Improved rotor flux observer for sensorless control of PMSM with adaptive harmonic elimination and phase compensation

In this paper, a sensorless control strategy of a permanent magnet synchronous machine (PMSM) based on an improved rotor flux observer (IFO) is proposed. Due to the unknown integral initial value and the high harmonics caused by current sampling and inverter nonlinearities, the flux linkage estimated by traditional rotor flux observer may be inaccurate. In order to address these issues, a self-adaptive band-pass filter (SABPF) is designed to eliminate the DC component and high-frequency harmonics of the estimated equivalent rotor flux linkage. Furthermore, in order to avoid that the design of PI parameter is influenced by the amplitude of equivalent rotor flux linkage, an improved phase-locked loop (IPLL) is employed to obtain the rotor speed and to normalize the estimated equivalent rotor flux linkage. In addition, angle shift caused by an SABPF is compensated to improve the accuracy of the estimated flux linkage angle. Besides, the parameter robustness of this method is analyzed in detail. Finally, simulation and experimental results demonstrate the effectiveness and parameter robustness of the proposed method.