Multi-string-converter with reduced specific costs and enhanced functionality

Abstract The development of a PV-converter based on the advanced Multi-String concept results in significantly reduced specific costs while still profiting from the well-known advantages of the string-converter technology developed by ISET and SMA in the mid-1990s. The paper deals with the basic considerations from a system’s point of view that resulted in the development of the Multi-String-converter. The features of the Multi-String-converter concerning operational behaviour and PV-system design are described. Due to enhanced capacity of the operational control unit the Multi-String-converter can be used additionally for active compensation of harmonics and reactive power in order to improve the power quality. An evaluation of Multi-String-converters in comparison with string-converters or conventional central-converter concepts is presented. The selected topology and the control strategy for the Multi-String-converter are introduced.