New Research Tools Enable Work to Stabilize the Power Grid
Power system researchers have developed new approaches and tools for monitoring fluctuations in electric power generation to minimize system failure. These fluctuations are power oscillations due to frequency differences in the network, resulting in loss of synchronization and instability of the power system. The researchers established a measurement-based approach for controlling the oscillation, set up a hardware-in-the-loop simulation for testing, and validated the effectiveness in realistic operating conditions in specific systems located in the U.S., Europe, Saudi Arabia, and Great Britain. This project was supported by 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 that is headquartered at the University of Tennessee-Knoxville (UTK).
One of the most important technical challenges facing the nation is how to address societal energy needs without continued heavy reliance on fossil fuels. The electric power system transmission infrastructure plays a critical role in any viable solution. These new tools advance CURENT’s vision of a nationwide or continent-wide transmission grid that is fully monitored and dynamically controlled in real-time for high efficiency, high reliability, low cost, better accommodation of renewable energy sources, full utilization of energy storage, and accommodation of responsive load. They were developed by researchers at UTK and Oak Ridge National Laboratory and made use of their FNET/GridEye wide area grid monitoring network, which provides independent observation of the entire electrical grid’s dynamic performance continuously and in real time. Oscillations are an inherent phenomenon in power systems that can threaten grid reliability if not managed appropriately. The new tools specifically support simulation and testing of a natural oscillation damping controller designed for different types of actuators—the part of the system that converts energy into mechanical force.
Damping (reducing or preventing) oscillation is essential for secure and stable system operation, as undamped oscillations often grow in magnitude over the span of seconds. The main factor leading to power oscillations is the frequency difference in the network. Utility frequency, line frequency, or mains frequency are the frequency level of the alternating current (AC) electricity used in transmission and distribution from electricity generation sources to customers. Put another way, they are the nominal frequency of the oscillations of AC in a wide-area synchronous grid transmitted from a power station to the end user. The exact frequency of the grid varies around nominal frequency, reducing when the grid is heavily loaded, and speeding up when lightly loaded.
Fundamental breakthroughs are needed to control the interconnection-wide dynamics of our extremely large and complex electric networks with tens of thousands of transmission lines, interconnections, and potentially millions of control points to be addressed.
