Pub Date : 2012-11-12DOI: 10.1109/ECCE.2012.6342800
J. M. Gálvez, Martin Ordonez, Tuan T. Nguyen, F. Luchino
This paper derives the natural trajectories for buck-boost converters and defines the Natural Switching Surface (NSS) control law to obtain enhanced transient responses. The study performed in the normalized geometrical domain provides understanding of the transient behavior of the converter and generality to the equations. The analytical framework proves that the converter can be operated at the physical limits. As a result, an excellent dynamic response during start-up and large load disturbances is achieved using the resulting Switching Surface (SS), accomplishing steady state in only one switching action. The analysis presented in this paper completes the theory of control using natural trajectories for basic topologies - buck and boost, with the addition of buck-boost. A design procedure, along with experimental results are presented to confirm the benefits of the normalization method and illustrate the qualities of the Natural Switching Surface.
{"title":"Boundary control of buck-boost converters: normalized trajectories and the Natural Switching Surface","authors":"J. M. Gálvez, Martin Ordonez, Tuan T. Nguyen, F. Luchino","doi":"10.1109/ECCE.2012.6342800","DOIUrl":"https://doi.org/10.1109/ECCE.2012.6342800","url":null,"abstract":"This paper derives the natural trajectories for buck-boost converters and defines the Natural Switching Surface (NSS) control law to obtain enhanced transient responses. The study performed in the normalized geometrical domain provides understanding of the transient behavior of the converter and generality to the equations. The analytical framework proves that the converter can be operated at the physical limits. As a result, an excellent dynamic response during start-up and large load disturbances is achieved using the resulting Switching Surface (SS), accomplishing steady state in only one switching action. The analysis presented in this paper completes the theory of control using natural trajectories for basic topologies - buck and boost, with the addition of buck-boost. A design procedure, along with experimental results are presented to confirm the benefits of the normalization method and illustrate the qualities of the Natural Switching Surface.","PeriodicalId":6401,"journal":{"name":"2012 IEEE Energy Conversion Congress and Exposition (ECCE)","volume":"75 1","pages":"358-363"},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87273947","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 : 2012-11-12DOI: 10.1109/ECCE.2012.6342830
A. Gautam, O. Ojo, M. Ramezani, O. Momoh
The nine-phase squirrel-cage induction motor designed for 4-pole operation can also be utilized to operate in 3 phase, 12 pole configuration by rearranging the stator winding connections using the pole phase modulation technique. The 9 phase 4 pole configuration can be used for extended high speed and low torque requirement, whereas the 3 phase, 12 pole arrangement can be utilized for low speed and high torque applications. By switching from one stator winding configuration to another, the nine-phase induction machine can be used for high torque, low speed and extended high speed range and low torque requirements in such applications as the electric vehicle and high speed elevators. In this paper, two comprehensive methods are presented to determine the parameters of the 36 stator slots machine in the two configurations. The parameters calculated using the magnetic circuit analysis and the field analysis using Finite Elements methods are validated by experimental results.
{"title":"Computation of equivalent circuit parameters of nine-phase induction motor in different operating modes","authors":"A. Gautam, O. Ojo, M. Ramezani, O. Momoh","doi":"10.1109/ECCE.2012.6342830","DOIUrl":"https://doi.org/10.1109/ECCE.2012.6342830","url":null,"abstract":"The nine-phase squirrel-cage induction motor designed for 4-pole operation can also be utilized to operate in 3 phase, 12 pole configuration by rearranging the stator winding connections using the pole phase modulation technique. The 9 phase 4 pole configuration can be used for extended high speed and low torque requirement, whereas the 3 phase, 12 pole arrangement can be utilized for low speed and high torque applications. By switching from one stator winding configuration to another, the nine-phase induction machine can be used for high torque, low speed and extended high speed range and low torque requirements in such applications as the electric vehicle and high speed elevators. In this paper, two comprehensive methods are presented to determine the parameters of the 36 stator slots machine in the two configurations. The parameters calculated using the magnetic circuit analysis and the field analysis using Finite Elements methods are validated by experimental results.","PeriodicalId":6401,"journal":{"name":"2012 IEEE Energy Conversion Congress and Exposition (ECCE)","volume":"16 1","pages":"142-149"},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87336540","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 : 2012-11-12DOI: 10.1109/ECCE.2012.6342685
A. Sparacino, B. Grainger, R. Kerestes, G. Reed
Medium Voltage DC (MVDC) infrastructure serves as a platform for interconnecting renewable electric power generation, including wind and solar. Abundant loads such as industrial facilities, data centers, and electric vehicle charging stations (EVCS) can also be powered using MVDC technology. MVDC networks are expected to improve efficiency by serving as an additional layer between the transmission and distribution level voltages for which generation sources and loads could directly connect with smaller rated power conversion equipment. This paper investigates an EVCS powered by a MVDC bus. A bidirectional DC-DC converter with appropriate controls serves as the interface between the EVCS and MVDC bus. Two scenarios are investigated for testing and comparing EVCS operation: 1) EVCS power supplied by the interconnected MVDC model and 2) EVCS power supplied by an equivalent voltage source. Comparisons between both are discussed. The CCM/DCM buck mode operation of the bidirectional DC-DC converter is explored as well as the system isolation benefits that come with its use.
{"title":"Design and simulation of a DC electric vehicle charging station connected to a MVDC infrastructure","authors":"A. Sparacino, B. Grainger, R. Kerestes, G. Reed","doi":"10.1109/ECCE.2012.6342685","DOIUrl":"https://doi.org/10.1109/ECCE.2012.6342685","url":null,"abstract":"Medium Voltage DC (MVDC) infrastructure serves as a platform for interconnecting renewable electric power generation, including wind and solar. Abundant loads such as industrial facilities, data centers, and electric vehicle charging stations (EVCS) can also be powered using MVDC technology. MVDC networks are expected to improve efficiency by serving as an additional layer between the transmission and distribution level voltages for which generation sources and loads could directly connect with smaller rated power conversion equipment. This paper investigates an EVCS powered by a MVDC bus. A bidirectional DC-DC converter with appropriate controls serves as the interface between the EVCS and MVDC bus. Two scenarios are investigated for testing and comparing EVCS operation: 1) EVCS power supplied by the interconnected MVDC model and 2) EVCS power supplied by an equivalent voltage source. Comparisons between both are discussed. The CCM/DCM buck mode operation of the bidirectional DC-DC converter is explored as well as the system isolation benefits that come with its use.","PeriodicalId":6401,"journal":{"name":"2012 IEEE Energy Conversion Congress and Exposition (ECCE)","volume":"53 1","pages":"1168-1175"},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84699575","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 : 2012-11-12DOI: 10.1109/ECCE.2012.6342682
F. Sichirollo, Simone Buso, Giorgio Spiazzi
A high power factor, high efficiency offline driver for LED lighting applications is presented in this paper. Among all the suitable candidate topologies, a multiple stage structure has been chosen, to guarantee the greatest possible flexibility, thanks to the use of optimized topologies both on line side and on load side. Galvanic isolation is provided by means of an intermediate DC transformer stage. A comparison between two different implementations of the latter has been performed in order to better understand advantages and disadvantages of the two proposed topologies and find out an optimal configuration. Despite the presence of multi-stage conversion, a high (>;90%) overall efficiency is achieved. Analytical and experimental results are provided.
{"title":"A high efficiency and high power factor offline converter for solid state street lighting applications","authors":"F. Sichirollo, Simone Buso, Giorgio Spiazzi","doi":"10.1109/ECCE.2012.6342682","DOIUrl":"https://doi.org/10.1109/ECCE.2012.6342682","url":null,"abstract":"A high power factor, high efficiency offline driver for LED lighting applications is presented in this paper. Among all the suitable candidate topologies, a multiple stage structure has been chosen, to guarantee the greatest possible flexibility, thanks to the use of optimized topologies both on line side and on load side. Galvanic isolation is provided by means of an intermediate DC transformer stage. A comparison between two different implementations of the latter has been performed in order to better understand advantages and disadvantages of the two proposed topologies and find out an optimal configuration. Despite the presence of multi-stage conversion, a high (>;90%) overall efficiency is achieved. Analytical and experimental results are provided.","PeriodicalId":6401,"journal":{"name":"2012 IEEE Energy Conversion Congress and Exposition (ECCE)","volume":"25 1","pages":"1188-1195"},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90600458","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 : 2012-11-12DOI: 10.1109/ECCE.2012.6342229
Y. Kano, T. Kosaka, N. Matsui, T. Takahashi, M. Fujistuna
This paper presents the design of concentrated winding IPMSM under the saliency-based sensorless drive using a high-frequency signal injection. The finite element (FE) analysis is used to examine the feasible region of the sensorless drive in consideration of the cross-coupling magnetic saturation and the space harmonics. The reliability of the feasible region is verified by experiment using two prototypes. Then, the influence of the IPM motor geometry on the feasible region is examined. Consequently, the design guideline is established to obtain a suitable motor geometry which can maximize the torque capability and stability of the sensorless drive. Under the restricted specifications of dimensions and requirements, the 100Nm-10kW 12-pole-18slot IPMSM is optimally designed for HEV applications. The validity of the proposed design is verified using the MATLAB/SIMULINK based dynamic simulator.
{"title":"Design of saliency-based sensorless drive IPM motors for hybrid electric vehicles","authors":"Y. Kano, T. Kosaka, N. Matsui, T. Takahashi, M. Fujistuna","doi":"10.1109/ECCE.2012.6342229","DOIUrl":"https://doi.org/10.1109/ECCE.2012.6342229","url":null,"abstract":"This paper presents the design of concentrated winding IPMSM under the saliency-based sensorless drive using a high-frequency signal injection. The finite element (FE) analysis is used to examine the feasible region of the sensorless drive in consideration of the cross-coupling magnetic saturation and the space harmonics. The reliability of the feasible region is verified by experiment using two prototypes. Then, the influence of the IPM motor geometry on the feasible region is examined. Consequently, the design guideline is established to obtain a suitable motor geometry which can maximize the torque capability and stability of the sensorless drive. Under the restricted specifications of dimensions and requirements, the 100Nm-10kW 12-pole-18slot IPMSM is optimally designed for HEV applications. The validity of the proposed design is verified using the MATLAB/SIMULINK based dynamic simulator.","PeriodicalId":6401,"journal":{"name":"2012 IEEE Energy Conversion Congress and Exposition (ECCE)","volume":"47 11 1","pages":"4362-4369"},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80611332","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 : 2012-11-12DOI: 10.1109/ECCE.2012.6342548
Changbyung Park, Sungwoo Lee, G. Cho, Suyong Choi, C. Rim
The IPTS for mobile robots which has the single wire layer of easily fabricable power floor structure and the evenly displaced multi pick-up structure for receiving uniform power is proposed. Due to its simple structure, a wide area power floor of 3.15 m2 (1.5 m × 2.1 m) could be fabricated as a proto type. Three pick-ups with evenly displaced angle and space are adopted considering the limited bottom area of the free moving mobile robot. The size and position of each pickup are optimized for the given sub winding size of the power floor and magnetic pole arrangement. Experiments for the prototype show that the proposed multi pick-up structure lowers the spatial output power variation and that enough output power of 10 W can be obtained for the mobile robots.
{"title":"Omni-directional inductive power transfer system for mobile robots using evenly displaced multiple pick-ups","authors":"Changbyung Park, Sungwoo Lee, G. Cho, Suyong Choi, C. Rim","doi":"10.1109/ECCE.2012.6342548","DOIUrl":"https://doi.org/10.1109/ECCE.2012.6342548","url":null,"abstract":"The IPTS for mobile robots which has the single wire layer of easily fabricable power floor structure and the evenly displaced multi pick-up structure for receiving uniform power is proposed. Due to its simple structure, a wide area power floor of 3.15 m2 (1.5 m × 2.1 m) could be fabricated as a proto type. Three pick-ups with evenly displaced angle and space are adopted considering the limited bottom area of the free moving mobile robot. The size and position of each pickup are optimized for the given sub winding size of the power floor and magnetic pole arrangement. Experiments for the prototype show that the proposed multi pick-up structure lowers the spatial output power variation and that enough output power of 10 W can be obtained for the mobile robots.","PeriodicalId":6401,"journal":{"name":"2012 IEEE Energy Conversion Congress and Exposition (ECCE)","volume":"9 1","pages":"2492-2497"},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87027168","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 : 2012-11-12DOI: 10.1109/ECCE.2012.6342714
Cheng Jin, M. Gao, X. Lv, Min Chen
In this paper, the structure and control method of microgrid in both islanded mode and grid-connected mode are presented. And a seamless transfer strategy for droop controlled distributed generations from islanded mode to grid-connected mode is proposed. This transfer strategy is based on droop method and consisted of frequency synchronization and phase synchronization. It could avoid a frequency and phase oscillation, and do not have an effect on the power sharing of droop control. After synchronizations the bypass switch closes at a zero-crossing of voltage, and at the same time the control mode charges from the voltage sources based on droop control to current sources. Simulation results are presented to show the performance and feasibility of this proposed strategy.
{"title":"A seamless transfer strategy of islanded and grid-connected mode switching for microgrid based on droop control","authors":"Cheng Jin, M. Gao, X. Lv, Min Chen","doi":"10.1109/ECCE.2012.6342714","DOIUrl":"https://doi.org/10.1109/ECCE.2012.6342714","url":null,"abstract":"In this paper, the structure and control method of microgrid in both islanded mode and grid-connected mode are presented. And a seamless transfer strategy for droop controlled distributed generations from islanded mode to grid-connected mode is proposed. This transfer strategy is based on droop method and consisted of frequency synchronization and phase synchronization. It could avoid a frequency and phase oscillation, and do not have an effect on the power sharing of droop control. After synchronizations the bypass switch closes at a zero-crossing of voltage, and at the same time the control mode charges from the voltage sources based on droop control to current sources. Simulation results are presented to show the performance and feasibility of this proposed strategy.","PeriodicalId":6401,"journal":{"name":"2012 IEEE Energy Conversion Congress and Exposition (ECCE)","volume":"11 1","pages":"969-973"},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81995589","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 : 2012-11-12DOI: 10.1109/ECCE.2012.6342354
T. Nguyen, Dong-Choon Lee
This paper suggests an operation and control strategy of an offshore wind farm based on a high-voltage DC (HVDC) transmission, where the variable-speed permanent-magnet synchronous generator (PMSG) wind turbine system is adopted. The HVDC transmission system consists of a hybrid of a twelve-pulse diode rectifier and a voltage-source converter (VSC) on offshore side, whereas a VSC is employed on AC grid side (GSVSC). For this topology, the twelve-pulse diode rectifier is capable of delivering a part of wind farm power, the rest of which is absorbed naturally by the wind farm VSC (WFVSC) since the WFVSC is controlled and operated as a voltage source of a constant frequency. At grid sags, a low-voltage ride-through of HVDC transmission is achieved, in which the HVDC link voltage is controlled by the WFVSC, and the wind farm output power is reduced by increasing the generator speeds. By utilizing the uncontrolled rectifier, a cost of HVDC converter is reduced compared with a case of the fully rated VSC, while the performance is the same. PSCAD/EMTDC simulation results for a 500-MW offshore wind farm have been shown to verify the validity of the proposed scheme.
{"title":"Control of offshore wind farms based on HVDC","authors":"T. Nguyen, Dong-Choon Lee","doi":"10.1109/ECCE.2012.6342354","DOIUrl":"https://doi.org/10.1109/ECCE.2012.6342354","url":null,"abstract":"This paper suggests an operation and control strategy of an offshore wind farm based on a high-voltage DC (HVDC) transmission, where the variable-speed permanent-magnet synchronous generator (PMSG) wind turbine system is adopted. The HVDC transmission system consists of a hybrid of a twelve-pulse diode rectifier and a voltage-source converter (VSC) on offshore side, whereas a VSC is employed on AC grid side (GSVSC). For this topology, the twelve-pulse diode rectifier is capable of delivering a part of wind farm power, the rest of which is absorbed naturally by the wind farm VSC (WFVSC) since the WFVSC is controlled and operated as a voltage source of a constant frequency. At grid sags, a low-voltage ride-through of HVDC transmission is achieved, in which the HVDC link voltage is controlled by the WFVSC, and the wind farm output power is reduced by increasing the generator speeds. By utilizing the uncontrolled rectifier, a cost of HVDC converter is reduced compared with a case of the fully rated VSC, while the performance is the same. PSCAD/EMTDC simulation results for a 500-MW offshore wind farm have been shown to verify the validity of the proposed scheme.","PeriodicalId":6401,"journal":{"name":"2012 IEEE Energy Conversion Congress and Exposition (ECCE)","volume":"19 1","pages":"3113-3118"},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85348147","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 : 2012-11-12DOI: 10.1109/ECCE.2012.6342273
D. Paschedag, M. Ferdowsi
The focus of this paper is on zero-crossing current distortion that commonly occurs in active power factor correction (PFC) circuits. Initially, it derives several equations which quantify the zero-crossing error. Then it proposes a new switching scheme which drastically mitigates the problem. Finally, it shows the effectiveness of the proposed method using simulation results. An H-bridge PFC topology is used.
{"title":"Elimination of zero-crossing distortion in a power factor correction circuit","authors":"D. Paschedag, M. Ferdowsi","doi":"10.1109/ECCE.2012.6342273","DOIUrl":"https://doi.org/10.1109/ECCE.2012.6342273","url":null,"abstract":"The focus of this paper is on zero-crossing current distortion that commonly occurs in active power factor correction (PFC) circuits. Initially, it derives several equations which quantify the zero-crossing error. Then it proposes a new switching scheme which drastically mitigates the problem. Finally, it shows the effectiveness of the proposed method using simulation results. An H-bridge PFC topology is used.","PeriodicalId":6401,"journal":{"name":"2012 IEEE Energy Conversion Congress and Exposition (ECCE)","volume":"35 1","pages":"4049-4052"},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86591831","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 : 2012-11-12DOI: 10.1109/ECCE.2012.6342238
Ming Li, C. Tse
Based on the time-domain decomposition of small-signal model in paralleled buck converters, two equivalent low-order loop gains, namely, common-mode and differential-mode loop gains, are derived to analyze and design the stability of the system with N converter modules. Specifically, the proposed loop gains are applied to two voltage-mode controlled buck converters under active current-sharing control. Experimental verification is performed to validate the effectiveness of the proposed loop gains on locating the stability boundary of design parameters.
{"title":"Common-mode and differential-mode loop gains of paralleled buck converters","authors":"Ming Li, C. Tse","doi":"10.1109/ECCE.2012.6342238","DOIUrl":"https://doi.org/10.1109/ECCE.2012.6342238","url":null,"abstract":"Based on the time-domain decomposition of small-signal model in paralleled buck converters, two equivalent low-order loop gains, namely, common-mode and differential-mode loop gains, are derived to analyze and design the stability of the system with N converter modules. Specifically, the proposed loop gains are applied to two voltage-mode controlled buck converters under active current-sharing control. Experimental verification is performed to validate the effectiveness of the proposed loop gains on locating the stability boundary of design parameters.","PeriodicalId":6401,"journal":{"name":"2012 IEEE Energy Conversion Congress and Exposition (ECCE)","volume":"69 1","pages":"4295-4300"},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90670502","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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