In this paper,the equivalent reluctance network model(ERNM)is used to calculate the magnetic circuit of a permanent magnet-assisted synchronous reluctance motor(PMASynRM)and calculate no-load air-gap magnetic field an...In this paper,the equivalent reluctance network model(ERNM)is used to calculate the magnetic circuit of a permanent magnet-assisted synchronous reluctance motor(PMASynRM)and calculate no-load air-gap magnetic field and electromagnetic torque.Iteration method is used to solve the relative permeability of iron core.A novel reluctance network model based on actual distribution of the magnetic flux inside the motor is established.The magnetomotive force(MMF)generated by armature winding affects the relative permeability of iron core,which is considered in the calculation of ERNM to improve the accuracy when the motor is under load.ERNM can be used to measure air-gap flux density,no-load back electromotive force(EMF),the average value of motor torque,the armature winding voltage under load,and power factor.The method of calculating the motor performance is proposed.The results of calculation are consistent with finite element method(FEM)and the computational complexity is much less than that of the FEM.The results of ERNM has been verified,which will provide a simple method for motor design and analysis.展开更多
In this paper, a Wavelength Division Multiplexing (WDM) network model based on the equivalent networks is described, and wavelength-dependent equivalent arc, equivalent networks, equivalent multicast tree and some oth...In this paper, a Wavelength Division Multiplexing (WDM) network model based on the equivalent networks is described, and wavelength-dependent equivalent arc, equivalent networks, equivalent multicast tree and some other terms are presented. Based on this model and relevant Routing and Wavelength Assign- ment (RWA) strategy, a unicast RWA algorithm and a multicast RWA algorithm are presented. The wave- length-dependent equivalent arc expresses the schedule of local RWA and the equivalent network expresses the whole topology of WDM optical networks, so the two algorithms are of the flexibility in RWA and the optimi- zation of the whole problem. The theoretic analysis and simulation results show the two algorithms are of the stronger capability and the lower complexity than the other existing algorithms for RWA problem, and the complexity of the two algorithms are only related to the scale of the equivalent networks. Finally, we prove the two algorithms’ feasibility and the one-by-one corresponding relation between the equivalent multicast tree and original multicast tree, and point out the superiorities and drawbacks of the two algorithms respectively.展开更多
In this paper,a 20kW vehicle built-in permanent magnet synchronous motor is taken as an example,and a magnetic barrier structure is added to the rotor of the motor to solve the uneven saturation problem of the rotor s...In this paper,a 20kW vehicle built-in permanent magnet synchronous motor is taken as an example,and a magnetic barrier structure is added to the rotor of the motor to solve the uneven saturation problem of the rotor side magnetic bridge.This structure improves the air-gap flux density waveform of the motor by influencing the internal magnetic flux path of the motor rotor,thus improving the sine of the no-load back EMF waveform of the motor and reducing the torque ripple of the motor.At the same time,Taguchi method is used to optimize the structural parameters of the added magnetic barrier.In order to facilitate the analysis of its uneven saturation phenomenon and improve the optimization effect,a simple equivalent magnetic network(EMN)model considering the uneven saturation of rotor magnetic bridge is established in this paper,and the initial values of optimization factors are selected based on this model.Finally,the no-load back EMF waveform distortion rate,torque ripple and output torque of the optimized motor are compared and analyzed,and the influence of magnetic barrier structure parameters on the electromagnetic performance of the motor is also analyzed.The results show that the optimized motor can not change the output torque of the motor as much as possible on the basis of reducing the waveform distortion rate of no-load back EMF and torque ripple.展开更多
Given large-scale modern power systems with pow er electronic converters,the numerical simulation with subsyn chronous oscillation(SSO)faces great challenges in engineering practice due to sharply enlarged modeling sc...Given large-scale modern power systems with pow er electronic converters,the numerical simulation with subsyn chronous oscillation(SSO)faces great challenges in engineering practice due to sharply enlarged modeling scale and high com putational burden.To reduce the modeling scale,network parti tion and equivalent becomes a vital technique in numerical sim ulations.Although several methods have been developed for net work equivalent,a generally accepted rule for network parti tion is still required.This paper proposes that the system can be partitioned into three parts,i.e.,the internal,the middle,and the external subsystems,in which the internal subsystem consists of all power electronic components,the middle subsys tem includes those selected AC dynamic components with de tailed models,and the remaining components and buses consti tute the external subsystem.The external subsystem is further represented by an equivalent RLC network determined by the frequency dependent network equivalent(FDNE)method.In the proposed method,the observability index and the electrical distance index are used to identify the interface between the middle and the external subsystems.Case studies based on a modified Hydro-Quebec system are used to verify the effective ness of the proposed method.展开更多
The ability to capture permeability of fractured porous media plays a significant role in several engineering applications, including reservoir, mining, petroleum and geotechnical engineering. In order to solve fluid ...The ability to capture permeability of fractured porous media plays a significant role in several engineering applications, including reservoir, mining, petroleum and geotechnical engineering. In order to solve fluid flow and coupled flow-deformation problems encountered in these engineering applications,both empirical and theoretical models had been proposed in the past few decades. Some of them are simple but still work in certain circumstances; others are complex but also need some modifications to be applicable. Thus, the understanding of state-of-the-art permeability evolution model would help researchers and engineers solve engineering problems through an appropriate approach. This paper summarizes permeability evolution models proposed by earlier and recent researchers with emphasis on their characteristics and limitations.展开更多
Aiming at obtaining high power density of surface-mounted and interior permanent magnet synchronous motor(SIPMSM),it is important to accurately calculate the temperature field distribution of SIPMSM,and a magnetic-the...Aiming at obtaining high power density of surface-mounted and interior permanent magnet synchronous motor(SIPMSM),it is important to accurately calculate the temperature field distribution of SIPMSM,and a magnetic-thermal coupling method is proposed.The magnetic-thermal coupling mechanism is analyzed.The thermal network model and finite element model are built by this method,respectively.The effects of power frequency on iron losses and temperature fields are analyzed by the magnetic-thermal coupling finite element model under the condition of rated load,and the relationship between the load and temperature field is researched under the condition of the synchronous speed.In addition,the equivalent thermal network model is used to verify the magnetic-thermal coupling method.Then the temperatures of various nodes are obtained.The results show that there are advantages in both computational efficiency and accuracy for the proposed coupling method,which can be applied to other permanent magnet motors with complex structures.展开更多
In this paper,a new equivalent magnetic network(EMN)model is established for a spoke-type permanent magnet(PM)vernier(PMV)machine.Two different modeling methods are proposed for different parts of the PMV machine,cons...In this paper,a new equivalent magnetic network(EMN)model is established for a spoke-type permanent magnet(PM)vernier(PMV)machine.Two different modeling methods are proposed for different parts of the PMV machine,considering that their magnetic field distributions are quite different.Hierarchical modeling method is proposed for the modeling of the rotor as the magnetic intensity of the rotor iron core presents gradient distribution along the radial direction.Mesh based reluctance network method is used for the modeling of flux modulation poles with irregular and unstable magnetic field distributions.Moreover,accurate PM leakage permeance calculation formulae are deduced to improve the simulation precision.The electromagnetic parameters,such as flux linkage,back electromagnetic force,electromagnetic torque and iron loss are predicted by the proposed EMN model.Finally,finite element analysis(FEA)and experimental results are given to verify the effectiveness of the proposed methods.展开更多
The problem of logical node(LN)importance quantification in an IEC 61850 based substation automation system(SAS)is investigated in this paper.First,a weighted and directed static complex network model is established b...The problem of logical node(LN)importance quantification in an IEC 61850 based substation automation system(SAS)is investigated in this paper.First,a weighted and directed static complex network model is established by analyzing the characteristics of SAS,according to IEC 61850.Then,we propose a method,which combines topology value and information adjunction value by introducing a first-order linear feedback controller to quantify the value of LNs.On this basis,some definitions for equivalent network conversion are proposed to greatly reduce the complexity of the original network topology.Also,the absolute value and relative value are introduced to quantify LN importance from the perspective of the node’s necessity and influence,respectively.Finally,simulation results of the case study demonstrate that the proposed method is effective and provides a broader and clearer perspective for viewing the logical node importance for IEC61850 based SAS.展开更多
基金This work was supported in part by the National Natural Science Foundation of China under Grant 51737008.
文摘In this paper,the equivalent reluctance network model(ERNM)is used to calculate the magnetic circuit of a permanent magnet-assisted synchronous reluctance motor(PMASynRM)and calculate no-load air-gap magnetic field and electromagnetic torque.Iteration method is used to solve the relative permeability of iron core.A novel reluctance network model based on actual distribution of the magnetic flux inside the motor is established.The magnetomotive force(MMF)generated by armature winding affects the relative permeability of iron core,which is considered in the calculation of ERNM to improve the accuracy when the motor is under load.ERNM can be used to measure air-gap flux density,no-load back electromotive force(EMF),the average value of motor torque,the armature winding voltage under load,and power factor.The method of calculating the motor performance is proposed.The results of calculation are consistent with finite element method(FEM)and the computational complexity is much less than that of the FEM.The results of ERNM has been verified,which will provide a simple method for motor design and analysis.
基金Supported by the Natrual Science Foundation of Shaanxi (No.2004A02) and Outstanding Scholar Project of P. R. China (2002).
文摘In this paper, a Wavelength Division Multiplexing (WDM) network model based on the equivalent networks is described, and wavelength-dependent equivalent arc, equivalent networks, equivalent multicast tree and some other terms are presented. Based on this model and relevant Routing and Wavelength Assign- ment (RWA) strategy, a unicast RWA algorithm and a multicast RWA algorithm are presented. The wave- length-dependent equivalent arc expresses the schedule of local RWA and the equivalent network expresses the whole topology of WDM optical networks, so the two algorithms are of the flexibility in RWA and the optimi- zation of the whole problem. The theoretic analysis and simulation results show the two algorithms are of the stronger capability and the lower complexity than the other existing algorithms for RWA problem, and the complexity of the two algorithms are only related to the scale of the equivalent networks. Finally, we prove the two algorithms’ feasibility and the one-by-one corresponding relation between the equivalent multicast tree and original multicast tree, and point out the superiorities and drawbacks of the two algorithms respectively.
基金supported by the National Natural Science Funds of China No.51907129Technology program of Liaoning province No.2021-MS-236。
文摘In this paper,a 20kW vehicle built-in permanent magnet synchronous motor is taken as an example,and a magnetic barrier structure is added to the rotor of the motor to solve the uneven saturation problem of the rotor side magnetic bridge.This structure improves the air-gap flux density waveform of the motor by influencing the internal magnetic flux path of the motor rotor,thus improving the sine of the no-load back EMF waveform of the motor and reducing the torque ripple of the motor.At the same time,Taguchi method is used to optimize the structural parameters of the added magnetic barrier.In order to facilitate the analysis of its uneven saturation phenomenon and improve the optimization effect,a simple equivalent magnetic network(EMN)model considering the uneven saturation of rotor magnetic bridge is established in this paper,and the initial values of optimization factors are selected based on this model.Finally,the no-load back EMF waveform distortion rate,torque ripple and output torque of the optimized motor are compared and analyzed,and the influence of magnetic barrier structure parameters on the electromagnetic performance of the motor is also analyzed.The results show that the optimized motor can not change the output torque of the motor as much as possible on the basis of reducing the waveform distortion rate of no-load back EMF and torque ripple.
基金supported by the Science and Technology Project of State Grid Zhejiang Electric Power Co.,Ltd.(No.5211JY21N001)the National Natural Science Foundation of China(No.51837004).
文摘Given large-scale modern power systems with pow er electronic converters,the numerical simulation with subsyn chronous oscillation(SSO)faces great challenges in engineering practice due to sharply enlarged modeling scale and high com putational burden.To reduce the modeling scale,network parti tion and equivalent becomes a vital technique in numerical sim ulations.Although several methods have been developed for net work equivalent,a generally accepted rule for network parti tion is still required.This paper proposes that the system can be partitioned into three parts,i.e.,the internal,the middle,and the external subsystems,in which the internal subsystem consists of all power electronic components,the middle subsys tem includes those selected AC dynamic components with de tailed models,and the remaining components and buses consti tute the external subsystem.The external subsystem is further represented by an equivalent RLC network determined by the frequency dependent network equivalent(FDNE)method.In the proposed method,the observability index and the electrical distance index are used to identify the interface between the middle and the external subsystems.Case studies based on a modified Hydro-Quebec system are used to verify the effective ness of the proposed method.
基金supported by the National Nature Science Foundation of China(No.51278383,No.51238009 and No.51025827)Key Scientific and Technological Innovation Team of Zhejiang Province(No.2011R50020)Key Scientific and Technological Innovation Team of Wenzhou(No.C20120006)
文摘The ability to capture permeability of fractured porous media plays a significant role in several engineering applications, including reservoir, mining, petroleum and geotechnical engineering. In order to solve fluid flow and coupled flow-deformation problems encountered in these engineering applications,both empirical and theoretical models had been proposed in the past few decades. Some of them are simple but still work in certain circumstances; others are complex but also need some modifications to be applicable. Thus, the understanding of state-of-the-art permeability evolution model would help researchers and engineers solve engineering problems through an appropriate approach. This paper summarizes permeability evolution models proposed by earlier and recent researchers with emphasis on their characteristics and limitations.
基金This work was supported by Natural Science Foundation of China(Item number:51777060,U1361109)Natural Science Foundation of Henan province(Item number:162300410117)the he innovative research team plan of Henan Polytechnic University(Item number:T2015-2).
文摘Aiming at obtaining high power density of surface-mounted and interior permanent magnet synchronous motor(SIPMSM),it is important to accurately calculate the temperature field distribution of SIPMSM,and a magnetic-thermal coupling method is proposed.The magnetic-thermal coupling mechanism is analyzed.The thermal network model and finite element model are built by this method,respectively.The effects of power frequency on iron losses and temperature fields are analyzed by the magnetic-thermal coupling finite element model under the condition of rated load,and the relationship between the load and temperature field is researched under the condition of the synchronous speed.In addition,the equivalent thermal network model is used to verify the magnetic-thermal coupling method.Then the temperatures of various nodes are obtained.The results show that there are advantages in both computational efficiency and accuracy for the proposed coupling method,which can be applied to other permanent magnet motors with complex structures.
基金Supported by National Natural Science Foundation of China under Grant 51577084Key Project of Natural Science Foundation of Jiangsu Higher Education Institutions under Grant 15KJA470002the Priority Academic Program Development of Jiangsu Higher Education Institutions.
文摘In this paper,a new equivalent magnetic network(EMN)model is established for a spoke-type permanent magnet(PM)vernier(PMV)machine.Two different modeling methods are proposed for different parts of the PMV machine,considering that their magnetic field distributions are quite different.Hierarchical modeling method is proposed for the modeling of the rotor as the magnetic intensity of the rotor iron core presents gradient distribution along the radial direction.Mesh based reluctance network method is used for the modeling of flux modulation poles with irregular and unstable magnetic field distributions.Moreover,accurate PM leakage permeance calculation formulae are deduced to improve the simulation precision.The electromagnetic parameters,such as flux linkage,back electromagnetic force,electromagnetic torque and iron loss are predicted by the proposed EMN model.Finally,finite element analysis(FEA)and experimental results are given to verify the effectiveness of the proposed methods.
基金This work was supported in part by the National Natural Science Foundation of China(U1866209)。
文摘The problem of logical node(LN)importance quantification in an IEC 61850 based substation automation system(SAS)is investigated in this paper.First,a weighted and directed static complex network model is established by analyzing the characteristics of SAS,according to IEC 61850.Then,we propose a method,which combines topology value and information adjunction value by introducing a first-order linear feedback controller to quantify the value of LNs.On this basis,some definitions for equivalent network conversion are proposed to greatly reduce the complexity of the original network topology.Also,the absolute value and relative value are introduced to quantify LN importance from the perspective of the node’s necessity and influence,respectively.Finally,simulation results of the case study demonstrate that the proposed method is effective and provides a broader and clearer perspective for viewing the logical node importance for IEC61850 based SAS.
