A novel method of the harmonic analysis by the multi-carrier PWM techniques in the multi-level inverter

This paper deals with a novel method in order to analyze the harmonic characteristics in the multilevel inverter. Generally, the magnitude of harmonic components is different according to the carrier PWM techniques, modulation index (M_i), and the level of multi-level inverter. The previous papers analyzed the harmonic characteristics from the viewpoint of the space vector. Hence, the calculation of the harmonic vector becomes difficult and complex in 4-level or more than 5-level. However, the proposed method of this paper reduced an amount of calculation and simplified the process of calculation by using the relationship between reference voltage and output phase voltage to load neutral. This paper analyzed the harmonic and it is applied to the multi-carrier PWM techniques in 5- level and other-level of cascaded inverter system.