A NPC transformerless single phase inverter with inner voltage boosting capability

Thanks to their characteristic quiet rail switching mechanism, derivatives of the basic half bridge converter, such as the Neutral Point Clamped topology, are advantaged among single stage, single phase, inverter configurations for PV applications by very low ground currents. On the other hand, as the majority of single stage inverters, they are unable to boost the input voltage, therefore featuring a narrow operating range. Moreover, if compared with full bridge derived topologies, half bridge derivatives require a double input voltage. A new inverter configuration, based on a three level Neutral Point Clamped configuration, owning an inner voltage boosting capability is presented in this paper. No extra high frequency switching devices are introduced, thus featuring reduced power losses. Moreover, no reactive currents flow back to the DC bus, due to the inner AC side bypass and no common mode current filters are required, thanks to the quite rail switching operation.