Selection of Excitation Operating Points of 10 MW HTS Exciting Double Stator Direct-Drive Wind Generators Having Single and Double Polarity Inner Stator

The high temperature superconducting (HTS) exciting double stator direct-drive wind generator (HTS-DSDDG) is a promising approach for offshore wind generation, due to the fact that double-stator structure is employed to simultaneously realize stationary seal of the cooling system and brushless of current transfer. In this paper, two kinds of placement strategies of HTS coils are proposed, denoted as single-polarity excitation and double-polarity excitation, respectively. Furthermore, the relationship between the consumption of HTS wires and the volume of the single-/double-polarity HTS-DSDDGs is quantitatively investigated to determine the excitation operating points of HTS coils. Since the different placement strategies of HTS coils will lead to differences of the excitation operating points, as well as differences of generator size and HTS wires consumption, the single-/double-polarity HTS-DSDDGs are compared in terms of the electromagnetic performance, the weight and the material cost. Finally, the conclusion is drawn that the 10 MW double-polarity HTS-DSDDG is lighter and lower cost than the single-polarity one.