Dynamic State Estimation for Multi-machine Power Grids Under Randomly Occurring Cyber-Attacks: A Decentralized Framework

Dynamic state estimation (DSE) plays a vitally important role in modern power systems, and the reliance on the communication network often render the systems to cyber-threats. This paper investigates the secure DSE problem for the multi-generator power grids in the presence of randomly occurring cyber-attacks. To facilitate the decentralized DSE, the synchronous generator is decoupled form the large-scale interconnected power grid with the aid of model decoupling method. A hybrid cyber-attack model, which includes three typical and representative attacks (i.e. denial-of-service attacks, bias injection attacks and replay attacks), is designed and launched in a random way. Attention is devoted to the secure algorithm design problem to light the negative impacts on the DSE performance from the nonlinearity/non-Gaussianity and the random occurrences of the cyber-attacks. Specifically, i) a likelihood function modification method is established where the knowledge of the hybrid-attack model is fully considered; and ii) the associated weights of the particles are updated according to the proposed likelihood function to resist the impacts caused by the randomly occurring cyber-attacks. Finally, simulation experiments with four scenarios are implemented on the IEEE 39-bus system and the corresponding analyses show the validity of the decentralized secure DSE scheme.