Sensorless starting control of brushless synchronous starter/generators for the full-speed range

Signal injection degrades the starting performance of the brushless synchronous starter/generator (BSSG), and reversible magnetic saliency of the main generator (MG) leads to failure for most traditional sensorless methods. A novel full-speed sensorless starting control method of BSSG is proposed to solve these problems. The main exciter (ME), mechanically coupled to MG, is used as a position sensor of MG at low speed. The position of ME is extracted from the hexagonal trajectory of the rotor current space vector and then converted into the rotation angle of MG. At standstill, a fast initial position detection of MG is conducted with the electromotive force (EMF) of MG, induced by the establishment of the field current of MG. Then, the continuous position of MG is the sum of the estimated rotation angle and initial position. At high speed, flux weakening of MG is achieved by changing the structure of ME, invalidating the approach dependent on ME. Thus, estimations at low speed are replaced by ones based on extended EMF of MG gradually before the structure change. Signal injection is not needed and effects of reversible magnetic saliency are avoided in this approach. The effectiveness of this method is verified by experiments.