Switched-Capacitors as Local Converters for Snake PV Modules: A Cost/Efficiency Exploration

In order to reduce the negative effect of partial shading and other sources of current mismatch within a module, smart reconfigurable modules allow altering the connections between groups of cells (cell-strings). With a proper algorithm managing these connections, we can make sure that the majority of the cells are operating close to their MPP, even when a part of the module is shaded. Such a smart reconfigurable module consists of some extra components. Switches are needed to change the interconnection scheme. Small, local converters collect power from multiple cell-strings. They step-up the voltage to reduce the current on the central bus they are connected to. At the end where we connect to the string-level bus, a module converter further regulates the voltage for the grid or the PV array. This topology was presented before where we showed that a smart reconfigurable module could recover up to 70% of the power lost to partial shading. In this paper we take a closer look at the local DC-DC converter. More precisely, we present a cost-efficiency analysis of different converter topologies. Taking into account practical limitations (economical limitations, number of components, maximum switch currents, maximum capacitance values, etc..) we estimate efficiency and projected cost. We show that Dickson pump (CR3) with 30-35m switches is the best candidate. This would result in a chip cost of about €1.5.