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Tuning the excitonic properties of ZnO:Sn thin films
摘要： The effects of Sn doping, deposition temperature, and post-annealing treatment on the excitonic behavior of ZnO:Sn (SZO) thin films deposited by dc-unbalanced magnetron sputtering have been studied. Sn doping induces the decrease of grain size and promotes the formation of oxygen vacancy-related trap states as indicated by A1 LO mode in Raman spectra and green emission in photoluminescence spectra. Using a critical point analysis of the dielectric functions from spectroscopic ellipsometry data analysis, Sn doping blueshifts the excitonic absorption and decreases the exciton lifetime via screening the electron-hole Coulomb interaction. By varying the deposition temperature from room temperature up to 300 °C (SZO-3), there is no change in excitonic absorption. Then, annealing of SZO-3 at 600 °C under oxygen environment (SZO-6) strongly improves the excitonic absorption as well as its lifetime. Critical point analysis on SZO-6 sample clearly reveals the excitonic transition at 3.38 eV and exciton-phonon complexes at 3.66 eV. Thus, the result is important to improve the functionality of doped ZnO with strong excitonic absorption for optoelectronic applications.
关键词： Annealing,Dc-unbalanced magnetron sputtering,Exciton,Thin films,Sn doped ZnO
更新于2025-09-23 15:23:52
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Characteristics of Vanadium Oxide Thin Films Fabricated by Unbalanced Magnetron Sputtering for Smart Window Application
摘要： Vanadium oxide (VOx) thin films were deposited by an unbalanced magnetron (UBM) sputtering system with a vanadium metal target and O2 reaction gas, and thermally treated at various annealing temperatures. In this work, the structural, electrical, and optical properties of the fabricated VOx films with various annealing temperatures were experimentally investigated. The UBM sputter grown VOx thin films exhibited amorphous structure, and had a very weak peak of V2O5 (002) owing to very thin films. However, the crystallite size of VOx films increased with increasing annealing temperature. The surface roughness of VOx films and average transmittance decreased with increasing annealing temperature. The resistivity of VOx films also decreased with increasing annealing temperature, while the electrical properties of films improved.
关键词： Transmittance,Unbalanced Magnetron Sputtering,Vanadium Oxide,Surface Roughness,Resistivity
更新于2025-09-23 15:23:52
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Mapping Development Pattern in China Using DMSP/OLS Nighttime Light Data
摘要： Unbalanced development may cause problems like inequality of living conditions and the lack of sustainability. Studies based on statistical data can hardly reveal the detailed characteristics of unbalanced development due to the limitation of statistical units, while the application of remote sensing data provides an effective solution. In this study, based on the DMSP/OLS nighttime light data, the development characteristics in China during 2000-2012 were analyzed from the perspectives of development level and speed. Meanwhile, development mechanism in different urbanization types was discussed to explore the trend of unbalanced development. The results reveal the severe unbalanced development pattern in China. It also indicates that the development gap between different regions will be widened, and the unbalanced development situation will be more notable in the near future.
关键词： DMSP/OLS,China,Unbalanced development
更新于2025-09-23 15:21:21
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Data-driven uncertainty analysis of distribution networks including photovoltaic generation
摘要： This paper investigates residential distribution networks with uncertain loads and photovoltaic distributed generation. An original probabilistic modeling of consumer demand and photovoltaic generation is presented that is based on the analysis of large set of data measurements. It is shown how photovoltaic generation is described by complex non-standard distributions that can be described only numerically. Probabilistic analysis is performed using an enhanced version of the Polynomial Chaos technique that exploits a proper set of polynomial basis functions. It is described how such functions can be generated from the numerically available data. Compared to other approximate methods for probabilistic analysis, the novel technique has the advantages of modeling accurately truly nonlinear problems and of directly providing the detailed Probability Density Function of relevant observable quantities affecting the quality of service. Compared to standard Monte Carlo method, the proposed technique introduces a simulation speedup that depends on the number of random parameters. Numerical applications to radial and weakly meshed networks are presented where the method is employed to explore overvoltage, unbalance factor and power loss, as a function of photovoltaic penetration and/or network configuration.
关键词： Photovoltaic generation,Data-driven models,Polynomial chaos,Unbalanced distribution networks,Probabilistic load flow,Uncertainty Analysis
更新于2025-09-23 15:21:01
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Improved-efficiency quasi-two-stage current-source-mode SIMO LED driver
摘要： The paper presents a modularized control strategy of doubly fed induction generator (DFIG) system, including the grid-side converter (GSC) and rotor-side converter (RSC), under unbalanced and harmonic grid voltage. The sequence decomposition process and complicated control reference calculation can be avoided in the proposed control strategy. From the perspective of power grid friendly operation, the control targets of DFIG system in this paper are chosen as: 1) smooth active and reactive power injected into the power grid; 2) balanced and sinusoidal current injected into the power grid. The RSC and GSC can work as two independent modules and the communication between RSC and GSC can be removed. Furthermore, the third harmonic current component, dc-link voltage fluctuation, and electromagnetic torque pulsation under the different control targets are theoretically analyzed. Finally, the availability of the proposed modularized control strategy of DFIG system under unbalanced and distorted grid voltage is verified by experiment results.
关键词： unbalanced and harmonic grid voltage,modularized control,doubly fed induction generator (DFIG) system,smooth active and reactive power,Balanced and sinusoidal current
更新于2025-09-23 15:21:01
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Development of threea??phase unbalanced power flow using local control of connected photovoltaic systems
摘要： With the increased number of installations of distributed photovoltaic (PV) systems within electricity distribution systems, power flow analysis is required to handle multiple PV systems. At present, PV systems are equipped with a local control function (LCF). The conventional algorithm is then applied for power flow analysis with the LCF of each PV system, where the power output of LCF of each PV system is calculated and used in the power flow calculation. The conventional algorithm is terminated when the voltage at each iteration of the power flow algorithm is converged. However, the conventional algorithm inevitably requires a lengthy calculation. This paper proposes a power flow algorithm that applies the Newton–Raphson technique to handle multiple PV systems with an LCF for a faster calculation. The LCF is approximated to have a continuous characteristic. The developed power flow algorithm can be used for a three-phase unbalanced distribution system and its effectiveness was demonstrated in a modified 19-node distribution system.
关键词： PV system,local control function,power flow algorithm,three-phase unbalanced distribution system
更新于2025-09-23 15:21:01
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Two Beam Initiation Threshold Measurements of Photo-Initiators for Laser Writing of Biocompatible 3D Structures
摘要： This paper presents an independent operation of the rotor-side converter (RSC) and grid-side converter (GSC) for a doubly fed induction generator (DFIG)-based wind energy conversion system under unbalanced grid voltage conditions. In this paper, the RSC is controlled to achieve four different control targets, including balanced stator current, sinusoidal rotor current, smooth stator active and reactive powers, and constant DFIG electromagnetic torque. The GSC is commanded to keep the dc voltage at a constant value. Additional feedback compensators using resonant regulators for the RSC are employed, and the decompositions of the positive and negative sequence components and calculations of the rotor negative current references can be avoided. Another similar compensator is used in the GSC to suppress the dc voltage ?uctuates and remove the GSC reactive power oscillations without the stator or rotor power information. The proposed method can make the RSC and GSC available to an independent operation with a simple implementation for higher reliability. The experimental results demonstrate the effectiveness of the proposed control strategy for both the RSC and GSC under unbalanced grid voltage conditions.
关键词： wind energy conversion system (WECS),resonant regulator,unbalanced grid voltage,independent operation,Doubly fed induction generator (DFIG)
更新于2025-09-23 15:21:01
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[IEEE 2019 IEEE 2nd International Conference on Automation, Electronics and Electrical Engineering (AUTEEE) - Shenyang, China (2019.11.22-2019.11.24)] 2019 IEEE 2nd International Conference on Automation, Electronics and Electrical Engineering (AUTEEE) - Influence of Grid-connected Photovoltaic Systems on Power Quality
摘要： This paper reviews the power quality indicators and evaluation methods specified in the IEEE. Based on the experiments, the power quality problems caused by the switching of small-scale single-phase photovoltaic (PV) systems and large-scale three-phase PV power plants are analyzed. Meanwhile, under the state of PV systems input and cut-out, the influence of load switching of different properties on power quality is analyzed. Experiments show that the switching of PV systems will lead to voltage sags and impulsive transients, as well as current waveform distortion. However, the input of PV systems has a good restraint effect on voltage sags and impulsive transients caused by loads switching.
关键词： impulsive transients,voltage sags,photovoltaic systems,unbalanced,harmonic distortion,power quality
更新于2025-09-23 15:21:01
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[IEEE 2019 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - Guangzhou, China (2019.5.19-2019.5.22)] 2019 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - Waveguide Switchable Bandstop and Bandpass Filters Using RF MEMS Switches
摘要： Modular multilevel converter (MMC) topology is discussed intensively as a crucial part of future dc grids, especially to integrate offshore wind power. While generalized voltage-source converter models are usually utilized for multiterminal investigations, conclusions on transient dc grid behavior and on ac–dc interactions during distorted ac grid conditions are hard to draw or are limited in their signi?cance. In this paper, a MMC-based dc grid framework with a tripartite focus on an internal converter as well as dc and ac grid control is presented. Besides, an evaluation of the implemented MMC model that incorporates the available arm sum voltage, a decoupled ac and dc current system control concept that is suitable to handle unbalanced voltage conditions is derived for HVDC applications. Combined with wind farm arrays, this collocation allows a meaningful examination of hybrid ACDC structures and the implemented dc grid control methodologies. To provide proof of the universal applicability of this framework, simulations are carried out on a ?ve-terminal system.
关键词： MMC energy balancing,unbalanced operation,wind power integration,HVDC grid control,Generalized modular multilevel converter (MMC) modeling,power converter
更新于2025-09-23 15:19:57
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Model and Experimental Study on Optical Fiber CT Based on Terfenol-D
摘要： A nonlinear hysteresis model of magneto-mechanical-thermo coupling for Terfenol-D materials is presented according to Wiss ferromagnetic theory, thermodynamics relations and Jiles–Atherton model. Numerical calculation and experimental results show that the mode well reflects the magnetostrictive characteristics of Terfenol-D rod under the coupling of stress, temperature and magnetic field. A fiber Bragg grating current transformer based on Terfenol-D material is designed according to the strain sensing mechanism of fiber Bragg grating and the demodulation principle of unbalanced M–Z interferometer. The theoretical analysis and research on the working characteristics of the fiber current transformer under the influence of different prestressing force and bias current are carried out. The results are important for the design and application of the current transformer with the Terfenol-D material.
关键词： current transformer,fiber Bragg grating,Terfenol-D,unbalanced M–Z interferometer
更新于2025-09-23 15:19:57