Four-legged converter 3-D SVM scheme over-modulation study

A novel three-dimensional space vector modulation (3-D SVM) along with two different overmodulation correction schemes is proposed for three-phase four-legged converters. Although the overmodulation is desired in motor drive applications for better bus voltage utilization, it can cause voltage distortion, and thus is undesirable in utility interface applications. The overmodulation case may occur during transient conditions. When it happens, the duty cycle will saturate, and the output voltage waveform quality deteriorates. In this paper, the overmodulation surface for a 3D SVM scheme is defined, and the correction methods that keep the system from entering into overmodulation are evaluated with computer simulation.