Comparison of High Frequency Voltage Injection Methods for Shaft Sensorless Control of Wound-Field Flux Switching Machine

This paper compares three shaft sensorless control schemes for wound-filed flux switching machines based on high frequency square-wave voltage injection. Because the machine has armature and field windings, high frequency voltage can be injected and processed in the armature winding, as the conventional PMSM, or injecting in one winding and processing the signals from the other winding. The analytic result shows that the scheme with d-axis voltage injection and q-axis current processing is generally similar to that used for PMSMs. An additional polarity identification is required to prevent phase error in the estimated position. However, schemes with injection and processing at separate windings have superior performance, and do not require polarity identification. In addition to the theoretical analysis, experimental verifications of the proposed sensorless control schemes are also presented.