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HVDC helps harness renewables and enables power sharing

How can technology support the growing need for electricity while ensuring a sustainable environment? High-voltage direct current (HVDC) is part of the answer.

Many of us would agree that our world is changing at a tremendous pace,  both economically and socially. While our world transforms around us, we have begun to recognize that this progress cannot come at the cost of the global environment. Our determination to support global development by delivering electricity in an efficient way with minimum environmental impact is driving the case for renewable energy.

Our transmission and distribution systems were not designed for this modern, power hungry world. Many of the AC grids in western countries have changed little since they were built over 50 years ago: compare that rate of development with the progress we have seen in other technologies, industry and urbanization.

We also need to accelerate the development of remote hydro power, alongside wind and solar. Renewable power sources bring new challenges for our power systems because large-scale developments cannot be built in residential or industrial areas. They must be built far from the consumers or be limited to small-scale plants linked to the distribution grid. Large-scale plants will provide large volumes of power, but only if we have the transmission infrastructure to deliver it to consumers. The contribution of distributed small-scale plants will be positive only if grid stability can be maintained.

Bottom line being that renewables alter the generation portfolio pattern of today creating further transmission needs as well as stability concerns. Another interesting aspect of renewables, hydro excluded, is natural intermittency. Solar or wind energy is hard to predict and therefore difficult to schedule, in the traditional sense, in the power dispatch planning.

Looking at renewable energy sources from a grid perspective it is not unrealistic to conclude that appropriate transmission infrastructure is needed to maintain grid stability and reliability. We need to overcome long distances – from generation to load – but also interconnect countries and grids in order to share power and spinning reserves.

All this so that we can fully utilize what we are currently investing greatly in – sustainable energy. Considering distances, capacity and performance requirements is where HVDC solutions come in. Having been around for nearly 60 years, this technology is well suited to help meet these challenges. Not only do HVDC systems enable low loss transmission but they also add system stability to our grids making them more resilient to unexpected contingencies.

Moving forward, HVDC technology will play a key role in our ambition to ensure a sustainable planet through integration of renewable energy sources and will also facilitate trade between countries and grids.

Related blog posts:
ABB achieves another milestone in electrical engineering – the hybrid HVDC breaker
From ‘joining the dots’ to ‘connecting the lines’

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  • Terry Noble

    Interesting.  Here are a few thoughts, are they valid? 
    DC advantages:
    1)  AC cycles at 60Hz which causes electronic friction whereas DC does not cycle.
    2)  DC uses two wires instead of three for AC?
    DC disadvantages:
    1)  DC would have to be inverted and rectified.
    2)  With its constant EMF field, DC wires would tend to attract each other more than AC's varying field.

  • ClaesW

    Hi Terry,
    Your thoughts are sound. In regards of the advantages it is true that we do not have any losses originating from the AC cycle (reactive current) which does facilitate the low-loss characteristics of HVDC transmission. The losses in a DC line mainly consist of resistive losses originating from the current giving the active power transfer overcoming the line resistance. Concerning the number of conductors, whether cables or over-head lines (OHL), there is only need for two or even one if ground return can be utilized. Another important advantage is, as mentioned in the blog, the excellent controllability of HVDC which is something that makes it very different from AC.
    It is true that inversion as well rectification is needed when connecting with AC networks, consequently requiring a converter station at each end of an HVDC line. Similarly an AC transmission line often requires a substation at each end of a line.
    The conductors, cables or OHLs, are not affected by each other in terms of mechanical stress (this can be neglected due to the distance between the conductors) but one factor which is important for DC as well as AC cables is the losses in terms of heat leaving the cables. The distance between the cables is carefully analyzed with detailed information of the soil as well as system design parameters as base.
    Best regards, Claes

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