© ABB GroupJune 26, 2013 | Slide 1

HVDC Grid Technology - Benefits andImpact on Optimal Power Flow ModelingConsiderationsFERC Tech Conference June 24-26, 2013

Xiaoming Feng, ABB, June 26, 2013

Optimality and Optimizability

f1

f2

§f2 is more optimizable than f1

§A suboptimal solution on f2 produces more return than optimal solution on f1

§Making the system more optimizable (controllable) is equally important tosolving the system to optimality

Role of model in model based control

§ Make sense of the system condition

§ Predict how the system condition is evolving

§ Answer what if questions

§ Predict the consequence of control actions andoptimize controls strategies

§ Quality of control depends on quality of system model(both the system behavior and the operationenvironment)

Motivation to Use Higher Fidelity Model

Control∆

Model Error∆

Approximate ModelExact Model

Financial Impact$$$

The power grid is AC, correct?

§ Not entirely

§ The grid of the future will have more DC

§ DC modeling can not be ignored or done as aninconvenience or exception

© ABB GroupJune 26, 2013 | Slide 5

HVDC Technology - CSC and VSC HVDC

§ CSC – Current source converter, thyrister based

§ VSC - Voltage source converter, IGBT based

© ABB GroupJune 26, 2013 | Slide 6

CSCVSC

Troll 1&2Troll 3&4Nelson River 2

CU-project

Vancouver IslandPole 1

Pacific Intertie

Pacific IntertieUpgrading

Pacific IntertieExpansionIntermountain

Blackwater

Rio Madeira

Inga-Shaba

Brazil-ArgentinaInterconnection I&II

EnglishChannelDürnrohrSardinia-Italy

Highgate

Châteauguay

Quebec-New England

Skagerrak 1-3

Konti-Skan

Baltic Cable

FennoSkan 1&2

Kontek

SwePol

ChandrapurPhadge

Rihand-Dadri

Vindhyachal

SakumaGezhouba-Shanghai

Three Gorges-Shanghai

Leyte-LuzonBroken Hill

New Zealand 1&2

Gotland Light

Gotland 1-3

Murraylink

Eagle Pass

Tjæreborg

Hällsjön

Directlink

Cross Sound

Italy-GreeceRapid City

Vizag II

Three Gorges-Guandong

Estlink

Valhall

Cahora Bassa

SapeiSquare Butte

Sharyland

Three Gorges-Changzhou

Outaouais

Caprivi Link

Hülünbeir- Liaoning

Lingbao II Extension

Xiangjiaba-Shanghai

BorWin1

NorNed

Apollo Upgrade

EWIC

IPP Upgrade

Itaipu

DolWin1Dolwin 2

NordBalt

Skagerrak 4

North East Agra

Jinping - SunanMackinac

58 HVDC Classic Projects since 195814 HVDC upgrades since 199019 HVDC Light Projects since 1997

Numerous HVDC projects and growing

Increasing controllability by HVDC- Trend to MTDC

© ABB GroupJune 26, 2013 | Slide 8

Statnett

wind-energy-the-facts.org mainstreamrp.compepei.pennnet.com

Statnett

wikipedia/desertec

claverton-energy.com

Desertec-australia.org

TresAmigos

IndiaMTDC

EWEA 20 Year Off Shore Network Master Plan (2009)

Why DC Transmission

§ High power long distances overhead or undergroundcable

§ Low transmission losses over long distances

§ Submarine cables over long distances. connection ofremote offshore wind power

§ Connection of asynchronous grids

§ Full control of power flow ( 4 quadrant control by VSC)

§ Grid stability enhancement

§ Black start

§ Small footprint for HVDC when overhead lines

§ Negligible magnetic fields compared with AC© ABB GroupJune 26, 2013 | Slide 9

§© ABB Group

§June 26, 2013 | Slide 10

Benefits of HVDC vs. HVAC

§ Higher transmission capacity

§ Possibility to use underground and subsea cables

§ Lower losses on long distances

§VSC HVDC*

§1 x ±400 kV

§1200 A

§1620 mm2

conductors

§HVAC

§2 x 400 kV

§2 x 1200 mm2

conductors

§Ene

rgy

Loss

es

§Transmission Line [km]§500 §1000

§5%

§10%§HVAC: 2 x 400 kV

§HVDC: 1 x ±400 kV

§AC/DC conversion losses

§ Overhead line with AC

§ Overhead AC line withFACTS

§ HVDC overhead line

§ Underground line with VSCHVDC or AC cable

Different technologies:

Same power transmitted

§*Voltage Source Converter : High Voltage Direct Current

HVDC technology developmentMore power and lower losses

Capacity up 6 timessince 2000;

Voltage up from+/- 100kV to +/-800kV since 1970

Capacity up 10times; losses downfrom 3% to 1% perconverter stationsince 2000

§HVDC Light

§HVDC Classic§Transmissioncapacity (MW)

§2,000

§4,000

§1970 §1990 §2010

§6,000

Voltage

kV

200

800

600

Xiangjiaba -Shanghai± 800 kV UHVDC.

World’s most

powerful link

commissioned

BorWin:400 MW, 200kmsubsea andunderground

World’s mostremote offshorewind park

15 March 2012

§|

Losses%

3

1

§400

§800

§2010§2000

§1000

6400MW over 2000 km at +/- 800 kV

Line loss comparison

© ABB GroupJune 26, 2013 | Slide 12

ROW Requirement for 6000 MW Transmission Line

© ABB GroupJune 26, 2013 | Slide 13

Configurations of VSC HVDC

© ABB GroupJune 26, 2013 | Slide 14

MonopoleBipole

Point of common couplingDC bus

PCC

DC bus

DC bus

DC bus

A three terminal DC Grid

© ABB GroupJune 26, 2013 | Slide 15

PCC1PCC3

PCC2

AC

AC

AC

§ Transformer/phase reactors

§ DC buses & DC cablenetwork/grounding resistors

§ AC/DC converters

The evolving power grid

AC grids with P2P (point to point) DC links

AC grids embedded or interconnected with MTDC grids

DC grid

AC grid

MTDC Grid needs a generalized approach

© ABB GroupJune 26, 2013 | Slide 17

§ Traditional approach for P2P DC link is to model it asequivalent power injection pair at the connecting ACbuses

§ This is not adequate for DC grid modeling in powerflow, contingency analysis to account for differentoperating configurations

DC Gird Modeling

© ABB GroupJune 26, 2013 | Slide 18

§ Transformer/phase reactors – same model as in AC OPF

§ DC buses & DC cable network/grounding resistors - KCL / KVLequations for resistive network)

§ More controls – PQ set point, slack converter DC voltage

§ AC/DC converters§ Loss modeling, - non linear converter loss function

§ + =

§ Operating limit (valve current, DC voltage …)

§ Loss model is not standardized

PCC1

PCC3

PCC2

AC

AC

AC

Impact on the system model

© ABB GroupJune 26, 2013 | Slide 19

§ The number of equation types increased

§ No longer a simple choice between rectangle or polarformulation

§ Non linear converter model does not lend itself to IVformulation simplification

Summary

§ For smart grid to be effective, power flow controllers arenecessary (Optimizability is as important as optimality)

§ Higher fidelity model is needed for feasibility as well asoptimality

§ Future grid will be a mix of AC and DC technologies

§ Full “AC” OPF needs to adopt high fidelity model for ACas well as DC, new algorithm/formulation must bedesigned considering this requirement

© ABB GroupJune 26, 2013 | Slide 20

§Question?

© ABB GroupJune 26, 2013 | Slide 21

© ABB GroupJune 26, 2013 | Slide 22