Cascaded DC–DC Converter Connection of Photovoltaic Modules

TitleCascaded DC–DC Converter Connection of Photovoltaic Modules
Publication TypeJournal Article
Year of Publication2004
AuthorsWalker G.R., Sernia P.C.
JournalIEEE Transactions on Power Electronics
Date Publishedjul
Keywords(PV), Cascaded converter, grid connected photovoltaic, Matlab efficiency simulation, maximum power point tracking (MPPT), module integrated converters (MICs), multilevel converter, series connected converter.
Abstract—New residential scale photovoltaic (PV) arrays are commonly connected to the grid by a single dc–ac inverter con- nected to a series string of pv panels, or many small dc–ac inverters which connect one or two panels directly to the ac grid. This paper proposes an alternative topology of nonisolated per-panel dc–dc converters connected in series to create a high voltage string con- nected to a simplified dc–ac inverter. This offers the advantages of a “converter-per-panel” approach without the cost or efficiency penalties of individual dc–ac grid connected inverters. Buck, boost, buck-boost, and Cúk converters are considered as possible dc–dc converters that can be cascaded. Matlab simulations are used to compare the efficiency of each topology as well as eval- uating the benefits of increasing cost and complexity. The buck and then boost converters are shown to be the most efficient topologies for a given cost, with the buck best suited for long strings and the boost for short strings. While flexible in voltage ranges, buck-boost, and Cúk converters are always at an efficiency or alternatively cost disadvantage.