Formulation of the line voltage THD of multilevel inverter with unequal DC sources

Multilevel inverters introduce harmonic to the network, beside their enormous advantages. THD is one of the most important indexes to evaluate harmonic contents of waveforms. Conventional method of line voltage THD calculation gives approximate answers but its accurate value is important. In this paper, a series of analytical formula is found to calculate line voltage THD of 5-level inverter with unequal DC sources instead of conventional method. Some advantages of emerged formulas of line voltage THD are: simplicity and rapidity in calculations, considering all harmonics and possibility of finding optimal switching angles analytically.