A guide to Nearest Level Modulation and Selective Harmonics Elimination modulation scheme for multilevel inverters

Calculation of firing angles for the efficient operation of multilevel inverter is very important. This paper gives a simple guide to calculate the firing angles for the operation of multilevel inverter. The firing angles are calculated for Nearest Level Modulation and Selective Harmonics Elimination which are the two very popular low switching frequency modulation schemes. The modulation schemes are implemented on a Multilevel DC-link inverter to generate a nine level output. The simulation is carried out using Matlab/Simulink software. The Matlab code to calculate the THD is also presented. Hardware result is shown to validate the simulation results. The code to execute the firing pulse in Atmega32 AVR microcontroller is also presented.