Solar PV modules are typically connected to an dc-dc converter for ensuring the operation at maximum available power. While the research work has shown us the possibilities of using different kinds of dc-dc converters, following three basic topologies are still widely used. 

For a PV system their designing is difficult. It is because contrary to a conventional converter, PV dc-dc converters have a current source input, that too, variable. Therefore, the designing process is not same. In a research paper by Weidong Xiao et,al. these three topologies are discussed in detail. The crux of their paper is the formula to calculate the input and output capacitance and inductor for these topologies.  I therefore recommend to read this paper once if you are working in this field.