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At least 235 records · Page 13

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DOE OSTI2022

Evaluation of Optimal Net Load Management in Microgrids Using Hardware-in-the-Loop Simulation

This paper presents the performance evaluation of a net load management (NLM) engine that balances load and generation in an isolated community to power a critical facility after a grid interruption event (e.g., the loss of a large generation unit). This NLM engine is particularly important for microgrid systems because it provides a high-speed, cost-optimal control solution to coordinate grid-forming inverters and to dispatch grid-following inverters and deferrable loads in microgrid systems to enhance grid resilience and reliability. The NLM algorithm cost-optimally dispatches the grid-following inverters and deferrable loads based on the demanded power and load priorities, and the grid-forming inverters use droop control to form system voltages and share active and reactive power. A controller-hardware-in-the-loop platform is developed to evaluate the control performance of the NLM algorithm with two sequential contingency events of lost generation units. The experimental results indicate that the NLM engine can maintain system stability, achieve the targeted system voltage and frequency, and balance load and generation to serve the critical facility with improved system resilience and reliability.

grid-following inverter↗

DOE OSTI2019

Impedance-Based Characterization of Power System Frequency Response: Preprint

This paper presents an impedance-based noninvasive approach for the characterization of power system frequency response in real time in the absence of a transient event. It measures transfer function response from the injected active power to the frequency at the point of interconnection for the estimation of inertia and primary frequency response of the system. The so-called frequency response function also shows the effects of the speed of primary frequency control. The paper also derives the relationship between the frequency response function and the network impedance seen from the point of interconnection. This relationship highlights how impedance captures the frequency response behavior of a network. The proposed methodology is demonstrated on a modified IEEE 9-bus system with 25% penetration of wind and PV generation; a 5-MW battery energy storage system is used for the injection of active power perturbations for the measurement of the frequency response function.

24 POWER TRANSMISSION AND DISTRIBUTION↗

DOE OSTI2024

Shape optimization and fluid control of near isothermal compressor for transcritical carbon dioxide cycle

The compressor holds great promise for enhanced energy efficiency over a wide range of vapor compression systems (VCS). However, the majority of them focused on liquid refrigerant injection or inter-stage cooling technologies to improve heat transfer. Increasing the heat transfer area provides another perspective to promote heat dissipation, which commonly involves shape optimization whilst bringing some limitations, mainly from the manufacturing side. To fill the research gap, this paper compares the performance of isothermal compressors under different compression chamber shapes and chamber connection configurations. Additionally, the fluid control of the liquid piston was combined with shape optimization to explore the potential for further heat transfer enhancement. The simulation results have demonstrated that the COP improvements can reach up to 9% compared with the baseline case by optimizing the chamber shape and properly controlling the liquid piston speed, which provides a guideline for designing and customizing the isothermal compression chamber.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

DOE OSTI2025

Chemical and Optical Control of Spin Crossover: Ultrafast XUV Spectroscopy of Molecular Magnets in Native Solvation Environments

With support from the US Department of Energy Office of Science, we have developed and utilized extreme ultraviolet (XUV) spectroscopy and sum frequency generation vibrational spectroscopy as probes of charge, spin, and solvation structure and dynamics in molecules and at interfaces. This work is crucial to advancing fundamental understanding of the processes that control the efficiency and speed of energy conversion and information processing in molecules and at interfaces. Accordingly, it has important applications for developing next generation technologies for information storage and processing with increasing data storage density and processing rates as well as developing new methods for efficient energy conversion and storage.

74 ATOMIC AND MOLECULAR PHYSICS↗

DOE OSTI2025

Site A5 - NREL Scanning Lidar (Halo Allsky SN235) / Reviewed Data

This dataset contains lidar data that have been standardized and quality-controlled through NREL/FIEXTA/LiDARGO (https://github.com/NREL/FIEXTA/tree/main/lidargo). Standardization rearranges the lidar data into convenient range vs beamID vs scanID coordinates that facilitates data analysis. The scan geometry (i.e., azimuth, elevation) is shifted on a regular grid based on the most likely angles within the scan file. Quality control of radial wind speed is performed through a generalized version of the dynamic lidar filter (Beck and Kuhn, 2017).

17 WIND ENERGY↗

DOE OSTI2025

Site A1 - ARM Scanning Lidar (Halo XR) / Reviewed Data

17 WIND ENERGY↗

DOE OSTI2026

FC Site 4.0 - NLR Scanning Lidar (Halo XR+ 235) / Standardized and Quality-Controlled Data

This dataset contains lidar data that have been standardized and quality-controlled through NatLabRockies/FIEXTA/LiDARGO (https://github.com/NatLabRockies/FIEXTA/tree/main/lidargo). Standardization rearranges the lidar data into convenient range vs beamID vs scanID coordinates that facilitate data analysis. The scan geometry (i.e., azimuth, elevation) is shifted on a regular grid based on the most likely angles within the scan file. Quality control of radial wind speed is performed through a generalized version of the dynamic lidar filter (Beck and Kuhn, 2017).

17 WIND ENERGY↗

DOE OSTI2026

FC Site 4.2 - NLR Scanning Lidar (Halo XR+ 199) / Standardized and Quality-Controlled Data

17 WIND ENERGY↗

DOE OSTI2026

FC Site 1.9 - NLR Scanning Lidar (Halo XR+ 200) / Standardized and Quality-Controlled Data

17 WIND ENERGY↗

DOE OSTI2016

THE MURCHISON WIDEFIELD ARRAY 21 cm POWER SPECTRUM ANALYSIS METHODOLOGY

We present the 21 cm power spectrum analysis approach of the Murchison Widefield Array Epoch of Reionization project. In this paper, we compare the outputs of multiple pipelines for the purpose of validating statistical limits cosmological hydrogen at redshifts between 6 and 12. Multiple independent data calibration and reduction pipelines are used to make power spectrum limits on a fiducial night of data. Comparing the outputs of imaging and power spectrum stages highlights differences in calibration, foreground subtraction, and power spectrum calculation. The power spectra found using these different methods span a space defined by the various tradeoffs between speed, accuracy, and systematic control. Lessons learned from comparing the pipelines range from the algorithmic to the prosaically mundane; all demonstrate the many pitfalls of neglecting reproducibility. We briefly discuss the way these different methods attempt to handle the question of evaluating a significant detection in the presence of foregrounds.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2022

Evaluation of Optimal Net Load Management in Microgrids Using Hardware-in-the-Loop Simulation

This presentation discusses the performance evaluation of a net load management (NLM) engine that balances load and generation in an isolated community to power a critical facility after a grid interruption event (e.g., the loss of a large generation unit). This NLM engine is particularly important for microgrid systems because it provides a high-speed, cost-optimal control solution to coordinate grid-forming inverters and to dispatch grid-following inverters and deferrable loads in microgrid systems to enhance grid resilience and reliability. The NLM algorithm cost-optimally dispatches the grid-following inverters and deferrable loads based on the demanded power and load priorities, and the grid-forming inverters use droop control to form system voltages and share active and reactive power. A controller-hardware-in-the-loop platform is developed to evaluate the control performance of the NLM algorithm with two sequential contingency events of lost generation units. The experimental results indicate that the NLM engine can maintain system stability, achieve the targeted system voltage and frequency, and balance load and generation to serve the critical facility with improved system resilience and reliability.

droop control↗

DOE OSTI2017

Assessment of System Frequency Support Effect of PMSG-WTG Using Torque-Limit-Based Inertial Control

To release the 'hidden inertia' of variable-speed wind turbines for temporary frequency support, a method of torque-limit-based inertial control is proposed in this paper. This method aims to improve the frequency support capability considering the maximum torque restriction of a permanent magnet synchronous generator. The advantages of the proposed method are improved frequency nadir (FN) in the event of an under-frequency disturbance; and avoidance of over-deceleration and a second frequency dip during the inertial response. The system frequency response is different, with different slope values in the power-speed plane when the inertial response is performed. The proposed method is evaluated in a modified three-machine, nine-bus system. The simulation results show that there is a trade-off between the recovery time and FN, such that a gradual slope tends to improve the FN and restrict the rate of change of frequency aggressively while causing an extension of the recovery time. These results provide insight into how to properly design such kinds of inertial control strategies for practical applications.

17 WIND ENERGY↗

DOE OSTI2024

Reinforcement Learning Control for Enhancing Marine Hydrokinetic Turbine Energy Generation

This paper proposes a reinforcement learning-based method to maximize power generation for a direct-drive marine hydrokinetic turbine. A high levelized cost of energy (LCOE) is preventative in the widespread adoption of many marine energy conversion technologies. A straightforward way to reduce LCOE is to increase conversion efficiency and ensure maximum energy generation. The proposed method utilizes a damping control methodology, varying applied generator torque via a linear relationship between the applied damping coefficient and rotor speed. A state-action-reward-state-action (SARSA) algorithm has been used to learn the optimal control action for a given flow velocity. The proposed SARSA methodology uses Gaussian radial basis functions to create a three-dimensional surface to estimate the relationship between damping coefficient, incoming flow velocity, and coefficient of power (C p ). Here, the SARSA algorithm was compared against a baseline optimal tip speed ratio controller over a year-long flow velocity case profile while considering the effects of biofouling on the turbine system, where the proposed RL method generated 0.92% more energy than the baseline.

Damp↗

DOE OSTI2023

Tuning Phase Lock Loop Controller of Grid Following Inverters by Reinforcement Learning to Support Networked Microgrid Operations

The dynamic operation of networked microgrids leads to varying topological configurations and generator commitments and dispatches. These variations correspond to systems with different electrical characteristics. The fixed control gains of high-speed power electronic devices may result in undesirable system performance when the electrical characteristics change significantly. As such, it is necessary to tune the control gains of power electronics devices to adapt to the changing system characteristics. This paper uses observer-based reinforcement learning to automatically tune the proportional-integral (PI) gains of phase lock loop (PLL) controller of grid-following (GFL) inverters to adapt to the changing system strengths, that would be seen in networked microgrid operations. Simulation results using an operational electric distribution system, modeled as networked microgrids, are presented to demonstrate the need and effectiveness of the proposed adaptive controls.

networked microgrids, reinforcement learning, grid↗

DOE OSTI2016

Independent Blade Pitch Controller Design for a Three-Bladed Turbine Using Disturbance Accommodating Control

Two independent pitch controllers (IPCs) based on the disturbance accommodating control (DAC) algorithm are designed for the three-bladed Controls Advanced Research Turbine to regulate rotor speed and to mitigate blade root flapwise bending loads in above-rated wind speed. One of the DAC-based IPCs is designed based on a transformed symmetrical-asymmetrical (TSA) turbine model, with wind disturbances being modeled as a collective horizontal component and an asymmetrical linear shear component. Another DAC-based IPC is designed based on a multiblade coordinate (MBC) transformed turbine model, with a horizontal component and a vertical shear component being modeled as step waveform disturbance. Both of the DAC-based IPCs are found via a regulation equation solved by Kronecker product. Actuator dynamics are considered in the design processes to compensate for actuator phase delay. The simulation study shows the effectiveness of the proposed DAC-based IPCs compared to a proportional-integral (PI) collective pitch controller (CPC). Improvement on rotor speed regulation and once-per-revolution and twice-per-revolution load reductions has been observed in the proposed IPC designs.

17 WIND ENERGY↗

DOE OSTI2016

Frequency tuning of polarization oscillations: Toward high-speed spin-lasers

Spin-controlled vertical-cavity surface-emitting lasers (spin-VCSELs) offer a high potential to overcome several limitations of conventional purely charged-based laser devices. Presumably, the highest potential of spin-VCSELs lies in their ultrafast spin and polarization dynamics, which can be significantly faster than the intensity dynamics in conventional devices. Here, we experimentally demonstrate polarization oscillations in spin-VCSELs with frequencies up to 44 GHz. The results show that the oscillation frequency mainly depends on the cavity birefringence, which can be tuned by applying mechanical strain to the VCSEL structure. A tuning range of about 34 GHz is demonstrated. By measuring the polarization oscillation frequency and the birefringence governed mode splitting as a function of the applied strain simultaneously, we are able to investigate the correlation between birefringence and polarization oscillations in detail. The experimental findings are compared to numerical calculations based on the spin-flip model.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2017

Multi-Speed Transmission For Commercial Delivery Medium Duty PEDVs

Successful completion of the proposed project will set a course for improving quality of life by overcoming key challenges in the gearbox for commercial-delivery, medium-duty, plug-in electric drive vehicles: It will reduce US dependency on foreign oil through the use of electric driven propulsion instead of fuel driven. It will reduce health risks by replacing tailpipe emissions in densely populated city centers. Finally, it will improve the performance-cost basis to meet or exceed the expectations of the targeted medium duty vehicle fleet owners and the independent customers. The proposed multi-speed transmission will narrow motor operation to the peak efficiency region, thereby increasing the electric powertrain efficiency to help close the range gap. Further, it will enhance customer satisfaction by improving vehicle acceleration, top speed and gradeability over the baseline. The project was conducted in three budget periods: In BP1: Technology Development, High-level vehicle powertrain models were used to optimize candidate transmission architectures and ratios along with a variety of traction motor characteristics for concept selection. The detailed driveline designs and component dynamics were investigated to meet medium-duty EV requirements; In BP2: Technology Development and Prototype Demonstration, The modeling and simulations with multi-speed transmissions were extended to other MD and HD EV platforms. Clean sheet design of a compact, lightweight, flexible, and modular, four-speed transmission was completed. Development of novel shifting and controls strategies were started and procurement of the prototype transmission and the controller hardware was begun; In BP3: Technology Integration, Testing, and Demonstration, Prototyping the four-speed automated mechanical transmission was completed. The transmission controls system and software development and preliminary gearbox dyno tests were done at Eaton. ORNL conducted integrated powertrain HIL tests. One of the prototype units was fully integrated into a Proterra BE35 demonstration electric bus. The shift control strategy was fine-tuned on the integrated vehicle at Eaton Marshall Proving Grounds. NREL tested the vehicle and validated the performance gains. Simulations predicted up to 20% increase in system energy efficiency depending on drive cycles, a top speed of greater than70 mph on flat road, 40% faster acceleration and a doubled gradeability with four-speed transmission as compared to the baseline EVs. Chassis Dyno Tests at NREL verified the simulation results of Eaton team and the HIL test results of ORNL team. The new four-speed EV transmission is efficient, reliable, modular, scalable, light weight, small size, and will be affordable. Furthermore, four-speed transmission enables downsizing of motor, battery and final drive, thereby reducing the total system cost.

33 ADVANCED PROPULSION SYSTEMS↗

DOE OSTI2019

Control of Hybrid Power Unit with a Mechanical Transmission in High-Speed Caterpillar Vehicles

Abstract—: The properties of a hybrid power unit in which a mechanical transmission rigidly connects the internal combustion engine to the driving wheels are considered. In this transmission, the torque created by the parallel electric field is summed with the torque generated by the engine in the event of overloading. The control algorithms developed for the electric power prevent its opposition to the mechanical power under any circumstances.

42 ENGINEERING↗