Renewable Systems Integration: Past Research Project Highlights

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Microgrid testing at Idaho National Laboratory
Microgrid testing facility at Idaho National Laboratory’s Energy Systems Lab in Idaho Falls.

Below you will find highlights of past U.S. Department of Energy (DOE)-funded research and development (R&D) projects to create new strategies for incorporating increasing amounts of wind energy into the power system while maintaining economic reliable operation of the grid. For information on renewable systems integration R&D projects currently being supported by DOE, click here

Grid Planning and Analysis

The office has being supporting efforts to inform power systems planners on how to best represent the characteristics of wind power. This issue is becoming more and more important as broad regional transmission planning efforts evolve.  Some highlights include planning and tool development and large-scale studies of future scenarios with large amounts of wind energy on the grid—such as a grid expansion and curtailment study (35% wind), Western Wind and Solar Integration Study (30% wind and 5% solar), Eastern Renewable Generation Integration Study (30% wind and solar), and National Offshore Wind Energy Grid Interconnection Study (54 GW offshore wind)—as well as more localized studies for both land-based and offshore wind.

Integration Studies

Reducing Wind Curtailment through Transmission Expansion

For this study, NREL simulated operation of the Western Interconnection under a scenario where 35% of electricity comes from wind in the year 2050 using PLEXOS, an integrated modeling tool commonly used by utilities and transmission organizations. The study includes a baseline scenario assuming no significant transmission expansion across the western grid, as well as three scenarios with varying levels of transmission buildout. The study found that building just four previously proposed transmission projects would reduce wind curtailment by about half. If the nation were to deploy additional transmission beyond those four proposed projects, wind curtailment would be reduced even further—allowing full use of wind energy, reducing generation costs, and unleashing additional economic and societal benefits.

Western Wind and Solar Integration Study (WWSIS)

WWSIS was conducted in three phases. Phase 1 showed that it is operationally possible to accommodate 30% wind and 5% solar energy if utilities substantially increase their coordination of operations over wider geographic areas and schedule their generation and interchanges on an intra-hour basis. Phase 2 focused on the wear-and-tear cost and emission impacts of cycling fossil-fueled generators due to high penetration of renewable energy and concluded that the negative impact of cycling is relatively small. Phase 3 further investigated the dynamic performance of the grid following a large disturbance and found out that with good system planning, sound engineering practices, and commercially available technologies, the Western Interconnection can withstand the crucial first minute after severe grid disturbance with high penetrations of wind and solar on the grid.

Eastern Renewable Generation Integration Study (ERGIS)

ERGIS provides insights on likely operational impacts of higher percentage—up to 30% on annual energy basis with instantaneous penetrations over 50%—of combined wind and photovoltaic (PV) generation in the Eastern Interconnection. The impacts of variable and uncertain conditions caused by wind and PV on reliability and economic condition were investigated. Specifically, a 5-minute scheduling was simulated to evaluate how electricity demand could be met by sub-hourly dispatch. The project also demonstrated advanced techniques for power system modeling.

National Offshore Wind Energy Grid Interconnection Study (NOWEGIS)

NOWEGIS was a national-level study (of the lower 48 states) that considered the resources, technologies, and regulatory environment that may advance or hinder the large-scale introduction of offshore wind into the U.S. energy portfolio. Findings from the report suggest that the United States has sufficient offshore wind energy resources to enable the installation of at least 54 gigawatts of offshore wind capacity, and that the appropriate transmission technologies already exist to connect this offshore wind energy to the grid.

Carolina Offshore Wind Integration Case Studies

The objective of the project was to remove market barriers that limit the deployment of offshore wind in the coastal regions. Duke Energy examined the impact of three different levels of offshore wind development in the Carolinas, including the need for additional transmission, increase of reserves, and system performance.

Great Lakes Offshore Wind Study

The goal of the project was to remove market barriers that may limit the deployment of offshore wind in the Great Lakes region. Case Western Reserve University’s case study identified specific integration needs for a 1,000-MW Lake Erie wind plant and recommended appropriate system upgrades. It also developed general recommendations for interconnecting large Great Lakes wind plants to the grid, including requirements and/or upgrades for transmission system characteristics.

Distributed Wind Integration Study

For this study, NREL examined the possible operational challenges associated with large additions of distributed wind generation. A two-step approach was taken:

  1. Study the voltage limitation factors for successful interconnection of large-scale wind generation at typical distribution feeders
  2. Study the impacts of smaller scale wind turbines, with power electronics, on steady-state system operations and voltage profiles. Impact of distributed wind on bulk power system, in particular, to the static and dynamic operation of ISO New England were investigated.  

Grid Planning Tools Development

Wind-Based Transmission Planning Tool Development

Idaho National Laboratory integrated Computation Fluid Dynamics (CFD)-enhanced dynamic line rating data sets as geospatial layers and developed a software architecture for a wind-based transmission planning tool. The tool will ultimately assist in identifying thermal constraints of new conductor routes to support increased wind penetration. 


Connecting the National Wind Technology Center to the Energy Systems Integration Facility at NREL

Two existing NREL testing capabilities, the Energy Systems Integration Facility and the National Wind Technology Center, were integrated into a combined multi-megawatt scale test bed for grid integration testing and demonstration of renewable technologies, energy storage and demand response at both transmission and distribution levels.

Wind Generator Modeling Development and Validation

For this project, NREL performed dynamic model development, simulation studies, and various investigations to better understand the dynamic behavior of the wind power plant and the power system under scenarios of high levels of wind penetration. Both individual turbine behavior and the collective behavior of wind power plants were included in the scope. The results of the work provided power system planners with various control options to utilize the capability of advanced controls for modern wind turbines, wind power plants, and power system.

Wind Plant Modeling Implementation

Sandia National Laboratories continued the effort to fully develop, validate, and disseminate wind turbine generator models for use in power system planning and analysis. The project helped to reduce wind integration barriers by making validated generic generator models available to system planners for use in interconnection studies, without the need to seek manufacturer-specific models which is a long and cumbersome process.

Grid Operation and Market Impact

While it has been shown that the electricity grid can reliably integrate much larger amounts of variable renewable energy than are currently deployed, the variability of wind energy and the uncertainty of wind forecasts bring new challenges for energy market and grid operation. The office has been working continuously with researchers and industry to identify the impacts and provide solutions. Some recent highlights include studying how wind technology can assist the power system through active power controls, and studying how wind can cool transmission lines thereby increasing transmission line capacity.

Active Power Controls from Wind Power

Researchers at NREL embarked on a comprehensive study to understand the ways in which wind power technology can assist the power system by providing control of its active power output. The study included a number of different power system simulations, control simulations, and actual field tests. It offers value insights into how wind power-provided active power controls can benefit numerous parties by reducing total production costs, increasing wind power revenues streams, improving grid reliability and security, and providing  efficient responses that are in many cases superior to the responses of conventional generation, all while limiting any structural and loading impacts that may shorten the life of wind turbines or its components.

Analysis Using Phasor Measurement Unit Data and Dynamic Analysis for Wind Power Generation

For this project, NREL developed tools to use phasor measurement unit data from power system planning and operation in the context of high penetration wind power generation. By collaborating with partners, methods were developed to improve situational awareness, measure real-time characteristics of power system dynamics, and track the stability margin of the power system. 

Stochastic Tool Evaluation for System Operations with Renewable Energy

For this project, Argonne National Laboratory evaluated the benefits of using stochastic scheduling and dispatch approaches by comparing the more advanced methods to traditional deterministic approaches, both from qualitative and quantitative perspectives. A consistent set of evaluation metrics, including system costs, reliability, energy and reserve prices, and computational requirements, was developed to assess different operational strategies. These metrics were used to evaluate the benefits of stochastic programming on a hypothetical test system.

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