Novel modulation techniques for three-level twelve-switch inverters with elimination of common-mode voltage

Abstract

This thesis proposes space vector modulation (SVM) strategies specifically tailored for three-level twelve-switch (3L-B12) inverters. Leveraging look-up tables for straightforward gating signal generation, these SVM methods offer significant flexibility in switching sequence design. This allows not only for the implementation of classical switching sequences but also for modifications to the SVM scheme. Firstly, the synchronized and symmetrical SVM techniques are presented for the 3L-B12 inverter. This approach utilizes synchronized frequency and symmetrical switching sequences to eliminate even-order harmonics, particularly beneficial in low switching frequency applications and enhancing waveform quality. Secondly, the common-mode voltage (CMV) elimination technique based on the proposed SVM strategy is carried out by solely employing medium voltage vectors and a zero voltage vector, which can effectively eliminate the CMV. Finally, a proposed neutral-point voltage balancing control is presented to mitigate the effects of unbalanced upper and lower DC voltages caused by small voltage vectors. The effectiveness of all proposed algorithms is validated through both MATLAB/Simulink’s simulations and experimental results.