Rotor Position Estimation Method Based on Harmonic Signal for a Wound-Field Synchronous Starter/Generator in the Low-Speed Region

During on-load starting process of an aviation wound-field synchronous starter/generator system, accurate rotor position information is required. Mechanical position sensor is susceptible to interference, increasing volume and weight, so online rotor position estimation is more desirable. Harmonics of main exciter (ME) caused by rotating rectifier are analyzed, and the fifth harmonic is used creatively to estimate rotor position in this article. In this method, by performing coordinate transformation on stator current of ME, rotor position increment is extracted and obtained through a low-pass filter. Meanwhile, taking advantage of the unidirectional conduction characteristics of rotating rectifier, a new idea to estimate initial rotor position is also proposed. In this approach, pulse signal is injected into the stator winding of main generator (MM) every fixed electrical angle, then the maximum and minimum current response correspond to that of MM's S and N pole respectively. Finally, combine initial rotor position and position increment, continuous rotor position of MM can be gained. The proposed methods avoid dependence on the saliency of MM, require no high-frequency signal injection and do not need secondary magnetic pole identification. Effectiveness and advantages of the proposed method are verified on the test.

I. Introduction

With the development of more/all electric aircraft power system, the integrated starter/generator (ISG) technology has been widely studied [1], [2]. Several types of machines can serve as ISG [3], [4], [5], and the wound-field synchronous starter/generator (WFSSG) is an excellent one with the merits of high reliability and so on, so it is very popular among many aircrafts [6], [7], [8]. Generally, WFSSG is just a generator to provide power for aircraft after aeroengine starting, and the starting power of aeroengine is supplied by the auxiliary compressed air unit. To simplify the pneumatic system and thus increase reliability, WFSSG can be also used as a starter to crank the aeroengine to ignition speed. Then WFSSG turns to the generation mode, and the ISG system is realized [6], [7], [8], [9].