A Rotor Position Estimation Method for LCI-fed Electrically Excited Synchronous Motors Based on a Third-Order ESO Observer

In the position sensorless control of Load Commutated Inverter (LCI)-fed electrically excited synchronous motor, the accurate acquisition of back electromotive force (EMF) and rotor position is crucial for achieving effective control. To precisely detect the back EMF, this paper employs an Extended State Observer (ESO) to estimate the motor's back EMF. Based on the voltage equations of the electrically excited synchronous motor in the two-phase stationary coordinate system, a third-order linear ESO model is constructed to achieve the observation of the extended back EMF. The extraction of the rotor position is accomplished using an third-order ESO-based Quadrature Phase-Locked Loop (ESO-QPLL), where the ESO replaces the PI component in the traditional PI-QPLL. Compared to the conventional PI-QPLL, the ESO-QPLL exhibits superior parameter adaptability and robustness. In this study, a simulation model is developed using MATLAB/Simulink to evaluate the feasibility of the proposed method, and its effectiveness is verified through simulation results.