Date of Award

8-2025

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Electrical and Computer Engineering (Holcomb Dept. of)

Committee Chair/Advisor

Dr. Sukumar Brahma

Committee Member

Dr. Ramtin Hadidi

Committee Member

Dr. Umesh Vaidya

Committee Member

Dr. Dingrui Li

Abstract

Renewable energy sources, mainly inverter-based resources (IBRs) such as solar and wind plants are being connected in large numbers to the bulk power grid in the United States and around the world. Additionally, generation using fossil fuels are being phased out, which results in the loss of rotor inertia, a key contributor to the transient stability of power systems. Therefore, the large-signal behavior of IBRs and its impact on transient stability must be studied.

This work studies this impact through the metric of critical clearing time (CCT). Impact of grid topology, generation mix and control modes of IBRs on CCT is studied and results are explained through physical reasoning. Two IEEE test systems are simulated on the real-time digital simulator (RTDS) to perform the studies, and valuable insight about system stability is gleaned to help the grid operator.

Electromagnetic transients (EMT) modeling provides an accurate and detailed simulation that considers the effect of individual components of the IBRs. However, EMT simulations are time consuming, computationally expensive, and difficult to parallelize. Simulating all the cases presented in this work took several days, even when using a real-time simulator. To improve the speed of the analysis, dynamic modes are derived for IBR topologies and integrated into a numerical method for transient stability. The developed models were validated by comparing the dynamic model output with the EMT outputs. The CCTs obtained for the EMT simulations were compared with the results obtained from the dynamic simulations to ensure the accuracy of the dynamic models. Due to the accurate dynamic models developed in this work the dynamic simulations accurately reproduce the results produced by EMT simulations, but are orders of magnitude faster, and can be performed in parallel with minimal effort.

Author ORCID Identifier

0009-0004-0900-5286

Available for download on Monday, August 31, 2026

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