Strengthening power system dynamic operation with the advent of increased renewable generation: Location and control of fast energy storage systems

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This research project seeks to increase power system robustness through the use of fast energy storage systems so the grid is better prepared to withstand failures and abnormal operation, which may lead to blackouts. The theoretical work of this project will also contribute to establishing a basis for dynamics studies for the future power system infrastructure. Several power system problems can be studied using the proposed mathematical development, such as controller designs for renewable generation, smart grid dynamic operation, electricity markets, and others. Besides advancing research knowledge on power system dynamics, this project will bring further development in control theory that is applicable to many other systems and industrial processes from the fields of electrical engineering, mechanical engineering, chemical engineering, and management. The PIs plan to leverage research results for curriculum development in new courses on power system dynamics and control. The researchers will also have support from the Office of Diversity, College of Engineering, and the Office of Information Technology at the University of Tennessee, Knoxville.This project will investigate a criterion to identify the best locations of fast energy storage systems (FESS) to improve power system dynamic performance and design appropriate controls for FESS. The future power grid is likely to be characterized by a high penetration of renewable energy interfaced to the grid through power electronics, and this may result in poor dynamic performance due to the reduction of inertia and a high variability on the generation side. To measure dynamic performance improvement, features such as frequency nadir, rate of change of frequency, and low frequency oscillation damping, among others, are considered. This work would be among the first to propose a solution for the FESS location problem while considering the full mathematical complexities of power system dynamics (large dimensionality, dynamics in different time scales, linear and nonlinear elements, and others). Although the modeling of this problem is highly complex, one of the proposal hypotheses is the existence of a criterion for FESS location based on specific physical characteristics of a power system, such as distribution of inertia, distribution of response speed of synchronous generators, and grid topology. Data analytics will be used to identify correlations between the optimal location and power system characteristics and, based on the numerical results, the theoretical development of the criterion will be derived. This characterization would allow planners to carefully strengthen the grid dynamics with the advent of increased renewable generation. In addition, this research seeks to establish three control strategies for FESS: (a) a continuous control scheme; (b) a discrete control scheme that determines the specific time when FESS need to change their discrete states (three states are considered: idle, discharge, and charge); and (c) a hybrid control scheme that combines the discrete state transitions and the continuous stored energy control within a particular discrete state. The hybrid control scheme is expected to provide the best dynamic improvement and, at the same time, is expected to extend the lifespan of FESS. The potential of phasor measurement units (PMUs) is considered to facilitate coordinating control loops among FESS, conventional generation, and renewable generation.