Interdependency in cyber-physical power systems enables efficient monitor and control, but also brings out many threats, leading to catastrophic blackouts. To address this problem, the propagation mechanism of cascading failure in systems is analyzed. In this paper, we propose the partial random coupling systems model, and detail the interactive mechanism between physical power grid and communication network. Then, the modified failure mechanism is present, including two-stage redistribution types of traffic loads in physical power grid, and stochastic routing strategies in communication network. In simulation, the impact of attack scenes and topology structure on systems robustness is studied. Compared with random attack, high degree/betweenness attack results in first-order transition of cascading failure at a critical point, and causes more serious damage on systems. Besides, we have proved the positive correlation between clustering coefficient and robustness. To random attack, the systems consisted of double-star network behave more robust than systems consisted of mesh network, and also indicate the misproportion of increase between average dependent degree and systems robustness.
Cascading failure triggered by tiny failure iteratively propagates between physical power grid and communication network, causing severe damage on cyber-physical power systems. In this paper, we study the protection strategies of active defense to improve the robustness of systems. Based on analysis of cascading failure in systems, we classify failure into three types, structural failure, overload failure, and interdependent failure. Due to the severe damage caused by overload failure, we propose four protection strategies of active defense, through interdicting propagation path of cascading failure, to prevent overload failure. Compared with traditional redundancy protection and structure optimization, the protection strategies are economical and efficient, and can defend unknown attack. In simulation analysis, the protection strategies of active defense are proved to be effective in prevention of cascading failure.
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