Sensorless Starting Control of a Brushless Synchronous Starter/Generator Based on Estimated Field Current of Its Main Generator

The estimated field current (EFC) of the main generator (MG) contains information related to the rotor position of the main exciter (ME). Besides, MG and ME are mounted on the same shaft of brushless synchronous starter/generator (BSSG). The electrical and structural features indicate that the sensorless control of MG can be conducted with EFC. Since EFCs are nonlinear and have abundant harmonics, their dynamic features are complex and lack research. Therefore, most of the existing rotor position estimation methods are only based on the steady-state characteristics of EFC, and the rotor position information of EFC is not fully exploited. To improve the dynamic performance, a novel sensorless starting control method of BSSG is proposed. First, the quantitative relationship between EFC and ME rotor position is revealed. According to this relationship, a dedicated demodulation method is designed to obtain the rotating angle of ME. Meanwhile, a novel fast initial rotor position detection method is proposed for MG. Finally, combining the rotating angle of ME and the initial rotor position of MG, a continuous rotor position of BSSG can be obtained. The effectiveness of the proposed method is verified by experiment.