With the development of the power grid into an automated system, phasor measurement units and phasor data concentrators are essential for real time control of the system. PMUs are time synchronized throughout the power system and take sample measurements in very small windows of time. Phasor Data Concentrators accept PMU data and time align the data so that a snapshot of the power system can be viewed in real time. It is unfeasible to possess enough real PMUs to thoroughly test PDCs, thus a Real Time PMU Simulator is desired. It is possible to implement a UNIX based PMU simulator that can emulate the behavior of real PMUs, while also allowing the user to alter the Synchrophasor data to test the response of a PDC. GPS is used to synchronize a UNIX machine to UTC time to match that of a real PMU. In this way, the PMU simulator will accurately behave as a PMU. This PMU data can be sent to PDCs to test the response of the device. To test extremes of the PDC, alterations were made to the PMU software to send irregular data to a PDC. The results conclude that the open source iPDC software is capable of being used for latency testing, sending late data frames, as well as sending corrupted data. The PMU simulator proved to be successful in the area of PDC testing. The purpose of this thesis is to demonstrate how the iPDC software can be implemented to test PDC's. / Master of Science

For decades, power engineers have used simulations to predict grid stability and voltage phase angles. Only recently have equipment been available to actually measure phase angle at points hundreds of miles away. A few of these systems are presently operating in the US by electric grids including the Electric Reliability Council of Texas (ERCOT) and California Independent System Operator (ISO). However, the systems are in their infancy and are far from being used to improve grid reliability. This thesis describes the only independent synchronized phasor network that exists in the US. Thanks to Schweitzer Engineering Laboratories (SEL), we are streaming in points from three locations plus the University of Texas at Austin (UT Austin) as of January 2009. This thesis will describe this network and grid analysis done this far. / text

Master of Science / Department of Electrical and Computer Engineering / Behrooz Mirafzal / In this thesis, a modified version of the phasor pulse width modulation (PPWM) switching method for use in a single-stage three-phase boost inverter is presented. Because of the required narrow pulses in the PPWM method and limitations in controller resolution, e.g. dSPACE, the desired switching pattern for a boost inverter requires a costly processor. A low resolution processor can cause pulse dropping which results in some asymmetric conditions in output waveforms of the boost inverter and therefore, an increase in the THD of the output waveform. In order to solve this problem, a new switching pattern is developed which guarantees symmetric conditions in the switching pattern by discretizing the switching pattern in every switching cycle. This switching pattern has been applied to a boost inverter model developed by SimPowerSystems toolbox of MATLAB/Simulink. The model has been simulated in a wide range of input DC voltage and load. Moreover, a laboratory-scaled three-phase boost inverter has been designed, built, and tested using an identical switching pattern in the same input voltage and load range. Both simulation and experimental results confirm the effectiveness of the new switching pattern.

Phasor measurement is a growth technology in the power grid industry. With new funding, grid reliability concerns, and power capacity margin motivating a smart grid transformation, phasor measurement and smart metering are taking center stage as the implementation methods for grid intelligence. This thesis proposes a novel concept for designing a next generation phasor measurement unit. The present generation phasor measurement unit relies upon venerable existing current and voltage transducer technology that is expensive, bulky, and not well suited to the modern age of digital and computerized control signals. Also, the rising proliferation of installed phasor measurement units will soon result in data overload and huge obligations for network bandwidth and processing centers. This brute-force approach is ill-advised. Forward thinking is required to foresee the future grid, its fundamental operation, and its sensor controller needs. A reasonably safe assumption is a future grid containing sensors numbering in the thousands or millions. This number of sensors cannot transmit raw data over the network without requiring enormous network capacity and data center processing power. This thesis proposes a novel concept—combining existing technologies such as improved current transducers and wireless precision time protocols to design a next generation phasor measurement unit. The unit is entirely self-contained. It requires no external connections due to inclusion of high performance transducers, processor, wireless radio, and even energy harvesting components. With easy, safe, and low cost installation, proliferation of thousands or millions of sensors becomes feasible. Also, with a scalable sensor network containing thousands or millions of parallel distributed processors, data reduction and processing within the network relieves the need for high bandwidth data transmission or supercomputing data centers.

State estimation is an important tool for power system monitoring and the present study involves integrating phasor measurement units in the state estimation process. Based on measurements taken throughout the network, the role of a state estimator is to estimate the state variables of the power system while checking that these estimates are consistent with the measurement set. In the case of power system state estimation, the state variables are the voltage phasors at each network bus.\ The classical state estimator currently used is based on SCADA (Supervisory Control and Data Acquisition) measurements. Weaknesses of the SCADA measurement system are the asynchronicity of the measurements, which introduce errors in the state estimation results during dynamic events on the electrical network.\ Wide-area monitoring systems, consisting of a network of Phasor Measurement Units (PMU) provide synchronized phasor measurements, which give an accurate snapshot of the monitored part of the network at a given time. The objective of this thesis is to integrate PMU measurements in the state estimator. The proposed state estimators use PMU measurements exclusively, or both classical and PMU measurements.\ State estimation is particularly useful to filter out measurement noise, detect and eliminate bad data. A sensitivity analysis to measurement errors is carried out for a state estimator using only PMU measurements and a classical state estimator. Measurement errors considered are Gaussian noise, systematic errors and asynchronicity errors. Constraints such as zero injection buses are also integrated in the state estimator. Bad data detection and elimination can be done before the state estimation, as in pre-estimation methods, or after, as in post-estimation methods. For pre-estimation methods, consistency tests are used. Another proposed method is validation of classical measurements by PMU measurements. Post-estimation is applied to a measurement set which has asynchronicity errors. Detection of a systematic error on one measurement in the presence of Gaussian noise is also analysed. \ The state estimation problem can only be solved if the measurements are well distributed over the network and make the network observable. Observability is crucial when trying to solve the state estimation problem. A PMU placement method based on metaheuristics is proposed and compared to an integer programming method. The PMU placement depends on the chosen objective. A given PMU placement can provide full observability or redundancy. The PMU configuration can also take into account the zero injection nodes which further reduce the number of PMUs needed to observe the network. Finally, a method is proposed to determine the order of the PMU placement to gradually extend the observable island. \ State estimation errors can be caused by erroneous line parameter or bad calibration of the measurement transformers. The problem in both cases is to filter out the measurement noise when estimating the line parameters or calibration coefficients and state variables. The proposed method uses many measurement samples which are all integrated in an augmented state estimator which estimates the voltage phasors and the additional parameters or calibration coefficients.

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.

Synchrophasor Measurement Units (PMUs) are devices that can not only measure but also time stamp voltage, current, frequency, among others. PMUs take these synchronized measurements as fast as 60 times per second; compared with the traditional 2-4 second SCADA measurements, PMUs bring a much clear and real-time picture of what is happening in the power system. PMUs have been increasingly deployed across transmission power grids worldwide. In the USA this is primarily done by utilities through projects sponsored mainly by SIGS and Smart Grid grants. There are different applications that synchrophasors can provide, including off-line and real-time applications. However, due to budget constraints, technology development and characteristics specific to each system, not all applications are equally suitable and essential for all electric power systems. This thesis provides a method for PMU applications prioritization based on the analysis and results of wide area disturbance events. / Master of Science

The process of Synchronization between two buses in a power system plays a vital role, especially during blackstart or bulk power system restoration period. The synchronization process is primarily monitored in the presence of experienced personnel at the substation level, which might not control or even predict the after effects of synchronization as soon as the synchronizing breaker between the two buses respective to the two islands is closed. However, with the advent of phasor measurement units (PMUs) providing time synchronized synchrophasor data, synchroscope functionality can now be implemented at a centralized remote control platform, usually the control room of the specific utility. This thesis presents a technique along with the actual implementation of such a PMU Synchroscope analytic developed as a part of the Department of Energy sponsored open and Extensible Control and Analytics platform for synchrophasor data (openECA project). The challenges faced to realize this functionality at the centralized remote location along with methods to overcome these hurdles have been discussed in the document. Additional features in comparison to the conventional synchroscope device are also added to facilitate a smoother and successful synchronization, reducing error on behalf of the user /operator and thus, facilitating a faster power system restoration. / Master of Science / Successful and proper synchronization between different nodes of a power system is one of the most crucial stages of restoring power after a major wide area electricity outage. Improper synchronization may lead to additional system outages and might delay the restoration process. In this regards, it is desired to perform this vital task at the electric utility’s central remote control room. This thesis develops an application to perform the successful reconnection between two nodes of a system overcoming the various challenges and incorporating system delays. The application designed is based on real-time measurements and is integrated with an open source framework platform for ease of the user.

Phasor measurement unit (PMU) applications on power grid monitoring systems have been implemented since the early ninety's. Large monitoring system network performance relies on the consistent measurements of PMUs across the system. This has become a major challenge for designers since large networks use PMUs from various manufacturers who likely implement different synchrophasor technologies to perform the phasor estimations. The current synchrophasor standard, the IEEE C37.118-2005 Synchrophasor Standard, covers adequately the steady-state characterization of PMUs but does not specify transient condition requirements. The North American Synchrophasor Initiative (NASPI) has developed a guide outlining the several tests required for dynamic characterization of PMUs. The National Institute of Standards and Technology (NIST) developed two PMU testing stands for steady-state conformance with the current standard and for dynamic performance testing. Since May 2010, Virginia Tech has been working closely with the NIST in developing a PMU testing system similar to the NIST designs for commercial testing of PMUs and research purposes, the Virginia Tech Calibration System. This thesis focuses on assessing the system accuracy differences between the designs, and the software interface modifications to adapt the new hardware. / Master of Science

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