Evaluation of losses in three-level neutral-point-clamped and T-type quasi-Z-source inverters with modified carrier based modulation method

In recent years, the significant growth of the number of inverters connected to the grid as a consequence of the development of renewable energy sources, especially photovoltaic modules, has caused that focus is on innovative inverter circuitries. This paper presents a comparison between two different configurations of three-phase three-level inverters: the neutral-point-clamped and the T-type. Both topologies have been combined with a quasi-Z-source network in order to obtain the straightforward benefits that it offers, by using a modulation technique which introduces shoot-through states. Conventional carrier based modulation techniques have been modified in order to optimize the switching pattern for the T-type circuit. Moreover, a comprehensive simulation study is performed in order to state if T-type topology could be considered as a good alternative to neutral-point-clamped topology.