Frequency-Modulated High-Gain Boost-Flyback DC-DC Converter for Renewable Energy Systems

This study introduces a new modified high-gain interleaved boost-flyback converter with pulse frequency modulation. In the proposed converter, a four-winding coupled inductor and a switching cell are utilized to achieve high voltage gain without requiring a large turn ratio. It presents soft commutation for a wide frequency range, the shared ground connection between source and load, continuous input current with low ripple, and low current oscillation even for cases with low-frequency output voltage ripple. These features make the proposed converter suitable for low-input voltage applications that require a high step-up gain, such as renewable energy systems. The proposed converter is analyzed in steady-state to provide the detailed principle of operation and characteristics, a static gain comparison, a design guide, and losses and efficiency analysis for all the components. Finally, experimental results were obtained from a 450-W prototype with an input voltage of 60/65 V, generating an output voltage of 480 V. The efficiency at peak power is 95.7%.