Improved sliding mode observer for position sensorless open-winding permanent magnet brushless motor drives

To enhance the accuracy of estimated rotor position for sensorless controlled permanent magnet synchronous motor, the strategy based on sliding mode observer (SMO) with dual second order generalized integrator (DSOGI) is proposed. The SMO is utilized to estimate the back electromotive force (EMF). Considering the estimated back-EMF harmonics resulting from both flux spatial harmonics and inverter nonlinearities, the DSOGI is applied to eliminate multiple orders harmonics and extract the fundamental wave of the estimated back-EMF for calculating the rotor position. Therefore, the DSOGI can effectively reduce the influence of the estimated back-EMF harmonics and improve the accuracy of rotor position estimation. 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 changed back-EMF magnitude at different speed. Finally, to illustrate the effectiveness of the proposed strategy, the experimental platform of an open-winding permanent magnet brushless motor is built. The comparison results verified that the drive system performance of both steady state and dynamic state is improved. © 2019, Electromagnetics Academy. All rights reserved.