Improved Power Decoupling Scheme for Single-Phase Grid-Connected Differential Inverter with Realistic Mismatch in Storage Capacitances

A single-phase differential inverter consists of two elementary dc-dc converters, sharing a common dc source and a common ac output terminal. The other ac terminals of the two converters are connected to the grid in the case of grid-connected applications. The differential inverter has subsequently been shown to have a differential flow path for power transfer and a common-mode path for shifting the usual second-order power oscillation away from the dc source. This capability is referred to as power decoupling, which when implemented properly, may prolong the lifespan of the dc source. Existing studies related to power decoupling using a differential inverter have however focused on developing control schemes with equal storage capacitances assumed for the two elementary converters. This is unquestionably not realistic since the two capacitances will vary in practice. It is therefore the intention of this paper to quantify ac and dc imperfections experienced by the differential inverter when storage mismatch occurs. A simple improved scheme is then proposed for raising performance of the differential inverter (or the differential rectifier where desired). Simulation and experimental results provided have verified the computation and control scheme developed.