Observer-based monitors and distributed wave controllers for electromechanical disturbances in power systems

The thesis deals with monitoring and control of system-wide electromechanical (or “swing”) dynamics in power systems. The first part of the thesis is devoted to observer-based monitoring, while the second part introduces novel decentralized controllers that exploit the wave nature of the swing disturbances in order to manipulate their propagation. Power system monitors can be used to estimate the full state of the system as well as identify and isolate a number of events (e.g., faults) using only sparse local measurements, all in the presence of various system disturbances. The thesis analyzes different observer realizations for the Differential Algebraic Equation (DAE) swing model of a power system, and highlights the advantages of designing singular observers (versus state-space observers) for DAE models. We investigate various design approaches, and introduce a novel graphical design approach using a directed graph that reflects system structure. Investigations into the type, number and placement of measurements are conducted. Design examples on small(9 bus) and large-scale (179 bus) power systems are discussed for both type of monitors. The second part of the thesis develops and exploits a spatio-temporally integrated view of electromechanical dynamics. This contrasts with the traditional approach of either studying temporal variations at fixed spatial points or investigating spatial variations of specified temporal behavior. We use a continuum model of the swing dynamics to expose the wave-like propagation of electromechanical disturbances and to gain insight for the design of controls. We develop strategies for decentralized control of these electromechanical waves, drawing on prototype controllers found in electromagnetic transmission line theory (e.g., matchedimpedance terminations) and active vibration damping (e.g., energy-absorbing controllers and vibration isolators). Finally, we propose various controllers to realize quenching or confining-and-quenching strategies, and test these in simulations of a 179-bus reduced-order representations of the WSCC network. Thesis Supervisor: George C. Verghese Title: Professor, Department of Electrical Engineering and Computer Science Thesis Supervisor: Bernard C. Lesieutre Title: Staff Scientist, Lawrence Berkeley National Laboratory

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