Biblio

With the increasing application of Information and Communication Technologies (ICTs), cyberattacks have become more prevalent against Cyber-Physical Systems (CPSs) such as the modern power grids. Various methods have been proposed to model the cybersecurity threats, but so far limited studies have been focused on the defensive strategies subject to the limited security budget. In this paper, the power supply reliability is evaluated considering the strategic allocation of defense resources. Specifically, the optimal mixed strategies are formulated by the Stackelberg Security Game (SSG) to allocate the defense resources on multiple targets subject to cyberattacks. The cyberattacks against the intrusion-tolerant Supervisory Control and Data Acquisition (SCADA) system are mathematically modeled by Semi-Markov Process (SMP) kernel. The intrusion tolerance capability of the SCADA system provides buffered residence time before the substation failure to enhance the network robustness against cyberattacks. Case studies of the cyberattack scenarios are carried out to demonstrate the intrusion tolerance capability. Depending on the defense resource allocation scheme, the intrusion-tolerant SCADA system possesses varying degrees of self-healing capability to restore to the good state and prevent the substations from failure. If more defense resources are invested on the substations, the intrusion tolerant capability can be further enhanced for protecting the substations. Finally, the actuarial insurance principle is designed to estimate transmission companies' individual premiums considering correlated cybersecurity risks. The proposed insurance premium principle is designed to provide incentive for investments on enhancing the intrusion tolerance capability, which is verified by the results of case studies.

Cybersecurity of the supervisory control and data acquisition (SCADA) system, which is the key component of the cyber-physical systems (CPS), is facing big challenges and will affect the reliability of the smart grid. System reliability can be influenced by various cyber threats. In this paper, the reliability of the electric power system considering different cybersecurity issues in the SCADA system is analyzed by using Semi-Markov Process (SMP) and mean time-to-compromise (MTTC). External and insider attacks against the SCADA system are investigated with the SMP models and the results are compared. The system reliability is evaluated by reliability indexes including loss of load probability (LOLP) and expected energy not supplied (EENS) through Monte Carlo Simulations (MCS). The lurking threats of the cyberattacks are also analyzed in the study. Case studies were conducted on the IEEE Reliability Test System (RTS-96). The results show that with the increase of the MTTCs of the cyberattacks, the LOLP values decrease. When insider attacks are considered, both the LOLP and EENS values dramatically increase owing to the decreased MTTCs. The results provide insights into the establishment of the electric power system reliability enhancement strategies.

The cybersecurity of the modern control system is becoming a critical issue to the cyber-physical systems (CPS). Mitigating potential cyberattacks in the control system is an important concern in the controller design to enhance the resilience of the overall system. This paper presents a novel robust control architecture for the PV converter system to mitigate the sensor and actuator attack and reduce the influence of the system uncertainty. The sensor and actuator attack is a vicious attack scenario when the attack signals are injected into the sensor and actuator in a CPS simultaneously. A p-synthesis robust control architecture is proposed to mitigate the sensor and actuator attack and limit the system uncertainty perturbations in a DC-DC photovoltaic (PV) converter. A new system state matrix and control architecture is presented by integrating the original system state, injected attack signals and system uncertainty perturbations. In the case study, the proposed μ-synthesis robust controller exhibits a robust performance in the face of the sensor and actuator attack.

The unified power flow controller (UPFC) has attracted much attention recently because of its capability in controlling the active and reactive power flows. The normal operation of UPFC is dependent on both its physical part and the associated cyber system. Thus malicious cyber attacks may impact the reliability of UPFC. As more information and communication technologies are being integrated into the current power grid, more frequent occurrences of cyber attacks are possible. In this paper, the cyber architecture of UPFC is analyzed, and the possible attack scenarios are considered and discussed. Based on the interdependency of the physical part and the cyber part, an integrated reliability model for UPFC is proposed and analyzed. The impact of UPFC on the overall system reliability is examined, and it is shown that cyber attacks against UPFC may yield an adverse influence.