Design interactions of a flexible stator mounting for a permanent magnet synchronous generator

A high pole number, permanent magnet, synchronous generator can be directly coupled to a low speed wind turbine thereby eliminating the need for a gearbox while still generating at 50 Hz. However, as the generator has a very small pole pitch, conventional damper windings cannot be used to damp power angle oscillations. Instead, damping is provided by connecting the stator to the nacelle by a spring and viscous damper. In this paper, the effect of spring stiffness, damping coefficient, and loading on the generator oscillation modes are examined by eigenvalue analysis. The implications for the design of generators with ratings typically found in wind turbine applications are elaborated