A randomized voltage vector switching scheme for three-level power inverters

In this paper, a feasibility study of a randomized space vector switching scheme for three-level inverters is reported. Based on the traditional space vector concept for pulse width modulation (PWM) inverter, the sequence of the space vector is randomized in this scheme. The overall vector, resulting from the randomization, is mathematically identical to that of the traditional space vector. It has been found that the randomized scheme can effectively spread the switching noise over a wide frequency range and at the same time keep the steady-state link capacitor voltage balanced. The proposed scheme has been implemented in real time in a digital controller and its features have been experimentally confirmed.