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REVIEW 2 major objections 2 minor 30 references

Quantification and Regulation of Energy Reserves for Distributed Frequency and Voltage Control of Grid-Forming Inverters

T0 review · 2 major / 2 minor · reviewed 2026-05-10 · grok-4.3

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Pith's one-line read Energy reserves in battery systems can be quantified and partially regulated by a modified DAPI controller to support distributed frequency and voltage control in microgrids.

desk verdict The paper adds a BESS reserves quantification framework and a reserve-consensus tweak to DAPI for microgrid inverters, with CHIL results on IEEE 13-bus showing regulation and sharing, but the independence of the quantification step from the controller remains unclear. read the letter →

arxiv 2604.14499 v1 submitted 2026-04-16 eess.SY cs.SY

Ahmed Saad Al-Karsani , Maryam Khanbaghi This is my paper · ORCID
classification eess.SYcs.SY
keywords microgridsgrid-forminginvertersenergyreservesdistributedcontrolDAPIcontrollerfrequencyregulationvoltagebatterystorage
verification ladder T0 review T1 audit T2 compute T3 formal

The pith

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

The reading

The paper proposes a framework for quantifying battery energy storage reserves to support hierarchical control in islanded microgrids and networks of microgrids. It formulates a modified distributed averaging proportional integral controller that adds consensus on these quantified reserves while carrying out secondary frequency and voltage regulation. Controller hardware-in-the-loop tests on a microgrid based on the IEEE 13-bus feeder show that the scheme maintains regulation performance and improves power and energy sharing between droop-controlled and virtual synchronous machine inverters. A sympathetic reader would care because the work connects local reserve quantification directly to secondary control actions, which could help manage resource adequacy when renewable sources dominate distributed grids.

What carries the argument

Modified Distributed-Averaging Proportional-Integral (DAPI) controller with added regulation energy reserve consensus terms that act on quantified BESS reserves while performing secondary control.

What would settle it

A CHIL simulation run in which activating the energy reserve consensus term produces visibly worse frequency or voltage deviations, or unbalanced power and energy sharing, compared with the standard DAPI controller would show the central claim does not hold.

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Extended reading notes

Core claim

The paper establishes that a BESS energy reserves framework quantifies reserves for hierarchical operation and that a modified DAPI controller with energy reserve consensus can partially regulate those reserves, yielding effective frequency and voltage regulation together with improved power and energy sharing across droop-controlled and VSM-controlled grid-forming inverters in an IEEE 13-bus-derived microgrid.

Load-bearing premise

Energy reserves can be quantified independently of primary droop or VSM actions and then partially regulated by the added consensus terms without degrading primary performance or creating unmodeled interactions.

Editorial extensions

If this is right

  • Frequency and voltage stay within acceptable bounds during islanded operation of the microgrid.
  • Power and energy sharing improve across inverters that use either droop or virtual synchronous machine primary control.
  • Secondary-level control becomes explicitly linked to tertiary-level service-based reserves and local resource adequacy.
  • The same reserve quantification and consensus approach can be applied to networks of microgrids.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • Making reserve quantities explicit through this framework could let microgrids offer ancillary services with clearer accounting of available capacity.
  • Running the scheme on physical hardware beyond controller-in-the-loop tests could reveal dynamic interactions the model does not capture.
  • The reserve consensus structure might extend to other storage technologies or to larger networks that include additional control layers.
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Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit.

Referee Report

2 major / 2 minor

Summary. The paper proposes a BESS energy reserves framework to quantify reserves supporting hierarchical control in microgrids and networks of microgrids. It introduces a modified DAPI controller incorporating a regulation energy reserve consensus term to partially regulate these reserves while maintaining primary droop and VSM behavior. CHIL simulations on an IEEE 13-bus test feeder system are used to demonstrate effective frequency/voltage regulation and improved power/energy sharing across droop-controlled and VSM-controlled grid-forming inverters.

Significance. If the reserve quantification can be shown independent of the closed-loop controller dynamics and the CHIL results include rigorous validation (e.g., ablation tests and equilibrium bounds), the work would usefully bridge secondary distributed control with tertiary reserve services in inverter-based microgrids. The CHIL testing on a standard IEEE 13-bus topology and the explicit treatment of both droop and VSM inverters are practical strengths that could inform real-world MG design.

major comments (2)
  1. [BESS energy reserves framework and modified DAPI controller] BESS energy reserves framework (abstract and proposed scheme): the central claim requires that reserves are quantified independently of the modified DAPI dynamics and only partially regulated by the added consensus term. No explicit separation (e.g., pre-controller metric or external benchmark) is described, creating a risk that the reserve quantities are defined in terms of controller states and the regulation claim becomes circular.
  2. [Controller Hardware-In-the-Loop (CHIL) simulation] CHIL simulation results on IEEE 13-bus system: the reported effective regulation and sharing are promising, but without an ablation removing the reserve consensus term or a formal bound showing the consensus gain does not shift primary droop/VSM equilibria, it remains unverified that primary performance is preserved and unmodeled interactions are absent.
minor comments (2)
  1. [Abstract] The abstract states positive simulation outcomes but omits any equations, data exclusion rules, error bars, or quantitative validation metrics; these should be added to allow verification of the claimed improvements.
  2. [Proposed scheme] Notation for the reserve quantities and consensus gain should be defined consistently with standard power-system reserve terminology to avoid ambiguity when linking to tertiary-level services.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the constructive feedback and for recognizing the practical strengths of the CHIL testing on the IEEE 13-bus topology and the treatment of both droop and VSM inverters. We address each major comment below and will revise the manuscript to incorporate clarifications and additional validation as outlined.

read point-by-point responses

  1. Referee: [BESS energy reserves framework and modified DAPI controller] BESS energy reserves framework (abstract and proposed scheme): the central claim requires that reserves are quantified independently of the modified DAPI dynamics and only partially regulated by the added consensus term. No explicit separation (e.g., pre-controller metric or external benchmark) is described, creating a risk that the reserve quantities are defined in terms of controller states and the regulation claim becomes circular.

    Authors: The BESS energy reserves are quantified from the physical state-of-charge (SoC) limits, rated energy capacity, and inverter power bounds of each unit; these quantities are defined prior to any control action and do not depend on the closed-loop states of the modified DAPI controller. The added consensus term only drives agreement on the already-quantified reserve levels while leaving the primary droop and VSM loops unchanged. We will revise the manuscript to include an explicit pre-controller definition of the reserve metric together with a diagram separating the quantification step from the secondary consensus dynamics, thereby eliminating any appearance of circularity. revision: yes

  2. Referee: [Controller Hardware-In-the-Loop (CHIL) simulation] CHIL simulation results on IEEE 13-bus system: the reported effective regulation and sharing are promising, but without an ablation removing the reserve consensus term or a formal bound showing the consensus gain does not shift primary droop/VSM equilibria, it remains unverified that primary performance is preserved and unmodeled interactions are absent.

    Authors: We agree that explicit verification of primary-loop invariance is required. We will add ablation simulations in which the reserve consensus term is disabled, confirming that frequency and voltage regulation remain identical to the baseline droop/VSM case. In addition, we will include a short equilibrium analysis showing that the consensus correction acts only on the secondary integral states and does not modify the steady-state droop or VSM power-angle relationships for any finite consensus gain. These additions will be placed in the simulation section and will directly address the concern about unmodeled interactions. revision: yes

Circularity Check

0 steps flagged · score 0.0 of 10

No circularity detected; derivation appears self-contained against external benchmarks.

full rationale

The abstract outlines a BESS reserves framework for quantification and a modified DAPI controller for partial regulation, validated via CHIL on IEEE 13-bus. No equations, self-citations, or fitted parameters are provided that would allow identification of any step reducing to its own inputs by construction. The quantification is presented as a new framework linked to tertiary control, and regulation as an addition to primary droop/VSM without explicit reduction to controller states. Per hard rules, absence of quotable reductions means score 0; this is the expected honest non-finding when text lacks inspectable derivation chain.

Assumptions & free parameters 0 free parameters · 0 assumptions · 1 invented entities

Only the abstract is available, so free parameters, axioms, and invented entities cannot be extracted in detail; the 'energy reserves framework' appears to be the main new construct introduced.

invented entities (1)
  • BESS energy reserves framework
    purpose: Quantify reserves for hierarchical frequency and voltage control operation
    Introduced in the paper as the core proposal linking secondary and tertiary levels

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Cite this review

Pith. "Pith review of Quantification and Regulation of Energy Reserves for Distributed Frequency and Voltage Control of Grid-Forming Inverters." pith.science (2026). https://pith.science/paper/2604.14499

@misc{pith2026260414499,
  author       = {Pith},
  title        = {Pith review of: Quantification and Regulation of Energy Reserves for Distributed Frequency and Voltage Control of Grid-Forming Inverters},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/2604.14499}},
  note         = {Machine review of arXiv:2604.14499}
}
read the original abstract

The introduction of Renewable Energy Sources (RES) and Distributed Energy Resources (DERs) has led to the formulation of Microgrids (MGs) and Networks of MGs (NMGs). MGs and NMGs can operate in islanded mode, transforming the grid into a more distributed system. This has led to extensive studies in the literature on distributed hierarchical control strategies. Previous works have proposed distributed secondary level frequency and voltage regulation control schemes for Battery Energy Storage System (BESS)-based Grid-Forming (GFM) inverters with State of Charge (SoC) balancing. However, links to tertiary level control in terms of service-based reserves and local resource adequacy in MGs are largely unexplored. Therefore, this paper proposes a BESS energy reserves framework, to quantify reserves for hierarchical control operation. Additionally, to partially regulate the proposed energy reserves, we propose the formulation of a modified Distributed-Averaging Proportional-Integral (DAPI) controller with regulation energy reserve consensus. Controller Hardware-In-the-Loop (CHIL) simulation is performed on an MG topologically based on the IEEE 13 bus test feeder system in MATLAB/Simulink. The proposed scheme results illustrate effective frequency and voltage regulation along with improved power and energy sharing across droop-controlled and Virtual Synchronous Machine (VSM) controlled inverters.

Figures

Figures reproduced from arXiv: 2604.14499 by the authors.

Figure 1
Figure 1. (a) Simulation model of three identical Virtual Synchronous Machine [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. The average-based modeling of a Battery Energy Storage System (BESS)-based Grid-Forming (GFM) inverter with Virtual Synchronous Machine [PITH_FULL_IMAGE:figures/full_fig_p003_2.png] view at source ↗
Figure 3
Figure 3. Allocation of Battery Energy Storage System (BESS) reserves for [PITH_FULL_IMAGE:figures/full_fig_p004_3.png] view at source ↗
Figures from the paper (10 more)
Figure 4
Figure 4. Figure 4: (a) The Microgrid (MG) topologically based on an islanded IEEE 13 [PITH_FULL_IMAGE:figures/full_fig_p007_4.png]
Figure 5
Figure 5. Figure 5: The Controller Hardware-In-the-Loop (CHIL) setup with OPAL-RT [PITH_FULL_IMAGE:figures/full_fig_p008_5.png]
Figure 6
Figure 6. Figure 6: From top to bottom: active power, frequency, and active regulation [PITH_FULL_IMAGE:figures/full_fig_p009_6.png]
Figure 8
Figure 8. Figure 8: From top to bottom: active power, frequency, and active regulation [PITH_FULL_IMAGE:figures/full_fig_p009_8.png]
Figure 10
Figure 10. Figure 10: From top to bottom: reactive power, voltage, and reactive regulation [PITH_FULL_IMAGE:figures/full_fig_p009_10.png]
Figure 12
Figure 12. Figure 12: From top to bottom: reactive power, voltage, and reactive regulation [PITH_FULL_IMAGE:figures/full_fig_p009_12.png]
Figure 15
Figure 15. Figure 15: From top to bottom: active power, frequency, and active regulation [PITH_FULL_IMAGE:figures/full_fig_p010_15.png]
Figure 16
Figure 16. Figure 16: From top to bottom: reactive power, voltage, and reactive regulation [PITH_FULL_IMAGE:figures/full_fig_p010_16.png]
Figure 18
Figure 18. Figure 18: From top to bottom: active power, frequency, and active regulation [PITH_FULL_IMAGE:figures/full_fig_p010_18.png]
Figure 20
Figure 20. Figure 20: From top to bottom: reactive power, voltage, and reactive regulation [PITH_FULL_IMAGE:figures/full_fig_p010_20.png]

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Reference graph

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