Low Speed Sensorless Current Control for PMSM with Search-Based Observer (SBO)

This paper presents sensorless current control of a PMSM using a Search-Based Observer (SBO) employing HF injection. A continuous pulsating scheme is employed and the variation of the HF current amplitudes due to magnetic saliency is discussed for different current/speed operating points. The internal processes of the SBO are outlined with a PLL-based scheme to select a suitable Look-Up Table depending on the instantaneous q-axis current and rotor speed operating point. Sensorless current control results are shown for constant speed - variable load and also variable speed - constant full load operation.