Partial Power Converter for a Two-Stage Photovoltaic Cascaded String Inverter

Tow-stage configurations used in photovoltaic (PV) architectures (microinverter, string inverter or multistring inverter), are commonly used because of the advantages in front of mismatch conditions. In case of a partial shading scenario (produced by cloudy days and dust accumulation), two-stage architectures reach higher efficiencies compared with the traditional central inverter. It is because, the DC-stage allows a wide voltage range in order to perform maximum power point tracking (MPPT). On the other hand, the additional stage increase the component counts and the conversion losses, which leads to a reduced efficiency compared with the single-stage inverters. This work presents a solution for the traditional two-stage configurations, where the partial power conversion (PPC) concept is implemented in the DC-stage. In that way, the DC-DC converter handles a reduced power allowing a volume reduce and increased power density. Moreover, the AC-stage is made using a cascaded H-bridge topology, which improves the power quality and reduces the components size. Simulations are implemented in order to validate the proposed work.