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Description:
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Significant advances in modern ac /ac power converter technologies and demands
of industries have reached beyond standard ac /ac power converters with voltage -source
inverters fed from diode rectifiers . Power electronics converters have been matured to
stages toward compact realization , increased high -power handling capability , and
improving utility interface . Modern ac /ac power converter topologies with various
control strategies have been introduced for the further improvements , such as matrix
converters , current -fed converters , PWM rectifiers , and active power filters . In this
dissertation , several new converter topologies are proposed in conjunction with
developed control schemes based on the modern ac /ac converters which enhance
performance and solve the drawbacks of conventional converters .
In this study , a new fault -tolerant PWM strategy is first proposed for matrix
converters . The added fault -tolerant scheme would strengthen the matrix converter
technology for aerospace and military applications . A modulation strategy is developed
to reshape output currents for continuous operation , against fault occurrence in matrix
converter drives .
This study designs a hybrid , high -performance ac /ac power converter for high
power applications , based on a high -power load commutated inverter and a mediumpower
voltage source inverter . Natural commutation of the load commutated inverter is
actively controlled by the voltage source inverter . In addition , the developed hybrid
system ensures sinusoidal output current /voltage waveforms and fast dynamic response
in high power areas .
A new topology and control scheme for a six -step current source inverter is
proposed . The proposed topology utilizes a small voltage source inverter , to turn off
main thyristor switches , transfer reactive load energy , and limit peak voltages across
loads . The proposed topology maximizes benefits of the constituent converters : highpower
handling capability of large thyristor -based current source inverters as well as fast
and easy control of small voltage source inverters .
This study analyzes , compares , and evaluates two topologies for unity power
factor and multiple ac /ac power conversions . Theoretical analyses and comparisons of
the two topologies , grounded on mathematical approaches , are presented from the
standpoint of converter kVA ratings , dc -link voltage requirements , switch ratings ,
semiconductor losses , and reactive component sizes . Analysis , simulation , and
experimental results are detailed for each proposed topology . |