Microgrids in the 21st century power system

Microgrids are seen as a fundamental building block of the emerging power system architecture.
Published: Wed 19 Oct 2016

Microgrids are fast evolving from essentially a standby power system in case of an outage for an individual consumer to an integral component of today’s power system. This is being enabled by the falling costs of solar and storage and their growth as distributed generation along with advances in control automation technology, which are opening the way for local aggregation and management in a decentralised system. [Engerati-New York Goes For Community Energy In A Big Way and Nice Grid - A Smart Solar District]

Microgrids can contribute to the integration of renewable energies and support energy security and grid resiliency, especially in extreme weather condition, with application in a wide variety of settings from off-grid locations to community initiatives and city centres. [Engerati-Microgrids – Key For Electrification and Microgrids, Microgrids, Microgrids]

In the most advanced market in the United States, such microgrids are still in the early stages of deployment. But current changes in the regulatory framework, for example in New York’s REV, are pointing towards a restructured distribution system in which portions of a utility’s service territory will be served by microgrids configured around locally sourced generation from distributed energy resources, under the control of a distribution system operator (DSO).

What then, are the perspectives and potential? According to a new white paper from the US National Electrical Manufacturers Association (NEMA), by 2025 fully controllable independent microgrids interconnected with DC links could allow for full decoupling from the AC electric power system and facilitate the segmentation of the distribution system - a new paradigm for electric grid management.

And it is especially prescient, comments consultant Jim Reilly, a consultant who is actively engaged with the standards development for microgrid controllers with the IEEE. "Intelligent control is paramount for microgrids becoming integrated into distribution systems, thus realizing their full benefits for the integration of renewables and reliability.”

The microgrid architecture

What is the route to this vision?

The complexity and configurations of microgrids will vary from one setting to another, depending on the energy requirements of the connected loads, but the constitutive components are similar, the white paper states. These include both dispatchable and non dispatchable generation, storage and critical and controllable loads.

At the heart is the microgrid controller, which combines hardware and software to manage the microgrid and its interaction with the utility grid in grid-connected or islanded modes. That and the associated energy management system with controls for power exchanges, generation, load, storage and demand response load management, is a high priority technology. In particular there is a need to reduce the cost of the installation of controllers and introduce more controllable equipment.

Regulation and standards

According to the white paper, regulatory issues are the overarching determinant of the role of the microgrid in the power delivery system. They are the single most important barrier to microgrid deployment, as both independent entities and as systems integrated within distribution utilities. Furthermore, the economics of the microgrid are greatly influenced by their participation in electricity and ancillary services markets.

Among the requirements is a microgrid regulatory framework to accommodate the interconnection and integration requirements of the DSO, so that they can adequately interact with and provide the ancillary service support to the distribution system.

In addition, coordinated and consistent electrical interconnection standards, communication standards and implementation guidelines are required to facilitate structured deployment of microgrids and their interaction with the distribution utility. Due to the infancy of the use of microgrid technologies, there are few standards that apply to microgrids as distinct, interconnected entities. Standards that match the unique characteristics of the microgrid are required. The ongoing IEEE and International Electrotechnical Commission (IEC) standardization activities related to DER and microgrids should help facilitate microgrid deployments and mitigate market barriers.

Barriers to microgrids

In addition to the regulatory and standards requirements, the white paper identifies several technology needs.

These include improvements and cost reductions in the current power electronic conversion and control technology, sensor and communication technology, protection and grid integration systems and generation from renewable energy resources electric storage systems.

New technology requirements pertain to DC power conversion, distribution systems, voltage and power flow control and protection relays and breakers.

Vision to 2030

To reach the 2025 vision the white paper presents a possible deployment scenario.

From 2016 onwards, grid-connected individual microgrids, utility-scale microgrids, and community-scale microgrids contribute to grid resilience and system efficiency through autonomous and islanded operation, system restoration services, participation in electricity energy and ancillary services markets and provision of premium power to critical loads.

From 2018 onwards, microgrids – owned and operated via an increasing number of business models and ownership structures – are able to interact with the DSO on a one-to-one basis and integrate with the distribution management system.

From 2020 onwards, multiple microgrids interacting together and with the grid will be justified based on their competitive economics and contributions to grid resilience and will require a secure and robust distribution system management controller. They will independently manage subsets of the distribution grid and facilitate a new approach to designing, operating, and managing distribution grids.

Further reading

NEMA: Powering Microgrids for the 21st-Century Electrical System

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