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Date of Award


Document Type

Campus Access Dissertation

Degree Name

Doctor of Philosophy in Electrical Engineering (PhD)

Administrative Home Department

Department of Electrical and Computer Engineering

Advisor 1

Bruce A. Mork

Committee Member 1

Jeffrey B. Burl

Committee Member 2

Sumit Paudyal

Committee Member 3

Raymond A. Swartz


This dissertation proposes and develops an EMTP-based time-domain approach for voltage stability assessment. Steady-state approaches for voltage stability analysis use linearized equations based on power frequency phasor analysis using the Jacobian matrix of the power system. Using these conventional methods, nonlinearities and resultant harmonics are not addressed, nor are frequency-dependencies or natural responses to step-changes in the system.

In order to implement this method all power system components need to be modeled in time-domain. Different load models and Var compensators have been developed in EMTP/ATP to conduct time-domain simulations. A Phasor Measurement Unit (PMU) model is also presented to provide a bridge between time and phasor domain analysis. Different case studies are shown in which time-domain analysis present the accurate results while steady state analysis include measurement and estimation errors.

Furthermore, a new Voltage Stability Index (VSI) is developed to detect impending voltage instability. A proposed multi-criteria index is developed based on different sub-indices calculated by monitoring different parameters of power system. the multi-level feature of the proposed index enables us to closely monitor voltage stability status and implement appropriate remedial actions when needed and avoid unnecessary actions.

Finally, the application of the proposed method and VSI in wide-area control and protection against voltage collapse is investigated. Novel wide-area control algorithms are developed based on voltage sensitivity analysis and the results for shunt capacitor and Static Var Compensator (SVC) control are compared to local-control strategies. It is shown that the voltage support provided by wide-area control strategy is more effective and will lead to a better voltage profile. The methods developed here can be directly implemented in smart grid infrastructure using a combination of synchrophasors and sampled values capabilities.