Low-distortion variable-level PWM technique

A multicarrier disposition pulse width modulation (PWM) technique that results in low harmonic distortion for a three-phase PWM inverter with a 5-level line-to-line output voltage waveform is discussed in the paper. Comparison with the conventional 5-level unipolar PWM technique for three-phase inverters reveals that the proposed strategy results in a high performance converter with minimised filter requirements since the amplitude of all harmonics is reduced. The resulting line-to-line voltage waveform has five levels at high and three levels at low amplitude modulation indexes (variable level). Harmonic analysis is presented, along with simulated and experimental results to support the theoretical considerations