Adaptive SFBEMF Observer-Based Position Estimation Method With DC Error Rejection for IPMSM Drives

Precise rotor position estimation is significant to guarantee excellent sensorless control of interior permanent magnet synchronous motor (IPMSM). A synchronous frequency-based back EMF (SFBEMF) observer with high-order phase-locked loop (PLL) is proposed to solve the problem of inaccurate position estimation. Due to the adverse effects of inverter nonlinearity, flux spatial harmonics, and current measurement offset error, the odd harmonics (especially fifth and seventh harmonics) and dc error are common in the back electromotive force (EMF), causing intolerable position error, and the traditional back EMF observer cannot address this problem well. Therefore, an SFBEMF observer, possessed of adaptive bandpass characteristic, is designed in this article to extract the accurate fundamental back EMF with unity gain and no phase lag. Besides, high-order PLL is employed to overcome the defect in second-order structure to obtain dynamic performance improvement. The feasibility of the proposed method is experimentally evaluated on a 1.5-kW IPMSM platform, and it proves that the rotor position and speed estimation capability is enhanced with the SFBEMF observer for superior sensorless control performance.