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The 2011 International Conference on Electric and Electronics (EEIC 2011)

作者： Jidong Wang Guanqing Yang Kun Liu Key Laboratory of Power System Simulation and Control of Ministry of Education Tianjin University

Space vector pulse width modulation(SVPWM) was widely used in inverter control for the advantages of fixed switching frequency, full utilization of DC-link voltage and better control precision. In recent years, SVPWM is gradually applied in the control method of active power filter(APF) as the APF mains is just one invert. The voltage vectors are composed based on the α-β axis in traditional SVPWM however, in this paper one x-y composed reference axis at 60 degree angles from each other is used instead. Compared with traditional method, the principle of the method is relatively simple and easy to implement. At the same time PI regulator is adopted for the DC-link voltage control. Finally simulation results show that the APF has a better compensation effect using this control method.

关键词： active power filter(APF),space vector PWM,PI control,simulation

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simulation of Voltage Sag Detection Method Based on DQ Transformation

Simulation of Voltage Sag Detection Method Based on DQ Trans...

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The 2011 International Conference on Electric and Electronics (EEIC 2011)

作者： Jidong Wang Kun Liu Guanqing Yang Key Laboratory of Power System Simulation and Control of Ministry of Education Tianjin University

The rapid detection of characteristics of voltage sag is an important prerequisite for using dynamic voltage restorer(DVR) for voltage compensation. This paper introduced an improved derivation detection method based on dq transformation. simulation was performed to analyze the advantages and disadvantages of both methods and compare them. Results showed that the improved detection method had shorter delay and better waveform of detection and met the requirements of accuracy and timeliness better.

关键词： voltage sag detection method dq transformation derivation

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power Quality Improvement for Mircrogrid in Islanded Mode

Power Quality Improvement for Mircrogrid in Islanded Mode

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2011 International Conference on power Electronics and Engineering Application

作者： Gao Xiaozhi Li Linchuan Chen Wenyan Key Laboratory of Power System Simulation and Control of Ministry of Education Tianjin University

The aim of this paper is to analyze and improve the power quality of island microgrid assuming that the distributed generators could meet the load active power requirement. The main power quality problems through analysis are the harmonics caused by power-electronic devices and voltage variation caused by high reactive power requirement. Based on economy and compensation performance, a combined system constructed by SVC and SAPF is designed to improve the power quality of microgrid in this paper, in which SAPF is adopted near the microsource to mitigate harmonic currents and SVC near the load to compensate reactive power so as to relieve the voltage variation. simulation results show the effectiveness of the combined system.

关键词： v/f control scheme microgrid power quality APF SVC

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A novel algorithm for distribution network reconfiguration based on evolutionary programming

A novel algorithm for distribution network reconfiguration b...

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International Conference on Advanced power system Automation and Protection (APAP)

作者： Bingda Zhang Liu Yang Key Laboratory of Power System Simulation and Control (Tianjin University) Ministry of Education 300072 China Key Laboratory of Power System Simulation and Control (Tianjin University) Ministry of Education (of Affiliation) Tianjin China

Because there are slow evolutionary process and difficult smooth convergence in evolutionary programming algorithm, a mutation operator for distribution network reconfiguration is proposed. In order to guarantee that new individuals from mutation is close to the optimal individual actively, times of topology restructure should be inversely proportional to evolutionary generations, and both selection operators for switch to open and to close should be set in the process of topology restructure. Simplified calculation methods of power loss of network, quadratic load moment and selection operators are given. The feasibility of method proposed above is verified in the system of the operation optimization and the assistant decision of the 10kV distribution network, which is located in Shangqiu power supply bureau, Henan Province.

关键词： Switches Topology Equations Load flow analysis Programming

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A neutral-point potential balancing algorithm for five-level ANPC converters

A neutral-point potential balancing algorithm for five-level...

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International Conference on Electrical Machines and systems (ICEMS)

作者： Kui Wang Yongdong Li Zedong Zheng State Key Laboratory of Control and Simulation of Power System and Generation Equipments Tsinghua University Beijing China

Five-level active neutral-point-clamped (ANPC) converter is a newly emerging topology which can overcome the drawbacks of traditional neutral-point clamped (NPC) converters and flying-capacitor (FC) converters. Its dc-link is subdivided into two equal parts and the main problem is the neutral-point (NP) potential balancing. In this paper, a NP potential balancing algorithm based on zero-sequence voltage injection is presented. By calculating the NP currents of all key zero-sequence voltages, the most appropriate zero-sequence voltage is selected to generate the demanded NP current. Moreover, by further limiting the span of injected zero-sequence voltages, the NP balancing algorithm can make the two IGBTs connected in series operate at fundamental frequency. A three-phase five-level ANPC inverter prototype was built up and experimental results are presented to verify the validity of this algorithm.

关键词： Capacitors Electric potential Switches Voltage control Inverters Insulated gate bipolar transistors Heuristic algorithms

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simulation of gas flows in micro/nano systems using the Burnett equations

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Journal of Physics: Conference Series 2012年第1期362卷

作者： Fubing Bao Xia Yu Jianzhong Lin Institute of Flow Measurement and Simulation China Jiliang University Hangzhou 310018 China Department of Mechanics State Key Laboratory of Fluid Power Transmission and Control Zhejiang University Hangzhou 310027 China

The gaseous flow characteristics in micro/nano systems are studied using the Burnett equations. The Burnett equations are the second-order approximation of the Chapman–Enskog solution to the Boltzmann equation. This set of equation is appropriate to describe the rarefied gas flows. Velocity slip and temperature jump boundary conditions are applied on solid surface. Several techniques, including the usage of relaxation method on slip values and Burnett terms, are introduced to increase the stability of the Burnett equations. Hence, convergent results at Knudsen number up to 0.5 are achieved for the first time. The results of the Burnett equations are first verified using the corresponding experimental and the DSMC data. The Navier-Stokes and the Burnett equations give almost the same result when the flow is in slip regime (Kn<0.0l). But when the flow is in transition regime (0.1systems. The pressure driven plane Poiseuille and the backward-facing step flows, the flows through micro filters are then studied. Different inlet to outlet pressure ratios, size effects, shape effects and boundary conditions are analyzed. The competitive relations of rarefied and compressible effects in micro gas flows are discussed.

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Numerical simulation on Small Scale Straight-blade and Twisted-blade Vertical Axis Wind Turbine

Numerical Simulation on Small Scale Straight-blade and Twist...

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2011 International Conference on Energy and Environment(ICEE 2011)

作者： Lv Yongzhe Jiang Dongxiang Jiang Yong State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Thermal Engineering Tsinghua University

This paper presents an analysis on the performance of vertical axis wind turbine of two types, namely straightblade vertical axis wind turbine(SB-VAWT) and twisted-blade vertical axis wind turbine(TB-VAWT). An attempt of this simulation is to identify which type performs better in the same wind conditions and swept area. Three-dimensional computational fluid dynamics(CFD) was adopted in this analysis, after solid models of them were generated. Preliminary results of torque, power and aerodynamics in the fluid field were obtained for discussion. Finally, there provided some guidance for future wind tunnel tests.

关键词： straight-blade vertical axis wind turbine twistedblade vertical axis wind turbine numerical simulation performance aerodynamics

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Numerical simulation on Small Scale Straight-blade and Twisted-blade Vertical Axis Wind T

Numerical Simulation on Small Scale Straight-blade and Twist...

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2011 SSITE International Conference on Future Material Research and Industry Application(FMRIA 2011)

作者： Lv Yongzhe Jiang Dongxiang Jiang Yong State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Thermal Engineering Tsinghua University

This paper presents an analysis on the performance of vertical axis wind turbine of two types, namely straight-blade vertical axis wind turbine(SB-VAWT) and twisted-blade vertical axis wind turbine(TB-VAWT)An attempt of this simulation is to identify which type performs better in the same wind conditions and swept areaThree-dimensional computational fluid dynamics(CFD) was adopted in this analysis, after solid models of them were generatedPreliminary results of torque, power and aerodynamics in the fluid field were obtained for discussionFinally, there provided some guidance for future wind tunnel tests.

关键词： straight-blade vertical axis wind turbine twisted-blade vertical axis wind turbine numerical simulation performance aerodynamics

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Research on surface electric field of parallel gap

Research on surface electric field of parallel gap

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2011 7th Asia-Pacific International Conference on Lightning, APL2011

作者： Yu, Junjie Yu, Zhanqing Zeng, Rong Chen, He Peng, Xiang State Key Laboratory of Control and Simulation of Power Systems and Generation Equipments Dept. of Electrical Engineering Tsinghua University Beijing 100084 China Maintenance and Test Center of EHV Power Transmission Company China Southern Power Grid Co. Ltd. Guangzhou 510663 China

ISBN: (纸本)9781457714665

With parallel gap, by controlling the motion path of the electric arc, effectively avoid burning and damaging the insulator during lightning strike so that the effect to reduce the accident rate of line is obvious. Because of simple structure, convenient installation and good economical efficiency, its importance in measures of lightning protection for transmitting line is continually improved. Electric field characteristics on the surface of parallel gap electrode have obvious influence on corona generation and the gap breakdown position and are the key parameters that must be considered in the design. Based on the finite element method, this paper sets up the analysis model of electric field of parallel gap including the tower, the conductor and the insulator, uses ANSOFT software for simulation, studies the surface electric field characteristics of parallel gap electrode, compares the electric field of four types of parallel gap put forward in the paper and analyzes the law of influence of parallel gap electrode parameters on the electric field characteristics. The results show that, when the short circuit distance is increased, the maximum values of electric field of ball end and snap ring body are obviously increased;the opening angle of snap ring is larger and the maximum value of electric field of ball end is higher;when the pipe diameter is increased, the maximum value of electric field of snap ring body is reduced considerably;the ball end is bigger and the maximum value of electric field of ball end is less;the ring pipe diameter is the structure parameter having the largest influence on the surface electric field;for the ball end at the end of ring electrode, the structure parameter having the largest influence on the electric field is the diameter of ball end. Reducing the distance that the ball end stands out of the ring plane can decrease the maximum value of electric field of ball end. © 2011 IEEE.

关键词： Finite element method

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Research on impulse discharge characteristics of parallel gap

Research on impulse discharge characteristics of parallel ga...

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2011 7th Asia-Pacific International Conference on Lightning, APL2011

作者： Chen, He Peng, Xiang Yu, Zhanqing Yu, Junjie Zeng, Rong Maintenance and Test Center of EHV Power Transmission Company China Southern Power Grid Co. Ltd. Guangzhou 510663 China State Key Laboratory of Control and Simulation of Power Systems and Generation Equipments Dept. of Electrical Engineering Tsinghua University Beijing 100084 China

ISBN: (纸本)9781457714665

With parallel gap, by controlling the motion path of the electric arc, effectively avoid burning and damaging the insulator during lightning strike so that its importance in measures of lightning protection for transmitting line is continually improved. Initial discharge position is key consideration during design of parallel gap and depends on discharge characteristics of parallel gap under the action of lightning surge when the lightning strikes the tower or line. This paper gives three types of parallel gap used to protect the composite insulator, sets up the impulse discharge test and observation platform including high-speed camera, studies the impulse discharge characteristics of parallel gap and analyzes the influence of structural parameters on the discharge characteristics. This study showed that there is randomness for discharge path of parallel gap;three types of parallel gap given in this paper can achieve 100% discharge rate of parallel gap;the determinant of discharge rate in the presupposition discharge area (PDA) is the distance that the presupposition discharge area stands out of the whole electrode plane. When this distance exceeds 20mm or more, it can ensure that most of the discharge occurs in the PDA;the parallel gap can reduce the insulation distance of 4000mm insulator about 40mm, U50 about 1%, which may approximately consider that the parallel gap has no influence on the insulating property of the insulator. © 2011 IEEE.

关键词： Electric arcs

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