By Lawrence Jones, Alstom Grid Inc.
Electricity generated from variable energy resources, with wind being the leading source, is developing rapidly worldwide and is expected to increase further. The installed wind generation capacity worldwide between 1990 and 2010 increased from 17 gigawatts to 194 GW. Despite such growth, misconceptions and questions about wind energy still exist. Examples include: Is there a limit of wind that can be accommodated by the grid? Can grid operators deal with the continually varying output of wind generation?
In its landmark 2008 report “20% Wind Energy by 2030: Increasing Wind Energy’s Contribution to U.S. Electricity Supply,” the U.S. Department of Energy (DOE) examined a scenario and found it feasible that wind power can contribute 20 percent to U.S. electricity supply by 2030 if challenges identified in that report are addressed. Nevertheless, effectively integrating much wind energy into current and future power grids is a prominent issue for grid operators, regulators and the electricity industry.
In response to the DOE’s solicitation for proposals addressing the potential challenges and solutions to realizing a scenario of 20 percent wind energy by 2030, researchers at Alstom Grid Inc. investigated and identified the best ways to guide operational strategies, business processes and control room tools supporting this objective. The study on renewable integration was funded by the American Recovery and Reinvestment Act (ARRA). It is a novel firsthand global account of how wind energy affects grid operations. It is based on views from the operators and engineers in control rooms around the world.
In the study, investigators surveyed 33 electric power system operators in 18 countries about wind integration, their operating policies, best practices, examples of excellence, lessons learned and decision support tools in place. The power systems surveyed have different network topologies, generation mixes and load profiles and a range of wind generation penetration levels. The wind power capacity referenced in this report is 141 GW, or 72 percent of the world’s total installed capacity. The power grids are in varying geographies with diverse weather regimes, and many of the utilities surveyed operate under dissimilar regulatory frameworks and in regulated or deregulated electricity markets.
The report provides an evaluation of how system operations worldwide are changing in response to increasing wind penetration. It provides insights into what has worked well, what has not and how operators see their responsibilities changing as more wind is introduced into the grid. It is the first time grid operators from across the globe have provided in-depth, consolidated feedback on how wind energy affects them and what concrete measures they are taking to manage their systems with the challenges posed by the increased variability and uncertainty wind generation presents. Grid operators, according to the study, are increasingly positive about integrating wind generation because they share best practices and learn about their peers’ successes. The participation worldwide from utilities with high wind generation penetration reflects the marked change in perception and attitudes toward wind and other variable generation.
Special emphasis was placed on how these utilities incorporate wind forecast information into operating policies, strategies, processes and decision support tools used by dispatchers in daily electric power grid operations. The findings reflect electric utility control centers’ approaches and ways in which their tactics have evolved. In addition, the survey focuses on control centers that have experienced fast rates of wind penetration in the past decade. This project clearly indicates more utilities are interested and open to using industry best practices and examples of excellence from their peers as the starting point for developing and deploying their own solutions.
Following are study results and examples of best practice tools and decision support systems used in control centers.
Operators Need Decision-Support Systems, Operational Processes
In recent years, utilities in the U.S. and other parts of the world developed varying levels of expertise and knowledge in how to operate power grids with increasing wind power generation. There might not be an insurmountable technical barrier to reaching the 20 percent wind energy by 2030 scenario described in the DOE report, but the findings suggest that such a scenario cannot be achieved without knowledgeable grid operators in control rooms equipped with the necessary decision-support tools. Grid operators must have accurate wind power forecast information.
Ninety-four percent of respondents said integrating wind energy will depend on tools in the control room, which is the nerve center for operating power systems. Increasungly, grid operators no longer passively plan for high wind generation penetration on their systems. Rather, operators are at different stages in deploying decision support tools necessary to integrate wind energy.
Best Practice Tools, Decision-Support Systems
A growing number of grid operators are interested in applying industry best practices and examples of excellence as the starting point for deploying their own decsion support systems built specifically to address wind energy integration at the control center level. Examples of best practice tools, processes and procedures based on the study are:
Grid operators in the U.S. and Europe identified nine best practice tools and decision-support systems used to integrate and manage wind energy, and in several cases solar energy:
1. Dispatch Decision Support Tool (DDST), Alberta Electric System Operator, Canada
2. Integrated Curtailment and Redispatch System (iCRS), Bonneville Power Administration, U.S.
3. Wind Security Assessment Tool (WSAT), Eirgrid, Ireland
4. Nordic Operational Information System (NOIS), Energinet, Denmark
5. Drift PlanlÃgnings System, Energinet, Denmark
6. ERCOT Large Ramp Alert System (ELRAS), Electric Reliability Council of Texas, U.S.
7. GeneraciÃ³n EÃ³lica MÃ¡xima Admisible en el Sistema (GEMAS), Red ElÃ©ctric de EspaÃ±a, Spain
8. Centro de Control de RÃ©gimen Especial (CECRE), Red ElÃ©ctric de EspaÃ±a, Spain
9. Insertion de la Production Eolienne dans le SystÃ¨me (IPES), RTE, France
Processes and Procedures
- Perform more frequent resource scheduling and dispatch.
- Integrate wind power forecast in congestion management and other processes.
- Provide wind plant dispatch instructions directly from the security-constrained economic dispatch (SCED) tool.
- Perform operational impact studies with strong participation from the internal engineering staff.
- Use the time-simulation based method that simulates all minute-by-minute deviations related to system operations, including computing critical system performance indicators such as the control performance standards (CPS).
- Annually review and update operational guidelines as more wind generation is connected to the system.
Integrating Wind Forecast in Decision-Support Systems
Grid operators overwhelmingly agreed forecasting is indispensible for integrating wind and other variable generation into the power grid. In addition, they said that equally important is integrating wind forecast information with the strategies and decision-support systems used in control room operations. The survey analysis highlights the applications and processes that, when incorporated with wind power forecasts, grid operators indicated were most valuable for integrating wind energy. Several grid operators already are implementing changes to their control room tools to cope with wind generation. Several others plan to do so. Figure 1 shows the extent to which respondents have integrated wind forecast in different processes and tools used in real-time operations.
Congestion management is one of a grid operator’s most important functions. Higher wind power penetration in the grid can introduce new power flow patterns in the transmission and distribution networks. These unexpected flows could overload some transmission lines, causing new operational limits and congestion in the system. Some 55 percent of respondents have integrated wind forecast in their software tools or processes to manage congestion. Large regional transmission organizations (RTOs), independent system operators (ISOs) and transmission system operators (TSOs) that are interconnected to neighboring utilities are included in this percentage.
Integrating Wind Power in Control Room Operations
With wind-generated capacity in power systems growing, control room strategies and decision-support systems must be enhanced to account for increased uncertainty and variability. Operators agree that incorporating wind power forecasts into control room applications and processes can help streamline wind energy integration. Several grid operators surveyed are changing control room tools, such as energy management systems (EMS) and market management systems (MMS), or soon will implement such changes.
In addition to software tools and processes, many respondents agree that higher wind generation penetration on the grid, coupled with the constant stream of large volumes of operational and nonoperational system data from disparate sources, will change dispatchers’ and other control room personnel’s roles and responsibilities.
Smarter Grids Increase Operational Flexibility, Aid Wind Integration
Efficient wind energy integration requires grid operators to have access to a proper mix of flexible resources on the supply side, delivery side and demand side. Smarter grids have improved operational flexibility with increased observational accuracy and by giving operators greater ability to control and maneuver certain loads, generation and storage resources and transmission networks. Around the world, governments, policymakers, regulators, utilities and other stakeholder groups propose smarter technologies and applications. Figure 2 shows the percentage of grid operators who have implemented or plan to implement several smart grid applications. Most respondents deploying demand response operate in regions or countries with competitive electricity markets.
Since its release and broad dissemination, the report is increasing industry wide understanding about the operational impacts of wind integration, how wind power forecasts are used and how they can be leveraged better. It is helping debunk myths and correct misconceptions about operators’ capability to manage power grids with high penetration of wind and other variable energy resources.
Lawrence Jones is Alstom Grid Inc.’s vice president of policy and regulatory affairs. He was the principal investigator of the Global Survey of Wind Integration in Control Centers funded by the DOE. He is a senior member of the IEEE.
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