Energy Manager Design for Microgrids

Abstract

No Abstract. First six paragraphs of Executive Summary follows: On-site energy production, known as distributed energy resources (DER), offers consumers many benefits, such as bill savings and predictability, improved system efficiency, improved reliability, control over power quality, and in many cases, greener electricity.  Additionally, DER systems can benefit electric utilities by reducing congestion on the grid, reducing the need for new generation and transmission capacity, and offering ancillary services such as voltage support and emergency demand response.   Local aggregations of distributed energy resources (DER) that may include active control of on-site end-use energy devices can be called microgrids.  Microgrids require control to ensure safe operation and to make dispatch decisions that achieve system objectives such as cost minimization, reliability, efficiency and emissions requirements, while abiding by system constraints and regulatory rules.  This control is performed by an energy manager (EM).  Preferably, an EM will achieve operation reasonably close to the attainable optimum, it will do this by means robust to deviations from expected conditions, and it will not itself incur insupportable capital or operation and maintenance costs.    Also, microgrids can include supervision over end-uses, such as curtailing or rescheduling certain loads.  By viewing a unified microgrid as a system of supply and demand, rather than simply a system of on-site generation devices, the benefits of integrated supply and demand control can be exploited, such as economic savings and improved system energy efficiency.  While the EM can provide supervision and suggest near-optimal operation of the microgrid, lower-level controllers, local to DER equipment and loads, may provide the actual control, upon receiving suggestions from the EM.  This structure must facilitate interoperability of diverse devices and would allow for individual devices to veto suggestions from the EM that the device perceives as unacceptable or dangerous.   Pure optimal performance of a microgrid would require an all-knowing EM, which is clearly not practical.  The set of information that affects microgrid performance must be examined to determine which information is most useful, which is obtainable, and at what cost.  Naturally, intertwined with this analysis is the process of determining how the EM will make use of the acquired information.   The Consortium for Electric Reliability Technology Solutions (CERTS) Distributed Energy Resource Integration (DERI) team has developed a specific microgrid concept (the CERTS Microgrid) that relies on local power electronic electrical control and has modular, dynamic adaptability.  However, such a dynamically reconfigurable microgrid places additional requirements on DER devices and on the EM.