Improved Position Sensorless Drive With Inductance Self-Identification Based on Unified Inner Loop Method for PMSM at Low Switching-to-Fundamental Frequency Ratio

Low switching-to-fundamental frequency ratios (SFRs) position sensorless drives are frequently employed in high-power or high-speed permanent magnet synchronous machine (PMSM) systems to address the limitations of position sensors. Aiming at the issue of increased steady-state position estimation error (SSPEE) caused by low SFRs, this article proposes a position sensorless control scheme using a unified inner loop design method (UILDM), equipped with inductance self-identification. This solution presents two salient features: first, it expands the back electromotive force (EMF) design loop, fully considering the impact of current control and SSPEE; second, by using the mechanism and derived accurate model of inductance mismatch, simple and robust inductance identification is realized. Benefiting from this, compared to existing researches, the observer obtains higher bandwidth and clearer performance analysis due to the completed loop. Simultaneously, the inductance self-identification has a lower computational cost and enhanced robustness without additional signal injection or high-frequency samplings. Finally, the effectiveness of the proposed control scheme is validated by simulation and experimental results with an SFR of 10.