Firsts for HVDC Light

A recent HVDC Light contract won from Samsung C&T Corp by Hitachi Energy is for a “first-of-its-kind sub-sea power transmission network in the MENA [Middle East and North Africa] region”, the company says.

The VSC (voltage source converter) based HVDC Light installation will connect ADNOC’s offshore operations to the onshore power grid in the United Arab Emirates owned and operated by Abu Dhabi National Energy Company PJSC (TAQA).

HVDC Light, together with Hitachi Energy’s MACH digital control platform, “will enable the transfer of cleaner and more efficiently generated power from the mainland to power ADNOC’s offshore production operations”, enabling the carbon footprint of those operations to be reduced by more than 30%.”

With a total capacity of 3200 MW, the two HVDC links will be “by far the most powerful power-from-shore solution in the MENA region to date”, says Hitachi Energy, which also notes that it is “the first HVDC power-from-shore solution outside Norwegian waters.”

Each HVDC link of the ADNOC installation will connect a cluster of offshore oil and gas production facilities to the mainland grid, a distance of up to 140 km for each cluster.

Hitachi Energy is supplying four converter stations, which convert AC power to DC for transmission in the subsea cables, then reconvert it to AC from DC for use in the offshore power systems. Hitachi Energy has also signed a long-term life-cycle service agreement, “leveraging digital technologies to ensure system availability and reliability over the HVDC links’ long operating life.”

Hitachi Energy reports growing interest from oil and gas companies in powering their offshore production facilities with lower carbon electricity from onshore power grids.

Successful first year for Kriegers Flak CGS Another HVDC Light success that Hitachi Energy can point to is the back-to-back HVDC Light installation that forms part of the Kriegers Flak Combined Grid Solution (CGS). The Kriegers Flak CGS, developed by Energinet of Denmark and 50Hz of Germany, was a world first in that it combines grid connections to offshore wind farms with an interconnector between countries. It achieved its first year of operation in mid December 2021 and has performed as planned, “smoothly exchanging renewable energy between Denmark and Germany, enabled by Hitachi Energy’s HVDC solution with its digital master controller system”, the company says.

Three offshore wind farms in the Baltic, two German (Baltic 1 and Baltic 2) and one Danish (Kriegers Flak), are integrated in the CGS.

The Kriegers Flak and Baltic 2 wind farms are less than 30 km apart and these are linked by means of two sea cables with a transmission capacity of 400 MW – forming the interconnector. The interconnector allows electricity to be traded in both directions – from Denmark to Germany and from Germany to Denmark.

The CGS back-to-back VSC installation employs two serially connected HVDC Light voltage source converters. One converter transforms AC from the Nordic interconnected system (Danish side) to DC. The other converter transforms this DC to the AC of the Continental Europe Synchronous Area (German side).

The back-to-back HVDC system is installed in Bentwisch, near Rostock, Germany. Constructing the back-to-back system on land was more economic than on an offshore platform and makes maintenance easier.

Due to the different voltage levels of the Danish and German grid connections (220 kV, Denmark; 150 kV, Germany), a transformer is installed on one of the two Danish offshore platforms that form part of the Kriegers Flak wind farm.

Among other things, the master controller (installed at the transmission control centre in Berlin/Neuenhagen): calculates the available capacity of the interconnector; prevents overloading by controlling the converter and/or wind farms; maximises feed-in from the wind farms through active system control; and controls power exchange between the grids of both countries via the back-to-back converters.

The Kriegers Flak CGS has been categorised as a “project of common interest” by the European Commission and was also supported under the European Energy Programme for Recovery (EEPR).

In the future, ever more flexible systems and interconnectors will be required to compensate for the fluctuating power generation of weather-dependent wind and solar power plants, says Energinet, and the Kriegers Flak CGS is a good example of this. As well increasing security of supply for both the German and Danish transmission systems, the new link facilitates the integration of regionally generated renewable power in Germany and in eastern Denmark.