Graduation Year

2024

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Electrical Engineering

Major Professor

Zhixin Miao, Ph.D.

Committee Member

Lingling Fan, Ph.D.

Committee Member

Hantao Cui, Ph.D.

Committee Member

Yasin Yilmaz, Ph.D.

Committee Member

Achilleas Kourtellis, Ph.D.

Keywords

Weak Grid, Series Compensation, EMT Modeling, Analytical Modeling, Grid Following, Grid Forming, Stability Analysis

Abstract

This dissertation explores the stability challenges posed by integrating Inverter-Based Resources (IBR) into power grids, particularly focusing on two major scenarios: IBRs connected to weak grid interconnections and their performance in series-compensated networks. With the increasing dependency on renewable energy sources, ensuring the stability of these grids is crucial. A multilayered investigative approach is employed, utilizing Electromagnetic Transient Simulations that model grid systems interfaced with IBRs. These simulations are pivotal as they emulate real-world stability issues and provide a foundational understanding of grid interactions. In this dissertation two major types of IBR control are modeled and analyzed: Grid Following Control and the Grid Forming Controls.

To delve deeper into these challenges, a non-linear analytical model is developed, pinpointing the underlying causes of the identified stability issues. This phase involves conducting various stability studies, including eigenvalue analysis and Bode diagrams, significantly enhancing the understanding of system dynamics and their implications for grid stability. Hardware simulations also play a crucial role, bridging the gap between theoretical models and real-world applications, thus confirming the viability of the proposed solutions.

Additionally, this dissertation introduces a novel coordination and control scheme for multiple IBRs operating in weak grids. This scheme enhances stability margins by modulating reactive current among the IBRs, as demonstrated through rigorous EMT simulations and validated in hardware testbeds. The results show that strategic coordination significantly improves both small-signal and large-signal stability.

Furthermore, a state-of-the-art digital twin framework using a re-configurable System-on-Chip dynamically models and analyzes the IBR-grid interface. Implemented on a National Instruments real-time controller, this digital twin effectively simulates and adjusts to real-time grid disturbances, offering a sophisticated tool for proactive grid management.

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