Rotor position estimation of brushless synchronous starter/generators by using the main exciter as a position sensor

Persistent signal injection in traditional sensorless methods leads to loss, noise, reduction of the starting torque of the main generator (MG) of the brushless synchronous starter/generator (BSSG), and complicated demodulation methods. Moreover, the reversible magnetic saliency of MG and multiple rectification modes of the rotating rectifier cause errors to most existing sensorless solutions of BSSG. To avoid these drawbacks, this paper proposes a novel method to estimate the rotor position of MG for zero- and low-speed operation. Since MG and the main exciter (ME) are mounted on the same shaft, ME is used as a position sensor, eliminating concerns of the reversible magnetic saliency of MG. With reliable indicators in all rectification modes, the position of ME is extracted from the hexagonal trajectory of the rotor current space vector of ME, which is caused by the rotating rectifier. With the estimated position of ME and signal injection into the stator of MG at standstill, the initial position of MG is detected. Then, signal injection is no longer needed and the continuous position of MG is obtained from the estimated rotation angle of ME and initial position of MG. Finally, the effectiveness of this method is verified by experiments.