LCL-Resonant-Tank Based Current Fed-Out DC–DC Converter for PV Off-Grid Hydrogen Production: Modeling, Control, and Optimization

The output-side current-fed (i.e., current fed-out) dc–dc converters have lower output current ripples compared with voltage-fed converters due to the output-side inductor, which is attractive for photovoltaic (PV) off-grid hydrogen production systems. This article presents an inductor-capacitor-inductor (LCL)-resonant-tank based current fed-out dc–dc (LCL-CFO) converter. With the variable frequency and phase shift modulation (VFPSM) employed, the mathematical model is deduced by using the first-harmonic approximation method, and the operating characteristics such as output voltage gain, soft-switching, and backflow power of the LCL-CFO converter are analyzed. On this basis, an efficiency optimization control strategy based on the VFPSM is proposed, which reduces the backflow power to the maximum extent while realizing the soft-switching of the LCL-CFO converter. Finally, a laboratory prototype of the LCL-CFO converter is built to verify the feasibility and effectiveness of the operation characteristics and the proposed efficiency optimization control strategy.