PMSM Sensorless Control by Injecting HF Pulsating Carrier Signal Into Estimated Fixed-Frequency Rotating Reference Frame

For permanent-magnet synchronous machines (PMSMs) sensorless control, the widely employed high-frequency (HF) pulsating carrier signal injection method is based on tracking the rotor saliency. It may face the problems of long convergence time, potential start-up failure, and limited system stability. Different from the conventional schemes, the proposed strategy is a direct estimation method. In which, a HF pulsating carrier voltage is injected into the estimated fixed-frequency rotating reference frame other than the estimated synchronous reference frame (SRF). With this approach, spatial saliency tracking observer, which is necessary in the conventional sensorless control, is removed to simplify the control structure and improve the system stability. Furthermore, the rotor position information is directly obtained from the response of injected HF pulsating carrier signal, which can avoid potential convergence failure of tracking observer. In addition, the compensation of system delays existing in the proposed sensorless control strategy is deduced to improve the accuracy of rotor position estimation. For magnetic polarity detection, a new method which has the advantages of high signal-to-noise ratio and low vibration is also investigated. Finally, the experimental results on a PMSM indicate that the rotor position with good steady state and dynamic performance can be obtained accurately with the proposed sensorless control strategy.