Pub Date : 2014-11-24DOI: 10.1109/NAPS.2014.6965391
M. Lauby, J. Bian, S. Ekisheva, M. Varghese
With higher penetrations of renewable energy resources, assessing frequency response trends becomes extremely important. It is a critical component to the reliable operation of the bulk power system, particularly during disturbances and restoration. This paper presents a new and comprehensive statistical method to evaluate the trends for the ERCOT and Québec Interconnections of the North American electric grid. The statistical analysis tests whether observable decreases or increases between four annual data points constitute a statistically significant trend. The probability distribution of frequency response and contributing factors to it changes over the years are also examined. The statistical significance tests and studies have indicated a stable general trend for the ERCOT and Québec Interconnections over time.
{"title":"Frequency response assessment of ERCOT and Québec Interconnections","authors":"M. Lauby, J. Bian, S. Ekisheva, M. Varghese","doi":"10.1109/NAPS.2014.6965391","DOIUrl":"https://doi.org/10.1109/NAPS.2014.6965391","url":null,"abstract":"With higher penetrations of renewable energy resources, assessing frequency response trends becomes extremely important. It is a critical component to the reliable operation of the bulk power system, particularly during disturbances and restoration. This paper presents a new and comprehensive statistical method to evaluate the trends for the ERCOT and Québec Interconnections of the North American electric grid. The statistical analysis tests whether observable decreases or increases between four annual data points constitute a statistically significant trend. The probability distribution of frequency response and contributing factors to it changes over the years are also examined. The statistical significance tests and studies have indicated a stable general trend for the ERCOT and Québec Interconnections over time.","PeriodicalId":421766,"journal":{"name":"2014 North American Power Symposium (NAPS)","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134395912","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 : 2014-11-24DOI: 10.1109/NAPS.2014.6965409
G. Zweigle, E. Blood
Modern electric power systems are extremely reliable but occasionally suffer from cascading failures initiated by localized asset removal. As lines and transformers overload and are taken out of service by protective relays, the system can progressively weaken. Network interconnections then enable regional instability to expand into a wide area. Protective relays have unique information about initial outage causes and local behavior. This includes identifying whether the actions of the protective relays are related to fault conditions or overloads. Meanwhile, synchrophasor technology now provides wide-area information in real time. The combination of local and wide-area information that is time-synchronized provides the ability to stabilize electric power systems in ways that minimize necessary control actions. This paper describes the development of a control system that applies local information in coordination with synchrophasor measurements to assess the complete state of the power system and differentiate a local phenomenon from the possibility of an overload-related cascade. The system executes a set of actions to contain and minimize the event. This paper verifies the efficacy of the proposed control system algorithms against cascading line outage scenarios applied to an IEEE standard test system.
{"title":"Distributed control with local and wide-area measurements for mitigation of cascading outages","authors":"G. Zweigle, E. Blood","doi":"10.1109/NAPS.2014.6965409","DOIUrl":"https://doi.org/10.1109/NAPS.2014.6965409","url":null,"abstract":"Modern electric power systems are extremely reliable but occasionally suffer from cascading failures initiated by localized asset removal. As lines and transformers overload and are taken out of service by protective relays, the system can progressively weaken. Network interconnections then enable regional instability to expand into a wide area. Protective relays have unique information about initial outage causes and local behavior. This includes identifying whether the actions of the protective relays are related to fault conditions or overloads. Meanwhile, synchrophasor technology now provides wide-area information in real time. The combination of local and wide-area information that is time-synchronized provides the ability to stabilize electric power systems in ways that minimize necessary control actions. This paper describes the development of a control system that applies local information in coordination with synchrophasor measurements to assess the complete state of the power system and differentiate a local phenomenon from the possibility of an overload-related cascade. The system executes a set of actions to contain and minimize the event. This paper verifies the efficacy of the proposed control system algorithms against cascading line outage scenarios applied to an IEEE standard test system.","PeriodicalId":421766,"journal":{"name":"2014 North American Power Symposium (NAPS)","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114872726","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 : 2014-11-24DOI: 10.1109/NAPS.2014.6965481
S. Chanda, V. Venkataramanan, A. Srivastava
Microgrids enable campus-scale facilities, like universities, or large corporations, a greater flexibility to manage their own distributed energy sources and in meeting their energy demands, even with power disturbances or outages in the grid. Simulation of these microgrids, which can disconnect or connect itself from the grid through a point of common coupling (PCC), yields insights into behavior of each load, if modeled in detail. Also, the simulation models are useful to investigate the effects of integrating new renewable generation in the distribution system. In this paper, the Real Time Digital Simulator (RTDS) is used to model the distribution system in real time and study the system dynamics in events of connection/disconnection to/from the main grid and disturbances. This paper reports results from simulation of a campus microgrid and its operation in several scenarios, by considering a representative model of the Washington State University campus electricity distribution system.
{"title":"Real time modeling and simulation of campus microgrid for voltage analysis","authors":"S. Chanda, V. Venkataramanan, A. Srivastava","doi":"10.1109/NAPS.2014.6965481","DOIUrl":"https://doi.org/10.1109/NAPS.2014.6965481","url":null,"abstract":"Microgrids enable campus-scale facilities, like universities, or large corporations, a greater flexibility to manage their own distributed energy sources and in meeting their energy demands, even with power disturbances or outages in the grid. Simulation of these microgrids, which can disconnect or connect itself from the grid through a point of common coupling (PCC), yields insights into behavior of each load, if modeled in detail. Also, the simulation models are useful to investigate the effects of integrating new renewable generation in the distribution system. In this paper, the Real Time Digital Simulator (RTDS) is used to model the distribution system in real time and study the system dynamics in events of connection/disconnection to/from the main grid and disturbances. This paper reports results from simulation of a campus microgrid and its operation in several scenarios, by considering a representative model of the Washington State University campus electricity distribution system.","PeriodicalId":421766,"journal":{"name":"2014 North American Power Symposium (NAPS)","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123422619","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 : 2014-11-24DOI: 10.1109/NAPS.2014.6965442
R. Belkacemi, A. Bababola, S. Zarrabian, R. Craven
In this work, a technique based on an adaptive Multi-Agent System algorithm is implemented to solve the complex problem of cascading failure events which lead to total blackout. This method proposes a solution to a variant of cascading failure events and is unique as previous literature focuses on identifying the possibility of occurrence of the cascading failures and then mitigates the failures. The proposed solution which utilizes pre-stated mathematical combinations that aim to redispatch the power from the generators is dynamically and experimentally applied in real-time, therefore it considers all the active factors and constraints involved as it halts the occurrence of cascading failures after an N-1 contingency. The distributed and intelligent algorithm is modeled to suit power system applications and then implemented on an experimental set up of the generation and transmission side of the IEEE 30-bus system utilizing a reconfigurable Smart Grid Laboratory hardware developed for testing distributed algorithms requiring two way communication capabilities.
{"title":"Multi-Agent System algorithm for preventing cascading failures in smart grid systems","authors":"R. Belkacemi, A. Bababola, S. Zarrabian, R. Craven","doi":"10.1109/NAPS.2014.6965442","DOIUrl":"https://doi.org/10.1109/NAPS.2014.6965442","url":null,"abstract":"In this work, a technique based on an adaptive Multi-Agent System algorithm is implemented to solve the complex problem of cascading failure events which lead to total blackout. This method proposes a solution to a variant of cascading failure events and is unique as previous literature focuses on identifying the possibility of occurrence of the cascading failures and then mitigates the failures. The proposed solution which utilizes pre-stated mathematical combinations that aim to redispatch the power from the generators is dynamically and experimentally applied in real-time, therefore it considers all the active factors and constraints involved as it halts the occurrence of cascading failures after an N-1 contingency. The distributed and intelligent algorithm is modeled to suit power system applications and then implemented on an experimental set up of the generation and transmission side of the IEEE 30-bus system utilizing a reconfigurable Smart Grid Laboratory hardware developed for testing distributed algorithms requiring two way communication capabilities.","PeriodicalId":421766,"journal":{"name":"2014 North American Power Symposium (NAPS)","volume":"2015 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129765634","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 : 2014-11-24DOI: 10.1109/NAPS.2014.6965477
Xu Zhang, A. Flueck, S. Abhyankar
This paper presents two sets of equivalent models for implicitly-coupled electromechanical and electromagnetic transient analysis: a Thevenin equivalent of the electromechanical network and a Norton equivalent of the electromechanical network. Due to the possible lack of voltage reference in the electromagnetic network, the Norton equivalent of the electromechanical network is not as robust as the Thevenin equivalent in implicitly-coupled transient simulation. Results demonstrating the advantage of the implicitly-coupled electromechanical and electromagnetic simulator with Thevenin equivalent of the electromechanical network are presented for a 3 bus test system.
{"title":"Equivalent models for implicitly-coupled electromechanical and electromagnetic transient analysis","authors":"Xu Zhang, A. Flueck, S. Abhyankar","doi":"10.1109/NAPS.2014.6965477","DOIUrl":"https://doi.org/10.1109/NAPS.2014.6965477","url":null,"abstract":"This paper presents two sets of equivalent models for implicitly-coupled electromechanical and electromagnetic transient analysis: a Thevenin equivalent of the electromechanical network and a Norton equivalent of the electromechanical network. Due to the possible lack of voltage reference in the electromagnetic network, the Norton equivalent of the electromechanical network is not as robust as the Thevenin equivalent in implicitly-coupled transient simulation. Results demonstrating the advantage of the implicitly-coupled electromechanical and electromagnetic simulator with Thevenin equivalent of the electromechanical network are presented for a 3 bus test system.","PeriodicalId":421766,"journal":{"name":"2014 North American Power Symposium (NAPS)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130590781","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 : 2014-11-24DOI: 10.1109/NAPS.2014.6965408
Zhaohao Ding, Piampoom Sarikprueck, L. Lee, Weijen Lee, Jie Shi, Heng Lu
To compensate for “missing money”, the Electric Reliability Council of Texas (ERCOT) has continued to increase the offer price cap since the nodal market opened in 2010. This provides financial opportunities for Load Serving Entities (LSE) to deploy demand response. This paper proposes a quasi-real time incentive based demand response (IBDR) scheme for LSE to take advantage of scarcity prices. Combined with the scheme is a hybrid spike price forecasting model also presented by this paper. Numerical case studies are conducted based on the realistic ERCOT load zone price data. The results illustrate the financial benefits achieved by this proposed IBDR scheme.
{"title":"Financial opportunities for LSE under scarcity price environment","authors":"Zhaohao Ding, Piampoom Sarikprueck, L. Lee, Weijen Lee, Jie Shi, Heng Lu","doi":"10.1109/NAPS.2014.6965408","DOIUrl":"https://doi.org/10.1109/NAPS.2014.6965408","url":null,"abstract":"To compensate for “missing money”, the Electric Reliability Council of Texas (ERCOT) has continued to increase the offer price cap since the nodal market opened in 2010. This provides financial opportunities for Load Serving Entities (LSE) to deploy demand response. This paper proposes a quasi-real time incentive based demand response (IBDR) scheme for LSE to take advantage of scarcity prices. Combined with the scheme is a hybrid spike price forecasting model also presented by this paper. Numerical case studies are conducted based on the realistic ERCOT load zone price data. The results illustrate the financial benefits achieved by this proposed IBDR scheme.","PeriodicalId":421766,"journal":{"name":"2014 North American Power Symposium (NAPS)","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132494029","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 : 2014-11-24DOI: 10.1109/NAPS.2014.6965399
Y. Chen, A. Domínguez-García, P. Sauer
This paper proposes a method to estimate transmission line flows in a power system during the transient period following a loss of generation or increase in load contingency by using linear sensitivity injection shift factors (ISFs). Traditionally, ISFs are computed from an offline power flow model of the system with the slack bus defined. The proposed method, however, relies on generalized ISFs estimated via the solution of a system of linear equations that arise from high-frequency synchronized measurements obtained from phasor measurement units. Even though the generalized ISFs are obtained at the pre-disturbance steady-state operating point, by leveraging inertial and governor power flows during appropriate time-scales, they can be manipulated to predict active transmission line flows during the post-contingency transient period.
{"title":"Generalized injection shift factors and application to estimation of power flow transients","authors":"Y. Chen, A. Domínguez-García, P. Sauer","doi":"10.1109/NAPS.2014.6965399","DOIUrl":"https://doi.org/10.1109/NAPS.2014.6965399","url":null,"abstract":"This paper proposes a method to estimate transmission line flows in a power system during the transient period following a loss of generation or increase in load contingency by using linear sensitivity injection shift factors (ISFs). Traditionally, ISFs are computed from an offline power flow model of the system with the slack bus defined. The proposed method, however, relies on generalized ISFs estimated via the solution of a system of linear equations that arise from high-frequency synchronized measurements obtained from phasor measurement units. Even though the generalized ISFs are obtained at the pre-disturbance steady-state operating point, by leveraging inertial and governor power flows during appropriate time-scales, they can be manipulated to predict active transmission line flows during the post-contingency transient period.","PeriodicalId":421766,"journal":{"name":"2014 North American Power Symposium (NAPS)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122187200","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 : 2014-11-24DOI: 10.1109/NAPS.2014.6965354
Manohar Singh, B. K. Panigrahi
In bidirectional fault feed distribution lines, the fault should be cleared from both the fault feeding sources ends simultaneously, so that impact of faults currents on the exiting over current relay coordination will be minimum. In existing over current relay coordination algorithms, it is observed that operating time gaps between primaries over current relays at near end and far end of faulted line are quite enough. This time gaps may redistribute the fault currents in the power networks which leads to cascading type of over current relay miscoordination in a properly coordinated power network. In this paper, the over current relay coordination problem formulation is modified in such a way to minimize the operating time gap between the primary over current relays at near and far ends with in a desired time margin such that the chance of redistribution of fault currents in the distribution network is eliminated. The proposed modified over current relay coordination algorithm is implemented in 8 bus test distribution system.
{"title":"Minimization of operating time gap between primary relays at near and far ends in overcurrent relay coordination","authors":"Manohar Singh, B. K. Panigrahi","doi":"10.1109/NAPS.2014.6965354","DOIUrl":"https://doi.org/10.1109/NAPS.2014.6965354","url":null,"abstract":"In bidirectional fault feed distribution lines, the fault should be cleared from both the fault feeding sources ends simultaneously, so that impact of faults currents on the exiting over current relay coordination will be minimum. In existing over current relay coordination algorithms, it is observed that operating time gaps between primaries over current relays at near end and far end of faulted line are quite enough. This time gaps may redistribute the fault currents in the power networks which leads to cascading type of over current relay miscoordination in a properly coordinated power network. In this paper, the over current relay coordination problem formulation is modified in such a way to minimize the operating time gap between the primary over current relays at near and far ends with in a desired time margin such that the chance of redistribution of fault currents in the distribution network is eliminated. The proposed modified over current relay coordination algorithm is implemented in 8 bus test distribution system.","PeriodicalId":421766,"journal":{"name":"2014 North American Power Symposium (NAPS)","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116055968","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 : 2014-11-24DOI: 10.1109/NAPS.2014.6965355
A. Nagarajan, R. Ayyanar
Large-scale penetration of distributed energy resources on the existing distribution feeders impact the dynamic behavior and pose the motivation to perform a transient analysis on the distribution feeders. But, performing transient analysis based on conventional time domain approach is extremely time consuming and impractical. Besides, existing models of the PV generator in the distribution system analysis tools (OpenDSS) are just capable of supporting the snapshot and quasi-static analyses. Capturing the dynamic effects of the PV generators will be necessary for studies such as the effect of controller bandwidth, effect of multiple voltage correction devices, and anti-islanding studies. Considering an IEEE 37-bus test feeder as basis this paper proposes a mathematical approach based on differential algebraic equations (DAE) for performing dynamic analysis of distribution feeders in OpenDSS. In a detailed manner, this paper explores the use of DAE for the impact analysis of large PV generators on the existing distribution feeders. This approach models selected states as ordinary differential equations with rest of the distribution system as algebraic equations. The procedure based on DAE is effective in handling proprietary vendor-supplied models. Significant reduction in the computation time has been obtained by employing the above mentioned approach as compared with a conventional time domain technique.
{"title":"Dynamic analysis of distribution systems with high penetration of PV generators using differential algebraic equations in OpenDSS","authors":"A. Nagarajan, R. Ayyanar","doi":"10.1109/NAPS.2014.6965355","DOIUrl":"https://doi.org/10.1109/NAPS.2014.6965355","url":null,"abstract":"Large-scale penetration of distributed energy resources on the existing distribution feeders impact the dynamic behavior and pose the motivation to perform a transient analysis on the distribution feeders. But, performing transient analysis based on conventional time domain approach is extremely time consuming and impractical. Besides, existing models of the PV generator in the distribution system analysis tools (OpenDSS) are just capable of supporting the snapshot and quasi-static analyses. Capturing the dynamic effects of the PV generators will be necessary for studies such as the effect of controller bandwidth, effect of multiple voltage correction devices, and anti-islanding studies. Considering an IEEE 37-bus test feeder as basis this paper proposes a mathematical approach based on differential algebraic equations (DAE) for performing dynamic analysis of distribution feeders in OpenDSS. In a detailed manner, this paper explores the use of DAE for the impact analysis of large PV generators on the existing distribution feeders. This approach models selected states as ordinary differential equations with rest of the distribution system as algebraic equations. The procedure based on DAE is effective in handling proprietary vendor-supplied models. Significant reduction in the computation time has been obtained by employing the above mentioned approach as compared with a conventional time domain technique.","PeriodicalId":421766,"journal":{"name":"2014 North American Power Symposium (NAPS)","volume":"292 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116208760","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 : 2014-11-24DOI: 10.1109/NAPS.2014.6965410
Maigha, M. Crow
A price responsive demand (PRD) market has been perceived as the future of electricity markets with the capability of achieving economic benefits. It lays the foundation of demand response at the customer level. Time of use structures have been implemented widely to achieve load reshaping. This paper introduces a clustering based methodology for obtaining optimal time of use structures (optimal number of levels and rate durations) based on historical load profiles and real-time prices. The study takes into account variation in weekday and weekend load profiles and also seasonal variations. A new hybrid policy that bridges the gap between seasonal time-of-use and critical peak pricing has been proposed.
{"title":"Clustering-based methodology for optimal residential time of use design structure","authors":"Maigha, M. Crow","doi":"10.1109/NAPS.2014.6965410","DOIUrl":"https://doi.org/10.1109/NAPS.2014.6965410","url":null,"abstract":"A price responsive demand (PRD) market has been perceived as the future of electricity markets with the capability of achieving economic benefits. It lays the foundation of demand response at the customer level. Time of use structures have been implemented widely to achieve load reshaping. This paper introduces a clustering based methodology for obtaining optimal time of use structures (optimal number of levels and rate durations) based on historical load profiles and real-time prices. The study takes into account variation in weekday and weekend load profiles and also seasonal variations. A new hybrid policy that bridges the gap between seasonal time-of-use and critical peak pricing has been proposed.","PeriodicalId":421766,"journal":{"name":"2014 North American Power Symposium (NAPS)","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121656154","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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