UC San Diego

The power grid is undergoing a transformative shift towards renewable and distributed energy resources (DERs) connected through power electronic inverters. This transition plays a vital role in addressing the climate crisis, reducing greenhouse gas emissions, and enhancing energy supply reliability. While these advancements improve grid resilience through localized generation, they also introduce challenges related to variability and intermittency, especially in frequency stability. Inverter-based DERs provide rapid response capabilities essential for functions like frequency regulation, requiring robust control strategies, advanced communication systems, and sophisticated algorithms for optimal resource allocation and real-time monitoring.

This research leverages inverter-based DERs for grid services, emphasizing real-world testing and validation. Chapter 1 integrates second-life electric vehicle (EV) batteries into grid service provision, addressing battery disposal and resource waste. We develop a control framework for a heterogeneous battery unifying system that optimizes the state of health of second-life batteries while delivering energy services. Our optimization algorithm minimizes reconditioning time and ensures reliability, validated through hardware-in-loop testing with Nissan Leaf batteries.

The research further extends to system-level frequency control strategies across distribution and transmission grids. In Chapter 2, we conduct real-world testing with 69 active and 107 passive DERs on the UCSD microgrid, overcoming technical barriers and evaluating both cyber and physical performance for distributed secondary frequency control. In Chapter 3, we introduce a decentralized method for dynamic inertia allocation that enhances real-time frequency stability in low-inertia transmission grids, utilizing instantaneous local frequency measurements and available inertia estimates to stabilize frequency within milliseconds.

Finally, Chapter 4 validates an optimal frequency controller for low and variable inertia transmission grids through real-time and electromagnetic transient-based methods. Key contributions include improved simulation accuracy and the effective use of microgrid grid-forming inverters for disturbance mitigation, providing precise real-time performance guarantees.

By connecting theoretical insights with practical applications, this research enhances the resilience and efficiency of the power grid, ultimately supporting a sustainable energy future and contributing to global efforts to mitigate climate change.