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Analysis and Control of Frequency Stability in Low-Inertia Power Systems: A Review

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IEEE/CAA Journal of Automatica Sinica 2024年第12期11卷 2363-2383页

作者： Changjun he Hua geng Kaushik Rajashekara Ambrish Chandra the Department of Automation Tsinghua University and also with Beijing National Research Center for Information Science and Technology Tsinghua University IEEE the University of Houston the Department of Electrical Engineering Ecole de Technologie Superieure University of Quebec

Power electronic-interfaced renewable energy sources(RES) exhibit lower inertia compared to traditional synchronous generators. The large-scale integration of RES has led to a significant reduction in system inertia, posing significant challenges for maintaining frequency stability in future power systems. This issue has garnered considerable attention in recent years. However, the existing research has not yet achieved a comprehensive understanding of system inertia and frequency stability in the context of low-inertia systems. To this end, this paper provides a comprehensive review of the definition, modeling,analysis, evaluation, and control for frequency stability. It commences with an exploration of inertia and frequency characteristics in low-inertia systems, followed by a novel definition of frequency stability. A summary of frequency stability modeling,analysis, and evaluation methods is then provided, along with their respective applicability in various scenarios. Additionally,the two critical factors of frequency control—energy sources at the system level and control strategies at the device level —are examined. Finally, an outlook on future research in low-inertia power systems is discussed.

关键词： Frequency control frequency stability definition low inertia power system with high penetration of renewable energy sources

Deformation-based longitudinal equivalent stiffness beam model for shield tunnel and its application in seismic deformation method

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Underground Space 2024年第4期17卷 280-299页

作者： pingliang Chen ping geng Junbo Chen Qi Yang Key Laboratory of Transportation Tunnel Engineering Ministry of EducationSouthwest Jiaotong UniversityChengdu 610031China State Key Laboratory of Intelligent Geotechnics and Tunnelling Chengdu 610031China Technology Center of Sichuan Road&Bridge Group Co. LtdChengdu 610041China

In the longitudinal seismic deformation method for shield tunnels,one of the most commonly used is the longitudinal equivalent stiffness beam model(LES)for simulating the mechanical behavior of the *** this model,axial deformation and bending deformation are independent,so the equivalent stiffness is a constant ***,the actual situation is that axial deformation and bending deformation occur simultaneously,which is not considered in *** present,we are not clear about the effect on the calculation results when axial deformation and bending deformation occur ***,in this paper,we improve the traditional LES by taking the relative deformation as a load and considering the coordinated deformation of axial and bending degrees of *** improved model is called DNLES,and its neutral axis equations are an explicit ***,we propose an iterative algorithm to solve the calculation model of the DNLES-based longitudinal seismic deformation *** a calculation example,we find that the internal forces based on LES are notably underestimated than those of DNLES in the compression bending zone,while are overestimated in the tension bending *** considering the combined effect,the maximum bending moment reached 13.7 times that of the LES model,and the axial pressure and tension were about 1.14 and 0.96 times,*** analysis reveals the coordinated deformation process in the axial and bending directions of the shield tunnel,which leads to a consequent change in equivalent *** explains why,in the longitudinal seismic deformation method,the traditional LES may result in unreasonable calculation results.

关键词： Shield tunnel Longitudinal seismic deformation method Longitudinal equivalent stiffness beam Combined axial and bending deformation

Exponential Set-Point Stabilization of Underactuated Vehicles Moving in Three-Dimensional Space

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IEEE/CAA Journal of Automatica Sinica 2022年第2期9卷 270-282页

作者： Xiaodong he Zhiyong Sun Zhiyong geng Anders Robertsson State Key Laboratory for Turbulence and Complex Systems Department of Mechanics and Engineering ScienceCollege of EngineeringPeking UniversityBeijing 100871China IEEE Department of Electrical Engineering Eindhoven University of Technology(TU/e)5600 MB Eindhoventhe Netherlands Department of Automatic Control LTHLund University22100 LundSweden

This paper investigates the stabilization of underactuated vehicles moving in a three-dimensional vector *** vehicle’s model is established on the matrix Lie group SE(3),which describes the configuration of rigid bodies globally and *** focus on the kinematic model of the underactuated vehicle,which features an underactuation form that has no sway and heave *** compensate for the lack of these two velocities,we construct additional rotation matrices to generate a motion of rotation coupled with ***,the state feedback is designed with the help of the logarithmic map,and we prove that the proposed control law can exponentially stabilize the underactuated vehicle to the identity group element with an almost global domain of ***,the presented control strategy is extended to set-point stabilization in the sense that the underactuated vehicle can be stabilized to an arbitrary desired configuration specified in ***,simulation examples are provided to verify the effectiveness of the stabilization controller.

关键词： Exponential stabilization logarithmic feedback matrix Lie group underactuated vehicle

Aging Characteristics, Stress Corrosion Behaviour and Role of Mg Segregation at Grain Boundary in 7175High-strength Al Alloy

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Journal of Materials Science & Technology 1998年第3期14卷 259-264页

作者： Song, Renguo geng, ping Zeng, Meiguang Zhang, Baojin Northeastern Univ Coll Sci Dept Mat Sci Shenyang 110006 Peoples R China

The aging characteristics, stress corrosion behavior and chemical composition of grain boundary in 7175 high-strength Al alloy during long term aging process have been investigated by hardness measurement, constant elongation rate testing (CERT) and energy spectroscopy analysis. The results indicate that double peaks in aged state feature the hardness and strength of 7175 Al alloy. Although the intensity of double peaks is almost equal, the stress corrosion resistance in the second peak-aged state is better than that of the first peak-aged state. The effects of Mg segregation on the binding energy of grain boundary have been calculated by using free electron theory developed in this paper. The results showed that Mg segregation plays a significant role in controlling stress corrosion susceptibility, which is consistent with the experimental results. (Edited author abstract) 32 Refs.

关键词： Aluminum alloys

Outage analysis of ANC in the FDD two-way fading channel with channel estimation error

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The Journal of China Universities of Posts and Telecommunications 2013年第2期20卷 12-18页

作者： geng Xuan LIU Feng he Chen College of Information Engineering Shanghai Maritime University School of Electronic Information and Electrical Engineering Shanghai Jiaotong University

This paper considers a frequency-division duplex （FDD） two-way channel with channel estimation error, where channel gains are independent of each other. It derives the exact closed-form outage probability expressions in the FDD system with analog network coding （ANC） by use of probability theory. To provide more insights, an approximated version for the exact outage probability is also developed in the medium-to-high signal-to-noise ratio （SNR） region. The simulation results show that the derived exact outage probabilities match the results of Monte Carlo simulations in all SNR regions, while the approximated outage probabilities also approach the simulation results when the channel condition is good. It is interesting that ANC in the FDD two-way channel is proved to outperform that of in the time-division duplex （TDD） channel by the computer simulation.

关键词： FDD outage probability two-way channel ANC

Relationship of causal effects in a causal chain and related inference

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Science China Mathematics 2004年第5期47卷 730-740页

作者： geng Zhi he Yangbo WANG Xueli School of Mathematical Sciences LMAM Peking University Beijing 100871 China School of Mathematical Sciences LMAM Peking University Beijing 100871 China School of Mathematical Sciences LMAM Peking University Beijing 100871 China

This paper discusses the relationship among the total causal effect and local causal effects in a causal chain and identifiability of causal effects. We show a transmission relationship of causal effects in a causal chain. According to the relationship, we give an approach to eliminating confounding bias through controlling for intermediate variables in a causal chain.

关键词： causal chain, causal inference, counterfactual model, graphical model, potential causal function.

Meta-analysis comparison of endoscopic papillary balloon dilatation and endoscopic sphincteropapillotomy

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World Journal of Gastroenterology 2013年第24期19卷 3883-3891页

作者： Hong-Chuan Zhao Liang he Da-Chen Zhou Xiao-ping geng Fa-Ming Pan Department of General Surgery the First Affiliated HospitalAnhui Medical University School of Public health Anhui Medical University

AIM: To assess endoscopic papillary balloon dilatation (EPBD) and endoscopic sphincteropapillotomy (EST) for common bile duct (CBD) stone removal using a meta-analysis. METHODS: Randomized controlled trials published from 1990 to 2012 comparing EPBD with EST for CBD stone removal were evaluated. This meta-analysis was performed to estimate short-term and long-term com-plications of these two treatments. The fixed random effect model or random effect model was established to analysis the data. Results were obtained by analyz-ing the relative risk, odds ratio, and 95%CI for a given comparison using RevMan 5.1. Statistical significance was defined asP he 1975 patients analyzed, 980 of them were treated with EPBD and 995 were treated with EST. Of the patient population, patients in the EPBDgroup were younger (OR=-1.16, 95%CI:-1.49 to 0.84, Phere were no significant differences in gender proportion, average size of stones, number of gallstones, previous cholecystectomy, the incidence of duodenal diverticulum, CBD diameter or the total follow-up time between EST and EPBD groups. Com-pared with EST, the total stone clearance in the EPBD group decreased (OR=0.64, 95%CI: 0.42 to 0.96,P=0.03), the use of stone extraction baskets significantly increased (OR=1.91, 95%CI: 1.41 to 2.59, Phe incidence of pancreatitis significantly increased (OR=2.79, 95%CI: 1.74 to 4.45, Phe incidence of bleeding (OR=0.12, 95%CI: 0.04 to 0.34, Phe stone re-currence rate also was significantly reduced in EPBD (OR=0.48, 95%CI: 0.26 to 0.90, P=0.02). There were no significant differences between the two groups with the incidence of stone removal at first attempt, hours of operation, total short-term complications and infection, perforation, or acute cholangitis. CONCLUSION: Although the incidence of pancreatiti

关键词： Common bile duct stone Endoscopic papil-lary balloon dilatation Endoscopic sphincteropapilloto-my Meta-analysis

Effect of electromagnetic swirling flow in slide-gate SEN on flow field in square billet continuous casting mold

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Acta Metallurgica Sinica(English Letters) 2012年第5期25卷 347-356页

作者： Dianqiao geng Hong LEI Jicheng he Haitao LIU Key Laboratory of National Education Ministry for Electromagnetic Processing of Materials North- eastern University Shenyang 110819 China State Key Laboratory of Rolling 8z Automation Northeastern University Shenyang 110819 ChinaManuscript received 15 March 2012 in revised form 16 May 2012

In order to weaken the bias flow in the submerged entry nozzle （SEN） with slide- gate, the rotating magnetic field was imposed. The numerical method was employed to investigate the effect of rotating magnetic field on the flow field in the SEN and the mold under different slide-gate opening ratios. Numerical results showed that when the slide-gate opening ratio is smaller than 100%, the flow field in the SEN and the mold become asymmetry and there is an obvious circulation under the slide- gate in the SEN. With increasing exciting current, the divergent angle of liquid steel at the SEN outlet increases, the impact depth of liquid steel in the mold decreases. With increasing slide-gate opening ratio, the impact depth of liquid steel in the mold increases and the required exciting current to weaken the bias flow should increase.

关键词： Square billet Electromagnetic swirling flow Slide-gate SEN Continuous casting Bias flow

Optimization of mixing time in a ladle with dual plugs

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International Journal of Minerals,Metallurgy and Materials 2010年第6期17卷 709-714页

作者： Dian-qiao geng Hong Lei Ji-cheng he Key Laboratory of Electromagnetic Processing of Materials （Ministry of Education of China） Northeastern University Shenyang 110819 China

Based on the two-phase fluid （Eulerian-Eulerian） model, a mathematical model about the gas-liquid flow and mixing behavior was developed to investigate the effect of the offset of dual plugs, the included angle of dual plugs with a center point, and gas flow rate on the mixing time in a ladle with dual plugs. Numerical results indicate that two types of recirculation zones exist in the ladle. One is the middle recirculation between gas and liquid plumes, and the other is the sidewall recirculation between plumes and the ladle sidewall. The correction shows that the mixing time is in proportion to -0.2676 power of gas flow rate. There is a unique optimum offset of dual plugs with a particular included angle, in turn, a unique optimum included angle of dual plugs exits with a particular offset.

关键词： ladles refining mixing time optimization numerical simulation