No abstract

Low-cost alkaline water electrolysis from renewable energy sources (RESs) is suitable for large-scale hydrogen production. However, fluctuating RESs lead to poor performance of alkaline water electrolyzers (AWEs) at low loads. Here we explore two urgent performance issues: inefficiency and inconsistency. Through detailed operation process analysis of AWEs and the established equivalent electrical model, we reveal the mechanisms of inefficiency and inconsistency of low-load AWEs are related to the physical structure and electrical characteristics. Furthermore, we propose a multi-mode self-optimization electrolysis converting strategy to improve the efficiency and consistency of AWEs. In particular, compared to a conventional dc power supply, we demonstrate using a lab-scale and large-scale commercially available AWE that the maximum efficiency can be doubled while the operation range of the electrolyzer can be extended from 30–100% to 10–100% of rated load. Our method can be easily generalized and can facilitate hydrogen production from RESs.

As dominant power sources, the safe and reliable operation of photovoltaic (PV) generators is crucial for the DC distribution network. This study analyzes the transient stability of PV generators under large disturbances and proposes a variable parameter control strategy to suppress the transient instability. First, the transient stability of the PV generators is analyzed using the proposed power–voltage evolution curve. It is found that the PV side easily suffers undervoltage faults during the transient process, which will cause instability of the system. Based on the revealed unstable mechanism, the variable parameter control is proposed to enhance the transient stability of PV generators. Finally, all the findings have been validated by hardware-in-loop tests.

With the widespread use of clean energy sources, there has been a growing interest in obtaining green and pure hydrogen from wind power. However, wind energy is characterized by randomness and volatility, which results in a low grid connection rate for wind turbines and makes it difficult to integrate wind energy into the power grid. In this context, this article proposes an adaptive coordinated control strategy considering the wind turbine, alkaline electrolyzer, battery, and local loads. Using the DC bus voltage as the connecting signal, adaptive power control and voltage control methods are developed for the wind turbine, energy storage battery, and electrolyzer to achieve power matching in the system. Finally, the proposed research results are validated through Matlab/Simulink simulation module.

Low-cost and mature alkaline water electrolysis is suitable for large-scale hydrogen production from renewable energy sources (RESs). However, the poor low-load performance of alkaline water electrolysers (AWEs) makes it difficult to follow fluctuant RESs in full range. For low-load AWEs, existing researches only pay attention to the impurity problem and its solutions, but here, we find other two urgent problems to be solved, namely inefficiency and inconsistency. Through the detailed operation process analysis of AWEs and the established equivalent electrical model, the inefficiency and inconsistency mechanisms of low-load AWEs are revealed. Furthermore, an overcurrent pulse-width modulation method is proposed to enhance the efficiency and consistency of AWEs. Especially, compared to the conventional dc power supply, 1) the maximum efficiency improvement can exceed two times, 2) the operation range can be extended to 10% of rated load. The proposed method just changes the power supply, it can be easily generalized and can facilitate the hydrogen production from RESs.