Abstract
Vulnerable parts in the cyber-physical power system can be maliciously attacked to trigger cascading failures. This paper proposes a defense framework with active and passive defense hybrid strategies. First, a comprehensive vulnerability assessment index is presented to identify vital nodes contributing to failure extension. The proposed index is based on both physical characteristics and topology. Physical characteristic is assessed through the optimal power flow to calculate the load losses. The topology index is obtained by the attacking node and calculating the nodes lost at the steady state. Then, the active and passive defense strategies are established. Deploying false nodes based on the comprehensive vulnerability index is set as the active defense strategy. Changing from centralized control mode to centralized-distributed control mode is the passive defense strategy. The system can defend against attacks with active and passive strategies effectively in the attacking experiments. Finally, we have made a profound study of the first-order percolation problem. The first-order percolation disappears under the active and passive defense strategies in a scale-free network, while the small world network transfers from the first-order percolation to the second-order percolation. The findings indicated that the diverse results resulted from their structure.