Potential critical risks of cascading failures in power systems can beidentified by exposing those critical electrical elements on which certaininitial disturbances may cause maximum disruption to power transmissionnetworks. In this work, we investigate cascading failures in power systemsdescribed by the direct current (DC) power flow equations, while initialdisturbances take the form of altering admittance of elements. The disruptionis quantified with the remaining transmission power at the end of cascadingprocess. In particular, identifying the critical elements and the correspondinginitial disturbances causing the worst-case cascading blackout is formulated asa dynamic optimization problem (DOP) in the framework of optimal controltheory, where the entire propagation process of cascading failures is put underconsideration. An Identifying Critical Risk Algorithm (ICRA) based on themaximum principle is proposed to solve the DOP. Simulation results on the IEEE9-Bus and the IEEE 14-Bus test systems are presented to demonstrate theeffectiveness of the algorithm.
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