1. MICROGRIDS: INTRODUCTION
The definition of a Microgrid by the U.S. Department of Energy Microgrid Exchange Group (MEG) is: “A Microgrid is a group of interconnected loads and distributed energy resources within clearly defined electrical boundaries that acts as a single controllable entity with respect to the grid. A Microgrid can connect and disconnect from the grid to enable it to operate in both grid-connected or island-mode.” [DOE12]
Microgrids can be considered as the building blocks of the Smartgrid, or even as an alternative path to what is nowadays starting to be known as a Supergrid.
Additionally, it can be divided into two broad categories: despachable (controllable output to meet fluctuations in demand) and non-despachable (uncontrollable and unpredictable output. [KELLY]
The emergence of the Microgrids came after realizing that the architecture of the electricity grid existing nowadays (Figure 1) is getting obsolete, since it is based on the idea of a top-down system, which is predicated on unidirectional energy flows. [ASMUS09]
The individual constituent parts will vary, but it will always have a Master Controller responsible of matching the load with generation in both island mode or grid-connected, provide real-time response and fault protection, connect and disconnect from the grid, and make predictive and forecasting analysis.
Also, it requires a fast and secure communication to monitor real-time connection status to act as Energy Manager. [SANCHEZ]
It also requires a protection system in which the sources are interfaced using power electronics, so it definitely needs unique protective solutions to provide functionality. [CERTS03]
As already explained, its operation differs to the traditional LV network. A LV network has high losses, and it is definitely not desirable to have lots of generated energy flowing over long distances, so the power has the necessity of being created locally. The Microgrid provides a Network Support, allowing the cooperation with the network to improve its operation. [KELLY]
2. STATE OF ART IN MICROGRID RESEARCH
The most advanced workshop about Microgrid R&D is held annually under the umbrella of U.S. Department of Energy, named the Microgrid Workshop. 2012’s meeting took place at the Illinois Institute of Technology (IIT), Chicago, Illinois, USA. The planning committee had representatives from four national laboratories, three universities and two consulting firms, all of them from Europe, South Korea, Japan and the USA. [DOE12]
The top 5 R&D topics relating to Microgrid Planning and Design are:
• System Architecture Engineering
o Definition of Microgrid Applications, Interfaces and Services
o Open Architectures That Promote Flexibility, Scalability and Security
• Modelling and Analysis
o Performance Optimization Methods and Uncertainty in the Modelling and Design Process (Figure 3)
• Power System Design
o DC Power Distribution Systems
o Microgrid Integration
The top 7 R&D topics relating to...