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At least 721 records · Page 40

All sources NASA NTRS DOE OSTI

DOE OSTI2016

Active Power Control of Wind Turbines for Ancillary Services: A Comparison of Pitch and Torque Control Methodologies

As wind energy generation becomes more prevalent in some regions, there is increased demand for wind power plants to provide ancillary services, which are essential for grid reliability. This paper compares two different wind turbine control methodologies to provide active power control (APC) ancillary services, which include derating or curtailing power generation, providing automatic generation control (AGC), and providing primary frequency control (PFC). The torque APC controller provides all power control through the power electronics whereas the pitch APC controller uses the blade pitch actuators as the primary means of power control. These controllers are simulated under various wind conditions with different derating set points and AGC participation levels. The metrics used to compare their performance are the damage equivalent loads (DELs) induced on the structural components and AGC performance metrics, which are used to determine the payments for AGC services by system operators in the United States. The simulation results show that derating the turbine reduces structural loads for both control methods, with the APC pitch control providing larger reductions in DELs, lower AGC performance scores, and higher root-mean-square pitch rates. Providing AGC increases the structural loads when compared to only derating the turbine, but even the AGC DELs are generally lower than those of the baseline control system. The torque APC control methodology also allows for more sustained PFC responses under certain derating conditions.

17 WIND ENERGY↗

DOE OSTI2018

Energy-Water Microgrid Opportunity Analysis at the University of Arizona's Biosphere 2 Facility

Microgrids provide reliable and cost-effective energy services in a variety of conditions and locations. There has been minimal effort invested in developing energy-water microgrids that demonstrate the feasibility and leverage synergies of operating renewable energy and water systems in a coordinated framework. Water systems can be operated in ways to provide ancillary services to the electrical grid and renewable energy can be utilized to power water-related infrastructure, but the potential for co-managed systems has not yet been quantified or fully characterized. Energy-water microgrids could be a promising solution to improve energy and water resource management for islands, rural communities, distributed generation, Defense operations, and many parts of the world lacking critical infrastructure. NREL and the University of Arizona have been jointly researching energy-water microgrid opportunities at the University's Biosphere 2 (B2) research facility. B2 is an ideal case study for an energy-water microgrid test site, given its size, its unique mission and operations, the criticality of water and energy infrastructure, and its ability to operate connected to or disconnected from the local electrical grid. Moreover, the B2 is a premier facility for undertaking agricultural research, providing an excellent opportunity to evaluate connections and tradeoffs at the food-energy-water nexus. In this study, NREL used the B2 facility as a case study for an energy-water microgrid test site, with the potential to catalyze future energy-water system integration research. The study identified opportunities for energy and water efficiency and estimated the sizes of renewable energy and storage systems required to meet remaining loads in a microgrid, identified dispatchable loads in the water system, and laid the foundation for an in-depth energy-water microgrid analysis. The foundational work performed at B2 serves a model that can be built upon for identifying relevant energy-water microgrid data, analytical requirements, and operational challenges associated with development of future energy-water microgrids.

24 POWER TRANSMISSION AND DISTRIBUTION↗

DOE OSTI2016

Modeling, control, and dynamic performance analysis of a reverse osmosis desalination plant integrated within hybrid energy systems

An RO (reverse osmosis) desalination plant is proposed as an effective, FLR (flexible load resource) to be integrated into HES (hybrid energy systems) to support various types of ancillary services to the electric grid, under variable operating conditions. To study the dynamic (transient) analysis of such system, among the various unit operations within HES, special attention is given here to the detailed dynamic modeling and control design of RO desalination process with a spiral-wound membrane module. The model incorporates key physical phenomena that have been investigated individually into a dynamic integrated model framework. In particular, the solution-diffusion model modified with the concentration polarization theory is applied to predict RO performance over a large range of operating conditions. Simulation results involving several case studies suggest that an RO desalination plant, acting as a FLR, can provide operational flexibility to participate in energy management at the utility scale by dynamically optimizing the use of excess electrical energy. Here, the incorporation of additional commodity (fresh water) produced from a FLR allows a broader range of HES operations for maximizing overall system performance and profitability. For the purpose of assessing the incorporation of health assessment into process operations, an online condition monitoring approach for RO membrane fouling supervision is addressed in the case study presented.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

NASA NTRS2001

A Framework for Control and Observation in Distributed Environments

As organizations begin to deploy large computational grids, it has become apparent that systems for observation and control of the resources, services, and applications that make up such grids are needed. Administrators must observe the operation of resources and services to ensure that they are operating correctly and they must control the resources and services to ensure that their operation meets the needs of users. Further, users need to observe the performance of their applications so that this performance can be improved and control how their applications execute in a dynamic grid environment. In this paper we describe our software framework for control and observation of resources, services, and applications that supports such uses and we provide examples of how our framework can be used.

Smith, Warren↗

DOE OSTI2016

The Effects of Denial-of-Service Attacks on Secure Time-Critical Communications in the Smart Grid

According to IEC 61850, many smart grid communications require messages to be delivered in a very short time. –Trip messages and sample values applied to the transmission level: 3 ms –Interlocking messages applied to the distribution level: 10 ms •Time-critical communications are vulnerable to denial-of-service (DoS) attacks –Flooding attack: Attacker floods many messages to the target network/machine. We conducted systematic, experimental study about how DoS attacks affect message delivery delays.

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2016

A Review of Hydrogen/Halogen Flow Cells

Flow batteries provide an energy-storage solution for various grid-related stability and service issues that arise as renewable-energy-generation technologies are adopted. Among the most promising flow-battery systems are those using hydrogen/halogen redox couples, which promise the possibility of meeting the cost target of the US Department of Energy (DOE), due to their fast and reversible kinetics and low materials cost. However, significant critical issues and barriers for their adoption remain. In this review of halogen/hydrogen systems, technical and performance issues, and research and development progress are reviewed. The information in this review can be used as a technical guide for research and development of related redox-flow-battery systems and other electrochemical technologies.

25 ENERGY STORAGE↗

DOE OSTI2022

Enhancement of phase change material hysteresis model: A case study of modeling building envelope in EnergyPlus

Nowadays, buildings are expected to offer demand side services to the power grid to enhance the electrical load flexibility, which leads to the concepts of grid-interactive efficient buildings (GEBs). Phase change material (PCM)-based thermal energy storage has seen increasing attention in recent years for peak load shifting of grid-interactive efficient buildings (GEBs). Numerical models are critical tools for design and evaluation of PCM-integrated systems. Most industrial-grade PCMs are reported to melt/freeze over a temperature range instead of at a unique temperature. Such thermal hysteresis effect significantly affects the reliability of simulation results because not only the heat transfer process depends on melting and freezing temperatures, the PCM thermal properties change significantly during the phase change process as well. This study is aimed to develop a model for the PCMs used in the building envelope with the capability to accurately simulate hysteretic behaviors. Further, this model is based on a two-phase assumption and is implemented in a whole building energy performance simulation program (i.e., EnergyPlus). A comparison between numerical results and experimental data shows that during a complete phase transition, the two-phase model could achieve a good agreement with the experimental data. During a partial phase transition, the two-phase model could lead to significant improvements compared to other alternative PCM models, including the existing PCM model in EnergyPlus. Last, whole building simulations were performed to study this model's performance regarding heating/cooling loads and zone mean air temperature of a given building. The results show that the difference in hourly heating/cooling loads introduced by the models was less than 1% in design conditions, while significant changes were observed in both hourly heating/cooling loads and zone mean air temperature when the PCM envelope underwent partial phase transition processes.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

DOE OSTI2016

Reaching new solar heights: integrating high penetrations of PV into the power system

Installed capacity of solar photovoltaics (PV) continues to grow rapidly in the US. High penetrations and can create operational and reliability challenges. PV integration shares some attributes and mitigation strategies with wind, and differs in some key ways that will be discussed. This study investigates PV integration challenges and examines mitigation issues for utilities planning for high penetrations of PV, with a focus on the Western Interconnection of the US. System balancing becomes more difficult due to a duck‐shaped net load curve. Flexibility in the remaining generators, load, and the PV itself, is critical in balancing the system. Reliability impacts from PV have been studied less and addressed less than system balancing issues, but become more important at high penetrations. Understanding essential reliability services from PV, weak grid issues with PV, and distributed PV impacts on bulk power system reliability is critical for planning of high penetrations of PV.

Lew, Debra↗

DOE OSTI2019

Reconfigurable and Dynamic Distribution Systems Enabled Using Self-Sustainable Minimal-Microgrids with Region Based Stability Guarantees

In this paper, a reconfigurable and dynamic distribution system is designed using self-sustainable minimal-microgrids (min-MGs). Particularly, multiple dynamic microgrids are implemented by aggregating local min-MGs in a controllable way to facilitate service restoration at critical grid infrastructures, especially during severe power outages (e.g., those induced by natural disasters). These dynamic microgrids are implemented surrounding inverter interfaced distributed energy resources (DERs) to pick up local critical loads. Stable transient process during neighboring microgrid disconnection and resynchronization is realized by involving additional control terms in the secondary control level. Meanwhile, in order to ensure a stable operation with dynamic topology change, a computationally efficient region-based stability assessment approach is developed to ensure stability guarantees of each inverter dominated min-MG with potential changes of external grids modeled as disturbances. In contrast to conventional point-by-point stability evaluation approaches, the proposed region-based stability analysis can intuitively exhibit the feasible region comprised of stable operating points and identify sufficient stability margin to tolerate disturbances of dynamic system topology variations. Theoretical analysis is verified using simulation in MATLAB/Simulink.

distribution systems↗

DOE OSTI2023

Testing GFM and GFL Inverters Operating With Synchronous Condensers

Inverter-based resources (IBRs) are quickly evolving into a source of reliability services to the electric grid. Penetration levels of variable generation are rapidly increasing, ranging from 60% -70% in some systems. To go further, a fundamental shift is required to address challenges associated with grid stability. Synchronous condensers (SCs) are considered an important complementary technology in such transitions. This paper provides one-of-a-kind insights into real experimental results from operating a real MW-scale system consisting of a 2.2-MVA grid-forming (GFM) and grid-following (GFL) battery energy storage system, 2.5-MVA SCs, and a 3-MVA load bank operating as a small, islanded grid. Challenges that are expected in larger systems were mimicked in this small but real system to demonstrate seamless transitions from one mode to another as well as stable operation with different combinations of GFM and GFM resources, including a "loss of last synchronous generator" case. The experimental results presented in this paper are a valuable resource to everyone involved in developing and validating models or developing controls of power systems consisting of inverters and synchronous condensers.

grid-following converter↗

DOE OSTI2015

Generalized Aggregation and Coordination of Residential Loads in a Smart Community

Flexibility from residential loads presents an enormous potential to provide various services to the smart grid. In this paper, we propose a unified hierarchical framework for aggregation and coordination of various residential loads in a smart community, such as Thermostatically Controlled Loads (TCLs), Distributed Energy Storages (DESs), residential Pool Pumps (PPs), and Electric Vehicles (EVs). A central idea of this framework is a virtual battery model, which provides a simple and intuitive tool to aggregate the flexibility of distributed loads. Moreover, a multi-stage Nash-bargainingbased coordination strategy is proposed to coordinate different aggregations of residential loads for demand response. Case studies are provided to demonstrate the efficacy of our proposed framework and coordination strategy in managing peak power demand in a smart residential community.

Hao, He↗

DOE OSTI2022

Enabling DER Participation in Frequency Regulation Markets

Distributed energy resources (DERs) are playing an increasing role in ancillary services for the bulk grid, particularly in frequency regulation. In this article, we propose a framework for collections of DERs, combined to form microgrids and controlled by aggregators, to participate in frequency regulation markets. Our approach covers both the identification of bids for the market clearing stage and the mechanisms for the real-time allocation of the regulation signal. The proposed framework is hierarchical, consisting of a top layer and a bottom layer. The top layer consists of the aggregators communicating in a distributed fashion to optimally disaggregate the regulation signal requested by the system operator. The bottom layer consists of the DERs inside each microgrid whose power levels are adjusted so that the tie line power matches the output of the corresponding aggregator in the top layer. The coordination at the top layer requires the knowledge of cost functions, ramp rates, and capacity bounds of the aggregators. We develop meaningful abstractions for these quantities respecting the power flow constraints and taking into account the load uncertainties and propose a provably correct distributed algorithm for optimal disaggregation of regulation signals among the microgrids.

24 POWER TRANSMISSION AND DISTRIBUTION↗

DOE OSTI2017

A Real-Time Greedy-Index Dispatching Policy for using PEVs to Provide Frequency Regulation Service

This article presents a real-time greedy-index dispatching policy (GIDP) for using plug-in electric vehicles (PEVs) to provide frequency regulation services. A new service cost allocation mechanism is proposed to award PEVs based on the amount of service they provided, while considering compensations for delayed-charging and reduction of battery lifetime due to participation of the service. The GIDP transforms the optimal dispatch problem from a high-dimensional space into a one-dimensional space while preserving the solution optimality. When solving the transformed problem in real-time, the global optimality of the GIDP solution can be guaranteed by mathematically proved “indexability”. Because the GIDP index can be calculated upon the PEV’s arrival and used for the entire decision making process till its departure, the computational burden is minimized and the complexity of the aggregator dispatch process is significantly reduced. Finally, simulation results are used to evaluate the proposed GIDP, and to demonstrate the potential profitability from providing frequency regulation service by using PEVs.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗

DOE OSTI2015

Multi-period Nash bargaining for Coordination of Distributed Energy Resources

Flexibility from distributed energy resources presents an enormous potential to provide various services to the smart grid. In this paper, we propose a unified hierarchical framework for aggregation and coordination of various flexible loads, such as commercial building Heating, Ventilation, and Air-Conditioning (HVAC) systems, Thermostatically Controlled Loads (TCLs), Distributed Energy Storages (DESs), residential Pool Pumps (PPs), and Electric Vehicles (EVs). Moreover, a multistage Nash-bargaining-based control strategy is proposed to coordinate different aggregations of flexible loads for demand response. Case studies are provided to demonstrate the efficacy of our proposed framework and coordination strategy in managing peak power demand in a community.

Hao, He↗

DOE OSTI2013

Combined Heat and Power: Enabling Resilient Energy Infrastructure for Critical Facilities

Critical infrastructure (CI) collectively refers to those assets, systems, and networks that, if incapacitated, would have a substantial negative impact on national or regional security, economic operations, or public health and safety. Combined heat and power (CHP) offers the opportunity to improve CI resiliency, mitigating the impacts of an emergency by keeping critical facilities running without any interruption in electric or thermal service. If the electricity grid is impaired, a specially configured CHP system can continue to operate, ensuring an uninterrupted supply of power and heating or cooling to the host facility.

Hampson, Anne↗

DOE OSTI2020

Connected Communities: A Multi-Building Energy Management Approach

Connected Communities (CCs) are collections of buildings and distributed energy resources (DERs) that incorporate integrated energy management strategies at the multi-building scale. Based on the research conducted for this report, RMI and NREL have identified examples of CCs that are enabling increasingly integrated solutions, sharing resources among buildings, and providing services back to the grid. As demonstrated by these examples, CCs can provide real and scalable solutions to mitigate energy costs, enable more flexibility in grid operations, and offer choices in meeting greenhouse gas (GHG) emissions goals. Nationwide examples of these solutions are included in the appendix of this report. In order to understand the most promising practices for the design, operation, and business models associated with CCs, a search was performed to create a nationwide inventory of CCs and multiple stakeholder interviews were conducted. Based on that research, this paper explores the many factors that influence the development and operation of CCs and evaluates their potential value.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

DOE OSTI2025

Classification of Cloud Particle Imagery and Thermodynamics (COCPIT): A New Databasing Tool for the Characterization of Cloud Particle Images Captured During DOE Field Campaigns

The Department of Energy for decades has explored the earth system and atmosphere through research and deployment of in-situ and remote sensing platforms during field campaigns. Among these datasets exists a vast supply of cloud particle images that provide visual insight into the complex microphysics in the clouds that span our globe. The millions of images collected over decades of deployments provides a unique opportunity to further our understanding of our atmosphere down to the crystal size. This work over the past 5 years has sought to organize these images into digestible datasets that can then be used by scientists to further our understanding of microphysics. A machine learning model was developed that categorizes over 1.5 million images across 11 weather events with over 90% accuracy according to particle type. The database was then extended to include dimensional characteristics of the particle as well as co-location of environmental properties, such as temperature and water content. Then, to initialize the connection between these data and our understanding of how crystals form and grow, weather research and forecasting simulations were run to generate the growth histories of the classified crystals. This research culminates with 2 databases per event: (1) a database of all classified crystals and their dimensional and environmental properties and (2) simulated growth histories of each crystal. Finally, a user interface was created to allow researchers to explore data statistics.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2025

Final Technical Report of a Feasibility Investigation of a Hydropower Flexibility Upgrade Kit

The project studied the feasibility of a concept for a flexibility upgrade kit called h-Dynamyk to improve the flexibility of U.S. hydropower plants and assessed its potential impact on the U.S. hydropower industry. This concept addresses the growing need for grid flexibility amid rising renewable energy adoption, such as wind and solar, which often introduce intermittency. The upgrade kit is intended to address challenges posed by aging turbine designs in meeting modern grid demands for flexibility services like frequency response, voltage control, spinning reserve, and black-start capabilities. Key features of the h-Dynamyk kit include siphon turbine assemblies, medium-voltage variable frequency drives (VFDs), and smart controls integrated with plant systems to optimize operations and extend equipment life. This nine-month discovery project successfully achieved its objectives by defining a baseline design and performance metrics for the h-Dynamyk flexibility upgrade kit, analyzing this baseline, and incorporating lessons learned from this analysis into a modified set of metrics and recommendations for future design and testing, which were further guided by field site studies.

13 HYDRO ENERGY↗