Sensorless Starting Control Method Based on Rotor's Direct-Axis Current of Main Exciter for Brushless Synchronous Starter/Generator in Low-Speed Region

The existing rotor position estimation methods for aviation brushless synchronous starter/generator (BSSG) are with such drawbacks as the complex signal processing and phase delay caused by filters. In this paper, by analyzing rotor current characteristics of main exciter (ME), a novel rotor position estimation method based on 'fixed-point sampling on rotor's direct-axis current of ME' used for main machine (MM) is proposed. The method is implemented by three steps: Firstly, rotor's direct and quadrature axis currents of ME is calculated by ME's stator voltage and current signals; Secondly, through fixed-point sampling on the calculated direct-axis current, and performing simple mathematical operations on sampled values, the sine and cosine information containing ME's rotor position information can be extracted, further, phase-locked loop is used to extract ME's rotor position; Finally, based on the structural characteristics of BSSG, rotor position increment of MM can be obtained, and combining MM's initial rotor position, MM's real-time rotor position is obtained to realize sensorless starting control of BSSG. The method avoids high-frequency signal injection and using of filters, and is without influence by MM's operating state and saliency variation. Experiment verifies the effectiveness and high accuracy of the proposed method.