ABSTRACT
The variable voltage or frequency requirements emphasize
the need and elaborate the increasing trend of using multilevel inverters in
modern drives and utility applications .The multi-level inverters carves out a
nearly sinusoidal voltage from a stair case like wave form and the distortion
level in the output voltage depends on the number of steps. Large electric
drives and utility applications require advanced power electronics converter to
meet the high power demands. As a result, multilevel power converter structure
has been introduced as an alternative in high power and medium voltage
situations. A multilevel converter not only achieves high power ratings, but
also improves the performance of the whole system in terms of harmonics, dv/dt
stresses, and stresses in the bearings of a motor. Several multilevel converter
topologies have been developed; i) diode clamped, ii) flying capacitors, and
iii) cascaded or H -bridge. As a
preliminary study the thesis examined and compared the most common multilevel
topologies found in the published literature. Starting from the essential
requirements, the different approaches to the construction of multilevel
inverter are explained and compared. In particular, aspects of total harmonic
distortion (THD) and modulation which are required or desirable for multilevel
converters are discussed. Sine-triangle carrier modulation is identified as the
most promising technique to pursue for both technical and pedagogical reasons.
CIRCUIT DIAGRAM:
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