This paper proposes a control strategy which extends the virtual-flux direct power control traditionally employed for the conventional two-level VSI to a three-level NPC inverter. This topology generates a higher number of output voltage levels, increasing the flexibility for selecting an appropriate voltage vector. The mid-point potential is controlled according to the direction of the mid-point current and the sign of the mid-point voltage deviation. The method is adapted to be used with an LCL output filter, where some undesirable characteristics, such as filter resonance, have to be compensated. Further investigation concerning the dependency of the mid-point voltage with the current phase-shift is given. Theoretical analysis is presented and the performance of the proposed method is verified by simulation.
{"title":"Virtual-Flux Direct Power Control for Mains Connected Three-Level NPC Inverter Systems","authors":"L. Serpa, J. Kolar","doi":"10.1541/IEEJIAS.128.491","DOIUrl":"https://doi.org/10.1541/IEEJIAS.128.491","url":null,"abstract":"This paper proposes a control strategy which extends the virtual-flux direct power control traditionally employed for the conventional two-level VSI to a three-level NPC inverter. This topology generates a higher number of output voltage levels, increasing the flexibility for selecting an appropriate voltage vector. The mid-point potential is controlled according to the direction of the mid-point current and the sign of the mid-point voltage deviation. The method is adapted to be used with an LCL output filter, where some undesirable characteristics, such as filter resonance, have to be compensated. Further investigation concerning the dependency of the mid-point voltage with the current phase-shift is given. Theoretical analysis is presented and the performance of the proposed method is verified by simulation.","PeriodicalId":325362,"journal":{"name":"2007 Power Conversion Conference - Nagoya","volume":"42 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115093614","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 : 2007-04-02DOI: 10.1109/PCCON.2007.373000
A. Srisawang, N. Boonpirom, Y. Prempraneerach, S. Nitta
This paper presents the analytical and experimental consideration of the common-mode noise generation in a single-switch (buck) converter comparison to a four-switch (full-bridge) converter by the viewpoint of circuit imbalance. The mechanism of the common-mode current (noise) generation in the buck converter and full-bridge converter can be explained by equivalent circuit of unbalanced model. Common-mode noise generation due to the effect of circuit imbalance of the buck and full-bridge converter is clarified by the experimental results.
{"title":"Analysis of Common-Mode Noise Generation in Single-Switch Converter Comparison With Four-Switch Converter Using Unbalanced Circuit Model","authors":"A. Srisawang, N. Boonpirom, Y. Prempraneerach, S. Nitta","doi":"10.1109/PCCON.2007.373000","DOIUrl":"https://doi.org/10.1109/PCCON.2007.373000","url":null,"abstract":"This paper presents the analytical and experimental consideration of the common-mode noise generation in a single-switch (buck) converter comparison to a four-switch (full-bridge) converter by the viewpoint of circuit imbalance. The mechanism of the common-mode current (noise) generation in the buck converter and full-bridge converter can be explained by equivalent circuit of unbalanced model. Common-mode noise generation due to the effect of circuit imbalance of the buck and full-bridge converter is clarified by the experimental results.","PeriodicalId":325362,"journal":{"name":"2007 Power Conversion Conference - Nagoya","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115662188","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}
In this paper, a forced air-cooled, 400 kHz, 10 kW Vienna rectifier with a power density of 8.5 kW/liter is presented. To further improve the power density, the switching frequency is increased to reduce the EMI filter volume. A design for an 18.5 kW/liter, 2.5 MHz rectifier is proposed. By using today's technology, it is calculated that the maximum power density for a forced air-cooled and water-cooled rectifier is 20.8 kW/liter and 24 kW/liter respectively. To achieve 30 kW/liter, improvements must be made in passive component material properties, reducing semiconductor losses and improving the cooling system.
{"title":"Towards a 30 kW/liter, Three-Phase Unity Power Factor Rectifier","authors":"S. Round, P. Karutz, M. Heldwein, J. Kolar","doi":"10.1541/IEEJIAS.128.481","DOIUrl":"https://doi.org/10.1541/IEEJIAS.128.481","url":null,"abstract":"In this paper, a forced air-cooled, 400 kHz, 10 kW Vienna rectifier with a power density of 8.5 kW/liter is presented. To further improve the power density, the switching frequency is increased to reduce the EMI filter volume. A design for an 18.5 kW/liter, 2.5 MHz rectifier is proposed. By using today's technology, it is calculated that the maximum power density for a forced air-cooled and water-cooled rectifier is 20.8 kW/liter and 24 kW/liter respectively. To achieve 30 kW/liter, improvements must be made in passive component material properties, reducing semiconductor losses and improving the cooling system.","PeriodicalId":325362,"journal":{"name":"2007 Power Conversion Conference - Nagoya","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125230121","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 : 2007-04-02DOI: 10.1109/PCCON.2007.373090
K. Miyagi, H. Takaya, H. Saito, K. Hamada
This paper proposes a new structure for the power MOSFET called FITMOStrade, which is capable of realizing an ultra-low on-resistance that exceeds the unipolar limit in the automotive breakdown voltage range (50 to 100 V). In the past, FITMOS was developed for use as a 60 V breakdown voltage element. However, the demand for high-output devices for vehicle system applications has been growing in recent years, and a high breakdown voltage element is needed to meet this demand. The authors therefore utilized an efficient design of experiment, the D-optimal design, in an attempt to simultaneously optimize the complexly linked multiple characteristics and factors of FITMOS. As a result, the authors verified conditions for obtaining characteristics for excellent breakdown voltage (BVds = 74.0 V), on-resistance (RonmiddotA = 36.4 mOmegamm2 @ Vg = 15 V, excluding substrate resistance), and threshold voltage (Vth = 3.0 V).
{"title":"Floating Island and Thick Bottom Oxide Trench Gate MOSFET (FITMOS) Ultra-Low On-Resistance Power MOSFET for Automotive Applications","authors":"K. Miyagi, H. Takaya, H. Saito, K. Hamada","doi":"10.1109/PCCON.2007.373090","DOIUrl":"https://doi.org/10.1109/PCCON.2007.373090","url":null,"abstract":"This paper proposes a new structure for the power MOSFET called FITMOStrade, which is capable of realizing an ultra-low on-resistance that exceeds the unipolar limit in the automotive breakdown voltage range (50 to 100 V). In the past, FITMOS was developed for use as a 60 V breakdown voltage element. However, the demand for high-output devices for vehicle system applications has been growing in recent years, and a high breakdown voltage element is needed to meet this demand. The authors therefore utilized an efficient design of experiment, the D-optimal design, in an attempt to simultaneously optimize the complexly linked multiple characteristics and factors of FITMOS. As a result, the authors verified conditions for obtaining characteristics for excellent breakdown voltage (BVds = 74.0 V), on-resistance (RonmiddotA = 36.4 mOmegamm2 @ Vg = 15 V, excluding substrate resistance), and threshold voltage (Vth = 3.0 V).","PeriodicalId":325362,"journal":{"name":"2007 Power Conversion Conference - Nagoya","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116934127","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 : 2007-04-02DOI: 10.1109/PCCON.2007.373074
K. Itoh, Y. Moriura, T. Satoh, K. Arimatsu, N. Nakayama, K. Kimoto, T. Doizaki, K. Dojoh
In the field of a hot strip mill facility of steel industry, there are needs of large power induction-heating equipment for energy saving and improvement of a product quality. We have delivered the 9,000 kW-1,500 Hz frequency converters for induction-heater, the largest in the world. We applied the series connection technology and the parallel connection technology of the thyristor to realize a high-power and high-frequency inverter. The analog-digital hybrid control has been developed to respond the flexible and fast acting control. The developed converter has been delivered to several factories and continues to operate. And more very large inverters up to around 23000 kW have been also realized by paralleling the 9000 kW converters.
{"title":"9000 kW-1500Hz Frequency Converter for Hot Bar Heater","authors":"K. Itoh, Y. Moriura, T. Satoh, K. Arimatsu, N. Nakayama, K. Kimoto, T. Doizaki, K. Dojoh","doi":"10.1109/PCCON.2007.373074","DOIUrl":"https://doi.org/10.1109/PCCON.2007.373074","url":null,"abstract":"In the field of a hot strip mill facility of steel industry, there are needs of large power induction-heating equipment for energy saving and improvement of a product quality. We have delivered the 9,000 kW-1,500 Hz frequency converters for induction-heater, the largest in the world. We applied the series connection technology and the parallel connection technology of the thyristor to realize a high-power and high-frequency inverter. The analog-digital hybrid control has been developed to respond the flexible and fast acting control. The developed converter has been delivered to several factories and continues to operate. And more very large inverters up to around 23000 kW have been also realized by paralleling the 9000 kW converters.","PeriodicalId":325362,"journal":{"name":"2007 Power Conversion Conference - Nagoya","volume":"35 1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123467983","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 : 2007-04-02DOI: 10.1109/PCCON.2007.372995
M. Hoshi, T. Hayashi, H. Tanaka, S. Yamagami
We have developed novel SIC devices, both a diode and a transistor, utilizing a Si/4H-SiC heteroj unction. A heterojunction diode (HJD) was fabricated with P+ polycrystalline silicon on an N- epitaxial layer of 4H-SiC. The HJD achieved lower Von and higher reverse blocking voltage than a commercial Schottky barrier diode (SBD) of SiC. Switching charcteristics of the HJD indicated almost zero reverse recovery similar to that of a SBD. A hetero junction tunneling transistor (HETT) was driven by an insulated gate electrode. The width of the heterojunction barrier was controlled by the gate bias to allow tunneling current to flow. The HETT was fabricated with N+ polycrystalline silicon on an N- 4H-SiC epitaxial layer. The channnel length of the HETT was almost zero and was expected to have low on-resistance.
{"title":"Novel SiC Power Devices utilizing a Si/4H-SiC Heterojunction","authors":"M. Hoshi, T. Hayashi, H. Tanaka, S. Yamagami","doi":"10.1109/PCCON.2007.372995","DOIUrl":"https://doi.org/10.1109/PCCON.2007.372995","url":null,"abstract":"We have developed novel SIC devices, both a diode and a transistor, utilizing a Si/4H-SiC heteroj unction. A heterojunction diode (HJD) was fabricated with P+ polycrystalline silicon on an N- epitaxial layer of 4H-SiC. The HJD achieved lower Von and higher reverse blocking voltage than a commercial Schottky barrier diode (SBD) of SiC. Switching charcteristics of the HJD indicated almost zero reverse recovery similar to that of a SBD. A hetero junction tunneling transistor (HETT) was driven by an insulated gate electrode. The width of the heterojunction barrier was controlled by the gate bias to allow tunneling current to flow. The HETT was fabricated with N+ polycrystalline silicon on an N- 4H-SiC epitaxial layer. The channnel length of the HETT was almost zero and was expected to have low on-resistance.","PeriodicalId":325362,"journal":{"name":"2007 Power Conversion Conference - Nagoya","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125365173","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 : 2007-04-02DOI: 10.1109/PCCON.2007.372997
Shen-Yuan Kuo, Tzung-Lin Lee, Chien-An Chen, Po-tai Cheng, C. Pan
Significant harmonics amplification in industry facilities has been reported. This phenomenon is identified as harmonic resonance between power factor correction capacitor banks and system inductors. Conventional active filter techniques aimed at harmonic current compensation are not effective under this resonance situation. This paper proposes a distributed active filter design for harmonics damping within industry facility. In this system, the active filter operates as a harmonic conductance with a droop characteristic. A droop control bewteen the harmonic volt-ampere reactive consumption of the active filter and its harmonic conductance is developed to coordinate the operation among individual active filters, so that each unit can share harmonic filtering workload in proportion to the rated capacity without any communications. Simulation results of a typical industry facility is implemented in this paper, and harmonic filtering performances discussed in detail. Laboratory prototype is conducted to valid the effectiveness of the proposed approach.
{"title":"Distributed Active Filters for Harmonic Resonance Suppression in Industrial Facilities","authors":"Shen-Yuan Kuo, Tzung-Lin Lee, Chien-An Chen, Po-tai Cheng, C. Pan","doi":"10.1109/PCCON.2007.372997","DOIUrl":"https://doi.org/10.1109/PCCON.2007.372997","url":null,"abstract":"Significant harmonics amplification in industry facilities has been reported. This phenomenon is identified as harmonic resonance between power factor correction capacitor banks and system inductors. Conventional active filter techniques aimed at harmonic current compensation are not effective under this resonance situation. This paper proposes a distributed active filter design for harmonics damping within industry facility. In this system, the active filter operates as a harmonic conductance with a droop characteristic. A droop control bewteen the harmonic volt-ampere reactive consumption of the active filter and its harmonic conductance is developed to coordinate the operation among individual active filters, so that each unit can share harmonic filtering workload in proportion to the rated capacity without any communications. Simulation results of a typical industry facility is implemented in this paper, and harmonic filtering performances discussed in detail. Laboratory prototype is conducted to valid the effectiveness of the proposed approach.","PeriodicalId":325362,"journal":{"name":"2007 Power Conversion Conference - Nagoya","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115246639","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 : 2007-04-02DOI: 10.1109/PCCON.2007.373008
J. Lai, Sung-Yeul Park, Seungryul Moon, Chien-Liang Chen
This paper presents a high-efficiency power conditioning system design that employs a soft-switched dc-dc converter and a soft-switched dc-ac inverter for a low-voltage 26-V, 5-kW solid oxide fuel cell. The dc-dc converter converts fuel cell voltage to a 400-V dc bus voltage using a 3-phase 6-leg phase-shift modulated converter to achieve higher than 96% peak efficiency with zero-voltage zero-current switching. The dc-ac inverter then produces 120/240V ac using a CoolMOS based soft-switching inverter to achieve 98% peak efficiency. The inverter output is universal for both standalone and grid-tie modes operation. The standalone load comes out of two sets of LC filter with a neutral line for equal voltage splits. For grid-tie mode, a circuit breaker needs to turn on, and an additional inductor is included for grid current ripple reduction. Test results indicated that peak efficiency of 94% is achieved for the two-stage power conversion PCS. In addition to high efficiency design, this paper also introduces advanced controls including fuel cell current ripple reduction using a current loop in the dc-dc converter and ac output current steady-state error reduction using an admittance compensation technique in the dc-ac inverter.
{"title":"A High-Efficiency 5-kW Soft-Switched Power Conditioning System for Low-Voltage Solid Oxide Fuel Cells","authors":"J. Lai, Sung-Yeul Park, Seungryul Moon, Chien-Liang Chen","doi":"10.1109/PCCON.2007.373008","DOIUrl":"https://doi.org/10.1109/PCCON.2007.373008","url":null,"abstract":"This paper presents a high-efficiency power conditioning system design that employs a soft-switched dc-dc converter and a soft-switched dc-ac inverter for a low-voltage 26-V, 5-kW solid oxide fuel cell. The dc-dc converter converts fuel cell voltage to a 400-V dc bus voltage using a 3-phase 6-leg phase-shift modulated converter to achieve higher than 96% peak efficiency with zero-voltage zero-current switching. The dc-ac inverter then produces 120/240V ac using a CoolMOS based soft-switching inverter to achieve 98% peak efficiency. The inverter output is universal for both standalone and grid-tie modes operation. The standalone load comes out of two sets of LC filter with a neutral line for equal voltage splits. For grid-tie mode, a circuit breaker needs to turn on, and an additional inductor is included for grid current ripple reduction. Test results indicated that peak efficiency of 94% is achieved for the two-stage power conversion PCS. In addition to high efficiency design, this paper also introduces advanced controls including fuel cell current ripple reduction using a current loop in the dc-dc converter and ac output current steady-state error reduction using an admittance compensation technique in the dc-ac inverter.","PeriodicalId":325362,"journal":{"name":"2007 Power Conversion Conference - Nagoya","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115524178","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 : 2007-04-02DOI: 10.1109/PCCON.2007.373108
T. Sato, T. Nabeshima, K. Nishijima, T. Nakano
A multi-phase dc-to-dc converter controlled by hysteretic PWM method is presented in this paper. An and-gated logic circuit is employed for the synchronization and its operating principle is described. A 5 V to 1.5 V prototype buck converter of two-phase is implemented for a POL power supply. From the experiments, it is confirmed that the proposed method can be well synchronized, and an excellent dynamic performance is archived for the large load current transients. In addition, improved power efficiency and a good current sharing characteristic is derived.
{"title":"Multi-Phase Converter Controlled by Hysteretic PWM Method","authors":"T. Sato, T. Nabeshima, K. Nishijima, T. Nakano","doi":"10.1109/PCCON.2007.373108","DOIUrl":"https://doi.org/10.1109/PCCON.2007.373108","url":null,"abstract":"A multi-phase dc-to-dc converter controlled by hysteretic PWM method is presented in this paper. An and-gated logic circuit is employed for the synchronization and its operating principle is described. A 5 V to 1.5 V prototype buck converter of two-phase is implemented for a POL power supply. From the experiments, it is confirmed that the proposed method can be well synchronized, and an excellent dynamic performance is archived for the large load current transients. In addition, improved power efficiency and a good current sharing characteristic is derived.","PeriodicalId":325362,"journal":{"name":"2007 Power Conversion Conference - Nagoya","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122971528","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 : 2007-04-02DOI: 10.1109/PCCON.2007.372911
Z.Q. Zhu
Halbach magnetised PM brushless machines are novel in that their magnetisation is self-shielding. They offer many attractive features, such as sinusoidal airgap field distribution and back-emf waveform, negligible cogging torque, potentially high airgap flux density and no need of rotor back-iron. Hence, they have recently attracted many research and development interests and extensive exploitation for their applications. This paper starts with a brief introduction of Halbach machines and compares the relative merits of ideal and segmented Halbach machines, as well as shaped magnet machines. It then describes various recent applications which exploit their novel features, ranging from automotive, aerospace, industrial servo, to domestic appliances. Finally, it reports an integrated design of sensorless high-speed Halbach motors.
{"title":"Recent Development of Halbach Permanent Magnet Machines and Applications","authors":"Z.Q. Zhu","doi":"10.1109/PCCON.2007.372911","DOIUrl":"https://doi.org/10.1109/PCCON.2007.372911","url":null,"abstract":"Halbach magnetised PM brushless machines are novel in that their magnetisation is self-shielding. They offer many attractive features, such as sinusoidal airgap field distribution and back-emf waveform, negligible cogging torque, potentially high airgap flux density and no need of rotor back-iron. Hence, they have recently attracted many research and development interests and extensive exploitation for their applications. This paper starts with a brief introduction of Halbach machines and compares the relative merits of ideal and segmented Halbach machines, as well as shaped magnet machines. It then describes various recent applications which exploit their novel features, ranging from automotive, aerospace, industrial servo, to domestic appliances. Finally, it reports an integrated design of sensorless high-speed Halbach motors.","PeriodicalId":325362,"journal":{"name":"2007 Power Conversion Conference - Nagoya","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128649077","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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