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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

Dispatchable Region for Active Distribution Networks Using Approximate Second-order Cone Relaxation

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CSEE journal of Power and Energy Systems 2023年第6期9卷 1999-2007页

作者： Zhigang Li Wenjing huang j.h.zheng Q.h.Wu School of Electric Power Engineering South China University of TechnologyGuangzhou 510640China

Uncertainty in distributed renewable generation threatens the security of power distribution *** concept of dispatchable region is developed to assess the ability of power systems to accommodate renewable generation at a given operating *** DC and linearized AC power flow equations are typically used to model dispatchable regions for transmission systems,these equations are rarely suitable for distribution *** achieve a suitable trade-off between accuracy and efficiency,this paper proposes a dispatchable region formulation for distribution networks using tight convex *** cone relaxation is adopted to reformulate AC power flow equations,which are then approximated by a polyhedron to improve ***,an efficient adaptive constraint generation algorithm is employed to construct the proposed dispatchable *** studies on distribution systems of various scales validate the computational efficiency and accuracy of the proposed method.

关键词： Dispatchable region distribution system renewable power generation second-order cone relaxation uncertainty

Many-objective optimization for coordinated operation of integrated electricity and gas network

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journal of Modern Power Systems and Clean Energy 2017年第3期5卷 350-363页

作者： Y.N.KOU j.h.zheng Zhigang LI Q.h.WU School of Electric Power Engineering South China University of TechnologyGuangzhou 510640China Department of Electrical Engineering and Electronics The University of LiverpoolLiverpool L693GJUK

This paper develops a many-objective optimization model, which contains objectives representing the interests of the electricity and gas networks, as well as the distributed district heating and cooling units, to coordinate the benefits of all parties participated in the integrated energy system(IES). In order to solve the many-objective optimization model efficiently, an improved objective reduction(IOR) approach is proposed, aiming at acquiring the smallest set of objectives. The IOR approach utilizes the Spearman’s rank correlation coefficient to measure the relationship between objectives based on the Pareto-optimal front captured by the multi-objective group search optimizer with adaptive covariance and Lévy flights algorithm, and adopts various strategies to reduce the number of objectives gradually. Simulation studies are conducted on an IES consisting of a modified IEEE 30-bus electricity network and a 15-node gas network. The results show that the many-objective optimization problem is transformed into a bi-objective formulation by the IOR. Furthermore,our approach improves the overall quality of dispatch solutions and alleviates the decision making burden.

关键词： Integrated energy system Gas network Electricity network Many-objective optimization Objective reduction

Stochastic Accelerated Alternating Direction Method of Multipliers for hedging Communication Noise in Combined heat and Power Dispatch

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CSEE journal of Power and Energy Systems 2023年第2期9卷 696-706页

作者： Zhigang Li Xinyu Liang Fan hu Wen Xiong Renbo Wu j.h.zheng Q.h.Wu School of Electric Power Engineering South China University of TechnologyGuangzhou 510641China Guangzhou Power Supply Bureau Guangdong Power Grid Co.LtdGuangzhouChina

Combined heat and power dispatch(ChPD)opens a new window for increasing operational flexibility and reducing wind power *** power and district heating systems are independently controlled by different system operators;therefore,a decentralized solution paradigm is necessary for ChPD,in which only minor boundary information is required to be exchanged via a communication ***,a nonideal communication environment with noise could lead to divergence or incorrect solutions of decentralized *** bridge this gap,this paper proposes a stochastic accelerated alternating direction method of multipliers(SA-ADMM)for hedging communication noise in *** algorithm provides a general framework to address more types of constraint sets and separable objective functions than the existing stochastic *** from the single noise sources considered in the existing stochastic approximation methods,communication noise from multiple sources is addressed in both the local calculation and the variable update *** studies of two test systems validate the effectiveness and robustness of the proposed SAADMM.

关键词： Alternating direction method of multipliers combined heat and power dispatch communication noise decentralized optimization

Effect of MR Element Slant Angle on Output Voltage of Magnetoresistive Device

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稀有金属材料与工程 2006年第A3期35卷 586-587页

作者： Y L jing Yu Shi h W Zhang X D jiang h j zheng School of Microelectronics and Solid-State Electronics University of Electronics Science and Technology of China Chengdu 610054 China

Correlation between optimum of MR element slant angle and the ratio of magnetic pole length to magnetoresistance element length on linear magnetic encoder is explored in this *** slant angle of MR element is different and increases in proportion to the ratio of magnetic pole length to MR element length by slant multi-phase filtering model.

关键词： magnetic encoder MR element sensor

Comparison and Error Analysis of Off-design and Design Models of Energy hubs

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CSEE journal of Power and Energy Systems 2019年第4期5卷 454-465页

作者： j.h.zheng jun huang Shan Deng Q.h.Wu Mengshi Li Xiaoxin Zhou Zhaoxia jing School of Electric Power Engineering South China University of TechnologyGuangzhou 510006China China Electric Power Research Institute Beijing 100192China

The accuracy of the simulation model has a pro-found impact on the optimal operation of the energy hubs(Ehs).however,in many articles,the constant model of the efficiency of equipment is adopted to formulate the operation system,which would probably lead to a simplification of the simulation ***,Ehs are typically operated under off-design condition due to the fluctuations in cooling,heating,electricity ***-over,even though the off-design characteristics are considered,few studies have suggested comparing the differences between those two models by considering the operation *** order to assess the effect of the off-design characteristics of Eh on the optimal operation accuracy in this paper,two test cases are performed on the fixed and variable load conditions,*** addition,the individual effect of off-design characteristics of each equipment on the optimal operation cost of the Eh is also investigated through four optimization *** is worth mentioning that the optimal operation problem of the Eh considering the off-design characteristics and on-off status of the equipment is a mixed integer non-linear programming problem(MINLP).By testing the design and off-design models on the two cases,the results of simulation demonstrate that the optimal operation cost for the off-design model is larger than that for the design ***,in the aspect of the authenticity of the system operation strategy,the off-design model performs better than the design ***,a larger relative error of the system operation cost between the two models can be observed when the Eh is operated under a relatively lower load condition,revealing that the influence of off-design characteristic on the optimal operation of Ehs is too significant to be neglected.

关键词： Design energy hubs MINLP off-design optimal operation

Multi-Objective optimization for stable and efficient cargo transportation of partial space elevator

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Defence Technology(防务技术) 2025年第2期44卷 17-29页

作者： Gefei Shi zheng h.Zhu School of Aeronautics and Astronautics Sun Yat-sen UniversityGuangzhou 510275China Shenzhen Key Laboratory of Intelligent Microsatellite Constellation Shenzhen 518107China Department of Mechanical Engineering York University4700 Keele StreetTorontoCanada

This paper proposed a new libration decoupling analytical speed function(LD-ASF)in lieu of the classic analytical speed function to control the climber's speed along a partial space elevator to improve libration stability in cargo *** LD-ASF is further optimized for payload transportation efficiency by a novel coordinate game theory to balance competing control objectives among payload transport speed,stable end body's libration,and overall control input via model predictive *** transfer period is divided into several sections to reduce computational *** validity and efficacy of the proposed LD-ASF and coordinate game-based model predictive control are demonstrated by computer *** results reveal that the optimized LD-ASF results in higher transportation speed,stable end body's libration,lower thrust fuel consumption,and more flexible optimization space than the classic analytical speed function.

关键词： Partial space elevator Stable transportation Libration decoupling analytical speed function Coordinate game Model predictive control Pareto optimization

Efficacy and Safety of Duloxetine on Osteoarthritis Knee Pain:A Meta-analysis of Randomized Controlled Trials

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Efficacy and Safety of Duloxetine on Osteoarthritis Knee Pai...

hugan Qingzhi exerts anti-inflammatory effects in a rat model of non-alcoholic fatty liver disease

2016年广东省药师周大会

作者： Z.Y.Wang S.Y.Shi S.j.Li F.Chen j h zheng h.Z.Lin W Zhou j.M.Lin Guangdong Province Key Laboratory for Biotechnology Drug Candidates School of Biosciences and BiopharmaceuticsGuangdong Pharmaceutical University Department of Pharmacy Zhujiang HospitalSouthern Medical University Department of Pharmacy Yue Bei people's HospitalShantou University Pharmaceutical Research & Development Zhujiang HospitalSouthern Medical University

Objectives:The aim of this meta-analysis was to evaluate the efficacy and safety of duloxetine for management of osteoarthritis knee(OAK) ***:A systematic literature search of articles for management of OAK using duloxetine were performed in Pub Med,EBSCO,EMBASE,Science Direct,MEDLINE,Clinical ***,Google Scholar,and Cochrane Central Register of Controlled Trials from the available date of inception until the latest issue(October 2013).Potentially relevant randomized controlled trials(RCTs) regarding to comparison of efficacy and safety of duloxetine with placebo for managing OAK pain were ***,studies with specific data regarding to pain reductions and response rate,PGI-I,functional improvement,Western Ontario and Mc Master Osteoarthritis Index(WOMAC),adverse events,TEAEs,mortality were included and analyzed,and those with confounding conditions were *** were assessed for quality using the jadad 5-point score for ***,a meta-analysis of all RCTs eligible for inclusion criteria was performed using Review Manager 5.1 meta-analysis ***:Three RCTs that enrolled 1,011 patients were included in our *** were statistically significant differences between patients taking duloxetine and those taking placebo with regard to the reductions in pain intensity [992 patients,mean difference(MD) =-0.88,95% confidence interval(CI)-1.11 to-0.65,p

关键词： duloxetine osteoarthritis knee pain meta-analysis randomized controlled trials

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Hugan Qingzhi exerts anti-inflammatory effects in a rat mode...