Proportional-type non-linear excitation controller with power angle reference estimator for single-machine infinite-bus power system

This study suggests a non-linear control algorithm for the exciter controlling a single-machine infinite-bus system, considering the non-linear dynamics with parameter and sudden input power variations. This study provides three contributions: (i) an estimation algorithm is designed to estimate the power angle operating point for the terminal voltage to be regulated to its desired value, incorporating the disturbance observer (DOB); (ii) a DOB-based proportional-type non-linear stabilising algorithm is systematically derived using the estimated power angle operating point; and (iii) it is rigorously shown that the proposed proportional-type non-linear controller always removes the steady-state errors without integral actions for error variables. The simulation results confirm the effectiveness of the proposed technique under several transmission line fault scenarios.