Permanent Magnet Wind Generator with Double Excitation for Smart Grids

The contribution begins with the attention that there is attention of directly grid connected wind turbine systems with generator designs adapting to the grid constraints. This paper considers permanent magnet synchronous generator topologies with rotor field coils to achieve reduced mass with good efficiency for smart grids. Conventional double-excited synchronous generators have surface mounted permanent magnets. However, the low relative permeability of PMs results in an increased air-gap size. This increased air-gap size limits the minimal copper-mass of the rotor-field-winding. To improve on this limitation, Interior permanent magnets (IPM) are used. Three rotor topologies with IPM are presented in this paper. The analysis of their 2D FEM results and optimization are shown considering their magnetizing current, torque, Back EMF for smart grids application. The three rotor topologies are compared on the overall active mass and their performance by considering PM and rotor copper mass, torque capabilities and efficiency. The spoke-type topology with rectangular magnets achieves the lowest total rotor mass reduction of 39% total mass reduction when compared to the topology with PMs that are buried horizontally. The reduced copper mass and flux variation capabilities are good characteristics in wind energy conversion generators with direct grid connections for smart grid.