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This paper introduces the concepts of platformless DC connections of offshore wind turbines. First, the paper describes the possible and preferred wind turbine drivetrain arrangements capable of producing sufficiently high DC voltage. Then, the electrical system designs appropriate for the platformless DC architectures are discussed. After that, the potential economic benefits of direct DC connections of offshore wind turbines are analyzed, showing significant CapEX reduction up to 20-25% when compared to the AC collection and transmission solutions. Control concepts of the wind farm plant and DC connection system are also briefly discussed. The paper concludes that the platformless DC connections would offer lower cost, higher efficiency and enhanced grid support, thus promising for medium and large offshore wind plants in many cases. [ABSTRACT FROM AUTHOR]

This paper describes voltage source converter (VSC) offshore technologies for expansion of point-to-point transmission systems to HVDC offshore grids. Today several gigawatt wind farm projects are underway or have been proposed in the North Sea, Baltic Sea and Atlantic Ocean. These first offshore VSC stations has been installed on oil and gas platforms for power from shore in 2005 or using structures that are lifted on site for connection of wind farms in 2010. New and innovative modular solutions for converter offshore platforms in the gigawatt-range have been developed. As the offshore wind generation increases it makes sense to connect the offshore converters into a multi-terminal grid for better utilization of the transmission systems and connection to balancing power. The key technological cornerstones to plan and start building the first parts of HVDC offshore grids are available today and the gaps for deployment of a full-fledged offshore grid are outlined. [ABSTRACT FROM PUBLISHER]