- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Cladding of Stellite-6/WC Composites Coatings by Laser Metal Deposition
摘要： This study aims to investigate the microstructure and hardness of multi-layered Stellite-6/WC metal-matrix composites coatings on metallic substrates cladded by laser metal deposition (LMD) for improvement of wear and corrosion resistances. As coating materials, Stellite-6 and WC-12wt.%Co powders were selected. Powder mixtures having various mixing-ratios of Stellite-6 and WC-12wt.%Co were provided vertically on S45C substrates by controlling powder feeding rates of the two powder feeders, individually. Stellite-6/WC composites which consist of three layers with different compositions were cladded on the S45C substrates by laser melting. Cross-sectional microstructure observation was carried out by using an optical microscope (OM). Vickers microhardness tests were conducted to evaluate hardness of the cladding layers and substrates. The experimental results demonstrate that hard multi-layered Stellite-6/WC metal-matrix composites coatings were successfully cladded on the S45C substrates. Property gradients in the Stellite-6/WC composites could be made due to the position-dependent chemical composition and microstructure made by controlling powder feeding rates of an LMD system.
关键词： Cladding,Additive Manufacturing (AM),Metal Matrix Composites (MMC),Laser Metal Deposition (LMD),Hard Materials
更新于2025-09-23 15:22:29
-
[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
-
[IEEE 2018 11th UK-Europe-China Workshop on Millimeter Waves and Terahertz Technologies (UCMMT) - HangZhou, China (2018.9.5-2018.9.7)] 2018 11th UK-Europe-China Workshop on Millimeter Waves and Terahertz Technologies (UCMMT) - Linear-to-Circular Polarization Conversion For Beam-Scanning Antenna Based On Self-Complementary Metasurface
摘要： Modular multilevel converters (MMC) are presently the converter topology of choice for voltage-source converter high-voltage direct-current (VSC-HVDC) transmission schemes due to their very high efficiency. These converters are complex, yet fast and detailed electromagnetic transients simulation models are necessary for the research and development of these transmission schemes. Excellent work has been done in this area, though little objective comparison of the models proposed has yet been undertaken. This paper compares for the first time, the three leading techniques for producing detailed MMC VSC-HVDC models in terms of their accuracy and simulation speed for several typical simulation cases. In addition, an improved model is proposed which further improves the computational efficiency of one method. This paper concludes by presenting evidence-based recommendations for which detailed models are most suitable for which particular studies.
关键词： HVDC transmission,electromagnetic-transient (EMT) simulation,voltage-source converter (VSC),modular multilevel converter (MMC),Accelerated model
更新于2025-09-23 15:19:57
-
[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Cu-doping Effects in CdSe <sub/>x</sub> Te <sub/>1-x</sub> /CdTe Solar Cells
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2025-09-19 17:13:59
-
[IEEE 2019 22nd International Conference on Electrical Machines and Systems (ICEMS) - Harbin, China (2019.8.11-2019.8.14)] 2019 22nd International Conference on Electrical Machines and Systems (ICEMS) - The Simulink of a stacked Large-Scale Photovoltaic Power Generation System
摘要： In traditional photovoltaic power generation system, the low voltage side (not more than 1kV) is connected to the inverter through a photovoltaic combiner box, and then delivered the power to the grid through a power frequency transformer. However, the system has high transmission loss, Low penetration of MPPT and high cost. This paper proposes a stacked photovoltaic power generation system structure, where each PV array is input into each bidirectional DC/DC converter independently, and the output side of the bidirectional DC/DC converter is connected in series to the input terminal of the three-phase full-bridge modular multilevel converter, finally achieve to connect the high voltage grid. The work in this paper, a simulation model of 10kV/100kW photovoltaic power generation system is built in MATLAB/Simulink platform, in order to verify the feasibility and reliability of the proposed system structure and control strategy.
关键词： DAB,PV array,Simulation,MMC,MPPT
更新于2025-09-16 10:30:52
-
Micromachining on Al-Sic Based Metal Matrix Composite Using DPSS Laser
摘要： Aluminum silicon carbide is a metal matrix composite largely used where strength to weight ratio and high thermal conductivity is primary in design criteria. It has wide application in Aerospace components, Automobiles & electronics industries. Present work deals in micro-grooving of this hard to machine material is carried out by diode pumped solid state pulsed Nd:YAG Laser. The experimental plan is carried out by CCD (central composite design) based on RSM (response surface methodology).Also the analysis of variance test is carried out to check the adequacy of the fitted regression mathematical models. Proper ranges of process parameters such as pulse width, pulse frequency, amount of current, assist air pressure were purposed. Screening test shows O2 as assist gas when used 0.2 to 1 kgf/cm2 pressure range gives best result because of its advantage during laser material interaction. The responses are taken as upper width deviation, lower width & depth deviation of micro-groove produced on Al-SiC material. The interaction effects of different parameters on responses are analyzed through surface plots generated. Optimal process parametric conditions are found out by utilizing meta-heuristic based search algorithm MOPSO (multi objective particle swamp optimization) technique.
关键词： MMC,ANOVA,Nd:YAG,RSM,SEM
更新于2025-09-12 10:27:22
-
Aluminium Matrix Composites Produced by Laser Based Additive Manufacturing
摘要： 3D laser metal deposition (LMD) based on the laser cladding is an established technique for additive manufacturing tasks. Also the laser cladding is a well-known technique to produce aluminum matrix composites reinforced by Si particles. High cooling rates typical for laser treatment enable to eliminate coarse Si particles formation which is a substantial disadvantage of in-situ Al-Si composites produced by traditional manufacturing processes like casting. The coarse Si particles formation reduces Al-Si composites mechanical properties. Extremely non-equilibrium solidification conditions typical for micro LMD process allow to obtain a further structure refinement and its mechanical properties improvement. In this paper the in-situ Al-Si composites produced by micro LMD process with different parameters sets were investigated by fine structure X-ray analysis. The structure and phase composition of in-situ Al-Si composites were described. The influence of cladding parameters on Al-Si composites structure was investigated.
关键词： MMC,aluminium matrix composites,Laser micro cladding,thin-wall parts,fine structure,additive manufacturing,aluminium alloys,X-ray analysis,thin wall
更新于2025-09-12 10:27:22
-
[IEEE 2018 IEEE Industry Applications Society Annual Meeting (IAS) - Portland, OR, USA (2018.9.23-2018.9.27)] 2018 IEEE Industry Applications Society Annual Meeting (IAS) - Novel Voltage Balancing Techniques for Modular Multilevel PV Inverters
摘要： Modular multilevel converters (MMC) are widely used in medium and high voltage transmission systems and in STATCOM applications for improving the power quality. In this paper, a modified configuration of MMC is considered to integrate a MW PV plant with the high voltage grid more likely at the transmission side of the power system. A string of PV panels is connected across each of the submodules (SMs) of the modular multilevel PV inverter (MMPI). In addition, two novel voltage-balancing techniques have been proposed to regulate the SM capacitor voltages of the MMPI at different maximum power point voltages. The first technique utilizes the concept of capacitor sorting based on their voltages. The proposed algorithm generates the switching states based on the voltages of the other SM capacitors and hence reduces the ripple in the capacitor voltage. In the second technique, a novel and simplified logic function based voltage balancing technique is developed. This technique is computationally efficient, reduces the ripple in capacitor voltage, eliminates the requirement of a look-up table and can be easily extended to an N-level MMPI. A three-level and seven-level MMPI is simulated in MATLAB/SIMULINK. The simulated MMPI is tested under two scenarios for different temperature and irradiance conditions and various waveforms are showcased to ensure the efficacy of the proposed techniques.
关键词： Modular multilevel PV inverter (MMPI),Logic function,Maximum power point tracking (MPPT),Modular multilevel converter (MMC),Voltage balancing
更新于2025-09-04 15:30:14
-
Hierarchical Metric Learning for Optical Remote Sensing Scene Categorization
摘要： We address the problem of scene classification from optical remote sensing (RS) images based on the paradigm of hierarchical metric learning. Ideally, supervised metric learning strategies learn a projection from a set of training data points so as to minimize intraclass variance while maximizing the interclass separability to the class label space. However, standard metric learning techniques do not incorporate the class interaction information in learning the transformation matrix, which is often considered to be a bottleneck while dealing with fine-grained visual categories. As a remedy, we propose to organize the classes in a hierarchical fashion by exploring their visual similarities and subsequently learn separate distance metric transformations for the classes present at the nonleaf nodes of the tree. We employ an iterative maximum-margin clustering strategy to obtain the hierarchical organization of the classes. Experiment results obtained on the large-scale NWPU-RESISC45 and the popular UC-Merced data sets demonstrate the efficacy of the proposed hierarchical metric learning-based RS scene recognition strategy in comparison to the standard approaches.
关键词： optical remote sensing (RS),Maximum margin clustering (MMC),metric learning
更新于2025-09-04 15:30:14