A novel approach for sensorless control of PM machines down to zero speed without signal injection or special PWM technique

A novel approach is developed in this paper for sensorless control of permanent magnet (PM) machines down to zero speed without signal injection or special pulsewidth modulation (PWM) techniques. Taking advantage of the low inductance in a PM machine, the phase current ripples under a conventional PWM excitation are measured to derive the rotor position and speed. The new approach can also be used to estimate the rotor position at standstill if a minor rotor saliency exists. Neither prior knowledge of machine parameters, nor any special signal injection, is needed for the rotor position detection. Sensorless control of a PM machine based on the proposed scheme has been investigated by comprehensive computer simulations. Experimental results are presented to verify the effectiveness of the approach.