The Quadrature Signals Synchronous Demodulation Method for Rotor Position Estimation of Three-Stage Synchronous Machine

In this article, based on the analysis of the rotor position estimation error caused by the asynchronous demodulation method and the low-pass filter (LPF), a novel quadrature signals synchronous demodulation method without the LPF is proposed for the sensorless starting control of the three-stage synchronous machine (TSSM). The second harmonic voltage caused by the rotating rectifier is employed as the high-frequency (HF) signal injected into the field winding of the main generator (MG). The cascade filter composed of the comb filter and the second-order generalized integrators (SOGI) is proposed to extract the HF response signals containing rotor position information and generate the quadrature signals simultaneously for rotor position estimation. Then, the synchronous demodulation method could be simplified to obtain the estimated rotor position with higher accuracy and reliability. Finally, the effectiveness of the proposed method is verified by the simulation and experiment results.