Simulation of single phase fuel cell powered transformerless multilevel inverter using H-Bridge cascade topology

Abstract

In this thesis, a multilevel inverter is constructed using H-Bridge Cascaded circuit to obtain output voltage for three, five, seven and nine level. It is operated without transformer to obtain a nominal voltage of240V. It needs DC voltage from fuel cell that will convert to the AC nominal voltage. This research was discussed about the output voltage waveform of the H-Bridge Cascaded multilevel inverter approaches the pure sine wave simulation. The simulation uses MA TLAB software to get the output waveform from fuel cell and the H-Bridge cascaded multilevel inverter topology. The topology is to obtain optimal values of voltage angle. The optimum voltage angle results will reduce the lowest (THD) total harmonic distortion and to be implemented in this research. The simulation results will be compared based on the THD results. As the level increases from three to nine levels, the THD shows significant improvement of reduces from 36.13% to 10.14%. Therefore, among three to nine levels of H-Bridge Cascaded multilevel inverter, only the nine levels was chosen for further analysis. The analysis was using SHEPWM switching technique. Comparison between the results analysis of nine levels for modulation indexes 0.75 to 1, has obtained that 10.14% is the best THD results. The comparison results are approximately equal between fuel cell and reference of previous researcher based on the simulation. Therefore, fuel cell also can be used as DC voltage source transformerless multilevel inverter.