A Transformerless generator-converter concept making feasible a 100 kV light weight offshore wind turbine: Part I - The generator

A novel HVDC technology which enables lightweight HVDC machines is described in two papers: Part I describes the concept of a segmented HVDC generator and some of its possible designs. Part II addresses the modular AC/DC-converter. In both papers the HVDC concept is applied in an electric drive for an offshore wind turbine. The HVDC technology is a modularized electric drive train in which the connection between VSC converter modules and machine modules will have a great influence on the required insulation thickness in the machine. Two main effects are obtained: Better insulation coordination within the machine and the possibility to exploit the benefits of HVDC insulation. A case study indicates the possibility to make a transformerless 100 kV DC electric drive for offshore wind turbines. The high voltage is achieved at the very first steps in the energy chain. For moderate transmission distances no further voltage transformation steps is necessary, thus minimizing the needed components for offshore energy transmission and increasing the total efficiency of the system.