Microgrid

Microgrid is a localized grouping of electricity sources and loads that normally operates connected to and synchronous with the traditional centralized electrical grid (macrogrid), but can disconnect and function autonomously as physical and/or economic conditions dictate. By this way, it paves a way to effectively integrate various sources of distributed generation (DG), especially Renewable Energy Sources (RES). It also provides a good solution for supplying power in case of an emergency by having the ability to change between islanded mode and grid-connected mode. On the other hand, control and protection are big challenges in this type of network configuration, which is generally treated as a hierarchical control.

A formal definition from the U.S. Department of Energy Microgrid Exchange Group states: A microgrid is a group of interconnected loads and distributed energy resources (DERs) 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.

From the definition from the EU research projects: microgrids comprise Low-Voltage (LV) distribution systems with distributed energy resources (DERs) (microturbines, fuel cells, PhotoVoltaics (PV), etc.), storage devices (flywheels, batteries) energy storage system and flexible loads. Such systems can be operated in both non-autonomous way(if interconnected to the grid) or in an autonomous way (if disconnected from the main grid). The operation of microsources in the network can provide distinct benefits to the overall system performance, if managed and coordinated efficiently.

The focus of campus microgrids is aggregating existing on-site generation with multiple loads that located in tight geography in which owner easily manage them.

These microgrids never connect to the Macrogrid and instead operate in an island mode at all times because of economical issue or geography position. Typically, an "off-grid" microgrid is built in areas that are far distant from any transmission and distribution infrastructure and, therefore, have no connection to the utility grid.

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Wikipedia