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IEEE power and Energy Society General Meeting

作者： Yiwei Qiu Jin Lin Feng Liu Yonghua Song State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Tsinghua University Beijing China The University of Macau Macau China

Imbalance of generation and load caused by volatile generations poses challenges on frequency regulation. AGC is required to respond to the generation fluctuations without violating operational and security constraints. While explicit model predictive control (EMPC) provides an approach, the partition number of the piecewise affine control laws grows exponentially with the number of constraints and prediction/control horizons, which hinders its application in large systems. In this paper, we propose an EMPC approach for AGC by approximating the control laws using Legendre polynomial series expansions, thus entirely eliminating the partition issue. Galerkin method is applied to the KKT conditions of EMPC's multiparametric quadratic programming (mp-QP) problem to compute the approximations. Case study in New England 39-bus system verifies the performance and efficiency of the proposed controller.

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A Voltage-fed control Method with Automatic Bidirectional power Switching Capability for CLLC and SR Buck Based Two Stage Converters

A Voltage-fed Control Method with Automatic Bidirectional Po...

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International Conference on power Electronics and Motion control (IPEMC)

作者： Huan Chen Hongsheng Chong Kai Sun You Zhou Hang Zhou John Fletcher State Key Lab of Control and Simulation of Power Systems and Generation Equipment Tsinghua University Beijing China Nation Institute of Clean and Low Carbon Energy Beijing China School of Electrical Engineering and Telecommunications University of New South Wales Sydney Australia

ISBN: (数字)9781728153018

ISBN: (纸本)9781728153025

The CLLC converter is widely used in bidirectional power conversion systems. The conventional control method for CLLC converter is pulse frequency modulation (PFM) method. However, PFM method can not realize smooth bidirectional power switching, because the driver signals for the primary and the secondary side switches are asymmetric. This paper proposed a voltage-fed control method for CLLC and Synchronous Rectified (SR) Buck two stage converters, which can realize the automatic and smooth bidirectional power switching for CLLC stage. In the proposed control method, the PWM signals for both the primary and the secondary switches are the same. The effectiveness of the proposed voltage-fed control method is verified by experiments.

关键词： Prototypes Switches Pulse width modulation control systems Automatic voltage control power electronics Transient analysis

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Grouping Methods for Facilitating Emergency Evacuations

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IFAC-PapersOnLine 2020年第5期53卷 845-850页

作者： Linyao Yang Ke Tan Xin Liu Xiao Wang Fei-Yue Wang State Key Laboratory for Management and Control of Complex Systems Institute of Automation Chinese Academy of Sciences Beijing China University of Chinese Academy of Sciences Beijing China State Key Laboratory of Nuclear Power Safety Monitoring Technology and Equipment Shenzhen China

It is widely believed that the motion of crowds can be described by the “social force” model, and small group behaviors have great impacts on evacuation efficiency as a common phenomenon in pedestrian evacuations. Some previous works have modeled group behaviors in social force models by depicting group members’ interaction forces. However, the impacts of different grouping schemes have not been considered and evaluated. This paper proposes four different grouping methods to explore the evacuation dynamics of different group structured pedestrians. Results show that group evacuations based on the spatial partitioning outperform those clustering-based schemes with the larger group number. More importantly, simulations indicate that the number of groups also highly affects the evacuation efficiency, and the larger the number of groups, the more efficient the evacuation.

关键词： Evacuation simulation Social force Clustering methods Agent based modeling

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Research on Lithium-ion Battery Safety Risk Assessment Based on Measured Information

Research on Lithium-ion Battery Safety Risk Assessment Based...

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Sustainable power and Energy Conference (iSPEC)

作者： Xuyan Zhou Lin Cheng Yuxiang Wan Ning Qi Liting Tian Feng You State Key Laboratory of Control and Simulation of Power Systems and Generation Equipments Tsinghua University Beijing China Energy Storage System Business Unite Tianjin Lishen Battery Joint-Stock Co. Ltd. Tianjin China

ISBN: (数字)9781728191645

ISBN: (纸本)9781728191652

Lithium-ion batteries have the advantages of high energy density, fast power response, recyclability, and convenient to movement, which are unsurpassed by other energy storage systems. However, safety issues such as thermal runaway of lithium-ion batteries have become the main bottlenecks restricting the development of their extensive applications. In practical applications, the demand for battery energy storage scale and specific energy continues to increase, and the contradiction between battery high safety and battery safety has become increasingly prominent. This paper proposes a lithium-ion battery safety risk assessment method based on online information. Effective predictions are essiential to avoid irreversible damage to the battery and ensure the safe operation of the battery energy storage system before a failure occurs. This paper is expected to provide novel risk assessment method and research idea for the development and design of high-safety battery systems.

关键词： Lithium-ion batteries Temperature measurement Voltage measurement Thermal management Battery charge measurement Safety Risk management

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Development and test research of 10kv DC circuit breaker based on the principle of coupled negative voltage

Development and test research of 10kv DC circuit breaker bas...

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The 16th IET International Conference on AC and DC power Transmission (ACDC 2020)

作者： W. Li B. Liu F. Xiao H. Wang Y. Wang W. Xie Z. Yu Shandong Taikai High-Voltage Switchgear Co. Ltd. Tai’an China China Electric Power Research Institute Beijing China Tsinghua University State Key Laboratory of Control and Simulation of Power System and Generation Equipment (Department of Electrical Engineering Beijing China

With the increase of multi-terminal flexible DC distribution network projects, medium-voltage DC circuit breaker, as the key equipment to remove DC short-circuit fault, plays a key role in the operation reliability of the whole DC distribution network. In order to meet the engineering needs of DC distribution network, a 10kV hybrid DC circuit breaker based on the coupling negative voltage principle is developed in this paper. Firstly, the topology and working principle of the DC circuit breaker are introduced. Furthermore, the design scheme of key components including fast mechanical switch, power electronic switch and coupling negative voltage device is given. Finally, a 10kV hybrid DC circuit breaker prototype is developed and tested. The results show that the 10kV hybrid DC circuit breaker can break 15kA short circuit current within 2ms, and has the characteristics of low loss and high reliability.

关键词： circuit breakers short-circuit currents DC distribution systems power distribution faults power distribution reliability

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Excellent electrical properties of zinc-oxide varistors by tailoring sintering process for optimizing line-arrester configuration

Excellent electrical properties of zinc-oxide varistors by t...

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International Conference on High Voltage Engineering and Application, ICHVE

作者： Pengfei Meng Wei Cao Chao Chen Shuai Wan Heng Xu Jun Hu Jinliang He Tsinghua University Beijing China Wuhan NARI Limited Liability Company State Grid Electric Power Research Institute Wuhan China Guangdong Aikang Electric Power Co. Ltd Guangzhou China State Key Laboratory of Control and Simulation of Power System and Generation Equipment Tsinghua University Beijing China

ISBN: (数字)9781728155111

ISBN: (纸本)9781728155128

We optimized the excellent electrical performance of zinc-oxide (ZnO) varistors doping of aluminum and indium by tailoring the sintering process. The surface morphology, nonlinear volt ampere properties, capacitance-voltage characteristics, and dielectric analyses were carried out. At a given aluminum and indium concentration, the average sample grain size ( d) increased as lengthening sintering time from 0.5 to 2.5 h. The voltage gradient ( E1mA) decreased from 602.4 V/mm to 356.7 V/mm. The residual voltage of the sintered varistors at the lightning impulse current ( 8/20 μs) decreased as the samples sintering holding time extended from 0.5 to 2.0 h. When the ZnO varistor was sintered for 1.5 h, the samples showed an excellent performance, with a reference voltage of 479.3 V/mm at 1 mA DC. When assembled in the line surge arresters, the obtained high-voltage-gradient ZnO varistors can decrease their length and residual voltage, which allows for better coordination of the line surge arrester with the insulators. This study has great significance to optimize line-arrester configurations and improve power-system stability.

关键词： Zinc oxide Varistors Arresters II-VI semiconductor materials Surges Insulators Dielectrics

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Review on Pumped Storage power Station in High Proportion Renewable Energy power System

Review on Pumped Storage Power Station in High Proportion Re...

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IEEE Student Conference on Electric Machines and systems

作者： Bingxin Sun Shuping Tian Jiang He Liande Liu Zhiqiang Wang Jiawei Guo Fei Xu Te Cheng Junhui Li Inner Mongolia Hohhot Pumped-Storage Power Generation Co LTD Hohhot China State Key Lab of Power Systems Tsinghua University Beijing China Key Laboratory of Modern Power System Simulation and Control & Renewable Energy Technology Ministry of Education (Northeast Electric Powe University) Jilin China

ISBN: (数字)9781728156224

ISBN: (纸本)9781728156231

Large scale renewable energy, represented by wind power and photovoltaic power, has brought many problems for the safe and stable operation of power system. Firstly, this paper analyzes the main problems brought by large-scale wind power and photovoltaic power integration into the power system. Secondly, the paper introduces the basic principle and engineering construction of pumped storage power station. Thirdly, the paper expounds in detail the current application of pumped storage power station in power system, and finally points out the main problems faced by the development of Pumped Storage power Station and the development trend, so as to provide reference for the construction and operation of pumped storage power station.

关键词： Photovoltaic systems Renewable energy sources Conferences Pumps Wind power generation Market research power systems

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First stirling-type cryocooler reaching lambda point of ~4He(2.17K) and its prospect in Chinese HUBS satellite project

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Science Bulletin 2019年第4期64卷 219-221页

作者： Jue Wang Changzhao Pan Tong Zhang Kaiqi Luo Xiaotong Xi Xianlin Wu Jianpeng Zheng Liubiao Chen Junjie Wang Yuan Zhou Hai Jin Wei Cui University of Chinese Academy of Sciences CAS Key Laboratory of Cryogenics Technical Institute of Physics and Chemistry Chinese Academy of Sciences Laboratoire National de Métrologie Et d'essais-Conservatoire National des Arts et Métiers (LNE-Cnam) State Key Laboratory of Control and Simulation of Power Systems and Generation Equipments Department of Electrical Engineering Tsinghua University Department of Physics and Center for Astrophysics Tsinghua University

The issue of "missing baryons” is always an unsolved mystery in galaxy cosmology, and an important reason for the great uncertainty of the galaxies' formation and evolution. To find the "missing" baryons, extra high-resolution spectral observation and imaging of the soft X-ray band (<1 kev) is required. However, the existing observation methods cannot meet this requirement. Therefore, Tsinghua University leads and proposes the Chinese "Hot Universe Baryon Surveyor (HUBS)" satellite program.

关键词： missing baryons HUBS missing

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Discrete effects on boundary conditions of the lattice Boltzmann method for fluid flows with curved no-slip walls

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Physical Review E 2020年第6期101卷 063307-063307页

作者： Liang Wang Shi Tao Xuhui Meng Kai Zhang Gui Lu Beijing Key Laboratory of Emission Surveillance and Control for Thermal Power Generation North China Electric Power University Beijing 102206 China School of Energy Power and Mechanical Engineering North China Electric Power University Beijing 102206 China Guangdong Provincial Key Laboratory of Distributed Energy Systems Dongguan University of Technology Dongguan 523808 China Division of Applied Mathematics Brown University Providence Rhode Island 02912 USA Key Laboratory of Condition Monitoring and Control for Power Plant Equipment of Ministry of Education North China Electric Power University Beijing 102206 China

The lattice Boltzmann method (LBM) has been formulated as a powerful numerical tool to simulate incompressible fluid flows. However, it is still a critical issue for the LBM to overcome the discrete effects on boundary conditions successfully for curved no-slip walls. In this paper, we focus on the discrete effects of curved boundary conditions within the framework of the multiple-relaxation-time (MRT) model. We analyze in detail a single-node curved boundary condition [Zhao et al., Multiscale Model. Simul. 17, 854 (2019)] for predicting the Poiseuille flow and derive the numerical slip at the boundary dependent on a free parameter as well as the distance ratio and the relaxation times. An approach by virtue of the free parameter is then proposed to eliminate the slip velocity while with uniform relaxation parameters. The theoretical analysis also indicates that for previous curved boundary schemes only with the distance ratio and the halfway bounce-back (HBB) boundary scheme, the numerical slip cannot be removed with uniform relaxation times virtually. We further carried out some simulations to validate our theoretical derivations, and the numerical results for the case of straight and curved boundaries confirm our theoretical analysis. Finally, for fluid flows with curved boundary geometries, resorting to more degrees of freedom from the boundary scheme may have more potential to eliminate the discrete effect at the boundary with uniform relaxation times.

关键词： Slip boundary effects Wall slip

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Circulation and Its Influence on Meshed Multiterminal DC Distribution System 2

Circulation and Its Influence on Meshed Multiterminal DC Dis...

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2nd IEEE International Conference on power and Energy Applications, ICPEA 2019

作者： Ding, Hailong Yuan, Zhichang Guo, Peiqian Song, Meng Li, Li State Key Lab. of Secty. Contr. and Simulation of Power Systems and Large-scale Generation Equipment Department of Electrical Engineering Tsinghua University Beijing China Electric Power Research Institute of Guangdong Power Grid Corporation Guangzhou China

ISBN: (纸本)9781728115962

The application demands of direct current distribution continue to increase owing to the development of DC transmission technologies and modern distribution systems. In netted multiterminal DC distribution systems, system circulating currents often occur because of the different positive and negative line parameters. In this study, the steady- state equivalent circuit model of four-terminal grid DC distribution system is established, and the mathematical expression of system circulation is theoretically derived. The variation characteristics of circulating currents caused by inconsistencies of positive and negative circuit parameters are quantitatively analyzed. The adverse effects of the system circulating currents on the operation and protection of the DC distribution system combined with the possible parameter changes in the actual power network are analyzed. On this basis, several feasible solutions are discussed, and the above- mentioned analyses are verified by MATLAB and PSCAD/EMTDC simulation. © 2019 IEEE.

关键词： MATLAB

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