A low-distortion variable-level PWM technique

A PWM method that results in low harmonic distortion for a 5-level PWM inverter is discussed in this paper. Comparison with the conventional 5-level unipolar PWM technique reveals that a greater number of vectors are produced with the proposed strategy thus resulting in high performance converter with minimized filter requirements since the amplitude of all harmonics is reduced. The resulting line-to-line voltage waveform has 5-levels at high and 3-levels at low modulation indexes (variable-level). Harmonic analysis is presented along with simulated and experimental results to support the theoretical considerations