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Real-time Dispatchable Region of Renewable Generation Constrained by Reactive Power and Voltage Profiles in AC Power Networks

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CSEE Journal of Power and Energy Systems 2020年第3期6卷 528-536页

作者： yanqi liu Zhigang Li q.H.Wu Haibo Zhang School of Electric Power Engineering South China University of TechnologyGuangzhou 510641China State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources North China Electric Power UniversityBeijing 102206China

A large amount of renewable energy generation(REG)has been integrated into power systems,challenging the operational security of power *** a real-time dispatch,system operators need to estimate the ability of the power network to accommodate REG with a limited reserve *** real-time dispatchable region(RTDR)is defined as the largest range of a power injection that the power network can accommodate in a certain dispatch interval for a given dispatch base ***-of-the-art research on the RTDR adopts a DC power flow model regardless of the voltage profiles and reactive power,which can overlook potentially insecure operational states of the *** address this issue,this paper proposes an AC power flow based RTDR model simultaneously considering the reactive power and voltage profiles *** nonlinear constraints in our model are approximated using a linear power flow model together with a polytope approximation technique for quadratic *** adaptive constraint generation algorithm is used to calculate the *** results using the IEEE 5-bus and 30-bus systems illustrate the advantages of the proposed model.

关键词： Dispatchable region linearization renewable energy generation reactive power

Equivalent Hamiltonian Equations Modelling and Energy Function Construction for MMC-HVDC in Hybrid AC/DC Power Systems

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CSEE Journal of Power and Energy Systems 2021年第4期7卷 821-831页

作者： yang liu Zehui Lin Kaishun Xiahou yuqing Lin q.H.Wu School of Electric Power Engineering South China University of TechnologyGuangzhou 510640China

This paper proposes an equivalent Hamiltonian equations model for the modular multilevel converter-based high-voltage direct-current(MMC-HVDC)transmission system,and constructs an energy function for multi-machine power systems with MMC-HVDC transmission *** equivalent Hamiltonian equations model is verified to be able to track the power output dynamics of the full model of an MMC-HVDC transmission *** theoretical and numerical studies have been undertaken to validate that the energy function proposed for hybrid AC/DC systems satisfies the conditions of an energy *** work of this paper bridges the gap between the well-developed direct methods of transient stability analysis and power systems with MMC-HVDC transmission lines.

关键词： Energy function equivalent Hamiltonian equations model hybrid AC/DC power system MMC-HVDC transient stability

Constructing an Energy Function for Power Systems with DFIGWT Generation Based on a Synchronous-generator-mimicking Model

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CSEE Journal of Power and Energy Systems 2022年第1期8卷 64-75页

作者： yang liu Chenying Xu Zehui Lin Kaishun Xiahou q.H.Wu the School of Electric Power Engineering South China University of TechnologyGuangzhou 510640China

In this paper we construct an energy function for multi-machine power systems with doubly-fed induction generator-based wind turbine(DFIGWT)according to a synchronous-generator-mimicking(SGM)model of the *** SGM model is proposed to approximate the dynamics of a *** to the modelling of a synchronous generator(SG),the internal dynamics of a DFIGWT are also described with differential equations of newly constructed virtual rotor angle and internal electromotive force(EMF)in the SGM ***,the power flow of a DFIGWT is expressed by nonlinear functions of its virtual rotor angle and internal *** SGM model bridges the gap between the irregular and complex modelling of DFIGWTs and the well-developed energy function construction techniques for SG *** on the SGM model,a numerical energy function is constructed for power systems with DFIGWT *** theoretical analysis and numerical studies were undertaken to validate that the proposed energy function satisfies the necessary conditions for an energy function of a power system.

关键词： DFIGWT energy function multi-machine power systems synchronous-generator-mimicking model

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 Zhongyang Chen Huanjin yao Lin yi q.H.Wu School of Electric Power Engineering South China University of TechnologyGuangzhou 510640China China Southern Power Grid Research Institute Guangzhou 510663China

This paper proposes a critical clearing time (CCT) estimation method by the domain of attraction (DA) of a state-reduction model of power systems using sum of squares (SOS) programming. By exploiting the property of the Jacobian matrix and the structure of the boundary of the DA, it is found the DA of the state-reduction model and that of the full model of a power system are topological isomorphism. There are one-to-one correspondence relationships between the number of equilibrium points, the type of equilibrium points, and solutions of the two system models. Based on these findings, an expanding interior algorithm is proposed with SOS programming to estimate the DA of the state-reduction model. State trajectories of the full model can be transformed to those of the state-reduction model by orthogonal or equiradius projection. In this way, CCT of a grid fault is estimated with the DA of the state-reduction model. The calculational burden of SOS programming in the DA estimation using the state-reduction model is rather small compared with using the full model. Simulation results show the proposed expanding interior algorithm is able to provide a tight estimation of DA of power systems with higher accuracy and lower time costs.

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

Improving high-temperature mechanical properties of cast CrFeCoNi high-entropy alloy by highly thermostable in-situ precipitated carbides

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Journal of Materials Science & Technology 2021年第13期72卷 29-38页

作者： X.W.liu N.Gao J.Zheng y.Wu y.y.Zhao q.Chen W.Zhou S.Z.Pu W.M.Jiang Z.T.Fan State Key Laboratory of Materials Processing and Die&Mould Technology School of Materials Science and EngineeringHuazhong University of Science and TechnologyWuhan430074China Institute of Nuclear Physics and Chemistry China Academy of Engineering PhysicsMianyang 621999China State Key Laboratory for Advanced Metals and Materials University of Science and Technology BeijingBeijing 100083China School of Materials Engineering Purdue UniversityWest LafayetteIN 47907USA Southwest Technology and Engineering Research Institute Chongqing 400039China Center for Electron Microscopy Wuhan UniversityWuhan 430072China

The Cr Fe Co Ni high-entropy alloy(HEA)exhibits excellent mechanical properties at lower temperatures due to its low stacking-fault energy,however,its medium-and high-temperature strengths are still *** consideration of the potential diversified applications,more strengthening approaches except for the previously proposed L12 phase hardening deserve further exploration due to its rapid coarsening tendency at high ***,we achieved significant high-temperature strengthening of the cast Cr Fe Co Ni HEA by in-situ precipitation of highly thermostable *** with 0.5 at.%and 1 at.%niobium and carbon were prepared by simple casting processes,*** cast,solute solution and aging.A highly thermostable microstructure was formed,which comprises very coarse grains accompanied with extensive thermostable carbide precipitates embedded,including submicrometer coherent Nb C particles in grain interiors and intergranular coherent M_(23)C_(6)*** high thermostability of microstructure,which is beneficial for the high-temperature loading,is ascribed to the synergy of lacking growth driving force and Zenner pinning effect by the *** properties tested at 673,873 and1073 K show that the yield strength and ultimate tensile strength are significantly increased by Nb/C doping,along with the elongation escalation at higher *** strengthening is mainly due to the precipitation hardening of carbide particles.

关键词： High-entropy alloy Carbides Precipitation High-temperature property Strengthening

A Fourier Spectral Moving Mesh Method for the Cahn-Hilliard Equation with Elasticity

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Communications in Computational Physics 2009年第2期5卷 582-599页

作者： W.M.Feng P.yu S.y.Hu Z.K.liu q.Du L.q.Chen Department of Materials Science and Engineering Pennsylvania State UniversityUniversity ParkPA 16802USA Department of Mathematics Pennsylvania State UniversityUniversity ParkPA 16802USA Pacific Northwest National Laboratory RichlandWA 99354USA

In recent years,Fourier spectral methods have emerged as competitive numerical methods for large-scale phase field simulations of microstructures in computational materials *** further improve their effectiveness,we recently developed a new adaptive Fourier-spectral semi-implicit method(AFSIM)for solving the phase field equation by combining an adaptive moving mesh method and the semi-implicit Fourier spectral *** this paper,we present the application of AFSIM to the Cahn-Hilliard equation with inhomogeneous,anisotropic *** implementations and test examples in both two and three dimensions are considered with a particular illustration using the well-studied example of mis-fitting particles in a solid as they approach to their equilibrium *** is shown that significant savings in memory and computational time is achieved while accurate solutions are preserved.

关键词： Phase field diffuse interface moving mesh adaptive mesh Fourier-spectral method adaptive spectral method Cahn-Hilliard equation elasticity

DyNAMIC ANALySIS OF ARREST OF BUCKLE PROPAGATION ON A BEAM ON A NONLINEAR ELASTIC FOUNDATION By FEM

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Acta Mechanica Solida Sinica 1997年第1期10卷 28-30,32-35页

作者： Zou, SZ Huang, yy liu, ZH qian, q SHASHI UNIV SHASHI 434000PEOPLES R CHINA HUAZHONG UNIV SCI & TECHNOL WUHAN 430074PEOPLES R CHINA ACAD SINICA INST MECHBEIJING 100080PEOPLES R CHINA

Based on the dynamic governing equation of propagating buckle on a beam on a nonlinear elastic foundation, this paper deals with an important problem of buckle arrest by combining the FEM with a time integration technique. A new conclusion completely different from that by the quasi-static analysis about the buckle arrestor design is drawn. This shows that the inertia of the beam cannot be ignored in the analysis under consideration, especially when the buckle propagation is suddenly stopped by the arrestors.

关键词： buckle propagation arrest of buckle beam on a nonlinear foundation finite element method

STUDy OF RAy IRRADIATION ON DIAMOND-LIKE CARBON FILMS

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Acta Metallurgica Sinica(English Letters) 2002年第1期15卷 26-32页

作者： G.A. liu T.M. Wang E.q Dept. of Appl. Phy. Southwest Jiaotong Univ. Chengdu 610031 China

Diamond-like carbon (DLC) films have been deposited on glass substrates usingradio-frequency (rf) plasma deposition method. Gamma -ray, ultraviolet (UV) ray were used toirradiate the DLC films. Raman spectroscopy and infrared (IR) spectroscopy were use to characterizethe changing characteristics of SP^3 C-H bond and hydrogen content in the films due to theirradiations. The results show that, the damage degrees induced by the UV ray on the SP^3 C-H bondsare much stronger than that by the gamma -ray. When the irradiation dose of gamma -ray reaches 1 OX10^4 Gy, the SP^3 C-H bond reduces about 50 percent in number. The square electrical resistance ofthe films is reduced due to the irradiation of UV ray and this is caused by severe oxidation of thefilms. By using the results on optical gap of the films and the fully constrained network theory,the hydrogen content in the as-deposited films is estimated to be l0-25at. percent.

关键词： diamond-like carbon film gamma -ray irradiation ultraviolet rayirradiation SP^3 C-H bond infrared transmittance

Analysis of vibration reduction level in an 8/6 switched reluctance machine by active vibration cancellation

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Journal of Zhejiang University-Science C(Computers and Electronics) 2010年第10期11卷 808-816页

作者： Xu liu Zai-ping PAN Z. q. ZHU School of Electrical Engineering Zhejiang University Hangzhou 310027 China Department of Electronic and Electrwal Engmeermg University of Sheffield Sheffield S1 3JD UK

This paper proposes an analytical model for predicting the maximum vibration reduction level in a four-phase 8/6 switched reluctance machine(SRM) by employing active vibration cancellation(AVC),one of the most effective and convenient methods for reducing the vibration and acoustic noise produced by *** on the proposed method,the factors that influence the vibration reduction level are analyzed in *** relationships between vibration and noise reduction levels at resonance frequency and rotor speed are ***,it is shown that a large damping factor will lead to smaller vibration reduction level with AVC while,in contrast,a large resonance frequency will increase the vibration reduction *** finite element analyses and experiments were carried out on a prototype 8/6 SRM to validate the proposed method.

关键词： Active vibration cancellation Analytical model Switched reluctance machine Vibration