Sensorless control strategy for doubly salient electro-magnetic machine based on the line-to-line excitation flux linkage

This article presents a sensorless control strategy based on the line-to-line excitation flux linkage for doubly salient electro-magnetic machine. The negative-going zero-crossing points of the line-to-line excitation flux linkage are detected to estimate the position and speed. To solve the problems of direct current (DC) bias and error accumulation in pure integrator, a combination of first-order low-pass filter and first-order high-pass filter is adopted to estimate the line-to-line flux linkage. Considering that the self-inductance obviously varies with the position and the phase current, an equivalent inductance is introduced to calculate the line-to-line excitation flux linkage in the whole period. The commutation error caused by the filter and the armature reaction is analysed and proved to be within +/- 6 degrees. The proposed method can be applied to either the three-state standard angle control or the six-state advanced angle control. The experiment platform based on a 9-kW/3000-rpm DSEM is built, and the validity and feasibility of the proposed strategy are proved.