An important problem in the Electrical Power System operation is the steady-state security prediction. In order to take into account the load uncertainty, in this paper the authors apply a Monte-Carlo method together with an opportune Security Index to evaluate in a preventive manner the probability to fall in insecure operating state, by determining the security index probability density function. For this aim, in a previous paper proposed by the authors, it has been possible to take advantage of an Artificial Neural Network, trained to evaluate the Security Index probability density function in presence of the optimal economical dispatching of the generation powers for the load forecast. In the present paper, a more complex scenario is considered where the security analysis can suggest to the dispatcher to determine also non-optimal economical operating conditions to improve security. So a new, more complex, organization of the Artificial Neural Network training stage, necessary in order to obtain increased generalization capacity in the production stage, has been considered. In the first part of the paper the used security index, the Monte-Carlo simulation and the neural network structure with its learning algorithm utilized by the authors for the particular problem are briefly recalled. Finally, a numerical application on a simple electrical test system is shown pointing out very encouraging results.
{"title":"Steady‐state security prediction in presence of load uncertainty","authors":"A. Testa, D. Menniti, C. Picardi, N. Sorrentino","doi":"10.1002/ETEP.4450080204","DOIUrl":"https://doi.org/10.1002/ETEP.4450080204","url":null,"abstract":"An important problem in the Electrical Power System operation is the steady-state security prediction. In order to take into account the load uncertainty, in this paper the authors apply a Monte-Carlo method together with an opportune Security Index to evaluate in a preventive manner the probability to fall in insecure operating state, by determining the security index probability density function. For this aim, in a previous paper proposed by the authors, it has been possible to take advantage of an Artificial Neural Network, trained to evaluate the Security Index probability density function in presence of the optimal economical dispatching of the generation powers for the load forecast. In the present paper, a more complex scenario is considered where the security analysis can suggest to the dispatcher to determine also non-optimal economical operating conditions to improve security. So a new, more complex, organization of the Artificial Neural Network training stage, necessary in order to obtain increased generalization capacity in the production stage, has been considered. In the first part of the paper the used security index, the Monte-Carlo simulation and the neural network structure with its learning algorithm utilized by the authors for the particular problem are briefly recalled. Finally, a numerical application on a simple electrical test system is shown pointing out very encouraging results.","PeriodicalId":50474,"journal":{"name":"European Transactions on Electrical Power","volume":"8 1","pages":"97-104"},"PeriodicalIF":0.0,"publicationDate":"2007-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/ETEP.4450080204","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"51094942","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}
A general mathematical model of a three-phase symmetrical induction motor expressed by means of state equations with line-to-line voltages as input variables is presented. Such a model permits the analysis of the dynamic behaviour of the motor supplied with unsymmetrical sinusoidal or non-sinusoidal voltage wave-forms. Simulation programs were written by means of MATLAB/Simulink software package. The presented model was used to simulate transient behaviour of the motor with unsymmetrical supplied voltages and its operation when fed from a symmetrical source (the mains) and from a six-step inverter. A mathematical model representing the induction motor operated with one phase disconnected was developed and simulated. Experimental results were compared with the simulated ones and good resemblance was observed.
{"title":"Modelling and simulation of unsymmetrical supplied three-phase induction motor","authors":"A. Zuckerberger, A. Alexandrovitz","doi":"10.1002/ETEP.4450060308","DOIUrl":"https://doi.org/10.1002/ETEP.4450060308","url":null,"abstract":"A general mathematical model of a three-phase symmetrical induction motor expressed by means of state equations with line-to-line voltages as input variables is presented. Such a model permits the analysis of the dynamic behaviour of the motor supplied with unsymmetrical sinusoidal or non-sinusoidal voltage wave-forms. Simulation programs were written by means of MATLAB/Simulink software package. The presented model was used to simulate transient behaviour of the motor with unsymmetrical supplied voltages and its operation when fed from a symmetrical source (the mains) and from a six-step inverter. A mathematical model representing the induction motor operated with one phase disconnected was developed and simulated. Experimental results were compared with the simulated ones and good resemblance was observed.","PeriodicalId":50474,"journal":{"name":"European Transactions on Electrical Power","volume":"6 1","pages":"189-194"},"PeriodicalIF":0.0,"publicationDate":"2007-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/ETEP.4450060308","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"51089975","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}
Current harmonics can be eliminated in each individual load. Such a compensation generally must be expensive. Harmonics are partly compensated between individual consumers. Therefore, the compensation of group of consumers seems to need lower cost than individual compensation. In the case of group compensation there are two possible approaches. The first approach uses compensators controlled by a current in common buses supplying a cluster of consumers. In the second approach a voltage waveform is chosen as a control data, the compensator should maintain a sinusoidal voltage. Such an approach needs not many compensators to ensure a proper quality of energy delivered. The purpose of the presented paper is to formulate the optimization problem for compensators location in power systems. It is shown that the problem leads to combinatorial optimization. The Travelling Salesman Problem and 0-1 Knapsack Problem are related to the presented combinatorial problem, but it seems, that there is not solved the combinatorial optimization problem which is identical to the considered one.
{"title":"The problem of harmonic compensators location","authors":"K. Mikolajuk","doi":"10.1002/ETEP.4450060606","DOIUrl":"https://doi.org/10.1002/ETEP.4450060606","url":null,"abstract":"Current harmonics can be eliminated in each individual load. Such a compensation generally must be expensive. Harmonics are partly compensated between individual consumers. Therefore, the compensation of group of consumers seems to need lower cost than individual compensation. In the case of group compensation there are two possible approaches. The first approach uses compensators controlled by a current in common buses supplying a cluster of consumers. In the second approach a voltage waveform is chosen as a control data, the compensator should maintain a sinusoidal voltage. Such an approach needs not many compensators to ensure a proper quality of energy delivered. The purpose of the presented paper is to formulate the optimization problem for compensators location in power systems. It is shown that the problem leads to combinatorial optimization. The Travelling Salesman Problem and 0-1 Knapsack Problem are related to the presented combinatorial problem, but it seems, that there is not solved the combinatorial optimization problem which is identical to the considered one.","PeriodicalId":50474,"journal":{"name":"European Transactions on Electrical Power","volume":"6 1","pages":"397-400"},"PeriodicalIF":0.0,"publicationDate":"2007-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/ETEP.4450060606","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"51090760","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}
Among the conventional methods there is no one method by which single-phase induction motors can be started, speed-controlled and reversed. The paper develops a new method for controlling single-phase induction motors with two symmetrical stator windings by placing two bidirectional solid-state switches (triacs), one in series with the main winding and the other with the auxiliary winding. Such a connection will perform all the required jobs namely: starting, speed control and reversing the direction of rotation. A motor representation in the d, q, 0 reference frame is presented. A state-space mathematical model has been developed to describe the system taking care ofthe discontinuities introduced by the triacs. Computer results for transient and steady-state conditions are presented. Also, experimental verification has been done.
在传统的方法中，没有一种方法可以实现单相异步电动机的启动、调速和反转。本文提出了一种控制具有两个对称定子绕组的单相异步电动机的新方法，即通过放置两个双向固态开关(triac)，一个与主绕组串联，另一个与辅助绕组串联。这种连接将完成所有所需的工作，即:启动、速度控制和反转旋转方向。给出了电机在d, q, 0参考系中的表示。一个状态空间数学模型已经被开发用来描述系统，考虑了由triacs引入的不连续。给出了暂态和稳态条件下的计算结果。并进行了实验验证。
{"title":"A new method using two triacs for control of single‐phase induction motor","authors":"M. A. Abdel-halim, I. Kamal","doi":"10.1002/ETEP.4450060613","DOIUrl":"https://doi.org/10.1002/ETEP.4450060613","url":null,"abstract":"Among the conventional methods there is no one method by which single-phase induction motors can be started, speed-controlled and reversed. The paper develops a new method for controlling single-phase induction motors with two symmetrical stator windings by placing two bidirectional solid-state switches (triacs), one in series with the main winding and the other with the auxiliary winding. Such a connection will perform all the required jobs namely: starting, speed control and reversing the direction of rotation. A motor representation in the d, q, 0 reference frame is presented. A state-space mathematical model has been developed to describe the system taking care ofthe discontinuities introduced by the triacs. Computer results for transient and steady-state conditions are presented. Also, experimental verification has been done.","PeriodicalId":50474,"journal":{"name":"European Transactions on Electrical Power","volume":"6 1","pages":"427-432"},"PeriodicalIF":0.0,"publicationDate":"2007-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/ETEP.4450060613","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"51091558","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}
To supply small loads located very far from low-cost generation areas local Diesel generation or transmission from the generation areas to loads are the alternatives to be considered. The competitiveness of the latter solution can be improved by the use of static devices, able to compensate active and/or reactive powers, installed in suitable locations of the transmission system. In this paper the possibility of installing at the Receiving End either a Static Var Compensator (SVC) or a Static Watt-Var Compensator (SWVC, that is a device able to work in the four quadrants of the P-Q plane) is discussed. A possible operating strategy is proposed for both devices, the loadability limits of various options are determined, and an economical comparison of the schemes without compensators and with SVC or SWVC is also carried out in a practical case of application.
{"title":"Improving the economic competitiveness of small‐load long‐distance AC transmission systems by the use of static compensators at the receiving end","authors":"M. Ceraolo","doi":"10.1002/ETEP.4450060403","DOIUrl":"https://doi.org/10.1002/ETEP.4450060403","url":null,"abstract":"To supply small loads located very far from low-cost generation areas local Diesel generation or transmission from the generation areas to loads are the alternatives to be considered. The competitiveness of the latter solution can be improved by the use of static devices, able to compensate active and/or reactive powers, installed in suitable locations of the transmission system. In this paper the possibility of installing at the Receiving End either a Static Var Compensator (SVC) or a Static Watt-Var Compensator (SWVC, that is a device able to work in the four quadrants of the P-Q plane) is discussed. A possible operating strategy is proposed for both devices, the loadability limits of various options are determined, and an economical comparison of the schemes without compensators and with SVC or SWVC is also carried out in a practical case of application.","PeriodicalId":50474,"journal":{"name":"European Transactions on Electrical Power","volume":"6 1","pages":"245-252"},"PeriodicalIF":0.0,"publicationDate":"2007-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/ETEP.4450060403","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"51089659","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}
Special Pulse-Width-Modulation (PWM) techniques capable of realizing true PWM operation of quasi-resonant DC-link inverters are presented. These techniques provide an increased value of the lowest switching time for higher carrier frequencies. The harmonic performances are extensively studied by simulation in comparison with conventional Space- Vector Modulation and a simple algorithm for real-time implementation is developed.
{"title":"Analysis of high‐frequency PWM techniques suitable for resonant inverters","authors":"D. Neacşu, D. Alexa","doi":"10.1002/ETEP.4450060307","DOIUrl":"https://doi.org/10.1002/ETEP.4450060307","url":null,"abstract":"Special Pulse-Width-Modulation (PWM) techniques capable of realizing true PWM operation of quasi-resonant DC-link inverters are presented. These techniques provide an increased value of the lowest switching time for higher carrier frequencies. The harmonic performances are extensively studied by simulation in comparison with conventional Space- Vector Modulation and a simple algorithm for real-time implementation is developed.","PeriodicalId":50474,"journal":{"name":"European Transactions on Electrical Power","volume":"6 1","pages":"183-188"},"PeriodicalIF":0.0,"publicationDate":"2007-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/ETEP.4450060307","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"51089895","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}
Modern multicycle-controlled equipment produce voltage fluctuations with repetition rates much higher than the highest frequency for type testing the IEC flickermeter under the standard IEC 61000-4-15. In order to equalize all flickermeters it is necessary to add an additional reference point for 33'/? Hz to the standard. The amount of d/%-values will be evaluated. Reference values for 120- V/60-Hz- and 230- V/60-Hz systems have been added.
{"title":"Calculating a new reference point for the iec‐flickermeter","authors":"W. Mombauer","doi":"10.1002/ETEP.4450080604","DOIUrl":"https://doi.org/10.1002/ETEP.4450080604","url":null,"abstract":"Modern multicycle-controlled equipment produce voltage fluctuations with repetition rates much higher than the highest frequency for type testing the IEC flickermeter under the standard IEC 61000-4-15. In order to equalize all flickermeters it is necessary to add an additional reference point for 33'/? Hz to the standard. The amount of d/%-values will be evaluated. Reference values for 120- V/60-Hz- and 230- V/60-Hz systems have been added.","PeriodicalId":50474,"journal":{"name":"European Transactions on Electrical Power","volume":"31 1","pages":"429-436"},"PeriodicalIF":0.0,"publicationDate":"2007-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/ETEP.4450080604","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"51098045","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}
This paper presents a variable structure control approach for the output voltage regulation of switched power converters. The most outstanding feature of this control technique is its robustness towards load and line voltage disturbances. A control implementation for a basic down converter based on state-space transformation wholly confirms this performance. An extension to inverter control results in reduced harmonic distortion in case of uncertain load characteristics. Analytical predictions are verified by experimental results.
{"title":"Robust control of switched power converters via sliding mode","authors":"B. Nicolas, M. Fadel, Y. Chéron","doi":"10.1002/ETEP.4450060611","DOIUrl":"https://doi.org/10.1002/ETEP.4450060611","url":null,"abstract":"This paper presents a variable structure control approach for the output voltage regulation of switched power converters. The most outstanding feature of this control technique is its robustness towards load and line voltage disturbances. A control implementation for a basic down converter based on state-space transformation wholly confirms this performance. An extension to inverter control results in reduced harmonic distortion in case of uncertain load characteristics. Analytical predictions are verified by experimental results.","PeriodicalId":50474,"journal":{"name":"European Transactions on Electrical Power","volume":"14 1","pages":"413-418"},"PeriodicalIF":0.0,"publicationDate":"2007-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/ETEP.4450060611","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"51090922","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}
In this paper some possibilities of further applications of a known Streamer Partial-Discharge Model are proposed. These possibilities refer to the relation between the observed partial-discharge (PD) magnitude and the applied field to the insulation. Furthermore, the model is a useful tool to investigate the sensitivity of a PD detector and also to compare the sensitivities between various PD detectors.
{"title":"Some possible new applications of a Partial-Discharge (PD) model and its relation to PD-detection sensitivity","authors":"M. Danikas","doi":"10.1002/ETEP.4450060616","DOIUrl":"https://doi.org/10.1002/ETEP.4450060616","url":null,"abstract":"In this paper some possibilities of further applications of a known Streamer Partial-Discharge Model are proposed. These possibilities refer to the relation between the observed partial-discharge (PD) magnitude and the applied field to the insulation. Furthermore, the model is a useful tool to investigate the sensitivity of a PD detector and also to compare the sensitivities between various PD detectors.","PeriodicalId":50474,"journal":{"name":"European Transactions on Electrical Power","volume":"80 1","pages":"445-448"},"PeriodicalIF":0.0,"publicationDate":"2007-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/ETEP.4450060616","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"51091297","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}
The paper presents a method and a numerical calculation program of the repartition of the earth-fault currents in the grounding systems of substations and of the HV line towers, as well as of the currents which flow in the shield wires of the overhead lines and/or in the sheaths and armourings of underground cahles. The program may be applied also to very extended networks for single-phase-to-ground (1-Φ-to-Gr) and phase-to-phase-to-ground (Φ-Φ-to-Gr) faults at any point. The program is based on the simulations of the earth resistances of the HV line towers by means of a transversal conductance uniformly distributed between the shield wires and earth, and which is assumed to be variable from stretch to stretch according to soil resistivity. Models are derived which are aimed at simulating the single and double-circuit overhead lines provided with shield wires, as well as the underground cables. These models consist in a single three-pole or four-pole equivalent circuit. The validity of the program is verified by comparison with the calculations carried out by the Electromagnetic Transients Program (EMTP). Mention is made of a study carried out for the Turkish 420/150-kV network. Some measures presented are aimed at reducing the currents which flow in the shield wires of the lines outgoing from the power plants/substations following faults nearby.
{"title":"Calculation of current flow in grounding systems of substations and of HV line towers, in line shield wires and cable sheaths during earth faults","authors":"F. Gatta, F. Iliceto","doi":"10.1002/ETEP.4450080202","DOIUrl":"https://doi.org/10.1002/ETEP.4450080202","url":null,"abstract":"The paper presents a method and a numerical calculation program of the repartition of the earth-fault currents in the grounding systems of substations and of the HV line towers, as well as of the currents which flow in the shield wires of the overhead lines and/or in the sheaths and armourings of underground cahles. The program may be applied also to very extended networks for single-phase-to-ground (1-Φ-to-Gr) and phase-to-phase-to-ground (Φ-Φ-to-Gr) faults at any point. The program is based on the simulations of the earth resistances of the HV line towers by means of a transversal conductance uniformly distributed between the shield wires and earth, and which is assumed to be variable from stretch to stretch according to soil resistivity. Models are derived which are aimed at simulating the single and double-circuit overhead lines provided with shield wires, as well as the underground cables. These models consist in a single three-pole or four-pole equivalent circuit. The validity of the program is verified by comparison with the calculations carried out by the Electromagnetic Transients Program (EMTP). Mention is made of a study carried out for the Turkish 420/150-kV network. Some measures presented are aimed at reducing the currents which flow in the shield wires of the lines outgoing from the power plants/substations following faults nearby.","PeriodicalId":50474,"journal":{"name":"European Transactions on Electrical Power","volume":"8 1","pages":"81-90"},"PeriodicalIF":0.0,"publicationDate":"2007-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/ETEP.4450080202","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"51094829","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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