Vinci says the contract, for German transmission system operator Amprion Offshore, is worth several hundred million Euros.
The converter platforms will be installed in the North Sea to connect several windfarms with Germany's national grid.
They will collect the alternating current generated by the windfarms and convert it into high voltage direct current for transport to the onshore stations, located up to 280km away.
The construction of the platforms will take place at Dragados Offshore's yard in Cadiz, Spain, and are expected to generate over 1,000 jobs over the next five years.
With total transmission capacity of 1.8GW, these platforms are designed to supply enough electricity for a major city of around two milion people - about the size of Hamburg - when they become operational in 2028.
The project is an important part of Germany's energy transition plan, says Vinci. Dragados Offshore has already been awarded two other HVDC contracts of this type, both of which are currently in progress.