A UNSW-led research team proposed two low-power ride-through strategies for standalone PV electrolysis systems to maintain stability during sudden fluctuations in solar energy without using battery storage.
A research team led by Australia’s University of New South Wales (UNSW) Sydney has proposed two new low-power ride-through (LPRT) project configurations for stand-alone PV electrolysis systems (PVEC).
LPRT is a control option for electrical equipment that allows it to remain connected and continue to operate, with reduced power, during brief mains disturbances, such as voltage drops, frequency deviations or partial power loss. When used in PV-powered electrolyzers, it can maintain system stability during dips in solar energy output by matching the electrolyzer’s power demand with the reduced electricity supply.
“The novelty of this study lies in the systematic comparison of single-stage and two-stage converter architectures for stand-alone PV electrolysis systems,” said corresponding author Kaiwen Sun. pv magazine. “We further included the proposal and experimental validation of two LPRT strategies, such as current reference reduction and control-mode switching, which prevent the DC link from collapsing during sudden solar power shortages without the need for battery storage.”
The study began with a comparative analysis of one- and two-stage flow interface architectures. Because PV modules and electrolyzers operate at significantly different voltage-current ranges, a power interface (DC/DC converter) was needed to match the two systems. In a single-stage configuration, a single converter connected the PV array directly to the electrolyzer, offering simplicity but limited control flexibility. In contrast, a two-stage architecture introduced an intermediate DC link with two converters, allowing more independent control of the PV and electrolyzer and improving system flexibility and stability under variable solar conditions.
The two-stage system operated in two modes. In mode 1, the PV array operated under Maximum Power Point Tracking (MPPT), while controlling the DC link, allowing the electrolyzer to track the available solar energy. In mode 2, the DC link was controlled and the electrolysis current was kept constant, allowing precise control of hydrogen production. However, in this mode, sudden drops in solar power can lead to a mismatch between generation and demand, potentially leading to DC link voltage instability. Low-power ride-through (LPRT) solved this problem by reducing the electrolyzer current to match the available PV power, or by switching back to mode 1, thereby maintaining stable operation.
The proposed approach was evaluated through both simulation and experimental validation. In simulation, a detailed 5 kW system model was developed, including the PV array, electrolyzer and power electronic converters. The system was tested under dynamic operating conditions, including sudden reductions in solar radiation. Experimental validation was performed using a 200 W laboratory prototype gallium nitride (GaN) based converter, which confirmed the simulation results under real operating conditions.
“The most surprising results include the two-stage converter that maintains hydrogen production at 0.58–1.01 Nm³/h with an electrolyzer system efficiency as high as 96.75%–97.12% with a 50% reduction in irradiance, the control mode switching strategy that stabilizes the system in less than 0.5 seconds, and the counterintuitive finding that the efficiency of the electrolyzer increases as the input power decreases (e.g. from 81.42% at 5 kW to 97.18% at 2.04 kW),” said Sun.
In conclusion, the researchers noted that their results clearly demonstrate that while a single-stage inverter is sufficient for small-scale systems, a two-stage architecture becomes essential for scaling PV electrolysis (PVEC) applications to industrial levels. At this larger scale, significant voltage mismatches make phased power conversion and advanced control functions critical for reliable and efficient operation.
“We will focus on the co-design and optimal energy management of hybrid energy storage systems integrated on the intermediate DC link, in addition to advanced control algorithms to enable fully dispatchable, on-demand green hydrogen production, while also exploring isolated converter topologies such as DAB and TAB for improved fault tolerance and scalability in hundred-kilowatt scale systems,” Sun said, referring to the future direction of the team’s work.
The research work was presented in “Improving the operational resilience of standalone photovoltaic electrolysis systems: a comparative analysis of one- and two-stage power interface architectures”, published in Applied energy. Scientists from Australia UNSW Sydneythe Dutch Delft University of Technology and the British University of Bath contributed to the research.
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