Modeling and Constraint-Aware Control of Pressure Dynamics in Water Electrolysis Systems

TL;DR

The paper tackles pressure constraint violations in water electrolysis under dynamic power by developing a control-oriented model of an alkaline electrolyzer and implementing a constraint-aware Reference Governor-based Power Governor to adjust input power $P_{in}$ and keep $p_{H_2}$ within manufacturer limits. The RG constructs a finite inner approximation $\Omega$ of the maximal admissible set and solves an online LP to compute a modified reference $v(t)$, ensuring constraint satisfaction with minimal deviation. Simulation results show the RG-based PG maintains pressure within bounds and outperforms a traditional low-pass filter, yielding higher hydrogen production and lower auxiliary energy consumption. The work demonstrates a practical approach to increasing electrolyzer flexibility in the presence of rapid power fluctuations, with potential benefits for integration with renewable energy sources.

Abstract

This paper addresses the challenge of pressure constraint violations in water electrolysis systems operating under dynamic power conditions, a problem common to both Proton Exchange Membrane and alkaline technologies. To investigate this issue, a control-oriented model of an alkaline electrolyzer is developed, capturing key pressure and flow dynamics. To manage rapid power fluctuations that may cause pressure to exceed manufacturer-defined operational boundaries, a model-based constraint-aware power governor based on the Reference Governor (RG) framework is proposed. Simulation results show that the strategy effectively maintains pressure within the specified operating range, outperforming conventional filtering methods while enhancing hydrogen production and reducing auxiliary energy consumption.

Figures (6)

• Figure 1: Illustrative electrolyzer system diagram with key variables. The variables in parentheses are state variables, while the variables in braces are input variables determined by the controllers.
• Figure 2: Block diagram of the pressure controllers. The variables in parentheses are state variables.
• Figure 3: Simulation result of pressure response $P_{H_2}(t)$ under large step changes in input power $P_{\text{in}}(t)$.
• Figure 4: Reference governor controller scheme. The signals are as follows: $y(t)$ is the constrained output, $r(t)$ is the desired reference, $v(t)$ is the modified reference command, and $x(t)$ is the system state.
• Figure 5: Comparison of power governor and conventional low-pass filter for pressure constraint management under large step changes in input power.