On the Distortion of Pulse-Width-Modulated Five-Level Asymmetric Multilevel Inverters

The use of multilevel inverters is increasing to achieve better power quality. Hence, it is essential to determine a modulation technique which can obtain optimum harmonic distortion of multilevel inverter output. This paper presents an analytical technique to determine the spectral components of an asymmetric five-level PWM inverter. To obtain the analytical expressions for the inverter output waveform, the double Fourier integral technique is used. Accuracy of this analysis was verified by comparing the total harmonic distortions and weighted total harmonic distortions obtained by this analysis, with the same obtained by simulations and experiments. This was done for various amplitude modulation index values, and the degree of asymmetry needed to achieve minimal output voltage distortion was determined for each of the considered index values.