Micro Grid

Author: Laurent Schmitt, Alstom Grid, France

Microgrids are one of the key components of the Smart Grid and have been called ‘the impatient upstarts of our energy future’.  While many microgrids projects share important characteristics beyond the common microgrid name, there are equally important differences across the growing number of microgrids across the globe. The purpose of this article is to present several European microgrids, focusing on their relative roles with respect to each other and to the overall energy eco-system. This will provide insights to how microgrid may evolve.  We start with a brief overview of the basic. What’s and Why’s of microgrids.

Microgrids are a fundamental component in enabling today’s electricity grid modernization to address growing demand, distributed generation, and environmental pressures. Electricity grids will host “constellation of microgrids,” enabling peer to peer energy transactions between them through the new possibilities of state-of-the-art Information and Communication Technology (ICT). These new architectures are designed to maintain system-wide energy optimum through the coordination of distributed microgrid optima.

Electricity companies have always done this to some extent. Traditionally communication was aone-way process and limited to connections with a reduced number of dispatchable generating points on wholesale/high voltage grid connections. Most of the consumption-end has historically been forecasted and considered as passive reconciled financially through meter readings happening a few months after the facts. Distribution operators had limited access to real-time meter information from their consumer and grid edge points. With Distributed energy resources expanding at grid edge Microgrids coordination requires communication to become multi-dimensional, with information flowing among subset of microgrid devices enabling distributed energy resources transactions through real-time.

In that context, Microgrids have progressively emerged as "the impatient upstarts of our energy future."  While many microgrid projects share important characteristics beyond their name and architectures, there are equally important differences across projects requiring to segment their applications. The purpose of this article is to analyse three key examples of microgrid projects illustrating that segmentation. This should provide insights to how microgrids are likely to evolve in the years to come.  In this introductory section, we start with a brief overview of the basic definition of and Microgrid.

What are Microgrids ?
Microgrids consist of a contiguous physical section of the grid and its inter-connected distributed energy resources (i.e. generators, loads, storage devices, electric vehicles) being able to operate as a coordinated electrical area against the rest of the energy system. It usually interconnects with one or several virtual power plants (VPP) whose role is typically to coordinate portfolios of Microgrids against energy wholesale markets. A Virtual Power Plant sometimes operates a single Microgrid when its footprint is large enough.

Why Microgrids?
The main benefits of a Microgrid is to improve the coordination of Distributed Energy Resources within its Grid footprint minimizing the impact to the rest of the energy system, typically:

  • Ensuring Service Continuity to its end user during grid outages: Microgrids can maintain minimal supply to critical loads accounting for the availability of their embedded generation and storage
  • Deferring capital investments on peak generation and grid assets: Microgrids can leverage their synchronized generation and storage during peak periods
  • Providing Services to the Grid during synchronized operation: Microgrids can operate as a single aggregator offering flexible energy and ancillary services to the rest of the grid
  • Minimizing its end user community environmental impact: Microgrids can maximize the use of renewable energies, whether distributed within their own footprint or absorbing surplus of renewable energy from the rest of the energy system

Quantitative assessment of the benefits of Microgrid are different for every project context, largely depending on country regulatory frameworks (renewable and grid tariffs, opportunity for demand response, payment for voltage regulation) and grid connection requirements (frequency & voltage controls, specific grid stability requirements).

Typical Microgrid segments
Several Microgrid segments have emerged over the past years, depending on the underlying business model:
 Downstream Grid edge Microgrids, operated by:
a/ either commercial industrial end users (large industries, private campus, hospitals)
b/ or public government bodies (school & university campus, military bases)
c/ or commercial organization acting as Energy Service and utility aggregator companies towards previous Microgrids end users

Primary focus is to support owner’s business operation with clean economic and reliable power.

  • Upstream Grid edge Microgrids, operated by:

a/ Grid operators and vertically integrated utility wishing to consider Microgrid services as an alternative Grid reinforcements in selected constrained areas
b/ Municipalities and cities wishing to facilitate and coordinate multi energy Microgrid operation to optimize asset investments across electrical, gas, heat, storage and EV charging networks typically.

Primary focus is to optimize network asset investment. Utility may also offer their services to private owners to maximize revenue streams within a given Microgrid investment.

  • Off Grid Microgrids typically corresponding to the electrification of remote villages with no direct connection with the main grid system.

 

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