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IEEE Energy Conversion Congress and Exposition, ECCE

作者： Xuesong Wang Zhengming Zhao Liqiang Yuan State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing China

For large current, switching devices such as MOSFET and IGBT, often have to be connected in parallel. Due to this reason, derating and preselection of the switching devices become necessary to develop high-power converters. The current imbalance can be produced by stray inductances, device characteristic difference or asymmetric circuit. Moreover, thermal imbalance is another important reason for current balancing. The static and transient characteristics of an IGBT vary sensitively with its junction temperature. This paper focuses on the current sharing of IGBTs in parallel with thermal imbalance. In this paper, an active gate control method which can achieve current balancing of the IGBTs in parallel with thermal imbalance, is explained and verified by experiments. This method can be applied to an actual 160kW/380V power electronics converter prototype for improving the utilization of the switching devices and enhancing system reliability.

关键词： Insulated gate bipolar transistors Junctions Temperature measurement Temperature Temperature control Logic gates Transient analysis

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A Review on Overvoltages in Microgrid

A Review on Overvoltages in Microgrid

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IEEE PES Asia-Pacific Power and Energy engineering Conference (APPEEC)

作者： Shuiming Chen Hongqiao Yu Department of Electrical Engineering State Key Laboratory of Control and Simulation of Power System and Generation Equipment Tsinghua University Beijing China

Now microgrid has aroused increasing attention due to energy sustainable development and the development of distributed generations (DG), such as micro-turbines, gas turbines, wind power, photovoltaic and fuel cells. This paper introduces the basic structure of microgrid and summarizes the overvoltages that can occur in microgrid, including ground fault overvoltages, resonant overvoltages, overvoltage related to voltage regulation, switching overvoltages of inner microgrid, transfer overvoltages from distribution network (such as lightning and switching overvoltages). By analysis, this paper obtains the following conclusion: resonant overvoltages and lightning stroke transfer overvoltages are the most serious for microgrid.

关键词： Surges Resonance Lightning Sustainable development Distributed control Wind turbines Wind energy Photovoltaic systems Solar power generation Fuel cells

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DC pre-excitation application in three-phase induction motor drive system

DC pre-excitation application in three-phase induction motor...

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IEEE International Symposium on Power Electronics for Distributed Generation systems (PEDG)

作者： Sideng Hu Zhengming Zhao Ting Lu Liqiang Yuan Department of Electrical Engineering State Key Laboratory of Control and Simulation of Power System and Generation Equipment Tsinghua University Beijing China

Due to the current restriction of semiconductor devices, the start-up is an extremely important process in the ASD (adjustable speed drive) system. DC pre-excitation is one of the effective solutions for increasing the starting torque and depressing the starting inrush current. However the effect of DC pre-excitation would be discounted if it could not be compatible with the induction motor drive control system. Also the stability of the DC pre-excitation application is related to its operational mode. This paper addresses the principle of DC pre-excitation and excavates its relationship with current control. The method to improve the stability of DC pre-excitation effectively shielding EMI is detailed. The relevant study has been implemented in a control system for a 55 kW and 160 kW induction motor and the simulation and experimental results validate the effectiveness of the proposed design method.

关键词： Induction motors Torque DC motors Electromagnetic interference Process control Variable speed drives Switches

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Approaches to enhance discrete control algorithms serving for motor drive system

Approaches to enhance discrete control algorithms serving fo...

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IEEE Energy Conversion Congress and Exposition, ECCE

作者： Sideng Hu Zhengming Zhao Liqiang Yuan Ting Lu Xuesong Wang State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing China

The discrete control technology for AC machine drives is widely applied in the industrial field. This paper aims to excavate new approaches to enhance the discrete control system in AC motor drive systems from following aspects: matching design for discrete subsystems, synchronization in the signal processing and dealing with the restrictions in the voltage output. The proposed approaches are incorporated with three key techniques applied in high performance induction motor drive systems: DC pre-excitation, parameter identification and flux observer with a sensorless control to verify the feasibility. The anti-interference and synchronization procedure in the implementation are also proposed. The experimental results from the test on 55kW/400V and 160kW/400V ASD (Adjustable Speed Drives) systems validate the effectiveness of the proposed approaches.

关键词： Switches Variable speed drives Observers Parameter estimation Pulse width modulation Induction motors

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Real-time vehicle detection based on quasi-shot segmentation

Real-time vehicle detection based on quasi-shot segmentation

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Congress on Image and Signal Processing, CISP

作者： Yan Liu Yaping Dai Meng Wang Zhongjian Dai Zubair Ahmed Memon BIT Beijing Key Laboratory of Automatic Control System Beijing China Department of Electrical Engineering Mehran University of Engineering & Technology Jamshoro Sindh Pakistan

In this paper, a Quasi-shot Segmentation Vehicle Detection (QSVD) method is proposed to improve the accuracy and robustness of traffic flow detection. The QSVD method is based on histogram intersection method to find the biggest difference between successive frames. Adjacent frames are considered in when vehicle is detected in current frame. Relying on the QSVD method, vehicle can be detected by signal peak and valley search and gradual transition shot detection problem can be resolved. The initial video is used to accomplish detection directly without image preprocessing. Experiments show that vehicles can be detected effectively by the QSVD method. The detection accuracy is remained at 93% or more.

关键词： Vehicles Vehicle detection Visualization Histograms Image segmentation Accuracy Real time systems

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Analysis for Pull-In Voltage of a Multilayered Micro-Bridge Driven by Electrostatic Force

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engineering（科研） 2010年第1期2卷 55-59页

作者： Y. LIU G.C. WANG H.Y. YANG Automobile College Chongqing University of Technology Key Laboratory of Automobile Parts & Test Technique in Chongqing Chongqing Engineering Research Center for Automobile Power System and Control

A trial solution for bending deflection of a multilayered micro-bridge subject to a voltage induced load is presented. The relation between the applied voltage and the displacements of the micro-bridge in the pull-in state is analyzed by energy method. Furthermore, two analytical expressions about normalized displacement and pull-in voltage are carried out. It’s proved that the value of normalized displacement is not influenced by residual stress if axial and shear deformation is ignored. Finally, the theoretical results are compared with that of FEM, and they show good agreement.

关键词： MEMS Electrostatic Actuation Multilayered Micro-Bridge Trial Solution Energy Method Pull-In Voltage

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Effects of interfacial pressure on tracking failure at XLPE cable joint by analyzing discharge light distribution

Effects of interfacial pressure on tracking failure at XLPE ...

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IEEE International Conference on Solid Dielectrics (ICSD)

作者： B. X. Du L. Gu Key Laboratory of Power System Simulation and Control of Ministry of Education Department of Electrical Engineering School of Electrical Engineering and Automation Tianjin University TJU Tianjin China

This paper investigated the effects of interfacial pressure on the discharge and tracking failure at the interface between XLPE and silicon rubber by analyzing the distribution of discharge light emitted during the failure process. The test sample was made by pressing together a piece of XLPE and a piece of transparent silicon rubber with the pressure of 20 kN/cm 2 , 100 kN/cm 2 and 300 kN/cm 2 , respectively. Test voltage was applied to a pair of plate-needle electrodes sandwiched at the interface with the insulation distance of 10 mm. The initial discharge voltage, the discharge light from discharge to tracking failure and the tracking patterns after failure were recorded with a digital camera. Then the discharge light was analyzed with an image processing method. Results show that the initial discharge voltage increases with the increase of pressure, which significantly influences the distribution characteristics of the discharge light and tracking pattern at the interface. The analysis of discharge light distribution is helpful in understanding the failure process and its mechanism at the interface between XLPE and silicon rubber found in prefabricated cable joint.

关键词： Discharges Insulation life Degradation Brightness Power cables Rubber Silicon

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Effect of temperature on electrical tree in silicone rubber

Effect of temperature on electrical tree in silicone rubber

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IEEE International Conference on Solid Dielectrics (ICSD)

作者： B. X. Du Z. L. May Gao T. Han Key Laboratory of Power System Simulation and Control of Ministry of Education Department of Electrical Engineering School of Electrical Engineering and Automation Tianjin University TJU Tianjin China

In this paper, room temperature vulcanized (RTV) silicone rubber (SiR) was employed as test sample to investigate the relationship between electrical tree propagation characteristics and the experiment temperature. Both the structures and growth characteristics of electrical tree in SiR were observed by using a digital camera and a microscope system. Obtained results show that electrical tree in RTV SiR is white gap tree channel, which all initiate from single branch, and the width of initiative single branch channel varies a lot with the electrical tree structure. The structure of electrical tree at experiment temperature from 30°C to 90°C in RTV SiR can be classified into four categories. They are branch, bush, pine branch and bush-pine mixed tree. The distribution of tree structures changes with the experiment. At the temperature of 30°C, branch tree take up a great proportion, however, bush tree becomes the dominant structure when the temperature rise up to 60°C and 90°C. The probability of tree initiation decreases obviously with the rise of the experiment temperature from 30°C to 90°C. All kinds of electrical tree grow rapidly in the first beginning of the treeing propagation, and this process lasts only a few minutes. In addition, a new parameter, the treeing proportion is introduced to describe propagation characteristics of bush tree.

关键词： Electrodes Rubber Temperature distribution Needles Power cables Cable insulation

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Application of nonlinear methods in tracking failure test of epoxy/SiO2 nanocomposite

Application of nonlinear methods in tracking failure test of...

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IEEE International Conference on Solid Dielectrics (ICSD)

作者： B. X. Du J. W. Zhang L. Gu H. J. Liu Key Laboratory of Power System Simulation and Control of Ministry of Education Department of Electrical Engineering School of Electrical Engineering and Automation Tianjin University TJU Tianjin China

This paper investigates the effect of nano-scale SiO 2 on the tracking failure properties of nanocomposites. Test samples were made by dispersing nano-scale SiO 2 powder in epoxy with the weight ratios of 0, 1, 3, 5, 7, 9 wt%. AC voltage was applied on a pair of needle-plate electrodes at the surface with the insulation distance of 10 mm. The time to tracking failure and discharge current were recorded. In order to distinguish the change of the tracking resistance from the confusing discharge current, a recurrence plot (RP) analysis of discharge current has been used. The patterns of the tracking failure were analyzed with fractal dimension (FD) method to quantify the carbonization degree. The results reveal that 3 wt% of nano-scale SiO 2 filler greatly increase the resistance to tracking failure of epoxy/SiO 2 nanocomposite.

关键词： Insulation life Degradation Discharges Surface discharges Surface treatment Loading Electrodes

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Discrete monkey algorithm and its application in transmission network expansion planning

Discrete monkey algorithm and its application in transmissio...

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IEEE General Meeting Power& Energy Society

作者： Jingran Wang Yixin Yu Yuan Zeng Wenpeng Luan Key Laboratory of Power System Simulation and Control Tianjin University TJU Tianjin China BC Hydro Engineering Burnaby BC Canada

ISBN: (纸本)9781424465491

Monkey algorithm (MA) is one of the evolution algorithms originally developed for optimization problems with continuous variables. In this paper, a discrete monkey algorithm (DMA) was proposed for transmission network expansion planning, one discrete optimization problem. It includes the representation of solution, the modification of objective function, climb process, watch-jump process, cooperation process, somersault process, stochastic perturbation mechanism and termination criteria. Large-step and small-step climb process are designed to avoid the disordered climb direction during the MA optimization process. Cooperation process and stochastic perturbation mechanism are also introduced to improve computational efficiency. The proposed method is applied to a 18-bus system and the IEEE 24-bus system. Numerical results demonstrate that DMA has powerful computational capability and is capable of solving different dimensions of expansion planning problems efficiently with small population size.

关键词： Planning Optimization Algorithm design and analysis Search problems Particle swarm optimization Smart grids

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