A WAMS information based transient stability real-time detection scheme for a multi-machine system

In this paper, a transient stability real-time detection scheme based on the WAMS information is proposed for the multimachine system. The relation between trajectory convexity and the Single Machine Infinite Bus (SMIB) system instability is demonstrated mathematically and graphically in the beginning. Based on the relation a simple and easy calculated instability criterion is proposed for the ideal SMIB system. By clustering and equivalence, the multi-machine power system is transformed into an equivalent SMIB system. To weaken the impact of equivalence error and nonautonomous factors, a supplementary instability criterion which only need the information of unbalanced power and angular velocity is proposed for the equivalent system. Thus the instability criterion is extended to the multi-machine system. Based on the instability criterion, a WAMS information based real-time detection scheme is proposed for a multi-machine system. The accuracy, reliability and fast detection speed of the scheme is verified through enormous simulation. Simulation results shows that the real-time detection scheme can correctly distinguish the stable and unstable cases. What´s more, in most unstable cases, the instability can be detected in 0.03-0.7 second after the disturbance removal and the equivalent angle is 90°-180°. By this scheme proposed in this paper, we realize the transient stability online detection for multi-machine system with WAMS information.