Evaluation of PM Rotor Topologies for Impedance Matching of Small-Scale Passive DC-Connected Wind Generator Systems

This paper forms part of a broader study that investigates the design of permanent magnet synchronous generators for small-scale passive dc-connected wind energy systems. Achieving satisfactory power matching between the wind generator and the wind turbine is often difficult with these systems and a method of impedance matching is necessary. In this paper, generators with different interior permanent magnet rotor topologies are compared with a surface-mounted permanent magnet rotor in terms of dc-grid impedance matching to obtain maximum turbine power point matching. The different wind generator topologies are optimised in a design process whereby internal impedance matching is reached as far as possible. It is shown that only the interior permanent magnet rotor topology generators satisfy the required internal impedance matching. The spoke-type interior permanent magnet generator is found to be superior.