Transmission operator Tennet awarded the contract following a competitive tender.
Tennet said the tender had resulted in a 15% reduction in costs. French firm Nexans will provide the cables, while Siemens will provide the high-voltage direct-current converter stations onshore and at sea.
Siemens said it would also deploy its direct-current compact switchgear for the first time.
"The new gas-insulated switchgear for 320kV requires as much as 95% less space compared to the current air-insulated solutions. If they are used on an offshore platform, the size of the platform can thus be reduced by approximately 10%," Siemens said.
Siemens has supplied four grid connections to Tennet, with two more planned
German offshore wind projects are competing for access to the DolWind6 system, but Dong Energy's Gode Wind 3 site has already secured a contract.
Commercial operation of the system is expected in 2023. Siemens said with this deal, it will have supplied six of the ten offshore direct-current connections in Germany.
