Thursday, July 31, 2014

The Integrated Grid: Addressing Core Questions and Challenges Facing the Industry

Nadav Enbar

Category: ,

The rise of distributed energy resources (DER) is prompting dramatic changes at the point of electricity consumption, often known as the “edge” of the power system. Amid this broad industry shift, utilities, system operators, and other stakeholders are increasingly being called upon to account for both the extent and timing of DER’s advantageous and adverse impacts at all levels of the network. EPRI’s research initiative, The Integrated Grid, aims to assist decision-makers in this endeavor by suggesting a process for harmonizing DER grid integration requirements with system planning and operations practices—one that also adheres to established standards of reliability and quality. Our approach considers the fundamentals of power system engineering and economics in an effort to ensure the optimal coexistence of DER and conventional grid assets.

With the intent of promoting ongoing discussion and knowledge share, the Integrated Grid Online Community represents a forum for considering the various questions and challenges facing the electricity industry that are germane to growing penetrations of DER on the electric system. Insights and discussion are intended to be organized along the following five organizing categories:


The broadest category, technologies essential to an integrated grid, includes not only mainstay distributed energy resources—such as photovoltaics (PV), fuel cells, and battery storage—but also other “edge” equipment that ranges from secondary voltage control to programmable thermostats. What features and creative new uses will be possible with these emerging technologies? How can these options be tested and verified in the field and laboratory? What is the impact of standards and codes on resource availability and effectiveness?


Within the existing framework of both basic infrastructures (poles, wires, and transformers) and advanced systems (such as automation or management systems), distribution systems are affected by the rapid growth of DER. How does DER impact traditional operational requirements, such as voltage regulation or the ability to clear faults? How can DER be combined with existing technologies on distribution systems, such as protective relaying and regulating transformers? EPRI and other stakeholders will address new analytical tools, such as DER hosting capacity, along with applications and guidelines for advanced equipment.

Bulk System

Although it is not at the “grid edge” by definition, bulk power flow remains a critical consideration for the health of the power system. With the growth of DER, fundamental needs of the system, such as resource adequacy or voltage performance, must be guaranteed under rapidly changing combinations of source and load. How much DER can be accommodated without making further infrastructure investment? Wind integration studies, which typically address bulk system concerns, and PV hosting capacity studies, which typically focus on distribution issues, attempt to assess this question. In both types of studies, the current physical infrastructure is assumed to be fixed while the distributed resource deployment is increased. This process continues until some planning or operational criteria are violated and the limit defined. Changes in grid planning and operation are open for discussion, whether it’s newly refined analytical methods for load-carrying capability or technical challenges like synthetic inertia.


Growth in DER presents both new opportunities and challenges for the traditional economic model under which energy generation and delivery is carried out. The costs and benefits of various investments fall under new categories and accrue to a new set of stakeholders. As a result, public, system-oriented studies, like those that consider the Value of Solar, are becoming common endeavors for utilities and consultants alike. What are the financial ramifications of new technology choices like DER? How is societal benefit or cost to be analyzed and represented in decision making?


DER’s rapid growth affects how business is conducted in the energy sector. Big questions continue to face decision-makers as they determine investment and operational strategies for utilities, developers, and end users. The impact of new regulations and portfolio standards on business approaches and the program design on DER adoption by individuals and businesses are critical areas of discussion. Will new stakeholder business models be created or modified under these new conditions? What is the impact of a growing uncertainty in both generation and load on utility strategy?

As we continue to build upon our discussions in the Integrated Grid Online Community, EPRI invites you to offer constructive feedback on the questions posed above as well as on our other discussion entries relative to these five thematic areas. Through our sharing of research and your input, we at EPRI hope to create a rich, informative experience that can keep pace with ever accelerating technology advances, regulatory change, and current events.

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