Stochastic Stability Analysis and Control of Secondary Frequency Regulation for Islanded Microgrids Under Random Denial of Service Attacks

As communication networks are increasingly implemented to support the information exchange between microgrid control centers and/or local controllers, they expose microgrids to cyber-attack threats. This paper aims to analyze the stochastic stability of islanded microgrids in the presence of random denial of service (DoS) attack and propose a mode-dependent resilient controller to mitigate the influence of DoS attacks. Specifically, the small-signal model of the microgrid under the DoS attack is integrated as a stochastic jump system with state continuity disruptions. A new vulnerability metric is defined by using observability Gramians of the stochastic jump system, to measure the vulnerability of the system regarding DoS attack choices. The Lyapunov function analysis is conducted to find conditions sustaining the stochastic stability of the islanded microgrid in the form of linear matrix inequalities. A mode-dependent control approach is proposed for microgrids to mitigate the influence of random DoS attacks. In case studies, the vulnerability analysis and time-domain simulation results show the performance of the investigated microgrid can be degraded when the random DoS attacks exist. When the proposed mode-based secondary frequency controllers are installed, the islanded microgrid can sustain its stability during the attacking period and system dynamics rapidly converge when the DoS attack is over.