Phasor Measurement Units (PMUs) are widely acknowledged as one of the most promising developments in the field of real-time monitoring of power systems. By aligning the time stamps of voltage and current phasor measurements that are consistent with Coordinated Universal Time (UTC), a coherent picture of the power system state can be achieved through either direct measurements or simple linear calculations. With the growing number of PMUs planned for installation in the near future, both utilities and research institutions are looking for the best solutions to the placement of units as well as to the applications that make the most of phasor measurements. This dissertation explores a method for optimal PMU placement as well as two applications of synchronized phasor measurements in state estimation. The pre-processing PMU placement method prepares the system data for placement optimization and reduces the size of the optimization problem. It is adaptive to most of the optimal placement methods and can save a large amount of computational effort. Depth of un-observability is one of the criteria to allow the most benefit out of a staged placement of the units. PMUs installed in the system provide synchronized phasor measurements that are highly beneficial to power system state estimations. Two related applications are proposed in the dissertation. First, a post-processing inclusion of phasor measurements in state estimators is introduced. This method avoids the revision of the existing estimators and is able to realize similar results as mixing phasor data with traditional SCADA with a linear afterwards step. The second application is a method to calibrate instrument transformers remotely using phasor measurements. Several scans of phasor measurements are used to accomplish estimating system states in conjunction with complex instrument transformer correction factors. Numerical simulation results are provided for evaluation of the calibration performance with respect to the number of scans and load conditions. Conducting theoretical and numerical analysis, the methods and algorithms developed in this dissertation are aimed to strategically place PMUs and to incorporate phasor measurements into state estimators effectively and extensively for better system state monitoring. Simulation results show that the proposed placement method facilitates approaching the exact optimal placement while keep the computational effort low. Simulation also shows that the use of phasor measurement with the proposed instrument transformer correction factors and proposed state estimation enhancement largely improves the quality of state estimations. / Ph. D.

Given an increasing tendency towards distributed generation and alternative energy sources, the power grid must be more carefully monitored in order to ensure stability. Phasor Measurement Units (PMUs) provide very good observation of a small area of a network, but their relatively high cost prevents them from being deployed at every point. Therefore, to monitor an entire network, State Estimation is still required. By combining these two techniques, the accuracy and speed of power network monitoring can be improved. This thesis presents a method for achieving this goal from both hardware and computational perspectives. Practical considerations for PMU placement are discussed, such as instrument transformer calibration, and an algorithm is developed to apply this technique to any power system. The resulting method is termed reconfigurable monitoring - computationally isolated areas which may be grouped as necessary to allow for flexibility in power system monitoring. / Master of Science

Synchronized phasor measurements, or synchrophasors, allow the measurement of voltage phase angle and frequency, and through the comparison of two or more phasor the stability of the grid can be studied. The acquisition of synchrophasors in possible using Phasor Measurement Units (PMUs) and Global Positioning System Technology (GPS). The purpose of this research is to study synchrophasor events in the Western Electricity Coordinating Council (WECC) grid. Several studies have been made in the Texas grid, and that allows a comparison of events in both grids. During this study, five different types of synchrophasor events were observed. The first type of events, which consist of a change in phase angle difference value followed by damped oscillations has also been observed in the Texas grid; however, the other 4 types of events are not common occurrences in the Texas grid. The characteristics of each of the five types of synchrophasor events have been analyzed in this thesis. / text

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

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.

<p>Today’s electrical transmission & distribution systems, are facing a number of challenges related to changing environmental, technical and business factors. Among these factors are, increased environmental restrictions leading to higher share of production from renewable and uncontrollable sources as well as local environmental concerns regarding construction of new transmission and distribution lines. The re-regulation of the electricity market has created a dynamic environment in which multiple organizations have to coordinate and cooperate in the operation and control of the power system. Finally, the high rate of devel-opment within the ICT field is creating many new opportunities for power system opera-tion and control, thanks to introduction of new technologies for measurement, communi-cation and automation.</p><p>As a result of these factors, Wide Area Monitoring and Control (WAMC) systems have been proposed. WAMC systems utilize new ICT based technologies to offer more accurate and timely data on the state of the power system. WAMC systems utilize Phasor Measure-ment Units (PMUs) that have higher data rates and are time synchronised using, GPS satel-lites. This allows synchronized observation of the dynamics of the power system, making it possible to manage the system at a more efficient and responsive level and apply wide area control and protection schemes. The success WAMC systems, on the other hand, are largely dependent on the performance of the Information and Communication Technology (ICT) infrastructure that would support them.</p><p>This thesis investigates the requirements on, and suitability of the ICT systems that support WAMC systems. This was done by identifying WAMC applications and the elicitation of their requirements. Furthermore, a set of simulation projects were carried out to determine the communication system characteristics such as delay and the impact of this delay on the WAMC system.</p><p>This thesis has several contributions. First, it provides summary and analysis of WAMC application priorities and requirements in the Nordic region. Secondly it provides simula-tion based comparison and evaluation of communication paradigms for WAMC systems. The research documented in this thesis addresses these paradigms by providing a compari-son and evaluation through simulation. Thirdly, the thesis provides insight to the possible sources of delay in WAMC architecture and the impact of these delays on data quality specifically data incompleteness. This provides insight on what applications are important to practitioners and what is the expected performance of these applications, as seen from the power system control and operation point of view.</p>

The strain on modern electrical power systems has led to an ever-increasing utilization of new information and communication technologies (ICT) to improve their efficiency and reliability. Wide area monitoring and control (WAMC) systems offer many opportunities to improve the real-time situational awareness in the power system. These systems are essen-tially SCADA systems but with continuous streaming of measurement data from the power system. The quality of WAMC systems and the applications running on top of them are heavily, but not exclusively, dependent on the underlying non-functional quality of the ICT systems. From an ICT perspective, the real-time nature of WAMC systems makes them susceptible to variations in the quality of the supporting ICT systems. The non-functional qualities studied as part of this research are performance, interoperability and cyber security. To analyze the performance of WAMC ICT systems, WAMC applications were identified, and their requirements were elicited. Furthermore, simulation models capturing typical utility communication infrastructure architectures were implemented. The simulation studies were carried out to identify and characterize the latency in these systems and its impact on data quality in terms of the data loss. While performance is a major and desirable quality, other non-functional qualities such as interoperability and cyber security have a significant impact on the usefulness of the sys-tem. To analyze these non-functional qualities, an enterprise architecture (EA) based framework for the modeling and analysis of interoperability and cyber security, specialized for WAMC systems, is proposed. The framework also captures the impact of cyber security on the interoperability of WAMC systems. Finally, a prototype WAMC system was imple-mented to allow the validation of the proposed EA based framework. The prototype is based on existing and adopted open-source frameworks and libraries. The research described in this thesis makes several contributions. The work is a systematic approach for the analysis of the non-functional quality of WAMC ICT systems as a basis for establishing the suitability of ICT system architectures to support WAMC applications. This analysis is accomplished by first analyzing the impact of communication architectures for WAMC systems on the latency. Second, the impact of these latencies on the data quali-ty, specifically data currency (end to end delay of the phasor measurements) and data in-completeness (i.e., the percentage of phasor measurements lost in the communication), is analyzed. The research also provides a framework for interoperability and cyber security analysis based on a probabilistic Monte Carlo enterprise architecture method. Additionally, the framework captures the possible impact of cyber security on the interoperability of WAMC data flows. A final result of the research is a test bed where WAMC applications can be deployed and ICT architectures tested in a controlled but realistic environment. / <p>QC 20130218</p>

The evolving complexity of electric power systems with higher levels of uncertainties is a new challenge faced by system operators. Therefore, new methods for power system prediction, monitoring and state estimation are relevant for the efficient exploitation of renewable energy sources and the secure operation of network assets. In order to estimate all possible operating conditions of power systems, this Thesis proposes the use of Gaussian mixture models to represent non-Gaussian correlated input variables, such as wind power output or aggregated load demands in the probabilistic load flow problem. The formulation, based on multiple Weighted Least Square runs, is also extended to monitor distribution radial networks where the uncertainty of these networks is aggravated by the lack of sufficient real-time measurements. This research also explores reduction techniques to limit the computational demands of the probabilistic load flow and it assesses the impact of the reductions on the resulting probability density functions of power flows and bus voltages. The development of synchronised measurement technology to support monitoring of electric power systems in real-time is also studied in this work. The Thesis presents and compares different formulations for incorporating conventional and synchronised measurements in the state estimation problem. As a result of the study, a new hybrid constrained state estimator is proposed. This constrained formulation makes it possible to take advantage of the information from synchronised phasor measurements of branch currents and bus voltages in polar form. Additionally, the study is extended to assess the advantages of PMU measurements in multi-area state estimators and it explores a new algorithm that minimises the data exchange between local area state estimators. Finally, this research work also presents the advantages of dynamic state estimators supported by Synchronised Measurement Technology. The dynamic state estimator is compared with the static approach in terms of accuracy and performance during sudden changes of states and the presence of bad data. All formulations presented in this Thesis were validated in different IEEE test systems.

Today’s electrical transmission &amp; distribution systems, are facing a number of challenges related to changing environmental, technical and business factors. Among these factors are, increased environmental restrictions leading to higher share of production from renewable and uncontrollable sources as well as local environmental concerns regarding construction of new transmission and distribution lines. The re-regulation of the electricity market has created a dynamic environment in which multiple organizations have to coordinate and cooperate in the operation and control of the power system. Finally, the high rate of devel-opment within the ICT field is creating many new opportunities for power system opera-tion and control, thanks to introduction of new technologies for measurement, communi-cation and automation. As a result of these factors, Wide Area Monitoring and Control (WAMC) systems have been proposed. WAMC systems utilize new ICT based technologies to offer more accurate and timely data on the state of the power system. WAMC systems utilize Phasor Measure-ment Units (PMUs) that have higher data rates and are time synchronised using, GPS satel-lites. This allows synchronized observation of the dynamics of the power system, making it possible to manage the system at a more efficient and responsive level and apply wide area control and protection schemes. The success WAMC systems, on the other hand, are largely dependent on the performance of the Information and Communication Technology (ICT) infrastructure that would support them. This thesis investigates the requirements on, and suitability of the ICT systems that support WAMC systems. This was done by identifying WAMC applications and the elicitation of their requirements. Furthermore, a set of simulation projects were carried out to determine the communication system characteristics such as delay and the impact of this delay on the WAMC system. This thesis has several contributions. First, it provides summary and analysis of WAMC application priorities and requirements in the Nordic region. Secondly it provides simula-tion based comparison and evaluation of communication paradigms for WAMC systems. The research documented in this thesis addresses these paradigms by providing a compari-son and evaluation through simulation. Thirdly, the thesis provides insight to the possible sources of delay in WAMC architecture and the impact of these delays on data quality specifically data incompleteness. This provides insight on what applications are important to practitioners and what is the expected performance of these applications, as seen from the power system control and operation point of view.

Given the ability of the Phasor Measurement Unit (PMU) to directly measure the system state and the increasing implementation of PMUs across the electric power industry, a natural expansion of state estimation techniques would be one that employed the exclusive use of PMU data. Dominion Virginia Power and the Department of Energy (DOE) are sponsoring a research project which aims to implement a three phase linear tracking state estimator on Dominion's 500kV network that would use only PMU measurements to compute the system state. This thesis represents a portion of the work completed during the initial phase of the research project. This includes the initial development and testing of two applications: the three phase linear state estimator and the topology processor. Also presented is a brief history of state estimation and PMUs, traditional state estimation techniques and techniques with mixed phasor data, a development of the linear state estimation algorithms and a discussion of the future work associate with this research project. / Master of Science