A Robust Magnetic Polarity Self-Sensing Method for Start Up of PM Synchronous Machine in Fanlike System

In the field of permanent magnet synchronous motor (PMSM) self-sensing control, the initial rotor position estimation is always important, for which the rotor magnetic polarity estimation is particularly a major task. This paper presents a robust rotor polarity estimation method based on the comprehensive utility of both magnetic saturation effect and rotor angular acceleration. The method can be used for the PMSM system for the fan or pumplike applications. In the method, pulsating-voltage-vector injection is used to track the d-axis and measure the incremental inductance variation of the estimated d-axis. The magnetic saturation effect is magnified by exciting a sinusoidal low-frequency d-axis current rather than the traditional dc current. The angular acceleration is then measured by exciting a positive ramp q-axis current. Both the incremental inductance variation and the angular acceleration contain the rotor polarity information. In this paper, these two methods are combined, as the latter method is to confirm the estimation of the former method. Thus, a robust self-sensing startup is guaranteed. Experimental results validate the effectiveness of the proposed algorithm.