Digitization Effect in Implementation of Hybrid Modulation Technique in CHBMLI

In this paper analysis has been done to study the digitization effect due to sampling upon digital implementation of Modified Hybrid PWM technique in multilevel inverter. A cascaded H-bridge multilevel inverter (CHBMLI) is considered for the modulation technique implementation. Multicarrier modulation method of Modified Hybrid PWM is considered for the analysis of the digitization effect. For better understanding of the digitization a comparison has been made with the phase shifted (PS) PWM. The variation of total harmonic distortion (THD) with respect to multisampling factor (sampling to carrier frequency ratio) has been discussed at different modulation indices for the modulation techniques. It has been observed that the load current waveform become stepped in nature due to sampling effect of the digitization and this leads to the appearance of the lower order harmonic components, i.e., 3rd, 5th, 7th etc. in the frequency spectrum. The results are verified through the digitization of modulation in the MATLAB/SIMULINK platform.