A distortion identification technique is presented based on Hilbert-Huang transform to identify distortion model and distortion frequency of distorted real-world image sequences. The distortion model is identified sim...A distortion identification technique is presented based on Hilbert-Huang transform to identify distortion model and distortion frequency of distorted real-world image sequences. The distortion model is identified simply based on Hilbert marginal spectral analysis after empirical mode decomposing. And distortion frequency is identified by analyzing the occurrence frequency of instantaneous frequency components of every intrinsic mode functions. Rational digital frequency filter with suitable cutoff frequency is designed to remove undesired fluctuations based on identification results. Experimental results show that this technique can identify distortion model and distortion frequency of displacement sequence accurately and efficiently. Based on identification results, distorted image sequence can be stabilized effectively.展开更多
The traveling wave fault location approach for overhead transmission lines is widely applied in actual power grids due to its better fault location accuracy compared with conventional power frequency data-based method...The traveling wave fault location approach for overhead transmission lines is widely applied in actual power grids due to its better fault location accuracy compared with conventional power frequency data-based methods.However,the traveling wave fault location approach is highly related to the frequency distortion phenomenon of traveling wave propagation velocity,which includes two parts:the distortion caused by the reflection and refraction of the transformer substation and the attenuation caused by the distributed resistance of transmission lines.This study aims to improve fault location accuracy,by developing a complete theoretical analysis of the distortion of traveling wave signals and an improved traveling wave fault location approach that considers distortion.Using the PSCAD/EMTDC simulation tool,a typical 500 kV case study model is established to verify the fault location accuracy of the proposed traveling wave fault location approach under the effects of different fault type,fault location,and grounding resistance.展开更多
The photovoltaic grid-connected inverter is an important interface between the photovoltaic power generation system and power grid.Its high-quality operation is directly related to the output power quality of the powe...The photovoltaic grid-connected inverter is an important interface between the photovoltaic power generation system and power grid.Its high-quality operation is directly related to the output power quality of the power grid.In order to further optimize the control effect of the quasi-Z source grid-connected photovoltaic inverter,a fuzzy proportional complex integral control(PCI)method is proposed for the current internal loop control.This method can eliminate the steady-state error,and has the characteristic of zero steady-state error adjustment for the AC disturbance signal of a specific frequency.The inductance-capacitance-inductance(LCL)filter is adopted in the grid-connected circuit,and the feedback capacitive current is taken as the control variable of the inner loop to form the active damping control method,which can not only effectively suppress the resonance of the LCL circuit,but also significantly inhibit the high-order harmonics in the grid-connected current.Finally,a system simulation model is built in MATLAB/Simulink to verify the superiority and effectiveness of the proposed method.展开更多
基金Supported by the President Fund of Graduate University, Chinese Academy of Sciences.
文摘A distortion identification technique is presented based on Hilbert-Huang transform to identify distortion model and distortion frequency of distorted real-world image sequences. The distortion model is identified simply based on Hilbert marginal spectral analysis after empirical mode decomposing. And distortion frequency is identified by analyzing the occurrence frequency of instantaneous frequency components of every intrinsic mode functions. Rational digital frequency filter with suitable cutoff frequency is designed to remove undesired fluctuations based on identification results. Experimental results show that this technique can identify distortion model and distortion frequency of displacement sequence accurately and efficiently. Based on identification results, distorted image sequence can be stabilized effectively.
基金supported by the Natural Science Foundation of China(No.52407113)the Natural Science Foundation of Shandong Province(No.ZR2024ME075)+1 种基金the Youth Science and Technology Innovation Support Program for Higher Education Institutions of Shandong Province(No.2024KJH134)the China Postdoctoral Science Foundation(No.2023M732045).
文摘The traveling wave fault location approach for overhead transmission lines is widely applied in actual power grids due to its better fault location accuracy compared with conventional power frequency data-based methods.However,the traveling wave fault location approach is highly related to the frequency distortion phenomenon of traveling wave propagation velocity,which includes two parts:the distortion caused by the reflection and refraction of the transformer substation and the attenuation caused by the distributed resistance of transmission lines.This study aims to improve fault location accuracy,by developing a complete theoretical analysis of the distortion of traveling wave signals and an improved traveling wave fault location approach that considers distortion.Using the PSCAD/EMTDC simulation tool,a typical 500 kV case study model is established to verify the fault location accuracy of the proposed traveling wave fault location approach under the effects of different fault type,fault location,and grounding resistance.
基金the Foundation of a Hundred Youth Talents Training Program of Lanzhou Jiaotong University under Grant No.2018-103the Colleges and University Scientific Research Funds of Gansu Province under Grant No.2017A-026。
文摘The photovoltaic grid-connected inverter is an important interface between the photovoltaic power generation system and power grid.Its high-quality operation is directly related to the output power quality of the power grid.In order to further optimize the control effect of the quasi-Z source grid-connected photovoltaic inverter,a fuzzy proportional complex integral control(PCI)method is proposed for the current internal loop control.This method can eliminate the steady-state error,and has the characteristic of zero steady-state error adjustment for the AC disturbance signal of a specific frequency.The inductance-capacitance-inductance(LCL)filter is adopted in the grid-connected circuit,and the feedback capacitive current is taken as the control variable of the inner loop to form the active damping control method,which can not only effectively suppress the resonance of the LCL circuit,but also significantly inhibit the high-order harmonics in the grid-connected current.Finally,a system simulation model is built in MATLAB/Simulink to verify the superiority and effectiveness of the proposed method.
