EFFECTS OF TORSIONAL DYNAMICS ON NONLINEAR GENERATOR CONTROL

The performance of a feedback-linearizing control for excitation contr ol of a synchronous generator is investigated with respect to unmodele d dynamics of both the turbine generator unit and the transmission net work, It is found that certain types of dynamics that were not modeled during the design of the control enter in a manner that does affect t he performance of the control, but that preserves the linearity of the closed-loop system, Moreover, the control acts to decouple the dynami cs associated with the machine from the dynamics of the transmission g rid, thus preventing subsynchronous resonance between the two subsyste ms when a series capacitor is used to compensate the transmission line , The stability robustness of the feedback-linearizing control is inve stigated with respect to a structured uncertainty, The uncertainty con sidered corresponds to the spring modes of the generator shaft and ent ers in such a way that analysis by Kharitonov's theorem is feasible, I t is shown that the control remains stable over a wide range of values of the shaft parameters, A sliding control is designed and compared t o the feedback-linearizing control with respect to performance degrada tion for this type of uncertainty, and it is found that, because of th e tight saturation limits on the control signal, the sliding control o ffers no discernable performance advantage for this type of structured uncertainty.