A Precise and Practical Harmonic Elimination Method for Multilevel Inverters

Multilevel inverters have been widely used in medium-and high-voltage applications. Selective harmonic elimination for the staircase voltage waveform generated by multilevel inverters has been studied extensively in the last decade. Most of the published methods on this topic were based on solving high-order multivariable polynomial equation groups derived from Fourier series expansion. This paper presents a different approach, which is based on equal area criteria and harmonic injection. With the proposed method, regardless of how many voltage levels are involved, only four simple equations are needed. The results of a case study with maximum of five switching angles show that the proposed method can be used to achieve excellent harmonic elimination performance for the modulation index range at least from 0.2 to 0.9. To demonstrate the adaptability of the proposed method for waveforms with a high number of switching angles, experimental results on a 1-MVA 6000-V 17-level cascade multilevel inverter are also shown at the end of this paper.