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Sound velocity in dense stellar matter with strangeness and compact stars

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Chinese Physics C 2021年第5期45卷 237-246页

作者： chengjun xia Zhenyu Zhu xia Zhou Ang Li School of Information Science and Engineering Zhejiang University Ningbo Institute of Technology.Ningbo 315100 China Department of Astronomy Xiamen UniversityXiamen 361005China Xinjiang Astronomical Observatory Chinese Academy of SciencesUrumqi 830011China

The phase state of dense matter in the intermediate density range(~1-10 times the nuclear saturation density)is both intriguing and unclear and can have important observable effects in the present gravitational wave era of neutron *** matter density increases in compact stars,the sound velocity is expected to approach the con-formal limit(cs/c=1/√3)at high densities and should also fulfill the causality limit(cs/c<1).However,its de-tailed behavior remains a prominent topic of *** was suggested that the sound velocity of dense matter could be an important indicator of a deconfinement phase transition,where a particular shape might be expected for its density *** this work,we explore the general properties of the sound velocity and the adiabatic index of dense matter in hybrid stars as well as in neutron stars and quark *** conditions are employed for the had-ron-quark phase transition with varying interface *** find that the expected behavior of the sound velocity can also be achieved by the nonperturbative properties of the quark phase,in addition to a deconfinement phase ***,it leads to a more compact star with a similar *** then propose a new class of quark star equation of states,which can be tested by future high-precision radius measurements of pulsar-like objects.

关键词： quark matter hadron-quark phase transition neutron star

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奇异夸克物质：从奇异子到奇异星

中国科学：物理学、力学、天文学 2016年第1期46卷 219-243页

作者：夏铖君中国科学院理论物理研究所、理论物理国家重点实验室北京100190

奇异夸克物质是量子色动力学预言的一种新型物质,由数量大致相同的u,d,s夸克和少量的电子组成.在20世纪七八十年代,Witten和Bodmer等人推测奇异夸克物质可能是强相互作用的真正基态.如果这个推测成立,那么必然存在由奇异夸克物质组成的... 详细信息

奇异夸克物质是量子色动力学预言的一种新型物质,由数量大致相同的u,d,s夸克和少量的电子组成.在20世纪七八十年代,Witten和Bodmer等人推测奇异夸克物质可能是强相互作用的真正基态.如果这个推测成立,那么必然存在由奇异夸克物质组成的集团结构,如奇异子和奇异星等.本文介绍奇异夸克物质的研究背景,在此基础之上,探讨奇异子和奇异星理论研究和实验探索的进展.为了更准确地描述奇异夸克物质集团的性质,本文应用夸克集团统一模型研究了从奇异子到奇异星各类不同大小的奇异夸克物质集团.发现奇异夸克物质集团的平均重子能量随重子数的增大而减小,并且其夸克核心部分的比电荷比之前理论计算得到的数值大.在核心表面处,还存在带负电粒子的一个电势阱,有可能为奇异夸克物质的探测提供新的线索.对于旋转的奇异星,由带电夸克核心转动所产生的磁场接近于脉冲星的磁场强度.

关键词：奇异夸克物质奇异子奇异星夸克集团统一模型

Research on the Optimized Network Configuration of DC Blocking Device

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Journal of Power and Energy Engineering 2014年第9期2卷 147-153页

作者： chengjun xia Yinggeng Xie Yun Zhou School of Electric Power South China University of Technology Guangzhou China

HVDC transmission system has considerable impact on the surrounding power transformers when the system is running in the unipolar ground mode, which will cause the DC magnetic biasing phenomenon on transformers. This problem would be more serious, after commission and operation of UHVDC transmission system in China. According to the Guangdong power grid under the influence of DC magnetic bias seriously, but little research about the using of blocking device, this paper proposed an optimization scheme about the usage of blocking device combination. Firstly, the subject studied the method of suppressing transformer neutral point DC depending on analysis the mechanism of magnetic biasing, and then found out the changes of power grid after using the capacitance blocking device which is popular used by Guangdong power grid. The particle swarm optimization (PSO) has been used to find a better way to suppress the DC in power grid, and combined with NSGA to solve the mixed integer programming problem. The final data validation of this method is valuable in engineering application.

关键词： Unipolar Ground Mode DC Magnetic Biasing Particle Swarm Optimization NSGA DC Blocking Device

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基于功率灵敏度的等值机出力定向调整策略

电力自动化设备 2019年第2期39卷 123-127,134页

作者：夏成军华夏李清华南理工大学电力学院广东广州510640 中国南方电网超高压输电公司检修试验中心广东广州510663

在校验动态等值前后一致性时发现等值前后由于平衡机出力变化会导致发生初始功角偏移的现象,针对该现象,分析了平衡机出力变化的原因和功角偏移的机理,提出一种基于功率灵敏度的等值机出力定向调整策略。在线路潮流控制量约束和机组出... 详细信息

在校验动态等值前后一致性时发现等值前后由于平衡机出力变化会导致发生初始功角偏移的现象,针对该现象,分析了平衡机出力变化的原因和功角偏移的机理,提出一种基于功率灵敏度的等值机出力定向调整策略。在线路潮流控制量约束和机组出力调控量约束的基础上,确定节点的功率调整量,根据灵敏度的大小和线路潮流偏差的大小提出控制节点的选取原则。从控制节点和相应调整量的确定上保证等值前后线路潮流偏差在要求的范围内,并通过等值机出力的定向调整实现消除平衡机功角差的目的,同时给出了相应的调整步骤和实现的策略流程。以南方电网某年度方式数据为例,验证了所提调整策略的正确性和有效性。

关键词：动态等值初始功角偏移功率灵敏度调整策略电力系统

Study on Identification of Inductive-Motors Load Partition Based on Coherence

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Journal of Power and Energy Engineering 2014年第9期2卷 162-169页

作者： chengjun xia Yun Zhou Kun Men Yinggeng Xie School of Electric Power South China University of Technology Guangzhou China Electric Power Research Institute of CSG China Southern Power Grid Guangzhou China

A new inductive motors load equivalence algorithm based on coherence is proposed in this paper. In order to partite motors load rapidly and accurately, fuzzy c-means clustering along with particle swarm optimization (PSO-FCM) algorithm is proposed to identify coherent motors base on its physical essence of fuzziness. The merits of PSO algorithm are independent to initial value and convergent to optimum value rapidly, and the validity function is constructed to assess clustering validity. The test on IEEE 39-Bus System is presented to evaluate the effectiveness of the new algorithm, the membership matrix definite not only coherence group of motors but also correlation value of coherence between motors. The algorithm can be used to partite motor load based on coherency in dynamic equivalence with power system operating on different modes.

关键词： Study on Identification of Inductive-Motors Load Partition Based on Coherence

Research on the Transient Power Characteristics of the Inverter for Yun-Guang UHVDC

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Journal of Power and Energy Engineering 2014年第9期2卷 176-181页

作者： chengjun xia Haiwen Lan Kun Men Guokai Liang School of Electric Power South China University of Technology Guangzhou China Electric Power Research Institute of CSG China Southern Power Grid Guangzhou China

During the transient period of large-disturbance of the received power grid, the power features of the inverter are of great important for the security and stability of the system. The research before is defective in that the constant control mode assumption and the rough HVDC simulation model. The paper establishes the PSCAD/EMTDC model for Yun-Guang EHVDC system, and analysis the transient real power and the reactive power of the inverter. With the analysis of logic for control mode, the author also introduces the physical processes of the peak of the reactive power. At last, the paper puts forward several strategies for suppressing the peak of the dynamic reactive power and real power recovery acceleration.

关键词： UHVDC Inverter Transient Power Features

Stop Control Strategy of Modular Multilevel Converter Based HVDC System

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Journal of Power and Energy Engineering 2014年第9期2卷 182-190页

作者： chengjun xia Bingmei Jin Junjun Liang Meng Li College of Electric Power South China University of Technology Guangzhou China

The stop control strategy of modular multilevel converter based HVDC transmission system is proposed. This stop process is divided into stages of energy feedback and energy consumption. The DC voltage controller is coordinated to the used modules per phase when active power is transmitted prior to reactive power, so that the energy is fed back to the AC power grid connected to the converter station which uses the fixed dc voltage controller. In addition, in view of the different forms connected to the grid, specifically when the converter station supplies power for passive network, the passive converter station can take a certain auxiliary trigger strategy to make its maximum energy feedback to the grid. Finally, a simulation system of the MMC-HVDC system is constructed in Matlab/Simulink environment, and simulation results show that the proposed stop strategies are effective.

关键词： Modular Multilevel Converter (MMC) Stop Control Energy Feedback

Analysis of Commutation Failure in Multi-Infeed HVDC System under Different Load Models

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Journal of Power and Energy Engineering 2014年第9期2卷 154-161页

作者： chengjun xia Zhongchao Yang Kun Men Yong Zhao School of Electric Power South China University of Technology Guangzhou China Electric Power Research Institute of CSG China Southern Power Grid Guangzhou China

HVDC technology has been widely used in modern power system. On one hand, HVDC has the advantages of economy, high efficiency and strong controllability. While on the other hand, it makes the dynamic characteristics of the power system becoming more and more complex. That puts forward a new challenge to system stability and raises new questions for power system simulation. This paper focuses on the interaction between AC and DC systems, especially the problem of commutation failure caused by AC system fault. Based on the data of China Southern Power Grid, this paper calculates the fault regions that may cause commutation failure and calculates the system critical clearance time under different load models, analyzes the impacts of different load models on commutation failure and the stability of AC/DC hybrid system.

关键词： AC/DC Hybrid System Commutation Failure Voltage of Converter Bus Load Model Power System Simulation

The Analysis of the Differences between Electromechanical Transients Simulation and Electromagnetic Transients Simulation

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Journal of Power and Energy Engineering 2014年第9期2卷 139-146页

作者： chengjun xia Haoyu Huang Kun Men Cuiqiong Chen School of Electric Power South China University of Technology Guangzhou China Electric Power Research Institute of CSG China Southern Power Grid Guangzhou China

The paper firstly interprets the differences between electromechanical transients program BPA and electromagnetic transients program EMTDC in the field of principle, model and algorithm. Then the authors carry out the simulation based on single-machine infinite-bus system and draw some conclusions. The time consumption of the simulation using EMTDC is much longer than the simulation using BPA under the same length of time. The results of BPA are close to those of EMTDC under steady conditions. The fundamental frequency component of the EMTDC results seems closer to the BPA results than its original value, but they still away from completely consistent. In this simulation of single-machine infinite-bus system, the transient stability results of BPA and EMTDC are close, but the results of BPA are apt to be more conservative. All the conclusions above have a certain reference value to both hybrid simulation and comprehensive analysis method in the study of the AC/DC digital simulation of large power grid.

关键词： Electromagnetic Transients Electromechanical Transients Simulation Difference