Using electrification and automation
economic benefits of DERs and support high levels of resilience. The exact architectures of DERMs can vary for different varieties of microgrids.
They must be completely self- sufficient. Networked or nested microgrids are networks of several individual DERs or microgrids connected to a common utility distribution system. They are usually controlled by a centralized supervisory system that balances the needs of the microgrid operation with support for the wider utility grid. The controller often assigns a hierarchy of importance to the microgrids and DERs to ensure that the most critical elements are protected. Applications for networked microgrids include community
microgrids, smart cities, and the emerging category of utility microgrids. Networked microgrids are a subcategory of grid-connected microgrids. All grid-connected microgrids are physically connected to the distribution grid, and they have a switching device at the point of common coupling (PCC) where the connection to the distribution grid occurs. During normal operation, a grid-connected microgrid is connected to the distribution grid. It can provide services to the grid, such as frequency and voltage regulation,
real and reactive power support, and demand response to mitigate capacity imitations. The microgrid is not connected to the utility distribution grid in an islanded operation. Islanding can occur because of a disruption in the distribution grid or for other needs like maintenance. When transiting from islanded to grid-connected operation, these microgrids need to sense the frequency of the distribution and synchronize operation before reconnecting. There are numerous microgrid applications, including campuses, hospitals and medical centers, commercial installations, communities, and industrial facilities. The newest application category is utility microgrids (Figure 3). Blurring the line Utility microgrids that blur the line between smart grids and microgrids are being deployed. In the process, the definition of a DER changes from a distributed energy resource to a dedicated energy resource. Utility microgrids are designed to reduce power outages due to extreme weather events, wildfires, and other unforeseen challenges. With existing grid architectures, large sections of the grid are de-energized for safety during extreme events.
Microgrid varieties
Microgrids can be classified by their applications and architecture. The three microgrid architectures are remote, networked, and grid- connected. Remote microgrids are in places like islands or remote mining and agricultural operations. They are also called off-grid microgrids and are physically separated from any utility BPS.
An important and unfortunate impact of those unscheduled and extensive power outages is to discourage the use of EVs. Utility microgrids are seen as a key to widespread EV adoption. Utility microgrids are being proposed and deployed across the U.S. For example, Southern California Edison (SCE) has proposed the development of Public Safety Power Shutoff Microgrids to help maintain electricity availability as widely as possible during wildfires. Other utilities refer to the new grid architecture as community microgrids (Figure 4). The islanding capability of utility microgrids is key to improving electricity availability on a more granular level than is currently possible. It’s expected to be deployed in a wide range of microgrid sizes, from complete residential communities to public Figure 4: Utility microgrids can include a wide range of assets spread over relatively wide geographic areas and blur the line between traditional microgrids and smart grids. (Image source: Edison International)
places, including schools and other strategic locations like fire stations, medical centers, and evacuation centers. EVSE installations are a crucial part of the designs of most of these community microgrids. As envisioned, the EVSE will support the grid connection of EVs as additional sources of backup power as well as for EV charging. Conclusion Electrification is necessary to ensure more sustainable power grids and drive reductions in CO2 emissions. Many electrification technologies like PV energy and EVs are not as predictable as the traditional resources they are replacing. That means electrification must be supported with advanced sensor networks and automated control systems in smart grids and microgrids.
Figure 3: Microgrids are often categorized by their application. (Image source: Siemens)
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