Design Method of a Direct-Drive Permanent Magnet Vernier Generator for a Wind Turbine System

In this study, a novel design method of a direct-drive (DD) permanent magnet vernier generator (PMVG) is proposed for a gearless, high-power, and lightweight wind turbine system. Once the maximum power requirement is given, the base and maximum speeds of the generator are first obtained from aerodynamic characteristics of the wind turbine blade. Then the necessary electrical circuit parameters of the generator are scoped with consideration of the maximum torque per ampere control scheme of a permanent magnet generator. To determine the generator geometries satisfying the scoped parameters, the correlations between the parameters and geometries of a PMVG with concentrated windings are deduced. Using the deduced correlations and the obtained parameters, a systematic design procedure of a PMVG is proposed. For a case study, a 5-kW DD-PMVG with the outer rotor is designed through the proposed method. The performance characteristics of the designed generator are analyzed with finite-element simulations and compared with analytically predicted results. Finally, the experimental results are provided.