Initially, the main purpose of the multilevel converter was to achieve a higher voltage capability of the converters. As the ratings of the components increases and the switching- and conducting properties improve, the secondary effects of applying multilevel converters become more and more advantageous. In recent papers, the reduced content of harmonics in the input and output voltage is highlighted, together with the reduced EMI (Tolbert & Peng, 1999). The multilevel converter distinguishes itself by being that converter in this survey with the lowest demands to the input filters. (or alternatively reduced number of switchings) (Rodriguez et al., 1999).
The switching losses of the multilevel converter are another feature, which is often accentuated. In (Marchesoni & Mazzucchelli, 1993), it is stated, that for the same harmonic performance the switching frequency can be reduced to 25% of the switching frequency of a two-level converter. Even though the conducting losses are higher for the multilevel converter, it is stated in (Tolbert & Peng, 1999) that the overall efficiency for the diode clamped multilevel converter is higher than the efficiency for a comparable two-level converter. Of course, the truth in this assertion depends on the ratio between the switching losses and the conducting losses.
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