Nonlinear single-variable optimisation studies of a.c. turbogenerator performance

A synthesis method is described that is used to produce optimised excitation control of an a.c. turbogenerator when subjected to a large disturbance. The proposed controller incorporates only one extra feedback signal into the excitation system in addition to the normal terminal voltage feedback signal, and the relative merits of four such proposed signals are fully discussed. The method uses single-variable optimisation techniques, incorporating successive quadratic or cubic approximations of a nonlinear polynomial, and, by using dynamic sensitivity methods, gives important additional information on the relative suitability of each of the four proposed feedback signals. An experimental investigation performed on a laboratory micromachine system is also described, and confirms the trends in changes in system transient behaviour predicted by the theoretical studies.