Cyber resilience enhancement for microgrid digitalization

• Main Author: Dai, Jiahong
• Other Authors: Xu Yan
• Format: Thesis-Doctor of Philosophy
• Language: English
• Published: Nanyang Technological University 2023
• Subjects: Engineering::Electrical and electronic engineering
• Online Access: https://hdl.handle.net/10356/171843
• Institution: Nanyang Technological University

Microgrid digitalization (MD) is emerging as one of the most innovative approaches for transforming existing power systems toward the future smart grid as the penetration level of distributed energy resources (DERs) is continuously increasing. It enables the traditional microgrid more flexibility and scalability and transforms it into a cyber-physical microgrid (CPM). However, the widely used information and communication technology (ICT) and high dependence on the communication network broaden the attack surface of the CPM. This challenge requires the CPM to be more resilient to these incidents in cyber domains that could support the normal operation of the physical domain. The cyber resilience of the CPM becomes critical in the context of communication failures and malicious cyberattacks. This thesis presents the study of cyber resilience in MD, a co-validation platform for end-to-end cyber resilience evaluation in both the cyber and physical domains, and the enhancement of cyber resilience in CPM against communication failure and cyberattacks. The thesis focuses on enhancing CPM's cyber resilience, considering the cybersecurity triad's availability and integrity. The contributions in this thesis are broadly divided into three parts. The first part proposed and developed a cross-domain validation platform for the cyber resilience evaluation in CPM. The objective of the testbed is to evaluate the impacts from the cyber to the physical domain in CPM and provide a strong-compatible platform to validate the performance of cyber resilience enhancement. The developed testbed separates the controllers and the communication network from the simulation environment to the real controllers and network devices. It enables metric capture by decoupling the storage, computation, and communication in the distributed system, which paths the way to enhance the cyber resilience of the control in CPM end-to-end. The second part proposes a moving target defense based cyber resilience enhancement solution to detect and mitigate denial-of-service attacks (DOSAs) in CPMs. The proposed method employs a rule-based and data-driven approach to achieve dynamic communication topology changes against attacks. The rule-based approach employs a side-channel detector and dynamic priority scheduling to interpret the interactions between the cyber and physical systems of microgrids. This cross-layer design is scalable to realistic controller and device constraints and is compatible with existing designs in both cyber and physical systems. The data-driven approach utilizes software defined networking to obtain real-time latency measurements and employs Q-learning to dynamically change routing flow, thereby changing the topology. It also guarantees survival through moving target defense, even against infinite-energy DoS attacks, at the cost of tolerable performance loss. Numerical simulations demonstrate the effectiveness of the proposed methods in ensuring the survival of certain controllers running on certain devices in realistic communication networks, even against adversarial attackers. The final part presents a blockchain-enabled cyber resilience enhancement framework against false data injection attacks (FDIAs) in CPMs. FDIAs can corrupt the information exchange among controller units and deviate microgrids from normal operation. The proposed framework uses the intrinsic security of blockchain to replace vulnerable information exchange with secure transactions. It deploys smart contracts on the enterprise-level HyperLedger blockchain to provide distributed secondary control and self-healing functions. The hardware-in-the-loop testbed allows for the evaluation of the impacts on both the cyber and physical domains, and the numerical simulations and real-world validation demonstrate the effectiveness of the proposed approaches.