Improved Rotor Position Observer for Sensorless Controlled Stator Permanent Magnet Motor Based on Second Order Generalized Integrator

In order to improve the accuracy of rotor position estimation for sensorless controlled stator permanent magnet motor, which back electromotive force (EMF) exhibits nonsinusoidal waves, by employing the second order generalized integrator (SOGI), a revised extended state observer is proposed. The estimated position fluctuation errors resulted from both flux spatial harmonics and the inverter nonlinearities are analyzed. The SOGI is utilized to eliminate the multiple harmonics and extract the fundamental of the estimated back EMF. In addition, the software quadrature phase-locked loop with back-EMF normalization is utilized to calculate the rotor position in order to eliminate the influence of the back-EMF magnitude change at different speed. Finally, the comparison experimental results verify the effectiveness of the proposed method.