High step-up resonant DC-DC converter with ripple-free input current for renewable energy systems

In this paper, we propose a high step-up resonant DC-DC converter with ripple-free input current for renewable energy systems. We use an input-current doubler and a switching mechanism employed at an output-voltage doubler to achieve high step-up voltage gain without having to use a transformer with high turns ratio. An active-clamp circuit installed on the primary side suppresses the surge voltage at the switch components and recycles the energy stored in the leakage inductance. A resonance that occurs at the secondary side of the converter is used to reduce the turn-off current and switching loss significantly, and to achieve high power conversion efficiency. The input-current ripple declines to zero theoretically because the duty cycle of the primary-side switches is always set to 0.5 regardless of the input voltages and load variations. The circuit operations, steady-state analysis, and design guideline of the proposed converter are also presented. A 600-W prototype converter has been fabricated to demonstrate the performance of the proposed converter.