Pub Date : 2008-03-12DOI: 10.1109/MEPCON.2008.4562377
A. El Aroudi, E. Alarcón, E. Rodriguez, M. Orabi
In this paper we study the dynamical behavior of a full bridge DC-AC buck inverter controlled by fixed frequency and PWM. After showing that the system can undergo both period doubling and Neimark-Sacker bifurcation at the fast scale (switching period) by using the exact switching model, we derive an exact solution discrete-time model able to predict both instability phenomena. The model is obtained without making the quasi-static approximation and it can be used to obtain the useful region in the multidimensional design parameter space from time domain simulations in a very fast and accurate manner.
{"title":"Modeling of switching frequency instabilities in buck-based DC-AC inverters by nonlinear time varying Poincaré mappings","authors":"A. El Aroudi, E. Alarcón, E. Rodriguez, M. Orabi","doi":"10.1109/MEPCON.2008.4562377","DOIUrl":"https://doi.org/10.1109/MEPCON.2008.4562377","url":null,"abstract":"In this paper we study the dynamical behavior of a full bridge DC-AC buck inverter controlled by fixed frequency and PWM. After showing that the system can undergo both period doubling and Neimark-Sacker bifurcation at the fast scale (switching period) by using the exact switching model, we derive an exact solution discrete-time model able to predict both instability phenomena. The model is obtained without making the quasi-static approximation and it can be used to obtain the useful region in the multidimensional design parameter space from time domain simulations in a very fast and accurate manner.","PeriodicalId":236620,"journal":{"name":"2008 12th International Middle-East Power System Conference","volume":"162 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125656593","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 : 2008-03-12DOI: 10.1109/MEPCON.2008.4562318
T. Kawady, H.E. Labna, A. Taalab
In this paper, a new method for detecting internal winding faults for both single phase and three phase power transformers is presented. Not only the winding faults (including phase and ground fault combinations) are covered, but those turn-turn ones are successfully detected as well. These turn-turn conditions represent a basic challenge for conventional differential protection schemes. Internal high impedance ground faults are also covered successfully with a wide range of fault resistance value. The discrimination between winding faults and the magnetizing inrush conditions is also verified. The performance of the proposed detector is investigated using EMTP simulation covering a variety of operating conditions. All applied test results verify the performance of the proposed detector for power transformer protection.
{"title":"A practical winding fault detector for power transformers","authors":"T. Kawady, H.E. Labna, A. Taalab","doi":"10.1109/MEPCON.2008.4562318","DOIUrl":"https://doi.org/10.1109/MEPCON.2008.4562318","url":null,"abstract":"In this paper, a new method for detecting internal winding faults for both single phase and three phase power transformers is presented. Not only the winding faults (including phase and ground fault combinations) are covered, but those turn-turn ones are successfully detected as well. These turn-turn conditions represent a basic challenge for conventional differential protection schemes. Internal high impedance ground faults are also covered successfully with a wide range of fault resistance value. The discrimination between winding faults and the magnetizing inrush conditions is also verified. The performance of the proposed detector is investigated using EMTP simulation covering a variety of operating conditions. All applied test results verify the performance of the proposed detector for power transformer protection.","PeriodicalId":236620,"journal":{"name":"2008 12th International Middle-East Power System Conference","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125889635","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 : 2008-03-12DOI: 10.1109/MEPCON.2008.4562350
E. Ozkop, H. Okumus
In this study, direct torque control (DTC) of induction motor is evaluated based on space vector modulation (SVM). DTC is a method to control machine with utilizing torque and flux of motor controlled. The torque and current ripple are occurred in the conventional DTC. Reason of undesired torque and current ripple is low number of voltage vectors applied to the motor controlled by the conventional DTC technique. SVM-DTC is a technique to reduce the ripple. SVM techniques have several advantages that are offering better DC bus utilization, lower torque ripple, lower total harmonic distortion in the AC motor current, lower switching loss, and easier to implement in the digital systems. Simulation results from the classical and improved DTC are presented and compared. Result shows that the torque, flux linkage and stator current ripple are decreased with the improved DTC.
{"title":"Direct torque control of induction motor using space vector modulation (SVM-DTC)","authors":"E. Ozkop, H. Okumus","doi":"10.1109/MEPCON.2008.4562350","DOIUrl":"https://doi.org/10.1109/MEPCON.2008.4562350","url":null,"abstract":"In this study, direct torque control (DTC) of induction motor is evaluated based on space vector modulation (SVM). DTC is a method to control machine with utilizing torque and flux of motor controlled. The torque and current ripple are occurred in the conventional DTC. Reason of undesired torque and current ripple is low number of voltage vectors applied to the motor controlled by the conventional DTC technique. SVM-DTC is a technique to reduce the ripple. SVM techniques have several advantages that are offering better DC bus utilization, lower torque ripple, lower total harmonic distortion in the AC motor current, lower switching loss, and easier to implement in the digital systems. Simulation results from the classical and improved DTC are presented and compared. Result shows that the torque, flux linkage and stator current ripple are decreased with the improved DTC.","PeriodicalId":236620,"journal":{"name":"2008 12th International Middle-East Power System Conference","volume":"25 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130561934","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 : 2008-03-12DOI: 10.1109/MEPCON.2008.4562308
A. El-Zein, M. E. El Bahy, M. Talaat
The shape of electrical trees is critical in determining the life of electrical insulation subject to this type of degradation. This paper identifies a physical basis for determining tree shape. A quantitative physical model for propagation of electrical tree structures in polymeric insulation is presented. In the present model the propagation of trees arises from the formation of electrodamage that precedes and surrounds the tree tip during the tree propagation process. A kinetic model for the electrical tree structures in solid polymeric insulation is developed, that allows for combined electrical and mechanical stresses. Also present an energy balance analysis during the tree growth process, and present results which show that the proposed model can give predicted tree shape type which in a good agreement with the experimental data of the tree growth subjected to a combined electrical and mechanical stress.
{"title":"Types of electrical trees in solid insulation under electrical and mechanical energy basis","authors":"A. El-Zein, M. E. El Bahy, M. Talaat","doi":"10.1109/MEPCON.2008.4562308","DOIUrl":"https://doi.org/10.1109/MEPCON.2008.4562308","url":null,"abstract":"The shape of electrical trees is critical in determining the life of electrical insulation subject to this type of degradation. This paper identifies a physical basis for determining tree shape. A quantitative physical model for propagation of electrical tree structures in polymeric insulation is presented. In the present model the propagation of trees arises from the formation of electrodamage that precedes and surrounds the tree tip during the tree propagation process. A kinetic model for the electrical tree structures in solid polymeric insulation is developed, that allows for combined electrical and mechanical stresses. Also present an energy balance analysis during the tree growth process, and present results which show that the proposed model can give predicted tree shape type which in a good agreement with the experimental data of the tree growth subjected to a combined electrical and mechanical stress.","PeriodicalId":236620,"journal":{"name":"2008 12th International Middle-East Power System Conference","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130161305","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 : 2008-03-12DOI: 10.1109/MEPCON.2008.4562410
M. El-Hadidy, D. Helmi, H. G. Negm, H. M. El-shaer
The analysis of the large systems blackouts during the last years have pointed out the need for the function of real-time wide area monitoring, protection and control (RT WAM PAC). Phaser measurements (PM) has proved to be the vital source of data necessary for many applications in power system RT WAM PAC. The paper explains this new technology, the reasons behind its use and points out the role it plays in the overall view of RT WAM PAC. The recent applications of the synchrophasors projects allover the world is highlighted. Generic and specific technical requirements for synchrophasors measurements are explained. The paper also illustrates, using actual recorded case from the fault recording system in the Egyptian Power Network, how the synchronized voltage phasors at different locations within the system, could be presented to the system operator during different operating states, using a software program designed specially for this purpose. A pilot project for PM in Egypt using the existing disturbance recorders is presented showing the benefits which could be gained from such a project.
{"title":"Starting Synchrophasor measurements in Egypt: A pilot project using fault recorders","authors":"M. El-Hadidy, D. Helmi, H. G. Negm, H. M. El-shaer","doi":"10.1109/MEPCON.2008.4562410","DOIUrl":"https://doi.org/10.1109/MEPCON.2008.4562410","url":null,"abstract":"The analysis of the large systems blackouts during the last years have pointed out the need for the function of real-time wide area monitoring, protection and control (RT WAM PAC). Phaser measurements (PM) has proved to be the vital source of data necessary for many applications in power system RT WAM PAC. The paper explains this new technology, the reasons behind its use and points out the role it plays in the overall view of RT WAM PAC. The recent applications of the synchrophasors projects allover the world is highlighted. Generic and specific technical requirements for synchrophasors measurements are explained. The paper also illustrates, using actual recorded case from the fault recording system in the Egyptian Power Network, how the synchronized voltage phasors at different locations within the system, could be presented to the system operator during different operating states, using a software program designed specially for this purpose. A pilot project for PM in Egypt using the existing disturbance recorders is presented showing the benefits which could be gained from such a project.","PeriodicalId":236620,"journal":{"name":"2008 12th International Middle-East Power System Conference","volume":"97 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122579750","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 : 2008-03-12DOI: 10.1109/MEPCON.2008.4562373
M. Kotb
New method for solving the maintenance schedule (MS) problem is proposed. Comparative study has been introduced between the proposed method and the other heuristic methods for (MS) for electric generation units. The study was implemented and tested on a model for MS problem. The new model introduces the ratio between cost per reserve power as an index to maximize the system's net reserve with minimum cost. Also, maximizing the net reserve , maximizing the system's net reserve rate and minimizing the system's risk methods were implemented and compared with the proposed method. All methods are subjected to the following constraints: generator unit maintenance duration, time constraint, crew availability, lower reserve limit and lower reserve rate limit.
{"title":"Maintenance scheduling of generating units in electric power system","authors":"M. Kotb","doi":"10.1109/MEPCON.2008.4562373","DOIUrl":"https://doi.org/10.1109/MEPCON.2008.4562373","url":null,"abstract":"New method for solving the maintenance schedule (MS) problem is proposed. Comparative study has been introduced between the proposed method and the other heuristic methods for (MS) for electric generation units. The study was implemented and tested on a model for MS problem. The new model introduces the ratio between cost per reserve power as an index to maximize the system's net reserve with minimum cost. Also, maximizing the net reserve , maximizing the system's net reserve rate and minimizing the system's risk methods were implemented and compared with the proposed method. All methods are subjected to the following constraints: generator unit maintenance duration, time constraint, crew availability, lower reserve limit and lower reserve rate limit.","PeriodicalId":236620,"journal":{"name":"2008 12th International Middle-East Power System Conference","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128815055","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 : 2008-03-12DOI: 10.1109/MEPCON.2008.4562310
A. Edris, L. Barthold, D. Douglas, W. Litzenberger, D. Woodford
The paper describes current developments for upgrading of existing AC transmission lines for substantial increase in power transfer capacity by a new concept of conversion to HVDC transmission. Traditionally, such a conversion has been contemplated as being three phase AC to bipolar DC. Recent patents by one of the authors have introduced the tripolar DC transmission concept, which maximizes the utilization of all three phase conductors and improves N-l operational constraints. Conversion consideration issues, e.g. selection of DC voltage rating, the need for re-insulation, etc. are investigated. The paper provides an overview of an Application Guide that is being prepared by EPRI for transmission engineers and planners contemplating upgrading AC transmission lines to HVDC transmission
{"title":"Upgrading AC transmission to DC for maximum power transfer capacity","authors":"A. Edris, L. Barthold, D. Douglas, W. Litzenberger, D. Woodford","doi":"10.1109/MEPCON.2008.4562310","DOIUrl":"https://doi.org/10.1109/MEPCON.2008.4562310","url":null,"abstract":"The paper describes current developments for upgrading of existing AC transmission lines for substantial increase in power transfer capacity by a new concept of conversion to HVDC transmission. Traditionally, such a conversion has been contemplated as being three phase AC to bipolar DC. Recent patents by one of the authors have introduced the tripolar DC transmission concept, which maximizes the utilization of all three phase conductors and improves N-l operational constraints. Conversion consideration issues, e.g. selection of DC voltage rating, the need for re-insulation, etc. are investigated. The paper provides an overview of an Application Guide that is being prepared by EPRI for transmission engineers and planners contemplating upgrading AC transmission lines to HVDC transmission","PeriodicalId":236620,"journal":{"name":"2008 12th International Middle-East Power System Conference","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115615972","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 : 2008-03-12DOI: 10.1109/MEPCON.2008.4562326
A. Amin, M.I. El-Korfolly, S. Mohammed
Uniformly sampled PWM is one of the most used pulse width modulation techniques in power electronics applications. The popularity of this technique arises from the fact of its simplicity to be digitally implemented. From the historical point of view, uniformly sampled PWM was originally used in the aim of sinusoidal waveform generation. This paper investigates and discusses, through simulation, the effects of the aliasing problem on the performance of uniformly sampled PWM in such cases in which this technique is used to represent modulating signals other than the sinusoidal. Moreover the paper suggests a solution for the problem and hence improves the performance of the produced PWM signal in these cases.
{"title":"Aliasing effects on uniformly sampled PWM","authors":"A. Amin, M.I. El-Korfolly, S. Mohammed","doi":"10.1109/MEPCON.2008.4562326","DOIUrl":"https://doi.org/10.1109/MEPCON.2008.4562326","url":null,"abstract":"Uniformly sampled PWM is one of the most used pulse width modulation techniques in power electronics applications. The popularity of this technique arises from the fact of its simplicity to be digitally implemented. From the historical point of view, uniformly sampled PWM was originally used in the aim of sinusoidal waveform generation. This paper investigates and discusses, through simulation, the effects of the aliasing problem on the performance of uniformly sampled PWM in such cases in which this technique is used to represent modulating signals other than the sinusoidal. Moreover the paper suggests a solution for the problem and hence improves the performance of the produced PWM signal in these cases.","PeriodicalId":236620,"journal":{"name":"2008 12th International Middle-East Power System Conference","volume":"117 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116177628","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 : 2008-03-12DOI: 10.1109/MEPCON.2008.4562365
M. EL-Shimy, M. Badr, O. Rassem
This paper presents a detailed analysis of the impact of large scale wind power generation on both the dynamic voltage stability and the transient stability of electric power systems. The following problems have been analyzed: different penetration of wind power impact on transient stability and on voltage stability (dynamic voltage stability) following a major fault in the transmission system, determination of the acceptable wind power penetration level in power system without deteriorating both transient stability and voltage stability of the system. Moreover, the effect of SVC on the system stability is studied.
{"title":"Impact of large scale wind power on power system stability","authors":"M. EL-Shimy, M. Badr, O. Rassem","doi":"10.1109/MEPCON.2008.4562365","DOIUrl":"https://doi.org/10.1109/MEPCON.2008.4562365","url":null,"abstract":"This paper presents a detailed analysis of the impact of large scale wind power generation on both the dynamic voltage stability and the transient stability of electric power systems. The following problems have been analyzed: different penetration of wind power impact on transient stability and on voltage stability (dynamic voltage stability) following a major fault in the transmission system, determination of the acceptable wind power penetration level in power system without deteriorating both transient stability and voltage stability of the system. Moreover, the effect of SVC on the system stability is studied.","PeriodicalId":236620,"journal":{"name":"2008 12th International Middle-East Power System Conference","volume":"258 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116232057","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 : 2008-03-12DOI: 10.1109/MEPCON.2008.4562389
M. Jannati, B. Vahidi, S. Hosseinian, H. Baghaee
Almost 70-90 % of faults in extra high voltage (EHV) transmission lines in modern interconnected power systems are intrinsically transient. The necessity of rapid fault clearing results in fast developing of protection equipments. Morever, need for reliable supplying of loads, lead to improve in single phase auto-reclosing equipments. In this paper, a new method is proposed to reduce dead time of transmission lines. Leads to improve the performance and efficiency of single phase auto-reclosing. In the occurrence of permanent faults, the proposed yardstick is accurate and authentic to diagnose fault's type (transient or permanent). To validate accuracy and authenticity of proposed method, a 765 kV transmission system is simulated in Electromagnetic Transients Program Software and results are presented.
{"title":"A new adaptive single phase auto-reclosure scheme for EHV transmission lines","authors":"M. Jannati, B. Vahidi, S. Hosseinian, H. Baghaee","doi":"10.1109/MEPCON.2008.4562389","DOIUrl":"https://doi.org/10.1109/MEPCON.2008.4562389","url":null,"abstract":"Almost 70-90 % of faults in extra high voltage (EHV) transmission lines in modern interconnected power systems are intrinsically transient. The necessity of rapid fault clearing results in fast developing of protection equipments. Morever, need for reliable supplying of loads, lead to improve in single phase auto-reclosing equipments. In this paper, a new method is proposed to reduce dead time of transmission lines. Leads to improve the performance and efficiency of single phase auto-reclosing. In the occurrence of permanent faults, the proposed yardstick is accurate and authentic to diagnose fault's type (transient or permanent). To validate accuracy and authenticity of proposed method, a 765 kV transmission system is simulated in Electromagnetic Transients Program Software and results are presented.","PeriodicalId":236620,"journal":{"name":"2008 12th International Middle-East Power System Conference","volume":"56 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125279732","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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