Employing the low switching frequency space vector modulators in multi-modular three-level converters

This paper presents a novel low switching frequency SVM in conjunction with a modified delayed sampling principle for generating the switching patterns of individual GTO-based three-level units of a multi-module converter structure. Alternative switching strategies are compared with respect to their impact on output voltage spectrum, switching frequency and THD. This paper also shows that the proposed low frequency switching strategies are well appropriate for capacitor voltage balancing too. The validity of the proposed switching schemes has been verified by simulation.