Based on the abnormal change of capacitor voltage caused by the fault of modular multilevel converter (MMC) sub-module (SM) switching device, a fast fault detection and diagnosis method is proposed in this paper. To enable effective consistency evaluation of numerous SM voltages, the density-based spatial clustering of applications with noise (DBSCAN) algorithm, which is an ideal analyzing method for the clustering analysis of big data, is applied to SM failure diagnosis in this paper. The DBSCAN is used to analyze the capacitor voltages of all sub-modules in the bridge arm, so as to realize the rapid detection and location of faulty SMs at the same time. The proposed method can be applied to any fault types of faults, including single fault, multiple faults in the same bridge arm, and multiple faults in different bridge arms. This method is not affected by the uncertainty of system parameters, and at the same time, has stronger applicability and faster diagnostic rate than the traditional methods. Experimental results demonstrate the validity of the proposed diagnosis strategy.
{"title":"Clustering algorithm based open-circuit failures diagnosis for modular multilevel converters","authors":"Z. Liu, L. Lin, T. Yin, Y. Huang","doi":"10.1049/icp.2021.2558","DOIUrl":"https://doi.org/10.1049/icp.2021.2558","url":null,"abstract":"Based on the abnormal change of capacitor voltage caused by the fault of modular multilevel converter (MMC) sub-module (SM) switching device, a fast fault detection and diagnosis method is proposed in this paper. To enable effective consistency evaluation of numerous SM voltages, the density-based spatial clustering of applications with noise (DBSCAN) algorithm, which is an ideal analyzing method for the clustering analysis of big data, is applied to SM failure diagnosis in this paper. The DBSCAN is used to analyze the capacitor voltages of all sub-modules in the bridge arm, so as to realize the rapid detection and location of faulty SMs at the same time. The proposed method can be applied to any fault types of faults, including single fault, multiple faults in the same bridge arm, and multiple faults in different bridge arms. This method is not affected by the uncertainty of system parameters, and at the same time, has stronger applicability and faster diagnostic rate than the traditional methods. Experimental results demonstrate the validity of the proposed diagnosis strategy.","PeriodicalId":242596,"journal":{"name":"2021 Annual Meeting of CSEE Study Committee of HVDC and Power Electronics (HVDC 2021)","volume":"2021 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130428386","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}
Grid-tied inverters have been widely adopted in distributed generation systems. The output current distortion and oscillation occur under certain conditions especially in the weak grid and multi-parallel inverters. To maintain the stability and ensure the dynamic and steady performance of current tracking, the controller parameters required iterative design and evaluation. Taking single phase inverter as an example, traditional design approaches are discussed first. Then, considering the difficulties in the parameter design process, deep reinforcement learning (DRL) is introduced to explore the optimal combination of controller parameters, by which the parameters of controllers can be automatically tuned. The realization of the DRL approach is discussed in detail and simulation validates the correctness of the attempt.
{"title":"Parameter design of grid-tied inverter using reinforcement learning","authors":"Z. Wang, W. Wang","doi":"10.1049/icp.2021.2547","DOIUrl":"https://doi.org/10.1049/icp.2021.2547","url":null,"abstract":"Grid-tied inverters have been widely adopted in distributed generation systems. The output current distortion and oscillation occur under certain conditions especially in the weak grid and multi-parallel inverters. To maintain the stability and ensure the dynamic and steady performance of current tracking, the controller parameters required iterative design and evaluation. Taking single phase inverter as an example, traditional design approaches are discussed first. Then, considering the difficulties in the parameter design process, deep reinforcement learning (DRL) is introduced to explore the optimal combination of controller parameters, by which the parameters of controllers can be automatically tuned. The realization of the DRL approach is discussed in detail and simulation validates the correctness of the attempt.","PeriodicalId":242596,"journal":{"name":"2021 Annual Meeting of CSEE Study Committee of HVDC and Power Electronics (HVDC 2021)","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129938774","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}
The Back-to-Back HVDC transmission system (BtB) based on modular multilevel converter (MMC), can realize the asynchronous (frequency or phase is not synchronized) interconnection of two regional power grids., and it can effectively solve the power grid security and stability problems caused by power transfer. However, the rectifier and inverter equipment of BtB are directly connected by smoothing reactors, making the electrical connection between devices closer. Therefore, fault interaction would be transmitted between the AC systems and the DC side of BtB. The paper first introduces the mathematical model and conventional control strategies of the system. Next, the transient characteristics of the AC and DC system under the asymmetric AC fault are analysed emphatically. Finally, the negative-sequence voltage feedforward compensator and DC voltage limiter are designed to improve the AC fault ride-through capability of the system. Finally, the effectiveness of proposed fault ride-through strategies is verified through PSCAD/EMTDC.
{"title":"Study on AC fault ride-through of a MMC back-to-back HVDC system","authors":"L. Quan","doi":"10.1049/icp.2021.2569","DOIUrl":"https://doi.org/10.1049/icp.2021.2569","url":null,"abstract":"The Back-to-Back HVDC transmission system (BtB) based on modular multilevel converter (MMC), can realize the asynchronous (frequency or phase is not synchronized) interconnection of two regional power grids., and it can effectively solve the power grid security and stability problems caused by power transfer. However, the rectifier and inverter equipment of BtB are directly connected by smoothing reactors, making the electrical connection between devices closer. Therefore, fault interaction would be transmitted between the AC systems and the DC side of BtB. The paper first introduces the mathematical model and conventional control strategies of the system. Next, the transient characteristics of the AC and DC system under the asymmetric AC fault are analysed emphatically. Finally, the negative-sequence voltage feedforward compensator and DC voltage limiter are designed to improve the AC fault ride-through capability of the system. Finally, the effectiveness of proposed fault ride-through strategies is verified through PSCAD/EMTDC.","PeriodicalId":242596,"journal":{"name":"2021 Annual Meeting of CSEE Study Committee of HVDC and Power Electronics (HVDC 2021)","volume":"2021 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129220591","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}
Multi-port power electronic transformer is the core equipment of AC/DC hybrid power grid and active distribution network. However, there are a large number of internal modules, including a large number of capacitors, high-frequency isolation transformers and other equipment, and the production cost is high. In response to its light weight requirement in engineering applications, this paper proposes a module multiplexing power electronic transformer (MM-PET). By dividing phase unit into upper, common and lower arms, and switching the arm multiplexing state via two arm switches, a quarter of the number of modules can be saved. The carrier phase shifted -nearest level segmented joint modulation strategy (CPS-NLM) and module capacitor voltage equalization strategy are designed to match the multiplexing topology. The simulation results based on PSCAD/EMTDC show that MM-PET can successfully complete capacitor voltage balancing and voltage conversion in the upper arm multiplexing mode and lower arm multiplexing mode respectively, effectively achieving the goal of lightweight.
{"title":"Topology and control strategy of module multiplexing power electronic transformer","authors":"A. Wang, S. Yuan, M. Feng, J. Xu, X. Jia, C. Zhao","doi":"10.1049/icp.2021.2579","DOIUrl":"https://doi.org/10.1049/icp.2021.2579","url":null,"abstract":"Multi-port power electronic transformer is the core equipment of AC/DC hybrid power grid and active distribution network. However, there are a large number of internal modules, including a large number of capacitors, high-frequency isolation transformers and other equipment, and the production cost is high. In response to its light weight requirement in engineering applications, this paper proposes a module multiplexing power electronic transformer (MM-PET). By dividing phase unit into upper, common and lower arms, and switching the arm multiplexing state via two arm switches, a quarter of the number of modules can be saved. The carrier phase shifted -nearest level segmented joint modulation strategy (CPS-NLM) and module capacitor voltage equalization strategy are designed to match the multiplexing topology. The simulation results based on PSCAD/EMTDC show that MM-PET can successfully complete capacitor voltage balancing and voltage conversion in the upper arm multiplexing mode and lower arm multiplexing mode respectively, effectively achieving the goal of lightweight.","PeriodicalId":242596,"journal":{"name":"2021 Annual Meeting of CSEE Study Committee of HVDC and Power Electronics (HVDC 2021)","volume":"53 5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122238310","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}
Power flow analysis is the basis for planning, design and optimized operation of Hybrid AC/DC microgrids. Aiming at the impact of the introduction of power electronic transformers on the power flow distribution of the Hybrid AC/DC microgrid, this paper will carry out the power flow analysis of the Hybrid AC/DC microgrid based on the power electronic transformer. First, the topology of the Hybrid AC/DC microgrid based on power electronic transformer is proposed, and the configuration of the source, load, and storage of the microgrid is given. Next, an equivalent model for power flow analysis of Hybrid AC/DC microgrid is established in Simulink. Finally, the power flow analysis of AC and DC hybrid microgrid with and without power electronic transformers is carried out respectively. The simulation results show that the power electronic transformer can make the Hybrid AC/DC microgrid fully consume new energy, and effectively realize the optimized and coordinated operation of source, grid, load, and storage.
{"title":"Power flow analysis of hybrid AC/DC microgrid based on power electronic transformer","authors":"Y. Chen, Q. Peng, B. Ouyang, B. Tian","doi":"10.1049/icp.2021.2540","DOIUrl":"https://doi.org/10.1049/icp.2021.2540","url":null,"abstract":"Power flow analysis is the basis for planning, design and optimized operation of Hybrid AC/DC microgrids. Aiming at the impact of the introduction of power electronic transformers on the power flow distribution of the Hybrid AC/DC microgrid, this paper will carry out the power flow analysis of the Hybrid AC/DC microgrid based on the power electronic transformer. First, the topology of the Hybrid AC/DC microgrid based on power electronic transformer is proposed, and the configuration of the source, load, and storage of the microgrid is given. Next, an equivalent model for power flow analysis of Hybrid AC/DC microgrid is established in Simulink. Finally, the power flow analysis of AC and DC hybrid microgrid with and without power electronic transformers is carried out respectively. The simulation results show that the power electronic transformer can make the Hybrid AC/DC microgrid fully consume new energy, and effectively realize the optimized and coordinated operation of source, grid, load, and storage.","PeriodicalId":242596,"journal":{"name":"2021 Annual Meeting of CSEE Study Committee of HVDC and Power Electronics (HVDC 2021)","volume":"144 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122003051","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}
Aiming at the startup control issue of doubly-fed induction generator (DFIG), the startup control method of DFIG is analyzed. Based on the mathematical model of DFIG, The equivalent circuit of the grid side converter (GSC) in the uncontrolled startup period is established, and the constant dc voltage control of the GSC in the controlled startup period is obtained, realizing the startup control goal of stable dc voltage in the GSC; then the startup control strategy of the rotor side converter (RSC) is put forward, and the startup control goal of the stator winding without impulses is realized. Finally, based on MATLAB/Simulink, the simulation model of DFIG is built, and the startup process of DFIG is simulated, verifying the effectiveness of the startup control method.
{"title":"Research on the startup control method of doubly-fed induction generator","authors":"F. Shiwen, Z. Xiangyang, H. Guoqing, L. Zhen","doi":"10.1049/icp.2021.2549","DOIUrl":"https://doi.org/10.1049/icp.2021.2549","url":null,"abstract":"Aiming at the startup control issue of doubly-fed induction generator (DFIG), the startup control method of DFIG is analyzed. Based on the mathematical model of DFIG, The equivalent circuit of the grid side converter (GSC) in the uncontrolled startup period is established, and the constant dc voltage control of the GSC in the controlled startup period is obtained, realizing the startup control goal of stable dc voltage in the GSC; then the startup control strategy of the rotor side converter (RSC) is put forward, and the startup control goal of the stator winding without impulses is realized. Finally, based on MATLAB/Simulink, the simulation model of DFIG is built, and the startup process of DFIG is simulated, verifying the effectiveness of the startup control method.","PeriodicalId":242596,"journal":{"name":"2021 Annual Meeting of CSEE Study Committee of HVDC and Power Electronics (HVDC 2021)","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131532704","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}
J. Zhang, Y. Han, X. Luo, J. Deng, J. Zhang, Y. Meng, F. Yu, S. He, J. Huang, L. Liu, L. Li
The ZnO arresters in 500kV AC filters in many converter stations have abnormal discharge during operation, which accelerated the aging of arresters and even caused arresters out of work. In this paper, through the disassembly experiment of the whole arresters and the test of the electrical characteristic parameters of the varistors, the failure reason and aging characteristics are preliminarily analyzed. Firstly, it is found that there are obvious cracks and surface discharge traces on one individual varistor of the F1 arrester for AC filter; while disassembling the F2 arrester for AC filter, it is found that the appearance of the porcelain sleeve and the internal va ristors of the arrester are intact. Secondly, The electrical characteristic parameters measurement results show that the electrical characteristic parameters of each varistor of F1 arrester for AC filt er are dispersed, as high as 8%; the DC reference volta ge U1mA and leakage current IL at 0.75 times U1mA of each varistor of F2 arrester for AC filter have obvious polarity effect. Therefore, it is preliminarily inferred that the frequent large impulse current is the main reason of the arresters failure, and p arameters dispersion and polarity effect of the varistors in one arrester are critical influencing factors.
{"title":"Failure analysis of ZnO arresters in the 500kV AC filter of the HVDC/UHVDC power transmission system","authors":"J. Zhang, Y. Han, X. Luo, J. Deng, J. Zhang, Y. Meng, F. Yu, S. He, J. Huang, L. Liu, L. Li","doi":"10.1049/icp.2021.2556","DOIUrl":"https://doi.org/10.1049/icp.2021.2556","url":null,"abstract":"The ZnO arresters in 500kV AC filters in many converter stations have abnormal discharge during operation, which accelerated the aging of arresters and even caused arresters out of work. In this paper, through the disassembly experiment of the whole arresters and the test of the electrical characteristic parameters of the varistors, the failure reason and aging characteristics are preliminarily analyzed. Firstly, it is found that there are obvious cracks and surface discharge traces on one individual varistor of the F1 arrester for AC filter; while disassembling the F2 arrester for AC filter, it is found that the appearance of the porcelain sleeve and the internal va ristors of the arrester are intact. Secondly, The electrical characteristic parameters measurement results show that the electrical characteristic parameters of each varistor of F1 arrester for AC filt er are dispersed, as high as 8%; the DC reference volta ge U1mA and leakage current IL at 0.75 times U1mA of each varistor of F2 arrester for AC filter have obvious polarity effect. Therefore, it is preliminarily inferred that the frequent large impulse current is the main reason of the arresters failure, and p arameters dispersion and polarity effect of the varistors in one arrester are critical influencing factors.","PeriodicalId":242596,"journal":{"name":"2021 Annual Meeting of CSEE Study Committee of HVDC and Power Electronics (HVDC 2021)","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133311441","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}
Aiming at a DC filter differential protection alarm event, by analyzing the waveform of transient fault and steady-state operation of the filter protection, combining with the structure and sampling principle of the filter CT, the reasons causing the protection alarm are eliminated one by one. Finally, the shunt path of the primary equipment is found and the fault points are located, which provides the basis for the DC filter to carry out maintenance work.
{"title":"Abnormal analysis of DC filter differential protection in converter station","authors":"H. Cong, X. Wu, L. Hang","doi":"10.1049/icp.2021.2541","DOIUrl":"https://doi.org/10.1049/icp.2021.2541","url":null,"abstract":"Aiming at a DC filter differential protection alarm event, by analyzing the waveform of transient fault and steady-state operation of the filter protection, combining with the structure and sampling principle of the filter CT, the reasons causing the protection alarm are eliminated one by one. Finally, the shunt path of the primary equipment is found and the fault points are located, which provides the basis for the DC filter to carry out maintenance work.","PeriodicalId":242596,"journal":{"name":"2021 Annual Meeting of CSEE Study Committee of HVDC and Power Electronics (HVDC 2021)","volume":"50 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130465597","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 term of switching-type controllable shunt reactor of ZHANGBEI to XIONG'AN ultra-high voltage (UHV) power transmission system, this paper study the character of open-circuit fault of controllable wiring in UHV switching-type controllable shunt reactor, the volt-ampere characteristic of open-circuit fault of controllable wiring is provided. Furthermore, this paper provided a method of the calculation of fault protection in open-circuit fault of controllable wiring, the simulation of RTDS is completed to prove its reliability effectiveness and accuracy.
{"title":"Research on the protection strategy of open-circuit fault of controllable wiring in 1000kV switching-type controllable shunt reactor","authors":"S. Zhang, M. Ren, Lei Zhou, L. Dong","doi":"10.1049/icp.2021.2542","DOIUrl":"https://doi.org/10.1049/icp.2021.2542","url":null,"abstract":"In term of switching-type controllable shunt reactor of ZHANGBEI to XIONG'AN ultra-high voltage (UHV) power transmission system, this paper study the character of open-circuit fault of controllable wiring in UHV switching-type controllable shunt reactor, the volt-ampere characteristic of open-circuit fault of controllable wiring is provided. Furthermore, this paper provided a method of the calculation of fault protection in open-circuit fault of controllable wiring, the simulation of RTDS is completed to prove its reliability effectiveness and accuracy.","PeriodicalId":242596,"journal":{"name":"2021 Annual Meeting of CSEE Study Committee of HVDC and Power Electronics (HVDC 2021)","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114884973","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}
Current sensing and measurement technology is the basis and reliable support for power grid system control, which directly affects the safe operation of electrical equipment in the system. Aiming at the difficulty of reliable and rapid detection of DC current in the distribution network, this paper develops the design of a DC instrument transformer based on tunneling magnetoresistance. First, the hardware design scheme of the DC instrument transformer is proposed, and the working process of the instrument transformer is given. Next, the key design technology of DC instrument transformer is given in Simulink, and the power flow analysis model of the distribution network is established to simulate and verify the detection function of the instrument transformer. Finally, the designed DC instrument transformer is used for DC current detection in the Suzhou medium-low voltage DC distribution network demonstration project. The results show that the DC instrument transformer can quickly and accurately detect the amplitude of the DC current, which can strongly support the power control and dispatch of the distribution network.
{"title":"Development and application of DC current sensor","authors":"Jun Tang, Min Ding, Dong Lv","doi":"10.1049/icp.2021.2571","DOIUrl":"https://doi.org/10.1049/icp.2021.2571","url":null,"abstract":"Current sensing and measurement technology is the basis and reliable support for power grid system control, which directly affects the safe operation of electrical equipment in the system. Aiming at the difficulty of reliable and rapid detection of DC current in the distribution network, this paper develops the design of a DC instrument transformer based on tunneling magnetoresistance. First, the hardware design scheme of the DC instrument transformer is proposed, and the working process of the instrument transformer is given. Next, the key design technology of DC instrument transformer is given in Simulink, and the power flow analysis model of the distribution network is established to simulate and verify the detection function of the instrument transformer. Finally, the designed DC instrument transformer is used for DC current detection in the Suzhou medium-low voltage DC distribution network demonstration project. The results show that the DC instrument transformer can quickly and accurately detect the amplitude of the DC current, which can strongly support the power control and dispatch of the distribution network.","PeriodicalId":242596,"journal":{"name":"2021 Annual Meeting of CSEE Study Committee of HVDC and Power Electronics (HVDC 2021)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129247050","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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