Large-scale Electric Grid Emulator Enables Research and Testing of Power System Technologies
The University of Tennessee-Knoxville (UTK)-operated electric grid emulator hardware testbed (HTB) serves as an exceptional planning tool for the future U.S. electric grid, enabling examination of grid infrastructure and new generation, transmission, and energy storage technologies, as well as cyberphysical measurement and communication schemes to identify and mitigate potential security threats. The HTB is an initiative of the Center for Ultra-Wide-Area Resilient Electric Energy Transmission Networks (CURENT), an NSF Engineering Research Center (ERC) supported by NSF and the U.S. Department of Energy and headquartered at UTK, with partner organizations including Northeastern University, Rensselaer Polytechnic Institute, and Tuskegee University.
CURENT’s HTB uses integrated data from three major U.S. power transmission grid models: The Eastern Interconnected (EI) System—from the Atlantic Ocean to the Rocky Mountain states; the Western Interconnected System—managed by the Western Electricity Coordinating Council (WECC) for states west of the Rocky Mountains; and, the Texas Interconnected System—managed by the Electricity Reliability Council of Texas (ERCOT). The testbed enables better research results because it is less dependent on numerical calculations—allowing more flexibility in system tests and it offers broad time scales in one system¾from microseconds for power electronics to milliseconds and seconds for power system event. It is also capable of performing prolonged real-time experiments and providing detailed system information simultaneously. The HTB is used to demonstrate interoperability between many different grid functions and controls, compare key features of a wide array of future electric grid technologies, and test real-time communication, protection, control, and power (and cyber security). The impact of renewable energy sources, responsive loads, and energy storage to the power grid can also be evaluated.
In the testbed, converters are connected at both the alternating current (AC) and direct current (DC) side with a rectifier at DC side. Because the power flows back and forth between AC and DC, the total power consumed in steady state is only the converter loss. The HTB gathers data from monitoring devices such as a power measurement unit or frequency disturbance recorder, and sends supervisory control commands, such as power dispatch, wind speed, and irradiance level, to emulators. Using a real-time embedded industrial controller, the HTB can be controlled remotely by LabVIEW (systems engineering software for applications that require test, measurement, and control) from the visualization and control room. Time delay effects in communication can also be emulated to make the system more realistic.
As just one example of the HTB’s special capabilities, its modular and reconfigurable converters have enabled testing of different system architectures such as high voltage (HV) DC vs. HVAC. An HVDC electric power transmission system (also called a power superhighway or an electrical superhighway) uses direct current for the bulk transmission of electrical power, in contrast with the more common HVAC systems. An HVDC line has lower power losses than an HVAC of the same capacity in practically all cases, which means more power is reaching its final destination. HVDC systems also have a lower environmental impact because they require fewer overhead lines to deliver the same amount of power as HVAC systems.
