Harmonic suppressed sensorless control for PMSM based on enhanced repetitive compensation sliding mode observer (SMO-ERC)

In permanent magnet synchronous motors (PMSMs) sensorless control, the sliding mode observer (SMO) has emerged as a solution for rotor position estimation due to its advantages of high robustness, low cost, and superior dynamic performance. However, the inevitable aperiodic and periodic disturbances present in the control system can induce harmonics in the back electromotive force (EMF), which affect the accuracy of position estimation. Conventional sliding mode observer with low-pass filter (SMO-LPF) inevitably introduces phase lag, parameter sensitivity, and signal discontinuity issues. This paper proposes a novel composite controller that combines enhanced repetitive control (ERC) and SMO. The method utilizes the periodic signal suppression capability of repetitive control (RC) to compensate for the harmonics of current, thereby reducing the interference of low-order harmonics on position observation. Additionally, approach ensures the stability of the sliding mode while retaining the strong robustness of the SMO. The simulation results demonstrate that the proposed controller exhibits excellent harmonic suppression capability in terms of magnitude-frequency characteristics. Furthermore, comprehensive simulation experiments including dynamic response analysis, robustness testing, and speed estimation accuracy verification have conclusively validated the effectiveness of the novel approach.