Rotor Position Estimation Based on Low-Frequency Signal Injection and Estimated Main Field Current for Wound-Field Synchronous Starter/Generator in the Low-Speed Region

Abstract

Due to reliability problems of mechanical position sensor, rotor position estimation technology is an alternative for the starting control of aircraft wound-field synchronous starter/generator. Reversible saliency and high frequency attenuation characteristics of main machine (MM) may lead to the failure of existing high-frequency signal-based estimation methods. In this paper, low-frequency signal (LFS) injection and novel signal extraction method are combined to estimate rotor position. Firstly, LFS is injected in MM's stator winding, and response signal containing rotor position information is induced in its rotor field winding. Then, the response signal can be extracted from the estimated main field current (EMFC) by band-pass filter. Further, the phase of extracted signal and injected LFS are obtained by two single-phase phase-locked loops (PLL) respectively. Then, the increment of rotor position can be obtained by the two PLLs. Meanwhile, by injecting a specific low frequency square wave, initial rotor position can also be extracted from EMFC, requiring no extra pole identification and phase compensation. Finally, combining initial rotor position and position increment, continuous rotor position of MM can be obtained. Effectiveness of the proposed method are verified by experiments.