Selective Harmonic Elimination Modulation Method For Multilevel Inverters

Multilevel converter technology has recently emerged as a very important alternative in the area of high-power applications. Several modulation methods have been applied to multilevel Inverters. The modulation methods with higher switching frequency reduce filter size but increases switching losses. The Step modulation method operates with low switching frequency has less switching losses but it requires large filter size. To reduce the filter size the number of levels of the inverter is increased but it increases the cost of the system. This paper presents a novel modulation method where additional notches are introduced in the multi-level output voltage. These notches eliminate harmonics at the low order/frequency and shifts it a higher order/frequency and hence the filter size is reduced without increasing the switching losses and cost of the system. The proposed modulation method is verified through simulation and such results are also validated practically using a five-level Diode-clamped inverter prototype.