Recently, Vernier permanent magnet (VPM) machines, one special case of magnetic\nflux-modulated (MFM) machines, benefiting from their compact, simple construction and low-speed/\nhigh-torque characteristics, have been receiving increasing interest. In this paper, the Vernier structure\nis integrated with an axial-flux PM machine to obtain the magnetic gear effect and produce an\nimproved torque density for direct-drive wind power generation application. Another advantage\nof the proposed machine is that the stator flux rotating speed can be relatively high when the shaft\nspeed is low. With this benefit, sensorless control strategy can be easily implemented in a wide speed\nrange. In this paper, an improved sliding mode observer (SMO) is proposed to estimate the rotor\nposition and the speed of the proposed machine. With the estimated shaft speeds, the maximum\npower point tracking (MPPT) control strategy is applied to maximize the wind power extraction.\nThe machine design and the sensorless MPPT control strategy are verified by finite element analysis\nand experimental verification.
Loading....