Variable frequency drives typically have employed dc voltage or current links
for power distribution between the input and output converters and as a means to
temporarily store energy. The dc link based power conversion systems have several
inherent limitations. One of the important limitations is the high switching loss
and high device stress which occur during switching intervals. This severely reduces
the practical switching frequencies. Additionally, while the cost, size, and weight of
the basic voltage sourced PWM drive is attractive, difficulties with input harmonics,
output dV/dt and over-voltage, EMI/RFI, tripping with voltage sags, and other
problems significantly diminish the economic competiveness of these drives. Add-ons
are available to mitigate these problems, but may result in doubling or tripling the
total costs and losses, with accompanying large increases in volume and weight.
This research investigates the design, control, operation and efficiency calculation
of a new power converter topology for medium and high power ac-ac, ac-dc and
dc-ac applications. An ac-link formed by an inductor-capacitor pair replaces the
conventional dc-link. Each leg of the converter is formed by two bidirectional switches.
Power transfer from input to output is accomplished via a link inductor which is first
charged from the input phases, then discharged to the output phases with a precisely
controllable current PWM technique. Capacitance in parallel with the link inductor
produces low turn-off losses. Turn-on is always at zero voltage as each switch swings
from reverse to forward bias. Reverse recovery is with low dI/dt and also is buffered
due to the link capacitance.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-3156 |
| Date | 15 May 2009 |
| Creators | Balakrishnan, Anand Kumar |
| Contributors | Toliyat, Hamid |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Thesis, text |
| Format | electronic, application/pdf, born digital |
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