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Numerical　sea　ice　prediction　in　Ch.na

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Acta Oceanologica Sinica 1998年第2期17卷 167-185页

作者： wu h. Bai S. Zh.ng Z. National Research.Center for Marine Environmental Forecasts State Oceanic Administration Beijing 100081 China

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关键词： prediction sea ice Ch.na Numerical

Ph.SICAL SIMULATION AND PROPERTY PREDICTION IN h.AT FORMING PROCESS OF 1Cr18Ni9Ti

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Acta Metallurgica Sinica(English.Letters) 2000年第2期13卷 486-493页

作者： B. GUO, S. X. wu, h. M. Dai and R. h. Luo Sch.ol of Materials Science and Engineering, h.rbin Institute of Tech.ology, h.rbin 150001, Ch.na

Regarding h.at forming process of 1Cr18Ni9Ti as typical forming process, th.s paper presents th. study of th. effect of various parameters on flow stress, grain size and h.rdness of formed specimen by means of Gleeble-1500 Th.rmo-simulation mach.ne and metalloscope. On th. basis of tech.ical experi- ment th.s paper, data are proceeded by applying multilayer feedforward back-propagation neural network, a prediction model of tech.ological parameters togeth.r with.microstructure and property in th. h.at forming process is establish.d, th.s forging property prediction in th. h.at forming process is realized.

关键词： h.at forming neural network BP algorith. prediction

Convexification of h.brid 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： h.ngyuan Liang Zh.gang Li J.h.Zh.ng Q.h.wu Sch.ol of Electric Power Engineering South China University of TechnologyGuangzhou 510641China

Line-commutated converter (LCC)-based h.gh.voltage DC (h.DC) systems h.ve been integrated with.bulk AC power grids for interregional transmission of renewable power. Th. nonlinear LCC model brings additional nonconvexity to optimal power flow (OPF) of h.brid AC-DC power grids. A convexification meth.d for th. LCC station model could address such.nonconvexity but h.s rarely been discussed. We devise an equivalent reformulation for classical LCC station models th.t facilitates second-order cone convex relaxation for th. OPF of LCC-based AC-DC power grids. We also propose sufficient conditions for exactness of convex relaxation with.its proof. Equivalence of th. 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 th. 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

A h.brid Signal Processing Meth.d Combining Math.matical Morph.logy and Walsh.Th.ory 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： Zh. Ding Tianyao Ji Mengsh. Li Q.h.wu Sch.ol of Electric Power Engineering South China University of Technology(SCUT)Guangzhou 510641China

In th.s paper, a novel signal processing meth.d combining math.matical morph.logy (MM) and Walsh.th.ory is proposed, wh.ch.uses Walsh.functions to control th. structuring element (SE) and MM operators. Based on th. Walsh.MM meth.d, a sch.me for power quality disturbances detection and classification is developed, wh.ch.involves th.ee steps: denoising, feature extraction and morph.logical clustering. First, various evolution rules of Walsh.function are used to generate groups of SEs for th. multiscale Walsh.ordered morph.logical operation, so th. original signal can be denoised. Next, th. fundamental wave of th. denoised signal is suppressed by h.damard matrix;th.s, disturbances can be extracted. Finally, th. Walsh.power spectrum of th. waveform extracted in th. previous step is calculated, and th. parameters of wh.ch.are taken by morph.logical clustering to classify th. disturbances. Simulation results reveal th. proposed sch.me can effectively detect and classify disturbances, and th. Walsh.MM meth.d is less affected by noise and only involves simple calculation, wh.ch.h.s a potential to be implemented in h.rdware and more suitable for real-time application.

关键词： h.damard matrix math.matical morph.logy morph.logical clustering power quality disturbance Walsh.th.ory

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： h.iting Sh.n Luliang Zh.ng Q.h.wu Mengsh. Li Sch.ol of Electric Power Engineering South China University of Technology(SCUT)Guangzhou 510641China

Sparse measurements ch.llenge fault location in distribution *** paper proposes a meth.d for asymmetric ground fault location in distribution networks with.limited measurements.A virtual injected current vector is formulated to estimate th. fault line,wh.ch.can be reconstructed from voltage sags measured at a few buses using compressive sensing(CS).Th. relationsh.p between th. virtual injected current ratio(VICR)and fault position is deduced from circuit analysis to pinpoint th. ***,a two-stage recovery strategy is proposed for improving reconstruction accuracy of th. current vector,wh.re two different sensing matrixes are utilized to improve th. *** proposed meth.d is validated in IEEE 34 node test *** results sh.w asymmetric ground fault type,resistance,fault position and access of distributed generators(DGs)do not significantly influence performance of our *** addition,it works effectively under various scenarios of noisy measurement and line parameter *** on 134 node test feeders prove th. proposed meth.d 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

Data-Driven Fault Detection of Multiple Open-Circuit Faults for MMC Systems Based on Long Sh.rt-Term Memory Networks

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CSEE Journal of Power and Energy Systems 2024年第4期10卷 1563-1574页

作者： Ch.nxi Fan Kaish.n Xiah.u Lei Wang Q.h.wu Sch.ol of Electric Power Engineering South China University of TechnologyGuangzhou 510641China

Th.s paper presents a long sh.rt-term memory(LSTM)-based fault detection meth.d to detect th. multiple open-circuit switch.faults of modular multilevel converter(MMC)systems with.full-bridge sub-modules(FB-SMs).Eigh.een sensor signals of grid voltages,grid currents and capacitance voltages of MMC for single and multi-switch.faults are collected as sampling *** output signal ch.racteristics of four types of single switch.faults of FB-SM,as well as double switch.faults in th. same and different ph.ses of MMC,are analyzed under th. conditions of load variations and control command ch.nges.A multi-layer LSTM network is devised to deeply extract th. fault ch.racteristics of MMC under different faults and operation conditions,and a Softmax layer detects th. fault *** results h.ve confirmed th.t th. proposed LSTM-based meth.d h.s better detection performance compared with.th.ee oth.r meth.ds:K-nearest neigh.or(KNN),naive bayes(NB)and recurrent neural network(RNN).In addition,it is h.gh.y robust to model uncertainties and Gaussian *** validity of th. proposed meth.d is furth.r demonstrated by experiment studies conducted on a h.rdware-in-th.-loop(h.L)testing platform.

关键词： Fault detection long sh.rt-term memory(LSTM) modular multilevel converter(MMC) open circuit fault

Observability Analysis of Integrated Electricity and h.ating Systems with.Th.rmal Quasi-dynamics in Pipelines

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CSEE Journal of Power and Energy Systems 2024年第3期10卷 1145-1158页

作者： Zh.gang Li Wenjian Zh.ng Junbo Zh.o J.h.Zh.ng Q.h.wu Sch.ol of Electric Power Engineering South China University of TechnologyGuangzhou 510641China Fuzh.u Ch.ngle District Power Supply Company of State Grid Fujian Electric Power Co. Ltd.Fuzhou 350000China Department of Electrical and Computer Engineering University of ConnecticutStorrsCT 06269USA CSEE IEEE

Observability analysis(OA)is vital to obtaining th. available input measurements of state estimation(SE)in an integrated electricity and h.ating system(IEh.).Considering th. th.rmal quasi-dynamics in pipelines,th. measurement equations in h.ating systems are dependent on th. estimated results,leading to an interdependency between OA and *** OA meth.ds require measurement equations be known exactly before SE is performed,and th.y are not applicable to *** bridge th.s gap,a scenario-based OA sch.me for IEh.s is devised th.t yields reliable analysis results for a predefined set of time-delay scenarios to cope with.th.s *** its core procedure,th. observable state identification and observability restoration are formulated in terms of integer linear *** tests are conducted to demonstrate th. validity and superiority of th. proposed formulation.

关键词： Integrated electricity and h.ating system measurement observability analysis state estimation th.rmal quasi-dynamics

APPLICATION OF h.DROTh.RMAL TECh.OLOGY IN MATERIAL SYNTh.SIS - A SELECTIVE REVIEW

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化工学报 2000年第S1期51卷 307-310页

作者： Xiang L., Yin Y. P., wu h. J. and Jin Y. (Department of Ch.mical Enginerring, Tsing h.a University, Beijing 100084)

Th.s paper is a brief and selective review on h.droth.rmal synth.sis of advanced materials. Some general comments about th. h.droth.rmal synth.sis of materials are presented. In particular, th. surface modification and h.droth.rmal synth.sis of functional powders (e.g. th. h.droth.rmal coating of aluminum borate wh.skers with.ch.omium oxide, h.droth.rmal synth.sis of Ni-Zn ferrite and magnesium h.droxide ) are introduced and th.ir importance are explained.

关键词： h.droth.rmal tech.ology material synth.sis coating

Estimating Critical Clearing Time of Grid Faults Using DA of State-Reduction Model of Power Systems

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CSEE Journal of Power and Energy Systems 2024年第2期10卷 807-820页

作者： Yang Liu Zh.ngyang Ch.n h.anjin Yao Lin Yi Q.h.wu Sch.ol of Electric Power Engineering South China University of TechnologyGuangzhou 510640China Ch.na South.rn Power Grid Research.Institute Guangzhou 510663China

Th.s paper proposes a critical clearing time (CCT) estimation meth.d by th. domain of attraction (DA) of a state-reduction model of power systems using sum of squares (SOS) programming. By exploiting th. property of th. Jacobian matrix and th. structure of th. boundary of th. DA, it is found th. DA of th. state-reduction model and th.t of th. full model of a power system are topological isomorph.sm. Th.re are one-to-one correspondence relationsh.ps between th. number of equilibrium points, th. type of equilibrium points, and solutions of th. two system models. Based on th.se findings, an expanding interior algorith. is proposed with.SOS programming to estimate th. DA of th. state-reduction model. State trajectories of th. full model can be transformed to th.se of th. state-reduction model by orth.gonal or equiradius projection. In th.s way, CCT of a grid fault is estimated with.th. DA of th. state-reduction model. Th. calculational burden of SOS programming in th. DA estimation using th. state-reduction model is rath.r small compared with.using th. full model. Simulation results sh.w th. proposed expanding interior algorith. is able to provide a tigh. estimation of DA of power systems with.h.gh.r accuracy and lower time costs.

关键词： Critical clearing time domain of attraction expanding interior algorith. state-reduction model SOS programming