Title page for ETD etd-12102001-152502


Type of Document Dissertation
Author Song, Byeong-Mun
Author's Email Address songb@gat.com, bmsong_vt@hotmail.com
URN etd-12102001-152502
Title Voltage Balancing Techniques for Flying Capacitors Used in Soft-Switching Multilevel Active Power Filters
Degree PhD
Department Electrical and Computer Engineering
Advisory Committee
Advisor Name Title
Lai, Jason Committee Chair
Keywords
  • Soft-Switching Topologies
  • Multilevel Converters
  • Active Power Filter
  • Voltage Balancing
  • Flying Capacitor
Date of Defense 2001-07-24
Availability unrestricted
Abstract
This dissertation presents voltage stabilization techniques for flying capacitors used in soft-switching multilevel active power filters. The proposed active filter has proved to be a solution for power system harmonics produced by static high power converters. However, voltage unbalance of the clamping capacitors in the active filter in practical applications was observed due to its unequal parameters. Thus, the fundamentals of flying capacitors were characterized dealing with voltage balancing between flying capacitors and dc capacitors under practical operation, rather than ideal conditions.

The study of voltage balancing provides the fundamental high-level solutions to flying capacitor based multilevel converter and inverter applications without additional passive balancing circuits. The use of proposed voltage balancing techniques made it possible to have a simple structure for solving the problems associated with the conventional bulky passive resistors and capacitor banks. Furthermore, the proposed control algorithms can be implemented with a real time digital signal processor. It can achieve the high performance of the active filter by compensating an adaptive gain to the controller. The effectiveness of the proposed controller was confirmed through various simulations and experiments.

The focus of this study is to identify and develop voltage stabilization techniques for flying capacitors used in a proposed active filter. The voltage unbalance is investigated and characterized to provide safe operations. After having defined the problems associated with the voltage unbalance, the most important voltage stabilization techniques are proposed to solve this problem, in conjunction with an instantaneous reactive power (IRP) control of an active filter.

In order to reduce the switching losses and improve the efficiency of the active filter, the proposed soft-switching techniques were evaluated through simulation and experimentation. Experimental results indicate that the proposed active filter achieved zero-voltage conditions in all of the main switches and zero-current turn-off conditions to the auxiliary switches during commutation processes. Also, various studies on soft-switching techniques, multilevel inverters, control issues and dynamics of the proposed active filter are discussed and analyzed in depth.

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  Appendix-1.pdf 235.07 Kb 00:01:05 00:00:33 00:00:29 00:00:14 00:00:01
  Appendix-2.pdf 396.95 Kb 00:01:50 00:00:56 00:00:49 00:00:24 00:00:02
  CH-0.pdf 39.42 Kb 00:00:10 00:00:05 00:00:04 00:00:02 < 00:00:01
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  CH-2.pdf 633.93 Kb 00:02:56 00:01:30 00:01:19 00:00:39 00:00:03
  CH-3.pdf 503.34 Kb 00:02:19 00:01:11 00:01:02 00:00:31 00:00:02
  CH-4.pdf 179.11 Kb 00:00:49 00:00:25 00:00:22 00:00:11 < 00:00:01
  CH-5.pdf 223.87 Kb 00:01:02 00:00:31 00:00:27 00:00:13 00:00:01
  CH-6.pdf 10.24 Kb 00:00:02 00:00:01 00:00:01 < 00:00:01 < 00:00:01
  Reference.pdf 43.03 Kb 00:00:11 00:00:06 00:00:05 00:00:02 < 00:00:01
  Vita.pdf 5.68 Kb 00:00:01 < 00:00:01 < 00:00:01 < 00:00:01 < 00:00:01

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