Influence of commutation delay and tube voltage drop on waveform distortion and its compensation in matrix converter

The output waveform distorts seriously at low modulation ratio, and there are not a paper analyze it overall yet. This paper gives a research on the problem from some facts, the narrow pulse, the commutation delay and tube voltage drop. The time of commutation delay varies as the direction of output current changes, equivalent to the addition or reduction of the vectors´ operation time, influencing the waveform distortion all the time. The tube voltage drop is constant generally. Its proportion of output voltage is so little that it can be ignored at high modulation ratio, while the condition inverse at low modulation ratio. Against two elements causing the distortion, this paper presents corresponding compensation method. The direct time compensation method is used for the waveform distorted by commutation delay and the feedforward compensation method is used for the tube voltage drop at very low modulation ratio. The experimental results verify the proposed method.