Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Frequency Security-Aware Production Scheduling of Utility-Scale Off-Grid Renewable P2H Systems Coordinating Heterogeneous Electrolyzers

Jie Zhu, Yiwei Qiu, Yangjun Zeng, Shahab Dehghan, Sheng Wang, Shi Chen, Buxiang Zhou

Abstract

Renewable power-to-hydrogen (ReP2H) enables large-scale renewable energy utilization and supports the decarbonization of hard-to-abate sectors, such as chemicals and maritime transport, via hydrogen-based renewable ammonia and methanol fuels. As a result, utility-scale ReP2H projects are expanding worldwide. However, off-grid ReP2H systems exhibit low inertia due to their converter-dominated nature, making frequency security a critical concern. Although recent studies show that electrolyzers can contribute to frequency regulation (FR), their support capability depends on operating states and loading levels, creating a trade-off between hydrogen output and frequency security. To address this challenge, this work develops a unified co-optimization framework for frequency security-aware production scheduling of utility-scale off-grid ReP2H systems coordinating heterogeneous electrolyzers. A system-level frequency response model is established to capture multi-stage FR from alkaline water electrolyzers (AWEs), proton exchange membrane electrolyzers (PEMELs), and other resources, including ammonia-fueled generators retrofitted in co-located chemical plants, battery energy storage, and wind turbines (WTs). Stage-wise transient frequency security constraints are derived, reformulated into tractable forms, and embedded into production scheduling, enabling coordinated on/off switching and load allocation across electrolyzers to maximize hydrogen output under uncertain renewable power input while enforcing frequency security constraints. Case studies based on real-world systems demonstrate that the proposed approach allows HPs to replace 55.52% and 96.85% of FR reserves from WTs and AFGs, respectively, while maintaining comparable hydrogen output. Year-long simulations show an average 28.96% increase in annual net profit resulting from reduced reliance on conventional reserves.

Frequency Security-Aware Production Scheduling of Utility-Scale Off-Grid Renewable P2H Systems Coordinating Heterogeneous Electrolyzers

Abstract

Renewable power-to-hydrogen (ReP2H) enables large-scale renewable energy utilization and supports the decarbonization of hard-to-abate sectors, such as chemicals and maritime transport, via hydrogen-based renewable ammonia and methanol fuels. As a result, utility-scale ReP2H projects are expanding worldwide. However, off-grid ReP2H systems exhibit low inertia due to their converter-dominated nature, making frequency security a critical concern. Although recent studies show that electrolyzers can contribute to frequency regulation (FR), their support capability depends on operating states and loading levels, creating a trade-off between hydrogen output and frequency security. To address this challenge, this work develops a unified co-optimization framework for frequency security-aware production scheduling of utility-scale off-grid ReP2H systems coordinating heterogeneous electrolyzers. A system-level frequency response model is established to capture multi-stage FR from alkaline water electrolyzers (AWEs), proton exchange membrane electrolyzers (PEMELs), and other resources, including ammonia-fueled generators retrofitted in co-located chemical plants, battery energy storage, and wind turbines (WTs). Stage-wise transient frequency security constraints are derived, reformulated into tractable forms, and embedded into production scheduling, enabling coordinated on/off switching and load allocation across electrolyzers to maximize hydrogen output under uncertain renewable power input while enforcing frequency security constraints. Case studies based on real-world systems demonstrate that the proposed approach allows HPs to replace 55.52% and 96.85% of FR reserves from WTs and AFGs, respectively, while maintaining comparable hydrogen output. Year-long simulations show an average 28.96% increase in annual net profit resulting from reduced reliance on conventional reserves.
Paper Structure (28 sections, 1 theorem, 50 equations, 15 figures, 5 tables)

This paper contains 28 sections, 1 theorem, 50 equations, 15 figures, 5 tables.

Table of Contents

  1. Introduction
  2. Background and motivation
  3. Literature review
  4. Contributions
  5. Modeling of frequency response from heterogeneous regulation resources in ReP2H systems
  6. Frequency support from HPs
  7. Frequency support from AFGs, BES and downstream chemical plant
  8. Ammonia-fueled generator (AFG)
  9. Wind turbine (WT)
  10. Battery energy storage (BES)
  11. Downstream chemical plant
  12. Multi-stage frequency regulation strategy
  13. Modeling of frequency dynamics and security metrics
  14. Staged frequency dynamics under disturbance
  15. Transient frequency security metrics and constraints
  16. ...and 13 more sections

Key Result

Proposition 1

Let $\tau_{\mathrm{nadir}}(H,R_1)$ denote eq:26 under a known $\Delta P_{\mathrm{dis}}$. For any $\Delta P_{\mathrm{dis}}>0$ and $H>0$, there exists a unique $R_1^*(H)>0$ such that $\tau_{\mathrm{nadir}}(H,R_1^*(H))=t_{\mathrm{DB2}}$, as shown in Fig. fig:FrequencyInterval(b). Define $R_1^{\mathrm{l Moreover, there exists a small time margin $\mu\ge 0$ such that for any $R_1\in(R_1^{\mathrm{lo}},R

Figures (15)

  • Figure 1: Schematic diagram of a typical off-grid ReP2H system.
  • Figure 2: Frequency control and dynamic load response of electrolyzers. (a) Frequency control diagram. (b) Equivalent circuit of the electrolysis stack. (c) Step responses of the AWE and PEMEL.
  • Figure 3: AWE Stack efficiency with different current density and temperature.
  • Figure 4: Comparison of the post-contingency frequency dynamics and PFR power under the proposed model \ref{['eq:22']} and the EMT benchmark. (a) Post-contingency frequency. (b) PFR power of AWEs. (c) PFR power of AFGs.
  • Figure 5: Frequency nadir dynamics. (a) Occurrence cases of the frequency nadir. (b) Time of the frequency nadir with varying reserve and inertia levels.
  • ...and 10 more figures

Theorems & Definitions (3)

  • Remark 1
  • Proposition 1
  • proof