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• Journal article
  Gu Y, Chaudhuri B, Green T, Xiaoyao Z, Ramachandran Jet al., 2025,

  Multi-layered defense against oscillations

  , IEEE Power and Energy Magazine, ISSN: 1540-7977

  Increasing shares of inverter-based resources (IBRs) in power grids are triggering complex dynamic interactions and new stability challenges. A particular challenge for system operators is poorly damped sub-synchronous oscillations (SSO) induced by adverse interaction among IBRs through the network. These oscillations are difficult to foresee, threaten system security and often force grid operators to limit the instantaneous share of IBRs. The Control and Power research group at Imperial College London are working with the Network Operability team in National Energy System Operator (NESO) in the UK to develop a multi-layered defense strategy to identify and mitigate the risk of poorly damped SSO. Starting from advanced IBR control design which is the genesis of the SSO problem, these layers are: 1) an enhanced IBR connection compliance process capture the risk of SSO more comprehensively, 2) new system strength metrices to identify parts of the grid vulnerable to SSO, 3) characterize operating point dependency of IBRs to detect incipient SSO near real-time and 4) post-event root-cause analysis for targeted and effective mitigation of SSO. Success of this research will enable secure grid operation with high fractions of renewables to facilitate net zero transition.

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• Conference paper
  Javaid MS, Chaudhuri B, Teng F, Akhtar Zet al., 2025,

  Impact of inner control in GFM-induced sub-synchronous oscillations

  , 2025 IEEE PES General Meeting, Publisher: IEEE

  n power systems dominated by grid-forming inverters (GFMs), strong grid conditions can lead to sub-synchronous oscillations (SSOs) due to the reduced time-scale separation between GFM control loops and network dynamics, potentially causing instability. Modal analysis reveals that states associated with inner control (comprising current and voltage control loops) and network dynamics are the primary contributors to these oscillatory modes. This paper provides an analytical explanation of adverse interactions between GFM inner control and network dynamics that lead to SSOs. Through damping ratio sensitivity analysis, we establish that increasing the current control closed-loop bandwidth and the voltage control proportional gaincan effectively mitigate these oscillations. The proposed control adjustments also prove effective in larger systems with 100% inverter-based resources penetration, comprising of a mix of both grid-following and grid-forming inverters.

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• Journal article
  Gao J, Chaudhuri B, Astolfi A, 2025,

  An explicit direct method for transient stability analysis of multimachine power systems with nonzero transfer conductances

  , IEEE Transactions on Control Systems Technology, ISSN: 1063-6536

  We propose an explicit analytical direct method for the transient stability analysis of multimachine power systems with nonzero transfer conductances (TCs). The proposed method addresses two issues. In the first issue, we study the transient stabilization of the entire power system through excitation control design. To this end, a globally well-defined Lyapunov function is constructed, and a locally well-defined dynamic passivity-based control law is proposed. The closed-loop equilibrium is therefore guaranteed to be locally asymptotically stable. In the second issue, we study the transient stability property of post-fault initial states. To this end, an optimization-based approach to calculate the critical level set of the proposed Lyapunov function is proposed. This allows to estimate an explicit region of attraction of the closed-loop equilibrium. Therefore, the transient stability property of a post-fault initial state can be directly assessed. A case study on the IEEE 10-machine 39-bus power system, to demonstrate the performance and effectiveness of the proposed direct method, is presented.

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• Conference paper
  Javaid M, Chaudhuri B, Teng F, Akhtar Zet al., 2025,

  A novel tuning method of grid-forming inverter voltage control

  , IEEE PowerTech 2025, Publisher: IEEE

  Grid-forming inverters (GFMs) may experience instabilityin strong grids, often resulting from voltage controlinterference, particularly when multiple voltage sources are electrically close. This issue is further exacerbated when control gains are obtained under avoidable assumptions. A temporary solution is to retune control gain, yet it yields suboptimal performance. To address this, we propose a novel tuning technique for GFM control that employs a concurrent design approach for d and q axes voltage control. The proposed method also incorporates the dynamics of an equivalent grid model in the design process. The required design specifications are translated into weighting functions, formulating the H∞ minimization problem for optimal tuning. The proposed tuning method is compared against direct synthesis and symmetrical optimum methods. The comparison reveals the advantages of the proposed method in mitigating the impact of grid strength. Their performance is evaluated on 9-bus and 11-bus test systems. It is shown that the proposed approach achieves higher control bandwidth and improved stability margins compared to conventional designs.

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• Journal article
  Javaid MS, Chaudhuri B, Teng F, Akhtar Zet al., 2025,

  EMT−RMS modeling trade-off for IBR-driven sub-synchronous oscillations

  , IEEE Transactions on Power Systems, ISSN: 0885-8950

  Low-frequency electromechanical oscillations (<2Hz) are time-separated from faster network dynamics, allowing network dynamics to be safely neglected in positive-sequence RMS (RMS+) studies. However, with increasing shares of inverter-based resources (IBRs), sub-synchronous oscillations (SSOs) occur at higher frequencies (>5 Hz) within the electromagnetic timescales. The shift challenges using RMS+ tools for planning IBR-dominated grids, as the time-scale separation is no longer as distinct as in synchronous machine-based systems. This paper demonstrates that relying on RMS+ studies in high-IBRscenarios can lead to erroneous conclusions about SSO, including a false assurance of stability. We explain how the interaction between IBR control and network dynamics affect the damping of SSO. This highlights the need for EMT-dq with network dynamics in a synchronously rotating reference frame as a middle ground between EMT-abc (point-on-wave) and RMS+ for studying IBR-drivenSSO. EMT-dq is computationally simpler than EMTabcand allows frequency-domain analysis for deeper insightand effective SSO mitigation. This emphasizes the necessity of established (rather than bespoke) EMT-dq tools to quickly screen SSO-prone scenarios for detailed investigation in EMT-abc.

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• Conference paper
  Tekcan E, Spyrou E, 2025,

  BMViewGB: an interactive web based tool for visualising the operations of the balancing mechanism in Great Britain

  , 24th Wind & Solar Integration Workshop, Publisher: IET, ISSN: 2732-4494

  The Balancing Mechanism (BM) is the main tool for keeping electricity supply and demand balanced in Great Britain, while respecting network constraints. Between April 2022 and March 2025, its costs were £2–3 billion per year, prompting participants to call for more efficient dispatch and greater transparency. To help meet these needs, the article presents BMViewGB, an open-source, map-based visualisation tool that displays the spatial distribution of BM costs and volumes. The straightforward map layout is designed for users with varied professional backgrounds and can also act as a foundation for further research, such as the development of digital simulators of the Balancing Mechanism.

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• Journal article
  Maity A, Brahma D, Senroy N, 2025,

  Identification of RoCoF sensitive areas of power system based on its controlling factors

  , ELECTRIC POWER SYSTEMS RESEARCH, Vol: 244, ISSN: 0378-7796
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• Journal article
  Pandey SR, Pinson P, Popovski P, 2025,

  Privacy-Aware Data Acquisition Under Data Similarity in Regression Markets

  , IEEE TRANSACTIONS ON NEURAL NETWORKS AND LEARNING SYSTEMS, Vol: 36, Pages: 10580-10591, ISSN: 2162-237X
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• Conference paper
  Gao J, Chaudhuri B, Astolfi A, 2025,

  Enhanced transient stabilization with damping assignment

  , 13th IFAC Symposium on Nonlinear Control Systems, Publisher: Elsevier, ISSN: 2405-8963

  The paper proposes an analytical nonlinear control approach for enhancing the transient performance of lossy multi-machine power systems. The prominent feature of thisapproach lies in the inclusion of damping assignment, whereby the oscillation of the power system frequency is dampened out more effectively. In this regard, the proposed control approach is said to achieve enhanced transient stabilization, which is desirable in practical applications.A case study demonstrates the enhanced performance of the proposed control approach over existing nonlinear control approaches.

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• Conference paper
  Brahma D, O'Malley M, Chaudhuri B, Bialek J, Gu Y, Green Tet al., 2025,

  A deeper perspective on IBR-driven oscillations

  , 23rd Wind & Solar Integration Workshop (WIW 2024), Publisher: The Institution of Engineering and Technology (IET), Pages: 1130-1137, ISSN: 2732-4494

  Inverter-based resources (IBRs) are pivotal in modern power systems to meet the net-zero carbon targets. The rapid integration of IBRs such as solar photovoltaics, wind turbines, and battery storage has introduced complex dynamic behaviours that challenge conventional power system stability paradigms. Unlike traditional synchronous generators, which are governed by standardized, physics-based models, IBRs are control-defined and feature vendor-specific models that operate across multiple overlapping time scales. This results in unique dynamic interactions in IBR-dominated grids with multiple causalities, giving rise to oscillatory phenomena not previously encountered. This paper provides a review of IBR-driven oscillations, emphasizing on their classification and current research efforts in oscillation tracing and mitigation. Two classification framework based on time-scale separation and causality, are explored to categorize IBR-induced oscillations, highlighting the challenges in the categorization process. The critical role of data, tools and methods for tracing oscillations is discussed, and current mitigation measures are outlined in the context of IBR-dominated system. Additionally, some open research questions related to the evolving landscape of IBR-induced oscillatory phenomena are discussed.

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