In order to fully utilize the transmission capacity of transmission lines, significant advances need to be achieved in power system control as applied to the damping of low-frequency electro-mechanical oscillations. Power system stability characteristics generally restrict the maximum allowable power transfers at thermal limits of the lines. The stability characteristics of power systems depend on damping devices and damping control strategies employed. While there are many devices that can be used in power systems to achieve damping, the strategies that are currently used to control these devices generally do not provide enough stability enhancement to enable operation near thermal limits. The development of better damping control strategies for large power systems is the focus of this research. This research concerns two related areas: 1) improved methods for power system identification to aid uncertainty model description; and 2) robust control methods that include these uncertainty models to dampen electro-mechanical power system oscillations. To improve power system damping over a set of operating points, methods of system transfer-function identification are needed which can account for non-zero initial conditions and noise. Transfer-function uncertainty models also need to be generated and included appropriately in robust controller design method. Two main goals of this research are: 1) to develop improved methods of identifying system transfer functions and uncertainty models under conditions where power system faults result in significant system changes and where post-fault system transfer-function identification must be accomplished in the presence of both power system noise and initial conditions on lightly damped modes of oscillation; and 2) to investigate and extend recent advances in robust multivariable control theory to obtain improved power system damping controller design method, methods that accommodate the transfer functions and uncertainty models obtained under 1 above.
