Parametric lightweight design of a direct-drive wind turbine electrical generator supporting structure for minimising dynamic response

Heavy, large and robust supporting structures are needed to keep the airgap clearance of direct-drive multi-MW wind turbine electrical generators open and stable. As rotating pieces of machinery, generators vibrate when their natural frequencies are excited introducing potentially large amplitude oscillations due to the forces acting on them that could cause structural fatigue, noise and, in the worst-case scenario, their sudden collapse. A novel procedure for cost-effective and dynamically efficient structural design of a generator has been developed through a series of different finite element studies for a proposed 3MW machine with a conical rotor structure working under extreme conditions. Following a parametric approach coupled with the use of a topology optimisation tool it was demonstrated that the structural mass and dynamic response of the machine can be minimised, while complying with the deflection requirements.