An online TL （transmission line） impedance TPIS （transmission line parameter identification system） using PMU （phasor measurement unit） was recently developed and implemented at CSG （china southern power grid c...An online TL （transmission line） impedance TPIS （transmission line parameter identification system） using PMU （phasor measurement unit） was recently developed and implemented at CSG （china southern power grid company）, Traditional approaches for TL impedance calculation only approximate the effect of conductor sags and ignore the dependence of impedances on temperature variation. Utilizing PMU measurements may improve the accuracy of TL parameters calculation. The challenge is that the parameters identified are very sensitive to noise and errors in PMU measurements, which are difficult to quantify and can be uncertain under different system operating/loading condition, TPIS provides an innovative yet practical problem formulation for TL sequence parameter estimation based on least-squares with linear constraints. A bootstrapping-based resampling technique is developed and a new metric is proposed to determine the credibility of the estimated sequence impedances. This paper discusses the proposed methodologies, challenges, as well as implementation issues identified during the development of TPIS.展开更多
In the frame of compressed sensing distributed video coding, the design of the quantization matrix directly affects the reconstruction quality of the receiving terminal of the video. In this article, we present a new ...In the frame of compressed sensing distributed video coding, the design of the quantization matrix directly affects the reconstruction quality of the receiving terminal of the video. In this article, we present a new design method of the Gaussian quantization matrix adapting to the compressed sensing coding, for that the distribution of the parameters of the image is featured of the characteristic of approximately normal distribution after measured by compressive sensing. By this way, the parameters of a certain quantity of the image frames depending on the video sequences generated by the Gaussian quantization matrix possess certain adaptive capacity. By comparison with the plan of the traditional quantization, the quantization matrix presented in this article would improve the reconstruction quality of the video.展开更多
China Southern Power Grid Company(CSG)recently developed and implemented an online PMU-based transmission line(TL)parameter identification system(TPIS).Traditionally,TL parameters are calculated based on transmission ...China Southern Power Grid Company(CSG)recently developed and implemented an online PMU-based transmission line(TL)parameter identification system(TPIS).Traditionally,TL parameters are calculated based on transmission tower geometries,conductor dimension,estimates of line length,conductor sags,etc.These parameters only approximate the effect of conductor sag and ignore the dependence of impedance parameters on temperature variation.Recent development in PMU technology has made it possible to calculate TL parameters accurately.The challenges are that such an application requires highly accurate PMU data while the accuracy of PMU measurements under different working/system conditions can be uncertain.With a large number of PMUs widely installed in its system,CSG plans to improve and update the EMS database using the newly developed TPIS.TPIS provides an innovative yet practical problem formulation and solution for TL parameter identification.In addition,it proposes a new metric that can be used to determine the credibility of the calculated parameters,which is missing in the literature.This paper discusses the methodologies,challenges,as well as implementation issues noticed during the development of TPIS.展开更多
Owing to its ability of modelling large deformations and the ease of dealing with moving boundary conditions,the material point method is gaining popularity in geotechnical engineering applications.In this paper,this ...Owing to its ability of modelling large deformations and the ease of dealing with moving boundary conditions,the material point method is gaining popularity in geotechnical engineering applications.In this paper,this promising Lagrangian method is applied to hydrodynamic problems to further explore its potential.The collapse of water columns with different initial aspect ratios is simulated by the material point method.In order to test the accuracy and stability of the material point method,simulations are first validated using experimental data and results of mature numerical models.Then,the model is used to ascertain the critical aspect ratio for the widely-used shallow water equations to give satisfactory approximation.From the comparisons between the simulations based on the material point method and the shallow water equations,the critical aspect ratio for the suitable use of the shallow water equations is found to be 1.展开更多
文摘An online TL （transmission line） impedance TPIS （transmission line parameter identification system） using PMU （phasor measurement unit） was recently developed and implemented at CSG （china southern power grid company）, Traditional approaches for TL impedance calculation only approximate the effect of conductor sags and ignore the dependence of impedances on temperature variation. Utilizing PMU measurements may improve the accuracy of TL parameters calculation. The challenge is that the parameters identified are very sensitive to noise and errors in PMU measurements, which are difficult to quantify and can be uncertain under different system operating/loading condition, TPIS provides an innovative yet practical problem formulation for TL sequence parameter estimation based on least-squares with linear constraints. A bootstrapping-based resampling technique is developed and a new metric is proposed to determine the credibility of the estimated sequence impedances. This paper discusses the proposed methodologies, challenges, as well as implementation issues identified during the development of TPIS.
文摘In the frame of compressed sensing distributed video coding, the design of the quantization matrix directly affects the reconstruction quality of the receiving terminal of the video. In this article, we present a new design method of the Gaussian quantization matrix adapting to the compressed sensing coding, for that the distribution of the parameters of the image is featured of the characteristic of approximately normal distribution after measured by compressive sensing. By this way, the parameters of a certain quantity of the image frames depending on the video sequences generated by the Gaussian quantization matrix possess certain adaptive capacity. By comparison with the plan of the traditional quantization, the quantization matrix presented in this article would improve the reconstruction quality of the video.
文摘China Southern Power Grid Company(CSG)recently developed and implemented an online PMU-based transmission line(TL)parameter identification system(TPIS).Traditionally,TL parameters are calculated based on transmission tower geometries,conductor dimension,estimates of line length,conductor sags,etc.These parameters only approximate the effect of conductor sag and ignore the dependence of impedance parameters on temperature variation.Recent development in PMU technology has made it possible to calculate TL parameters accurately.The challenges are that such an application requires highly accurate PMU data while the accuracy of PMU measurements under different working/system conditions can be uncertain.With a large number of PMUs widely installed in its system,CSG plans to improve and update the EMS database using the newly developed TPIS.TPIS provides an innovative yet practical problem formulation and solution for TL parameter identification.In addition,it proposes a new metric that can be used to determine the credibility of the calculated parameters,which is missing in the literature.This paper discusses the methodologies,challenges,as well as implementation issues noticed during the development of TPIS.
基金supported by the European Union Seventh Framework Program(FP7/2007-2013)under grant agreement No.PIAG-GA-2012-324522“MPM-DREDGE”
文摘Owing to its ability of modelling large deformations and the ease of dealing with moving boundary conditions,the material point method is gaining popularity in geotechnical engineering applications.In this paper,this promising Lagrangian method is applied to hydrodynamic problems to further explore its potential.The collapse of water columns with different initial aspect ratios is simulated by the material point method.In order to test the accuracy and stability of the material point method,simulations are first validated using experimental data and results of mature numerical models.Then,the model is used to ascertain the critical aspect ratio for the widely-used shallow water equations to give satisfactory approximation.From the comparisons between the simulations based on the material point method and the shallow water equations,the critical aspect ratio for the suitable use of the shallow water equations is found to be 1.
