Design of a Superconducting Synchronous Generator With LTS Field Windings for 12 MW Offshore Direct-Drive Wind Turbines

Offshore wind generation is an important trend of global wind power generation. To reduce the cost of energy of offshore wind generation, high-power direct-drive wind turbines are being pursued around the world. With the development of superconductors and related technologies, superconducting (SC) generator offers a possible technological approach to produce large-scale direct-drive wind turbines with a modest cost. A design of a SC wind generator (SCWG) for offshore direct-drive wind turbines is presented in this paper. The proposed SCWG is an electrically-excited synchronous generator with stationary field windings made of low temperature superconductor wires. The electromagnetic design considerations on SCWG are studied. The description on design of copper rotor and SC stator are presented. Several key design technologies including rotor cooling and supporting structure design, SC field winding design, and cryogenic refrigeration system for SC magnets are analyzed. The weight and cost of the proposed SCWG are estimated and compared with that of a permanent magnet wind generator (PMWG) design and several existing similar SCWG designs. It is found that the proposed SCWG is 46% lighter than the PMWG with the same specifications. Moreover, a rough estimation of material cost of the SCWG is carried out, and comparison analysis of cost is also performed.