Bulk Power System Integration of Variable Generation - Program 173

Program Description Program Overview Environmentally driven regulations such as state-mandated renewable energy standards and federal air and water standards, along with improved economic viability for wind and solar generation, have resulted in the increased implementation of renewable energy. Much of the estimated development of renewables comprises variable resources such as wind generation and solar photovoltaics (PV), which, when integrated with the grid, create many new challenges for maintaining reliable system operation. Future projections are that a more significant build-out of these variable renewable resources is likely. With these developments, power system planners and operators require new tools and resources to ensure a reliable, secure, and cost-effective supply of electricity to consumers. New tools needed include improved and/or new sources of system flexibility to respond to and accommodate the increase in energy variability and uncertainty, the development of additional transmission infrastructure to deliver energy from remote locations, and planning and operational methods and software to effectively build and use these new resources. EPRI s Bulk Power System Integration of Variable Generation (VG) research program addresses these needs. Research Value The Bulk Power System Variable Generation Integration research program provides variable generation integration analytics; development of planning and protection methods, tools, and models; and development of operator methods and tools to reliably and economically integrate wind and solar PV generation. This is accomplished through a collaborative process wherein EPRI works hand-in-hand with its utility and independent system operator (ISO) members to identify existing research gaps and associated project needs that would provide value to EPRI members. Once identified, the EPRI Bulk Variable Generation Integration team of technical and project management experts works with members and the world s foremost experts in related research areas to structure and conduct specific projects that creates value by delivering a combination of products that provide value in the near-term, mid-term, and long-term. Finally, this value is transferred to members through collaborative advisory and task force interactions, workshops and webcasts, and companyspecific applications and demonstrations of the developed methods and tools. EPRI's Bulk Power System Variable Generation Integration research program delivers value by using the shared experiences and understanding of EPRI's utility and ISO members in conjunction with the expertise of EPRI's staff and network of contractors to conduct research projects that lead to actual methods and tools used by system planners and operators responding to the challenges of high penetrations of VG. EPRI also engages with external industry standards, regulatory, and research efforts to ensure that the EPRI research program is taking advantage of broader industry efforts and advancing the state of the art. For example, EPRI staff serves on the leadership group of the North American Electric Reliability Corporation (NERC) Integrating Variable Generation Task Force (IVGTF), ensuring that members' perspectives are incorporated into the activities of such groups and that EPRI research is designed to help members respond to the requirements that emerge from such efforts. EPRI's research program also strives to give members near-term, mid-term, and long-term value. For example, the 2014 Bulk System Variable Generation Integration research program will continue efforts to validate existing generic wind generation dynamic models that are being used for interconnection and planning studies today, while conducting research to develop operator tools that will suggest generation re-dispatch and/or transmission network reconfiguration solutions to post-contingency or variability events. 1

2 Electric Power Research Institute Portfolio 2014 Accomplishments The Bulk Power System Integration of Variable Generation program is a relatively new program at EPRI, having begun in 2010, but it has already provided significant industry leadership and helped create a number of valuable reports and tools: Generic Models and Model Validation for Wind and Solar PV Generation (1021763, 1025475): These reports describe the recommended generic wind turbine dynamic models develop through industry efforts with significant leadership from EPRI, as well as the related model validation efforts conducted by EPRI. This work has already resulted in the inclusion of improved generic models in existing commercial dynamic stability software packages. Wind Turbine Generator Model Validation Software Tool (WTGMV) Version 1.0 (1024346): This software tool takes wind turbine disturbance response measurement data as an input and provides for automated validation of the associated dynamic model or provides optimized model parameter values to obtain a validated model. Evaluation of Potential Bulk System Reliability Impacts of Distributed Resources (1024349): This report describes the potential bulk system reliability issues that may be expected with increased penetration of distributed energy resources (DER), and illustrates modeling of the potential impacts of one of these issues low-voltage disconnection of DER on the bulk system using a case study example. Stochastic Optimal Power Flow for Reserve Determination (1024348): This software report describes a stochastic optimal-power-flow-based algorithm for determining the optimal operating reserves to be carried for near-term future periods considering wind/pv forecast uncertainty and other system uncertainties. The report also describes the first application of the method with a participating ISO. Wind and PV Generation Probabilistic Model for Planning Studies (1024347): This report describes the 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. This program also provides continued interaction and representation of member interests through the NERC Integration of Variable Generation Task Force (IVGTF) leadership team and the Utility Variable Generation Integration Group (UVIG). Current Year Activities In 2014, EPRI's Bulk System Variable Generation Integration research program will offer its members a focused research portfolio with the following objectives: Develop and validate wind generation and solar PV dynamic models for system planning studies and develop automated validation tools to enable members to validate their own models. Develop methods and tools to probabilistically represent wind and PV output relative to load, capturing their inherent variability and uncertainty, to support risk-based transmission planning and other advanced analytical methods. Develop models that adequately represent the short-circuit response of wind and solar PV generators, and evaluate the implications of high levels of these resources on existing protection schemes, devices, and associated relay settings. Develop methods and tools to determine operating reserve requirements for high levels of variable generation, with consideration of all other system uncertainties. Promote new and improved wind and solar PV forecasting methods by demonstrating the integration of new and existing forecasts into specific utility/iso operational functions, and validation of the value derived from the forecasts. Develop methods, models, and tools for adequately assessing the impacts of high levels of inverterbased, variable, and uncertain wind and PV generation on system voltage and frequency performance, and evaluate methods for mitigating these impacts. Estimated 2014 Program Funding 2.0M

3 Electric Power Research Institute Portfolio 2014 Program Manager Daniel Brooks, 865-218-8040, dbrooks@epri.com Summary of Projects PS173A System Planning Methods, Tools, and Analytics (072093) Project Set Description This project set focuses on developing methods and tools for supporting resource adequacy and transmission planning for systems that must accommodate the variability and uncertainty of high levels of variable generation such as wind and solar PV. Planners for these systems need validated models of these new technologies and system planning/analysis platforms that use these models while representing the uncertainty of output from variable resources over time. This project set includes research to provide these new models, tools, and methods. Project Number Project Title Description P173.003 Model Development and Validation This project intends to develop a model validation tool for producing generic nonproprietary models of wind turbine and solar photovoltaic generation. P173.006 Probabilistic Planning This project develops methods and tools that allow transmission planners to incorporate and consider the added variability and uncertainty of VG when evaluating system reliability and facility upgrades that will be required to support future generation and load requirements. P173.009 Impact of Renewables on System Protection This project will address technical issues faced by protection and planning engineers when performing protection-related studies on systems with high penetrations of renewable energy resources. P173.003 Model Development and Validation (067489) Description Many states have already passed renewable energy requirements, and there is still the prospect of federal requirements. 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 integrated 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 the way in which these devices respond to voltage and frequency variations in the power grid. In 2012, EPRI collaborated with the Western Electricity Coordinating Council (WECC), International Electrotechnical Commission (IEC), Institute of Electrical and Electronics Engineers (IEEE), and other industry groups to finalize the development of model specifications for the second generation of generic wind turbine generator (WTG) models, particularly of types 3 and 4. In addition, through non-disclosure agreements with several WTG manufacturers, EPRI obtained measured WTG response data that contributed to model validation using these newly developed models. Lastly, a new simple model validation tool, the Wind Turbine Generator Model Validation (WTGMV) tool, was developed and released.

4 Electric Power Research Institute Portfolio 2014 Work was also done on developing PV models. In 2013, model validation efforts for both wind and PV models continued, with the main goals of obtaining measured response data at the point of interconnect of wind power plants and utility-scale PV plants, and exploring ways of performing model validation for the entire aggregate plant model. In 2014, EPRI will incorporate the new plant-level validation methods into a new release of the WTGMV tool. Additionally, the WTGMV tool will be extended to include validation and parameter derivation for PV models. Research in 2014 will build on the 2012-2013 methods, models, and tools to continue the model validation effort related to wind generation by attempting to obtain measured response data at the point of interconnect for wind power plants, and extending the validation methods and WGMVT to utility-scale PV plants. The scope of the validation capability will be extended to explore ways of performing model validation for the entire aggregate plant model. If this work is successful, the new plant-level integration approach for both wind and PV will be incorporated into the next release of the WTGMV tool. This work will be done in collaboration with the WECC Renewable Energy Modeling Task Force, the IEC, and other industry groups to ensure industry-wide acceptance and access to multiple potential sources of data. Impact This work will publicly disseminate models and a tool to facilitate model validation for generic wind turbine and photovoltaic generation models. Validated dynamic models of wind and PV will lead to increased system security and more efficient use of new and existing transmission assets. How to Apply Results The model development results have been disseminated through public forums (for example, WECC) to facilitate the adoption of the newly developed models by commercial power system simulation software vendors. These software vendors are aiming to have the models available in 2013 for use by planners. Subsequent model developments that may be approved based on the plant-level validation work in 2014 will be similarly shared and delivered through the existing commercial tool vendors. The WGMVT model validation tool has an associated manual, together with a tutorial, to instruct users as to how the tool can and should be used with disturbance response data to derive validated dynamic models. While generator owners bear the responsibility of providing validated models to the planning authority, the MGMVT provides the capability for planners to assess the validity of the models provided and suggest changes that may be needed given that wind and PV owners often do not have sufficient understanding of power system dynamics to develop sufficient models themselves. 2014 Products Product Title & Description Technical Update on Generic Wind and Solar PV model development and validation Planned Completion Date 12/31/14 Product Type Technical Update Wind Turbine Generator and PV Model Validation Tool Version 2.0 12/31/14 Software

5 Electric Power Research Institute Portfolio 2014 P173.006 Probabilistic Planning (069256) Description The past decade has seen a significant increase in the levels of variable generation (predominantly wind and solar PV), and the coming decades are expected to see further increases due to a range of regulatory, policy and economic drivers. At the same time, global interest in the smart grid has accelerated, with an increasing number of smart meters that will likely lead the way for smart grid deployments and demand response. The proliferation of high levels of variable generation and demand response will require grid planners to incorporate much higher levels of variability and 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. The objective of this project is to develop the necessary tools and methods to characterize the variability and uncertainty of wind and PV relative to the variability and uncertainty of load for consideration in risk-based planning approaches and other advanced planning and operations analysis methods. Research in 2014 will utilize work performed in 2012 and 2013 to develop methods and tools for generating Composite Load/Wind/PV Levels (CLL) with associated probabilities from chronological time-series wind, PV, and load data. Further characterization of the variable energy resources and controllable loads will be investigated to look for improvements in the CLL tool that is to be delivered in 2013. In addition, other variability and uncertainty characteristics of wind and PV and controllable loads will be evaluated with respect to their impact on transmission planning and operations. Such considerations are expecting to include the energy-limited nature of demand response, specific aspects of distributed PV to consider, and the non-gaussian nature of variable generation. Aspects of these deemed influential will be considered for incorporation into various methods and tools being developed in other EPRI Grid Operations and Planning projects, many of which need characterization of variable generation and controllable load in a form that can be used by the relevant tools. Examples include the following: A CLL tool from this project for deriving probabilistic representation of wind, PV, and load levels for inclusion in risk-based transmission planning tools such as the TransCARE tool that is utilized in Project 40.022 The Optimal Reserve Determination method and tool from Project 173.005, which requires information on the stochastic nature of wind and PV The System Flexibility Screening Tool and methods from Project 40.019, which looks to determine how demand response can contribute as a flexible resource. Impact Transmission planners are tasked with 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 the added uncertainty when evaluating system reliability and facility upgrades that will be required to support future generation and load requirements. By representing the uncertainties related to variable generation and demand response, planners will be able to efficiently plan system upgrades and avoid intentional overbuild solely for the purpose of providing planning margins to cover these known uncertainties. How to Apply Results Planners and operators will be able to utilize the documented methods to understand how to probabilistically represent wind and PV output with load incorporating the inherent uncertainties and correlation between them. The tools and methods developed can be integrated into members planning procedures to ensure that the uncertainty associated with variable generation and demand response is rigorously represented. Webcasts will be held regularly to engage members in research efforts and facilitate information sharing.

6 Electric Power Research Institute Portfolio 2014 2014 Products Product Title & Description Characterization of the probabilistic nature of variable generation and demand response: This technical update reports on findings from the research and model development to characterize variable generation and demand response for multiple planning applications. The focus is on characterizing new resources such that they can be considered in a wide range of planning and operational contexts. Planned Completion Date 12/31/14 Product Type Technical Update P173.009 Impact of Renewables on System Protection (073570) Description As the penetration of renewable energy resources into the transmission grid increases, the impact of renewables on the protection of the system is becoming a challenging topic for protection and planning engineers. Under fault conditions, the power electronics associated with converter-interfaced wind turbine generators (WTGs) and photovoltaics (PV) can produce current waveform signatures that are significantly different than those of traditional synchronous or asynchronous generators. Traditional short-circuit modeling techniques and the associated models in commercially available packages are not accurate enough and do not accurately represent the behavior of renewable energy resources during short-circuit events. As a result, protection and system planning engineers are required to make judgments based on limited information about the short-circuit behavior of these devices. The primary objectives of this research project are to develop accurate short-circuit models for renewable energy resources, and evaluate the impact of renewable energy resources on system protection. New learning will result from an improved understanding of how these devices affect system protection and improved short-circuit models for system studies. This project will address the technical issues faced by protection and planning engineers when analyzing systems with high-penetration renewable energy resources. Improved short-circuit models of converterinterfaced renewable energy resources will be developed to help protection and planning engineers conduct protection-related studies such as relay setting, protection coordination, and circuit breaker duty analysis. Impact This research will contribute to the reliable operation of systems with existing renewable resources by providing tools and guidelines protection engineers need to reevaluate the protection schemes of their system, and contribute to the performance of more accurate planning studies for assessing the integration of new renewables in the system. How to Apply Results The guidelines, methodologies, and models developed through this project are expected to help members perform short-circuit analysis of bulk power systems with large penetrations of wind and/or photovoltaic generation, as well as determine protection settings to maintain appropriate protection and coordination margins. Once validated, the developed short-circuit models will be shared with commercial software vendors to ensure that they are incorporated into the tools members use to conduct protection studies.

7 Electric Power Research Institute Portfolio 2014 2014 Products Product Title & Description Impact of Renewable Energy Resources on System Protection: As the percentage integration of renewable energy resources into the transmission grid is continuously increasing, the impact of renewables on the protection of the system is becoming a challenging topic for protection and planning engineers. Under fault conditions, the power electronics associated with converter interfaced wind turbine generators (WTGs) and photovoltaics (PVs) can produce current waveform signatures that are significantly different from those of traditional synchronous or asynchronous generators. Traditional short-circuit modeling techniques and the associated models existing in commercially available packages are not accurate enough and do not accurately represent the behavior of renewable energy resources during short-circuit events. As a result, protection and system planning engineers are required to make judgments based on limited information about the short circuit behavior of these devices. This project will address the technical issues faced by protection and planning engineers when analyzing systems with high-penetration renewable energy resources. Improved short-circuit models of converter interfaced renewable energy resources will be developed to help protection and planning engineers conduct protection related studies such as relay setting, protection coordination and circuit breaker duty analysis. Planned Completion Date Product Type 12/15/14 Technical Report PS173B System Operations Methods, Tools, and Analytics (072095) Project Set Description This project set focuses on developing methods and tools to use in the operational planning time frame. These include decision support to allow operators to more reliably and efficiently schedule resources to meet demand, improve frequency control, understand the possible transmission impact of baseload generation cycling, and to integrate variable resource forecasting. Project Number Project Title Description P173.005 Optimal Reserve Determination and Security Constraint Optimum Power Flow P173.010 PV and Wind Forecasting Integrated into Operations P173.011 Voltage and Frequency Performance with High Levels of Variable Generation This project develops methods and tools that allow operators to more reliably and efficiently schedule resources to meet demand while maintaining adequate reserves in the operational planning time frame, and to provide dispatch decision support and methods for improved frequency control in real-time operations. This project will perform research in areas related to variable generation forecasting and its integration into system operations. It will also provide technology watch in this area, which will be of increasing importance with high penetrations of VG. By identifying and focusing on key areas that show the most promise for improving system operations, better usage of existing and new forecasts can be obtained. The project will examine voltage and frequency performance under high variable generation penetrations. Models, metrics and methods to assess the impact of renewables will be examined and, if necessary, developed. Case studies will utilize these results to demonstrate the impacts of high renewables penetration. The capabilities of wind and PV to contribute to system voltage and frequency performance under different assumptions of generator performance will be assessed.

8 Electric Power Research Institute Portfolio 2014 P173.005 Optimal Reserve Determination and Security Constraint Optimum Power Flow (069255) Description The variability and uncertainty associated with variable renewable generation such as wind and solar photovoltaics (PV) can have a significant impact on system performance and market operation as penetration levels increase. Specifically, variability and uncertainty make it much more challenging for system operators to schedule the most economical set of resources to meet system requirements and determine operating reserve requirements to ensure reliability. Consequently, new operational scheduling and control methods and tools are needed to ensure reliable system operation in the most efficient and economical manner. A stochastic optimal power flow (OPF) application has been developed that can improve generator scheduling and reserve determination by including the stochastic nature of wind and load when scheduling a system. This type of application results in a schedule that is more robust to changes in wind and load and reduces total expected costs. In 2014, EPRI will continue to develop the stochastic OPF Reserve Determination and Rapid Redispatch applications with utility case studies. These case studies are an important part of devising practical implementations and technology transfer. Prior work in this project through 2013 has provided development of two operations applications: Reserve Determination/Validation: Assesses existing reserve schedules to ensure that they are adequate. Rapid Redispatch: Rapidly determines optimal dispatches to respond to random forecast errors and contingencies. In 2014, EPRI will emphasize demonstrating these applications with prototype tools at scale, so that they can be used on operators and schedulers' desks. EPRI will collaborate with commercial EMS vendors to ensure that tool prototyping is coordinated in a way that allows the results to be used by vendors developing commercial tools that integrate with utility and independent system operator (ISO) EMS products. 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. Power system operators and operational planners will have new capabilities to reduce the expected costs of providing operating reserves over time. How to Apply Results Participants will be able to apply information from technical reports and implement recommendations for Reserve Validation and Rapid Redispatch applications. Members will also have the opportunity to participate in a supplemental project to demonstrate these tools on their specific system. In addition, EPRI will coordinate with EMS vendors and project participants to develop and test developed prototype tools or modified system algorithms.

9 Electric Power Research Institute Portfolio 2014 2014 Products Product Title & Description Technical Advances and Practical Implementation of Stochastic Reserve Determination: The report is designed to help members realize the benefits of this technology in their own business processes through practical experience of working with member utilities through case studies of their actual power system and business processes. Members can use this report to create specifications for implementing Reserve Determination and Rapid Redispatch applications by preferred vendors. The report will include and reference the implemented case studies that can help verify implementations. Planned Completion Date 12/31/14 Product Type Technical Update P173.010 PV and Wind Forecasting Integrated into Operations (073571) Description As the penetration of variable generation increases on power systems in many areas, the challenges associated with operating systems with increased levels of variability and uncertainty will become more significant. One of the keys to reducing integration impacts for weather-driven renewable output (i.e., wind and PV) is better forecasting of variable output in day-ahead and shorter time scales. However, improved forecasting techniques in isolation, without appropriately integrating those forecasts into specific operational processes, do little to reduce the integration burden. Therefore, it is important to understand how improvements in forecast accuracy can benefit system operations and determine the best way to integrate forecasts into existing and future decision-making processes. This project will provide a technology watch of issues related to forecasting wind and solar PV as well as integration of forecasts into operations for various system operators. In addition, EPRI will target specific areas of high potential value to develop new metrics/standards for forecast accuracy, conduct research of advanced forecasting methods, and develop operational techniques for integrating the forecasts to improve reliability and reduce operating costs. This project will be closely coordinated with a related supplemental project in Program 173 on applying PV forecasting in distribution and transmission operations. That project will focus on case studies and demonstration projects showing the value of existing and new forecasting techniques and integration of these forecasting methods in operations. This project will focus on technology watch, best practices, targeted research areas (such as fleet forecasting of PV), and advanced techniques (such as stochastic methods). The joint outcome of the two projects will be a greater understanding of forecasting needs and value for system operations, together with improved methods and practices to integrate forecasting. Research in 2013 included interviews and a survey of utilities, ISOs, and forecasting vendors to outline the current state of forecasting to illustrate good examples of how forecasting is used in a variety of aspects of system operations and identify important future forecasting improvements and developments cited by both utilities/isos and forecasting vendors. The 2014 work will examine prioritized improvements relating to integrating forecasts identified in the 2013 work. It is expected that these may include forecast valuation and the possible usage of probabilistic forecasts. Impact This project will provide a platform that will allow different forecasting methods to be understood and compared. Methods will be developed to allow members to better understand how to use forecasts in their individual operational processes. Technology watch will allow a synthesis of developments throughout the industry to be put in context. Working with vendors, new techniques can be explored, and the value of using them quantified. Aggregate forecasts of wind and PV will be developed to better integrate both of these resources.

10 Electric Power Research Institute Portfolio 2014 How to Apply Results Results will be applied in numerous ways: The technology watch can be used to make better decisions in terms of choosing forecasting vendors and understanding how forecasting best fits into various operations functions. Developed forecast valuation analysis will provide a basis for determining the key decision-making processes that can be improved through better forecasting, and the costs that can be justified to do so. Existing real-time operations and operations planning functions will be examined to identify areas where existing processes might be changed to better integrate forecasts to improve overall system reliability and economics. 2014 Products Product Title & Description Integration of variable generation forecasts into system operations: This update will describe research completed in this project in 2014. This includes the results from analysis of the value of forecasting in multiple applications, metrics developed to assess accuracy in terms of system integration and insights and lessons learned from research into the use of aggregated PV and wind forecasts and probabilistic forecasts. Planned Completion Date 12/31/14 Product Type Technical Update P173.011 Voltage and Frequency Performance with High Levels of Variable Generation () Description Increasing levels of variable generation, particularly wind and solar PV, present various operational challenges including maintaining system voltage and frequency performance with high penetrations of these mostly inverter-connected, variable, and uncertain resources. Much work in the past decade has shown that the non-synchronous nature of most wind and all PV generation could have significant impacts on bulk system reliability if not properly accounted for in system planning and operation. This includes impacts on frequency response due to displacement of conventional resources of frequency response, and impacts on steady-state and transient voltage stability. Of particular concern is the current growth in distributed energy resources (DER), the vast majority of which are distributed rooftop and small-scale PV. These distributed resources, if not well understood, could have serious implications for bulk system stability. This project will examine potential system voltage and frequency impacts of high penetrations of renewable resources on the bulk system, develop mitigating strategies, and evaluate new technologies and resources to support those strategies. This project will incorporate research conducted over the past two years by two other EPRI projects: the 2012 project titled "Bulk System Reliability Impacts of Distributed Energy Resources" (P173.007), and the 2012 2013 project titled "Frequency Response Adequacy" (P40.020). Those projects analyzed voltage performance with high levels of PV and frequency performance with high levels of wind, respectively. The 2014 research in this project will build upon that work, focusing on: Performing case studies to further assess impact and mitigation approaches. Case studies will allow demonstration of the possible impacts and the benefits of certain mitigating strategies. These can come in the form of interconnection requirements or grid codes, new market services, operational protocols, etc. The project will examine how different mitigating strategies can be utilized, and determine the costs and benefits of each.

11 Electric Power Research Institute Portfolio 2014 Evaluating existing simulation models and tools for assessing these impacts. The use of new tools that better model issues such as frequency response and frequency regulation over several seconds to hours will be evaluated. New modeling techniques such as this will be investigated to ensure they are meeting end-users' goals; if required, additional modeling capabilities may be developed, either by EPRI or working with vendors. Evaluating potential new resources for supporting system voltage and frequency response. While the characteristics of wind and PV offer some challenges, the power electronics by which these technologies interconnect to the grid may be controlled in a way to utilize them for supporting system frequency and voltage. This potential, and the potential of other emerging resources to contribute to frequency and voltage performance, will be assessed. Impact Improve understanding of the requirements for ensuring voltage and frequency performance, including the requirements for interconnection standards. Improve reliability from the consideration of frequency response metrics and requirements. Increase understanding of the impacts of and mitigation strategies for distributed energy resources. Reduce operating costs by utilizing the most economical resources to provide frequency response at interconnection and Balancing Authority levels. Improve operational protocols with high levels of renewable generation. How to Apply Results Members can use this project's technical report as a reference to analyze system events to assess the voltage and frequency performance of the bulk power system and to identify resources requirements (e.g., operating reserves or reactive power provision from distributed PV) for adequate primary and secondary frequency responses as well as steady-state and transient voltage stability. 2014 Products Product Title & Description Voltage and frequency performance: case studies and lessons learned: This technical update will describe the work done in the first year of this project. This builds on previous work, as well as existing industry efforts, and will examine some of the key aspects identified at the start of the project. This includes possible model, metric or method development, as well as focused case studies to analyze impacts and mitigating strategies. Planned Completion Date 12/31/14 Product Type Technical Update

12 Electric Power Research Institute Portfolio 2014 Supplemental Projects Solar Forecasting in Transmission and Distribution Applications (073495) Background, Objectives, and New Learning As the penetration of solar photovoltaic (PV) at both distributed and utility scale increases in many areas, the challenges associated with integrating this resource intermittent resource will increase. One of the key elements needed by system operators is accurate forecasts that can help them manage operations. While wind forecasting is a well-understood technology, solar forecasting is yet to be as extensively developed and understood. This project will concentrate on developing and applying solar forecasts into utility/independent system operator (ISO) operations at both distribution and transmission levels, to enable better integration of these resources. Solar forecasting in particular, fleet forecasting for large amounts of distributed rooftop PV will be developed and validated against real data for accuracy, allowing improvement in forecasting techniques. Multiple case studies will be conducted to demonstrate and quantify the value of forecasts in terms of costs and reliability. This will allow a greater understanding of the benefits of improved forecasting. This project also aims to improve the integration of forecasting into the different operational decision making processes (e.g., unit commitment, economic dispatch, reserve deployment, distribution operations) to maximize the benefits from forecasts. Finally, the project will also examine the use of more advanced techniques, either in operational decision making or in forecasting methods, and demonstrate the benefits of these to different systems. Comparing across the multiple case studies will allow a greater understanding of the value of forecasting for different systems and the different methods that can be used to deploy forecasts and demonstrate best practices for usage of forecasting in system operations. Project and Summary This project will focus on case studies that investigate numerous aspects of the issue of integration of solar PV forecasting. The work will be closely coordinated with the Program 173 base research and development (R&D) project on wind and PV forecasting. That project will focus on technology watch, best practices, targeted research areas, and advanced techniques (such as stochastic methods). This project will focus on application of new learnings from the base research project, as well as demonstration of existing and new forecasting techniques, with a particular focus on working with different types of participants (ISOs, transmission operations, distribution operations) to show the value of existing and newly developed forecasting methods. The joint outcome of the two projects can lead to a broad understanding of forecasting needs for system operations, together with improved methods to integrate VG forecasting and demonstration of the value of doing so. This project will consist of multiple case studies. The focus for each case study will vary depending on the specific utility/iso needed; the general tasks will be chosen from the scope of work outlined below. This focus of each case study will be determined working with individual utility case study partners based on their needs and system specifics. If possible, joint case studies consisting of transmission and distribution entities (or transmission and distribution groups in a utility with both), as well as the associated ISO (if applicable) will allow a more thorough investigation of the major issues and a more complete case study. In addition to the specific case results that will be provided to each case study utility, general findings will be coalesced from the case studies comprised by the collaborative effort into a guideline for best practices for integration of solar forecasts into system operations. Utilities and ISOs will be able to sign up for this project and elect not to participate as a case study for a reduced price, and obtain only the sanitized shared results.

13 Electric Power Research Institute Portfolio 2014 Benefits This project will provide members with a greater understanding of the value of solar forecasting and the benefits of improved forecasting. Additionally, by identifying the key areas where forecasts are used, and then working with forecasting vendors, forecasts can be better targeted and designed for those decision making processes that are of most value. Thus the economic and reliability value of forecasts can be identified for different case studies, and this can be used to better integrate forecasting into decision making. The benefit of collaborative research in this project will be that knowledge will be shared by all participants, and the results will be applicable to the individual case study entities. Lessons learned and contrasting results from different case studies, together with the value of forecasts in different system operation functions, will be compiled and shared to allow a greater understanding of the value that forecasting brings and the benefits achievable from new forecasting methods. The reasons behind different results and experiences will also be examined.