T. Lobos - Academia.edu (original) (raw)
Papers by T. Lobos
Electric Power Systems Research, 1991
Computers & Electrical Engineering, 1982
This paper identifies a range of simple computational procedures for calculating the impedance of... more This paper identifies a range of simple computational procedures for calculating the impedance of transmission lines in real-time, designed to be implemented on microprocessors for the purpose of line protection. The methods use two, three, or four sampling values of current and voltage and are appropriate for short or medium-length transmission lines of up to 220kV. The various methods are compared with each other in respect to accuracy and speed of implementation. Special attention is given to those methods which reduce the errors produced by d.c. offset voltages and currents. Several improvements are made on the procedures that have so far appeared in the literature.
2008 Conference on Human System Interactions, 2008
Signal parameters estimation is an important prerequisite for assessment of power quality (PQ) in... more Signal parameters estimation is an important prerequisite for assessment of power quality (PQ) indices. Nowadays, large amounts of measured data need to be automatically processed for appropriate and useful data mining in PQ. Especially, modern wind generators are often seen as sources of PQ disturbances, which should be constantly supervised. The authors propose an application of modified singular value decomposition
IEEE Transactions on Power Delivery, 2006
... For detection of appearances of sags, a multiresolution analysis tree has been applied [15]. ... more ... For detection of appearances of sags, a multiresolution analysis tree has been applied [15]. ... We applied the multires Page 3. JANIK AND LOBOS: AUTOMATED CLASSIFICATION OF POWER-QUALITY DISTURBANCES 1665 Fig. ...
7th International Conference on Developments in Power Systems Protection (DPSP 2001), 2001
CITATIONS 12 READS 51 4 authors, including:
2004 11th International Conference on Harmonics and Quality of Power (IEEE Cat. No.04EX951), 2004
This is a companion paper to a paper of the same title, Part I, in which the theoretical aspects ... more This is a companion paper to a paper of the same title, Part I, in which the theoretical aspects of some spectrum estimation methods for analysis of non-stationary voltages and currents in power systems with nonlinear loads are analysed. In particular, the Prony model and rootMusic method are taken into account. In this paper, numerical applications of the methods presented in Part I are discussed, in order to illustrate their implementation problems and practical applications. To investigate the methods, several experiments were performed using non-stationary voltage and current waveforms in a supply system of a dc arc furnace. For comparison, similar experiments were repeated using the Short-Time Fourier Transform. The comparison proved the effectiveness of the new methods; however, their computational efforts can be much more complex. Conclusions and recommendations are made concerning the framework of each method.
2007 IEEE International Symposium on Diagnostics for Electric Machines, Power Electronics and Drives, 2007
Proper estimation of voltage parameters has a significant meaning for power converters control sy... more Proper estimation of voltage parameters has a significant meaning for power converters control systems. One of the measured parameter, directly associated with control process, is frequency of basic component. Unfortunately, power converters generate wide spectrum of harmonics as well as interharmonics, that makes difficult in estimation of frequency of basic component. Measurement carried out in industrial applications exhibits complex nature
2001 IEEE Porto Power Tech Proceedings (Cat. No.01EX502), 2001
... The paper [4] presents a new method of real-time measurement of power system frequency based ... more ... The paper [4] presents a new method of real-time measurement of power system frequency based on Prony model. A distribution system was simulated using the EMTP (Electromagnetic Transient Program) software. ...
Modern frequency power converters generate a wide spectrum of harmonics components. Large convert... more Modern frequency power converters generate a wide spectrum of harmonics components. Large converters systems can also generate noncharacteristic harmonics and interharmonics. The spectrum estimation methods, based on the Fourier transform, suffer from the major problem of resolution. A novel approach to harmonic and interharmonic analysis, based on the "subspace" methods, is proposed. The Prony method as applied for signal analysis was also tested for this purpose. Both the high-resolution methods do not show the disadvantages of the traditional tools and allow exact estimation of the interharmonics frequencies. To investigate the methods several experiments were performed using simulated signals, current waveforms at the output of an industrial frequency converter and current waveforms during out-of-step operation of a synchronous generator. For comparison, similar experiments were repeated using the FFT. The comparison proved the superiority of the new methods. However, ...
Ninth International Conference on Harmonics and Quality of Power. Proceedings (Cat. No.00EX441), 2000
2003 International Conference Physics and Control. Proceedings (Cat. No.03EX708), 2003
IEEE International Symposium on Intelligent Signal Processing, 2003, 2003
... Tadeusz Lobos, Jacek Rezmer, Tomasz Sikorski Wroclaw University of Technology, Department of ... more ... Tadeusz Lobos, Jacek Rezmer, Tomasz Sikorski Wroclaw University of Technology, Department of Electrical Engineering ... First, Gabor has adapted the Fourier Transform to define the S(I,W), assuming that the signal is stationary when seen through a window of limited extent. ...
2003 IEEE Bologna Power Tech Conference Proceedings,, 2003
Modern frequency power converters generate a wide spectrum of harmonic components. Large converte... more Modern frequency power converters generate a wide spectrum of harmonic components. Large converter systems can also generate noncharacteristic harmonics and interharmonics. Standard tools of harmonic analysis based on the Fourier transform assume that only harmonics are present and the periodicity intervals are fixed, while periodicity intervals in the presence of interharmonics are variable and very long. In the case of frequency converters the periods of the main component are unknown. The Prony method as applied for signal analysis in power frequency converter was tested in the paper. The method does not show the disadvantages of the traditional tools and allow exact estimation the frequencies of all or dominant components, even when the periodicity intervals are unknown. To investigate the appropriateness of the method several experiments were performed. For comparison, similar experiments were repeated using the FFT. The comparison proved the superiority of the Prony method.
IECON 2006 - 32nd Annual Conference on IEEE Industrial Electronics, 2006
Auxiliary static converters in transportation power systems generate not only characteristic harm... more Auxiliary static converters in transportation power systems generate not only characteristic harmonics but also non characteristic harmonics and interharmonics. Representation of signals in time and frequency domain has been of interest in signal processing areas for many years, especially taking in the limelight time-varying non-stationary signals. Standard tools of harmonic analysis based on the Fourier transform are not suitable for analysis in this case. In this paper the ESPRIT method was tested for this purpose that allows an accurate and detailed estimation of parameters of currents in the power supply of auxiliary devices in traction systems, also interharmonic frequencies with their changes in time.
EUROCON 2007 - The International Conference on "Computer as a Tool", 2007
International Journal of Electrical Power & Energy Systems, 2009
Voltage dips and transients are the most commonly encountered power quality disturbances in wind ... more Voltage dips and transients are the most commonly encountered power quality disturbances in wind farms. Signal parameters estimation is an important prerequisite for power quality enhancement and for improving the fault-ride capability of wind farms and consequently, the voltage stability of the whole network. This paper examines the application of advanced signal processing methodologies such as the Prony method and
Revista médica de Chile, 1993
In order to investigate the L pneumophila seroprevalence in healthy adult population of Santiago,... more In order to investigate the L pneumophila seroprevalence in healthy adult population of Santiago, Chile, a serologic survey of antibodies to serogroups 1 through G was performed. Sera of 100 blood donors were studied with the indirect fluorescent antibody method. Positive results (> or = 1.64) were obtained in five samples. Titres > or = 1:128 were not observed. We conclude that the seroprevalence of L pneumophila in Santiago is 5% and that a single titre > or = 1:256 suggests the diagnosis of legionellosis. The low seroprevalence in Santiago is in agreement with the few cases of legionellosis reported.
2007 IEEE Lausanne Power Tech, 2007
Wind converters impact on power quality is crucial for power system operation. This paper present... more Wind converters impact on power quality is crucial for power system operation. This paper presents assessment of transients originating in a system with induction generator driven by wind turbine and compensated by capacitor bank. Prony algorithm and wavelets have been applied to determine signal parameters in different operation modes of wind generation unit. Detailed power quality studies on transients are
2001 Power Engineering Society Summer Meeting. Conference Proceedings (Cat. No.01CH37262), 2001
... without Synchronization H.-J. Koglin, M. Albert Saarland Umvemty Saatnuecken,Germany ... III.... more ... without Synchronization H.-J. Koglin, M. Albert Saarland Umvemty Saatnuecken,Germany ... III. POWERAPPROACH In the power approach the conjugated currents of eq. (2) are multiplied by the voltage at the tap point: * * * LA +La+Lc 'ELLA +QL4La+YL4LC 'o (8) ...
Electric Power Systems Research, 1991
Computers & Electrical Engineering, 1982
This paper identifies a range of simple computational procedures for calculating the impedance of... more This paper identifies a range of simple computational procedures for calculating the impedance of transmission lines in real-time, designed to be implemented on microprocessors for the purpose of line protection. The methods use two, three, or four sampling values of current and voltage and are appropriate for short or medium-length transmission lines of up to 220kV. The various methods are compared with each other in respect to accuracy and speed of implementation. Special attention is given to those methods which reduce the errors produced by d.c. offset voltages and currents. Several improvements are made on the procedures that have so far appeared in the literature.
2008 Conference on Human System Interactions, 2008
Signal parameters estimation is an important prerequisite for assessment of power quality (PQ) in... more Signal parameters estimation is an important prerequisite for assessment of power quality (PQ) indices. Nowadays, large amounts of measured data need to be automatically processed for appropriate and useful data mining in PQ. Especially, modern wind generators are often seen as sources of PQ disturbances, which should be constantly supervised. The authors propose an application of modified singular value decomposition
IEEE Transactions on Power Delivery, 2006
... For detection of appearances of sags, a multiresolution analysis tree has been applied [15]. ... more ... For detection of appearances of sags, a multiresolution analysis tree has been applied [15]. ... We applied the multires Page 3. JANIK AND LOBOS: AUTOMATED CLASSIFICATION OF POWER-QUALITY DISTURBANCES 1665 Fig. ...
7th International Conference on Developments in Power Systems Protection (DPSP 2001), 2001
CITATIONS 12 READS 51 4 authors, including:
2004 11th International Conference on Harmonics and Quality of Power (IEEE Cat. No.04EX951), 2004
This is a companion paper to a paper of the same title, Part I, in which the theoretical aspects ... more This is a companion paper to a paper of the same title, Part I, in which the theoretical aspects of some spectrum estimation methods for analysis of non-stationary voltages and currents in power systems with nonlinear loads are analysed. In particular, the Prony model and rootMusic method are taken into account. In this paper, numerical applications of the methods presented in Part I are discussed, in order to illustrate their implementation problems and practical applications. To investigate the methods, several experiments were performed using non-stationary voltage and current waveforms in a supply system of a dc arc furnace. For comparison, similar experiments were repeated using the Short-Time Fourier Transform. The comparison proved the effectiveness of the new methods; however, their computational efforts can be much more complex. Conclusions and recommendations are made concerning the framework of each method.
2007 IEEE International Symposium on Diagnostics for Electric Machines, Power Electronics and Drives, 2007
Proper estimation of voltage parameters has a significant meaning for power converters control sy... more Proper estimation of voltage parameters has a significant meaning for power converters control systems. One of the measured parameter, directly associated with control process, is frequency of basic component. Unfortunately, power converters generate wide spectrum of harmonics as well as interharmonics, that makes difficult in estimation of frequency of basic component. Measurement carried out in industrial applications exhibits complex nature
2001 IEEE Porto Power Tech Proceedings (Cat. No.01EX502), 2001
... The paper [4] presents a new method of real-time measurement of power system frequency based ... more ... The paper [4] presents a new method of real-time measurement of power system frequency based on Prony model. A distribution system was simulated using the EMTP (Electromagnetic Transient Program) software. ...
Modern frequency power converters generate a wide spectrum of harmonics components. Large convert... more Modern frequency power converters generate a wide spectrum of harmonics components. Large converters systems can also generate noncharacteristic harmonics and interharmonics. The spectrum estimation methods, based on the Fourier transform, suffer from the major problem of resolution. A novel approach to harmonic and interharmonic analysis, based on the "subspace" methods, is proposed. The Prony method as applied for signal analysis was also tested for this purpose. Both the high-resolution methods do not show the disadvantages of the traditional tools and allow exact estimation of the interharmonics frequencies. To investigate the methods several experiments were performed using simulated signals, current waveforms at the output of an industrial frequency converter and current waveforms during out-of-step operation of a synchronous generator. For comparison, similar experiments were repeated using the FFT. The comparison proved the superiority of the new methods. However, ...
Ninth International Conference on Harmonics and Quality of Power. Proceedings (Cat. No.00EX441), 2000
2003 International Conference Physics and Control. Proceedings (Cat. No.03EX708), 2003
IEEE International Symposium on Intelligent Signal Processing, 2003, 2003
... Tadeusz Lobos, Jacek Rezmer, Tomasz Sikorski Wroclaw University of Technology, Department of ... more ... Tadeusz Lobos, Jacek Rezmer, Tomasz Sikorski Wroclaw University of Technology, Department of Electrical Engineering ... First, Gabor has adapted the Fourier Transform to define the S(I,W), assuming that the signal is stationary when seen through a window of limited extent. ...
2003 IEEE Bologna Power Tech Conference Proceedings,, 2003
Modern frequency power converters generate a wide spectrum of harmonic components. Large converte... more Modern frequency power converters generate a wide spectrum of harmonic components. Large converter systems can also generate noncharacteristic harmonics and interharmonics. Standard tools of harmonic analysis based on the Fourier transform assume that only harmonics are present and the periodicity intervals are fixed, while periodicity intervals in the presence of interharmonics are variable and very long. In the case of frequency converters the periods of the main component are unknown. The Prony method as applied for signal analysis in power frequency converter was tested in the paper. The method does not show the disadvantages of the traditional tools and allow exact estimation the frequencies of all or dominant components, even when the periodicity intervals are unknown. To investigate the appropriateness of the method several experiments were performed. For comparison, similar experiments were repeated using the FFT. The comparison proved the superiority of the Prony method.
IECON 2006 - 32nd Annual Conference on IEEE Industrial Electronics, 2006
Auxiliary static converters in transportation power systems generate not only characteristic harm... more Auxiliary static converters in transportation power systems generate not only characteristic harmonics but also non characteristic harmonics and interharmonics. Representation of signals in time and frequency domain has been of interest in signal processing areas for many years, especially taking in the limelight time-varying non-stationary signals. Standard tools of harmonic analysis based on the Fourier transform are not suitable for analysis in this case. In this paper the ESPRIT method was tested for this purpose that allows an accurate and detailed estimation of parameters of currents in the power supply of auxiliary devices in traction systems, also interharmonic frequencies with their changes in time.
EUROCON 2007 - The International Conference on "Computer as a Tool", 2007
International Journal of Electrical Power & Energy Systems, 2009
Voltage dips and transients are the most commonly encountered power quality disturbances in wind ... more Voltage dips and transients are the most commonly encountered power quality disturbances in wind farms. Signal parameters estimation is an important prerequisite for power quality enhancement and for improving the fault-ride capability of wind farms and consequently, the voltage stability of the whole network. This paper examines the application of advanced signal processing methodologies such as the Prony method and
Revista médica de Chile, 1993
In order to investigate the L pneumophila seroprevalence in healthy adult population of Santiago,... more In order to investigate the L pneumophila seroprevalence in healthy adult population of Santiago, Chile, a serologic survey of antibodies to serogroups 1 through G was performed. Sera of 100 blood donors were studied with the indirect fluorescent antibody method. Positive results (> or = 1.64) were obtained in five samples. Titres > or = 1:128 were not observed. We conclude that the seroprevalence of L pneumophila in Santiago is 5% and that a single titre > or = 1:256 suggests the diagnosis of legionellosis. The low seroprevalence in Santiago is in agreement with the few cases of legionellosis reported.
2007 IEEE Lausanne Power Tech, 2007
Wind converters impact on power quality is crucial for power system operation. This paper present... more Wind converters impact on power quality is crucial for power system operation. This paper presents assessment of transients originating in a system with induction generator driven by wind turbine and compensated by capacitor bank. Prony algorithm and wavelets have been applied to determine signal parameters in different operation modes of wind generation unit. Detailed power quality studies on transients are
2001 Power Engineering Society Summer Meeting. Conference Proceedings (Cat. No.01CH37262), 2001
... without Synchronization H.-J. Koglin, M. Albert Saarland Umvemty Saatnuecken,Germany ... III.... more ... without Synchronization H.-J. Koglin, M. Albert Saarland Umvemty Saatnuecken,Germany ... III. POWERAPPROACH In the power approach the conjugated currents of eq. (2) are multiplied by the voltage at the tap point: * * * LA +La+Lc 'ELLA +QL4La+YL4LC 'o (8) ...