Design and Analysis of Resilient Distribution Systems

Abstract

Distribution system resilience is an emerging topic of interest given the rising numbers of extreme events and their adverse impacts on the power grid (for example, Hurricane, Maria in Puerto Rico, USA and the cyber-attacks on the power grid in Ukraine). The area of power system resilience is both interesting and challenging given the varied definitions of resilience and multiple factors that impact it. This report provides a detailed discussion on resilience in the context of power systems, the importance of resilience in distribution systems, the impact of distributed generation on distribution system resilience, and the state-of-the-art and research gaps in modeling and design of resilient distribution systems. Literature review showed that distributed generation resources can enhance grid resilience by enabling islanded operation of distribution systems during prolonged grid outages. However, planning for such resilient distribution systems requires performing modeling and analysis over multiple timescales ranging from milliseconds to several days. Moreover, both technical and economic parameters must be considered. To design the resilience of the distribution system, the REopt tool has been utilized. The REopt tool provides insights into the energy requirements for a certain number of days of autonomy; however, it is limited to analyzing energy balanced systems and does not support network model system. Therefore, to enhance the reliability of the system, the same data obtained from REopt is used in the EMTP tool. EMTP, integrated with MATLAB/Simscape modeling, is chosen for network modeling, and handling unbalanced system scenarios. In normal conditions, the data obtained from REopt is utilized to model the system in Simscape using two grid-following inverters along with grid connection. However, using multiple grid-following inverters can lead to tuning issues and slower system response. During outages, the data obtained from REopt is also incorporated in Simscape modeling, where the battery is configured as a grid-forming inverter, while the Solar PV system remains grid-following. In this configuration, the grid connection is eliminated, as the grid-forming inverter can emulate the behavior of a grid by delivering and absorbing power as needed.