Pub Date : 2008-06-10DOI: 10.1109/ISNCC.2008.4627510
T. Thanh, S. Schostan, K.-D. Dettmann, Detlef Schulz
At low-voltage level there is already a commercial measurement device that is able to identify the grid impedance in dependency of time and frequency. Since at the low-voltage level a four-wire system and at the medium-and high-voltage level a three-wire system is installed, the method to identify the grid impedance has to be varied. This paper proposes a method that could be applied for the identification of the time and frequency dependent grid impedance at the medium- and high-voltage level. Another aspect that has to be considered is how to dimension the variable switched resistive load, which is necessary to stimulate the grid. The power-range of this load is limited by the maximum allowable voltage drop in the grid. Furthermore it is important to investigate what kind of power terms are caused by the nonsinusoidal stimulation of the grid in balanced and unbalanced configurations. For this purpose the power theory of Fryze is applied.
{"title":"Nonsinusoidal power caused by measurements of grid impedances at unbalanced grid voltages","authors":"T. Thanh, S. Schostan, K.-D. Dettmann, Detlef Schulz","doi":"10.1109/ISNCC.2008.4627510","DOIUrl":"https://doi.org/10.1109/ISNCC.2008.4627510","url":null,"abstract":"At low-voltage level there is already a commercial measurement device that is able to identify the grid impedance in dependency of time and frequency. Since at the low-voltage level a four-wire system and at the medium-and high-voltage level a three-wire system is installed, the method to identify the grid impedance has to be varied. This paper proposes a method that could be applied for the identification of the time and frequency dependent grid impedance at the medium- and high-voltage level. Another aspect that has to be considered is how to dimension the variable switched resistive load, which is necessary to stimulate the grid. The power-range of this load is limited by the maximum allowable voltage drop in the grid. Furthermore it is important to investigate what kind of power terms are caused by the nonsinusoidal stimulation of the grid in balanced and unbalanced configurations. For this purpose the power theory of Fryze is applied.","PeriodicalId":143815,"journal":{"name":"2008 International School on Nonsinusoidal Currents and Compensation","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2008-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120838843","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 : 2008-06-10DOI: 10.1109/ISNCC.2008.4627496
D. Floricau, E. Floricau, M. Dumitrescu
The 3L-NPC (three-level neutral-point-clamped) is the most popular multilevel converter used in high-power medium-voltage applications. An important disadvantage of this structure is the unequal distribution of losses among the switches. The performances of 3L-NPC structure were improved by developing the 3L-ANPC (Active-NPC) converter which has more degrees of freedom. In this paper the switching states and the loss distribution problem are studied for different PWM strategies. A new PWM strategy is also proposed in the paper. It has numerous advantages: (a) natural doubling of the apparent switching frequency without using the flying-capacitor concept, (b) dead times do not influence the operating mode at 50% of the duty cycle, (c) operating at both high and small switching frequencies without structural modifications and (d) better balancing of loss distribution in switches. The PSIM simulation results are shown in order to validate the proposed PWM strategy and the analysis of the switching states.
{"title":"Natural doubling of the apparent switching frequency using three-level ANPC converter","authors":"D. Floricau, E. Floricau, M. Dumitrescu","doi":"10.1109/ISNCC.2008.4627496","DOIUrl":"https://doi.org/10.1109/ISNCC.2008.4627496","url":null,"abstract":"The 3L-NPC (three-level neutral-point-clamped) is the most popular multilevel converter used in high-power medium-voltage applications. An important disadvantage of this structure is the unequal distribution of losses among the switches. The performances of 3L-NPC structure were improved by developing the 3L-ANPC (Active-NPC) converter which has more degrees of freedom. In this paper the switching states and the loss distribution problem are studied for different PWM strategies. A new PWM strategy is also proposed in the paper. It has numerous advantages: (a) natural doubling of the apparent switching frequency without using the flying-capacitor concept, (b) dead times do not influence the operating mode at 50% of the duty cycle, (c) operating at both high and small switching frequencies without structural modifications and (d) better balancing of loss distribution in switches. The PSIM simulation results are shown in order to validate the proposed PWM strategy and the analysis of the switching states.","PeriodicalId":143815,"journal":{"name":"2008 International School on Nonsinusoidal Currents and Compensation","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2008-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114853071","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 : 2008-06-10DOI: 10.1109/ISNCC.2008.4627481
V. Staudt
Several power theories trying to explain the difference between the physically defined active power and the apparent power are known - and under discussion. This paper gives an overview of a universal time-domain power theory mainly developed by Fryze, Buchholz and Depenbrock. It is verified by theoretical considerations and explained by examples. The theory allows the assessment of loads concerning effectivity of energy transfer and the application-specific splitting of currents into desirable and undesirable components - which in turn can, e.g., be compensated.
{"title":"Fryze - Buchholz - Depenbrock: A time-domain power theory","authors":"V. Staudt","doi":"10.1109/ISNCC.2008.4627481","DOIUrl":"https://doi.org/10.1109/ISNCC.2008.4627481","url":null,"abstract":"Several power theories trying to explain the difference between the physically defined active power and the apparent power are known - and under discussion. This paper gives an overview of a universal time-domain power theory mainly developed by Fryze, Buchholz and Depenbrock. It is verified by theoretical considerations and explained by examples. The theory allows the assessment of loads concerning effectivity of energy transfer and the application-specific splitting of currents into desirable and undesirable components - which in turn can, e.g., be compensated.","PeriodicalId":143815,"journal":{"name":"2008 International School on Nonsinusoidal Currents and Compensation","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2008-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128161827","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 : 2008-06-10DOI: 10.1109/ISNCC.2008.4627482
E. Tedeschi, P. Tenti
A theoretical background for the design and coordinated control of multiple compensation equipment acting in the same network is presented. It makes use of instantaneous power terms which are conservative in every network and naturally extend the usual power definitions to the case of distorted voltages and currents. Based on the theoretical approach, a system-level and equipment-level control algorithm is developed, which allows cooperative operation of static VAR compensators (SVC) and active power filters (APF).
{"title":"Cooperative design and control of distributed harmonic and reactive compensators","authors":"E. Tedeschi, P. Tenti","doi":"10.1109/ISNCC.2008.4627482","DOIUrl":"https://doi.org/10.1109/ISNCC.2008.4627482","url":null,"abstract":"A theoretical background for the design and coordinated control of multiple compensation equipment acting in the same network is presented. It makes use of instantaneous power terms which are conservative in every network and naturally extend the usual power definitions to the case of distorted voltages and currents. Based on the theoretical approach, a system-level and equipment-level control algorithm is developed, which allows cooperative operation of static VAR compensators (SVC) and active power filters (APF).","PeriodicalId":143815,"journal":{"name":"2008 International School on Nonsinusoidal Currents and Compensation","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2008-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117159739","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 : 2008-06-10DOI: 10.1109/ISNCC.2008.4627495
D. Olaru, D. Floricau
The instabilities arising in the power delivery network may cause serious problems for the whole system security. The most difficult detectable event is the energy balance phenomena. This has specific evolution characteristics, which are not so easy to be observed. The paper presents a real type situation, studied on a physically realized model, on a reduced scale. It is based on a permanent magnet synchronous motor. This is susceptible to give similar balance phenomena as conventional loaded equipment. The supply source is tuned as to obtain quasi-stable motion. The current and voltage evolution is represented in the phasespsila plane. To result a smooth enough wave, regression methods are used. In order to obtain useful information about the instability characteristics, special indicator functions are used. They emphasize, on one hand, the relative balance parameters and, on the other hand, the most unstable moment of evolution. This gives a discontinuous evolution for the derivativespsila variation for the current wave. The paper presents, as well, the mathematical background and the methods used for the processing of the measured parameters.
{"title":"Numerical detection of the current instability phenomena due to the balance of the electric machines","authors":"D. Olaru, D. Floricau","doi":"10.1109/ISNCC.2008.4627495","DOIUrl":"https://doi.org/10.1109/ISNCC.2008.4627495","url":null,"abstract":"The instabilities arising in the power delivery network may cause serious problems for the whole system security. The most difficult detectable event is the energy balance phenomena. This has specific evolution characteristics, which are not so easy to be observed. The paper presents a real type situation, studied on a physically realized model, on a reduced scale. It is based on a permanent magnet synchronous motor. This is susceptible to give similar balance phenomena as conventional loaded equipment. The supply source is tuned as to obtain quasi-stable motion. The current and voltage evolution is represented in the phasespsila plane. To result a smooth enough wave, regression methods are used. In order to obtain useful information about the instability characteristics, special indicator functions are used. They emphasize, on one hand, the relative balance parameters and, on the other hand, the most unstable moment of evolution. This gives a discontinuous evolution for the derivativespsila variation for the current wave. The paper presents, as well, the mathematical background and the methods used for the processing of the measured parameters.","PeriodicalId":143815,"journal":{"name":"2008 International School on Nonsinusoidal Currents and Compensation","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2008-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126370062","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 : 2008-06-10DOI: 10.1109/ISNCC.2008.4627493
M. Dumitrescu
The paper proposes to study a real industrial power system and to presents the digital harmonic analysis using EDSA technical software. The objectives of the study are to evaluate the potentially negative impact of non-linear loads on the system, and to study possible techniques that will minimize this impact. On this goal, will be presented eight harmonic interesting analysis cases and will be considered three different working conditions (alternatives) of the analyzed power system.
{"title":"Harmonic digital simulation technique on an industrial environment","authors":"M. Dumitrescu","doi":"10.1109/ISNCC.2008.4627493","DOIUrl":"https://doi.org/10.1109/ISNCC.2008.4627493","url":null,"abstract":"The paper proposes to study a real industrial power system and to presents the digital harmonic analysis using EDSA technical software. The objectives of the study are to evaluate the potentially negative impact of non-linear loads on the system, and to study possible techniques that will minimize this impact. On this goal, will be presented eight harmonic interesting analysis cases and will be considered three different working conditions (alternatives) of the analyzed power system.","PeriodicalId":143815,"journal":{"name":"2008 International School on Nonsinusoidal Currents and Compensation","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2008-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121691781","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 : 2008-06-10DOI: 10.1109/ISNCC.2008.4627483
L. Czarnecki
The paper introduces readers to currently the most advanced power theory of electrical systems with non-sinusoidal voltages and currents, along with fundamentals of their compensation, based on the concept of currentspsila physical components (CPC). It includes single-phase systems and unbalanced three-phase systems with linear, time-invariant (LTI) and harmonic generating loads (HGLs).
{"title":"Currents’ Physical Components (CPC) concept: A fundamental of power theory","authors":"L. Czarnecki","doi":"10.1109/ISNCC.2008.4627483","DOIUrl":"https://doi.org/10.1109/ISNCC.2008.4627483","url":null,"abstract":"The paper introduces readers to currently the most advanced power theory of electrical systems with non-sinusoidal voltages and currents, along with fundamentals of their compensation, based on the concept of currentspsila physical components (CPC). It includes single-phase systems and unbalanced three-phase systems with linear, time-invariant (LTI) and harmonic generating loads (HGLs).","PeriodicalId":143815,"journal":{"name":"2008 International School on Nonsinusoidal Currents and Compensation","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2008-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122885792","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 : 2008-06-10DOI: 10.1109/ISNCC.2008.4627489
S. Czapp
The most popular means of protection against indirect contact in low voltage systems is automatic disconnection of supply, since it is a simple and economically attractive way to achieve safety in an electrical installation. As a protective device, residual current devices (RCDs) are commonly used. In certain conditions using the RCDs is obligatory. The widespread application of static converters, especially frequency converters, results in installing RCDs in circuits where nonsinusoidal earth fault current flows. The earth fault current in the output circuit of frequency converters comprises harmonics and interharmonics, whose order mainly depends on the PWM frequency. The level of higher frequency components in the earth fault current may exceed the fundamental one. The nonsinusoidal earth fault current influences tripping of the residual current devices. In the paper, results of the theoretical analysis and the laboratory tests of residual current devices operation are presented and discussed. They prove that in some cases higher frequency components cause improper tripping of the residual current devices and a real hazard of electrocution exists.
{"title":"The effect of earth fault current harmonics on tripping of residual current devices","authors":"S. Czapp","doi":"10.1109/ISNCC.2008.4627489","DOIUrl":"https://doi.org/10.1109/ISNCC.2008.4627489","url":null,"abstract":"The most popular means of protection against indirect contact in low voltage systems is automatic disconnection of supply, since it is a simple and economically attractive way to achieve safety in an electrical installation. As a protective device, residual current devices (RCDs) are commonly used. In certain conditions using the RCDs is obligatory. The widespread application of static converters, especially frequency converters, results in installing RCDs in circuits where nonsinusoidal earth fault current flows. The earth fault current in the output circuit of frequency converters comprises harmonics and interharmonics, whose order mainly depends on the PWM frequency. The level of higher frequency components in the earth fault current may exceed the fundamental one. The nonsinusoidal earth fault current influences tripping of the residual current devices. In the paper, results of the theoretical analysis and the laboratory tests of residual current devices operation are presented and discussed. They prove that in some cases higher frequency components cause improper tripping of the residual current devices and a real hazard of electrocution exists.","PeriodicalId":143815,"journal":{"name":"2008 International School on Nonsinusoidal Currents and Compensation","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2008-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133136173","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 : 2008-06-10DOI: 10.1109/ISNCC.2008.4627518
R. Strzelecki, M. Wojciechowski
The paper presents the control system of shunt active power filter (APF) with predictive reference current calculation and model based predictive current control. The novel estimator and predictor of grid EMF is proposed for AC voltage sensorless operation of APF. Proposed control system provides control of APF current with high precision and dynamics limited only by filter circuit parameters. There are presented experimental results achieved for 50 kVA APF and simulation results for design of the 2 MVA APF.
{"title":"New control system of the shunt active power filter","authors":"R. Strzelecki, M. Wojciechowski","doi":"10.1109/ISNCC.2008.4627518","DOIUrl":"https://doi.org/10.1109/ISNCC.2008.4627518","url":null,"abstract":"The paper presents the control system of shunt active power filter (APF) with predictive reference current calculation and model based predictive current control. The novel estimator and predictor of grid EMF is proposed for AC voltage sensorless operation of APF. Proposed control system provides control of APF current with high precision and dynamics limited only by filter circuit parameters. There are presented experimental results achieved for 50 kVA APF and simulation results for design of the 2 MVA APF.","PeriodicalId":143815,"journal":{"name":"2008 International School on Nonsinusoidal Currents and Compensation","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2008-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115683166","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 : 2008-06-10DOI: 10.1109/ISNCC.2008.4627500
K. Debowski, M. Pasko
The problems presented in the paper deal with a three-phase four-wire system. The considered system is composed of: the three-phase asymmetrical voltage source with periodical nonsinusoidal waveforms, inner impedances of the voltage source and asymmetrical linear three-phase loads. In contrast to earlier approaches the voltage source is not symmetrical. In the paper a method of symmetrization of these systems has been proposed. After symmetrization it is possible to obtain symmetrical line currents of the system. Their RMS values and active power losses on source impedances can be lower. Moreover, the source can generate greater active power than before symmetrization. The working point after symmetrization can be obtained by means of connection of a symmetrizing system. The main goal is to use the symmetrizing system composed of LC one-ports, but generally it is necessary to use the active symmetrizing system. Their structure is determined as a result of a synthesis process. In this paper the symmetrization problem has been solved by using the symmetrical components theory and compensation of reactive power for each harmonic of the voltage under consideration.
{"title":"Symmetrization of asymmetrical three-phase load supplied from asymmetrical non-ideal voltage source with periodic nonsinusoidal waveforms","authors":"K. Debowski, M. Pasko","doi":"10.1109/ISNCC.2008.4627500","DOIUrl":"https://doi.org/10.1109/ISNCC.2008.4627500","url":null,"abstract":"The problems presented in the paper deal with a three-phase four-wire system. The considered system is composed of: the three-phase asymmetrical voltage source with periodical nonsinusoidal waveforms, inner impedances of the voltage source and asymmetrical linear three-phase loads. In contrast to earlier approaches the voltage source is not symmetrical. In the paper a method of symmetrization of these systems has been proposed. After symmetrization it is possible to obtain symmetrical line currents of the system. Their RMS values and active power losses on source impedances can be lower. Moreover, the source can generate greater active power than before symmetrization. The working point after symmetrization can be obtained by means of connection of a symmetrizing system. The main goal is to use the symmetrizing system composed of LC one-ports, but generally it is necessary to use the active symmetrizing system. Their structure is determined as a result of a synthesis process. In this paper the symmetrization problem has been solved by using the symmetrical components theory and compensation of reactive power for each harmonic of the voltage under consideration.","PeriodicalId":143815,"journal":{"name":"2008 International School on Nonsinusoidal Currents and Compensation","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2008-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115787809","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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