20as%20published%2022%20Dec.pdfhttp://www.gwec.net/index.php?id=131http://www.seco.cpa.state.tx.us/re_rps-portfolio.htmhttp://www.seco.cpa.state.tx.us/re_rps-portfolio.htmhttp://www.gwec.net/index.php?id=131http://www.eirgrid.com/media/GCS%202011-2020%20as%20published%2022%20Dec.pdfhttp://www.hydroquebec.com/publications/en/annual_report/pdf/rapport-annuel-2010.pdfhttp://www.hydroquebec.com/publications/en/annual_report/pdf/rapport-annuel-2010.pdfhttp://www.hydroquebec.com/generation/index.htmlhttp://www.ercot.com/content/news/presentations/2011/ERCOT%20Quick%20Facts%20-%20March%202011.pdfhttp://www.centrodeinformacao.ren.pt/EN/InformacaoExploracao/Pages/DiagramadeCargadaRNT.aspxhttp://www.ree.es/ingles/operacion/curvas_demanda.asphttp://www.gwec.net/index.php?id=9http://www.eirgrid.com/media/Transmission%20Forecast%20Statement%202011-2017-web%20version2.pdfhttp://www.iwea.com/index.cfm/page/barchart


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In erconnec ion21 Maximum expor /imporcapaci y or 2011 (MW)

Expor /imporupgrade (MW)

Expec edcommissioning

NSW o QLD 672/1,298 300/600 2010/11 o 2014/15

VIC o NSW 3,200/1,900 0/500 2010/11 o 2014/15

VIC o SA 680/580 240/250 2025/26 o 2029/30

AS o VIC 594/478 0 No applicable

All Island 80/45022 500 201122

Iberian Peninsula 500 (+900)/1,300 (+600)23 1,5002,700201424 2020 +

ERCO 86025 5,00026 In orma ion no available

Québec 8,060/11,05027 1,20028 2015

21 In orma ion corresponding o he NEM was provided by James Lindley based on N NDP modelling da a.22 N C values or win er 2010/2011 published by EN SO-E:

h ps://www.en soe.eu/leadmin/user_upload/_library/n c/archive/N C-Values-Win er-2010-2011.pd 23 N C values or win er 2010/2011 published by EN SO-E. Figures in bracke s correspond o expor /impor

o Morocco.24 Expec ed commissioning according o he en Year Ne work Developmen Plan published by EN SO-E,

available on:h ps://www.en soe.eu/index.php?id=23225 Te ERCO con rol area is no synchronously connec ed o he Eas ern or Wes ern In erconnec ion bu

i can exchange abou 860 MW wi h he Sou hwes Power Pool and Mexico hrough DC links. Source:h p://www. erc.gov/marke -oversigh /mk -elec ric/ exas.asp#in er (Accessed 26/9/2011)

26 Tis gure corresponds o he proposed res Amigas projec , which will link he Eas ern In erconnec ion,Wes ern In erconnec ion and he ERCO sys em. Source: h p://www. resamigasllc.com/docs/ERCO _ A.pd

27 Values published by Hydro Québec on: h p://www.hydroquebec.com/ ransenergie/en/index.h ml (Accessed 26/9/2011)

28 Projec o increase he energy in erchange capaci y be ween Québec and New England by building a 1,200-MW

in erconnec ion o link Québec’s power grid wi h new Hampshire’s. Commissioning is scheduled or 2015.Source:h p://www.hydroquebec.com/projec s/new-hampshire.h ml(Accessed 26/9/2011)

able 2: NEM in erconnec or upgrade plans compared wi h o her selec ed regions.Source: Various, see oo no es.

S UDY APPROACH

2

https://www.entsoe.eu/fileadmin/user_upload/_library/ntc/archive/NTC-Values-Winter-2010-2011.pdfhttps://www.entsoe.eu/index.php?id=232http://www.ferc.gov/market-oversight/mkt-electric/texas.asp#interhttp://www.hydroquebec.com/transenergie/en/index.htmlhttp://www.hydroquebec.com/projects/new-hampshire.htmlhttp://www.hydroquebec.com/projects/new-hampshire.htmlhttp://www.hydroquebec.com/transenergie/en/index.htmlhttp://www.ferc.gov/market-oversight/mkt-electric/texas.asp#interhttps://www.entsoe.eu/index.php?id=232https://www.entsoe.eu/fileadmin/user_upload/_library/ntc/archive/NTC-Values-Winter-2010-2011.pdf


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B. Wind power in egra ion s udies

Wind power in egra ion s udies are impor an or power sys ems expec ing large windpower developmen s. Prominen s udies have been per ormed in Europe and Nor h Ame-

rica covering sys em-wide issues as well as coun ry (or s a e) based issues, while a myriado academic s udies has been published in journals dealing wi h specic issues on a moregeneral basis.

Te approach used in WP4(A) or he review o in erna ional wind in egra ion s udies isshown in Figure 4.

• Survey 113 wind in egra ion s udies in in erna ional arena• Ca egorise s udies in o high, medium and low relevance o he NEM

• Selec 16 mos relevan s udies ou o ca egories high (& medium)I. Fil ering

• Review & summarise six NEM-rela ed wind in egra ion s udies (by AEMO)• Review WP1 & WP2 repor s• Review he 16 selec ed s udies in de ail• Iden i y issues relevan o NEM

• Conduc workshop o discuss consolida ion process, gain eedbackand develop recommenda ions wi h AEMO o have a s ronger link

o he NEM

• Develop se o recommenda ions or u ure wind in egra ion s udies inhe NEM

• Hand in inal repor

2. Gatheringinformation

3. Consolidation

4. Report

Figure 4: Ou line o approach or WP4(A). Source: energynau ics

Firs , s udies inves iga ing wind in egra ion issues were surveyed rom various regions o heworld where wind power has seen signican grow h. In o al 113 s udies were selec ed,varying rom region-wide sys em s udies o academic papers on specic in egra ion issues.

Tese s udies were ranked as having a high, medium or low relevance o he purpose ohis work package, which is o iden i y echnical issues and approaches ha are likely o be

impor an or a wind in egra ion s udy or he NEM. In de ermining he ranking, ac ors suchas he level o similari y o he s udy region o he NEM (island sys ems or weakly in ercon-nec ed power sys ems), he level o wind pene ra ion assessed in he s udy and he level ocoverage o echnical issues were considered. AEMO s aff were involved in his process, oadd an insigh based on ac ual experience wi h he NEM.

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From he comple e lis o s udies, 16 were selec ed o ensure ha all key echnical issueswere discussed in some way. In his process, ocus was placed on island sys ems wi h weakin erconnec ions o neighbouring sys ems like Ireland, Spain and Por ugal, exas, Québec,Wes ern Aus ralia and New Zealand.

In addi ion, s udies rom he New York ISO were reviewed due i s similari y wi h he NEM, inhaving a 5-minu e real- ime marke in conjunc ion wi h a day-ahead marke .

able 3 lis s he selec ed 16 s udies selec ed. A more de ailed lis can be viewed in Appen-dix 8.1.

S udy Area Organisa ion(and consul an )

Da epublished

Name

NA IONAL/SINGLE AREA S UDIES

ERCO( exas, USA)

Elec rici y Relia-bili y Council o

exas (GE Energy,ABB)

2008-032010-12

Analysis o Wind Genera ion Impac on ERCOAncillary Services Requiremen s, GE Energy.

ERCO CREZ Reac ive Power Compensa ionS udy, ABB.

HydroQuébec(Canada)

Hydro Québec(Hydro Québec ,RE Power)

2009-102010-10

Assessmen o AGC and Load Following De ini ionsor Wind In egra ion S udies in Québec, I. Kamwa,

e al., Ar icle in Proceedings: 8 h In erna ional

Workshop on Large Scale In egra ion o WindPower and on ransmission Ne works or O shoreWind Farms 255-265.

A New Simula ion Approach or he Assessmen oWind In egra ion Impac s on Sys em Opera ions,M. de Mon igny, e al., Ar icle in Proceedings: 9 hIn erna ional Workshop on Large Scale In egra iono Wind Power and on ransmission Ne works orO shore Wind Farms 460-467.

Frequency Con rol in Québec wi h DFIGWind urbines, M. Dernbach, e al., Ar icle inProceedings: 9 h In erna ional Workshop on

Large Scale In egra ion o Wind Power and onransmission Ne works or O shore Wind Farms342-347.

ranspower(New

Zealand)

New ZealandElec rici yCommission( ranspowerSys em Opera or)

2007-03 –

2008-06

Wind Genera ion Inves iga ion Projec (WGIP),ranspower NZ.

Wes ernPower

(Wes ernAus ralia)

Wes ern Power 2010-01 E ec s o increased pene ra ion o in ermi en

genera ion in he SWIS.

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S udy Area Organisa ion(and consul an )

Da epublished

Name

Germany

Deu sche Energie-Agen ur GmbH(DEWI, E-ONNe z, EWI, RWE,Va en all)

2005-022010-11

DENA Grid S udy I: Energy ManagemenPlanning or DENA Grid S udy I: EnergyManagemen Planning or he In egra ion oWind Energy in o he Grid in Germany, Onshoreand O shore by 2020.

DENA Grid S udy II: In egra ion o RenewableEnergy Sources in he German Power SupplySys em rom 2015-2020 wi h an Ou look o2025.

NYISO

(New York,USA)

he New YorkS a e EnergyResearch andDevelopmen

Au hori y andNew York Inde-penden Sys emOpera or (GEEnergy, NYISO)

2005-03

2010-09

he E ec o In egra ing Wind Power on ransmis-sion Sys em Planning, Reliabili y and Opera ions,GE Energy.

Growing Wind: Final Repor o he NYISO 2010Wind Genera ion S udy, NYISO.

Minneso a(USA)

Minneso aDepar men oCommerce O iceo Energy Securi y( he Minneso a

ransmissionOwners)

2008-06 Minneso a Dispersed Renewable Genera ionransmission S udy Vol. I, II and III.

IMO(Wes ernAus ralia)

IndependenMarke Opera or(ROAM Consul -ing, McLennanMagasanikAssocia es,Sinclair KnighMerz)

2010-08–2010-11

Renewable Energy Genera ion Working Group:

Summary o Processes and Ou comes, IMO

Work Package 1:

Scenarios or Modelling Renewable Genera ion inhe SWIS, ROAM Consul ing.

Work Package 2:

Reserve Capaci y and Reliabili y Impac s,McLennan Magasanik Associa es.

Work Package 3:

Assessmen o FCS and echnical Rules, ROAMConsul ing.

Work Package 4:

echnical Rules, Sinclair Knigh Merz.

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REGIONAL S UDIES

IberianPeninsula

(Spain andPor ugal)

Red Eléc ricaEspaña, SpainRede Eléc ricaNacional, Por ugal

2005-05S udy o Wind Energy S abili y in he IberianPeninsula (Con iden ial)29

All Island(Ireland

and Nor hIreland)

Governmen s oIreland and Nor hIreland ( NEI)EirGrid (Eco ysand DIgSILEN )

2008-012010-06

All Island Grid S udy: ransmission Ne workAssessmen or All-Island Grid S udy (WS3), NEI.

All Island SO Facili a ion o Renewables S udies,Eco ys and DIgSILEN GmbH.

Nor hernEurope

Risoe Na ionalLabora ory(SIN EF)

2005-11Wind Power In egra ion in a Liberalised Elec rici yMarke (WILMAR): Sys em S abili y Analysis(WP5), SIN EF.

Europe

EN SO-E andEuropean

Commission(EN SO-E)

2010-03European Wind In egra ion S udy (EWIS):

owards a Success ul In egra ion o Large ScaleWind Power in o European Elec rici y Grids

SPP (USA)Sou hwes PowerPool (CharlesRiver Associa es)

2010-01 Sou h Wes Power Pool Wind In egra ion S udy

ACADEMIC S UDIES

IEA25(Global)

In erna ionalEnergy Agency(V )

2009 IEA Wind ask 25 Phase I 2006-2008, H.Hol inen, e al., 2009.

Reserves(Global) NREL 2010-10

Opera ing Reserves and Wind Power In egra ion:An In erna ional Comparison, M. Milligan, e al.,Na ional Renewable Energy Labora ory.

SC curren(General) NREL 2010-10

Wind Power Plan Shor -Circui CurrenCon ribu ion or Di eren Faul and Wind

urbine opologies, V. Gevorgian, e al., Na ionalRenewable Energy Labora ory.

able 3: Overview o selec ed wind in egra ion s udies. Source: energynau ics

As seen rom he Organisa ion (and consul an ) column, mos o he sys em-wide s udiesare nanced by he governmen s or ransmission sys em opera ors ( SOs). Tis reec s

he ac ha wind power developmen is mainly driven by poli ical ini ia ive while heresponsibili y or ensuring a secure supply o cus omers lies on he shoulders o he sys emopera or. Tere ore i makes sense ha many s udies are co-nanced by hese wo bodies.Ei her SOs in coopera ion (in he case o EWIS) or independen consul an s (in he case oERCO ) are con rac ed o ac ually per orm he s udies so as o promo e in orma ion sharingunder conden iali y agreemen s and o have an unbiased view.

29 Some European s udies are no published in he public domain due o conden iali y issues. In orma ionregarding he me hodology and resul s has been ob ained as bes as possible by energynau ics based onsummary repor s and hrough dialog wi h relevan European SOs.

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S ep 3

able 4 below gives a summary o he six NEM s udies reviewed.

S udy area Organisa ion(and consul an )

Da epublished

Name

Sou hAus ralia Elec raNe 2008-12 In ernal Elec raNe Repor

Vic oria VENCORP[now AEMO] 2007-12Capaci y o he Vic orian Elec rici y ransmissionNe work o In egra e Wind Power

asmania ransend 2009-05 Fu ure wind genera ion in asmania s udy

Sou hAus ralia

NEMMCO[now AEMO](DIgSILEN )

2005-06Assessmen o Po en ial Securi y Risks due o HighLevels o Wind Genera ion in Sou h Aus ralia -S age 1.1

NEMClean EnergyCouncil (ROAMConsul ing)

2010-04 ransmission Conges ion and RenewableGenera ion

Sou hAus ralia

Elec rici y SupplyIndus ry PlanningCouncil

2003-03 Sou h Aus ralia Wind Power S udy

able 4: Overview o wind in egra ion s udies in he NEM. Source: AEMO

As wi h o her wind in egra ion s udies around he world, he s udies wi hin he NEM are

ofen commissioned by he SOs. However, he s udies ocus on issues wi hin a single s a eonly and here are no prominen s udies ha cover NEM-wide issues. A more de ailed liscan be viewed in Appendix 8.2.

S ep hree involved de ailed discussions wi h AEMO s aff in a workshop o pu he in er-media e ndings in he perspec ive o he NEM. Te workshop discussed key issues andconclusions rom he inves iga ion and sough o iden i y he aspec s ha are relevan or

he NEM, which o hese have no ye been adequa ely inves iga ed, whe her he s udy ap-proaches can be adop ed or he NEM and wha assump ions can be made or each specic

inves iga ion.

Having pu he analysis in he con ex o he NEM, he nal s ep involved presen ing heconsolida ed in orma ion in a repor or he public domain, as well as an in ernal repor .Te repor presen s issues mos relevan o wind in egra ion in he NEM, and recommendsapproaches ha could be adop ed by AEMO o inves iga e hem.

S UDY APPROACH

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KEY ECHNICAL ISSUES

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3. KEY ECHNICAL ISSUES

Te ollowing sec ions orm he main body o analysis, describing each issue lis ed in Figu-re 5 in de ail. Common me hodologies adop ed and he ndings o wind impac s udies are

repor ed in order o draw conclusions on whe her hey are applicable o he NEM con ex .Tese conclusions should allow a se o recommenda ions o be developed or how AEMOcan under ake a NEM-wide wind in egra ion s udy in he u ure.

3.1. GENERA ION ADEQUACY

Te issue: Power sys ems mus have adequa e capaci y o supply and deliverpower required by cus omers a any ime. Te capaci y o supply is dic a ed by

he availabili y o he source. For conven ional power plan s his can be assumedo be cons an a he level i is designed o opera e, however, or wind power

plan s i is inevi ably variable, as wi h o her in ermi en renewable energy genera ion suchas hydro and solar power. Fur her o his, all power plan s are subjec o scheduled main e-nance, here ore canno be available all o he ime. Tere ore, or a sys em o be adequa e

here mus be sufficien genera ion o cover demand during periods o low genera ion avai-labili y, while a he same ime cover or cri ical con ingencies such as he sudden loss o helarges power group delivering o he sys em30. Wi h he peak demand projec ed o grow in

he NEM (as wi h many o her coun ries in he world), genera ion capaci y mus be expanded.

Possible impac o increasing wind pene ra ion: Te uncer ain y resul ingrom wind in ermi ency and long- erm wind orecas ing makes i challengingo de ermine how much wind power will ac ually be available and can be consi-

dered as ‘rm’ genera ion capaci y. Tis can become an issue when wind powerreplaces conven ional power genera ion, because an underes ima ion o rm wind capaci ywill cause an over-supply in he sys em, implying redundan inves men , while an overes i-ma ion could lead o power shor ages. In addi ion, wi h wind power expec ed o replacere iring conven ional power plan s, he larges power group or assessmen o con ingencyreserve may become a group o wind power plan s, and, here may be ewer uni s ha can

provide con ingency reserve.

ypical me hods used or s udying he issue: o es ima e genera ion adequacy,each power plan is assigned a capaci y credi , which indica es he likelihood o

he genera or being available when i is needed. According o he NERC 2009repor 31, he capaci y credi o a wind power plan can be de ermined in wo ways:

30 (37) Page 51531 (98) Page 38

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• Reliabili y-based me hod: Es ima ion o he Effec ive Load Carrying Capaci y (ELCC) owind genera ion based on calcula ion o reliabili y me rics; and

• Approxima ion me hod:Calcula ion o he capaci y ac or o wind genera ion during

specied ime periods ha represen high-risk reliabili y periods ( ypically peak hours).

Te mos recommended me hod, bo h by he IEA ask 25 repor32 and he NREL repor33,is he reliabili y-based me hod.

Reliabili y-based me hod

Assessmen o genera ion adequacy is ofen based on reliabili y me rics such as Loss o LoadExpec a ion (LOLE), Loss o Load Probabili y (LOLP) or Loss o Energy Expec a ion (LOEE),which indica e he likelihood ha sys em load will no be me by he available genera ion aa given ime. Te level o reliabili y required is ofen expressed in erms o a percen age ormaximum hours per year ha genera ion canno mee load, and is ypically de ermined by

he power sys em opera or.

Using hese me rics, he capaci y value o wind can be es ima ed by calcula ing he Effec-ive Load Carrying Capaci y (ELCC), which is he amoun o addi ional load ha can be

served a he arge reliabili y level wi h he addi ion o he genera or being considered.Tis may also be compared rela ive o a per ec ly-reliable genera ing uni or a benchmark

conven ional uni (5).

Signican da a and rigorous analysis is required o de ermine he capaci y value o windpower genera ion using his me hod. For example, or a chronological me hod as describedin he IEA ask 25 repor (2), hourly or sub-hourly load and wind genera ion da a coveringa period o 10-30 years would be required o accura ely es ima e he capaci y credi . In hecase where ex ensive da a is no available, wind da a rom numerical wea her predic ionmodels can be used o produce wind speed es ima es o he required level o de ail. Tiscan hen be conver ed o realis ic represen a ions o large scale wind power produc ion. An

al erna ive approach, o use sequen ial Mon e Carlo o simula e wind genera ion re ainingdiurnal and seasonal charac eris ics has been used in Iberia34 and he All Island Grid s udy35,however, his me hod is no recommended36 unless he process is benchmarked againsseveral years o ac ual wind da a.

32 (2) Page 13233 (7) Page 2634 (47) Page 77

35 (121) Pages 53-5536 (7) Page 10

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Ano her approach in he reliabili y-based me hod is o use requency dis ribu ion or du-ra ion curves. Tis approach immedia ely conver s wind power ime series in o probabili ydensi y o power levels, o be combined wi h he probabili ies o conven ional powers a ions’ availabili ies (2). Te DENA s udy uses his approach (6), which uses probabili y

dis ribu ions o wind and conven ional power o calcula e how much conven ional powercan be replaced wi h wind wi hou compromising he level o reliabili y.

Capaci y value is sensi ive o he iming o wind energy delivery rela ive o peak load periods.Correla ion o wind genera ion and load is difficul o calcula e, here ore, i is impor an ouse wind and load proles ha come rom a common wea her driver o calcula e capaci yvalue, such as his orical da a. In addi ion, da a rom several years is pre erred o a single yearbecause here is ofen signican variabili y in wind ELCC rom year o year (7).

Approxima ion me hod

Te approxima ion me hod calcula es he wind capaci y value as he capaci y ac or achievedby wind genera ion in peak periods. Tis me hod is no as accura e as he reliabili y-basedme hod, bu is used in several s udies because i requires less in ensive calcula ions and noas much da a. Tis me hod is predominan ly used in he USA (2). Te s udy per ormed byNYSERDA on New York ISO (5) demons ra es his me hod by calcula ing he wind capaci y

ac or during peak periods be ween 2 o 6 pm rom June hrough o Augus , and 4 o 8 pmrom December hrough o February (2). Te capaci y credi calcula ed wi h his approxi-

ma ion me hod is compared wi h a number o o her me hods including a reliabili y me hodbased on hree years o da a.

A summary o he da a requiremen s or each me hod is shown in he ollowing Figure 6.

Load

Wind

Conven ionalgenera ion

ime series da a• hourly, e c.• 10 - 30 years

ime series da acoupled wi h load

• Usable capaci y• Forced ou age

Load dura ioncurve

Probabili y densi y,varying by mon h

or season

Probabili ydis ribu ion

Peak load

Capaci y ac ora peak load

N/A

Approxima eFrequency dis ribu ionCronological

Figure 6: Da a requiremen s or ypical me hods o calcula e wind power capaci y credi . Source: energynau ics

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In erna ional experience:Many wind in egra ion s udies inves iga e windimpac on genera ion adequacy. O he s udies reviewed, hese include heDENA s udy, he s udies in NYISO, he All Island Grid s udy, s udies in he

Iberian Peninsula, IMO in Wes ern Aus ralia, as well as o her prominen s udies

such as he Wes ern Wind and Solar In egra ion S udy (3) and Eas ern Wind In egra ionand ransmission S udy (4) (no reviewed).

able 5 gives a summary o he level o capaci y credi s calcula ed by each o he s udies.

S udy Capaci y credi (me hod)

IEA2537 5-40%

Spain38 10% (Mon e Carlo)

All Island39 20% (ELCC/Mon e Carlo)

DENA 5-6% (Dura ion curve)

New York ISO40 10% (Peak Period)

ESIPC41 8% (Peak Period)

able 5: Capaci y credi calcula ed in each s udy reviewed. Source: Various

37 (2) Page 15638 According o ar icle by Red Eléc rica Spain due o be published in Wind Power in Power Sys ems, Ed. 2,

Edi or Tomas Ackermann39 (121) Page 21 and 25

40 (2) Page 8941 (10) Page 4

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Capacity credit of wind power

45 %40 %35 %30 %25 %20 %15 %10 % 5 %

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

C a p a c i t y c r e d i t

Wind power pene ra ion as % o peak load

x

x

x

x

x

x

x

UK 2007

US Minneso a 2004

US Minneso a 2006

US New York on-off-shore

US Cali ornia

x

xGermany

Mid Norway 3 Wind Farms

Mid Norway 1 Wind Farm

Ireland ESBNG 5GW

Ireland ESBNG 6.5GW

Figure 7: Capaci y credi o wind power. Source: Reproduced wi h permission rom (2) Page 185

I can be seen rom Figure 7 ha capaci y credi reduces wi h higher pene ra ion levels.However, his does no necessarily mean ha less conven ional capaci y can be replacedby wind power, bu ra her ha a new wind plan added o a sys em wi h high wind powerpene ra ion levels will subs i u e less han he rs wind plan s in he sys em (9).

Conclusions: Capaci y credi calcula ions or wind power can be adap ed o reli-abili y calcula ion me hods used by he sys em opera or. However, o accura ely

assess he impac o he orecas error o wind genera ion on reliabili y requiresda a ha demons ra es wind produc ion charac eris ics coupled wi h sys em de-

mand. Mon e Carlo me hods are ofen used o regenera e wind power da a in cases wherereal measuremen -based da a is lacking, however, his is a a compromise o accuracy since

here will be a weaker correla ion wi h load.

Al hough i is easy o demons ra e how wind power con ribu es o energy adequacy, i ismore difficul o ascer ain he con ribu ion o power demand adequacy because wind (andwea her) is uncer ain and variable. Tis can be mi iga ed o some level by aggrega ion acrosswider geographic areas (e.g. covering differen balancing areas) and coupling wi h s orageop ions or demand-side managemen , however, inevi ably resul s indica e ha he higher he

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pene ra ion level o wind power he lower he capaci y credi42.

In addi ion, wi h variable orms o genera ion like wind and solar PV expec ed o replaceconven ional orms o genera ion, ra her han be buil in addi ion o i , he genera ion ha

con ribu es o con ingency reserve may be reduced.

Relevance or NEM sys em:Te 2003 Sou h Aus ralian S udy by ESIPC (10),makes a comparison o he capaci y ac or resul ing rom calcula ions based onpeak load periods, an all hour analysis, and a summer peak hours analysis. I

was ound ha while he average ou pu rom wind power is higher during hesummer peak hours, i does no necessarily provide more power during he periods o peakload. I concludes ha he con ribu ion rom wind genera ion during he peak hours o hesummer mon hs is no sufficien ly reliable o be considered ‘rm’ supply.

In he con ex o he NEM, he capaci y ac or or wind power in each S a e is calcula ed bycomparing he average his orical wind genera ion ou pu wi h i s ra ed capaci y. Te abili y

o mee seasonal maximum demand is calcula ed rom he minimum level o ou pu availablea leas 85% o he ime during he op 10% o he seasonal demands in a region43.

Based on in erna ional experiences, his conclusion should be revised as mos in erna ionals udies consider a capaci y credi or wind power. I is par icularly impor an o consider hewhole NEM area or capaci y credi calcula ion o wind power.

Recommenda ions:Te calcula ions used o de ermine he con ribu ion owind genera ion in reliabili y s udies should be based on a reliabili y calcula ionme hod ra her han a simplied me hod as i gives a more accura e indica ion ohe rm con ribu ion o wind power genera ion o genera ion adequacy. How-

ever, ex ensive da a is required ha demons ra es wind produc ion charac eris ics coupledwi h sys em demand. Tere ore, AEMO should selec he mos appropria e me hodologybased on:

• he manda ed level o reliabili y,

• ype o da a available, and• he amoun o wind pene ra ion expec ed.

42 (2) Page18443 (122) Page 12

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S udies ha lookin o he issue

Resul s

DENANYISO

IMO-WA

All IslandIberia

WWIS44

EWI S45IEA 25 ESIPC

• Exis ing reliabili y calcula ion me hods can be used o calcula e capaci ycredi o wind power

• I is impor an ha wind power da a used or reliabili y calcula ions isclosely correla ed wi h he load da a

• Wind power con ribu es o energy adequacy• he higher he pene ra ion level o wind genera ion he lower he

capaci y credi• Aggrega ion over large geographic area reduces uncer ain y rela ed o

variabili y, here ore improves he capaci y credi o wind power genera ion• Genera ion wi h par icular reserve response charac eris ics may be required

o main ain required reliabili y level• Wind power coupled wi h s orage or DSM can improve capaci y credi

Genera ionadequacy

• Abili y o power supply o mee energy and power demand, even duringaul s o genera ion uni s and ransmission lines

• Energy consump ion and peak demand are ypically increasing•

Cer ain reserve capaci y above demand mus also be secured• Increasing share o renewable energy is driven by poli ical decisions• Long- erm reliabili y is a sys em issue

Wind impac Wind orecaserror a ec ingwind poweravailabili y

ChallengeAccura ely assess he impaco wind orecas errors on

genera ion adequacy

Figure 8: Summary o issues involving genera ion adequacy. Source: energynau ics

44 Wes ern Wind and Solar In egra ion S udy45 Eas ern Wind In egra ion and ransmission S udy

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3.2. GRID PLANNING

Te issue: Even i here is sufficien genera ion capaci y, i i canno be deliveredo he consumers, he sys em is s ill no adequa e. Tere ore, ensuring sufficien

delivery capaci y is also par o power sys em adequacy. Power ow in a sys emcan be limi ed due o hermal and vol age equipmen ra ings, reac ive powerreserve requiremen s and he dynamic charac eris ics o he ne work. Te grid mus be de-signed so ha supply can be delivered o consumers wi hou viola ing any o hese limi s. Iis also impor an o build in a cer ain level o redundancy o cover or con ingency si ua ionssuch as when here is a aul on a ransmission line (N-1 si ua ion).

Possible impac o increasing wind pene ra ion: Tese impac s are no uniqueo wind power; hey are par o s andard grid planning prac ices. However,

wind power is ofen available in remo e loca ions requiring grid ex ensions orhey are connec ed o he dis ribu ion ra her he ransmission ne work, which is

more suscep ible o vol age issues. Due o he shor cons ruc ion lead- ime o wind powercompared o conven ional power plan s and ransmission equipmen , i is impor an ounders and po en ial problems and prepare mi iga ion or high wind pene ra ion even i iis an icipa ed in some years’ ime.

ypical me hods used or s udying he issue:ransmission planning s udiesare ypically based on s eady-s a e load ow and vol age analysis or u uregenera ion scenarios. In some cases ( ypically in Europe), ocus is placed on he

available rans er capabili y be ween balancing areas, while inves iga ions in ohe dynamic s abili y limi s would be required or de ailed planning s udies.

In erna ional experience: Mos s udies assess he impac o wind power gene-ra ion on he ransmission grid in order o iden i y rein orcemen effor s hawill be required o suppor he u ure in egra ion o wind power. O he s udies

reviewed, hese include he DENA s udy (6), he ranspower wind in egra ions udy (11), All Island Grid s udy (12), s udies o he Iberian power sys em46, EWIS (13), aswell as Sou hwes Power Pool (14) and New York ISO (15) in he USA.

Tere is a general endency in Europe (wi h he excep ion o he Iberian Peninsula andoffshore projec s) or wind power plan s o be connec ed a he dis ribu ion level, whilein he USA he power plan s are larger in size (and ofen remo e in loca ion) hence con-nec ed o a higher vol age ne work. Tis explains why dis ribu ion codes and vol age sup-por requiremen s or wind power plan s have been developed and adop ed rapidly inEuropean coun ries, whereas large ransmission projec s have been seen predominan lyin he USA.

46 Summaries o he S udy o Wind Energy S abili y in he Iberian Peninsula by Red Eléc rica España, Spainand Rede Eléc rica Nacional, Por ugal available on:h p://www.ewec2006proceedings.in o/allles2/743_Ewec2006 ullpaper.pd h p://onlinelibrary.wiley.com/doi/10.1002/we.253/pd

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http://www.ewec2006proceedings.info/allfiles2/743_Ewec2006fullpaper.pdfhttp://onlinelibrary.wiley.com/doi/10.1002/we.253/pdfhttp://onlinelibrary.wiley.com/doi/10.1002/we.253/pdfhttp://www.ewec2006proceedings.info/allfiles2/743_Ewec2006fullpaper.pdf


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In exas (16) or example, i was recognised ha here was a severe lack o incen ive or buil-ding ransmission lines o ca er or wind power, which is generally available in remo e par s o

he ne work. o overcome his problem, compe i ive renewable energy zones (CREZ) havebeen crea ed and s ra egic ransmission planning has been underway o ca er or hese regions

o connec o he ERCO ne work.

Developing ransmission al erna ives based on s udies o he bes wind resource availabili yhas also been carried ou in a s udy or he Sou hwes Power Pool, in Midwes USA and inCali ornia. In Europe, an ex ensive s udy was per ormed by he SOs in he Iberian Peninsula, and heGerman DENA s udy also iden ied he need or large ransmission projec s o help in egra e

he Nor h Sea Offshore grid o he land-based grid. Since in Europe however, he lead imeor ransmission projec s can be more han a decade, some s udies, such as EWIS iden ied he

need o implemen shor - erm in ermediary measures.

Conclusions: Given he unique charac eris ics o loca ion and shor lead ime orwind power expansion, he ransmission Sys em Opera or ( SO) mus an icipa eand prepare o address po en ial issues be ore hey arise. Solu ions range rom

implemen ing vol age con rol requiremen s or wind power plan s, upgrading hedis ribu ion and ransmission grid o accommoda e larger power ows in he long- erm, and

o op imise he use o curren ly-ins alled equipmen in he shor - erm.

Many power sys em opera ors are now realising ha , compared o radi ional ransmissionplanning where he main concern was designing supply sys ems which can mos efficien lysupply demand cen res, major changes are required o he planning process o effec ivelyin egra e wind power and o her renewable energies. When large ransmission projec s suchas grid ex ensions o remo e areas are required, poli ically-backed schemes such as he CREZprojec appear o be mos effec ive (16).

Relevance or NEM sys em:Mos wind resources in he NEM are loca ed a asignican dis ance rom he main demand cen res, implying ha grid ex en-

sion and rein orcemen s may be required or effec ive in egra ion o windpower. However, grid augmen a ions in he NEM are marke -driven, here ore

only ake place i here is seen o be a marke bene . Tis has he po en ial o crea e anobs acle o wind in egra ion as wind power. Effec ively, plan developers require a con-nec ion op ion o build, while he grid will no be ex ended un il he plan is genera ingand crea ing marke bene s.

Fur hermore, wind power plan s in he NEM end o be larger han hose in Europe, andAus ralia’s widespread adop ion o he la es urbine echnologies is expec ed o be slower

han Europe or Nor h America since here is no manu ac uring base onshore. echnical per or-mance requiremen s in he NEM will here ore need o be sufficien o manage vol age issues.

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Recommenda ions:For efficien in egra ion o wind power, i is recommendedha he grid planning approach is reviewed o iden i y s ra egies o be er

accommoda e he par iculari ies o wind power.

In he shor erm however, wind power may increase conges ion on grid, and here oreace cur ailmen wi hou adequa e grid rein orcemen s. o avoid his, here are shor - ermmeasures o manage he expec ed power ows ha can be inves iga ed.

3.3. S EADY S A E ANALYSIS

Te issue: Wi h he connec ion o new wind power plan s, ac ive and reac ivepower is injec ed in differen par s o he power sys em, al ering he powerow charac eris ics in such a way ha hermal and vol age limi s may be vio-

la ed.

Possible impac o increasing wind pene ra ion: Te addi ion o new genera-ing capaci y may:

• change he power ow, so N-1 cri eria migh be viola ed in cer ain cases;• change he vol age prole, requiring addi ional reac ive power suppor measures, or• displace conven ional genera ion, changing he amoun and loca ion o

available reac ive power supply.

ypical me hods used or s udying he issues:Mos wind in egra ion s udiesobserve his impac hrough power ow simula ions based on a se o con-di ions which emula e he “wors case” scenario. Te wors case scenario is a

si ua ion which resul s in high power rans ers across he grid. Tis may occur ina high demand si ua ion when he load cen re is a long way rom genera ion, such as is hecase in Aus ralia, where all he available power has o be rans erred o he load cen res in

he ci ies. High power rans ers are also possible in a low demand si ua ion combined wi hhigh wind power ou pu , as i occurs in Spain, where wind power genera ion can displace

o her genera ion ha may be closer o he load cen re, bu more expensive.

In erna ional experience: In he s udy o he Iberian Peninsula sys em (17), as-sessmen was done using win er peak and summer off-peak demand scenarioscombined wi h hree differen levels o wind power in egra ion. Te coun ry

was divided in our zones o s udy he inuence o wind power in he rans-mission sys em. Wind power genera ion is se up o 80% o he ins alled capaci y in hes udied zone, while he wind power genera ion in he o her hree zones is xed according

o s udies o s a is ical produc ion da a. Solar genera ion was also considered in he s udy.Load ow analysis was conduc ed o s udy ne work con ingency si ua ions (N, N-1 andN-2), and shor -circui scenarios were also simula ed o s udy he power sys em recovery

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afer a dis urbance. ransien s abili y simula ions were solved o valida e wind powerproduc ion scenarios ha have been admissible in he s eady-s a e s udies. Te plannedwind and solar power genera ion mus be capable o providing mainly dynamic vol a-ge con rol, given he massive pene ra ion o hese new echnologies. Simula ions were

carried ou during 20 seconds rom he beginning o he hree-phase aul s, s udying inpar icular he vol age recovery and how wind power pene ra ion affec s he power sys-em. Dynamic vol age con rol implemen a ion was emphasised, since wi hou i , vol age

dips would be deeper and more ex ensive, resul ing in an unaccep able si ua ion rom hepoin o view o ransien s abili y.

Even i long- erm s udies can iden i y ne work augmen a ion requiremen s, he ac ual con-s ruc ion o ransmission in ras ruc ure can ake a long ime and shor - erm solu ions arerequired. Te European Wind In egra ion S udy (EWIS) (13) per ormed year-round markeanalysis coupled wi h de ailed represen a ions o he ne works o assess use o in erconnec-

ors. Tis s udy iden ied ha Europe would encoun er signican problems rela ed o loopows, and recommended ways o deal wi h he si ua ion using he resources available un ilmajor grid rein orcemen s could be pu in place.

Te Irish All Island (12) grid s udy used securi y-cons rained op imised power ow (OPF)o assess how much he new renewable elec rici y sources were going o con ribu e o load

ow in he sys em. Tis approach iden ied how wha por ion o u ure power sys emupgrades are ins iga ed by wind in egra ion, separa e o hose upgrades required or con-ven ional genera ion or change in demand. Tis approach can also help accoun or cos s.

Mos o he wind in egra ion s udies look a a speci ied amoun o wind power and uses eady-s a e analysis o de ermine grid upgrades necessary o in egra e i . However, he

inal priori ies or upgrades are ypically based on economic and marke in egra ions udies.

he Minneso a s udy (18) is unique in ha i aims o de ermine he maximum capaci yo wind power ha can be ins alled a 42 po en ial connec ion poin s. A any single con-nec ion poin a maximum o 40 MW can be connec ed. here ore power low s udies

are per ormed s ar ing wi h 40 MW o wind power capaci y. I his resul s in a viola ion,he connec ed capaci y in he model is reduced by 5 MW and he resul ing power low

is checked again. his process is con inued un il no more viola ions occur, and or all42 si es.

Relevance or NEM sys em: Wind power already has signican inuence onhe power ow in cer ain areas o he ne work and i s relevance will increase as

more wind power is in roduced. For example, a s udy by Vencorp (19), iden i-ed ha he increased injec ion o wind power a cer ain poin s o he ne work

may resul in hermal overloads and low vol ages requiring rein orcemen and suppor mea-

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sures o be implemen ed. Te impac on reac ive power requiremen s appear o be cri icalin he ne works o Vic oria, Sou h Aus ralia and asmania or dealing wi h large quan i ieso wind power in egra ion (19), (20), (21). Fur hermore, or he rela ively isola ed sys emso Sou h Aus ralia, a minimum level o conven ional genera ion remaining online near he

major load cen re, o provide vol age suppor , was ound o be cri ical (20).

Recommenda ions: Based on he charac eris ics o he ransmission ne workand wind resource availabili y, i is recommended ha a number o u ure rene-wable energy developmen scenarios are used o s udy he possible augmen-a ion requiremen s and associa ed cos s. In his way a sys em which is prepared

or a varie y o possible u ure direc ions can be developed a leas cos . In addi ion oassessmen s based on he wors case scenarios, which are ypcially summer-peak scenarios,off-peak scenarios coupled wi h high wind power ou pu , as well as si ua ions subjec oex reme wea her can also assis in he design o a robus sys em.

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S udies ha lookin o he issue

Resul s

DENAMinneso a

IberiaAll Island

EWISSPP

IEA 25

Elec raNeVencorp

ansendNEMMCO-SA

• Impac s on grid adequacy are no unique o wind power.• Wind in egra ion on large scale requires major grid augmen a ions because:

– wind power is o en available in remo e loca ions requiring grid ex ension – wind power is o en connec ed a dis ribu ion level ra her han

ransmission level, which is more suscep ible o vol age issues• ransmission planning me hods need o be modi ied o suppor renewable

energy in egra ion, par icularly loca ion and lead- ime.• In he shor - erm, wind power may increase conges ion on grid, requiring

emporary measures such as FAC S, DSM or s orage.• Wind power may need o be cur ailed i here is insu icien grid adequacy.

Grid adequacy

• Abili y o deliver available genera ion o demand even during aul s ogenera ion uni s and ransmission lines (N-1)

• Energy consump ion and peak demand are ypically increasing• Increasing share o renewable energy is driven by poli ical decisions• Re iremen o nuclear and coal power plan s• Long- erm reliabili y is a sys em issue

Wind impacLoca ion and capaci y

• Remote location

• Distribution or transmission connected

• Short lead time for construction

ChallengeAdap ransmission

planning procedureso ease he in e-

gra ion o renewableenergy sources.

Figure 9: Summary o issues involving grid adequacy. Source: energynau ics

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3.4. POWER SYS EM SECURI Y

Power sys em securi y is concerned wi h he abili y o he sys em o wi hs and con ingencies,se requiremen s or genera ion reserve and limi s o ransmission loading, as well as o avoid

cascading ou ages leading o a blackou . Overall securi y is managed by pro ec ion schemes,se o opera e a he opera ing limi s or vol age, requency and curren .

Figure 10 depic s he differen issues ha affec sys em securi y. I should be no ed ha heseaspec s are no unique o wind power in egra ion; ra her hey mus be es ed or addi ion oall ypes o new genera ion as well as any sys em augmen a ions. Tese issues are explainedin more de ail in he ollowing sec ions.

Power SystemSecurity

Sub synchronousin erac ion

- Power elec ronicdevices

Small-signal s abili y

- Oscilla ory mode

ransien s abili y

- Faul ride hroughcapabili y

Frequency response

- Iner ia- Primary reserve

Faul level

- Shor -circui curren

Figure 10: Issues affec ing power sys em securi y. Source: energynau ics

3.4.1. RANSIEN ANALYSIS

Te issue: Te goal o ransien analysis is o assess he abili y o he power sys-em o main ain synchronism when subjec o a severe ransien dis urbance

such as a aul on ransmission lines, loss o genera ion, or loss o a large load.Genera ing uni s may lose synchronism and be disconnec ed by heir own pro-

ec ion sys ems i a aul persis s on he power sys em beyond a cri ical period.

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Possible impac o increasing wind pene ra ion:Te addi ion o new genera-ing capaci y may:

• change he sys em s abili y charac eris ic by displacing synchronous

genera ion, and• make pos - aul recovery more challenging i wind power plan s (WPPs) areripped during he aul .

For he second poin in par icular, he capabili y o he WPP o remain connec ed duringand ollowing a aul ( aul ride- hrough) is impor an .

I he wind urbine is an old model, and he grid code does no require he wind power plan so ride hrough aul s, pro ec ion devices may disconnec hem when a ransien even occurs, a -ec ing he abili y o he sys em o re urn o a s able opera ing poin afer he con ingency even .

Te degree o which he wind power plan con ribu es o aul ride- hrough and pos con-ingency recovery o he sys em can here ore have an impac (worsening or improving) onhe recovery o he sys em afer he aul , which is he ‘ ransien response.’

ypical me hods used or s udying he issues:Loss o synchronism due o ransienins abili y will be eviden wi hin 2 o 3 seconds o he ini ial dis urbance. Tere ore,

ransien s abili y is assessed using dynamic simula ions, where parame ers such ashe genera or ro or angles, machine speeds, and bus vol ages are observed while a

aul is applied or a xed amoun o ime, cleared, and he behaviour is observed or some 20-30seconds afer he aul , un il he sys em becomes s able or a genera ing uni becomes uns able.

Ligh ly loaded cases and high wind pene ra ion cases are more suscep ible o ransien ins a-bili y because here are less synchronous genera ors online which normally provide reac ivepower suppor during and afer a aul .

In erna ional experience:Te s udy by ranspower New Zealand 47 inves iga-ed he impac o wind power in egra ion on s abili y-rela ed cons rain s. Te

cons rain s limi power ows be ween areas o levels where power sys em ran-sien s abili y can be main ained. Te cons rain may be increased or decreased

depending on he new genera ion’s capabili y o suppor sys em s abili y. Tis is no uniqueo new wind power genera ion. However, wind power’s abili y o suppor sys em s abili y

varies grea ly wi h he ype o echnology employed. Te analysis in his s udy showed haold Fixed Speed Induc ion Genera ion (FSIG) absorbs reac ive power during and afer a

aul , worsening he ransien s abili y per ormance. Tese kinds o uni s will even ually ripoff when here is a dis urbance on he power sys em unless addi ional dynamic reac ivesuppor (e.g. s a ic compensa ors) is buil .

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O her ypes o urbines such as Doubly Fed Induc ion Genera ors (DFIG) and Full Scale Fre-quency Conver ers (FSFC) have improved aul ride- hrough capabili y, and have he po en-

ial o improve ransien per ormance. However, his is largely relian on he requiremen ss ipula ed by he Grid Code.

In sys ems where he wind urbines are no equipped wi h aul ride- hrough (FR ) capa-bili ies, he main objec ive o he s udy is o de ermine he amoun o wind genera ion hawould be disconnec ed due o he dis urbance.

For example in Spain and Por ugal, many o he already ins alled wind urbines are no equip-ped wi h FR capabili y and s udies48 have shown ha large quan i ies o wind power wouldbe swi ched off during a vol age dip. Based on his nding, a new FR requiremen wasin roduced, as well as coordina ed opera ion and con rol schemes, improved orecas ingand aggrega ion echniques. On he o her side in Germany, FR requiremen s or he wind

urbines o remain connec ed bu no provide reac ive power suppor has been in place orover a decade. Tere ore, many o he old wind power plan s are available or genera ion

ollowing a aul . All new wind power plan s as well as re-powered plan s mus comply wi han upda ed requiremen or he wind urbine o con ribu e reac ive curren during a aul in

he same manner as a synchronous genera or. o ge he requiremen s righ , i is impor ano have accura e modelling o he dynamic charac eris ics and aul ride- hrough capabili y

o differen urbine echnologies ha are in he sys em. In his con ex , he German DENAgrid s udy was per ormed wi h a varie y o wind power plan capabili ies incorpora ed.

Mos sys ems hese days have FR requiremen s in heir grid codes. Tere ore, u ure windpower plan s are expec ed o have low vol age ride- hrough (LVR ) capabili ies as well asa cer ain level o vol age con rol. Mos s udies per ormed in Europe and he USA consider

hese aspec s when assessing he impac on ransien s abili y.

Relevance or NEM sys em:In he NEM, ransien s abili y was inves iga ed inhe s udies carried ou or Sou h Aus ralia (20) (23), asmania (21) and Vic oria

(19), where he mos wind power grow h is expec ed. In roduc ion o windgenera ion was no ound o signican ly degrade ransien s abili y. However,

WPP models were no available or he ransien s udies.

In some o he s udies, reac ive power suppor and aul ride- hrough requiremen s wereme wi h s a ic compensa ors, here ore hese are included in he analysis. However, de-pending on he expec a ion o

lessons learned from wind integration studies

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