Grid Integration of Sandbank 24 Offshore Wind Farm Using LCC HVDC Connection

SUMMARY The Sandbank 24 project is planned to be the world's largest offshore wind farm and is to be located in the North Sea, off the German coast. The wind farm project has received planning permission for the pilot phase. The pilot phase will consist of 80 single wind turbine generators with a capacity of up to 5 MW each. The wind power generated by wind farm will be transmitted via approximately 190km offshore cables and then 50km onshore land cables, and eventually to the E.ON 380kV grid at the Brunsbuttel connection point. Any wind farm installations must meet the Grid Code requirements for connection. However, difficulties have been encountered in meeting these requirements, especially for fault ride through, reactive power and voltage control. In terms of wind farm grid connection, there are number of solutions available, including AC connection, AC combined with FACTS and High Voltage DC (HVDC) connection. With reference to HVDC connection solution, there are two different HVDC transmission technologies, i.e. Voltage Source Converter using IGBTs (VSC HVDC) and Line Commutated Converter using thyristors (LCC HVDC). This paper presents a comparison of various connection solutions for connecting such a large remote offshore wind farm into the grid, including main technical issues, manufacturing feasibility and availability, practical technical solutions and grid code compliance.. The impacts of new offshore connection regulation in Germany on the Sandbank 24 offshore wind farm grid connection are also discussed. The paper mainly describes the commercial and technical benefits of using the LineCommutated Converter HVDC (LCC HVDC) for connecting such a large offshore wind farms to the grid. Case studies of using hybrid HVDC solution which comprises a LCC HVDC and a STATCOM for connecting the 400MW Sandbank 24 offshore wind farm are presented. Simulation results in particular the dynamic fault ride through capability studies show the satisfactory performance and grid code compliance of the proposed LCC HVDC solution during various conditions such as power variation, grid AC fault, etc.