Transmission System Issues for Renewables
The successful integration of renewable resources requires supportive governmental policies, favorable economics, and the proper application of technology. Governmental policies often view renewable development in the broader context of societal good. Renewable resource development may diversify fuel supplies, positively affect the environment by improving air and water quality, and potentially develop local economies. Government policies establish locations for siting renewable resources and the transmission that may be necessary to successfully integrate those resources. These policies weigh the overall potential benefits against the societal costs of renewable integration and establish the rules that determine winners and losers of system expansion.
Regulatory frameworks for electric service can be very different across the world. Some of these electric service frameworks are subject to complete government ownership and control, others have vertically integrated and regulated power companies, and additional ones have some combination of electricity markets and transmission, which may consist of both regulated and merchant facilities. Across these regulatory frameworks, government policies often drive the economics of renewable development. The development and integration of renewable resources are promoted through governmental policies that are consistent over time, establish simple and swift infrastructure siting processes, and provide economic incentives to developers. Policies need to be coordinated across national, regional, subregional, and local governmental entities. All of these factors reduce risks and costs to investors, whether they are governmental agencies or competitors in a free market, because the policies identify who pays and who benefits from infrastructure development and when money changes hands.
The total system costs of new fossil plants and their associated transmission may be less expensive than renewable development due to the relatively high capital costs of wind, photovoltaic, and hydro facilities and the additional burden of transmission costs when re–newable supplies are remote from load centers. To achieve other societal benefits, governmental entities may influence economic decisions by providing subsidies and tax abatements for renewable resources and transmission development. The subsidization of renewable resources and transmission may provide other benefits, such as advancing technological development and improving reliable system performance.
When policies or economics collide with physics, physics always wins. Even so, engineering without respecting regulatory or economic constraints is not engineering. Renewable development has triggered the application of new technologies. Physical improvements to wind generators are sometimes being made faster than suitable models can be developed and made universally available to system planners and operators. Transmission technologies are advancing rapidly as shown by the widespread application of flexible alternating current transmission systems, the use of ultra-high-voltage technologies for both dc and ac facilities, and new methods of analysis that are improving the reliable and economical planning and operation of the power system.
In This Issue
The articles in this issue discuss the lessons learned for integrating renewable resources and build upon the November 2011 issue of IEEE Power & Energy Magazine. Governmental policies and frameworks for promoting renewable development are discussed for countries around the world. The issue also discusses some of the physical aspects for planning and operating systems with large amounts of intermittent renewable resources.
The regulatory framework for transmission planning policies con–tinues to evolve. As required by Order 1000 of the U.S. Federal Energy Regulatory Commission, U.S. transmission entities will be required to plan their system to address several interregional planning issues and to meet public policy objectives, many of which are likely to require planning for renewable resources. The article titled “Flexible Connections” describes several regulatory frameworks and the lessons learned. Feed-in tariffs, quota systems, and an auction system have been used to pay for new renewable resources and to determine needed transmission expansion projects. South America is addressing many of the common physical concerns for planning and operating intermittent resources. The need for coordinated development of renewable resources and required transmission is clear.
In China, the government has the ability to make and implement policy decisions rapidly and can build renewable projects and associated transmission development in extraordinarily short time frames. “By Leaps and Bounds” describes the large amounts of wind power already in service, the tremendous amounts of additional potential development, and the advanced transmission technologies being used to integrate renewable resource sites with distant load centers. New ultra-high-voltage dc and ac transmission facilities are being planned and built across the country. A key lesson is the need for timely planning that fully coordinates expected resource expansion with the transmission system improvements, which may lag desired in-service dates.
“Penetrating Insights” summarizes issues that must be addressed to successfully integrate large amounts of wind power and some of the physical solutions that may be applied. The article discusses the need for and implementation of low voltage ride through, reactive power and regulation, and multiplant control. The benefits of diversifying wind resource locations and having accurate forecasting are also discussed. The perspectives and experiences from Europe, China, and North America provide valuable lessons and show the need for a flexible system response.
Demand is emerging for offshore wind power, a technology often having favorable capacity factors and high capacity values as compared with onshore wind farms. Offshore wind farms, however, also present many challenges that can add costs for their design, construction, operation, and maintenance. “Twixt Land and Sea” discusses some of the considerations for improving the design of the collector system, the wind power plant, and the wind power plant integration into the mainland transmission system.
Online security analysis is required to establish secure operating limits that must consider thermal, voltage, and stability constraints. The calculation of these limits using near real-time information is a complex task further complicated when the system has many intermittent resources with variable and uncertain production. The online dynamic security assessment for the Irish power system is discussed in “Safety in Numbers.” The article discusses the measurements, modeling, computation, reporting and visualization, control, and other functions of the main modules of the dynamic online security assessment system.
The final article, “The Golden Spike,” discusses a business model and technological plans for a merchant transmission project that will have the ability to transfer power across three separate interconnections. Plans for the Tres Amigas project call for flexibly changing power transfers among the Western Interconnection, the Eastern Interconnection, and the Texas Interconnection based on energy price differences. The project plans include also having the ability to integrate with potential future solar and wind power in the area. Tres Amigas is a stage project, initially using voltage source converters and 345 kv gas insulated substation equipment and lines, with expansion options for using battery energy storage and line commutated converters.
I’m very grateful to ISO New England where I work with extraordinarily capable staff on exceptionally interesting projects. The ISO has been supportive of IEEE, my favorite volunteer organization that has provided me with outstanding professional development and a network of good friends across the globe. Thank you to the authors of this issue who have worked really hard and have readily shared their remarkable expertise. A particular thank you to Mel Olken, the editor of IEEE Power and Energy Magazine, a friend and mentor of almost 35 years who provided me with the opportunity of serving as a guest editor of this issue.