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Active splitting strategy searching approach based on MISOCP with consideration of power island stability

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Journal of Modern Power Systems and Clean Energy 2019年第3期7卷 475-490页

作者： Yifan ZHOU Wei HU Yong MIN le zheng Department of Electrical Engineering Tsinghua UniversityBeijing100084China Department of Cardiothoracic Surgery Stanford UniversityStanfordUSA

Active splitting control utilizes real-time decision and system-level splitting to prevent cascading blackouts and to maintain power supply under severe disturbances. Splitting strategy searching(SSS) is one of the most crucial issues in active splitting control for deciding‘‘where to split’’. SSS determines the splitting surface in real time to properly divide the asynchronous generators into isolated islands with an optimal control effect. In this paper, an SSS approach that focuses on island stability is presented. The proposed SSS approach is designed to ensure a rational stability margin and regulation ability on each island during and after the transient process of system splitting. This method includes the active/reactive power flow feasibility constraints and voltage/angle stability constraints in the steady state as well as the frequencyresponse capability constraints in the transient process. By considering the island stability constraints in the SSS, the proposed approach can avoid the splitting strategies with poor stability performance. Therefore, the major advantage of the proposed approach is that it can ensure better island static and transient stability during and after the splitting control. In addition, the entire model is formulated as a mixed-integer second-order cone programming(MISOCP)model. Thus, it can be rapidly solved by using commercial optimization solvers. Numerical simulations of a realistic provincial power system in central China demonstrate thevalidity of the proposed approach and the necessity of considering the island stability issues.

关键词： Splitting strategy searching(SSS) Mixed-integer second-order cone programming(MISOCP) Controlled islanding Static stability margin Transient stability Power system

Influence of silicon on the microstructures, mechanical properties and stretch-flangeability of dual phase steels

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International Journal of Minerals,Metallurgy and Materials 2014年第8期21卷 755-765页

作者： le-yu Zhou Dan Zhang Ya-zheng Liu School of Materials Science and Engineering University of Science and Technology Beijing

Uniaxial tension tests and hole-expansion tests were carried out to determine the influence of silicon on the microstructures, mechanical properties, and stretch-flangeability of conventional dual-phase steels. Compared to 0.03wt% silicon, the addition of 1.08wt% silicon induced the formation of finer ferrite grains （6.8μm ） and a higher carbon content of martensite （Cm≈ 0.32wt%）. AS the silicon level increased, the initial strain-hardening rate （n value） and the uniform elongation increased, whereas the yield strength, yield ratio, and stretch-flangeability decreased. The microstructures were observed after hole-expansion tests. The results showed that low carbon content martensite （Cm ≈ 0.19wt%） can easily deform in coordination with ferrite. The relationship between the mechanical properties and stretch-flangeability indicated that the steel with large post-uniform elongation has good stretch-flangeability due to a closer plastic incom- patibility of the ferrite and martensite phases, which can effectively delay the production and decohesion of microvoids.

关键词： dual-phase steel silicon content mechanical properties microstructure strain hardening

Angle measurement technology based on magnetization vector for narrow space applications

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Nanotechnology and Precision Engineering 2020年第3期3卷 167-173页

作者： Yinguo Huang Shiyu Zhang le Gao Yelong zheng State Key Laboratory of Precision Measuring Technology and Instruments Tianjin UniversityTianjin 300072China Science and Technology on Rotorcraft Aeromechanics Laboratory China Helicopter Research and Development InstituteJingdezhen 333001China

With the wide application of laser in the field of skin plastic surgery, micro laser galvanometer scanner has made great progress in this field with its portability. However, the measurement method used to measure the deflection angle of laser galvanometer in the narrow space of scanner with high precision remains to be studied. In this paper, an angle measurement method based on magnetic field is proposed, and the effect of the shapes of permanent magnets(PMs) on the measurement is studied by theoretical and experimental study under the condition that the maximum available space for the PMs is a 10 mm side cube. An angle measuring experimental device is set up, and the contrast experiment is carried out with different PMs which are the same as simulation. The experimental results show that cylindrical PM is more suitable than other PMs, which is consistent with the simulation results, and the maximum nonlinearity error is 0.562%. This method has the advantages of small volume,non-contact measurement, small moment of inertia, good dynamic response and no external excitation for the PMs, so it has a broad application prospect in micro laser galvanometer scanner.

关键词： Micro laser galvanometer scanner Deflection angle Narrow space Shapes of permanent magnets Nonlinearity error

Photochemical microfluidic synthesis of vitamin D_3 by improved light sources with photoluminescent substrates

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Chinese Journal of Chemical Engineering 2021年第1期34卷 204-211页

作者： Wenhao Niu Yuanzhi zheng Ying Li le Du Wei Liu The State Key Laboratory of Chemical Resource Engineering Beijing Key Laboratory of Membrane Science and TechnologyBeijing University of Chemical TechnologyBeijing 100029China

This study presents a novel technique for the controllable preparation of photoluminescent substrates to enhance the photochemical microfluidic synthesis of vitamin D_*** dip-coating method to prepare the substrates was experimentally optimized,and the corresponding emission behaviors were systematically *** substrates were successfully used to enhance the ultraviolet B(UVB) emission of a low-power light source(e.g.,an 8 W lamp),whose UVB emission intensity was increased by approximately 11 *** virtue of the novel light source,the productivity of a single set of photochemical microreactor with a 12-meter-long channel(0.6 mm i.d.) was increased to 1.83 kg·a^(-1),which was 42% higher than that of a 100 W lamp,and no cooling devices were *** method is simple and has great potential to replace traditional medium-pressure mercury lamps for UVB-irradiated photochemical reactions.

关键词： Microfluidics Photochemistry Composites UVB emission Vitamin D_3

Improved Deep Belief Network and Model Interpretation Method for Power System Transient Stability Assessment

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Journal of Modern Power Systems and Clean Energy 2020年第1期8卷 27-37页

作者： Shuang Wu le zheng Wei Hu Rui Yu Baisi Liu State Key Laboratory of Power System Department of Electrical EngineeringTsinghua UniversityBeijing 100084China Stanford University StanfordCalifornia 94305USA Southwest Branch State Grid Corporation of ChinaChengdu 610041China

The real-time transient stability assessment(TSA)and emergency control are effective measures to suppress accident expansion,prevent system instability,and avoid large-scale power outages in the event of power system ***,real-time assessment is extremely demanding on computing speed,and the traditional method is not *** this paper,an improved deep belief network(DBN)is proposed for the fast assessment of transient stability,which considers the structural characteristics of power system in the construction of loss *** learning has been effective in many fields,but usually is considered as a black-box *** the perspective of machine learning interpretation,this paper proposes a local linear interpreter(LLI)model,and tries to give a reasonable interpretation of the relationship between the system features and the assessment result,and illustrates the conversion process from the input feature space to the high-dimension representation *** proposed method is tested on an IEEE new England test system and demonstrated on a regional power system in *** result demonstrates that the proposed method has rapidity,high accuracy and good interpretability in transient stability assessment.

关键词： Transient stability assessment(TSA) representation learning deep belief network(DBN) local linear interpretation(LLI) visualization emergency control

Surface decarburization characteristics and relation between decarburized types and heating temperature of spring steel 60Si2MnA

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International Journal of Minerals,Metallurgy and Materials 2013年第8期20卷 720-724页

作者： Chao-lei Zhang le-yu Zhou Ya-zheng Liu School of Materials Science and Engineering University of Science and Technology Beijing

The characteristics of complete and partial decarburizations in spring steel 60Si2MnA were systematically investigated, including the microstructure, the hardness gradient, and the formation mechanism. The relation between decarburized types and heating temperature of the steel was comprehensively discussed. It is found that heating temper- ature has an important influence on the decarburized types. With the rise of heating temperature, the decarburized types change from no decarburization to complete decarburization, complete and partial decarburizations, partial decarburiza- tion, and no decarburization.

关键词： spring steel decarburization temperature microstructure hardness

Visible light responsive N-F-codoped TiO_2 photocatalysts for the degradation of 4-chlorophenol

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Journal of Environmental Sciences 2011年第11期23卷 1919-1924页

作者： Xiaohong Li Haidong Zhang Xuxu zheng Zhongyi Yin le Wei Laboratory of Applied Catalysis Engineering Research Centre for Waste Oil Recovery Technology and EquipmentMinistry of EducationChongqing Technology and Business UniversityChongqing 400067China Environmental and Biological Engineering Institute Chongqing Technology and Business UniversityChongqing 400067China

N-F-codoped TiO2 （NFTO） photocatalysts were synthesized by a simple sol-gel process with tetrabutyl titanate （Ti（OBu）4 ） as the precursor of TiO 2 and ammonium fluoride （NH4 F） as the source of N and *** synthesized photocatalysts were investigated by X- ray diffraction （XRD）,X-ray photoelectron spectroscopy （XPS）,ultraviolet-visible diffuse reflectance spectroscopy （UV-Vis DRS） and photodegradation reaction tests of 4-chlorophenol under visible light irradiation to understand the relationship between the structure of NFTO catalyst and corresponding photocatalytic *** crystal phase and particle size of catalysts were found to be largely affected by the calcination *** addition,N-F-codoping could inhibit phase transition of TiO2 from anatase to *** presence of N and F atoms in the lattice of TiO2 is responsible for the visible light catalytic *** UV-Vis DRS tests,the spectrum of NFTO exhibited red shift compared with Degussa P25 and the band gap was reduced to around 2.92 *** optimal calcination temperature and dopant concentration conditions,the NFTO photocatalyst exhibited the highest activity in the photodegradation reaction tests of 4-chlorophenol under visible light irradiation with a degradation rate of 75.84%.Besides,the 5-recycle test showed that NFTO photocatalyst could be reused and its activity kept stable under visible light irradiation.

关键词： TiO2 N-F-codoping photocatalyst sol-gel process

Design and experimental study of a practical Osculating Inward Cone Waverider Inlet

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Chinese Journal of Aeronautics 2016年第6期29卷 1582-1590页

作者： He Xuzhao Zhou zheng Qin Si Wei Feng le Jialing Science and Technology on Scramjet Laboratory Hypervelocity Aerodynamics Institute of CARDC

A design method based on tip to tail streamline tracing and osculating inward cone methods is discussed for designing the integrated Osculating Inward Cone Waverider Inlet（OICWI）. A practical geometrical constrained experimental model of OICWI is designed based on the validated design method. It has a total contraction ratio of 4.61 and inner contraction ratio is 2.0. Wind-tunnel tests have been conducted for the OICWI model at free stream Mach number（Ma） of 4.0, 3.5 and 3.0 respectively. The experimental results show that the OICWI has high flow capture ratio and compression abilities. It can self-start at Ma= 3.5 and 4.0 and its flow capture ratio is 0.73 at Ma= 4.0, and Angle of Attack（AOA） 0°. The research results show that the OICWI has advantages of inward cone waverider and streamline tracing inlet. Present OICWI is a novel approach for waverider inlet integration studies and it will promote the use of waverider inlet integration configuration in the studies of airbreathing hypersonic vehicles.

关键词： Inlet Integration design Inward turning cone Waverider Wind tunnel experiment

Is there a silver lining? Aggregation and photo-transformation of silver nanoparticles in environmental waters

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Journal of Environmental Sciences 2015年第8期27卷 259-262页

作者： Qi zheng Michael Zhou Wenchao Deng X.Chris le Key Laboratory of Optoelectronic Chemical Materials and Devices of Ministry of Education Jianghan University Institute of Environment and Health Jianghan University Division of Analytical and Environmental Toxicology University of Alberta

The nanotechnology industry advances rapidly,and at the vanguard are the promising silver nanoparticles（Ag NPs）,which have diverse *** nanometer-sized particles have been shown to inhibit the ability of bacteria to produce adenosine triphosphate（ATP）,a molecule necessary for chemical energy transport in *** antimicrobial properties of Ag NPs（and Ag＋）make them valued antibacterial

关键词： Silver nanoparticles(AgNPs) Nanomaterials Water chemistry Aggregation Transformation Toxicology Dissolved organic matter(DOM)