Selective harmonic power optimization in multilevel inverter output

The determination of switching instances in multilevel converters has been of interest in recent years. In this paper, a search technique to find the values of the switching angles of the output waveform of a multilevel inverter for harmonic optimization is described. The technique is based on the steepest descent algorithm which searches for the minimum value of the power harmonic distortion of the low order harmonics in the output waveform, according to the value of the modulation index set at the beginning of the optimization process. The algorithm uses the power equations of the harmonics rather than the voltage equations to achieve the search process. A high convergence rate is achieved with this technique.