Pub Date : 1989-04-11DOI: 10.1109/MELCON.1989.50091
L. de Haro, J. Besada
It is noted that many clusters are built (or could be modeled) with their horn apertures embedded in a finite metallic plane. A quite general method to describe the cluster radiated fields is presented. The proposed method uses either the electric field model or Chu's model and adds the rays diffracted by the metallic plane edge to calculate the modal aperture excitations and radiation field patterns. A horn cluster analysis procedure is developed taking into account the finite aperture plane. The results obtained using cylindrical horns are shown to provide a better prediction (mainly over crosspolar fields) than that obtained with a simple model without the use of the geometrical theory of diffraction.<>
{"title":"Mutual coupling analysis between apertures embedded in a finite ground plane","authors":"L. de Haro, J. Besada","doi":"10.1109/MELCON.1989.50091","DOIUrl":"https://doi.org/10.1109/MELCON.1989.50091","url":null,"abstract":"It is noted that many clusters are built (or could be modeled) with their horn apertures embedded in a finite metallic plane. A quite general method to describe the cluster radiated fields is presented. The proposed method uses either the electric field model or Chu's model and adds the rays diffracted by the metallic plane edge to calculate the modal aperture excitations and radiation field patterns. A horn cluster analysis procedure is developed taking into account the finite aperture plane. The results obtained using cylindrical horns are shown to provide a better prediction (mainly over crosspolar fields) than that obtained with a simple model without the use of the geometrical theory of diffraction.<<ETX>>","PeriodicalId":380214,"journal":{"name":"Proceedings. Electrotechnical Conference Integrating Research, Industry and Education in Energy and Communication Engineering',","volume":"131 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1989-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122065059","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1989-04-11DOI: 10.1109/MELCON.1989.50108
A. Cartaxo, A. de Albuquerque
A fully analytical method for the computation and optimization of jitter performance in an optical fiber communication regenerator is presented. The general theory is capable of dealing, in an analytical form, with most of the jitter problems arising in clock recovery systems. This theory is capable of dealing with any type of line-code, nonlinearity, narrow bandpass filter, and photodetector device.<>
{"title":"Jitter characterization in optical fibre communication","authors":"A. Cartaxo, A. de Albuquerque","doi":"10.1109/MELCON.1989.50108","DOIUrl":"https://doi.org/10.1109/MELCON.1989.50108","url":null,"abstract":"A fully analytical method for the computation and optimization of jitter performance in an optical fiber communication regenerator is presented. The general theory is capable of dealing, in an analytical form, with most of the jitter problems arising in clock recovery systems. This theory is capable of dealing with any type of line-code, nonlinearity, narrow bandpass filter, and photodetector device.<<ETX>>","PeriodicalId":380214,"journal":{"name":"Proceedings. Electrotechnical Conference Integrating Research, Industry and Education in Energy and Communication Engineering',","volume":"107 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1989-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123148805","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1989-04-11DOI: 10.1109/MELCON.1989.50063
A. Goiser, M. Sust
CMOS digital correlators with extended on-chip signal processing capabilities strongly increase the applicability of digital matched filters (DMFs) in noncoherent direct sequence spread spectrum receivers. However, the digital concept gives rise to problems caused by time- and amplitude-quantization at analog-to-digital (A/D) conversion prior to correlation. In the present work, a noncoherent receiver structure, using a sampling window technique to prevent timing errors due to oscillator uncertainties, is reviewed. In order to improve the system performance in the presence of CW (continuous wave) interference, a 2-bit A/D-converter (ADC) with adaptive thresholds is proposed. The performance of a DMF receiver using 2-bit A/D conversion as well as hard limiting is compared with that of an analog matched filter receiver. By the use of the 2-bit ADC instead of the hard limiter, a performance improvement is obtained, and, when interferences have a strong CW content, the analog counterpart is even outperformed.<>
{"title":"Spread spectrum communications using CMOS digital correlators","authors":"A. Goiser, M. Sust","doi":"10.1109/MELCON.1989.50063","DOIUrl":"https://doi.org/10.1109/MELCON.1989.50063","url":null,"abstract":"CMOS digital correlators with extended on-chip signal processing capabilities strongly increase the applicability of digital matched filters (DMFs) in noncoherent direct sequence spread spectrum receivers. However, the digital concept gives rise to problems caused by time- and amplitude-quantization at analog-to-digital (A/D) conversion prior to correlation. In the present work, a noncoherent receiver structure, using a sampling window technique to prevent timing errors due to oscillator uncertainties, is reviewed. In order to improve the system performance in the presence of CW (continuous wave) interference, a 2-bit A/D-converter (ADC) with adaptive thresholds is proposed. The performance of a DMF receiver using 2-bit A/D conversion as well as hard limiting is compared with that of an analog matched filter receiver. By the use of the 2-bit ADC instead of the hard limiter, a performance improvement is obtained, and, when interferences have a strong CW content, the analog counterpart is even outperformed.<<ETX>>","PeriodicalId":380214,"journal":{"name":"Proceedings. Electrotechnical Conference Integrating Research, Industry and Education in Energy and Communication Engineering',","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1989-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123351443","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1989-04-11DOI: 10.1109/MELCON.1989.49992
M. Papadopoulos, N. Hatziargyriou
Repercussions of the connection of dispersed wind turbines to the steady-state operation of the local grid are examined. An interactive computer program is used which provides the voltage fluctuations and the line losses at selected points of a typical 20 kV rural distribution feeder with and without wind turbines. The results presented indicate that utilities will not face serious voltage regulation problems because of the connection of small wind turbines to their distribution networks. Line losses are also not seriously affected. Shunt capacitors may substantially improve the voltage profiles and reduce the line losses.<>
{"title":"Repercussions from the connection of wind turbines to the local grid","authors":"M. Papadopoulos, N. Hatziargyriou","doi":"10.1109/MELCON.1989.49992","DOIUrl":"https://doi.org/10.1109/MELCON.1989.49992","url":null,"abstract":"Repercussions of the connection of dispersed wind turbines to the steady-state operation of the local grid are examined. An interactive computer program is used which provides the voltage fluctuations and the line losses at selected points of a typical 20 kV rural distribution feeder with and without wind turbines. The results presented indicate that utilities will not face serious voltage regulation problems because of the connection of small wind turbines to their distribution networks. Line losses are also not seriously affected. Shunt capacitors may substantially improve the voltage profiles and reduce the line losses.<<ETX>>","PeriodicalId":380214,"journal":{"name":"Proceedings. Electrotechnical Conference Integrating Research, Industry and Education in Energy and Communication Engineering',","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1989-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121066484","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1989-04-11DOI: 10.1109/MELCON.1989.50014
Ping-Ya Zhao, Zhenya He
Various existing multidimensional system identification theories and techniques are reviewed. Particular attention is given to various modeling and parameter estimation techniques. State space, conditional Markovian simultaneous autoregressive, and finite-order autoregressive moving average methods and their various variants are discussed. Maximum-likelihood, least-squares, and other commonly used techniques are also studied.<>
{"title":"On multidimensional system identification","authors":"Ping-Ya Zhao, Zhenya He","doi":"10.1109/MELCON.1989.50014","DOIUrl":"https://doi.org/10.1109/MELCON.1989.50014","url":null,"abstract":"Various existing multidimensional system identification theories and techniques are reviewed. Particular attention is given to various modeling and parameter estimation techniques. State space, conditional Markovian simultaneous autoregressive, and finite-order autoregressive moving average methods and their various variants are discussed. Maximum-likelihood, least-squares, and other commonly used techniques are also studied.<<ETX>>","PeriodicalId":380214,"journal":{"name":"Proceedings. Electrotechnical Conference Integrating Research, Industry and Education in Energy and Communication Engineering',","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1989-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134434872","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1989-04-11DOI: 10.1109/MELCON.1989.50153
G. Di Cataldo, G. Nunnari
A tool for electric circuit design implemented by using an expert system is proposed. The package, which runs on an IBM PC or compatible, has been created essentially to provide a suitable learning technique for students in electrical engineering involved in electric circuit synthesis. The criteria utilized to implement the software package and the advantages of the proposed approach are outlined and illustrated. The role of the expert system in easily codifying and systematically using formal and heuristic knowledge is emphasized. The features of a particular shell in building the described tool are shown.<>
{"title":"LED: an educational tool for electric circuit design","authors":"G. Di Cataldo, G. Nunnari","doi":"10.1109/MELCON.1989.50153","DOIUrl":"https://doi.org/10.1109/MELCON.1989.50153","url":null,"abstract":"A tool for electric circuit design implemented by using an expert system is proposed. The package, which runs on an IBM PC or compatible, has been created essentially to provide a suitable learning technique for students in electrical engineering involved in electric circuit synthesis. The criteria utilized to implement the software package and the advantages of the proposed approach are outlined and illustrated. The role of the expert system in easily codifying and systematically using formal and heuristic knowledge is emphasized. The features of a particular shell in building the described tool are shown.<<ETX>>","PeriodicalId":380214,"journal":{"name":"Proceedings. Electrotechnical Conference Integrating Research, Industry and Education in Energy and Communication Engineering',","volume":"82 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1989-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134619085","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1989-04-11DOI: 10.1109/MELCON.1989.49984
N.H. Yukseler
A general method is developed for the measurement of the symmetrical components of multiphase systems. The approach involves step-by-step elimination for the segregation of desired sequence quantities instead of using static networks: thus, it is reliable and precise. The measurement of sequence voltages and currents is considered for two, three, four, five, and six-phase systems.<>
{"title":"A new method for measurement of multi-phase electrical quantities' components in power conversion and transmission systems","authors":"N.H. Yukseler","doi":"10.1109/MELCON.1989.49984","DOIUrl":"https://doi.org/10.1109/MELCON.1989.49984","url":null,"abstract":"A general method is developed for the measurement of the symmetrical components of multiphase systems. The approach involves step-by-step elimination for the segregation of desired sequence quantities instead of using static networks: thus, it is reliable and precise. The measurement of sequence voltages and currents is considered for two, three, four, five, and six-phase systems.<<ETX>>","PeriodicalId":380214,"journal":{"name":"Proceedings. Electrotechnical Conference Integrating Research, Industry and Education in Energy and Communication Engineering',","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1989-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131009537","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1989-04-11DOI: 10.1109/MELCON.1989.50070
J. Vinyes, J. Riera, E. Vázquez
An effort is made to analyze the admission delay of an X.25 connection, modeling the virtual circuit as an equivalent server with parameters related to the behaviour measurable by the X.25 user. The authors review M. Reiser's (1978) mean value analysis of a virtual circuit with window flow control, Norton's theorem is used to obtain an equivalent server allowing the evaluation of the X.25 admission delay. An M/M/m system is proposed as an approximate equivalent system of the X.25 virtual circuit, which produces a very tight and conservative bound of the actual performance.<>
{"title":"M/M/m modelling of access delay to X.25 virtual circuits","authors":"J. Vinyes, J. Riera, E. Vázquez","doi":"10.1109/MELCON.1989.50070","DOIUrl":"https://doi.org/10.1109/MELCON.1989.50070","url":null,"abstract":"An effort is made to analyze the admission delay of an X.25 connection, modeling the virtual circuit as an equivalent server with parameters related to the behaviour measurable by the X.25 user. The authors review M. Reiser's (1978) mean value analysis of a virtual circuit with window flow control, Norton's theorem is used to obtain an equivalent server allowing the evaluation of the X.25 admission delay. An M/M/m system is proposed as an approximate equivalent system of the X.25 virtual circuit, which produces a very tight and conservative bound of the actual performance.<<ETX>>","PeriodicalId":380214,"journal":{"name":"Proceedings. Electrotechnical Conference Integrating Research, Industry and Education in Energy and Communication Engineering',","volume":"72 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1989-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132829349","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1989-04-11DOI: 10.1109/MELCON.1989.49986
R. Castro, A. Gomes, J.J.M. Ferreira de
The transient behavior of an induction generator in a small hydro plant following disturbances in the utility's transmission and distribution system was studied, and some conclusions concerning the protection and control of small hydro plants with induction generators are drawn. Two perturbations were considered: a sudden loss of load situation and a three-phase short circuit in the feeder. In both cases it was assumed that reclosure of the utility's breaker would occur. From the studies performed it was concluded that the relays operated properly. In the situations considered both the over-frequency and the under-frequency relays were inhibited. It is stressed that the results are strongly dependent on the sizing of the shunt capacitor bank.<>
{"title":"Transient behaviour of an induction generation in small hydro plants","authors":"R. Castro, A. Gomes, J.J.M. Ferreira de","doi":"10.1109/MELCON.1989.49986","DOIUrl":"https://doi.org/10.1109/MELCON.1989.49986","url":null,"abstract":"The transient behavior of an induction generator in a small hydro plant following disturbances in the utility's transmission and distribution system was studied, and some conclusions concerning the protection and control of small hydro plants with induction generators are drawn. Two perturbations were considered: a sudden loss of load situation and a three-phase short circuit in the feeder. In both cases it was assumed that reclosure of the utility's breaker would occur. From the studies performed it was concluded that the relays operated properly. In the situations considered both the over-frequency and the under-frequency relays were inhibited. It is stressed that the results are strongly dependent on the sizing of the shunt capacitor bank.<<ETX>>","PeriodicalId":380214,"journal":{"name":"Proceedings. Electrotechnical Conference Integrating Research, Industry and Education in Energy and Communication Engineering',","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1989-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130203604","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1989-04-11DOI: 10.1109/MELCON.1989.49988
S. Kavatza, G. Contaxis
The authors present a suboptimal optimization method for solving the annual hydrothermal scheduling problem. Hydrothermal scheduling is performed in order to find the optimum allocation of hydro energy so that the annual operating cost of a mixed hydro-thermal system is minimized. The hydrothermal scheduling problem is decomposed into three subproblems: maintenance of thermal units, dispatch of thermal units, and dispatch of hydro units. The algorithm takes into consideration the stochastic nature of the water inflows to the reservoir and the forced outage rates of the thermal units. Maintenance scheduling is performed based on the levelized risk criterion, dispatch of the thermal units is determined based on probabilistic techniques, while the dispatch of the hydro units is formulated as a constrained optimization problem. Results obtained by the application of the algorithm to a case study showing the effect of the hydro units are reported.<>
{"title":"Hydrothermal scheduling of power system with stochastic inflows","authors":"S. Kavatza, G. Contaxis","doi":"10.1109/MELCON.1989.49988","DOIUrl":"https://doi.org/10.1109/MELCON.1989.49988","url":null,"abstract":"The authors present a suboptimal optimization method for solving the annual hydrothermal scheduling problem. Hydrothermal scheduling is performed in order to find the optimum allocation of hydro energy so that the annual operating cost of a mixed hydro-thermal system is minimized. The hydrothermal scheduling problem is decomposed into three subproblems: maintenance of thermal units, dispatch of thermal units, and dispatch of hydro units. The algorithm takes into consideration the stochastic nature of the water inflows to the reservoir and the forced outage rates of the thermal units. Maintenance scheduling is performed based on the levelized risk criterion, dispatch of the thermal units is determined based on probabilistic techniques, while the dispatch of the hydro units is formulated as a constrained optimization problem. Results obtained by the application of the algorithm to a case study showing the effect of the hydro units are reported.<<ETX>>","PeriodicalId":380214,"journal":{"name":"Proceedings. Electrotechnical Conference Integrating Research, Industry and Education in Energy and Communication Engineering',","volume":"16 5","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1989-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"113978910","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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