Optimum control strategies for transient as well as oscillatory instability of power systems

A coordinated dynamic braking strategy and excitation control for arresting 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 system states and other measurable quantities. Assumptions that the reference machine is large and that it is not equipped with dynamic braking lead to a simpler control strategy. The excitation strategy can also be significantly simplified by relaxing the constraints on the rotor angle. Computer simulation of a multimachine power system shows that a coordinated application of braking resistor-capacitor and excitation strategies controls the transients effectively