Multistage Adversarial Game for Cyber-Physical Attacks Protection of Smart Grids

A smart grid is a large-scale cyber-physical fusion system where the physical layer and the cyber layer are interdependent. Attackers only need to invade the cyber layer, relying on its control function and cascading failures, to paralyze the smart grid. To analyze the real interaction between adversaries in the smart grid, we propose a new multistage adversarial game model that protects smart grid against cyber-physical attacks. Attackers can destroy the regional control center of the cyber layer, whereas defenders can strengthen the physical layer nodes. The solution of such game is based on the Minimax-Q algorithm. Both attackers and defenders can actively participate in the game and maximize their minimum rewards in this multistage game. Cascading failures and optimal load shedding are utilized to design the reward function. We apply this model to IEEE 39-bus system and compare it with a nonadversarial game. When defenders are passive players, the load loss is 52.48${\mathrm{{\% }}}$ after two actions by the attacker. When defenders are active players, it takes at least four pairs of confrontation actions to inflict a 50${\mathrm{{\% }}}$ load loss. The results show that attacks on the cyber layer are more destructive and also give rise to various defense strategies.