In a large and dense power network, the transmission lines, the generators and the loads are considered to be continuous functions of space. The continuum technique provides a macro-scale analytical tool to gain an insight into the mechanisms by which the disturbances initiated by faults and other random events propagate in the continuum. This dissertation presents one-dimensional and two-dimensional discrete models to illustrate the propagation of electromechanical waves in a continuum system. The more realistic simulations of the non-uniform distribution of generators and boundary conditions are also studied. Numerical simulations, based on the swing equation, demonstrate electromechanical wave propagation with some interesting properties. The coefficients of reflection, reflection-free termination, and velocity of propagation are investigated from the numerical results. Discussions related to the effects of electromechanical wave propagation on protection systems are given. In addition, the simulation results are compared with field data collected by phasor measurement units, and show that the continuum technique provides a valuable tool in reproducing electromechanical transients on modern power systems. Discussions of new protection and control functions are included. A clear understanding of these and related phenomena will lead to innovative and effective countermeasures against unwanted trips by the protection systems, which can lead to system blackouts. / Ph. D.

A new methodology is proposed to investigate the large-signal stability of interconnected power electronics systems. The approach consists of decoupling the system into a source subsystem and a load subsystem, and stability of the entire system can be analyzed based on investigating the feedback loop formed by the interconnected source/load system. The proposed methodology requires two stages: (1) since the source and the load are unknown nonlinear subsystems, system identification, which consists of isolating each subsystem into a series combination of a linear part and a nonlinear part, must be performed, and (2) stability analysis of the interconnected system is conducted thereafter based on a developed stability criterion suitable for the nonlinear interconnected-block-structure model. Applicability of the methodology is verified through stability analysis of PWM converters and a typical power electronics system. / Ph. D.

This thesis investigates the impacts of superconducting magnetic energy storage (SMES) unit on the power system first-swing stability by the impedance model of the SMES unit and EMTP simulations. The impedance model of the SMES unit is established in this thesis for study purpose. It has been concluded that SMES unit can greatly improve the power system first-swing stability. Based on the theoretical analysis and simulation results, the concept of the "Stability Protection Zone" of the SMES unit is proposed. Future work directions are discussed in the conclusion part. / Master of Science

In this thesis, we apply nonlinear Koopman mode analysis to decompose the swing dynamics of a power system into modes of oscillation, which are identified by analyzing the Koopman operator, a linear infinite-dimensional operator that may be defined for any nonlinear dynamical system. Specifically, power system modes of oscillation are identified through spectral analysis of the Koopman operator associated with a particular observable. This means that they can be determined directly from measurements. These modes, referred to as Koopman modes, are single-frequency oscillations, which may be extracted from nonlinear swing dynamics under small and large disturbances. They have an associated temporal frequency and growth rate. Consequently, they may be viewed as a nonlinear generalization of eigen-modes of a linearized system. Koopman mode analysis has been also applied to identify coherent swings and coherent groups of machines of a power system. This will allow us to carry out a model reduction of a large-scale system and to derive a precursor to monitor the loss of transient stability. / Master of Science

Increasing dynamics in power systems on account of renewable integration, electric vehicle penetration and rising demands have resulted in the exploration of energy storage for potential solutions. Recent technology- and industry-driven developments have led to a drastic decrease in costs of these storages, further advocating their usage. This thesis compiles the author's research on optimal integration of energy storage. Unpredictability is modelled using random variables favouring the need of stochastic optimization algorithms such as Lyapunov optimization and stochastic approximation. Moreover, consumer interactions in a competitive environment implore the need of topics from game theory. The concept of Nash equilibrium is introduced and methods to identify such equilibrium points are laid down. Utilizing these notions, two research contributions are made. Firstly, a strategy for controlling heterogeneous energy storage units operating at different timescales is put forth. They strategy is consequently employed optimally for arbitrage in an electricity market consisting of day-ahead and real-time pricing. Secondly, energy storages owned by consumers connected to different nodes of a power distribution grid are coordinated in a competitive market. A generalized Nash equilibrium problem is formulated for their participation in arbitrage and energy balancing, which is then solved using a novel emph{weighted} Lyapunov approach. In both cases, we design real-time algorithms with provable suboptimality guarantees in terms of the original centralized and equilibrium problems. The algorithms are tested on realistic scenarios comprising of actual data from electricity markets corroborating the analytical findings. / Master of Science

This thesis demonstrates the value of integrating electrical distribution engineering analysis with Geographic Information Systems (GIS). The 37-Node IEEE Feeder model was used as the base distribution system in this study. It was modeled separately, both in software capable of unbalanced load-flow and in an industry-standard GIS environment. Both tools utilized were commercially available, off-the shelf products indicative of those used in academia and in basic GIS installations. The foundational data necessary to build these models is representative of information required by a variety of utility departments for a multitude of applications. It is inherent to most systems within an enterprise-level, business-wide data model and therefore can be used to support a variety of applications. In this instance, infrastructure information is assumed to be managed and housed with the GIS. This data provides the required information as input for load-flow calculations. The engineering analysis is performed within DistributionSystem 4.01 and its output is passed back to the GIS in tabular format for incorporation. This thesis investigates the transfer of information between GIS and DistributionSystem 4.01 and demonstrates the extended display capabilities in the GIS environment. This research is implemented on a small scale, but is intended to highlight the need for standardization and automatic integration of these systems as well as others that are fundamental to the effective management of electrical distribution systems. / Master of Science

Multiple STATCOM units in proximity have been adopted in power transmission systems in order to obtain better voltage regulation and share burdens. Throughout stability assessment in this dissertation, it is shown, for the first time, that STATCOMs could interact with each other in a negative way in the small-signal sense due to their control, causing voltage instability, while loads and transmission lines showed small effects. Since this voltage stability problem is induced by STATCOMs, d-q frame impedance-based stability analysis was used, for the first time, to explore the inherent power system instability problem with presence of STATCOMs as it provides an accurate understanding of the root cause of instability within the STATCOM control system. This dissertation first proposes the impedance model in d-q frame for STATCOMs, including dynamics from synchronization, current and voltage loops and reveals the significant features compared to other types of grid-tied converters that 1) impedance matrix strongly coupled in d and q channel due to nearly zero power factor, 2) different behaviors of impedances at low frequency due to inversed direction of reactive power and 3) coupled small-signal propagation paths on the voltage at point of common coupling from synchronization and ac voltage regulation. Using the proposed impedance model, this dissertation identifies the frequency range of interactions in a viewpoint of d-q frame impedances and pinpointed that the ac voltage regulation was the main reason of instability, masking the effects of PLL in power transmission systems. Due to the high impedance of STATCOMs compared to that of transmission lines around the frequency range of interactions, STATCOMs were seen to interact with each other through the transmission lines. A scaled-down 2-STATCOM power grid was built to verify the conclusions experimentally. / Ph. D. / STATCOMs have been proven a type of effective power electronics device for reactive power compensations and people are trying to install multiple STATCOMs in proximity in power systems in order to have better performances. This dissertation, for the first time, evaluates the operation of multiple STATCOMs in proximity and finds out that they could interact with each other in a negative way in the small-signal sense due to their control, causing voltage instability, while loads and transmission lines showed small effects. Since this voltage stability problem is induced by STATCOMs, d-q frame impedance-based stability analysis was used, for the first time, to explore the inherent power system instability problem with presence of STATCOMs as it provides an accurate understanding of the root cause of instability within the STATCOM control system. To this end, an impedance model of STATCOMs is proposed, which accurately explains the terminal behaviors of STATCOMs. Using the model, this dissertation identifies the frequency range of interactions in a viewpoint of d-q frame impedances and pinpointed that the ac voltage regulation was the main reason of instability, masking the effects of PLL in power transmission systems. All the above is validated experimentally in a scaled-down 2-STATCOM power system.

Developing microgrids is an attractive solution for integrating inverter-based resources (IBR) in the power system. Distributed control is a potential strategy for controlling such microgrids. However, a major challenge toward the proliferation of distributed control is cybersecurity. A false data injection (FDI) attack on a microgrid using distributed control can have severe impacts on the operation of the microgrid. Simultaneously, a microgrid needs to be protected from system faults to ensure the safe and reliable delivery of power to loads. However, the irregular response of IBRs to faults makes microgrid protection very challenging. A microgrid is also susceptible to faults inside IBR converters. These faults can remain undetected for a long time and shutdown an IBR. This dissertation first proposes a method that reconstructs communicated signals using their autocorrelation and crosscorrelation measurements to make distributed control more resilient against FDI attacks. Next, this dissertation proposes a protection scheme that works by classifying measured harmonic currents using support vector machines. Finally, this dissertation proposes a protection and fault-tolerant control strategy to diagnose and clear faults that are internal to IBRs. The proposed strategies are verified using time-domain simulation case studies using the PSCAD/EMTDC software package. / Doctor of Philosophy / Renewable energy resources, such as wind, solar, and geothermal, are interfaced with the grid using DC-to-AC power electronic converters, popularly known as inverters. These “inverterbased resources (IBR)” are mostly distributed and located near consumers. During outages, IBRs can be used to provide power to customers. This gives developers the idea of integrating IBRs in microgrids. A microgrid is a miniature grid that consists of IBRs and customers. A microgrid is normally connected to the grid but can disconnect from the grid and operate on its own. To run efficiently, a microgrid uses fast and reliable communication between IBRs to create a high-performance distributed control strategy. However, this creates cybersecurity concerns for microgrids. This dissertation proposes a cybersecure distributed control strategy to make sure microgrids can keep their advantages. This dissertation also proposes a protection method that relies on machine learning to clear short circuits in the microgrid. Finally, this dissertation proposes a strategy to diagnose failures inside IBRs and ride through them. The proposed solutions are verified using the industry-grade simulation software PSCAD/EMTDC.

This work presents a centralized control scheme applied to a power system. The scheme has adaptive characteristics which allow the controller to keep track of the changing power system operating point and to control nonlinear functions of state variables. Feedback to the controller is obtained from phasor measurements at chosen power system buses, generator field voltage measurements, and state estimators. Control effort is aimed at minimizing the oscillations and influencing the power system state trajectory through the control of linear and nonlinear functions of state variables during a power system disturbance. The main contributions of this dissertation are the simultaneous introduction and utilization of measurement based terms in the state and output equations in the derivation and implementation of the control law, the study of limits on controller performance as the state residual vector becomes very large, and the simulation of the performance of local state estimators to prove the need for faster phasor measurement systems. The test system is a hypothetical 39-Bus AC power system consisting of typical components which have been sufficiently modelled for the simulation of power system performance in a dynamic stability study. / Ph. D.

Yes / Clean water demand has significantly increased due to the rise in the global population. However, most water on the Earth has high saline content that cannot be consumed directly; only about one over forty of the total water source is freshwater. Desalinated water is one of the potential solutions to meet the growing demand for freshwater, which is highly energy intensive. This paper analyses the energy, economic and environmental performance of a 5 m3/day PV (photovoltaic) powered reverse osmosis (RO) desalination system. Three scenarios of PV-RO with and without battery storage and diesel generator hybrid systems have been analyzed and investigated for the annual estimate load, net present value, and payback period of the water and electricity production costs. Also, the CO2 avoidance over the lifetime operation of all scearios is evaluated. This study shows that the PV-RO system without battery with 6.3 kW PV panels installed and with a 2-days water storage tank system is the most profitable economically f. For this scenario, the Levelized Cost of Electricity (LCOE), Levelized Cost of Water (LCOW), and Payback Period (PBP) are found to be $0.154/kWh, $0.627/m3, and five years, respectively. In addition, for this scenario, the CO2 emissions avoidance was the maximum (111,690 kg.CO2eq per year) compared to other scenarios.