Low frequency oscillations are detrimental to the goals of maximum power transfer and optimal power system security. A contemporary solution to this problem is the addition of power system stabilizers to the automatic voltage regulators on the generators in the power system. The damping provided by this additional stabilizer provides the means to reduce the inhibiting effects of the oscillations. This thesis is an investigation of the use of synchronized phasor measurements as input signals for power system stabilizers installed on the generators of a two-area, 4-machine test power system. A remote measurement feedback controller has been designed and placed in the test power system. Synchronized phasor measurements from optimally sited measurement units were shown to improve the damping of low-frequency inter-area oscillations present in the test system when the proposed controller was included in the generator feedback control loop. The benefit of the damping of these oscillations was evident through the ability to increase the tie-line power flowing in the test system once the proposed control scheme was implemented. Time-domain simulations were used to verify the robustness of the proposed control during severe events, such as a short- circuit or sudden large variations of load. / Master of Science

Wide-area monitoring for the power system is a key tool for preventing the power system from system wide failure. State Estimation (SE) is an essential and practical monitoring tool that has been widely used to provide estimated values for each quantity within energy management systems (EMS) in the control center. However, monitoring larger power systems coordinated by regional transmission operators has placed an enormous operational burden on current SE techniques. A distributed state estimation (DSE) algorithm with a hierarchical structure designed for the power system industry is much more computationally efficient and robust especially for monitoring a wide-area power system. Moreover, considering the deregulation of the power system industry, this method does not require sensitive data exchange between smaller areas that may be competing entities. The use of phasor measurement units (PMUs) in the SE algorithm has proven to improve the performance in terms of accuracy and converging speed. Being able to synchronize the measurements between different areas, PMUs are perfectly suited for distributed state estimation. This dissertation investigates the benefits of the DSE using PMU over a serial state estimator in wide area monitoring. A new method has been developed using available PMU data to calculate the reference angle differences between decomposed power systems in various situations, such as when the specific PMU data of the global slack bus cannot be obtained. The algorithms were tested on six bus, I standard 30 bus and I 118-bus test cases. The proposed distributed state estimator has also been implemented in a test bed to work with a power system real-time digital simulator (RTDS) that simulates the physical power system. PMUs made by SEL and GE are used to provide real-time inputs to the distributed state estimator. Simulation results demonstrated the benefits of the PMU and distributed SE techniques. Additionally a constructed test bed verified and validated the proposed algorithms and can be used for different smart grid tests.

The growth of Distributed Energy Resources is accelerating, causing significant changes in utility distribution systems due to the bidirectionality of power flow. As a result, protection systems will require upgrades to operate with these new requirements. The current-only directional relay (CODR) is a novel proposal that detects the direction of fault currents without the need for new devices, but instead upgrades the software logic of existing devices, making it a cost-effective solution. This work provides a complete description of how to implement a hardware testbed to review the CODR method. Findings show that CODR performs successfully in a real environment, but its algorithm needs to be upgraded if used in distribution systems where lines have a non-negligible resistive component. / Master of Science / The use of renewable energy sources, such as solar panels and wind turbines, is growing rapidly. This is causing changes in the way electricity is distributed, as power can now flow in both directions. To keep up with these changes, the systems that protect the electricity grid need to be updated. One cost-effective solution is to use a new type of relay, called the current-only directional relay (CODR), which can detect the direction of fault currents without the need for new devices. This work describes how to test the CODR method using a hardware testbed. The results show that the CODR performs well in a real environment, but its algorithm needs to be updated for use in certain types of distribution systems.

In a typical utility control center, there could be hundreds of applications running to take care of day-to-day functionality. In many cases, these applications are custom-built by different vendors. With the expectation for high reliability of the electric power grid, many utilities are increasingly moving towards sharing data with each other and with security coordinators. But this data exchange is hampered by incompatible electrical applications built on proprietary data formats and file systems. Electric Power Research Institute's (EPRI‟s) Common Information Model (CIM) was envisioned as a one-sizeits-all data model to remove incompatibility between applications. This research work utilizes the CIM models to exchange power system models and measurements between a state estimator application and sensor web application. The CIM was further extended to include few unique devices from the shipboard medium voltage DC power system. Finally, a wide-area monitoring test bed was set up at MSU to perform wide-area monitoring using phasor measurement units (PMU). The outputs from the Phasor Data Concentrator (PDC) were then converted into CIM/XML documents to make them compatible with the sensor web application. These applications have created advancements in power system monitoring and interoperability

Complete resection is correlated to better patient outcome in aggressive cancers such as glioblastoma. Optical biopsy refers to a family of techniques utilizing optical properties of living targets to make diagnoses where a biopsy would conventionally be used. Such a technology can potentially guide neurosurgeons in removing glioblastomas. Diffuse reflectance (DR) and Time-resolved fluorescence (TRF) have previously been investigated for their ability to measure biomarkers indicative of cancer. One of the difficulties faced in using TRF as a diagnostic tool is that multiple endogenous fluorophores will simultaneously contribute to the signal. This makes it difficult to attribute fluorescence lifetimes or spectral changes to one type of molecule in the tissue. This thesis focuses on the challenge of separating the components in a TRF measurement and their fractional contributions. A DR-TRF instrument was designed and built and characterized using fluorescent dyes. An orthonormal basis deconvolution method combined with a Fourier-domain method were tested for their ability to unmix fluorescent components in a hyperspectral TRF measurement. This method was tested on dye mixtures and retrieved fluorescence lifetimes of 4.6±0.4 ns and 2.7±0.2 ns in a mixture of Fluorescein and Coumarin-6 at concentrations of 5 μM each. It was also tested on an ex-vivo brain tissue where the fluorescence was approximated as a sum of 2 components. / Thesis / Master of Applied Science (MASc)

In recent years, the subject of wide-area synchronized measurements has gained a significant amount of attention from the power system researchers. All of this started with the introduction of the Phasor Measurement Unit (PMU), which added a new perspective in the field of wide-area measurement systems (WAMS). With the ever evolving technologies over the years and the need for a more cost effective solution for synchronized frequency measurements, the Frequency Monitoring Network (FNET) was developed and introduced by the Power IT laboratory at Virginia Tech. The FNET is comprised of many Frequency Disturbance Recorders (FDR) geographically distributed throughout the United States. The FDR is a dedicated data acquisition device deployed at the distribution level, which allows for a lower cost and easily deployable WAMS solution. With Internet connectivity and GPS timing synchronization, the FDR provides high accuracy frequency, voltage magnitude and voltage angle data to the remote servers. Although the current FDR design is up to the standard in terms of the measurement accuracy and portability, it is of interest to further the research into alternative architectures and leverage the ever advancing technologies in high speed computing. One of the purposes of this dissertation is to present novel design options for a new generation of FDR hardware design. These design options will allow for more flexibility and to lower reliance on some vendor specific components. More importantly, the designs seek to allow for more computation processing capabilities so that more accurate frequency and angle measurements may be obtained. Besides the fact that the accuracy of frequency and angle measurement is highly dependent on the hardware and the algorithm, much can be said about the role of timing synchronization and its effects on accurate measurements. Most importantly, the accuracy of the frequency and angle estimation is highly dependent on the sampling time of local voltage angles. The challenges to accurate synchronized sampling are two folds. One challenge has to do with the inherent fallbacks of the GPS receiver, which is relatively high cost and limited in availability when the satellite signal is degraded. The other challenge is related to the timing inaccuracies of the sampling pulses, which is attributed to the remainder that results from the imperfect division of the processor counter. This dissertation addresses these issues by introducing the implementation of the high sensitivity (indoor) GPS and network timing synchronization, which aims to increase the availability of frequency measurements in locations that would not have been possible before. Furthermore, a high accuracy timing measurement system is introduced to characterize the accuracy and stability of the conventional crystal oscillator. To this end, a new method is introduced in close association with some prior work in generating accurate sampling time for FDR. Finally, a new method is introduced for modeling the FDR based on the sampling time measurements and some results are presented in order to motivate for more research in this area. / Ph. D.

This thesis investigates and develops a direct method for transient stability analysis using the energy approach [1] and the Phasor Measurement Units (PMUs). The originality of this new method results from a combination of a prediction of the post-fault trajectory based on the PMUs and the Transient Energy Function of a multimachine system. Thanks to the PMUs, the weakness of the direct methods, which is the over-simplification of the generator model, is overcome. This new method consists of fitting a curve to the data of the post-fault path provided by PMUs and identifying the controlling unstable equilibrium point (c.u.e.p.). Two second-order linear models have been estimated and evaluated from a prediction viewpoint. These are a polynomial function and an auto-regressive model. These parameters have been estimated by means of the least-squares estimator. They have been compared to the model proposed by Y. Ohura et al. [6], which has been upgraded into an iterative algorithm. The post-fault trajectory is predicted until the exit point located on the Potential Energy Boundary Surface (p.e.b.s.) is reached. In order to detect with efficiency this exit point and to find the c.u.e.p., it is proposed a combination of the so called "Ball-Drop" method [22] and an improved version of the Shadowing method. These combined procedures give accurate results when they are compared to the step-by-step method, which directly integrates the differential equations using a fourth-order Runga-Kutta method. The simulations have been carried out on a 3-machine system and on the 10-machine New-England power system. / Master of Science

The Phasor Measurement Unit provides clear data for ease of grid visibility. A major component of the device is the Global Positioning System (GPS) for time synchronization across the board. However, this device has become more susceptible to cyber-attacks such as spoofing. This paper constructs an opensource testbed for the playback of PMU data and testing of cyberattacks on PMUs. Using a local GPS device to simulate what is done in the PMU, MATLAB for data conversion, and Linux operating system running on Ubuntu, the simulator can be constructed. The spoofing attack is done by adding a phase shift of the incoming data to simulate that the data is coming from a different time stamp and shifts between the original. Finally, it is all brought together by viewing the output in an open source Phasor Data Concentrator (PDC) to validate the process. / Master of Science / To monitor the bulk electrical grid, devices used to calculate at what level the grid is at and what point in time as well. These devices that are called Phasor Measurement Units and send this data to the control center for engineers to process and make decisions. Within each device is a Global Positioning System (GPS) to tell which device is sending data and at what time. The GPS device is what is susceptible to be entered by malicious individuals. To better prepare and prevent this, a testbed would be a good solution to test if the preventative measure works. However, the best of the best costs too much money, so the next best solution is an open source test bed that could be implemented anyway. The work in this paper constructs an opensource testbed and simulates a full GPS spoofing attack.

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.

The phasor measurement unit (PMU) is considered to be one of the most important measuring devices in the future of power systems. The distinction comes from its unique ability to provide synchronized phasor measurements of voltages and currents from widely dispersed locations in an electric power grid. The commercialization of the global positioning satellite (GPS) with accuracy of timing pulses in the order of 1 microsecond made possible the commercial production of phasor measurement units. Simulations and field experiences suggest that PMUs can revolutionize the way power systems are monitored and controlled. However, it is perceived that costs and communication links will affect the number of PMUs to be installed in any power system. Furthermore, defining the appropriate PMU system application is a utility problem that must be resolved. This thesis will address two key issues in any PMU initiative: placement and system applications. A novel method of PMU placement based on incomplete observability using graph theoretic approach is proposed. The objective is to reduce the required number of PMUs by intentionally creating widely dispersed pockets of unobserved buses in the network. Observable buses enveloped such pockets of unobserved regions thus enabling the interpolation of the unknown voltages. The concept of depth of unobservability is introduced. It is a general measure of the physical distance of unobserved buses from those known. The effects of depth of unobservability on the number of PMU placements and the errors in the estimation of unobserved buses will be shown. The extent and location of communication facilities affects the required number and optimal placement of PMUs. The pragmatic problem of restricting PMU placement only on buses with communication facilities is solved using the simulated annealing (SA) algorithm. SA energy functions are developed so as to minimize the deviation of communication-constrained placement from the ideal strategy as determined by the graph theoretic algorithm. A technique for true real time monitoring of voltage security using synchronized phasor measurements and decision trees is presented as a promising system application. The relationship of widening bus voltage angle separation with network stress is exploited and its connection to voltage security and margin to voltage collapse established. Decision trees utilizing angle difference attributes are utilized to classify the network voltage security status. It will be shown that with judicious PMU placement, the PMU angle measurement is equally a reliable indicator of voltage security class as generator var production. A method of enhancing the weighted least square state estimator (WLS-SE) with PMU measurements using a non-invasive approach is presented. Here, PMU data is not directly inputted to the WLS estimator measurement set. A separate linear state estimator model utilizing the state estimate from WLS, as well as PMU voltage and current measurement is shown to enhance the state estimate. Finally, the mathematical model for a streaming state estimation will be presented. The model is especially designed for systems that are not completely observable by PMUs. Basically, it is proposed to estimate the voltages of unobservable buses from the voltages of those observable using interpolation. The interpolation coefficients (or the linear state estimators, LSE) will be calculated from a base case operating point. Then, these coefficients will be periodically updated using their sensitivities to the unobserved bus injections. It is proposed to utilize the state from the traditional WLS estimator to calculate the injections needed to update the coefficients. The resulting hybrid estimator is capable of producing a streaming state of the power system. Test results show that with the hybrid estimator, a significant improvement in the estimation of unobserved bus voltages as well as power flows on unobserved lines is achieved. / Ph. D.