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HVDC
Boosting power with HVDC Light®
Fast-track solution increases capacity of existing
infrastructure to help meet EU emissions targets
Hydro
Wind
Solar
AC
Europe`s challenge is to find environmentally acceptable
technologies that can increase power capacity and remove
the bottlenecks in existing transmission right-of-ways,
creating a stronger, smarter continental power infrastructure.
To cope with rising electricity consumption and enable the
integration of more renewable energy sources (RES) into the
energy mix, Europe must strengthen its transmission grids
and improve controllability. This is especially true as large offshore wind parks under development in the North Sea region
come online.
The integration of European transmission systems is part of
a ten year plan driven by 42 transmission system operators
(TSOs) comprising the European Network of Trans­m ission
System Operators for Electricity (ENSTO-E). EU legislation is
driving development of a Pan-European grid, with concerns
about security of energy supply, competitive and integrated
continental power markets, and the secure integration of new
generation sources to help meet emissions reduction targets
(EU 20/20/20). In addition to managing more unplanned and
intermittent electricity production, Europe needs new power
corridors, but costly overhead lines are time-consuming to
build and enjoy little public acceptance. The challenge is to
install fast-track solutions that can transmit several GW
(gigawatts) of bulk electricity and remove local bottlenecks,
without protests and delays.
DC
One solution is HVDC (high-voltage direct current) Light,
VSC (voltage source converter) technology, which in­creases capacity and improves controllability of existing
transmission grids. Converting existing AC (alternating
current) lines to DC (direct current) can double or triple
power capacity with minimum interruption.
Where AC solutions are predominant, power can still be
transmitted by using high-voltage AC or DC technologies.
HVDC technology was introduced about 60 years ago to
transmit electricity underwater from mainland Sweden to the
island of Gotland, and Nordic countries have built similar connections since then. Planned new interconnectors will help
the Pan-European grid integrate large hydroelectric resources
in Scandinavia and large wind power resources in northwestern Europe. In 1984 the Itaipu interconnection in Brazil introduced long-distance HVDC hydroelectric overland transmission, rated at ±600 kV (kilovolts). Voltage for HVDC Classic
CSC (current source converters) increased to ±800 kV in
China, and now transmits more than 7000 megawatts (MW)
of electricity over long distances with very low losses.
Increased power by converting 400 kV AC to DC
System study (feasibility)
System study (verification)
Identify AC line and substations
Mapping of line and substations
Suitable DC line configuration
Line & substation design
Suitable DC converter
AC/DC line conversion
Consequence study
AC/DC substation conversion
MW
7000
Improvement of
parallel AC-grid
6000
Transmission
5000
line power
4000
2000
1000
0
AC
DC 400
DC 500
kV
By converting a 400 kV transmission line to 400 kV or 500 kV DC it is
possible to significantly increase power transfer. How much has to be
investigated from case to case.
ABB introduced HVDC Light VSC in 1997, focusing on moderate voltages and power ratings for cable applications. Today,
there are more than ten systems in operation including cable
and overhead line solutions. DolWin2, the world’s largest
offshore wind farm connection, increases the HVDC Light
voltage rating to ±320 kV and 900 MW. A modular concept
enables voltages as high as ±500 kV, and is an opportunity
to convert existing 220 kV and 400 kV AC lines to DC at
even higher voltage capacities. This can double or even triple
the power capacity of existing power corridors, and also
improves the parallel AC system: a smart fast-track solution
to increase grid transfer capability.
Converting one 400 kV line or a double circuit 220 kV line
from AC to DC can increase transmitted power by more
than 1000 MW. Converting a double circuit 400 kV line
(2x3 conductors) to a triple 500 kV DC line (3x2 conductors) can increase transmitted power by 5000 MW taking
into account more efficient use of the parallel AC-system.
Step one is a feasibility study to identify a transmission line
and substation suitable for AC/DC conversion. Based on this,
a potential DC line configuration is established and possible
voltage and current values calculated. The type and rating
of DC converter is then chosen. A consequence study later
examines load, reliability, induction effects, corona, magnetic
fields and power quality. In addition to technical investigations,
a commercial study calculating costs and benefits is also
necessary.
The decision to proceed is followed by a verifying system
study, and the transmission line and substation are mapped
to create a detailed design. Work must be carefully planned
and performed to minimize interruption time of the existing
line and substation.
The main advantage of an AC/DC conversion is the grid`s
increased power transfer capability, accomplished with
minimal environmental impact, investment cost and time.
Additional benefits include:
−−
−−
−−
−−
−−
Improved power flow control
Improved network reliability/redundancy (bi-pole)
Easier to establish dynamic current rating
Minor modifications possible to existing live lines
Underground installation easier in sensitive areas
If proper preparations are done (line insulators changed on
the live line and converter station and substation bypasses
built while still running AC) the effective interruption can be
less than one month.
The applications suitable for an AC/DC conversion include:
− − Connecting increased remote generation, such as wind
power, to load centers
− − Increase capacity between interconnected energy markets
− − De-bottlenecking congested areas by integrating DC links
in the AC grid
For more information please contact:
ABB AB
Grid Systems – HVDC
SE-771 80 Ludvika, Sweden
Tel: +46 240 78 20 00
Fax: +46 240 61 11 59
www.abb.com/hvdc
POW-0077 rev.0
3000