ALEGrO

Until November 2020 the grids of Belgium and Germany, two neighbours at the core of the European market, had no direct connection at all. ALEGrO, short for Aachen Liège Electricity Grid Overlay, closed that gap with a single 90 km cable buried the whole way from Lixhe, near Liège, to Oberzier, near Düren.

The two operators, Elia in Belgium and Amprion in Germany, inaugurated it on 9 November 2020. Market trading followed in steps: the day-ahead market from 18 November and the intraday market from 8 December. The EU treated it as a Project of Common Interest and part-funded it through the TEN-E programme.

The technology is a voltage-source converter at each end, the HVDC PLUS system from Siemens Energy, which uses modular multilevel converters. That choice matters for a link buried inside two meshed AC grids. Because the flow on a DC link is set by the operator, it does not simply follow the path of least resistance through the surrounding AC lines. Siemens Energy says the link strengthens supply security in the Aachen–Cologne region and describes the converters as a firewall that stops disturbances spreading from one grid into the other. During commissioning the link also demonstrated a black start, re-energising part of a dead grid from the other side, which Siemens Energy called a first for this interconnector.

“ALEGrO is a central electricity bridge in the heart of Europe, which couples the internal electricity market even more intensively,” Amprion’s chief executive Hans-Jürgen Brick said at the opening.

The first year gave a measurable answer. Elia reported in November 2021 that ALEGrO had been available 93% of the time and had carried exchanges totalling 4.5 TWh. For a first-of-its-kind link on a busy border, that is a strong record.

Siemens Energy says the project came in on time and on budget but gives no cost. The underground-cable technique it relies on is explained in the HVDC explainer.