Dissertation Defense Announcement for Tahmid Ibne Mannan – 02/10/2026 at 10 AM

Dissertation Title:
Conducted Electromagnetic Interference (EMI) in Medium Voltage (MV) Power Electronics Systems: Measurement, Mitigation and Aging Effects

When:
10 February 2026, 10:00 AM.

Where:
Simrall 228

Candidate:
Tahmid Ibne Mannan

Degree:
Doctor of Philosophy in Electrical and Computer Engineering.

Committee Members:
Dr. Seungdeog Choi, Dr. Masoud Karimi, Dr. John E. Ball, Dr. Ryan Green.

Abstract:
As Medium Voltage (MV) power electronics systems, i.e., electric vehicles (EVs), electric ships, and power electronic building blocks (PEBBs), transition toward Wide-Bandgap (WBG) semiconductors, the resulting high dv/dt and di/dt transitions have intensified the challenges of Electromagnetic Interference (EMI) compliance. This dissertation addresses the critical gap in MV conducted EMI research by investigating three interconnected pillars: high precision measurement, theoretical boundaries of hybrid EMI mitigation approach, and the impact of component reliability on long-term compliance. First, to resolve the limitations of existing commercial measurement equipment, this work presents the design and validation of a patented, compact, single-stage Line Impedance Stabilization Network (LISN). This tool surpasses current commercial specifications in both voltage and power capability, offering a scalable methodology for EMI characterization in MV systems. Second, the dissertation provides the first rigorous mathematical and theoretical quantification of the bandwidth limitations in Active EMI Filters (AEF) for MV applications. While it was qualitatively known that MV-rated injection capacitors possess high Equivalent Series Inductance (ESL), this research analytically characterizes the "hard ceiling" these parasitic parameters impose on EMI attenuation and loop stability. The direct impact of these limitations in a hybrid EMI filter architecture is deduced quantitatively, specifically focusing on the size of CM chokes. Along with this, a comparative study of nanocrystalline (NC) and ferrite chokes are presented, which demonstrates how material selection and careful geometric design can be crucial in a synergistic hybrid EMI filter approach. Finally, this research identifies a critical temporal dimension to EMI compliance. Through a 500-hour experimental aging study of Y-capacitors, a direct correlation is established between physical component degradation and the erosion of EMI safety margins. The findings reveal that aging-induced shifts in capacitance and ESR can lead to a 7–9 dB increase in noise levels, potentially pushing a previously compliant system into regulatory failure. Collectively, these contributions establish a "reliability-aware" framework for MV EMI design, ensuring that modern power converters achieve not only immediate compliance but long-term electromagnetic compatibility.