Closed-loop control on PMSG torque in direct-drive wind power generation system without speed sensor

In this paper, a speed sensorless double-loop control method is researched for PMSG-based direct-drive wind power generation system in order to improve the torque control accuracy without speed sensor. A second order sliding mode observer is proposed based on the linear flux model of interior PMSG. The rotor position is obtained from the defined linear electromotive force with a phase-locked loop. Meanwhile, the stator flux and electromagnetic torque are estimated based on the novel observer proposed in this paper. With the estimated rotor position and the torque, a double-loop control system for PMSG is designed. Finally, the effectiveness of the proposed method is validated by the experimental results.