Multi-Stage-Structure-Based Rotor Position Estimation for a Wound-Field Synchronous Starter/Generator in the Low-Speed Region

This paper proposes a novel on-line rotor position estimation method for an aircraft wound-field synchronous starter/generator (WFSSG) in the low-speed region. The method is based on the fact that mutual inductance between stator and rotor windings of the main machine (MM) varies with the rotor position, so it is independent of magnetic saliency. High-frequency (HF) rotating voltage is imposed in the stator windings of the MM, and the rotor position information is extracted from the HF response current signals in the stator windings of the main exciter (ME) in WFSSG. Theoretical expressions of the HF response current signals containing rotor position information in the rotor and stator windings of the ME are derived. Then, harmonics in the ME stator windings are analyzed, and optimum frequencies of the injected HF voltage for MM and excited voltage for the ME are obtained. Also, a novel signal processing method without time delay is adopted to improve the signal-to-noise ratio of the extracted rotor position information. The performance of the proposed method is verified by the experimental results, and accurate rotor position can be estimated even if the magnetic saliency of the MM changes greatly during the start-up process.