Identifying critical risks of cascading failures in power systems

Potential critical risks of cascading failures in power systems can be identified by exposing those critical electrical components on which certain initial disturbances may cause maximum disruption to the systems. The authors investigated the cascading failures in power systems described by the direct current power flow equations, where the initiating disturbances (natural or anthropic factors) give rise to changes in admittances of one or multiple transmission lines. The disruption is quantified with the remaining transmission power at the end of the cascading process. In particular, identifying the critical branches and the corresponding initial disturbances causing the worst-case cascading blackout is formulated as a dynamic optimisation problem (DOP) in the framework of optimal control theory, where the entire propagation process of cascading failures is considered. An Identifying Critical Risk Algorithm based on the maximum principle is proposed to solve the DOP. Simulation results on the IEEE 9-Bus and the IEEE 14-Bus test systems are presented to demonstrate the effectiveness of the algorithm.