A dual boost-NPC inverter working in time sharing mode

摘要

A two-stage converter working in dual mode time sharing is proposed for single-phase photovoltaic applications. The converter encompasses a dual boost front end and a single-phase three-level Neutral Point Clamped grid inverter. According to the time sharing strategy, the boost stage is by-passed and only the Neutral Point Clamped inverter is operated when the input voltage is greater than the actual absolute value of the grid voltage. Otherwise, the boost stage operates as a current shaper and the inverter works in unfolder mode. As only one of the two stages of the converter is active at a time, power losses are reduced. Moreover, a suitable input DC voltage amplification is provided, extending the input voltage range. This also enables the exploitation of a neutral point clamped inverter, which, thanks to the characteristic quite rail switching, generates very low leakage ground currents.