新能源的大规模并网对电力系统的低碳减排具有重要意义,但电能的远距离输送也给电力系统安全稳定带来了挑战,其中可用输电能力(available transfer capability,ATC)是评价系统安全裕度的重要指标。在低碳减排背景下,如何协调决策ATC与...新能源的大规模并网对电力系统的低碳减排具有重要意义,但电能的远距离输送也给电力系统安全稳定带来了挑战,其中可用输电能力(available transfer capability,ATC)是评价系统安全裕度的重要指标。在低碳减排背景下,如何协调决策ATC与碳排放之间的关系具有现实意义。建立了一种基于机会约束规划并计及碳排放约束的随机ATC协调决策模型。通过多目标规划优化决策ATC与碳排放,采用法线边界交叉法求解该多目标优化问题。针对风电出力的不确定性,构造随机ATC的机会约束规划模型,采用基于半不变量法和原对偶内点法的启发式算法进行求解。最后采用IEEE 30节点系统及某地区实际电网验证所提模型的有效性和实用性。结果表明,所提模型协调了电力系统安全性与环保性之间的关系,对运行调度人员具有指导意义。展开更多
借助虚拟电厂(virtual power plant,VPP)平台,兼顾多元互补的电源侧与综合考虑需求响应的负荷侧的双侧协调配合,在考虑VPP经济性与可再生能源消纳的基础上,增加环保性目标,建立VPP源-荷协调多目标优化调度模型。针对多目标优化问题,首...借助虚拟电厂(virtual power plant,VPP)平台,兼顾多元互补的电源侧与综合考虑需求响应的负荷侧的双侧协调配合,在考虑VPP经济性与可再生能源消纳的基础上,增加环保性目标,建立VPP源-荷协调多目标优化调度模型。针对多目标优化问题,首先根据法线边界交叉法(normal boundary intersection,NBI)将其转化为一系列单目标优化问题,再利用自适应免疫遗传算法求解这类单目标优化问题,获得一系列均匀分布的Pareto最优解,最后根据层次-熵值组合赋权法决策出折中最优解。以某区域VPP为例进行仿真,验证所提方法可兼顾VPP的经济性、环保性与可再生能源消纳,同时表明源-荷协调运行的VPP,通过优化调度能有效提高可再生能源消纳水平,降低系统运行成本和对环境的污染。展开更多
With the linear interpolation method, an improved absorbing boundary condition（ABC）is introduced and derived, which is suitable for the alternating-direction-implicit finite- difference time-domain （ADI-FDTD） meth...With the linear interpolation method, an improved absorbing boundary condition（ABC）is introduced and derived, which is suitable for the alternating-direction-implicit finite- difference time-domain （ADI-FDTD） method. The reflection of the ABC caused by both the truncated error and the phase velocity error is analyzed. Based on the phase velocity estimation and the nonuniform cell, two methods are studied and then adopted to improve the performance of the ABC. A calculation case of a rectangular waveguide which is a typical dispersive transmission line is carried out using the ADI-FDTD method with the improved ABC for evaluation. According to the calculated case, the comparison is given between the reflection coefficients of the ABC with and without the velocity estimation and also the comparison between the reflection coefficients of the ABC with and without the nonuniform processing. The reflection variation of the ABC under different time steps is also analyzed and the acceptable worsening will not obscure the improvement on the absorption. Numerical results obviously show that efficient improvement on the absorbing performance of the ABC is achieved based on these methods for the ADI-FDTD.展开更多
With the rural concealed communication cable as the study object, the shielding effectiveness of different slot shapes was analyzed by using LBEM （linear boundary element method）. The engineering example results sho...With the rural concealed communication cable as the study object, the shielding effectiveness of different slot shapes was analyzed by using LBEM （linear boundary element method）. The engineering example results showed that for twocore shielded cable, the coupling capacitance of trapezoid slots （asymmetric and symmetric） changed the most, followed by rectangular slots （asymmetric and symmetric）, and the changes of wedge slots were the smallest, but the change tenden- cies were consistent. In addition, with the increase of slot width of different slots, the coupling capacitance of tow-cored shielded cable showed small change.展开更多
As watershed algorithm suffers from over-segmentation problem, this paper presented an efficient method to resolve this problem. First, pre-process of the image using median filter is made to reduce the effect of nois...As watershed algorithm suffers from over-segmentation problem, this paper presented an efficient method to resolve this problem. First, pre-process of the image using median filter is made to reduce the effect of noise. Second, watershed algorithm is employed to provide initial regions. Third, regions are merged according to the information between the region and boundary. In the merger processing based on the region information, an adaptive threshold of the difference between the neighboring regions is used as the region merge criteria, which is based on the human visual character. In the merger processing on the boundary information, the gradient is used to judge the true boundary of the image to avoid merging the foreground with the background regions. Finally, post-process to the regions using mathematical morphology open and close filter is done to smooth object boundaries. The experimental results show that this method is very efficient.展开更多
The development of a two dimensional numerical wave tank （NWT） with a rocker or piston type wavemaker based on the high order boundary element method （BEM） and mixed Eulerian-Lagrangian （MEL） is examined. The ca...The development of a two dimensional numerical wave tank （NWT） with a rocker or piston type wavemaker based on the high order boundary element method （BEM） and mixed Eulerian-Lagrangian （MEL） is examined. The cauchy principle value （CPV） integral is calculated by a special Gauss type quadrature and a change of variable. In addition the explicit truncated Taylor expansion formula is employed in the time-stepping process. A modified double nodes method is assumed to tackle the comer problem, as well as the damping zone technique is used to absorb the propagation of the free surface wave at the end of the tank. A variety of waves are generated by the NWT, for example; a monochromatic wave, solitary wave and irregular wave. The results confirm the NWT model is efficient and stable.展开更多
The second reference state of the open XYZ spin chain with non-diagonal boundary terms is studied. The associated Bethe states exactly yield the second set of eigenvalues proposed recently by functional Bethe Ansatz.
In this paper, the approximate solution to the linear fredholm-stieltjes integral equations of the second kind （LFSIESK） by using the generalized midpoint rule （GMR） is introduced. A comparison resu｜ts depending ...In this paper, the approximate solution to the linear fredholm-stieltjes integral equations of the second kind （LFSIESK） by using the generalized midpoint rule （GMR） is introduced. A comparison resu｜ts depending on the number of subintervals ＂n＂ are calculated by using Maple 18 and presented. These results are demonstrated graphically in a particular numerical example. An algorithm of this application is given by using Maple 18.展开更多
文摘新能源的大规模并网对电力系统的低碳减排具有重要意义,但电能的远距离输送也给电力系统安全稳定带来了挑战,其中可用输电能力(available transfer capability,ATC)是评价系统安全裕度的重要指标。在低碳减排背景下,如何协调决策ATC与碳排放之间的关系具有现实意义。建立了一种基于机会约束规划并计及碳排放约束的随机ATC协调决策模型。通过多目标规划优化决策ATC与碳排放,采用法线边界交叉法求解该多目标优化问题。针对风电出力的不确定性,构造随机ATC的机会约束规划模型,采用基于半不变量法和原对偶内点法的启发式算法进行求解。最后采用IEEE 30节点系统及某地区实际电网验证所提模型的有效性和实用性。结果表明,所提模型协调了电力系统安全性与环保性之间的关系,对运行调度人员具有指导意义。
文摘借助虚拟电厂(virtual power plant,VPP)平台,兼顾多元互补的电源侧与综合考虑需求响应的负荷侧的双侧协调配合,在考虑VPP经济性与可再生能源消纳的基础上,增加环保性目标,建立VPP源-荷协调多目标优化调度模型。针对多目标优化问题,首先根据法线边界交叉法(normal boundary intersection,NBI)将其转化为一系列单目标优化问题,再利用自适应免疫遗传算法求解这类单目标优化问题,获得一系列均匀分布的Pareto最优解,最后根据层次-熵值组合赋权法决策出折中最优解。以某区域VPP为例进行仿真,验证所提方法可兼顾VPP的经济性、环保性与可再生能源消纳,同时表明源-荷协调运行的VPP,通过优化调度能有效提高可再生能源消纳水平,降低系统运行成本和对环境的污染。
基金The National Natural Science Foundation of China(No.60702027)the Free Research Fund of the National Mobile Communications Research Laboratory of Southeast University (No.2008B07)the National Basic Research Program of China(973 Program)(No.2007CB310603)
文摘With the linear interpolation method, an improved absorbing boundary condition（ABC）is introduced and derived, which is suitable for the alternating-direction-implicit finite- difference time-domain （ADI-FDTD） method. The reflection of the ABC caused by both the truncated error and the phase velocity error is analyzed. Based on the phase velocity estimation and the nonuniform cell, two methods are studied and then adopted to improve the performance of the ABC. A calculation case of a rectangular waveguide which is a typical dispersive transmission line is carried out using the ADI-FDTD method with the improved ABC for evaluation. According to the calculated case, the comparison is given between the reflection coefficients of the ABC with and without the velocity estimation and also the comparison between the reflection coefficients of the ABC with and without the nonuniform processing. The reflection variation of the ABC under different time steps is also analyzed and the acceptable worsening will not obscure the improvement on the absorption. Numerical results obviously show that efficient improvement on the absorbing performance of the ABC is achieved based on these methods for the ADI-FDTD.
基金Supported by the Science and Technology Program of the Education Department of Shaanxi Provincial Government(09JK378)the Key Scientific Research Fund of Shaanxi University of Technology(SLGKY12-02)~~
文摘With the rural concealed communication cable as the study object, the shielding effectiveness of different slot shapes was analyzed by using LBEM （linear boundary element method）. The engineering example results showed that for twocore shielded cable, the coupling capacitance of trapezoid slots （asymmetric and symmetric） changed the most, followed by rectangular slots （asymmetric and symmetric）, and the changes of wedge slots were the smallest, but the change tenden- cies were consistent. In addition, with the increase of slot width of different slots, the coupling capacitance of tow-cored shielded cable showed small change.
文摘As watershed algorithm suffers from over-segmentation problem, this paper presented an efficient method to resolve this problem. First, pre-process of the image using median filter is made to reduce the effect of noise. Second, watershed algorithm is employed to provide initial regions. Third, regions are merged according to the information between the region and boundary. In the merger processing based on the region information, an adaptive threshold of the difference between the neighboring regions is used as the region merge criteria, which is based on the human visual character. In the merger processing on the boundary information, the gradient is used to judge the true boundary of the image to avoid merging the foreground with the background regions. Finally, post-process to the regions using mathematical morphology open and close filter is done to smooth object boundaries. The experimental results show that this method is very efficient.
基金Foundation item： Supported by the National Natural Science Foundation of China （Grant No.51009038/E091002）.
文摘The development of a two dimensional numerical wave tank （NWT） with a rocker or piston type wavemaker based on the high order boundary element method （BEM） and mixed Eulerian-Lagrangian （MEL） is examined. The cauchy principle value （CPV） integral is calculated by a special Gauss type quadrature and a change of variable. In addition the explicit truncated Taylor expansion formula is employed in the time-stepping process. A modified double nodes method is assumed to tackle the comer problem, as well as the damping zone technique is used to absorb the propagation of the free surface wave at the end of the tank. A variety of waves are generated by the NWT, for example; a monochromatic wave, solitary wave and irregular wave. The results confirm the NWT model is efficient and stable.
基金Supports by the National Natural Science Foundation of China under Grant Nos. 11075125 and 11031005
文摘The second reference state of the open XYZ spin chain with non-diagonal boundary terms is studied. The associated Bethe states exactly yield the second set of eigenvalues proposed recently by functional Bethe Ansatz.
文摘In this paper, the approximate solution to the linear fredholm-stieltjes integral equations of the second kind （LFSIESK） by using the generalized midpoint rule （GMR） is introduced. A comparison resu｜ts depending on the number of subintervals ＂n＂ are calculated by using Maple 18 and presented. These results are demonstrated graphically in a particular numerical example. An algorithm of this application is given by using Maple 18.
