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arxiv: 2604.02622 · v1 · submitted 2026-04-03 · 📡 eess.SY · cs.SY

Synchronous Condensers: Enhancing Stability in Power Systems with Grid-Following Inverters

Amir Sajadi , Barry Mather , Bri-Mathias Hodge This is my paper

Pith reviewed 2026-05-13 20:38 UTC · model grok-4.3

classification 📡 eess.SY cs.SY
keywords synchronous condensersgrid-following inverterspower system stabilityangular stabilityfrequency responsevoltage stabilityelectromagnetic transient simulationslocation optimization
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The pith

Synchronous condensers enhance angular stability, frequency response, and voltage stability in power systems dominated by grid-following inverters, though their location must be chosen carefully to avoid destabilizing interactions.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

Large-scale integration of grid-following inverters reduces the stability of modern power grids. This paper examines synchronous condensers as a mitigation approach even though the condensers themselves do not form the grid. Electromagnetic transient simulations show that the condensers strengthen angular stability, frequency response, and voltage stability. The analysis also demonstrates that interactions between synchronous condensers can produce instability when their locations are poorly chosen. A reader would care because the work identifies a practical hardware addition that can support the shift toward high shares of inverter-based resources without sacrificing grid security.

Core claim

The paper establishes that synchronous condensers enhance angular stability, frequency response, and voltage stability in power systems with high shares of grid-following inverters. Electromagnetic transient simulations illustrate the underlying mechanisms and show both the stabilizing benefits of well-placed condensers and the destabilizing behavior that can arise from their mutual interactions.

What carries the argument

Synchronous condensers, which are rotating machines without prime movers that supply or absorb reactive power while contributing mechanical inertia to the grid.

Load-bearing premise

The electromagnetic transient simulations accurately represent real-world dynamics and that the chosen test cases and condenser placements are representative of practical grid conditions.

What would settle it

Field measurements or detailed real-grid data from a system containing synchronous condensers at locations identified in simulation as destabilizing, showing whether the predicted instability actually occurs.

Figures

Figures reproduced from arXiv: 2604.02622 by Amir Sajadi, Barry Mather, Bri-Mathias Hodge.

Figure 2
Figure 2. Figure 2: Frequency stability for three cases examined for with [PITH_FULL_IMAGE:figures/full_fig_p005_2.png] view at source ↗
Figure 1
Figure 1. Figure 1: One-line diagram of the case study As a second goal of these simulation, to assess the grid strength enhancement capabilities of SynCos, we defined the base case scenario as a case with two GFL-IBRs and one synchronous generator. We made this decision based upon an observation from our recent study that produced the tutorial on GFL-IBR integration [38]. In the former study, we incremen￾tally supplanted syn… view at source ↗
Figure 4
Figure 4. Figure 4: Phase angle fast dynamics for four cases examined for [PITH_FULL_IMAGE:figures/full_fig_p006_4.png] view at source ↗
Figure 3
Figure 3. Figure 3: Frequency response for four cases examined for the [PITH_FULL_IMAGE:figures/full_fig_p006_3.png] view at source ↗
Figure 5
Figure 5. Figure 5: Active and reactive power response of SynCos - the [PITH_FULL_IMAGE:figures/full_fig_p006_5.png] view at source ↗
Figure 7
Figure 7. Figure 7: Phase angle fast transients for different [PITH_FULL_IMAGE:figures/full_fig_p007_7.png] view at source ↗
Figure 6
Figure 6. Figure 6: Active power transient response of synchronous gen [PITH_FULL_IMAGE:figures/full_fig_p007_6.png] view at source ↗
Figure 8
Figure 8. Figure 8: Frequency response for cases examined for the system [PITH_FULL_IMAGE:figures/full_fig_p008_8.png] view at source ↗
Figure 9
Figure 9. Figure 9: Frequency fast dynamics for cases examined with [PITH_FULL_IMAGE:figures/full_fig_p008_9.png] view at source ↗
Figure 11
Figure 11. Figure 11: Frequency response for cases with two SynCo - vary [PITH_FULL_IMAGE:figures/full_fig_p008_11.png] view at source ↗
Figure 12
Figure 12. Figure 12: Frequency response for low-inertia cases with two [PITH_FULL_IMAGE:figures/full_fig_p009_12.png] view at source ↗
Figure 13
Figure 13. Figure 13: Frequency response for low-inertia cases with two [PITH_FULL_IMAGE:figures/full_fig_p009_13.png] view at source ↗
read the original abstract

Large-scale integration of inverter-based resources into power grids worldwide is challenging their stability and security. This paper takes a closer look at synchronous condensers as a solution to mitigate stability challenges caused by the preponderance of grid-following inverters. It finds that while they are not grid-forming assets themselves, they could enhance grid stability. Throughout this paper, different facets of power system stability and their underlying phenomena are discussed. In addition, instances of instability and mitigation strategies using synchronous condenser are demonstrated using electromagnetic transient simulations. The analysis in this paper highlights the underlying mechanism by which synchronous condensers enhance angular stability, frequency response, and voltage stability. Moreover, it underscores the criticality of their choice of location by demonstrating the destabilizing behavior that could be initiated by the interactions of synchronous condensers.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 2 minor

Summary. The manuscript examines the role of synchronous condensers (SCs) as a mitigation strategy for stability challenges arising from high penetration of grid-following inverters. It claims that SCs, though not grid-forming, enhance angular stability, frequency response, and voltage stability, while underscoring that their placement is critical because interactions among SCs can initiate destabilizing behavior. These findings are demonstrated exclusively through electromagnetic transient (EMT) simulations on selected test cases.

Significance. If the observed stability improvements and placement sensitivities prove generalizable beyond the specific EMT cases, the work would offer practical value for grid operators planning SC deployments in inverter-dominated networks. The EMT approach captures fast transients relevant to real-world inverter interactions, providing concrete examples of both benefits and risks that could inform operational guidelines.

major comments (2)
  1. [Simulation results and case studies] The central claim that SC placement can induce destabilizing interactions rests on EMT case studies without accompanying small-signal eigenvalue analysis or transfer-function derivations to isolate the underlying mechanism (e.g., inertia, short-circuit ratio, or AVR dynamics). This leaves open whether the observed instability is a general physical effect or an artifact of unstated PLL tuning, network topology, or inverter parameters in the chosen test system.
  2. [Methodology and simulation setup] No parameter sensitivity sweeps are reported on SC inertia constant, damping coefficients, or AVR gains, nor is there validation of the EMT model against measured data from real installations. Without these, the criticality of location cannot be distinguished from model-specific assumptions, undermining the generality of the placement warning.
minor comments (2)
  1. [Abstract and Introduction] The abstract and introduction would benefit from explicit references to the specific EMT software, test-system parameters (e.g., short-circuit ratios, inverter control settings), and the number of simulation scenarios examined.
  2. [Figures] Figure captions should include the exact SC locations, inertia values, and disturbance types used in each case to allow readers to assess reproducibility.

Simulated Author's Rebuttal

2 responses · 1 unresolved

We appreciate the referee's constructive comments on our manuscript. We agree that additional discussion of mechanisms and sensitivity analysis would strengthen the presentation of our EMT-based findings on SC placement effects, and we will revise accordingly while maintaining the focus on simulation evidence for nonlinear interactions.

read point-by-point responses

  1. Referee: [Simulation results and case studies] The central claim that SC placement can induce destabilizing interactions rests on EMT case studies without accompanying small-signal eigenvalue analysis or transfer-function derivations to isolate the underlying mechanism (e.g., inertia, short-circuit ratio, or AVR dynamics). This leaves open whether the observed instability is a general physical effect or an artifact of unstated PLL tuning, network topology, or inverter parameters in the chosen test system.

    Authors: EMT simulations were deliberately chosen to capture the full nonlinear dynamics and fast transients arising from SC-inverter interactions, including PLL effects, which small-signal linearization around a single operating point would not fully reveal. The test cases employ standard parameters drawn from established literature models, and the destabilizing behavior emerges consistently with specific SC placements across the studied networks. In the revised manuscript we will add a dedicated discussion subsection that explains the observed mechanisms (e.g., how SCs modify effective short-circuit ratios and introduce additional coupling paths) directly from the EMT results, without overstating generality beyond the simulated conditions. revision: partial

  2. Referee: [Methodology and simulation setup] No parameter sensitivity sweeps are reported on SC inertia constant, damping coefficients, or AVR gains, nor is there validation of the EMT model against measured data from real installations. Without these, the criticality of location cannot be distinguished from model-specific assumptions, undermining the generality of the placement warning.

    Authors: We will add parameter sensitivity sweeps on SC inertia constant and AVR gains for the critical placement cases in the revised manuscript to demonstrate that the location-dependent instability persists across reasonable ranges of these parameters. Validation against measured data from real installations is not feasible in this work, as we do not have access to such proprietary data; the EMT models follow standard industry and IEEE-recommended parameters commonly used in the literature. revision: partial

standing simulated objections not resolved
  • Validation of the EMT models against measured data from real synchronous condenser installations

Circularity Check

0 steps flagged

EMT case studies demonstrate stability effects using standard models with no self-referential derivations or fitted predictions

full rationale

The paper's central results rest on electromagnetic transient simulations of specific test cases involving grid-following inverters and synchronous condensers. No equations, parameters fitted to subsets of data, or self-citations are invoked to generate 'predictions' that reduce to the inputs by construction. The discussion of mechanisms (angular stability, frequency response, voltage support, and location sensitivity) is presented as interpretive commentary on simulation outcomes rather than an analytical chain that loops back to definitions or prior author results. This structure keeps the work independent of the circularity patterns listed.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Abstract-only review yields no explicit free parameters, axioms, or invented entities; the work relies on standard power-system modeling assumptions not enumerated here.

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Reference graph

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