Pub Date : 2007-07-01DOI: 10.1109/PCT.2007.4538470
M. S. Kumari, G. Priyanka, M. Sydulu
This paper describes the performance of two population based search algorithms (Genetic Algorithms and Particle Swarm Optimization) when applied to Optimal Power Flow (OPF) including Static VAR Compensator (SVC) and Thyristor Controlled Series Compensator (TCSC) devices. The OPF optimizes a power system operating objective function, while satisfying a set of system operating constraints. The basic OPF solution is obtained with fuel cost minimization as the objective function and the optimal settings of the power system are determined. OPF can also be formulated for reactive power optimization, as minimization of system active power losses and improving the voltage stability in the system. In the present paper different objective functions that reflect Fuel cost minimization, System power loss minimization, Voltage Stability Enhancement (L-index minimization), Power loss minimization with SVC device and Power loss minimization with combined application of SVC and TCSC devices have been considered. To monitor and improve voltage stability in power system, minimization of sum of squared L-indices of all the load buses is considered as objective function in OPF. This index also guides the optimal location for VAR compensation. During normal operating conditions a planning engineer requires that all line flows and voltages are within limits while minimizing investment (including losses). While during outage conditions, line loading and voltages are again desired within limits while minimizing investment. It is important to obtain feasible solutions with in a minimal amount of engineering time.
{"title":"Comparison of Genetic Algorithms and Particle Swarm Optimization for Optimal Power Flow Including FACTS devices","authors":"M. S. Kumari, G. Priyanka, M. Sydulu","doi":"10.1109/PCT.2007.4538470","DOIUrl":"https://doi.org/10.1109/PCT.2007.4538470","url":null,"abstract":"This paper describes the performance of two population based search algorithms (Genetic Algorithms and Particle Swarm Optimization) when applied to Optimal Power Flow (OPF) including Static VAR Compensator (SVC) and Thyristor Controlled Series Compensator (TCSC) devices. The OPF optimizes a power system operating objective function, while satisfying a set of system operating constraints. The basic OPF solution is obtained with fuel cost minimization as the objective function and the optimal settings of the power system are determined. OPF can also be formulated for reactive power optimization, as minimization of system active power losses and improving the voltage stability in the system. In the present paper different objective functions that reflect Fuel cost minimization, System power loss minimization, Voltage Stability Enhancement (L-index minimization), Power loss minimization with SVC device and Power loss minimization with combined application of SVC and TCSC devices have been considered. To monitor and improve voltage stability in power system, minimization of sum of squared L-indices of all the load buses is considered as objective function in OPF. This index also guides the optimal location for VAR compensation. During normal operating conditions a planning engineer requires that all line flows and voltages are within limits while minimizing investment (including losses). While during outage conditions, line loading and voltages are again desired within limits while minimizing investment. It is important to obtain feasible solutions with in a minimal amount of engineering time.","PeriodicalId":356805,"journal":{"name":"2007 IEEE Lausanne Power Tech","volume":"167 11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116542576","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 : 2007-07-01DOI: 10.1109/PCT.2007.4538489
S. Cole, D. Van Hertem, R. Belmans
Although Belgium and Germany are neighbouring countries, there is no direct high-voltage line between them. A study that assessed the opportunity of an ac high-voltage line between the two countries was performed at request of Belgian, German, and Luxembourgian governments. The result of the technical study was that no substantial import capacity can be achieved. In this paper, the conclusions of a new study are presented. This study considers the connection of Belgium and Germany via an HVDC link. It is shown that HVDC can increase import capacity significantly. It would be the first HVDC land cable connection in the UCTE grid.
{"title":"Connecting Belgium and Germany using HVDC: A Preliminary Study","authors":"S. Cole, D. Van Hertem, R. Belmans","doi":"10.1109/PCT.2007.4538489","DOIUrl":"https://doi.org/10.1109/PCT.2007.4538489","url":null,"abstract":"Although Belgium and Germany are neighbouring countries, there is no direct high-voltage line between them. A study that assessed the opportunity of an ac high-voltage line between the two countries was performed at request of Belgian, German, and Luxembourgian governments. The result of the technical study was that no substantial import capacity can be achieved. In this paper, the conclusions of a new study are presented. This study considers the connection of Belgium and Germany via an HVDC link. It is shown that HVDC can increase import capacity significantly. It would be the first HVDC land cable connection in the UCTE grid.","PeriodicalId":356805,"journal":{"name":"2007 IEEE Lausanne Power Tech","volume":"53 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116709882","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 : 2007-07-01DOI: 10.1109/PCT.2007.4538564
Xiaoling Ding, T. Littler, J. Morrow, P. Crossley, V. Terzija, M. O’Malley
Variations in the phase angle difference between a remote 11 kV connected wind farm and the centre of Belfast during a typical working day are investigated in the paper. The results obtained using phasor measurement units (PMUs) are compared with the data generated using a PSS/E simulator configured to model the N. Ireland network. The study investigates the effect of changes in the load demand and the wind farm output power on the phase angles at various locations on the network. The paper finally describes how a major system disturbance on the All-Ireland network was monitored and analysed using PMUs located at Queen's University, Belfast and University College Dublin.
{"title":"Synchronized Phasor Measurement on the All-Ireland Electrical Network","authors":"Xiaoling Ding, T. Littler, J. Morrow, P. Crossley, V. Terzija, M. O’Malley","doi":"10.1109/PCT.2007.4538564","DOIUrl":"https://doi.org/10.1109/PCT.2007.4538564","url":null,"abstract":"Variations in the phase angle difference between a remote 11 kV connected wind farm and the centre of Belfast during a typical working day are investigated in the paper. The results obtained using phasor measurement units (PMUs) are compared with the data generated using a PSS/E simulator configured to model the N. Ireland network. The study investigates the effect of changes in the load demand and the wind farm output power on the phase angles at various locations on the network. The paper finally describes how a major system disturbance on the All-Ireland network was monitored and analysed using PMUs located at Queen's University, Belfast and University College Dublin.","PeriodicalId":356805,"journal":{"name":"2007 IEEE Lausanne Power Tech","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125205235","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 : 2007-07-01DOI: 10.1109/PCT.2007.4538428
A. Berizzi, C. Bovo, M. Delfanti, M. Merlo
In the Italian day-ahead energy market, it is possible to trade the electrical energy without taking into account the technical limits of the generation units (e.g. minimum up time, minimum down time, ramp rate limits). Therefore, the output of the day-ahead energy market may be not feasible for some generating units. In this case, the relevant market operator has to modify the scheduling of the unit through the participation to the adjustment market. This paper presents a model to define the power profile for generating units on the base of the hourly amounts of energy exchanged in the day-ahead energy market, taking into account the technical constraints of generators (ramp rate limits). The proposed model has been tested using data given by a day- ahead energy market simulator, applied to the Italian electric system.
{"title":"Enforcing ramp rate limits on Italian Adjustment Market","authors":"A. Berizzi, C. Bovo, M. Delfanti, M. Merlo","doi":"10.1109/PCT.2007.4538428","DOIUrl":"https://doi.org/10.1109/PCT.2007.4538428","url":null,"abstract":"In the Italian day-ahead energy market, it is possible to trade the electrical energy without taking into account the technical limits of the generation units (e.g. minimum up time, minimum down time, ramp rate limits). Therefore, the output of the day-ahead energy market may be not feasible for some generating units. In this case, the relevant market operator has to modify the scheduling of the unit through the participation to the adjustment market. This paper presents a model to define the power profile for generating units on the base of the hourly amounts of energy exchanged in the day-ahead energy market, taking into account the technical constraints of generators (ramp rate limits). The proposed model has been tested using data given by a day- ahead energy market simulator, applied to the Italian electric system.","PeriodicalId":356805,"journal":{"name":"2007 IEEE Lausanne Power Tech","volume":"44 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125683656","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 : 2007-07-01DOI: 10.1109/PCT.2007.4538376
F. Viawan, D. Karlsson
This paper investigates voltage and reactive power control in radial and closed loop distribution systems and how the presence of distributed generation (DG) affects the control. Comparative analysis between voltage and reactive power control in radial and closed loop feeders, based on coordination of OLTC, substation capacitors (the shunt capacitors installed at the substation secondary bus) and feeder capacitors (the shunt capacitors located somewhere along the feeder) is presented. The known benefit of closed loop operation is examined in a case study. It is shown that the feeder losses and the voltage fluctuation decrease with the change from radial to closed loop operation. The decrease of voltage fluctuation in the feeder is shown not to reduce the OLTC and capacitor operation. It is also shown that in a certain case closed loop operation can even decrease the maximum allowed DG capacity in the feeders. Further, while it is known that the closed loop operation can defer the distribution line upgrade due to load growth, if the contingency operation is taken into account, the closed loop operation will even earlier request the distribution line upgrade.
{"title":"Voltage and Reactive Power Control in Closed Loop Feeders with Distributed Generation","authors":"F. Viawan, D. Karlsson","doi":"10.1109/PCT.2007.4538376","DOIUrl":"https://doi.org/10.1109/PCT.2007.4538376","url":null,"abstract":"This paper investigates voltage and reactive power control in radial and closed loop distribution systems and how the presence of distributed generation (DG) affects the control. Comparative analysis between voltage and reactive power control in radial and closed loop feeders, based on coordination of OLTC, substation capacitors (the shunt capacitors installed at the substation secondary bus) and feeder capacitors (the shunt capacitors located somewhere along the feeder) is presented. The known benefit of closed loop operation is examined in a case study. It is shown that the feeder losses and the voltage fluctuation decrease with the change from radial to closed loop operation. The decrease of voltage fluctuation in the feeder is shown not to reduce the OLTC and capacitor operation. It is also shown that in a certain case closed loop operation can even decrease the maximum allowed DG capacity in the feeders. Further, while it is known that the closed loop operation can defer the distribution line upgrade due to load growth, if the contingency operation is taken into account, the closed loop operation will even earlier request the distribution line upgrade.","PeriodicalId":356805,"journal":{"name":"2007 IEEE Lausanne Power Tech","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131134354","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 : 2007-07-01DOI: 10.1109/PCT.2007.4538402
C. Hoga
One of the most crucial issues in the field of substation automation is the use of Industrial Ethernet. Compared to earlier communication systems, such as the DNP and IEC 60870-5 protocols, Ethernet has its base not in the industrial sector but in the office environment. To be fully usable in the fields of substation and factory automation, it requires additional features in the following areas: (1) reliability (2) hardness suitable for substation environment conditions (3) power supplies suitable for substations (4) services enabling short response times (5) redundancy during the last ten years, the enormous progress made in these areas has led to the decision to include Industrial Ethernet in the IEC 61850 project. Ongoing development in the fields of Industrial Ethernet will lead to new, comprehensive solutions using IEC 61850, especially in the field of process-bus applications.
{"title":"New Ethernet Technologies for Substation Automation","authors":"C. Hoga","doi":"10.1109/PCT.2007.4538402","DOIUrl":"https://doi.org/10.1109/PCT.2007.4538402","url":null,"abstract":"One of the most crucial issues in the field of substation automation is the use of Industrial Ethernet. Compared to earlier communication systems, such as the DNP and IEC 60870-5 protocols, Ethernet has its base not in the industrial sector but in the office environment. To be fully usable in the fields of substation and factory automation, it requires additional features in the following areas: (1) reliability (2) hardness suitable for substation environment conditions (3) power supplies suitable for substations (4) services enabling short response times (5) redundancy during the last ten years, the enormous progress made in these areas has led to the decision to include Industrial Ethernet in the IEC 61850 project. Ongoing development in the fields of Industrial Ethernet will lead to new, comprehensive solutions using IEC 61850, especially in the field of process-bus applications.","PeriodicalId":356805,"journal":{"name":"2007 IEEE Lausanne Power Tech","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121865776","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 : 2007-07-01DOI: 10.1109/PCT.2007.4538309
E. Scholtz, M. Larsson, P. Korba
In this paper we describe a method suitable for real-time estimation of parameters of differential algebraic equation (DAE) dynamical models, generally used to model power systems. The method uses multiple observers that run in parallel, processing the same measured data from the process under consideration. The outputs from these observers are then used in a secondary least-squares estimation (LSE) process in order to identify the unknown parameters. We will demonstrate this parameter estimation using multiple observers (PEMO) on a single machine infinite bus (SMIB) example (where the generator inertia, prime mover torque and damping of the generator are unknown). This method can also be used as a fault detection, isolation and identification (FDI) filter that tracks parameter changes that can be indicative of such events as line outages, load and generation changes in a power system. We illustrate this concept on a nine-bus example.
{"title":"Real-time Parameter Estimation of Dynamic Power Systems using Multiple Observers","authors":"E. Scholtz, M. Larsson, P. Korba","doi":"10.1109/PCT.2007.4538309","DOIUrl":"https://doi.org/10.1109/PCT.2007.4538309","url":null,"abstract":"In this paper we describe a method suitable for real-time estimation of parameters of differential algebraic equation (DAE) dynamical models, generally used to model power systems. The method uses multiple observers that run in parallel, processing the same measured data from the process under consideration. The outputs from these observers are then used in a secondary least-squares estimation (LSE) process in order to identify the unknown parameters. We will demonstrate this parameter estimation using multiple observers (PEMO) on a single machine infinite bus (SMIB) example (where the generator inertia, prime mover torque and damping of the generator are unknown). This method can also be used as a fault detection, isolation and identification (FDI) filter that tracks parameter changes that can be indicative of such events as line outages, load and generation changes in a power system. We illustrate this concept on a nine-bus example.","PeriodicalId":356805,"journal":{"name":"2007 IEEE Lausanne Power Tech","volume":"25 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132607444","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 : 2007-07-01DOI: 10.1109/PCT.2007.4538611
S. Jafarabadi, S.M. Kouhsari
An approach has been proposed in this paper for processing unbalanced operating conditions in transient stability calculations. The suggested method combined positive sequence network usually used for traditionally balanced transient stability program with zero and negative sequence network which are available for traditional unsymmetrical fault routines. The zero and negative bus matrixes are usually available in sparse nature within any commercial software to handle large scale power system analysis. Therefore, they can be easily used in unbalanced transient stability routines, as described in this paper. Besides, a method is presented to evaluate DC offset currents in system branches during the phasor-based transient stability run. The DC offset arise from the stator and network transients during switching (including faults). Conventional phasor-based transient stability programs ignore the occurrences of such a DC offset in their simulation process. Approximating of DC and negative sequence current braking effects in AC machines and modeling negative, ground and overcurrent instantaneous protective equipments behavior in transient stability simulation are the main benefits of the proposed method. Computer test results in comparison with results carried out by detailed three-phase time-domain simulations using power system blockset (PSB) of MATLAB, show clearly the effectiveness of the method.
{"title":"A Proposed Method for Processing Unbalanced Conditions and DC Offset Currents in Transient Stability Analysis","authors":"S. Jafarabadi, S.M. Kouhsari","doi":"10.1109/PCT.2007.4538611","DOIUrl":"https://doi.org/10.1109/PCT.2007.4538611","url":null,"abstract":"An approach has been proposed in this paper for processing unbalanced operating conditions in transient stability calculations. The suggested method combined positive sequence network usually used for traditionally balanced transient stability program with zero and negative sequence network which are available for traditional unsymmetrical fault routines. The zero and negative bus matrixes are usually available in sparse nature within any commercial software to handle large scale power system analysis. Therefore, they can be easily used in unbalanced transient stability routines, as described in this paper. Besides, a method is presented to evaluate DC offset currents in system branches during the phasor-based transient stability run. The DC offset arise from the stator and network transients during switching (including faults). Conventional phasor-based transient stability programs ignore the occurrences of such a DC offset in their simulation process. Approximating of DC and negative sequence current braking effects in AC machines and modeling negative, ground and overcurrent instantaneous protective equipments behavior in transient stability simulation are the main benefits of the proposed method. Computer test results in comparison with results carried out by detailed three-phase time-domain simulations using power system blockset (PSB) of MATLAB, show clearly the effectiveness of the method.","PeriodicalId":356805,"journal":{"name":"2007 IEEE Lausanne Power Tech","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133274478","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 : 2007-07-01DOI: 10.1109/PCT.2007.4538462
H. Agahi, M. Karrari, A. Mahmoodzadeh
In this paper, two new methods for synchronous generator parameter estimation are presented. In the first method, a third order nonlinear model of the system is transformed to a linear regression form, without any linearization or simplification. Then, parameters are estimated using ordinary and parallel strategies. The second method indicates that if rotor speed, rotor angle and active and reactive powers are measured, all parameters can be estimated directly using simple approaches. The simulation results show good accuracy of the estimated parameters in both methods.
{"title":"Two New Methods for Synchronous Generator Parameter Estimation","authors":"H. Agahi, M. Karrari, A. Mahmoodzadeh","doi":"10.1109/PCT.2007.4538462","DOIUrl":"https://doi.org/10.1109/PCT.2007.4538462","url":null,"abstract":"In this paper, two new methods for synchronous generator parameter estimation are presented. In the first method, a third order nonlinear model of the system is transformed to a linear regression form, without any linearization or simplification. Then, parameters are estimated using ordinary and parallel strategies. The second method indicates that if rotor speed, rotor angle and active and reactive powers are measured, all parameters can be estimated directly using simple approaches. The simulation results show good accuracy of the estimated parameters in both methods.","PeriodicalId":356805,"journal":{"name":"2007 IEEE Lausanne Power Tech","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133416610","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 : 2007-07-01DOI: 10.1109/PCT.2007.4538644
H. Mori, S. Saito
This paper proposes a new method for identifying network topology in power system state estimation. Network topology identification is important to carry out state estimation appropriately. The mathematical formulation may be expressed as a mixed integer optimization problem that has state variables in continuous number and network topology in binary number. To solve it, this paper makes use of parallel tabu search (PTS) and the weighted least absolute value (WLAV) state estimator. The former is used to solve a combinatorial optimization problem efficiently. The latter gives a reliable estimate with the robust model criterion. The proposed method is tested in the IEEE 14-node and IEEE 118-node systems.
{"title":"A Hybrid Method of PTS and WLAV for State Estimation Including Network Topology Identification","authors":"H. Mori, S. Saito","doi":"10.1109/PCT.2007.4538644","DOIUrl":"https://doi.org/10.1109/PCT.2007.4538644","url":null,"abstract":"This paper proposes a new method for identifying network topology in power system state estimation. Network topology identification is important to carry out state estimation appropriately. The mathematical formulation may be expressed as a mixed integer optimization problem that has state variables in continuous number and network topology in binary number. To solve it, this paper makes use of parallel tabu search (PTS) and the weighted least absolute value (WLAV) state estimator. The former is used to solve a combinatorial optimization problem efficiently. The latter gives a reliable estimate with the robust model criterion. The proposed method is tested in the IEEE 14-node and IEEE 118-node systems.","PeriodicalId":356805,"journal":{"name":"2007 IEEE Lausanne Power Tech","volume":"358 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132240182","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：