Pub Date : 2008-06-10DOI: 10.1109/ISNCC.2008.4627516
M. Gwóźdź
Present tendencies of evaluation current distortion compensation methods aim to work out such compensator (serial or parallel active filter), which would be able to realize real time compensation. The assumed aim of parallel active filter work is dynamic compensation of differential current which is the difference between load current and reference current. Unfortunately dynamics of every real power electronics current source, being essential part of parallel filter, is limited. Responsible for this is finite inductance of coil at the output of inverter, being part of current source. Proposed idea of increasing dynamics of active filter depends on temporarily changing inductance of this coil. It can be done with using two windings coil, similar to transformer, which second winding is temporarily short-circuited, resulting in decreasing inductance of equivalent circuit of coil so dynamics of current source is higher.
{"title":"Power electronics active filter with controlled dynamics","authors":"M. Gwóźdź","doi":"10.1109/ISNCC.2008.4627516","DOIUrl":"https://doi.org/10.1109/ISNCC.2008.4627516","url":null,"abstract":"Present tendencies of evaluation current distortion compensation methods aim to work out such compensator (serial or parallel active filter), which would be able to realize real time compensation. The assumed aim of parallel active filter work is dynamic compensation of differential current which is the difference between load current and reference current. Unfortunately dynamics of every real power electronics current source, being essential part of parallel filter, is limited. Responsible for this is finite inductance of coil at the output of inverter, being part of current source. Proposed idea of increasing dynamics of active filter depends on temporarily changing inductance of this coil. It can be done with using two windings coil, similar to transformer, which second winding is temporarily short-circuited, resulting in decreasing inductance of equivalent circuit of coil so dynamics of current source is higher.","PeriodicalId":143815,"journal":{"name":"2008 International School on Nonsinusoidal Currents and Compensation","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114612354","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.2008.4627494
L. Furmankiewicz
The article presents the program spectral line method of module error correction in linear input circuits. The method requires the knowledge of the frequency characteristics of the module errors and the phase errors of the input circuit to be corrected. The method was used for frequency error correction of measurement transformers applied in electronic power transducers. Such input circuits are nonlinear and distort the measured signals. The article presents the analysis of the influence of the nonlinearity of the input circuits upon the effectiveness of correction of frequency errors of the input circuit module at measurements of the root-mean-square value.
{"title":"Influence of the nonlinearity of measurement transformers on effectiveness of module error correction","authors":"L. Furmankiewicz","doi":"10.1109/ISNCC.2008.4627494","DOIUrl":"https://doi.org/10.1109/ISNCC.2008.4627494","url":null,"abstract":"The article presents the program spectral line method of module error correction in linear input circuits. The method requires the knowledge of the frequency characteristics of the module errors and the phase errors of the input circuit to be corrected. The method was used for frequency error correction of measurement transformers applied in electronic power transducers. Such input circuits are nonlinear and distort the measured signals. The article presents the analysis of the influence of the nonlinearity of the input circuits upon the effectiveness of correction of frequency errors of the input circuit module at measurements of the root-mean-square value.","PeriodicalId":143815,"journal":{"name":"2008 International School on Nonsinusoidal Currents and Compensation","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129347840","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.2008.4627491
A. Pavas, V. Staudt, H. Torres-Sanchez
This paper introduces the responsibilities assignment problem (RAP) and discusses existing methodologies by theory and examples. The RAP can be understood as the evaluation and determination of the power quality disturbances and of the power quality conditions detriment concerning source and amount. Selected details of this problem are presented in this paper, in order to provide a conceptual background to understand the problem itself and to interprete the characteristics of the currently available assessment methodologies. The existing methodologies are summarized, their principles, characteristics, and application are illustrated by means of an example. From the application results, a comparison of the mentioned methodologies is shown to point out advantages and differences. In the framework of the conference this paper could start and support a discussion about the assigment of responsibilities related to power quality disturbances propagation and improvements of the existing methodologies.
{"title":"Discussion on existing methodologies for the Responsibilities Assignment Problem","authors":"A. Pavas, V. Staudt, H. Torres-Sanchez","doi":"10.1109/ISNCC.2008.4627491","DOIUrl":"https://doi.org/10.1109/ISNCC.2008.4627491","url":null,"abstract":"This paper introduces the responsibilities assignment problem (RAP) and discusses existing methodologies by theory and examples. The RAP can be understood as the evaluation and determination of the power quality disturbances and of the power quality conditions detriment concerning source and amount. Selected details of this problem are presented in this paper, in order to provide a conceptual background to understand the problem itself and to interprete the characteristics of the currently available assessment methodologies. The existing methodologies are summarized, their principles, characteristics, and application are illustrated by means of an example. From the application results, a comparison of the mentioned methodologies is shown to point out advantages and differences. In the framework of the conference this paper could start and support a discussion about the assigment of responsibilities related to power quality disturbances propagation and improvements of the existing methodologies.","PeriodicalId":143815,"journal":{"name":"2008 International School on Nonsinusoidal Currents and Compensation","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125440136","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.2008.4627515
M. Szlosek, B. Świątek, Z. Hanzelka
It can be shown, that many flickermeters do not yield credible output readings although the manufacturers declare their compliance with the requirements of standard IEC 61000-4-15. Modifications or revisions to the standard and increasing the number of requirements, what is currently taking place, seem to be interim actions, whose results are dubious. On the other hand, it should be acknowledged that since over ten years the standardization of voltage fluctuations is based on the UIE flickermeter. The authorspsila idea is to treat a flickermeter - from its analogue input to the output of block 4 - as a black box, filled in by a designer accordingly to its decision, while maintaining the IN/OUT characteristics in conformity with those of the flickermeter regarded as a standard one.
{"title":"Application of neural networks to voltage fluctuations measurement — neural networks flickermeter","authors":"M. Szlosek, B. Świątek, Z. Hanzelka","doi":"10.1109/ISNCC.2008.4627515","DOIUrl":"https://doi.org/10.1109/ISNCC.2008.4627515","url":null,"abstract":"It can be shown, that many flickermeters do not yield credible output readings although the manufacturers declare their compliance with the requirements of standard IEC 61000-4-15. Modifications or revisions to the standard and increasing the number of requirements, what is currently taking place, seem to be interim actions, whose results are dubious. On the other hand, it should be acknowledged that since over ten years the standardization of voltage fluctuations is based on the UIE flickermeter. The authorspsila idea is to treat a flickermeter - from its analogue input to the output of block 4 - as a black box, filled in by a designer accordingly to its decision, while maintaining the IN/OUT characteristics in conformity with those of the flickermeter regarded as a standard one.","PeriodicalId":143815,"journal":{"name":"2008 International School on Nonsinusoidal Currents and Compensation","volume":"188 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124312738","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.2008.4627505
R. Klempka
On the basis of the current trends for solving complex technical problems, a new concept of power quality improvement is proposed. It consists in creating a distributed system for supply conditions improvement in a given islanding power system, in e.g. geographical terms (with determined points of delivery), or as an internal installation system of an industrial consumer.
{"title":"Distributed system for electrical power quality improvement","authors":"R. Klempka","doi":"10.1109/ISNCC.2008.4627505","DOIUrl":"https://doi.org/10.1109/ISNCC.2008.4627505","url":null,"abstract":"On the basis of the current trends for solving complex technical problems, a new concept of power quality improvement is proposed. It consists in creating a distributed system for supply conditions improvement in a given islanding power system, in e.g. geographical terms (with determined points of delivery), or as an internal installation system of an industrial consumer.","PeriodicalId":143815,"journal":{"name":"2008 International School on Nonsinusoidal Currents and Compensation","volume":"219 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124326733","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.2008.4627499
J. Kaniewski, Z. Fedyczak
This paper deals with a quadrature phase shifter based on a hybrid transformer (HT) for power flow control and for transient stability improvement in AC transmission systems. This paper presents an operational description, a modelling and a theoretical analysis of the properties of the proposed solution. The steady-state analysis is based on the averaged state-space method and four terminal descriptions, and is verified both by means of the simulation and experimental investigations.
{"title":"Modelling and analysis of a three-phase quadrature phase shifter with a hybrid transformer","authors":"J. Kaniewski, Z. Fedyczak","doi":"10.1109/ISNCC.2008.4627499","DOIUrl":"https://doi.org/10.1109/ISNCC.2008.4627499","url":null,"abstract":"This paper deals with a quadrature phase shifter based on a hybrid transformer (HT) for power flow control and for transient stability improvement in AC transmission systems. This paper presents an operational description, a modelling and a theoretical analysis of the properties of the proposed solution. The steady-state analysis is based on the averaged state-space method and four terminal descriptions, and is verified both by means of the simulation and experimental investigations.","PeriodicalId":143815,"journal":{"name":"2008 International School on Nonsinusoidal Currents and Compensation","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115456254","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.2008.4627507
B. Dobrucký, M. Pokorny, M. Beňová
The paper deals with the virtual approach and application of orthogonal transform theory, used for ordinary single-phase system to its transformation into equivalent two-axes system. It is well known that the analysis of multiphase systems can be more simple using the Park/Clarke transform into two-axis stationary (alpha, beta) or rotary (d, q) reference frame. The above transform can be used for electrical machines as well as for power electronic systems. The projection of time state-space vector for any quantity of symmetrical three-phase system in Gauss complex plane (alpha + jbeta) shows out six-side symmetry of vector quantity trajectory. Then, analysis of such system can be focused on the interval equal to 1/6 of the time period only. It is clear that when using similar transform of single-phase quantity into equivalent two-axes orthogonal system it will be possible to use all advantages as in three-phase transformed system with respect of 4-side symmetry instead of 6-side of previous case. Analysis in such orthogonal coordinates system will then be identical to the three-phase one under Park/Clarke transform, including determination of instantaneous reactive power. The presented method creates a virtual two-phase system from the original singlephase system by adding a new fictitious phase. The new thought is based on the idea that ordinary singlephase quantity can be complemented by virtual fictitious phase so that both of them will together create orthogonal system, as is usual in three-phase systems. Application of above-mentioned theory makes it possible to use complex methods of analysis as instantaneous reactive power method. Both, the active and reactive powers can be determined by this way. Practical application of the method is outlined for the case of active and reactive power determination for single-phase power active filter, unified power flow controller, and dynamic voltage restorer, Fig.1 [14], [15], [17] - [19].
{"title":"Instantaneous single-phase system power demonstration using virtual two phase theory","authors":"B. Dobrucký, M. Pokorny, M. Beňová","doi":"10.1109/ISNCC.2008.4627507","DOIUrl":"https://doi.org/10.1109/ISNCC.2008.4627507","url":null,"abstract":"The paper deals with the virtual approach and application of orthogonal transform theory, used for ordinary single-phase system to its transformation into equivalent two-axes system. It is well known that the analysis of multiphase systems can be more simple using the Park/Clarke transform into two-axis stationary (alpha, beta) or rotary (d, q) reference frame. The above transform can be used for electrical machines as well as for power electronic systems. The projection of time state-space vector for any quantity of symmetrical three-phase system in Gauss complex plane (alpha + jbeta) shows out six-side symmetry of vector quantity trajectory. Then, analysis of such system can be focused on the interval equal to 1/6 of the time period only. It is clear that when using similar transform of single-phase quantity into equivalent two-axes orthogonal system it will be possible to use all advantages as in three-phase transformed system with respect of 4-side symmetry instead of 6-side of previous case. Analysis in such orthogonal coordinates system will then be identical to the three-phase one under Park/Clarke transform, including determination of instantaneous reactive power. The presented method creates a virtual two-phase system from the original singlephase system by adding a new fictitious phase. The new thought is based on the idea that ordinary singlephase quantity can be complemented by virtual fictitious phase so that both of them will together create orthogonal system, as is usual in three-phase systems. Application of above-mentioned theory makes it possible to use complex methods of analysis as instantaneous reactive power method. Both, the active and reactive powers can be determined by this way. Practical application of the method is outlined for the case of active and reactive power determination for single-phase power active filter, unified power flow controller, and dynamic voltage restorer, Fig.1 [14], [15], [17] - [19].","PeriodicalId":143815,"journal":{"name":"2008 International School on Nonsinusoidal Currents and Compensation","volume":"120 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114055996","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.2008.4627480
E. Watanabe, H. Akagi, M. Aredes
This paper presents a tutorial about compensation of nonsinusoidal systems based on the instantaneous active and reactive power theory or the p-q theory. The history related to this theory is presented and then the definitions of real, imaginary and zero-sequence powers are introduced. The physical meanings of each of these powers are explained and some basic compensation examples are shown considering different active power conditioners. It is shown that this theory can be very practical for understanding problems due to nonsinusoidal voltages or currents. It is especially interesting for the design of power conditioners for three-wire or four-wire three-phase system with or without distortions in voltages and currents.
{"title":"Instantaneous p-q power Theory for compensating nonsinusoidal systems","authors":"E. Watanabe, H. Akagi, M. Aredes","doi":"10.1109/ISNCC.2008.4627480","DOIUrl":"https://doi.org/10.1109/ISNCC.2008.4627480","url":null,"abstract":"This paper presents a tutorial about compensation of nonsinusoidal systems based on the instantaneous active and reactive power theory or the p-q theory. The history related to this theory is presented and then the definitions of real, imaginary and zero-sequence powers are introduced. The physical meanings of each of these powers are explained and some basic compensation examples are shown considering different active power conditioners. It is shown that this theory can be very practical for understanding problems due to nonsinusoidal voltages or currents. It is especially interesting for the design of power conditioners for three-wire or four-wire three-phase system with or without distortions in voltages and currents.","PeriodicalId":143815,"journal":{"name":"2008 International School on Nonsinusoidal Currents and Compensation","volume":"38 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115788060","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.2008.4627512
I. Korotyeyev, Z. Fedyczak, P. Szcześniak
This paper deals with a three-phase matrix-reactance frequency converter (MRFC). The analysed MRFC topology is based on the boost matrix-reactance chopper (MRC) with a load synchronous connected switch (LSCS) set arranged as in the step-up matrix converter (MC). The MRFC in question makes it possible to obtain a load output voltage much greater than the input voltage. Presented in this paper is a description of a new method for the analysis of the steady and transient state properties of the presented MRFC. The analytical method based on d-q transformation is proposed for solving non-stationary equations, which we derive as a mathematical model of the state-space averaged method applying to the analysis of the discussed MRFC. The analysis results are obtained for a classical Venturini control strategy. Furthermore, for the verification of the theoretical analysis the simulation test results are also presented.
{"title":"Steady and transient state analysis of a matrix-reactance frequency converter based on a boost PWM AC matrix-reactance chopper","authors":"I. Korotyeyev, Z. Fedyczak, P. Szcześniak","doi":"10.1109/ISNCC.2008.4627512","DOIUrl":"https://doi.org/10.1109/ISNCC.2008.4627512","url":null,"abstract":"This paper deals with a three-phase matrix-reactance frequency converter (MRFC). The analysed MRFC topology is based on the boost matrix-reactance chopper (MRC) with a load synchronous connected switch (LSCS) set arranged as in the step-up matrix converter (MC). The MRFC in question makes it possible to obtain a load output voltage much greater than the input voltage. Presented in this paper is a description of a new method for the analysis of the steady and transient state properties of the presented MRFC. The analytical method based on d-q transformation is proposed for solving non-stationary equations, which we derive as a mathematical model of the state-space averaged method applying to the analysis of the discussed MRFC. The analysis results are obtained for a classical Venturini control strategy. Furthermore, for the verification of the theoretical analysis the simulation test results are also presented.","PeriodicalId":143815,"journal":{"name":"2008 International School on Nonsinusoidal Currents and Compensation","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129464972","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.2008.4627503
R. Klosinski
Factors characterizing the electrical energy quality (e.g. THD) are determined on the basis of voltage and current signals spectrum. The spectrum estimation errors come from the spectrum leakage caused by the non-coherent sampling and distortions appearing in the input circuits of the measuring system. This paper concerns the problem of accurate reconstruction of the nonlinearly distorted signal spectrum. The proposed method of the periodic input signal reconstruction (e.g. the CT primary current) is based on the modeling of the nonlinear system in a periodic steady state by a set of circular parametric operators (CPOs). This method requires coherent sampling of the measured signal that is inconvenient because of the electro-energetic system natural frequency changes. To avoid this limitation the reconstruction calculations are transferred to the spectral domain. The spectrum of the reconstructed signal is determined by means of the spectral version of the CPO (i.e. the SCPO) on the basis of the spectrum of the distorted signal. A modified discrete Fourier transform (MDFT) is used to determine the distorted signal spectrum. The MDFT is designed for the non-coherently sampled signal high accuracy spectrum analysis. The DFT modification idea consists in the adjustment of base function frequencies of the Fourier series to the analyzed signal harmonics frequencies. Some results of experiments are included.
{"title":"Reconstruction of spectrum of the nonlinearly distorted periodic signals sampled non-coherently","authors":"R. Klosinski","doi":"10.1109/ISNCC.2008.4627503","DOIUrl":"https://doi.org/10.1109/ISNCC.2008.4627503","url":null,"abstract":"Factors characterizing the electrical energy quality (e.g. THD) are determined on the basis of voltage and current signals spectrum. The spectrum estimation errors come from the spectrum leakage caused by the non-coherent sampling and distortions appearing in the input circuits of the measuring system. This paper concerns the problem of accurate reconstruction of the nonlinearly distorted signal spectrum. The proposed method of the periodic input signal reconstruction (e.g. the CT primary current) is based on the modeling of the nonlinear system in a periodic steady state by a set of circular parametric operators (CPOs). This method requires coherent sampling of the measured signal that is inconvenient because of the electro-energetic system natural frequency changes. To avoid this limitation the reconstruction calculations are transferred to the spectral domain. The spectrum of the reconstructed signal is determined by means of the spectral version of the CPO (i.e. the SCPO) on the basis of the spectrum of the distorted signal. A modified discrete Fourier transform (MDFT) is used to determine the distorted signal spectrum. The MDFT is designed for the non-coherently sampled signal high accuracy spectrum analysis. The DFT modification idea consists in the adjustment of base function frequencies of the Fourier series to the analyzed signal harmonics frequencies. Some results of experiments are included.","PeriodicalId":143815,"journal":{"name":"2008 International School on Nonsinusoidal Currents and Compensation","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116316379","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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