자료유형  

 학위논문

Control Number  

0017160970

International Standard Book Number  

9798382841366

Dewey Decimal Classification Number  

621.3

Main Entry-Personal Name  

Farooq, Maida.

Publication, Distribution, etc. (Imprint  

[S.l.] : Cornell University., 2024

Publication, Distribution, etc. (Imprint  

Ann Arbor : ProQuest Dissertations & Theses, 2024

Physical Description  

145 p.

General Note  

Source: Dissertations Abstracts International, Volume: 85-12, Section: B.

General Note  

Advisor: Afridi, Khurram.

Dissertation Note  

Thesis (Ph.D.)--Cornell University, 2024.

Summary, Etc.  

요약Line-interfaced power converters are crucial in modern electronics, facilitating efficient energy conversion and seamless integration of renewable energy sources, storage systems, and grid-connected loads. Yet, ensuring their stable and reliable operation presents significant control challenges, especially with increasing demands for high performance. This thesis introduces control and design methodologies to improve performance of line-interfaced power converters. The power converters covered in this thesis are ac-dc converters for LED driver and data center applications and ac-dc-ac converters for data center applications.The thesis addresses challenges in designing the input current control loop for the PFC stage of an LED driver, focusing on achieving high power density with a small inductance. A systematic design methodology is proposed for the input current control loop, evaluating three compensator types for optimal input current shaping. Additionally, a feedforward in conjunction with feedback controller is introduced to mitigate input voltage variations, ensuring well-regulated LED current. Experimental validation is conducted on a prototype 150-W, 50-W/in3 offline LED driver, demonstrating the effectiveness of the proposed control strategies.Following this, the control of high-power paralleled ac-dc converter modules is introduced. A new droop control strategy ensures equal output current distribution between paralleled modules when powering a common load. An analytical model facilitates the design of the input-current-based droop control. Experimentation with two 1-kW universal-input to 28-V isolated ac-dc converter modules validates the proposed droop control design.Next, a high-power-density ac-dc-ac converter tailored for online UPS applications is introduced. The thesis focusses on overcoming primary control challenges, especially regarding the dual-mode functionality of the dc-ac inversion stage. The control challenges arising from mismatched dynamics in the dual-mode inversion stage are identified and adaptive feedback, dynamic cancellation, and feedforward-enhanced feedback control strategies to achieve low output voltage THD without increasing control complexity are proposed. Analytical assessments and detailed design guidelines for these control strategies are provided. Experimental validation using a 1-kW prototype online UPS demonstrates significant reduction in output voltage THD compared to standard feedback control, with output voltage THD as low as 2.9% across a wide operating range.Finally, to achieve higher power densities and a low-profile form factor (1U), a comprehensive control and design methodology is presented. A methodology is developed to optimize the converter design by considering trade-offs between overall efficiencies and power densities. A novel control strategy based on mixed duty-ratio and frequency modulation is proposed to ensure soft-switching of all inverter transistors and well-regulated output voltage. A 1-kVA prototype online UPS, utilizing GaN transistors and operating at switching frequencies up to 2 MHz, achieves a power density of 60.4 W/in3 and maintains a low-profile form factor (1U ≝1.75 inch height).

Subject Added Entry-Topical Term  

Electrical engineering.

Subject Added Entry-Topical Term  

Applied physics.

Index Term-Uncontrolled  

Renewable energy

Index Term-Uncontrolled  

Ac-dc converter

Index Term-Uncontrolled  

Frequency modulation

Index Term-Uncontrolled  

Storage systems

Added Entry-Corporate Name  

Cornell University Electrical and Computer Engineering

Host Item Entry  

Dissertations Abstracts International. 85-12B.

Electronic Location and Access  

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Control Number  

joongbu:656169