By utilizing the time difference of arrival （TDOA） and frequency difference of arrival （FDOA） measurements of signals received at a number of receivers, a constrained least-square （CLS） algorithm for estimating ...By utilizing the time difference of arrival （TDOA） and frequency difference of arrival （FDOA） measurements of signals received at a number of receivers, a constrained least-square （CLS） algorithm for estimating the position and velocity of a moving source is proposed. By utilizing the Lagrange multipliers technique, the known relation between the intermediate variables and the source location coordinates could be exploited to constrain the solution. And without requiring apriori knowledge of TDOA and FDOA measurement noises, the proposed algorithm can satisfy the demand of practical applications. Additionally, on basis of con- volute and polynomial rooting operations, the Lagrange multipliers can be obtained efficiently and robustly allowing real-time imple- mentation and global convergence. Simulation results show that the proposed estimator achieves remarkably better performance than the two-step weighted least square （WLS） approach especially for higher measurement noise level.展开更多
Phasor measurement units(PMU) are playing an increasingly important role in power system dynamic security monitoring and control. However, the wide-area deployments of the renewable energy sources and the high voltage...Phasor measurement units(PMU) are playing an increasingly important role in power system dynamic security monitoring and control. However, the wide-area deployments of the renewable energy sources and the high voltage direct current(HVDC) transmission bring a large number of inter-harmonics to the power grid, which may result in further power system security problems. The impacts of inter-harmonics on synchrophasor measurements are revealed. This paper derives the phasor expressions of the signal, which contains the fundamental component and the inter-harmonics. It is found that the inter-harmonics will lead to the subsynchronous oscillation of the phasor measurements. The frequency transmutation principle between the harmonic and the phasor oscillation is revealed. Then, the field PMU data recorded during a subsynchronous oscillation, which occurred in an area of China with a high concentration of wind farms and HVDC transmission lines, are studied. A geographical wiring diagram with the subsynchronous oscillation distribution depicts the severe consequences of the inter-harmonics. In addition, the correctness of the theoretical derivation and the possibility of the inter-harmonics monitoring are verified.展开更多
Rotor blades fault of aeroengine compressor is mostly caused by mechanical and aerodynamic excitation.And the excitation factor of high intensity sound wave to rotor blades should not be ignored.Experimental researche...Rotor blades fault of aeroengine compressor is mostly caused by mechanical and aerodynamic excitation.And the excitation factor of high intensity sound wave to rotor blades should not be ignored.Experimental researches are conducted on a multistage high pressure compressor.When high level vibration occurs on the first stage of rotor blades, the noise spectrum presents typical characteristic for discrete multi-tone in the compressor.The amplitude of blade vibration displacement and the sound pressure level of characteristic frequency noise increases and decreases simultaneously and reaches the maximum value at the same time.This frequency merely occur on a certain speed range and is locked in a specific range which presents no variation with the rotating speed.When high level vibration occurs on the first stage of rotor blades, the noise spectrum presents a sharp peak and the propagation state of the characteristic frequency is a helix structure in the compressor.It can be confirmed that acoustic resonance occurs in the multistage compressor.The acoustic resonance frequency and its side band frequencies are generated by modulation of a rotating noise source at the rotor speed which is the excitation source of the rotor blades vibration.展开更多
The stability control of surrounding rock for large or super-large section chamber is a difficult technical problem in deep mining condition.Based on the in-site geological conditions of Longgu coal mine,this paper us...The stability control of surrounding rock for large or super-large section chamber is a difficult technical problem in deep mining condition.Based on the in-site geological conditions of Longgu coal mine,this paper used the dynamic module of FLAC3D to study the response characteristics of deep super-large section chamber under dynamic and static combined loading condition.Results showed that under the static loading condition,the maximum vertical stress,deformation and failure range are large,where the stress concentration coefficient is 1.64.The maximum roof-to-floor and two-sides deformations are 54.6 mm and 53.1 mm,respectively.Then,under the dynamic and static combined loading condition:(1)The influence of dynamic load frequency on the two-sides is more obvious;(2)The dynamic load amplitude has the greatest influence on the stress concentration degree,and the plastic failure tends to develop to the deeper;(3)With the dynamic load source distance increase,the response of surrounding rock is gradually attenuated.On this basis,empirical equations for each dynamic load conditions were obtained by using regression analysis method,and all correlation coefficients are greater than 0.99.This research provided reference for the supporting design of deep super-large section chamber under same or similar conditions.展开更多
The major problem in current online diagnosis and analysis for power system oscillation is mainly concerned with finding the oscillation source in a fast and correct way using the data collected by the Wide Area Measu...The major problem in current online diagnosis and analysis for power system oscillation is mainly concerned with finding the oscillation source in a fast and correct way using the data collected by the Wide Area Measurement System(WAMS).This paper for the first time proposes a scheme of cut set energy based on WAMS.Independent of accurate parameters,the scheme can make full use of WAMS data based on cut set energy construction and fast calculation to locate the source during oscillation.Afterwards,a scheme of torque decomposition is proposed,based on which the controller’s torque can be divided into damping torque and synchronous torque by calculation through WAMS data,and this paper puts forward the abnormal response and simulation models calibration of influential controllers.Analysis of an oscillation case shows how the cut set energy scheme and the torque decomposition scheme are applied in a real-world power system,and the schemes are proven to be reliable and practical in identifying and locating oscillation sources.展开更多
将DDS技术应用于超短波射频通信频率源中,比较了几种常见的小步进频率源的设计方案,设计实现了一种＂锁相环-直接数字频率合成器-锁相环＂（PLL＋DDS＋PLL）结构的高性能频率源。与传统的频率源设计相比,新的设计更能够满足工程应用过...将DDS技术应用于超短波射频通信频率源中,比较了几种常见的小步进频率源的设计方案,设计实现了一种＂锁相环-直接数字频率合成器-锁相环＂（PLL＋DDS＋PLL）结构的高性能频率源。与传统的频率源设计相比,新的设计更能够满足工程应用过程中小步进、低相噪、高集成度的需求;设计频率源输出频率范围为1 766.5~1 771.5 MHz,步进0.000 5 Hz,相位噪声在距输出频率10 k Hz处小于–95 d Bc,杂散抑制度优于70 d Bc。展开更多
基金supported by the National High Technology Research and Development Program of China (863 Program) (2010AA7010422 2011AA7014061)
文摘By utilizing the time difference of arrival （TDOA） and frequency difference of arrival （FDOA） measurements of signals received at a number of receivers, a constrained least-square （CLS） algorithm for estimating the position and velocity of a moving source is proposed. By utilizing the Lagrange multipliers technique, the known relation between the intermediate variables and the source location coordinates could be exploited to constrain the solution. And without requiring apriori knowledge of TDOA and FDOA measurement noises, the proposed algorithm can satisfy the demand of practical applications. Additionally, on basis of con- volute and polynomial rooting operations, the Lagrange multipliers can be obtained efficiently and robustly allowing real-time imple- mentation and global convergence. Simulation results show that the proposed estimator achieves remarkably better performance than the two-step weighted least square （WLS） approach especially for higher measurement noise level.
文摘Phasor measurement units(PMU) are playing an increasingly important role in power system dynamic security monitoring and control. However, the wide-area deployments of the renewable energy sources and the high voltage direct current(HVDC) transmission bring a large number of inter-harmonics to the power grid, which may result in further power system security problems. The impacts of inter-harmonics on synchrophasor measurements are revealed. This paper derives the phasor expressions of the signal, which contains the fundamental component and the inter-harmonics. It is found that the inter-harmonics will lead to the subsynchronous oscillation of the phasor measurements. The frequency transmutation principle between the harmonic and the phasor oscillation is revealed. Then, the field PMU data recorded during a subsynchronous oscillation, which occurred in an area of China with a high concentration of wind farms and HVDC transmission lines, are studied. A geographical wiring diagram with the subsynchronous oscillation distribution depicts the severe consequences of the inter-harmonics. In addition, the correctness of the theoretical derivation and the possibility of the inter-harmonics monitoring are verified.
基金co-supported by the National Natural Science Foundation of China(Nos.51576009,11661141020 and 51711530036)the Aeronautical Science Foundation of China(No.20151554002)。
文摘Rotor blades fault of aeroengine compressor is mostly caused by mechanical and aerodynamic excitation.And the excitation factor of high intensity sound wave to rotor blades should not be ignored.Experimental researches are conducted on a multistage high pressure compressor.When high level vibration occurs on the first stage of rotor blades, the noise spectrum presents typical characteristic for discrete multi-tone in the compressor.The amplitude of blade vibration displacement and the sound pressure level of characteristic frequency noise increases and decreases simultaneously and reaches the maximum value at the same time.This frequency merely occur on a certain speed range and is locked in a specific range which presents no variation with the rotating speed.When high level vibration occurs on the first stage of rotor blades, the noise spectrum presents a sharp peak and the propagation state of the characteristic frequency is a helix structure in the compressor.It can be confirmed that acoustic resonance occurs in the multistage compressor.The acoustic resonance frequency and its side band frequencies are generated by modulation of a rotating noise source at the rotor speed which is the excitation source of the rotor blades vibration.
基金Project(2018YFC0604703)supported by the National Key R&D Program of ChinaProjects(51804181,51874190)supported by the National Natural Science Foundation of China+3 种基金Project(ZR2018QEE002)supported by the Shandong Province Natural Science Fund,ChinaProject(ZR2018ZA0603)supported by the Major Program of Shandong Province Natural Science Foundation,ChinaProject(2019GSF116003)supported by the Key R&D Project of Shandong Province,ChinaProject(SDKDYC190234)supported by the Shandong University of Science and Technology,Graduate Student Technology Innovation Project,China。
文摘The stability control of surrounding rock for large or super-large section chamber is a difficult technical problem in deep mining condition.Based on the in-site geological conditions of Longgu coal mine,this paper used the dynamic module of FLAC3D to study the response characteristics of deep super-large section chamber under dynamic and static combined loading condition.Results showed that under the static loading condition,the maximum vertical stress,deformation and failure range are large,where the stress concentration coefficient is 1.64.The maximum roof-to-floor and two-sides deformations are 54.6 mm and 53.1 mm,respectively.Then,under the dynamic and static combined loading condition:(1)The influence of dynamic load frequency on the two-sides is more obvious;(2)The dynamic load amplitude has the greatest influence on the stress concentration degree,and the plastic failure tends to develop to the deeper;(3)With the dynamic load source distance increase,the response of surrounding rock is gradually attenuated.On this basis,empirical equations for each dynamic load conditions were obtained by using regression analysis method,and all correlation coefficients are greater than 0.99.This research provided reference for the supporting design of deep super-large section chamber under same or similar conditions.
基金supported by the Science and Technology Project of the State Grid Corporation under Grant XT71-16-029。
文摘The major problem in current online diagnosis and analysis for power system oscillation is mainly concerned with finding the oscillation source in a fast and correct way using the data collected by the Wide Area Measurement System(WAMS).This paper for the first time proposes a scheme of cut set energy based on WAMS.Independent of accurate parameters,the scheme can make full use of WAMS data based on cut set energy construction and fast calculation to locate the source during oscillation.Afterwards,a scheme of torque decomposition is proposed,based on which the controller’s torque can be divided into damping torque and synchronous torque by calculation through WAMS data,and this paper puts forward the abnormal response and simulation models calibration of influential controllers.Analysis of an oscillation case shows how the cut set energy scheme and the torque decomposition scheme are applied in a real-world power system,and the schemes are proven to be reliable and practical in identifying and locating oscillation sources.
文摘将DDS技术应用于超短波射频通信频率源中,比较了几种常见的小步进频率源的设计方案,设计实现了一种＂锁相环-直接数字频率合成器-锁相环＂（PLL＋DDS＋PLL）结构的高性能频率源。与传统的频率源设计相比,新的设计更能够满足工程应用过程中小步进、低相噪、高集成度的需求;设计频率源输出频率范围为1 766.5~1 771.5 MHz,步进0.000 5 Hz,相位噪声在距输出频率10 k Hz处小于–95 d Bc,杂散抑制度优于70 d Bc。
