Design Concepts for High-Voltage Variable-Capacitance DC Generators

The transmission requirements of the next generation of offshore wind farms, such as the Round Two U.K. offshore development proposals, may rely on high-voltage direct current (HVDC) technology for at least a part of their power collection and transmission requirements. HVDC technology is particularly suited for the transmission of high powers through large lengths of submarine cables; however, its application is limited by the high cost of offshore ac-dc converter stations. This paper therefore investigates the feasibility of the direct generation of HVDC power using a novel generator topology, as an alternative solution to the generation-transmission requirements of large offshore wind farms. A variable-capacitance generator uses electrostatic fields to generate an HVDC output with a minimum of power conditioning and is based on a previous work that suggests system power densities comparable with the conventional generator-transformer-rectifier systems to be achievable.