A Generic Bandwidth Determination Method for 3rd-LESO and Analysis of the Extended 4th-LESO Candidates in Saliency-Based Sensorless Control

The linear extended state observers (LESOs) have been widely employed in the saliency-based sensorless control of interior permanent magnet synchronous motor (IPMSM) drives for position and speed tracking. The performances of the LESO are mainly determined by its bandwidth. This paper focuses on the bandwidth determination of the third-order (3rd)-LESOs used in saliency-based sensorless control. A generic method for determining the bandwidth of the 3rd-LESO is proposed by means of the open-loop transfer function, by which both the position and speed tracking performances can be further revealed. The desired bandwidth can be roughly achieved by adjusting the natural frequency and subsequently precisely tuned via two damping factors for the specific application of sensorless control. Subsequently, general guidelines of the bandwidth determination are proposed and summarized. Moreover, an intuitive and improved fourth-order (4th)-LESO, which is extended from the conventional 3rd-LESO, is proposed and comprehensively analyzed for its application in the sensorless control. Compared with the conventional 3rd-LESO, the proposed 4th-LESO exhibits improved capability of the high frequency noise rejection and thus it is a promising candidate for the saliency-based sensorless control. Finally, all the theoretical analyses are verified experimentally on a 1-kW IPMSM drive.