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At least 955 records · Page 53

All sources NASA NTRS DOE OSTI

DOE OSTI2025

Performance Evaluation of a Single-Phase Grid-Forming Inverter Through Hardware Experiments

This study conducts hardware experiments to assess the performance of a commercial single-phase grid-forming (GFM) inverter using a purely hardware-based approach. We adhere to a testing protocol for the GFM inverter and enhance it by exploring the transient performance of GFM inverters across various grid dynamic events. Quantifiable performance metrics are established for each testing scenario to gain insights into the performance of the single-phase GFM inverters. Based on the comprehensive tests, the following observations are summarized: 1) The performance of the single-phase GFM inverter is satisfactory, and it is capable of being the islanding master for residence homes when the main grid is gone. 2) For frequency response, the inverter is able to stay connected but cannot inject the needed active power to support the grid. This may be improved by the manufacturer by using droop control. 3) The GFM inverter exhibits harmful transients in voltage and frequency during islanding operation, which can be enhanced by maintaining the same operating points before and after the breaker is open.

black start↗

DOE OSTI2025

Lower Snake River Dams Contribution to Grid Services

Hydroelectric generation and water storage have long been components of the clean energy mix, providing both reliable steady output and operational flexibility. As variable renewable energy sources such as wind and solar increasingly replace traditional generation, the role of all flexible resources—including hydropower—in balancing supply and demand continues to evolve. This study examined the contribution of the Lower Snake River (LSR) Dam plants to Bonneville Power Administration grid services in maintaining power system reliability within the Western Interconnection. By analyzing publicly available data, the study evaluated various reliability services through performance metrics including energy capacity, balancing and ramping, voltage and reactive power support, frequency response, and transmission impact. Results indicated that the LSR plants deliver services as expected based on their size, contributing to the balancing process, ramping capabilities, and operational reserves, particularly during peak load conditions and weather events, while also providing measurable frequency and voltage support to the grid.

13 HYDRO ENERGY↗

NASA NTRS1981

A program to evaluate a control system based on feedback of aerodynamic pressure differentials

The use of aerodynamic pressure differentials to position a control surface is evaluated. The system is a differential pressure command loop, analogous to a position command loop, where the surface is commanded to move until a desired differential pressure across the surface is achieved. This type of control is more direct and accurate because it is the differential pressure which causes the control forces and moments. A frequency response test was performed in a low speed wind tunnel to measure the performance of the system. Both pressure and position feedback were tested. The pressure feedback performed as well as position feedback implying that the actuator, with a break frequency on the order of 10 Rad/sec, was the limiting component. Theoretical considerations indicate that aerodynamic lags will not appear below frequencies of 50 Rad/sec, or higher.

Levy, D. W.↗

DOE OSTI2024

Performance Evaluation of a Single-Phase Grid-Forming Inverter Through Hardware Experiments

dynamic performance↗

DOE OSTI2022

Development of coated heat flux gauges for fast responding measurements

Thermal systems often exhibit transient behaviors that have important implications for the operation of the system and can be difficult to predict. For these reasons, experimental testing is often required to ensure system durability requirements are achieved. One important parameter governing the survivability of components in hot, high-stress environments is the heat flux into the part that dictates the temperature distribution for the component. However, sensors required to experimentally characterize heat fluxes in extreme environments must also be resilient. Here, this study presents the development of coated heat transfer gauges capable of robust, high-frequency measurements in turbine research facilities. The addition of a protective coating increases the durability of the gauge, but inherent of that coating is the attenuation of high-frequency temperature penetrations. As a result, this study first outlines the use of analytical solutions to define a gauge design for a specific frequency range and heat transfer, ensuring that subsurface signals can be rectified to surface conditions through inverse methods. Then, the fabrication of polyimide substrate sensors with a parylene-F coating is described. Micro surface heaters added to the custom sensors were used to determine important geometric and thermal properties necessary to calculate accurate surface heat flux. Ultimately, this work shows increased sensor robustness in a turbine test bed and experimentally validates that the frequency response of the fabricated sensors meet the design intent.

47 OTHER INSTRUMENTATION↗

NASA NTRSDate not supplied

An Improved Impedance Eduction Process for the NASA Langley GFIT

The Grazing Flow Impedance Tube (GFIT) is regularly employed to characterize the frequency response of acoustic liners through the eduction of their specific acoustic impedance. Acoustic pressures acquired in the facility are processed with various eduction methods to arrive at these impedance values. Recent implementation of the Swept-Sine Method provides much greater frequency resolution when characterizing the acoustic properties of a liner. The attendant increase in data that must be processed from this method has highlighted a need for greater efficiency in educing acoustic impedance. The current work details efforts to improve the eduction process through use of a hybrid approach that combines a Prony-based method with the Convected Helmholtz-based calculation generally used for this type of data. Comparisons of efficiency and accuracy are shown for this new hybrid approach versus earlier methods for three acoustic liners tested under various conditions in the GFIT with stepped-sine and recently implemented swept-sine sources.

Eduction↗

NASA NTRS1989

Wideband phase-locked angular modulator

A phase-locked loop (PLL) angular modulator scheme has been proposed which has the characteristics of wideband modulation frequency response. The modulator design is independent of the PLL closed-loop transfer function H(s), thereby allowing independent optimization of the loop's parameters as well as the modulator's parameters. A phase modulator implementing the proposed scheme was built to phase modulate a low-noise phase-locked signal source at the output frequency of 2290 MHz. The measurement results validated the analysis by demonstrating that the resulting baseband modulation bandwidth exceeded that of the phase-locked loop by over an order of magnitude. However, it is expected to be able to achieve much wider response still.

Nguyen, L.↗

NASA NTRS1976

Response analysis of flexible aircraft with active control

The small-perturbation equations of motion of a flexible aircraft with an active control technology (ACT) system are developed to evaluate the stability and performance of the controlled aircraft. The total aircraft system is formulated in state vector format and the system of equations is completed with fully unsteady and low-frequency aerodynamics for arbitrary, complex configurations based on a potential aerodynamic method. The ACT system equations are incorporated in the digital computer program FCAP (Flight Control Analysis Program) which can be used for the analysis of complete aircraft configurations, including control system, with either low-frequency or fully unsteady aerodynamics. The application of classical performance analyses including frequency response, poles and zeros, mean-square response, and time response in FCAP in state vector format is discussed.

Noll, R. B.↗

DOE OSTI2023

Criticality of Inverter Controller Order in Power System Dynamic Studies – Case Study: Maui Island

Not Available

Kenyon, Rick Wallace↗

DOE OSTI2015

Active power control of solar PV generation for large interconnection frequency regulation and oscillation damping

Because of zero greenhouse gas emission and decreased manufacture cost, solar photovoltaic (PV) generation is expected to account for a significant portion of future power grid generation portfolio. Because it is indirectly connected to the power grid via power electronic devices, solar PV generation system is fully decoupled from the power grid, which will influence the interconnected power grid dynamic characteristics as a result. In this study, the impact of solar PV penetration on large interconnected power system frequency response and inter-area oscillation is evaluated, taking the United States Eastern Interconnection (EI) as an example. Furthermore, based on the constructed solar PV electrical control model with additional active power control loops, the potential contributions of solar PV generation to power system frequency regulation and oscillation damping are examined. The advantages of solar PV frequency support over that of wind generator are also discussed. Finally, simulation results demonstrate that solar PV generations can effectively work as ‘actuators’ in alleviating the negative impacts they bring about.

14 SOLAR ENERGY↗

NASA NTRS1977

Manual control of yaw motion with combined visual and vestibular cues

Measurements are made of manual control performance in the closed-loop task of nulling perceived self-rotation velocity about an earth-vertical axis. Self-velocity estimation was modelled as a function of the simultaneous presentation of vestibular and peripheral visual field motion cues. Based on measured low-frequency operator behavior in three visual field environments, a parallel channel linear model is proposed which has separate visual and vestibular pathways summing in a complementary manner. A correction to the frequency responses is provided by a separate measurement of manual control performance in an analogous visual pursuit nulling task. The resulting dual-input describing function for motion perception dependence on combined cue presentation supports the complementary model, in which vestibular cues dominate sensation at frequencies above 0.05 Hz. The describing function model is extended by the proposal of a non-linear cue conflict model, in which cue weighting depends on the level of agreement between visual and vestibular cues.

Zacharias, G. L.↗

NASA NTRS1989

Aircraft propeller induced structure-borne noise

A laboratory-based test apparatus employing components typical of aircraft construction was developed that would allow the study of structure-borne noise transmission due to propeller induced wake/vortex excitation of in-wake structural appendages. The test apparatus was employed to evaluate several aircraft installation effects (power plant placement, engine/nacelle mass loading, and wing/fuselage attachment methods) and several structural response modifications for structure-borne noise control (the use of wing blocking mass/fuel, wing damping treaments, and tuned mechanical dampers). Most important was the development of in-flight structure-borne noise transmission detection techniques using a combination of ground-based frequency response function testing and in-flight structural response measurement. Propeller wake/vortex excitation simulation techniques for improved ground-based testing were also developed to support the in-flight structure-borne noise transmission detection development.

Unruh, James F.↗

NASA NTRS2013

Optimal Recursive Digital Filters for Active Bending Stabilization

In the design of flight control systems for large flexible boosters, it is common practice to utilize active feedback control of the first lateral structural bending mode so as to suppress transients and reduce gust loading. Typically, active stabilization or phase stabilization is achieved by carefully shaping the loop transfer function in the frequency domain via the use of compensating filters combined with the frequency response characteristics of the nozzle/actuator system. In this paper we present a new approach for parameterizing and determining optimal low-order recursive linear digital filters so as to satisfy phase shaping constraints for bending and sloshing dynamics while simultaneously maximizing attenuation in other frequency bands of interest, e.g. near higher frequency parasitic structural modes. By parameterizing the filter directly in the z-plane with certain restrictions, the search space of candidate filter designs that satisfy the constraints is restricted to stable, minimum phase recursive low-pass filters with well-conditioned coefficients. Combined with optimal output feedback blending from multiple rate gyros, the present approach enables rapid and robust parametrization of autopilot bending filters to attain flight control performance objectives. Numerical results are presented that illustrate the application of the present technique to the development of rate gyro filters for an exploration-class multi-engined space launch vehicle.

Orr, Jeb S.↗

NASA NTRS2017

Finite Element Modeling and Analysis of Mars Entry Aeroshell Baseline Concept

The structure that is developed and analyzed in this project must be able to survive all the various load conditions that it will encounter along its course to Mars with the minimal amount of weight and material. At this stage, the goal is to study the capability of the structure using a finite element model (FEM). This FEM is created using a python script, and is numerically solved in Nastran. The purpose of the model is to achieve an optimization of mass given specific constraints on launch and entry. The generation and analysis of the baseline Rigid Mid-Range Lift to Drag Ratio Aeroshell model is a continuation and an improvement on previous work done for the FEM. The model is generated using Python programming with the axisymmetric placement of nodes for beam and shell elements. The shells are assigned a honeycomb sandwich material with an aluminum honeycomb core and composite face sheets, and the beams are assigned the same material as the shell face sheets. There are two load cases assigned to the model: Earth launch and Mars entry. The Earth launch case consists of pressure, gravity, and vibration loads, and the Mars entry case consists of just pressure and gravity loads. The Earth launch case was determined to be the driving case, though the analyses are performed for both cases to ensure the constraints are satisfied. The types of analysis performed with the model are design optimization, statics, buckling, normal modes, and frequency response, the last of which is only for the Earth launch load case. The final results indicated that all of the requirements are satisfied except the thermal limits, which could not yet be tested, and the normal modes for the Mars entry. However, the frequency limits during Mars entry are expected to be much higher than the lower frequency limits set for the analysis. In addition, there are still improvements that can be made in order to reduce the weight while still meeting all requirements.

Ahmed, Samee W.↗

NASA NTRS2003

Performance Analysis of a Cost-Effective Electret Condenser Microphone Directional Array

Microphone directional array technology continues to be a critical part of the overall instrumentation suite for experimental aeroacoustics. Unfortunately, high sensor cost remains one of the limiting factors in the construction of very high-density arrays (i.e., arrays containing several hundred channels or more) which could be used to implement advanced beamforming algorithms. In an effort to reduce the implementation cost of such arrays, the authors have undertaken a systematic performance analysis of a prototype 35-microphone array populated with commercial electret condenser microphones. An ensemble of microphones coupling commercially available electret cartridges with passive signal conditioning circuitry was fabricated for use with the Langley Large Aperture Directional Array (LADA). A performance analysis consisting of three phases was then performed: (1) characterize the acoustic response of the microphones via laboratory testing and calibration, (2) evaluate the beamforming capability of the electret-based LADA using a series of independently controlled point sources in an anechoic environment, and (3) demonstrate the utility of an electret-based directional array in a real-world application, in this case a cold flow jet operating at high subsonic velocities. The results of the investigation revealed a microphone frequency response suitable for directional array use over a range of 250 Hz - 40 kHz, a successful beamforming evaluation using the electret-populated LADA to measure simple point sources at frequencies up to 20 kHz, and a successful demonstration using the array to measure noise generated by the cold flow jet. This paper presents an overview of the tests conducted along with sample data obtained from those tests.

Humphreys, William M., Jr.↗

NASA NTRS2006

Solar Wind Excitation of Pc5 Fluctuations in the Magnetosphere and on the Ground

The primary purpose of this paper is to show the strong link between solar wind compressional fluctuations in the 1-8 mHz frequency range and Pc5 fluctuations in the magnetosphere near the magnetopause, at geosynchronous orbit, over the poles, and on the ground. We focus on a time interval in March and April 2002 when there was a favorable alignment of satellites combined with ten high speed solar wind streams. We used the S3C Great Observatory: specifically, ACE and Wind in the solar wind, Geotail near the magnetopause, GOES 8 and 10 at geosynchronous orbit, Cluster over the poles, and CANOPUS/CARISMA ground stations near the footpoints of magnetic field lines connected to either the magnetopause or the GOES satellites. Using four examples and a statistical survey we show that magnetospheric Pc5 fluctuations exist regardless of IMF orientation and for a wide range of speeds and dynamic pressures; the amplitude and power of magnetospheric fluctuations depends primarily on the amplitude and power of solar wind dynamic pressure fluctuations. The driving and response frequency of these geoeffective fluctuations is in the range 0.5 - 4 mHz. The most striking magnetospheric response occurs when the solar wind speed, dynamic pressure, and dynamic pressure fluctuations all increase at approximately the same time, as frequently occurs near the leading edge of high speed streams. We show evidence of oscillating Poynting Flux at the magnetopause determined using Geotail data that both excites a FLR and propagates evanescently inward. These observations suggest that, at least for this time interval at spring equinox, the entry path is from the dayside equatorial magnetopause inward; multiple field line resonances may be excited from the magnetopause to geosynchronous orbit by propagating compressional waves, with the power decreasing inward away from the magnetopause.

Kessel, Ramona L.↗

DOE OSTI2011

Validation of the Electrical Properties of the ITER ICRF Antenna using Reduced-Scale Mock-Ups

Experimental measurements on reduced-scale mock-ups allow validating the electrical properties and RF numerical optimization of the ITER ICRF antenna. Frequency response in the different regions of the antenna is described and key parameters for performance improvement are given. Coupling is improved by acting on the front-face geometry (strap width, antenna box depth and vertical septa recess). The 4-port junction acts as a frequency filter and together with the service stub performs pre-matching in the whole frequency band. Influence of the Faraday screen on coupling is limited. The effect of voltage limitation on the maximum total radiated power is given. The importance of a good decoupling network and of grounding is emphasized. Finally the control of the antenna wave spectrum is performed by implementing feedback controlled load-resilient matching and decoupling options and control algorithms are tested.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

NASA NTRS1990

An experimental modal testing/identification technique for personal computers

A PC-based system for mode shape identification is evaluated. A time-domain modal identification procedure is utilized to identify the mode shapes of a beam apparatus from discrete time-domain measurements. The apparatus includes a cantilevered aluminum beam, four accelerometers, four low-pass filters, and the computer. The method's algorithm is comprised of an identification algorithm: the Eigensystem Realization Algorithm (ERA) and an estimation algorithm called Minimum Model Error (MME). The identification ability of this algorithm is compared with ERA alone, a frequency-response-function technique, and an Euler-Bernoulli beam model. Detection of modal parameters and mode shapes by the PC-based time-domain system is shown to be accurate in an application with an aluminum beam, while mode shapes identified by the frequency-domain technique are not as accurate as predicted. The new method is shown to be significantly less sensitive to noise and poorly excited modes than other leading methods. The results support the use of time-domain identification systems for mode shape prediction.

Roemer, Michael J.↗