Design specifications and optimisation of a directly grid-connected PM wind generator

This paper forms part of a broader study on the design and implementation of a slip-synchronous permanent magnet wind generator. This is a gearless, direct-drive generator connected directly to the utility grid without a power electronic converter. The system consists of two integrated generating units, a directly turbine connected slip permanent magnet generator and a conventional grid-connected permanent magnet synchronous generator. The focus of this study is to define the exact design requirements of the directly grid connected synchronous generator unit from the relevant grid code specifications, and to find the optimum design subject to these requirements. Due to the direct grid connection there are clear differences in the design requirements of this machine and those of conventional PM wind generators connected to the grid via a converter. Different generator topologies are evaluated with regard to ease of manufacturing, active mass, PM content and suitability for direct grid connection. Simulation results are presented and measured results are given for an existing directly grid-connected PM generator to confirm the FE-calculations.