A DC-DC converter topology for multiple-input photovoltaic configurations

The voltages generated from renewable sources, such as wind and solar energy, often vary because of environmental changes. When the input voltage drops to a value lower than that of the battery, it will fail to recharge. Cascaded buck-boost converters are conventionally used to step-up or step-down the input voltage, but these are relatively complex and costly. This paper describes a new battery charging system based on a non-inverting buck-boost converter. The proposed two-switch converter requires one less inductor and capacitor compared with the conventional SEPIC (single-ended primary inductor converter) to achieve the non-inverted output voltage. The model is validated through simulation results from one and multiple sources with constant and variable input voltages. Test results show stable operating performance under both steady-state and transient conditions. A maximum power point tracking algorithm is successfully applied to the proposed multiple input converter configuration. The system is suitable for both low-voltage portable charging devices and grid-connected photovoltaic/battery systems.