Design and Analysis of a New HTS Double-Stator Doubly Fed Wind Generator

With the advent of high-temperature superconducting (HTS) materials, increasing attention is given to HTS machines, which have good application potentials in large wind turbine systems. In theory, HTS machines can be much more compact than conventional machines, by virtue of the large excitation current and high efficiency of the former, because the losses in the superconducting wires are virtually zero. In this paper, a novel 3-MW HTS double-stator doubly fed synchronous machine is proposed for wind power generation. The key of the proposed generator is that the magnetic field produced by the dc superconducting field coils in the inner stator is modulated by the rotating iron poles, and the resultant field will finally interact with the magnetomotive force produced by the ac armature windings in the outer stator to produce a constant magnetic torque in the rotor. The main advantage of this doubly fed machine is that the superconducting field coils are stationary. Hence, the cryostat and the exciter are also stationary, which significantly simplifies the cooling and excitation systems. Due to the flexibly controllable excitation current, the generator can have a constant voltage output when the wind speed varies. The performance of the proposed machine is analyzed using the finite-element method.