Bulk Power System Integration of Variable Generation - Program 173

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1 Bulk Power System Integration of Variable Generation - Program 173 Program Description Program Overview A number of ongoing environmentally driven regulatory issues including greenhouse gas reductions and associated CO 2 reduction initiatives, the U.S. Clean Water Act: Cooling Water Intake Structures, and the U.S. Clean Air Act: Interstate and Mercury Rules have resulted in increased implementation of renewable energy resources and adoption of distributed generation (DG) and demand-side resources. Much of the estimated development of renewables comprises variable resources such as wind generation and solar photovoltaics (PV), which when integrated with the system at large scales create many new challenges for maintaining reliable system operation. Research Value EPRI research and development in the area of bulk power system integration of variable generation and controllable load will produce knowledge and tools that will help system operators and planners: Understand the impacts of variable generation and controllable load on system reliability Control variable generation and controllable load to minimize operational risks Design robust transmission systems to integrate variable generation and controllable load Develop system and industry standards that ensure efficient and reliable operation. The Bulk Power System Integration of Variable Generation program offers members both short- and long-term value that can be realized in a number of ways: Anticipating future developments, creating new strategies, and outlining roadmaps Developing methods and tools Demonstrating and deploying technologies Providing training and staff development Sharing knowledge, information, and experience Engaging with industry standards development Building networks and conducting outreach. Accomplishments The Bulk Power System Integration of Variable Generation program was created in Program products and accomplishments in 2009 and 2010 included: Development of methods and tools to support risk-based transmission planning that integrates the uncertainty of variable generation and controllable loads when evaluating system facility requirements Development of methods and tools to determine operating reserve requirements for high levels of variable generation with consideration of all other system uncertainties Specification of the requirements for operational tools and methods to support dispatch and supply surplus/deficiency decisions for high levels of variable generation Development and validation of wind generation, solar PV, and other emerging flexible resource dynamic models for system planning studies Continued interaction and representation of member interests through the NERC IVGTF leadership team. p. 1

2 Current Year Activities In 2011, this research program expects to accomplish these objectives: Understand the state of the art, best practices, and gaps of existing tools Prepare a set of requirement specifications for expanding the capabilities of analytical tools to deal with the variability of resources Explore advanced methodologies to deal with the uncertainty of variable generation and controllable load Produce case studies to support development of member standards and processes as well as industry standards for ensuring system reliability. Estimated 2011 Program Funding $1.5M Program Manager Daniel Brooks, , dbrooks@epri.com Summary of Projects Project Number Project Title Description P Grid Performance and Modeling of Variable Generation and Evolving Power System Resources P Operator Tools for Scheduling, Reserve Determination, and Frequency Control with Variable Generation P Advanced Planning Tools to Study the Impact of Variable Generation and Controllable Loads P Evaluation of Potential Bulk System Reliability Impacts of Distributed Resources and Potential Mitigating Strategies This project aims to describe the technical performance requirements of variable generation and other emerging generation technologies, help develop generic non-proprietary models for planning the integration of such resources into the utility grid, and guide efforts in model validation. This project will develop methods and tools that allow operators to more reliably and efficiently schedule resources to meet demand while maintaining adequate reserves in the operational planning timeframe, and provide dispatch decision support and methods for improved frequency control in real-time operations. This project develops methods and tools that allow transmission planners to incorporate and consider the added uncertainty when evaluating system reliability and evaluating facility upgrades that will be required to support future generation and load requirements. This project will provide an evaluation of the potential adverse impacts that high levels of distributed energy resources may have on bulk system reliability, and guidelines for mitigating such negative impacts. Bulk Power System Integration of Variable Generation - Program 173 p. 2

3 P Grid Performance and Modeling of Variable Generation and Evolving Power System Resources (067489) Key Research Question Many states have passed renewable energy requirements, and the prospects for a federal requirement seem good. Many of these requirements include specific targets for wind and solar generation. As a result, there is an increasing effort to develop bulk system interconnected wind and central solar PV plants and integrate solar PV panels in residential and commercial constructions. When connected to the distribution system in sufficient quantities, PV generation is capable of impacting power grid behavior during system disturbances. It is important to understand the characteristics of wind and solar PV generation, as well as other emerging resources, whether bulk-system interconnected or distributed, with respect to how these devices respond to voltage and frequency variations in the power grid. Wind, PV, solar thermal, demand response, plug-in hybrid electric vehicles (PHEVs), and other evolving system resources have performance characteristics that can differ from those of conventional generation. System planners and operators, as well as owners of the new system resources, need to understand the requirements for each technology to supply services required by the system. This project will investigate and develop technical specifications for the dynamic performance of evolving power system resources. For example, can wind and solar PV provide sufficient inertia and primary frequency response to maintain system stability when conventional rotating generators are offline Or should PV have fault ride-through, as is now accepted and implemented for wind power plants This effort will build on work begun in 2010 that involved working with industry groups to validate existing wind generation dynamic models and identify PV dynamic model requirements. The 2011 project will provide for completing PV model development and validation, and extending these modeling specifications to other emerging technologies such solar thermal, energy storage, demand response, and PHEVs. The order of development will be prioritized with project members. In addition to furthering technical specifications for advanced resources to provide system performance needs, this project will also develop guidelines for representing such devices in bulk system planning studies. This effort will: Review available technical literature on inverter-based PV testing and modeling, and review any readily available field measurements for existing PV installations. This literature and data review will also be conducted for other advanced sources, such as PHEVs, to serve as the basis for developing bulk system modeling guidelines for such devices in future efforts. Identify gaps that may exist in the understanding of inverter-based PV generation that potentially limit the ability to develop representative bulk transmission system models. Determine whether further laboratory testing of certain units may provide a better understanding of such issues. If so, develop a plan for obtaining equipment, develop test plans, and conduct additional tests in the future. Similar gaps should be identified for other evolving resources. Continue to evaluate the ability of wind, PV, and other emerging resources to support system stability by providing inertia and primary frequency response during system disturbances. Develop a detailed scope for project work to develop models for inverter-based solar generation and other evolving resources, and methods to include representation of these devices in commercially available bulk power system planning tools. Such models need to be non-proprietary and open for use by all, disseminated to the industry to allow their implementation in standards and widely used commercial power system analysis software. This effort would coordinate with ongoing efforts by IEEE, WECC, and other organizations developing models for variable generation resources. The project would also aim to develop ways to validate the models. Bulk Power System Integration of Variable Generation - Program 173 p. 3

4 Based on a literature search and experience with wind generation, provide a qualitative assessment of the potential impacts that a large proliferation of inverter-based distributed generation, such as PV, may have on the bulk transmission grid. Accordingly, make recommendations on what aspects of standards and future inverter-based PV and DG control strategies may need to be investigated and revised to address those issues. Such standards development is clearly outside the scope of EPRI's work, and the goal would be to make technical recommendations to standard organizations such as NERC. As part of the project, we will hold an industry workshop to describe developments of emerging resource dynamic models such as both bulk and distributed solar PV, stationary energy storage, and plug-in electric vehicles. In addition, on-going industry model validation efforts and needs will be discussed. Impact This work is necessitated by the growing demand for renewable and distributed generation technologies. On the system modeling and planning side, existing tools and models do not yet adequately represent the breadth of capabilities and performance of these emerging technologies. Being able to develop the models needed and technical performance guidelines for applying these new technologies will be a significant step in providing system planners with the tools they require to plan the power system in coming years. This research can help members by: Defining the control features and capabilities that emerging variable generation sources need to match existing generation technologies Providing models, and guidance on the use of models, for these new technologies for system planning studies Validating existing or in-development models. How to Apply Results This project will provide workshops, tutorials and training webcasts. It will also disseminate key results and models through industry forums such as IEEE and CIGRE Products Product Title & Description Grid Performance and Modeling of Variable Generation and Evolving Power System Resources Report Planned Completion Date Product Type 12/31/11 Technical Report P Operator Tools for Scheduling, Reserve Determination, and Frequency Control with Variable Generation (069255) Key Research Question The variability and uncertainty associated with variable renewable generation such as wind and solar PV can have a significant impact on system performance and market operation as penetration levels increase. Specifically, the variability and uncertainty makes it much more challenging for system operators to schedule the most economical set of resources to meet system requirements, determine operating reserve requirements to ensure reliability, and maintain real-time frequency and voltage performance to established standards. Consequently, new operational scheduling and control methods and tools are needed to ensure reliable system operation in the most efficient and economical manner. Bulk Power System Integration of Variable Generation - Program 173 p. 4

5 For example, new NERC requirements for Operational and Planning Reserve (BAL-002-RFC-02, RES-001-1) recognize the need for improved methodologies and algorithms beyond the traditional contingency analysis to accommodate increasing levels of uncertainty in the behavior of intermittent resources and demand response. Current practice, which uses a deterministic approach, is no longer sufficient. New approaches are needed to support operational decision making. Further, operators need better visualization, situational awareness, and dispatch support tools to discern how to manage increased variability and uncertainty with an expanding set of resources such as demand response, energy storage, and PHEVs, which are themselves not understood by operators and subject to uncertainties. EPRI will continue work begun in 2009 to develop stochastic models to determine robust energy and reserve schedules, and determine how to integrate these into prototype tools that can be utilized on operator and schedulers' desks. Through a supplemental project, EPRI is working to develop a prototype operator decisionmaking tool that may serve as a platform for integrating the stochastic scheduling and reserve determination algorithms that are being developed. EPRI will collaborate with commercial EMS vendors to ensure that tool prototyping is coordinated in a way that allows the results to be utilized by vendors in developing commercial tools that integrate with utility and ISO EMS products. EPRI will also draw on studies from small islanded systems with high wind penetrations, and engage operators from other systems with increasing variable generation penetration, to identify potential performance impacts and needs. This project may also engage automated generation control (AGC) vendors for one or more systems on which new algorithms might be tested. Impact Power system operators and planners will have new capabilities to optimally schedule generation to meet demand and determine reserve requirements that balance the introduction of emerging energy resources with system reliability. This project will also provide system operators with insights into the potential impacts of variable generation on frequency control, as well as new methods for minimizing any negative impacts on system frequency performance. How to Apply Results EPRI will provide project status updates and training webcasts to communicate the strengths and applications of the developed operator tools and methods. Participants will read the technical report and implement recommendations for additional scheduling, dispatch, and frequency-control tools and systems. Participants will work with associated vendors to develop and test developed prototype tools or modified AGC system algorithms Products Product Title & Description Operator Tools for Scheduling, Reserve Determination, and Frequency Control with Variable Generation Report Planned Completion Date Product Type 12/31/11 Technical Report Bulk Power System Integration of Variable Generation - Program 173 p. 5

6 P Advanced Planning Tools to Study the Impact of Variable Generation and Controllable Loads (069256) Key Research Question Global climate concerns are influencing the ever-increasing role that renewable and highly variable generation will play as future energy sources. At the same time, interest in the smart grid has accelerated in the United States and the rest of world, with smart meters connected to customers with controllable loads likely leading the way for smart grid deployments. The proliferation of high levels of variable generation and controllable loads will require grid planners to incorporate much higher levels of uncertainty in their models to adequately represent the many potential system scenarios that might result. These models will be necessary to maintain grid reliability and reduce system development and operating costs. Research is needed to develop advanced risk-based planning tools that integrate the planning and operation of customer demand, energy storage, and renewable generation. In the absence of such tools, system operators are more likely to be required to operate in system configurations and scenarios that may not have been adequately studied in the system planning. Or, transmission planners may take a very conservative approach in planning to ensure sufficient margin exists to cover unstudied configuration and scenarios, resulting in inefficient infrastructure upgrades and overbuilt capacity. System planners need this project to properly evaluate transmission capacity requirements and grid reliability when higher levels of variable generation and controllable loads are anticipated. In 2011, the project includes the following activities: Model the uncertainties associated with renewables, including wind and solar. Usually, wind farms and solar collection points are combined or treated as a single entity in steady-state power flow models; such simplifications result in low-accuracy simulation. A rigorous probabilistic mathematical model will be developed to capture variations of renewable generations as well as take into account the correlation of these variable generations with system loads. This work will incorporate research results by EPRI and others on modeling the intermittent nature of renewable generation. Develop system load shapes and load factors with various assumptions of penetration scenarios of controllable loads, before and after applying control. EPRI will also identify ways that controllable loads can be utilized as control variables that can decrease or increase at various points in a bulk power transmission system. Develop advanced planning tools to perform reliability assessments for comparing alternative transmission expansion plans to accommodate a high penetration of renewables and controllable loads. EPRI will implement the developed model on existing probabilistic and risk-based transmission planning tools (such as TRELSS/TransCARE enumerative procedure based). Impact Transmission planners are tasked with efficiently building a grid that operators can reliably operate. Increased uncertainty in generation dispatch patterns and load patterns increases the complexity of the planners' problem. This project develops methods and tools that allow transmission planners to incorporate and consider that added uncertainty when evaluating system reliability and facility upgrades that will be required to support future generation and load requirements. By explicitly representing the uncertainties related to variable generation and controllable loads, planners will be able to more efficiently plan system upgrades and avoid intentional overbuild solely for the purpose of providing planning margins to cover these known uncertainties. Bulk Power System Integration of Variable Generation - Program 173 p. 6

7 How to Apply Results The project's products will help members understand how to conduct advanced planning for the entire power supply and delivery chain. Members will be able to use the best available data and information about load composition and load models that recognize all resources and demands. Typical system load shapes will be available for members to use for system studies. Business cases for applying energy storage will be excellent sources of information for members planning a possible role for energy storage in their future systems. Survey results and summaries of regulatory impacts, as well as the value of ancillary services, will also be valuable. Webcasts will be held regularly to engage members in research efforts and facilitate information transfer Products Product Title & Description Advanced Planning Tools to Study the Impact of Variable Generation and Controllable Loads Report Advanced Planning Tools to Study the Impact of Variable Generation and Controllable Loads Software Planned Completion Date Product Type 12/31/11 Technical Report 12/31/11 Software P Evaluation of Potential Bulk System Reliability Impacts of Distributed Resources and Potential Mitigating Strategies (070599) Key Research Question Many of the emerging resources expected to significantly impact the electric power system will be distributed resources that are integrated on a decentralized basis at medium- or low-voltage levels. These distributed resources include various types of distributed generation including solar PV, various demand response programs, plug-in hybrid electric vehicles (PHEVs), and stationary distributed energy storage. While these resources offer potential benefits to the bulk system, there are many potential adverse bulk system reliability implications with widespread proliferation of small distributed resources that are not visible at the bulk system level. For example, IEEE Standard 1547, which provides minimum requirements for interconnection of distributed generators, calls for grid-tied DG to separate from the distribution system within a specified minimum time when abnormal conditions such as voltage or frequency deviations are detected. For a transmission disturbance resulting in abnormal conditions across a large distributed generation base, having the DG disconnect may pose a further risk to bulk system reliability. This project will evaluate the potential magnitude of bulk system reliability impacts of high penetrations of distributed resources and potential mitigating options. Possible adverse interactions to be investigated may include: Lack of visibility/controllability of DER at any given time Ramping/variability issues that could affect bulk system operations Low-voltage ride-through, frequency ride-through, and coordination with IEEE Standard 1547 Potential system protection considerations, including impacts on UFLS Potential problems with coordination of system restoration Scheduling/forecasting impacts on baseload/cycling generation mix Reactive power control. EPRI will build upon preliminary work conducted by a NERC Integrating Variable Generation Task Force (IVGTF) work group to identify potential bulk system reliability impacts of distributed resources. EPRI will attempt to evaluate and quantify the potential impacts through case studies of systems where distributed resources are already beginning to become significant. For example, the Big Island of Hawaii already has more than 9 MW of distributed PV installed, which represents a non-trivial aggregate resource on a system where Bulk Power System Integration of Variable Generation - Program 173 p. 7

8 load varies between 100 and 200 MW. By developing models of such systems that include both bulk system and distributed resources in a single model, potential bulk system reliability implications and potential solutions can be evaluated. These results will then be extended to larger systems so that recommendations and guidelines can be made for altering or developing standards that ensure that the benefits of distributed resources can be obtained while minimizing risks to the bulk system. As part of the project, an industry workshop will be held to identify specific areas in which the proliferation of distributed resources may impact bulk system reliability. Additionally, potential mitigation approaches to ensure sufficient visibility and control exists will be addressed. Impact This project will provide the analytical foundation and guidance for reviewing existing standards and distribution interconnection practices to ensure that bulk system reliability is not inadvertently impacted with the proliferation of distributed energy resources (DER). This project will provide an analytical basis for reconciling distribution system and bulk power system needs for high penetrations of distributed resources. Further, the project will provide substantive evaluations for determining whether high levels of distributed resources may require new bulk system network design practices, and whether NERC registry criteria may need to be broadened to include smaller generators not covered by the current registry criteria. How to Apply Results The project s analytical results and resulting operating and planning guidelines should be disseminated through each company s operations, planning, and standards functions to ensure that appropriate processes are developed as emerging distributed resources become more broadly integrated. In addition to the information made available through project reports, workshops will be held to ensure that results are understood and incorporated into each functional practice area. Finally, EPRI staff will continue to coordinate and lead industry efforts such as the NERC IVGTF work group to ensure that project participant inputs and interests are integrated into various industry standards-development processes Products Product Title & Description Evaluation of Potential Bulk System Reliability Impacts of Distributed Resources and Potential Mitigating Strategies Update Planned Completion Date 12/31/11 Product Type Technical Update Bulk Power System Integration of Variable Generation - Program 173 p. 8