Resilient Protection of Medium Voltage DC Microgrids Against Cyber Intrusion

Abstract

Differential current protection has been a reliable approach for line protection in DC systems. However, due to its dependence on communication for terminal current information, resiliency of such a protection approach is poor against external cyber intrusions (ECI) of different types, i.e., false data injection (FDI) and time synchronization attacks (TSA). As a result of which, the system is prone to collapse due to line tripping in the presence of coordinated ECIs. The scope of paper is to propose a resilient protection approach for medium voltage DC (MVDC) microgrids differentiating between the real faults and the ECIs in a system. The approach also detects ECIs on an adjacent line occurring simultaneous to a real fault where the system deploys current limiting reactors (CLR). Phase-modal transformation is carried out to obtain the mode voltages (line and zero) across these CLRs. The mode voltages across the faulty mode networks are utilised along with differential current protection to propose a resilient protection approach against ECIs, which is sensitive to high impedance faults (HIFs). Further, a sensitivity function is formulated which gives the variation of decisive variables i.e., mode voltages with respect to change in decisive parameters i.e., fault resistance and fault location.