An Extendable High Step-Up DC-DC Converter with Dual-Switch CI Topology for PV Applications

This article presents a high-step-up DC-DC converter with a coupled inductor (CI) designed for boosting low PV voltage levels to higher DC bus voltages. The proposed topology integrates two-switch boost cells with a coupled inductor structure. The coupled inductor in the proposed converter not only increases the output voltage but also provides an additional degree of freedom for controlling the voltage and current stresses of the switches and can be modularly extended to further enhance the conversion ratio. In addition, an extendable pump capacitor unit (PCU) is incorporated to achieve a very high voltage gain. Based on the charge–discharge behavior of the switched capacitors, the output voltage is further increased without significantly increasing the component count. Owing to the low number of components and the simple structure, the converter features low input current ripple and a high overall voltage gain, making it suitable for high step-up PV applications and interfacing PV modules with DC buses. Although the proposed topology can be extended in two ways, for clarity of analysis, it is initially investigated in its basic (non-extended) form. The proposed topology, boosting operation, key operating waveforms, and control strategy are validated by detailed experimental results.