Sensorless Control of a PMSM Synchronous Motor at Low Speed

This paper presents a self-sensing technique for a surface-mounted permanent-magnet synchronous machine (SM-PMSM) based on high frequency voltage injection. The reactances of the high frequency model vary as a function of rotor position and a simple method based on measured currents and voltages can be used to identify those reactances. Using the motor reactances, the rotor position and velocity are determined. The proposed technique is relatively independent of the machine parameters and it can be applied to any type of synchronous machine. The proposed technique has been tested experimentally for a commercial SM-PMSM machine. The experimental results have demonstrated the feasibility of the proposed technique