A Voltage Sag Supporter Utilizing a PWM-Switched Autotransformer

TLDR: In this paper, the authors proposed a scheme for voltage sag support based on a pulse width modulated autotransformer, which can correct the voltage by either boosting the input voltage during voltage sag events or reducing the voltage during swell events.

Abstract: This paper proposes a novel distribution-level voltage control scheme that can compensate voltage sag and swell conditions in three-phase power systems. Faults occurring in power distribution systems or facilities in plants generally cause the voltage sag or swell. Sensitivity to voltage sags and swells varies within different applications. For sensitive loads, even a voltage sag of short duration can cause serious problems. Normally, a voltage interruption triggers a protection device, which causes the shutdown of the entire load. In order to mitigate power interruptions, this paper proposes a scheme for voltage sag support based on a pulse width modulated autotransformer. The proposed scheme is able to quickly recognize the voltage sag or swell condition, and it can correct the voltage by either boosting the input voltage during voltage sag events or reducing the voltage during swell events. The key advantage in this voltage control topology is that it uses only one controlled switch per phase to control the output voltage, thereby resulting in minimum cost per kVA. The paper presents the new voltage control topology, as well as the voltage detection method, the snubber design, and the commutation logic for the thyristor bypass switch. Experiments have been carried out to verify the validity of the proposed scheme

Figures

Figure 4.13. Commutation scheme showing the positive thyristor current.

Figure 5.5. Overall IGBT fault detection circuit for bypass and PWM mode.

Figure 5.10. Logic and logic circuit for checking faults in thyristor gate driver.

Figure 5.9. The exclusive OR signal between the thyristor gate signal and its FB signal.

Table 2.1 Summary of the CEA, NPL, and EPRI power quality survey.

Figure 2.8. Configuration of a UPFC.

Full text

A VOLTAGE SAG SUPPORTER UTILIZING A
PWM-SWITCHED AUTOTRANSFORMER
A Thesis
Presented to
The Academic Faculty
by
Dong-Myung Lee
In Partial Fulfillment of the Requirements for the Degree
Doctor of Philosophy
In
Electrical Engineering
School of Electrical & Computer Engineering
Georgia Institute of Technology
Atlanta, GA 30332-0250
April 2004

ii
A VOLTAGE SAG SUPPORTER UTILIZING A
PWM-SWITCHED AUTOTRANSFORMER
Approved:
________________________
Dr. Thomas G. Habetler, Chairman
________________________
Dr. Ronald G. Harley
________________________
Dr. A.P. Sakis Meliopoulos
Date Approved: April 8, 2004 4

iii
To My Parents,
My Loving Wife, Joo-Youn,
And My Daughters, Do-Young and Do-Yun.

iv
ACKNOWLEDGEMENT
Without the involvement and support of many people in my studies, it would not
have been possible for me to complete this work.
I would like to express my gratitude to my adviser Dr. Thomas G. Habetler for his
support, help, and guidance. I have benefited tremendously from his knowledge and
experience in the fields of power electronics, and machine drives.
I am extremely grateful to Dr. Ronald G. Harley for his invaluable inputs and
guidance throughout the project.
I would like to thank Dr. A.P. Sakis Meliopoulos, Dr. David G. Taylor, and Dr.
Stephen L. Dickerson for their time and for serving on my thesis committee.
I would like to acknowledge Southern State Inc. (SSI) for financial support to
conduct this research.
I really express my gratitude to Mr. Joe Rostron of SSI for his wise technical
suggestion and enthusiasm for this research work.
I am indebted to Mr. Tom Keister of JSL, Inc. for his invaluable hardware work, and
for his help during various stages of the project. Without his endless, much of this work
would not have been completed.
I wish to thank my colleagues, Dr. Sang-Bin Lee, Dr. Jung-Wook Park, Jae-Hyeong
Seo, Young-Kook Lee, Xianghui Huang, Satish Rajagopalan, Salman Mohagheghi, Zhi
Gao, Jahagirdar Deepak, and Afroz Imam for their help.

v
I would like to express my thanks to Jin-Woo Jung, Tae-Hyeong Kim, Hyun-Soo
Kang, and Hee-Sung Moon for their encouragement and support.
I am deeply indebted to my wife, and my daughters for their love, caring, and
understanding. Without their love and support, this journey would have been much
harder.
I would like to express my sincere gratitude to my wife’s parents, my brother-in-law,
and my sister-in-law for their love, and support.
I am eternally grateful to my parents, my brother, and my sister for being a constant
source of encouragement and motivation throughout my life.