The growth of wind energy penetration level in distribution system raises the concern about its impact on the operation of the power system, especially voltage stability and power loss. Among the major concerns, this ...The growth of wind energy penetration level in distribution system raises the concern about its impact on the operation of the power system, especially voltage stability and power loss. Among the major concerns, this paper studied the impact of connecting wind Turbine (WT) in radial distribution system with different penetration levels and different power factor (lead and lag) on power system voltage stability and power loss reduction. Load flow calculation was carried out using forward-backward sweep method. The analysis proceeds on 9- and 33-bus radial distribution systems. Results show that voltage stability enhancement and power loss reduction should be considered as WT installation objective.展开更多
Selecting the best type of equipment among available switches with different prices and reliability levels is a significant challenge in distribution system planning.In this paper,the optimal type of switches in a rad...Selecting the best type of equipment among available switches with different prices and reliability levels is a significant challenge in distribution system planning.In this paper,the optimal type of switches in a radial distribution system is selected by considering the total cost and reliability criterion and using the weighted augmented epsilon constraint method and combinatorial optimization.A new index is calculated to assess the robustness of each Pareto solution.Moreover,for each failure,repair time is considered based on historical data.Monte Carlo simulations are used to consider the switch failure uncertainty and fault repair time uncertainty in the model.The proposed framework is applied to an RTBS Bus-2 test system.Furthermore,the model is also applied to an industrial system to verify the proposed method’s excellent performance in larger practical engineering problems.展开更多
In this work,the reversal of radial glow distribution induced by reversed magnetic field is reported.Based on the Boswell antenna which is symmetric and insensitive to the magnetic field direction,it seems such a phen...In this work,the reversal of radial glow distribution induced by reversed magnetic field is reported.Based on the Boswell antenna which is symmetric and insensitive to the magnetic field direction,it seems such a phenomenon in theory appears impossible.However,according to the diagnostic of the helicon waves by magnetic probe,it is found that the direction of magnetic field significantly affects the propagation characteristic of helicon waves,i.e.,the interchange of the helicon waves at the upper and the lower half of tube was caused by reversing the direction of magnetic field.It is suggested that the variation of helicon wave against the direction of magnetic field causes the reversed radial glow distribution.The appearance of the traveling wave does not only improve the discharge strength,but also determines the transition of the discharge mode.展开更多
Nowadays the optimal allocation of distributed generation (DG) in the distribution network becomes the popular research area in restructuring of power system. The capacitor banks introduced in the distribution network...Nowadays the optimal allocation of distributed generation (DG) in the distribution network becomes the popular research area in restructuring of power system. The capacitor banks introduced in the distribution networks for reactive power compensation also have the capacity to minimize the real and reactive power losses occurred in the system. Hence, this research integrates the allocation of renewable energy DG and capacitor banks in the radial distribution network to minimize the real power loss occurred in the system. A two-stage methodology is used for simultaneous allocation of renewable DG and capacitor banks. The optimum location of renewable energy DG and capacitor banks is determined using the distributed generation sitting index (DGSI) ranking method and the optimum sizing of DG and capacitor banks is found out for simultaneous placement using weight improved particle swarm optimization algorithm (WIPSO) and self adaptive differential evolution algorithm (SADE). This two-stage methodology reduces the burden of SADE and WIPSO algorithm, by using the DGSI index in determining the optimal location. Hence the computational time gets reduced which makes them suitable for online applications. By using the above methodology, a comprehensive performance analysis is done on IEEE 33 bus and 69 bus RDNs and the results are discussed in detail.展开更多
With the growing number and capacity of photovoltaic(PV)installations connected to distribution networks,power quality issues related to voltage regulation are becoming relevant problems for power distribution compani...With the growing number and capacity of photovoltaic(PV)installations connected to distribution networks,power quality issues related to voltage regulation are becoming relevant problems for power distribution companies and for PV owners.In many countries,like Italy,this has required the revision of the standards concerning the connection to the public distribution network of distributed renewable generation.The new standards require a flexible operation of generation plants that have to be capable to change the active and reactive power dynamically in function of the network parameters(i.e.frequency and network local voltage)in local control or following external commands.Therefore,this paper investigates the use of smart inverter in a critical PV installation,where relevant voltage fluctuations exist.A case study,with real network parameters monitoring data and measurements,is discussed in the paper with the aim of showing how‘smart’features of new inverters can be implemented to increase PV plant integration in low voltage distribution networks.展开更多
A new method to determine the radial distribution of attenuation in single-mode optical fibers is proposed. As an example, radiation-induced losses in gamma-irradiated germanosilicate fibers are characterized at 633 nm.
We present the isothermal susceptibility(XT)for the typical binary polycondensation system of Af-Bg type,and relate XT to the weight-average degree of polymerization in terms of the Kirkwood-Buff(KB)theory.The investi...We present the isothermal susceptibility(XT)for the typical binary polycondensation system of Af-Bg type,and relate XT to the weight-average degree of polymerization in terms of the Kirkwood-Buff(KB)theory.The investigation is based on a new expression of XT for mixtures,which is still expressed by the KB integrals(KBIs)but endowed with an explicit physical interpretation.For polymerization systems,it is proposed that the KBIs can be further decomposed according to whether there exists a bond between particles when conversions(extents of reaction)of functional groups are incorporated into the KBIs.In this way,XT is directly decomposed into its relevant components as well.This is especially useful to reveal the relationship between local structures and average properties of various polymerization systems.As a consequence,the effect of polymerization on XT is greatly simplified in comparison with the free energy route.Therefore,we have provided a very simple method to carry out some thermodynamic properties of polymerization systems.展开更多
A formalism of solid state physics has been applied to provide an additional tool for the research of cosmological problems. It is demonstrated how this new approach could be useful in the analysis of the Cosmic Micro...A formalism of solid state physics has been applied to provide an additional tool for the research of cosmological problems. It is demonstrated how this new approach could be useful in the analysis of the Cosmic Microwave Background (CMB) data. After a transformation of the anisotropy spectrum of relict radiation into a special two-fold reciprocal space it was possible to propose a simple and general description of the interaction of relict photons with the matter by a “relict radiation factor”. This factor enabled us to process the transformed CMB anisotropy spectrum by a Fourier transform and thus arrive to a radial electron density distribution function (RDF) in a reciprocal space. As a consequence it was possible to estimate distances between Objects of the order of ~102 [m] and the density of the ordinary matter ~10-22 [kg.m-3]. Another analysis based on a direct calculation of the CMB radiation spectrum after its transformation into a simple reciprocal space and combined with appropriate structure modelling confirmed the cluster structure. The internal structure of Objects may be formed by Clusters distant ~10 [cm], whereas the internal structure of a Cluster consisted of particles distant ~0.3 [nm]. The work points in favour of clustering processes and to a cluster-like structure of the matter and thus contributes to the understanding of the structure of density fluctuations. As a consequence it may shed more light on the structure of the universe in the moment when the universe became transparent for photons. On the basis of our quantitative considerations it was possible to derive the number of particles (protons, helium nuclei, electrons and other particles) in Objects and Clusters and the number of Clusters in an Object.展开更多
The compatibility of polylactic acid(PLA)/polybutylene succinate(PBS)blends was studied by molecular dynamics and mesoscopic dynamics,which is a controversial issue in experiments.Six simulation models of PLA/PBS with...The compatibility of polylactic acid(PLA)/polybutylene succinate(PBS)blends was studied by molecular dynamics and mesoscopic dynamics,which is a controversial issue in experiments.Six simulation models of PLA/PBS with different composition ratios(100/0,90/10,80/20,70/30,60/40,0/100)were constructed.The radial distribution function,hydrogen bond,free energy density,order parameter and iso-density surface morphology of the PLA/PBS systems were simulated and analyzed.Due to the formation of hydrogen bonds and van der Waals bonds between different elements of PLA chains and PBS chains,the PLA/PBS blends exhibit good compatibility at all composition ratios.展开更多
文摘The growth of wind energy penetration level in distribution system raises the concern about its impact on the operation of the power system, especially voltage stability and power loss. Among the major concerns, this paper studied the impact of connecting wind Turbine (WT) in radial distribution system with different penetration levels and different power factor (lead and lag) on power system voltage stability and power loss reduction. Load flow calculation was carried out using forward-backward sweep method. The analysis proceeds on 9- and 33-bus radial distribution systems. Results show that voltage stability enhancement and power loss reduction should be considered as WT installation objective.
文摘Selecting the best type of equipment among available switches with different prices and reliability levels is a significant challenge in distribution system planning.In this paper,the optimal type of switches in a radial distribution system is selected by considering the total cost and reliability criterion and using the weighted augmented epsilon constraint method and combinatorial optimization.A new index is calculated to assess the robustness of each Pareto solution.Moreover,for each failure,repair time is considered based on historical data.Monte Carlo simulations are used to consider the switch failure uncertainty and fault repair time uncertainty in the model.The proposed framework is applied to an RTBS Bus-2 test system.Furthermore,the model is also applied to an industrial system to verify the proposed method’s excellent performance in larger practical engineering problems.
基金financially supported by National Natural Science Foundation of China(Nos.11175024,11375031,11505013)BJNSFC(No.KZ201510015014)+2 种基金Beijing Municipal Natural Science Foundation(No.4162024)State Key Laboratory of Electrical Insulation and Power Equipment(No.EIPE15208)Beijing municipal coordination innovation program 2011
文摘In this work,the reversal of radial glow distribution induced by reversed magnetic field is reported.Based on the Boswell antenna which is symmetric and insensitive to the magnetic field direction,it seems such a phenomenon in theory appears impossible.However,according to the diagnostic of the helicon waves by magnetic probe,it is found that the direction of magnetic field significantly affects the propagation characteristic of helicon waves,i.e.,the interchange of the helicon waves at the upper and the lower half of tube was caused by reversing the direction of magnetic field.It is suggested that the variation of helicon wave against the direction of magnetic field causes the reversed radial glow distribution.The appearance of the traveling wave does not only improve the discharge strength,but also determines the transition of the discharge mode.
文摘Nowadays the optimal allocation of distributed generation (DG) in the distribution network becomes the popular research area in restructuring of power system. The capacitor banks introduced in the distribution networks for reactive power compensation also have the capacity to minimize the real and reactive power losses occurred in the system. Hence, this research integrates the allocation of renewable energy DG and capacitor banks in the radial distribution network to minimize the real power loss occurred in the system. A two-stage methodology is used for simultaneous allocation of renewable DG and capacitor banks. The optimum location of renewable energy DG and capacitor banks is determined using the distributed generation sitting index (DGSI) ranking method and the optimum sizing of DG and capacitor banks is found out for simultaneous placement using weight improved particle swarm optimization algorithm (WIPSO) and self adaptive differential evolution algorithm (SADE). This two-stage methodology reduces the burden of SADE and WIPSO algorithm, by using the DGSI index in determining the optimal location. Hence the computational time gets reduced which makes them suitable for online applications. By using the above methodology, a comprehensive performance analysis is done on IEEE 33 bus and 69 bus RDNs and the results are discussed in detail.
文摘With the growing number and capacity of photovoltaic(PV)installations connected to distribution networks,power quality issues related to voltage regulation are becoming relevant problems for power distribution companies and for PV owners.In many countries,like Italy,this has required the revision of the standards concerning the connection to the public distribution network of distributed renewable generation.The new standards require a flexible operation of generation plants that have to be capable to change the active and reactive power dynamically in function of the network parameters(i.e.frequency and network local voltage)in local control or following external commands.Therefore,this paper investigates the use of smart inverter in a critical PV installation,where relevant voltage fluctuations exist.A case study,with real network parameters monitoring data and measurements,is discussed in the paper with the aim of showing how‘smart’features of new inverters can be implemented to increase PV plant integration in low voltage distribution networks.
文摘A new method to determine the radial distribution of attenuation in single-mode optical fibers is proposed. As an example, radiation-induced losses in gamma-irradiated germanosilicate fibers are characterized at 633 nm.
基金supported by the Natural Science Foundation of Hebei Province,China(No.B2022201050)the Interdisciplinary Research Program of Natural Science of Hebei University,China(No.DXK202112).
文摘We present the isothermal susceptibility(XT)for the typical binary polycondensation system of Af-Bg type,and relate XT to the weight-average degree of polymerization in terms of the Kirkwood-Buff(KB)theory.The investigation is based on a new expression of XT for mixtures,which is still expressed by the KB integrals(KBIs)but endowed with an explicit physical interpretation.For polymerization systems,it is proposed that the KBIs can be further decomposed according to whether there exists a bond between particles when conversions(extents of reaction)of functional groups are incorporated into the KBIs.In this way,XT is directly decomposed into its relevant components as well.This is especially useful to reveal the relationship between local structures and average properties of various polymerization systems.As a consequence,the effect of polymerization on XT is greatly simplified in comparison with the free energy route.Therefore,we have provided a very simple method to carry out some thermodynamic properties of polymerization systems.
文摘A formalism of solid state physics has been applied to provide an additional tool for the research of cosmological problems. It is demonstrated how this new approach could be useful in the analysis of the Cosmic Microwave Background (CMB) data. After a transformation of the anisotropy spectrum of relict radiation into a special two-fold reciprocal space it was possible to propose a simple and general description of the interaction of relict photons with the matter by a “relict radiation factor”. This factor enabled us to process the transformed CMB anisotropy spectrum by a Fourier transform and thus arrive to a radial electron density distribution function (RDF) in a reciprocal space. As a consequence it was possible to estimate distances between Objects of the order of ~102 [m] and the density of the ordinary matter ~10-22 [kg.m-3]. Another analysis based on a direct calculation of the CMB radiation spectrum after its transformation into a simple reciprocal space and combined with appropriate structure modelling confirmed the cluster structure. The internal structure of Objects may be formed by Clusters distant ~10 [cm], whereas the internal structure of a Cluster consisted of particles distant ~0.3 [nm]. The work points in favour of clustering processes and to a cluster-like structure of the matter and thus contributes to the understanding of the structure of density fluctuations. As a consequence it may shed more light on the structure of the universe in the moment when the universe became transparent for photons. On the basis of our quantitative considerations it was possible to derive the number of particles (protons, helium nuclei, electrons and other particles) in Objects and Clusters and the number of Clusters in an Object.
基金supported by the National Natural Science Foundation of China[11672086].
文摘The compatibility of polylactic acid(PLA)/polybutylene succinate(PBS)blends was studied by molecular dynamics and mesoscopic dynamics,which is a controversial issue in experiments.Six simulation models of PLA/PBS with different composition ratios(100/0,90/10,80/20,70/30,60/40,0/100)were constructed.The radial distribution function,hydrogen bond,free energy density,order parameter and iso-density surface morphology of the PLA/PBS systems were simulated and analyzed.Due to the formation of hydrogen bonds and van der Waals bonds between different elements of PLA chains and PBS chains,the PLA/PBS blends exhibit good compatibility at all composition ratios.
