AC Loss Analysis and Modular Cryostat Design of a 10-MW High-Temperature Superconducting Double Stator Flux Modulation Machine

Superconducting (SC) machines are one of the best candidates for large-scale direct-drive wind power generation because of its high torque density. In a traditional SC synchronous machine, either armature windings or field windings need to rotate, which makes the structure of the machine complicated. To solve this problem, a high temperature superconducting (HTS) double stator flux modulation (DSFM) machine was proposed. In this machine, the armature windings and SC field windings are placed in outer stator and inner stator, respectively, and the machine works through flux modulation effect by reluctance rotor. Due to modulation effect, there is a high content of harmonic in this machine. Thus, it is important to analyze harmonics influence on SC coils, especially the SC coils ac loss. In this article, the losses of a 10MW HTS-DSFM machine are calculated and analyzed. It turns out that the ac losses of SC coils in this machine is higher compared with the traditional SC synchronous machine. From analytical calculation, the ac magnetic field perpendicular to the tape surface have strong impacts on the SC coils. In order to reduce the ac losses, some suppression methods are adopted on machine structures and SC thermostat. Then, cryostats are designed and the cooling budgets are evaluated. At last, the comprehensive performances of the machine are calculated and its economy in the long term is verified.