pwc-archive/papers-with-abstracts huggingface dataset:
Nonlinear PDE Constrained Optimal Dispatch of Gas and Power: A Global Linearization Approach
Authors: Yuan Li, Shuai Lu, Wei Gu, Yijun Xu, Ruizhi Yu, Suhan Zhang, Zhikai Huang
Date: 2024-09-02 00:00:00

The coordinated dispatch of power and gas in the electricity-gas integrated energy system (EG-IES) is fundamental for ensuring operational security. However, the gas dynamics in the natural gas system (NGS) are governed by the nonlinear partial differential equations (PDE), making the dispatch problem of the EG-IES a complicated optimization model constrained by nonlinear PDE. To address it, we propose a globally linearized gas network model based on the Koopman operator theory, avoiding the commonly used local linearization and spatial discretization. Particularly, we propose a data-driven Koopman operator approximation approach for the globally linearized gas network model based on the extended dynamic mode decomposition, in which a physics-informed stability constraint is derived and embedded to improve the generalization ability and accuracy of the model. Based on this, we develop an optimal dispatch model for the EG-IES that first considers the nonlinear gas dynamics in the NGS. The case study verifies the effectiveness of this work. Simulation results reveal that the commonly used locally linearized gas network model fails to accurately capture the dynamic characteristics of NGS, bringing potential security threats to the system.
Geometric Scaling Laws for Axial Flux Permanent Magnet Motors in In-Wheel Powertrain Topologies
Authors: Olaf Borsboom, Arnab Bhadra, Mauro Salazar, Theo Hofman
Date: 2024-09-02 00:00:00

In this paper, we present geometric scaling models for axial flux motors (AFMs) to be used for in-wheel powertrain design optimization purposes. We first present a vehicle and powertrain model, with emphasis on the electric motor model. We construct the latter by formulating the analytical scaling laws for AFMs, based on the scaling concept of RFMs from the literature, specifically deriving the model of the main loss component in electric motors: the copper losses. We further present separate scaling models of motor parameters, losses and thermal models, as well as the torque limits and cost, as a function of the design variables. Second, we validate these scaling laws with several experiments leveraging high-fidelity finite-element simulations. Finally, we define an optimization problem that minimizes the energy consumption over a drive cycle, optimizing the motor size and transmission ratio for a wide range of electric vehicle powertrain topologies. In our study, we observe that the all-wheel drive topology equipped with in-wheel AFMs is the most efficient, but also generates the highest material cost.
A Novel Massive Random Access in Cell-Free Massive MIMO Systems for High-Speed Mobility with OTFS Modulation
Authors: YanFeng Hu, Dongming Wang, Xinjiang Xia, Jiamin Li, Pengcheng Zhu, Xiaohu You
Date: 2024-09-02 00:00:00

In the research of next-generation wireless communication technologies, orthogonal time frequency space (OTFS) modulation is emerging as a promising technique for high-speed mobile environments due to its superior efficiency and robustness in doubly selective channels. Additionally, the cell-free architecture, which eliminates the issues associated with cell boundaries, offers broader coverage for radio access networks. By combining cell-free network architecture with OTFS modulation, the system may meet the demands of massive random access required by machine-type communication devices in high-speed scenarios. This paper explores a massive random access scheme based on OTFS modulation within a cell-free architecture. A transceiver model for uplink OTFS signals involving multiple access points (APs) is developed, where channel estimation with fractional channel parameters is approximated as a block sparse matrix recovery problem. Building on existing superimposed and embedded preamble schemes, a hybrid preamble scheme is proposed. This scheme leverages superimposed and embedded preambles to respectively achieve rough and accurate active user equipment (UEs) detection (AUD), as well as precise channel estimation, under the condition of supporting a large number of access UEs. Moreover, this study introduces a generalized approximate message passing and pattern coupling sparse Bayesian learning with Laplacian prior (GAMP-PCSBL-La) algorithm, which effectively captures block sparse features after discrete cosine transform (DCT), delivering precise estimation results with reduced computational complexity. Simulation results demonstrate that the proposed scheme is effective and provides superior performance compared to other existing schemes.
Stability of multiplexed NCS based on an epsilon-greedy algorithm for communication selection
Authors: Harsh Oza, Irinel-Constantin Morarescu, Vineeth S. Varma, Ravi Banavar
Date: 2024-09-02 00:00:00

In this letter, we study a Networked Control System (NCS) with multiplexed communication and Bernoulli packet drops. Multiplexed communication refers to the constraint that transmission of a control signal and an observation signal cannot occur simultaneously due to the limited bandwidth. First, we propose an epsilon-greedy algorithm for the selection of the communication sequence that also ensures Mean Square Stability (MSS). We formulate the system as a Markovian Jump Linear System (MJLS) and provide the necessary conditions for MSS in terms of Linear Matrix Inequalities (LMIs) that need to be satisfied for three corner cases. We prove that the system is MSS for any convex combination of these three corner cases. Furthermore, we propose to use the epsilon-greedy algorithm with the epsilon that satisfies MSS conditions for training a Deep Q Network (DQN). The DQN is used to obtain an optimal communication sequence that minimizes a quadratic cost. We validate our approach with a numerical example that shows the efficacy of our method in comparison to the round-robin and a random scheme.
Sparse Mamba: Introducing Controllability, Observability, And Stability To Structural State Space Models
Authors: Emadeldeen Hamdan, Hongyi Pan, Ahmet Enis Cetin
Date: 2024-08-31 00:00:00
Tasks: Mamba, State Space Models

Structured state space models' (SSMs) development in recent studies, such as Mamba and Mamba2, outperformed and solved the computational inefficiency of transformers and large language models at small to medium scale. In this work, we introduce the concept of controllability and observability to the original Mamba SSM's architecture in our Sparse-Mamba (S-Mamba) for natural language processing (NLP) applications. Moreover, we reinforce stability on the $nxn$ $A$ matrix on Mmaba2. The Mamba SSMs architecture drops the need for attention layers or multilayer perception blocks in transformers. However, current Mamba models lack reinforcement of controllability in state-space equations for computing the $A$, $B$, $C$, and $D$ matrices at each time step, leading to increased complexity and computational costs. Furthermore, the $A$ matrix in Mamba2 is not always stable. We demonstrate a reduction of parameters compared to the first published Mamba and Mamba2. We showcase an improvement in perplexity by 5\% and a decrease in training time by 3\% after reinforcing controllability and observability on the original Mamba architecture in our proposed S-Mamba. We further enforce stability on the $A$ matrix in Mamba2 to improve the loss and perplexity of the model. The controllable and stable $n \times n$ state matrix $A$ is sparse, and it has only $n$ free parameters. Our novel approach will ensure controllable/observable and stable SSMs, which will be the gate key for Mamba3.
Leaky Wave Antenna-Equipped RF Chipless Tags for Orientation Estimation
Authors: Onel L. A. López, Zhu Han, Ashutosh Sabharwal
Date: 2024-08-31 00:00:00
Tasks: Scene Understanding, TAG

Accurate orientation estimation of an object in a scene is critical in robotics, aerospace, augmented reality, and medicine, as it supports scene understanding. This paper introduces a novel orientation estimation approach leveraging radio frequency (RF) sensing technology and leaky-wave antennas (LWAs). Specifically, we propose a framework for a radar system to estimate the orientation of a \textit{dumb} LWA-equipped backscattering tag, marking the first exploration of this method in the literature. Our contributions include a comprehensive framework for signal modeling and orientation estimation with multi-subcarrier transmissions, and the formulation of a maximum likelihood estimator (MLE). Moreover, we analyze the impact of imperfect tag location information, revealing that it minimally affects estimation accuracy. Exploiting related results, we propose an approximate MLE and introduce a low-complexity radiation-pointing angle-based estimator with near-optimal performance. We derive the feasible orientation estimation region of the latter and show that it depends mainly on the system bandwidth. Our analytical results are validated through Monte Carlo simulations and reveal that the low-complexity estimator achieves near-optimal accuracy and that its feasible orientation estimation region is also approximately shared by the other estimators. Finally, we show that the optimal number of subcarriers increases with sensing time under a power budget constraint.
Flexible Ramping Product Procurement in Day-Ahead Markets
Authors: Ogun Yurdakul, Erik Ela, Farhad Billimoria
Date: 2024-08-31 00:00:00

Flexible ramping products (FRPs) emerge as a promising instrument for addressing steep and uncertain ramping needs through market mechanisms. Initial implementations of FRPs in North American electricity markets, however, revealed several shortcomings in existing FRP designs. In many instances, FRP prices failed to signal the true value of ramping capacity, most notably evident in zero FRP prices observed in a myriad of periods during which the system was in acute need for rampable capacity. These periods were marked by scheduled but undeliverable FRPs, often calling for operator out-of-market actions. On top of that, the methods used for procuring FRPs have been primarily rule-based, lacking explicit economic underpinnings. In this paper, we put forth an alternative framework for FRP procurement, which seeks to set FRP requirements and schedule FRP awards such that the expected system operation cost is minimized. Using real world data from U.S. ISOs, we showcase the relative merits of the framework in (i) reducing the total system operation cost, (ii) improving price formation, (iii) enhancing the the deliverability of FRP awards, and (iv) reducing the need for out-of-market actions.
Optimization-Based Control of Distributed Battery Storage in Distribution Networks
Authors: Wilhiam de Carvalho, Ahmad Attarha, Hemanshu R. Pota
Date: 2024-08-31 00:00:00
Tasks: global-optimization

We propose a combined global-local control approach to regulate voltage and minimize power losses in distribution networks with high integration of distributed energy resources (DERs). Local controllers embed the fast acting proportional volt-var-watt control law and have their gain (slope) coefficients updated regularly by a global optimization problem at a slower time-scale. Design of optimal coefficients preserve overall system stability and encapsulate inverter and energy limits of controllable DERs. The proposed approach is formulated based on a linear network model (LinDistFlow) and suitable approximations to produce a convex multi-period optimization formulation. Numerical simulations with real-world customer data and two different distribution feeders revealed that our approach provides substantial voltage regulation, while reducing losses by 11 per cent and peak substation power by 26 per cent compared to other state-of-the-art algorithms.
Lyapunov Neural ODE State-Feedback Control Policies
Authors: Joshua Hang Sai Ip, Georgios Makrygiorgos, Ali Mesbah
Date: 2024-08-31 00:00:00
Tasks: Adversarial Robustness, Decision Making

Deep neural networks are increasingly used as an effective way to represent control policies in various learning-based control paradigms. For continuous-time optimal control problems (OCPs), which are central to many decision-making tasks, control policy learning can be cast as a neural ordinary differential equation (NODE) problem wherein state and control constraints are naturally accommodated. This paper presents a NODE approach to solving continuous-time OCPs for the case of stabilizing a known constrained nonlinear system around an equilibrium state. The approach, termed Lyapunov-NODE control (L-NODEC), uses a novel Lyapunov loss formulation that incorporates an exponentially-stabilizing control Lyapunov function to learn a state-feedback neural control policy. The proposed Lyapunov loss allows L-NODEC to guarantee exponential stability of the controlled system, as well as its adversarial robustness to perturbations to the initial state. The performance of L-NODEC is illustrated in two problems, including a dose delivery problem in plasma medicine, wherein L-NODEC effectively stabilizes the controlled system around the equilibrium state despite perturbations to the initial state and reduces the inference time necessary to reach equilibrium.
Facilitating AI and System Operator Synergy: Active Learning-Enhanced Digital Twin Architecture for Day-Ahead Load Forecasting
Authors: Costas Mylonas, Titos Georgoulakis, Magda Foti
Date: 2024-08-31 00:00:00
Tasks: Active Learning, Load Forecasting, Management

In this paper, we introduce a synergistic approach between artificial intelligence and system operators through an innovative digital twin architecture, integrated with an active learning framework, to enhance short-term load forecasting. Central to this architecture is the incorporation of sophisticated data pipelines, facilitating the real-time ingestion, processing and analysis of grid-related data. Utilizing a recurrent neural network architecture, our model generates day-ahead load forecasts together with prediction confidence intervals, strengthening system operator trust in the model's predictive reliability and enhancing their ability to respond to evolving grid conditions effectively. The active learning framework iteratively refines the predictions by incorporating real-time feedback based on forecast uncertainty, utilizing newly available data to continuously enhance forecasting accuracy and confidence. This AI-assisted strategy is exemplified in a case study of the Greek transmission system. It demonstrates the potential to transform short-term load forecasting, thereby increasing the reliability and operational efficiency of modern power grids. This approach marks a significant step forward in the digitalization and intelligent management of power systems.
Fast and Efficient Estimation of Resonant Modes: A Case Study of Mechanical Drivelines
Authors: Amin Rezaeizadeh, Silvia Mastellone
Date: 2024-08-28 00:00:00
Tasks: parameter estimation

This work presents the development of an online parameter estimation algorithm for the identification of resonating modes in a linear system of arbitrary order. The method employs a short-time Fourier transform of the input and output signals and uses a recursive least square (RLS) algorithm to detect resonant frequencies and damping factors of the resonant modes.
Evaluating the Impact of Multiple DER Aggregators on Wholesale Energy Markets: A Hybrid Mean Field Approach
Authors: Jun He, Andrew L. Liu
Date: 2024-08-27 00:00:00
Tasks: Reinforcement Learning (RL)

The integration of distributed energy resources (DERs) into wholesale energy markets can greatly enhance grid flexibility, improve market efficiency, and contribute to a more sustainable energy future. As DERs -- such as solar PV panels and energy storage -- proliferate, effective mechanisms are needed to ensure that small prosumers can participate meaningfully in these markets. We study a wholesale market model featuring multiple DER aggregators, each controlling a portfolio of DER resources and bidding into the market on behalf of the DER asset owners. The key of our approach lies in recognizing the repeated nature of market interactions the ability of participants to learn and adapt over time. Specifically, Aggregators repeatedly interact with each other and with other suppliers in the wholesale market, collectively shaping wholesale electricity prices (aka the locational marginal prices (LMPs)). We model this multi-agent interaction using a mean-field game (MFG), which uses market information -- reflecting the average behavior of market participants -- to enable each aggregator to predict long-term LMP trends and make informed decisions. For each aggregator, because they control the DERs within their portfolio under certain contract structures, we employ a mean-field control (MFC) approach (as opposed to a MFG) to learn an optimal policy that maximizes the total rewards of the DERs under their management. We also propose a reinforcement learning (RL)-based method to help each agent learn optimal strategies within the MFG framework, enhancing their ability to adapt to market conditions and uncertainties. Numerical simulations show that LMPs quickly reach a steady state in the hybrid mean-field approach. Furthermore, our results demonstrate that the combination of energy storage and mean-field learning significantly reduces price volatility compared to scenarios without storage.
Hierarchical Optimal Dispatch of Active Distribution Networks Considering Flexibility Auxiliary Service of Multi-community Integrated Energy Systems
Authors: Chunling Wang, Chunming Liu, Xiulin Zhou, Yang Li, Gaoyuan Zhang
Date: 2024-08-23 00:00:00

Active distribution networks (ADNs) are the main platforms for carrying large-scale distributed renewable energy and flexible resources, and multi-community integrated energy systems (MCIESs) may become important flexible resource supplies in ADNs owing to their multi-energy synergistic and complementary advantages. To fully utilize the flexible regulation potential of MCIESs for ADNs, a novel hierarchical stochastic dispatch approach for ADNs that considers flexibility auxiliary services of MCIESs is proposed. In this approach, a flexibility auxiliary service pricing strategy that combines adjustment cost and flexibility margin is established by evaluating the operational flexibility of MCIESs. In addition, considering renewable uncertainty, an MCIES-ADN flexibility interaction mechanism based on insufficient flexibility risk is designed to optimize their operation strategies and reduce the uncertainty risk. In the solution phase, an analytical target cascading theory-based distributed solving method is developed to realize decoupling and parallel solving of multiple stakeholders. The simulation results for a PG&E 69-node system with three CIESs demonstrate that the proposed approach not only improves MCIES revenue but also enhances ADN flexibility to consume renewable energy, which provides a fundamental way for efficient application of regional mutual aid.
Surface Flux Transport Modeling using Physics Informed Neural Networks
Authors: Jithu J Athalathil, Bhargav Vaidya, Sayan Kundu, Vishal Upendran, Mark C. M. Cheung
Date: 2024-09-03 00:00:00

Studying the magnetic field properties on the solar surface is crucial for understanding the solar and heliospheric activities, which in turn shape space weather in the solar system. Surface Flux Transport (SFT) modeling helps us to simulate and analyse the transport and evolution of magnetic flux on the solar surface, providing valuable insights into the mechanisms responsible for solar activity. In this work, we demonstrate the use of machine learning techniques in solving magnetic flux transport, making it accurate. We have developed a novel Physics-Informed Neural Networks (PINN)-based model to study the evolution of Bipolar Magnetic Regions (BMRs) using SFT in one-dimensional azimuthally averaged and also in two-dimensions. We demonstrate the efficiency and computational feasibility of our PINN-based model by comparing its performance and accuracy with that of a numerical model implemented using the Runge-Kutta Implicit-Explicit (RK-IMEX) scheme. The mesh-independent PINN method can be used to reproduce the observed polar magnetic field with better flux conservation. This advancement is important for accurately reproducing observed polar magnetic fields, thereby providing insights into the strength of future solar cycles. This work paves the way for more efficient and accurate simulations of solar magnetic flux transport and showcases the applicability of PINN in solving advection-diffusion equations with a particular focus on heliophysics.
Network reconstruction may not mean dynamics prediction
Authors: Zhendong Yu, Haiping Huang
Date: 2024-09-06 00:00:00
Tasks: Prediction

With an increasing amount of observations on the dynamics of many complex systems, it is required to reveal the underlying mechanisms behind these complex dynamics, which is fundamentally important in many scientific fields such as climate, financial, ecological, and neural systems. The underlying mechanisms are commonly encoded into network structures, e.g., capturing how constituents interact with each other to produce emergent behavior. Here, we address whether a good network reconstruction suggests a good dynamics prediction. The answer is quite dependent on the nature of the supplied (observed) dynamics sequences measured on the complex system. When the dynamics are not chaotic, network reconstruction implies dynamics prediction. In contrast, even if a network can be well reconstructed from the chaotic time series (chaos means that many unstable dynamics states coexist), the prediction of the future dynamics can become impossible as at some future point the prediction error will be amplified. This is explained by using dynamical mean-field theory on a toy model of random recurrent neural networks.
Mechanisms underlying the response of mouse cortical networks to optogenetic manipulation
Authors: Alexandre Mahrach, Guang Chen, Nuo Li, Carl van Vreeswijk, David Hansel
Date: 2019-07-01 00:00:00

GABAergic interneurons can be subdivided into three subclasses: parvalbumin positive (PV), somatostatin positive (SOM) and serotonin positive neurons. With principal cells (PCs) they form complex networks. We examine PCs and PV responses in mouse anterior lateral motor cortex (ALM) and barrel cortex (S1) upon PV photostimulation in vivo. In layer 5, the PV response is paradoxical: photoexcitation reduces their activity. This is not the case in ALM layer 2/3. We combine analytical calculations and numerical simulations to investigate how these results constrain the architecture. Two-population models cannot account for the results. Networks with three inhibitory populations and V1-like architecture account for the data in ALM layer 2/3. Our data in layer 5 can be accounted for if SOM neurons receive inputs only from PCs and PV neurons. In both four-population models, the paradoxical effect implies not too strong recurrent excitation. It is not evidence for stabilization by inhibition.
Parallax in angular sensitive powder diffraction tomography
Authors: Peter Modregger, Ahmar Khaliq, Felix Wittwer
Date: 2024-08-30 00:00:00

While a few methods for the determination of depth-resolved strain distributions each with inherent limitations are available, tomographic reconstruction has been applied to this problem in only a limited sense. One of the challenges was the potential impact of geometric parallax, which constitutes a non-negligible lateral offset of diffraction information arising from different sample depths at the detector. Here, the effect of parallax was investigated and two main results have emerged. First, the impact of parallax was found to be additive to other offset contributions, which implies a straightforward correction. Second, for tomographic scans utilizing a full 360{\deg} rotation parallax has been found to have no impact on reconstructions of angular information.