Sensitivity Analysis in the Optimal Design of Synchronous Machine Regulators

The usual procedure for the optimal design of linear regulators for synchronous machines is to minimize a chosen quadratic cost function subject to the system dynamics constraints. However, the optimal control synthesized in such a straightforward fashion is unsatisfactory, since it is dependent on the particular choice of system control parameters made by the investigators. Furthermore, in practice, there may be a departure of these parameters from their nominal values. In an attempt to resolve these difficulties, the paper presents a method of synthesizing optimal control in such a way as to minimize a certain cost function, while choosing the system controllable parameters in the region of near-zero sensitivity. Considering a three-machine system as an illustrative example, this method is used as a basis for the selection of voltage regulator gains. It is shown that choosing the gains in the region of low sensitivity of the optimal cost function enhances the system transient response. The method is simple and is capable of handling multi-parameter sensitivity analysis in the framework of optimal control.