Improved Rotor Position Estimation Method for Brushless Synchronous Starter/Generator Based on Field Harmonic Signals Self-Injection Scheme

An improved rotor position estimation method for a brushless synchronous starter/generator (BSSG) operating at 0 and low speed based on the field harmonic self-injection scheme is proposed. The second harmonic generated by the rotating rectifier in the field winding of the main generator (MG) is employed as a self-injected high-frequency (HF) signal instead of an extra signal injection. An improved rotor position asynchronous demodulation method without a low-pass filter (LPF) is presented to achieve the simple signal processing, where a dual second-order generalized integrator (DSOGI) is designed to extract the response HF signals and their orthogonal signals. The phase shift of rotor position due to the signal extraction procedure is analyzed, and the corresponding compensation strategy is given to achieve a high-accuracy estimated rotor position for the sensorless starting control. Finally, the feasibility and effectiveness of the proposed rotor position estimation method are verified through the comparative simulation and experiment results.