Supergrid Technology Beats Expectations

HVDC breaker Source AlstomAn industrial research consortium that is a who’s-who of the European power industry says development of technologies to produce high-voltage DC (HVDC) supergrids accelerated in 2012 — “surpassing expectations.” The assessment comes in the supergrids technology roadmap updated earlier this month by Friends of the Supergrid, whose members include power equipment suppliers such as Siemens, ABB and Alstom, as well as transmission system operators and renewable energy developers.

Summarizing the conclusions of an expert group within the International Council on Large Electric Systems — better known as CIGRE, its French acroynm — the Friends of the Supergrid says there is now no doubt as to the feasibility of HVDC networks ferrying renewable energy resources from wherever they are in surplus to wherever they are needed: “CIGRE Working Group B4–52 considered this question, specifically whether it was technically and economically feasible to build a DC Grid, and the answer was yes.”

The Friends’ roadmap notes accelerated progress in several core HVDC components. Research enabling use of a broader range of products as subsea and underground HVDC cables is expanding the supplier base for supergrid lines. Another core technology moving fast according to Friends of the Supergrid (FOSG) is the voltage source converter (VSC) variant of AC-DC converters that interface HVDC lines with the AC grid.

VSC is a critical improvement over the original or “classical” HVDC technology. The latter excels at moving high power over long distances, but it is unlikely enabler for meshed DC grids because it must reverse the polarity of an HVDC line to reverse its current. VSC technology is more flexible, and has recently been ordered for use in groundbreaking multi-terminal HVDC projects. Sweden’s South-West Link, for example, is expected to open next year with three terminals, and a fourth converter is to extend the line to Norway by 2018.

Also noted by the Friends’ roadmap are recent developments in VSC converters that can break HVDC current, such as the advanced VSC converter tested by Alstom in February (photo above), and the hybrid electro-mechanical breaker announced by ABB in November.

Within this decade European grid operators will begin to assemble HVDC lines into the world’s first HVDC network connecting North Sea wind farms, Mediterranean solar plants and Scandinavian hydropower, asserts Friends’ chairman Marcello del Brenna, CEO of Italian high-voltage cable manufacturer Prysmian PowerLink. That is, says del Brenna, if the policies are in place to drive it forward. He called on European Union policy makers to eliminate barriers to a truly integrated power market, and to “put in place the regulatory framework to enable large scale interconnection” between its members.

Interconnection is a longstanding problem but one where there has been recent progress. In 2008 the European Commission brought in Mario Monti — the former EC competition commissioner who more recently served as Italy’s prime minister — to secure a critically-needed link between France and Spain that had been stalled for 15 years. Next year that link is to start up with two HVDC cables driven by the world’s first gigawatt-scale VSC-based converters.

This post was created for Energywise, IEEE Spectrum’s blog on green power, cars and climate

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