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

In this paper the use of an LLC resonant converter used as MPPT-tracker in the photovoltaic field has been studied. Two different utilization schemes has been considered: direct connection of the PV module to the grid and the string connection scheme. Each solution is limited from the efficiency of the power converter, due mainly to the transformer. In this work the impact of the transformer design on size and losses have been considered in both cases and compared each other to obtain indications that permits to choose the best topology. Both transformers are been constructed using an hard interleaved coil scheme and the same ferrite material. Comparing the designs can be observed that the transformer for the direct connection to the grid has the volume and the weight that is tens times greater than the string solution, so the final converter is bigger. In conclusion the weight and the volume can be reduced with the string derived solution