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Infrastructure Resilience Conference 2018

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Modeling and Identification of Worst-Case Cascading Failures in Power Systems

Cascading failures in power systems normally occur as a result of initial disturbances or faults on electrical elements, closely followed by situational awareness errors of human operators. It remains a great challenge to systematically trace the source of cascading failures in power systems. In this work, we develop a mathematical model to describe the cascading dynamics of transmission lines in power networks. In particular, the direct current (DC) power flow equation is employed to calculate the transmission power on the branches. By regarding the disturbances (i.e., admittance changes) on the branches as the control inputs, we formulate the problem of determining the initial disturbances causing the cascading blackout of power grids in the framework of optimal control theory, and the magnitude of disturbances or faults on the selected branches can be obtained by solving the system of algebraic equations. Moreover, an iterative search algorithm is proposed to look for the optimal solution leading to the worst-case cascading failures. Theoretical analysis guarantees the asymptotic convergence of the iterative search algorithm. Finally, numerical simulations are carried out on the IEEE 14 Bus System to validate the proposed approach. More importantly, the validation results demonstrate that power networks can be completely destroyed by disruptive disturbances on certain branches. In the simulations, the convergence rate of the iterative search algorithm depends on the initial condition of the numerical solver while solving the system of algebraic equation in each iteration. The proposed approach allows us to determine the most disruptive disturbances on the targeted branch, which provides a new perspective of designing the corresponding protection strategy to enhance the resilience and stability of power systems and interdependent critical infrastructure systems. Future work includes improving the cascading dynamics of power system with the AC power flow equation and designing cooperative control strategies of protective relay to protect power systems

Chao Zhai
Singapore-ETH Centre; Nanyang Technological University
Singapore

Hehong Zhang
Singapore-ETH Centre; Nanyang Technological University
Singapore

Gaoxi Xiao
Singapore-ETH Centre; Nanyang Technological University
Singapore

 

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