Cyber-Controlled Smart Microgrid Systems of the Future: The High Penetration of Renewable and Green Energy Sources
Ali Keyhani
Ohio State Univ, Columbus, OH, USA ;
This paper appears in : New Research Directions for Future Cyber-Physical Energy Systems, Sheraton Baltimore City Center Hotel Baltimore, Maryland
Date: June 2009
Abstract:
In the first part of this talk the research issues of smart grid system have been presented as related to the development of future cyber control of smart grid systems. The mission of the North American Electric Reliability Corporation (NERC) is to ensure the reliability of the bulk power system in North America. NERC develops and enforces reliability standards for control centers to monitor the bulk power system and to assure the stability of the US interconnected grid system, consisting of a number of regional reliability centers. Similarly, it is natural to expect that future Cyber-Controlled Smart Microgrid Systems will be developed for the NERC mandated reliability centers of the U.S. grid. The cyber-fusion point (CFP) represents a node of the smart grid system where the renewable and green energy system is connected to large scale interconnected systems. The CFP is the node in the system that receives data from upstream, that is, from the interconnected network, and downstream, that is, from the microgrid renewable and green energy (MRG) system and its associated smart metering systems. The CFP node is the smart node of the system where the status of the network is evaluated and controlled, and where economic decisions are made as to how to operate the local MRG. A CFP also evaluates whether its MRG should be operated as an independent grid system or as a grid system separate from the large interconnected system. Cyber system is the backbone of the communication system for the collection of data on the status of the interconnected network system.
The MRG’s energy management system (EMS) communicates with individual smart meters located at residential, commercial, and industrial customer sites. The smart meters can control loads, such as air conditioning systems, electric ranges, electric water heaters, electric space heaters, refrigerators, washers, and dryers using Ethernet TCP/IP sensors, transducers, and communication protocol. The smart grid concept assumes a cluster of loads and micro-sources, operating as a single controllable system. To the utility, this cluster becomes a single dispatchable load which can respond in seconds. The point of interconnection in the smart microgird is represented by a node where the microgrid is connected to the utility system. Future research in cyber monitoring and control will seek to provide predictive models to track states in the system and to provide distributed intelligence and self-healing control technology. For a smart microgrid to participate in energy management, voltage, and frequency control, its inverter must be controlled to operate as a steam generator. An inverter can be made to operate in the same three modes to provide only active power or reactive power, or both active and reactive power. In the second part of this talk, the control of inverters in power flow, voltage and current control, and load sharing control in distributed generation system have been presented.