Design and Analysis of Permanent-Magnet Vernier Machine for Direct-Driven Wind Power Generator Considering Pole-Slot Combinations

Wind power turbines have increasingly attracted attention as a renewable energy source. Gearboxes in wind turbines reduce their efficiency, require periodic maintenance, and result in gearbox failure. Consequently, direct-driven generators with a high torque density have emerged as an alternative because they transmit the high torque of the wind turbine directly. Permanent-magnet vernier machines (PMVMs) possess a simple and robust structure and significantly high torque density at low speeds. Although various topologies and pole-slot combinations of PMVMs have been considered to enhance their performance, studies on fractional-slot distributed-winding PMVMs (FSDW PMVMs) remain limited compared with those on fractional-slot concentrated-winding PMVMs (FSCW PMVMs). In this study, we designed eight models, including permanent magnet synchronous machines (PMSMs), FSDW, and FSCW PMVMs for direct-driven wind power generators. Their performances in terms of torque density, torque ripple, losses, and power factor were compared and verified using finite element analysis. The FSDW PMVM was proposed as the best model for direct-driven wind power generators based on the torque density, torque ripple, and possibility of performance improvement.