Cascaded DC-DC converter for a reliable standalone PV fed DC load

To extract maximum available power from the PV system many maximum power point tracking (MPPT) algorithms with DC-DC converter have been proposed in the literature. However, due to change in load or environmental conditions, the output voltage from the DC-DC converter varies. The variable output voltages are not suitable for many applications requiring constant voltage. To overcome this difficultly, a cascaded DC-DC converter with battery storage system for standalone application is proposed in this paper. The proposed system comprises of a PV system connected with a boost DC-DC converter to deliver the available maximum power to the DC bus. A Single-ended primary inductor converter (SEPIC) is connected to the DC bus to provide regulated DC voltage to the load. A battery with charge controller is connected to the DC bus to improve the reliability of the system. The efficacy of the proposed topology is verified through the experimental studies pursued on a prototype PV connected converter system developed in the laboratory. Robustness studies with regard to variation in environmental parameters such as solar insolation and load variation were made. MPPT and voltage regulation algorithms were implemented in LABVIEW platform using data acquisition boards.