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Due to the academic value and the wide applications, the
objective of this dissertation is centered around the study
of AC to AC converters as well as the corresponding
applications to induction motor drives. The main contributions
of this disserta- tion are : (1) A new step up AC/DC
converter is proposed as a pre-stage of the AC/AC converter to
achieve high input power quality, bidirectional power flow,
and very low output voltage ripple. (2) Another new AC/DC
converter is proposed as a pre- stage to achieve both step up
and step down function, simpler control and power circuits as
well as high input power quality. (3) An adaptive DC-link
voltage AC/AC converter is proposed for induction motor
drives. By extracting the zero vector quantity, the new
converter is able to adapt its DC link voltage to
minimize the unnecessary switching actions of the
inverter part. Hence, better efficiency can be achieved.
(4) A soft switching matrix converter is proposed to
eliminate the dis- advantages of existing matrix converters
such as lower efficien- cy, requiring lock-out time of the gate
signals of the converter , sensitive to unbalance or
distortion of the source voltage as well as complicated
control and snubber circuit. (5)nother economic DC link AC/AC
converter is proposed forduction motor drives. The new AC/AC
converter requires onlyee active switches for the inverter
portion. In addition , application of the new AC/AC converter
to the induction motor drive can still achieve high
performance. (6) Based on the previous economic DC-link
AC/AC converter, a novel adaptive vector controller is
proposed for the induction motor drive. (7)nstead of using
the previous new AC/AC converter, a modifieddaptive
magnetizing-flux-oriented controller is also proposedr the
commonly used induction motor drive to eliminate thefluence
of parameter changes.
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