A parameter-robust sliding mode observer for speed sensorless torque control of PMSG in wind power generation system

With the capacity of wind turbine developing towards high power, permanent magnet synchronous generator (PMSG) based direct-drive wind power generation system (WPGS) is drawing more and more attentions. In order to improve the reliability and efficiency, as well as the cost-performance ratio of this type of WPGS, speed sensorless torque control is usually demanded. The conventional mathematic models used to develop sliding mode observers (SMOs) are complicated for engineering practices and the electromagnetic torque (EMT) estimation based on current models are very sensitive to parameter mismatches. In this paper, a novel simplified mathematic model is proposed to develop an improved SMO, by which the rotor position orientation and the EMT estimation are realized conveniently and robustly. With the observer, a speed sensorless torque closed-loop control system is established. The accuracy of the observed values and the performance of the total dual-loop control system are verified with simulation and experiments.