Rotor Position Estimation for Aviation Three-stage Starter/Generators in the Low-speed Region based on Pseudo-Random-Frequency Sinusoidal Injection

The pseudo-random-frequency signal injection method helps to decrease the intensity of acoustic noise generated by high-frequency signal injection. When running as a motor in the starting process, the aviation three-stage brushless synchronous starter/generator is in a high overload condition and the drastic change of the armature current will cause the saliency of the main machine to disappear or even reverse, which results in the failure of traditional rotor position estimation method based on saliency. This paper uses the multistage structure of the three-stage brushless synchronous starter/generator and the mutual inductance between the armature windings and field windings. By injecting two pseudo- random-frequency sinusoidal voltage signals with a phase difference of 90° into the αβ-axis of the main machine's stator and using square wave auxiliary signal to sample the current response signal of the main exciter's stator, the rotor position of the main machine can be estimated and the acoustic noise can be decreased.