IEEE Power & Energy Magazine - January/February 2014 - 50

Anything that can be done to limit the
outage extent or ease return to service
should be considered.
hours after the blackout. figure 6(b) shows the areas restored
on long island about two hours following the start of csc.

Offshore Applications
vsc technology has broadened the application base for
hvdc transmission to include offshore applications. vsc
enables power to be fed from onshore generation to offshore
platforms or to the onshore grid from offshore wind generation. voltage stability is improved, since large concentrations
of shunt reactive power compensation are not required. The
converters control frequency and voltage for the offshore
platform. a vsc is self-commutated and can feed a passive
load without any local generation. vsc hvdc has therefore
been used to serve offshore oil and gas production platforms
with more efficient power generation from shore. vscbased hvdc links have also been used for generator outlet
transmission from remote, high-power offshore wind farms
where the use of ac cables or conventional hvdc are impractical. Both offshore applications require specially tailored
vsc control methods for getting started and during normal

operation. in the case of power from shore, the dc link must
be able to start up and feed platform loads with no local generation. in the case of offshore wind plants, the dc link has
to feed auxiliary power and exciting power to the wind plant
when the wind is either blowing too weakly or too strongly
to sustain generation. during normal operation, the link must
be able to operate with nontraditional generation, e.g., wind
turbine generators with either double-fed induction generators or full-power converters. offshore applications utilize a
voltage-frequency control mode for normal operation, with
the converter acting as a constant voltage phasor. With power
from shore, the offshore converter acts as an infinite source
feeding the production platform. With an offshore wind farm,
the converter acts as an ideal slack bus, collecting whatever
power is generated. a subapplication of the same control
mode is black-start control mode, which is used for initial
energization or with zero wind generation.

Battery Energy Storage: Golden Valley
Electric in Fairbanks, Alaska
vscs can be combined with battery energy storage systems (Besss) to assist in system restoration. With hvdc
transmission, the dc voltage is too high to accommodate a

table 1. BESS performance statistics
(source: http://www.gvea.com/energy/bess).
Outages Prevented

(a)
Cross-Sound Cable Energized
for About Two Hours

(b)

figure 6. (a) Areas restored on Long Island 14 August
2003, 23:30, 7 h after the 2003 Northeast blackout and (b)
areas restored on Long Island 10 h after the blackout, on 15
August 2003, 02:30.
50

ieee power & energy magazine

Year

Total Number
of Outages
Covered*

Average Number of
Prevented Outages per
Meter

2003

Fewer than one

2004

2005

5.6

2006

7.5

2007

2008

2.3

2009

2.6

2010

3.9

2011

1.7

2012

2.6

*Outages covered include both local generation and transmission
outages and outages due to loss of power from Anchorage via the
Intertie.

january/february 2014

http://www.gvea.com/energy/bess

Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - January/February 2014