Research on Supercapacitor Charging Efficiency of Photovoltaic System

The model of supercapacitor and its charging performance with constant voltage charging mode, constant current charging mode and constant power charging mode were studied. A numerical method to calculate the efficiency of these charging modes was inducted. To analyze the storage performance of supercapacitor in PV system, using this method, the maximum charging efficiencies of supercapacitor when its terminal voltage raise from zero to the rated voltage with different charging modes were presented. The multi-stage charging efficiency curves were retrieved, which indicated that the constant power charging mode is more suitable when supercapacitor are charged in PV system. A MPPT plus constant power control charging strategy using two-stage Buck-Boost converter to charge supercapacitor in PV system was proposed. The simulation results showed that this strategy effectively ensure the charging efficiency of the system.