A Homopolar HTSG Topology for Large Direct-Drive Wind Turbines

For offshore wind energy, there is a trend toward larger wind turbines. The increased mass of a power-takeoff system increases the installation cost of the turbine. Direct-drive superconducting generators have the potential to reduce the installation cost of wind turbines. For a successful entry to the offshore-wind-energy market, a high-temperature superconducting generator should be as reliable as conventional generators. It is proposed that a stationary superconducting direct-current-field winding may increase the reliability of the generator. An axial-flux homopolar generator topology is proposed to be used in low-speed high-torque applications. The topology is modified by using two superconducting field windings to obtain a bipolar flux-density distribution for higher power density. Different core types and dimensions were examined to find the most suitable design, and a conceptual design of a 6-MW 12-r/min generator is presented.