Two recent studies sponsored by the U.S. Department of Energy (DOE) and the National Renewable Energy Laboratory (NREL) have examined the impacts of integrating high penetrations of wind and solar energy on the Eastern and Western electric grids. The Eastern Wind Integration and Transmission Study (EWITS), initiated in 2007, examined the impact on power system operations of reaching 20% to 30% wind energy penetration in the Eastern Interconnection. The Western Wind and Solar Integration Study (WWSIS) examined the operational implications of adding up to 35% wind and solar energy penetration to the Western Interconnect. Both studies examined the costs of integrating variable renewable energy generation into the grid and transmission and operational changes that might be necessary to address higher penetrations of wind or solar generation. This paper identifies key insights from these regional studies for integrating high penetrations of renewables in the U.S. electric grid. The studies share a number of key findings, although in some instances the results vary due to differences in grid operations and markets, the geographic location of the renewables, and the need for transmission.

This book outlines the challenges that increasing amounts of renewable and distributed energy represent when integrated into established electricity grid infrastructures, offering a range of potential solutions that will support engineers, grid operators, system planners, utilities, and policymakers alike in their efforts to realize the vision of moving toward greener, more secure energy portfolios. Covering all major renewable sources, from wind and solar, to waste energy and hydropower, the authors highlight case studies of successful integration scenarios to demonstrate pathways toward overcoming the complexities created by variable and distributed generation.

Renewable Energy Integration for Bulk Power Systems: ERCOT and the Texas Interconnection looks at the practices and changes introduced in the Texas electric grid to facilitate renewable energy integration. It offers an informed perspective on solutions that have been successfully demonstrated, tested, and validated by the Electric Reliability Council of Texas (ERCOT) to meet the key challenges which engineers face in integrating increased levels of renewable resources into existing electric grids while maintaining reliability. Coverage includes renewable forecasting, ancillary services, and grid and market operations. Proved methods and their particular use scenarios, including wind, solar, and other resources like batteries and demand response, are also covered. The book focuses on a real-world context that will help practicing engineers, utility providers, and researchers understand the practical considerations for developing renewable integration solutions and inspire the future development of more innovative strategies and theoretical underpinnings.

The stability of the North American electric power grids under conditions of high penetrations of wind and solar is a significant concern and possible impediment to reaching renewable energy goals. The 33% wind and solar annual energy penetration considered in this study results in substantial changes to the characteristics of the bulk power system. This includes different power flow patterns, different commitment and dispatch of existing synchronous generation, and different dynamic behavior from wind and solar generation. The Western Wind and Solar Integration Study (WWSIS), sponsored by the U.S. Department of Energy, is one of the largest regional solar and wind integration studies to date. In multiple phases, it has explored different aspects of the question: Can we integrate large amounts of wind and solar energy into the electric power system of the West? The work reported here focused on the impact of low levels of synchronous generation on the transient stability performance in one part of the region in which wind generation has displaced synchronous thermal generation under highly stressed, weak system conditions. It is essentially an extension of WWSIS-3. Transient stability, the ability of the power system to maintain synchronism among all elements following disturbances, is a major constraint on operations in many grids, including the western U.S. and Texas systems. These constraints primarily concern the performance of the large-scale bulk power system. But grid-wide stability concerns with high penetrations of wind and solar are still not thoroughly understood. This work focuses on 'traditional' fundamental frequency stability issues, such as maintaining synchronism, frequency, and voltage. The objectives of this study are to better understand the implications of low levels of synchronous generation and a weak grid on overall system performance by: 1) Investigating the Western Interconnection under conditions of both high renewable generation (e.g., wind and solar) and low synchronous generation (e.g., significant coal power plant decommitment or retirement); and 2) Analyzing both the large-scale stability of the Western Interconnection and regional stability issues driven by more geographically dispersed renewable generation interacting with a transmission grid that evolved with large, central station plants at key nodes. As noted above, the work reported here is an extension of the research performed in WWSIS-3.

Americans' safety, productivity, comfort, and convenience depend on the reliable supply of electric power. The electric power system is a complex "cyber-physical" system composed of a network of millions of components spread out across the continent. These components are owned, operated, and regulated by thousands of different entities. Power system operators work hard to assure safe and reliable service, but large outages occasionally happen. Given the nature of the system, there is simply no way that outages can be completely avoided, no matter how much time and money is devoted to such an effort. The system's reliability and resilience can be improved but never made perfect. Thus, system owners, operators, and regulators must prioritize their investments based on potential benefits. Enhancing the Resilience of the Nation's Electricity System focuses on identifying, developing, and implementing strategies to increase the power system's resilience in the face of events that can cause large-area, long-duration outages: blackouts that extend over multiple service areas and last several days or longer. Resilience is not just about lessening the likelihood that these outages will occur. It is also about limiting the scope and impact of outages when they do occur, restoring power rapidly afterwards, and learning from these experiences to better deal with events in the future.