IEEE Power & Energy Magazine - November/December 2017 - 91

source-converter HVdc projects are, at present, limited in
large power transfer applications, although the technology is
improving and configurations exist to allow for direct competition with traditional HVdc.
Some of the strongest terrestrial wind in the world is located
in the panhandles of Texas and Oklahoma, western Kansas,
Nebraska, western Iowa, and the eastern Dakotas. This is often
referred to as the "wind belt" and is depicted in purple areas on
the National Renewable Energy Laboratory (NREL) map shown
in Figure 4. This wind resource translates to several hundreds of
gigawatts of potential wind power that remain largely untapped
due to the lack of infrastructure to move it to the markets on the
coasts where the majority of load and population exist. The map
also depicts the existing U.S. grid at 345 kV and greater.
The United States built a small number of HVdc projects between the 1960s and early 1980s that tapped remote
resources and moved them to load. Since that time, markets
have been implemented, siting laws have become tougher,
and, today, regulatory paradigms for cost allocation of interregional projects are very limited; this means that new projects
are not easily built. A few independent developers are trying
to develop HVdc infrastructure today. Figure 5 shows some of
the projects currently under development.
Several wide-area planning studies have identified HVdc
as an economically attractive way to integrate high-renewable
penetrations. These studies include the 2008 Joint Coordinated

System Plan, the 2011 Eastern Wind Integration and Transmission Study, the 2012 EI Planning Collaborative, and Southwest
Power Pool's 2013 Integrated Transmission Plan. One that is
ongoing now, the DOE's Interconnection Seams Study (see www
.nrel.gov/analysis/seams.html) managed by the NREL, is exploring the value, under a high-renewable future, of increasing
the existing U.S. 1,310 MW of back-to-back (B2B) transmission
capacity across the north-south "seam" between the EI and the
WI. The group is studying three different designs, the first of
which increases cross-seam transmission at only seven existing HVdc B2B facilities. A second design increases cross-seam
transmission via three HVdc lines terminated within the EI and
WI, respectively; it is potentially attractive because it leapfrogs
some of what otherwise might be ac transmission bottlenecks
between the seam and the coastal load centers. A third design,
shown in Figure 6, is a macrogrid overlay, an HVdc network
spanning most of the United States.
Analysis of these three designs began with CEP of G&T,
as described in the "Cooptimization of G&T" section. Results
of this work show that, relative to zero cross-seam transmission growth, the three designs provide economic benefit (in
terms of net present value over the 15-year planning horizon)
of US$15 billion, US$25 billion, and US$65 billion, respectively. These benefits originate from
✔ fuel-cost savings, as inexpensive, high-quality wind
and solar displace coal and natural-gas-fired generation

figure 6. An HVdc macrogrid overlay.
november/december 2017

ieee power & energy magazine

http://www.nrel.gov/analysis/seams.html

Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - November/December 2017