The role of HVDC in the energy transition

The growing number of offshore windfarms and international grid links help the UK to secure the energy supply and meet sustainability targets. But effectively and efficiently transmitting electricity over long distances would not be possible without high voltage direct current (HVDC) and filter resistors.

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The UK has four times more offshore windfarms in operation than in 2012, with the number set to rise significantly as the government looks to reach its goal of generating 50 gigawatts (GW) of offshore wind by 2030.

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Along with this rise, international and intercontinental grid links have increased as the UK trades excess power with other countries, much of which is generated by renewable means.

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The benefits of trading excess power include:

?? Saving energy

?? Preventing Brits paying to turn off turbines when more energy is generated than the grid can handle

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As the UK currently has 13.9 GW offshore wind capacity compared to its 50 GW goal, this output must be used efficiently by keeping energy loss at a minimum. Although alternating current (AC) is standard in electrical power transmission, the current often concentrates near the conductor’s surface — known as the skin effect — which causes energy loss.

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How HVDC helps

HVDC is a transmission system that uses direct current (DC) for the transfer of power over long distances, such as those between remote offshore windfarms and the grid.

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Using HVDC enables:

?? Effective transmission due to its uniform current density throughout the line

?? The trading of excess power between unsynchronised AC distribution systems that run at a set frequency and cannot be connected to those with a different frequency.

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As HVDC does not have a frequency, multiple circuits can be interconnected and converted to both system voltage and frequency levels of the system at point of use.

While HVDC is used for international grid links, it must be converted back to AC at the local grid level. However, converters create harmonic distortion, which can cause lower efficiency, overheating and increased chance of equipment failure.

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Therefore, harmonic filter resistors are a vital part of HVDC and static VAR compensator (SVC) converter stations, helping to remove harmonics by dissipating them as heat. This ensures a safe and assured power supply for the UK and countries across the continent.

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The UK’s rollout of offshore windfarms currently puts it among world leaders, and with the pipeline of projects close to 100 GW, Britain could soon supply many countries with surplus energy. With the ever-increasing need for sustainable energy, HVDC ensures that countries across the world can safely and securely benefit from wind power.

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To learn more about how Cressall's resistors can be used in offshore applications, visit the website or follow the company page for more updates.