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@inproceedings{ssm2024allerton,
  abstract = {Barrier functions constitute an effective tool for assessing and enforcing safety-critical constraints on dynamical systems.  To this end, one is required to find a function $h$ that satisfies a Lyapunov-like differential condition, thereby ensuring the invariance of its zero super-level set $h_\ge 0$.  This methodology, however, does not prescribe a general method for finding the function $h$ that satisfies such differential conditions, which, in general, can be a daunting task. In this paper, we seek to overcome this limitation by developing a generalized barrier condition that makes the search for $h$ easier. We do this in two steps. First, we develop integral barrier conditions that reveal equivalent asymptotic behavior to the differential ones, but without requiring differentiability of $h$. Subsequently, we further replace the stringent invariance requirement on $h≥0$ with a more flexible concept known as recurrence. A set is ($τ$-)recurrent if every trajectory that starts in the set returns to it (within $τ$ seconds) infinitely often. We show that, under mild conditions, a simple sign distance function can satisfy our relaxed condition and that the ($τ$-)recurrence of the super-level set $h_≥ 0$ is sufficient to guarantee the system's safety.},
  author = {Shen, Yue and Sibai, Hussein and Mallada, Enrique},
  booktitle = {60th Allerton Conference on Communication, Control, and Computing},
  grants = {CPS-2136324, Global-Centers-2330450},
  keywords = {Barrier Functions},
  month = {09},
  pages = {1-8},
  pubstate = {presented},
  record = {accepted Jul 2024, submitted Jul 2024},
  title = {Generalized Barrier Functions: Integral Conditions & Recurrent Relaxations},
  url = {https://mallada.ece.jhu.edu/pubs/2024-Allerton-SSM.pdf},
  year = {2024}
}

@inproceedings{smg2024pesgm,
  abstract = {This paper presents a decentralized stability analysis of power systems comprising grid-forming (GFM) inverters. We leverage a decentralized stability framework capable of ensuring the stability of the entire interconnection through individual assessments at each bus. The key novelty lies in incorporating voltage dynamics and their coupling with reactive power, in addition to the angle dynamics and their coupling with active power. We perform loop transformation to address the challenge posed by the non-Laplacian nature of the network Jacobian matrix in this case. This methodology is applied to characterize conditions on the droop gains of GFM controllers that can preserve system-wide stability. Our proposed stability criteria exhibit scalability and robustness, and can be extended to accommodate delays, variations in network conditions, and plug-and-play of new components in the network.},
  author = {Siahaan, Zudika and Mallada, Enrique and Geng, Sijia},
  bdsk-url-3 = {https://doi.org/10.1109/PESGM51994.2024.10689037},
  booktitle = {PES General Meeting},
  doi = {10.1109/PESGM51994.2024.10689037},
  grants = {CPS-2136324, CAREER-1752362, Global Centers-2330450},
  month = {06},
  pages = {1-5},
  record = {presented Jun. 2024, accepted Mar. 2024, submitted Nov. 2023},
  title = {Decentralized Stability Criteria for Grid-Forming Control in Inverter-Based Power Systems},
  url = {https://mallada.ece.jhu.edu/pubs/2024-PESGM-SMG.pdf},
  year = {2024}
}

@inproceedings{plbmg2024pesgm,
  abstract = {We consider the problem of controlling the frequency response of weakly-coupled multi-machine multi-inverter low-inertia power systems via grid-forming inverter-based resources (IBRs). In contrast to existing methods, our approach relies on dividing the larger system into multiple strongly-coupled subsystems, without ignoring either the underlying network or approximating the subsystem response as an aggregate harmonic mean model. Rather, through a structured clustering and recursive dynamic shaping approach, the frequency response of the overall system to load perturbations is shaped appropriately. We demonstrate the proposed approach for a three-node triangular configuration and a small-scale radial network. Furthermore, previous synchronization analysis for heterogeneous systems requires the machines to satisfy certain proportionality property. In our approach, the effective transfer functions for each cluster can be tuned by the IBRs to satisfy such property, enabling us to apply the shaping control to systems with a wider range of heterogeneous machines.},
  author = {Poolla, Bala Kameshwar and Lin, Yashen and Bernstein, Andrey and Mallada, Enrique and Groß, Dominic},
  bdsk-url-3 = {https://doi.org/10.1109/PESGM51994.2024.10688717},
  booktitle = {PES General Meeting},
  doi = {10.1109/PESGM51994.2024.10688717},
  grants = {CPS-2136324, CAREER-1752362, Global Centers-2330450},
  month = {06},
  pages = {1-5},
  record = {presented Jun. 2024, accepted Mar. 2024, submitted Nov. 2023},
  title = {Dynamic Shaping of Grid Response of Multi-Machine Multi-Inverter Systems Through Grid-Forming IBRs},
  url = {https://mallada.ece.jhu.edu/pubs/2024-PESGM-PLBMG.pdf},
  year = {2024}
}