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Distributed Energy Resources Integration

CERTS Microgrid Concept

AEP/CERTS Microgrid Schematic

AEP/CERTS Microgrid Schematic

A key feature of a microgrid, is its ability, during a utility grid disturbance, to separate and isolate itself from the utility seamlessly with little or no disruption to the loads within the microgrid (e.g., in the CERTS Microgrid concept, no impacts on power quality). Then, when the utility grid returns to normal, the microgrid automatically resynchronizes and reconnects itself to the grid, in an equally seamless fashion.

A critical feature of the CERTS Microgrid is its presentation to the surrounding distribution grid as a single self-controlled entity. A CERTS Microgrid appears to the grid as indistinguishable from other customer sites that do not include DER. This presentation means that the microgrid avoids many of the current concerns associated with integrating DER, such as how many DER the system can tolerate before their collective electrical impact begins to create problems like excessive current flows into faults and voltage fluctuations.

The CERTS Microgrid concept seeks to provide this technically challenging functionality without extensive (i.e., expensive) custom engineering. In addition, the design of the CERTS Microgrid also provides high system reliability and great flexibility in the placement of distributed generation within the microgrid. The CERTS Microgrid is intended to offer these functionalities at much lower costs than traditional approaches by incorporating peer-to-peer and plug-and-play concepts for each component within the microgrid.

The peer-to-peer concept insures that no single component, such as a master controller or a central storage unit, is required for operation of the microgrid. Therefore, by its very design, the CERTS Microgrid can continue operating with loss of an individual component or generator. (With one additional source, (N+1) it can insure even higher levels of reliability.)

The plug-and-play concept means that a distributed energy resources unit can be placed at any point within the microgrid without re-engineering its controls. The plug-and-play functionality is similar to the flexibility one has with home appliances. That is, just as an appliance can be plugged in wherever there is an outlet, one can similarly locate distributed energy resources units at any location within a facility or building where they might be most needed. This is in sharp contrast to the traditional model, which clusters distributed generation at a single point in order to make the electrical integration tasks simpler. In combined heat and power applications, the plug-and-play model facilitates placing distributed energy resources immediately adjacent to heat loads, thereby allowing more effective use of waste heat without a complex heat distribution system, such as steam and chilled water pipes, and the energy losses associated with them. The CERTS Microgrid Concept has been demonstrated through a research partnership with American Electric Power at a full scale test bed built near Columbus, Ohio.

Contact:

Robert Lasseter
University of Wisconsin/PSERC
(608) 262-0186

http://certs.lbl.gov