© 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