An Alternative to High Frequency Current Detection Techniques for Zero Speed Sensorless Control of AC Motor Drives

The paper presents the main features of the Zero Sequence Technique (ZST), a sensorless algorithm for AC motor drives able to work at low and zero speed with full torque capability. The proposed method is different in principle than any other sensorless technique and much simpler on the implementation aspects, although it still belongs to the class of air gap flux estimators. A distinctive characteristic of the approach is that it also allows us to detect the amplitude of the air gap flux, thus exploiting full flux sensing capability not limited to only flux position estimation. Experimental and Finite Element Analysis results validate the performance of the method in comparison with standard sensorless techniques based on detecting the amplitude variation of high frequency currents.