Dynamic Behavior of a Class of Wind Turbine Generators During Randon Wind Fluctuations

Common in the design of wind turbine generators of the multi-megawatt size is a soft shaft in the low speed part of the drive train. The presence of the soft shaft gives rise to a low frequency torsional mode involving an oscillation where the hub and blades swing relative to the generator. It is shown that normal wind variations can excite this mode resulting in large oscillatory fluctuations in the drive train torques as well as in the generated electric power. Methods of improving the dynamic performance are examined.