In a competitive environment reactive power management is an essential service provided by independent system operator taking into account the voltage security and transmission losses. The system operator adopts a tra...In a competitive environment reactive power management is an essential service provided by independent system operator taking into account the voltage security and transmission losses. The system operator adopts a transparent and non-dis-criminatory procedure to procure the reactive power supply for optimal deployment in the system. Since generators’ are the main source of reactive power generation and the cost of the reactive power should be considered for their noticeable impact on both real and reactive power marginal prices. In this paper, a method based on marginal cost theory is presented for locational marginal prices calculation for real and reactive power considering different reactive power cost models of generators’ reactive support. With the presence of FACTS controllers in the system for more flexible operation, their impact on nodal prices can not be ignored for wheeling cost determination and has also to be considered taking their cost function into account. The results have been obtained for hybrid electricity market model and results have also been computed for pool model for comparison. Mixed Integer Non-linear programming (MINLP) approach has been formulated for solving the complex problem with MATLAB and GAMS interfacing. The proposed approach has been tested on IEEE 24-bus Reliability Test System (RTS).展开更多
Query efficiency is bottleneck of XML data cube aggregate query. pXCube is a kind of XML data cube model based on path calculation. Join operations are avoided in this model, but the query efficiency of fact cell is b...Query efficiency is bottleneck of XML data cube aggregate query. pXCube is a kind of XML data cube model based on path calculation. Join operations are avoided in this model, but the query efficiency of fact cell is become a new bottleneck. This paper focuses on parallel technology of cloud computing to improve query efficiency of pXCube. Mixed partitioning strategy for fact and dimensions is applied in pXCube cloud model, and the same partitioned vector is adopted. Query parallel algorithm of pXCube cloud model is presented as well. Experiments show that the query cost of pXCube cloud model decreases with the increasing number of parallel nodes gradually. The query cost of fact fragments of each node are close to or even lower than join operations of dimensions, and the Speedup is with better linear. So the model is well suited for decision supported query.展开更多
The parameters of power system slowly change with time due to environmental effects or may change rapidly due to faults. It is preferable that the control technique in this system possesses robustness for various faul...The parameters of power system slowly change with time due to environmental effects or may change rapidly due to faults. It is preferable that the control technique in this system possesses robustness for various fault conditions and disturbances. The used flexible alternating current transmission system （FACTS） in this paper is an advanced super-conducting magnetic energy storage （ASMES）. Many control techniques that use ASMES to improve power system stability have been proposed. While fuzzy controller has proven its value in some applications, the researches applying fuzzy controller with ASMES have been actively reported. However, it is sometimes very difficult to specify the rule base for some plants, when the parameters change. To solve this problem, a fuzzy model reference learning controller （FMRLC） is proposed in this paper, which investigates multi-input multi-output FMRLC for time-variant nonlinear system. This control method provides the motivation for adaptive fuzzy control, where the focus is on the automatic online synthesis and tuning of fuzzy controller parameters （i.e., using online data to continually learn the fuzzy controller that will ensure that the performance objectives are met）. Simulation results show that the proposed robust controller is able to work with nonlinear and nonstationary power system （i.e., single machine-infinite bus （SMIB） system）, under various fault conditions and disturbances.展开更多
In this paper, we first briefly introduce the concepts of clickstream data and data warehouse, analyze twoexisting clickstream star schema click star schema and session star schema in webhouse, then induce a new mod-e...In this paper, we first briefly introduce the concepts of clickstream data and data warehouse, analyze twoexisting clickstream star schema click star schema and session star schema in webhouse, then induce a new mod-el transaction star model based on them, and expressed the method of bringing out the model. Comparing withthe two schemas mentioned above, its most apparent speciality is that it includes a series of meaningful page-view se-quence rather than a single click. Thus, on the one hand it improves the query performance of data, on the other handit is in favor of executing more deepen analysis data mining, and simplifies the process of data pretreatment. Atlast ,the paper verifies its' feasibility and validity using association rules based on the model.展开更多
文摘In a competitive environment reactive power management is an essential service provided by independent system operator taking into account the voltage security and transmission losses. The system operator adopts a transparent and non-dis-criminatory procedure to procure the reactive power supply for optimal deployment in the system. Since generators’ are the main source of reactive power generation and the cost of the reactive power should be considered for their noticeable impact on both real and reactive power marginal prices. In this paper, a method based on marginal cost theory is presented for locational marginal prices calculation for real and reactive power considering different reactive power cost models of generators’ reactive support. With the presence of FACTS controllers in the system for more flexible operation, their impact on nodal prices can not be ignored for wheeling cost determination and has also to be considered taking their cost function into account. The results have been obtained for hybrid electricity market model and results have also been computed for pool model for comparison. Mixed Integer Non-linear programming (MINLP) approach has been formulated for solving the complex problem with MATLAB and GAMS interfacing. The proposed approach has been tested on IEEE 24-bus Reliability Test System (RTS).
基金supported by National Natural Science Foundation of China under Grant No. 61072091
文摘Query efficiency is bottleneck of XML data cube aggregate query. pXCube is a kind of XML data cube model based on path calculation. Join operations are avoided in this model, but the query efficiency of fact cell is become a new bottleneck. This paper focuses on parallel technology of cloud computing to improve query efficiency of pXCube. Mixed partitioning strategy for fact and dimensions is applied in pXCube cloud model, and the same partitioned vector is adopted. Query parallel algorithm of pXCube cloud model is presented as well. Experiments show that the query cost of pXCube cloud model decreases with the increasing number of parallel nodes gradually. The query cost of fact fragments of each node are close to or even lower than join operations of dimensions, and the Speedup is with better linear. So the model is well suited for decision supported query.
文摘The parameters of power system slowly change with time due to environmental effects or may change rapidly due to faults. It is preferable that the control technique in this system possesses robustness for various fault conditions and disturbances. The used flexible alternating current transmission system （FACTS） in this paper is an advanced super-conducting magnetic energy storage （ASMES）. Many control techniques that use ASMES to improve power system stability have been proposed. While fuzzy controller has proven its value in some applications, the researches applying fuzzy controller with ASMES have been actively reported. However, it is sometimes very difficult to specify the rule base for some plants, when the parameters change. To solve this problem, a fuzzy model reference learning controller （FMRLC） is proposed in this paper, which investigates multi-input multi-output FMRLC for time-variant nonlinear system. This control method provides the motivation for adaptive fuzzy control, where the focus is on the automatic online synthesis and tuning of fuzzy controller parameters （i.e., using online data to continually learn the fuzzy controller that will ensure that the performance objectives are met）. Simulation results show that the proposed robust controller is able to work with nonlinear and nonstationary power system （i.e., single machine-infinite bus （SMIB） system）, under various fault conditions and disturbances.
文摘In this paper, we first briefly introduce the concepts of clickstream data and data warehouse, analyze twoexisting clickstream star schema click star schema and session star schema in webhouse, then induce a new mod-el transaction star model based on them, and expressed the method of bringing out the model. Comparing withthe two schemas mentioned above, its most apparent speciality is that it includes a series of meaningful page-view se-quence rather than a single click. Thus, on the one hand it improves the query performance of data, on the other handit is in favor of executing more deepen analysis data mining, and simplifies the process of data pretreatment. Atlast ,the paper verifies its' feasibility and validity using association rules based on the model.
