Mathematical approach to THD optimisation in multilevel convertors

The paper is related to the problem of generating the high quality AC voltage waveforms using multilevel converters. This technique can be applied especially in the distributed power energy systems with renewable DC voltage sources like photovoltaic farms and fuel cells. A novel approach to the synthesis of AC voltage waveforms, considering minimising of THD by use of analytical methods like Fourier transform is presented. The analysis of the obtained waveforms is presented as well as examples of chosen parameter optimisation. The meaning of the THD factor from the construction point of view is analysed and a new bandwidth factor THDB, containing more information about the frequency range of harmonic components is proposed in the paper.