HVDC Technology - raeng.org.uk · Results from IOTP indicate the overall benefits are in order of...
Transcript of HVDC Technology - raeng.org.uk · Results from IOTP indicate the overall benefits are in order of...
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HVDC Technology
Phil Sheppard
Head of Network Strategy
Alternating Current (AC) Direct Current (DC)
Was developed to allow power transfer
at higher voltage (to minimise losses)
Power flows depending on system
impedance (limited control over
powerflow)
Worldwide choice of power
transmission technology (at different
frequencies)
Conventional power generation is AC
Power system was initially a DC system!
More cost effective for longer power transmission
Allows control of power at different routes
Allows connection of different synchronised AC zones zones (even at different frequencies)
AC vs DC Power Transmission
IGBT based Voltage Source
Operable in AC grids with low short
circuit levels
Independent control of P&Q
Power reversal and Fast Ramp Up/Down
Capability
Harmonics only seen at Switching
Frequency (xkHz)
Smaller converter station
Can energise an AC network (black start
capability)
Thyristors based Line Commutated
Converter
Lower converter losses
Less critical DC line-to-ground faults
Filter Switching Required for Different
Dispatch Levels
Commutation Failure and Operation in
Weak Networks
Larger converter station
Can only operate in an energised AC
network
Voltage Source Converter
(VSC)
Current Source Converter
(CSC)
HVDC Technologies
CSC and VSC
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Basslink
(Tasmania
2005) LCC
500MW
Transbay
(USA 2010)
VSC 400 MW
Caprivi Link
(Namibia
2009) VSC
300MW
Borwin 1
(Germany
2009) VSC
400 MW
Inelfe (France
– Spain 2013)
VSC 1000MW
KII Channel
(Japan 2000)
LCC 2800MW
Skagerrak 4
(Norway
2014) VSC
700MW
Sapei (Italy
2011) LCC
800MW
North East
Agra (India
2015)
8000MW
Xiangjiaba -
Shanghai
(China 2011)
LCC 6400MW
Western Link
(UK 2016)
LCC 2200MW
Jinping Sunan
(China 2013)
LCC 7200MW
Worldwide HVDC experience
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Present AC interconnector capacity limited by stability constraint
2.2 GW DC Link (subsea) from Scotland to England
To further increase the capacity to over 6 GW
To enhance system stability (power control, POD)
Why not AC?
Expensive Option Compared to DC
Long Lead Time
Visual Impact
Two DC links of smaller capacity would be expensive
Technology: Line Commutated Current:
2.2 GW and higher HVDC converters are based on proven technology
(Current Source Converter)
Offer a short-term rating (to 2.4GW)
Low losses and no black start requirement favour CSC design
DC cables of 600kV rating is a significant benefit (first in the world).
Use of HVDC Technology in GB
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Given the size of the Round 3
windfarms, an integrated solution
in comparison to radial offers 25%
reduced overall Cost (including the
onshore reinforcements required)
Fault detection
Fault Isolation
- Lack of DC Breakers
Converter control co-ordination
Power reversal
Integrated Offshore Windfarms
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Operating in an islanded network with
low system strength (short circuit
level)
Windfarm/Converter Control
DC/AC Faults
(detection/isolation/system recovery)
Loss of Array
Power Sharing (multiple DC Links)
Power Quality
System Frequency
Loss of infeed
Low Voltage Ride Through
Frequency Control
System Stability
Voltage Control
Power Oscillations
Power Reversal
Power Quality
SSR/SSTI
Control Interaction
Power System Studies for HVDC
Projects – long list…!
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Improvements in the
design of DC breaker
which allows for
better “meshed” DC
networks (multi-
terminal)
VSC converter design
to reduce the losses
Ancillary services
from DC links such as
Rapid Frequency
Response, Power
Oscillation Damping
Multi-vendor Control platform for
multi-terminal development
Innovations in the world of DC
Technology
HVDC R&D in National Grid
Over 30 live R&D projects on
HVDC technology
Working closely with UK and
International Universities and
Manufacturers
One of World’s leading
Transmission companies in
HVDC modelling
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Results from IOTP indicate the overall
benefits are in order of £1billion for the
current connection programme (2017
onwards)
If projects connect after 2020 improved
technology should be available and a
further benefit up to £2billion can be
potentially achieved
Results currently present only comparison
of capital costs
Cost Benefit Analysis, which includes
operational cost considerations is
underway
Current work shows the Integrated
offshore concept bring overall benefits
Local Boundary EC3
P1
P2
P3
P4
P5P6
2030 TEC
Doggerbank
Creyke Beck
(CREB4)
Lackenby
(LACK4)
Tod Point
(new s/s)
Local Boundary EC7
1 GW
1 GW
ONSHORE AREA OFFSHORE AREA
1.8 GW
Killingholme
(KILL4)
Walpole
(WALP4)
Local Boundary EC1
P1
Hornsea
1 GW
1 GW
1.8GW *P5b
Bramford
(BRAM4)
P1a
P2a
Norwich Main
(NORM4)
Local Boundary EC5
East Anglia
Bacton
(new s/s)
P3
2GW
P5a
P2b
P1b
P3a
P3b
1.8GW
P6a
P6b
P6cP4a
P4b
1.8GW*
Lowestoft
(new s/s)
1.2GW
1GW
Boundary B9
(2800MW)
Boundary B7
(3500MW)
Boundary B7a
(3400MW)
Boundary B8
(2700MW)
Boundary B6
(2500MW)
P4
1.8GW
Onshore
Actions:
+ QB Opt
(1 x 200MW)
(3 x 300MW)
(2 x 500MW)
P2
(7 x 300MW)
(1GW)
(1GW)
Bootstrap
2.5GW
Onshore
Actions:
+ QB Opt
Benefits of East Coast Integration
Potential North Sea offshore grid
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HVDC Technology
Search:
national grid high
voltage direct current
fact sheet