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1
Mishra, Chetan. "Optimal Substation Coverage for Phasor Measurement Unit Installations." Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/78056.
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The PMU has been found to carry great deal of value for applications in the wide area monitoring of power systems. Historically, deployment of these devices has been limited by the prohibitive cost of the device itself. Therefore, the objective of the conventional optimal PMU placement problem is to find the minimum number devices, which if carefully placed throughout the network, either maximize observability or completely observe subject to different constraints. Now due to improved technology and digital relays serving a dual use as relay & PMU, the cost of the PMU device itself is not the largest portion of the deployment cost, but rather the substation installation. In a recently completed large-scale deployment of PMUs on the EHV network, Virginia Electric & Power Company (VEPCO) has found this to be so. The assumption then becomes that if construction work is done in a substation, enough PMU devices will be placed such that everything at that substation is measured. This thesis presents a technique proposed to minimize the number of substation installations thus indirectly minimizing the synchrophasor deployment costs. Also presented is a brief history of the PMU and its applications along with the conventional Optimal PMU placement problem and the scope for expanding this work.Master of Science
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Sukhavasi, Vijay Krishna. "Steady State Testing and Analysis of a Phasor Measurement Unit." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/46328.
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Phasor Measurement Units (PMUs) have been instrumental in building a reliable and robust Power System. Recent blackouts have increased the importance of PMUs and PMUs from various manufacturers are being installed in the in large quantities in the North American Grid. The interoperability and accuracy of these PMUs is important to obtain full benefit of the wide area monitoring systems. With the large number of installed PMUs it has become necessary to validate their performance and understand the limitations of each model. A test system was built by NIST in cooperation with NASPI to test for compliance to the existing IEEE C37.118 standard. This thesis presents the development of a Steady State Test System at Virginia Tech based on the NIST Steady State Testing system. The various issues that were faced during the process of development are discussed and the methodology implemented for solving these problems is described. This thesis also presents the additional benefits derived from the results obtained when different PMUs were tested using the Virginia Tech PMU Steady State Test System.Master of Science
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Wu, Zhongyu. "Synchronized Phasor Measurement Units Applications in Three-phase Power System." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/51660.
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Phasor Measurement Units (PMUs) are widely acknowledged as one of the most significant developments in the field of real-time monitoring of power system. By aligning time stamps of voltage and current phasor measurements, which 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 installed or planned to be installed in the near future, both utilities and research institutions are looking for novel applications of synchrophasor measurements from these widely installed PMUs. In this dissertation, the author proposes two new PMUs measurements applications: three-phase instrument transformer calibration, and three-phase line parameter calculation with instrument transformers.
First application is to calibrate instrument transformers. Instrument transformers are the main sensors used in power systems. They provide isolation between high voltage level of primary side and metering level of the secondary side. All the monitoring and measuring systems obtain input signals from the secondary side of instrument transformers. That means when instrument transformers are not accurate, all the measurements used in power system are inaccurate. The most important job of this dissertation is to explore a method to automatically calibrate all the instrument transformers in the power system based on real-time synchrophasor measurements.
The regular instrument transformer calibration method requires the instrument transformer to be out of service (offline) and calibrated by technicians manually. However, the error of instrument transformer changes when environment changes, and connected burden. Therefore, utilities are supposed to periodically calibrate instrument transformers at least once a year. The high labor and economic costs make traditional instrument transformer calibration method become one of the urgent problems in power industry. In this dissertation we introduce a novel, low cost and easy method to calibrate three-phase instrument transformers. This method only requires one three-phase voltage transformer at one bus calibrated in advance. All other instrument transformers can be calibrated by this method as often as twice a day, based on the synchrophasor measurements under different load scenarios.
Second application is to calculate line parameters during calibrating instrument transformers. The line parameters, line impedance and line shunt admittance, as needed by utilities are generated by the computer method. The computer method is based on parameters, such as the diameter, length, material characteristics, the distance among transmission line, the distance to ground and so on. The formulas to calculate line parameters have been improved and re-modeled from time to time in order to increase the accuracy. However, in this case, the line parameters are still inaccurate due to various reasons. The line parameters errors do affect the instrument transformers calibration results (with 5% to 10% error). To solve this problem, we present a new method to calculate line parameters and instrument transformers in the same processing step.
This method to calibrate line parameter and instrument transformers at the same time only needs one pre-calibrated voltage transformer and one pre-calibrated current transformer in power system. With the pre-calibrated instrument transformers, the line parameter as well as the ratio correction factors of all the other instrument transformers can be solved automatically. Simulation results showed the errors between calculated line parameters and the real line parameter, the errors between calibrated ratio correction factors and the real ratio correction factors are of the order of 10e-10 per unit. Therefore, high accuracy line parameters as well as perfectly calibrated instrument transformers can be obtained by this new method. This method can run automatically every day. High accuracy and dynamic line parameters will significantly improve power system models. It will also increase the reliability and speed of the relay system, enhance the accuracy of power system analysis, and benefit all other researches using line parameters. New methods of calculating line parameter and the instrument transformer calibrations will influence the whole power industry significantly.Ph. D.
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Retty, Hema A. "Evaluation and Standardizing of Phasor Data Concentrators." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/32064.
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The power grid is interconnected in many ways; so that when disturbances occur in a small region, their effects can be seen across large areas causing major blackouts. In order to isolate the fault, measurements taken at different times throughout the blackout need to be collected and analyzed. With each measurement device having its own time source, time alignment can be a quite tedious and lengthy process. The need for a new time synchronized measurement device has arrived. The Phasor Measurement Units (PMU) is not only GPS time synchronized, but it also takes measurements as voltage and current phasors.
PMUs are becoming an integral part in many power system applications from load flow analysis and state estimation to analyzing blackout causes. Phasor Data Concentrators (PDC) collect and process PMU data. As such, it is important that PMU and PDC communication is seamless. PDCs are set up at multiple utilities and power authorities and also need to be able to communicate and send data to one another seamlessly to encompass analysis of large measurement systems. If these devices are not working similarly when processing and sending/receiving data, unnecessary problems may arise. Therefore it is important that there is an expectation as to how they should work. However, what is expected from these devices is not entirely clear. For this reason, standards such as IEEE C37.118.2-2011 [5] have been proposed to help make operation as uniform as possible. Unfortunately, the standards for PDCs are lacking and tend to only set up communication protocols. To help normalize PDCs, these standards need to be expanded to include all PDC operations and give little room for discrepancy as to what a PDC should do in any given situation. Tests have been performed on PDCs not only to see how they match up to current standards but on how they act outside of the standards.Master of Science
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Kersey, Philip Michael. "Applications of PMUSimulator in PDC Testing." Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/32090.
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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 PDCâ s.Master of Science
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Chen, Jiaxiong. "Power System State Estimation Using Phasor Measurement Units." UKnowledge, 2013. http://uknowledge.uky.edu/ece_etds/35.
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State estimation is widely used as a tool to evaluate the real time power system prevailing conditions. State estimation algorithms could suffer divergence under stressed system conditions. This dissertation first investigates impacts of variations of load levels and topology errors on the convergence property of the commonly used weighted least square (WLS) state estimator. The influence of topology errors on the condition number of the gain matrix in the state estimator is also analyzed. The minimum singular value of gain matrix is proposed to measure the distance between the operating point and state estimation divergence.
To study the impact of the load increment on the convergence property of WLS state estimator, two types of load increment are utilized: one is the load increment of all load buses, and the other is a single load increment. In addition, phasor measurement unit (PMU) measurements are applied in state estimation to verify if they could solve the divergence problem and improve state estimation accuracy.
The dissertation investigates the impacts of variations of line power flow increment and topology errors on convergence property of the WLS state estimator. A simple 3-bus system and the IEEE 118-bus system are used as the test cases to verify the common rule. Furthermore, the simulation results show that adding PMU measurements could generally improve the robustness of state estimation.
Two new approaches for improving the robustness of the state estimation with PMU measurements are proposed. One is the equality-constrained state estimation with PMU measurements, and the other is Hachtel's matrix state estimation with PMU measurements approach. The dissertation also proposed a new heuristic approach for optimal placement of phasor measurement units (PMUs) in power system for improving state estimation accuracy. In the problem of adding PMU measurements into the estimator, two methods are investigated. Method I is to mix PMU measurements with conventional measurements in the estimator, and method II is to add PMU measurements through a post-processing step. These two methods can achieve very similar state estimation results, but method II is a more time-efficient approach which does not modify the existing state estimation software.
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Ghassempour, Aghamolki Hossein. "Phasor Measurement Unit Data-based States and Parameters Estimation in Power System." Scholar Commons, 2016. http://scholarcommons.usf.edu/etd/6505.
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The dissertation research investigates estimating of power system static and dynamic states (e.g. rotor angle, rotor speed, mechanical power, voltage magnitude, voltage phase angle, mechanical reference point) as well as identification of synchronous generator parameters. The research has two focuses:
i. Synchronous generator dynamic model states and parameters estimation using real-time PMU data.
ii.Integrate PMU data and conventional measurements to carry out static state estimation.
The first part of the work focuses on Phasor Measurement Unit (PMU) data-based synchronous generator states and parameters estimation. In completed work, PMU data-based synchronous generator model identification is carried out using Unscented Kalman Filter (UKF). The identification not only gives the states and parameters related to a synchronous generator swing dynamics but also gives the states and parameters related to turbine-governor and primary and secondary frequency control. PMU measurements of active power and voltage magnitude, are treated as the inputs to the system while voltage phasor angle, reactive power, and frequency measurements are treated as the outputs. UKF-based estimation can be carried out at real-time. Validation is achieved through event play back to compare the outputs of the simplified simulation model and the PMU measurements, given the same input data. Case studies are conducted not only for measurements collected from a simulation model, but also for a set of real-world PMU data. The research results have been disseminated in one published article.
In the second part of the research, new state estimation algorithm is designed for static state estimation. The algorithm contains a new solving strategy together with simultaneous bad data detection. The primary challenge in state estimation solvers relates to the inherent non-linearity and non-convexity of measurement functions which requires using of Interior Point algorithm with no guarantee for a global optimum solution and higher computational time. Such inherent non-linearity and non-convexity of measurement functions come from the nature of power flow equations in power systems.
The second major challenge in static state estimation relates to the bad data detection algorithm. In traditional algorithms, Largest Normalized Residue Test (LNRT) has been used to identify bad data in static state estimation. Traditional bad data detection algorithm only can be applied to state estimation. Therefore, in a case of finding any bad datum, the SE algorithm have to rerun again with eliminating found bad data. Therefore, new simultaneous and robust algorithm is designed for static state estimation and bad data identification.
In the second part of the research, Second Order Cone Programming (SOCP) is used to improve solving technique for power system state estimator. However, the non-convex feasible constraints in SOCP based estimator forces the use of local solver such as IPM (interior point method) with no guarantee for quality answers. Therefore, cycle based SOCP relaxation is applied to the state estimator and a least square estimation (LSE) based method is implemented to generate positive semi-definite programming (SDP) cuts. With this approach, we are able to strengthen the state estimator (SE) with SOCP relaxation. Since SDP relaxation leads the power flow problem to the solution of higher quality, adding SDP cuts to the SOCP relaxation makes Problem’s feasible region close to the SDP feasible region while saving us from computational difficulty associated with SDP solvers. The improved solver is effective to reduce the feasible region and get rid of unwanted solutions violate cycle constraints. Different Case studies are carried out to demonstrate the effectiveness and robustness of the method.
After introducing the new solving technique, a novel co-optimization algorithm for simultaneous nonlinear state estimation and bad data detection is introduced in this dissertation. ${\ell}_1$-Norm optimization of the sparse residuals is used as a constraint for the state estimation problem to make the co-optimization algorithm possible. Numerical case studies demonstrate more accurate results in SOCP relaxed state estimation, successful implementation of the algorithm for the simultaneous state estimation and bad data detection, and better state estimation recovery against single and multiple Gaussian bad data compare to the traditional LNRT algorithm.
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Hurtgen, Michaël. "Wide-area state estimation using synchronized phasor measurement units." Doctoral thesis, Universite Libre de Bruxelles, 2011. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209924.
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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.
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished
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Quint, Ryan David. "Practical Implementation of a Security-Dependability Adaptive Voting Scheme Using Decision Trees." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/35667.
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Todayâ s electric power system is operated under increasingly stressed conditions. As electrical demand increases, the existing grid is operated closer to its stable operating limits while maintaining high reliability of electric power delivery to its customers. Protective schemes are designed to account for pressures towards unstable operation, but there is always a tradeoff between security and dependability of this protection.
Adaptive relaying schemes that can change or modify their operation based on prevailing system conditions are an example of a protective scheme increasing reliability of the power system. The purpose of this thesis is to validate and analyze implementation of the Security-Dependability Adaptive Voting Scheme. It is demonstrated that this scheme can be implemented with a select few Phasor Measurement Units (PMUs) reporting positive sequence currents to a Phasor Data Concentrator (PDC). At the PDC, the state of the power system is defined as Stressed or Safe and a set of relays either vote or perform normal operation, respectively.
The Adaptive Voting Scheme was implemented using two configurations: hardware- and software-based PDC solutions. Each was shown to be functional, effective, and practical for implementation. Practicality was based on the latency of Wide Area Measurement (WAM) devices and the added latency of relay voting operation during Stressed conditions. Phasor Measurement Units (PMUs), Phasor Data Concentrators (PDCs), and relay operation delays were quantified to determine the benefits and limitations of WAMS protection and implementation of the voting scheme. It is proposed that the delays injected into the existing protection schemes would have minimal effect on the voting scheme but must be accounted for when implementing power system controls due to the real-time requirements of the data.Master of Science
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Nuqui, Reynaldo Francisco. "State Estimation and Voltage Security Monitoring Using Synchronized Phasor Measurements." Diss., Virginia Tech, 2001. http://hdl.handle.net/10919/28266.
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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.
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Silva, Raphael Philipe Mendes da. "Algoritmos genéticos aplicados à estimação fasorial em sistemas elétricos de potência." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/18/18154/tde-05102012-091637/.
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Esta trabalho apresenta a análise e implementação de uma técnica inteligente, o algoritmo genético (AG), para implementação de unidades de medição fasoriais, denominadas PMUs (Phasor Measurement Units). A disponibilidade dos fasores em diversos pontos de um sistema elétrico de potência (SEP) é importante, tanto para monitoramento quanto para controle, proteção e estudo do sistema. Entretanto, a obtenção de tais fasores só têm sentido se os mesmos possuírem o mesmo referencial no tempo. Este referencial é conseguido através de sinais de satélites GPS (Global Positioning System) que sincronizam as PMUs instaladas nos pontos de interesse. Existe uma vasta quantidade de m´métodos que podem ser utilizados para que, de posse das formas de onda discretizadas de tensão e corrente, estime-se os fasores correspondentes e as frequências locais. Este projeto apresenta os AGs como ferramenta de estimação para a obtenção de uma PMU com todas as vantagens relativas a tais algoritmos. Além disso, uma versão do AG que utiliza menos recursos computacionais , o algoritmo genético compacto (AGc) também será estudado. Um estudo norteado pela norma internacional C37.118 compara o desempenho dos AGs com dois métodos tradicionais de medição fasorial, um baseado na transformada discreta de Fourier e outro baseado em um filtro phase-locked loop. Dados sintéticos e provenientes de simulações são utilizados para avaliar o desempenho dos algoritmos desenvolvidos. Para tirar vantagem da natureza paralela dos algoritmos genéticos, um estudo da implementação do AGc em FPGA (field programmable gate array) utilizando a linguagem VHDL e realizado a fim de estudar a implementação embarcada em PMUs.This work presents the implementation and analysis of an intelligent technique, the genetic algorithm (GA), for the implementation of phasor measurement units (PMUs). The estimation of phasors in several spots in an electrical power system is important for the monitoring, control, protection and study of this system. However, these phasors must be in a common time reference in order to be usefull. This reference is achieved by using signals provided by the Global Positioning System (GPS) that synchronize the PMUs installed in the system. There are several techniques that can be used to estimate the phasors and local frequency using current and voltage wave signals. This project introduces the GAs as a phasor estimation tool applied to PMUs. Besides that, a version of the GA that demands less computational resources, the compact Genetic Algorithm is studied and implemented. A detailed study is performed using the international standard C37.118 as a guide comparing the GAs with two traditional techniques. The two traditional techniques are based on the DFT (Discrete Fourier transform) and a phaselocked loop filter (PLL). Synthetic and simulated data is used to evaluate the performance of the implemented algorithms. In order to take advantage of the parallel behavior of the genetic algorithms, a study of its implementation in FPGA (field programmable gate array) using the VHDL language is performed to make the genetic algorithms useful in real PMUs.
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Zora, Leydi Tatiana. "Thesis PMU Applications Prioritization Based in Wide Area Disturbance Events." Thesis, Virginia Tech, 2015. http://hdl.handle.net/10919/71829.
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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
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CASTELLO, PAOLO. "Algorithms for the synchrophasor measurement in steady-state and dynamic conditions." Doctoral thesis, Università degli Studi di Cagliari, 2014. http://hdl.handle.net/11584/266420.
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Phasor measurement units (PMUs) are becoming one of the key issues of power network monitoring. They have to be able to perform accurate estimations of current and voltage signals either under steady-state or dynamic conditions.
The first part of this PhD thesis analyses the impact of the phasor models on the estimation accuracy, focuses on algorithms proposed in the literature for the estimation of phasors and studies their performance under several different conditions.
On the basis of the results of this analysis, in the second part of this thesis an innovative approach to improve the performance of synchrophasor estimation is presented. The method proposes a modified version of the synchrophasor estimation algorithm which uses the non-orthogonal transform defined as Taylor-Fourier Transform (TFT) and which is based on a Weighted Least Squares (WLS) estimation of the parameters of a second order Taylor model of the phasor. The aim of the proposed enhancements is to improve the performance of the algorithm in presence of fast transient events and to achieve a Phasor Measurement Unit that is simultaneously compliant with both M and P compliance classes, suggested by the synchrophasor standard IEEE C37.118.1. In particular, while the TFT based adaptive algorithm is used for synchrophasor estimation, frequency and Rate of Change of Frequency (ROCOF) are estimated using the higher derivatives outputs of the adaptive TFT. Frequency estimation feedback is used to tune the algorithm and achieve better performance in off-nominal conditions. The proposed approaches are validated by means of simulations in all the static and dynamic conditions defined in the standard.
In the last chapter, the algorithm proposed above is used in a novel architecture, compliant to IEC 61850, for a distributed IED-based PMU, to be used in electrical substations. In particular, a measurement architecture based on process bus and sampled values synchronized with IEEE 1588-2008 is proposed, so that voltage and current signals are acquired by a Merging Unit device, while the PMU signal processing is performed on a IED (Intelligent Electronic Device), in compliance with IEEE C37.118.1-2011.
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Almutairi, Abdulaziz. "Enhancement of power system stability using wide area measurement system based damping controller." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/enhancement-of-power-system-stability-using-wide-area-measurement-system-based-damping-controller(7d98d164-8051-4662-ad18-374620d28a00).html.
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Contemporary power networks are gradually expanding incorporating new sources of electrical energy and power electronic based devices. The major stability issue in large interconnected power systems is the lightly damped interarea oscillations. In the light of growth of their incidents there are increased concerns about the effectiveness of current control devices and control systems in maintaining power system stability. This thesis presents a Wide Area Measurement System (WAMS) based control scheme to enhance power system stability. The control scheme has a hierarchical (two-level) structure comprising a Supplementary Wide-Area Controller (SWAC) built on top of existing Power System Stabilisers (PSSs). The SWAC's focus is on stabilising the critical interarea oscillations in the system while leaving local modes to be controlled entirely by local PSSs. Both control systems in the two levels work together to maintain system stability. The scheme relies on synchronised measurements supplied by Phasor Measurement Units (PMUs) through the WAMS and the only cost requirement is for the communication infrastructure which is already available, or it will be in the near future. A novel linear quadratic Gaussian (LQG) control design approach which targets the interarea modes directly is introduced in this thesis. Its features are demonstrated through a comparison with the conventional method commonly used in power system damping applications. The modal LQG approach offers simplicity and flexibility when targeting multiple interarea modes without affecting local modes and local controllers, thus making it highly suitable to hierarchical WAMS based control schemes. Applicability of the approach to large power systems is demonstrated using different scenarios of model order reduction. The design approach incorporates time delays experienced in the transmission of the SWAC's input/output signals. Issues regarding values of time delays and required level of detail in modelling time delays are thoroughly discussed. Three methods for selection of input/output signals for WAMS based damping controllers are presented and reviewed. The first method uses modal observability/controllability factors. The second method is based on the Sequential Orthogonalisation (SO) algorithm, a tool for the optimal placement of measurement devices. Its application is extended and generalised in this thesis to handle the problem of input/output signal selection. The third method combines clustering techniques and modal factor analysis. The clustering method uses advanced Principal Component Analysis (PCA) where its draw backs and limitations, in the context of power system dynamics' applications, are overcome. The methods for signal selection are compared using both small signal and transient stability analysis to determine the best optimal set of signals. Enhancement of power system stability is demonstrated by applying the proposed WAMS based control scheme on the New England test system. The multi-input multi-output (MIMO) WAMS based damping controller uses a reduced set of input/output signals and is designed using the modal LQG approach. Effectiveness of the control scheme is comprehensively assessed using both small signal and transient stability analysis for different case studies including small and large disturbances, changes in network topology and operating condition, variations in time delays, and failure of communication links.
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Huang, Liling. "Electromechanical Wave Propagation in Large Electric Power Systems." Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/11054.
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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.
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Retty, Hema. "Load Modeling using Synchrophasor Data for Improved Contingency Analysis." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/78328.
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For decades, researchers have sought to make the North American power system as
reliable as possible with many security measures in place to include redundancy. Yet the
increasing number of blackouts and failures have highlighted the areas that require
improvement. Meeting the increasing demand for energy and the growing complexity of the
loads are two of the main challenges faced by the power grid. In order to prepare for
contingencies and maintain a secure state, power engineers must perform simulations using
steady state and dynamic models of the system. The results from the contingency studies are
only as accurate as the models of the grid components. The load components are generally the most difficult to model since they are controlled by the consumer. This study focuses on
developing static and dynamic load models using advanced mathematical approximation
algorithms and wide area measurement devices, which will improve the accuracy of the system
analysis and hopefully decrease the frequency of blackouts.
The increasing integration of phasor measurement units (PMUs) into the power system
allows us to take advantage of synchronized measurements at a high data rate. These devices
are capable of changing the way we manage online security within the Energy Management
System (EMS) and can enhance our offline tools. This type of data helps us redevelop the
measurement-based approach to load modeling.
The static ZIP load model composition is estimated using a variation of the method of
least squares, called bounded-variable least squares. The bound on the ZIP load parameters
allows the measurement matrix to be slightly correlated. The ZIP model can be determined
within a small range of error that won't affect the contingency studies. Machine learning is used
to design the dynamic load model. Neural network training is applied to fault data obtained
near the load bus and the derived network model can estimate the load parameters. The neural network is trained using simulated data and then applied to real PMU measurements. A PMU algorithm was developed to transform the simulated measurements into a realistic
representation of phasor data. These new algorithms will allow us to estimate the load models
that are used in contingency studies.Ph. D.
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Qiu, Bin. "Next Generation Information Communication Infrastructure and Case Studies for Future Power Systems." Diss., Virginia Tech, 2002. http://hdl.handle.net/10919/27308.
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As the power industry enters the new century, powerful driving forces, uncertainties and new services and functions are compelling electric utilities to make dramatic changes in the way they communicate. Expanding network services such as real time monitoring are also driving the need for more increasing bandwidth in the communication network backbone. These needs will grow further as new remote real-time protection and control applications become more feasible and pervasive. This dissertation addresses two main issues for the future power system information infrastructure: communication network infrastructure and associated power system applications.
Optical network no doubt will become the predominate network for the next generation power system communication. The rapid development of fiber optic network technology poses new challenges in the areas of topology design, network management and real time applications. Based on advanced fiber optic technologies, an all-fiber network was investigated and proposed. The study will cover the system architecture and data exchange protocol aspects.
High bandwidth, robust optical network could provide great opportunities to the power system for better service and efficient operation. In the dissertation, different applications were investigated. One of the typical applications is the SCADA information accessing system. An Internet-based application for the substation automation system will be presented. VLSI (Very Large Scale Integration) technology is also used for one-line diagrams auto-generation. High transition rate and low latency optical network is especially suitable for power system real time control. In the dissertation, a new local area network based Load Shedding Controller (LSC) for isolated power system will be presented. By using PMU and fiber optic network, an AGE (Area Generation Error) based accurate wide area load shedding scheme will also be proposed. The objective is to shed the load in the limited area with minimum disturbance.Ph. D.
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Quint, Ryan David. "Response-Based Synchrophasor Controls for Power Systems." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/50576.
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The electric power grid is operated with exceptionally high levels of reliability, yet recent large-scale outages have highlighted areas for improvement in operation, control, and planning of power systems. Synchrophasor technology may be able to address these concerns, and Phasor Measurement Units (PMUs) are actively being deployed across the Western Interconnection and North America. Initiatives such as the Western Interconnection Synchrophasor Program (WISP) are making significant investments PMUs with the expectation that wide-area, synchronized, high-resolution measurements will improve operator situational awareness, enable advanced control strategies, and aid in planning the grid.This research is multifaceted in that it focuses on improved operator awareness and alarming as well as innovative remedial controls utilizing synchrophasors. It integrates existing tools, controls, and infrastructure with new technology to propose applications and schemes that can be implemented for any utility. This work presents solutions to problems relevant to the industry today, emphasizing utility design and implementation. The Bonneville Power Administration (BPA) and Western Electricity Coordinating Council (WECC) transmission systems are used as the testing environment, and the work performed here is being explored for implementation at BPA. However, this work is general in nature such that it can be implemented in myriad networks and control centers.
A Phase Angle Alarming methodology is proposed for improving operator situational awareness. The methodology is used for setting phase angle limits for a two-tiered angle alarming application. PMUs are clustered using an adapted disturbance-based probabilistic rms-coherency analysis. While the lower tier angle limits are determined using static security assessment between the PMU clusters, the higher tier limits are based on pre-contingency operating conditions that signify poorly damped post-contingency oscillation ringdown. Data mining tools, specifically decision trees, are employed to determine critical indicators and their respective thresholds. An application is presented as a prototype; however, the methodology may be implemented in online tools as well as offline studies.
System response to disturbances is not only dependent on pre-contingency conditions but also highly dependent on post-contingency controls. Pre-defined controls such as Special Protection Schemes (SPSs) or Remedial Action Schemes (RAS) have a substantial impact on the stability of the system. However, existing RAS controls are generally event-driven, meaning they respond to predetermined events on the system. This research expands an existing event-driven voltage stability RAS to a response-based scheme using synchrophasor measurements. A rate-of-change algorithm is used to detect substantial events that may put the WECC system at risk of instability. Pickup of this algorithm triggers a RAS that provides high-speed wide-area reactive support in the BPA area. The controls have proved effective for varying system conditions and topologies, and maintain stability for low probability, high consequence contingencies generally dismissed in today\'s deterministic planning studies.
With investments being made in synchrophasor technology, the path of innovation has been laid; it\'s a matter of where it goes. The goal of this research is to present simple, yet highly effective solutions to problems. Doing so, the momentum behind synchrophasors can continue to build upon itself as it matures industry-wide.
Ph. D.
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Zhong, Zhian. "Power Systems Frequency Dynamic Monitoring System Design and Applications." Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/28707.
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Recent large-scale blackouts revealed that power systems around the world are far from the stability and reliability requirement as they suppose to be. The post-event analysis clarifies that one major reason of the interconnection blackout is lack of wide area information. Frequency dynamics is one of the most important parameters of an electrical power system. In order to understand power system dynamics effectively, accurately measured wide-area frequency is needed. The idea of building an Internet based real-time GPS synchronized wide area Frequency Monitoring Network (FNET) was proposed to provide the imperative dynamic information for the large-scale power grids and the implementation of FNET has made the synchronized observations of the entire US power network possible for the first time. The FNET system consists of Frequency Disturbance Recorders (FDR), which work as the sensor devices to measure the real-time frequency at 110V single-phase power outlets, and an Information Management System (IMS) to work as a central server to process the frequency data. The device comparison between FDR and commercial PMU (Phasor Measurement Unit) demonstrate the advantage of FNET. The web visualization tools make the frequency data available for the authorized users to browse through Internet.
The research work addresses some preliminary observations and analyses with the field-measured frequency information from FNET. The original algorithms based on the frequency response characteristic are designed to process event detection, localization and unbalanced power estimation during frequency disturbances. The analysis of historical cases illustrate that these algorithms can be employed in real-time level to provide early alarm of abnormal frequency change to the system operator. The further application is to develop an adaptive under frequency load shedding scheme with the processed information feed in to prevent further frequency decline in power systems after disturbances causing dangerous imbalance between the load and generation.Ph. D.
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Sanchez, Ayala Gerardo. "Centralized Control of Power System Stabilizers." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/51754.
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This study takes advantage of wide area measurements to propose a centralized nonlinear controller that acts on power system stabilizers, to cooperatively increase the damping of problematic small signal oscillations all over the system. The structure based on decision trees results in a simple, efficient, and dependable methodology that imposes much less computational burden than other nonlinear design approaches, making it a promising candidate for actual implementation by utilities and system operators.
Details are given to utilize existing stabilizers while causing minimum changes to the equipment, and warranting improvement or at least no detriment of current system behavior. This enables power system stabilizers to overcome their inherent limitation to act only on the basis of local measurements to damp a single target frequency. This study demonstrates the implications of this new input on mathematical models, and the control functionality that is made available by its incorporation to conventional stabilizers.
In preparation of the case of study, a heuristic dynamic reduction methodology is introduced that preserves a physical equivalent model, and that can be interpreted by any commercial software package. The steps of this method are general, versatile, and of easy adaptation to any particular power system model, with the aggregated value of producing a physical model as final result, that makes the approach appealing for industry. The accuracy of the resulting reduced network has been demonstrated with the model of the Central American System.Ph. D.
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Ghanavati, Goodarz. "Statistical Analysis of High Sample Rate Time-series Data for Power System Stability Assessment." ScholarWorks @ UVM, 2015. http://scholarworks.uvm.edu/graddis/333.
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The motivation for this research is to leverage the increasing deployment of the phasor measurement unit (PMU) technology by electric utilities in order to improve situational awareness in power systems. PMUs provide unprecedentedly fast and synchronized voltage and current measurements across the system. Analyzing the big data provided by PMUs may prove helpful in reducing the risk of blackouts, such as the Northeast blackout in August 2003, which have resulted in huge costs in past decades.
In order to provide deeper insight into early warning signs (EWS) of catastrophic events in power systems, this dissertation studies changes in statistical properties of high-resolution measurements as a power system approaches a critical transition. The EWS under study are increases in variance and autocorrelation of state variables, which are generic signs of a phenomenon known as critical slowing down (CSD).
Critical slowing down is the result of slower recovery of a dynamical system from perturbations when the system approaches a critical transition. CSD has been observed in many stochastic nonlinear dynamical systems such as ecosystem, human body and power system. Although CSD signs can be useful as indicators of proximity to critical transitions, their characteristics vary for different systems and different variables within a system.
The dissertation provides evidence for the occurrence of CSD in power systems using a comprehensive analytical and numerical study of this phenomenon in several power system test cases. Together, the results show that it is possible extract information regarding not only the proximity of a power system to critical transitions but also the location of the stress in the system from autocorrelation and variance of measurements. Also, a semi-analytical method for fast computation of expected variance and autocorrelation of state variables in large power systems is presented, which allows one to quickly identify locations and variables that are reliable indicators of proximity to instability.
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Souza, José Renato Cozzolino Rodrigues de. "Um estudo sobre o desempenho de algoritmos de estimação de frequência visando unidades de medição fasorial." Niterói, 2017. https://app.uff.br/riuff/handle/1/3936.
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A estimação correta de frequência é essencial para a operação de diversos equipamentos de proteção, regulação e controle, os quais são necessários para operação adequada do Sistema Interligado Nacional A tecnologia de Sistemas de Medição Fasorial Sincronizada (Synchronized Phasor Measurement Systems - SPMS), baseia-se em uma rede de Unidades de Medição Fasorial (Phase Measurement Unit - PMU). Duas grandezas importantes medidas pela PMUs são a frequência e a taxa de variação da frequência. Este trabalho apresenta o resultado de estudo comparativo de algoritmos de estimação de frequência no âmbito de medição fasorial sincronizada. Foram avaliados os modelos propostos originalmente pela Norma IEEE C37.118, por seu documento de alteração ( IEEE Std. C37.118.1a-2014 Amendment), alem de três diferentes tipos de algoritmos baseados em PLLs (Phasor Locked Loop). As avaliações foram executadas com base nos testes descritos na Norma IEEE C37.118 e seus respectivos requisitos de conformidade. Verificou-se que as modificações apresentadas pelo documento Amendment foram necessárias para que o modelo de PMU proposto atendesse os requisto para todos os testes. Em relação aos modelos de PLL, verificou-se que uma versão do algoritmo (chamada aqui de PLL de Classe III) foi bem superior às demais e também melhor que o algoritmo sugerido pelo Amendment no que se refere ao teste de derivada da frequência e de modulação de fase.
An accurate frequency estimation is essential for the operation of Electric Power System regarding protection and control. Synchronized Phasor Measurement Systems - SPMS are based on a network composed by Phasor Measurement Units (Phase Measurement Unit - PMU). Two important parameters measured by the PMUs are the frequency and the frequency rate of change. This paper presents the results of a comparative study of frequency estimation algorithms within synchronized phasor measurement context. The reference model proposed in by IEEE C37.118 standard was compared with three different algorithms based on PLLs (Phasor Locked Loop). The evaluations were performed based on the compliance requirements described in IEEE C37.118. It was also found that the PLLs models have superior performance than model reference for P PMU suggested by Standard. Regarding the reference model for PMU M, there is a need to implement anti-aliasing filters for the standard inter-harmonics tests. After that, it was observed that the dynamic performances of PLLs studied at work are compatible with the algorithms suggested by the standard for the PMU M.
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Yang, Xuan. "Distributed state estimation with the measurements of Phasor Measurement Units." Thesis, University of Birmingham, 2013. http://etheses.bham.ac.uk//id/eprint/4479/.
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The world-wide application of Phasor Measurement Units (PMUs) brings great benefit to power system state estimation. The synchronised measurements from PMUs can increase estimation accuracy, synchronise states among different systems, and provide greater applicability of state estimation in the transient condition. However, the integration of synchronised measurements with state estimation can introduce efficiency problems due to the substantial burden of data. The research is divided into two parts: finding a solution to cope with the computational efficiency problem and developing a transient state estimation algorithm based on synchronised measurements from PMUs. The computational efficiency problems constitute important considerations in the operation of state estimation. To improve the low computational efficiency, two distributed algorithms are proposed in Chapters 4 and 5. In these two algorithms, the modelling, structure, and solution are described, and the corresponding procedures of bad data processing are presented. Numerical results on the IEEE 30-bus, 118-bus and 300-bus systems can verify the effectiveness of the two proposed algorithms. A novel transient state estimation algorithm based on synchronised measurements is proposed in Chapter 6. Considering the scanning cycle and sampling rate of PMU measurements, the proposed algorithm can estimate transient states in a practical way. The performance of the proposed algorithm is demonstrated in a transient simulation on the IEEE 14-bus system.
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Sobrinho, André Sanches Fonseca. "Desenvolvimento de uma unidade de medição fasorial otimizada para sistemas de distribuição." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/18/18153/tde-05052016-114303/.
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Os sistemas elétricos de distribuição estão evoluindo rapidamente devido à penetração de geração distribuída e ao crescimento na utilização de avançadas estruturas de medição e sistemas de gerenciamento de distribuição de energia elétrica. Esta evolução traz consigo novos desafios devido à intermitência da geração, a qual pode gerar impactos indesejáveis nos sistemas de distribuição, como a interação de diferentes harmônicos. As Unidades de Medição Fasorial (PMUs) tem potencial para desempenhar um importante papel no monitoramento de sistemas elétricos de distribuição por meio dos fasores com medidas temporalmente sincronizadas de tensão e corrente em vários locais do sistema, oferecendo assim inúmeras possibilidades para estimar o estado de uma rede de distribuição. Porém, para serem utilizadas amplamente em redes de distribuição, é necessário que as PMUs apresentem um menor custo e possuam algumas características funcionais exclusivas para o uso nestas redes. Assim, o objetivo desta tese consiste no desenvolvimento de uma unidade de medição fasorial de baixo custo com características originais para o uso no nível de distribuição de energia elétrica, tais como medição fasorial nas redes de média e baixa tensão utilizando a modelagem dos transformadores e a identificação e estimação dos parâmetros da causa de ocorrência de distúrbios elétricos. Para isso, foram construídos dois protótipos da unidade de medição fasorial proposta neste trabalho, visando verificar a sincronização na medição de fasores de tensão e corrente. Os protótipos também foram acoplados à rede com diferentes combinações de impedância e alimentaram variadas cargas, onde foi possível através das técnicas implementadas nos equipamentos identificar e estimar os parâmetros elétricos da origem (rede ou carga) da ocorrência de variações na tensão e potência fornecidas pela rede distribuição.Power distribution systems are evolving at a high pace largely due to the proliferation of distributed energy resources and the growing utilization of advanced metering infrastructures and distribution management system. This evolution is also leading to new challenges due large penetration of intermittent distributed generation, which can lead to noticeable impacts on distribution feeders. Phasor Measurement Units (PMUs) have the potential to play an essential role in power distribution system monitoring. For providing synchronized measurements of voltage and current phasors at various system locations, PMUs offer numerous possibilities for ascertaining information relating to the state of the power distribution system. However, to be used widely in power distribution systems, its necessary that PMUs get a low cost and have some exclusive features for these systems. Thus, the main objective of this thesis have consisted of developing a low cost Phasor Measurement Unit with original features proposed for distribution level, such as compatibility with low and medium voltage power networks using transformer modeling and also the identification and parameter estimation of the cause of electrical disturbances. So, they were built two prototypes of the Phasor Measurement Unit, in order to verify the synchronization in the measurement of voltage and current phasors. The prototypes were also coupled to the network with different combinations of impedance and they fed varying loads, where it was possible through the techniques implemented in the equipment identify and estimate electrical parameters of the cause (network or load) of variations in voltage and power supplied by the network distribution.
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Frazão, Rodrigo José Albuquerque. "MÉTODOS ALTERNATIVOS PARA ESTIMAÇÃO DE ESTADO EM SISTEMAS DE ENERGIA ELÉTRICA." Universidade Federal do Maranhão, 2012. http://tedebc.ufma.br:8080/jspui/handle/tede/475.
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The state estimation process applied to electric power systems aims to provide a trustworthy ―image‖, coherent and complete of the system operation, allowing an efficient monitoring. The state estimation is one of the most important functions of energy management systems. In this work, will be proposed alternative methods of state estimation for electric power systems in the levels of transmission, subtransmission and distribution. For transmission systems are proposed two hybrid methods considering the insertion of conventional measurements combined with phasor measurements based on phasor measurement unit (PMU). To estimate the state in subtransmission systems is proposed an alternative method which, in occurrence of failures in active and/or reactive meters in the substations, uses a load forecasting model based on criteria similar days and application of artificial neural networks. This process of load forecasting is used as a generator of pseudo measurements in state estimation problem, which takes place through the propagation of phasor measurements provided by a PMU placed in the boundary busbar. For the distribution system state estimation the proposed method uses the mathematical method of weighted least squares with equality constraints by modifying the set of measurements and the state variables. It is also proposed a methodology evaluation of the PMUs measurement channel availability for observability analysis. The application of the proposed methods to test systems shows that the results are satisfactory.
O processo de estimação de estado aplicado a sistemas elétricos de energia tem como objetivo fornecer uma imagem confiável, coerente e completa da operação do sistema, permitindo um monitoramento eficiente. A estimação de estado é uma das funções mais importantes dos sistemas de gerenciamento de energia. Neste trabalho são propostos métodos alternativos de estimação de estado para sistemas elétricos nos níveis de transmissão, subtransmissão e de distribuição. Para sistemas de transmissão são propostos dois métodos híbridos considerando a inserção das medições convencionais combinadas com medições fasoriais baseadas na unidade de medição fasorial (PMU - Phasor Measurement Unit). Para a estimação de estado em sistemas de subtransmissão é proposto um método alternativo que, na ocorrência de falhas nos medidores de potência ativa e/ou reativa das subestações, utiliza um modelo de previsão de carga baseado no critério de dias similares e na aplicação de redes neurais artificiais. Esse processo de previsão de carga é utilizado como gerador de pseudomedições na estimação de estado, que se dá através da propagação da medição fasorial fornecida por uma PMU alocada no barramento de fronteira. Para sistemas de distribuição o método de estimação de estado proposto consiste em aplicar o método de mínimos quadrados ponderados com restrições de igualdade, modificando-se o plano de medição e as variáveis de estado. Também é proposta uma metodologia para avaliação da disponibilidade dos canais de medições da PMU e o seu impacto na observabilidade do sistema. A aplicação dos métodos propostos a sistemas teste mostram que os resultados obtidos são satisfatórios.
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Freeman, Matthew A. "Multi-area power system state estimation utilizing boundary measurements and phasor measurement units ( PMUs)." Thesis, Texas A&M University, 2006. http://hdl.handle.net/1969.1/4178.
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The objective of this thesis is to prove the validity of a multi-area state estimator and investigate the advantages it provides over a serial state estimator. This is done utilizing the IEEE 118 Bus Test System as a sample system. This thesis investigates the benefits that stem from utilizing a multi-area state estimator instead of a serial state estimator. These benefits are largely in the form of increased accuracy and decreased processing time. First, the theory behind power system state estimation is explained for a simple serial estimator. Then the thesis shows how conventional measurements and newer, more accurate PMU measurements work within the framework of weighted least squares estimation. Next, the multi-area state estimator is examined closely and the additional measurements provided by PMUs are used to increase accuracy and computational efficiency. Finally, the multi-area state estimator is tested for accuracy, its ability to detect bad data, and computation time.
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Mazloomzadeh, Ali. "Development of Hardware in the Loop Real-Time Control Techniques for Hybrid Power Systems Involving Distributed Demands and Sustainable Energy Sources." FIU Digital Commons, 2014. http://digitalcommons.fiu.edu/etd/1666.
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The future power grid will effectively utilize renewable energy resources and distributed generation to respond to energy demand while incorporating information technology and communication infrastructure for their optimum operation. This dissertation contributes to the development of real-time techniques, for wide-area monitoring and secure real-time control and operation of hybrid power systems.
To handle the increased level of real-time data exchange, this dissertation develops a supervisory control and data acquisition (SCADA) system that is equipped with a state estimation scheme from the real-time data. This system is verified on a specially developed laboratory-based test bed facility, as a hardware and software platform, to emulate the actual scenarios of a real hybrid power system with the highest level of similarities and capabilities to practical utility systems. It includes phasor measurements at hundreds of measurement points on the system. These measurements were obtained from especially developed laboratory based Phasor Measurement Unit (PMU) that is utilized in addition to existing commercially based PMU’s. The developed PMU was used in conjunction with the interconnected system along with the commercial PMU’s. The tested studies included a new technique for detecting the partially islanded micro grids in addition to several real-time techniques for synchronization and parameter identifications of hybrid systems.
Moreover, due to numerous integration of renewable energy resources through DC microgrids, this dissertation performs several practical cases for improvement of interoperability of such systems. Moreover, increased number of small and dispersed generating stations and their need to connect fast and properly into the AC grids, urged this work to explore the challenges that arise in synchronization of generators to the grid and through introduction of a Dynamic Brake system to improve the process of connecting distributed generators to the power grid.
Real time operation and control requires data communication security. A research effort in this dissertation was developed based on Trusted Sensing Base (TSB) process for data communication security. The innovative TSB approach improves the security aspect of the power grid as a cyber-physical system. It is based on available GPS synchronization technology and provides protection against confidentiality attacks in critical power system infrastructures.
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Khiabani, Vahidhossein. "Multi-Objective Optimal Phasor Measurement Units Placement in Power Systems." Diss., North Dakota State University, 2014. https://hdl.handle.net/10365/27029.
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The extensive development of power networks has increased the requirements for robust, reliable and secure monitoring and control techniques based on the concept of Wide Area Measurement System (WAMS). Phasor Measurement Units (PMUs) are key elements in WAMS based operations of power systems. Most existing algorithms consider the problem of optimal PMU placement where the main objective is to ensure observability. They consider cost and observability of buses ignoring the reliability aspect of both WAMS and PMUs. Given the twin and conflicting objectives of cost and reliability, this dissertation aims to model and solve a multi-objective optimization formulation that maintains full system observability with minimum cost while exceeding a pre-specified level of reliability of observability. No unique solution exists for these conflicting objectives, hence the model finds the best tradeoffs. Given that the reliability-based PMU placement model is Non-deterministic Polynomial time hard (NP-hard), the mathematical model can only address small problems. This research accomplishes the following: (a) modeling and solving the multi-objective PMU placement model for IEEE standard test systems and its observability, and (b) developing heuristic algorithms to increase the scalability of the model and solve large problems. In short, early consideration of the reliability of observability in the PMU placement problem provides a balanced approach which increases the reliability of the power system overall and reduces the cost of reliability. The findings are helpful to show and understand the effectiveness of the proposed models. However the increased cost associated with the increased reliability would be negligible when considering cost of blackouts to commerce, industry, and society as a whole.
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O'Flynn, Alexander W. "Testing of Phasor Measurement Units (PMUs) for Distribution Network Applications." Thesis, Queensland University of Technology, 2020.
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Enabling islanded operation of power distribution networks will greatly improve the reliability of supply for customers. Measurement devices such as Phasor Measurement Units (PMUs) are required to protect and control the islanded network. PMUs are widely used in transmission network. This thesis examines whether existing PMUs meet the performance requirements to enable islanded distribution network operation.
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Wehbe, Yasser. "Model Estimation of Electric Power Systems by Phasor Measurement Units Data." Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4419.
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This dissertation tackles the online estimation of synchronous machines' power subsystems electromechanical models using the output based Phasor Measurements Units (PMUs) data while disregarding any inside data. The research develops state space models
and estimates their parameters and states. The research tests the developed algorithms against models of a higher and of the same complexity as the estimated models.
The dissertation explores two estimations approaches using the PMUs data: i)non-linear Kalman filters namely the Extended Kalman Filter (EKF) and then the Unscented
Kalman Filter (UKF) and ii) Least Squares Estimation (LSE) with Finite Differences (FN) and then with System Identification. The EKF based research i) establishes a decoupling
technique for the subsystem the rest of the power system ii) finds the maximum number of parameters to estimate for classical machine model and iii) estimates such parameters
. The UKF based research i) estimates a set of electromechanical parameters and states for the flux decay model and ii) shows the advantage of using a dual estimation filter with
colored noise to solve the difficulty of some simultaneous state and parameter estimation.
The LSE with FN estimation i) evaluates numerically the state space differential equations and transform the problem to an overestimated linear system whose parameters
can be estimated, ii) carries out sensitivity studies evaluating the impact of operating conditions and iii) addresses the requirements for implementation on real data taken from
the electric grid of the United States. The System Identification method i) develops a linearized electromechanical model, ii) completes a parameters sub-set selection study using
si8ngular values decomposition, iii) estimates the parameters of the proposed model and iv) validates its output versus the measured output.
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Ashton, Phillip Michael. "Exploiting phasor measurement units for enhanced transmission network operation and control." Thesis, Brunel University, 2014. http://bura.brunel.ac.uk/handle/2438/9063.
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In order to achieve binding Government targets towards the decarbonisation of the electricity network, the GB power system is undergoing an unprecedented amount of change. A series of new technologies designed to integrate massive volumes of renewable generation, predominantly in the form of offshore wind, asynchronously connecting to the periphery of the transmission system, are transforming the requirements of the network. This displacement of traditional thermal generation is leading to a significant reduction in system inertia, thus making the task of system operation more challenging. It is therefore deemed necessary to develop tools and technologies that provide far greater insight into the state of the power system in real-time and give rise to methods for improving offline modelling practices through an enhanced understanding of the systems performance. To that extent PMUs are seen as one of the key enablers of the Smart Grid, providing accurate time-synchronised measurements on the state of the power system, allowing the true dynamics of the power system to be captured and analysed. This thesis provides an analysis of the existing PMU deployment on the GB transmission system with a view to the future system monitoring requirements. A critical evaluation and comparison is also provided on the suitability of a University based Low Voltage PMU network to further enhance the visibility of the GB system. In addition a novel event detection algorithm based on Detrended Fluctuation Analysis is developed and demonstrated, designed to determine the exact start time of a transmission event, as well as the suitability of such an event for additional transmission system analysis, namely inertia estimation. Finally, a reliable method for the estimation of total system inertia is proposed that includes an estimate of the contribution from residual sources, of which there is currently no visibility. The proposed method identifies the importance of regional inertia and its impact to the operation of the GB transmission system.
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Brueni, Dennis J. "Minimal PMU placement for graph observability : a decomposition approach /." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-10312009-020314/.
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Deo, Samarth. "Synchronized Phasor Measurement Units : Implementation of PMU Algorithm on HVDC Control Platform." Thesis, KTH, Industriella informations- och styrsystem, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-138551.
Full textAbstract:
Power Systems most often operate in the margins of stability limits. With power grids becoming even more automated now, Phasor Measurement Units (PMU’s) and Phasor Data Concentrators (PDC’s) become essential for real-time control of the system. Since PMU’s are time synchronized, the phasors can be compared at the substations, studied for any faults and analyzed at the same time. These PMU’s report the measured magnitude, phasor angle of voltages and currents in real synchronized time in different locations. One good way to measure these quantities is to use the Discrete Fourier Transform (DFT) and analyze the signal as a digital signal. However with transients and noise present in the input signal, DFT might not be the best approach for measurement and/or protection. With the IEEE C37.118 (Standard for Synchrophasor for Power Systems) 2011 version emphasizing on the importance of the two classes of PMU’s- P-class for Protection and M-class for Measurement; every vendor now has to label their products with one of these classes. There is a high precision required for P-class PMU’s whereas a good reporting rate for M-class. Recently The North-American Synchrophasor Initiative (NASPI) and Western Electricity Coordinating Council (WECC) also gave filtering specifications and frequency response of an industry compliant PMU. This thesis discusses the various frequency estimation algorithms, which are compliant with the NASPI/WECC standards. Further such an algorithm is implemented on ABB proprietary hardware and tested against dynamic tests.
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Tuku, Woldu. "Distributed state estimation using phasor measurement units (PMUs)for a system snapshot." Kansas State University, 2012. http://hdl.handle.net/2097/14129.
Full textAbstract:
Master of ScienceDepartment of Electrical and Computer Engineering
Noel N. Schulz
As the size of electric power systems are increasing, the techniques to protect, monitor and control them are becoming more sophisticated. Government, utilities and various organizations are striving to have a more reliable power grid. Various research projects are working to minimize risks on the grid. One of the goals of this research is to discuss a robust and accurate state estimation (SE) of the power grid. Utilities are encouraging teams to change the conventional way of state estimation to real time state estimation. Currently most of the utilities use traditional centralized SE algorithms for transmission systems. Although the traditional methods have been enhanced with advancement in technologies, including PMUs, most of these advances have remained localized with individual utility state estimation. There is an opportunity to establish a coordinated SE approach integration using PMU data across a system, including multiple utilities and this is using Distributed State Estimation (DSE). This coordination will minimize cascading effects on the power system. DSE could be one of the best options to minimize the required communication time and to provide accurate data to the operators. This project will introduce DSE techniques with the help of PMU data for a system snapshot. The proposed DSE algorithm will split the traditional central state estimation into multiple local state estimations and show how to reduce calculation time compared with centralized state estimation. Additionally these techniques can be implemented in micro-grid or islanded system.
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Fish, Adbul-Aziz. "Optimal placement of phasor measurement units using the Advanced Matrix Manipulation algorithm." Master's thesis, University of Cape Town, 2013. http://hdl.handle.net/11427/5223.
Full textAbstract:
Includes abstract.Includes bibliographical references.
This thesis investigates the problem of the Optimal Placement scheme of Phasor Measurement Units in electrical power systems for State Estimation to facilitate improved monitoring and control of the system parameters. The research work done for this thesis begins with review of Supervisory Control and Data Acquisition systems (SCADA). SCADA-based systems are currently employed for condition monitoring and control of industrial and utility electrical power systems. For utility power networks, the main problem with voltage and current phasor data captured by SCADA systems is that they are not synchronised with respect to each other in a present-time or Real-time framework. This implies that both magnitude and phase angle of the measured phasors tend to get affected by slow data flow provided by SCADA to the points of utilization and also by differences in time instants of data capture. These factors inhibit theefficiency and quality of the power system monitoring and control. “Phasor Measurement Unit” (PMU) is a relatively new technology that, when employed in power networks, offers real-time synchronised measurements of the voltages at buses and currents along the lines that connect them. This is accomplished by using a GPS based monitoring system which facilitates time synchronisation of measurements and unlike SCADA, makes the measured data available in Real-Time format. SCADA is not able to provide Real-time data due to the low speeds at which RTUs (Remote Terminal Units) provide data. Availability of time-stamped phasor measurements makes PMUs preferable for power system monitoring and control applications such as State Estimation, Instability Prediction Analysis, Real-time Monitoring of the system conditions, Islanding Detection, System Restoration and Bad Data Detection.
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Yuill, William. "The optimal placement of phasor measurement units and their effects on state estimation." Master's thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/10686.
Full textAbstract:
Phasor measurement units (PMUs) are a key new technology for use in electric power systems as a backbone for sensing and measurement and to improve interface and decision support using instantaneous PMU data which will drive faster simulations and advanced visualisation tools that will help system operators assess dynamic challenges to system stability. The two main objectives of this work are to investigate and develop 1. a method for the algorithmic placement of a minimum number of PMUs into a system to ensure full observability, 2. conventional, hybrid and linear state estimation techniques to incorporate and utilize PMU measurement data to perform state estimation and to study the effects that differing PMU placement positions have on the accuracy of the resultant state estimator solution.
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Kamireddy, Srinath. "Comparison of state estimation algorithms considering phasor measurement units and major and minor data loss." Master's thesis, Mississippi State : Mississippi State University, 2008. http://library.msstate.edu/etd/show.asp?etd=etd-11072008-121521.
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Golshani, Mohammad. "Novel performance evaluation of information and communication technologies to enable wide area monitoring systems for enhanced transmission network operation." Thesis, Brunel University, 2015. http://bura.brunel.ac.uk/handle/2438/11918.
Full textAbstract:
The penetration of renewable energy sources has increased significantly in recent years due to the ongoing depletion of conventional resources and the transition to a low carbon energy system. Renewable energy sources such as wind energy are highly intermittent and unpredictable in nature, which makes the operation of the power grid more dynamic and therefore more complex. In order to operate the power system reliably under such conditions, Phasor Measurement Units (PMUs) through the use of satellite technology can offer a state-of-the-art Wide Area Monitoring System (WAMS) for improving power system monitoring, control and protection. They can improve the operation by providing highly precise and synchronised measurements near to real-time with higher frequency and accuracy. In order to achieve such objectives, a high-speed and reliable communications infrastructure is required to transfer time-critical PMU data from remote locations to the control centre. The signals measured by PMUs are transmitted across Local and Wide Area Networks, where they may encounter excessive delays. Signal delays can have a disruptive effect and make applications at best inefficient and at worse ineffective. The main research contribution of this thesis is the performance evaluation of communication infrastructures for WAMS. The evaluation begins from inside substations and continues over wide areas from substations to control centre. Through laboratory-based investigations and simulations, the performance of communications infrastructure in a typical power system substation has been analysed. In addition, the performance evaluation of WAMS communications infrastructure has been presented. In the modelling and analysis, an existing WAMS as installed on the GB transmission system has been considered. The actual PMU packets as received at the Phasor Data Concentrator (PDC) were captured for latency analysis. A novel algorithmic procedure has been developed and implemented to automate the large-scale latency calculations. Furthermore, the internal delays of PMUs have been investigated, determined and analysed. Subsequently, the WAMS has been simulated and detailed comparisons have been performed between the simulated model results and WAMS performance data captured from the actual WAMS. The validated WAMS model has been used for analysing possible future developments as well as to test newly proposed mechanisms, protocols, etc. in order to improve the communications infrastructure performance.
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Ekechukwu, Chinedum. "Improving Low Voltage Ride-Through Requirements (LVRT) Based on Hybrid PMU, Conventional Measurements in Wind Power Systems." Thesis, Karlstads universitet, Avdelningen för fysik och elektroteknik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-31449.
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Previously, conventional state estimation techniques have been used for state estimation in power systems. These conventional methods are based on steady state models. As a result of this, power system dynamics during disturbances or transient conditions are not adequately captured. This makes it challenging for operators in control centers to perform visual tracking of the system, proper fault diagnosis and even take adequate preemtive control measures to ensure system stability during voltage dips. Another challenge is that power systems are nonlinear in nature. There are multiple power components in operation at any given time making the system highly dynamic in nature. Consequently, the need to study and implement better dynamic estimation tools that capture system dynamics during disturbances and transient conditions is necessary. For this thesis work, we present the Unscented Kalman Filter (UKF) which integrates Unscented Transformation (UT) to Kalman Filtering. Our algorithm takes as input the output of a synchronous machine modeled in MATLAB/Simulink as well as data from a PMU device assumed to be installed at the terminal bus of the synchronous machine, and estimate the dynamic states of the system using a Kalman Filter. We have presented a detailed and analytical study of our proposed algorithm in estimating two dynamic states of the synchronous machine, rotor angle and rotor speed. Our study and result shows that our proposed methodology has better efficiency when compared to the results of the Extended Kalman Filter (EKF) algorithm in estimating dynamic states of a power system. Our results are presented and analyzed on the basis of how accurately the algorithm estimates the system states following various simulated transient and small-signal disturbances.
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Yoon, Yeo Jun. "Study of the utilization and benefits of phasor measurement units for large scale power system state estimation." Texas A&M University, 2005. http://hdl.handle.net/1969.1/3345.
Full textAbstract:
This thesis will investigate the impact of the use of the Phasor Measurement Units
(PMU) on the state estimation problem. First, incorporation of the PMU measurements in a
conventional state estimation program will be discussed. Then, the effect of adding PMU
measurements on the state estimation solution accuracy will be studied. Bad data
processing in the presence of PMU measurements will also be presented. Finally, a multiarea
state estimation method will be developed. This method involves a two level
estimation scheme, where the first level estimation is carried out by each area
independently. The second level estimation is required in order to coordinate the solutions
obtained by each area and also to detect and identify errors in the boundary measurements.
The first objective of this thesis is to formulate the full weighted least square state
estimation method using PMUs. The second objective is to derive the linear formulation of
the state estimation problem when using only PMUs. The final objective is to formulate a
two level multi-area state estimation scheme and illlustrate its performance via simulation
examples.
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Guo, Tingyan. "On-line identification of power system dynamic signature using PMU measurements and data mining." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/online-identification-of-power-system-dynamic-signature-using-pmu-measurements-and-data-mining(989938d4-c236-48a7-a653-17326937f5b4).html.
Full textAbstract:
This thesis develops a robust methodology for on-line identification of power system dynamic signature based on incoming system responses from Phasor Measurement Units (PMUs) in Wide Area Measurement Systems (WAMS). Data mining techniques are used in the methodology to convert real-time monitoring data into transient stability information and the pattern of system dynamic behaviour in the event of instability. The future power system may operate closer to its stability limit in order to improve its efficiency and economic value. The changing types and patterns of load and generation are resulting in highly variable operating conditions. Corrective control and stabilisation is becoming a potentially viable option to enable safer system operation. In the meantime, the number of WAMS projects and PMUs is rising, which will significantly improve the system situational awareness. The combination of all these factors means that it is of vital importance to exploit a new and efficient Transient Stability Assessment (TSA) tool in order to use real-time PMU data to support decisions for corrective control actions. Data mining has been studied as the innovative solution and considered as promising. This work contributes to a number of areas of power systems stability research, specifically around the data driven approach for real-time emergency mode TSA. A review of past research on on-line TSA using PMU measurements and data mining is completed, from which the Decision Tree (DT) method is found to be the most suitable. This method is implemented on the test network. A DT model is trained and the sensitivity of its prediction accuracy is assessed according to a list of network uncertainties. Results showed that DT is a useful tool for on-line TSA for corrective control approach. Following the implementation, a generic probabilistic framework for the assessment of the prediction accuracy of data mining models is developed. This framework is independent of the data mining technique. It performs an exhaustive search of possible contingencies in the testing process and weighs the accuracies according to the realistic probability distribution of uncertain system factors, and provides the system operators with the confidence level of the decisions made under emergency conditions. After that, since the TSA for corrective control usually focuses on transient stability status without dealing with the generator grouping in the event of instability, a two-stage methodology is proposed to address this gap and to identify power system dynamic signature. In this methodology, traditional binary classification is used to identify transient stability in the first stage; Hierarchical Clustering is used to pre-define patterns of unstable dynamic behaviour; and different multiclass classification techniques are investigated to identify the patterns in the second stage. Finally, the effects of practical issues related to WAMS on the data mining methodologies are investigated. Five categories of issues are discussed, including measurement error, communication noise, wide area signal delays, missing measurements, and a limited number of PMUs.
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Gyawali, Sanij. "Dynamic Load Modeling from PSSE-Simulated Disturbance Data using Machine Learning." Thesis, Virginia Tech, 2020. http://hdl.handle.net/10919/100591.
Full textAbstract:
Load models have evolved from simple ZIP model to composite model that incorporates
the transient dynamics of motor loads. This research utilizes the latest trend on Machine
Learning and builds reliable and accurate composite load model. A composite load model
is a combination of static (ZIP) model paralleled with a dynamic model. The dynamic
model, recommended by Western Electricity Coordinating Council (WECC), is an induction
motor representation. In this research, a dual cage induction motor with 20 parameters
pertaining to its dynamic behavior, starting behavior, and per unit calculations is used as
a dynamic model. For machine learning algorithms, a large amount of data is required.
The required PMU field data and the corresponding system models are considered Critical
Energy Infrastructure Information (CEII) and its access is limited. The next best option for
the required amount of data is from a simulating environment like PSSE. The IEEE 118 bus
system is used as a test setup in PSSE and dynamic simulations generate the required data
samples. Each of the samples contains data on Bus Voltage, Bus Current, and Bus Frequency
with corresponding induction motor parameters as target variables. It was determined that
the Artificial Neural Network (ANN) with multivariate input to single parameter output
approach worked best. Recurrent Neural Network (RNN) is also experimented side by side
to see if an additional set of information of timestamps would help the model prediction.
Moreover, a different definition of a dynamic model with a transfer function-based load
is also studied. Here, the dynamic model is defined as a mathematical representation of
the relation between bus voltage, bus frequency, and active/reactive power flowing in the
bus. With this form of load representation, Long-Short Term Memory (LSTM), a variation
of RNN, performed better than the concurrent algorithms like Support Vector Regression
(SVR). The result of this study is a load model consisting of parameters defining the load
at load bus whose predictions are compared against simulated parameters to examine their
validity for use in contingency analysis.Master of Science
Independent system Operators (ISO) and Distribution system operators (DSO) have a responsibility to provide uninterrupted power supply to consumers. That along with the longing to keep operating cost minimum, engineers and planners study the system beforehand and seek to find the optimum capacity for each of the power system elements like generators, transformers, transmission lines, etc. Then they test the overall system using power system models, which are mathematical representation of the real components, to verify the stability and strength of the system. However, the verification is only as good as the system models that are used. As most of the power systems components are controlled by the operators themselves, it is easy to develop a model from their perspective. The load is the only component controlled by consumers. Hence, the necessity of better load models. Several studies have been made on static load modeling and the performance is on par with real behavior. But dynamic loading, which is a load behavior dependent on time, is rather difficult to model. Some attempts on dynamic load modeling can be found already. Physical component-based and mathematical transfer function based dynamic models are quite widely used for the study. These load structures are largely accepted as a good representation of the systems dynamic behavior. With a load structure in hand, the next task is estimating their parameters. In this research, we tested out some new machine learning methods to accurately estimate the parameters. Thousands of simulated data are used to train machine learning models. After training, we validated the models on some other unseen data. This study finally goes on to recommend better methods to load modeling.
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Badayos, Noah Garcia. "Machine Learning-Based Parameter Validation." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/47675.
Full textAbstract:
As power system grids continue to grow in order to support an increasing energy demand, the system's behavior accordingly evolves, continuing to challenge designs for maintaining security. It has become apparent in the past few years that, as much as discovering vulnerabilities in the power network, accurate simulations are very critical. This study explores a classification method for validating simulation models, using disturbance measurements from phasor measurement units (PMU). The technique used employs the Random Forest learning algorithm to find a correlation between specific model parameter changes, and the variations in the dynamic response. Also, the measurements used for building and evaluating the classifiers were characterized using Prony decomposition. The generator model, consisting of an exciter, governor, and its standard parameters have been validated using short circuit faults. Single-error classifiers were first tested, where the accuracies of the classifiers built using positive, negative, and zero sequence measurements were compared. The negative sequence measurements have consistently produced the best classifiers, with majority of the parameter classes attaining F-measure accuracies greater than 90%. A multiple-parameter error technique for validation has also been developed and tested on standard generator parameters. Only a few target parameter classes had good accuracies in the presence of multiple parameter errors, but the results were enough to permit a sequential process of validation, where elimination of a highly detectable error can improve the accuracy of suspect errors dependent on the former's removal, and continuing the procedure until all corrections are covered.Ph. D.
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Khan, Mukhtaj. "Hadoop performance modeling and job optimization for big data analytics." Thesis, Brunel University, 2015. http://bura.brunel.ac.uk/handle/2438/11078.
Full textAbstract:
Big data has received a momentum from both academia and industry. The MapReduce model has emerged into a major computing model in support of big data analytics. Hadoop, which is an open source implementation of the MapReduce model, has been widely taken up by the community. Cloud service providers such as Amazon EC2 cloud have now supported Hadoop user applications. However, a key challenge is that the cloud service providers do not a have resource provisioning mechanism to satisfy user jobs with deadline requirements. Currently, it is solely the user responsibility to estimate the require amount of resources for their job running in a public cloud. This thesis presents a Hadoop performance model that accurately estimates the execution duration of a job and further provisions the required amount of resources for a job to be completed within a deadline. The proposed model employs Locally Weighted Linear Regression (LWLR) model to estimate execution time of a job and Lagrange Multiplier technique for resource provisioning to satisfy user job with a given deadline. The performance of the propose model is extensively evaluated in both in-house Hadoop cluster and Amazon EC2 Cloud. Experimental results show that the proposed model is highly accurate in job execution estimation and jobs are completed within the required deadlines following on the resource provisioning scheme of the proposed model. In addition, the Hadoop framework has over 190 configuration parameters and some of them have significant effects on the performance of a Hadoop job. Manually setting the optimum values for these parameters is a challenging task and also a time consuming process. This thesis presents optimization works that enhances the performance of Hadoop by automatically tuning its parameter values. It employs Gene Expression Programming (GEP) technique to build an objective function that represents the performance of a job and the correlation among the configuration parameters. For the purpose of optimization, Particle Swarm Optimization (PSO) is employed to find automatically an optimal or a near optimal configuration settings. The performance of the proposed work is intensively evaluated on a Hadoop cluster and the experimental results show that the proposed work enhances the performance of Hadoop significantly compared with the default settings.
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Chenine, Moustafa. "Wide area monitoring and control systems application communication requirements and simulation /." Licentiate thesis, Stockholm : Skolan för elektro- och systemteknik, Kungliga Tekniska högskolan, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-11316.
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Valverde, Mora Gustavo Adolfo. "Uncertainty and state estimation of power systems." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/uncertainty-and-state-estimation-of-power-systems(18c48a22-7ea2-4db2-9112-078a1eac6fe7).html.
Full textAbstract:
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.
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Pal, Anamitra. "PMU-Based Applications for Improved Monitoring and Protection of Power Systems." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/51093.
Full textAbstract:
Monitoring and protection of power systems is a task that has manifold objectives. Amongst others, it involves performing data mining, optimizing available resources, assessing system stresses, and doing data conditioning. The role of PMUs in fulfilling these four objectives forms the basis of this dissertation. Classification and regression tree (CART) built using phasor data has been extensively used in power systems. The splits in CART are based on a single attribute or a combination of variables chosen by CART itself rather than the user. But as PMU data consists of complex numbers, both the attributes, should be considered simultaneously for making critical decisions. An algorithm is proposed here that expresses high dimensional, multivariate data as a single attribute in order to successfully perform splits in CART.
In order to reap maximum benefits from placement of PMUs in the power grid, their locations must be selected judiciously. A gradual PMU placement scheme is developed here that ensures observability as well as protects critical parts of the system. In order to circumvent the computational burden of the optimization, this scheme is combined with a topology-based system partitioning technique to make it applicable to virtually any sized system.
A power system is a dynamic being, and its health needs to be monitored at all times. Two metrics are proposed here to monitor stress of a power system in real-time. Angle difference between buses located across the network and voltage sensitivity of buses lying in the middle are found to accurately reflect the static and dynamic stress of the system. The results indicate that by setting appropriate alerts/alarm limits based on these two metrics, a more secure power system operation can be realized.
A PMU-only linear state estimator is intrinsically superior to its predecessors with respect to performance and reliability. However, ensuring quality of the data stream that leaves this estimator is crucial. A methodology for performing synchrophasor data conditioning and validation that fits neatly into the existing linear state estimation formulation is developed here. The results indicate that the proposed methodology provides a computationally simple, elegant solution to the synchrophasor data quality problem.Ph. D.
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Zhu, Kun. "Data Quality in Wide-Area Monitoring and Control Systems : PMU Data Latency, Completness, and Design of Wide-Area Damping Systems." Doctoral thesis, KTH, Industriella informations- och styrsystem, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-129078.
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The strain on modern electrical power system operation has led to an ever increasing utilization of new Information Communication Technology (ICT) systems to enhance the reliability and efficiency of grid operation. Among these proposals, Phasor Measurement Unit (PMU)-based Wide-Area Monitoring and Control (WAMC) systems have been recognized as one of the enablers of “Smart Grid”, particularly at the transmission level, due to their capability to improve the real-time situational awareness of the grid. These systems differ from the conventional Supervisory Control And Data Acquisition (SCADA) systems in that they provide globally synchronized measurements at high resolutions. On the other hand, the WAMC systems also impose several stringent requirements on the underlying ICT systems, including performance, security, and availability, etc. As a result, the functionality of the WAMC applications is heavily, but not exclusively, dependent on the capabilities of the underlying ICT systems. This tight coupling makes it difficult to fully exploit the benefits of the synchrophasor technology without the proper design and configuration of ICT systems to support the WAMC applications. The strain on modern electrical power system operation has led to an ever increasing utilization of new Information Communication Technology (ICT) systems to enhance the reliability and efficiency of grid operation. Among these proposals, Phasor Measurement Unit (PMU)-based Wide-Area Monitoring and Control (WAMC) systems have been recognized as one of the enablers of “Smart Grid”, particularly at the transmission level, due to their capability to improve the real-time situational awareness of the grid. These systems differ from the conventional Supervisory Control And Data Acquisition (SCADA) systems in that they provide globally synchronized measurements at high resolutions. On the other hand, the WAMC systems also impose several stringent requirements on the underlying ICT systems, including performance, security, and availability, etc. As a result, the functionality of the WAMC applications is heavily, but not exclusively, dependent on the capabilities of the underlying ICT systems. This tight coupling makes it difficult to fully exploit the benefits of the synchrophasor technology without the proper design and configuration of ICT systems to support the WAMC applications. In response to the above challenges, this thesis addresses the dependence of WAMC applications on the underlying ICT systems. Specifically, two of the WAMC system data quality attributes, latency and completeness, are examined together with their effects on a typical WAMC application, PMU-based wide-area damping systems. The outcomes of this research include quantified results in the form of PMU communication delays and data frame losses, and probability distributions that can model the PMU communication delays. Moreover, design requirements are determined for the wide-area damping systems, and three different delay-robust designs for this WAMC application are validated based on the above results. Finally, a virtual PMU is developed to perform power system and communication network co-simulations. The results reported by this thesis offer a prospect for better predictions of the performance of the supporting ICT systems in terms of PMU data latency and completeness. These results can be further used to design and optimize the WAMC applications and their underlying ICT systems in an integrated manner. This thesis also contributes a systematic approach to design the wide-area damping system considering the PMU data latency and completeness. Finally, the developed virtual PMU, as part of a co-simulation platform, provides a means to investigate the dependence of WAMC applications on the capabilities of the underlying ICT systems in a cost-efficient manner.QC 20131015
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Peric, Vedran. "Non-intrusive Methods for Mode Estimation in Power Systems using Synchrophasors." Doctoral thesis, KTH, Elkraftteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-182134.
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Real-time monitoring of electromechanical oscillations is of great significance for power system operators; to this aim, software solutions (algorithms) that use synchrophasor measurements have been developed for this purpose. This thesis investigates different approaches for improving mode estimation process by offering new methods and deepening the understanding of different stages in the mode estimation process. One of the problems tackled in this thesis is the selection of synchrophasor signals used as the input for mode estimation. The proposed selection is performed using a quantitative criterion that is based on the variance of the critical mode estimate. The proposed criterion and associated selection method, offer a systematic and quantitative approach for PMU signal selection. The thesis also analyzes methods for model order selection used in mode estimation. Further, negative effects of forced oscillations and non-white noise load random changes on mode estimation results have been addressed by exploiting the intrinsic power system property that the characteristics of electromechanical modes are predominately determined by the power generation and transmission network. An improved accuracy of the mode estimation process can be obtained by intentionally injecting a probing disturbance. The thesis presents an optimization method that finds the optimal spectrum of the probing signals. In addition, the probing signal with the optimal spectrum is generated considering arbitrary time domain signal constraints that can be imposed by various probing signal generating devices. Finally, the thesis provides a comprehensive description of a practical implementation of a real-time mode estimation tool. This includes description of the hardware, software architecture, graphical user interface, as well as details of the most important components such as the Statnett’s SDK that allows easy access to synchrophasor data streams.The Doctoral Degrees issued upon completion of the programme are issued by Comillas Pontifical University, Delft University of Technology and KTH Royal Institute of Technology. The invested degrees are official in Spain, the Netherlands and Sweden, respectively.
QC 20160218
FP7 iTesla
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Fan, Wen. "ADVANCED FAULT AREA IDENTIFICATION AND FAULT LOCATION FOR TRANSMISSION AND DISTRIBUTION SYSTEMS." UKnowledge, 2019. https://uknowledge.uky.edu/ece_etds/144.
Full textAbstract:
Fault location reveals the exact information needed for utility crews to timely and promptly perform maintenance and system restoration. Therefore, accurate fault location is a key function in reducing outage time and enhancing power system reliability.
Modern power systems are witnessing a trend of integrating more distributed generations (DG) into the grid. DG power outputs may be intermittent and can no longer be treated as constants in fault location method development. DG modeling is also difficult for fault location purpose. Moreover, most existing fault location methods are not applicable to simultaneous faults. To solve the challenges, this dissertation proposes three impedance-based fault location algorithms to pinpoint simultaneous faults for power transmission systems and distribution systems with high penetration of DGs.
The proposed fault location algorithms utilize the voltage and/or current phasors that are captured by phasor measurement units. Bus impedance matrix technique is harnessed to establish the relationship between the measurements and unknown simultaneous fault locations. The distinct features of the proposed algorithms are that no fault types and fault resistances are needed to determine the fault locations. In particular, Type I and Type III algorithms do not need the information of source impedances and prefault measurements to locate the faults. Moreover, the effects of shunt capacitance are fully considered to improve fault location accuracy. The proposed algorithms for distribution systems are validated by evaluation studies using Matlab and Simulink SimPowerSystems on a 21 bus distribution system and the modified IEEE 34 node test system. Type II fault location algorithm for transmission systems is applicable to untransposed lines and is validated by simulation studies using EMTP on a 27 bus transmission system.
Fault area identification method is proposed to reduce the number of line segments to be examined for fault location. In addition, an optimal fault location method that can identify possible bad measurement is proposed for enhanced fault location estimate. Evaluation studies show that the optimal fault location method is accurate and effective.
The proposed algorithms can be integrated into the existing energy management system for enhanced fault management capability for power systems.