Self-sensing Control of a Synchronous Homopolar Machine Using Field Current Response from Phase-shifted PWM

The reliability and cost of the electric drives can be improved by implementation of a sensorless control. One of the most challenging problems is the sensorless control at zero speed, where self-sensing methods should be implemented. Synchronous homopolar motor has major advantage for encoderless operation due to the presence of a field winding. The position estimation for low and zero speeds can be implemented using stator voltage injection together with analysis of the response in the field current. In order to decrease negative impact of the self-sensing position estimation to the performance of the drive, the phase-shifted PWM was proposed to generate the voltage injection into stator windings. The developed self-sensing control strategy was implemented, and simulation results are provided.