Reliability Studies in Information and Communication Technologydominated Distribution Systems: Adequacy Assessment of Cyber-Physical Distribution Networks Including Microgrids

Abstract

In the past decade, the emergence of high-speed, reliable, and smart computer systems has caused a revolution in control systems, and digital systems are replacing traditional and analogous control systems in industries. Power systems are not an exception, and Information and Communication Technologies (ICTs) are increasingly integrated into these systems. Due to the increasing deployment of ICTs in power infrastructures, the power systems will become “cyber-physical power systems.” While it is exciting to contemplate all the benefits that ICTs bring to power systems, we deal with not-so-perfect components and designs of ICTs, so failures do occur in these technologies; therefore, ICTs influence the reliability of the overall system. With this perspective, the fundamental objective of this Ph.D. research work is to develop suitable methodologies for assessing the impact of ICT component failures on the reliability of cyber-physical distribution systems and microgrids. To achieve the primal objectives of this study, three novel reliability assessment frameworks are proposed for Cyber-Physical Microgrids (CPMGs) and Cyber-Physical Distribution Systems (CPDSs). This thesis includes two parts. Part 1 consists of five chapters and intends to provide supplementary explanations for the appended papers in Part 2. This part presents a comprehensive overview of the literature on the reliability of CPDSs and CPMGs. It explains the Monte Carlo Simulation (MCS) and state enumeration method, which were used to develop the reliability assessment frameworks. It also provides some additional simulation results. The proposed frameworks are explained in the appended papers. In the first paper, an MCS-based framework for the adequacy assessment of grid-connected CPMGs is developed. The impact of the failure of ICT components involved in the system control on the reliability of grid-connected CPMGs is investigated through the proposed framework. This framework can also be applied to isolated CPMGs with minimum effort. This framework is further extended in the second paper to include multi-microgrid considerations. In addition, a methodology is proposed to investigate the impact of ICT components’ failure on the functioning of protection and restoration systems when a centralized scheme is adopted for system protection. Both of these frameworks are based on MCS. While reliability assessment methods based on MCS are effective and can include the detail of the system as desired, they are relatively time-consuming. In this regard, a novel analytical methodology is proposed in the third paper for the adequacy assessment of Cyber-Physical Multi-Microgrid (CPMMG) distribution systems to accelerate the procedure. The proposed framework uses the state enumeration method, classification of components, graph theory, reliability block diagram, and probability theory. Besides the main objectives that define the main research questions of this thesis, several other questions were raised, which are partially answered in this thesis. In response to these research questions, a detailed model for the reliability assessment of solar farms is proposed, a generic scheme for treating uncertainties associated with the duration of contingency events is outlined, and two new reliability indices are formulated to take the impact of ownership of the microgrids in a multi-microgrid system into account. The effectiveness of the proposed methodologies is demonstrated by applying them to suitable case studies. Further support is provided by analyzing the impact of device-level failures of cyber systems on the reliability of CPMGs and CPMMG distribution networks through quantifying well-known reliability indices. In brief, the primary conclusion of this thesis is that the adverse impact of device-level failures of cyber systems on the reliability of distribution systems and microgrids can be effectively mitigated by improving the cyber system topology and adding redundancy for critical cyber components in the system. In such an enhanced cyber system, the adverse impact of cyber failures compared to the functionalities they bring to distribution systems is negligible. However, to achieve such a cyber system, reliability studies are crucial.