Design and analysis of the reduction of harmonics at single phase inverter output

The aim of this paper is to present a technique to reduce the harmonics in output voltage of a single phase inverter. An investigation is carried out with a circuit based on paralleling of two inverters by using interface reactors. Sinusoidal pulse-width modulation is used to generate the gating signals of the inverters. There is a phase difference between the gating signals of parallel branches. By varying the phase difference, an analysis is done to find the best situation when maximum harmonic elements can be reduced. Another two analyses are done by varying frequency ratio and modulation index. A conclusion is made about the finest modulation index depending on RMS value of fundamental component and presence of the 3rd, 5th & 7th harmonic components. Relation between frequency ratio and a specific harmonic component is also studied. A new equation is established which can be used to eliminate up to certain harmonic components setting a specific frequency ratio.