OPTIMUM CONTROL STRATEGIES FOR TRANSIENT AS WELL AS OSCILLATORY INSTABILITY OF POWER-SYSTEMS

A co-ordinated dynamic braking strategy and excitation control to arre st the first swing instability as well as subsequent oscillations in a power system is proposed. Comparison is made between braking resistor , resistor-reactor and resistor-capacitor strategies with and without excitation control. The control strategies are obtained in terms of sy stem states and other measurable quantities. Assumptions that the refe rence machine is large and that it is not equipped with dynamic brakin g facility lead to a simpler control strategy. Excitation strategy can also be significantly simplified by relaxing the constraints on the r otor angle. Computer simulation of a multi-machine system shows that a co-ordinated application of braking resistor-capacitor and excitation strategy controls the transients effectively.