A space-vector modulated sensorless direct-torque control for direct-drive PMSG wind turbines

Abstract

This paper proposes a space-vector modulation (SVM)-based direct-torque control (DTC) scheme for a permanent magnet synchronous generator (PMSG) used in a variable-speed direct-drive wind power generation system. A quasi-sliding-mode observer (QSMO) that uses a finite sampling frequency is proposed to estimate the rotor position and stator flux linkage based on the current model of the PMSG. The optimal torque command is directly obtained and used for DTC by which the maximum power point tracking (MPPT) control of the wind turbine generator is achieved without the need of any wind speed or rotor position sensors. In addition to realizing the fixed switching frequency and low flux and torque ripples, the benefits of the proposed control also include the removal of a torque observer, which leads to reduced computational cost, improved dynamic response, and enhanced robustness of the whole system. Simulation studies on a 3-kW PMSG wind turbine demonstrate the effectiveness of the proposed SVM-DTC algorithm with 10 kHz controlling frequency.