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Twenty-Second Annual IEEE Applied power Electronics Conference and Exposition (APEC 07), vol.2

作者： Hua BAI Zhengming Zhao Department of Electrical Engineering State Key Laboratory of Control and Simulation of Power System and Generation Equipment Tsinghua University Beijing China

The integrated gate commutated thyristors (IGCTs) are commonly used for construction of high voltage three-level PWM controlled voltage source converter/inverters. When the output voltage is greater than the maximum rated voltage, IGCTs are connected in series. To ensure the safe and reliable operation of the converter/inverters, special measures are required to equalize the voltages across the IGCTs connected in series. An effective method for balancing voltages is to use resistors for static voltage balancing and RC snubber circuits for dynamic voltage balancing. However, most of the previous research work reported in the literature focused on the dynamic circuit design for converters of the BUCK topology. Trade off is made only between the performance of dynamic voltage balancing and the turn-on loss without any consideration of di/dt endurance and any procedural steps, which makes the design procedure not suitable for converters of the three-level topology. Based on a functional model of IGCTs, this paper presents a procedure for optimum design of the dynamic voltage balancing circuit for a 6 kV/1250 kW inverter. The specific transient processes in the three-level topology with dynamic snubber circuit are simulated and the mechanisms are analyzed, which is absent in the previous work.

关键词： IGCT Dynamic equivalent circuit Three-level inverter Dead band

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The propagation characteristics of electromagnetic wave generated from partial discharges in power transformer by FDTD simulation

The propagation characteristics of electromagnetic wave gene...

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2007 Annual Report - Conference on Electrical Insulation and Dielectric Phenomena, CEIDP

作者： Tang, Zhiguo Li, Chengrong Wang, Wei Wang, Hui Wang, Li Ding, Yansheng Beijing Key Laboratory of High Voltage and EMC Ministry of Education North China Electric Power University Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control Ministry of Education North China Electric Power University State Grid Corporation of China 100081 Beijing China Beijing Key Laboratory of High Voltage and EMC School of Electric and Electronic Engineering North China Electric Power University P.O. No.88 Beijing 102206 China

The radiation and propagation of electromagnetic (EM) waves generated from PD caused by the obstruction of main transformer components are studied by FDTD simulation in order to get more information for PD location and diagnosis. Current filament, perfect conductive cylinder and perfect conductive spiral coil models are used to simulate the radiation and the influences of iron-core and transformer coil to the propagation of EM *** results demonstrate dynamic propagation process of EM waves in time order, and prove the correctness of the shortest optical path principle. But the attenuation and distortion of EM waves-especially the first peak amplitude-caused by the obstruction of large solid conductive obstacle like iron-core are quite intensive that it may cause great difficulties to identify exact arriving time position of incident waves coming along the shortest optical path. While the influences of the coil to the propagation of EM waves are so little that HF EM waves can penetrate it in almost linear path. ©2007 IEEE.

关键词： Electromagnetic waves

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Vector control for a twelve-phase synchronous motor

Vector control for a twelve-phase synchronous motor

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International Conference on Electrical Machines and systems (ICEMS)

作者： Dejia Zhou Zhengming Zhao Shanming Wang Jianyun Chai State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Department of Electrical Engineering and Applied Electronic Technology Tsinghua University Beijing 100084 China State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Tsinghua University Beijing China

A twelve-phase synchronous motor with four Y-connected 3-phase symmetrical windings displaced in turn by 15deg is modeled by using flux linkages as state variables, and an optimized method for the vector control is proposed with the simulation results. The observing model for magnetizing flux linkage at the direct-axis is derived whereby a vector control scheme of a twelve-phase synchronous motor, and related simulation is constructed in this paper. Using switch blocks to model the functions of twelve-phase voltage-fed inverter is convenient for simulating the driving system. The results of the simulations show that the torque and magnetizing flux linkage can be controlled separately, and the dynamic characteristics of the motor are satisfied with the operating requirements.

关键词： Machine vector control Synchronous motors Couplings Magnetic separation Magnetic flux Switches Optimization methods Voltage Inverters Torque control

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Short-term Reliability Online Evaluation Basing On Transient state Probability

Short-term Reliability Online Evaluation Basing On Transient...

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IEEE General Meeting power& Energy Society

作者： Lin Cheng Haitao Liu Xin Zou Yuanzhang Sun Electrical Engineering Department at Tsinghua University Electrical Engineering School State Key Lab of Power System Control and Simulation Tsinghua University

The reliability of the power system in a future short term is studied according to the current state. Basing on this, we can alarm and prevent the outage to assure the safety and reliability of the power system. Traditional reliability is an expected value of long-term reliability level under the fixed operating mode, which cannot reflect the real time reliability level under the current operational state. This essay presents the novel conception and algorithm of online evaluating the short-term reliability in order to study the operational reliability level. The influence of the variable system states on the reliability level is reflected according to the real time operational information provided by the SCADA/EMS/WAMS. Markov process is adopted to solve the transient state probability of the components, so that forecasting the system state basing on the transient probability is possible. The probability of the system state and the reliability indices of the system changes as the time varying. The analysis and the assessment of IEEE RTS-79 system indicates that there are great differences between the short-term and long-term reliability indices, and only the transient probability evaluation can assess the short-term probability properly. In this paper the relationship between the enumerating number of the system states and the forecasting time is also studied. The result indicates that only a few system states are needed to get relative high degree of evaluation accuracy, which can be applied online. IEEE RTS-79 case study is calculated to verify this conclusion.

关键词： power system reliability power system transients power system security Markov processes Real time systems Steady-state Reliability theory Safety Medical services Time varying systems

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Safe Operating Area of High power Three-level Neutral Point Clamped Voltage Source Inverters Equipped with IGCTs

Safe Operating Area of High Power Three-level Neutral Point ...

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International Conference on Electrical Machines and systems 2007(ICEMS2007)(第十届国际电机与系统会议)

作者： Liqiang YUAN Zhengming ZHAO Fanbo HE Mohd Eltawil State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Electrical Engineering Tsinghua University China

To design and analyze the behavior of high power inverter, the definition and application of the inverter's own safe operating area (SOA) are presented in this paper. The relation between the switch devices behaviors and the other components of the inverter is playing a key role in the description of the novel SOA. Based on the proposed idea, the optimization of a real 1.25MW/3.3kV inverter equipped with IGCTs is presented and analyzed. The corresponding experimental results are shown.

关键词： Voltage Pulse width modulation inverters Semiconductor optical amplifiers Switches Induction motors power harmonic filters power system simulation Variable speed drives Circuits Topology

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Sensitivity analysis for AC/DC hybrid power systems

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Dianli Xitong Zidonghua/Automation of Electric power systems 2007年第12期31卷 45-49页

作者： Liu, Chongru Zhang, Boming Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control North China Electric Power University Beijing 102206 China State Key Lab. of Power Systems Department of Electrical Engineering Tsinghua University Beijing 100084 China

The interactions between AC and DC systems in the steady-state condition of power systems are investigated. Through a sensitivity analysis, the influence of DC control parameters on the operation of AC/DC systems and that of AC control parameters on other AC parameters with the DC system existing are discussed. The sensitivity matrices and the influence factors between AC and DC systems are analyzed from various points of view. The sensitivity analysis made in this paper is expected to be of practical significance in such problems as load flow control, parameter regulation, voltage estimation, etc.

关键词： Electric power transmission networks

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The Propagation Characteristics of Electromagnetic Wave Generated from Partial Discharges in power Transformer by FDTD simulation

The Propagation Characteristics of Electromagnetic Wave Gene...

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2007 Annual Report Conference on Electrical Insulation and Dielectric Phenomena, vol.1

作者： Zhiguo Tang Chengrong Li Wei Wang Hui Wang Li Wang Yansheng Ding Beijing Key Laboratory of High Voltage & EMC North China Electric Power University China Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control Ministry of Education North China Electric Power University China State Grid Corporation of China Beijing China

The radiation and propagation of electromagnetic (EM) waves generated from PD caused by the obstruction of main transformer components are studied by FDTD simulation in order to get more information for PD location and diagnosis. Current filament, perfect conductive cylinder and perfect conductive spiral coil models are used to simulate the radiation and the influences of iron-core and transformer coil to the propagation of EM waves. The results demonstrate dynamic propagation process of EM waves in time order, and prove the correctness of the shortest optical path principle. But the attenuation and distortion of EM waves-especially the first peak amplitude-caused by the obstruction of large solid conductive obstacle like iron-core are quite intensive that it may cause great difficulties to identify exact arriving time position of incident waves coming along the shortest optical path. While the influences of the coil to the propagation of EM waves are so little that HF EM waves can penetrate it in almost linear path.

关键词： Electromagnetic propagation Electromagnetic scattering Character generation power generation Partial discharges power transformers Finite difference methods Time domain analysis Electromagnetic radiation Coils

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Visible target imaging system validation for hardware-in-the-loop

Visible target imaging system validation for hardware-in-the...

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Summer Computer simulation Conference 2006, SCSC 2006, Part of the 2006 Summer simulation Multiconference, SummerSim 2006

作者： Yu, Hong He, Qiuru Lei, Jie Du, Huijie Zhang, Ying State Key Laboratory of Control System Simulation Beijing Simulation Center 52 Yongding Road Beijing China

ISBN: (纸本)9781622763528

This paper describes visible target imaging simulation system and validation activities at Beijing simulation Center. The target size and position models and target energy output are validated here. The target size validation is based on comparison of visible seeker data collected in the HWIL simulation to theory calculation;the target position validation is based on comparison of visible seeker data collected in the HWIL simulation to demands setting values;and the target energy validation is based on comparison of gray levels from the projector to the luminance provided by an institute of targets property research or by visual inspection.

关键词： Hardware-in-the-loop simulation

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Analyzing the energy spectra of ion beams emitted from x-pinch plasma

Analyzing the energy spectra of ion beams emitted from x-pin...

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IEEE International Conference on Plasma Science (ICOPS)

作者： Xiaobing Zou Rui Liu Xinxin Wang Guixin Zhang Chengmu Luo Min Han Department of Electrical Engineering State Key Laboratory of Control and Simulation of Power System and Generation Equipment Tsinghua University Beijing China

Summary form only given. Between the output electrodes of a 500 kV/400 kA/100 ns pulsed-power generator, two Al wires each with diameter of 10-100 mum crossing and touching at a single point constitute an "x" shape load. The cross position explodes first and then pinches axially to form so-called X-pinch plasma as current is delivered to the "x" wires. In order to analyze the energy spectra of ion beams emitted from x-pinch, a compact Thomson spectrometer was designed and constructed. It consists of an entrance window, a pair of small permanent magnets, an exit pinhole, and a high sensitive nuclear track detector of CR-39 plastic plate. Ion beams experience deflections in the electromagnetic field, and then hit the target (CR-39 plastic) at different positions and form craters, then the craters form different parabolic track with different ratio of ion mass to ion charge. By counting the track density of the parabolas, charge state resolved energy spectra of ion beams were obtained

关键词： Ion beams Plasmas Target tracking Wires Plastics Electrodes Pulse shaping methods Pulse generation Shape Magnetic analysis

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Analysis and Experimental Study of Slot Effect in Synchronous Reluctance Permanent Magnet Motors

Analysis and Experimental Study of Slot Effect in Synchronou...

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International Conference on power Electronics and Motion control (IPEMC)

作者： Wei Guo Zhengming Zhao Yingchao Zhang Department of Electrical Engineering State Key Laboratory of Control and Simulation of Power System and Generation Equipment Tsinghua University Beijing China

Slot effect in synchronous reluctance motors with permanent magnet assisted (SR-PM) are deeply analyzed, reduced and verified by experiments in this paper. The three different type sample SR-PM motors are introduced firstly. Then how the rotor layer numbers affect the torque characteristics is deeply analyzed, including the torque-angle, steady operating torque and position-setting torque. Then the reduction method is presented with simulation results. The detail experiment results are given in the final. The results shows that both more layers and stator slot skewing can reduce the teeth harmonics. However for the rotor with sintered NdFeB magnet, stator slot skewed is the best way because it only has few layers due to manufacture reason

关键词： Magnetic analysis Permanent magnet motors Reluctance motors Rotors Synchronous motors Torque Stators power system simulation Manufacturing Servomotors

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