Search

Your search keyword '"Moffat, Keith"' showing total 635 results
Start Over Author "Moffat, Keith"
635 results on '"Moffat, Keith"'

1. DeePC-Hunt: Data-enabled Predictive Control Hyperparameter Tuning via Differentiable Optimization

Author

Cummins, Michael, Padoan, Alberto, Moffat, Keith, Dorfler, Florian, and Lygeros, John

Subjects
Mathematics - Optimization and Control
Abstract

This paper introduces Data-enabled Predictive Control Hyperparameter Tuning via Differentiable Optimization (DeePC-Hunt), a backpropagation-based method for automatic hyperparameter tuning of the DeePC algorithm. The necessity for such a method arises from the importance of hyperparameter selection to achieve satisfactory closed-loop DeePC performance. The standard methods for hyperparameter selection are to either optimize the open-loop performance, or use manual guess-and-check. Optimizing the open-loop performance can result in unacceptable closed-loop behavior, while manual guess-and-check can pose safety challenges. DeePC-Hunt provides an alternative method for hyperparameter tuning which uses an approximate model of the system dynamics and backpropagation to directly optimize hyperparameters for the closed-loop DeePC performance. Numerical simulations demonstrate the effectiveness of DeePC in combination with DeePC-Hunt in a complex stabilization task for a nonlinear system and its superiority over model-based control strategies in terms of robustness to model misspecifications.

Published
2024

2. Publisher Correction: Development and assessment of a machine learning tool for predicting emergency admission in Scotland

Author

Liley, James, Bohner, Gergo, Emerson, Samuel R., Mateen, Bilal A., Borland, Katie, Carr, David, Heald, Scott, Oduro, Samuel D., Ireland, Jill, Moffat, Keith, Porteous, Rachel, Riddell, Stephen, Rogers, Simon, Thoma, Ioanna, Cunningham, Nathan, Holmes, Chris, Payne, Katrina, Vollmer, Sebastian J., Vallejos, Catalina A., and Aslett, Louis J. M.

Published
2024
Full Text
View/download PDF

4. Architecture for Co-Simulation of Transportation and Distribution Systems with Electric Vehicle Charging at Scale in the San Francisco Bay Area

Author

Panossian, Nadia V, Laarabi, Haitam, Moffat, Keith, Chang, Heather, Palmintier, Bryan, Meintz, Andrew, Lipman, Timothy E, and Waraich, Rashid A

Subjects
Engineering, Affordable and Clean Energy, electric vehicle, grid integration, utility power, electricity distribution, agent-based transportation model, charger siting, co-simulation, Physical Sciences, Built environment and design, Physical sciences
Abstract

This work describes the Grid-Enhanced, Mobility-Integrated Network Infrastructures for Extreme Fast Charging (GEMINI) architecture for the co-simulation of distribution and transportation systems to evaluate EV charging impacts on electric distribution systems of a large metropolitan area and the surrounding rural regions with high fidelity. The current co-simulation is applied to Oakland and Alameda, California, and in future work will be extended to the full San Francisco Bay Area. It uses the HELICS co-simulation framework to enable parallel instances of vetted grid and transportation software programs to interact at every model timestep, allowing high-fidelity simulations at a large scale. This enables not only the impacts of electrified transportation systems across a larger interconnected collection of distribution feeders to be evaluated, but also the feedbacks between the two systems, such as through control systems, to be captured and compared. The findings are that with moderate passenger EV adoption rates, inverter controls combined with some distribution system hardware upgrades can maintain grid voltages within ANSI C.84 range A limits of 0.95 to 1.05 p.u. without smart charging. However, EV charging control may be required for higher levels of charging or to reduce grid upgrades, and this will be explored in future work.

Published
2023

5. Robust online joint state/input/parameter estimation of linear systems

Author

Brouillon, Jean-Sébastien, Moffat, Keith, Dörfler, Florian, and Ferrari-Trecate, Giancarlo

Subjects
Electrical Engineering and Systems Science - Systems and Control, Statistics - Machine Learning
Abstract

This paper presents a method for jointly estimating the state, input, and parameters of linear systems in an online fashion. The method is specially designed for measurements that are corrupted with non-Gaussian noise or outliers, which are commonly found in engineering applications. In particular, it combines recursive, alternating, and iteratively-reweighted least squares into a single, one-step algorithm, which solves the estimation problem online and benefits from the robustness of least-deviation regression methods. The convergence of the iterative method is formally guaranteed. Numerical experiments show the good performance of the estimation algorithm in presence of outliers and in comparison to state-of-the-art methods., Comment: 6 pages, 2 figures

Published
2022

6. Using Voltage Phasor Control to Avoid Distribution Network Constraint Violations

Author

Moffat, Keith and von Meier, Alexandra

Subjects
Electrical Engineering and Systems Science - Systems and Control
Abstract

In this paper, we introduce Voltage Phasor Control (VPC), also known as Phasor Based Control, as a novel way of implementing Optimal Power Flow (OPF). Unlike conventional OPF, in which the power flow optimization broadcasts power injections, the VPC power flow optimization broadcasts voltage phasor setpoints to feedback controllers distributed throughout the network which respond to disturbances in real time. In this paper, we demonstrate that VPC can actively manage distributed energy resources to avoid voltage magnitude and line flow constraint violations in power distribution networks. We provide sensitivities and bounds that quantify how the distributed voltage phasor feedback control reduces the effect of disturbances on the network voltages and line flows. Using simulations, we compare the performance of VPC with the related but more conventional Voltage Magnitude Control (VMC). The sensitivities, bounds, and simulations provide implementation insights, which we highlight, for how distribution network operators can use VPC and VMC to avoid constraint violations., Comment: 9 pages, 8 figures. Pre-print submitted to the 2022 Power Systems Computation Conference

Published
2022

7. Bayesian Error-in-Variables Models for the Identification of Power Networks

Author

Brouillon, Jean-Sébastien, Fabbiani, Emanuele, Nahata, Pulkit, Moffat, Keith, Dörfler, Florian, and Ferrari-Trecate, Giancarlo

Subjects
Electrical Engineering and Systems Science - Systems and Control, Statistics - Machine Learning
Abstract

The increasing integration of intermittent renewable generation, especially at the distribution level,necessitates advanced planning and optimisation methodologies contingent on the knowledge of thegrid, specifically the admittance matrix capturing the topology and line parameters of an electricnetwork. However, a reliable estimate of the admittance matrix may either be missing or quicklybecome obsolete for temporally varying grids. In this work, we propose a data-driven identificationmethod utilising voltage and current measurements collected from micro-PMUs. More precisely,we first present a maximum likelihood approach and then move towards a Bayesian framework,leveraging the principles of maximum a posteriori estimation. In contrast with most existing con-tributions, our approach not only factors in measurement noise on both voltage and current data,but is also capable of exploiting available a priori information such as sparsity patterns and knownline parameters. Simulations conducted on benchmark cases demonstrate that, compared to otheralgorithms, our method can achieve significantly greater accuracy.

Published
2021

9. Hardware-In-the-Loop Benchmarking Setup for Phasor Based Control Validation

Author

Baudette, Maxime, Swartz, Jaimie, Moffat, Keith, Pakshong, Jasper, Chu, leo, Gehbauer, Christoph, and von Meier, Alexandra

Abstract

Phasor Based Control is a novel approach to controlling Distributed Energy Resources that aims at relieving various constraints that arise in the distribution grid. It isa two-layer control system with a supervisory control that coordinates distributed controllers to reach voltage phasor targets. The distributed controllers use local synchrophasor measurements and operate as feedback controllers. This control method is currently under development with several algorithms being under consideration for both the central and ditributed components. In this paper, we present the experimental setup that was prepared to prototype a hardwareimplementation and validate the control method in Hardware-In-the-Loop.

Published
2021

12. Femtosecond structural dynamics drives the trans/cis isomerization in photoactive yellow protein

Author

Pande, Kanupriya, Hutchison, Christopher DM, Groenhof, Gerrit, Aquila, Andy, Robinson, Josef S, Tenboer, Jason, Basu, Shibom, Boutet, Sébastien, DePonte, Daniel P, Liang, Mengning, White, Thomas A, Zatsepin, Nadia A, Yefanov, Oleksandr, Morozov, Dmitry, Oberthuer, Dominik, Gati, Cornelius, Subramanian, Ganesh, James, Daniel, Zhao, Yun, Koralek, Jake, Brayshaw, Jennifer, Kupitz, Christopher, Conrad, Chelsie, Roy-Chowdhury, Shatabdi, Coe, Jesse D, Metz, Markus, Xavier, Paulraj Lourdu, Grant, Thomas D, Koglin, Jason E, Ketawala, Gihan, Fromme, Raimund, Šrajer, Vukica, Henning, Robert, Spence, John CH, Ourmazd, Abbas, Schwander, Peter, Weierstall, Uwe, Frank, Matthias, Fromme, Petra, Barty, Anton, Chapman, Henry N, Moffat, Keith, van Thor, Jasper J, and Schmidt, Marius

Subjects
Biological Sciences, Chemical Sciences, Theoretical and Computational Chemistry, Bacterial Proteins, Crystallography, Isomerism, Light, Photochemical Processes, Photons, Photoreceptors, Microbial, Protein Conformation, Time Factors, General Science & Technology
Abstract

A variety of organisms have evolved mechanisms to detect and respond to light, in which the response is mediated by protein structural changes after photon absorption. The initial step is often the photoisomerization of a conjugated chromophore. Isomerization occurs on ultrafast time scales and is substantially influenced by the chromophore environment. Here we identify structural changes associated with the earliest steps in the trans-to-cis isomerization of the chromophore in photoactive yellow protein. Femtosecond hard x-ray pulses emitted by the Linac Coherent Light Source were used to conduct time-resolved serial femtosecond crystallography on photoactive yellow protein microcrystals over a time range from 100 femtoseconds to 3 picoseconds to determine the structural dynamics of the photoisomerization reaction.

Published
2016

14. Power Grid Parameter Estimation Without Phase Measurements: Theory and Empirical Validation

Author

Brouillon, Jean-Sébastien, Moffat, Keith, Dörfler, Florian, Ferrari-trecate, Giancarlo, Brouillon, Jean-Sébastien, Moffat, Keith, Dörfler, Florian, and Ferrari-trecate, Giancarlo

Abstract

Reliable integration and operation of renewable distributed energy resources requires accurate distribution grid models. However, obtaining precise models is often prohibitively expensive, given their large scale and the ongoing nature of grid operations. To address this challenge, considerable efforts have been devoted to harnessing abundant consumption data for automatic model inference. The primary result of the paper is that, while the impedance of a line or a network can be estimated without synchronized phase angle measurements in a consistent way, the admittance cannot. Furthermore, a detailed statistical analysis is presented, quantifying the expected estimation errors of four prevalent admittance estimation methods. Such errors constitute fundamental model inference limitations that cannot be resolved with more data. These findings are empirically validated using synthetic data and real measurements from the town of Walenstadt, Switzerland, confirming the theory. The results contribute to our understanding of grid estimation limitations and uncertainties, offering guidance for both practitioners and researchers in the pursuit of more reliable and cost-effective solutions.

Published
2024

15. Learning, Control and Optimization for Electricity Distribution Networks

Author

Moffat, Keith

Subjects
Electrical engineering, Control, DERMS, Distribution Networks, Learning, Optimization, Power Systems
Abstract

Traditionally, utility distribution companies have treated electricity distribution networks as passive loads, assuming that the possibility of network constraint violations cannot be managed by controlling distributed energy resources (DERs) such as electric vehicle charging stations. The emergence of edge computing has made it possible for DER management systems (DERMS) to control the power injected/extracted by DERs in real time. By actively managing DERs when necessary, DERMS both increase interconnection availability and reduce the need for infrastructure upgrades. This dissertation presents several tools that can either make power-injection decisions for a DERMS or that support the system’s decision-making. These tools include Unsupervised Impedance and Topology Estimation, Multiple Model Adaptive Power System State Estimation, Voltage Phasor Control, Linearized Output Projected Gradient Descent Feedback Optimization, and Nullspace-Based Power Flow Linearization. The focus of the work is to develop theory which can explain when and how to use these tools on real distribution networks. A large portion of this dissertation develops the theory behind Nullspace-Based Power Flow Linearization, a novel interpretation of power flow linearization that explicitly considers constant-voltage buses, phasor angle-reference ambiguity, and power balance. This dissertation also includes a comment that was submitted in August 2022 on CPUC Proceeding R2207005. With Proceeding R2207005, the California Public Utilities Commission is investigating new rules and price structures for utilities which will change the future of DER management in California.

Published
2022

41. Time-resolved serial crystallography captures high-resolution intermediates of photoactive yellow protein

Author

Tenboer, Jason, Basu, Shibom, Zatsepin, Nadia, Pande, Kanupriya, Milathianaki, Despina, Frank, Matthias, Hunter, Mark, Boutet, Sébastien, Williams, Garth J., Koglin, Jason E., Oberthuer, Dominik, Heymann, Michael, Kupitz, Christopher, Conrad, Chelsie, Coe, Jesse, Roy-Chowdhury, Shatabdi, Weierstall, Uwe, James, Daniel, Wang, Dingjie, Grant, Thomas, Barty, Anton, Yefanov, Oleksandr, Scales, Jennifer, Gati, Cornelius, Seuring, Carolin, Srajer, Vukica, Henning, Robert, Schwander, Peter, Fromme, Raimund, Ourmazd, Abbas, Moffat, Keith, Van Thor, Jasper J., Spence, John C. H., Fromme, Petra, Chapman, Henry N., and Schmidt, Marius

Published
2014

Catalog

Books, media, physical & digital resources
See catalog results