Impact of Stator Segmentation on Forces and Vibrations in PM Generators for Offshore Wind Power

The ModHVDC concept is a modular permanent magnet generator which uses insulated stator segments with dedicated power electronic converters to produce HVDC. This could significantly reduce the number of required power conversion steps for HVDC-connected offshore wind parks. However, the concept poses structural challenges to the machine design, which are investigated in this paper. It is observed that segmentation of the stator has two major effects on the harmonic forces that occur inside in the machine: the addition of low spatial order harmonics, referred to as the segment harmonics, and an increase of the cogging torque. In addition, the structural integrity of the stator was found to be reduced. Based on these findings, design recommendations are put forward to mitigate the downsides of stator segmentation.