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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

A Novel Three Phase Oak Ridge DC / AC Converter for Wireless Grid Tied Applications

In this study, a novel three phase oak ridge dc to ac converter is introduced for wireless mobility energy storage (WMES) applications to support the grid demand during peak times. The proposed topology can be used in a bi-directional operation between ac grid and dc terminals of energy storage by accomplishing unity power factor. Inherent merit of the technology can directly merge dc input to the high frequency and 60 Hz grid frequency by superimposing through the wireless coils. Theoretical and simulation results are validated by the simulation analysis for 20 kW output power. The functionality of the proposed three phase system is established by using 6 inches air gap between the couplers with the input of 675 V DC and output of 277 V AC, RMS . The system overall design analysis is demonstrated for simulation analysis and simulation results are presented achieving 3% current total harmonic distortion (THD) and 0.99 power factor (PF) at full load 20 kW wireless power transfer.

Asa, Erdem↗
DOE OSTI2022

A 1MHz Oak Ridge AC / DC Converter for UAV Contactless Charger Implementation

In this paper, a 1 MHz single-phase Oak Ridge Converter (ORC) AC/DC wireless power transfer (WPT) system is introduced for unmanned air vehicle (UAV) charging applications. The proposed advanced solution eliminates the design, weight, volume, and the cost of the power factor correcting (PFC) front-end rectifier compared to the conventional practices. Additionally, grid power quality requirements can be achieved with the presented innovative idea. With this method, single stage WPT primary side uses the hybrid grid frequency and high frequency (60 Hz and 1 MHZ) from ac source through the coupler coils and to UAV battery with GaN FETs. Experimental results of the single-phase system is presented to confirm the mathematical analyses with the source voltage of 110 VAC, RMS and output voltage of 40 VDC at 1 kW power with 6 inches air gap between couplers. The primary coupler consists of a ferrite-backed single-turn coil with a radius of 1.5 ft, and the secondary coupler is made with an air-core single-turn coil with radius of 1.2 ft. The system overall ac to dc efficiency is measured 77 % acquiring 0.99 power factor (PF) and 3.3 % current total harmonic distortion (THD) at 1 kW power.

Asa, Erdem↗
DOE OSTI2020

Recent Development of Frequency Estimation Methods for Future Smart Grid

The frequency estimated by the Phasor Measurement Unit (PMU) is a critical index of power system status and supports many smart grid applications. The future smart grid features high penetration of renewables and more fast-moving power electronics inverters but raises challenges to the reliable frequency estimation. This article presents three methods to address these challenges. First, an enhanced zero-crossing algorithm was developed to track the fast-changing frequency in system dynamics. Second, we propose a technology that can tolerate the system transient and suppress the outliers. Third, an algorithm was developed to export high time-resolution frequency estimations with minimum computational effort. All of the proposed methods are realized in hardware and compared with classical frequency estimation methods. The testing results indicate that the proposed methods have excellent performance. They can be used in future PMUs and provide reliable and high time resolution data for smart grid applications.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2026

Modeling Framework for Data Center

This chapter highlights the critical need for advanced modeling of data centers due to their rapidly increasing energy consumption and impact on grid reliability. Driven by the demand for AI applications, data centers are projected to consume a significant portion of US energy by 2028, putting stress on an already challenged power grid. The chapter emphasizes the importance of "fast" time-scale models to understand the dynamic interactions between data centers and the grid, especially given the rapid power fluctuations of AI workloads. It outlines a modeling framework that includes both offline and real-time EMT domain simulations, detailing the necessary representations for various components like utility interfaces, transformers, IT loads, UPS, cooling loads, Battery Energy Storage Systems (BESS), generators, protection systems, and higher-level control systems. While standard simulation tools like PSCAD offer basic models, custom development is often required to accurately capture the unique and fast-changing behaviors of modern data centers. The chapter also discusses key metrics and test cases for validating these models, focusing on transient load responses, protection relay coordination, and demand flexibility. Finally, it addresses the challenges of modeling large-scale data centers, such as computational complexity and the trade-off between model fidelity and practicality, suggesting hybrid modeling approaches as a solution. The overarching goal is to create a robust framework that helps assess data center impacts on grid stability, identify vulnerabilities, and inform the development of standards for reliable integration of these large loads into the bulk power system.

25 ENERGY STORAGE↗
DOE OSTI2025

A Method for Estimation and Suppression of Quasi-Periodic Noise

Electromagnetic interference, particularly from sources such as light fixtures and power supplies, negatively affects the function and performance of electronic systems. This noise, often quasi-periodic in nature, contains harmonic structure that can be used for noise estimation and suppression. This work proposes a novel method for tracking and filtering such noise signals that reduces the comb filter bandwidth required for noise estimation and suppression by tracking the instantaneous frequency of the fundamental component.

42 ENGINEERING↗
DOE OSTI2023

Nuclear Power's Future Role in a Decarbonized U.S. Electricity System

This study explores the potential future role of nuclear energy in a decarbonized U.S. electricity system through a multi-model comparison approach. We employ four state-of-the-art CEMs with native and harmonized input assumptions, layered with different policy and technology trajectories. Comparing outputs across models, technology assumptions, and policy scenarios informs model understanding, interpretation, and development decisions. Under current policies, models differ in their projections for nuclear retirements, but nuclear power plants consistently run with high capacity factors and new builds only occur in scenarios with very low nuclear costs. String power sector carbon policies drive models to align in keeping existing nuclear capacity and employing nuclear plant flexibility, but they may not be enough to bring new nuclear capacity online in the absence of significant cost declines. Therefore, significant economic deployment of new nuclear capacity requires both a stringent electric sector CO2 policy and very low cost assumptions for new nuclear. While these scenarios should not be interpreted as predictions, they are informative for understanding differing model assessments of the relative competitiveness of nuclear energy under a range of policy and technology conditions.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2021

Electrical and optical characterizations of spin-orbit torque

To further reduce the energy consumption in spin–orbit torque devices, it is crucial to precisely quantify the spin–orbit torque (SOT) in different materials and structures. In this work, heavy metal/ferromagnet and heavy metal/ferrimagnet heterostructures are employed as the model systems to compare the electrical and optical methods for the SOT characterization, which are based on the anomalous Hall effect and the magneto-optical Kerr effect, respectively. It is found that both methods yield the consistent SOT strength for the current-driven magnetization switching measurements and the harmonic measurements. Our results suggest that the optical method is a feasible and reliable tool to investigate SOT, which is a powerful way to develop insulator-based magnetic systems in the future.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2020

Modeling and Harmonic Stability of MMC-HVDC With Passive Circulating Current Filters

A modular multilevel converter (MMC) is an emerging converter technology widely used in wind power applications using high-voltage direct current (HVDC) transmission, and it has been largely investigated in medium-voltage solar harvesting as well as electric motor drives. Different from studies dealing with active circulating current control loops, this paper focuses on impedance modeling and harmonic stability studies for MMCs with passive circulating current filters (PCCFs). A power stage circuit including a PCCF is transformed and remodeled to obtain small-signal formulations. This transformation leads to additional high-order matrix computing complexity due to the added impedance subnetwork matrix from the PCCF as well as relevant crossed-frequency impacts. To simplify the computational burden, the proposed model aims to solve one arm equation instead of all six MMC arm equations. To achieve this result, additional challenges occur when the MMC is connected to a renewable energy source instead of the grid voltage, where low-level zero-sequence components might exist in the neutral point of three phases, especially in the case of no integrated advanced modular voltage balancing control, which prevents computational simplification. To overcome this challenge, further impedance matrix adjustments are conducted in this paper to theoretically suppress the impact of zero-sequence harmonics when obtaining small-signal impedance, taking into account the frequency coupling effect. Finally, simulations are carried out to validate the developed impedance model under different operating scenarios. Harmonic stability case studies of MMCs with PCCFs connected to renewable energy current sources are also presented, where frequency-domain stability analyses based on Bode diagrams are compared to time-domain simulation waveforms and FFTs, which validate the effectiveness of the proposed impedance model.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2025

Synchro-Waveform-Based Event Identification Using Multi-Task Time-Frequency Transform Networks

Influenced by the transient dynamics and reduced inertia characteristics of high-penetration renewable energy systems, power system events frequently exhibit distinct characteristics such as high-frequency components including wide-band oscillations and hyper-harmonics. This makes standard systems face challenges including significant latency and reduced accuracy due to limited data resolution. However, current methods face significant limitations, including insufficient pattern capture ability, low noise immunity, limited feature learning, and restricted localization capabilities, thereby hindering real-time performance. To tackle this issue, this paper proposed a novel synchro-waveform-based event identification approach via a Multi-task Time-frequency Transform Network (MTTNet). Initially, a Time-frequency Transform Block (TTB) is developed to extract both local and global information. The TTB leverages both Fourier and S-transforms to derive comprehensive time-frequency information from synchro-waveforms. Subsequently, a multi-task learning strategy is employed to identify the type and distinguish localization of events. Integrating the TTB and multi-task learning, the MTTNet is designed for synchro-waveform-based event identification, incorporating an adaptive weighting strategy and simplified computation for the S-transform. Two different datasets, comprising simulated and actual synchro-waveforms, are collected from the IEEE 123 bus system and a real-world high-penetration renewable energy system using a universal grid analyzer. Extensive experiments on various conditions are carried out. In conclusion, results demonstrated that the MTTNet consistently surpasses both basic and advanced baselines, with maximum improvements of 13.24% and 9.86%, respectively, while reducing the calculation burden by 15-19 times to achieve real-time event identification.

Event identification↗
DOE OSTI2024

Experimental Validation of a Modular All-Electric Power Take-Off Topology for Wave Energy Converter Enabling Marine Renewable Energy Interconnection

Power electronic converters are an enabling technology for the emerging marine energy applications, such as using ocean waves to produce electricity. This paper outlines the power take-off system and its key components used in a wave energy converter offering modularity and scalability to generate power efficiently. The proposed power take-off system was implemented based on a modular multilevel converter and could be deployed to convert any alternating current electrical energy to a different alternating current for interconnection to grid or non-grid applications. Examples of widespread deployment are supplying electricity to coastal communities or producing clean drinking water. The analysis using both the simulation tests and laboratory experiments verified the design objectives and basic functionality of the developed power take-off system. An acceptable response using a field programmable gate array-based controlled laboratory testbench was achieved, complying with guidelines specified in the prevalent industry standards. Seamless operation during steady-state and transients for the studied wave energy converter was achieved as supported by the obtained results. The key findings of this work were experimentally examined under different load conditions, direct current bus voltage fluctuations, and generator speed–torque regulation. The ability of the power take-off system to generate high-power quality of the waveforms, e.g., against adhering to the IEEE 519-2022 standard for total harmonic distortion limits, is also confirmed.

Engineering↗
DOE OSTI2024

Single-mode squeezed-light generation and tomography with an integrated optical parametric oscillator

Quantum optical technologies promise advances in sensing, computing, and communication. A key resource is squeezed light, where quantum noise is redistributed between optical quadratures. We introduce a monolithic, chip-scale platform that exploits the χ (2) nonlinearity of a thin-film lithium niobate (TFLN) resonator device to efficiently generate squeezed states of light. Our system integrates all essential components—except for the laser and two detectors—on a single chip with an area of one square centimeter, reducing the size, operational complexity, and power consumption associated with conventional setups. Using the balanced homodyne measurement subsystem that we implemented on the same chip, we measure a squeezing of 0.55 decibels and an anti-squeezing of 1.55 decibels. We use 20 milliwatts of input power to generate the parametric oscillator pump field by using second harmonic generation on the same chip. Our work represents a step toward compact and efficient quantum optical systems posed to leverage the rapid advances in integrated nonlinear and quantum photonics.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2020

Dirac oscillator: An alternative basis for nuclear structure calculations

The isotropic harmonic oscillator supplemented by a strong spin-orbit interaction has been the cornerstone of nuclear structure since its inception more than seven decades ago. In this paper we introduce—or rather re-introduce—the “Dirac oscillator,” a fully relativistic basis that has all the desired attributes of the ordinary harmonic oscillator while naturally incorporating a strong spin-orbit coupling. To assess the power and flexibility of the Dirac oscillator basis in the solution of nuclear structure problems within the framework of covariant density-functional theory. Here, self-consistent calculations of binding energies and ground-state densities for a selected set of doubly magic nuclei are performed using the Dirac oscillator basis and are then compared against results obtained with the often-used Runge-Kutta method. Results obtained using the Dirac oscillator basis reproduce with high accuracy those derived using the Runge-Kutta method and suggest a clear path for a generalization to systems with axial symmetry. Although the harmonic oscillator with spin-orbit corrections has been the staple of the nuclear shell model since the beginning, the Dirac oscillator is practically unknown among the nuclear physics community. In this paper we illustrate the power and flexibility of the Dirac oscillator and suggest extensions to the study of systems without spherical symmetry, as required in constrained calculations of nuclear excitations.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

A Comprehensive Review of Practical Issues for Interoperability Using the Common Information Model in Smart Grids

Smart grids with interoperability improve grid reliability by collecting system information and transferring it to an energy management system and associated applications through a seamless end-to-end connection. To achieve interoperability, it is required to exchange the semantic information within the different domains. The international electrotechnical commission has established the Common Information Model (CIM) tool, which is a standard application programming interface for the exchange of semantic information in power systems. CIM provides a robust framework for accurate data sharing, merging, and transformation into reusable information. However, as CIM provides a basic framework for information exchange, various practical issues arise in establishing an energy management system capable of exchanging information using CIM. This paper aims to offer a comprehensive understanding by summarizing and categorizing the research on the practical use of CIM for interoperability in smart grids. Many papers are analyzed and the issues are classified into CIM extension, harmonization, and validation to address the issues that arise when establishing an integrated information exchange system.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2023

Power Solitons in Inverter-based Electric Energy Systems: Observation, Analysis and Implications

The discovery of an unfamiliar class of nonlinear energy waves in electric energy systems with dominating coupled inverter-based energy resources has been reported in a recent research project. Whenever there are slight but persistent differences among the reference signals used by inverters in pulse-width modulation, i.e., a weak group modulation instability condition, the unfamiliar energy waves appear, which contain not only the familiar frequency components present in electric power systems but also self-organized components in the ultra-high frequency region of the energy spectrum. These components are found to be exploding solitary waves with concentrated energy masses, hence we call them power solitons. This paper explains the work of the discovery reported, and the implications of the presence of power solitons for grid integration of inverter-based resources and power system protection.

14 SOLAR ENERGY↗
DOE OSTI2024

Wideband Impedance Passivation of MMCs for Suppressing Harmonic Oscillations

Harmonic instability and associated oscillation events have become one of the main concerns in MMC-based HVdc systems. These oscillations can appear in the range from a few hundred hertz to several kilohertz, and the root cause is identified as delay-induced negative damping of MMC impedance appearing at the system resonance frequency. Here, this paper introduces a wideband impedance reshaping method through MMC control to eliminate such negative damping for both grid-following (GFL) and grid-forming (GFM) MMCs, which makes the MMC impedance completely passive from the second harmonic frequency upward, thus preventing all harmonic oscillations. First, simplified impedance models of MMCs are derived for the harmonic stability analysis and the impedance reshaping control design. Next, a passivity-based impedance reshaping method is presented, as well as practical considerations for its implementation. In addition, to maintain the MMC's disturbance ride-through capability, an adaptive activation scheme is developed, which enables the wideband impedance reshaping control only in the presence of harmonic oscillation events. The effectiveness of the proposed method is validated by frequency domain analysis and by electromagnetic transient (EMT) simulations of two typical MMC-based power systems.

17 WIND ENERGY↗
DOE OSTI2026

Brushless Excitation for Wound-field Synchronous Machines using Multi-harmonic Windings

Wound-field synchronous machines (WFSM) are promising alternatives to electric machines with permanent magnets (PM). The ability to control the rotor field in these machines makes them well-suited to safety critical applications, while the absence of rare-earth permanent magnets makes these machines sustainable. The WFSM rotor excitation schemes have traditionally used carbon brushes, which significantly reduces the reliability of these machines, limiting their widespread adoption. To overcome this limitation and improve the reliability of WFSMs, several brushless rotor excitation schemes have been developed. However, most of these systems require additional windings or dedicated power electronics, making them expensive and limiting achievable power-density. In this paper a new brushless excitation scheme is proposed. In this scheme, a multiphase, multi-harmonic stator winding is designed. This winding can independently control two spatial harmonics in the airgap of the machine; the first to create torque and the second to wirelessly transfer power to the rotor to excite it.

Gadiyar, Nishanth [ORNL] (ORCID:0000000348267524)↗
DOE OSTI2023

Complex field reversal dynamics in nanomagnetic systems

Nanomagnetic materials, built from thin, patterned films of ferromagnetic materials, began as analogues to frustrated magnetism. Their low energy of operation and emergent properties make them strong candidates for physics-based devices. A recent model of how nanomagnetic domains flip, the Glauber mean-field model, is used here to understand how systems of nanomagnets evolve when opposed by external field. This reversal can be expressed in an analytical form in the case of one-dimensional chains and trees at zero temperature, where the cascade of spin flips gives rise to harmonic power spectra. Finally, the same cascades in two and three dimensions form fractal field reversal clusters whose shape depends on the strength of the field and the tuning of interactions between nanomagnets.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Harmonics and Stability Evaluation of Converter-Interfaced Combined Heat and Power Units

Grid integration of medium-sized combined heat and power (CHP) units is challenging due to strict grid codes and conventional generators lack of control flexibility to meet these grid codes. Adding a two-stage ac-dc-ac power electronics interface between the generator and the utility grid will accelerate the interconnection process of CHP units. For the dc-ac stage, a voltage source converter (VSC) has been widely used as a grid-tied inverter because of its fast control and low total harmonics distortion (THD). In this paper, several topologies of generator-side rectifiers for ac-dc power conversion are explored and analyzed. The harmonics impact of various rectifiers on the CHP generator are evaluated. The overall cost of the electrical system, when using various types of rectifiers, is assessed and the VSC back-to-back converter interface configuration is found to be optimal. The overall system stability is also examined using small-signal impedance analysis to assess potential instability issues at the system level.

CHP, Harmonics, Generator Rectifier Unit, DC Imped↗