Speed sensor-less control of an induction motor with rotor flux tracking at very low speed

This paper presents a novel method to estimate the rotor flux position of an induction motor by injecting high frequency signal at very low speed including zero. When the high frequency fluctuating signal is injected in the terminal of an induction motor, the difference of impedance between d-axis and q-axis of the synchronous rotating reference frame can be measured. And this phenomenon is explained by a high frequency model of induction motor, which is oriented with high frequency signal space vector. So the rotor flux angle can be tracked by tuning the space vector of high frequency signal. Experimental results are provided to verify that this algorithm is robust against parameters variation and load change.