A microgrid can be defined as a group of interconnected loads and distributed energy resources within clearly defined electrical boundaries that act as a single controllable entity with respect to the grid and that automatically connects and disconnects from the grid to enable it to operate in both grid connected or “islanded” mode. Power electronics for each micro-source can provide the control and flexibility for the microgrid to meet its power demands. The Microgrid controls need to ensure that: ? 1. New micro-sources (Solar PV, Fuel Cells, Micro-turbines etc.) can be added to the system without modification of existing equipment. ? 2.The Microgrid can connect to or isolate itself from the grid in a rapid seamless fashion. ? 3. Active and Reactive power can be independently controlled . ? 4.Voltage sag and system imbalances can be corrected . ? 5. Satisfy the Microgrid load dynamics . Each Micro-source has its own controller that interfaces to the micro-source power electronics. Even though the micro-source controllers are designed so communication to each other device is not required having a Distributed Control System (DCS) that monitors all the micro-source controllers and the loads of the entire Microgrid aids operations and provides more robust control. A DCS provides operations with the ability to view the status of the entire Microgrid in a common location. In addition, central logic can quickly detect separation of main distribution grid to switch modes of devices to help ensure frequency is maintained. It can also be a platform for intelligent load shedding to replace standard under-frequency load shed systems and can provide a common interface to an Energy Management System.
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