Extension of stable operating regions of synchronous machines using low-sensitivity excitation control

In the usual design of optimal linear regulators for synchronous machines, the controller is designed for a particular set of system operating conditions. However, in actual system operation, these conditions are subject to load demands. Consequently, the optimal controller designed for a certain operating condition will no longer yield a satisfactory performance at others. The paper endeavours to overcome this problem by proposing a method for designing optimal controllers with low sensitivity to systemloading conditions, while avoiding the complexity of the resulting controller structure. A numerical example involving a synchronous machine swinging against an infinite busbar is used to demonstrat the usefulness of low-sensitivity controllers in extending the stable operating region.