(WBG) Devices Based Switched Capacitor Multiport Multilevel Single Phase AC/DC/AC Converter ...

203 Pages·2016·2.16 MB·English

Wide‎Bandgap (WBG) Devices Based Switched Capacitor Multiport Multilevel Single
Phase AC/DC/AC Converter for UPS Applications

DISSERTATION

Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy
in the Graduate School of The Ohio State University

By
Mohammed Faham Alsolami
Graduate Program in Electrical and Computer Engineering

The Ohio State University
2016

Dissertation Committee:
Professor Jin Wang, advisor
Professor Longya Xu
Professor Mahesh S. Illindala
Professor Hsian-Hua Tseng, Graduate Faculty Representative
© Copyright by
Mohammed Faham Alsolami
2016
Abstract

In recent years, with the advances of technology, extensive research has been dedicated
toward the design of uninterruptible power supply (UPS). UPS systems are designed to
provide clean, conditioned, and uninterruptible power to critical equipment such as
computers, medical equipment, storage systems, and various industrial equipment. The
UPS systems are the preferred solution to power quality problems because of their
highest level of power quality and proven functionality against all types of line
disturbances that occur in electrical grids, such as undervoltage, overvoltage, sag, swell
and noise.
Among different types of UPS systems, the on-line “double conversion” UPS is widely
recognized as the preferred topology in performance, power conditioning, and load
protection. However, the on-line UPS systems are not suitable for applications lower than
5 kVA due to the high cost and their large size and weight. Lower efficiency also is
inherent to this topology because of the double-conversion stages of on-line UPS
systems. Today, with the prominence of new semiconductor devices such as wide
bandgap (WBG) devices, several advantages may be achieved when applied to on-line
UPS systems.
In this dissertation, a novel topology of a modular uninterruptible power supply (UPS)
system, based on switched capacitor circuit and WBG devices, is proposed. This work
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deals with the development of a multilevel, single-phase, transformerless on-line UPS
with universal input/output voltage rating (120 V/240 V) for the ac side and (200 V/400
V) for the dc side. The system consists of a one-stage power conversion of an ac/dc/ac
five-level with boost functionality. In this type of configuration, size, cost and efficiency
are improved due to the reduced number of passive components, and thermal
requirements and no need of isolation transformers in the multilevel operation. Moreover,
the new topology can operate at different operation voltage levels, for example five-level
or/and three-level operation. Furthermore, it has the desired characteristics of making a
seamless transition from normal to backup mode during power failures and vice versa, as
well as providing controlled voltage at the dc bus link. A complete set of simulation and
experimental results based on a 2 kVA test prototype of the proposed UPS is presented to
demonstrate its operation modes under different operating conditions and efficiency. A
peak efficiency of 98.3% has been achieved
In the single-phase UPS applications there is an inherent problem of second-order ripple
power on the dc link, which can generate a ripple on the dc bus voltage at twice the line
frequency when the output voltage and current are sinusoidal. It is usually necessary to
connect a very large electrolytic capacitor or a storage element such as an LC filter to the
dc side to reduce the low-frequency voltage ripples. However, such a large capacitor or
LC filter is not desirable because of the short lifetime of the capacitor, and the inherent
parameter variation with time. In this dissertation, a new approach to the dc-link 120 Hz
ripple cancellation is presented. The approach does not require additional components. It
utilizes the superior features of the circuit structure and the theoretical analysis confirms
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that the ripple components can be entirely eliminated from the system. As a result, a
small size dc-link capacitor of about 20 μF can be achieved.
Batteries are an important component in UPS systems. If batteries fail to operate
properly, the whole UPS system fails to perform its function. In fact, batteries are the
weakest component in the UPS system. Therefore, the proper design of a battery-powered
electrical system requires determining the state of health (SOH). In this dissertation a
retired Plug-in Hybrid Electrical Vehicle (PHEV) is tested and cycled forty times and the
main battery parameters from a capacity (Ah) and internal resistance (Rs) are measured.
Results show that retired vehicle batteries are suitable for residential applications
requiring relatively high energy density and low power capability.

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Dedication

This document is dedicated to my parents.

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Acknowledgments

In the name of Allah, the Most Gracious, and Most Merciful
All praises and thanks are due to Allah, Almighty God, who said in His glorious book
“Nay, but Allah must thou serve, and be among the thankful!”, and peace be upon His
messenger Muhammed, who said: “Whoever is not thankful to people then he cannot be
thankful to Allah, either”.
My deepest gratitude is to my advisor, Dr. Jin Wang for his valuable guidance,
scholarly inputs and consistent encouragement. I have been amazingly fortunate to have
an advisor who gave me the freedom to explore on my own, and at the same time the
guidance to recover when my steps faltered. This work was possible only because of the
unconditional support, the patience, and the encouragement he provided to overcome
many crisis situations and to finish this dissertation. A person with an amicable and
positive disposition, he has always made himself available to clarify my doubts despite
his busy schedules and I consider it as a great opportunity to do my doctoral program
under his guidance and to learn from his research expertise.
I am deeply grateful to my committee members, Dr. Longya Xu, Dr. Mahesh S.
Illindala, and Dr. Hsian-Hua Tseng, for the valuable discussions that helped me to
improve important technical details of my work and for their insightful comments and
constructive criticisms that enhanced the technical soundness of my research.
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I am also grateful to the following former and current colleagues in CHPPE center at
The Ohio State University. I would like to express my special thanks to Dr. Feng Guo, Dr.
Cong Li, Dr. Luis Herrera, and Dr. Mark Scott for their various forms of support, help
and guidance and for numerous discussions and lectures on related topics that helped me
improve my knowledge in the area when I started my graduate study and research work.
A special thank goes to Karun Potty for his help during the experimental work. Also, I
would like to acknowledge Xuan Zhang, He Li, Chengcheng Yao, Lixing Fu, Boxu Hu,
Balaji Narayanasamy, Amol Deshpande, and Arvind Shanmuganaathan. And also I
would like to thank my close friend Taha Koroglu. He was always willing to help and
give his best suggestions.
I owe my deepest thanks to my whole family in Saudi Arabia for their unconditional
love and support, which is the greatest gift I ever received to continue my PhD study. My
deepest appreciation goes to my beloved parents for all of their support and teachings
throughout all of my life. Through all challenges and difficulties, they have always been
there for me with their love and support.
Finally, I would like to express my appreciation to Saudi Government that provides
me the opportunity to study and complete this research.

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Vita

2009……………………………B.S. Electrical Engineering, King Abdul-Aziz University
2012……………………………M.S. Electrical Engineering, The Ohio State University
2012 to present……………….Graduate Research Associate, Department of Electrical
and Computer Engineering, The Ohio State
University

Publications
[1] M. Alsolami, J. Wang, and L. Herrera, "DC ripple current reduction on
multilevel, multiport, single-phase DC/AC converter for renewable energy
applications," in Wide Bandgap Power Devices and Applications (WiPDA), 2015
IEEE 3rd Workshop on, 2015, pp. 312-318.
[2] M. Alsolami, M. Scott, and W. Jin, "A gallium nitride device based switched
capacitor multilevel converter for UPS applications," in Applied Power
Electronics Conference and Exposition (APEC), 2015 IEEE, 2015, pp. 1002-
1007.
[3] H. Li, M. Alsolami, Y. Xiao, X. Dong, K. Zhu, and J. Wang, "Life test design for
retired xEV batteries aiming at smart home applications," in Energy Conversion
Congress and Exposition (ECCE), 2015 IEEE, 2015, pp. 4967-4972.
[4] F. Guo, H. Li, C. Yao, M. Alsolami, A. Lang, X. Lu, et al., "Residential usage
profile optimization and experimental implementation of the retired HEV battery
with a hybrid microgrid testbed," in Energy Conversion Congress and Exposition
(ECCE), 2014 IEEE, 2014, pp. 428-435.
[5] F. Guo, L. Herrera, M. Alsolami, H. Li, P. Xu, X. Lu, et al., "Design and
development of a reconfigurable hybrid Microgrid testbed," in Energy Conversion
Congress and Exposition (ECCE), 2013 IEEE, 2013, pp. 1350-1356.
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[6] F. Guo, L. Fu, H. Li, M. Alsolami, X. Zhang, J. Wang, et al., "A dual-input full-
bridge current-source isolated DC/DC converter based on Quasi-Switched-
Capacitor circuit for Photovoltaic systems with energy storage," in Applied Power
Electronics Conference and Exposition (APEC), 2015 IEEE, 2015, pp. 1757-
1762.
[7] F. Guo, L. Fu, H. Li, M. Alsolami, X. Zhang, J. Wang, et al., "A full-bridge
current-source isolated DC/DC converter with reduced number of switches and
voltage stresses for photovoltaic applications," in Wide Bandgap Power Devices
and Applications (WiPDA), 2014 IEEE Workshop on, 2014, pp. 133-138.

Fields of Study
Major Field: Electrical and Computer Engineering

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