Sensorless control of doubly salient electromagnetic machine based on coordinate transformation

The sensorless control technology is widely adopted for various applications. In this paper, a novel sensorless control based on coordinate transformation is proposed for doubly salient electromagnetic machine (DSEM). Based on the characteristics of the back electromotive force (EMF), the rotor position signals would be constructed. In order to acquire the commutation instant accurately, two different coordinates are defined and named as original coordinate and transformed coordinate. The detection of three-phase terminal voltages and coordinate transformation are realized in the digital signal process chip of DSP2812, and the estimated position signal is gained by the zero-crossing point of the terminal voltage in the transformed coordinate. The terminal voltage in the transformed coordinate is shifted from the terminal voltage in the original coordinate which is detected by DSP2812. Detailed analysis of DSEM's terminal voltage and the transform angle between two 3-phase coordinates at different speeds are involved in this paper. The sensorless control method is independent with the PWM technologies. A 18kW DSEM prototype is built and the above analysis is verified by the experimental results.