Impact of modulation schemes on the power capability of high-power converters with low pulse ratios

The design of modulation schemes at low pulse ratios is a known topic. However, most of previous work has focused on Optimized Pulse Patterns, e.g. Selective Harmonic Elimination (SHE). For industrial applications, standard carrier modulators are still highly attractive in many cases. Unfortunately, few papers presented insightful studies on carrier modulators at extremely low pulse ratios. This paper covers this gap. At extremely low pulse ratios, several special phenomena of carrier modulators are observed. Their mechanisms are explained in detail. Moreover, a quantitative comparison between different carrier-based modulation schemes is presented. Based on that, several design criteria for modulators at low pulse ratios are proposed at the end.