This study was conducted to determine the content,distribution and transformation of iron oxides in the soils of the Middle Euphrates regions in Iraq.The study included four sites:Tuwairij area in Karbala Governorate,...This study was conducted to determine the content,distribution and transformation of iron oxides in the soils of the Middle Euphrates regions in Iraq.The study included four sites:Tuwairij area in Karbala Governorate,College of Agriculture at the University of Kufa in Najaf Governorate,College of Agriculture at the University of Qadisiyah in Diwaniyah Governorate,and the Nile District in Babylon Governorate.The results showed that the soils of Najaf and Qadisiyah were superior in terms of their content of total free iron oxides(Fet)compared to the soils of Karbala and Babylon.The relative distribution of free iron oxides was generally close among the studied sites,with a homogeneous pattern in the distribution of these oxides within the soil horizons.As for silicate iron oxides(Fes),a homogeneous pattern was observed in the soil of Babylon with its content increasing with depth,while these patterns varied in the soils of Karbala,Najaf and Qadisiyah.Regarding the ratios of crystalline iron oxides(Fed/Fet),the study showed that the Babylon and Qadisiyah soils recorded the highest values,while these values were lower in the Najaf and Karbala soils.On the other hand,amorphous iron oxides(FeO)showed similar values in the Najaf and Qadisiyah soils.In general,these results clearly showed the effect of environmental and geochemical factors of the study areas on the distribution and transformations of iron oxides in the soil of the Middle Euphrates regions.展开更多
With increasing the number of wind power generators,the consumption time of electromagnetic simulation of the wind farm explodes.To reduce the simulation time while meeting the accuracy requirement,a genetic clusterin...With increasing the number of wind power generators,the consumption time of electromagnetic simulation of the wind farm explodes.To reduce the simulation time while meeting the accuracy requirement,a genetic clustering-based equivalent model is proposed for the wind farm with numerous doubly fed induction generators.In the proposed model,active power together with the reactive power and the wind speed are selected to form the set of clustering indicators.A normalization technique is utilized to cope with the multiple orders of magnitude in these factors.An exponential fitness value is formulated as a function of the sorting number of the primary fitness value,and the fitness-based selection probability is constructed to overcome the property of premature and slow convergence of the genetic clustering algorithm.The sum of squares due to error is used to determine the optimal clustering number.In addition,a decoupled parameter equivalence method is adopted to obtain the equivalent parameters of the collection network.Simulation results and comparisons with various methods under different voltage scenarios show the feasibility and effectiveness of the proposed model.展开更多
Electric locomotives on the horizon will integrate SiC inverters,promising quicker switching and lower losses than traditional setups.However,in addition to the steep rising edge,the inverter-fed motor drive system fa...Electric locomotives on the horizon will integrate SiC inverters,promising quicker switching and lower losses than traditional setups.However,in addition to the steep rising edge,the inverter-fed motor drive system faces challenges such as high common-mode voltage(CMV)and high motor terminal surge voltage swing rate(dv/dt).To tackle these hurdles,this paper proposes a novel tailored traction control system for three-phase locomotive motors.This innovative strategy utilises nearstate space vector pulse width modulation(NSVPWM),selectively removing space vectors with high CMV to generate modulation signals.Complemented by a slew rate capacitor configuration,the aim is to reduce CMV while effectively suppressing motor-side voltage slew rate.To validate this approach,experimental waveforms from on-site inverter-fed motor drive systems have been analysed to derive high-frequency parameters of long-line cables and variable frequency motors to mimic real locomotive operating conditions better.Through experimental research and comparative simulations against traditional methods,this study reveals a significant 33.3%reduction in CMV compared to traditional systems.Furthermore,it achieves an impressive decrease in the rise/fall slope,down to 86.6%,while ensuring nearly zero electrical power consumption.展开更多
Wide-band oscillations have become a significant issue limiting the development of wind power.Both large-signal and small-signal analyses require extensive model derivation.Moreover,the large number and high order of ...Wide-band oscillations have become a significant issue limiting the development of wind power.Both large-signal and small-signal analyses require extensive model derivation.Moreover,the large number and high order of wind turbines have driven the development of simplified models,whose applicability remains controversial.In this paper,a wide-band oscillation analysis method based on the average-value model(AVM)is proposed for wind farms(WFs).A novel linearization analysis framework is developed,leveraging the continuous-time characteristics of the AVM and MATLAB/Simulink’s built-in linearization tools.This significantly reduces modeling complexity and computational costs while maintaining model fidelity.Additionally,an object-based initial value estimation method of state variables is introduced,which,when combined with steady-state point-solving tools,greatly reduces the computational effort required for equilibrium point solving in batch linearization analysis.The proposed method is validated in both doubly fed induction generator(DFIG)-based and permanent magnet synchronous generator(PMSG)-based WFs.Furthermore,a comprehensive analysis is conducted for the first time to examine the impact of the machine-side system on the system stability of the nonfully controlled PMSG-based WF.展开更多
文摘This study was conducted to determine the content,distribution and transformation of iron oxides in the soils of the Middle Euphrates regions in Iraq.The study included four sites:Tuwairij area in Karbala Governorate,College of Agriculture at the University of Kufa in Najaf Governorate,College of Agriculture at the University of Qadisiyah in Diwaniyah Governorate,and the Nile District in Babylon Governorate.The results showed that the soils of Najaf and Qadisiyah were superior in terms of their content of total free iron oxides(Fet)compared to the soils of Karbala and Babylon.The relative distribution of free iron oxides was generally close among the studied sites,with a homogeneous pattern in the distribution of these oxides within the soil horizons.As for silicate iron oxides(Fes),a homogeneous pattern was observed in the soil of Babylon with its content increasing with depth,while these patterns varied in the soils of Karbala,Najaf and Qadisiyah.Regarding the ratios of crystalline iron oxides(Fed/Fet),the study showed that the Babylon and Qadisiyah soils recorded the highest values,while these values were lower in the Najaf and Karbala soils.On the other hand,amorphous iron oxides(FeO)showed similar values in the Najaf and Qadisiyah soils.In general,these results clearly showed the effect of environmental and geochemical factors of the study areas on the distribution and transformations of iron oxides in the soil of the Middle Euphrates regions.
基金the National Key R&D Program of China(No.2019YFE0114700)the Key R&D Program in Hunan Province of China(No.2021GK2020)+1 种基金the Natural Science Foundation of Hunan Province of China(No.2021JJ30079)the Project of Philosophy and Social Science Research in Yiyang City(No.2022YS191)。
文摘With increasing the number of wind power generators,the consumption time of electromagnetic simulation of the wind farm explodes.To reduce the simulation time while meeting the accuracy requirement,a genetic clustering-based equivalent model is proposed for the wind farm with numerous doubly fed induction generators.In the proposed model,active power together with the reactive power and the wind speed are selected to form the set of clustering indicators.A normalization technique is utilized to cope with the multiple orders of magnitude in these factors.An exponential fitness value is formulated as a function of the sorting number of the primary fitness value,and the fitness-based selection probability is constructed to overcome the property of premature and slow convergence of the genetic clustering algorithm.The sum of squares due to error is used to determine the optimal clustering number.In addition,a decoupled parameter equivalence method is adopted to obtain the equivalent parameters of the collection network.Simulation results and comparisons with various methods under different voltage scenarios show the feasibility and effectiveness of the proposed model.
文摘Electric locomotives on the horizon will integrate SiC inverters,promising quicker switching and lower losses than traditional setups.However,in addition to the steep rising edge,the inverter-fed motor drive system faces challenges such as high common-mode voltage(CMV)and high motor terminal surge voltage swing rate(dv/dt).To tackle these hurdles,this paper proposes a novel tailored traction control system for three-phase locomotive motors.This innovative strategy utilises nearstate space vector pulse width modulation(NSVPWM),selectively removing space vectors with high CMV to generate modulation signals.Complemented by a slew rate capacitor configuration,the aim is to reduce CMV while effectively suppressing motor-side voltage slew rate.To validate this approach,experimental waveforms from on-site inverter-fed motor drive systems have been analysed to derive high-frequency parameters of long-line cables and variable frequency motors to mimic real locomotive operating conditions better.Through experimental research and comparative simulations against traditional methods,this study reveals a significant 33.3%reduction in CMV compared to traditional systems.Furthermore,it achieves an impressive decrease in the rise/fall slope,down to 86.6%,while ensuring nearly zero electrical power consumption.
基金supported by the National Natural Science Foundation of China under Grant 52277072.
文摘Wide-band oscillations have become a significant issue limiting the development of wind power.Both large-signal and small-signal analyses require extensive model derivation.Moreover,the large number and high order of wind turbines have driven the development of simplified models,whose applicability remains controversial.In this paper,a wide-band oscillation analysis method based on the average-value model(AVM)is proposed for wind farms(WFs).A novel linearization analysis framework is developed,leveraging the continuous-time characteristics of the AVM and MATLAB/Simulink’s built-in linearization tools.This significantly reduces modeling complexity and computational costs while maintaining model fidelity.Additionally,an object-based initial value estimation method of state variables is introduced,which,when combined with steady-state point-solving tools,greatly reduces the computational effort required for equilibrium point solving in batch linearization analysis.The proposed method is validated in both doubly fed induction generator(DFIG)-based and permanent magnet synchronous generator(PMSG)-based WFs.Furthermore,a comprehensive analysis is conducted for the first time to examine the impact of the machine-side system on the system stability of the nonfully controlled PMSG-based WF.
