Unified-transformer buck-flyback switched-capacitor differential power processor with function of charge balance

Abstract

This paper proposes a new converter topology for PV systems that performs maximum power point tracking (MPPT) with differential power processing (DPP) and charge balancing of battery voltages. The proposed system can control each of the PV modules independently and it can also perform charge balancing for each of the battery cells (modules). Buck converter and Buck-flyback converter are used in the converter circuit which performs as a DPP converter and a string converter in the system. In addition, a capacitor connected to the input of the DPP converter operates as a switched capacitor in the proposed circuit. When PV modules and power conditioning system (PCS) are placed far from each other, inserting switched capacitor between the transformer and the secondary buck converters eliminates all high-frequency parasitic components resulting to all high-frequency losses. The proposed system is analyzed by steady-state equations and by computer simulations. Finally, the proposed system is also verified by a hardware experiments.