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1
Jones, Kevin David. "Three-Phase Linear State Estimation with Phasor Measurements". Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/32119.
Testo completoAbstract (sommario):
Given the ability of the Phasor Measurement Unit (PMU) to directly measure the system state and the increasing implementation of PMUs across the electric power industry, a natural expansion of state estimation techniques would be one that employed the exclusive use of PMU data. Dominion Virginia Power and the Department of Energy (DOE) are sponsoring a research project which aims to implement a three phase linear tracking state estimator on Dominionâ s 500kV network that would use only PMU measurements to compute the system state. This thesis represents a portion of the work completed during the initial phase of the research project. This includes the initial development and testing of two applications: the three phase linear state estimator and the topology processor. Also presented is a brief history of state estimation and PMUs, traditional state estimation techniques and techniques with mixed phasor data, a development of the linear state estimation algorithms and a discussion of the future work associate with this research project.Master of Science
2
Chen, Jian. "Accurate frequency estimation with phasor angles". Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-12042009-020203/.
Testo completo
3
Chen, Jiaxiong. "Power System State Estimation Using Phasor Measurement Units". UKnowledge, 2013. http://uknowledge.uky.edu/ece_etds/35.
Testo completoAbstract (sommario):
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.
4
Zhou, Ming. "Advanced System Monitoring with Phasor Measurements". Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/27813.
Testo completoAbstract (sommario):
Phasor Measurement Units (PMUs) are widely acknowledged as one of the most promising developments in the field of real-time monitoring of power systems. By aligning the time stamps of voltage and current phasor measurements that are consistent with Coordinated Universal Time (UTC), a coherent picture of the power system state can be achieved through either direct measurements or simple linear calculations. With the growing number of PMUs planned for installation in the near future, both utilities and research institutions are looking for the best solutions to the placement of units as well as to the applications that make the most of phasor measurements.
This dissertation explores a method for optimal PMU placement as well as two applications of synchronized phasor measurements in state estimation. The pre-processing PMU placement method prepares the system data for placement optimization and reduces the size of the optimization problem. It is adaptive to most of the optimal placement methods and can save a large amount of computational effort. Depth of un-observability is one of the criteria to allow the most benefit out of a staged placement of the units. PMUs installed in the system provide synchronized phasor measurements that are highly beneficial to power system state estimations. Two related applications are proposed in the dissertation. First, a post-processing inclusion of phasor measurements in state estimators is introduced. This method avoids the revision of the existing estimators and is able to realize similar results as mixing phasor data with traditional SCADA with a linear afterwards step. The second application is a method to calibrate instrument transformers remotely using phasor measurements. Several scans of phasor measurements are used to accomplish estimating system states in conjunction with complex instrument transformer correction factors. Numerical simulation results are provided for evaluation of the calibration performance with respect to the number of scans and load conditions.
Conducting theoretical and numerical analysis, the methods and algorithms developed in this dissertation are aimed to strategically place PMUs and to incorporate phasor measurements into state estimators effectively and extensively for better system state monitoring. Simulation results show that the proposed placement method facilitates approaching the exact optimal placement while keep the computational effort low. Simulation also shows that the use of phasor measurement with the proposed instrument transformer correction factors and proposed state estimation enhancement largely improves the quality of state estimations.Ph. D.
5
Khan, Muhammad Ayaz. "State Estimation and Voltage Phasor Measurements in Distribution Networks". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018.
Cerca il testo completoAbstract (sommario):
The thesis faces the problem of the use of phasor measurement units (PMU) for the state estimation in distribution networks, and in particular the problem of a suitable phasor estimation in different buses of a distribution network in absence of proper time synchronization with the universal time reference. In particular, an approach recently proposed by Mingotti et al. to obtain an equivalent synchronization, starting from asynchronous measurement has been presented and tested. This method assumes the availability of a distributed measurement system where each remote unit is a power meter. The algorithm implemented in Matlab by Mingotti et al. has been studied and tested by a comparison with the load flow results provided by the Electromagnetic Transient Program (EMTP-RV). The algorithm adopts two different methods for voltage phasor estimation, the first calculate the phasors as a linear combination of measured voltages, the second makes use of the longitudinal equivalent impedances of the network branches. In order to tune the load flow calculation environment, different case studies have been analyzed, and in particular the European Medium Voltage distribution test network and the European Low voltage distribution test network proposed by CIGRE Task Force C6.04.02. During the analysis, for each bus, voltages, currents and phase displacements are calculated and compared with the benchmark results reported in the Cigré brochure. A four-buses network has been considered to test both methods of the above mentioned algorithm. The obtained results are very close to the one provided by EMTP. The accuracy of the algorithm appears to get worse in case of lightly loaded network, a behaviour that is justified by the small phase displacements that the voltages show in these condition. The studied equivalent synchronization procedure can be usefully implemented to achieve a widespread monitoring of a power network at affordable cost.
6
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.
Testo completoAbstract (sommario):
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
7
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/.
Testo completoAbstract (sommario):
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.
8
Nuqui, Reynaldo Francisco. "State Estimation and Voltage Security Monitoring Using Synchronized Phasor Measurements". Diss., Virginia Tech, 2001. http://hdl.handle.net/10919/28266.
Testo completoAbstract (sommario):
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.
9
Wehbe, Yasser. "Model Estimation of Electric Power Systems by Phasor Measurement Units Data". Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4419.
Testo completoAbstract (sommario):
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.
10
Tuku, Woldu. "Distributed state estimation using phasor measurement units (PMUs)for a system snapshot". Kansas State University, 2012. http://hdl.handle.net/2097/14129.
Testo completoAbstract (sommario):
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.
11
Zhang, Xuan. "High Precision Dynamic Power System Frequency Estimation Algorithm Based on Phasor Approach". Thesis, Virginia Tech, 2004. http://hdl.handle.net/10919/31001.
Testo completoAbstract (sommario):
An internet-based, real-time, Global Positioning System (GPS) ---synchronized relative to the wide-area frequency-monitoring network (FNET) ---has been developed at Virginia Tech. In this FNET system, an algorithm that employs the relationship between phasor angles and deviated frequency [13] is used to calculate both frequency and its rate of change. Tests of the algorithm disclose that, for non-pure sinusoidal input (as compared to pure sinusoidal input), significant errors in the output frequency will result. Three approaches for increasing the accuracy of the output frequency were compared. The first---increasing the number of samples per cycle N---proved ineffective. The second---using the average of the first estimated frequencies rather than the instant first estimated frequency as the resampling frequency---produces a moderate increase in accuracy of the frequency estimation. The third---multiple resampling---significantly increased accuracy. But both the second and the third become ineffective to the extent the input is not pure sinusoidal.
From a practical standpoint, attention needs to be paid toward eliminating noise in the input data from the power grid so as to make it more purely sinusoidal. Therefore, it will be worthwhile to test more sophisticated digital filters for processing the input data before feeding it to the algorithm.Master of Science
12
Ghassempour, Aghamolki Hossein. "Phasor Measurement Unit Data-based States and Parameters Estimation in Power System". Scholar Commons, 2016. http://scholarcommons.usf.edu/etd/6505.
Testo completoAbstract (sommario):
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.
13
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.
Testo completoAbstract (sommario):
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.
14
Guo, Hengdao. "Frequency Tracking and Phasor Estimation Using Least Squares and Total Least Squares Algorithms". UKnowledge, 2014. http://uknowledge.uky.edu/ece_etds/57.
Testo completoAbstract (sommario):
System stability plays an important role in electric power systems. With the development of electric power system, the scale of the electric grid is now becoming larger and larger, and many renewable energy resources are integrated in the grid. However, at the same time, the stability and safety issues of electric power system are becoming more complicated. Frequency and phasors are two critical parameters of the system stability. Obtaining these two parameters have been great challenges for decades. Researchers have provided various kinds of algorithms for frequency tracking and phasor estimation. Among them, Least Squares (LS) algorithm is one of the most commonly used algorithm. This thesis studies the LS algorithm and the Total Least Squares (TLS) algorithm working on frequency tracking and phasor estimation. In order to test the performance of the two algorithms, some simulations have been made in the Matlab. The Total Vector Error (TVE) is a commonly used performance criteria, and the TVE results of the two algorithms are compared. The TLS algorithm performs better than LS algorithm when the frequencies of all harmonic components are given.
15
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.
Testo completoAbstract (sommario):
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.
16
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.
Testo completoAbstract (sommario):
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.
17
Culliss, Jerel Alan. "A Method for PMU-Based Reconfigurable Monitoring". Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/35646.
Testo completoAbstract (sommario):
Given an increasing tendency towards distributed generation and alternative energy sources, the power grid must be more carefully monitored in order to ensure stability. Phasor Measurement Units (PMUs) provide very good observation of a small area of a network, but their relatively high cost prevents them from being deployed at every point. Therefore, to monitor an entire network, State Estimation is still required. By combining these two techniques, the accuracy and speed of power network monitoring can be improved. This thesis presents a method for achieving this goal from both hardware and computational perspectives. Practical considerations for PMU placement are discussed, such as instrument transformer calibration, and an algorithm is developed to apply this technique to any power system. The resulting method is termed reconfigurable monitoring - computationally isolated areas which may be grouped as necessary to allow for flexibility in power system monitoring.Master of Science
18
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.
Testo completoAbstract (sommario):
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.
19
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.
Testo completo
20
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.
Testo completoAbstract (sommario):
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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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.
Testo completoAbstract (sommario):
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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Li, Xiaojuan. "Estimations of power system frequency, phasors and their applications for fault location on power transmission lines". University of Western Australia. School of Electrical, Electronic and Computer Engineering, 2008. http://theses.library.uwa.edu.au/adt-WU2008.0125.
Testo completoAbstract (sommario):
The thesis is devoted to the development of new algorithms for estimation of system frequency, power system phasors and transmission line fault location in the context of power system protection and control. A z-transform signal model combined with a nonlinear post-filtering scheme to estimate the operating frequency in a power system is first developed in the thesis. The signal model parameters are identified by an optimisation method in which the error between the model output and the actual signal that represents a voltage or current in the power system is minimised. The form and the structure of the signal model do not require iterations in the optimisation process for parameter identification. The system operating frequency is directly evaluated from the model parameters. Effects of noise and any frequency components other than the operating or supply-frequency on the accuracy are countered very effectively by applying a median post-filtering on the time series representing the frequency estimates derived from the model. Extensive simulation studies and comparisons with previously-published frequency estimation techniques confirm the high performance of the method developed in the thesis in terms of accuracy and time delay. With respect to power system phasor estimation, a method is developed based on waveform interpolation in the discrete time-domain to counter the spectral leakage errors arising in forming, by discrete Fourier transform (DFT), the supply frequency phasors representing power system voltages and currents when there are system frequency deviations from the nominal value. The interpolation scheme allows DFT evaluation to be performed with a time window length which is exactly equal to the fundamental period of the voltage or current waveform. Comparative studies presented in the thesis confirm the improvements achieved by the method proposed over other previouslypublished techniques in terms of accuracy and computing time. With the availability of accurate operating frequency and phasor estimates, an optimal fault location method based on multi-conductor distributedparameter line model is developed. The method is a general one which is applicable to any transmission line configurations, including multi-terminal lines. The fault location method is based on the minimisation of an objective function in which the fault distance is a variable. The objective function is formed from combining the phase-variable distributed-parameter equations of individual line sections from the fault point to the line terminals. The multivariable minimisation leads to high accuracy and robustness of the fault location algorithm in which any voltage/current measurement errors, including sampling time synchronisation errors, are represented in the estimation procedure as variables in addition to the fault distance. Extensive simulation studies are performed to verify that the method developed is highly accurate and robust. The thesis is supported by two international publications of which the candidate is a joint author.
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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.
Testo completoAbstract (sommario):
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.
24
Zhao, Junbo. "A Robust Dynamic State and Parameter Estimation Framework for Smart Grid Monitoring and Control". Diss., Virginia Tech, 2018. http://hdl.handle.net/10919/83423.
Testo completoAbstract (sommario):
The enhancement of the reliability, security, and resiliency of electric power systems depends on the availability of fast, accurate, and robust dynamic state estimators. These estimators should be robust to gross errors on the measurements and the model parameter values while providing good state estimates even in the presence of large dynamical system model uncertainties and non-Gaussian thick-tailed process and observation noises. It turns out that the current Kalman filter-based dynamic state estimators given in the literature suffer from several important shortcomings, precluding them from being adopted by power utilities for practical applications. To be specific, they cannot handle (i) dynamic model uncertainty and parameter errors; (ii) non-Gaussian process and observation noise of the system nonlinear dynamic models; (iii) three types of outliers; and (iv) all types of cyber attacks. The three types of outliers, including observation, innovation, and structural outliers are caused by either an unreliable dynamical model or real-time synchrophasor measurements with data quality issues, which are commonly seen in the power system.
To address these challenges, we have pioneered a general theoretical framework that advances both robust statistics and robust control theory for robust dynamic state and parameter estimation of a cyber-physical system. Specifically, the generalized maximum-likelihood-type (GM)-estimator, the unscented Kalman filter (UKF), and the H-infinity filter are integrated into a unified framework to yield various centralized and decentralized robust dynamic state estimators. These new estimators include the GM-iterated extended Kalman filter (GM-IEKF), the GM-UKF, the H-infinity UKF and the robust H-infinity UKF. The GM-IEKF is able to handle observation and innovation outliers but its statistical efficiency is low in the presence of non-Gaussian system process and measurement noise. The GM-UKF addresses this issue and achieves a high statistical efficiency under a broad range of non-Gaussian process and observation noise while maintaining the robustness to observation and innovation outliers. A reformulation of the GM-UKF with multiple hypothesis testing further enables it to handle structural outliers. However, the GM-UKF may yield biased state estimates in presence of large system uncertainties. To this end, the H-infinity UKF that relies on robust control theory is proposed. It is shown that H-infinity is able to bound the system uncertainties but lacks of robustness to outliers and non-Gaussian noise. Finally, the robust H-infinity filter framework is proposed that leverages the H-infinity criterion to bound system uncertainties while relying on the robustness of GM-estimator to filter out non-Gaussian noise and suppress outliers. Furthermore, these new robust estimators are applied for system bus frequency monitoring and control and synchronous generator model parameter calibration. Case studies of several different IEEE standard systems show the efficiency and robustness of the proposed estimators.Ph. D.
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Krčál, Vít. "Ověření funkce metody Vdip na fyzikálním modelu VN soustavy". Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2019. http://www.nusl.cz/ntk/nusl-400576.
Testo completoAbstract (sommario):
This Master's thesis is focused on creating of an algorithm which calculates changes of negative-sequence voltages and currents from their instantaneous values. That allows to conduct localization of asymmetrical faults in MV network in line with the Vdip method, which is based on monitoring the changes of negative-sequence components at distribution substations and at a sub-transmission station. The algorithm is being developed in Matlab environment with continuous implementation of partial procedures which are being assessed and compared with each other. A study of phasor estimating methods is carried out with pointing out related problems which are mainly caused by Ripple control and deviation of system frequency from its nominal value. Optimization precautions are designed to mitigate these problems. For elimination of the Ripple control effects a method based on averaging is presented. The deviation of system frequency is dealt with by resampling the original data recordings. The analysis processes are tested by both simulation signals and real measured data. The optimized algorithm enables precise calculation of negative-sequence components changes which is the main contribution of this thesis. The constructed algorithm is used in verification of the Vdip method on physical model of MV network. For these purposes a simple distribution network is created within which ground faults on different places and with different resistances are realised. The results of localization are not convincing which is mainly caused by specific features of laboratory power line models which are constructed with heterogenous parameters.
26
Ängquist, Lennart. "Synchronous Voltage Reversal Control of Thyristor Controlled Series Capacitor". Doctoral thesis, KTH, Electrical Systems, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3396.
Testo completoAbstract (sommario):
Series compensation of transmission lines is an effectiveand cheap method of improving the power transmission systemperformance. Series capacitors virtually reduces the length ofthe line making it easier to keep all parts of the power systemrunning in synchronism and to maintain a constant voltage levelthroughout the system. In Sweden this technology has been inuse since almost 50 years.
The possibility to improve the performance of the ACtransmission system utilizing power electronic equipment hasbeen discussed a lot since about ten years. Some newsemiconductor based concepts have been developed beside thesince long established HVDC and SVC technologies. The ThyristorControlled Series Capacitor (TCSC) is one such concept. Byvarying the inserted reactance an immediate and well-definedimpact on the active power flow in the transmission line isobtained. Several potential applications, specifically poweroscillation damping, benefit from this capability. The conceptimplied the requirement to design a semiconductor valve, whichcan be inserted directly in the high-voltage power circuit.This certainly presented a technical challenge but thestraightforward approach appeared to be a cost-effectivealternative with small losses.
It was also realized that the TCSC exhibits quite differentbehaviour with respect to subsynchronous frequency componentsin the line current as compared to the fixed series capacitorbank. This was a very interesting aspect as the risk ofsubsynchronous resonance (SSR), which just involves such linecurrent components, has hampered the use of series compensationin power systems using thermal generating plants.
The thesis deals with the modelling and control aspects ofTCSC. A simplifying concept, the equivalent, instantaneousvoltage reversal, is introduced to represent the action of thethyristor controlled inductive branch, which is connected inparallel with the series capacitor bank in the TCSC. The idealvoltage reversal is used in the thesis in order to describe andexplain the TCSC dynamics, to investigate its apparentimpedance at various frequencies, as a platform forsynthesizing the boost control system and as the base elementin deriving a linear, small-signal dynamical model of thethree-phase TCSC. Quantitative Feedback Theory (QFT) then hasbeen applied to the TCSC model in order to tune its boostregulator taking into account the typical variation ofparameters that exists in a power system. The impact of theboost control system with respect to damping of SSR is finallybeing briefly looked at.
Keywords:Thyristor Controlled Series Capacitor, TCSC,FACTS, reactive power compensation, boost control, phasorestimation, Quantitative Feedback Theory, subsynchronousresonance, SSR.
27
Oubrahim, Zakarya. "On electric grid power quality monitoring using parametric signal processing techniques". Thesis, Brest, 2017. http://www.theses.fr/2017BRES0102/document.
Testo completoAbstract (sommario):
Cette thèse porte sur la surveillance des perturbations de la qualité de l’énergie d’un réseau électrique via des techniques paramétriques de traitement du signal. Pour élaborer nos algorithmes de traitement du signal, nous avons traité les problèmes d’estimation des différentes grandeurs du réseau électrique triphasé et de classification des perturbations de la qualité d'énergie. Pour ce qui est du problème d’estimation, nous avons développé une technique statistique basée sur le maximum de vraisemblance. La technique proposée exploite la nature multidimensionnelle des signaux électriques. Elle utilise un algorithme d’optimisation pour minimiser la fonction de vraisemblance. L’algorithme utilisé permet d’améliorer les performances d’estimation tout en étant d’une faible complexité calculatoire en comparaison aux algorithmes classiques. Une analyse plus poussée de l’estimateur proposé a été effectuée. Plus précisément, ses performances sont évaluées sous un environnement incluant entre autres la pollution harmonique et interharmonique et le bruit. Les performances sont également comparées aux exigences de la norme IEEE C37.118.2011. La problématique de classification dans les réseaux électriques triphasés a plus particulièrement concerné les perturbations que sont les creux de tension et les surtensions. La technique de classification proposée consiste globalement en deux étapes : 1) une pré-classification du signal dans l’une des 4 préclasses établis et en 2) une classification du type de perturbation à l’aide de l’estimation des composants symétriques.Les performances du classificateur proposé ont été évaluées, entre autres, pour différentes nombre de cycles, de SNR et de THD. L’estimateur et le classificateur proposés ont été validés en simulation et en utilisant les données d’un réseau électrique réel du DOE/EPRI National Database of Power System Events. Les résultats obtenus illustrent clairement l’efficacité des algorithmes proposés quand à leur utilisation comme outil de surveillance de la qualité d’énergieThis thesis deals with electric grid monitoring of power quality (PQ) disturbances using parametric signal processing techniques. The first contribution is devoted to the parametric spectral estimation approach for signal parameter extraction. The proposed approach exploits the multidimensional nature of the electrical signals.For spectral estimation, it uses an optimization algorithm to minimize the likelihood function. In particular, this algorithm allows to improve the estimation accuracy and has lower computational complexity than classical algorithms. An in-depth analysis of the proposed estimator has been performed. Specifically, the estimator performances are evaluated under noisy, harmonic, interharmonic, and off-nominal frequency environment. These performances are also compared with the requirements of the IEEE Standard C37.118.2011. The achieved results have shown that the proposed approach is an attractive choice for PQ measurement devices such as phasor measurement units (PMUs). The second contribution deals with the classification of power quality disturbances in three-phase power systems. Specifically, this approach focuses on voltage sag and swell signatures. The proposed classification approach is based on two main steps: 1) the signal pre-classification into one of 4 pre-classes and 2) the signature type classification using the estimate of the symmetrical components. The classifier performances have been evaluated for different data length, signal to noise ratio, interharmonic, and total harmonic distortion. The proposed estimator and classifier are validated using real power system data obtained from the DOE/EPRI National Database of Power System Events. The achieved simulations and experimental results clearly illustrate the effectiveness of the proposed techniques for PQ monitoring purpose
28
Zadeh, Ramin Agha. "Performance control of distributed generation using digital estimation of signal parameters". Thesis, Queensland University of Technology, 2010. https://eprints.qut.edu.au/47011/1/Ramin_Agha_Zadeh_Thesis.pdf.
Testo completoAbstract (sommario):
The Queensland University of Technology (QUT) allows the presentation of a thesis for the Degree of Doctor of Philosophy in the format of published or submitted papers, where such papers have been published, accepted or submitted during the period of candidature. This thesis is composed of seven published/submitted papers, of which one has been published, three accepted for publication and the other three are under review. This project is financially supported by an Australian Research Council (ARC) Discovery Grant with the aim of proposing strategies for the performance control of Distributed Generation (DG) system with digital estimation of power system signal parameters.
Distributed Generation (DG) has been recently introduced as a new concept for the generation of power and the enhancement of conventionally produced electricity. Global warming issue calls for renewable energy resources in electricity production. Distributed generation based on solar energy (photovoltaic and solar thermal), wind, biomass, mini-hydro along with use of fuel cell and micro turbine will gain substantial momentum in the near future. Technically, DG can be a viable solution for the issue of the integration of renewable or non-conventional energy resources. Basically, DG sources can be connected to local power system through power electronic devices, i.e. inverters or ac-ac converters. The interconnection of DG systems to power system as a compensator or a power source with high quality performance is the main aim of this study. Source and load unbalance, load non-linearity, interharmonic distortion, supply voltage distortion, distortion at the point of common coupling in weak source cases, source current power factor, and synchronism of generated currents or voltages are the issues of concern.
The interconnection of DG sources shall be carried out by using power electronics switching devices that inject high frequency components rather than the desired current. Also, noise and harmonic distortions can impact the performance of the control strategies. To be able to mitigate the negative effect of high frequency and harmonic as well as noise distortion to achieve satisfactory performance of DG systems, new methods of signal parameter estimation have been proposed in this thesis. These methods are based on processing the digital samples of power system signals. Thus, proposing advanced techniques for the digital estimation of signal parameters and methods for the generation of DG reference currents using the estimates provided is the targeted scope of this thesis. An introduction to this research – including a description of the research problem, the literature review and an account of the research progress linking the research papers – is presented in Chapter 1.
One of the main parameters of a power system signal is its frequency. Phasor Measurement (PM) technique is one of the renowned and advanced techniques used for the estimation of power system frequency. Chapter 2 focuses on an in-depth analysis conducted on the PM technique to reveal its strengths and drawbacks. The analysis will be followed by a new technique proposed to enhance the speed of the PM technique while the input signal is free of even-order harmonics. The other techniques proposed in this thesis as the novel ones will be compared with the PM technique comprehensively studied in Chapter 2.
An algorithm based on the concept of Kalman filtering is proposed in Chapter 3. The algorithm is intended to estimate signal parameters like amplitude, frequency and phase angle in the online mode. The Kalman filter is modified to operate on the output signal of a Finite Impulse Response (FIR) filter designed by a plain summation. The frequency estimation unit is independent from the Kalman filter and uses the samples refined by the FIR filter. The frequency estimated is given to the Kalman filter to be used in building the transition matrices. The initial settings for the modified Kalman filter are obtained through a trial and error exercise.
Another algorithm again based on the concept of Kalman filtering is proposed in Chapter 4 for the estimation of signal parameters. The Kalman filter is also modified to operate on the output signal of the same FIR filter explained above. Nevertheless, the frequency estimation unit, unlike the one proposed in Chapter 3, is not segregated and it interacts with the Kalman filter. The frequency estimated is given to the Kalman filter and other parameters such as the amplitudes and phase angles estimated by the Kalman filter is taken to the frequency estimation unit.
Chapter 5 proposes another algorithm based on the concept of Kalman filtering. This time, the state parameters are obtained through matrix arrangements where the noise level is reduced on the sample vector. The purified state vector is used to obtain a new measurement vector for a basic Kalman filter applied. The Kalman filter used has similar structure to a basic Kalman filter except the initial settings are computed through an extensive math-work with regards to the matrix arrangement utilized.
Chapter 6 proposes another algorithm based on the concept of Kalman filtering similar to that of Chapter 3. However, this time the initial settings required for the better performance of the modified Kalman filter are calculated instead of being guessed by trial and error exercises. The simulations results for the parameters of signal estimated are enhanced due to the correct settings applied. Moreover, an enhanced Least Error Square (LES) technique is proposed to take on the estimation when a critical transient is detected in the input signal. In fact, some large, sudden changes in the parameters of the signal at these critical transients are not very well tracked by Kalman filtering. However, the proposed LES technique is found to be much faster in tracking these changes. Therefore, an appropriate combination of the LES and modified Kalman filtering is proposed in Chapter 6. Also, this time the ability of the proposed algorithm is verified on the real data obtained from a prototype test object.
Chapter 7 proposes the other algorithm based on the concept of Kalman filtering similar to those of Chapter 3 and 6. However, this time an optimal digital filter is designed instead of the simple summation FIR filter. New initial settings for the modified Kalman filter are calculated based on the coefficients of the digital filter applied. Also, the ability of the proposed algorithm is verified on the real data obtained from a prototype test object.
Chapter 8 uses the estimation algorithm proposed in Chapter 7 for the interconnection scheme of a DG to power network. Robust estimates of the signal amplitudes and phase angles obtained by the estimation approach are used in the reference generation of the compensation scheme. Several simulation tests provided in this chapter show that the proposed scheme can very well handle the source and load unbalance, load non-linearity, interharmonic distortion, supply voltage distortion, and synchronism of generated currents or voltages. The purposed compensation scheme also prevents distortion in voltage at the point of common coupling in weak source cases, balances the source currents, and makes the supply side power factor a desired value.
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Marsolla, Rafael. "Estimação fasorial em tempo real utilizando um algoritmo genético compacto multiobjetivo". Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/18/18154/tde-02062015-151039/.
Testo completoAbstract (sommario):
A medição fasorial sincronizada é utilizada hoje como forma de aprimorar a operação de um Sistema Elétrico de Potência (SEP), empregando unidades de medição fasorial estrategicamente localizadas e instaladas. Estas realizam a aquisição do sinal elétrico e posteriormente a estimação dos fasores de tensão e corrente sincronizados no tempo, os quais indicam o comportamento do SEP em uma localidade específica. Este trabalho multidisciplinar propõe a análise e implementação de um método computacional evolutivo, o Algoritmo Genético Compacto Multiobjetivo (AGCM) aplicado ao problema de medição fasorial, amplamente utilizado por exemplo, no monitoramento de um SEP, comportando-se assim como uma unidade medidora de fasor, ou Phasor Measurement Unit (PMU). O AGCM aqui apresentado tem como principal característica a análise multiobjetiva do problema. Pelo fato de todo SEP ser trifásico, é proposto esta nova abordagem, onde é considerando para a estimação fasorial as três fases de forma conjunta, e não mais estimadas independentemente. Assim o AGCM proposto considera em seu mapeamento genético dos indivíduos, as características do sinais das três fases, diferentemente da abordagem mono-objetivo, onde cada fase do SEP é modelada sobre um indivíduo diferente. Posteriormente para garantir a eficácia do método evolutivo quando em operação em um cenário de tempo real, é proposto uma plataforma de aquisição de dados e processamento, inspirada em trabalhos anteriormente desenvolvidos, permitindo a integração de todos os módulos que formarão um PMU para análise fasorial em tempo real. Aqui um sistema de Global Positioning System (GPS) existente é proposto como forma de sincronismo entre os PMUs, sincronizando uma gama de equipamentos em um única referência de tempo, com a precisão necessária. Para auxiliar na integração dos módulos necessários, uma biblioteca de funções desenvolvida no LSEE será expandida permitindo a execução do método evolutivo diretamente em uma interface Field Programmable Gate Array (FPGA) a qual atuará como um coprocessador genético da plataforma de tempo real. Os resultados aqui apresentados foram obtidos seguindo especificações normativas, através de sinais gerados sinteticamente, e também utilizando o Alternative Transient Program (ATP), permitindo assim ensaios mais realísticos para a validação dos métodos evolutivos.The synchronized phasor measurement is used today as a way to enhance the operation of an Electric Power System (EPS), using phasor measurement units strategically located and installed. They perform the acquisition of the electrical signal and then, the estimation of the voltage and current phasors, synchronized in time, which indicates the SEPs behavior in a specific location. This multidisciplinary work proposes the analysis and implementation of an evolutionary computing method, the Multibjective Compact Genetic Algorithm (MCGA) applied to the phasor estimation method used in EPS, known as an Phasor Measurement Units (PMUs). The MCGA presented here has as a main characteristic the multiobjective analysis of the problem. Because all EPSs have three phases, this new approach is proposed , which is considering the phasor estimation for the three phases together, instead of doing it for each phase independently.Thus the proposed MCGA includes in its genetic mapping of individuals, the characteristics of the signals of the three phases, unlike the monoobjective where each phase of the Electric Power System (EPS) is modeled using a different individual. In order to ensure the effectiveness of the evolutionary method when operating in a real time scenario, a platform for data acquisition and processing is proposed, inspired by previous work, allowing the integration of all the modules that composes a PMU for real-time phasor analysis. A Global Positioning System (GPS) is proposed as a way to synchronize different PMUs, integrating pieces of equipment in a single time reference, with the precision required. In order to assist in the integration of the required modules, a library of functions developed in the Laboratory of Electric Power Systems will be expanded allowing the execution of the evolutionary method directly on a Field Programmable Gate Array (FPGA) interface, which will act as a genetic co-processor of a real-time platform. The results presented here were obtained following normative specifications, through signals generated synthetically, and also using the Alternative Transient Program (ATP), allowing more realistic tests to validate the evolutionary methods.
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Ângelos, Eduardo Werley Silva dos. "Modelagem tempo real de sistemas de energia elétrica considerando sincrofasores e estimação de estado descentralizada". Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/18/18154/tde-10012014-161654/.
Testo completoAbstract (sommario):
Esta tese investiga novas estratégias para a construção de modelos em tempo real de Sistemas Elétricos de Potência. Busca-se a melhoria das funções de Estimação de Estado e aplicações correlatas por meio da consideração da medição fasorial sincronizada, fornecida por dispositivos PMUs, em ambientes onde as regiões monitoradas são de domínios de empresas diferentes e cuja distribuição geográfica apresenta distâncias consideráveis, como é o caso brasileiro. Uma das tarefas mais críticas dentro deste contexto é a representação adequada de sistemas não monitorados, que devem ser modelados de forma precisa, robusta e, preferencialmente, considerando dados que são acessíveis ao operador. A incorporação de redes externas em estimação multiárea é efetuada por uma etapa adicional de estimação ou embutida diretamente nos processos iterativos locais, mediante, neste último caso, a exigência de contínuos fluxos de dados entre áreas. No entanto, constata-se, neste estudo, que modelos clássicos de Equivalentes Externos reduzidos, particularmente os modelos tipo Ward, atendem satisfatoriamente aos requisitos computacionais e de precisão do problema, desde que sejam devidamente atualizados a cada mudança do ponto de operação. Desta forma, considerando sincrofasores de tensão e de corrente coletados por PMUs em regiões de fronteira, desenvolve-se um modelo de Estimação de Estado Descentralizada em que a etapa de pós-processamento por agentes externos independentes é removida, permitindo a obtenção do estado interconectado em um único passo, sem intercâmbio de dados operacionais em tempo real. Dois modelos são implementados, que diferem essencialmente na forma de tratamento dos dados de equivalentes externos. A metodologia é codificada em linguagem C++, sendo validada nos Sistemas IEEE de 14, 30 e 118 barras sob várias configurações de medição e de particionamento, mediante análise estatística e comparação de estimativas com valores de referência. Os resultados obtidos indicam a viabilidade da proposta para o fornecimento de modelos de estimação de estado mais confiáveis, adaptados à atual tendência de descentralização de redes elétricas, sem grandes alterações nas funções já existentes e sob um custo computacional reduzido. Sugerem também a factibilidade do tratamento conjunto das funções relacionadas a Estimação de Estado e Equivalentes Externos.New approaches for the real time modelling of Power Systems are investigated in this work. The improvement of State Estimation and related functions is pursued with the aid of synchronized measurements gathered by PMU devices, in a multi-owner environment where utilities are independent and distributed across large distances, as in the Brazilian interconnected system case. One of the critical tasks on this subject is the correct representation of non-monitored networks in precise and feasible way, where less data traffic between operators is preferable. In Multiarea State Estimation, the incorporation of external networks is usually performed as the additional estimation phase or directly included in local estimation models by means of inter-area communication channels. This research shows that classic models of External Equivalents, specially Ward types, meet the computational and precision requirements of the problem if they are correctly updated after changes in the operating point. Thus, by using voltage and current synchrophasors measured by boundary PMUs, a Decentralized State Estimation model is developed, where the need for a post-processing higher coordination step is suppressed, allowing the interconnected state to be found rapidly, in a single step and with no real time data exchange. Two strategies of including on-line information about External Equivalents are proposed, taking it as regular measurements or constraints to be imposed in the classical formulation. A computational software coded in C++ language is built to support the models, which are validated with the IEEE-14, 30 and 118 test bed systems, under several placement strategies and split network schemes. A consistent statistical analysis of the results is also performed, where outcomes are compared with reference values of a regular estimator. Results indicate the feasibility to generate reliable and robust real time models, without significant changes in existing energy management applications, and also shows the greater benefits of integrating State Estimation and External Equivalents into a single framework.
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Silva, Chrystian Dalla Lana da. "Estimação fasorial aplicada a relés de proteção numéricos utilizando os métodos de ajuste de curvas e redes neurais artificiais". Universidade Federal de Santa Maria, 2014. http://repositorio.ufsm.br/handle/1/8536.
Testo completoAbstract (sommario):
Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorThis dissertation proposes two methodologies for the phasor estimation on protective relays in Electrical Power Systems. Firstly, a theoretical introduction of signal processing, the structure of a protective relay and phasor estimation algorithms is presented, including some of the algorithms used on the electrical system, as well as the two proposed methodologies. The first one makes use of the concept of curve-fitting, while the other uses Artificial Neural Networks, both with the goal of performing the real-time estimation of the signal amplitude and phase angle. Secondly, it is made a comparative analysis of the two proposed methods with four well-known and currently used algorithms. This comparison is made through the creation of several test signals with different simulation parameters. From these simulations, six performance indexes are used for the quantitative evaluation of each algorithm, from where the most effective method can be determined through the arithmetic mean of these indexes. Lastly, after all the simulation cases have been presented, a summary of the characteristics of each algorithm is made, based in their numerical results. Then, based on the values obtained on each performance index, the strong and weak points are highlighted, as well as the general classification of each method.
Essa dissertação propõe duas metodologias para a estimação fasorial em relés de proteção em Sistemas Elétricos de Potência. Primeiramente é apresentada uma introdução teórica ao processamento de sinais, à estrutura do relé de proteção, e aos algoritmos de estimação fasorial propriamente ditos, incluindo alguns dos algoritmos utilizados no sistema elétrico, assim como as duas metodologias propostas. A primeira delas faz uso do conceito de ajuste de curvas, enquanto que a segunda utiliza Redes Neurais Artificiais, ambas com o objetivo de realizar a estimação da amplitude e ângulo de fase de um sinal em tempo real. Em um segundo momento, é feita a análise comparativa dos dois métodos propostos com quatro algoritmos bastante conhecidos e utilizados nos relés numéricos. A comparação é feita através da criação de diversos sinais de teste com diferentes parâmetros de simulação. A partir dessas simulações, são usados seis índices de desempenho para a avaliação quantitativa de cada algoritmo, de onde, a partir da média aritmética destes índices, pode-se determinar o método mais eficaz para cada caso. Por fim, após todos os testes terem sido realizados, com base em seus resultados numéricos, é realizada uma condensação das características de cada algoritmo. Com base nos valores obtidos em cada índice de desempenho, são destacados os pontos fortes e fracos, bem como a classificação geral de cada método.
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Ghafari, Christophe. "Innovative numerical protection relay design on the basis of sampled measured values for smartgrids". Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAT113/document.
Testo completoAbstract (sommario):
Avec le paradigme du réseau intelligent, les ingénieurs de protection ont maintenant à leur disposition une large gamme de nouvelles technologies de communication. Parmi elles, la norme CEI 61850-9-2 a introduit le concept de bus de procédé qui permet l'envoi de valeurs échantillonnées horodatées à un temps absolu depuis les transformateurs de mesure du terrain jusqu’aux relais de protection numériques. Ces derniers peuvent intégrer la fonction d'unité de mesure de phaseur qui peut être utilisé pour échanger des synchrophaseurs entre les fonctions de protection et pour une nouvelle protection anti-îlotage. Les relais de fréquence et de dérivée de fréquence sont, de nos jours, les méthodes anti-îlotage les plus couramment employées, mais leurs performances ne sont pas satisfaisantes. Dans ce contexte, une nouvelle génération de techniques de traitement du signal pour les relais de protection ayant des échantillons horodatées comme signal d'entrée et intégrant la mesure de synchrophaseurs est nécessaire. Cette thèse étudie d'abord l'impact des valeurs échantillonnées sur le traitement du signal. Trois solutions sont ensuite proposées pour calculer les phaseurs, les fréquences et les dérivées de fréquence dans diverses conditions statiques et dynamiques, puis testées par simulation. Enfin, un algorithme de mesure de synchrophaseurs incorporé dans le traitement de signal initial est proposé. Cet algorithme a été testé selon la dernière version de la norme d'unité de mesure de phaseur et les résultats obtenus sont conformes aux exigences de mesureWith the Smart Grid paradigm, protection engineers now have available to them a large range of new communication technologies. Among them, IEC Standard 61850-9-2 has introduced the process bus concept which permits sending of absolute time-stamped digitized analogue values from the instrument transformers of the field to numerical relays. The latter can incorporate the phasor measurement unit function which can be used for exchanging synchrophasors between protection functions and for new anti-islanding protection. Frequency and rate-of-change-of-frequency relays are, nowadays, the most commonly employed anti-islanding methods but their performance is not satisfactory. In this context, a new generation of signal processing techniques for protection relays having time-stamped digitized analogue values as input signal with synchrophasors measurement capability is required. This thesis first studies the impact of sampled measured values on the signal processing. Three solutions are then proposed to compute phasor, frequency and rate-of-change-of-frequency estimates under various static and dynamic conditions, and tested via simulation. Finally, a synchronized phasor measurement algorithm incorporated into the initial signal processing is proposed. This algorithm has been tested following the latest version of the phasor measurement unit standard and the results obtained comply with the measurement requirements
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Melo, Igor Delgado de. "Estimação estática de estados harmônicos em redes trifásicas de distribuição monitoradas por PMUs: uma abordagem considerando curvas diárias de carga". Universidade Federal de Juiz de Fora (UFJF), 2018. https://repositorio.ufjf.br/jspui/handle/ufjf/8019.
Testo completoAbstract (sommario):
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CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Este trabalho apresenta uma nova metodologia para a estimação de estados harmônicos em redes de distribuição de energia elétrica, a partir da modelagem de problemas de otimização, em uma abordagem estática. Assume-se que medições fasoriais sincronizadas são obtidas continuamente por um número reduzido de PMUs (Phasor Measurement Units) estrategicamente alocadas no sistema. Correntes harmônicas passantes em todos os ramos da rede elétrica são variáveis de estado a serem estimadas em coordenadas retangulares. Valendo-se do uso de leis de Kirchhoff, outras grandezas elétricas são calculadas como fasores de tensão, potências ativa e reativa. Os problemas de otimização são modelados para cada ordem harmônica individualmente e para cada intervalo de tempo em que o algoritmo for executado, com o objetivo de estimar estados harmônicos ao longo do tempo, considerando curvas diárias de carga. A função objetivo é determinada a partir do método dos mínimos quadrados ponderados, almejando minimizar o somatório das diferenças quadráticas entre os valores medidos e os valores correspondentes estimados pelo método proposto. Para as barras não monitoradas por PMUs, potências ativa e reativa são consideradas como restrições de desigualdade com limites inferiores e superiores definidos por fatores percentuais, assumindo incertezas sobre as variações de carregamento e componentes harmônicas a serem estimadas em intervalos de tempo regulares. Os problemas de otimização são resolvidos usando o método de pontos interiores com barreira de segurança adaptado, em que a solução ótima é dada sem violação de restrições, através da introdução de um parâmetro de relaxamento que permite que os valores inferiores e superiores das restrições que atingirem seus respectivos valores limites sejam relaxados para que a solução ótima seja encontrada. Sistemas teste de distribuição de energia elétrica trifásicos, topologicamente radial são utilizados para validação da metodologia proposta. Análises de sensibilidade são consideradas para avaliar o tempo computacional, número de PMUs alocadas, geração distribuída, filtro harmônico e parâmetros usados pelo algoritmo proposto. Vantagens deste trabalho incluem número limitado de PMUs a ser instalado, identificação de múltiplas fontes harmônicas, estimação de curvas diárias de carga e componentes harmônicas ao longo do tempo, com erros de estimação reduzidos.
This work presents a novel methodology for harmonic state estimation in electric power distribution networks, based on optimization problems formulation, in a static approach. It is assumed that synchronized phasor measurements are continuously obtained using a reduced number of PMUs (Phasor Measurement Units) strategically allocated into the system. Harmonic branch currents passing through the branches of the network are the state variables to be estimated in rectangular coordinates. Based on Kirchhoff’s laws, other electrical quantities are calculated, such as voltage phasors, active and reactive powers. An optimization problem is modelled for each harmonic order individually and for each time interval in which the algorithm is executed, with the objective of estimating harmonic states along the time, considering daily load curves. The objective function is determined based on the weighted least squares method, aiming to minimize the sum of the quadratic difference between measured and estimated values by the proposed method. For the buses which are not monitored by PMUs, active and reactive powers are considered as inequality constraints, with lower and upper limits defined by percentage factors, assuming uncertainties over daily load curves and harmonic components to be estimated in regular time intervals. The optimization problems are solved using the modified safety barrier interior point method, in which the optimal solution is provided with no constraints violation, by the introduction of a relaxation parameter which allows the upper and lower bounds of the constraints which reached their corresponding limits to be relaxed in such a way that the optimal solution is obtained. Three-phase electrical distribution test systems, with radial topology are used for the validation of the proposed methodology. Sensitivity analysis are considered in order to evaluate computational time, distributed generation, harmonic filter and parameters used by the proposed algorithm. Advantages of this work include limited number of PMUs to be installed, multiple harmonic sources identification, estimation of daily load curves and harmonic components along the time, with reduced estimation errors.
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Vahidnia, Arash. "Wide area control through aggregation of power systems". Thesis, Queensland University of Technology, 2013. https://eprints.qut.edu.au/61186/1/Arash_Vahidnia_Thesis.pdf.
Testo completoAbstract (sommario):
This thesis was a step forward in improving the stability of power systems by applying new control and modelling techniques. The developed methods use the data obtained from voltage angle measurement devices which are synchronized with GPS signals to stabilize the system and avoid system-wide blackouts in the event of severe faults.
New approaches were developed in this research for identifying and estimating reduced dynamic system models using phasor measurement units. The main goal of this research is achieved by integrating the developed methods to obtain a feasible wide-area control system for stabilizing the power systems.
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Borges, Guilherme Pereira. "Análise de observabilidade e identificação de medidas críticas para sistemas de medição formados por medidas convencionais e fasoriais sincronizadas". Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/18/18154/tde-08062011-150636/.
Testo completoAbstract (sommario):
Neste trabalho de dissertação propõe-se uma metodologia para análise de observabilidade (restauração e identificação de ilhas) e identificação de medidas críticas para sistemas de medição formados por medidas convencionais (medidas de amplitude de tensão e de potência obtidas via sistema SCADA) e medidas fasoriais sincronizadas. A metodologia possibilita análise e restauração da observabilidade a partir da fatoração triangular da matriz jacobiana, associada a um sistema de medição possuindo medidas convencionais e fasoriais sincronizadas. Para identificar as ilhas observáveis, no caso de o sistema não ser observável como um todo, a metodologia faz uso do conceito de caminhos de fatoração, associado à matriz jacobiana fatorada. As medidas críticas são identificadas a partir da análise da estrutura da matriz H \'delta\' t, que é obtida a partir da fatoração triangular da matriz jacobiana. A metodologia proposta é simples, de execução rápida, de fácil implantação e não exige a solução de equações algébricas. Dessa forma a mesma atende aos requisitos para operação em tempo-real. Com o intuito de mostrar como a metodologia proposta funciona, são apresentados exemplos da sua aplicação em um sistema teste de 4 barras. Vale destacar que resultados de diversas simulações computacionais, utilizando os sistemas teste do IEEE (14, 30 e 57 barras), têm demonstrado a eficiência da metodologia.This dissertation proposes a methodology for observability analysis (restoration and identification of observable islands) and identification of critical measurements for metering systems composed of both synchronized phasor and conventional measurements (power and voltage magnitude measurements). The methodology enables observability analysis and restoration via the triangular factorization of the jacobian matrix associated with metering systems formed by those two types of measurements. The identification of observable islands is carried out through the analysis of the path graphs associated with the factorization of the jacobian matrix. Critical measurements are identified via analysis of the structure of the H \'delta\' t matrix, which is obtained by the triangular factorization of the jacobian matrix. The methodology is simple, fast and easy to implement and does not require solutions of any algebraic equation. Consequently, it is useful for real-time operation. Small numerical examples, using a 4-bus test system, showing the application of the proposed methodology are presented. The IEEE 14, 30 and 57 bus systems with different measurement scenarios were used to evaluate the performance of the proposed methodology.
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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/.
Testo completoAbstract (sommario):
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.
Testo completoAbstract (sommario):
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Previous issue date: 2012-01-23Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
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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Souza, Matheus Alberto de. "Detecção e identificação de perdas comerciais de energia elétrica: uma abordagem para smart grids". Universidade Federal de Juiz de Fora (UFJF), 2016. https://repositorio.ufjf.br/jspui/handle/ufjf/3066.
Testo completoAbstract (sommario):
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O presente trabalho tem por objetivo apresentar uma metodologia para a detecção de perdas comerciais de energia em sistemas de distribuição, bem como a identificação do usuário fraudulento em Infraestruturas Avançadas de Medição, próprias de Smart Grids. ParaaetapadedetecçãodeperdascomerciaisdeenergiaéutilizadoumEstimadorEstático de Estados Trifásico baseado em Medições Fasoriais Sincronizadas (Phasor Measurements Units - PMUs). Essa etapa visa detectar os transformadores na rede de distribuição, os quais, apresentam indícios de furtos/fraudes de energia, através da observância da curva de carga estimada. A próxima etapa visa identificar os consumidores, conectados aos transformadores suspeitos, que cometem o ato ilícito. Para isto, treinou-se uma Rede Neural Artificial (RNA) de Kohonen para clusterizar os consumidores honestos de acordo compadrõesdeconsumosemelhantes,apartirdedadosdeconsumoprovenientesdosSmart Meters decadacliente. ParacadaclassedefinidapelaRNAdeKohonencriou-seumaRNA MultiLayer Perceptron (MLP) para fins de classificação dos consumidores em duas classes, honestos ou fraudulentos. As duas grandes contribuições do trabalho estão em utilizar a técnica de detecção para diminuir o número de Falsos Positivos (FP) das metodologias de classificação, sem a necessidade de medições individuais nos transformadores, e a utilização de RNAs a partir de dados de medições do sistema de distribuição de forma robusta, em que não há a necessidade de medições sem perdas comerciais de energia para todos os consumidores do sistema. A forma de tratamento dos dados de medições ainda possibilita manter a privacidade dos usuários, questão bastante debatida no cenário mundial. Foram realizados testes para a etapa de detecção de perdas comerciais com os sistemas IEEE 33 Barras e IEEE 70 barras. Para a etapa de identificação do consumidor fraudulento foram utilizados dados de consumo reais de mais de 5000 consumidores provenientes de Smart Meters liberados pela Autoridade de Eletricidade e Energia Sustentável da Irlanda. Os testes mostraram bons resultados tornando a metodologia proposta aplicável na detecção e identificação de perdas comerciais de energia elétrica em Smart Grids.
This work aims to present a methodology for the detection of energy theft in distribution systems as well as the identification of the fraudulent users considering Advanced Metering Infrastructure, widely used in Smart Grids. For the stage of energy theft detection, a Static Three Phase State Estimator based on Synchronised Phasor Measurement Units (PMUs) is used. This step aims to detect the transformers in the distribution network, which have evidence of energy theft, by observing the estimated load curve. The next step is to identify consumers, connected to suspected transformers, which are stealing energy. For this, a Kohonen Artificial Neural Network (ANN) was trained to clustering honest consumers according to similar patterns of consumption, with the consumption data from the Smart Meters at every customer. For each class defined by the Kohonen ANN a MultiLayer Perceptron (MLP) ANN for classification of consumers into two classes, honest or fraudulent was created. The two major contributions of this work are the use of energy theft detection technique to reduce the number of false positives (FP) from the classification methods, without the need for individual measurements on the transformers, andtheuseofANNfromdistributionsystemmeasurementsmakethetechiniquerobust, in which there is no need for measurements without comercial loss of energy for all consumers. The way that the measurement data is treated allows maintaining the privacy of the consumers which is a debated question on the world. Tests were conducted for energy theft detection step with IEEE 33 Buses and IEEE 70 Buses systems. For the fraudulent user identification step, actual consumption data were used over 5000 consumers from their SmartMetersreleasedbytheElectricityAuthorityandSustainableEnergyofIreland. The tests showed good results making the proposed methodology applicable in the detection and identification of energy theft in Smart Grids.
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Formiga, Diego Alves. "Estima??o de Fasores para Prote??o de Sistemas El?tricos Baseada em M?nimos Quadrados e Morfologia Matem?tica". Universidade Federal do Rio Grande do Norte, 2012. http://repositorio.ufrn.br:8080/jspui/handle/123456789/15485.
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Previous issue date: 2012-12-18Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior
This work proposes a new technique for phasor estimation applied in microprocessor numerical relays for distance protection of transmission lines, based on the recursive least squares method and called least squares modified random walking. The phasor estimation methods have compromised their performance, mainly due to the DC exponential decaying component present in fault currents. In order to reduce the influence of the DC component, a Morphological Filter (FM) was added to the method of least squares and previously applied to the process of phasor estimation. The presented method is implemented in MATLABr and its performance is compared to one-cycle Fourier technique and conventional phasor estimation, which was also based on least squares algorithm. The methods based on least squares technique used for comparison with the proposed method were: forgetting factor recursive, covariance resetting and random walking. The techniques performance analysis were carried out by means of signals synthetic and signals provided of simulations on the Alternative Transient Program (ATP). When compared to other phasor estimation methods, the proposed method showed satisfactory results, when it comes to the estimation speed, the steady state oscillation and the overshoot. Then, the presented method performance was analyzed by means of variations in the fault parameters (resistance, distance, angle of incidence and type of fault). Through this study, the results did not showed significant variations in method performance. Besides, the apparent impedance trajectory and estimated distance of the fault were analysed, and the presented method showed better results in comparison to one-cycle Fourier algorithm
Prop?e-se neste trabalho uma nova t?cnica de estima??o fasorial, a ser utilizada em rel?s num?ricos microprocessados digitais para prote??o de dist?ncia de linhas de transmiss?o, baseada no m?todo dos m?nimos quadrados recursivo, denominada m?nimos quadrados em caminhada aleat?ria modificada. Os m?todos de estima??o fasorial t?m seu desempenho comprometido devido, principalmente, ? componente DC de decaimento exponencial presente nas correntes de falta. Para reduzir a influ?ncia da componente DC, agregou-se ao m?todo de m?nimos quadrados um Filtro Morfol?gico (FM) aplicado previamente ao processo de estima??o fasorial. O m?todo apresentado foi implementado em ambiente MATLABr e o seu desempenho comparado aos m?todos convencionais de estima??o fasorial, tamb?m baseados em m?nimos quadrados, e ao algoritmo de Fourier de um ciclo. Os m?todos baseados na t?cnica de m?nimos quadrados utilizados para compara??o com o m?todo proposto foram: recursivo ponderado, com reinicializa??o da covari?ncia e caminhada aleat?ria. As an?lises de desempenho das t?cnicas foram realizadas por meio de sinais sint?ticos e sinais oriundos de simula??es no Alternative Transient Program (ATP). Em compara??o aos demais m?todos de estima??o fasorial, o m?todo proposto apresentou resultados satisfat?rios no que se refere ? velocidade de resposta, oscila??o em regime permanente e percentual de overshoot. Em seguida, o m?todo proposto teve seu desempenho analisado frente ?s varia??es nos par?metros de falta (resist?ncia, dist?ncia, ?ngulo de incid?ncia e tipo de falta). Nesse estudo, constatou-se que o m?todo n?o sofreu varia??es significativas em seus resultados. Al?m disso, analisou-se a trajet?ria da imped?ncia aparente e dist?ncia estimada da falta, ao qual o m?todo proposto apresentou melhores resultados em compara??o ao algoritmo de Fourier de um ciclo
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Fantin, Camila dos Anjos. "Metodologia para estimação de estado trifásica em sistemas de distribuição incorporando medidas SCADA, virtuais, pseudo-medidas e medidas fasoriais sincronizadas". Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/18/18154/tde-01022017-150726/.
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Este trabalho propõe o desenvolvimento e implantação, em computador, de uma metodologia para tratamento de diversas etapas do processo de estimação de estado em Sistemas de Distribuição (SDs), que possibilite um tratamento adequado para as particularidades dos SDs no contexto atual (com poucas medidas disponíveis) e futuro (contando com mais medidas SCADA, com as Medidas Fasoriais Sincronizadas (MFSs) e com as avançadas infra-estruturas de medição), ou seja, que possibilite: análise de sistemas desbalanceados e desequilibrados, com ramais monofásicos, bifásicos e trifásicos; o tratamento de sistemas radiais e malhados sem perda de precisão; uma modelagem adequada dos componentes dos SDs, considerando as várias possibilidades de conexão dos transformadores e dos reguladores de tensão; o tratamento de diversos tipos de medidas (medidas convencionais obtidas pelo sistema SCADA, medidas virtuais, pseudo-medidas de carga e de dados históricos e MFSs), ponderando-as de acordo com as respectivas precisões. A metodologia proposta baseia-se no método dos mínimos quadrados ponderados, trabalha no nível dos alimentadores e compreende os seguintes quatro estágios: Estágio 1 geração de pseudo-medidas de carga; Estágio 2 - análise e restauração de observabilidade e identificação de medidas críticas; Estágio 3 - estimação de estado propriamente dita; e Estágio 4 - processamento de erros grosseiros. Tendo em vista as respostas coerentes das diversas simulações realizadas com os alimentadores de teste trifásicos de 4 e 34 barras do IEEE, demonstra-se satisfatoriamente a performance da metodologia proposta.This thesis proposes a multi-phase unbalanced distribution system (DS) state estimation methodology based on the weighted least squares technique, which allows: load pseudo-measurement modeling; observability analysis and restoration by selecting the required pseudo-measurements (load pseudo-measurements and/or historical measurement data); identication of critical measurements; state estimation; and, nally, gross errors processing. The proposed methodology intends to be a practical tool able to be applied to a variety of DSs, considering latest and future realities. Therefore, the proposed methodology has the following features: (i) includes all realistic DS modeling details, such as, various types of transformer and voltage regulator connections, the presence of single, two and three-phase circuits, as well as the possibility of both the mutual coupling between phases and the shunt susceptance; (ii) treat three-phase networks with high resistance/reactance ratios in a unied framework; and (iii) process measurements with very distinct qualities, some of them are real-time measurements provided by Supervisory Control Data Acquisition (SCADA) systems, Advanced Metering Infrastructure (AMI), Phasor Measurement Units (PMUs), other are virtual measurements (information provided by the buses of zero power injection) and also the pseudo-measurements (load pseudo-measurements, load proles and historical measurement data). Several simulations results (with IEEE 34 and 4 node test feeders) have demonstrated satisfactory performance of the proposed methodology.
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Pereira, Ingrid Soares. "Estimação de estados em redes de distribuição de energia elétrica baseada em medições fasoriais". Universidade Federal de Juiz de Fora, 2015. https://repositorio.ufjf.br/jspui/handle/ufjf/1126.
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Este trabalho apresenta uma nova abordagem para o problema de Estimação de Estados em Redes de Distribuição de Energia Elétrica utilizando os dados históricos de cargas e medidas obtidas pelos Sistemas de Medição Fasorial Sicronizada (PMUs – Phasor Measurement Units). Nesta formulação as tensões em módulo e fase são escolhidas como variáveis de estados e o problema é matematicamente formulado como um problema de otimização com restrições de igualdade e desigualdade. A função objetivo é formada pela soma quadrática dos resíduos de estimação, definidos como a diferença entre os valores medidos através das PMUs e os valores calculados. As restrições de igualdade são as injeções de potencia ativa e reativa nulas nas barras de passagem. As restrições de desigualdade estão associadas às potências ativas e reativas das barras não monitoradas, onde admite-se limites inferiores e superiores em função dos dados históricos das cargas (potências ativas e reativas). Estudos de casos são realizados utilizando-se um sistemas simples 10 barras, e os sistemas IEEE da literatura de 33 e 84 barras. Os dados de medições fasoriais foram obtidos utilizandose um programa computacional de cálculo de fluxo de potência. Os resultados da estimação de estados utilizando a metodologia proposta foram obtidos através de simulações no ambiente MATLAB e comparados com os resultados do programa de fluxo de potência para validação. A utilização de medição fasorial sincronizada nos entroncamentos e no final dos ramais do sistema de distribuição associada à utilização de restrições de desigualdade para as potências ativas e reativas das cargas não monitoradas são as principais contribuições deste trabalho.
This work presents a new approach to the State Estimation problem in Electrical Distribution Networks using historical data loads and measurements obtained by Phasor Measurement Units (PMUs). In this formulation voltage magnitudes and angles are chosen as state variables and the problem is mathematically formulated as an optimization problem with equality and inequality constraints. The objective function is formed by the quadratic sum of weighted measurements residues, which are defined as the difference between the PMU measurements and the calculated values. The equality constraints are defined as the zero injections of active and reactive power at the no load buses. The inequality constraints are associated with active and reactive powers of non-monitored buses, bounded by a given limit, superior or inferior in relation to historical data loads (active and reactive powers). Case studies are performed using a simple 10-bus test system, and the 33 and 84 buses IEEE test systems. The data phasor measurements were obtained using a computer program that calculates power flow. The state estimation results using the proposed methodology were obtained through simulations in MATLAB environment and compared with the results of power flow program for validation. The use of synchronized phasor measurement at the beginning and at the end of the lateral feeders of the distribution system associated with the use of inequality constraints for active and reactive power for the non-monitored loads are the main contributions of this work.
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Vianello, Rodrigo. "Estimação de fasores na presença de harmônicos, decaimentos CC exponencial e inter-harmônicos exponencialmente amortecidos". Universidade Federal de Juiz de Fora (UFJF), 2010. https://repositorio.ufjf.br/jspui/handle/ufjf/3053.
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CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
O presente trabalho apresenta a proposição de duas metodologias inovadoras no campo da estimação fasorial. A primeira delas propõe a estimação do fasor da componente fundamental na presença de harmônicos e decaimento CC exponencial e é baseada na aplicação de filtros DFT (Discrete Fourier Transform) e de alguns métodos de processamento de sinais, tais como janelamento, modulação e DTFT (Discrete Time Fourier Transform). A segunda metodologia também propõe a estimação do fasor da componente fundamental, mas em um cenário mais complexo onde estão presentes no sinal, além dos harmônicos e decaimento CC exponencial, as oscilações subsíncronas. Esta metodologia é baseada na aplicação de redes neurais artificiais e de alguns métodos de processamento de sinais. Ambas as metodologias foram avaliadas frente a métodos tradicionais de estimação fasorial e apresentaram desempenhos superiores na presença de ruídos.
Thisthesispresents thepropositionoftwonovelmethodsin thefieldofphasor estimation. The first proposes to estimate the phasor of the fundamental component in the presence of harmonicsandexponentialdecayingDC.ThismethodologyisbasedontheapplicationoffiltersDFT (Discrete Fourier Transform) and some methods of signal processing such as windowing, modulation and DTFT (Discrete Time Fourier Transform). The second approach also proposes to estimate the phasor of the fundamental component, but in a more complex scenario formed for harmonics, exponential decaying DC and the sub-synchronous oscillations . This methodology isbasedontheapplicationofartificialneuralnetworksandsomemethodsofsignalprocessing. Both methods were evaluated against traditional methods of phasor estimation and the simulations showed that the two proposed methods were more accurate then others in presence of noise.
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Azad, Abul K. "Robust Speech Filter And Voice Encoder Parameter Estimation using the Phase-Phase Correlator". Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/97221.
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In recent years, linear prediction voice encoders have become very efficient in terms of computing execution time and channel bandwidth usage while providing, in the absence of im- pulsive noise, natural sounding synthetic speech signals. This good performance has been achieved via the use of a maximum likelihood parameter estimation of an auto-regressive model of order ten that best fits the speech signal under the assumption that the signal and the noise are Gaussian stochastic processes. However, this method breaks down in the presence of impulse noise, which is common in practice, resulting in harsh or non-intelligible audio signals. In this paper, we propose a robust estimator of correlation, the Phase-Phase correlator that is able to cope with impulsive noise. Utilizing this correlator, we develop a Robust Mixed Excitation Linear Prediction encoder that provides improved audio quality for voiced, unvoiced, and transition speech segments. This is achieved by applying a statistical test to robust Mahalanobis distances for identifying the outliers in the corrupted speech signal, which are then replaced with filtered signals. Simulation results reveal that the proposed method outperforms in variance, bias, and breakdown point three other robust approaches based on the arcsin law, the polarity coincidence correlator, and the median- of-ratio estimator without sacrificing the encoder bandwidth efficiency and the compression gain while remaining compatible with real-time applications. Furthermore, in the presence of impulsive noise, the proposed speech encoder speech perceptual quality also outperforms the state of the art in terms of mean opinion score.Doctor of Philosophy
Impulsive noise is a natural phenomenon in everyday experience. Impulsive noise can be analogous to discontinuities or a drastic change in natural progressions of events. Specifically in this research the disrupting events can occur in signals such as speech, power transmission, stock market, communication systems, etc. Sudden power outage due to lighting, maintenance or other catastrophic events are some of the reasons why we may experience performance degradation in our electronic devices. Another example of impulsive noise is when we play an old damaged vinyl records, which results in annoying clicking sounds. At the time instance of each click, the true music or speech or simply the audible waveform is completely destroyed. Other examples of impulse noise is a sudden crash in the stock market; a sudden dive in the market can destroy the regression and future predictions. Unfortunately, in the presence of impulsive noise, classical methods methods are unable to filter out the impulse corruptions. The intended filtering objective of this dissertation is specific, but not limited, to speech signal processing. Specifically, research different filter model to determine the optimum method of eliminating impulsive noise in speech. Note, that the optimal filter model is different for time series signal model such as speech, stock market, power systems, etc. In our studies we have shown that our speech filter method outperforms the state of the art algorithms. Another major contribution of our research is in speech compression algorithm that is robust to impulse noise in speech. In digital signal processing, a compression method entails in representing the same signal with less data and yet convey the the same same message as the original signal. For example, human auditory system can produce sounds in the range of approximately 60 Hz and 3500 Hz, another word speech can occupy approximately 4000 Hz in frequency space. So the challenge is, can we compress speech in one of half of that space, or even less. This is a very attractive proposition because frequency space is limited but the wireless service providers desires to service as many users as possible without sacrificing quality and ultimately maximize the bottom line. Encoding impulse corrupted speech produces harsh quality of synthesized audio. We have shown if the encoding is done with the proposed method, synthesized audio quality is far superior to the sate of the art.
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Talbot, Brian Mark. "Characterization of phase estimation techniques to guide phasic stimulation for brain machine interfacing". Thesis, Boston University, 2012. https://hdl.handle.net/2144/31616.
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Thesis (M.S.)--Boston UniversityPLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you.
While much work on brain-machine interfaces (BMI) focuses on decoding neural signals to drive external plants (e.g. a robotic arm), there is increasing interest in the delivery of central neural stimulation, for applications including feedback control (e.g. robotic arm proprioception), or the replacement of impaired sensory function (e.g. haptic prostheses). In many cases, the effects of stimulation can be influenced by pre-stimulus neural activity. Specifically, oscillatory activity contributes significantly to modulating neural responsiveness, and effective use of cortical stimulating BMIs may require phase dependent input. This work compares Hilbert transform and extended Kalman filter (EKF) methods for controlling stimulation at targeted phases of ongoing neural oscillations. Accuracy of stimulation timing and computational latency were the primary criteria used to assess both approaches. Algorithmic performance was evaluated on signals ranging from noisy sinusoids to previously recorded cortical local field potentials. Characterizing the abilities and limitations of these two filtering techniques is a step towards the development of user-defined phase stimulation in BMIs.
2031-01-01
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Schettino, Bruno Montesano. "Método para detecção e compensação dos efeitos causados pela saturação dos TCs de proteção com meios adaptativos para mitigação da influência do ruído e dos desvios de frequência". Universidade Federal de Juiz de Fora, 2015. https://repositorio.ufjf.br/jspui/handle/ufjf/1142.
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Este trabalho propõe um método para detectar a saturação dos núcleos dos transformadores de corrente (TCs) utilizados na proteção de sistemas elétricos de potência (SEPs), além de promover a compensação de seus efeitos através da correção do sinal de corrente secundária distorcido pela saturação. Técnicas de processamento de sinais baseadas no filtro diferenciador de segunda ordem de Savitzky-Golay são utilizadas para localizar os pontos de transição entre partes do sinal de corrente distorcidas e não distorcidas pela saturação. Em seguida, um processo de estimação baseado no critério dos mínimos quadrados que utiliza exclusivamente amostras do sinal contidas nas regiões não distorcidas é efetuado, extraindo os parâmetros necessários à promoção da correção do sinal. As influências do ruído e dos desvios de frequência de operação do SEP foram analisadas, tendo sido desenvolvidos e incorporados meios adaptativos para mitigar seus efeitos. Os algoritmos desenvolvidos foram implementados em MATLAB e a avaliação de desempenho foi realizada utilizando sinais extraídos de simulações de falta ocorridas em um sistema modelado em um simulador digital em tempo real (RTDS). Os resultados indicaram que o método proposto atingiu desempenho satisfatório, independente dos parâmetros do TC e dentro de uma ampla gama de cenários da falta analisados. Além disso, o método mostrou-se robusto em relação ao ruído e eficiente na mitigação dos erros provocados pelos desvios de frequência. Ainda, os recursos técnicos e computacionais necessários para sua execução indicam que o método proposto é passível de implementação nos atuais dispositivos de proteção disponibilizados pela indústria.
This work proposes a method for detecting the saturation of the current-transformer cores used in the protection of electric power systems and promote the compensation for its effects by correcting the secondary current signal distorted due to the saturation. Signal processing techniques based on the second order differentiator Savitzky-Golay filter are used for locating the transition points between distorted and undistorted parts of the current signal. Then, an estimation process based on the least squares criteria that uses exclusively signal samples included in the undistorted regions is performed, extracting the parameters needed for the signal correction. The influences of the noise and the frequency offset were analysed, and adaptive means to mitigate their effects were developed and incorporated. The developed algorithms were implemented in MATLAB and performance evaluation was performed using the signals taken from fault simulations in a system modeled on a real time digital simulator (RTDS). The results indicated that the proposed method reaches a satisfactory performance, regardless of the CT parameters and within a wide range of analysed fault scenarios. Moreover, the method showed to be robust relative to the noise and effective in mitigating the errors due to the frequency offsets.
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Aleixo, Renato Ribeiro. "Proposta e implementação de uma Micro-PMU". Universidade Federal de Juiz de Fora (UFJF), 2018. https://repositorio.ufjf.br/jspui/handle/ufjf/6641.
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CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Este trabalho tem como objetivo a proposta de uma Unidade de Medição Fasorial (do inglês, Phasor Measurement Unit)(PMU), de baixo custo, voltada para o monito-ramento da distribuição de energia elétrica. O medidor proposto pode ser conectado à rede de baixa tensão, possibilitando assim o monitoramento dos sistemas de dis-tribuição e transmissão de energia. O algoritmo de estimação fasorial que compõe o software embarcado do equipamento faz uso do filtro Savitzky-Golay como aproxima-ção da derivada, necessária no processo de estimação da frequência do componente fundamental do sinal. O hardware utilizado é composto pelo microprocessador ARM TM4C1294NCPDT da Texas Instruments, um módulo GPS NEO-6M da uBlox, um módulo Wi-Fi ESP8266, além de um circuito de condicionamento do sinal analógico. O sincronismo das medições realizadas é garantido graças ao sinal composto por um pulso por segundo fornecido pelo GPS. Para o envio dos dados gerados pelo medidor pro-posto, o protocolo definido na norma vigente para PMUs foi utilizado. As estimações podem ser armazenadas e vizualizadas em tempo real através de um software monitor de dados de sincrofasores. Os resultados contemplam os testes exigidos pela norma, avaliando-se o erro total da estimação do fasor, o erro de frequência e o erro de taxa de variação da frequência. Por último, a fim de se reafirmar o sincronismo existente entre as medições realizadas por mais de um equipamento, estimou-se os fasores e a frequência em pontos distintos do sistema 4 Barras do IEEE, simulado em tempo real no RTDS, onde pode-se observar a estimação correta da defasagem entre duas barras desse sistema.
The present work proposes of a low cost Phasor Measurement Unity (PMU), for monitoring the power distribution system. The proposed meter can be connected at the low voltage level, making possible the monitoring of the distribution system and the transmission system. The algorithm used to compute the phasor estimation that composes the embedded software in the equipment uses the Savitzky-Golay filter to approximate the differentiation process, necessary in the frequency estimation of the fundamental component of the signal. The hardware of the equipment is composed by a microprocessor AMR TM4C1294NCPDT of Texas Instruments, a uBlox GPS NEO-6M module, a Wi-Fi ESP8266 module and an analog conditioning circuit. The synchronism of the measurements is guaranteed due to a pulse per second signal from the GPS module. For the transmission of the data generated by the PMU, the protocol suggested by the standard is used. The estimated parameters can be visualized in real time through the Synchrophasor Data Monitor Software. The results contemplate the tests required by the IEEE standard C37.118.1 and the analyses of the total vector error, frequency error and rate of change of frequency error. Finally, to attest the synchronism between different PMUs, a test in a Real Time Digital Simulator (RTDS) was made, where the 4 bus IEEE system was simulated. The difference of the angles estimated for different buses was computed and the obtained values were according to the expected.
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Vigliassi, Marcos Paulo. "Algoritmo evolutivo multiobjetivo em tabelas e matriz HΔ para projeto de sistemas de medição para estimação de estado". Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/18/18154/tde-19052017-154501/.
Testo completoAbstract (sommario):
O problema de projeto de sistemas de medição, para efeito de Estimação de Estado em Sistemas Elétricos de Potência, é um problema de otimização multiobjetivo, combinatório, que exige a investigação de um grande número de possíveis soluções. Dessa forma, metaheurísticas vêm sendo empregadas para sua solução. Entretanto, a maioria delas trata o problema de forma mono-objetivo e as poucas que consideram uma formulação multiobjetivo, não contemplam todos os requisitos de desempenho que devem ser atendidos para obtenção de um Sistema de Medição Confiável (SMC) (observabilidade e ausência de Medidas Críticas, Conjuntos Críticos de Medidas, Unidades Terminais Remotas Críticas e Unidades de Medição Fasoriais Críticas). Propõe-se, nesta tese, uma formulação multiobjetivo para o problema de projeto de sistemas de medição de uma forma mais ampla, considerando todas requisitos de desempenho que devem ser atendidos para obtenção de um SMC. Propõe-se, ainda, o desenvolvimento e implantação, em computador, de um método para tratamento desse problema, considerando o trade-off entre os requisitos de desempenho e o custo, fazendo uso do conceito de Fronteira de Pareto. O método possibilita, em uma única execução, a obtenção de quatro tipos de sistemas de medição, a partir da análise de soluções não dominadas. O método permite o projeto de sistemas de medição novos e o aprimoramento de sistemas de medição já existentes, considerando a existência apenas de medidas convencionais SCADA, apenas de Medidas Fasoriais Sincronizadas ou a existência dos dois tipos de medidas. O método proposto faz uso de um Algoritmo Evolutivo Multiobjetivo e do procedimento de obtenção e análise da matriz HΔ. Esse procedimento permite a realização de uma Busca Local, minimizando o custo para atendimento de cada um dos requisitos de desempenho mencionados acima. Simulações são realizadas utilizando dados dos sistemas de 6, 14, 30, 118 e 300 barras do IEEE, bem como do sistema de 61 barras da Eletropaulo, de forma a ilustrar, testar e validar o método proposto. Alguns dos resultados dessas simulações são comparados com resultados obtidos por outros métodos encontrados na literatura.Metering system planning for power system state estimation is a multi-objective, combinatorial optimization problem that may require the investigation of many possible solutions. As a consequence, meta-heuristics have been employed to solve the problem. However in the majority of them the multi-objective problem is converted in a mono-objective problem and those few considering a multi-objective formulation do not consider all the performance requirements that must be attended in order to obtain a Reliable Metering System (RMS) (system observability and absence of Critical Measurements, Critical Sets, Critical Remote Terminal Units and Critical Phasor Measurement Units). This thesis proposes a multi-objective formulation for the metering system planning problem in a wide way, that is, considering all the performance requirements that must be attended to obtain a RMS. This thesis also proposes the development and implementation, in computer, of a method to solve the metering system planning problem, considering the trade-off between the two conflicting objectives of the problem (minimizing cost while maximizing the performance requirements) making use of the concept of Pareto Frontier. The method allows, in only one execution, the project of four types of metering systems, from the analysis of non-dominated solutions. The method enable the design of new metering systems as well as the improvement of existing ones, considering the existence of only conventional SCADA measurements, or only synchronized phasor measurements or the existence of both types of measurements. The proposed method combines a multi-objective evolutionary algorithm based on subpopulation tables with the properties of the so-called HΔ matrix. The subpopulations tables adequately model several metering system performance requirements enabling a better exploration of the solution space. On the other hand, the properties of the HΔ matrix enable a local search that improves the evolutionary process and minimizes the computational effort. Simulations results with IEEE 6, 14, 30, 118 and 300-bus test systems and with a 61-bus system of Eletropaulo illustrate the efficiency of the proposed method. Some of the results of these simulations will be compared with those published in literature.
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Melo, Igor Delgado de. "Estimação de estado harmônico para sistemas radiais de distribuição usando medição fasorial sincronizada". Universidade Federal de Juiz de Fora, 2015. https://repositorio.ufjf.br/jspui/handle/ufjf/234.
Testo completoAbstract (sommario):
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Este trabalho objetiva apresentar uma metodologia capaz de estimar os componentes harmônicos em sistemas de distribuição com topologia radial utilizando PMUs (Phasor Measurement Units). Os estados a serem estimados serão as correntes passantes em todas as linhas do sistema em coordenadas retangulares. Uma vez que essas correntes são obtidas, torna-se possível o cálculo de outras grandezas elétricas através das equações de fluxo de potência e leis de Kirchhoff. A metodologia considera poucas unidades de medição fasorial (as PMUs) instaladas efetuando a leitura dos sinais de tensões nodais e correntes nas linhas com distorção harmônica. A fim de restaurar a observabilidade do sistema por completo, são considerados dados históricos de demanda de potência ativa/reativa, os quais serão tratados como restrições de desigualdades excursionando entre um valor mínimo e máximo considerados em um problema de otimização não linear que visa diminuir a diferença entre os valores monitorados pelas PMUs e os calculados pela metodologia. As mencionadas restrições permitem ao estimador o acompanhamento das variações sofridas ao longo do tempo na curva de carga para a frequência fundamental e também para as demais frequências. A abordagem proposta neste trabalho considera a modelagem trifásica de equipamentos e linhas de distribuição, portanto, são modelados os efeitos de acoplamento mútuo entre fases e a operação não linear de equipamentos de eletrônica de potência tiristorizados. O método demonstra eficiência não apenas em estimar os componentes harmônicos de um certo espectro considerado no estudo, como também se mostra uma ferramenta prática de detecção e identificação de fontes harmônicas no sistema elétrico de potência, além de explicitar um exemplo prático do uso de PMUs no que tange ao monitoramento de redes de distribuição, carentes de acompanhamento em tempo real. A metodologia ainda se mostra capaz de ser aliada a grandes estudos contextualizados em qualidade de energia, uma vez que permite a estimação de índices de distorção harmônica.
This work aims to present a methodology which is capable of estimating harmonic components for distribution systems with radial topology, using PMUs (Phasor Measurement Units). The estimated states will be all branch currents of the system expressed in rectangular coordinates. Once these currents are obtained, it is possible to calculate other electrical quantities using power flow equations and also Kirchhoff’s law. The methodology considers the installation of a few number of phasor measurement units which will measure voltage and branch currents signals distorted by harmonic sources. In order to make the whole system observable, historical data of active/reactive power demand will be treated as inequality constraints varying between minimum and maximum limits described in a non linear optimization problem, which aims to minimize the difference between the values monitored by PMUs and the ones calculated by the methodology. The already mentioned constraints allows the accompaniment of the variations occured in a typical load curve during a period of time for the fundamental frequency and also for their multiples, allowing the accompaniment of the harmonic load curve, normally unknown. The proposed approach considers a three-phase modelling of equipments and distribution lines, subject to their mutual coupling effects caused by mutual impedances between the lines. It will also be considered electronic-based devices using thyristors located along the distribution feeder, injecting harmonic currents in the system. The method demonstrates efficiency in estimating the harmonic states of the net and also in detecting and identifying harmonic sources in an eletric power system, besides showing a practical use of PMUs for the monitoring of distribution systems, lacking in information and real-time accompaniment. The method also enables the estimation of power quality indicators such as total harmonic distortion.
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Shaw, Christopher. "Synchronization for Burst-Mode APSK". International Foundation for Telemetering, 2009. http://hdl.handle.net/10150/606120.
Testo completoAbstract (sommario):
ITC/USA 2009 Conference Proceedings / The Forty-Fifth Annual International Telemetering Conference and Technical Exhibition / October 26-29, 2009 / Riviera Hotel & Convention Center, Las Vegas, NevadaWe derive bounds on the performance of data-aided joint estimators for timing offset, carrier phase offset, and carrier frequency offset for use in an APSK packet-based communication link. It is shown that the Cramér-Rao Bound (CRB) is a function of the training sequence, the signal-to-noise ratio (SNR), and the pulse shape. We also compute APSK training sequences of different lengths that minimize the CRB for each of the parameters.
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Monchenko, O. V. "Uncertainly estimation in phase ultrasound method". Thesis, National Aviation University, 2014. http://er.nau.edu.ua/handle/NAU/25036.
Testo completoAbstract (sommario):
The new multi-layer materials widely be used in aircraft. In the article present the new method of multi-layer material thickness measurement, which is based on the digital Hilbert transformation and the signal unwrapped phase analysis and offered uncertainly estimation for two-layers materials.