DOE Study Reveals Control Strategies for Wind Development

by Kristen Wright, senior editor

A sexy, exciting renewable source of electricity generation is winking at utilities across the globe. “Here I am, and I’m available,” it flirts. It’s young and attractive, but it has a reputation for standing up its suitors. Even Merriam-Webster defines “variable” in a word: fickle. Despite that variability, the electric utility industry is learning how to predict wind’s arrival and departure.

“There’s a lot to learn from small grid operators,” said Lawrence E. Jones in January during the third annual Electric Light & Power Executive Conference.

Jones, vice president for North American regulatory affairs, policy and industry relations at Alstom Grid Inc., was the primary researcher on a recent Department of Energy (DOE) Report, “Strategies and Decision Support Systems for Integrating Variable Energy Resources in Control Centers for Reliable Grid Operations.” The report is in response to the DOE’s solicitation for proposals that address the potential challenges and solutions to achieving its goal of “20% Wind Energy by 2030: Increasing Wind Energy’s Contribution to U.S. Electricity Supply.”

That original 2008 DOE report examined a scenario and found it possible to contribute 20 percent of the U.S. electricity supply with wind power by 2030 if challenges in the report were addressed. Jones and the other researchers wanted to investigate and identify the best ways to guide operational strategies, business processes and control room tools that support the DOE’s overall wind objective.

Jones presented his findings during a conference panel on bringing renewable energy to the grid.

He shared insights from the 33 grid operators in 18 countries he surveyed about wind integration, wind forecast information, operating policies, best practices, examples of excellence, lessons learned and decision-support tools that dispatchers use in the daily operations of electric power grids. The participants included:

  • 12 European transmission systems operators,
  • Nine members of the Association of Very Large Power Grid Operators,
  • Six U.S. regional transmission organizations/independent system operators,
  • Four U.S. transmission utilities,
  • Four Canadian transmission system operators,
  • Three German transmission system operators,
  • Two Australian transmission system operators,
  • One transmission system operator each from China, India, Korea, New Zealand and South Africa, and
  • One European power grid monitoring and coordination company.

“The current approach of electric utility control centers and ways in which these tactics have evolved are reflected in the findings,” the report’s executive summary states. “The survey also focuses on those control centers that have experienced fast rates of wind penetration in the past decade.”

The power systems studied in the report have different network topologies, mix generation, load profiles and penetration levels of wind generation.

The combined amount of wind power capacity in the report is 141 gigawatts (GW), Jones said. That’s 72 percent of the world’s total installed capacity. By the end of 2010, about 194.4 GW of installed wind capacity worldwide was operable—a 22 percent increase over 2009, according to the report.

“Electricity generated from variable energy resources (VER), with wind being the leading source, is developing rapidly worldwide—and is only expected to increase further,” according to the report’s executive summary.

The U.S. accounts for more than 40 GW of total installed capacity. In 2010, China surpassed the U.S. in installed wind capacity, Jones said.

The following are excerpts from the executive summary:

  • Wind power forecasting. Wind power forecast is the most important prerequisite for successfully integrating wind energy into power systems. Predictability of wind plant output is the key to managing uncertainty. The accuracy or error of the wind forecast is of paramount concern for a grid operator. The error affects the level of confidence that operators place in the data, how it may be integrated or not, and how it is used in the control room.
  • Centralized wind forecasting program is best for reliable grid operations. A broad agreement among operators exists today that, in order to effectively integrate wind energy into power system operations, centralized forecasting is the current best approach for reliably operating power grids with wind generation. Therefore, grid operators around the world are acquiring centralized wind forecasting systems and services. Eighty percent of respondents in this study have implemented some form of centralized wind forecasting system or are in the process of putting one in place. A few grid operators still rely on decentralized wind power forecasting, but even in those cases, a transition to the centralized approach seems inevitable. Since completing the survey, important new developments at one U.S. operator of a regional grid and electricity market have emerged that suggest a move towards a hybrid approach, comprised of both centralized and decentralized forecasting. The hybrid approach is currently the subject of preliminary discussions in other North American regions with electricity markets.
  • Wind forecasting products. For many grid operators, Day-Ahead (DA) forecast has been the focus of much research attention. Tremendous improvements have been made to reduce the DA forecasting errors. However, as grid operators and researchers learn more about wind variability and the operational impacts of wind in different timescales, efforts are underway to continuously improve the accuracy and use of other forecast products …. Two of the most highly ranked products, ramp and ensemble forecasting, receive special attention in this report, based on additional interviews with respondents and the results from the survey literature.
  • Integration of wind forecast in decision-support systems. With wind generation increasing in power systems, it is important to integrate wind forecast information with the strategies and decision-support systems used in control room operations. The survey analysis highlights the different applications and processes that, when incorporated with wind power forecasts, are perceived to have the most value for integrating wind energy. Several grid operators are already implementing changes to the tools in their control rooms to cope with wind generation or they have plans to do so.
  • Congestion management. Congestion management is one of the most important functions of the grid operator. Higher penetration of wind power in the grid can introduce new patterns in the flow of power in the transmission and distribution networks. These unexpected flows could overload some transmission lines, causing new operational limits and congestion in the system. About 55 percent of respondents have integrated wind forecast in their software tools or processes to manage congestion. Large RTOs/ISOs and TSOs that are interconnected to neighboring utilities were included in this percentage.
  • Real time. Twenty-five percent or more of all the respondents have incorporated wind forecast in real-time applications and processes for managing voltage stability, unit commitment (UC), state estimation (SE), regulation, load following, economic dispatch (ED), contingency reserves and contingency analysis (CA). SE, ED, CA, regulation and load following are implemented as part of the energy management system (EMS) in control centers. In most cases, UC and contingency reserve calculation are also integrated with the EMS. Yet, the extent to which wind power forecast has been integrated with these EMS applications varies.

The following conclusions are excerpts from the report:

  • More and more grid operators are interested in applying industry best practices and examples of excellence as the starting point for deploying their own decision-support systems built specifically to address wind energy integration at the control center level.
  • Reaching the ambitious goal of 20 percent wind energy by 2030 in the U.S. will be difficult if existing decision-support tools in utility control centers do not evolve to meet the new challenges.
  • Grid operators worldwide are increasingly positive about integrating wind generation as they share best practices and learn about the successes of their peers.
  • Wind power forecasting is indispensible for successful wind integration.
  • Efficiently integrating wind energy in power systems requires that forecast and uncertainty information be incorporated into real-time decision-support systems and planning tools.
  • Higher levels of wind generation have shown to create uncommon system conditions and consequences that operators must learn to manage.
  • Efficient integration of wind energy requires grid operators to have access to a proper mix of flexible resources ranging on the supply side, delivery side and demand side.
  • Having skilled operators is necessary for wide-scale deployment and the integration of wind and other variable energy resources.
  • Achieving and maintaining the highest levels of situational awareness in control centers is, in general, of pivotal importance to grid operators and will be the case especially for systems characterized by high penetration of wind energy.
  • Integrating wind generation could require changes in the physical grid, as well as changes in operational business processes and information technology solutions at work in control centers.

An article on predictive operations by Dr. Jones will appear in the March/April issue. The report may be found at http://www.1.eere.energy.gov/wind/pdfs/doe_wind_integration_report.pdf

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