Pub Date : 1999-07-27DOI: 10.1109/PEDS.1999.794532
S. Azzopardi, J. Vinassa, C. Zardini
In this paper, we investigate the behavior of 1200 V punch-through (PT) and nonpunch-through (NPT) IGBTs under unclamped inductive switching (UIS) stress at various temperature and peak collector current values. UIS conditions, occurring when the freewheeling diode in parallel to the load has failed, submit the device to high voltage and high current simultaneously. The results show that 1200 V NPT-IGBTs, which did not fail in these experiments, present a higher ruggedness than 1200 V PT-IGBTs. Generally, NPT-IGBTs are more sensitive to the peak collector current variation than to the temperature. Furthermore, the dynamic breakdown voltage value is equal to the static breakdown voltage during the avalanche mode. As for the PT-IGBTs, their behaviour depends strongly on the temperature and also on the peak collector current values. More precisely, the dynamic breakdown voltage value is reduced and is considerable depending on the test conditions. This reduction is due to an excess of positive charges in the drift region which does not allow the expansion of the electric field. This phenomenon is emphasized when the temperature rises.
在本文中，我们研究了在不同温度和集电极峰值电流值下，1200 V穿通(PT)和非穿通(NPT) igbt在非箝位电感开关(UIS)应力下的行为。当与负载并联的自由转动二极管失效时，将设备同时置于高压和大电流下。结果表明，与1200 V pt - igbt相比，1200 V npt - igbt在这些实验中没有失效，具有更高的坚固性。一般来说，npt - igbt对峰值集电极电流的变化比对温度的变化更敏感。在雪崩模式下，动态击穿电压值与静态击穿电压值相等。至于pt - igbt，它们的行为在很大程度上取决于温度和集电极的峰值电流值。更准确地说，动态击穿电压值被降低，并且根据测试条件是相当大的。这种减少是由于在漂移区过量的正电荷，不允许扩大电场。当温度升高时，这种现象更加突出。
{"title":"Performances of 1200 V punch-through and nonpunch-through IGBTs under unclamped inductive switching","authors":"S. Azzopardi, J. Vinassa, C. Zardini","doi":"10.1109/PEDS.1999.794532","DOIUrl":"https://doi.org/10.1109/PEDS.1999.794532","url":null,"abstract":"In this paper, we investigate the behavior of 1200 V punch-through (PT) and nonpunch-through (NPT) IGBTs under unclamped inductive switching (UIS) stress at various temperature and peak collector current values. UIS conditions, occurring when the freewheeling diode in parallel to the load has failed, submit the device to high voltage and high current simultaneously. The results show that 1200 V NPT-IGBTs, which did not fail in these experiments, present a higher ruggedness than 1200 V PT-IGBTs. Generally, NPT-IGBTs are more sensitive to the peak collector current variation than to the temperature. Furthermore, the dynamic breakdown voltage value is equal to the static breakdown voltage during the avalanche mode. As for the PT-IGBTs, their behaviour depends strongly on the temperature and also on the peak collector current values. More precisely, the dynamic breakdown voltage value is reduced and is considerable depending on the test conditions. This reduction is due to an excess of positive charges in the drift region which does not allow the expansion of the electric field. This phenomenon is emphasized when the temperature rises.","PeriodicalId":254764,"journal":{"name":"Proceedings of the IEEE 1999 International Conference on Power Electronics and Drive Systems. PEDS'99 (Cat. No.99TH8475)","volume":"42 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124813005","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 : 1999-07-27DOI: 10.1109/PEDS.1999.792804
T. Liang, Jiann-Fuh Chen, C. Chu, Kuen-Jyh Chen
In this paper, the unbalanced current in the 12-pulse phase control AC/DC converters was studied. The 12-pulse /spl Delta/-Y type AC/DC converter will keep a balanced voltage with 30/spl deg/ phase shifted at the low coupling coefficient condition, but an unbalanced current will be obtained in the 12-pulse autotransformer phase shift AC/DC converter at the low coupling coefficient condition. The theoretical phasor analysis of the unbalanced current was presented and a feedback controller was designed to overcome this problem. Finally, a 3 kW 12-pulse autotransformer phase shifted AC/DC converter was implemented to demonstrate the theoretical analysis.
{"title":"Analysis of 12 pulse phase control AC/DC converter","authors":"T. Liang, Jiann-Fuh Chen, C. Chu, Kuen-Jyh Chen","doi":"10.1109/PEDS.1999.792804","DOIUrl":"https://doi.org/10.1109/PEDS.1999.792804","url":null,"abstract":"In this paper, the unbalanced current in the 12-pulse phase control AC/DC converters was studied. The 12-pulse /spl Delta/-Y type AC/DC converter will keep a balanced voltage with 30/spl deg/ phase shifted at the low coupling coefficient condition, but an unbalanced current will be obtained in the 12-pulse autotransformer phase shift AC/DC converter at the low coupling coefficient condition. The theoretical phasor analysis of the unbalanced current was presented and a feedback controller was designed to overcome this problem. Finally, a 3 kW 12-pulse autotransformer phase shifted AC/DC converter was implemented to demonstrate the theoretical analysis.","PeriodicalId":254764,"journal":{"name":"Proceedings of the IEEE 1999 International Conference on Power Electronics and Drive Systems. PEDS'99 (Cat. No.99TH8475)","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133226510","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 : 1999-07-27DOI: 10.1109/PEDS.1999.794540
C. Mei, S. Panda, J. Xu, K. Lim
An induction motor drive based on direct torque control (DTC) allows high dynamic performance to be obtained with a very simple hysteresis control scheme. In this paper, the problem of stator flux drooping at low speeds has been investigated. By rotating the original flux sectors defined for conventional DTC near the sector boundaries, it is possible to maintain stator flux within the prescribed hysteresis bands and therefore improve the stator flux in the machine as well as the harmonic contents of stator currents. Moreover, the use of the proposed scheme also results in a reduction of overall inverter switching frequency. The effectiveness of the proposed scheme is evaluated through simulation studies, and is also supported with experimental results obtained from a 1.5 kW induction motor driven in a laboratory environment.
{"title":"Direct torque control of induction motor-variable switching sectors","authors":"C. Mei, S. Panda, J. Xu, K. Lim","doi":"10.1109/PEDS.1999.794540","DOIUrl":"https://doi.org/10.1109/PEDS.1999.794540","url":null,"abstract":"An induction motor drive based on direct torque control (DTC) allows high dynamic performance to be obtained with a very simple hysteresis control scheme. In this paper, the problem of stator flux drooping at low speeds has been investigated. By rotating the original flux sectors defined for conventional DTC near the sector boundaries, it is possible to maintain stator flux within the prescribed hysteresis bands and therefore improve the stator flux in the machine as well as the harmonic contents of stator currents. Moreover, the use of the proposed scheme also results in a reduction of overall inverter switching frequency. The effectiveness of the proposed scheme is evaluated through simulation studies, and is also supported with experimental results obtained from a 1.5 kW induction motor driven in a laboratory environment.","PeriodicalId":254764,"journal":{"name":"Proceedings of the IEEE 1999 International Conference on Power Electronics and Drive Systems. PEDS'99 (Cat. No.99TH8475)","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114647918","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 : 1999-07-27DOI: 10.1109/PEDS.1999.794588
J.H. Alimeling, W. Hammer
In this paper a new toolbox, PLECS, for the fast simulation of power electronic circuits under Simulink is presented. This toolbox provides the means for modeling large power electronic systems containing both electrical circuits and controllers. The program is based on a state-space formulation for circuits that consist of linear elements (RLC), transformers, sources, meters and ideal switches. Diodes, thyristors, IGBTs and other nonlinear elements such as saturable inductors can be assembled by combining linear elements and switches. Thus, a piece-wise linear model is attained which leads to a stable and fast simulation. An attached benchmark simulation demonstrates the capability of PLECS.
{"title":"PLECS-piece-wise linear electrical circuit simulation for Simulink","authors":"J.H. Alimeling, W. Hammer","doi":"10.1109/PEDS.1999.794588","DOIUrl":"https://doi.org/10.1109/PEDS.1999.794588","url":null,"abstract":"In this paper a new toolbox, PLECS, for the fast simulation of power electronic circuits under Simulink is presented. This toolbox provides the means for modeling large power electronic systems containing both electrical circuits and controllers. The program is based on a state-space formulation for circuits that consist of linear elements (RLC), transformers, sources, meters and ideal switches. Diodes, thyristors, IGBTs and other nonlinear elements such as saturable inductors can be assembled by combining linear elements and switches. Thus, a piece-wise linear model is attained which leads to a stable and fast simulation. An attached benchmark simulation demonstrates the capability of PLECS.","PeriodicalId":254764,"journal":{"name":"Proceedings of the IEEE 1999 International Conference on Power Electronics and Drive Systems. PEDS'99 (Cat. No.99TH8475)","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114528715","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 : 1999-07-27DOI: 10.1109/PEDS.1999.794548
S. Watanabe, P. Boyagoda, M. Nakaoka, H. Takano
This paper presents a two-paralleled PWM amplifier using switch-mode power current tracking technique in order to generate a gradient magnetic field in the magnetic resonance imaging (MRI) system. This circuit has 8-IGBTs at their inputs/outputs so as to realize further high-power density. A digital control scheme can minimize the current ripple and improve its control response in the gradient coils (GCs). It is proved that the proposed technique will highly enlarge the diagnostic target and improve the image quality of MRI.
{"title":"Analysis on a PWM power conversion amplifier with IGBT macro model to generate gradient magnetic fields in MRI systems","authors":"S. Watanabe, P. Boyagoda, M. Nakaoka, H. Takano","doi":"10.1109/PEDS.1999.794548","DOIUrl":"https://doi.org/10.1109/PEDS.1999.794548","url":null,"abstract":"This paper presents a two-paralleled PWM amplifier using switch-mode power current tracking technique in order to generate a gradient magnetic field in the magnetic resonance imaging (MRI) system. This circuit has 8-IGBTs at their inputs/outputs so as to realize further high-power density. A digital control scheme can minimize the current ripple and improve its control response in the gradient coils (GCs). It is proved that the proposed technique will highly enlarge the diagnostic target and improve the image quality of MRI.","PeriodicalId":254764,"journal":{"name":"Proceedings of the IEEE 1999 International Conference on Power Electronics and Drive Systems. PEDS'99 (Cat. No.99TH8475)","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122906289","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 : 1999-07-27DOI: 10.1109/PEDS.1999.794600
Hyosung Kim, H. Akagi
This paper proposed the rotating p-q-r reference frames where one instantaneous active power p, and two instantaneous reactive powers q/sub q/, q/sub r/ were defined in 3-phase 4-wire systems. The three power components are linearly independent, so that compensating for the two instantaneous reactive powers leads to control the two components of the current space vector independently. With the theory, this paper shows that the neutral current of a 3-phase 4-wire system can be eliminated by only compensating for the instantaneous reactive power using no energy storage element. Simulation results verify the theory very well.
{"title":"The instantaneous power theory on the rotating p-q-r reference frames","authors":"Hyosung Kim, H. Akagi","doi":"10.1109/PEDS.1999.794600","DOIUrl":"https://doi.org/10.1109/PEDS.1999.794600","url":null,"abstract":"This paper proposed the rotating p-q-r reference frames where one instantaneous active power p, and two instantaneous reactive powers q/sub q/, q/sub r/ were defined in 3-phase 4-wire systems. The three power components are linearly independent, so that compensating for the two instantaneous reactive powers leads to control the two components of the current space vector independently. With the theory, this paper shows that the neutral current of a 3-phase 4-wire system can be eliminated by only compensating for the instantaneous reactive power using no energy storage element. Simulation results verify the theory very well.","PeriodicalId":254764,"journal":{"name":"Proceedings of the IEEE 1999 International Conference on Power Electronics and Drive Systems. PEDS'99 (Cat. No.99TH8475)","volume":"85-86 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117144385","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 : 1999-07-27DOI: 10.1109/PEDS.1999.794606
Hae-Ryong Choi, H. Mok, G. Choe, Chung-Yun Won, Kyu Sik Kim
An inverter arc welding machine applying a DCM boost converter is presented in this paper. First, the basic operation and principle is reviewed. Controller design is intended to force voltage ripple to minimize, and dynamic response to enhance. A feedforward scheme for an inverter arc welding machine is developed, and that is verified by simulation and experiment. The improved power factor characteristics of inverter arc welding machine known as low power factor system with nonlinear property, are shown and evaluated compared to the conventional scheme.
{"title":"Enhanced characteristics of DCM boost converter for inverter arc welding system","authors":"Hae-Ryong Choi, H. Mok, G. Choe, Chung-Yun Won, Kyu Sik Kim","doi":"10.1109/PEDS.1999.794606","DOIUrl":"https://doi.org/10.1109/PEDS.1999.794606","url":null,"abstract":"An inverter arc welding machine applying a DCM boost converter is presented in this paper. First, the basic operation and principle is reviewed. Controller design is intended to force voltage ripple to minimize, and dynamic response to enhance. A feedforward scheme for an inverter arc welding machine is developed, and that is verified by simulation and experiment. The improved power factor characteristics of inverter arc welding machine known as low power factor system with nonlinear property, are shown and evaluated compared to the conventional scheme.","PeriodicalId":254764,"journal":{"name":"Proceedings of the IEEE 1999 International Conference on Power Electronics and Drive Systems. PEDS'99 (Cat. No.99TH8475)","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130862565","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 : 1999-07-27DOI: 10.1109/PEDS.1999.792825
A.Y.K. Wong, D. Cheng, Y. Lee
This paper studies a single phase shunt active power filter (APF) using a bi-directional full-bridge converter with capacitive energy storage to compensate for the harmonics generated by nonlinear loads. The usage of a capacitor as a reactive power source for the APF simplifies the circuitry. The harmonic current reference is obtained by feeding the load current signal into a 50 Hz notch filter. The simple and fast hysteresis control strategy involving only a few analog and logic components makes it attractive for the low power domestic application. The usefulness of the proposed control algorithm is confirmed by simulation as well as by experimental results.
{"title":"Harmonic compensation for nonlinear loads by active power","authors":"A.Y.K. Wong, D. Cheng, Y. Lee","doi":"10.1109/PEDS.1999.792825","DOIUrl":"https://doi.org/10.1109/PEDS.1999.792825","url":null,"abstract":"This paper studies a single phase shunt active power filter (APF) using a bi-directional full-bridge converter with capacitive energy storage to compensate for the harmonics generated by nonlinear loads. The usage of a capacitor as a reactive power source for the APF simplifies the circuitry. The harmonic current reference is obtained by feeding the load current signal into a 50 Hz notch filter. The simple and fast hysteresis control strategy involving only a few analog and logic components makes it attractive for the low power domestic application. The usefulness of the proposed control algorithm is confirmed by simulation as well as by experimental results.","PeriodicalId":254764,"journal":{"name":"Proceedings of the IEEE 1999 International Conference on Power Electronics and Drive Systems. PEDS'99 (Cat. No.99TH8475)","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124068183","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 : 1999-07-27DOI: 10.1109/PEDS.1999.792732
P. Dahono, Slamet Riyadi, Ahmad Mudawari, Y. Haroen
This paper presents an output ripple analysis of multiphase DC-DC power converters having an output LC filter. Analytical expressions for the output voltage ripple of two- and three-phase DC-DC power converters are derived. Influence of the coupling coefficient of the output filter inductor on the output ripple is investigated. Because the unique parameters of the LC filter cannot be determined solely based on the specified maximum output ripple, an additional criterion based on minimum energy storage is introduced. A comparative evaluation of single-phase, two-phase, and three-phase DC-DC power converters is presented. The validity of the proposed analysis method is verified by experimental results.
{"title":"Output ripple analysis of multiphase DC-DC converters","authors":"P. Dahono, Slamet Riyadi, Ahmad Mudawari, Y. Haroen","doi":"10.1109/PEDS.1999.792732","DOIUrl":"https://doi.org/10.1109/PEDS.1999.792732","url":null,"abstract":"This paper presents an output ripple analysis of multiphase DC-DC power converters having an output LC filter. Analytical expressions for the output voltage ripple of two- and three-phase DC-DC power converters are derived. Influence of the coupling coefficient of the output filter inductor on the output ripple is investigated. Because the unique parameters of the LC filter cannot be determined solely based on the specified maximum output ripple, an additional criterion based on minimum energy storage is introduced. A comparative evaluation of single-phase, two-phase, and three-phase DC-DC power converters is presented. The validity of the proposed analysis method is verified by experimental results.","PeriodicalId":254764,"journal":{"name":"Proceedings of the IEEE 1999 International Conference on Power Electronics and Drive Systems. PEDS'99 (Cat. No.99TH8475)","volume":"47 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126350525","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 : 1999-07-27DOI: 10.1109/PEDS.1999.794531
H. Iwamoto, H. Takahashi, M. Tabata, K. Satoh
A new PT-type trench gate IGBT has been developed using a local lifetime control in the n+ buffer layer. A prototype was developed after analyzing the device and estimating its characteristics using simulation. Both the result of simulation and that of measurement of the prototype have matched. Though the chip area is about 40/spl sim/50% smaller than the conventional IGBT, the newly developed IGBT's on-state voltage is about two-thirds (1.8 V, typically), its switching loss is about 80%, and has a larger reverse bias switching withstand capability. Also, a high-speed diode with excellent soft recovery characteristic was developed using local lifetime control in anode-side n-layer. As a result, a reduction of surge voltage, noise, and switching power loss has been achieved. This paper presents the structures and characteristics of the new IGBT and diode and their analysis results.
{"title":"New 1200 V power modules with sophisticated trench gate IGBT and superior soft recovery diode","authors":"H. Iwamoto, H. Takahashi, M. Tabata, K. Satoh","doi":"10.1109/PEDS.1999.794531","DOIUrl":"https://doi.org/10.1109/PEDS.1999.794531","url":null,"abstract":"A new PT-type trench gate IGBT has been developed using a local lifetime control in the n+ buffer layer. A prototype was developed after analyzing the device and estimating its characteristics using simulation. Both the result of simulation and that of measurement of the prototype have matched. Though the chip area is about 40/spl sim/50% smaller than the conventional IGBT, the newly developed IGBT's on-state voltage is about two-thirds (1.8 V, typically), its switching loss is about 80%, and has a larger reverse bias switching withstand capability. Also, a high-speed diode with excellent soft recovery characteristic was developed using local lifetime control in anode-side n-layer. As a result, a reduction of surge voltage, noise, and switching power loss has been achieved. This paper presents the structures and characteristics of the new IGBT and diode and their analysis results.","PeriodicalId":254764,"journal":{"name":"Proceedings of the IEEE 1999 International Conference on Power Electronics and Drive Systems. PEDS'99 (Cat. No.99TH8475)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125837589","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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