Pub Date : 2007-12-26DOI: 10.1109/IREP.2007.4410514
R. Eriksson, V. Knazkins, L. Soder
There are several possibilities to improve the first swing transient stability in a power system. One adequate option is to use the high controllability of the HVDC if HVDC is available in the system. This paper presents a control strategy for HVDC to improve the first swing transient. The strategy controls the power through the HVDC to make the system more transient stable during disturbances. The proposed control strategy consists of the PD-controller and feed-forward control, the use of a PD-controller is appropriate since it has the property of fast response. To improve the first swing oscillation even more the feed-forward control is used, since the behavior of system due to the disconnection is known. Two bench mark power systems are subjected to large disturbances to examine the effectiveness of the proposed strategy. Depending on how the power through the HVDC is controlled the transients damp differently. The PD-controller works well and damps the first swing oscillation transient so the system remains stable. When a power step also is applied after the line is disconnected, the transient swing becomes lower and the behaviour of the system is better. There is also a possibility to improve the first swing oscillation even more, by applying a power step through the HVDC which will compensate for the lack of power due to the disconnection of the line caused by the disturbance.
{"title":"On the assessment of the impact of a conventional HVDC on a test power system","authors":"R. Eriksson, V. Knazkins, L. Soder","doi":"10.1109/IREP.2007.4410514","DOIUrl":"https://doi.org/10.1109/IREP.2007.4410514","url":null,"abstract":"There are several possibilities to improve the first swing transient stability in a power system. One adequate option is to use the high controllability of the HVDC if HVDC is available in the system. This paper presents a control strategy for HVDC to improve the first swing transient. The strategy controls the power through the HVDC to make the system more transient stable during disturbances. The proposed control strategy consists of the PD-controller and feed-forward control, the use of a PD-controller is appropriate since it has the property of fast response. To improve the first swing oscillation even more the feed-forward control is used, since the behavior of system due to the disconnection is known. Two bench mark power systems are subjected to large disturbances to examine the effectiveness of the proposed strategy. Depending on how the power through the HVDC is controlled the transients damp differently. The PD-controller works well and damps the first swing oscillation transient so the system remains stable. When a power step also is applied after the line is disconnected, the transient swing becomes lower and the behaviour of the system is better. There is also a possibility to improve the first swing oscillation even more, by applying a power step through the HVDC which will compensate for the lack of power due to the disconnection of the line caused by the disturbance.","PeriodicalId":214545,"journal":{"name":"2007 iREP Symposium - Bulk Power System Dynamics and Control - VII. Revitalizing Operational Reliability","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125931116","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 : 2007-12-26DOI: 10.1109/IREP.2007.4410573
Yuqing Jin, C. Qin, Feng Wu, Jingdong Han, Qun Xu, Deng-jun Yan, P. Ju
A new method for the measurement of the rotor angles and the phasors of power systems is proposed in this paper. Based on this method, the angle and phase measurement unit (APMU) has been developed. The rotor angles can be measured directly with speed signals of generators instead of being calculated with the power equations of the generator. Hence, the measurement precision of the rotor angle is improved. Based on the APMU and the Global Position System (GPS), a wide area measurement system (WAMS) has been constructed in the HeNan power grid (HNPG), China. The control center for the WAMS was also developed. The server in the control center collects the real-time data from all the APMUs, analyzes the operation state of the power network, records the dynamic responses of the power system under disturbances, and displays the information with the graphical user interface (GUI). The measurements were also applied in the detection of low frequency oscillation, on-line state estimation and parameter estimation of synchronous generators.
{"title":"The power Angle and Phase Measurement Units based Wide Area Measurement System and its application","authors":"Yuqing Jin, C. Qin, Feng Wu, Jingdong Han, Qun Xu, Deng-jun Yan, P. Ju","doi":"10.1109/IREP.2007.4410573","DOIUrl":"https://doi.org/10.1109/IREP.2007.4410573","url":null,"abstract":"A new method for the measurement of the rotor angles and the phasors of power systems is proposed in this paper. Based on this method, the angle and phase measurement unit (APMU) has been developed. The rotor angles can be measured directly with speed signals of generators instead of being calculated with the power equations of the generator. Hence, the measurement precision of the rotor angle is improved. Based on the APMU and the Global Position System (GPS), a wide area measurement system (WAMS) has been constructed in the HeNan power grid (HNPG), China. The control center for the WAMS was also developed. The server in the control center collects the real-time data from all the APMUs, analyzes the operation state of the power network, records the dynamic responses of the power system under disturbances, and displays the information with the graphical user interface (GUI). The measurements were also applied in the detection of low frequency oscillation, on-line state estimation and parameter estimation of synchronous generators.","PeriodicalId":214545,"journal":{"name":"2007 iREP Symposium - Bulk Power System Dynamics and Control - VII. Revitalizing Operational Reliability","volume":"158 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122427332","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 : 2007-12-26DOI: 10.1109/IREP.2007.4410570
H. Sarmiento
This paper presents relevant aspects of a project to design and install a FCL of the resonant link type. This device consists of a series reactor and capacitor, tuned to 60 Hz. The series capacitor is shunted by a saturable reactor when a fault occurs.
{"title":"A fault current limiter based on an LC resonant circuit: Design, scale model and prototype field tests","authors":"H. Sarmiento","doi":"10.1109/IREP.2007.4410570","DOIUrl":"https://doi.org/10.1109/IREP.2007.4410570","url":null,"abstract":"This paper presents relevant aspects of a project to design and install a FCL of the resonant link type. This device consists of a series reactor and capacitor, tuned to 60 Hz. The series capacitor is shunted by a saturable reactor when a fault occurs.","PeriodicalId":214545,"journal":{"name":"2007 iREP Symposium - Bulk Power System Dynamics and Control - VII. Revitalizing Operational Reliability","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130728698","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 : 2007-12-26DOI: 10.1109/IREP.2007.4410554
I. Dobson, K. R. Wierzbicki, Janghoon Kim, Hui Ren
Blackouts become widespread by initial failures propagating in a diverse and intricate cascade of rare events. We describe this complicated cascade using a bulk probabilistic model in which the initial failures propagate randomly according to a branching process. The branching process parameters can be statistically estimated from observed data or simulations and then used to efficiently predict the probability distribution of blackout size. We review the current testing of these methods on simulations and observed data and discuss the next steps towards achieving verified and practical methods for quantifying cascading failure of electric power systems. The ability to efficiently quantify cascading blackout risk from observed data and simulations could offer new ways to monitor power transmission system reliability and quantify the reliability benefit of proposed improvements.
{"title":"Towards quantifying cascading blackout risk","authors":"I. Dobson, K. R. Wierzbicki, Janghoon Kim, Hui Ren","doi":"10.1109/IREP.2007.4410554","DOIUrl":"https://doi.org/10.1109/IREP.2007.4410554","url":null,"abstract":"Blackouts become widespread by initial failures propagating in a diverse and intricate cascade of rare events. We describe this complicated cascade using a bulk probabilistic model in which the initial failures propagate randomly according to a branching process. The branching process parameters can be statistically estimated from observed data or simulations and then used to efficiently predict the probability distribution of blackout size. We review the current testing of these methods on simulations and observed data and discuss the next steps towards achieving verified and practical methods for quantifying cascading failure of electric power systems. The ability to efficiently quantify cascading blackout risk from observed data and simulations could offer new ways to monitor power transmission system reliability and quantify the reliability benefit of proposed improvements.","PeriodicalId":214545,"journal":{"name":"2007 iREP Symposium - Bulk Power System Dynamics and Control - VII. Revitalizing Operational Reliability","volume":"186 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116111049","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 : 2007-12-26DOI: 10.1109/IREP.2007.4410564
Eric M. Fleming, I. Hiskens
The paper presents a model for a solid oxide fuel cell (SOFC) stack operating at relatively low pressures. The model incorporates the electrochemical reaction dynamics and the major voltage losses in SOFCs, but is not concerned with the thermal dynamics. A DC-DC boost converter interfaces the SOFC stack to a DC bus, where an ultra-capacitor provides energy storage. The paper presents a control system for the converter which regulates the DC-bus voltage along with the fuel cell current. A control strategy is proposed for the inverter that interfaces the SOFC plant to the AC grid. The controller regulates the grid-side voltage and the active power delivered to the grid, and takes into account the phase-locked loop (PLL) dynamics. The results of an example in which two SOFC plants provide power to a microgrid are presented. The simulation includes disconnection from the main grid, autonomous operation, and re-synchronization with the main grid.
{"title":"Dynamics of a microgrid supplied by solid oxide fuel cells","authors":"Eric M. Fleming, I. Hiskens","doi":"10.1109/IREP.2007.4410564","DOIUrl":"https://doi.org/10.1109/IREP.2007.4410564","url":null,"abstract":"The paper presents a model for a solid oxide fuel cell (SOFC) stack operating at relatively low pressures. The model incorporates the electrochemical reaction dynamics and the major voltage losses in SOFCs, but is not concerned with the thermal dynamics. A DC-DC boost converter interfaces the SOFC stack to a DC bus, where an ultra-capacitor provides energy storage. The paper presents a control system for the converter which regulates the DC-bus voltage along with the fuel cell current. A control strategy is proposed for the inverter that interfaces the SOFC plant to the AC grid. The controller regulates the grid-side voltage and the active power delivered to the grid, and takes into account the phase-locked loop (PLL) dynamics. The results of an example in which two SOFC plants provide power to a microgrid are presented. The simulation includes disconnection from the main grid, autonomous operation, and re-synchronization with the main grid.","PeriodicalId":214545,"journal":{"name":"2007 iREP Symposium - Bulk Power System Dynamics and Control - VII. Revitalizing Operational Reliability","volume":"86 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124013251","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 : 2007-12-26DOI: 10.1109/IREP.2007.4410555
S. Hamilton, C. Vartanian, M. E. Johnson, A. Feliachi, K. Schoder, P. Hines
This paper describes the concept of improving operation of a distribution circuit of the future through installment of interoperable devices, including distributed energy resources (DER) that are controlled using a multi-agent system approach. This concept for improving distribution service is being considered by SCE's DER Program, with additional assistance from West Virginia University in the development of a conceptual implementation methodology that includes multi-agent control.
{"title":"Circuit of the future: Interoperability and SCE’s DER program","authors":"S. Hamilton, C. Vartanian, M. E. Johnson, A. Feliachi, K. Schoder, P. Hines","doi":"10.1109/IREP.2007.4410555","DOIUrl":"https://doi.org/10.1109/IREP.2007.4410555","url":null,"abstract":"This paper describes the concept of improving operation of a distribution circuit of the future through installment of interoperable devices, including distributed energy resources (DER) that are controlled using a multi-agent system approach. This concept for improving distribution service is being considered by SCE's DER Program, with additional assistance from West Virginia University in the development of a conceptual implementation methodology that includes multi-agent control.","PeriodicalId":214545,"journal":{"name":"2007 iREP Symposium - Bulk Power System Dynamics and Control - VII. Revitalizing Operational Reliability","volume":"40 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124898130","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 : 2007-12-26DOI: 10.1109/IREP.2007.4410516
V. Agarwal, L. Tsoukalas
Electric signals are affected by numerous factors, random events, and corrupted with noise, making them nonlinear and non-stationary in nature. In recent years, the application of empirical mode decomposition (EMD) technique to analyze nonlinear and non-stationary signals has gained importance. It is an empirical approach to decompose a signal into a set of oscillatory modes known as intrinsic mode functions (IMFs). Based on an empirical energy model of IMFs, the statistically significant information content is established and combined. In this paper, we demonstrate an approach to detect power quality disturbances in noisy conditions. The approach is based on the statistical properties of fractional Gaussian noise (fGn).
{"title":"Denoising electrical signal via Empirical Mode Decomposition","authors":"V. Agarwal, L. Tsoukalas","doi":"10.1109/IREP.2007.4410516","DOIUrl":"https://doi.org/10.1109/IREP.2007.4410516","url":null,"abstract":"Electric signals are affected by numerous factors, random events, and corrupted with noise, making them nonlinear and non-stationary in nature. In recent years, the application of empirical mode decomposition (EMD) technique to analyze nonlinear and non-stationary signals has gained importance. It is an empirical approach to decompose a signal into a set of oscillatory modes known as intrinsic mode functions (IMFs). Based on an empirical energy model of IMFs, the statistically significant information content is established and combined. In this paper, we demonstrate an approach to detect power quality disturbances in noisy conditions. The approach is based on the statistical properties of fractional Gaussian noise (fGn).","PeriodicalId":214545,"journal":{"name":"2007 iREP Symposium - Bulk Power System Dynamics and Control - VII. Revitalizing Operational Reliability","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125074505","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 : 2007-12-26DOI: 10.1109/IREP.2007.4410544
Hua Bai, V. Ajjarapu
In this paper relay margin is derived in terms of bus voltage. With the variation of bus voltage during system disturbance the relay margin will also consequently vary to form a trajectory which is proposed as the relay margin trajectory. The sensitivity of the relay margin trajectory is investigated to quantify the rate of the relay margin variation. Based on the relay margin we propose a vulnerable relay indicator which samples the smallest relay margin over the interested time span. Based on the vulnerable relay indicator, another two indicators--severe contingency indicator and system security indicator are proposed. These three inherently related indicators together compose a framework for system security analysis. Vulnerable relay indicator is applied to identify the most vulnerable relays based on which the severe contingency indicator is obtained. System security indicator is sequentially gained based on those two indicators to identify the transmission vulnerability for the power system security analysis. Numerical test result on a test system is presented.
{"title":"Relay margin trajectory based identification of transmission vulnerability for power system security assessment","authors":"Hua Bai, V. Ajjarapu","doi":"10.1109/IREP.2007.4410544","DOIUrl":"https://doi.org/10.1109/IREP.2007.4410544","url":null,"abstract":"In this paper relay margin is derived in terms of bus voltage. With the variation of bus voltage during system disturbance the relay margin will also consequently vary to form a trajectory which is proposed as the relay margin trajectory. The sensitivity of the relay margin trajectory is investigated to quantify the rate of the relay margin variation. Based on the relay margin we propose a vulnerable relay indicator which samples the smallest relay margin over the interested time span. Based on the vulnerable relay indicator, another two indicators--severe contingency indicator and system security indicator are proposed. These three inherently related indicators together compose a framework for system security analysis. Vulnerable relay indicator is applied to identify the most vulnerable relays based on which the severe contingency indicator is obtained. System security indicator is sequentially gained based on those two indicators to identify the transmission vulnerability for the power system security analysis. Numerical test result on a test system is presented.","PeriodicalId":214545,"journal":{"name":"2007 iREP Symposium - Bulk Power System Dynamics and Control - VII. Revitalizing Operational Reliability","volume":"59 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122452222","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 : 2007-12-26DOI: 10.1109/IREP.2007.4410543
E. Lopez-Luis, M.A. Garcia-Dominguez, D. Ruiz-Vega
Continuation power flow is one of the proposed long term voltage stability assessment methods. This method attempts to find the voltage stability limit by computing a sequence of very long term equilibrium points, using a static model derived from the equilibrium conditions of the complete non linear dynamic model. During the early stages of the Continuation Power Flow method development, the emphasis was totally addressed to the Continuation method algorithm itself and, in these conditions, the conventional load flow model was the preferred system model. As shown in this paper, using the conventional load flow model, based on unacceptable simplifying assumptions, always produces unrealistic voltage stability results, even when analyzing small academic test systems. This is shown by comparing the results of the Continuation Power Flow method, using the conventional load flow model, to the ones obtained with an improved representation of load characteristics and synchronous generator reactive power limits.
{"title":"The effect of improved system modeling in the continuation power flow method","authors":"E. Lopez-Luis, M.A. Garcia-Dominguez, D. Ruiz-Vega","doi":"10.1109/IREP.2007.4410543","DOIUrl":"https://doi.org/10.1109/IREP.2007.4410543","url":null,"abstract":"Continuation power flow is one of the proposed long term voltage stability assessment methods. This method attempts to find the voltage stability limit by computing a sequence of very long term equilibrium points, using a static model derived from the equilibrium conditions of the complete non linear dynamic model. During the early stages of the Continuation Power Flow method development, the emphasis was totally addressed to the Continuation method algorithm itself and, in these conditions, the conventional load flow model was the preferred system model. As shown in this paper, using the conventional load flow model, based on unacceptable simplifying assumptions, always produces unrealistic voltage stability results, even when analyzing small academic test systems. This is shown by comparing the results of the Continuation Power Flow method, using the conventional load flow model, to the ones obtained with an improved representation of load characteristics and synchronous generator reactive power limits.","PeriodicalId":214545,"journal":{"name":"2007 iREP Symposium - Bulk Power System Dynamics and Control - VII. Revitalizing Operational Reliability","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128473552","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 : 2007-12-26DOI: 10.1109/IREP.2007.4410528
A. Chowdhury, D. Koval
In an attempt to re-regulate the distribution segment of an electric power system, public utility commissions (PUCs) are increasingly adopting a reward/penalty framework in order to guarantee acceptable electric supply reliability. This reward/penalty framework is commonly known as performance based ratemaking (PBR). A PBR framework is introduced to provide distribution utilities with incentives for economic efficiency gains in the competitive generation and transmission markets. A distribution utility's historical reliability performance records could be utilized to create practical PBR mechanisms. This paper presents actual reliability performance history from two different Canadian utilities used to develop PBR frameworks for use in a re-regulated environment. An analysis of financial risk related to historic reliability data is presented by including reliability index probability distributions in a PBR plan. In addition, this paper identifies a number of factors and issues that should be considered in generating a PBR plan for a distribution utility. A brief analysis of cause contributions to reliability indices also is performed and presented in this paper. The historic reliability based PBR framework developed in this paper will find practical applications in the emerging deregulated electricity market.
{"title":"Risk assessment approach for re-regulated distribution systems","authors":"A. Chowdhury, D. Koval","doi":"10.1109/IREP.2007.4410528","DOIUrl":"https://doi.org/10.1109/IREP.2007.4410528","url":null,"abstract":"In an attempt to re-regulate the distribution segment of an electric power system, public utility commissions (PUCs) are increasingly adopting a reward/penalty framework in order to guarantee acceptable electric supply reliability. This reward/penalty framework is commonly known as performance based ratemaking (PBR). A PBR framework is introduced to provide distribution utilities with incentives for economic efficiency gains in the competitive generation and transmission markets. A distribution utility's historical reliability performance records could be utilized to create practical PBR mechanisms. This paper presents actual reliability performance history from two different Canadian utilities used to develop PBR frameworks for use in a re-regulated environment. An analysis of financial risk related to historic reliability data is presented by including reliability index probability distributions in a PBR plan. In addition, this paper identifies a number of factors and issues that should be considered in generating a PBR plan for a distribution utility. A brief analysis of cause contributions to reliability indices also is performed and presented in this paper. The historic reliability based PBR framework developed in this paper will find practical applications in the emerging deregulated electricity market.","PeriodicalId":214545,"journal":{"name":"2007 iREP Symposium - Bulk Power System Dynamics and Control - VII. Revitalizing Operational Reliability","volume":"127 28","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"113939828","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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