An on-line initial rotor position estimation method for three-stage brushless synchronous machines

According to saliency of the main generator of three-stage brushless synchronous machines, the information of rotor position is implied in performance of stator inductances due to the magnetic saturation effect. This paper studied the principle of initial rotor position estimation of main generators by injecting modulated pulse voltage vectors, and developed the pulse voltage injection scheme according to the characteristics of the rotor excitation current of the main generator. Researches focused on the relationship between the d-axis current variations and voltage vector positions. Because the excitation current of the main generator contains pulsating components, which would influence the precision of rotor position detection, Fourier analysis method and α-β-γ filter were adopted to analysis the difference data of d-axis response currents. Experimental results show that the proposed method simplifies the conventional pulse voltage injection scheme, which needs to detect rotor d-axis direction first and then determine the positive direction. This method has good detection stability, and can effectively reduce the impact of the rotor excitation current pulsation on the detection accuracy.