Robust Adaptive Transient Stabilization of a Synchronous Generator with Parameter Uncertainty *

A robust nonlinear state feedback control achieving transient stabilization is designed on the basis of a third order model of a synchronous generator connected to an infinite bus, relying on the well-understood nonlinearities of the model but not on the parameters which, with the exception of the synchronous speed, are not assumed to be known and are also allowed to be time-varying (within known bounds) to account for unmodelled dynamics. Sudden mechanical power failures, short circuits, infinite bus perturbations may drive the generator outside its stability region and therefore out of step. The proposed robust nonlinear excitation control prevents the machine from going out of step in the presence of mechanical and/or electrical parameter perturbations: when all parameters are equal to their nominal values, the operating condition is the only equilibrium point of the closed loop system with an explicitly computable stability region; boundedness and L∞ and L2 disturbance attenuations are guaranteed from the power angle and relative speed regulation errors with respect to time-varying parameter variations from nominal values. An adaptive option can be added to the nonlinear robust controller which guarantees asymptotic speed regulation if the parameter variations from nominal values become constant.