Wind Plant Modeling and Interconnection Users Group Scope

Background: The rated capacity of wind generation in many U.S. control areas has grown to the point where the influence on transmission system operations and performance can no longer safely be judged as negligible. As with other transmission-connected elements, appropriate models of wind plants are necessary for the range of engineering studies employed to assess these impacts and ensure the reliable operation of the network.

Wind plants pose some major challenges for modeling in power system calculations and simulations. Relative to conventional generation facilities, wind plants are comprised of large numbers of small units, and the turbines themselves employ technologies for energy conversion and control that are not well known to power system engineers. Some early models for commercial wind turbines have been developed and are available, but there is very little application experience and guidance upon which to draw, and the validation efforts for these existing models have not been exhaustive.

This type of situation is not new to the industry, as the introduction of any new technology for transmission system application imposes similar challenges for modeling. The power system engineering community, especially through the efforts of technical committees within the IEEE Power Engineering Society, has been able to keep pace with important technology advancements in transmission system design and engineering. With wind generation, however, the situation is a bit more critical given the industry growth rate, the short project lead times, and the rapid evolution in wind turbine technology and wind plant design practices.

Scope and Activities: By leveraging established relationships with all of the stakeholders, the UWIG Wind Plant Modeling and Interconnection User Group aims to meet the immediate and critical needs of the wind generation and power industries. The activities will focus on assessing the impact of wind generation on the transmission network, including wind turbine and wind plant modeling, dynamic performance, and short circuit behavior; the influence of wind plant design on interconnection performance, and best practices and standards for wind plant interconnection.

Because the industry efforts in this area are really just beginning, the list of needs is substantial. The Users Group will prioritize and develop recommendations for meeting these needs, in accordance with the following outline:

1. Wind Turbine and Wind Plant Models for Transmission System Studies

• Maintain existing models
• Create new models
• Evaluate alternate modeling methods
• Provide model validation assistance and maintain measurement database
• Provide application expertise
• Provide a modeling forum for users
• Provide model evaluations and recommendations
• Assist vendors with modeling requirements and model developments

• Evaluate new tools and methods for studies of wind generation
• Maintain case studies and benchmark data
• Assist with development of interconnection guidelines
• Standardize FERC Order 2003 interconnection study requirements

• Institute of Electrical and Electronic Engineers (IEEE)
• American Wind Energy Association (AWEA)
• International Electrotechnical Commission (IEC)
• International Energy Agency (IEA)
• Western Electricity Coordinating Council (WECC)

In support of the activities outlined above, some additional description related to the activities of the User Group follows:

Models

• Work to create, maintain, and evaluate information related to computer models for both new and existing wind turbine technologies and other commercial products to be used in power system studies
• Assist in efforts to validate new and existing computer models against available laboratory data and field measurements
• Develop new information - new models, application expertise and guidance, validation - when required and supported by User Group members or the UWIG
• Provide support to User Group members engaged in studies, evaluations, or performance measurements of wind generation facilities on their systems
• Document experience with existing models and make recommendations for enhancements or new developments that will better meet the needs of the engineering community
• Assist participating vendors of wind turbines or other products for wind plant applications with the specification and development of appropriate models for their technologies
• Provide a forum for User Group members to share experience and lessons learned from their own use and application of wind turbine and wind plant models

Transmission System Studies

• Evaluate new tools and techniques for studies of transmission networks with wind generation facilities
• Offer support and assistance for a wide range of computer tools, including GE PSLF, PTI PSS/E, EMTP and PSCAD, etc.
• Participate in industry activities to develop wind plant interconnection guidelines
• Participate in industry activities to develop a standard approach to performing interconnection studies required under FERC Order 2003

Liaison

• Maintain liaison with IEEE Power Engineering Society, AWEA, IEC, IEA, WECC, and other technical committees working in this area
• Provide support to other UWIG User Groups (e.g. Distributed Wind User Group for turbine modeling) where appropriate

Communication and Education: User Group results will be provided over the web and through meeting participation. The following communication means will be employed:

• Database of models and measurements
• Forum for online discussions
• Annotated bibliography with links to source documents
• Technical sessions at UWIG meetings
• Seminars
• Paper presentations at industry meetings

User Group Startup: The initial activities of the User Group will focus on assessing the ongoing work and development in this area and prioritizing the various industry needs. We would like to identify User Group members who would be able to contribute to one or more of the following activities during the startup phase. We especially encourage the participation of power system engineers who can contribute to the modeling and study work, and interconnection requirements definition.

The User Group members will identify and prioritize specific needs and open technical questions related to wind turbine and wind plant modeling in power system studies. The items of highest priority will be evaluated in detail, and recommendations will be made as to how these might be addressed by UWIG or other parties.

The PSS/E models developed by the Electric Reliability Council of Texas (ERCOT) will be acquired and an evaluation of these models by the User Group will be initiated as an ongoing activity. Case studies employing these models will be documented, as will experience with the model applications and any questions regarding their use or validity. The User Group will also explore mechanisms by which these models can be adapted for the GE PSLF platform with the appropriate parties.

The User Group will seek to support and assist with opportunities for collecting laboratory or field measurement data for the purpose of model validation.

Over the past two or three years, an increasing number of technical papers, articles, and presentations have been appearing in the industry literature. While significant in number, they are scattered over a variety of journals and technical conference proceedings. To keep the members apprised of this growing body of work, the User Group will compile and begin maintaining an annotated bibliography, with links to electronic documents where possible.

Finally, the User Group will work to establish liaison with outside organizations engaged in related work, such as the IEEE, AWEA, IEC, IEA, and WECC. Relevant goals, objectives and activities of these organizations will be tracked, and opportunities to constructively engage and contribute to their work will be sought.

NREL Participation: The activities of the Wind Plant Modeling and Interconnection User Group have good synergy with some ongoing initiatives and activities at NREL. The dynamometer test facility, for example, has the potential to provide very detailed measurement information for characterizing the electro-dynamic performance of individual wind turbines. NREL is currently a participating member of the IEA Annex XXI that is focused on the very topic of developing dynamic models for wind turbines and wind plants. Ed Muljadi's work in characterizing the steady-state performance of wind plants through detailed modeling and calculation can provide a solid basis for moving forward with questions related to both small- and large-signal dynamic phenomena. The NREL program will contribute to specific activities of the User Group.

New activities that will contribute to the users group objectives include a dynamic model validation exercise for a utility company in the southwest U.S. In this effort, newly available dynamic wind turbine models for PSS/E will be used to construct various representations of a large wind plant. The effect of the amount of detail in the wind plant model on the dynamic behavior as viewed at the point of interconnection to the transmission system will be explored. The exposure of the plant to turbine trips for faults on the transmission network will also be investigated.

Work to be included in User Group Scope

• Early experience with PSS/E model application (ERCOT)
• Wind turbine vendor model development efforts (GE, Vestas, Mitsubishi, others)
• Wind plant and turbine steady state and dynamic models (NREL)
• PacifiCorp wind plant staged fault testing
• WECC dynamic working group activities 
• IEA Annex XXI
• Ontario Hydro research activities 
• MISO dynamic studies for MTEP03 
• AWEA Interconnection Guidelines 
• FERC Order 2003

For more information, please send e-mail to info@uwig.org