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Squeezed back-to-back correlations of K+K- in d+Au collisions at sNN1/2=200 GeV and Au+Au collisions at sNN1/2=62.4 GeV

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Chinese Physics C 2019年第7期43卷 61-69页

作者： Yong Zhang Jing Yang Weihua Wu School of Mathematics and Physics Jiangsu University of TechnologyChangzhouJiangsu 213001China School of Science Inner Mongolia University of Science & TechnologyBaotouInner Mongolia Autonomous Region 014010China School of Physics and School of International Education Teachers Changchun Normal UniversityChangchun 130032China

We investigate the squeezed back-to-back correlations（BBC） of K+K-, caused by the mass modification of particles in the dense medium formed in d + Au collisions at sNN1/2= 200 GeV and Au + Au collisions at sNN1/2= 62.4 GeV. Considering that some kaons may not be affected by the medium, we further study the BBC functions of K+K-when parts of all kaons have a mass-shift. Our results indicate that the BBC functions of K+K-can be observed when only ～10% of all kaons have a mass-shift in d + Au collisions at sNN1/2 = 200 GeV and the peripheral collisions of Au + Au at sNN1/2= 62.4 GeV. Since the BBC function is caused by the mass-shift due to the interactions between the particle and the medium, the successful detection of the BBC function indirectly marks that the dense medium has formed in these collision systems. We suggest the experimental measurement of the BBC function of K+K- in d + Au collisions at sNN1/2 = 200 GeV and peripheral collisions of Au + Au at sNN1/2 = 62.4 GeV.

关键词： squeezed back-to-back correlations K^+K^- mass modification dense medium

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A back-to-back VSC-HVDC System of Yu-E Power Transmission Lines to Improve Cross-region Capacity

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CSEE Journal of Power and Energy Systems 2020年第1期6卷 64-71页

作者： Yinbiao Shu Guangfu Tang Hui Pang China Huaneng Group Co. Ltd.Xicheng DistrictBeijing 100031China Global Energy Interconnection Research Institute Co. Ltd.Changping DistrictBeijing 102209China

With the rapid development of hydropower in the southwest of China, the energy transmitted by ultra high volt- age direct current (UHVDC) is ever increasing. At the same time, the power grid continues to expand westward, creating a service area. The stability of the Southwest China Power Grid is becoming a major issue. It is necessary to coordinate the development of hydropower and the construction of cross-region interconnections to optimize the grid structure. The Yu-E denotes the connection between the two region Yu (Chongqing) and E (Hubei) in China. The Yu-E project is a back-to-back voltage source converter based high voltage direct current (VSC-HVDC) project designed to realize an asynchronous connection of the Southwest and Central China Power Grids. The project will improve the bi-directional power support capability and optimize the grid structure. In addition, the Yu-E project will improve hydropower cross-region transmission capacity and enable the Southwest China Power Grid to utilize the power from the Three Gorges in the Central China Power Grid. In this paper, the fault isolation, low-frequency oscillation, sub-synchronous oscillation and short-circuit level are investigated and analyzed. Meanwhile, the impact of the Yu-E project on AC systems is studied in detail. In the end, the overall system design of the Yu-E project is introduced. The research results show that the Yu-E project can increase the transmission capability of the Southwest and Central China Power Grids, and enhance the stability of asynchronously interconnected AC systems. At the same time, the Yu-E project also serves as a demonstration project for the future development and application of VSC technology for the world.

关键词： Additional control asynchronous interconnec-tion back-to-back system design VSC-HVDC

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Discussion on back-to-back two-stage centrifugal compressor compact design techniques

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Frontiers of Mechanical Engineering 2013年第4期8卷 390-400页

作者： Lei HUO Huoxing LIU School of Jet Propulsion Beihang University

Design a small flow back-to-back two-stage centrifugal compressor in the aviation turbocharger,the compressor is compact structure,small axial length,light *** parts have a great influence on their overall performance ***,the stationary part of the back-to-back two-stage centrifugal compressor should pay full attention to the diffuser,bend,return vane and volute *** also impact downstream return vane,making the flow in circumferential direction is not uniformed,and several blade angle of attack is drastically changed in downstream of the volute with the airflow can not be rotated to required *** of high-pressure rotor blades change due to non-uniformed of flow in circumferential direction,which makes individual blade load distribution changed,and affected blade passage load decreased to reduce the capability of work,the tip low speed range increases.

关键词： back-to-back two-stage centrifugal compressor design Internal flow

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Complete Localization of HVDC back-to-back Project Realized

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Electricity 2006年第1期17卷 21-24页

作者： Yu Xinqiang Liang Xuming Wang Zuli Ye Qing（Translated） Department of construction and Operation State Grid Corporation 不详

The first completely localized DC back-to-back project for asynchronous interconnection between Northwest and Central China plays an important role in realizing national power grid interconnection, spurring indigenous manufacturing industries and promoting DC transmission equipment. Insisting on the principle of autonomous innovation, this project was based on domestic forces in every aspect, from engineering organization, system design, equipment completion, engineering design, equipment manufacturing and procurement to construction and debugging. By passing through strict quality control, intermediate supervision and acceptance test and assessment, the project has been proved up to world advanced level.

关键词： power grid interconnection back-to-back DC converter station

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back-to-back三电平永磁同步电机调速系统的研究与实现

Back-to-back三电平永磁同步电机调速系统的研究与实现

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作者：刘雨杰北京工业大学

学位级别：硕士

电能方便清洁、高效灵活,是能源消耗的主要方式。目前在能源紧张的局势下,电能的高效利用变得愈加重要。因此如何保证电能满足负载需要,实现高效的功率变换就逐渐成为国内外学者所关注的热点问题之一。随着功率变换技术和器件工艺水平... 详细信息

电能方便清洁、高效灵活,是能源消耗的主要方式。目前在能源紧张的局势下,电能的高效利用变得愈加重要。因此如何保证电能满足负载需要,实现高效的功率变换就逐渐成为国内外学者所关注的热点问题之一。随着功率变换技术和器件工艺水平的不断提高,PWM变换器在电能变换领域得到了广泛应用,如电网输配电、电机调速系统等。本课题以永磁同步电机四象限调速控制应用为研究对象,对背对背(back-to-back)三电平功率变换控制系统展开研究。文中针对系统的控制需求,设计了系统不同工况下的控制策略,搭建了调速系统实验平台,完成了相关的理论仿真和系统实验。此外针对三电平PWM控制中的中点不平衡问题,本文设计了中点平衡控制策略,并应用于系统实现。文中,首先在对back-to-back三电平永磁同步电机调速系统总体拓扑结构分析的基础上,对系统不同工况下的功率变换器数学模型和电机数学模型分别进行建模研究。然后根据电网电压定向矢量控制思想和永磁同步电机矢量控制思想,分别设计实现了系统正向运行控制策略和反向运行控制策略。并且,在对三电平SVPWM控制方法及主电路中点不平衡产生机理进行研究分析的基础上,考虑小矢量对中点电流作用效果的差异性,设计了中点平衡控制策略。其次,本文在MATLAB/Simulink软件平台上搭建了系统仿真模型,并完成了一系列的仿真实验。仿真结果充分验证了系统控制策略的正确性和可行性。再次,在理论分析和仿真验证的基础上,本文对系统的硬件电路设计过程、主要器件选型以及控制软件流程进行了详细阐述。最后,结合三电平变频调速系统拓扑结构,本文搭建了永磁同步电机调速系统实验平台,并分别完成了系统正、反向运行实验,取得了大量的实验结果。各项实验数据的分析结论表明该控制系统具有较好的动态和稳态性能,从而充分证明了该控制系统策略研究、硬件电路设计和控制软件实现的有效性和可实现性。

关键词： back-to-back 三电平变换器中点平衡

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A Scheme on Adaption Detection of Large-capacity Wind Turbines to the Power Grid

A Scheme on Adaption Detection of Large-capacity Wind Turbin...

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2011 International Conference on Advanced Power System Automation and Protection(APAP 2011)

作者： JI Ping* DAI ChaoBo WU ShouYuan JIN XueFen LI Xin China Electric Power Research Institute Beijing 100192 China

It was presented that a design scheme on adaption detection device for large-capacity wind turbines to the power grid, based on back-to-back voltage source converter parallel system. The voltage-current dual closed loop control strategy was used in converter modules connecting to power grid, to maintain the voltage of DC capacitor at a predetermined value, and make the detection device run with the unity power factor. In converters connected to a wind turbine, it was designed that master-slave control strategy including feedward control segment. Voltage control was used in the master module to maintain the output voltage of the detection device at the expected value, and simulate the interconnected voltage of wind turbines. Besides, voltage disturbances, such as frequency disturbances, voltage fluctuation disturbances, negative sequence voltage disturbances, etc., were also simulated in the master module. In slave modules, current control was used to ensure the module output current can match its own capacity, and meet the bidirectional power transmission requirements further. According to design requirements, using actual parameters of AC / DC and DC / AC converters made by the Infineon Technologies, parameters of key components in the detection device were designed and calculated in detail. Simulation of designed adaptive detection device was carried out by using PSCAD/EMTDC, in accordance with the above proposed control strategy and designed parameters of components. The device can work in 35kV rated voltage;output voltage frequency disturbance from 45Hz to 60Hz;output negative sequence voltage disturbance with variable amplitude and phase, imbalance less than 10%;output voltage fluctuation disturbances, amplitude fluctuations between -10% and +10%, frequency from 0.5Hz to 25Hz. The output voltage imbalance of the detection device ranges from 0 to 4%, and the total harmonic distortion is between 0 and 5%.

关键词： wind generation adaption to power grid back-to-back voltage source converter (VSC) master-slave con- trol

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