High-Temperature superconducting (HTS) generators are being considered as a competitive candidate in large direct-drive (DD) wind turbines because of their features of being lightweight and compact. Normally a large air gap is inevitable in partially HTS generators, sacrificing the torque producing capability. In this paper, multi-phase armature windings for HTS generators are investigated to reduce the air gap length in HTS generators while not compromising generators' performance. Therefore, the torque density of HTS generators can be improved without any added costs. Five different multi-phase armature winding schemes are studied in the paper. Their performance regarding torque production and rotor losses in a 10 MW DD HTS generator are examined. The findings show that employing multi-phase armature windings can reduce the mechanical air gap without generating extra eddy current losses in the rotor, and the torque production can be improved by up to 9.1%. In addition, the alternating magnetic field reaching the HTS field winding are also reduced by using multi-phase armature windings, resulting in lower AC losses and cooling costs.

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Direct drive high temperature superconducting (HTS) wind turbine generators have been proposed to tackle challenges for ever increasing wind turbine ratings. Due to smaller reactances in HTS generators, higher fault currents and larger transient torques could occur if sudden short circuits happen at generator terminals. In this paper, a finite element model that couples magnetic fields and the generator’s equivalent circuits is developed to simulate short circuit faults. Afterwards, the model is used to study the transient performance of a 10 MW HTS wind turbine generator under four different short circuits, i.e., three-phase, phase-phase clear of earth, phase-phase-earth, and phase-earth. The stator current, fault torque, and field current under each short circuit scenario are examined. Also included are the forces experienced by the HTS field winding under short circuits. The results show that the short circuits pose great challenges to the generator, and careful consideration should be given to protect the generator. The findings presented in this paper would be beneficial to the design, operation and protection of an HTS wind turbine generator.@en

Direct drive high temperature superconducting (HTS) wind turbine generators have been proposed to tackle challenges for ever increasing wind turbine ratings. Due to smaller reactances in HTS generators, higher fault currents and larger transient torques could occur if sudden short circuits happen at generator terminals. In this paper, a finite element model that couples magnetic fields and the generator’s equivalent circuits is developed to simulate short circuit faults. Afterwards, the model is used to study the transient performance of a 10 MW HTS wind turbine generator under four different short circuits, i.e., three-phase, phase-phase clear of earth, phase-phase-earth, and phase-earth. The stator current, fault torque, and field current under each short circuit scenario are examined. Also included are the forces experienced by the field winding under short circuits. The results show that the short circuits pose great challenges to the generator, and careful consideration should be given to protect the generator. The results presented in this paper would be beneficial to the design, operation and protection of an HTS wind turbine generator.@en