Off-grid power delivery from photovoltaic (PV) systems to electrolyzers serves as a key pathway toward sustainable green hydrogen production, with the PV output voltage adapted to the electrolyzer operating voltage by dc/dc converters. However, a systematic understanding of the performance trade-offs between different converter architectures and their associated control strategies is still lacking, particularly for ensuring robust operation under intermittent solar conditions. This paper presents a systematic comparative study of single- and dual-stage dc/dc converter architectures for standalone PV-electrolyzer (PVEC) systems. The study investigates the fundamental control trade-offs, comparing the single-stage's rigid electrolyzer-following operation with the dual-stage's superior flexibility in providing direct electrolyzer current regulation. To enhance operational resilience, two distinct low power ride-through (LPRT) strategies are proposed and analyzed for the dual-stage configuration, ensuring stable power delivery during significant solar power reductions. The feasibility and performance of the proposed architectures and control strategies are validated through both 5 kW system simulations and experiments on a 200 W GaN-based hardware prototype. The results demonstrate that while the single-stage architecture is viable for small-scale systems, the dual-stage configuration's enhanced control flexibility and scalability are essential for large-scale, storage-ready PVEC applications.

The dual-active-bridge (DAB) converter serves as a crucial galvanic isolating solution to provide dc grid-forming for dc elements in low-voltage direct-current (LVdc) systems. Key performance metrics such as efficiency, current stress, power density, and cost of DAB converter are chiefly subject to the optimal design of magnetic components and modulation strategies. However, existing DAB converter designs yield compromised solutions that optimize a limited subset of these metrics. This article develops a comprehensive analytical framework to characterize DAB converter operation across three key dimensions: 1) zero-voltage switching (ZVS) range; 2) power rating utilization; and 3) reactive power. To achieve a well-balanced design, a holistic optimization methodology is proposed, integrating multiobjective particle swarm optimization (MOPSO) with triple phase-shift control. By optimally selecting the transformer turns ratio and product of switching frequency and series inductance, the proposed MOPSO approach can collectively or selectively improve these performance aspects, enabling tailored DAB converter designs to meet diverse performance objectives. Experimental validation on a 1-kW DAB converter prototype demonstrates enhanced ZVS capability, improved utilization of converter rating, reduced reactive power, and achieves a peak efficiency over 95.9%.

Partially rated DC interlinking converters are recognized for their high-gain power regulation capabilities, which effectively synergize active power across DC microgrids (DCMGs). Integrating energy storage units (ESUs) to address the intermittent nature of renewables in DCMGs has become an enhanced requirement for these converters. This article proposes a partially rated multiport interlinking converter (PMIC) that incorporates a distributed ESU. The PMIC controls a floating voltage and a bidirectional shunt current on the DC line, ensuring full galvanic isolation for the ESU while operating at a low DC-link voltage. It regulates multidirectional power flow and balances power during peak and off-peak periods. A decentralized droop-based power flow control strategy is proposed for the PMIC, which distributes renewable energy generation, load consumption, and ESU utilization proportionally across the system. The control strategy includes two tailored continuously differentiable activation functions, Sigmoid and Hyperbolic Tangent, to facilitate autonomous global power-sharing and seamless ESU engagement. Simulation and experimental case studies confirm the PMIC's capability to smooth renewable energy fluctuations and enhance the power and voltage profiles of DCMGs.