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CSEE Journal of Power and Energy Systems 2024年第2期10卷 756-766页

作者： Yanxiong Lei Guiping Du Tuhuan Li Wenjie Ma Xueyi Wang School of Electric Power South China University of TechnologyGuangzhou 510641China

Integrated battery chargers are highly effective for saving costs and improving the power density of on-board chargers in electric vehicles (EVs), However, achieving torque elimination of the commonly used three-phase (3p) motors during the fast-charging process is challenging. In this paper, the general torque cancelation law applied in 3p permanent magnet synchronous motors (PMSMs) and induction motors (IMs) is derived to design high power density integrated fast battery chargers. Two novel integrated systems with fast-charging and vehicle-to-grid (V2G) capabilities are proposed based on this law. The main advantages of the proposed systems are: (1) Two filter inductors are constituted by the stator windings while charging, and only one external inductor and several contactors are supplemented to the motor-drive circuit. Therefore, the proposed integrated systems possess high power density;(2) The 3p open-winding (OW) motor is employed, with no need to modify the propulsion system or redesign the interior structure of the motor;(3) Employing an individual controller for each phase of the inner current loop control, the proposed systems realize unity power factors and low current harmonics in the fast-charging and V2G mode. Simulation and experimental results verify the feasibility of the proposed topologies and control strategies.

关键词： Electric vehicles(EVs) fast charging integrated battery charger 3p PMSM/IM torque cancelation

Convexification of Hybrid AC-DC Optimal Power Flow with Line-Commutated Converters

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CSEE Journal of Power and Energy Systems 2024年第2期10卷 617-628页

作者： Hongyuan Liang Zhigang Li J.H.Zheng Q.H.Wu School of Electric Power Engineering South China University of TechnologyGuangzhou 510641China

Line-commutated converter (LCC)-based high-voltage DC (HVDC) systems have been integrated with bulk AC power grids for interregional transmission of renewable power. The nonlinear LCC model brings additional nonconvexity to optimal power flow (OPF) of hybrid AC-DC power grids. A convexification method for the LCC station model could address such nonconvexity but has rarely been discussed. We devise an equivalent reformulation for classical LCC station models that facilitates second-order cone convex relaxation for the OPF of LCC-based AC-DC power grids. We also propose sufficient conditions for exactness of convex relaxation with its proof. Equivalence of the proposed LCC station models and properties, exactness, and effectiveness of convex relaxation are verified using four numerical simulations. Simulation results demonstrate a globally optimal solution of the original OPF can be efficiently obtained from relaxed model.

关键词： AC-DC power system convex relaxation linecommutated converter optimal power flow second-order cone programming

Location of Asymmetric Ground Fault Using Virtual Injected Current Ratio and Two-stage Recovery Strategy in Distribution Networks

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CSEE Journal of Power and Energy Systems 2024年第1期10卷 151-161页

作者： Haiting Shan Luliang Zhang Q.H.Wu Mengshi Li School of Electric Power Engineering South China University of Technology(SCUT)Guangzhou 510641China

Sparse measurements challenge fault location in distribution networks.This paper proposes a method for asymmetric ground fault location in distribution networks with limited measurements.A virtual injected current vector is formulated to estimate the fault line,which can be reconstructed from voltage sags measured at a few buses using compressive sensing(CS).The relationship between the virtual injected current ratio(VICR)and fault position is deduced from circuit analysis to pinpoint the fault.Furthermore,a two-stage recovery strategy is proposed for improving reconstruction accuracy of the current vector,where two different sensing matrixes are utilized to improve the incoherence.The proposed method is validated in IEEE 34 node test feeder.Simulation results show asymmetric ground fault type,resistance,fault position and access of distributed generators(DGs)do not significantly influence performance of our method.In addition,it works effectively under various scenarios of noisy measurement and line parameter error.Validations on 134 node test feeders prove the proposed method is also suitable for systems with more complex structure.

关键词： Distribution networks fault location reconstruction accuracy two-stage recovery virtual injected current ratio

A Hybrid Signal Processing Method Combining Mathematical Morphology and Walsh Theory for Power Quality Disturbance Detection and Classification

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CSEE Journal of Power and Energy Systems 2024年第2期10卷 584-592页

作者： Zhi Ding Tianyao Ji Mengshi Li Q.H.Wu School of Electric Power Engineering South China University of Technology(SCUT)Guangzhou 510641China

In this paper, a novel signal processing method combining mathematical morphology (MM) and Walsh theory is proposed, which uses Walsh functions to control the structuring element (SE) and MM operators. Based on the Walsh-MM method, a scheme for power quality disturbances detection and classification is developed, which involves three steps: denoising, feature extraction and morphological clustering. First, various evolution rules of Walsh function are used to generate groups of SEs for the multiscale Walsh-ordered morphological operation, so the original signal can be denoised. Next, the fundamental wave of the denoised signal is suppressed by Hadamard matrix;thus, disturbances can be extracted. Finally, the Walsh power spectrum of the waveform extracted in the previous step is calculated, and the parameters of which are taken by morphological clustering to classify the disturbances. Simulation results reveal the proposed scheme can effectively detect and classify disturbances, and the Walsh-MM method is less affected by noise and only involves simple calculation, which has a potential to be implemented in hardware and more suitable for real-time application.

关键词： Hadamard matrix mathematical morphology morphological clustering power quality disturbance Walsh theory

A Probing Model of Secret Key Generation Based on Channel Autocorrelation Function

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China Communications 2024年第6期21卷 163-175页

作者： Xia Enjun Hu Binjie Shen Qiaoqiao School of Electronic and Information Engineering South China University of TechnologyGuangzhou 510641China

Secret key generation(SKG)is a promising solution to the problem of wireless communications security.As the first step of SKG,channel probing affects it significantly.Although there have been some probing schemes,there is a lack of research on the optimization of the probing process.This study investigates how to optimize correlated parameters to maximize the SKG rate(SKGR)in the time-division duplex(TDD)mode.First,we build a probing model which includes the effects of transmitting power,the probing period,and the dimension of sample vectors.Based on the model,the analytical expression of the SKGR is given.Next,we formulate an optimization problem for maximizing the SKGR and give an algorithm to solve it.We conclude the SKGR monotonically increases as the transmitting power increases.Relevant mathematical proofs are given in this study.From the simulation results,increasing appropriately the probing period and the dimension of the sample vector could increase the SKGR dramatically compared to a yardstick,which indicates the importance of optimizing the parameters related to the channel probing phase.

关键词： channel autocorrelation function channel probing optimization problem physical layer security secret key generation

Sub-nanosized vanadate hybrid clusters maintain glucose homeostasis and restore treatment response in inflammatory disease in obese mice

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Nano Research 2024年第3期17卷 1818-1826页

作者： Kun Chen Shengqiu Liu Yujun Wei South China Advanced Institute for Soft Matter Science and Technology School of Emergent Soft MatterSouth China University of TechnologyGuangzhou 510641China Guangdong Provincial Key Laboratory of Technique and Equipment for Macromolecular Advanced Manufacturing South China University of TechnologyGuangzhou 510641China Guangdong Provincial Key Laboratory of Functional and Intelligent Hybrid Materials and Devices South China University of TechnologyGuangzhou 510641China

Obesity is closely related with insulin resistance and chronic inflammation.Here,we report that unsaturated lipid-modified polyoxovanadates(ULPOVs)can restrict weight gain of diet-induced obese mice and improve their glycemic control and obesity-associated inflammation.Oral administration of the sub-nanosized ULPOVs at a low dosage for 7 weeks reduces the body weight and almost normalizes the blood glucose levels of obese mice fed on a high-fat diet.ULPOV treatment increases the activity of the nuclear receptor peroxisome proliferator-activated receptorγ(PPARγ)and reduces intestinal caloric intake,which may be the main reason for blood sugar and body weight control.In addition to insulin-sensitizing,PPARγactivation induced by ULPOV treatment in obese mice with atopic dermatitis(AD)promotes the type 2 T helper(TH_(2))cell selective responses and therapeutic effects on immune dysregulation caused by obesity.These data suggest sub-nanosized polyoxovanadate clusters as a class of potential candidates to relieve symptoms accompanied by diet-induced obesity.

关键词： polyoxovanadates lipid modification glucose homeostasis obesity inflammatory disease peroxisome proliferator-activated receptorγ(PPARγ)

In-situ additive manufacturing of high strength yet ductility titanium composites with gradient layered structure using N_(2)

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International Journal of Extreme Manufacturing 2024年第3期6卷 387-409页

作者： Yunmian Xiao Changhui Song Zibin Liu Linqing Liu Hanxiang Zhou Di Wang Yongqiang Yang School of Mechanical and Automotive Engineering South China University of TechnologyGuangzhou 510641People’s Republic of China

It has always been challenging work to reconcile the contradiction between the strength and plasticity of titanium materials.Laser powder bed fusion(LPBF) is a convenient method to fabricate innovative composites including those inspired by gradient layered materials.In this work,we used LPBF to selectively prepare Ti N/Ti gradient layered structure(GLSTi)composites by using different N_(2)–Ar ratios during the LPBF process.We systematically investigated the mechanisms of in-situ synthesis Ti N,high strength and ductility of GLSTi composites using microscopic analysis,TEM characterization,and tensile testing with digital image correlation.Besides,a digital correspondence was established between the N_(2) concentration and the volume fraction of LPBF in-situ synthesized Ti N.Our results show that the GLSTi composites exhibit superior mechanical properties compared to pure titanium fabricated by LPBF under pure Ar.Specifically,the tensile strength of GLSTi was more than 1.5times higher than that of LPBF-formed pure titanium,reaching up to 1100 MPa,while maintaining a high elongation at fracture of 17%.GLSTi breaks the bottleneck of high strength but low ductility exhibited by conventional nanoceramic particle-strengthened titanium matrix composites,and the hetero-deformation induced strengthening effect formed by the Ti N/Ti layered structure explained its strength-plasticity balanced principle.The microhardness exhibits a jagged variation of the relatively low hardness of 245 HV0.2 for the pure titanium layer and a high hardness of 408 HV0.2 for the N_(2) in-situ synthesis layer.Our study provides a new concept for the structure-performance digital customization of 3D-printed Ti-based composites.

关键词： laser powder bed fusion layered structure composites in-situ synthesis TiN strength-plasticity synergy

Effect of Ni on Mg based hydrogen storage alloy Mg_3Nd

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Rare Metals 2006年第Z1期25卷 289-294页

作者： TONG Yanqing OUYANG Liuzhang ZHU Min College of Mechanical Engineering South China University of Technology Guangzhou 510641 China College of Mechanical Engineering South China University of Technology Guangzhou 510641 China College of Mechanical Engineering South China University of Technology Guangzhou 510641 China

Magnesium-neodymium based alloys were prepared by induction melting in an alumina crucible under protection of pure argon atmosphere. XRD patterns show that the as-melted Mg-Nd and Mg3NdNi0.1 diffraction peaks can be excellently indexed with D03 structure (BiF3 type, space group Fm3m). The lattice constant of Mg3Nd phase is 0.7390 nm, which is determined by XRD analysis using Cohen′s extrapolation method. The reversible hydrogen storage capacity reaches 1.95wt.% for Mg3Nd and 2.68wt.% for Mg3NdNi0.1. The desorption of hydrogen takes place at 291 ℃ for Mg3Nd and at 250 ℃ for Mg3NdNi0.1. The alloys could absorb hydrogen at room temperature with rapid hydriding and dehydriding kinetics after only one cycle. The enthalpy (ΔH) and entropy (ΔS) of Mg3Nd-H dehydriding reaction were -68.2 kJ·mol-1 H2 and -0.121 kJ·(K·mol)-1 H2 determined by using van′t Hoff plot according to the pressure-composition-isotherms (P-C-I) curve measured at different temperatures. Hydrogen absorption kinetic property of Mg3NdNi0.1 alloy was also measured at room temperature.

关键词： magnesium hydrogen storage rare earth induction melting

Smoothed-Particle Hydrodynamics Simulation of Ship Motion and Tank Sloshing under the Effect of Regular Waves

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Fluid Dynamics & Materials Processing 2024年第5期20卷 1045-1061页

作者： Mingming Zhao Jialong Jiao School of Civil Engineering and Transportation South China University of TechnologyGuangzhou510641China

Predicting the response of liquefied natural gas(LNG)contained in vessels subjected to external waves is extremely important to ensure the safety of the transportation process.In this study,the coupled behavior due to ship motion and liquid tank sloshing has been simulated by the Smoothed-Particle Hydrodynamics(SPH)method.Firstly,the sloshing flow in a rectangular tank was simulated and the related loads were analyzed to verify and validate the accuracy of the present SPH solver.Then,a three-dimensional simplified LNG carrier model,including two prismatic liquid tanks and a wave tank,was introduced.Different conditions were examined corresponding to different wave lengths,wave heights,wave heading angles,and tank loading rates.Finally,the effects of liquid tank loading rate on LNG ship motions and sloshing loading were analyzed,thereby showing that the SPH method can effectively provide useful indications for the design of liquid cargo ships.

关键词： LNG carrier tank sloshing seakeeping inner and external fluid coupling Smoothed Particle Hydrodynamics(SPH)

Efficient energy transfer from self-trapped excitons to Mn^(2+) dopants in CsCdCl_(3):Mn^(2+) perovskite nanocrystals

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International Journal of Minerals,Metallurgy and Materials 2024年第6期31卷 1456-1461页

作者： Anran Zhang Xinquan Zhou Ranran Gu Zhiguo Xia State Key Laboratory of Luminescent Materials and Devices Guangdong Provincial Key Laboratory of Fiber Laser Materials and Applied TechniquesSchool of Materials Science and EngineeringSouth China University of TechnologyGuangzhou 510641China School of Physics and Optoelectronics South China University of TechnologyGuangzhou 510641China

Mn^(2+)doping has been adopted as an efficient approach to regulating the luminescence properties of halide perovskite nano-crystals(NCs).However,it is still difficult to understand the interplay of Mn^(2+)luminescence and the matrix self-trapped exciton(STE)emission therein.In this study,Mn^(2+)-doped CsCdCl_(3) NCs are prepared by hot injection,in which CsCdCl_(3) is selected because of its unique crystal structure suitable for STE emission.The blue emission at 441 nm of undoped CsCdCl_(3) NCs originates from the defect states in the NCs.Mn^(2+)doping promotes lattice distortion of CsCdCl_(3) and generates bright orange-red light emission at 656 nm.The en-ergy transfer from the STEs of CsCdCl_(3) to the excited levels of the Mn^(2+)ion is confirmed to be a significant factor in achieving efficient luminescence in CsCdCl_(3):Mn^(2+)NCs.This work highlights the crucial role of energy transfer from STEs to Mn^(2+)dopants in Mn^(2+)-doped halide NCs and lays the groundwork for modifying the luminescence of other metal halide perovskite NCs.

关键词： perovskite nanocrystals self-trapped excitons luminescence energy transfer