Offshore Electricity Infrastructure in Europe - European Wind Energy ...

esults
1986 (the Cross Channel link connecting France and
Great Britain). In contrast, the experience with HVDC
VSC technology is much shorter. The largest operational
VSC interconnector is Estlink (350 MW, 2006).
While equipment manufacturers expect VSC systems
of up to 1,000 MW to be available in the coming years,
it is likely that the VSC power capacity will remain lower
than that available for CSC for the next ten years.
The advantages of VSC over CSC technology are the
ability to independently form a voltage reference which
is very useful at an offshore hub for the connection of
a wind farm, its compact size (and weight) compared
to CSC, and its higher operational flexibility with regards
to the direction of power flows. At present the
converters do incur larger power losses than their
CSC equivalents. In conclusion, the advantages of
VSC technology in an offshore environment mean that
it will be the HVDC technology of choice for the connection
of offshore wind farms. However, for those
interconnectors requiring a large capacity but not the
specific features of VSC technology, the interconnector
project developers will probably opt for the less
experimental, higher commercially available capacity
of CSC technology, particularly if no wind farm connections
are anticipated in the short term.
4.3.2 Hub-to-hub solutions –
case study evaluation
The development of interconnectors between wind
farm hubs would be the beginning of a truly meshed
offshore grid. Instead of connecting wind farms individually
to shore and interconnecting the countries
with a direct interconnection, the interconnection can
be built between the wind farm hubs. The hub-to-hub
solution implies that the offshore wind farms, along
with their hub connection to shore, would be built first
or in parallel with the hub-to-hub interconnector. This
development may be considered wind driven as wind
farm hub connections are the driver to install large
HVDC VSC converters offshore with trade as a potentially
beneficial add-on. This is similar to the option of
dividing the wind farm connection in order to connect
to two countries as discussed in Section 4.3.1, but
is in contrast to the option of connecting wind farms
to planned interconnectors where international power
exchange is mostly the key driver.
Technically, to operate efficiently a complex multi-terminal
meshed configuration is likely to require the use
of HVDC VSC technology and the availability of fast
HVDC circuit breakers in order to limit the propagation
of faults throughout the whole network. Equipment
manufacturers have confirmed to the OffshoreGrid
FIGURE 4.12: PROTOTYPE GRIdS WITh dIFFERENT cONFIGURATION IllUSTRATING ThE APPROAch FOR cOMPARISON OF REAl
SITUATIONS IN ThE cASE STUdY [3]
Country A Country B Country A
Country C
Country B
Country C
(a) hubs with integrated interconnectors (b) hubs and point-to-point interconnectors
46 OffshoreGrid – Final Report