Unified control for synchronous-machine stabilisation

This paper describes the theory and procedure for the design of a unified control to improve the stability of a synchronous machine whenever a major disturbance occurs. Using a nonlinear state-space model in directphase quantities, a direct-optimisation technique has been used to derive the unified controls that are effective for the most common types of balanced and unbalanced faults. Practical considerations such as the relative frequency of occurrence of various faults are taken into account. It is shown that the unified controls give an improved system performance over that obtained with the use of conventional controls.