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DOE OSTI · 1823426

Which IBRs are Causing Oscillations? A Flexible and Scalable Impedance Scan Tool to Evaluate Small-Signal Stability, Control Interactions, and Oscillations in IBR Grids

Shah, Shahil (ORCID:0000000230532863)·Koralewicz, Przemyslaw (ORCID:0000000150040957)·Yan, Weihang·Gevorgian, Vahan·Fan, Lingling·Miao, Zhixin
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Abstract

This presentation describes the impedance scan tool developed by NREL to evaluate small-signal stability, control interactions, and oscillations in IBR grids.

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control interactionsinverter-based resourcesoscillationsrenewable generationresonancestabilityWIND ENERGY

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Shah, Shahil (ORCID:0000000230532863), Koralewicz, Przemyslaw (ORCID:0000000150040957), Yan, Weihang, Gevorgian, Vahan, Fan, Lingling, Miao, Zhixin. 2021-09-25. Which IBRs are Causing Oscillations? A Flexible and Scalable Impedance Scan Tool to Evaluate Small-Signal Stability, Control Interactions, and Oscillations in IBR Grids. https://www.osti.gov/biblio/1823426

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DOE OSTI2024

Identifying Potential Sub-Synchronous Oscillations Using Impedance Scan Approach: Preprint

This paper presents an impedance scan study on the real-world power system in Australia that has observed 17 to 20 Hz intermittent subsynchronous oscillations. Through the impedance scan of each of the IBRs, both individually and collectively, potential resonance modes are identified. The impedance scans were carried out using electromagnetic transient PSCAD models of the network. The network comprises of site-specific, black-boxed models of IBRs supplied by the generators. The impedance scan approach was divided in three major steps: (1) the first step is to identify IBRs where impedance analysis needs to be performed based on the magnitude of oscillations observed at their points of interconnection (POIs); (2) the second step focuses on performing impedance scans at selected IBRs in single-machine infinite-bus (SMIB) configuration to identify internal resonance modes of an IBR and to evaluate if any of these modes become unstable under certain grid conditions; (3) the third step performs impedance scans at a few selected IBRs while connected to the wider network model to obtain the impedance response of both the IBR and the grid - this step evaluates control interactions among IBRs. The impedance scan study found that a few IBRs have an underdamped resonance mode at around 17 Hz, which becomes unstable under a certain operating condition. Another interesting finding was that certain IBRs increase the effective grid impedance seen by another IBR in proximity for a particular operating condition. Under this operating condition, the resulting subsynchronous oscillation mode is more pronounced due to a combination of control interactions among IBRs through the transmission network under study and a resonance mode inside the IBRs.

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DOE OSTI2023

A Reversed Impedance-Based Stability Criterion for IBR Grids

The existing impedance-based stability criterion is effective for analyzing local control interactions; however, it is difficult to scale the existing criterion to analyze wide-area control interactions among numerous IBRs through a complex power system network. The scaled version of the existing criterion requires the impedance response of each IBR in the system as well as of the network looking from all the IBRs. It is quite challenging to obtain all these impedance responses because of the computational effort and the requirement of separately scanning the impedance of the network and the IBRs. We propose a reversed criterion for the impedance-based stability analysis to address these problems. In contrast to the existing criterion, the reversed criterion analyzes the stability of a power system when an IBR is disconnected from the system. The reversed criterion estimates the impact of an IBR on the frequency and damping of power system oscillation modes using the impedance scans of only the IBR and the grid at its terminal. It can be sequentially applied at different IBRs to evaluate their impact on the power system stability. In addition to scalability, the reversed criterion gives flexibility to focus only on a few selected IBRs, depending on their rating, the magnitude of oscillations observed at their terminals, and the vendor support available for implementing stabilizing control system updates. The reversed criterion is demonstrated on a 14-bus power system with 100% IBRs.

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