Electric grids across the world are experiencing an ever increasing number of extreme events ranging from extreme weather events to cyberattacks. Such extreme events have the potential to cause widespread power outages and even a blackout. A vast majority of power outages impacting the U.S. electric grid impact the distribution system. There are an estimated five million miles of distribution lines in the US electric grid. A majority of these lines are low-clearance overhead lines making them even more susceptible to damage during extreme events. However, this vital component of the U.S. electric grid remained neglected until recently.
In recent decades, the integration of distributed energy resources (DERs) such as solar photovoltaic systems and battery energy storage systems at the grid edge have provided a major opportunity for enhancing the resilience of distribution systems. These DERs can be used to restore power supply when the bulk grid becomes unavailable. However, managing the interactions among different types of DERs has been challenging. Low inertia and significant differences in time constants of operation between conventional generation and inverter based resources (IBRs) are some of these challenges. Widespread deployment of microgrid controller capabilities can be a promising solution to manage these interactions.
However, due to interoperability and integration challenges of optimization and dynamics control systems, power conversion systems and communication systems, the adoption of microgrids especially in underserved communities has been slow.
The research presented in this dissertation is a significant step forward in this direction by proposing an approach which integrates optimal dispatch, sequential microgrid restoration and control algorithms. Potential cyberattack paths are identified by creating a detailed cyber-physical system model for microgrids. A two-tiered intrusion detection system is developed to detect and mitigate cyberattacks within the cyber layer itself. The developed sequential microgrid restoration algorithm coordinates optimal DER dispatch with the operation of legacy devices with no remote control or communication capabilities and net-metered loads with limited communications. By better utilizing the control capabilities of IBRs, reliance on low-latency centralized control algorithms has also been reduced. The developed approach systematically ensures adequate availability of control during dispatch and restoration to maintain microgrid stability. This research can thus pave the way for faster and more cost-effective deployment of microgrids. / Doctor of Philosophy / A U.S. National Academy of Engineering report has described the power grid as the greatest engineering achievement of the 20th century. The power grid is a complex interconnected system consisting of the power transmission system and the distribution system. The power transmission system consists of the power lines seen while driving on the freeways and the large power generating stations consisting of renewable, coal or nuclear power plants. Ensuring the reliable operation of the transmission system has always been a priority.
The distribution system on the other hand consists of pole top transformers seen closer to homes which reduce the voltage to levels safe for electrical appliances. It also consists of the millions of miles of low-clearance overhead distribution lines deployed across the U.S. that provide electricity to every household. This critical part of U.S. electricity infrastructure had remained neglected which is the reason why 90% of power outages impact the distribution system. In recent decades, the integration of renewable energy sources like solar systems and battery storage systems has created an unprecedented opportunity for increasing the resilience of distribution systems against extreme events. These energy sources can provide power supply when the transmission system becomes unavailable. However, ensuring safe and reliable integrated operation of these sources with conventional diesel generators especially while isolated from the transmission system is challenging.
This is where microgrids, which are self-sufficient miniature power grids, can help. Microgrids provide required control, communication and cybersecurity features necessary for reliable integrated operation of renewable and conventional energy sources. However, the challenges involved with interoperability of these systems has slowed down the deployment of microgrids especially in underserved communities. This is the research gap addressed in this dissertation. This research provides an approach for integrating the optimization, control, power electronics and cybersecurity systems. Reliance on expensive low-latency communication systems is reduced by utilizing the emerging capabilities of power electronics devices used for integrating the renewable energy sources with the electric power grid. Voltage control devices already deployed in the distribution systems which do not have remote control or communication capabilities have also been coordinated with energy sources. The research presented in this dissertation is a significant step forward for increasing access to power supply during outages and for reducing the time and cost of deployment of microgrids.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/119062 |
| Date | 22 May 2024 |
| Creators | Jain, Akshay Kumar |
| Contributors | Electrical Engineering, Liu, Chen-Ching, Southward, Steve C., Centeno, Virgilio A., Kekatos, Vasileios, Schneider, Kevin Paul, Ampadu, Paul K. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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