A new method for connecting of photovoltaics modules in dc microgrid

The objective of this article is to present a new method for linking of photovoltaic modules in dc microgrids to power supply to a battery bank or to a load. The proposed system is comprises by two stage of conversion. The first stage performs MPPT of photovoltaic module. The second stage is comprises by buck-boost converter based on the three-state commutation cell (3SCC). This converter is used to divider a main voltage bus into even voltage sub-bus. This first advantage is voltage reduction of main bus without transformer, under these circunstances increases overall system efficiency and decrease the voltage stress on the switch in the first stage. Other advantage is that the 3SCC when employed to this purpose allows using smaller filters as the filters operates at twice the switching frequency. Furthermore, in continuous conduction mode the 3SCC uses 50 % of duty cycle, providing a more reduction of filter sizes. On the other hand, this paper shows that an appropriate drive of switching transistors provides immunities to saturation problem of commutation cell transformer. Simulations results are shown proving the feasibility of the proposed system. Experimental results will be shown in the final work.