OEDI SI/Scenarios/Grid Impedance Estimation

From Open Energy Information

Grid Impedance Estimation​ Summary

  • Date Created: 2024/04/17
  • Organization: University of South Florida and ORNL
  • Objective: Estimate the Thevenin equivalent at the point of interconnection (POI) for an inverter-based resource (IBR) plant based on measured SCADA data, in order to characterize grid strength and evaluate potential low-frequency oscillations.
  • Use Case: DER Aggregation Algorithm
  • Methodology
    • Inputs
      • Outputs
        • Configuration


          Docker Container

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          Run Locally

          http://localhost:8080/edit_scenario?Grid Impedance Estimation
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          Input Data

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            Output Data

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              References


                Back to DER Aggregation Algorithm


              1. The interconnection grid viewed at the POI bus is a Thevenin equivalent circuit. Two critical parameters are the Thevenin equivalent voltage source’s magnitude and the Thevenin equivalent impedance.
              2. The test system’s parameters can be estimated based on the trend of Power and Voltage.
              3. Measurement-Based Thevenin Estimation (Method 1): Track real power 𝑃 ramping from near zero up to a high level while monitoring the corresponding POI voltage 𝑉. If the reactive power 𝑄 Q is near zero during this period, the inverter current in the dq-frame is primarily 𝑖 𝑑 = 𝑃 / 𝑉 i d ​ =P/V. By comparing changes in 𝑃 and 𝑉 , one can solve for the grid reactance 𝑋 𝑔.
              4. Oscillation-Based Approach (Method 2): During periods when the plant experiences low-frequency oscillations (e.g., 0.1-Hz var oscillations), record the voltage and reactive power (or the q-axis current) waveforms. A small-signal relationship between Δ 𝑉 and Δ 𝑄 (or Δ 𝑖 𝑞 ) can reveal the proportionality factor, from which 𝑋 𝑔 ​ can be inferred.
              5. SCADA Data (1-second or higher resolution). Real power, reactive power , and bus voltage measured at the POI.
              6. Records covering ramp-up conditions (e.g., morning solar ramp) and/or times when 0.1-Hz var oscillations occur.
              7. Estimated Grid Impedance
              8. Grid Strength Indicator: Derived from the estimated 𝑋 𝑔 and the plant’s rating.
              9. Event Characterization: Identification of conditions under which 0.1-Hz oscillations or other low-frequency phenomena
              10. https://hub.docker.com/r/openenergydatainitiative/ornl-grid-impedance-estimation
              11. https://github.com/fllseu/IBR-Data-for-Stability/tree/main/event%201
              12. SCADA Data (1-second or higher resolution). Real power, reactive power , and bus voltage measured at the POI.
              13. https://github.com/fllseu/IBR-Data-for-Stability/tree/main/event%201
              14. L. Fan, Z. Miao, D. Piper, D. Ramasubramanian, L. Zhu and P. Mitra, "Analysis of 0.1-Hz Var Oscillations in Solar Photovoltaic Power Plants," in IEEE Transactions on Sustainable Energy, 2022, doi: 10.1109/TSTE.2022.3220083.
                15. Retrieved from "https://openei.org/w/index.php?title=OEDI_SI/Scenarios/Grid_Impedance_Estimation&oldid=1085611"