Improved Rotor Position Estimation Method of Brushless Electrically Excited Synchronous Starter/Generator

This article presents an improved rotor position estimation method for a brushless electrically excited synchronous starter/generator (BESSG). Based on the multistage characteristics of BESSG, a high-frequency voltage is injected into the stator side of the main machine (MM), and the estimated rotor position is obtained through the estimation of excitation current. To suppress the estimated rotor position harmonic error caused by inverter nonlinearities, a novel phase-locked loop based on the gradient descent algorithm is proposed. In this method, the weight of harmonics is adjusted iteratively to improve the accuracy and reliability of the rotor position estimation. Experimental results have verified the feasibility of the proposed strategy.