Power System Transient Stability Enhancement by Optimal Simultaneous Control of Active and Reactive Power

Abstract

Effective utilization of the thyristorly controlled shunt elements to power system transient stability enhancement requires a strategy of the optimal simultaneous active and reactive power control. A strategy of such optimal control is derived in the paper from direct Lyapunov method as the strategy which forces the fastest dissipation of the total system energy in the transient state. This theoretical control strategy uses two control signals based on the state variables locally not available at the shunt element bus. It is proved in the paper that both theoretical signals can be replaced by the time derivative of two electric quantities derived from local measurements. Control algorithm based on these quantities gives smooth and very effective regulation. Tests done for two and multi-machine systems have confirmed validity and robustness of the proposed new control trategy and control signals.