The harmonic selection elimination of multi-level converters

Multi-level converters have many advantages than the traditional two-level PWM converters, and they are widely used in DC-AC transforming. An important issue in multi-level converters design is the voltage wave sinusoidal and the elimination of the lower harmonics. In this paper, a mathematical method is discussed to calculate the appropriate switching angles to eliminate the selected harmonics, and the mathematical Sturm theory is used to estimate the number of the solutions of the switching angles, and the dichotomy is used to compute the switching angles of each individual device in a multi-level converter. It is shown that for a range of the modulation index m , the switching angles can be chosen to produce the desired fundamental V/sub 1/ = V/sub 1/ (m) while at the same time the selected harmonics, for example, 5/sup th/, 7/sup th/ are eliminated.