Pub Date : 2011-05-11DOI: 10.1109/POWERENG.2011.6036508
A. Božiček, B. Blazic, I. Papič
This paper presents an optimization approach in predictive control of voltage source converters (VSC). Basic predictive controllers are derived in discrete time domain and use the approximate mathematical models of the VSC based device to predict its electrical response. The proposed optimization approach, the time-optimal current controller (TOCC), predicts the state of electrical variables also for more sampling periods ahead This results in better dynamics of the device. Predicting the current path during current transients allows the estimation of transient duration which is (considering the predefined operation boundaries of the VSC device) used as the optimization function. The instantaneous reference voltage vector defined with the optimization procedure generates current vector which follows the predicted optimal current path that demands the shortest time to reach stationary state The simulations of the TOCC prove stable, robust and relatively simple operation, while showing evident advantages in comparison with other fast controllers.
{"title":"Time-optimal operation of a predictive current controller for voltage source converters","authors":"A. Božiček, B. Blazic, I. Papič","doi":"10.1109/POWERENG.2011.6036508","DOIUrl":"https://doi.org/10.1109/POWERENG.2011.6036508","url":null,"abstract":"This paper presents an optimization approach in predictive control of voltage source converters (VSC). Basic predictive controllers are derived in discrete time domain and use the approximate mathematical models of the VSC based device to predict its electrical response. The proposed optimization approach, the time-optimal current controller (TOCC), predicts the state of electrical variables also for more sampling periods ahead This results in better dynamics of the device. Predicting the current path during current transients allows the estimation of transient duration which is (considering the predefined operation boundaries of the VSC device) used as the optimization function. The instantaneous reference voltage vector defined with the optimization procedure generates current vector which follows the predicted optimal current path that demands the shortest time to reach stationary state The simulations of the TOCC prove stable, robust and relatively simple operation, while showing evident advantages in comparison with other fast controllers.","PeriodicalId":166144,"journal":{"name":"2011 International Conference on Power Engineering, Energy and Electrical Drives","volume":"67 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-05-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115009008","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 : 2011-05-11DOI: 10.1109/POWERENG.2011.6036470
H. Mehranfar, A. Baghramian, Fatemeh Rafieinia
A voltage sag compensator based on a switched autotransformer by RBHVC (random band hysteresis voltage control) is proposed in this paper, which can compensate the deep voltage sags. The traditional voltage sag compensators cannot compensate the deep and long-duration voltage sags. The advantage of proposed compensator in this paper is that it uses only one controlled switch per phase with no energy storages. Also the control scheme purposed here distributes the harmonic spectrum of the load voltage and reduces its total harmonic distortion (THD). Different voltage sag events have been simulated by MATLAB/SEVIULINK software. The results of simulations verify the ability of proposed method to mitigate deep voltage sag events.
{"title":"Mitigation of deep voltage sag utilizing switched autotransformer with RBHVC","authors":"H. Mehranfar, A. Baghramian, Fatemeh Rafieinia","doi":"10.1109/POWERENG.2011.6036470","DOIUrl":"https://doi.org/10.1109/POWERENG.2011.6036470","url":null,"abstract":"A voltage sag compensator based on a switched autotransformer by RBHVC (random band hysteresis voltage control) is proposed in this paper, which can compensate the deep voltage sags. The traditional voltage sag compensators cannot compensate the deep and long-duration voltage sags. The advantage of proposed compensator in this paper is that it uses only one controlled switch per phase with no energy storages. Also the control scheme purposed here distributes the harmonic spectrum of the load voltage and reduces its total harmonic distortion (THD). Different voltage sag events have been simulated by MATLAB/SEVIULINK software. The results of simulations verify the ability of proposed method to mitigate deep voltage sag events.","PeriodicalId":166144,"journal":{"name":"2011 International Conference on Power Engineering, Energy and Electrical Drives","volume":"40 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-05-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115214422","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 : 2011-05-11DOI: 10.1109/POWERENG.2011.6036558
Ó. Duque-Pérez, D. Morinigo-Sotelo, M. Perez-Alonso
Electrical monitoring is currently considered as a standard in preventive maintenance and is the reference method for the diagnosis of medium-large machines, standing out the technique known as motor current signature analysis. Numerous successful line-driven motor fault detection methods are reported in the literature. However, inverter-fed motor systems and utility driven motors with high harmonic content still require more attention. In these cases, fault detection is more difficult due to remarkable noise on the line current, transient operating conditions, closed-loop controller bandwidths and, above all, the presence of many time harmonics introduced by the supply. This harmonic content, which is normally known as a major side effect, gives rise to extra signatures and turns out to be useful in distinguishing faulty current spectrum patterns from healthy ones.
{"title":"Diagnosis of induction motors fed by supplies with high harmonic content using motor current signature analysis","authors":"Ó. Duque-Pérez, D. Morinigo-Sotelo, M. Perez-Alonso","doi":"10.1109/POWERENG.2011.6036558","DOIUrl":"https://doi.org/10.1109/POWERENG.2011.6036558","url":null,"abstract":"Electrical monitoring is currently considered as a standard in preventive maintenance and is the reference method for the diagnosis of medium-large machines, standing out the technique known as motor current signature analysis. Numerous successful line-driven motor fault detection methods are reported in the literature. However, inverter-fed motor systems and utility driven motors with high harmonic content still require more attention. In these cases, fault detection is more difficult due to remarkable noise on the line current, transient operating conditions, closed-loop controller bandwidths and, above all, the presence of many time harmonics introduced by the supply. This harmonic content, which is normally known as a major side effect, gives rise to extra signatures and turns out to be useful in distinguishing faulty current spectrum patterns from healthy ones.","PeriodicalId":166144,"journal":{"name":"2011 International Conference on Power Engineering, Energy and Electrical Drives","volume":"254 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-05-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121023323","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 : 2011-05-11DOI: 10.1109/POWERENG.2011.6036437
Syafii, K. M. Nor, M. Abdel-Akher
This paper proposes parallel algorithm of a general three-phase load flow calculation based on symmetrical components. The proposed algorithm comprises of two part i.e. sequence admittance matrix construction and sequence decoupled algorithm for sequence networks solver which have three independent sub-problems corresponding to positive, negative, and zero-sequence networks. These two parts are solved concurrently using multi-core parallel processing. The IEEE 8500-node test feeder is used to test the robustness of the algorithm for large system problem. The large unbalanced load connected to the center-tapped transformer solved using an iterative forward and backward sweep analysis method based on voltage drop analysis. The result showed that parallel three-phase load flow produced execution speedup and proved the ability to handle large scale problems.
{"title":"Parallel three-phase load flow analysis for large scale unbalanced distribution networks","authors":"Syafii, K. M. Nor, M. Abdel-Akher","doi":"10.1109/POWERENG.2011.6036437","DOIUrl":"https://doi.org/10.1109/POWERENG.2011.6036437","url":null,"abstract":"This paper proposes parallel algorithm of a general three-phase load flow calculation based on symmetrical components. The proposed algorithm comprises of two part i.e. sequence admittance matrix construction and sequence decoupled algorithm for sequence networks solver which have three independent sub-problems corresponding to positive, negative, and zero-sequence networks. These two parts are solved concurrently using multi-core parallel processing. The IEEE 8500-node test feeder is used to test the robustness of the algorithm for large system problem. The large unbalanced load connected to the center-tapped transformer solved using an iterative forward and backward sweep analysis method based on voltage drop analysis. The result showed that parallel three-phase load flow produced execution speedup and proved the ability to handle large scale problems.","PeriodicalId":166144,"journal":{"name":"2011 International Conference on Power Engineering, Energy and Electrical Drives","volume":"46 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-05-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126153665","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 : 2011-05-11DOI: 10.1109/POWERENG.2011.6036481
V. Plaček, J. Hrdlička
This paper describes some problems concerning control of small-scale biomass boilers. A commercially available boiler equipped with additional instrumentation has been used as an experimental platform for research purposes. In the paper are discussed grate sweeping effects on fluctuations in boiler operation that have been weakened by algorithm alternations. Another problem discussed in the paper is transient states generation during on/off control of the boiler heat output. These states cause decrease in overall efficiency of the boiler and they can be also source of increased emissions of gaseous pollutants in the flue gas. As a solution the on/off algorithm has been replaced by continuous linear controller that is able to control the transient states in a desired manner.
{"title":"Influence of control on environmental and economical aspects of small-scale biomass boiler","authors":"V. Plaček, J. Hrdlička","doi":"10.1109/POWERENG.2011.6036481","DOIUrl":"https://doi.org/10.1109/POWERENG.2011.6036481","url":null,"abstract":"This paper describes some problems concerning control of small-scale biomass boilers. A commercially available boiler equipped with additional instrumentation has been used as an experimental platform for research purposes. In the paper are discussed grate sweeping effects on fluctuations in boiler operation that have been weakened by algorithm alternations. Another problem discussed in the paper is transient states generation during on/off control of the boiler heat output. These states cause decrease in overall efficiency of the boiler and they can be also source of increased emissions of gaseous pollutants in the flue gas. As a solution the on/off algorithm has been replaced by continuous linear controller that is able to control the transient states in a desired manner.","PeriodicalId":166144,"journal":{"name":"2011 International Conference on Power Engineering, Energy and Electrical Drives","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-05-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116557068","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 : 2011-05-11DOI: 10.1109/POWERENG.2011.6036546
Emanuel C. Meireles, A. Martins
Cascaded H-bridge multilevel inverters are highly modular converters particularly suitable for generating high output voltages and connecting independent dc sources like solar arrays or fuel cells. Three-phase multilevel inverters based on cascaded H-bridge inverters require a large number of control signals, particularly if the number of levels is high. In this case, Field-Programmable Gate Array appears as the right solution to generate the control signals for the multilevel inverter. This paper presents the analysis and design of a FPGA-based multi-carrier PWM control method for a five-level three-phase inverter suitable for photovoltaic applications and shows simulation and experimental data demonstrating the expected theoretical results.
{"title":"Control of cascaded H-bridge inverters using an FPGA-based platform","authors":"Emanuel C. Meireles, A. Martins","doi":"10.1109/POWERENG.2011.6036546","DOIUrl":"https://doi.org/10.1109/POWERENG.2011.6036546","url":null,"abstract":"Cascaded H-bridge multilevel inverters are highly modular converters particularly suitable for generating high output voltages and connecting independent dc sources like solar arrays or fuel cells. Three-phase multilevel inverters based on cascaded H-bridge inverters require a large number of control signals, particularly if the number of levels is high. In this case, Field-Programmable Gate Array appears as the right solution to generate the control signals for the multilevel inverter. This paper presents the analysis and design of a FPGA-based multi-carrier PWM control method for a five-level three-phase inverter suitable for photovoltaic applications and shows simulation and experimental data demonstrating the expected theoretical results.","PeriodicalId":166144,"journal":{"name":"2011 International Conference on Power Engineering, Energy and Electrical Drives","volume":"114 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-05-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130322993","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 : 2011-05-11DOI: 10.1109/POWERENG.2011.6036525
A. Abdel-Khalik, S. Ahmed
The performance of fault-tolerant modular PM machines depends on the proper selection of the pole and slot numbers which results in negligible coupling between phases. The preferred slot and pole number combinations eliminate the effect of low order harmonics in the stator MMF and thereby the vibration and stray loss are reduced. In this paper, three machines, with an external rotor design and identical machine dimensions, are designed with different slots per phase per pole (SPP) ratios. A simulation study is carried out using FEA to compare the performance of the three designed machines in terms of machine torque density, ripple torque, core loss, and machine efficiency. The simulation study is extended to study the performance under fault conditions.
{"title":"Comparative study of five-phase in-wheel fault-tolerant modular PM machines with different number of rotor poles","authors":"A. Abdel-Khalik, S. Ahmed","doi":"10.1109/POWERENG.2011.6036525","DOIUrl":"https://doi.org/10.1109/POWERENG.2011.6036525","url":null,"abstract":"The performance of fault-tolerant modular PM machines depends on the proper selection of the pole and slot numbers which results in negligible coupling between phases. The preferred slot and pole number combinations eliminate the effect of low order harmonics in the stator MMF and thereby the vibration and stray loss are reduced. In this paper, three machines, with an external rotor design and identical machine dimensions, are designed with different slots per phase per pole (SPP) ratios. A simulation study is carried out using FEA to compare the performance of the three designed machines in terms of machine torque density, ripple torque, core loss, and machine efficiency. The simulation study is extended to study the performance under fault conditions.","PeriodicalId":166144,"journal":{"name":"2011 International Conference on Power Engineering, Energy and Electrical Drives","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-05-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123662828","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 : 2011-05-11DOI: 10.1109/POWERENG.2011.6036527
Xinghuo Yu
Smart Grids are electric networks that employ innovative and intelligent monitoring, control, communication, and self-healing technologies to deliver better connections and operations for generators and distributors, flexible choices for consumers, and reliability and security of electricity supply. Smart Grids are complex and dynamical networks in nature that face many new theoretical and practical challenges for the future developments. Intelligent Systems and Control, on the other hand, offer enabling technologies for Smart Grids developments, such as theories and methodologies for developing artificially intelligent systems and technologies that mimic human intelligence to handle complex situations in uncertain environments with simplexity. These include, for example, neural and evolutionary computation, fuzzy systems, knowledge-based systems, multi-agent systems, complex networks, decision support systems, nonlinear control theories embedded with intelligent mechanisms of sensing, reasoning and learning. In this speech, we will first give a brief introduction of both Smart Grids and Intelligent Systems and Control and their recent developments, and then examine the issues associated with interplay of Smart Grids and Intelligent Systems and Control. We will discuss potential new ways of simplifying the modelling, assessment and control tasks of Smart Grids using Intelligent Systems and Control technologies. We will also look into new research challenges that Smart Grids present to Intelligent Systems and Control research. The synergies between these two fields will also be highlighted. Some of our recent research results will be shown as case studies to demonstrate the potential that this interplay will bring to both Smart Grids and Intelligent Systems and Control.
{"title":"Interplay of Smart Grids and Intelligent Systems and Control","authors":"Xinghuo Yu","doi":"10.1109/POWERENG.2011.6036527","DOIUrl":"https://doi.org/10.1109/POWERENG.2011.6036527","url":null,"abstract":"Smart Grids are electric networks that employ innovative and intelligent monitoring, control, communication, and self-healing technologies to deliver better connections and operations for generators and distributors, flexible choices for consumers, and reliability and security of electricity supply. Smart Grids are complex and dynamical networks in nature that face many new theoretical and practical challenges for the future developments. Intelligent Systems and Control, on the other hand, offer enabling technologies for Smart Grids developments, such as theories and methodologies for developing artificially intelligent systems and technologies that mimic human intelligence to handle complex situations in uncertain environments with simplexity. These include, for example, neural and evolutionary computation, fuzzy systems, knowledge-based systems, multi-agent systems, complex networks, decision support systems, nonlinear control theories embedded with intelligent mechanisms of sensing, reasoning and learning. In this speech, we will first give a brief introduction of both Smart Grids and Intelligent Systems and Control and their recent developments, and then examine the issues associated with interplay of Smart Grids and Intelligent Systems and Control. We will discuss potential new ways of simplifying the modelling, assessment and control tasks of Smart Grids using Intelligent Systems and Control technologies. We will also look into new research challenges that Smart Grids present to Intelligent Systems and Control research. The synergies between these two fields will also be highlighted. Some of our recent research results will be shown as case studies to demonstrate the potential that this interplay will bring to both Smart Grids and Intelligent Systems and Control.","PeriodicalId":166144,"journal":{"name":"2011 International Conference on Power Engineering, Energy and Electrical Drives","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-05-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114708321","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 : 2011-05-11DOI: 10.1109/POWERENG.2011.6036482
P. Cruz, A. de la Villa-Jaén, A. Gómez-Expósito, J. A. Pérez
This paper analyzes the uncertainty in the measurement of 50-Hz current on high voltage overhead conductors by means of low-cost magnetic field sensors (inductive coils) located at the electric clearance from the conductors. It is assumed that no external magnetic field sources exist in the vicinity. Expanded uncertainty associated with the measurement of current under a single-phase system is evaluated. The results are validated in a lab setup. A single sensor is considered first, followed by the case of 3 sensors. In this last case, due to the redundancy the least squares method is applied to reduce the uncertainty of the measurement.
{"title":"Uncertainty assessment and validation of current remote measurement on high voltage overhead conductors","authors":"P. Cruz, A. de la Villa-Jaén, A. Gómez-Expósito, J. A. Pérez","doi":"10.1109/POWERENG.2011.6036482","DOIUrl":"https://doi.org/10.1109/POWERENG.2011.6036482","url":null,"abstract":"This paper analyzes the uncertainty in the measurement of 50-Hz current on high voltage overhead conductors by means of low-cost magnetic field sensors (inductive coils) located at the electric clearance from the conductors. It is assumed that no external magnetic field sources exist in the vicinity. Expanded uncertainty associated with the measurement of current under a single-phase system is evaluated. The results are validated in a lab setup. A single sensor is considered first, followed by the case of 3 sensors. In this last case, due to the redundancy the least squares method is applied to reduce the uncertainty of the measurement.","PeriodicalId":166144,"journal":{"name":"2011 International Conference on Power Engineering, Energy and Electrical Drives","volume":"51 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-05-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126282804","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 : 2011-05-11DOI: 10.1109/POWERENG.2011.6036507
H. Maciejewski, G. Anders, J. Endrenyi
This paper is devoted to the problem of estimating the end of life of electric power equipment. Several statistical methods and models commonly used in reliability engineering are discussed, focusing on (a) the technical merit of each described method, and (b) the suitability of each method for determining the end of life of power equipment. Description of statistical methods considers both censored and uncensored observations. The problem of model selection for analysis of censored data is given special consideration: a novel approach is proposed for this. The points made in the text are illustrated by several numerical examples pertaining to the lifetime of transformers, however the methods can be applied for other types of electric or electronic equipment (e.g., electronic relays).
{"title":"On the use of statistical methods and models for predicting the end of life of electric power equipment","authors":"H. Maciejewski, G. Anders, J. Endrenyi","doi":"10.1109/POWERENG.2011.6036507","DOIUrl":"https://doi.org/10.1109/POWERENG.2011.6036507","url":null,"abstract":"This paper is devoted to the problem of estimating the end of life of electric power equipment. Several statistical methods and models commonly used in reliability engineering are discussed, focusing on (a) the technical merit of each described method, and (b) the suitability of each method for determining the end of life of power equipment. Description of statistical methods considers both censored and uncensored observations. The problem of model selection for analysis of censored data is given special consideration: a novel approach is proposed for this. The points made in the text are illustrated by several numerical examples pertaining to the lifetime of transformers, however the methods can be applied for other types of electric or electronic equipment (e.g., electronic relays).","PeriodicalId":166144,"journal":{"name":"2011 International Conference on Power Engineering, Energy and Electrical Drives","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-05-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132223134","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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