Structural Optimisation of Offshore Direct-Drive Wind Turbine Generators Including Static and Dynamic Analyses

Abstract

Abstract One way to achieve increased wind capacity is by installing larger and more efficient wind turbines, which results in larger/heavier generators. Direct-drive, permanent magnet generators are favoured due to their increased efficiency, but the added weight is an issue, as this drives up the cost of the nacelle and turbine support structure, along with increasing the manufacturing and installation costs. Therefore, minimizing the mass, particularly the structural mass, of these low speed generators is becoming much more important. A vast amount of research has been done on trying to reduce the electromagnetically ‘active’ materials, but it is the supporting structure or ‘inactive’ materials, that makes up the biggest percentage of the generator’s mass. Therefore, this paper studies the statics and dynamics of a large offshore direct-drive generator’s supporting structure and the opportunities for light-weighting, as well as improvements to the generator’s rotor structure through structural optimisation. The indicator for optimised design is system weight under each predefined scenario. These scenarios will cover different design considerations of the generator’s rotor structure.