Contents I. Introduction
DFIG and direct drive PSMG are two frequently reported methods for wind power generation. One problems associated with DFIG is the presence of the gearbox coupling the wind turbine to the generator. This mechanical element suffers from considerable faults and requires significant maintenance. To improve reliability of the wind mill and reduce maintenance cost, the gearbox can be eliminated by using direct-drive PMSG wind turbine system. This method enables operation of the turbine at its maximum power coefficient over a wide range of wind speeds, leading to a better energy capturing from the wind and reduced mechanical stress on the shaft. The PSMG can be designed to rotate at a speed range of 20–200 r/min, depending on the rated power. Several wind generator manufacturers incorporate multi-pole permanent-magnet generators into their wind turbines (e.g., Jeumont, Lagerwey, Zephyro). As a high-reliability and maintenance-free solution, direct-drive permanent magnet synchronous generator is promising in wind power generation, especially for off-shore applications[l], [2].
