LLC resonant converters in PV applications comparison of topologies considering the transformer design

In this paper the use of an LLC resonant converter as Maximum Power Point Tracker (MPPT) in a photovoltaic application is presented. Two different implementations are considered: direct connection of the photovoltaic (PV) module to the grid and the string connection circuit. In Each solution the power converter efficiency is mainly limited by the step-up transformer. The impact of the transformer design on size and losses is considered in both cases with the view to choose the best topology. Both transformers are constructed using a hard interleaved coil structure and the same ferrite material. Finally, it is shown that the direct connection to the grid has a volume and a weight that is ten times greater than the string solution.