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.