Grid Code Frequency Response Working GroupSystem Inertia Antony Johnson, System Technical Performance

Overview

Background to System Inertia

Transmission System need

Future Generation Scenarios

Initial Study Work

International Experience and Manufacturer Capability

Transmission System Issues

Conclusions

Frequency Change

Under steady state the mechanical and electrical energy must be balanced

When the electrical load exceeds the mechanical energy supplied, the system frequency will fall.

The rate of change of frequency fall will be dependant upon the initial Power mismatch and System inertia

The speed change will continue until the mechanical power supplied to the transmission system is equal to the electrical demand.

Why is Inertia Important

Inertia is the stored rotating energy in the system

Following a System loss, the higher the System Inertia (assuming no frequency response) the longer it takes to reach a new steady state operating frequency.

Directly connected synchronous generators and Induction Generators will contribute directly to System Inertia.

Modern Generator technologies such as Wind Turbines or wave and tidal generators which decouple the prime mover from the electrical generator will not necessarily contribute directly to System Inertia

Under the NGET Gone Green Scenario, significant volumes of new generation are unlikely to contribute to System Inertia

What is inertia?

Loss of Generatoron the system

Frequency Falls as demand > generation

Stored energy delivered to grid as MW

The stored energy is proportional to the speed of rotation squared3 types of event cause a change in frequency

Loss of generation (generator, importing HVDC link etc)Loss of load Normal variations in load and generator output

The maths behind inertia

∂f/∂t = Rate of change of frequency∆P = MW of load or generation lost2H = Two times the system inertia in MWs / MVA

∂f∂t

∆P2H=

∂f/∂t = Rate of change of frequency∆P = MW of load or generation lost2H = Two times the system inertia in MWs / MVA

∂f∂t

∆P2H=

H = Inertia constant in MWs / MVAJ = Moment of inertia in kgm2 of the rotating massω = nominal speed of rotation in rad/sMVA = MVA rating of the machine

½Jω2

MVAH =H = Inertia constant in MWs / MVAJ = Moment of inertia in kgm2 of the rotating massω = nominal speed of rotation in rad/sMVA = MVA rating of the machine

½Jω2

MVAH =

Typical H for a synchronous generator can range from 2 to 9 seconds (MWs/MVA)

An NGET Future Scenario

Plant closures12GW Coal & oil LCPD7.5GW nuclearSome gas & additional coal

Significant new renewable29 GW wind (2/3 offshore)Some tidal, wave, biomass & solar PVRenewable share of generation grows from 5% to 36%

Significant new non renewable build3GW of new nuclear3GW of new supercritical coal (some with CCS)

11GW of new gas

Electricity demand remains flat (approx 60 GW)Reductions from energy efficiency measuresIncreases from heat pumps & cars

Strategic Reinforcements

Sizewell

Pembroke

Osbaldwick

RowdownBeddington

ChessingtonWest

Landulph

Abham

Exeter

Axminster

Chickerell

Mannington

Taunton

Alverdiscott

Hinkley Point

Bridgwater

Aberthaw

Cowbridge

PyleMargam

SwanseaNorth

CardiffEast

Tremorfa

Alpha SteelUskmouthUpper Boat

Cilfynydd

ImperialPark

Rassau

Whitson

Seabank

Iron Acton

Walham

Melksham

Minety DidcotCulham

Cowley

Bramley

Fleet

Nursling

Fawley Botley Wood

Lovedean

Bolney

NinfieldDungeness

Sellindge

Canterbury

E de F

Kemsley

Grain

Kingsnorth

Rayleigh Main

Littlebrook

Tilbury

Warley

Barking

W.HamCity Rd

BrimsdownWaltham

Ealing

Mill HillWillesden

Watford

St Johns

Wimbledon

New Hurst

Elstree

Rye House

N.Hyde

Sundon

Laleham

Iver

Amersham Main

WymondleyPelham

Braintree

BurwellMain

Bramford

EatonSocon

Grendon

EastClaydon

Enderby

Walpole

NorwichMain

Coventry

Berkswell

Rugeley

Cellarhead

IronbridgeBushbury

Penn

Willenhall

OckerHill

KitwellOldbury

Bustleholm

Nechells HamsHall

BishopsWood

Feckenham

Legacy

Trawsfynydd

Ffestiniog

Dinorwig

Pentir

Wylfa

Deeside

Capenhurst Frodsham

Fiddlers

Rainhill

KirkbyListerDrive

Birkenhead

WashwayFarm

Penwortham

Carrington

SouthManchester

Daines

Macclesfield

Bredbury

Stalybridge

Rochdale

WhitegateKearsley

Elland

Stocksbridge

WestMelton

Aldwarke

Thurcroft

BrinsworthJordanthorpe

Chesterfield

Sheffield CityNeepsend

Pitsmoor

Templeborough ThorpeMarsh

Keadby

WestBurton

Cottam

HighMarnham

Staythorpe

Stanah

Heysham

Padiham

Hutton

BradfordWest Kirkstall Skelton

Poppleton

Thornton

Quernmore

Monk

EggboroughFerrybridge

Killingholme

SouthHumberBank Grimsby

West

Drax

Lackenby

GreystonesGrangetown

Saltholme

Norton

Spennymoor

Tod PointHartlepool

Hart Moor

Hawthorne Pit

Offerton

West BoldonSouth ShieldsTynemouth

StellaWest

Harker

Eccles

Blyth

IndianQueens

Coryton

RatcliffeWillington

Drakelow

Shrewsbury

Cross

Weybridge

Cross

Wood

North

FrystonGrange

Ferry

Winco Bank

Norton Lees

Creyke BeckSaltend North

Saltend South

Hackney

BaglanBay

LeightonBuzzard

PatfordBridge

Northfleet EastSinglewell

Fourstones

Humber Refinery

SpaldingNorth

West Thurrock

ISSUE B 12-02-09 41/177619 C Collins Bartholomew Ltd 1999

Dingwall

Dounreay

Newarthill

Cumbernauld

Kincardine

WishawStrathaven

KilmarnockSouth

Ayr

Coylton

Inveraray

HelensburghDunoon

Inverkip

DevolMoor

Hunterston

Sloy

Fort William

Bonnybridge

Neilston

Ceannacroc

Conon

Fort AugustusFoyers

Inverness

Stornoway

Elvanfoot

Kaimes

Glenrothes

Westfield

Grangemouth

Longannet

Linmill

Bathgate

Errochty Power Station

TornessCockenzie

Keith

Thurso

FasnakyleBeauly

Deanie

Lairg

Shin

Nairn

Kintore

Blackhillock

Elgin

Keith

Peterhead

Persley

Fraserburgh

InvergarryQuoich

CulligranAigas Kilmorack

GrudieBridge

Mossford

OrrinLuichart

Alness

Brora

CassleyDunbeath

Mybster

St. Fergus

Strichen

Macduff

Boat ofGarten

Redmoss

Willowdale

Clayhills

Dyce

Craigiebuckler

Woodhill

Tarland

DalmallyKillin

Errochty

Tealing

GlenagnesDudhope

Milton of CraigieDudhope

Lyndhurst

CharlestonBurghmuir

Arbroath

Fiddes

Bridge of Dun

Lunanhead

St. Fillans

Finlarig

LochayCashlie

Rannoch

TummelBridge

Clunie

Taynuilt

Nant

Cruachan

PortAnn

Carradale

Auchencrosh

Lambhill

ClydesMill

Glenluce

NewtonStewart

Maybole

Dumfries Ecclefechan

Berwick

Hawick

Galashiels

Dunbar

Meadowhead

Saltcoats

HunterstonFarm

SP TRANSMISSION LTD.

Kilwinning

Currie

Cupar

Leven

Redhouse

Glenniston

SCOTTISH HYDRO-ELECTRICTRANSMISSION

Telford Rd.Gorgie

KilmarnockTown

Busby

Erskine

Strathleven

MossmorranDunfermline

Broxburn

Livingston

Whitehouse

ShrubhillPortobello

Devonside

StirlingWhistlefield

SpangoValley

Ardmore

Broadford

Dunvegan

NGC

Easterhouse

EastKilbrideSouth

Gretna

Chapelcross

THE SHETLAND ISLANDS

Tongland

GlenMorrison

Clachan

400kV Substations275kV Substations400kV CIRCUITS275kV CIRCUITS

Major Generating Sites Including Pumped Storage

Connected at 400kVConnected at 275kVHydro Generation

TRANSMISSION SYSTEM REINFORCEMENTS

Langage

BlacklawWhitelee

Iverkeithing

Marchwood

BickerFenn

Coalburn

REINFORCED NETWORK

Under Construction or ready to startConstruction subject to consents

Very strong need case

Series Capacitors

RedbridgeTottenham

Strong need case

Future requirement, but no strongneed case to commenceat present

‘Gone Green 2020’

Quantitative Analysis

The effect of System Inertia is being quantitatively analysed through two methods:-

Energy Balance spread sheet approach

Utilising simple predictive output models based on an energy balance

System Study using a Test Network

Utilising Dynamic System Models

Energy Balance Spread Sheet Approach

System Considered

16.5 GW of Wind, 6.9 GW Nuclear, 1.6 GW Carbon Capture

Load Response 2% per Hz

Assumed loss – 1800MW

System Balanced at t = 0 seconds

Inertia considered in isolation

General Conclusion

The higher the inertia the longer it takes for the steady state frequency to be reached.

See subsequent slides

Energy Balance Spread Sheet – ResultsWind Generation with and Without Inertia

Variation in Inertia - Low Resolution

46

46.5

47

47.5

48

48.5

49

49.5

50

50.5

0 10 20 30 40 50 60

Time (s)

Freq

uenc

y Hz

H=0 H=3

Energy Balance Spread Sheet – ResultsWind Generation with and Without Inertia

Variation in Inertia - High Resolution

48.2

48.4

48.6

48.8

49

49.2

49.4

49.6

49.8

50

50.2

0 1 2 3 4 5 6

Time (s)

Freq

uenc

y (H

z)

H=0 H=3

Test network

G~TEST MACH..

-0.0

00.

051.

42

General Load

1353

.29

0.00

trf_1

07_1

07G

-9815...-3189...26.53

1

trf_1

07_1

07G

9826

.2..

3634

.4..

26.5

3

1

trf_1

05_1

05G

-1494...-195.4..83.63

1

trf_1

05_1

05G

1499.5..404.7383.63

1

trf_1

06_1

06G

3

3998

.8..

810.

2084

.52

1

trf_1

06_1

06G

3

-3989...-182.4..84.52

1trf_106_106G1

3999

.0..

1244

.2..

85.6

0

1

trf_106_106G1

-3987...-678.6..85.60

1

trf_102_102G

-1993...-175.1..87.43

1

trf_102_102G

1999

.5..

458.

3587

.43

1

trf_1

03_1

03G

2826

.0..

-34.

9185

.40

1

trf_1

03_1

03G

-2816...440.5785.40

1

Shunt 1

0.0086.98

1

Shunt 4

-0.00-150.8..

1

Shunt 3

-0.00-187.6..

1

Shunt 2

-0.00-17.75

1

G~sy

m_1

03_G

3_B

565.

21-6

.98

80.1

1

G ~

sym

_102

_G2

1999

.5..

458.

3582

.06

trf_1

02_1

01_T

1

-1960...-35.6764.63

trf_1

02_1

01_T

1

1971.5..192.8864.63

G~sy

m_1

03_G

3_E

565.

21-6

.98

80.1

1

G~sy

m_1

03_G

3_D

565.

21-6

.98

80.1

1

G~sy

m_1

03_G

3_C

565.

21-6

.98

80.1

1

G~sy

m_1

03_G

3_A

565.

21-6

.98

80.1

1

lod_107_L7

19196...1947.8..

lod_106_L6

9.71-0.00

lod_105_L5

1051.6..286.80

lod_104_L4

9.58-0.00

lod_103_L3

958.39287.52

lod_102_L2

21.650.00

lod_101_L1

1319.9..180.89

lne_

106_

107_

C7

-9380...1241.6..92.66

lne_

106_

107_

C7

9380.7..-168.3..92.66

G~sy

m_1

07_G

7

9826

.2..

3634

.4..

52.3

8

G~sy

m_1

06_G

3

3998

.8..

810.

2090

.67

G~sy

m_1

06_G

1

3999

.0..

1244

.2..

93.0

7

trf_1

06_1

04_T

3

1275.3..-515.5..69.04

trf_1

06_1

04_T

3

-1275...572.7769.04

lne_

104_

101_

C6

-557.7..284.5264.29

lne_

104_

101_

C6

604.65-239.4..64.29

lne_

104_

101_

C5

-557.7..284.5264.29

lne_

104_

101_

C5

604.65-239.4..64.29

lne_105_104_C2

86.05-78.8811.72

lne_105_104_C2

-84.7048.7311.72

lne_105_104_C1

86.05-78.8811.72

lne_105_104_C1

-84.7048.7311.72

trf_1

06_1

05_T

2

1491.5..-361.7..77.03

trf_1

06_1

05_T

2

-1491...456.6477.03

G~

sym_105_G5

1499.5..404.7377.66

lne_

105_

103_

C4

643.43-165.8..66.87

lne_

105_

103_

C4

-610.1..214.0566.87

lne_

105_

103_

C3

643.43-165.8..66.87

lne_

105_

103_

C3

-610.1..214.0566.87

lne_103_101_C8

-568.3..246.6461.25

lne_103_101_C8

571.72-208.7..61.25

106 GEN3

21.6

70.

9912

.46

105 GEN 21.510.98

14.67

103 GEN

20.6

40.

9425

.69

107 GEN

21.7

20.

99-0

.59

106 GEN1

21.9

71.

0011

.25

102 GEN

21.9

51.

0026

.54

107 BUS007 408.481.02-2.88

106 BUS006 405.011.013.63

105 BUS005 273.961.007.02

104 BUS004 273.981.005.80

103 BUS003 273.260.99

17.51

102 BUS002 408.691.02

18.65

101 BUS001 278.181.01

14.11

DIg

SILE

NT

Basic GB system representation

Approx 23GW demand

10 generators

5 generators providing frequency response

1320 MW load switched in (equivalent to loss of a 1320 MW generator)

Base case large disturbance – normal system inertia

60.0048.0036.0024.0012.000.000 [s]

50.04

49.86

49.68

49.50

49.32

49.14

106 BUS006: Electrical Frequency in Hz

X = 10.400 s

49.183 Hz

60.0048.0036.0024.0012.000.000 [s]

2.28E+4

2.24E+4

2.21E+4

2.18E+4

2.14E+4

2.11E+4

NON FREQENCY RESPONSE: Generation, Active Power in MW

X = 10.400 s

21331.314 MW

22713 MW

60.0048.0036.0024.0012.000.000 [s]

3027.

2812.

2596.

2381.

2166.

1951.

FREQUENCY RESPONSE: Generation, Active Power in MW

DIg

SILE

NT

Decreasing system inertia – large disturbance(½ and ¾ base case inertia)

60.0048.0036.0024.0012.000.000 [s]

50.10

49.78

49.46

49.14

48.82

48.50

106 BUS006: Frequency (Hz) base case inertia106 BUS006: Frequency (Hz) 0.5 x base case inertia106 BUS006: Frequency (Hz) 0.25 x base case inertia

Y = 48.800 Hz

60.0048.0036.0024.0012.000.000 [s]

2.28E+4

2.24E+4

2.21E+4

2.18E+4

2.14E+4

2.11E+4

NON FREQENCY RESPONSE: Total active power from generators NOT providing frequency reponse - base case inertiaNON FREQENCY RESPONSE: Total active power from generators NOT providing frequency reponse - 0.5 x base case inertiaNON FREQENCY RESPONSE: Total active power from generators NOT providing frequency reponse - 0.25 x base case inertia

60.0048.0036.0024.0012.000.000 [s]

3095.

2865.

2636.

2407.

2177.

1948.

FREQUENCY RESPONSE: Total active power from generators providing frequency reponse - base case inertiaFREQUENCY RESPONSE: Total active power from generators providing frequency reponse - 0.5 x base case inertiaFREQUENCY RESPONSE: Total active power from generators providing frequency reponse - 0.25 x base case inertia

DIg

SILE

NT

International Experience and Manufacturer Capability

Hydro Quebec requires Generating Units in a Power Plant to have an inertia constant which is compatible with the inertia constants of existing Power Plants in the same region. The minimum inertia for wind power must equate to 3.5s.

GE Wind advertise a Wind Inertia Control on their Website

Enercon have completed modelling and field tests on a wind turbine and published a paper on this subject

Other manufacturers are believed to be investigating an inertial capability

Transmission System Issues

Optimum Performance Capability requirements based on the minimum needs of the Transmission System.

Prevention of under and over frequency incidents

Control System Design and performance

Filtering requirements if any (Noise Generation?)

Overall Co-ordination

Inertial contribution – Delivered from all plant

Primary Response – FSM – Containment

Secondary Response – FSM - Correction

Conclusions

Machine inertia significantly affects the rate and rise and rate of fall of System Frequency

It is likely to be cheaper (although some form of quantitative analysis would be required) to require all generators to contribute to System Inertia rather than having no requirement and requiring larger volumes of fast acting frequency response?

Non Discrimination

The inertial delivery requirements needs to be quantified

Delivery / Capability

Control System Settings / Filtering