Stealth cyber attacks in microgrids: detectability and observability

This chapter discusses a cooperative mechanism for detecting potentially deceptive cyber attacks that attempt to disregard average voltage regulation and current sharing in cyber-physical microgrids. Considering a set of conventional cyber attacks, the detection becomes fairly easy for distributed observer-based techniques. However, a well-planned set of balanced attacks, termed as the stealth attack, can bypass the conventional observer-based detection theory as the control objectives are met without any physical errors involved. In this chapter, we discuss the formulation and associated scope of instability from stealth attacks to deceive distributed observers realizing the necessary and sufficient conditions to model such attacks. To address this issue, two disagreement indices (DIs) for each agent are introduced to detect potential threats to voltage and current, which accurately identify the attacked agent(s) under various scenarios. To facilitate detection under worst cases, the DIs from the secondary voltage control sublayer are strategically cross-coupled to the current sublayer, which ultimately disorient the control objectives in the presence of stealth attacks and provide a clear norm for triggering defense mechanisms. Finally, its performance is simulated under many potential threats on sensors and communication links.