A new hybrid SVPWM strategy to minimize the neutral point voltage ripple of a three-level T-type converter

This paper proposes a new hybrid space vector pulse width modulation (SVPWM) strategy to minimize the neutral point voltage ripple of a three-level T-type converter. The origin of neutral point voltage ripple is analyzed in detail. Then, the controllability of a nearest three vectors (N3V) based SVPWM on the neutral point voltage balancing is investigated. In the uncontrollable regions of the N3V SVPWM approach, a non N3V based SVPWM is incorporated to balance the neutral point voltage with a switching cycle based profile. The non N3V based SVPWM is realized by replacing the medium voltage vector of the three nearest vectors (NVs) with a large voltage vector in an appropriate way. By introducing an offset vector, the reference voltage vector of the three-level converter can be synthesized in a way similar to that of a two-level converter. The effectiveness and the advantages of the proposed hybrid SVPWM scheme are verified by the simulation results in Matlab @ Simulink.