Offshore wind-powered interconnector ‘black starts’ grid

Transmission system operators (TSOs) 50Hertz and Energinet have successfully used offshore wind power to perform a live simulation of a power grid restart.

They used voltage supplied from two German offshore wind farms and a wind-powered cable connecting Denmark and Germany to restart the grid after a simulated power outage at a German coal plant.

This was the first time a land and sea interconnector and offshore wind power was used to restart a power plant, according to 50Hertz.

Black start capability allows for electricity generation to be restored without relying on external electric power transmission networks.

In 50Hertz and Energinet’s simulation, a coal-fired power plant in Rostock, Germany, was completely separated from the grid.

Energinet, then provided 380kV voltage via the recently inaugurated 400MW Combined Grid Solutions interconnector – which connects Germany and Denmark, and integrates EnBW’s Baltic 1 and Baltic 2 offshore wind farms – and newly constructed converter systems in substation near the port of Rostock. 

German TSO 50Hertz explained that the substation’s back-to-back converter synchronises and connects the two asynchronous power systems of Denmark and Germany.

This helped to restart the Rostock coal plant, successfully simulating the restart of a power grid, 50Hertz and Energinet explained.

Dirk Biermann, chief markets and system operations officer at 50Hertz, said: “This successful start-up attempt illustrates the importance of cooperation at European level in the age of renewables.”

Transmissions system operators regularly test the capability of their grid restoration plans to be prepared for a power outage, but typically use storage capacity from gas-fired power stations because they do not need external power sources to start up.