Synchronous Demodulation Method of Rotor Position Estimation for Brushless Synchronous Starter/Generator Using Self-Harmonic Signal Injection

This article proposes a novel synchronous demodulation method of rotor position estimation for brushless synchronous starter/generator (BSSG) at zero and low speed based on self-harmonic signal injection. Instead of the conventional external voltage signal injection, second harmonic in the field winding of the main generator is employed as the indirectly injected high-frequency signal into the rotor winding. In order to achieve the synchronous demodulation scheme, a synchronous demodulation signal generated from the field current of the main exciter by specific second-order generalized integrators is proposed, and the corresponding synchronous demodulation method for the high-accuracy rotor position estimation has been improved based on the cascaded filters. Finally, the proposed rotor position estimation method for the sensorless starting control of BSSG is verified by simulation and experiment results, and a high-accuracy estimated rotor position could be obtained for the high-performance output of BSSG.