A flexible load adaptive control strategy for efficient photovoltaic hydrogen generation system

Abstract

The adaptive adjustment of the input current in proton exchange membrane electrolyzers (PEMEL) can provide several benefits, including the enhancement of PEMEL efficiency and the extension of its operating lifespan within an optimal range. This study presents a novel configuration for a photovoltaic (PV) hydrogen generation system that allows for the direct integration of PV. Moreover, the utilization of the triple-phase shift (TPS) modulation technique is implemented in order to achieve maximum power point tracking (MPPT) control within dual active bridge (DAB) DC/DC converters. The proposed strategy offers a pre-control approach for active adjustment of flexible loads to mitigate the mismatch between power output and load caused by fluctuations in renewable energy sources. This mismatch can lead to excessive current ripple, which in turn can impact the safe functioning of the PEMEL. In tandem with the analysis of the factors that contribute to ripple and the properties of the Electrical Spring (ES), relevant multiple variables are selected as control signals for the control strategy. This is done to effectively regulate the magnitude of non-essential loads and consequently reduce the ripple in the PEMEL system. The use of the ES pre-control technique effectively addresses the issue of delayed response of the PEMEL to PV oscillations, which is attributed to the large time-lag characteristics of electrolyzers. The simulation results at steady-state conditions and sudden changes in lighting conditions demonstrate concurrently that the overall control strategy yields a reduction in current stress in the DAB to 30.09% and 51.59%, respectively, enables MPPT in PV systems, and decreases the input current ripple of PEMEL to 80.1% and 57.67%, showing stronger anti-disturbance ability.