Distributed Generation (DG) technologies such as photovoltaic cells, wind-power, micro-turbines and fuel cells have the potential to significantly reduce emissions and ultimately perhaps the production cost as well. Connecting them to the distribution grid however is a subject of major concern.
One way of dealing with this could be to take a systems approach, viewing the generator and the associated loads as a subsystem or ‘microgrid’ that can be separated from the main grid. Such a microgrid would operate in parallel with the grid (when connected) or in island mode (when disconnected). It would disconnect from the grid during significant events (faults, voltage collapses), providing UPS services to its loads. If desired, it could also disconnect when the quality of power from the grid fell below certain standards.
Such a microgrid approach allows for local control of the DG unit, thereby reducing or eliminating the need for central dispatch. It also has the potential to provide a higher local reliability than provided by the power system as a whole. The objective is to provide the features of microgrids without a complex control system requiring detailed engineering for each application.
In this way, microgrids could enable a high penetration of DG without requiring redesign or re-engineering of the entire distribution system.
IEEE published an interesting study on microgrids. It discusses the concept, investigates the requirements for control systems, and works out a theoretical case study.
The design and construction of a full scale microgrid is currently in progress with the support of the California Energy Commission.
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