A High Step-Up Coupled-Inductor-Integrated DC–DC Multilevel Boost Converter With Continuous Input Current

A high step-up converter for interfacing renewable energy generation is proposed. The converter is composed of a modified quasi-Z-source network, a three-winding coupled inductor, and an <inline-formula> <tex-math notation="LaTeX">$m$ </tex-math></inline-formula>-layer stacked switched capacitor. The proposed converter regulates the output voltage using turn ratios (<inline-formula> <tex-math notation="LaTeX">$n_{1}$ </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">$n_{2}$ </tex-math></inline-formula>) of the coupled inductor, stacked layers <inline-formula> <tex-math notation="LaTeX">$m$ </tex-math></inline-formula> of the switched capacitor, and duty cycle <inline-formula> <tex-math notation="LaTeX">$D$ </tex-math></inline-formula>. The converter possesses the advantages of high voltage gain, continuous input current, the low voltage stress on the switch <inline-formula> <tex-math notation="LaTeX">$S$ </tex-math></inline-formula>, passive clamping circuits, and high efficiency. Essentially, the integration of a three-winding coupled inductor and stacked switched capacitor enhances the voltage gain of the converter. Owing to the low voltage stress on the switch, MOSFET with low ON-resistance can be adopted to reduce the switching and conduction losses. The low input current ripple prolongs the lifetime of the renewable energy module. In addition, the passive clamp circuit recycles leakage inductance energy and limits switch voltage spike. The expansion of stacked switched-capacitor layers can be effectively utilized to further optimization of the high-voltage-gain converter. A detailed analysis of the operating principle and the steady-state analysis are presented. Finally, the converter is verified by a 200-W prototype, and the experimental results are in good agreement with the theoretical analysis.