Theses and Dissertations

Advisor

Wallace, David

Committee Member

Choi, Seungdeog

Committee Member

Fu, Yong

Committee Member

Fang, Xin

Committee Member

Diao, Junming

Date of Degree

5-10-2024

Original embargo terms

Embargo 2 years

Document Type

Dissertation - Open Access

Major

Electrical and Computer Engineering

Degree Name

Doctor of Philosophy (Ph.D)

College

James Worth Bagley College of Engineering

Department

Department of Electrical and Computer Engineering

Abstract

Common mode (CM) electromagnetic interference (EMI) can compromise electronics systems, interfere with communication systems, and degrade mechanical systems. Multiple inverters can also generate excessive CM EMI that often exceeds individual inverter EMI standards. Due to their weight, volume, cost, and suboptimal performance, active and passive filters and chokes are inefficient as EMI mitigation options. By utilizing frequency modulation (FM) or spread spectrum frequency modulation (SSFM), EMI energy is dispersed. In spite of not requiring expensive, bulky, and heavy filters, these techniques produce significant ripples in output voltages and currents. This dissertation uses enhanced sinusoidal frequency modulation to reduce CM EMI output, bridging the gap between existing EMI solutions: 1) To reduce performance degradation, a state-of-the-art FM topology with duty cycle correction is proposed. Due to large output voltage and current ripples, FM techniques have limited bandwidth and utilization. Duty cycle correction allows for a wider FM bandwidth with better EMI attenuation while minimizing output ripple performance tradeoffs. 2) CM EMI accumulation is a growing concern in power converter networks. Even if each converter complies with EMI regulations, multiple converters may produce CM EMI that exceeds EMI standards in parallel operation. A novel algorithm is proposed to suppress CM EMI in a large-scale network using SFMCW frequency indexing. The algorithm minimizes aggregate EMI by minimizing switching frequency overlap among converters. 3) CM EMI noise in complex systems presents a critical challenge. Since standalone converters are rarely affected by CM EMI phases, they were usually overlooked in most studies until recently. CM currents generated by multiple converters can be added or subtracted based on phase differences. The CM currents in large systems with multiple inverters are distributed randomly, resulting in multiple peaks and nulls. In order to reduce network EMI, a sinusoidal FM technique with phase shift is proposed to attenuate CM EMI on multiple parallel inverters. This method overcomes conventional methods' critical disadvantages, including the need for accurate component characterization and modeling, and reducing CM EMI without additional passive components.

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