Ambient-Frequency-Data Based System-Level Inertia Estimation Using Physical Equation and its Practice on Hawaii Islands

Hongyu Li, Shutang You, Zhihao Jiang, Jin Tan, Andy Hoke, Jingzi Liu, Lin Zhu, Brad Rockwell, Cameron Kruse, Yilu Liu

Research output: Contribution to journalArticlepeer-review


In this paper, a practical ambient-frequency-data-based inertia estimation method using a physical equation is proposed and validated by real measurement data from Hawaii island grids. With high renewable penetration, accurate inertia estimation is important and urgent. Ambient frequency oscillation always exists in power grids, so the proposed method has advantages of real-time inertia estimation and no need for additional disturbances. This paper first developed the physical equation for inertia estimation to offer a clear mechanism for easy implementation in practice. To apply the proposed method in actual grids, a practical method to extract the ambient frequency oscillation from frequency measurement is further proposed. The inertia estimation using the physical equation is validated by KIUC simulation data and HECO field data, in which error rates are around 2% and 8%, respectively. Practical inertia estimation is challenging due to the large amounts of resources contributing to the power grid's effective inertia, but the method provided in this paper can offer a novel way for practical inertia estimation, which can help renewable penetration to boost carbon-free grid.
Original languageAmerican English
Number of pages11
JournalIEEE Transactions on Power Systems
StatePublished - 2024

NREL Publication Number

  • NREL/JA-5D00-86621


  • ambient frequency oscillation
  • analytical method
  • inertia estimation
  • island grids
  • physical equation


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