Initial position estimation of permanent magnet synchronous motors based on variation behavior of winding inductances

An estimation method of initial rotor position is a difficult research branch in permanent magnet synchronous motors(PMSM), it is also an important research branch in sensorless technique. In PMSM with a saliency pole structured rotor, influenced by saliency effects, the self-inductance and mutual-inductance present periodicity variation, Starting from this feature, Firstly, the method of injecting high frequency low voltage pulses is utilized for identifying the line inductance and then the influence of winding current to line inductance are thorough analyzed by Fourier series decomposition. Secondly, using the rotational coordinate transformation, the fundamental harmonic and third harmonic can be eliminated to some extent, and then the inductance can be presented by a sine function, then the position vs. inductance characteristics are modeled for estimating the rotor position. The experimental results show that the proposed method estimates the initial rotor position reliably and efficiently.