by Shay Bahramirad and Joseph Svachula, ComEd; Amin Khodaei, University of Denver; and Julio Romero Aguero, Quanta Technology
Greater Chicago electric utility Commonwealth Edison (ComEd) recently won a Department of Energy (DOE) grant to develop an advanced microgrid controller with applications to community microgrids.
These microgrids are much more than backup generation for residential customers. A microgrid is “a group of interconnected loads and Distributed Energy Resources (DERs) with clearly defined electrical boundaries that acts as a single controllable entity with respect to the grid,” according to the DOE.
ComEd will lead a select group of power and energy industry authorities from universities, national labs, manufacturers, consulting firms and software developers in this effort. ComEd will gain invaluable experience in transforming traditional electricity supply and delivery plus firsthand knowledge on future integrated grids. The experience also will pave the way for other utilities to adopt new business models and embrace anticipated changes in utility operations.
DERs consist of distributed generation and distributed energy storage (DES) installed at utility facilities, e.g., distribution substations, distributed generation sites or consumer premises. Microgrids may be operated in two modes:
1. Interconnected to the grid. Under this mode, a microgrid can import, export or have zero power exchange with the grid. This type of operation generally is designed for normal conditions (no system contingencies). Its objective is to improve grid performance and efficiency by using local DERs, e.g., to defer capacity investments, reduce system losses, improve local reliability, etc.
2. Disconnected from the grid. Under this mode, a microgrid is allowed to operate islanded from the grid, also known as intentional islanding. This type of operation requires the DERs within the microgrid to be dispatched in a coordinated fashion to provide voltage and frequency regulation. Successful islanded operation also may entail the implementation of energy demand management, e.g., demand response or curtailment, to achieve generation-load balance. This type of operation generally is intended to provide service to remote locations-permanent islanded operation-or to provide continuous supply during contingencies-temporary islanded operation. In the latter case, the microgrid is expected to return to interconnected operation after the contingency has been addressed.
Application to Communities
Community microgrids recently have emerged as an alternative to address the rising societal demands for electric infrastructures that can provide premium reliability and power quality levels while being economic and environmentally friendly. Studies on community microgrids, however, are limited although microgrids have been investigated extensively in literature. Most microgrid studies and development efforts are devoted to:
1. Campus microgrids because of the availability of research funding and internal expertise in engineering and science;
2. Remote microgrids because they offer a more efficient and viable solution to provide electric service than upgrading or building transmission and distribution facilities; and
3. Military microgrids because of Department of Defense support and viability in providing self-sustaining small power grids that are required to address the mission-critical energy needs of military bases.
Lacking are detailed studies on design and development of community microgrids and extensive discussions of value propositions of the viable technology.
Significance, Benefits, Challenges
Community microgrids are emerging as a potential solution to address the following trends:
1. Residential consumers, who use more than one-third of the electric energy produced in the U.S., according to EPRI, are demanding better reliability and power quality;
2. Utility grids are experiencing unprecedented intermittent renewable distributed generation motivated by attractive incentives and regulations designed to address socioeconomic and environmental concerns;
3. Commercial and industrial consumers’ needs for high reliability and premium quality power are growing because they may possess sensitive loads; and
4. Society is demanding more resilient power delivery infrastructures because of growing dependence on electric service for vital activities such as transportation, e.g., the emergence of plug-in electric vehicles, and the well-documented grid vulnerability issues exposed by recent natural disasters such as Superstorm Sandy.
Community microgrids introduce opportunities for consumers and the operation and planning of the power system, including:
1. Improved reliability by introducing self-healing at the local distribution network;
2. Improved resiliency by offering capability to withstand low-probability, high-impact events and quickly returning to normal operating state;
3. Emission reduction by the diversification of energy sources;
4. Reduced costs of recurring system upgrades by deferring investments on new transmission and distribution facilities;
5. Enhanced energy efficiency by reducing transmission and distribution losses and allowing the implementation of optimal load control and resource dispatch;
6. Higher power quality by enabling local control of frequency, voltage, load and the rapid response from DES; and
7. The potential to reduce energy costs by using distributed generation technologies with dropping prices.
The transition from the conventional utility grid to smart community microgrids and the enhanced use of DER and controllable loads are anticipated to change extensively how communities use electricity.
Several major obstacles, however, exist to achieving rapid, widespread deployment of community microgrids:
High capital cost. Yes, microgrids require significant upfront investments, but they are essential and bring value beyond what is measured by the economic metrics used today. Microgrid developers must convince consumers that microgrid benefits exceed the capital costs. Microgrid benefits must be scrutinized and compared with the microgrid capital cost for ensuring a complete return on investment and justifying microgrid deployment. Accurately assessing microgrid economic benefits is challenging because of significant data uncertainty. Some of the assessment results, such as reliability or resiliency improvements, are difficult for consumers to understand when represented in supply availability terms.
Lack of consumer knowledge. The second obstacle is the lack of consumer knowledge on potential impacts of distributed generation and load scheduling strategies, which will persist as long as consumers lack keen knowledge of load scheduling strategies or are unwilling to contribute in energy management efforts in microgrids.
This obstacle could be eliminated by educating microgrid consumers about anticipated benefits. The financial incentives offered to consumers, who would consider load scheduling strategies, is the most powerful driver for performing load scheduling.
Smart metering, advanced devices and building management systems are reducing this barrier.
Ownership and regulatory framework. Several regulatory aspects remain unresolved, including microgrid ownership, third-party generation participation, investment recovery and inclusion in utility rate cases. Changes in the regulatory framework are required to drive this resiliency effort.
As these challenges are addressed, more widespread deployment of community microgrids will occur to the point that smart communities might act as a core component of future power systems.
Community microgrids could be viable solutions to challenges of economy, reliability and environment while providing unprecedented benefits for local consumers and the whole power system.
Community microgrids leverage the existing utility distribution infrastructure, thus the utility must play an active role to ensure microgrids realize their maximum value and deliver all proposed benefits.
Community microgrids would be built upon the existing utility distribution network and would not be successful unless fully implemented and adopted by utilities.
As this technology becomes more viable and advantageous, more utility involvement would be needed to ensure sustainable deployment to the point that utilities could ensure benefits and promote community microgrids.
ComEd is pushing power innovation by leading efforts to implement and design community microgrids.
Shay Bahramirad, Ph.D., is manager of smart grid and technology at ComEd where she leads the microgrid and smart city effort. She is an adjunct professor at Illinois Institute of Technology and technical chair of the 2014 and 2016 IEEE PES T&D Expo.
Amin Khodaei, Ph.D., is an assistant professor in the Department of Electrical and Computer Engineering at University of Denver. He is technical chair of the 2016 IEEE PES T&D Expo in Dallas.
Joseph Svachula is vice president of engineering and smart grid at ComEd. He was co-chair of the 2014 IEEE PES T&D Expo in Chicago.
Julio Romero Aguero, Ph.D., is senior director of distribution and executive advisor at Quanta Technology. He is vice chair of the IEEE distribution subcommittee and editor of IEEE Transactions on Smart Grid and Power Delivery.
The opinions expressed are solely of the authors and do not necessarily reflect the positions or opinions of any entity or organization with which the authors may be affiliated.
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