Date of Award:

12-2025

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Electrical and Computer Engineering

Committee Chair(s)

Regan Zane (Committee Chair) Hongjie Wang (Committee Co-Chair)

Committee

Regan Zane

Committee

Hongjie Wang

Committee

Dragan Maksimović

Committee

Luca Corradini

Committee

Mario Harper

Abstract

As the global community becomes increasingly aware of the need to reduce greenhouse gas emissions and reliance on fossil fuels, transitioning to electric mobility emerges as a critical step towards a more sustainable and energy-efficient future. One of the major barriers to the mass adoption of battery electric vehicles is the lack of convenient, fast, and accessible charging stations. Long charging times and limited charger availability contribute to range anxiety. To address this challenge, improvements in public charging infrastructure and the development of reliable, high-efficiency, high-power converters are required.

Typically, a grid-tied ac-dc converter with a two-stage architecture, consisting of ac-dc and dc-dc stages, is used. However, it suffers from low power density due to filtering requirements and high switching losses, which often limit the switching frequency in high-power converters. Recently, single-stage topologies have gained attention for EV charging applications as they offer high power density and efficiency due to a single conversion stage. However, many single-stage topologies remain relatively new and not yet well established. Their industrial adoption is constrained by challenges such as control complexity, grid current distortion, and a lack of comprehensive design-oriented analysis. Furthermore, as modular architectures are typically employed in high-power chargers, further research is required to address stability and system integration requirements.

This dissertation investigates three-phase unfolding-based single-stage ac-dc converter topologies, specifically for EV charging applications that require a wide operating range. The dissertation focuses on two key applications: a 350 kW extreme fast charging (XFC) system for Level 3 plug-in charging, and a dc current distribution architecture for both static and dynamic wireless charging. Initially, this thesis explores an unfolding-based rectifier utilizing a T-type resonant converter. Furthermore, a novel unfolding-based topology is proposed for high-power dc current distribution systems. The stability and control of the modular dc current distribution system, comprising multiple dc-dc converters connected in an input-parallel, output-series configuration, alongside a centralized three-phase Unfolder, are thoroughly analyzed and subsequently validated.

Overall, the thesis presents a design-oriented analysis of various unfolding-based topologies, with a focus on wide operating range EV charging applications.

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