Frequency Characteristics of Indirect High Frequency Signal Injection Method for Sensorless Starting Control of Aircraft Starter-Generator

This paper proposed an indirect high frequency signal injection (HFSI) method of rotor position estimation for three-stage brushless synchronous machine (TSBSM) used as starter/generator in the variable frequency AC power system. The high frequency signal is injected into the stator windings of the main exciter of TSBSM during three-phase excitation method, then, the high frequency response signal within the AC excitation voltages is injected indirectly into the field winding of main generator through the rotary rectifier for the rotor position estimation in the starting processing. Due to the nonlinear property of rotary rectifier and side effect of rotor speed on the high frequency response signal, the frequency-response analysis for the rotor position estimation error is proposed for the optimized frequency selection of HFSI method, where the rotor position is detected by the asynchronous demodulation method and the initial position angle is calibrated according to the polarity of induced current in main generator stators during the establishment of excitation field. Finally, the proposed analysis of the frequency-response characteristics and the sensorless starting control method are verified to be effective and validated by the simulation and experimental results.